WO2000061007A1

WO2000061007A1 - Interconnect cable for an ultrasound monitoring apparatus

Info

Publication number: WO2000061007A1
Application number: PCT/GB2000/001414
Authority: WO
Inventors: Mark Graham Blunden
Original assignee: Deltex (Guernsey) Limited
Priority date: 1999-04-13
Filing date: 2000-04-13
Publication date: 2000-10-19
Also published as: GB9908426D0; AU4417200A

Abstract

The invention provides an interconnect cable (11) for use in conjunction with an ultrasound probe (7) and host processor (9), the components combining to provide an ultrasound haemodynamic monitor. The interconnect cable (11) is characterised in having an amplifier (13) incorporated therein, preferably adjacent the connection (19) to the probe (7), which operates to amplify signals received from the probe and therefore to render the monitor less susceptible to extraneous noise.

Description

INTERCONNECT CABLE FOR AN ULTRASOUND MONITORING APPARATUS

Field of the Invention

This invention relates to ultrasound monitoring apparatus and in particular, though not necessarily solely, to a Doppler ultrasound instrument used to measure and indicate cardiac function.

Background

A variety of instruments used in the medical field employ Doppler ultrasound as the basis for measuring velocity or flow through blood vessels. Typically, ultrasound transmit and receive crystals are aligned so as to insonate the vessel of interest; and the received signals, being signals reflected from moving red blood cells, are first analysed to determine blood velocity, and then combined with a computation of vessel cross- sectional area to give a measure of blood flow through the vessel.

The present applicant has, for some time, been manufacturing and selling an instrument for determining cardiac function. This instrument incorporates a probe which is inserted into the patient's oesophagus, the probe having mounted on the outer end thereof, ultrasound transmit and receive crystals. In use, the probe is aligned so that the patients descending aorta is insonated with ultrasound.

The system processor which generates the transmit signal and analyses the receive signal is, of necessity, located outside the patient and, generally, some distance from the patient. The processor is connected to the probe by means of a patient interconnect cable (PIC).

It is a consequence of this arrangement that relatively weak signals from the receive crystal or transducer must be fed through a relatively long cable path before being passed into the main system where the signals can be amplified. This combination of a relatively long cable path and weak, non- amplified transducer signal, results in the total system being susceptible to noise pick-up. In any event, signal to noise ratios in apparatus of this type are generally very low so that the susceptibility of the received signal to further noise, makes meaningful and accurate signal processing that much more difficult.

It is therefore an object of this invention to provide an ultrasound monitoring apparatus and /or a method of processing signals in such a form of apparatus, which will go at least some way in reducing system susceptibility to noise, or which will at least provide a useful choice.

Summary of the Invention

Accordingly, in one aspect, the invention provides an ultrasound monitoring apparatus including a probe engageable with a human subject ; a processor operable to process signals received by said probe; and an interconnect cable to connect said probe to said processor, said apparatus being characterised in that said interconnect cable includes signal amplification means operable to amplify signals received by said probe prior to receipt of said signals by said processor.

Preferably said interconnect cable includes a first connection at one end thereof engageable with a complimentary connection on said probe, said signal amplification means being located wit_hin, or adjacent to, said first connection.

Said signal amplification means is conveniently incorporated in a circuit board powered from said processor.

In a second aspect the invention provides a patient interconnect cable operable to interconnect a probe engageable with a human subject, with a processor operable to process signals received by said probe, said patient interconnect cable including first connection means constructed and arranged for engagement with said probe; second connection means constructed and arranged for engagement with said processor; and signal amplification means operable to amplify signals received by said patient interconnect cable from said probe.

Preferably said signal amplification means are located in, or adjacent to, said first connection means.

Preferably said patient interconnect cable further includes signal processing capability and/or analogue to digital signal conversion means.

In a third aspect the invention comprises a method of treating signals received by a probe engageable with a human subject, said probe forming part of an ultrasound monitoring apparatus which apparatus further includes a processor operable to process said signals, said method comprising amplifying said signals received by said probe before inputting said signals into said system processor.

In a fourth aspect the invention comprises a method of reducing the impedance of a receive signal in an ultrasound monitoring apparatus comprising a probe engageable with a human subject; a processor operable to process signals received by said probe; an-i an interconnect cable interconnecting said probe to said processor, said method comprising amplifying signals received by said probe before inputting said signals into said processor.

Preferably said method includes amp]_Lfying signals received by said probe within said interconnect cable.

Many variations in the way the present invention can be performed will present themselves to those skilled in the art. The description which follows is intended as an illustration only of one means of performing the invention and the lack of description of variants should not be regarded as limiting.

Wherever possible, a description of a specific element should be deemed to include equivalents thereof whether in existence now or in the future. The scope of the invention should be limited by the appended claims alone. Brief Description of the Drawings

One form of the invention will now be described with reference to the accompanying drawings in which:

Figure 1 : shows a schematic system outline of a Doppler ultrasound cardiac output monitor incorporating the various aspects of the invention;

Figure 2: shows a plan view of a patient interconn ect cable suitable for use in the monitor shown in Figure 1 ; and

Figure 3: shows a schematic layout for certain electrical components incorporated in the cable shown in Figure 2.

Detailed Description of Working Embodiment

As shown in Figure 1 of the drawings, the present invention relates to ultrasound monitoring apparatus 5, in this case a Doppler ultrasound cardiac function monitor. In the form shown, the monitor 5 includes a probe 7 engageable with a human subject to insonate an organ or vessel with ultrasound and to receive ultrasound signals reflected from red blood cells passing through the organ or vessel. In the case of the cardiac function monitor described herein, the probe 7 comprises a disposable elongate flexible catheter-like device having ultrasound transmit and receive crystals mounted at one end thereof, and having a connector provided at the other end. The probe, as depicted and described herein, is inserted into the oesophagus of a sedated patient so that the ultrasound transmit and receive crystals are located adjacent to, and aligned at 45° to, the descending aorta. The monitor 5 further includes a system processor 9 which is constructed and arranged to cause the probe 7 to emit ultrasound, and which receives electronic signals derived from the reflected ultrasound and processes these signals to obtain measures of blood velocity.

In the particular form of monitor shown, the probe 7 is connected to the system processor 9 through a patient interconnect cable (PIC) 11. This is the normal configuration since the probe, being a disposable item, is generally of a length just sufficient to ensure the connector at one end thereof clears the patient's mouth by a small margin, whilst the system processor 9 may well be located some distance away.

It is a characteristic of Doppler cardiac function monitors of the type described, that the signal to noise ratio is very low and accurate isolation of the true signal from the background noise is difficult. In prior art monitors of this type, the problem has been exacerbated by the fact that the reflected signals are only amplified after receipt within the system processor 9 and because the signals are weak, and the cable distance between probe and processor is relatively long, the total system is prone to noise pick-up.

The present invention provides a solution to this problem by including a signal amplifier 13 in the PIC 11. The amplifier 13 is preferably located on or within the cable as close to the connection with the probe 7 as is practically possible.

Referring now to Figure 2, the PIC 11 is shown comprising a flexible centre cord section 15 having a connector 17 at one end thereof to enable connection into the system processor 9, and a further connector 19 at the other end thereof to enable connection to the disposable probe 7.

The centre cord section 15 can be of any form suitable for the intended application but may, for example, comprise a multi core, score screened cable. The connector 17 may, for example, comprise a FISCHER 10-way plug.

The connector 19 typically comprises two halves formed from an insulating material which, when combined, envelop and house a printed circuit board 21. Edge connector 23 fixed to the PCB 21 projects through a locating and sealing waϋ section 25 of the connector to define a connection point with a complimentary shaped connector (not shown] forming part of the probe 7.

The PCB 21 is powered from the system processor 9 through the centre cable section 15 and, in accordance with the invention, includes a signal amplifier thereon as will be described in greater detail below.

Turning now to Figure 3, the PIC 11 , and more particularly the PCB 21 , is provided with a number of electronic components to enable not only the performance of the invention claimed herein, but also to enable the full functions of a particular form of disposable ultrasound probe to be realised.

In the form shown, the PCB has mounted thereon, connector socket 23, transformer 27, tuned amplifier circuit 28, and power and decoupling circuit 29. The PCB 21 may further include line filter components 30 to remove noise induced in the

5 volt supply line from the host system processor; and a probe coupling/data release circuit 31 , but these features are governed by a particular form of probe which may be used with the PIC 11 , and will therefore not be described in greater detail herein.

As stated above, connector socket 23 has a number of terminals corresponding to various functional features of the probe 7. Thus, T_x and R_x carry ultrasound signals to and from the transmit and receive crystals, respectively, of the probe 7. Similarly, terminals SDA and SCL form part of an industry standard I²C communications bus which allows data to be communicated between the probe 7 and the host system processor 9, via the PIC 11.

Transformer 27 is a simple unitary component providing isolation of the transmit crystal (not shown] incorporated in the probe 7. In a similar manner transformer T2 included in the tuned amplifier circuit 28, provides isolation to the receive crystal (not shown) also included in the probe 7. T2 also acts, in combination with capacitor Cl , to provide high input impedence at the Doppler ultrasound frequency selected for the system - in this case 4Mhz. The tuned circuit not only ensures high impedence in a very narrow spectral band about 4Mhz, but also ensures impedence approaches zero either side of the band. The high input impedence ensures less loading of the crystal. The 'tuning' of the circuit about the Doppler frequency ensures sensitivity of the device to just the frequency of interest and therefore makes the system less susceptible to extraneous 'noise'.

Finally, the tuned circuit 28 includes amplifier U1A which is onfigured to have a gain of 2 and to provide a low impedence drive for the PIC 11.

Power input and decoupling circuit 29 provides power and decoupling for the tuned circuit 28 via the system processor 9.

It will thus be appreciated that the configuration herein described causes the weak reflected signals received by the probe 7 to be amplified very near source. The strong amplified signals from a low impedance source results in a system which is much less susceptible to noise pick-up with the result that system signal to noise ratio is greatly improved. A further advantage of the system described herein is that it readily provides for additional capability, such as processing power, to be included in the PIC. This, in turn, would enable additional intelligence to be built into the disposable probe 7 such that signals from the probe could be conditioned and digitised before be passed back to the host processor 9 through the in-built communication bus.

Claims

1) An ultrasound monitoring apparatus including a probe engageable with a human subject; a processor operable to process signals received by said probe; and an interconnect cable to connect said probe to said processor, said apparatus being characterised in that said interconnect cable includes signal amplification means operable to amplify signals received by said probe prior to receipt of said signals by said processor.

2) Apparatus as claimed in claim 1 wherein said interconnect cable includes a first connection at one end thereof engageable with a complimentary connection on said probe, said signal amplification means being located within, or adjacent to, said first connection

3] Apparatus as claimed in claim 1 or claim 2 wherein said signal amplification means is incorporated in a circuit board powered from said system processor.

4) A patient interconnect cable operable to interconnect a probe engageable with a human subject, with a processor operable to process signals received by said probe, said patient interconnect cable including first connection means constructed and arranged for engagement with said probe; second connection means constructed and arranged for engagement with said processor; and signal amplification means operable to amplify signals received by said patient interconnect cable from said probe. 5) A cable as claimed in claim 4 wherein said signal amplification means are located in, or adjacent to, said first connection means.

6) A cable as claimed in claim 4 or claim 5 further including signal processing capability and /or analogue to digital signal conversion means.

7] A method of treating signals received by a probe engageable with a human subject, said probe forming part of an ultrasound monitoring apparatus which apparatus further includes a processor operable to process said signals, said method comprising amplifying said signals received by said probe before inputting said signals into said system processor.

8] A method as claimed in claim 7 wherein said apparatus further includes a patient interconnect cable interconnecting said probe to said system processor and wherein said method includes amplifying said signals within said patient interconnect cable.

9) A method of reducing the impedance of a receive signal in an ultrasound monitoring apparatus comprising a probe engageable with a human subject; a processor operable to process signals received by said probe; and an interconnect cable interconnecting said probe to said processor, said method comprising amplifying signals received by said probe before inputting said signals into said processor. 10) A method as claimed in claim 9 including amplifying signals received by said probe within said interconnect cable.

11) Ultrasound monitoring apparatus when constructed arranged and operable substantially as hereinbefore described with reference to, and as illustrated in, the accompanying drawings.

12) A patient interconnect cable for use in ultrasound monitoring apparatus when constructed arranged and operable substantially as hereinbefore described with reference to, and as illustrated in, Figures 2 and 3 of the accompanying drawings.