JPS60177250A - Measuring head for detecting high resolution nuclear resonance signal - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention has a transmitter/receiver device that can be placed on a subject placed in a homogeneous constant magnetic field. The present invention relates to a measurement head for high-resolution nuclear resonance measurements.

A measuring head of the type mentioned at the beginning was published in the magazine “Science
214, November 16, 1981, pages 660-662.

By "predetermined region" we mean hereafter a small surface region or a region near the surface, which is different from the known whole-object measurement as is known in nuclear magnetic resonance tomography. The size of the "predetermined area" then essentially depends on the size of the measuring head used in each case. This is because measurements are taken only in the vicinity of the plane on which the measurement head is placed on the object.

It is known to use nuclear resonance and also high-resolution nuclear resonance examination methods for diagnostic purposes. In this case, the patient's body or body part is always placed in a magnetic system, which generates a sufficiently homogeneous constant magnetic field in the macroscopic area of the body or body part.

For excitation of nuclear resonance, a high-frequency magnetic field with the following frequency is applied in the perpendicular direction to a constant magnetic field, that is, the relationship between the strength of the constant magnetic field and the strength of the constant magnetic field is fixed as an inherent constant or a natural constant for each different type of nucleus. A high-frequency magnetic field of the same frequency must be applied.

In so-called nuclear magnetic resonance tomography, a high-frequency magnetic field is generated by a large saddle-shaped coil, so that the desired cross-sectional images of the patient's body or body parts can be produced in nuclear magnetic resonance tomography.

The disadvantage of generating high-frequency magnetic fields in this way over a large space is that, on the one hand, the patient's body or body parts are heated excessively by the high-frequency irradiation, and on the other hand, the disadvantages of a high-frequency device over a large space are the high radio-frequency magnetic field strengths. If the interference beam leaks to the outside, this interference beam may interfere with nearby measurement equipment, and the interference beam may also enter the saddle coil device from the outside, falsifying the measurement results. be.

Therefore, it is known from the journal articles mentioned at the outset to use small surface coils placed on problem areas of the body instead of saddle-shaped coils that span large spaces. In the case of organs that are relatively deep, for example, during animal experiments, the organ to be examined (liver) is exposed and a coil is placed over the organ.

However, it is often the case that only the surface area of the body being examined, or at least the near-surface area, is of concern, so that a small surface coil device is sufficient, which does not harm the patient due to excessive radiofrequency radiation, and Excessive interference beams are not emitted, and the system is less likely to be affected by interference radiation.

Therefore, this type of surface coil is always used in the following cases, i.e. when it is impossible to extract the analyte and it is desired to measure it in a living body at a relatively small cost (so-called in-vivo measurement). , and are used whenever it is undesirable or impossible to introduce the body or body part into the examination head.

“Review of Scientific Ins.
From the paper by Volino et al. in vol. 39, No. 17, 1968, pages 1660-1665, helical coil resonance for electron spin resonance measurements carried out in the microwave region (X-region). The device is known.

For these measurements, a test tube is used which fills the entire internal space of the helical coil; it is also possible to immerse the entire helical coil in the liquid.

Based on the traveling waves propagating in the helical coil, virtually the entire internal space of the helical coil is filled with each component of the electric field, so that when a probe or test head is inserted, the coil resonator is This results in a significant drop in quality.

That is, the quality (Q) of an air-core coil is one order of magnitude lower than that of a normal cavity resonator, and the resulting loss in sensitivity can only be partially compensated for in the case of a coil resonator by: That is, even if the filling factor is increased compared to a cavity resonator by completely filling the internal space of the coil, only partial compensation can be achieved. In any case, in the case of such a coil resonator, it is necessary not to fill the entire internal space of the coil with the test material. This means cannot be used for in-vivo measurements in living organisms. Furthermore, in the case of undisclosed coil resonators, sufficient utilization of the external field does not take place, and the separation of the magnetic and electric field regions does not take place, nor is it at all possible for the specimen in question with finite dimensions. .

Papers in the journal QST, June 1976, No. 11-1
From page 4, it is known to use coiled resonators for Ham radio, in which a coil is surrounded by a coaxial shield which may be open at both ends. In the case of such resonators, which are designed exclusively as filters and whose transmission and reception characteristics cannot therefore be controlled, it is not possible, as is usual in radio technology, to have field lines in the external region of the resonator. is considered important. For this either the shield is closed at both ends with a conductive bottom, so that the coil is placed in a conductive casing closed on either side, or the coaxial shield is axially extended over the ends of the coil. is extended to the extent that only a negligible component of the leakage field of the coil exits. This is therefore not possible in the case of surface measurements of the type mentioned at the outset. This is because in such known coil resonators, according to regulations, no field lines can and should not go out to the outside. Also, no precautions are taken to create areas of high magnetic and electric field strength.

A closer examination of surface coils for nuclear resonance measurements of the type mentioned at the outset reveals that these surface coils suffer from several systematic drawbacks.

Problem to be Solved An important drawback is that in such surface coils there is no spatial separation of the electric and magnetic fields. This means that the region of the body to be examined only needs to be supplied with a high magnetic field rather than a high electric field to excite nuclear resonance, and what is undesirable about this is that the sensitivity of the measurement head is reduced due to dielectric loss in the body. It is to be damaged.

Another disadvantage of surface coils is that they are relatively narrow strips, so that to excite different types of nuclei, separate measurement heads with different surface coils must be used. It must not happen. When changing the examination head, the measurement location generally changes, especially in the case of restless patients, so that in the case of successive measurements of several types of nuclei, sometimes comparable measurement results are no longer obtainable. As a result, in the case of the first type of nuclei it is not possible to first adjust the instrumentation with relatively strong nuclear resonance signals and then detect the actual significant nuclear resonance spectra in the case of other types of nuclei.

A further disadvantage of the known surface coils is that, despite their relatively small dimensions compared to the saddle coils mentioned at the beginning, they always have some residual radiation and are therefore also affected by interference radiation. This means that it is easy to receive.

In the case of conventional nuclear spin tomography, i.e., image display of cross-sections of the body, a constant magnetic field homogeneity of 10-5 is sufficient;
When using a measuring head mounted as mentioned in the introduction, the detection of high-resolution nuclear resonance spectra requires at least 10
-7 homogeneity is required. For the detection of such high-resolution nuclear resonance spectra, it is therefore necessary to carefully set up a constant magnetic field at the measurement point, ie in the region to be examined of the patient's body or body part, before the start of the measurement. Such adjustments must be made as quickly as possible so as not to subject the patient to an unduly long examination period and to place an economical burden on the equipment.

Furthermore, it is known to increase the richness of the nuclear resonance spectra during measurements of one species by "decoupling" the nuclei of another species, i.e. simultaneously exciting or saturating them with strong radio frequency fields. . Usually protons are decoupled and nuclei of other species are measured. A high high-frequency power is required for the decoupling, which results in an increased risk of noise or disturbances in the electrical characteristics in the known devices mentioned at the outset with saddle-shaped coils and mounted planar coils.

It is therefore desirable to be able to carry out such decoupling experiments also in the case of mounted measuring heads.

The object of the invention is therefore a measurement of the type mentioned at the outset, in which the region of the object to be examined in question is penetrated practically exclusively by a high-frequency magnetic field, and in which different types of nuclei can be measured without changing the measuring head. It is an object of the present invention to provide a measurement head which is capable of carrying out measurements in which the transmitted interference beam is minimized, thereby making the measurement less susceptible to interference from external interference radiation.

Means for Solving the Problem To solve this problem, according to the invention, in a measuring head of the type mentioned at the outset, the transmitting and receiving device is constructed as a coil conductor with a coaxial shield, the coaxial shield at least open at one end;
The lower end of the coil conductor has no connection part, and the uppermost turn of the coil conductor, which is connected to the shield via the connection part, is located approximately in the plane of the open upper end and forms a mounting plane here. That's what I do.

The problem underlying the invention is solved, on the other hand, in the following way: First, under the frequency of protons (H1
) - a relatively high-frequency vibrational mode in which nuclear resonance occurs is excited in the coil conductor, the homogeneity of a constant magnetic field is optimized under observation of one line of the proton-nuclear resonance spectrum, and then
Other nuclear types under that frequency, e.g. C13, P3
1, Na23, and the nuclear resonance signals of other types of nuclei are measured.

In that case, broadband excitation in different vibrational modes is
Optionally, this can be done with individual frequency adjustment of the individual vibrational modes, so that the excitation frequency can be switched from the proton resonance to the resonance of other species of nuclei by a simple electrical switch. Advantageous properties are exploited.

The proton spectrum is then particularly suitable for homogenizing the magnetic field, since the increasing homogeneity of the magnetic field directly manifests itself in the linearity of the spectrum, and in the case of strong signals the spectrum can be observed after each excitation. This is because the magnetic field can be continuously homogenized. This has significant advantages over field homogenization in the case of nuclei of other species, since measurement periods of, for example, several minutes are required for the detection of nuclear resonance spectra of nuclei of other species; As a result, adjustment of the constant magnetic field for homogenization is always possible only within a few minutes, which results in a significantly longer adjustment time for the entire device.

The above-mentioned problem, which is the basis of the invention, is solved by an embodiment of the invention in the following way: the first irradiation of the radio-frequency field, for example for the excitation of the proton resonance, is achieved by using a radio-frequency sheet coil (saddle coil). The measurement head is placed on the subject's body in a direction perpendicular to the plane of the planar coil in order to measure, for example, nuclei of other species.

Therefore, in order to take advantage of the advantageous dimensions and design of the measuring head according to the invention in this way, according to an advantageous embodiment of the invention the measuring head can be simply inserted into a conventional nuclear resonance tomography machine and, in addition, can be inserted therein. It is added to the saddle-shaped coil provided in the saddle-shaped coil and is placed in a direction perpendicular to the saddle-shaped coil. Due to the 90° rotated arrangement of the respective coil axes of the measuring head according to the invention and the special shielding properties, no interference radiation from the saddle-shaped coil into the measuring head occurs or actually occurs.

The end of the coil conductor remote from the mounting plane can be constructed differently. In the case of so-called λ/2 devices, for example, a flap-shaped symmetric structure (in which the end facing away from the support plane is the same as the support plane) results. In a preferred embodiment a so-called λ/4 structure is used, the other end of the coaxial shield being closed. This embodiment is particularly advantageous because a further improvement in the shielding properties is achieved by closing the shield at the opposite end.

Furthermore, this device is particularly short in the axial direction, which is particularly advantageous because the measuring head according to the invention can be used perpendicularly to the direction of the constant magnetic field, i.e. perpendicularly to the axis of the solenoid magnet system. This is because it is only necessary to place the subject under test. However, in such a coordinate direction perpendicular to the axis of the constant magnetic field, there is relatively little space inside the solenoid magnet system.

According to a further embodiment, the open end forming the support plane is covered with a cover made of electrically non-conductive material, the
The cover has a number of radially extending conductor tracks, the outer ends of which transition into the casing forming the shield, and the inner ends of which converge, without touching, in the central area of the cover. .

The advantage of this measure is that the small electrical high-frequency leakage fields that still remain are short-circuited by the conductor track above the mounting plane.

This makes it possible to further reduce the dielectric losses in the subject or the measuring body and also to further reduce the disturbances (noise) due to emitted or captured disturbing radiation.

According to a further embodiment, a first adjustment device is provided in which the spacing between the free end of the coil conductor and the other end of the closed coaxial shield is variable.

The advantage of this measure is that the adjustment to the desired resonance frequency is particularly simple when applying a λ/4 resonator, i.e. at the lowest possible resonance frequency of the fundamental vibration mode. .

Adjustment is effected in this case by bringing the metal disc, in particular the bottom part corresponding to the radial cross-sectional shape of the shield, close to the "open end". It is clear that instead of the close proximity of the metal disks, the insertion of metal cylinders or the additional connection of capacitors as lumped constant elements can then take place in a manner known per se.

According to a further embodiment, a further adjustment device is provided, in which the electric field E produced by the coil conductor is
It is applied at a predetermined point in the axial direction, and at this predetermined point the electric field E assumes a maximum value only in one predetermined vibration mode.

A particular advantage of this measure is that the frequency adjustment of the individual vibration modes is possible independently of one another.

A relatively high frequency vibration mode has, for example, a plurality of maximum values of the electric field strength, ie a maximum value at a location where a relatively low frequency vibration mode does not have a maximum value. By loading at the point of such a maximum value, which occurs only in the higher frequency vibration modes, it is possible, for example, to reduce the frequency of the higher vibration modes without affecting the resonant frequencies of the lower vibration modes. . In that way, it is possible to adjust the ratio of the frequencies of the different vibrational modes to be different from the theoretically occurring odd multiples, i.e. to adjust the ratio of the frequencies of the different vibrational modes to be different from the theoretically occurring odd multiples, i.e. to obtain different frequencies corresponding to the nuclear resonance frequencies of the various nuclei in the measuring head. It can be adjusted to obtain a resonant frequency. The frequency ratios of different types of nuclei are then characteristic or natural constants and, as is known, do not correspond to odd multiples.

According to another embodiment, a second
A tuning device is provided, the second adjusting device having an electrically conductive lug, one end of the jig being connected to a casing forming a shield and the other end being displaceable in a radial force plane. In this way, the maximum electric field strength can be applied by simply turning the screw.

According to another embodiment of such a selective adjustment of the maximum value of the electric field strength, a third adjusting device is provided in the interior space of the coil conductor, the third adjusting device being transverse to the axis of the coil conductor. It comprises an open loop with a plane arranged in the direction, which loop is connected on one side with a casing forming a shield.

The regulating device just mentioned is particularly suitable for regulating fixedly defined base loads.

According to an advantageous embodiment for optimizing the adaptation of the measuring head to the lead wire, a further adjustment device, preferably in the form of an adjustable capacitor, is provided in the connection of the coil conductor and the shield. . The advantage of this method is that the insulated lead wires passing through the shielded casing can be brazed directly to the open ends of the lead wires and then coupled.
A fine adjustment of the impedance is carried out via an adjustable capacitor, so that a precise adaptation to a partial impedance of, for example, 50 Ω is possible.

According to another embodiment of the invention, the coil conductor is connected to an adjustable high frequency transmitter.

This measure has the following significant advantages:

According to the field strength distribution of the high-frequency magnetic field in the subject, which is obtained by the field lines of the high-frequency magnetic field that enters the subject's body starting from the open end of the measurement head, the strength of the high-frequency magnetic field is directed inward from the surface of the subject. decreases. By adjusting the amplitude of the high-frequency magnetic field, a high-frequency magnetic field strength of the following magnitude is generated at a predetermined depth below the surface of the object, that is, the so-called 90° condition is satisfied, that is, the maximum signal collection is achieved. (which means that the spins of the nuclei of the type to be tested are 90° from their rest position when a high-frequency magnetic field is applied.
This is because the magnetic field is rotated, so a high-frequency magnetic field strength of such magnitude is generated. On the other hand, a high-frequency magnetic field that satisfies the so-called 180° condition is applied to other regions of the subject, for example.
As a result, it is as if almost no signal is emitted from those areas.

Therefore, by adjusting the amplitude of the high-frequency magnetic field, it is possible to select a deep part of the object.

Other advantages will become apparent from the accompanying drawing and description.

Example Next, the present invention will be explained using figures.

In FIG. 1, numeral 10 indicates a magnet system arranged in a space having three-dimensional coordinates x, y, and z. The spatial coordinate z coincides with the axis of the magnet system 10. In axis z there is located a schematically illustrated subject or measuring body 11, for example the entire body of a patient, or a body part, for example an arm or a leg. However, it is clear that the measuring head of the invention can also be used in the case of non-organic specimens and living or non-living tissues.

A lead wire 13 extends from the measuring head 12 to an electronic circuit not shown in FIG.

The magnet system 10 is shown only schematically and consists of a so-called double Helmholtz device with two pairs of Helmholtz coils 14. The Helmholtz coil 14 has all three three-dimensional coordinates x
, y, z with high homogeneity. In other words, the measuring body 1 in the direction perpendicular to the coordinate z
If a high-frequency magnetic field is applied simultaneously to 1, nuclear resonance will occur in the entire homogeneous region.

FIG. 2 shows the field distribution in the measuring head 12 of the invention.

The measuring head 12 essentially consists of a coil conductor 20, also referred to in the technical literature as a "helix". For ease of understanding of the coil conductor 20, FIG. 2 shows the uppermost turn 21 and the lowermost turn 21.
Turn) 22 only is shown. A second important element of the measuring head 12 of the invention is a grounded shield 23, which is provided coaxially around the coil winding 20, for example. Shield 23 having a longitudinal axis 24 has an upper open end 25 and a lower closed end 26. In the embodiment of FIG. 2, the position of the coil conductor 20 on the axis 24 is as follows: the uppermost turn connected to the shield 23 via the connection 28 is substantially open upward. It is such that it lies in the plane of the end 25 and forms there a mounting plane 27 , ie a plane on which the measuring head 12 rests on the subject measurement body 11 .

That is, from an electrical point of view, the coil winding 20 is connected to the grounded shield 2 at the upper open end 25 via the connection 28.
3, while being electrically open in the region of its lowermost turn 22 at a distance from the lower closed end 26 of the shield 23.

As a result, as shown in FIG. 2, as a field distribution, lines of magnetic force B are generated at the left side of the axis 24, and electric lines of force E are generated at the right side of the axis 24. The magnetic field lines B are closed in the radial plane of the coil conductor 20 and extend in particular above the open end 25 into free space. When the measurement head 12 is placed on the object to be measured or the body to be measured 11 within the mounting plane 27, the strength of the magnetic field will be distributed inside the body to be measured 11 along the coordinate d in FIG. decreases towards

In contrast, the electric field lines E extend substantially in the intermediate space between the coil conductor 20 and the shield 23, so that they do not practically appear towards the outside. In the region above the mounting plane 27, no leakage field (stray electric field) of the electric lines of force E can be observed. Furthermore, E-field lines (electric lines of force)
decreases from bottom to top.

In the so-called λ/4 resonator shown in the electrical diagram in FIG. 2, the lower end 26 of the shield 23 is closed. It goes without saying that a so-called λ/2 device can be used instead of the device shown in FIG. 2, and in this λ/2 device, the device shown in FIG. The remaining upper part of the device of FIG. 2, cut radially in a substantially plane, is connected downwardly with an identical part in flap symmetry (with folded overlapping symmetry). In this case, the same part has a downward end and an upper open end 25.
It has a configuration that matches. As you can easily see, the second
In the case of the λ/4 device shown, it is much shorter in length and is completely shielded downwards, so that it is generally suitable for detecting magnetic resonance spectra within the magnet system 10.

FIG. 3 shows a concrete embodiment of the measuring head 12 already shown in FIG. In the embodiment of FIG. 3, the shield 23 is a pot-shaped casing 30 made of an electrically conductive material. A conducting wire 31 is insulated near the upper edge of the casing 30 and is passed through the wall and connected or brazed to the coil conducting wire 20. The conductor 31 is connected to the measuring electronics, which is generally designated 32 in FIG. First of all, a control device 33 belongs to the measurement electronics 32, by which the different transmission and reception processes, data processing and output of the measurement results are controlled. The device 33 thus controls, for example, a high-frequency transmitter 34, the output of which can be adjusted via an attenuator 35 or a controllable output stage.

On the other hand, the receiving section is provided with a receiving amplifier 36, and the output side of this receiving amplifier is connected to the control device 33. Furthermore, the control device 33 is connected to a recording device 37 or a similar indicating device, for example a picture screen. As can be seen in particular with reference to FIG. 4, the measuring head 12 of the invention is provided with a total of four adjustment devices.

The first adjustment device 38 consists of a bottom or bottom element 39 of substantially non-conductive material, provided that this bottom element has an electrically conductive coating 40 . A threaded rod 41 is attached to the lower surface of the bottom portion 39.
is provided, which rod is connected to the jacket 40 and passes through a threaded hole in the bottom of the casing 30 to the outer ring 4.
It is connected to 2. This wheel can be turned by hand,
When the threaded rod 41 is thereby rotated, the electrically conductive coating 40 of the bottom part 39 is moved into the bottom part of the casing 30 in the axial direction of the casing.

The spacing h1 between the conductive coating and the lower free end 43 of the coil conductor 20 allows adjustment of the resonant frequency of the fundamental vibration mode, ie the lowest frequency at which the measuring head of the invention can resonate.

The second adjusting device 50 consists of an electrically conductive lug 51, one end 52 of which is electrically conductively coupled to the inner surface of the case 30.
For example, it is brazed.

Screws 5 arranged radially through the casing 30
3, the central area or free end of the lug 51
It can be displaced radially.

The screw 53 is located at a distance h2 from the upper edge of the casing 30.

A third adjusting device 55 is arranged to act at an equal distance h2 from the upper edge of the casing 30, and this third adjusting device 55 acts in an open position in a plane radial to the coil conductor 20. It consists of a loop 56. Via an axially extending conductor 57 and a bent radially extending conductor 58, the open loop 56 is fixedly connected to the inner surface of the housing 30, in particular by soldering, and is grounded.

The system formed by the coil conductor 20 and the shield casing 30 is capable of resonating in different vibration modes. In addition to the fundamental modes mentioned, there is a correspondingly large number of relatively high vibrational modes at relatively high resonant frequencies.

For these relatively high vibration modes, the casing 30
A large number of maximum values of the electric field strength occur along the longitudinal axis of the coil conductor 20. However, these additional maxima do not exist for relatively low vibrational modes, especially the fundamental mode. The distance h2 is such that the maximum electric field strength is located in the axial direction of the casing 3.
It corresponds to the distance taken from the upper edge of 0. By the way, by using the second adjusting device, it is possible to continuously apply a maximum value of a relatively high vibration mode by turning the screw 53, while using the third adjusting device, a constant load can be applied.

Thus, by means of one or both of the adjusting devices 50, 55, the resonant frequency of the higher vibrational mode can be reduced by: the ratio of the resonant frequency of the higher vibrational mode to that of the fundamental mode. can be reduced so as to obtain a ratio different from the theoretical value of an odd number of times.

When adjusting that ratio, the frequency ratio of different types of nuclei, e.g. the ratio of protons on the one hand and carbon isotope C13 on the other hand, i.e. approximately 80 M for H1, for example
Hz and 20.1 MHz for C13.

As already mentioned, the coupling of the coil conductor 20 takes place via an insulated conductor 31 to the casing 30, the free end of which is soldered to the uppermost turn of the coil conductor 20. It is attached. As is clear from FIG. 4, the connection points of the conducting wire 31 and the connection points of the ground connection point 28 are evenly spaced at a predetermined angle over the circumference of the uppermost turn 21. Since only a relatively coarse adjustment is possible due to the definition of this angle, the fourth adjustment device 60
(this consists in particular of adjustable capacitors at the leads or short-circuit points) so that a predetermined termination impedance, for example a characteristic impedance of 50 Ω, occurs when looking from the outside into the conductor 31. I can do it. It is clear that instead of a single capacitor it is also possible to use several capacitors in parallel connection as the fourth regulating device, which capacitors effectively form a short circuit for the high frequencies used.

Furthermore, as is clear from Figures 3 and 5, the shield 2
The upper open end of 3 (see FIG. 2) can be closed with a cover 62, which essentially consists of a plastic plate 63. A conductor track 64 is applied to a non-conductive plastic plate 63, which conductor track 64 extends star-shaped, ie in the radial direction, as can be seen in FIG. The conductor track 64 is connected to the electrically conductive housing 30 at the outer edge via a soldering point 65 and extends from the outer edge inwardly towards the center, not even reaching its center and mutually extending. No contact between them.

As is immediately apparent when the right half of FIG. 2 is considered in conjunction with FIG.
is shorted. The cover 62 with the conductor tracks 64 therefore ensures that virtually no leakage fields occur above the support plane 27.

The measuring head 12 described in detail above can be used to perform different operations.

According to the known measurement method of nuclear magnetic resonance tomography, a measuring body 11 is placed inside a magnet system 10 and a measuring head 12 is placed in accordance with FIG. The magnetic lines of force B, which correspond to the left half of FIG. 2, therefore penetrate the measuring body and cause nuclear resonance as long as they extend perpendicularly to the coordinate direction z. By appropriate adjustment of the ratio of constant magnetic field strength and irradiated measurement frequency, different types of nuclei can be excited.

The resulting nuclear resonance generates a signal voltage in the high-frequency circuit of the measuring head 12. At that time, the signal voltage is
6 and converted into a corresponding spectral signal (this is known).

By adjusting the attenuator 35, the distribution of high-frequency magnetic field strength inside the measuring body 11 can be adjusted as follows.
In 1, a high frequency magnetic field strength is generated at a predetermined depth d below the mounting plane 27, and the spin measured by this high frequency magnetic field strength can be adjusted so as to be displaced or rotated by exactly 90°. . It is clear that by adjusting the attenuator 35 a selection of the measuring plane in the coordinate direction d can be effected.

Furthermore, the measuring head can be adjusted by means of the adjusting devices 38, 50, 55, i.e. both for relatively high frequencies, corresponding for example to protons, and for relatively low measuring frequencies, for example for C13. resonates (resonance)
You can adjust it as you see fit.

By the way, first, proton resonance is excited by the measurement head 12. Due to the high intensity of the proton signal, a proton spectrum can be observed after each excitation. Means for homogenizing the constant magnetic field, which are not shown in FIG.
him coil), the constant magnetic field can be adjusted under simultaneous observation of the proton spectrum in such a way that the linewidth in the proton spectrum is reduced to a minimum value. For this minimum value the homogeneity of the constant magnetic field is particularly good.

Now, while the measuring head 12 remains in its resting position on the measuring body 11, the measuring electronics 32 is switched to a relatively low frequency corresponding to a nucleus of the C13 type. C13 measurements are therefore carried out with particularly good homogeneity.

Furthermore, the measuring head 12 of FIG. 1 can be used in the simultaneous presence of a high-frequency saddle coil. In that case, the magnetic field lines of the constant magnetic field, the high-frequency field from the measuring head 12 and the high-frequency field from the saddle coil are respectively perpendicular to each other.

Decoupling field using high frequency saddle coil,
For example, a decoupling field for protons can be applied to the measuring body 11, while for example a (proton-decoupled) C13 nuclear resonance spectrum is simultaneously detected by the measuring head 12 itself. Due to the respective high-frequency field direction of the decoupling field and the perpendicular orientation of the measuring field, a particularly reduced interference radiation from the high-frequency saddle coil into the measuring head 12 of the invention results. This is because the shielding 23 on practically either side additionally provides a sharp separation between the decoupling circuit and the measuring circuit.

Effects of the Invention The advantage obtained by the measuring head of the present invention is that only the magnetic lines of force are irradiated to the outside by the coil conductor, while the electric lines of force are exclusively confined between the coil conductor and the shield, that is, in the internal space thereof. It means that it acts outward only on an incidental scale. Electrical losses in the area under test therefore occur only to a negligible extent. Another advantage is that the coil conductor, due to its structure, can be excited in multiple vibrational modes at different frequencies, so that the measurement head of the invention can be used to detect the nuclear resonance of various types of nuclei without having to replace the measurement head. can be used in a wide frequency range that enables excitation of Therefore, the nuclear resonance spectra of various types of nuclei can be detected in immediate sequential time order using one measuring head placed on the subject. This allows, on the one hand, one and the same analyte region to be acquired for the spectra of various nuclei, and on the other hand, the entire measurement to be completed within the shortest possible time. This advantage just mentioned also provides significant economic advantages. This is because medical-diagnostic nuclear resonance equipment is expensive to procure and it is a great advantage to amortize the cost of this type of equipment over as many measurements as possible. With a suitable design of the measuring head of the invention, it can for example be inserted into a surgically opened body and placed in an exposed organ. It can also be exposed, for example in animal experiments, so that the organs can be placed on the measuring head cover.

Furthermore, an important advantage achieved by the measuring head of the invention is that due to the shielding surrounding the coil conductor, on the one hand, virtually no interference radiation is emitted to the outside, in particular because the electric field is confined inside the shield. Furthermore, the measurement result cannot be influenced in a corresponding manner by disturbing radiation penetrating from the outside, especially since inside the shield the electrical coupling of the closed field lines towards the outside is substantially This is because it cannot be done legally.

[BRIEF DESCRIPTION OF THE DRAWINGS] FIG. 1 is a spatial three-dimensional view of a spectrometer device in which the measuring head of the present invention is used, and FIG. 2 is a cross-sectional view of the measuring head of the present invention for explaining the resulting field distribution. 3 is a conceptual diagram showing a specific embodiment of the measuring head of the present invention together with a necessary electronic evaluation device, and FIG.
FIG. 5 is a plan view of the embodiment of the measuring head of the present invention shown in FIG. 3; FIG. DESCRIPTION OF SYMBOLS 10... Magnet system, 11... Test object, 12... Measurement head, 13... Lead wire, 14... Helmholtz coil, 20... Coil winding, 23... Shield,
30...Casing, 39...Bottom or bottom element.

Claims (14)

[Claims] 1. A measurement head for high-resolution nuclear resonance measurement in a predetermined spatial region of the subject, the transmitting and receiving device having a transmitting and receiving device that can be placed on a subject placed in a homogeneous constant magnetic field. is configured as a coil conductor (20) with a coaxial shield (23), said coaxial shield (23) being open at least at one end (25), and the lower end of the coil conductor (20) being connected. The uppermost turn (body) of the coil conductor (20), which has no part and is connected to the shield (23) via the connection part (28), is located approximately in the plane of the open upper end, where A measuring head for the detection of high-resolution nuclear resonance signals, characterized in that it forms a mounting plane (27). 2. 2. Measuring head according to claim 1, wherein the other end (26) of the shield (23) is closed, so that the measuring head (12) forms a λ/4 resonator. 3. The open end (25) forming the support plane (27) is covered with a cover (62) made of electrically non-conductive material, the cover (62) having a number of radially extending conductor tracks (
64), the outer ends of the conductor tracks transition into the casing (30) forming the shield (23), the inner ends of which, without touching, converge in the central area of the cover (62). A measuring head according to claim 1 or 2. 4. A first adjustment device (38) is provided in which the electrical distance h1 between the free end (43) of the coil conductor (20) and the other end (26) of the closed coaxial shield (23) is variable. A measuring head according to claim 2 or 3. 5. The first adjusting device (38) has a bottom or bottom element (39).
), which element has an electrically conductive coating (40) and is configured in accordance with the radial cross-sectional shape of the shield (23), said bottom element comprising a casing (30) forming the shield (23). 5. Measuring head according to claim 4, which can be screwed on. 6. Another same adjustment device (50, 55) is provided in which the electric field E produced by the coil conductor (20) is applied at a predetermined point in the axial direction, at which the electric field E is equal to one predetermined point. The measuring head according to any one of claims 1 to 5, which takes the maximum value only in the vibration mode. 7. A second adjusting device (50) is provided between the coil conductor (20) and the shield (23), the second adjusting device having a conductive lug (51) and one end of the lug connecting the shield (23). 7. Measuring head according to claim 6, which is connected to the forming casing (30) and whose other end is radially displaceable. 8. 7. Measuring head according to claim 6, wherein the third adjustment device (55) is provided in the internal space of the coil conductor (20). 9. The third adjusting device (55) has an open loop (56) with a plane arranged transversely to the axis of the coil conductor (20), which loop is connected to a casing (30) forming a shield (23). 9. Measuring head according to claim 8, which is connected on one side. 10. A measuring head according to any one of claims 1 to 9, wherein the second adjustment device (60) is arranged at the connection between the coil conductor (20) and the shield (23). 11. 11. Measuring head according to claim 10, wherein the fourth adjusting device (60) is formed from an adjustable capacitor. 12. 12. Measuring head according to claim 1, wherein the coil conductor (20) is connected to a high-frequency transmitter (34) of adjustable amplitude. 13. First, a relatively high-frequency vibration mode under which proton-nuclear resonance occurs is excited in the coil conductor (20), and under the observation of one line of the proton-nuclear resonance spectrum, the homogeneity of a constant magnetic field is determined. is optimized and then other nuclear types such as C13, P31, Na
The measurement head according to any one of claims 1 to 12, wherein the measurement head shifts to a low frequency vibration mode in which 23 occurs, and further measures nuclear resonance signals of other types of nuclei. 14. The first irradiation of the high-frequency field is carried out on the area using a high-frequency sheet coil (saddle coil), for example for anti-vibration of proton resonance, and then the measurement head (
12) is placed on the subject's body (11) in a direction perpendicular to the plane of the planar coil, for example, for measurement of nuclei of other species. Measuring head described in any of the above.