CA1057845A - Ultrasonic imaging method and apparatus - Google Patents
Ultrasonic imaging method and apparatusInfo
- Publication number
- CA1057845A CA1057845A CA260,592A CA260592A CA1057845A CA 1057845 A CA1057845 A CA 1057845A CA 260592 A CA260592 A CA 260592A CA 1057845 A CA1057845 A CA 1057845A
- Authority
- CA
- Canada
- Prior art keywords
- filter
- echo signals
- depth
- bandpass filter
- signals
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S15/00—Systems using the reflection or reradiation of acoustic waves, e.g. sonar systems
- G01S15/88—Sonar systems specially adapted for specific applications
- G01S15/89—Sonar systems specially adapted for specific applications for mapping or imaging
- G01S15/8906—Short-range imaging systems; Acoustic microscope systems using pulse-echo techniques
- G01S15/895—Short-range imaging systems; Acoustic microscope systems using pulse-echo techniques characterised by the transmitted frequency spectrum
- G01S15/8954—Short-range imaging systems; Acoustic microscope systems using pulse-echo techniques characterised by the transmitted frequency spectrum using a broad-band spectrum
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B8/00—Diagnosis using ultrasonic, sonic or infrasonic waves
- A61B8/08—Detecting organic movements or changes, e.g. tumours, cysts, swellings
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
- G01N29/04—Analysing solids
- G01N29/06—Visualisation of the interior, e.g. acoustic microscopy
- G01N29/0609—Display arrangements, e.g. colour displays
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
- G01N29/04—Analysing solids
- G01N29/06—Visualisation of the interior, e.g. acoustic microscopy
- G01N29/0609—Display arrangements, e.g. colour displays
- G01N29/0645—Display representation or displayed parameters, e.g. A-, B- or C-Scan
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
- G01N29/34—Generating the ultrasonic, sonic or infrasonic waves, e.g. electronic circuits specially adapted therefor
- G01N29/341—Generating the ultrasonic, sonic or infrasonic waves, e.g. electronic circuits specially adapted therefor with time characteristics
- G01N29/343—Generating the ultrasonic, sonic or infrasonic waves, e.g. electronic circuits specially adapted therefor with time characteristics pulse waves, e.g. particular sequence of pulses, bursts
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
- G01N29/44—Processing the detected response signal, e.g. electronic circuits specially adapted therefor
- G01N29/4454—Signal recognition, e.g. specific values or portions, signal events, signatures
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
- G01N29/44—Processing the detected response signal, e.g. electronic circuits specially adapted therefor
- G01N29/4463—Signal correction, e.g. distance amplitude correction [DAC], distance gain size [DGS], noise filtering
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/52—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S15/00
- G01S7/52017—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S15/00 particularly adapted to short-range imaging
- G01S7/52046—Techniques for image enhancement involving transmitter or receiver
- G01S7/52047—Techniques for image enhancement involving transmitter or receiver for elimination of side lobes or of grating lobes; for increasing resolving power
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/52—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S15/00
- G01S7/52017—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S15/00 particularly adapted to short-range imaging
- G01S7/52046—Techniques for image enhancement involving transmitter or receiver
Abstract
ABSTRACT OF THE DISCLOSURE
The ultrasonic imaging method and apparatus comprises an ultrasonic wave transducer supplied with recurrent multi-frequency energy pulses for pulse insonification of an object under investigation with ultrasonic waves. Resultant echo waves from the object are directed onto the transducer for converting the same to electrical signals which are supplied to a signal processor which includes a variable bandpass filter. One or more of the filter characteristics are varied as a function of depth from which the echo signals are returned for enhanced resolution and signal-to-noise ratio of the received signal. Preferably, the filter is matched to the noise and signal spectra of the system. For B scan operation wherein reverberated acoustic pulses are derived from a range of depths a time variable filter is employed for time varying operation thereof.
The ultrasonic imaging method and apparatus comprises an ultrasonic wave transducer supplied with recurrent multi-frequency energy pulses for pulse insonification of an object under investigation with ultrasonic waves. Resultant echo waves from the object are directed onto the transducer for converting the same to electrical signals which are supplied to a signal processor which includes a variable bandpass filter. One or more of the filter characteristics are varied as a function of depth from which the echo signals are returned for enhanced resolution and signal-to-noise ratio of the received signal. Preferably, the filter is matched to the noise and signal spectra of the system. For B scan operation wherein reverberated acoustic pulses are derived from a range of depths a time variable filter is employed for time varying operation thereof.
Description
1~3~ a.~
~AC~GROUND OF THE INVENTION
This invention relates to ultrasonic imaging method and apparatus and, ln particular, to pulse echo method and apparatus wherein short broadband ultrasonic pulses are applied to the object under investigation, travel into the object, and are re-flected by boundries and discontinuities therein to be returned to the transducer. The received echo signals which are derived from different depths within the object are supplied to a suitable ~ -display, and the transducer is moved relative to the object to provide for a two-dimensional display. The above-described technique, generally referred to as B-scan, often utilizes a cathode ray tube display in which one of the deflection voltages is proportional to the transducer position, the orthogonal de-~ flection voltage is proportional to the time elapsed since the ! energizing pulse, and the cathode ray tube beam is modulated by the received pulse intensity. The resulting image is of a -section of the object lying in the plane of the propagating ultra- ~;
sonic waves. A narrow beam is employed which often is focused at an operating depth within the object field for improved .j . .
lateral resolution.
Such pulse echo method and means of ultrasonic imaging j often are employed for imaging of living organisms. Pulses that are reflected from scatterers further within the organism ~, experience greater attenuation, and it is common practice to ` contpensate for such difference in attenuation by tlme variable ~-gain amplification of the received signal. It will be understood, however, that the attenuation within organs or other tissues varies also with frequency of the ultrasonic wave. In particular, , the attenuation coefficient of tissue increases substantially `
linearly with frequency, with the high frequency spectral com~
ponents of the returned signal being attenuated more severely :', .
, - 2 -7 ~ L~ t j than the low frequency components. Typically, the center fre-quency of the received signal drops in frequency with depth of penetration, first at a moderate rate, then s-teeply, and finally at a low ra~e. In brief, not only is the amplitude of the return signal -time dependent, but the spectral distribu-tion of the return energy pulse also is time~depth dependent. Prior art echographic ultrasonic imaging system and method typical~ly include timetime variable gain amplifying means in the signal processing system for increased gain with range to offset the loss of signal strength caused by tissue absorption without provision to com-pensate for changes in the spectral distribution of the return signal with time, or depth of penetration.
SUMMARY OF THE INVENTION
;~ An object of this invention is the provision of method and apparatus for ultrasonic imaging which overcome the above-mentioned shortcomings of prior art arrangements, and which in-clude means to compensate for changes in the spectral distribu-tion of the received signal with changes in range. ;
.:.
; An object of this invention is the provision of method ~;
;- 20 and apparatus for ultrasonic imaging which include signal pro-cessing means for the received signal which provide for improved resolution and/or signal to noise ratio by use of spectral dis-tribution compensation means.
An object of this invention is the provision oE an improved signal processing arrangement for ultrasonic imaging apparatus to compensate for changes in the spectral distribution ;
of the received ultrasonic signal produced by changes in distance ; traveled within the object under investigation.
Briefly, the above and other objects and advantages are ; 30 achieved by use, in an ultrasonic imaging system, of signal pro-.,:
cessing means which includes variable bandpass filter means .~, ~ .
, having one or more ilter characteristics which are varied, or controlled, in accordance with the time of travel of the ult.ra-sonic pulse wave wi.thin the object unde.r i:nvestigation. Control-lable bandpass filter characteristics include, for example, filter transmission, bandwidth, and center fxeque:ncy. For A and B scan methods of ultrasonic examination filter characteristics are time varied in accordance with the depth from which the echo signals are received, and for C scan operation the filter charac-teristics are adjusted to match the selected range setting.
Generally, the filter center frequency, bandwidth and upper, or high, frequency cutoff frequency are reduced with increased oper-~ ating depth for improved system operatioh.
'I ~ore particular~ly there is provided in an ultrasonic I system for the examination of the interior of objects, such as .1 body parts, the combination comprising: ~ :
means for insonification of an object under examination with a broadband ultrasonic wave signal, means for receiving echo signals from discontinuities over a .
range of depths within the insonified object and for converting the same to electrical signals,means for filtering said electrical signals by bandpass filter ~
means having a filter transmission factor as a function of fre- .
quency which is variable, and means for compensating for depth dependent changes in the ~ .
spectral distribution of the echo signals by time varying the .. ~1`
filter transmission factor versus frequency characteristic of the ..
~ bandpass filter means in accordance with the depth of the dis-., continuity from which the echo signal is reflected.
There is also provided in a method for the non-invasive ` 30 exam.ination of objects such as body parts, the steps of ~.
., .
; .
- 4 _ ~ .
e insonifying at least a por-tion of the body part w.ith a beam of broadband acoustic energy to produce echo signals from within the body, receiving echo signals from within the body and converting the same to electrical signals, passing the electrical signals through bandpass ilter means having a variable filter transmission factor versus frequency ~:
characteristic, and :~ time varying the filter transmission factor versus frequency 10 characteristic of the bandpass filter in relationship with the -~
; depth from which the echo signals are received while receiving echo signals from over a range of depths within the body for com- .
pensating for depth dependent changes in the spectral distribu-tion of echo signals.
There is further provided in an ultrasonic system for the examination of the interior body parts, or the like, the :
combination comprising, .
means for recurrent pulse insonification of a body part under ~ -. examination, 20 means for receiving echo signals from discontinuities within .
said body part over a time period following pulse insonification, `. which signals have a spectral distribution dependent upon the depth within the body part from which the signal is received, and : for converting received echo signals to electrical signals, , bandpass filter means having variable operating characteris- .
i tics through which said electrical signals and passed, and means for time varying operating characteristics of the band-pass~filter means while passing said electrical signals there- -through for relating filter operating characteristlcs with the time varying spectral distribution of the electrical signal.
- .
- 5 - ~:
There is also provided in a pulse operated ultrasonic imaging apparatus of the type which includes ultrasonic wave `~
transducer means for transmitting ultrasonic wave pulses into an object to be exa~ined and for converting reflected ultrasonic waves received over a range of depths therewithin into an elec-trical signal, the spectral distribution of said reflected ultra-sonic waves being dependent upon the depth from which they are received, a receiver for processing said electrical signal, said receiver 10 including time variable filter means~ and ;
means for time varying said time variable filter means while processing said electrical signal produced by ultrasonic waves ;
received from over a range of depths to compensate for changes in the spectral distribution of the reflected ultrasonic waves with depth.
The invention will be better understood from the follow-ing description taken in connection with the accompanying drawings.
In the drawings, wherein like reference characters refer to the ;
same parts in the several views:
Fig. 1 is a block diagram of a B scan ultrasonic imag-ing system which includes signal processing means embodying this invention; ' Fig. 2 shows, on a common frequency scale, frequency spectra of return signals obtained from different depths, the return signals after time gain compensation, and curves showing bandL~ass filter transmission factors as a function of frequency for the different depth return signals; ;
Fig. 3 is a schematic diagram illustrating a prior art type variable filter means which may be employed in the novel signal processing means of this invention shown in Fig. l; and Fig. 4 is a timing diagram for use in explaining the operation of the ultrasonic imaging apparatus shown in Fig. 1.
j i`' ' .
.. -. , , , .. , . 1 7~
Reference first is made to Fig. 1 wherein there is shown an ultrasonic imaging arrangement comprising a transducer ; 10 which, in the illustrated arrangement is used both for trans-mitting and receiving ultrasonic pulse signals. For purposes of illustration the transducer is shown immersed in a container 12 containing a suitable acoustic transmission medium 14 such as water for the support of acoustic waves. Ultrasonic compres-sional wave pulses generated by the transducer lO are transmitted through an acoustic lens 16 in the fluid medium and coupled through an acoustically transparent window 17 to the subject 18 under investigation for focusing of the pulses within the subject.
Such arrangements are well adapted for imaging living organisms such as the heart in a living body, however it will be apparent that the invention is not limited to any such particular applica-tion or use. Preferably, a broad band pulse is supplied to the transducer 10 from a gated signal source 20 through a power am-plifier 22 ~or multifrequency pulse insonification of the subject 18. Typically, pulses of ultrasonic waves within the range of, -~-, say, 1 to 10 M~z may be employed. The signal source 20 is re- ;
currently gated on as by use of a transmitter gate generator 24 under control of signals from a timing and control unit 26.
Periodic pulse operation generally is employed, although aperi-odic and continuous wave mode operation may be used. Also, it will be understood that the invention is not limited to use with ~ -any particular broad band signal source. For example, broad band operation by use of a short pulse source, or as by use of a pulse or a continuous sweep frequency, frequency modulated (e.g. chirp), random noise, or the like, signal source is contemplate~.
Ultrasonic pulses reflected from the boundaries and internal discontinuities of the subject 18 are received by the transducer 10 and the resultant electrical signals are supplied , :
~ - 7 -: , ~, ;
., to a gated amplifier 28 which is gated on and off duriny the receiving and trans~itting portions, respectively, oE the operat-ing cycle under control of the timing and control unit 26. If desired, a transmit/receive switch, not shown, could be employed in the connection of the transducer 10 to the signal source 20 and signal processor, or receiver, 30, which switch would elimin-ate the need to gate -the amplifier -to prevent blocking of the receiver by the transmitter pulses. -~;
In accordance with the present invention the signal pro-cessor includes a variable gain/filter compensation unit 32 to which the amplified echo signals are supplied. ~or purposes of ~`
illustration the compensation unit 32 is shown comprising separate variable gain amplifier 34 and variable filter 36 units. As will become apparent hereinbelow the amplifier and filter units simply , may be combined in the form of a single variable gain/filter multi-~ stage amplifier having the desired variable gain and bandpass ;~ filter characteristics.
~ For use in A and B scan operations, wherein the return . - .
signals are received from a range of distances within the subject, the variable gain amplifier and filter means 34 and 36, respec-tively, are time varied. As noted above the employment of time variable signal amplification in ultrasonic diagnostic systems is well known and includes the use of a varlable gain amplifier~
having a gain which is time varied in accordance with the lapsed ` time from the last transmitted pullse. In the illustrated arrange-: . , ment the gain of the variable gain amplifier 34 is varied in accordance with the output from a gain ~unction generator 38, with the timing of the operation of the generator 38 being under con- -trol of the timing and control unit 26. Often, the generator 38 simply comprises a ramp generator with an output signal which .
functions to increase the gain of amplifier 34 in proportion to ,t . . .
; .. : ~ ' range in a manner to offset -the loss of signal caused by acoustic absorption within the subject. Instead of a fixed function generator, an adjustable function generator may be used whereby a signal of desired shape easily may be ob-tained for control of amplifier gain. In any case, -time variable gain implification is well known as disclosed, for example, in the publication "Physical Principles of Ultrasonic Diagnosis" - Academic Press, London, England, by P.N.T. Wellsl copyright 1969, and no addi-tional description of such operation is believed to be required.
In the illustrated arrangement filter characteristics of the variable filter means 36 are controlled by a filter func-~
tion generator 40, with ~iming of the operation of the generator 40 being provided by the timing and control unit 26. For the illustrated B-scan operation the filter transmission factor as a function of frequency of the variable filter 36 is varied as a function of time by output from the filter function generator 40 for improved lateral and longitudinal resolution of the system as well as improved signal to noise ratio in a manner described in detail hereinbelow with reference to Fig. 2. For present pur-. . j .
`20 poses it will be seen that the output from the variable gain/
filter compensation uni-t 32 is applied to a broad band compres-sion amplifier 42 comprising, for example, a DC coupled log ampli-;fier with a compression factor of 40 to 60 dB. The amplifier output is detected by an envelope detector 44 comprising, for example, a full wave rectifier with low pass filter means and having as an output a signal which is proportional to the enve-lope of the broad band high frequency signal output from the amplifier 42. For the illustrated B scan operation, the detector output is supplied to a cathode ray tube display 46 and, in particular, to the control grid thereof to intensity modulate the ~-electron beam. It here will be noted that for A scan operation ,:' .
~' 9 _ '~,~, ,, ,~,.
:;, , t,'i'~
the detec-tor output simply may be supplied as a deflection signal to a cathode ray tube for deflection of the beam in one direction while a ramp signal synchronized with the transmi-tter operation is supplied as a deflection signal for deflection of the beam in an orthogonal direction.
For the illustrated B scan operation the transducer 10 t~
and associated focusing lens 16 are~moved with a scanning motion relative to the subject 18. In Fig. 1 the transducer and lens are shown mounted on a movable platform 48 connected to a scanning ;~
- 10 mechanism 50 through a mechanical linkage 52. Linear and/or sec-tor scanning may be employed and for purposes of illustration ; linear scanning across the object 18 in the direction of the arrow , 5~ is shown. The scanning mechanism includes a scan position information circuit having an output which is connected to the timing and control unit 26 having outputs for synchronizing the transmitting, receiving and display scanning operations, including the operation of a deflection an~ blanking generator 56. One out-put from generator 56 comprises a deflection voltage which is pro-portional to the transducer position along its scan, and another output which comprises an orthogonal deflection voltage which is proportional to the time elapsed since the last pulse was trans-mitted. The invention is not limited to use with any particular scanning arrangement. For èxample, the acoustic wa-~e from the ~-:
transducer may be deflected to sweep the wave over the object without relative movement of the transducer and object. Also, the `~ use of a transducer array is contemplated in place of the illus-. . .
trated transducer. ~;
As noted above the attention coefficient of tissue com- ;-prising the subject 18 increases approximately linearly with fre- ~ ~
: . ,~. :--quency such that the high frequency spectral components of the echo si~nals are attenuated more severely than the low frequency :. ~
~ components. Reference is made to Fig. 2 wherein exemplary spec~
.,' ~ .
`, ,.~ ~j,,," - 1 0 - ~ :
,1, ~ r.' . ~'' ` .
7 ~ L~ ~
tral distribution curves of pulse energy received by the trans-ducer 10 (Fig. 2A) and of the amplified signal from variable gain amplifier 34 (Fig. 2s) are shown for signals received from the adjacent boundary of the subject 18~with the acoustic medium~ and for echo signals received from internal discontinuities at 2 and 4 centimeters from the boundary, which curves are labeled Ocm, 2cm, and 4cm, respectively, in Fig. 2. The center frequencies for the echo signals received from the OCD1, 2cm, and ~cm levels are identified on the frequency scale as fo-0, fo-2, and fo--4, respectively. From Fig. 2A it will be seen that the amplitude bandwidth and center frequency of the received signal decrease with depth of penetration. In practice, the center frequency first drops at a moderate rate, then steeply, and then at a lower rate with increased signal penetration.
; The transmission factor versus frequency characteristic of the variable filter 36 is controlled so as to enhance resolu-~ tion, both lateral and longitudinal, and/or improve signal to noise - ratio. As is understood, lateral resolution is proportional to frequency and so improves with increased frequency, and longitu- ;
dinal resolution is proportional to bandwidth and so improves with increased signal bandwidth. On the other hand, the signal to noise ratio improves with a decrease in the bandwidth. The con-flicting requirements for improved operation thereby require tradeoffs in the design and operation of the variable filter 36 and, in practice, the variable filter characteris-tics are chosen for optimization of operation of the associated ultrasonic imag-~ll ing system. Obviously, the filter design not only depends upon -~ the frequency and characteristics of the received signals, but depends also upon the nature of the interference, or noise, to be rejected. For present purposes it will be assumed that the noise ' level is substantially uniform throughout the operating frequency spectrum.
' - 1 1 --' ~ ~
' '~ .
,~-. .. .
Reference now is made -to sections C, D and E of Fiy. 2 wherein -the filter transmission factor of the variable filter 36 - as a function of frequency at the above mentioned, O, 2 and 4 centimeter depths, respectively/ are shown in solid lines. At zero depth the variable filter has a wide transmission band cen-tered substantially at the center frequency fo-O of the received signal. The low and high frequency cut off frequencies ~cl-O and ~ -fch-O are identified for the Ocm filter transmission factor versus frequency curve of Fig. 2C.
At shallow depths (e.g. at 2cm.) where the center fre-quency fo-2 of the received signal is reduced, the illustrated filter transmission characteristics are altered so as to reduce the high frequency cutoff frequency to a frequency fch-2. (See Fig.
2D.) The variable filter bandwidth and center frequency also are decreased with the center frequency of the variable fil~er being shifted downwardly at substantially the same rate as the received signal center frequency fo decreases with depth of penetration. `~
As penetration increases the received signal decreases such that the signal to noise ratio also decreases. Consequently, the filter characteristics become of greater importance at greater operating depths. Fig. 2E shows the filter characteristic for operation at the 4cm depth. There, the filter high frequency cut-off frequency fch-4 is further reduced, the filter center fre-quency substantially coincides with the center frequency fo-4 of the received signal, and the transmission band is reduced in width for operation with the narrower frequency spectrum of the received signal.
It will be understood that the filter transmission fac-tor versus frequency curves shown at C, D and E of Fig. 2 are for purposes of illustrating operation of one suitable variable filter means, and that the invention is not limited specifically thereto.
For example, where the signal to noise ratio is relatively large, ~ 12 -o5-. ~;,, ,, :
1 13 ~at shallow depths, ~e.g. at 2cm) the fil-ter may be operated with substantially the same transmission charac-teristics as exist at the Ocm depth. Thus, although the high frequency spectral com-ponents are a-ttenuated more than the low frequency components, at shallow depths it of-ten is advantageous to main-tain the high frequency filter -transmission since the high frequency operation provides for good lateral and longitudinal, or depth, resolution~
Therefore, substantially the same illustrated filter characteris-tics for operation at Ocm. may be employed at shallow depths to, say 2cm. At increased depths, the characteristics could be varied in the manner described abbve, wherein the high frequency cutoff frequency decreases with increased depth.
In another modification of the invention the variable filter is provided with a substantially fixed low frequency cutoff ~ -frequency f'cl identified in Fig. 2, the low frequency end of the variable filter characteristics of such a modified filter being ; shown in bro~en lines in sections C, D and E of Fig. 2. The upper frequency end of the filter characters may remain as illustrated in full line. The design of such a filter, wherein only the high frequency cutoff frequency is variable may be simpler than that . of a filter in which the low fre~uency cutoff frequency also is varied. With this arrangement the filter is provided with a low , .
frequency cutoff frequency which best matches the low frequency `~ characteristic of the received frequency spectrum at substantially maximum operating depth, which, in the illustrated arrangement is on the order of six centimeters. Obviously, changes in the filter transmission factor which involve other than the high frequency ., cutoff frequency, bandwidth and center frequency changes may be employed as desired, or required.
~ 30 ', ~ ~ .
It will be understood -that where -the echo signal is time variable, as with the illustrated B scan arranyement of Fig. l the transmission factor versus frequency characteristic of the filter also i5 time varied, and that Fig. 2 simply illustrates operation at three specific depths. OEten, the particular time varying filter characteristic of any given fil-ter is readily matched to the system response characteristic by the proper selection of waveform output, or outputs, from the filter function generator 40. As noted above, in some instances the signal used to control the variable gain amplifier 34 also may be used for control of the variable filter whereby only a single gain/filter functlon genera-tor is required.
The prior art includes numerous filter means which exhibit a filter transmission factor versus frequency function which is readily variable, and it will be apparent that the pre-; sent invention is not limited to the use of any particular type of such variable filter means. There are numerous variations of variable bandpass filters of the type which may be employed in the combination of this invention, including both active and passive types. Pi, L and T section filters, and combinationsthereof may be utilized. In U.S. Patent No. 3,192,491 dated June 29, 1965, by Hesselberth et al, there are shown double tuned band- `
pass filters of the type which may be used, and the teachings and subject matter of the patent specifically are incorporated herein ' by reference. Also, as noted above, the variable gain and vari-- able filter functions preferably are included in a single multi-stage unit which includes suitable variable amplifying and fil-tering means by which the desired signal compensation may be per-formed. Preferably, the phase characteristics of the variable ;~
filter should remain constant over the operating range thereof.
. .
f~ "i ; ~:
ltJ~ 7~ ~
As noted above, for A and B scan operation a time vari-able filter is employed. Such filters often include voltage variable reactance elements, such as voltage variable capacitors, to which the output from the filter function generator 40 is supplied through suitable high capacitance d-c blocking capacitors and isolating resistors for voltage control of the capacitance thereof. ~aractor diodes often are employed for such purposes.
For C scan operation variable capacitors simply may be employed which are manually variable in accordance with the range setting of the imaging system.
For purposes of illustration a simplified prior art variable filter circuit is shown in Fig. 3 to which reference now is made. There, a T-section bandpass filter is shown comprising two series LC circuits 60 and 62 in the filter arms and a paral-; lel LC circuit 64 in the leg thereof The circuits 60, 62 and 64 include variakle capacitors 66, 68, and 70, respectively, used for tuning. For C scan operation, the capacitors may be manually variable in accordance with range setting of the imaging system.
,3 For the illustrated B scan arrangement wherein the filter trans-mission factor is time varied, voltage variable capacitor elements, ~ ;
such as varactor diodes may be used for the capacitors 66, 68 and 70. In such case suitable high capacitance d-c blocking capacitors i and isolating resistors, not shown, are included in the connection `~
of the filter function generator to the varactor diodies for vol- `~
i tage control of diode capacitance. With such an arrangement the generator output may supply a control voltage for the simultaneous increase of the capacitance of capacitors 66, 68 and 70 with time ~-~ during the receiving portion of the cycle to reduce the filter ~`
. .
center frequency accordingly. Simultaneous bandwidth control of the simplified filter is shown provided by means of a variable resistor 72 in series circuit with inductor 7~ in the parallel .:
,~ ~
~ l3~ 71~ ~
resonant circuit 69, the value of which is decreased with time during the receiving portion of the cycle. As the resistance decreases the slope of the fllter transmission function increases to effectively decrease the filter pass band. The variable re- ~
sistor 72 may comprise, for example, a field effect transistor -which functions as a voltage controlled resistor with the yate thereof connected to the output from the filter function generator 40 for control of the resistance thereof. The showing of the prior art simplified variable filter means of Fig. 3 simply is to facilitate an understanding of the novel signal processing means of the illustrated ultrasonic diagnostic apparatus which includes variable filter means. The actual filter employed would be tailored to the operating characteristics of the system and, as noted above easily may be includéd in the conventional variable : .: .
gain amplifier means.
Although the operation of the ultrasonic diagnostic -:. ~
apparatus,of this invention is believed to be apparent from the ~
above description, a brief description thereof with reference to ~ -the timing diagram of Fig. 4 now will be made. The transducer 10 i and lens 16 are moved across the object 18 in the direction of the arrow 54 by the scanning mechanism 50. A scan position signal is produced by the scan position circuit of the scanning mecha- ;~
nism and supplied to the timing and control unit 26 from which control signals for timing the operation of the transmitter, receiver, and cathode ray tube scanning means are obtained. Broad-band narrow beam ultrasonic waves ar~ generated during the trans-mit pulse period 76 shown in Fig. 4, which pulse is initiated at time Tl and is terminated at time T2. The pulse travels through the lens 16 and into the subject 18 to be reflected at the bound- ~;
ary of the subject with the fluid 14 and from different levels at discontinuities within the'subject. Af-ter a time delay period, .~ ~
, - 16 -- v . . . ..
. . . . . .; . , .
' , ' ' ', . : : . .
.. . . . .. . . . ... .
.. . .. .
7~
between times T2 and T3, -the receiver is gated on Eor processing the echo signals as shown at 73. During operation of the receiver between times T3 and T4 the gain oE the variable gain amplifier 34 is increased as indicated by gain curve 80 of Fig. 4 Eor in-creased amplification of the echo signals received from a greater depth within -the subject in the well known manner. In accordance with the present invention, during the receiver operation the transmission factor of the variable filter 36 is controlled for enhanced resolution and/or signal to noise ratio.
Here, Eor purposes of illustra-tion, at time T3 the filtex center frequency, curve 82, is shown decreasing with time from fo-0 to substantially match, or follow, the decrease in the -echo signal center frequency with depth of penetration. Simul-taneously, the filter bandwidth, curve 84, and filter high fre-quency cutoff frequency, curve 86, are decreased with time to better fit the bandwidth of the echo signal for improved signal to noise ratio. At time T4 the receiving operation is terminated, another transmitter pulse is initiated at time T5, ~nd the above described operating cycle is repeated. ~;
The invention having been described in detail in 1 accordance with the requirements of the Patent Statutes various ; other changes and modifications will suggest themselves to those skilled in this art, and it~is intended that such changes shall fall within the spirit and scope of the invention as defined in the appended claims.
:
.'' ''' '' ' .~' .
: .:
` !~ .. . :, :, :
' :'.'. ' . . ' . ' . ' ' ~
~AC~GROUND OF THE INVENTION
This invention relates to ultrasonic imaging method and apparatus and, ln particular, to pulse echo method and apparatus wherein short broadband ultrasonic pulses are applied to the object under investigation, travel into the object, and are re-flected by boundries and discontinuities therein to be returned to the transducer. The received echo signals which are derived from different depths within the object are supplied to a suitable ~ -display, and the transducer is moved relative to the object to provide for a two-dimensional display. The above-described technique, generally referred to as B-scan, often utilizes a cathode ray tube display in which one of the deflection voltages is proportional to the transducer position, the orthogonal de-~ flection voltage is proportional to the time elapsed since the ! energizing pulse, and the cathode ray tube beam is modulated by the received pulse intensity. The resulting image is of a -section of the object lying in the plane of the propagating ultra- ~;
sonic waves. A narrow beam is employed which often is focused at an operating depth within the object field for improved .j . .
lateral resolution.
Such pulse echo method and means of ultrasonic imaging j often are employed for imaging of living organisms. Pulses that are reflected from scatterers further within the organism ~, experience greater attenuation, and it is common practice to ` contpensate for such difference in attenuation by tlme variable ~-gain amplification of the received signal. It will be understood, however, that the attenuation within organs or other tissues varies also with frequency of the ultrasonic wave. In particular, , the attenuation coefficient of tissue increases substantially `
linearly with frequency, with the high frequency spectral com~
ponents of the returned signal being attenuated more severely :', .
, - 2 -7 ~ L~ t j than the low frequency components. Typically, the center fre-quency of the received signal drops in frequency with depth of penetration, first at a moderate rate, then s-teeply, and finally at a low ra~e. In brief, not only is the amplitude of the return signal -time dependent, but the spectral distribu-tion of the return energy pulse also is time~depth dependent. Prior art echographic ultrasonic imaging system and method typical~ly include timetime variable gain amplifying means in the signal processing system for increased gain with range to offset the loss of signal strength caused by tissue absorption without provision to com-pensate for changes in the spectral distribution of the return signal with time, or depth of penetration.
SUMMARY OF THE INVENTION
;~ An object of this invention is the provision of method and apparatus for ultrasonic imaging which overcome the above-mentioned shortcomings of prior art arrangements, and which in-clude means to compensate for changes in the spectral distribu-tion of the received signal with changes in range. ;
.:.
; An object of this invention is the provision of method ~;
;- 20 and apparatus for ultrasonic imaging which include signal pro-cessing means for the received signal which provide for improved resolution and/or signal to noise ratio by use of spectral dis-tribution compensation means.
An object of this invention is the provision oE an improved signal processing arrangement for ultrasonic imaging apparatus to compensate for changes in the spectral distribution ;
of the received ultrasonic signal produced by changes in distance ; traveled within the object under investigation.
Briefly, the above and other objects and advantages are ; 30 achieved by use, in an ultrasonic imaging system, of signal pro-.,:
cessing means which includes variable bandpass filter means .~, ~ .
, having one or more ilter characteristics which are varied, or controlled, in accordance with the time of travel of the ult.ra-sonic pulse wave wi.thin the object unde.r i:nvestigation. Control-lable bandpass filter characteristics include, for example, filter transmission, bandwidth, and center fxeque:ncy. For A and B scan methods of ultrasonic examination filter characteristics are time varied in accordance with the depth from which the echo signals are received, and for C scan operation the filter charac-teristics are adjusted to match the selected range setting.
Generally, the filter center frequency, bandwidth and upper, or high, frequency cutoff frequency are reduced with increased oper-~ ating depth for improved system operatioh.
'I ~ore particular~ly there is provided in an ultrasonic I system for the examination of the interior of objects, such as .1 body parts, the combination comprising: ~ :
means for insonification of an object under examination with a broadband ultrasonic wave signal, means for receiving echo signals from discontinuities over a .
range of depths within the insonified object and for converting the same to electrical signals,means for filtering said electrical signals by bandpass filter ~
means having a filter transmission factor as a function of fre- .
quency which is variable, and means for compensating for depth dependent changes in the ~ .
spectral distribution of the echo signals by time varying the .. ~1`
filter transmission factor versus frequency characteristic of the ..
~ bandpass filter means in accordance with the depth of the dis-., continuity from which the echo signal is reflected.
There is also provided in a method for the non-invasive ` 30 exam.ination of objects such as body parts, the steps of ~.
., .
; .
- 4 _ ~ .
e insonifying at least a por-tion of the body part w.ith a beam of broadband acoustic energy to produce echo signals from within the body, receiving echo signals from within the body and converting the same to electrical signals, passing the electrical signals through bandpass ilter means having a variable filter transmission factor versus frequency ~:
characteristic, and :~ time varying the filter transmission factor versus frequency 10 characteristic of the bandpass filter in relationship with the -~
; depth from which the echo signals are received while receiving echo signals from over a range of depths within the body for com- .
pensating for depth dependent changes in the spectral distribu-tion of echo signals.
There is further provided in an ultrasonic system for the examination of the interior body parts, or the like, the :
combination comprising, .
means for recurrent pulse insonification of a body part under ~ -. examination, 20 means for receiving echo signals from discontinuities within .
said body part over a time period following pulse insonification, `. which signals have a spectral distribution dependent upon the depth within the body part from which the signal is received, and : for converting received echo signals to electrical signals, , bandpass filter means having variable operating characteris- .
i tics through which said electrical signals and passed, and means for time varying operating characteristics of the band-pass~filter means while passing said electrical signals there- -through for relating filter operating characteristlcs with the time varying spectral distribution of the electrical signal.
- .
- 5 - ~:
There is also provided in a pulse operated ultrasonic imaging apparatus of the type which includes ultrasonic wave `~
transducer means for transmitting ultrasonic wave pulses into an object to be exa~ined and for converting reflected ultrasonic waves received over a range of depths therewithin into an elec-trical signal, the spectral distribution of said reflected ultra-sonic waves being dependent upon the depth from which they are received, a receiver for processing said electrical signal, said receiver 10 including time variable filter means~ and ;
means for time varying said time variable filter means while processing said electrical signal produced by ultrasonic waves ;
received from over a range of depths to compensate for changes in the spectral distribution of the reflected ultrasonic waves with depth.
The invention will be better understood from the follow-ing description taken in connection with the accompanying drawings.
In the drawings, wherein like reference characters refer to the ;
same parts in the several views:
Fig. 1 is a block diagram of a B scan ultrasonic imag-ing system which includes signal processing means embodying this invention; ' Fig. 2 shows, on a common frequency scale, frequency spectra of return signals obtained from different depths, the return signals after time gain compensation, and curves showing bandL~ass filter transmission factors as a function of frequency for the different depth return signals; ;
Fig. 3 is a schematic diagram illustrating a prior art type variable filter means which may be employed in the novel signal processing means of this invention shown in Fig. l; and Fig. 4 is a timing diagram for use in explaining the operation of the ultrasonic imaging apparatus shown in Fig. 1.
j i`' ' .
.. -. , , , .. , . 1 7~
Reference first is made to Fig. 1 wherein there is shown an ultrasonic imaging arrangement comprising a transducer ; 10 which, in the illustrated arrangement is used both for trans-mitting and receiving ultrasonic pulse signals. For purposes of illustration the transducer is shown immersed in a container 12 containing a suitable acoustic transmission medium 14 such as water for the support of acoustic waves. Ultrasonic compres-sional wave pulses generated by the transducer lO are transmitted through an acoustic lens 16 in the fluid medium and coupled through an acoustically transparent window 17 to the subject 18 under investigation for focusing of the pulses within the subject.
Such arrangements are well adapted for imaging living organisms such as the heart in a living body, however it will be apparent that the invention is not limited to any such particular applica-tion or use. Preferably, a broad band pulse is supplied to the transducer 10 from a gated signal source 20 through a power am-plifier 22 ~or multifrequency pulse insonification of the subject 18. Typically, pulses of ultrasonic waves within the range of, -~-, say, 1 to 10 M~z may be employed. The signal source 20 is re- ;
currently gated on as by use of a transmitter gate generator 24 under control of signals from a timing and control unit 26.
Periodic pulse operation generally is employed, although aperi-odic and continuous wave mode operation may be used. Also, it will be understood that the invention is not limited to use with ~ -any particular broad band signal source. For example, broad band operation by use of a short pulse source, or as by use of a pulse or a continuous sweep frequency, frequency modulated (e.g. chirp), random noise, or the like, signal source is contemplate~.
Ultrasonic pulses reflected from the boundaries and internal discontinuities of the subject 18 are received by the transducer 10 and the resultant electrical signals are supplied , :
~ - 7 -: , ~, ;
., to a gated amplifier 28 which is gated on and off duriny the receiving and trans~itting portions, respectively, oE the operat-ing cycle under control of the timing and control unit 26. If desired, a transmit/receive switch, not shown, could be employed in the connection of the transducer 10 to the signal source 20 and signal processor, or receiver, 30, which switch would elimin-ate the need to gate -the amplifier -to prevent blocking of the receiver by the transmitter pulses. -~;
In accordance with the present invention the signal pro-cessor includes a variable gain/filter compensation unit 32 to which the amplified echo signals are supplied. ~or purposes of ~`
illustration the compensation unit 32 is shown comprising separate variable gain amplifier 34 and variable filter 36 units. As will become apparent hereinbelow the amplifier and filter units simply , may be combined in the form of a single variable gain/filter multi-~ stage amplifier having the desired variable gain and bandpass ;~ filter characteristics.
~ For use in A and B scan operations, wherein the return . - .
signals are received from a range of distances within the subject, the variable gain amplifier and filter means 34 and 36, respec-tively, are time varied. As noted above the employment of time variable signal amplification in ultrasonic diagnostic systems is well known and includes the use of a varlable gain amplifier~
having a gain which is time varied in accordance with the lapsed ` time from the last transmitted pullse. In the illustrated arrange-: . , ment the gain of the variable gain amplifier 34 is varied in accordance with the output from a gain ~unction generator 38, with the timing of the operation of the generator 38 being under con- -trol of the timing and control unit 26. Often, the generator 38 simply comprises a ramp generator with an output signal which .
functions to increase the gain of amplifier 34 in proportion to ,t . . .
; .. : ~ ' range in a manner to offset -the loss of signal caused by acoustic absorption within the subject. Instead of a fixed function generator, an adjustable function generator may be used whereby a signal of desired shape easily may be ob-tained for control of amplifier gain. In any case, -time variable gain implification is well known as disclosed, for example, in the publication "Physical Principles of Ultrasonic Diagnosis" - Academic Press, London, England, by P.N.T. Wellsl copyright 1969, and no addi-tional description of such operation is believed to be required.
In the illustrated arrangement filter characteristics of the variable filter means 36 are controlled by a filter func-~
tion generator 40, with ~iming of the operation of the generator 40 being provided by the timing and control unit 26. For the illustrated B-scan operation the filter transmission factor as a function of frequency of the variable filter 36 is varied as a function of time by output from the filter function generator 40 for improved lateral and longitudinal resolution of the system as well as improved signal to noise ratio in a manner described in detail hereinbelow with reference to Fig. 2. For present pur-. . j .
`20 poses it will be seen that the output from the variable gain/
filter compensation uni-t 32 is applied to a broad band compres-sion amplifier 42 comprising, for example, a DC coupled log ampli-;fier with a compression factor of 40 to 60 dB. The amplifier output is detected by an envelope detector 44 comprising, for example, a full wave rectifier with low pass filter means and having as an output a signal which is proportional to the enve-lope of the broad band high frequency signal output from the amplifier 42. For the illustrated B scan operation, the detector output is supplied to a cathode ray tube display 46 and, in particular, to the control grid thereof to intensity modulate the ~-electron beam. It here will be noted that for A scan operation ,:' .
~' 9 _ '~,~, ,, ,~,.
:;, , t,'i'~
the detec-tor output simply may be supplied as a deflection signal to a cathode ray tube for deflection of the beam in one direction while a ramp signal synchronized with the transmi-tter operation is supplied as a deflection signal for deflection of the beam in an orthogonal direction.
For the illustrated B scan operation the transducer 10 t~
and associated focusing lens 16 are~moved with a scanning motion relative to the subject 18. In Fig. 1 the transducer and lens are shown mounted on a movable platform 48 connected to a scanning ;~
- 10 mechanism 50 through a mechanical linkage 52. Linear and/or sec-tor scanning may be employed and for purposes of illustration ; linear scanning across the object 18 in the direction of the arrow , 5~ is shown. The scanning mechanism includes a scan position information circuit having an output which is connected to the timing and control unit 26 having outputs for synchronizing the transmitting, receiving and display scanning operations, including the operation of a deflection an~ blanking generator 56. One out-put from generator 56 comprises a deflection voltage which is pro-portional to the transducer position along its scan, and another output which comprises an orthogonal deflection voltage which is proportional to the time elapsed since the last pulse was trans-mitted. The invention is not limited to use with any particular scanning arrangement. For èxample, the acoustic wa-~e from the ~-:
transducer may be deflected to sweep the wave over the object without relative movement of the transducer and object. Also, the `~ use of a transducer array is contemplated in place of the illus-. . .
trated transducer. ~;
As noted above the attention coefficient of tissue com- ;-prising the subject 18 increases approximately linearly with fre- ~ ~
: . ,~. :--quency such that the high frequency spectral components of the echo si~nals are attenuated more severely than the low frequency :. ~
~ components. Reference is made to Fig. 2 wherein exemplary spec~
.,' ~ .
`, ,.~ ~j,,," - 1 0 - ~ :
,1, ~ r.' . ~'' ` .
7 ~ L~ ~
tral distribution curves of pulse energy received by the trans-ducer 10 (Fig. 2A) and of the amplified signal from variable gain amplifier 34 (Fig. 2s) are shown for signals received from the adjacent boundary of the subject 18~with the acoustic medium~ and for echo signals received from internal discontinuities at 2 and 4 centimeters from the boundary, which curves are labeled Ocm, 2cm, and 4cm, respectively, in Fig. 2. The center frequencies for the echo signals received from the OCD1, 2cm, and ~cm levels are identified on the frequency scale as fo-0, fo-2, and fo--4, respectively. From Fig. 2A it will be seen that the amplitude bandwidth and center frequency of the received signal decrease with depth of penetration. In practice, the center frequency first drops at a moderate rate, then steeply, and then at a lower rate with increased signal penetration.
; The transmission factor versus frequency characteristic of the variable filter 36 is controlled so as to enhance resolu-~ tion, both lateral and longitudinal, and/or improve signal to noise - ratio. As is understood, lateral resolution is proportional to frequency and so improves with increased frequency, and longitu- ;
dinal resolution is proportional to bandwidth and so improves with increased signal bandwidth. On the other hand, the signal to noise ratio improves with a decrease in the bandwidth. The con-flicting requirements for improved operation thereby require tradeoffs in the design and operation of the variable filter 36 and, in practice, the variable filter characteris-tics are chosen for optimization of operation of the associated ultrasonic imag-~ll ing system. Obviously, the filter design not only depends upon -~ the frequency and characteristics of the received signals, but depends also upon the nature of the interference, or noise, to be rejected. For present purposes it will be assumed that the noise ' level is substantially uniform throughout the operating frequency spectrum.
' - 1 1 --' ~ ~
' '~ .
,~-. .. .
Reference now is made -to sections C, D and E of Fiy. 2 wherein -the filter transmission factor of the variable filter 36 - as a function of frequency at the above mentioned, O, 2 and 4 centimeter depths, respectively/ are shown in solid lines. At zero depth the variable filter has a wide transmission band cen-tered substantially at the center frequency fo-O of the received signal. The low and high frequency cut off frequencies ~cl-O and ~ -fch-O are identified for the Ocm filter transmission factor versus frequency curve of Fig. 2C.
At shallow depths (e.g. at 2cm.) where the center fre-quency fo-2 of the received signal is reduced, the illustrated filter transmission characteristics are altered so as to reduce the high frequency cutoff frequency to a frequency fch-2. (See Fig.
2D.) The variable filter bandwidth and center frequency also are decreased with the center frequency of the variable fil~er being shifted downwardly at substantially the same rate as the received signal center frequency fo decreases with depth of penetration. `~
As penetration increases the received signal decreases such that the signal to noise ratio also decreases. Consequently, the filter characteristics become of greater importance at greater operating depths. Fig. 2E shows the filter characteristic for operation at the 4cm depth. There, the filter high frequency cut-off frequency fch-4 is further reduced, the filter center fre-quency substantially coincides with the center frequency fo-4 of the received signal, and the transmission band is reduced in width for operation with the narrower frequency spectrum of the received signal.
It will be understood that the filter transmission fac-tor versus frequency curves shown at C, D and E of Fig. 2 are for purposes of illustrating operation of one suitable variable filter means, and that the invention is not limited specifically thereto.
For example, where the signal to noise ratio is relatively large, ~ 12 -o5-. ~;,, ,, :
1 13 ~at shallow depths, ~e.g. at 2cm) the fil-ter may be operated with substantially the same transmission charac-teristics as exist at the Ocm depth. Thus, although the high frequency spectral com-ponents are a-ttenuated more than the low frequency components, at shallow depths it of-ten is advantageous to main-tain the high frequency filter -transmission since the high frequency operation provides for good lateral and longitudinal, or depth, resolution~
Therefore, substantially the same illustrated filter characteris-tics for operation at Ocm. may be employed at shallow depths to, say 2cm. At increased depths, the characteristics could be varied in the manner described abbve, wherein the high frequency cutoff frequency decreases with increased depth.
In another modification of the invention the variable filter is provided with a substantially fixed low frequency cutoff ~ -frequency f'cl identified in Fig. 2, the low frequency end of the variable filter characteristics of such a modified filter being ; shown in bro~en lines in sections C, D and E of Fig. 2. The upper frequency end of the filter characters may remain as illustrated in full line. The design of such a filter, wherein only the high frequency cutoff frequency is variable may be simpler than that . of a filter in which the low fre~uency cutoff frequency also is varied. With this arrangement the filter is provided with a low , .
frequency cutoff frequency which best matches the low frequency `~ characteristic of the received frequency spectrum at substantially maximum operating depth, which, in the illustrated arrangement is on the order of six centimeters. Obviously, changes in the filter transmission factor which involve other than the high frequency ., cutoff frequency, bandwidth and center frequency changes may be employed as desired, or required.
~ 30 ', ~ ~ .
It will be understood -that where -the echo signal is time variable, as with the illustrated B scan arranyement of Fig. l the transmission factor versus frequency characteristic of the filter also i5 time varied, and that Fig. 2 simply illustrates operation at three specific depths. OEten, the particular time varying filter characteristic of any given fil-ter is readily matched to the system response characteristic by the proper selection of waveform output, or outputs, from the filter function generator 40. As noted above, in some instances the signal used to control the variable gain amplifier 34 also may be used for control of the variable filter whereby only a single gain/filter functlon genera-tor is required.
The prior art includes numerous filter means which exhibit a filter transmission factor versus frequency function which is readily variable, and it will be apparent that the pre-; sent invention is not limited to the use of any particular type of such variable filter means. There are numerous variations of variable bandpass filters of the type which may be employed in the combination of this invention, including both active and passive types. Pi, L and T section filters, and combinationsthereof may be utilized. In U.S. Patent No. 3,192,491 dated June 29, 1965, by Hesselberth et al, there are shown double tuned band- `
pass filters of the type which may be used, and the teachings and subject matter of the patent specifically are incorporated herein ' by reference. Also, as noted above, the variable gain and vari-- able filter functions preferably are included in a single multi-stage unit which includes suitable variable amplifying and fil-tering means by which the desired signal compensation may be per-formed. Preferably, the phase characteristics of the variable ;~
filter should remain constant over the operating range thereof.
. .
f~ "i ; ~:
ltJ~ 7~ ~
As noted above, for A and B scan operation a time vari-able filter is employed. Such filters often include voltage variable reactance elements, such as voltage variable capacitors, to which the output from the filter function generator 40 is supplied through suitable high capacitance d-c blocking capacitors and isolating resistors for voltage control of the capacitance thereof. ~aractor diodes often are employed for such purposes.
For C scan operation variable capacitors simply may be employed which are manually variable in accordance with the range setting of the imaging system.
For purposes of illustration a simplified prior art variable filter circuit is shown in Fig. 3 to which reference now is made. There, a T-section bandpass filter is shown comprising two series LC circuits 60 and 62 in the filter arms and a paral-; lel LC circuit 64 in the leg thereof The circuits 60, 62 and 64 include variakle capacitors 66, 68, and 70, respectively, used for tuning. For C scan operation, the capacitors may be manually variable in accordance with range setting of the imaging system.
,3 For the illustrated B scan arrangement wherein the filter trans-mission factor is time varied, voltage variable capacitor elements, ~ ;
such as varactor diodes may be used for the capacitors 66, 68 and 70. In such case suitable high capacitance d-c blocking capacitors i and isolating resistors, not shown, are included in the connection `~
of the filter function generator to the varactor diodies for vol- `~
i tage control of diode capacitance. With such an arrangement the generator output may supply a control voltage for the simultaneous increase of the capacitance of capacitors 66, 68 and 70 with time ~-~ during the receiving portion of the cycle to reduce the filter ~`
. .
center frequency accordingly. Simultaneous bandwidth control of the simplified filter is shown provided by means of a variable resistor 72 in series circuit with inductor 7~ in the parallel .:
,~ ~
~ l3~ 71~ ~
resonant circuit 69, the value of which is decreased with time during the receiving portion of the cycle. As the resistance decreases the slope of the fllter transmission function increases to effectively decrease the filter pass band. The variable re- ~
sistor 72 may comprise, for example, a field effect transistor -which functions as a voltage controlled resistor with the yate thereof connected to the output from the filter function generator 40 for control of the resistance thereof. The showing of the prior art simplified variable filter means of Fig. 3 simply is to facilitate an understanding of the novel signal processing means of the illustrated ultrasonic diagnostic apparatus which includes variable filter means. The actual filter employed would be tailored to the operating characteristics of the system and, as noted above easily may be includéd in the conventional variable : .: .
gain amplifier means.
Although the operation of the ultrasonic diagnostic -:. ~
apparatus,of this invention is believed to be apparent from the ~
above description, a brief description thereof with reference to ~ -the timing diagram of Fig. 4 now will be made. The transducer 10 i and lens 16 are moved across the object 18 in the direction of the arrow 54 by the scanning mechanism 50. A scan position signal is produced by the scan position circuit of the scanning mecha- ;~
nism and supplied to the timing and control unit 26 from which control signals for timing the operation of the transmitter, receiver, and cathode ray tube scanning means are obtained. Broad-band narrow beam ultrasonic waves ar~ generated during the trans-mit pulse period 76 shown in Fig. 4, which pulse is initiated at time Tl and is terminated at time T2. The pulse travels through the lens 16 and into the subject 18 to be reflected at the bound- ~;
ary of the subject with the fluid 14 and from different levels at discontinuities within the'subject. Af-ter a time delay period, .~ ~
, - 16 -- v . . . ..
. . . . . .; . , .
' , ' ' ', . : : . .
.. . . . .. . . . ... .
.. . .. .
7~
between times T2 and T3, -the receiver is gated on Eor processing the echo signals as shown at 73. During operation of the receiver between times T3 and T4 the gain oE the variable gain amplifier 34 is increased as indicated by gain curve 80 of Fig. 4 Eor in-creased amplification of the echo signals received from a greater depth within -the subject in the well known manner. In accordance with the present invention, during the receiver operation the transmission factor of the variable filter 36 is controlled for enhanced resolution and/or signal to noise ratio.
Here, Eor purposes of illustra-tion, at time T3 the filtex center frequency, curve 82, is shown decreasing with time from fo-0 to substantially match, or follow, the decrease in the -echo signal center frequency with depth of penetration. Simul-taneously, the filter bandwidth, curve 84, and filter high fre-quency cutoff frequency, curve 86, are decreased with time to better fit the bandwidth of the echo signal for improved signal to noise ratio. At time T4 the receiving operation is terminated, another transmitter pulse is initiated at time T5, ~nd the above described operating cycle is repeated. ~;
The invention having been described in detail in 1 accordance with the requirements of the Patent Statutes various ; other changes and modifications will suggest themselves to those skilled in this art, and it~is intended that such changes shall fall within the spirit and scope of the invention as defined in the appended claims.
:
.'' ''' '' ' .~' .
: .:
` !~ .. . :, :, :
' :'.'. ' . . ' . ' . ' ' ~
Claims (18)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. In an ultrasonic system for the examination of the interior of objects, such as body parts, the combination com-prising:
means for insonification of an object under exam-ination with a broadband ultrasonic wave signal;
means for receiving echo signals from discontin-uities over a range of depths within the insonified object and for converting the same to electrical signals, means for filtering said electrical signals by band-pass filter means having a filter transmission factor as a function of frequency which is variable, and means for compensating for depth dependent changes in the spectral distribution of the echo signals by time varying the filter transmission factor versus frequency charac-teristic of the bandpass filter means in accordance with the depth of the discontinuity from which the echo signal is reflected.
means for insonification of an object under exam-ination with a broadband ultrasonic wave signal;
means for receiving echo signals from discontin-uities over a range of depths within the insonified object and for converting the same to electrical signals, means for filtering said electrical signals by band-pass filter means having a filter transmission factor as a function of frequency which is variable, and means for compensating for depth dependent changes in the spectral distribution of the echo signals by time varying the filter transmission factor versus frequency charac-teristic of the bandpass filter means in accordance with the depth of the discontinuity from which the echo signal is reflected.
2. In an ultrasonic system as defined in claim 1 wherein, said means for insonification of an object under examination comprises means for recurrent pulse insonification of the object, and said means for compensating for depth dependent changes in the spectral distribution of the echo signals is recurrently operated for recurrently time varying the filter transmission factor versus frequency characteristic of the bandpass filter means in accordance with the time lapsed from the preceding pulse insonification of the object.
3. In an ultrasonic system as defined in claim 1 wherein the passband of the bandpass filter means is time varied by said means for compensating for depth dependent changes in the spectral distribution of the echo signals by time varying the filter transmission factor versus frequency characteristic of the bandpass filter while receiving the echo signals.
4. In an ultrasonic system as defined in claim 1 wherein the center frequency of the bandpass filter means is time varied by said means for compensating for depth dependent changes in the spectral distribution of the echo signals by time varying the filter transmission factor versus frequency characteristic of the bandpass filter while receiving the echo signals.
5. In an ultrasonic system as defined in claim 4 wherein the passband of the bandpass filter means is simul-taneously time varied with the center frequency thereof.
6. In an ultrasonic system as defined in claim 1 wherein the high frequency cutoff frequency of the bandpass filter means is time varied by said means for compensating for depth dependent changes in the spectral distribution of the echo signals by time varying the filter transmission factor versus frequency characteristic of the bandpass filter while receiving the echo signals.
7. In an ultrasonic system as defined in claim 1 including envelope detecting means for envelope detection of the filtered electrical signals, and means for displaying the detected signals.
8. In an ultrasonic system as defined in claim 7 wherein said display means includes a cathode ray tube for B-scan display of the detected signals, said means for insoni-fication of an object under examination includes means for recurrent pulse insonification of the object, and wherein the filter transmission factor versus frequency characteristic of the bandpass filter is time varied and the cathode ray tube beam is deflected in one direction in accor-dance with the time elapsed from the preceding pulse operation of the insonification means, and including means for relatively sweeping ultrasonic waves produced by the insonification means and the insonified object in a scanning motion, and means for deflecting the cathode ray tube beam in an orthogonal direction in synchronization with said scanning motion of the ultrasonic waves relative to the insonified object.
9. In a method for the non-invasive examination of objects such as body parts, the steps of insonifying at least a portion of the body part with a beam of broadband acoustic energy to produce echo signals from within the body, receiving echo signals from within the body and converting the same to electrical signals, passing the electrical signals through bandpass filter means having a variable filter transmission factor versus frequency characteristic, and time varying the filter transmission factor versus frequency characteristic of the bandpass filter in relation-ship with the depth from which the echo signals are received while receiving echo signals from over a range of depths within the body for compensating for depth dependent changes in the spectral distribution of echo signals.
10. In a method for the non-invasive examination of objects as defined in claim 9 wherein the filter transmission factor versus frequency characteristic of the bandpass filter which is time varied comprises the filter passband which is reduced as the depth from which the echo signals are received is increased.
11. In a method for the non-invasive examination of objects as defined in claim 9 wherein the filter transmission factor versus frequency characteristic of the bandpass filter which is time varied comprises the filter center frequency which is reduced as the depth from which the echo signals are received is increased.
12. In a method for the non-invasive examination of objects as defined in claim 11 wherein the passband of the band-pass filter simultaneously is reduced as the filter center fre-quency is reduced.
13. In a method for the non-invasive examination of objects as defined in claim 9 wherein the insonifying step in-cludes recurrently insonifying with broadband acoustic energy pulses, and the receiving step recurrently is effected after said pulse insonification.
14. In a method for the non-invasive examination of objects as defined in claim 9 wherein the step of time varying the filter transmission factor versus frequency characteristic of the bandpass filter means comprises reducing the high fre-quency cutoff frequency of the filter means as the depth from which the echo signals are received increases.
15. In an ultrasonic system for the examination of the interior body parts, or the like, the combination comprising, means for recurrent pulse insonification of a body part under examination, means for receiving echo signals from discontinuities within said body part over a time period fol-lowing pulse insonification, which signals have a spectral dis-tribution dependent upon the depth within the body part from which the signal is received, and for converting received echo signals to electrical signals, bandpass filter means having variable operating characteristics through which said electrical signals are passed, and means for time varying operating characteristics of the bandpass filter means while passing said electrical signals therethrough for relating filter operating character-istics with the time varying spectral distribution of the electrical signal.
16. In a method for the non-invasive examination of the interior of objects such as living organisms, or the like, the steps of, pulse insonifying at least a portion of an object to be examined with an acoustic energy beam to produce echo signals from discontinuities within the object, receiving over a time period following said pulse insonifying step echo signals from within the body, which echo signals have a spectral distribution dependent upon the depth from which the signal is received, converting the received echo signals to electrical signals, passing the electrical signals through bandpass filter means having a variable filter transmission factor versus frequency characteristic, and time varying the filter transmission factor versus frequency characteristic of said bandpass filter means while the electrical signals are passed therethrough to match the variable filter transmission factor versus frequency characteristic of said bandpass filter means with the time varying spectral dis-tribution of the electrical signal for improving the signal to noise ratio of the electrical signals.
17. In a pulse operated ultrasonic imaging apparatus of the type which includes ultrasonic wave transducer means for transmitting ultrasonic wave pulses into an object to be examined and for converting reflected ultrasonic waves received over a range of depths therewithin into an electrical signal, the spectral distribution of said reflected ultrasonic waves being dependent upon the depth from which they are received, a receiver for processing said electrical signal, said receiver including time variable filter means; and means for time varying said time variable filter means while processing said electrical signal produced by ultra-sonic waves received from over a range of depths to compensate for changes in the spectral distribution of the reflected ul-trasonic waves with depth.
18. In an ultrasonic imaging apparatus of the type defined in claim 17 wherein said transducer means produces ultrasonic wave beams with said pulse operation thereof, means for scanning said ultrasonic wave beam within said object, visual display means responsive to the output from the receiver for displaying a B-scan image of a section of the object, and means for generating timing pulses representative of the scanning position of the beam for timing operation of the transmitter, the time variable filter means, and the visual display means.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US90/000351A US4016750B1 (en) | 1975-11-06 | 1975-11-06 | Ultrasonic imaging method and apparatus |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1057845A true CA1057845A (en) | 1979-07-03 |
Family
ID=24523648
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA260,592A Expired CA1057845A (en) | 1975-11-06 | 1976-09-03 | Ultrasonic imaging method and apparatus |
Country Status (7)
| Country | Link |
|---|---|
| US (1) | US4016750B1 (en) |
| JP (2) | JPS5259975A (en) |
| CA (1) | CA1057845A (en) |
| DE (1) | DE2641901C2 (en) |
| FR (1) | FR2331018A1 (en) |
| GB (1) | GB1536930A (en) |
| SE (1) | SE428504B (en) |
Families Citing this family (93)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4131021A (en) * | 1976-03-04 | 1978-12-26 | Rca Corporation | High resolution pulse-echo ultrasonic-imaging display system |
| US4131024A (en) * | 1976-03-04 | 1978-12-26 | Rca Corporation | Pulse-echo ultrasonic-imaging display system |
| US4131023A (en) * | 1976-03-04 | 1978-12-26 | Rca Corporation | Pulse-echo ultrasonic-imaging display system |
| US4131022A (en) * | 1976-03-04 | 1978-12-26 | Rca Corporation | Pulse-echo ultrasonic-imaging display system |
| US4131025A (en) * | 1976-07-26 | 1978-12-26 | Rca Corporation | Pulse-echo ultrasonic-imaging display system |
| US4138999A (en) * | 1976-10-29 | 1979-02-13 | Thomas D. Eckhart | Anatomy testing and measuring device |
| DE2724437B1 (en) * | 1977-05-31 | 1978-06-15 | Siemens Ag | Ultrasonic imaging device that works according to the pulse-echo method |
| US4158308A (en) * | 1977-09-22 | 1979-06-19 | Automation Industries, Inc. | Time-variable bandwidth ultrasonic testing apparatus |
| US4138895A (en) * | 1977-10-20 | 1979-02-13 | Rca Corporation | Switchable depth of focus pulse-echo ultrasonic-imaging display system |
| US4168628A (en) * | 1977-10-20 | 1979-09-25 | Rca Corporation | Pulse-echo ultrasonic-imaging display system having time-varied effective aperture |
| US4204433A (en) * | 1977-11-07 | 1980-05-27 | Litton Industrial Products, Inc. | Computerized ultrasonic scanner with technique-select |
| EP0003658A3 (en) * | 1978-02-09 | 1979-09-05 | United Kingdom Atomic Energy Authority | Improvements in or relating to an ultrasonic nondestructive testing apparatus |
| FR2443113B1 (en) * | 1978-06-30 | 1985-12-06 | Deutsch Pruef Messgeraete | METHOD AND DEVICE FOR TRANSMITTING ACOUSTIC PULSES, PARTICULARLY IN THE FIELD OF ULTRA-SOUNDS, AND APPLICATION OF SUCH PULSES IN PARTICULAR TO NON-DESTRUCTIVE CONTROL OF MATERIALS |
| US4228688A (en) * | 1979-02-26 | 1980-10-21 | Automation Industries, Inc. | Accurate distance amplitude compensation |
| US4226121A (en) * | 1979-03-02 | 1980-10-07 | Knospler William M | Ultrasonic imaging system and improved signal processor therefor |
| US4733668A (en) * | 1979-09-04 | 1988-03-29 | North American Philips Corporation | Method and apparatus for compensation during ultrasound examination |
| DE2949991C2 (en) * | 1979-12-12 | 1986-05-28 | Siemens AG, 1000 Berlin und 8000 München | Device for ultrasonic scanning |
| US4310853A (en) * | 1980-07-30 | 1982-01-12 | Technicare Corporation | Data simulation in sector scan imaging systems |
| US4324140A (en) * | 1980-07-31 | 1982-04-13 | The United States Of America As Represented By The Secretary Of The Navy | Electronically simulated rotating prism for ultrasonic beam scanning |
| JPS5754411U (en) * | 1980-09-12 | 1982-03-30 | ||
| JPS57170236A (en) * | 1981-04-14 | 1982-10-20 | Yokogawa Electric Works Ltd | Ultrasonic diagnostic apparatus |
| JPS57179745A (en) * | 1981-04-30 | 1982-11-05 | Fujitsu Ltd | Method and device for measuring material property by ultrasonic wave |
| JPS57203434A (en) * | 1981-06-08 | 1982-12-13 | Tokyo Shibaura Electric Co | Ultrasonic diagnostic apparatus |
| JPS57204479A (en) * | 1981-06-12 | 1982-12-15 | Fujitsu Ltd | Ultrasonic transmitting and receiving device |
| JPS5829455A (en) * | 1981-08-18 | 1983-02-21 | 株式会社東芝 | Ultrasonic diagnostic apparatus |
| JPS5855850A (en) * | 1981-09-30 | 1983-04-02 | Fujitsu Ltd | System for measuring medium characteristic with reflected ultrasonic wave |
| JPS58138435A (en) * | 1982-02-12 | 1983-08-17 | 株式会社東芝 | Ultrasonic pulse doppler apparatus |
| JPS58152546A (en) * | 1982-03-04 | 1983-09-10 | 横河電機株式会社 | Reflective wave receiver system of ultrasonic diagnostic apparatus |
| US4442713A (en) * | 1982-03-09 | 1984-04-17 | Sri International | Frequency varied ultrasonic imaging array |
| US4446740A (en) * | 1982-03-09 | 1984-05-08 | Sri International | Frequency controlled hybrid ultrasonic imaging arrays |
| JPS58163345A (en) * | 1982-03-19 | 1983-09-28 | 横河電機株式会社 | Echo signal treating circuit of ultrasonic photography apparatus |
| US4475397A (en) * | 1982-07-19 | 1984-10-09 | General Electric Company | Method and means for attaining ultrasonic attenuation by vector sample averaging |
| US4452085A (en) * | 1982-04-19 | 1984-06-05 | General Electric Company | Method and means for generating time gain compensation control signal for use in ultrasonic scanner and the like |
| US4475395A (en) * | 1982-07-16 | 1984-10-09 | General Electric Company | Method for recognizing different frequency dependent scatter mechanisms in non-homogeneous tissues |
| US4475396A (en) * | 1982-07-16 | 1984-10-09 | General Electric Company | Method of determining ultrasonic attenuation of tissue using reflective tomographic reconstruction |
| DE3218440A1 (en) * | 1982-05-15 | 1983-11-17 | Krautkrämer GmbH, 5000 Köln | ULTRASONIC TEST DEVICE FOR DESTRUCTION-FREE MATERIAL TESTING |
| US4475400A (en) * | 1982-07-16 | 1984-10-09 | General Electric Company | Method and means for improving image in an ultrasonic scanning system |
| US4463592A (en) * | 1982-07-16 | 1984-08-07 | General Electric Company | Method of determining operating characteristics of ultrasonic scanning systems |
| US4534221A (en) * | 1982-09-27 | 1985-08-13 | Technicare Corporation | Ultrasonic diagnostic imaging systems for varying depths of field |
| FR2534707A1 (en) * | 1982-10-13 | 1984-04-20 | Labo Electronique Physique | MEDIUM EXPLORATION APPARATUS BY ULTRASOUND ULTRASONOGRAPHY |
| US4472972A (en) * | 1982-10-27 | 1984-09-25 | General Electric Company | Ultrasound imaging system employing operator controlled filter for reflected signal attenuation compensation |
| EP0116901A3 (en) * | 1983-02-10 | 1986-06-25 | DEUTSCHE FORSCHUNGSANSTALT FÜR LUFT- UND RAUMFAHRT e.V. | Apparatus for ultrasonic testing |
| DE3469321D1 (en) * | 1983-02-22 | 1988-03-17 | Toshiba Kk | Ultrasonic diagnostic apparatus |
| JPS59193380A (en) * | 1983-04-18 | 1984-11-01 | Yokogawa Medical Syst Ltd | Azimuth angle conforming type phased array sonar |
| US4561019A (en) * | 1983-05-16 | 1985-12-24 | Riverside Research Institute | Frequency diversity for image enhancement |
| US4546772A (en) * | 1983-08-08 | 1985-10-15 | General Electric Company | Method and means for determining ultrasonic wave attenuation in tissue using phase locked loop |
| FR2556844B1 (en) * | 1983-12-14 | 1987-11-13 | Labo Electronique Physique | APPARATUS FOR EXAMINING MEDIA BY ULTRASONIC ECHOGRAPHY |
| JPS60127457A (en) * | 1983-12-14 | 1985-07-08 | Fujitsu Ltd | Ultrasonic medium characteristic value measuring apparatus |
| US4584880A (en) * | 1984-06-04 | 1986-04-29 | Dymax Corporation | Tissue signature tracking tranceiver |
| US5261280A (en) * | 1984-06-04 | 1993-11-16 | Stephen G. Matzuk | Tissue signature tracking transceiver |
| US4574635A (en) * | 1984-11-02 | 1986-03-11 | North American Philips Corporation | Monitoring of frequency shift of ultrasound pulses in tissue |
| US4691571A (en) * | 1985-03-04 | 1987-09-08 | Dymax Corporation | Tissue signature tracking transceiver having upconverted IF amplification |
| US4624143A (en) * | 1985-03-22 | 1986-11-25 | Sri International | Ultrasonic reflex transmission imaging method and apparatus with external reflector |
| US4608868A (en) * | 1985-03-22 | 1986-09-02 | Sri International | Ultrasonic reflex transmission imaging method and apparatus |
| US4730495A (en) * | 1985-03-22 | 1988-03-15 | Sri International | Ultrasonic reflex transmission imaging method and apparatus |
| US4873984A (en) * | 1986-05-30 | 1989-10-17 | Hewlett-Packard Company | Techniques for calculating ultrasonic integrated backscatter using frequency or time domain techniques |
| US4788981A (en) * | 1986-10-16 | 1988-12-06 | Olympus Optical Co., Ltd. | Pulse compression apparatus for ultrasonic image processing |
| US4949318A (en) * | 1989-06-01 | 1990-08-14 | Patrick Paul H | Hydroacoustic sonar equipment |
| US5280787A (en) * | 1990-01-25 | 1994-01-25 | Commonwealth Scientific And Industrial Research Organisation | Ultrasonic method and apparaus for determination of vessel location and size |
| AU638548B2 (en) * | 1990-01-25 | 1993-07-01 | Commonwealth Scientific And Industrial Research Organisation | Ultrasonic method and apparatus for determination of vessel location and size |
| FR2662501B1 (en) * | 1990-05-28 | 1994-11-18 | Valtubes | METHOD FOR DETECTING DEFECTS ON METAL TUBES WITH INTERNAL HELICAL RIBS. |
| JPH0330882U (en) * | 1990-08-15 | 1991-03-26 | ||
| US5218869A (en) * | 1992-01-14 | 1993-06-15 | Diasonics, Inc. | Depth dependent bandpass of ultrasound signals using heterodyne mixing |
| US5482044A (en) * | 1992-01-14 | 1996-01-09 | Diasonics Ultrasound, Inc. | Direct demodulation in ultrasound instruments |
| GB9502448D0 (en) * | 1995-02-08 | 1995-03-29 | Mccue Plc | Simulation of bone in ultrasonic assessment apparatus |
| US6005827A (en) | 1995-03-02 | 1999-12-21 | Acuson Corporation | Ultrasonic harmonic imaging system and method |
| US5678554A (en) * | 1996-07-02 | 1997-10-21 | Acuson Corporation | Ultrasound transducer for multiple focusing and method for manufacture thereof |
| US5608690A (en) * | 1995-03-02 | 1997-03-04 | Acuson Corporation | Transmit beamformer with frequency dependent focus |
| US6027448A (en) * | 1995-03-02 | 2000-02-22 | Acuson Corporation | Ultrasonic transducer and method for harmonic imaging |
| US5585720A (en) * | 1995-10-23 | 1996-12-17 | Western Atlas International, Inc. | Signal processing method for multiexponentially decaying signals and application to nuclear magnetic resonance well logging tools |
| EP0851241B1 (en) | 1996-11-26 | 2006-05-24 | ATL Ultrasound, Inc. | Ultrasonic diagnostic imaging of response frequency differing from transmit frequency |
| US5891037A (en) * | 1997-12-18 | 1999-04-06 | Acuson Corporation | Ultrasonic Doppler imaging system with frequency dependent focus |
| US6213946B1 (en) | 1998-12-24 | 2001-04-10 | Agilent Technologies, Inc. | Methods and apparatus for speckle reduction by orthogonal pulse compounding in medical ultrasound imaging |
| US6896658B2 (en) * | 2001-10-20 | 2005-05-24 | Zonare Medical Systems, Inc. | Simultaneous multi-mode and multi-band ultrasonic imaging |
| US6685645B1 (en) * | 2001-10-20 | 2004-02-03 | Zonare Medical Systems, Inc. | Broad-beam imaging |
| JP2001095798A (en) * | 1999-10-01 | 2001-04-10 | Matsushita Electric Ind Co Ltd | Ultrasonic picture taking procedure and ultrasonic wave diagnosis apparatus |
| US6516667B1 (en) | 2000-03-07 | 2003-02-11 | Koninklijke Philips Electronics N.V. | Ultrasonic harmonic signal acquisition |
| US7604594B2 (en) * | 2004-08-04 | 2009-10-20 | General Electric Company | Method and system of controlling ultrasound systems |
| US7610791B2 (en) * | 2006-03-09 | 2009-11-03 | Southwest Research Institute | Time-gain control method and system for long-range guided-wave inspection and monitoring |
| US20080132791A1 (en) * | 2006-11-30 | 2008-06-05 | Hastings Harold M | Single frame - multiple frequency compounding for ultrasound imaging |
| US8444564B2 (en) * | 2009-02-02 | 2013-05-21 | Jointvue, Llc | Noninvasive diagnostic system |
| WO2012063928A1 (en) * | 2010-11-11 | 2012-05-18 | オリンパスメディカルシステムズ株式会社 | Ultrasonic observation device, method for operating ultrasonic observation device, and operation program for ultrasonic observation device |
| EP2599441B1 (en) * | 2010-11-11 | 2019-04-17 | Olympus Corporation | Ultrasonic observation apparatus, method of operating the ultrasonic observation apparatus, and operation program of the ultrasonic observation apparatus |
| JPWO2012063930A1 (en) * | 2010-11-11 | 2014-05-12 | オリンパスメディカルシステムズ株式会社 | Ultrasonic diagnostic apparatus, method for operating ultrasonic diagnostic apparatus, and operation program for ultrasonic diagnostic apparatus |
| JP6207518B2 (en) * | 2011-11-10 | 2017-10-04 | コーニンクレッカ フィリップス エヌ ヴェＫｏｎｉｎｋｌｉｊｋｅ Ｐｈｉｌｉｐｓ Ｎ．Ｖ． | Improved large volume 3D ultrasound imaging |
| WO2015028945A2 (en) | 2013-08-27 | 2015-03-05 | Koninklijke Philips N.V. | Variable frequency control of collapsed mode cmut transducer |
| GB201322803D0 (en) * | 2013-12-20 | 2014-02-05 | Hydrason Solutions Ltd | Improvements in or relating to sonar apparatus |
| JP6351365B2 (en) * | 2014-05-14 | 2018-07-04 | キヤノン株式会社 | Photoacoustic apparatus, information processing method, program |
| KR101496167B1 (en) * | 2014-07-08 | 2015-02-26 | 주식회사 힐세리온 | Portable Ultrasonic Diagnostic apparatus and power efficiency improvement method thereof |
| WO2017149421A1 (en) | 2016-03-03 | 2017-09-08 | Koninklijke Philips N.V. | Ultrasonic cmut transducer array with improved depth of field |
| FR3068134B1 (en) * | 2017-06-23 | 2021-01-08 | Vallourec Tubes France | NON DESTRUCTIVE CONTROL FOR COMPLEX SHAPED TUBULAR PRODUCT |
| US10905401B2 (en) * | 2017-07-09 | 2021-02-02 | The Board Of Trustees Of The Leland Stanford Junior University | Ultrasound imaging with spectral compounding for speckle reduction |
| CN112816558B (en) * | 2021-01-07 | 2023-07-07 | 中国航空制造技术研究院 | Variable-frequency ultrasonic detection method and device for silicon carbide fiber reinforced composite material |
Family Cites Families (14)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB796600A (en) * | 1955-04-14 | 1958-06-18 | Siemens Reiniger Werke Ag | Ultrasonic impulse apparatus comprising transmitting and receiving components for measuring small impulse travel times |
| US2921465A (en) * | 1957-04-10 | 1960-01-19 | Curtiss Wright Corp | Acoustic translating device |
| US3033029A (en) * | 1958-01-14 | 1962-05-08 | Sperry Prod Inc | Amplifier gain compensator for variable ultrasonic signal response |
| US3276249A (en) * | 1962-09-24 | 1966-10-04 | Southern Gas Ass | Ultrasonic measuring apparatus |
| US3309914A (en) * | 1963-10-07 | 1967-03-21 | Automation Ind Inc | Ultrasonic inspection |
| FR1390766A (en) * | 1963-10-07 | 1965-02-26 | Automation Ind Inc | Ultrasonic material testing method and apparatus |
| US3367173A (en) * | 1964-02-21 | 1968-02-06 | Haffrel Instr Inc | Device for sonic and ultrasonic internal scanning of solid and fluid media |
| DE1573614A1 (en) * | 1965-10-18 | 1970-06-04 | J U H Krautkraemer Ges F Elekt | Ultrasonic material testing method for analyzing the form of defects |
| US3307408A (en) * | 1966-08-10 | 1967-03-07 | Int Research & Dev Co Ltd | Synchronous filter apparatus in which pass-band automatically tracks signal, useful for vibration analysis |
| US3617994A (en) * | 1969-01-28 | 1971-11-02 | William E Glenn Jr | Sonography system |
| FR2049304A5 (en) * | 1969-06-06 | 1971-03-26 | Realisations Ultrasoniques Sa | |
| NL7217703A (en) * | 1972-12-28 | 1974-07-02 | ||
| US3815409A (en) * | 1973-02-15 | 1974-06-11 | A Macovski | Focused sonic imaging system |
| JPS5519392B2 (en) * | 1973-07-25 | 1980-05-26 |
-
1975
- 1975-11-06 US US90/000351A patent/US4016750B1/en not_active Expired - Lifetime
-
1976
- 1976-09-03 CA CA260,592A patent/CA1057845A/en not_active Expired
- 1976-09-09 GB GB37419/76A patent/GB1536930A/en not_active Expired
- 1976-09-17 DE DE2641901A patent/DE2641901C2/en not_active Expired
- 1976-10-20 FR FR7631625A patent/FR2331018A1/en active Granted
- 1976-10-21 JP JP51125591A patent/JPS5259975A/en active Granted
- 1976-10-21 SE SE7611703A patent/SE428504B/en not_active IP Right Cessation
-
1986
- 1986-08-07 JP JP61184383A patent/JPS62167542A/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| SE7611703L (en) | 1977-05-07 |
| SE428504B (en) | 1983-07-04 |
| GB1536930A (en) | 1978-12-29 |
| JPS62167542A (en) | 1987-07-23 |
| US4016750B1 (en) | 1994-04-05 |
| US4016750A (en) | 1977-04-12 |
| JPS6260098B2 (en) | 1987-12-15 |
| FR2331018B1 (en) | 1982-08-13 |
| DE2641901A1 (en) | 1977-05-12 |
| JPS6224094B2 (en) | 1987-05-27 |
| FR2331018A1 (en) | 1977-06-03 |
| DE2641901C2 (en) | 1986-04-03 |
| JPS5259975A (en) | 1977-05-17 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CA1057845A (en) | Ultrasonic imaging method and apparatus | |
| US4676105A (en) | Tissue signature tracking transceiver | |
| US5218869A (en) | Depth dependent bandpass of ultrasound signals using heterodyne mixing | |
| KR100380227B1 (en) | Ultrasound Spectral Contrast Imaging | |
| US5261280A (en) | Tissue signature tracking transceiver | |
| MXPA96001754A (en) | Images by spectro ultrason contrast | |
| EP0042288A1 (en) | Ultrasonic imaging apparatus | |
| US20050075565A1 (en) | Ultrasonic transmission/reception apparatus | |
| DE60020724T2 (en) | ULTRASONIC TRANSMITTER AND RECEIVER WITH PULSE COMPRESSION | |
| JPS58152546A (en) | Reflective wave receiver system of ultrasonic diagnostic apparatus | |
| US4452085A (en) | Method and means for generating time gain compensation control signal for use in ultrasonic scanner and the like | |
| EP0222450B1 (en) | Method and apparatus for estimating the ultrasound attenuation - vs - frequency slope of a propagation medium from the complex envelope of a signal | |
| US4520670A (en) | Method and apparatus for generating short ultrasonic echo pulses | |
| JP4455685B2 (en) | System for removing a signal of a predetermined frequency from a received signal | |
| JP3244536B2 (en) | Ultrasound diagnostic equipment | |
| JPS6128301B2 (en) | ||
| JPH029813B2 (en) | ||
| JPS5941731B2 (en) | Ultrasound diagnostic equipment | |
| Ermert et al. | Acoustical Imaging Using an Optimal Combination of Signal Prefil Tering and Pulse Compression | |
| Holographic | 134 CHAPTER 8 CLASSIFICATION OF ARRAY SYSTEMS | |
| JPS6322522Y2 (en) | ||
| Shyam et al. | Adaptive inverse filtering with chirp for medical ultrasound | |
| JPS5821577A (en) | Ultrasonic wave transmission/reception system | |
| JPH0321182B2 (en) | ||
| JPH0339145A (en) | Filter for controlling automatically quality of picture in ultrasonic diagnosis apparatus |