DE10127850B4 - Apparatus for carrying out nuclear magnetic resonance investigations inside organic bodies - Google Patents

Abstract

Apparatus for carrying out nuclear magnetic resonance investigations inside organic bodies,
with a, at least one hollow channel (12) having endoscope (10) which can be introduced into the interior of the body;
with an MR coil (22) through the hollow channel (12) feasible and the distal end of the endoscope (10) can be positioned superior, wherein the MR coil (22) has a flexible electrical conductor (24); and
with an elastic tube (26), along the interior of which the flexible electrical conductor (24) is at least partially guided, wherein the tube can be filled with a medium and in the filled state can assume a loop-like shape with a looping diameter which is greater than the diameter the hollow channel (12),
the maximum loop diameter being at least 15 cm.

Description

Of the Use of nuclear magnetic resonance spectroscopy (NMR, nuclear magnetic ) Studies in medicine finds multiple application and allows also two-and-through layered construction - three-dimensional Illustrations of the body or single organs (MRI, magnetic resonance imaging). Depending on the examination method can on This way, irritations in tissue areas are detected For example, to diagnose ligament injuries or for detection cancerous ulcers inside the body serve.

Far Commonly used are closed magnetic resonance tomographs (MRT, magnetic tomography), which have a voluminously formed, annular housing, in the large-sized magnetic coil systems for generating strong magnetic fields (eg 1.5 Tesla) are. In addition to the large-sized Magnetic coil systems, a nuclear magnetic resonance tomograph a coil unit to Generation of a high-frequency alternating field, in the case of resonance is partially absorbed by the nuclear spins. The absorption and the resulting echo signals can with the help of a receiver or MR coil, also housed in the annular array is, detected and by appropriate reinforcement on a recording device, for example an oscillograph.

by virtue of technical limitations, in particular the signal strength, as well due to blurring the figure, which by the movement, z. B. the respiratory movement caused by the patient are with such MRI scanners certain organ areas not representable. For example, in the stomach wall a patient can not reliably differentiate individual tissue layers.

to Avoid unnecessary Operations and for however, the selection of a suitable therapy concept is an accurate one Diagnostics about one possible differentiated representation of the tissues indispensable, otherwise situation and size of one Tumors can not be detected.

NMR images higher spatial Resolution are to get if an MR coil over a magnetic field compatible endoscope is inserted into the interior of the body. The for Not only are such materials used in such an endoscope Magnetic field compatible, but also compatible with the body, so biocompatible.

By the biocompatible endoscopes can MR coils directly on site to the tissue area to be examined be brought, for. B. with the help of a gastroscope in the stomach, around the localization, the size, the Growth, the stage and / or the infiltration depth of a detected diagnose malignant gastric tumors more accurately. In other words: the MR coil becomes through the magnetic field compatible endoscope intracorporeally into a hollow organ introduced. The detected signal is led to the outside, amplified, digitally processed - i. d. R. by spectral analysis by Fourier transformation - and as Image and / or spectrum for a subsequent diagnosis made visible. With the help of this technique Is it possible, Locally examined tissue areas minimally invasive in terms of their tissue structure and type.

from time to time be for used experimentally with endoscopes rigid MR coils whose Design and size depending on corresponding investigation requirements and NMR resonance frequencies are formed. Therefor In particular, solenoid coils whose coil diameter are suitable maximum of the size of the diameter of the execution channel within the endoscope. Typical diameters are under 10 mm.

so small sized MR coils can only record small image details with a low penetration depth. The penetration depth is the depth in which still shots of the coil is removed in the body can be included. To big tumors to be able to map have to Therefore, small MR coils intracorporeal relative to those to be examined Areas are moved. The depth of a tumor, however, can can not be determined due to the limited penetration depth. In order to is a big tumor can not be imaged in the required manner with small MR coils.

a Way out form coils with a single turn or wire loop, which are made of shape-memory metal (Quick et al.: "Single-Loop Coil Concept for Intravascular Magnetic Resonance Imaging; Magnetic Resonance in Medicine (1999) 751-758). Such coils can pressed together with a small diameter through the passageway within the endoscope guided become and unfold when in the body at the distal end of the endoscope escape. The diameter of the unfolded coil at the place of measurement can be so much bigger, as the diameter of the feedthrough channel. Has a larger coil diameter a stronger one Signal and thus a higher one Sensitivity, a larger image detail and a better penetration depth. The orientation of unfolded Coil in the room leaves However, do not control in the known system.

It has also been proposed ( DE 197 46 735 and (Quick et al .: "Single Loop Coil Concept for Intravascular Magnetic Resonance Imaging"; Magnetic Resonance in Medicine (1999) 751-758)), a coil of flexible electrical conductor on a catheter, e.g. As a vascular catheter to mount on the surface of the inflatable balloon. In the case of vascular catheters, such a balloon is primarily used for percutaneous transluminal angioplasty (PTA), ie for the occlusion of blocked vessels. With the help of a catheter prepared in this way, the walls of vessels can be examined by MRI. For this purpose, the catheter is first introduced into the vessel, the balloon is deflated. Once the place to be examined has been reached in the vessel, the balloon is inflated. This increases the diameter of the coil located on the surface of the balloon. The size of the coil is however limited by the size of the inflatable balloon.

Also the US 5,035,231 proposes an endoscope device for medical nuclear magnetic resonance (NMR). The device is equipped inter alia with a passage channel (hollow channel) and a feasible NMR measuring probe. In addition, the endoscope has window-like openings, which are required for observation and lighting tasks. Preferably, the tip of the feasible part is made of a magnetically neutral material. The NMR measuring probe has a transmitter component, which can be passed through the channel of the endoscope. It is connected at one end to the NMR measuring device and capable of transmitting high-frequency signals. Connected to the other end of the transmitter component is a loop-like antenna, with only one turn, made of a partially elastic material and positioned in front of the opening of the feedthrough channel. In this case, the maximum diameter of the antenna loop substantially corresponds approximately to the outer diameter of the insertable part of the endoscope.

In the JP 03212262 A an endoscope is described, which is equipped with a flexible insertion part. In addition, a control element is attached to the rear end of the insertion part. Attached to the front end of the flexible flexible insertion part is a loop antenna (loop antenna) connected to signal lines which are passed through the insertion part. The antenna is preferably made of copper wire or a coaxial cable made of a resilient sheath and a gold-plated conductor, or of a superelastic admixture (alloy) and a copper wire. The loop-shaped shape of the antenna is realized by the elastic properties of the materials used. After insertion of the insertion part, one of the signal lines is pulled taut and the antenna loop is pulled together so that the outer dimension of the antenna loop is smaller than the outer diameter of the tip of the insertion part. Then the antenna is moved in the direction of the front end and unfolded there over a guide slot to full size again.

The JP 03244435 describes a coil variant for carrying out examinations with the aid of magnetic resonance imaging (MRI), which offers a possibility of passing a resonator (coil) through the forceps channel of an endoscope and directly detecting MR measurement signals with this resonator. In this case, a coil consisting of a winding, used in unit with a cable as the resonator. As material for the production of the coil, a shape memory alloy (shape memory alloy) is used, which contracts or expands with temperature changes. Upon cooling, the material contracts and the reduced coil (resonator) can be passed through the forceps channel of the endoscope. In the interior of the object to be examined, the material heats up, the coil expands and assumes its original shape / size, which is required for the measurement of the MR signals.

task The invention is the possibilities for NMR imaging of areas inside organic body to improve.

These The object is solved by the inventions according to the independent claims. advantageous Further developments of the inventions are characterized in the subclaims.

The inventive device comprises an endoscope, preferably a gastroscope, with at least a hollow channel or through-channel. Through this hollow channel is led an MR coil. The MR coil serves as a receiver coil in one of its sections for NMR images, and her leadership is so long that the said section at the distal end, so z. B. in the stomach, can protrude from the endoscope. The MR coil has a flexible electrical conductor. Further, an elastic hose provided along the interior of the flexible electrical conductor at least partially guided is, wherein the tube is filled with a medium and in the filled state adopt a loop-like shape with a looping diameter can, who is bigger as the diameter of the hollow channel. The maximum loop diameter is at least 15 cm.

The flexible electrical conductor consists for example of a 1 mm thick, flexible Kup wire, which is wound at the distal end of the endoscope into a coil with one turn. This winding runs in the loop or torus-shaped interior of the elastic tube, where it is essentially guided in a circle.

It is possible, too, to place the electrical conductor so that after the exit of the Ladder from the distal end of the hollow channel more than a sling is formed. This is achieved by the conductor several times wound in the hose becomes.

The Shape of the tube is substantially torus-shaped. Preferably exists the hose is made of a straight section, which is also fully inserted Condition is located in the endoscope and two wires of the electrical conductor leads. This straight hose section ends in a fork. At both ends the fork closes the toroidal Hose section on which only one wire of flexible electric Conductor leads, this vein is a noose, loop or 180 ° turn training and running back into the endoscope.

When Material for the hose is z. B. latex, whereby the electric Ladder additionally insulated becomes.

Of the Hose is for example with a gas, preferably air, too fill, so inflate, whereby the tube is transferred into a largely rigid circular shape, if the tube projects beyond the distal end of the endoscope. To inflate a connection to a syringe can be provided.

So can Loop diameter of 15 cm and more can be achieved. At a Diameter of 15 cm and multiple winding of the coil can be high inductors and thus achieves high sensitivity, penetration depth and spatial resolution become.

in the deflated state falls the hose and thus the flexible electrical conductor together. It then occupies a space of about 4 × 6 mm, typically the maximum diameter of the preferably oval hollow channel of the endoscope at least 7 mm, so that the endoscope itself does not over 12 to 13 mm thick, otherwise it is no longer z. B. can be inserted through a gullet. The MR coil can thus in the unfolded state through the hollow channel of the endoscope and may be distally withdrawn unfold the hollow channel, so that within the body a Wire loop, which for purposes of NMR studies as Reception coil can be used.

ever after the length which results in the distal end of the hollow channel superior wire loop their size. By continuous variation of the loop diameter can both the penetration depth changed be as well as a vote on different frequencies of the high-frequency alternating magnetic field are made.

By the NMR images or spectra obtained in this way are most accurate tissue information of large or large volume Tissue areas possible. This is a high significance for the current tissue condition possible, the for a determination of a subsequent operation strategy indispensable is.

Of the flexible electrical conductor may preferably at least in the Area that projects beyond the endoscope distally, from a shape memory metal, for example made of a nickel-titanium alloy, z. As NiTinol, be made, the distal of the endoscope outstanding section of the electrical conductor a shape originally embossed him accepts. Preferably, an approximately circular loop shape should imprinted be one way as possible in this way size, area enclosed by the loop to obtain.

The Orientation of the unfolded coil in space can be controlled, on the one hand the usual control the movement of the endoscope tip is exploited and on the other hand the proximal end of the MR coil is rotated. becomes the hollow channel of the endoscope formed in its cross section oval, the distal to the hollow canal superior Schlinge forced by rotation of the endoscope with turned. The Position or orientation of the coil in the room can then over the Sight channel of the endoscope to be controlled.

The formed according to the invention, flexible, deployable and stabilizable MR coil can be used specifically for Recording of NMR images and spectra are used intracorporeally. Besides with the stepless possible variations connected to the loop size Benefits can intracorporal cavities different sizes are examined. The MRI measurement is carried out i. d. R. online, so the endoscopy and the radiologist already during endoscopic procedure, the MRI information is available.

in the The invention will be explained in more detail below with reference to exemplary embodiments which are shown schematically in the figures. Same reference numbers in the individual figures designate the same elements. In detail shows:

1 a schematic representation of a gastroscope with its cross section;

2 a schematic representation of an MR coil; and

3 a circuit diagram of a resonant circuit for an MR coil.

1 shows a gastroscope 10 with a hollow or feedthrough channel 12 , a flushing channel 14 for water or air, a lighting channel 16 for introducing light and a viewing channel 18 for a fiber bundle for observing what happened at the distal end 20 of the gastroscope, z. B. by a fiber bundle of 15000 fibers, corresponding to 15000 pixels. The channels can be seen in the sectional view I. The implementation channel 12 is used to pass the MR coil at the distal end 20 can stand out. Its inlet and outlet are rounded so as not to injure the elastic tube during insertion and removal. The flushing channel 14 is used in particular for rinsing the viewing optics. Its outlet may slightly deviate in the direction from the longitudinal axis of the gastroscope and towards the exit of the viewing channel 18 be angled, whereby the rinse water is directed more towards the optics to achieve a targeted rinsing of the optics.

The execution channel 12 has an oval cross-section with a longitudinal diameter of about 8 mm. In addition to the channels each have a wall thickness of at least 0.25 mm, so that the total diameter of the gastroscope including its shell is about 12 to 12.5 mm.

The Gastroscope is made up of individual discs, each with one straight and alternating a concave and a convex side, thereby the flexibility of the gastroscope is ensured. The diameter the slices is 10.8 mm. The total length of the gastroscope is between 1025 and 1100 mm.

When Materials are used only magnetically neutral materials, So in particular no magnetizable metals, the magnetic field and interfere with the NMR recordings would. The gastroscope is thus magnetic field compatible. Further, in particular the case of the gastroscope biocompatible.

2 shows the MR coil 22 consisting of a noose 24 formed as an electrical conductor and preferably made of a shape-memory metal, which is in the desired loop geometry distal to the hollow channel 12 of the gastroscope 10 unfolded.

The electrical conductor of the sling 24 is made with an elastic tube made of biocompatible material 26 wrapped, which is filled with a gas. In the inflated state, the hose takes 26 and with it the noose 24 essentially a circular shape.

The hose 26 gets into a fork 28 led from where he turned out to be a simple hose section 30 continue. In the hose section 30 are the electrical conductors 31 that's from the noose 24 forward recorded radio frequency signals.

The hose section 30 flows into a crotch stopper 32 , which has the function, the air flow in the hose 30 . 26 from the electrical wires 31 . 36 to disconnect, so the electrical wires from the hose 30 to lead out. At the crotch stopper 32 is over a hose section 34 a syringe 35 connected, which serves the hose 26 inflate. To communicate the hose sections 34 and 30 by means of the crotch stopper 32 ,

The electrical line 36 is to a matching box 38 connected, which serves to tune the resonance frequency of the MR coil to the respective proton resonance frequency, and their function in connection with 3 is explained in more detail.

The matching box 38 is via electrical connections 40 connected to a data processing system in which the processing of the signals to NMR images takes place.

The length of the conductor 24 . 31 . 36 . 40 is dimensioned such that the loop forming distally on the gastroscope 24 . 26 is sufficiently large. Depending on the desired loop size, the surgeon can use the electrical conductor 24 into the interior of the hollow channel 12 of the gastroscope 10 move in, to the complete disappearance of the noose 24 within the hollow channel 12 , For this purpose, preferably (not shown) thread on the gastroscope 10 provided, with the help of which it can be adjusted how deep the flexible electrical conductor 24 in the gastroscope 10 is introduced. In addition, there is a locking device (not shown) around the MR coil 22 in the gastroscope 10 to fix, reducing the length and thus the diameter of the sling 24 is fixed.

3 shows a circuit diagram of a resonant circuit for an MR coil. Between the inlets and outlets 31 the conductor loop or loop 24 is located in the extension of the conductor loop, a capacitor with a capacity of 10 pF. Conductor loop and capacitance form a resonant circuit. The conductor loop has only one turn and is referred to as a "single loop coil".

Immediately after the conductor loop 24 are the electrical conductors 31 each interrupted by a capacitor with a capacity of 22 pF. These three capacitances coarsely adjust the conductor loop to a frequency of approximately 65 MHz. However, since the shape of the conductor loop is affected by contact z. B. can change with the inner stomach wall, it requires a variable and accurate tuning to the proton resonance frequency of z. B. 63.8 MHz to meet. This vote takes place in the matching box 38 ,

The conduction of the radio frequency (RF) signal picked up by the coil to the matching box 38 takes place by means of two lambda / 2 coaxial cables 36 , Since the wavelength lambda of the RF signal of about 65 MHz in the coaxial cable is about 180 cm, the length of the cable is about 90 cm. This length leads to minimal reflections. The coaxial cables are made of non-magnetic material so as not to interfere with NMR imaging.

The inlets and outlets 31 the conductor loop 24 are each connected to the center conductor of the coaxial cable. The jacket of the two coaxial cables is grounded. The two grounded coats are additionally over several solder joints 42 coupled together, so that neither a noticeable capacity nor a noticeable inductance arises between the two coaxial cables. The center conductors are thus ideally shielded.

The matching box 38 is equipped with three capacitors with 0 to about 30 pF variable capacitance. In this case, the center conductor of a coaxial cable via a so-called tuning capacitor CT is connected to the ground. The center conductor of the other coaxial cable is on the one hand also connected via a tuning capacitor CT to the ground. Parallel to this, the second center conductor is still via a so-called matching capacitor CM with an electrical connection 40 connected for the subsequent further processing of the signals.

About the adjustable capacities CT, the fine tuning of the resonant frequency of the resonant circuit is performed the MR coil in the range of 60 to 65 MHz. About the matching capacitor CM, the tuning of the resonant circuit to the impedance of the Coaxial cable 36 to avoid reflections. The impedance of the coaxial cable is 50 ohms.

With This circuit helped the MR coil to the proton resonance frequency of 63.8 MHz in physiological saline. at This frequency was used in physiological saline Goodness Q reached from 12.5 under load of. The quality is defined as the quotient of the resonance frequency and the half width the resonance line. "Last" is the simulation the conditions in the stomach during an analysis. As the stomach during an analysis with air or nitrogen is inflated and the body tissues mainly consists of water and salts, the simulation is in air above the Surface of a Saline carried out.

10

gastroscope

12

Hollow- or duct

14

irrigation channel

16

lighting channel

18

viewing channel

20

distal End of the gastroscope

22

MR coil

24

loop

26

tube

28

fork socket

30

hose section

31

electrical ladder

32

fork plug

34

hose section

35

syringe

36

electrical management

38

matching box

40

electrical connections

42

solder connections

Claims (4)

Device for carrying out nuclear magnetic resonance examinations in the interior of organic bodies, with one, at least one hollow channel ( 12 ) endoscope ( 10 ), which can be introduced into the interior of the body; with an MR coil ( 22 ) passing through the hollow channel ( 12 ) and the distal end of the endoscope ( 10 ) is positionally superior, wherein the MR coil ( 22 ) a flexible electrical conductor ( 24 ) having; and with an elastic hose ( 26 ), along the interior of which the flexible electrical conductor ( 24 ) is at least partially guided, wherein the tube is filled with a medium and in the filled state can assume a loop-like shape with a looping diameter which is greater than the diameter of the hollow channel ( 12 ), the maximum loop diameter being at least 15 cm. Device according to the preceding claim, characterized in that the diameter of the loop ( 24 . 26 ) is variably adjustable. Device according to one of the preceding Claims, characterized in that the flexible electrical conductor ( 24 ) is at least partially formed of a shape memory metal. Device according to one of the preceding claims, characterized in that the hollow channel ( 12 ) of the endoscope ( 10 ) has an oval shape.