Antenna, antenna assembly, method and tomography system

Abstract

The invention relates to an antenna and an antenna assembly for an imaging method, to a method for adjusting the length of an antenna and to a tomography system, in particular for magnetic resonance tomography (MRT) or simultaneous positron emission tomography and MRT (PET-MRT). An antenna (1) for an imaging method comprises a radiation section (2) and a feed section (3). The feed section (3) comprises a capacitor (11) and an inductor (15).

Description

[0001] Antenna, antenna arrangement, method and tomography system

[0002] Description

[0003] The invention relates to an antenna and an antenna arrangement for an imaging method, a method for adjusting the length of an antenna and a tomography system, in particular for magnetic resonance imaging (MRI) or simultaneous positron emission tomography-MRI (PET-MRI).

[0004] Magnetic resonance imaging (MRI) is a non-invasive imaging technique for examining body parts, allowing high-resolution cross-sectional images of the body to be generated for medical diagnostics. It is based on the resonant excitation of certain atomic nuclei contained within or introduced into the body, particularly hydrogen nuclei, using strong magnetic fields and alternating magnetic fields in the radiofrequency range (nuclear magnetic resonance). This excites an electrical signal in a receiving antenna. A strong static magnetic field, the B0 field, is superimposed by a high-frequency alternating magnetic field, the B1 field. The frequency of B1 is proportional to the B0 field. MRI can produce high-resolution images.

[0005] To perform MRI, high-frequency antennas – also known as coils – are used, which are arranged on or around the body or body part to be examined. The close-to-body arrangement is particularly the case with ultra-high-field MRI (magnetic flux density > 7T) to enable greater penetration depth and generate a symmetrical B1 field pattern. Antenna arrangements with several antennas, also known as multi-channel antennas, multi-channel antennas or multi-channel (antenna) arrays, are used to generate a more homogeneous or spatially expanded magnetic field, increase coverage and / or accelerate image acquisition. An antenna arrangement can also be used to optimally cover and examine specific body parts. An antenna arrangement allows the arrangement of a number and, if necessary, several antennas to be adapted to the respective case.In other words, the shape and / or size of antennas can be provided as a personalized / dedicated antenna array. As an example of such an antenna, a J-pole antenna is described in WO 2020 244 689 A1. Previous antennas require a lot of space, particularly in the feed area. This limits the arrangement of antennas in arrays. Furthermore, the large space requirement leads to comparatively large mutual couplings between the antennas in an antenna array, especially with closely packed antennas. This is due to electromagnetic interaction between the individual antennas. This changes the radiation pattern and the input impedance. This results in additional modes in the frequency spectrum. Furthermore, the efficiency of power transmission and the ability to improve homogeneity through B1 shimming or parallel transmission techniques are reduced.The coupling between two antennas decreases with increasing distance. Thus, the number of antennas per area or volume, and thus the achievable resolution (via the achievable SNR) of the imaging technique, is limited.

[0006] The object of the invention is to provide an improved antenna, antenna arrangement, and an improved method and tomography system. In particular, the disadvantages of the prior art are to be at least partially remedied.

[0007] This object is achieved by an antenna according to claim 1, as well as by the antenna arrangement, the method, and the tomography system according to the independent claims. Advantageous embodiments are specified in the subclaims.

[0008] To solve this problem, an antenna for an imaging technique is used. The antenna has a radiating section and a feeding section. The feeding section includes a capacitance and an inductance.

[0009] It has been shown that with a capacitance and an inductance, the behavior of a J-pole antenna can be achieved without requiring the space required by a J-pole antenna. Due to the small space requirement, a dense antenna arrangement can be created in which a comparatively high number of antennas can be accommodated in a small space without the coupling between the antennas becoming too great. This makes it possible to create a highly efficient arrangement. Due to the high number of channels, i.e. antennas, per area and / or volume, the performance of the parallel transmission and thus also the uniformity or homogeneity of the B1 field can be improved and the signal-to-noise ratio can be increased. This further improves the quality and informativeness of the image. In addition, the antenna according to the invention can be manufactured using standard components and is therefore particularly cost-effective and technically simple.Overall, the invention enables a particularly simple construction of the feed part and thus of the antenna.

[0010] The antenna can, in principle, be designed analogously to a J-pole antenna, a monopole, or a dipole. The feed section of such a conventional antenna is then designed according to the invention. Thus, a conventional antenna can be designed according to the invention by replacing the feed section.

[0011] The radiating section is particularly designed for transmitting and / or receiving electromagnetic radiation. The radiating section can be essentially or completely straight. It is typically a linear antenna or a rod antenna. However, a curved radiating section can also be provided. This allows the antenna to be optimally adapted to the spatial conditions.

[0012] The feed section is particularly configured to feed the radiation section. In one embodiment, the antenna is an end-fed antenna. This is particularly the case with J-pole antennas and monopoles. This ensures that the cable connecting the antenna to the MRI system does not interfere with the main antenna or the main antenna arrangement. Alternatively, particularly in the case of a dipole, the feed section is located approximately midway along the length of the antenna.

[0013] Typically, the radiation section and the feed section are electrically connected to one another. The feed section typically has a first terminal, and the radiation section typically has a second terminal. The connection between the first terminal and the second terminal can be designed to be non-destructively detachable or non-destructively detachable. The radiation section can merge seamlessly into the feed section. The radiation section and the feed section are in particular adjacent, preferably directly adjacent.

[0014] In particular, the antenna has an antenna connection for connecting or feeding the antenna. The antenna connection can be suitable for connecting a coaxial cable. Preferably, the feed section has the antenna connection. The feed section can also have one or more control connections. In particular, the radiating section has no further connections except for the second connection.

[0015] A capacitor and an inductor are electrical components. Capacitors and inductors are also referred to as lumped elements. In particular, compact lumped components are used. This allows for particularly compact installation space.

[0016] In one embodiment, the feed section comprises an electrical circuit. In particular, the electrical circuit comprises the antenna connection, the capacitance, and the inductance. In one embodiment, the capacitance and the inductance are connected in series. In particular, the antenna connection and / or a branch to the first connection for connecting the radiating section is also connected in series with the inductance and the capacitance. In particular, the antenna connection is arranged between the antenna and the capacitance. In particular, the branch to the first connection is arranged between the capacitance and the antenna, preferably on the side opposite the antenna connection. In one embodiment, a circuit of the feed section comprises, in this order, the branch to the first connection, the inductance, the antenna connection, and the capacitance.

[0017] The capacitance is, in particular, a capacitor or a component that can act as a capacitor, such as a capacitance diode. A capacitor with a fixed capacitance can be used. The capacitance serves to adapt the antenna to the given conditions of the specific measurement. For example, the impedance between the antenna and the output of the RF system intended for feeding it can be adapted. The inductance is, in particular, a coil. A coil with a fixed inductance can be used.

[0018] The antenna is a transmitting and / or receiving device for an imaging procedure, for example, for MRI or MR spectroscopy. It can be a pure transmitting antenna. In this case, different antennas are used for transmitting and receiving. A different antenna is then required for receiving. In MRI, for example, the antenna is used to generate or transmit radio-frequency (RF) excitation pulses, in particular a radio-frequency alternating magnetic field, and / or to receive or detect magnetic resonance signals, in particular by detecting an electrical voltage induced in the antenna. In particular, the antenna is a radio-frequency antenna that operates at a frequency in the radio wave or radio frequency range, in particular in the MHz range, or is designed for such a range. Future applications may also operate in the GHz range. The antenna can therefore generate and / or detect a radio-frequency field.It can also be called a radio frequency or RF antenna.

[0019] The imaging procedure is typically a diagnostic and / or medical procedure. It is used, in particular, to take images of the body or part of the body of a living being, for example, a human or an animal, from which information about the health status of the living being can be derived.

[0020] In one embodiment, the capacitance is a variable capacitance, in particular a variable capacitor. Accordingly, the capacitance can be variably adjusted within a specific range.

[0021] Each object to be measured, for example, a body or body part or a phantom, requires a specific electrical capacitance. The variable capacitance according to this embodiment makes it possible to set the appropriate electrical capacitance for each measurement to be performed. Consequently, no component needs to be replaced to obtain the required electrical capacitance. In one example, the capacitance can be variable within a range of at least 0.1 pF, preferably at least 1 pF, and / or at most 100 pF, preferably 10 pF.

[0022] In one embodiment, the capacitance is designed as a capacitance diode. In particular, the electrical capacitance can be influenced in this way. A capacitance diode is also called a varicap or varactor. The capacitance can be varied by changing the applied voltage. The capacitance can be easily controlled or changed electrically, automatically, and if necessary remotely. This makes it particularly easy to adjust the required electrical capacitance.

[0023] In one embodiment, the feed section has a second capacitance. In particular, the second capacitance serves to match the antenna. Matching the antenna can serve to adjust the impedance between the antenna and the output of the RF system provided for feeding the antenna. In this way, power or signals can be transmitted efficiently and with low loss. The second capacitance can be arranged on the side of the inductor. The second capacitance can be arranged adjacent to the antenna connection and / or the inductor.

[0024] A

[0025] In one embodiment, the length of the radiation section is thus half the wavelength. The length of the radiation section is measured longitudinally, specifically between a connection of the feed section and the outermost, opposite point of the radiation section. At a field strength of 7 T, half the wavelength is approximately 50 cm. This can be a suitable size, for example, for examining the human body.

[0026] In one embodiment, the feed section has a second inductance. This allows, in particular, a shortening of the antenna's radiation section. This allows, for example, the examination of smaller body parts or animals with the same high field strength.

[0027] To make the antenna shorter than half the wavelength at the same frequency, a second inductor can be used. The second inductor is arranged, in particular, directly or indirectly adjacent to the first terminal. The second inductor is arranged, in particular, directly or indirectly adjacent to the branch to the first terminal. The inductor, the second inductor, and / or any additional inductor can, for example, be a coil or have a meandering or similar structure.

[0028] Alternatively or additionally, the feed section can have an additional capacitor to allow an extension of the antenna's radiating section. A combination of one or more additional capacitors and one or more second inductors can be provided to selectively switch the respective components, for example, with an electrical switch such as a PIN diode.

[0029] An inductor, second inductor and / or additional inductor can be used to tune the antenna. This can provide a better tuned antenna for the specific application. For example, it can be tuned to a desired frequency and / or the antenna can be tuned to a different magnetic field strength of a different MRI system. The length of the radiation section has a significant influence on the tuning. This design has the advantage of achieving greater flexibility in the antenna. An antenna can be adapted in terms of its length depending on the respective requirements, for example the spatial or geometric requirements of the measuring device. There is no need to redesign the feed section; instead, a suitable second inductor can be easily arranged to make up for the missing geometric length of the antenna.of the radiating section electrically. This provides a particularly flexible antenna. This provides increased flexibility, particularly compared to the already advantageous J-pole antenna. Adaptations can be made to specific conditions, such as the intended use, field strength, and target imaging area. This allows for a wide variety of antenna arrangements to be produced based on a single antenna design.

[0030] In one embodiment, the feed section has one or more selectively activatable additional inductances. An additional inductance can be implemented as a coil. Selectively activatable means that the additional inductances can be switched so that a current from the antenna can flow through them or not. They are therefore selectively active or inactive. In the active state, they act as an inductance and thus influence the inductance of the antenna. In the inactive state, they typically have no effect on the feed section's circuit. An additional inductance can also be present if no second inductance is present.

[0031] One or more additional inductances may be present. In one embodiment, one or more additional inductances are present, connected in parallel with the inductance and / or the second inductance. In one embodiment, one or more additional inductances are present, connected in series with the inductance and / or the second inductance. The respective electrical inductances can be determined according to known rules.

[0032] In particular, an additional inductance is provided to enable the desired shortening of the radiating section. Depending on the activated or inactivated state of the additional inductance, two different lengths of the radiating section are then possible. With more than one additional inductance, correspondingly more different lengths can be realized. Different combinations of different subcircuits with respective additional inductances enable additional lengths.

[0033] In particular, the supply section comprises an electrical switch, such as a PIN diode, for activating one or more auxiliary inductors. Alternatively, a MEMS switch or any other MR-compatible switch can be used. In this way, activation and deactivation can be easily controlled electrically and, if necessary, remotely. A PIN diode is particularly suitable and can be provided easily and inexpensively. In particular, an electrical switch is provided for each auxiliary inductor and / or for each group of auxiliary inductors.

[0034] In one embodiment, the feed section has an electrical switch, such as a PIN diode, for switching the antenna on and off. Alternatively, a MEMS switch or any other MR-compatible switch can be used. In this way, the current flow through the feed section can be activated or deactivated, thus turning the antenna on or off. In particular, the electrical switch is arranged to interrupt the electrical circuit of the feed section. Accordingly, the electrical switch is typically connected in series with the antenna terminal, the capacitance, the inductance, and / or the branch to the first switch.

[0035] In one embodiment, the antenna or an associated antenna arrangement is an antenna or antenna arrangement for magnetic resonance imaging (MRI), ultra-high-field MRI, magnetic resonance spectroscopy (MRS), and / or, in particular, simultaneous positron emission tomography-MRI (PET-MRI). Alternatively or additionally, the antenna can be an antenna for MR single-proton emission computed tomography (MR-SPECT), MR-LINAC (a linear accelerator combined with a magnetic resonance imaging scanner), and / or MR-guided ultrasound. In one configuration, the antenna arrangement is an antenna arrangement for a combination of two or more of the aforementioned methods.

[0036] PET and SPECT are methods that use radioactive tracers to visualize specific metabolic processes and / or molecular pathways. In this way, insights into physiological and metabolic processes can be obtained with a high degree of specificity and sensitivity. According to the invention, the antenna arrangement can be used for a combination of these methods with MR. In one embodiment, the radiation section of the antenna is made of a material that is essentially PET and / or SPECT-transparent, for example, copper or aluminum. Essentially PET and / or SPECT-transparent materials result in low to negligible attenuation and scattering in PET or SPECT. In particular, the essentially PET and / or SPECT-transparent material is a metal with a low atomic number. Copper and aluminum are particularly well suited as materials for the radiation section.In this way, the antenna can be used as described in tomography systems for simultaneous MR-PET / SPECT. In one embodiment, the radiating portion of the antenna is made of an MR-compatible material that is substantially transparent to gamma rays and / or minimally scatters gamma photons.

[0037] The radiation section is, in particular, an electrical conductor connected at one end. The length of the radiation section is typically at least a factor of 5, in particular at least a factor of 10, longer than the height and width of the radiation section, i.e., the extensions in the two extension directions transverse to the longitudinal extension. In one embodiment, the radiation section of the antenna is very thin. Very thin means, in particular, that the radiation section is at most a factor of 3 to 5 thicker than the skin depth at the desired frequency. The radiation section can be a wire, for example; a thin design is particularly advantageous in hybrid systems such as MR-PET or MR-SPECT. In pure MR systems, a thicker radiation section can also be provided, for example in the form of a coaxial cable.

[0038] In one embodiment, the region of the feed section adjacent to the radiating section is arranged on the same straight line as the radiating section. In other words, the radiating section and the feed section merge into one another in a straight line. In an alternative or supplementary embodiment, the region of the feed section adjacent to the radiating section is arranged at an angle to the radiating section. In other words, a kink and / or bend is present between the radiating section and the feed section. This can also be referred to as an antenna with an inclined feed section.

[0039] A further aspect of the invention is an antenna arrangement for an imaging method. The antenna arrangement comprises at least two antennas according to the invention. All features, configurations, and advantages of the antenna described above also apply to the antenna arrangement, and vice versa.

[0040] In particular, the antenna array contains at least 4 and / or at most 64 antennas or 32 antennas, preferably at least 6 and / or at most 16 antennas. A high number such as 16 antennas or more can only be achieved through the space-saving antenna design according to the invention.

[0041] Preferably, the radiating sections of the antennas run parallel to each other. Depending on the desired frequency and target object, the lengths can be adjusted, shortened, or lengthened by providing a second inductor and / or one or more additional inductors as described above.

[0042] In one embodiment, the antenna arrangement comprises a positioning unit for positioning the antennas relative to one another and / or to a body to be examined. To adapt to the shape and / or size of the body or body part to be examined, the positioning unit can be adapted to the shape and / or size of the body or body part to be examined. The positioning unit can be spatially adapted to the antennas, for example, to antennas of different lengths, as described below. The positioning unit can be designed as a holding device for holding the receiving coils. It can be designed for the fixed positioning of the receiving coils relative to one another or relative to one another. It can be a solid object that can be arranged on a body or body part or into which a part of a body can be inserted.The positioning unit can be designed as a fastening unit for mechanically securing the receiving coils to one another. In particular, the receiving coils are arranged side by side.

[0043] In one embodiment, at least two antennas of the antenna arrangement have radiation sections of different lengths. Typically, the radiation sections are arranged parallel to one another. The feed sections of the at least two antennas can be arranged in a common plane. The feed sections of the at least two antennas can be arranged in a common feed part. The radiation sections can accordingly extend from the feed sections to different distances. In this way, spatially or geometrically adapted antenna arrangements can be produced. The field of view can be geometrically adapted. For example, the sensitive area in the region of the patient's mouth can be reduced or removed and / or a special focus can be placed on the patient's brain.In addition, accessibility and thus comfort during use of the system can be improved, for example, through suitable recesses. Blockages can also be prevented and / or the B1 field can be adjusted.

[0044] In one embodiment, at least three or at least four antennas of the antenna arrangement have radiation sections of different lengths. In particular, the length of radiation sections of different lengths differs by at least 10% relative to the respective longest radiation section. In one embodiment, the radiation sections of at least two antennas have at least substantially the same length. Deviations of a maximum of 3% are permissible. In one embodiment, several groups of antennas are present, wherein the radiation sections of antennas in different groups each have different lengths, wherein the radiation sections within a group each have the same length.

[0045] In one embodiment, the antenna arrangement comprises a radiating section, wherein the radiating sections of the antennas are arranged in the radiating section. In one embodiment, the antenna arrangement comprises a feeding section, wherein the feeding sections of the antennas are arranged in the feeding section. The feeding section can be arranged adjacent to the radiating section.

[0046] The entire antenna arrangement can be divided into two separate, spatially separated parts: a radiation section and a feed section. The feed section typically comprises all feed sections and / or no feed sections are present in the radiation section. The radiation section can therefore be arranged in the measurement area of ​​the tomography system. This makes it possible to have no feed sections and thus no high-density components such as capacitors in the measurement area. In the case of PET and / or SPECT, this reduces artifacts caused by the components and enables significantly higher imaging quality.

[0047] In particular, the antennas of the antenna arrangement define a hollow body in which a body or body part can be arranged. The antennas are arranged around the hollow body, in particular evenly distributed. In particular, the radiating parts of the antennas are arranged around the hollow body and / or define the hollow body. Thus, a human or animal body, or a part thereof, can be accommodated in the hollow body and irradiated there.

[0048] In particular, the hollow body has a circular-cylindrical basic shape. In this case, the antennas can be arranged in a regular polygon, such as a regular hexagon, octagon, or dodecagon, when viewed along the central axis of the basic shape. Basic shape means that parts of the hollow body or the antenna arrangement can deviate from the circular-cylindrical shape. The actual shape of the hollow body does not have to be exactly a circular cylinder.

[0049] In one embodiment, the radiation sections of at least two antennas are arranged so as to cross one another. This means that the radiation sections intersect (form a cross) in at least one viewing direction. The radiation sections form an angle α with each other that is not equal to zero. The angle α can be between 30° and 90°, in particular between 45° and 90°. The antenna arrangement can comprise several pairs of two antennas arranged so as to cross one another.

[0050] The intersecting arrangement of the radiation sections achieves even more effective electromagnetic decoupling between the two antennas. Thus, even greater decoupling and / or an even denser arrangement of the antennas can be achieved.

[0051] A further aspect of the invention is a method for adjusting the length of an antenna according to the invention, in which an additional inductance is activated to compensate for a changed length of the radiation section. In this way, a specific length of the radiation section can be set, which is in particular shorter than half the wavelength. In particular, the method further comprises

[0052] A

[0053] Providing a radiation section with a length Activation occurs, in particular, via a PIN diode. Activation changes an inductance in the feed section, so that a certain missing geometric length of the radiating part is electrically compensated. All features, configurations, and advantages of the antenna and antenna arrangement described above also apply to the method, and vice versa. A further aspect of the invention is a tomography system, in particular for magnetic resonance imaging (MRI) or simultaneous positron emission tomography-MRI (PET-MRI). The tomography system comprises an antenna according to the invention or an antenna arrangement according to the invention. In particular, antennas of the tomography system are arranged such that the feed sections are located outside a measurement range of the tomography system.All features, designs and advantages of the antenna, antenna arrangement and method described above also apply to the tomography system and vice versa.

[0054] Further embodiments of the invention are explained in more detail below with reference to figures.

[0055] They show:

[0056] Figures 1 to 7: different antennas according to the invention;

[0057] Figure 8: a photograph of an antenna according to the invention;

[0058] Figure 9: Test results of the antenna from Figure 9;

[0059] Figure 10: Photos of several antennas according to the invention;

[0060] Figures 11 and 12: antenna arrangements according to the invention;

[0061] Figure 13: a schematic representation of the use of a

[0062] antenna arrangement,

[0063] Figures 14 to 20: further antennas according to the invention, as well as

[0064] Figures 21 and 22: further antenna arrangements according to the invention.

[0065] Figure 1 shows an antenna 1 according to the invention for an imaging method. This comprises a straight radiation section 2 and a directly adjoining feed section 3. The radiation section 2 is designed, for example, as an electrical conductor made of copper or aluminum connected at one end. The feed section 3 generally has a first terminal 27, which is electrically connected to a second terminal 28 of the radiation section 2. Thus, the feed section 3 can feed the radiation section 2. In the example shown, the connection is integral and cannot be removed without damage. The feed section 3 also has an antenna terminal 20, to which, for example, a coaxial cable for feeding the antenna can be connected. The signal can be applied to the central conductor, while the external shielding is grounded.The antenna connection 20 is part of an electrical circuit of the feed section 3. The feed section 3 further comprises a capacitor 11 and an inductor 15. It has been demonstrated that the behavior of a J-pole antenna can be achieved with this simple and space-saving circuit. The circuit is connected to the first connection 27 of the feed section at branch 26. By using small components, the feed section 3 can be manufactured extremely small.

[0066] Figure 2 shows a further embodiment based on the antenna 1 from Figure 1. The only difference from Figure 1 is that the capacitance 11 is designed as a variable capacitance 12.

[0067] Figure 3 shows a further embodiment based on the antenna 1 of Figure 2. In addition to the antenna 1 of Figure 2, the antenna 1 shown here includes a second capacitance 14 to adjust the antenna. Of course, an antenna with a second capacitance 14 can also be equipped with a fixed capacitance 11 according to Figure 1.

[0068] Figure 4 shows a further embodiment based on the antenna 1 from Figure 3. Instead of the variable capacitance, the antenna shown here comprises a capacitance diode 13, which allows automatic adjustment of the electrical capacitance. In addition, the antenna from Figure 4 comprises a second inductance 16, which is arranged between the branch 26 and the first connection 27. This allows the adjustment of a different, in particular shorter, radiation section 2. Of course, an antenna with a second inductance 16 can also be equipped with a fixed capacitance 11 according to Figure 1, a variable capacitance 12 according to Figure 2 and / or without a second capacitance 14 as in Figures 1 and 2.

[0069] Figure 5 shows a further embodiment based on the antenna 1 from Figure 4. In addition to the antenna 1 shown in Figure 4, the antenna 1 from Figure 5 has two additional inductors 17, 18 that can be selectively activated with respective PIN diodes 21, 22. The additional inductors are connected in series with one another and in parallel with the inductor 15 and the second inductor 16. This allows the total inductance to be selectively adjusted to use a specific length of the radiating section 2. The antenna 1 shown here is electrically adjustable and tunable. This is possible remotely. Figure 5 also shows only one example, the components of which can be combined as desired. For example, an antenna with one or two additional inductors 17, 18 can also be equipped without a second inductor 16, without a second capacitor 14, and / or with a fixed capacitor 11 or variable capacitor 12.

[0070] Figure 6 shows the antenna 1 from Figure 5 without the second capacitor 14. Furthermore, the assembly 19, which includes the additional inductors 17, 18, is highlighted with a dashed line. To the right of this, one or more additional assembly units 19 can be arranged to provide additional, variably activated additional inductors. Thus, the antenna 1 can be adjusted for a variety of different lengths of the radiating section 2.

[0071] Figure 7 shows an embodiment based on the antenna 1 from Figure 4. In addition to the components shown in Figure 4 and described above, the antenna 1 from Figure 7 has two electrical switches in the form of PIN diodes 23 to interrupt the circuit of the feed section. The PIN diodes 23 are shown in dotted lines. This is to show that exemplary positions are shown here. In principle, one PIN diode is sufficient to interrupt the circuit. This can be arranged in one of the positions shown or in a different position. Of course, each of the antennas 1 shown in Figures 1 to 6 and / or deviating therefrom and described above could have a PIN diode according to Figure 7 at any point in the circuit.

[0072] Figure 8 shows a photograph of an exemplary antenna 1 with a radiating section 2 and a feed section 3 according to the invention. The small space requirement of the feed section is clearly visible. In the antenna 1 shown, the radiating section has a length of 30 cm and is designed as a thin copper conductor. The capacitance is designed as a trimming capacitor, whose electrical capacitance can be varied between 1 and 10 pF. The inductance is approximately 150 nH. A second capacitance is approximately 1.8 pF. A second inductance is approximately 33 nH.

[0073] Figure 9 shows test results of the antenna 1 from Figure 9, which were determined using a network analyzer. The input reflection factor S11 is shown in dB over the wavelength A in MHz. The center of the x-axis is at 297.2 MHz and the shown range is 200 MHz. It can be seen that the peak of the input reflection factor S11 at approximately 297.2 MHz is approximately -25 dB. The antenna is tuned to 300 MHz. Figure 10 shows several antennas 1 according to the invention, all tuned to the same frequency. The antennas 1 have radiation sections 2 of different lengths. The antennas 1 accordingly have different second inductances and / or additional inductances (cf. Figures 3 to 6) that make this possible. The scale shown for comparison purposes shows that the lengths of radiation sections 2 are approximately 10 cm, 25 cm and 30 cm.From this it can be seen that the invention allows large differences in the length of the radiation section and thus provides a particularly flexible antenna.

[0074] Figure 11 shows an antenna arrangement 10. Typically, parallel antennas 1 are arranged to surround a hollow body 6. The antennas 1 are arranged such 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 to be examined using the imaging method. The concealed antennas 1 are shown in dashed lines. For reasons of clarity, only six antennas 1 are shown. In total, however, 12, 16, 24, or 32 antennas 1 can be present here, for example. Such a number of antennas is only possible due to the small space requirement of the antennas 1 according to the invention, which also leads to extensive decoupling of the individual antennas. This allows for effective control of the B1 efficiency and the specific absorption rate.

[0075] For example, the individual antennas are not all fed the same way, as in conventional arrangements, but can be controlled individually. This allows for improved decoupling. Typically, all antennas in an antenna array are tuned to the same frequency.

[0076] The radiation sections 2 of the antennas 1 together form a radiation part 8 of the antenna arrangement 10. The feed sections 3 of the antennas 1 together form a feed part 9, which can be arranged at the right end of the radiation part 8 and thus of the hollow body 6 and preferably directly adjoins the radiation part 8. Accordingly, the antennas 1 preferably all have the same orientation. The radiation part 8 and the feed part 9 are spatially separated from one another, so that the radiation part 8 can be arranged in the measuring range of the tomography system and the feed part 9 can be arranged outside the measuring range. Figure 12 shows a further antenna arrangement 10 based on the antenna arrangement from Figure 11. For reasons of clarity, only the differences are discussed here. In contrast to Figure 10, pairs 5 of adjacent antennas 1 are arranged crossing one another.In this way, an even greater decoupling of the individual antennas 1 can be achieved.

[0077] For reasons of clarity, the feed sections of the antennas 1 are not shown in Figure 12. In particular, the feed sections of the antennas 1 together form a feed section, as in Figure 11. Here, too, only three pairs 5 are shown; however, typically, 6, 8, 10, 12, 14, or 16 pairs are present.

[0078] Figure 13 shows the application of the antenna according to the invention with radiation section 2 and feed section 3 in a tomography system. The antennas of an antenna arrangement form a hollow body, for example as in Fig. 11 , in which the patient's head 25 is positioned. Located above and below the head, from the inside out, are a PET system, an optional body antenna, a (gradient) compensation coil 32, and the magnets 33 for the strong magnetic field of the MRI. The copper conductors selected as radiation sections 2 and the design in which the feed sections 3 are arranged outside the field of view ensure minimal attenuation and scattering, so that only a negligible influence on the PET occurs. The system is thus compatible not only with MRI systems, but also with hybrid MRI-PET / -SPECT systems.

[0079] In one embodiment, the antenna connection has two conductors. In particular, a first conductor, in particular a central conductor, carries a signal. In particular, a second conductor is grounded. In particular, a first conductor is connected to the capacitance. In particular, a second conductor is connected to the inductance. The connection can be a direct or indirect connection. With a direct connection, the respective components are directly electrically connected to one another, without other components such as branches or electrical components or concentrated components being present in between. At least one further component is present between indirectly connected components. For example, a capacitance can be arranged between the second conductor and the inductance. In particular, the first conductor is directly connected to the capacitance. In particular, the first conductor is connected in series with the capacitance.In particular, the second conductor is connected in series with the inductor. In particular, a series circuit is present in which the capacitor is connected in series with the antenna terminal and the inductor, in that order. One or more additional components can be located between the antenna terminal and the inductor.

[0080] Figures 14 to 20 show further antennas 1 according to the invention, from which it can be seen that the size and shape of the radiation section 2 can be variably selected, for example, depending on the magnetic field strength and / or the body part to be examined. The antennas 1 differ only in the size and shape of the radiation sections 2. The feed section 3 shown in each case—purely by way of example—is the feed section from Figure 3, to whose description reference is made here. However, any other feed section according to the invention can also be used in any combination for each of Figures 14 to 20, e.g., a feed section 2 according to one of Figures 1, 2, or 4 to 7.

[0081] In one embodiment, the extent of the radiation section corresponds, at least in one spatial direction, in particular in several or all spatial directions, to the size of the field of view PET FOV of a system for positron emission tomography (PET), for simultaneous positron emission tomography-MRI (PET-MRI), and / or MR single-proton emission computed tomography (MR-SPECT). In one embodiment, the radiation section is limited in at least one spatial direction, in particular in several or all spatial directions, to the size of the field of view PET FOV of the PET / PET-MRI / SPECT system. The radiation section has a maximum extent equal to the field of view. In particular, the radiation section is located in the field of view and / or can be positioned there. This is indicated purely schematically in Figure 14, but can equally apply to the antennas of any other figure.The PET / SPECT / PET-MRI system and the antenna can be part of a tomography system according to the invention.

[0082] In one embodiment, two antennas are superimposed such that a radiating section of a first antenna is arranged within the radiating section of a second antenna.

[0083] A further aspect of the invention is an antenna arrangement for an imaging method. The antenna arrangement comprises at least two antennas, wherein at least one antenna is an antenna according to the invention. All features, configurations, and advantages of the antenna described above also apply to the antenna arrangement, and vice versa. Figures 21 and 22 schematically show antenna arrangements according to the invention. Figure 21 shows an assembly B comprising two antennas 1, which are referred to below as channels. The radiation section 2 of channel 1 C1 is configured as a rectangle, circular, or square. The radiation section 2 of channel 2 C2 is, for example, straight or designed as a rod. Alternatively, the antenna of channel 1 C1 can have a radiation section 2 of any desired shape that defines an outwardly defined area.Alternatively or additionally, the antenna of channel 2 C2 can have a radiation section 2 of any shape or be designed as a J-pole antenna and / or without inductance. The radiation section 2 of channel 2 C2 is located within the radiation section 2 of channel 1 C1. To the right and left of module B, additional modules Bx are indicated by placeholders. In particular, these modules are constructed analogously to module B. More than three modules B can be present.

[0084] Figure 22 shows two assemblies B, each consisting of two antennas 1 arranged next to one another. As in Figure 21, this is an antenna with a rectangular or square radiation section and an antenna with a straight radiation section 1. Here, too, the radiation sections 2 of one or both antennas can be shaped alternatively as described above. The antennas 1 in Figures 21 and 22 also have, purely by way of example, the feed section 3 from Figure 3 and can alternatively have any other feed section 3 according to the invention. To the right and left of the assembly B, further assemblies Bx are indicated here by placeholders. In particular, these are constructed analogously to the assembly B. There can be more than four assemblies B.

[0085] List of reference symbols

[0086] Antenna 1

[0087] Radiation section 2

[0088] Feed section 3

[0089] Couple 5

[0090] Hollow body 6

[0091] Circular cylindrical basic shape 7

[0092] Radiation part 8

[0093] Supply section 9

[0094] Antenna arrangement 10

[0095] Capacity 11

[0096] Variable capacity 12

[0097] Capacitor diode 13

[0098] Second capacity 14

[0099] Inductance 15 Second Inductance 16

[0100] Additional inductance 17, 18

[0101] Unit 19

[0102] Antenna connection 20

[0103] PIN diode 21, 22, 23

[0104] Patient 25

[0105] Junction 26

[0106] First connection 27

[0107] Second connection 28

[0108] PET System 30

[0109] Body antenna 31

[0110] Compensating coil 32

[0111] Magnets 33

[0112] Input reflection factor in dB S11 [dB]

[0113] Wavelength in MHz A [MHz]

[0114] Field of view PET FOV

[0115] First channel C1

[0116] Second channel C2

[0117] Third channel C3

[0118] Fourth channel C4

[0119] Assembly B

[0120] Additional assembly Bx

Claims

Claims 1. Antenna (1) for an imaging method, wherein the antenna (1) has a radiation section (2) and a feed section (3), characterized in that the feed section (3) comprises a capacitor (11) and an inductance (15).

2. Antenna (1) according to the preceding claim, characterized in that the capacitance (11) is a variable capacitance (12), in particular a variable capacitor.

3. Antenna (1) according to one of the preceding claims, characterized in that the capacitor (11) is designed as a capacitance diode (20).

4. Antenna (1) according to one of the preceding claims, characterized in that the feed section (3) has a second capacitance (14) to adapt the antenna (1).

5. Antenna (1) according to one of the preceding claims, characterized in that the feed section (3) has a second inductance (16) to enable a shortening of the radiation section (2) of the antenna (1).

6. Antenna (1) according to one of the preceding claims, characterized in that the feed section (3) has one or more selectively activatable additional inductances (17, 18), wherein the feed section (3) has in particular an electrical switch such as a PIN diode (21, 22) for activating one or more additional inductances (17, 18).

7. Antenna (1) according to one of the preceding claims, characterized in that the feed section (3) has a PIN diode (23) for switching the antenna (1) on and off.

8. Antenna (1) according to one of the preceding claims, characterized in that the antenna (1) is an antenna (1) for magnetic resonance imaging (MRI), ultra-high field MRI, Magnetic resonance spectroscopy (MRS) and / or positron emission tomography-MRI (PET-MRI).

9. Antenna (1) according to one of the preceding claims, characterized in that the radiation section (2) of the antenna (1) is made of a substantially PET and / or SPECT-transparent material, for example copper or aluminum.

10. Antenna (1) according to one of the preceding claims, characterized in that the antenna (1) is an end-fed antenna (1).

11. Antenna arrangement (10) for an imaging method, comprising at least two antennas (1) according to one of the preceding claims.

12. Antenna arrangement (10) according to the preceding claim, characterized in that at least two antennas (2) of the antenna arrangement (10) have radiation sections (2) of different lengths.

13. Antenna arrangement (10) according to one of the two preceding claims, characterized in that the antenna arrangement (10) has a radiation part (8), wherein the radiation sections (2) of the antennas (1) are arranged in the radiation part (8), and / or that the antenna arrangement (10) has a feed part (9) which is in particular adjacent to the radiation part (8), wherein the feed sections (3) of the antennas (1) are arranged in the feed part (9) are arranged.

14. Antenna arrangement (10) according to one of the three preceding claims, characterized in that the radiation sections (2) of at least two antennas (1) are arranged crossing one another.

15. Method for adjusting the length of an antenna (1) according to one of claims 1 to 10, in which an additional inductance (17, 18) is activated, in particular by means of a PIN diode, in order to compensate for a changed length of the radiation section (2).

16. Tomography system, in particular for magnetic resonance imaging (MRI) or simultaneous positron emission tomography-MRI (PET-MRI), comprising an antenna (1) according to one of claims 1 to 10 or an antenna arrangement (10) according to one of claims 11 to 15, wherein Antennas of the tomography system are arranged in particular such that the feed sections (3) are located outside a measuring range of the tomography system.

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