DE102010024432A1 - Local coil for use in magnetic resonance device for patient, has conductor loops arranged opposite to each other along offset directions, where part of conductor loops is designed for balancing offset such that rows of loops end on lines - Google Patents

Abstract

The coil (1) has antenna-conductor loops (3, 3A, 3E) arranged in adjacent rows (SR-1, SR-2, SR-3) and inductively decoupled from each other by a geometric overlap. The conductor loops are arranged opposite to each other along alternating offset directions (R1-R3) such that an overlapping area (Ux) of the conductor loops of one of the rows is arranged offset to an overlapping area of the conductor loops of other row. A part of the conductor loops is designed for balancing the offset such that the adjacent rows of the loops end on lines (L1, L2) transverse to the offset directions. Independent claims are also included for the following: (1) a method for designing a local coil (2) a method for measuring magnetic resonance signals.

Description

The invention relates to a local coil for a magnetic resonance apparatus having a magnetic resonance antenna array, which comprises a plurality of antenna conductor loops arranged in parallel adjacent rows. Furthermore, the invention relates to a magnetic resonance apparatus with such a local coil, a method for setting up a local coil and a method for measuring magnetic resonance signals.

In the magnetic resonance examination of certain organs or body parts of a patient, so-called surface antennas are used to receive the magnetic resonance signals (MR signals) and possibly also to emit the radio-frequency signals required to excite the nuclear spins. During the examination, these surface antennas are arranged relatively close to the organ or body part to be examined, preferably directly on the body surface of the patient. Because they are located closer to the regions of interest, these surface antennas, unlike remote patient-mounted antennas, have the advantage of having a larger fill factor. As a result, the useful signal is attenuated less and reduces the noise caused by the electrical losses within the body of the patient, with the result that the so-called signal-to-noise ratio (SNR) is in principle better than in a remotely located antenna. A disadvantage, however, is that a single surface antenna is only able to produce an effective image within a certain spatial extent, which is of the order of the diameter of the conductor loop of the surface antenna. Therefore, the applications for such individual surface antennas are very limited because of the limited observation area. Although the observation area can be expanded by increasing the diameter of the conductor loop of the surface antenna. With the enlargement of the conductor loop but at the same time again an increase in the electrical losses in the body of the patient and associated greater noise is connected. When using a single surface antenna, therefore, a middle path between the best possible resolution on the one hand and the widest possible observation range on the other must always be chosen.

One way to increase the viewing area without reducing resolution to the same extent is to use a so-called local coil with a magnetic resonance antenna array comprising a plurality of individually operable antenna conductor loops disposed in adjacent rows.

The individual antenna conductor loops of the antenna array are usually designed as simple loops with shortening capacitors arranged therein. But it can also be other types of conductor loops, for example, with multiple turns, so-called butterfly loops or saddle coils. Usually, such a local coil in addition to the antenna array also has one or more preamplifiers, a wiring that leads from the housing of the local coil to a connector with which the local coil can be connected to the receiving system of the magnetic resonance system, and possibly other electronics within it housing the Local coil or on the cable, such as sheath wave barriers etc.

The exact geometry of the individual antenna elements within such a local coil is crucial for the application width, d. H. for which purposes the local coil can be used, for the image quality, in particular the SNR, and the possibilities for measuring time reduction through the use of parallel imaging methods. Both the size of the entire local coil, ie. H. the complete antenna array, as well as the geometric design of the individual antenna conductor loops and their position to each other a crucial role. The overall size of the local coil is important as it is the relevant parameter for the illumination. If with a local coil z. B. a liver is to be completely illuminated, the local coil in the z-direction (parallel to the axis of the patient tunnel) and in the x-direction (the second horizontal direction perpendicular to the z-direction in the system coordinate system) must be dimensioned accordingly. The size of the individual antenna conductor loops is important because smaller antenna conductor loops have a stronger SNR rise in their vicinity than large antenna conductor loops. The number of antenna conductor loops is critical in parallel imaging methods because they rely on using the spatial limitations of the profiles of the individual antenna conductor loops. Namely, the individual antenna conductor loops inherently provide a spatial coding in this method, which can be used in the parallel imaging method. Acceleration in parallel imaging is accomplished by omitting phase encoding steps. In order to nevertheless be able to produce an image from such a "subsampled" k-space, the local coil must have several antenna conductor loops in the phase coding direction. The more antenna conductor loops the local coil has in the phase coding direction, the higher the acceleration factors can be realized and the shorter the measuring time.

A problem with the use of such an antenna array, however, is that a high-frequency current in an antenna array Conductor loop can induce a voltage in an adjacent antenna conductor loop. This is commonly referred to as inductive coupling of the antenna conductor loops. The inductive coupling means that a signal generated in one of the adjacent antenna conductor loops automatically also causes a signal component in the adjacent antenna conductor loop. The inductive coupling thus degrades the signal-to-noise ratio. In addition, the effort in evaluating the signals of coupled antenna conductor loops is greater than in non-coupled antenna conductor loops. Therefore, an inductive coupling of the antenna conductor loops should be avoided as far as possible.

One way to decouple adjacent antenna conductor loops is to overlap the adjacent antenna conductor loops by a certain amount so that the inductive coupling between the respective antenna conductor loops is minimal overall.

Such "geometric" or "inductive" decoupling is readily possible when dealing with antenna conductor loops that are immediately adjacent to each other within a row or column of the antenna array. The problem, however, is the decoupling of conductor loops which adjoin diagonally in adjacent rows and columns. Thus, an overlap of the diagonally adjacent conductor loops would mean that a central area of four conductor loops is covered at the same time. This leads in these areas to an undesirable signal increase, which u. U. can lead to artifacts.

Therefore, currently in practice surface antennas are usually used with antenna arrays in which the diagonally adjacent conductor loops are not decoupled within the antenna array, but in which only by a sufficient distance between the conductors of the diagonally adjacent antenna conductor loops and by appropriate decoupling of The antennas arranged preamplifier is trying as well as possible to achieve a decoupling.

Another possibility for decoupling would be the use of so-called wound transformers for the decoupling of adjacent or diagonal antenna conductor loops. For this purpose, a part of the individual antenna conductor loops is wound several times, and these wound transformer then superimpose an adjacent coil. However, this leads to additional rigid areas within the antenna conductor loops, so that this reduces the flexibility of the local coil. However, as flexible a local coil as possible is desirable in order to achieve optimum molding on the body of the patient. Even with a decoupling by additional discrete circuit elements additional rigid areas would arise within the local coil.

It is therefore an object of the present invention to further develop a local coil in such a way that the individual antenna conductor loops are decoupled from one another in a simple manner and yet the local coil can be flexibly adapted to an examination object, for example a patient's body or test subjects, with the optimum illumination area possible ,

This object is achieved by a local coil according to claim 1 and by a method for constructing a local coil according to claim 13.

In the case of a local coil according to the invention, both the antenna conductor loops adjacent to one another in a row and the antenna conductor loops adjoining one another in adjacent rows are each inductively coupled to one another by a geometrical overlap. Ie. All antenna conductor loops arranged adjacently to one another overlap in a boundary region by a certain amount. In this case, the rows of antenna conductor loops are offset in alternating offset directions, in each case parallel to a longitudinal direction of the rows of antenna conductor loops, in such a way that an overlapping region of two antenna conductor loops of one row leads to an overlapping region of two antenna conductor loops of an adjacent row offset, d. H. spaced from each other, is arranged. In this way it is ensured that overlapping areas of adjacent rows do not overlap and thus a maximum overlap of three antenna conductor loops occurs. Nevertheless, all individual antenna conductor loops, which adjoin one another, are inductively decoupled from one another by an overlap. The offset is done for this purpose preferably by a certain offset dimension corresponding to a part of an antenna conductor loop. Particularly preferably, the rows are mutually offset by half an antenna conductor loop.

According to the invention, at least a part of the antenna conductor loops to compensate for the offset is so formed that they rewrite different areas and thereby adjacent rows of antenna conductor loops in the offset direction front and back substantially on a line transverse to the offset direction.

The inventive combination of the design and arrangement of the invention individual antenna conductor loops within the magnetic resonance antenna array is achieved on the one hand that all antenna conductor loops are purely inductively decoupled from each other, without additional elements are required, which limit the local coil in their flexibility. The above-described problem that certain areas in the local coil of four antenna conductor loops are covered simultaneously and can lead to an undesirable signal increase, is thereby avoided. Nevertheless, it is ensured that the local coil as a whole has a simple geometric illumination area, for example a rectangular illumination area as usual, and in particular the greatest possible illumination, based on the external dimensions of the local coil, is achieved.

The geometry and size of the overlapping surfaces are chosen so that the inductive coupling between the respective overlapping antenna conductor loops is minimal. By connected with minimal effort purely inductive decoupling of both the conductor loops in a row and the adjacent conductor loops in adjacent rows and a particularly cost-effective design of the local coil is achieved. Thus, since in principle no additional external conductor loop elements are required and no quadruple overlap of individual antenna conductor loops is required, these antenna arrays can be produced with conventional printing or etching methods simply on two opposite sides of a conductor foil. It is only necessary that the conductor loops are printed in sections on the different sides of the conductor foil and at certain points a through-hole is made in order to achieve a crossover between the conductor loops of adjacent rows.

In addition, the simple construction results in the desired flexibility with a still increased mechanical stability and robustness, which is of considerable value in the practical use of these local coils.

In the method according to the invention for constructing such a local coil, it is already ensured during the production of the antenna conductor loops, for example in the case of an imprint on a conductor foil, that all antenna conductor loops are applied in such a way that antenna conductor loops adjoining each other are in each case geometrically overlapped are inductively coupled from one another, wherein the rows of antenna conductor loops are offset in alternating offset directions against each other so that an overlapping region of two antenna conductor loops of a row is offset to an overlapping region of two antenna conductor loops of an adjacent row. In addition, the design of the antenna conductor loops is such that at least a portion of the antenna conductor loops to compensate for the offset are formed so that they rewrite different areas and thereby transverse adjacent rows of antenna conductor loops in the offset direction front and rear substantially in a line to the offset direction end.

Such a local coil can basically be used in a wide variety of types of magnetic resonance apparatus, i. H. Both in magnetic resonance devices with a cylindrical all-round, open on the open side patient space as well as in magnetic resonance devices with three-sided open patient space. Likewise, an application in a wide variety of types of magnetic resonance devices with different magnetic field strengths is possible.

An inventive method for measuring magnetic resonance signals is characterized in that for this purpose a local coil according to the invention is used. However, the local coil can be used not only for receiving magnetic resonance signals, but also for transmitting high-frequency signals to stimulate the generation of magnetic resonance signals.

The dependent claims and the further description contain particularly advantageous embodiments and further developments of the invention, wherein in particular the claims of one category can also be developed analogously to the claims of one of the other categories.

In a preferred variant, the shape of the individual antenna conductor loops is selected such that at least in some of the rows, the antenna conductor loops lying in the offset direction and / or the antenna conductor loops lying in the offset direction offset the offset. In such a construction, for. B. every other row be designed so that each front and rear, the antenna conductor loops are larger or smaller, so that in every second row of the offset is compensated and all other antenna elements are the same.

In a very particularly preferred variant, an edge-antenna conductor loop with a larger area is alternately provided on opposite sides of the local coil in each row, transverse to the offset direction of the rows of antenna conductor loops, than the other antenna conductor loops of the row. In two mutually shifted in the same direction of offset rows, ie at every next but one row are in this Variant so the edge antenna conductor loops are the same design.

If, for example, all other antenna conductor loops have essentially the same external dimensions, and in each case an offset of the rows takes place alternately by half the width of an antenna conductor loop in the longitudinal direction, the first edge antenna conductor loop only has to be disposed on every other row on opposite sides in the offset direction one and a half times as wide as the other antenna conductor loops of the series. This automatically results in the entire antenna array being able to cover a substantially rectangular area while still achieving the desired offset between the individual rows of antenna conductor loops and thus the required decoupling.

In order to achieve maximum flexibility of such a local coil in its application, it is advantageous if the local coil - as already mentioned above - can be positioned in any direction on the examination subject. Therefore, in a preferred variant, the local coil has a position detection device for determining an orientation of the local coil in the room with respect to at least two spatial directions. If the location of the local coil in space is thus recognized, then this position information can be transmitted to the magnetic resonance system so that the position of the individual antenna conductor loops in the room can be taken into account in the later evaluation of the signals.

For this purpose, the local coil particularly preferably has a magnetic field sensor device for measuring a magnetic field in which the local coil is located, wherein the magnetic field can be determined in at least two spatial directions. For example, this may be a suitable arrangement of Hall probes with associated electronics. It can then be used the B ₀ -Grundfeld the magnet to determine the coil orientation in space and forward them to the magnetic resonance system as position information.

In another alternative embodiment, the local coil is provided, for example, with markers that can be recognized by an optical detection device of the magnetic resonance device in order to determine the position. Conversely, the local coil can also be equipped with an optical detection device in order, for example, to identify markers within the patient's space of the magnetic resonance apparatus and to determine its own position from this. Furthermore, it is also possible to determine the position with the aid of a plurality of radio signals which are transmitted by different points.

As already explained above, a large number of individually controllable antenna conductor loops require corresponding space in order to accommodate the associated electronics. Such electronic components include, for example, suitable preamplifiers to bring the received signal to a certain level. In more recent products, the magnetic resonance signal can also be converted to an intermediate frequency within the local coil. A receiver mounted in the magnetic resonance system then filters and digitizes the signal received by the local coil and transmits the data of the digital signal processing, which then derives an image or a spectrum from the measurement, which can then be made available to the user, for example for diagnosis , It would also be conceivable to carry out the digitization already within the local coil.

However, all of these electronic components make a coil mechanically heavy and relatively rigid. In order to achieve sufficient flexibility, preferably predetermined groups of adjacent antenna conductor loops of the magnetic resonance antenna array are each assigned locally arranged electronic assemblies which pre-process the signals received from the associated antenna conductor loops. These "electronics clusters" can each have their own small housing. For example, two adjacent antenna conductor loops in a row are preferably assigned their own electronics cluster. Such a solution, with smaller electronic assemblies instead of a large electronic assembly, allows great mechanical flexibility of the local coil in two directions.

In a particularly preferred variant, an electronic module has a multiplexer device, i. H. a suitable multiplexing circuit arrangement, in order to superimpose signals received from different antenna conductor loops in a multiplexing method for transmission to a receiving unit of the magnetic resonance apparatus. The use of a multiplexing method reduces the cables required for transmission within the local coil or from the local coil to the receiving system of the magnetic resonance apparatus.

This is preferably done in a frequency division multiplex method. For example, if two adjacent antenna conductor loops belonging to one electronics cluster are superimposed, two sidebands of the transmission frequency can be used and the magnetic resonance signals of one antenna conductor loops are transmitted on one sideband and those of the other antenna conductor loop on the other sideband.

Preferably, the cables leading to different electronic assemblies are brought together in a central coil, preferably a central electronic module, in the local coil. From there they can then be continued by a common connecting cable to connect the local coil to a receiving device of the magnetic resonance device.

In order to achieve the highest possible acceleration factors, the local coil particularly preferably has a magnetic resonance antenna array with three rows of antenna conductor loops. Particularly preferably, six antenna conductor loops are arranged in each row. That is, the local coil then has a total of eighteen individual antenna conductor loops. When using a magnetic resonance antenna array with three rows of antenna conductor loops so the middle row is shifted from the two outer rows.

Up to now, anterior abdominal coils with 3 × 2 antenna conductor loops or with 4 × 4 antenna conductor loops have been used in practice. With these local coils, acceleration factors of AF = 4 are hardly clinically usable, since the SNR degradation in the parallel imaging with AF = 4 and only four antenna conductor loops in the phase encoding direction often provides no usable results. In addition, the antenna conductor loops are relatively rigid and can not be adapted well to the anatomy of the patient, especially in the abdomen area. For cardiac imaging, acceleration factors of AF = 3 to 4 are required to reduce the relatively long measurement times. The previous long measurement times are one of the reasons why cardiac examinations are performed only with a relatively small proportion of magnetic resonance systems and radiologists often prefer other examination methods.

By means of a locally constructed local coil with three rows of six antenna conductor loops and the nevertheless achieved flexibility, acceleration factors of AF = 4 can also be produced with very good clinically utilizable quality. Possibly. Depending on the specific application, even higher acceleration factors of AF = 5 or AF = 6 can be achieved.

Preferably, the antenna conductor loops are designed so that they essentially circumscribe an octagonal area, with the most preferred embodiment being the transverse and longitudinal direction of the offset direction, ie H. which are perpendicular to the longitudinal direction of the rows and longitudinal sides longer than the obliquely extending sides of the antenna conductor loops. This octagonal shape has the advantage that the conductor track sections, at which the tracks of adjacent antenna conductor loops intersect to form the overlap areas, meet perpendicularly at the point of intersection. This minimizes the coupling between the conductor loops.

In a particularly preferred variant, the antenna conductor loops have a width between 5 cm and 30 cm transversely to a longitudinal direction of the antenna conductor loop rows. In the longitudinal direction of the rows, the antenna conductor loops particularly preferably have a width between 5 cm and 30 cm. If the variant of an antenna array is selected in which only one edge antenna element is alternately larger on every other row on opposite sides, this is approximately one and a half times as wide as the remaining antennas, for example, with an offset of half the antenna conductor loop width Conductor loops in the row.

The invention will be explained in more detail below with reference to the accompanying figures with reference to embodiments. Show it:

1 1 is a schematic representation of an embodiment of a local coil according to the invention with an antenna array with eighteen antenna conductor loops,

2 a plan view of an embodiment of a local coil according to the invention with an antenna array as in 1 ,

In the 1 shown local coil 1 has a total of three rows SR ₁ , SR ₂ , SR ₃ , each with six individual antenna conductor loops 3 . 3A on. The rows SR ₁ , SR ₂ , SR ₃ extend in the longitudinal direction of the local coil 1 , in the 1 is in the x / z plane of the coordinate system of the magnetic resonance tomography device and is aligned with its longitudinal direction in the x direction. In principle, however, the local coil can be positioned as desired. Nevertheless, in the following, for the sake of simplicity, the spatial directions x, y in 1 With reference made, without limiting the invention thereby.

The individual antenna conductor loops 3 . 3A each have a conductor track, which describes an octagonal shape with four longer sides and four longer sides diagonally connecting shorter sides (hereinafter also called "corner sections"). The longer sides run parallel to the outer edges of the local coil 1 ie in 1 in x-direction and z-direction. On the longer sides, the conductor strips are each interrupted. At these interruptions C acting as shortening capacitors capacitive elements (not shown) are arranged.

Within a row SR ₁ , SR ₂ , SR ₃ each adjacent antenna conductor loops overlap 3 . 3A . 3E around a certain overlap area U _X whose size is chosen so that the respective antenna conductor loops 3 . 3A . 3E as well as possible are inductively decoupled from each other. So that two adjacent antenna conductor loops 3 . 3A . 3E can form the overlap region U _X , each cross the interconnects of the octagonal antenna conductor loops 3 . 3A . 3E in the diagonal corner sections.

The tracks of the antenna conductor loops 3 . 3A . 3E are each printed in the form of copper strips in a conventional manner on a flexible conductor foil, wherein the conductor tracks of an antenna conductor loop 3 . 3A . 3E partially printed on the front side and partly on the back of the conductor foil and are each connected by plated through. This ensures that the tracks of various adjacent antenna conductor loops 3 . 3A . 3E can cross over each other in isolation without further effort.

Each of the antenna conductor loops 3 . 3A . 3E is also provided in a conventional manner with elements (not shown), such as switching devices such as pin diodes or the like, to the antenna conductor loop 3 . 3A . 3E to bring out of resonance, ie to detune, if the respective antenna conductor loop 3 . 3A . 3E should not receive. This is the case, for example, when a magnetic resonance signal is being emitted by other antennas. In this case, a resonant antenna conductor loop would directly receive the magnetic resonance signal and lead to disturbances in the excitation.

As in 1 As can be seen, the rows are SR ₁ , SR ₂ , SR ₃ of antenna conductor loops 3 . 3A . 3E are set so close in the z-direction that they also overlap, and the middle row SR ₂ is opposite to the two outer rows SR ₁ , SR ₃ in a direction parallel to the longitudinal direction, ie in 1 shifted in the x direction, extending offset direction R2 and the two outer rows SR ₁ , SR ₃ are in the opposite direction of offset R ₁ , R ₃ relative to the middle row SR ₂ shifted. The offset of the rows SR ₁ , SR ₂ , SR ₃ against each other is chosen so that the antenna conductor loops 3 are offset by half conductor width b _x in the offset direction R ₁ , R ₂ , R ₃ . In this way, also the overlapping areas U _X between adjacent antenna conductor loops 3 . 3A . 3E a row opposite the overlapping areas U _{X of} an adjacent row SR ₁ , SR ₂ , SR ₃ offset from each other.

As a result, it is possible for the adjacent rows SR ₁ , SR ₂ , SR ₃ to overlap in each case by an overlapping area U _Z without resulting in an overlap of four individual antenna conductor loops 3 . 3A . 3E comes. At most, three antenna conductor loops overlap here 3 . 3A . 3E namely, always two adjacent antenna conductor loops in a row 3 . 3A . 3E with an adjacent antenna conductor loop 3 . 3A . 3E the side row.

To still ensure that the entire antenna array 2 Apart from the corners and small notches 9 at the boundary between two antenna conductor loops 3 . 3A . 3E , circumscribes a substantially rectangular outer shape and thus also has a nearly rectangular illumination profile, have the edge-antenna conductor loops 3A . 3E each at the beginning and end of a row SR ₁ , SR ₂ , SR ₃ a slightly different shape than the middle antenna conductor loops 3 on.

In particular, each of the three rows SR ₁ , SR ₂ , SR ₃ circumscribes the first antenna conductor loop, viewed in the respective offset direction R ₁ , R ₂ , R ₃ 3A a larger area, namely about one and a half times as large area as the middle antenna conductor loops 3 , This ensures that all rows SR ₁ , SR ₂ , SR ₃ on both sides of the local coil 1 (transverse to the row longitudinal direction, ie in the z direction in 1 ) each end on a line L ₁ , L ₂ .

The each at the offset direction R ₁ , R ₂ , R ₃ at the end lying edge-antenna conductor loop 3E is with respect to its octagonal shape in each row at their respective to the outer edge of the local coil 1 facing side slightly adapted to an optimal overlap with the enlarged first edge antenna element 3A to reach the adjacent row, in particular, so that the intersection between the adjacent conductor loops is again in the middle of the corner sections of the octagon.

Two neighboring antenna conductor loops each 3 . 3A . 3E Here are a separate electronics cluster 4 . 4M assigned. This electronics cluster 4 . 4M is in each case in the overlapping area U _{X of} the two antenna conductor loops 3 . 3A . 3E arranged. In this electronics cluster 4 . 4M Each is a board with the necessary electronic components, in particular two preamplifiers 6 housed to that of the associated antenna conductor loops 3 . 3A . 3E amplify and preprocess received magnetic resonance signals. Also the elements for detuning the antenna conductor loop 3 . 3A . 3E For example, the pin diodes may be in the electronics cluster 4 . 4M be housed on the board. In particular, each of these electronics clusters has one Multiplexer circuitry 5 which serves the purpose of the two antenna conductor loops 3 . 3A . 3E superimpose incoming signals in a frequency division multiplexing. In this way, the signals of both antenna conductor loops 3 . 3A . 3E via a common cable 7 from the electronics cluster 4 be carried away. For this purpose, a thin single, coaxially shielded cable is sufficient 7 with an outer diameter of about 1 to 1.1 mm. All of these cables 7 become a central electronics cluster 4M guided. Here are the individual cables 7 in a hunt group 8th brought together and from there in a thick connection cable 13 , which again has an outer shield around all individual cables, led to the receiving system of the magnetic resonance system. This will be explained later on 2 explained.

In addition, two Hall probes H _x , H _z with suitable evaluation electronics are arranged in the central electronics cluster 4M in order to measure a magnetic field in the two spatial directions x, z, in which the local coil 1 currently located. In this way, with the aid of the basic magnetic field applied in the magnetic resonance system, the orientation of the local coil 1 be determined. This can then also be transferred via a control cable to the receiving system of the magnetic resonance system, so that there the orientation of the local coil can be taken into account within the magnetic resonance device. This is important to allow the individual antenna conductor loops 3 . 3A . 3E be properly associated with their location. In addition, from the central electronics cluster 4M Pass identity information to the receiving system of the magnetic resonance system, based on which the system the exact type of local coil 1 and identify their design so as to be able to correctly process the signals transmitted by the local coil, in particular, for example, also to correctly demultiplex the transmitted signals. This information, such as a unique identity and / or type code, is stored in a memory (not shown) in the central electronics cluster 4M deposited.

2 shows the outer structure of the local coil 1 , Here it can be seen that the individual electronics clusters each in separate housings 11 which are in a housing 10 of the magnetic resonance antenna array 2 the local coil 1 are integrated. This case 10 (in 1 the external contours are shown) is flexible, for example made of a soft foam, whereas the individual housing 11 the electronics cluster are rigid. The housing 10 the local coil 1 also has a large number of recesses 17 on which for even greater flexibility of the local coil 1 to care.

In 2 is also shown that the case 11M of the central electronics cluster 4M with a connector 12 for the connection cable 13 is provided. At a junction 15 is this connection cable 13 with the connector 12 releasably connected. At its free end is the connection cable 13 with a connector 14 provided with the connecting cable 13 can be connected to the receiving system of the magnetic resonance system.

As already mentioned, the connection cable points 13 a variety of single cables, which are from the individual electronics clusters 4 . 4A come, ie a total of nine individual cables, the superimposed in the frequency multiplex magnetic resonance signals from two individual antenna conductor loops 3 . 3A . 3E transmitted, as well as at least one communication line on what information from the local coil 1 be transferred to the magnetic resonance system, such as the current orientation and / or the identification information. In addition, the connection cable contains 13 at least one control line with which the magnetic resonance system z. As the pin diodes or similar switching devices within the antenna conductor loops 3 . 3A . 3E can be controlled in order to detune them in the transmission case, when a transmission of magnetic resonance signals by another antenna takes place. The communication line and the control line can be realized with a suitable coding in a physical cable. At certain intervals is the connection cable 13 with standing wave barriers 16 provided to propagate sheath waves on the shield of the connection cable 13 to avoid.

In the present embodiment, the conductor loop width b _{z of} the individual antenna conductor loops 3 . 3A . 3E in z-direction at the maximum point in each case approx. 14.5 cm. Likewise, the conductor loop width b _{x, A is} in the offset direction R ₁ , R ₂ , R ₃ each first edge conductor loops 3A about 14.5 cm. The remaining antenna conductor loops 3 . 3E each have in the longitudinal direction of a conductor loop width b _x of only two-thirds of this conductor loop width b _{x, A of} the first edge-antenna conductor loop 3A on, ie a conductor loop width b _x of 9.7 cm. In principle, however, the invention can be constructed with antenna conductor loops of any size. However, it has been found that this size is particularly advantageous in clinical use.

As the embodiment shown in the figures shows, it is possible by the construction according to the invention to produce a local coil in a very simple and effective manner, which on the one hand has a very high number of individual antenna conductor loops and which a very good and simple complete inductive decoupling all allows mutually adjacent antenna conductor loops at the same time maximum illumination range with respect to the outer dimensions of the local coil and glöeichzeitig allows great flexibility of the local coil.

It is again pointed out at this point that the structure shown concretely in the figures is only an exemplary embodiment and that the basic principle of the antenna array designed according to the invention can also be varied without departing from the scope of the invention as far as it is concerned the claims are given. For the sake of completeness, it is also pointed out that the use of indefinite articles does not exclude "a" or "one", that the characteristics in question can also be present multiple times.

LIST OF REFERENCE NUMBERS

1

local coil

2

Magnetic resonance antenna array

3

Antenna conductor loop

3A

first edge antenna conductor loop

3E

last edge antenna conductor loop

4

electronics assembly

4M

central electronic module

5

Multiplexer circuitry

6

preamplifier

7

electric wire

8th

hunt

9

notch

10

Housing of the local coil

11

Housing of the electronics cluster

11M

Housing of the central electronics cluster

12

joint

13

connection cable

14

connector

15

junction

16

Standing wave trap

17

recess

C

interruption

L ₁ , L ₂

line

R ₁ , R ₂ , R ₃

offset direction

SR ₁ , SR ₂ ,

SR3 Row of antenna conductor loops

x, z

spatial direction

b _x, b _z b _{x, A}

Conductor loop width

U _X , U _Z

overlap area

H _X , H _Z

Hall probe

Claims (15)

Local coil ( 1 ) with a magnetic resonance antenna array ( 2 ), which a plurality of in adjacent rows (SR ₁ , SR ₂ , SR ₃ ) arranged antenna conductor loops ( 3 . 3A . 3E ), wherein mutually adjoining antenna conductor loops ( 3 . 3A . 3E ) are each inductively decoupled from each other by a geometric overlap (U _X , U _Z ), wherein the rows (SR ₁ , SR ₂ , SR ₃ ) of antenna conductor loops ( 3 . 3A . 3E ) in alternating offset directions (R ₁ , R ₂ , R ₃ ) are offset from one another such that an overlapping region (U _X ) of two antenna conductor loops ( 3 . 3A . 3E ) of a row (SR ₁ , SR ₂ , SR ₃ ) to an overlapping area (U _X ) of two antenna conductor loops ( 3 . 3A . 3E ) of an adjacent row (SR ₁ , SR ₂ , SR ₃ ) is arranged offset, and thereby at least a part of the antenna conductor loops ( 3 . 3E . 3A ) are adapted to compensate for the offset so that they rewrite different areas and thereby adjacent rows (SR ₁ , SR ₂ , SR ₃ ) of antenna conductor loops ( 3 . 3A . 3E ) in the offset direction (R ₁ , R ₂ , R ₃ ) at the front and rear substantially on a line (L ₁ , L ₂ ) transverse to the offset direction (R ₁ , R ₂ , R ₃ ). Local coil according to Claim 1, characterized in that, at least in the case of a part of the rows (SR ₁ , SR ₂ , SR ₃ ), the antenna conductor loop in front in the offset direction (FIG. 3A ) and / or in the offset direction at the end of the antenna conductor loop ( 3E ) compensate the offset. Local coil according to claim 2, characterized in that alternately on opposite, transversely to the direction of offset (R ₁ , R ₂ , R ₃ ) of the rows (SR ₁ , SR ₂ , SR ₃ ) of antenna conductor loops ( 3 . 3A . 3E ) lying sides of the local coil ( 1 ) in each row (SR ₁ , SR ₂ , SR ₃ ) an edge antenna conductor loop ( 3A ) a larger area than the other antenna conductor loops ( 3 . 3E ) of the series (SR ₁ , SR ₂ , SR ₃ ). Local coil according to one of Claims 1 to 3, characterized by a position detection device (H _X , H _Z ) for determining an orientation of the local coil ( 1 ) in space, with respect to at least two spatial directions (x, z). Local coil according to one of Claims 1 to 4, characterized by a magnetic field sensor device (H _X , H _Z ) for measuring a magnetic field in which the local coil ( 1 ), in at least two spatial directions (x, z). Local coil according to one of Claims 1 to 5, characterized in that in each case one group of adjacent antenna conductor loops ( 3 . 3A . 3E ) a locally arranged electronic assembly ( 4 . 4M ) associated with the associated antenna conductor loops ( 3 . 3A . 3E ) preprocessed received signals. Local coil according to claim 6, characterized in that an electronic assembly ( 4 . 4M ) a multiplexer device ( 5 ) of various antenna conductor loops ( 3 . 3A . 3E ) to superimpose received signals in a multiplexing process, preferably frequency multiplexing. Local coil according to claim 6 or 7, characterized in that to various electronic assemblies ( 4 ) leading cables ( 6 ) at a central station, preferably a central electronic module ( 4M ), in the local coil ( 1 ) are merged. Local coil according to one of Claims 1 to 6, characterized in that the magnetic resonance antenna array has three rows (SR ₁ , SR ₂ , SR ₃ ) of antenna conductor loops ( 3 . 3A . 3E ) and / or that in each row (SR ₁ , SR ₂ , SR ₃ ) six antenna conductor loops ( 3 . 3A . 3E ) are arranged. Local coil according to one of Claims 1 to 9, characterized in that the antenna conductor loops ( 3 . 3A . 3E ) essentially describe an octagonal area. Local coil according to one of Claims 1 to 10, characterized in that the antenna conductor loops ( 3 . 3A . 3E ) transverse to a longitudinal direction of the rows (SR ₁ , SR ₂ , SR ₃ ) of antenna conductor loops ( 3 . 3A . 3E ) have a conductor loop width (b _z ) between 5 cm and 30 cm and / or that the antenna conductor loops ( 3 . 3A . 3E ) in the longitudinal direction of the rows (SR ₁ , SR ₂ , SR ₃ ) have a conductor loop width (b _x , b _{x, A} ) between 5 cm and 30 cm. Local coil according to one of Claims 1 to 11, characterized in that the magnetic resonance antenna array ( 2 ) in a housing ( 10 ) is arranged made of flexible material Magnetic resonance apparatus with a local coil ( 1 ) according to one of claims 1 to 12. Method for constructing a local coil ( 1 ) with a magnetic resonance antenna array ( 2 ), which a plurality of in adjacent rows (SR ₁ , SR ₂ , SR ₃ ) arranged antenna conductor loops ( 3 . 3A . 3E ), wherein mutually adjacent antenna conductor loops ( 3 . 3A . 3E ) are each arranged so that they are inductively decoupled from each other by a geometric overlap (U _X , U _Z ), wherein the rows (SR ₁ , SR ₂ , SR ₃ ) of antenna conductor loops ( 3 . 3A . 3E ) in alternating offset directions (R ₁ , R ₂ , R ₃ ) are offset from one another such that an overlapping region (U _X , U _Z ) of two antenna conductor loops ( 3 . 3A ) of a row to an overlapping region (U _X , U _Z ) of two antenna conductor loops ( 3 . 3A . 3E ) of an adjacent row and at least a part of the antenna conductor loops ( 3 . 3A . 3E ) to compensate for the offset so that they rewrite different areas and thereby adjacent rows (SR ₁ , SR ₂ , SR ₃ ) of antenna conductor loops ( 3 . 3A . 3E ) in the offset direction (R ₁ , R ₂ , R ₃ ) at the front and back substantially on a line (L ₁ , L ₂ ) transverse to the offset direction. Method for measuring magnetic resonance signals, wherein the magnetic resonance signals with a local coil ( 1 ) with a magnetic resonance antenna array ( 2 ) are detected, which a plurality of in adjacent rows (SR ₁ , SR ₂ , SR ₃ ) arranged antenna conductor loops ( 3 . 3A . 3E ), wherein mutually adjacent antenna conductor loops ( 3 . 3A ) are each arranged so that they are inductively decoupled from each other by a geometric overlap (U _X , U _Z ), wherein the rows (SR ₁ , SR ₂ , SR ₃ ) of antenna conductor loops ( 3 . 3A . 3E ) are offset in alternating offset directions (R ₁ , R ₂ , R ₃ ) from one another such that an overlapping region (U _X , U _Z ) of two antenna conductor loops ( 3 . 3A . 3E ) of a row (SR ₁ , SR ₂ , SR ₃ ) to an overlapping area (U _X , U _Z ) of two antenna conductor loops ( 3 . 3A . 3E ) of an adjacent row (SR ₁ , SR ₂ , SR ₃ ) and at least a part of the antenna conductor loops ( 3 . 3A . 3E ) are adapted to compensate for the offset so that they rewrite different areas and thereby adjacent rows (SR ₁ , SR ₂ , SR ₃ ) of antenna conductor loops ( 3 . 3A . 3E ) in the offset direction (R ₁ , R ₂ , R ₃ ) at the front and rear substantially on a line (L ₁ , L ₂ ) transverse to the offset direction (R ₁ , R ₂ , R ₃ ).

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