ANTENNA ASSEMBLY FOR A TOMOGRAPHY SYSTEM

Abstract

The present disclosure relates to an antenna assembly for an imaging method, a use of an antenna assembly and a tomography system, in particular for MRI or simultaneous MR-PET/-SPECT. An antenna assembly for an imaging method comprises at least two antennas, wherein each of the two antennas is designed as a J-pole antenna with a radiation section and a feed section. The radiation sections of the two antennas are arranged crossing each other. In this way, effective decoupling of the antennas is achieved by simple means.

Claims

1. An antenna assembly for an imaging method, the antenna assembly comprising at least two antennas, each of the two antennas configured as a J-pole antenna with a radiation section and a feed section, wherein the radiation sections of the two antennas are arranged crossing each other.

2. The antenna assembly of claim 1, wherein the antenna assembly is an antenna assembly for magnetic resonance imaging (MRI), ultra-high field MRI, MR positron emission tomography (MR-PET), MR single proton emission computed tomography (MR-SPECT), MR linac and/or MR ultrasound.

3. The antenna assembly of claim 1, wherein the antenna assembly is an antenna assembly for simultaneous MR-PET/-SPECT.

4. The antenna assembly of claim 1, wherein the radiation sections of the two antennas form an angle ? between 30? and 90? between one another.

5. The antenna assembly of claim 1, wherein the two antennas are arranged in a common plane.

6. The antenna assembly of claim 1, wherein the antenna assembly comprises several pairs of two antennas arranged crossing each other in each case.

7. The antenna assembly of claim 5, wherein each pair of antennas is arranged in a plane, wherein the planes of two adjacent pairs of antennas form an angle ? between each other, wherein: ?=0? or 0?<??90?.

8. The antenna assembly of claim 1, wherein the radiation section of each of the two antennas is produced from a material substantially transparent to PET and/or SPECT, for example copper or aluminum.

9. The antenna assembly of claim 1, wherein the antenna assembly has between 4 and 32 antennas.

10. The antenna assembly of claim 1, wherein the antennas of the antenna assembly define a hollow body in which a body or a body part can be arranged.

11. The antenna assembly of claim 10, wherein the hollow body has a circular cylindrical basic shape.

12. The antenna assembly of claim 1, wherein the antenna assembly has a radiation part and a feed part adjacent to the radiation part, wherein the radiation sections of the antennas are arranged in the radiation part and the feed sections of the antennas are arranged in the feed part.

13. The antenna assembly of claim 1, wherein the antenna assembly comprises at least two antennas arranged adjacent to each other, which are designed as J-pole antennas with a radiation section and a feed section, wherein the at least two antennas are arranged alternately at a first angle and a second angle different from the first angle in relation to a reference surface.

14. A method of using an antenna assembly in a tomography system, the method comprising providing the antenna assembly having at least two antennas, each of the two antennas configured as a J-pole antenna with a radiation section and a feed section, wherein the radiation sections of the two antennas are arranged crossing each other, and acquiring imaging via MRI or simultaneous MR-PET/-SPECT using the antenna assembly.

15. A tomography system adapted for MRI or simultaneous MR-PET/-SPECT, the system comprising an antenna assembly having at least two antennas, each of the two antennas configured as a J-pole antenna with a radiation section and a feed section, wherein the radiation sections of the two antennas are arranged crossing each other, and wherein the antenna assembly is arranged in particular such that the feed sections are located outside a measuring range of the tomography system.

16. The antenna assembly of claim 4, wherein the radiation sections of the two antennas form an angle ? between 45? and 90? between one another.

17. The antenna assembly of claim 1, wherein the two antennas are arranged in a common plane.

18. The antenna assembly of claim 1, wherein each pair of antennas is arranged in a plane, wherein the planes of two adjacent pairs of antennas form an angle ? between each other, wherein: ?=0? or 0?<??90?.

19. The antenna assembly of claim 9, wherein the antenna assembly has between 6 and 16 antennas.

20. The antenna assembly of claim 1, wherein the antenna assembly has a radiation part and a feed part adjacent to the radiation part, wherein the radiation sections of the antennas are arranged in the radiation part and the feed sections of the antennas are arranged in the feed part.

Description

BRIEF DESCRIPTIONS OF THE DRAWINGS

[0042] The figures show:

[0043] FIG. 1: a schematic representation of a J-pole antenna;

[0044] FIG. 2: a schematic representation of an antenna assembly according to the present disclosure;

[0045] FIG. 3: a schematic representation of a further embodiment of an antenna assembly according to the present disclosure;

[0046] FIG. 4: a schematic representation of a further embodiment of an antenna assembly according to the present disclosure;

[0047] FIG. 5: a perspective schematic representation of a further embodiment of an antenna assembly according to the present disclosure;

[0048] FIG. 6: a sectional drawing of an antenna assembly in which two antennas are arranged alternately at a first angle and a second angle in relation to a reference surface,

[0049] FIG. 7A-7C: schematic representations of further embodiments of the antenna assembly according to the present disclosure.

DETAILED DESCRIPTION

[0050] FIG. 1 shows an antenna 1 in the shape of a J-pole antenna. This comprises a straight radiation section 2 and an immediately adjacent feed section 3. The feed section 3 is U-shaped. The radiation section 2 merges seamlessly into a leg of the U. This creates the characteristic J-shape of antenna 1.

[0051] The radiation section 2 serves for transmitting and receiving or exclusively transmitting electromagnetic signals of an imaging method such as, for example, MRI or simultaneous MR-PET/-SPECT. The feed section 3 is used to feed the antenna 1, or more precisely the radiation section 2.

[0052] The cross-section of the antenna 1 is designed in particular so that it does not cause any abrupt changes in the absorption coefficients for y-radiation. For example, the cross-section is circular or elliptical. This can prevent artifacts in PET/-SPECT imaging. The antenna 1 is preferably thin. In the sense of the present disclosure, thin means, for example, a thickness corresponding to 3 to 5 times the penetration depth of the radio frequency field into the antenna.

[0053] The two dotted lines mark the upper end of the antenna 1 and the boundary between the radiation section 2 and the feed section 3. The length of the radiation section 2 between the two dotted the U-shape is typically

[00003]$\frac{?}{2}.$

The length of the feed section 3 from the lower dotted line to the lower end of the U-shape is typically

[00004]$\frac{?}{4}.$

This can be adapted as described above.

[0054] FIG. 2 shows a first embodiment of an antenna assembly 10 according to the present disclosure. Two J-pole antennas, for example like the one shown in FIG. 1, are arranged here in such a way that the radiation sections 2 of the two antennas 1 cross each other. A crossing point 9 is formed. The two antennas 1 form an angle ? of approximately 75? between each other. The angle ? is the smaller angle measured between the radiation sections 2 of the two antennas 1. This angle can be determined by the design of the antenna assembly, the research objective and the target object. The angle may be between approximately 0 degrees (worst decoupling; strong coupling, almost parallel radiation sections) and 90 degrees (best decoupling, perpendicular to each other). In this way, a decoupling of the two antennas 1 from each other is achieved, which allows more antennas 1 to be arranged per volume and/or per surface. The imaging method is thus improved, in particular the uniformity and the signal-to-noise ratio are increased.

[0055] FIG. 3 shows a further embodiment of an antenna assembly 10 according to the present disclosure. In contrast to the antennas 1 in FIGS. 1 and 2, the antennas 1 in the embodiment shown here have a kink between the respective radiation section 2 and the respective feed section 3. The angle of this kink can be arbitrary. Although the radiation sections 2 form approximately the same angle ? between each other as in FIG. 2, the feed sections 3 of the two antennas 1 are arranged in parallel here as an example. In other words, the feed sections 3 have the same orientation. This can, for example, improve accessibility and/or facilitate the connection. Deviating from this, different angles and/or vertical or horizontal alignments can also be achieved.

[0056] FIG. 4 shows a further embodiment of an antenna assembly 10 according to the present disclosure. This comprises three pairs 5, each consisting of two antennas 1 arranged crossing each other. Each pair 5 of antennas 1 is shown here as an example as in FIG. 2. It is also possible for one or more pairs 5 to be configured according to FIG. 3. One or more individual antennas 1 can also be designed with a kink according to FIG. 3. Deviating from this, there may also be an odd number of antennas 1, for example one antenna 1 and three pairs 5 and possibly a further antenna 1. This is particularly the case with planar antenna assemblies.

[0057] A characteristic feature of the antenna assembly 10 in FIG. 4 is that all pairs 5 and thus all antennas 1 are arranged in a common plane 4. In a viewing direction perpendicular to the plane of the drawing, the antenna assembly 10 is therefore only rod-shaped, wherein the thickness of the rod corresponds to the cross-section of the radiation section 2 and/or the feed section 3.

[0058] Due to the arrangement shown, decoupling is also achieved between the first and third antennas 1. This has a similar effect to the decoupling between the first and second antennas 1. Therefore, the distance between the first antenna 1 and the third antenna 1 can be reduced.

[0059] FIG. 5 shows a further embodiment of an antenna assembly 10 according to the present disclosure, in which pairs 5 of antennas 1 are arranged crossing each other in such a way that they surround a hollow body 6. The antennas 1 are arranged so that their radiation sections 2 surround the hollow body 6. The hollow body 6 has a circular cylindrical basic shape 7. A body part or a body can be accommodated in the hollow body 6 in order to be examined using the imaging method. The radiation sections 2 of the antennas 1 together form a radiation part 8 of the antenna assembly 10. For reasons of clarity, only three pairs 5 of antennas 1 are shown. However, a total of six or eight pairs 5 of antennas 1 are typically present here.

[0060] For reasons of clarity, the feed sections of the antennas 1 are not shown in FIG. 5. In particular, the feed sections of the antennas 1 together form a feed part, which may be arranged at the left end or at the right end of the radiation part 8 and thus of the hollow body 6 and preferably directly adjoins the radiation part 8. Preferably, the antennas 1 therefore all have the same orientation.

[0061] It can be seen that the angle ? (not shown here) between the two crosswise arranged radiation sections 2 is smaller than in the previously described configurations. For example, the angle ? here is between 25? and 35?, in particular around 30?. In this way, the elongated geometry of the cylinder, which may be used to examine a human head, for example, and at the same time the intersecting arrangement of the radiation sections 2 according to the present disclosure can be realized. In this way, sufficient decoupling of the antennas 1 of the respective pair of antennas 5 is still achieved, which enables the shown significantly denser arrangement of antennas 1 compared to the prior art and in this way improves the imaging method. The angle could also be more than 15?, more than 20? or more than 25?, for example.

[0062] Each pair 5 of intersecting antennas 1 is arranged in a plane 4, of which two planes 4 are drawn by way of example. In each case, adjacent planes 4 have an angle ? between them, which is 45? in the example shown here. In this example, there are a total of eight pairs 5 of antennas 1, which form a regular octagon with eight angles of 45? when viewed in the longitudinal direction of the hollow body 6.

[0063] FIG. 6 shows another antenna assembly 10 for an imaging method with twelve respectively adjacent antennas 1, each of which is designed as a J-pole antenna with a radiation section 2 and a feed section 3. The antennas 1 are arranged alternately at a first angle and a second angle different from the first angle in relation to a reference surface 4. A sectional drawing of an antenna assembly 10, which defines a hollow body 6 and has a circular cylindrical basic shape, is shown in the radial direction. There are twelve antennas 1 evenly distributed around the circumference of the circle. The sectional plane shown runs through the feed part of the antenna assembly 10, so that each antenna 1 can be recognized by its feed section 3, which is represented by two circular conductors. These represent the leg of the U. The plane of each antenna 1 is spanned by these circular conductors.

[0064] The reference surface 4 is the lateral surface of the circle. It is therefore a curved reference surface 4. The antennas 1 are arranged alternately at an angle of 0? and 90? to the reference surface 4. The antennas 1 are therefore alternately aligned along the reference surface 4 (shown as filled circles) and perpendicular to the reference surface 4 (shown as circles with a white core). For clarity, one antenna 1 of each of the two described orientations is circled with a dotted line and thus highlighted. Adjacent antennas 1 have an angle ? between them, which in this case is 60? due to the twelve antennas. In this way, the antennas 1 are decoupled from each other, allowing more antennas 1 to be arranged per volume or per surface. In this way, the imaging method is improved, in particular the resolution is increased. This embodiment can be combined as desired with the intersecting (crossing) arrangement of the antennas 1 according to the present disclosure described above in order to achieve a further improved decoupling.

[0065] In particular, the antenna assembly 10 comprises a positioning unit for positioning the antennas 1 in relation to each other and/or to a body to be examined. This can be designed as a holding device for holding the antennas 1 and/or as a fastening unit for mechanically fastening the antennas 1 to one another. The positioning unit can, for example, have the basic circular cylindrical shape 7. The positioning unit may be adapted to the shape and/or size of the body or body part to be examined, here for example the human head.

[0066] MRI, PET and SPECT stand as well-established medical imaging modalities used in current routine clinical practice. MRI, predominantly utilizing hydrogen nuclei (1H), is renowned for its capacity to produce high-quality structural and anatomical images. Its strength lies in delivering exceptional soft tissue contrast, making it valuable for visualizing detailed internal structures in the body. Furthermore, MRI is capable of obtaining functional information, allowing for the assessment of various physiological processes alongside anatomical details. This combination of structural and functional data renders MRI a versatile tool in the diagnosis and monitoring of a wide range of medical conditions. PET and SPECT are nuclear medicine imaging techniques which relies on the detection of different radiotracers to generate images that highlight metabolic and biochemical processes within the body. The combined use of MR-PET or MR-SPECT enhances the complementary nature of the information they provide, resulting in a more holistic understanding of both structure and function. This integrated approach strengthens diagnostic capabilities and aids in formulating comprehensive treatment strategies in clinical settings.

[0067] An MRI scanner is primarily composed of a magnet to create a strong static magnetic field (B.sub.0), a gradient system for spatial encoding, and a radiofrequency (RF) system designed to excite the spins of the subject and receive MR signals. The RF field generated by the RF system, such as RF coil or antenna, is referred to as the B.sub.1 field.

[0068] For ultra-high field (UHF) MRI applications (B.sub.0?7T), radiating antennas have been implemented as they offer optimal imaging performance at the field strength where uniform excitation throughout the imaging region becomes challenging due to the shortened RF wavelength.

[0069] Known decoupling methods are mostly not suitable for all relevant imaging methods, e.g. simultaneously operating MR-PET systems, since any added material and physical components degrades PET performance.

[0070] Arranging the number of channels or antennas per area and/or volume improves the functionality and efficiency of parallel transmission and thus the homogeneity of the transmit field and specific absorption rate (SAR) and increases the signal-to-noise ratio (SNR). A more effective B1 field is achieved in the area of the crossing point due to the presence of two closely adjacent antennas. The crossing point can therefore be selected so that it is located in the target area where a particularly high sensitivity or a particularly high penetration depth is required. The crossing point can in principle be freely selected according to the respective requirements. In case of several pairs of antennas, the crossing points may be at the same positions and/or at different positions. The antenna may be a transmit and receive device for an imaging method. The radiation section is configured in particular for transmitting and/or receiving electromagnetic signal. A J-pole antenna can also be referred to as a J-shape antenna element. The length of the radiation section is preferably

[00005]$\frac{?}{2}$

in a free space. The length of the reed section is preferably

[00006]$\frac{?}{4}$

in a free space. Simultaneous MR-PET/-SPECT can also be referred to as simultaneously operating hybrid MR-PET/-SPECT.

[0071] In one configuration, the radiation section 2 of at least one antenna 1 is subdivided into two or three sections. In particular, at least one section, two sections or each section runs in an at least substantially straight course. There may be curves or kinks between the individual sections. The crossing point of the radiation sections of the two antennas may be formed by the first sections 11 or the second sections 12 of each of the two antennas crossing each other.

[0072] In one configuration, a first section 11 of the radiation section 2 is positioned directly adjacent to the feed section 3. The first section 1 may be a straight extension of one leg of the feed section 3. A second section 12 may be positioned adjoining the first section 11. There may be a curve or kink between the first and second sections 11, 12. A third section 13 may be positioned adjoining the second section 12. There may be a further curve or kink between the second and third sections 12, 13. The first and third sections 11, 13 may be arranged in parallel, in particular along the same axis. The second sections 12 may be arranged crossing each other.

[0073] The focusing area, i.e. the area in which the highest B1 sensitivity and efficiency can be achieved, typically corresponds to an area of the crossing point 9 or adjacent to the crossing point 9 of the radiation sections. By varying the crossing point, the focusing area can be varied, as shown in FIGS. 7A to 7C.

[0074] In FIG. 7A, the crossing point 9 is arranged substantially in the center of the radiation sections 1. In other words, the first section 11 and the third section 13 are substantially of equal length. A corresponding MR image is shown to the right of the diagram. It can be seen that the brightest region or focusing region which represents the highest SNR is arranged at the same height as the crossing point 9.

[0075] In FIG. 7B, the crossing point 9 is located at a higher level. The first section 11 of each radiation section 2 is substantially longer than the third section 13. Thus, the crossing point 9 is located further away from the feed sections 3. The corresponding MR image shows that the focus region is also at a higher position.

[0076] To the contrary, FIG. 7C shows an embodiment in which the crossing point 9 and the focus region are arranged on a lower level due to short first sections 11 and long third sections 13.

[0077] It can be seen that the focus section can be shifted or positioned according to the requirements by positioning the crossing point at the desired position, for example by varying the lengths of the first sections 11 and third sections 13.

[0078] Antennas as shown in FIGS. 7A to 7C can also be used to form arrays, for example as shown in FIG. 5. This enables to optimize and enhance the image quality of the target region, e.g. motor cortex or cerebrum in a human head.

LIST OF REFERENCE SIGNS

[0079] Antenna 1 [0080] Radiation section 2 [0081] Feed section 3 [0082] Plane 4 [0083] Pair 5 [0084] Hollow body 6 [0085] Circular-cylindrical basic shape 7 [0086] Radiation part 8 [0087] Crossing point 9 [0088] Antenna assembly 10 [0089] Angle ? [0090] Angle ? [0091] First section 11 [0092] Second section 12 [0093] Third section 13