Wireless array for small animal imaging

Abstract

The present invention relates to a wireless array for small animal imaging, comprising at least a plurality of passive resonant coils, wherein any one of the passive resonant coils and two adjacent passive resonant coils partially overlap to form two first regions, and the two first regions partially overlap to form a second region. Three passive resonant coils are combined with and overlap each other to perform decoupling processing on a wireless array, thereby preventing occurrence of coupling from affecting an excitation process and a receiving process. When a small animal is loaded with a wireless array for use, the wireless array can be directly applied to a clinical whole-body scanner to acquire a magnetic resonance image of the small animal, and does not need to be used in cooperation with a special device for the small animal, so that there is no need to apply an ultra-high field strength and to be compatible with additional cable interfaces produced by different manufacturers, and the purpose of increasing the signal-to-noise ratio of the image of the small animal can be achieved.

Description

A wireless array for imaging small animals Technical Field

[0001] This invention relates to the field of magnetic resonance imaging equipment technology, and more particularly to a wireless array for imaging small animals. Background Technology

[0002] High-resolution magnetic resonance imaging of small animals (such as mice and rats) is increasingly being used in experimental neurology and neuroscience research to investigate brain injury or brain plasticity, as well as to monitor longitudinal volume changes or drug treatment in the same animal over time. Dedicated ultra-high field animal scanners can achieve high spatial resolution imaging and excellent soft tissue contrast.

[0003] However, existing high-resolution magnetic resonance imaging (MRI) techniques for small animals still face the following problems: dedicated ultra-high field animal MRI systems have scanning sequences that cannot correspond to clinical sequences, failing to fully simulate the actual situation of human imaging. Furthermore, the small animal imaging coils used in clinical MRI systems have disadvantages such as requiring custom-made coils, high cost, needing additional cable interfaces, and incompatibility with MRI systems from different vendors.

[0004] In summary, improving the signal-to-noise ratio of small animal imaging is a problem that urgently needs to be solved in current technologies. Summary of the Invention

[0005] To improve the signal-to-noise ratio of small animal imaging, this invention proposes a wireless array for small animal imaging.

[0006] The technical solution adopted in this invention is a wireless array for imaging small animals, comprising multiple passive resonant coils with detuned circuits, wherein any one passive resonant coil and two adjacent passive resonant coils with detuned circuits partially overlap to form two first regions, and the two first regions partially overlap to form a second region.

[0007] Preferably, the number of passive resonant coils is three.

[0008] Preferably, the passive resonant coil is in the shape of a regular octagon.

[0009] Preferably, the two first regions on a passive resonant coil are both parallelograms, or the two first regions are parallelograms and hexagons, respectively.

[0010] Preferably, the parallelogram and the hexagon have the same area.

[0011] Preferably, the second region is triangular in shape, and the long side of the parallelogram in the first region is the side of the regular octagon of the passive resonant coil.

[0012] Preferably, the size of the wireless array matches the size of the area to be tested.

[0013] Preferably, the passive resonant coils are all mounted on a flexible structure.

[0014] Preferably, an adjustable capacitor is connected in series in the passive resonant coil.

[0015] Preferably, the detuned circuit is a parallel LC circuit controlled by two pairs of bidirectional diodes.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] This application discloses a wireless array for small animal imaging, comprising multiple passive resonant coils. Each passive resonant coil partially overlaps with two adjacent passive resonant coils to form two first regions, and the two first regions partially overlap to form a second region. This overlapping arrangement of the three passive resonant coils decouples the wireless array, preventing coupling from affecting the excitation and reception processes. Furthermore, given the same size of passive resonant coils, the overlapping arrangement allows for a smaller wireless array size, making it suitable for small animal applications. When used on small animals equipped with the wireless array, it can be directly applied to clinical whole-body scanners to obtain magnetic resonance imaging of small animals without requiring specialized small animal equipment. Instead, it can be used with different wired receiving coils, eliminating the need for ultra-high field strength and compatibility with additional cable interfaces from different manufacturers.

[0018] Compared with the prior art, the wireless array for small animal imaging disclosed in this application can improve the signal-to-noise ratio of small animal imaging. Attached Figure Description

[0019] The present invention will now be described in detail with reference to the embodiments and accompanying drawings, wherein:

[0020] Figure 1 shows a structural diagram of a wireless array for small animal imaging provided according to an embodiment of the present invention;

[0021] Figure 2 shows a circuit diagram of a single passive resonant coil in a wireless array for small animal imaging provided according to an embodiment of the present invention;

[0022] Figure 3 shows a structural diagram of a wireless array for small animal imaging combined with a commercial knee coil according to an embodiment of the present invention;

[0023] Figure 4 shows a high-resolution imaging result of a rat brain using a wireless array for small animal imaging provided according to an embodiment of the present invention;

[0024] Figure 5 shows the experimental results of water phantom imaging in a wireless array for small animal imaging provided by an embodiment of the present invention, in conjunction with different commercially available matching coils. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings. Examples of embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar components or components having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0026] This invention discloses a wireless array for imaging small animals, comprising multiple passive resonant coils, wherein any one passive resonant coil and two adjacent passive resonant coils partially overlap to form two first regions, and the two first regions partially overlap to form a second region.

[0027] The overlapping arrangement of three passive resonant coils decouples the wireless array, preventing coupling from affecting the excitation and reception processes. Furthermore, with the same size passive resonant coils, this overlapping arrangement allows for a smaller wireless array, making it suitable for use on small animals. When used on small animals equipped with the wireless array, it can be directly applied to clinical whole-body scanners to obtain magnetic resonance imaging (MRI) images without the need for specialized small animal equipment. This eliminates the need for ultra-high field strength and additional cable interfaces compatible with different manufacturers. Compared to existing technologies, the wireless array for small animal imaging disclosed in this application improves the signal-to-noise ratio of small animal imaging.

[0028] This invention proposes a simple, commercially compatible wireless array for magnetic resonance imaging (MRI) systems. The array is passive, eliminating cables, baluns, and a series of connecting devices. Its simple structure allows for easy placement on any part of the animal being scanned. It can be used close to the animal's surface, avoiding the surgical risks and biocompatibility issues associated with implanted coils. It can be directly placed on the scanning site of the animal and is compatible with commercially available RF receiving coils. Simultaneously, it enhances the image signal-to-noise ratio and improves the spatial resolution of the image. The wireless array consists of multiple resonant loops, with these passive resonant coils decoupled from each other through overlapping. The wireless array eliminates the need for cables and connectors, allowing direct placement on the area requiring signal enhancement. It is compatible with MRI equipment from different vendors and can achieve enhanced image signal-to-noise ratio when used with various RF receiving coils.

[0029] A wireless array for small animal imaging primarily employs a loop structure, which locally enhances the received signal without altering the transmit field B1+. It can be used with any RF receiving coil. The size of the wireless array affects both imaging depth and range, and its size and the dimensions of individual passive resonant coils can be adjusted by specifying the areas requiring enhancement. The passive resonant coils of the wireless array are controlled by the switching on and off of a pair of opposing PIN diodes to ensure transparency to the RF transmit field. Decoupling is achieved by partially overlapping the passive resonant coils, canceling out the magnetic flux between them to decouple the units.

[0030] The feasibility of the wireless array provided by this invention was demonstrated through experiments, as shown in Figures 4 and 5. The experiments demonstrated that, for the wireless array used in conjunction with the knee coil, the wireless array significantly improved the signal-to-noise ratio (SNR) of rat brain tissue in the vicinity of the wireless array. Compared to the rat coil, the wireless array used in conjunction with the knee coil can improve the SNR in the rat brain region by approximately four times or more, meeting the requirements for high-resolution imaging, high SNR, and high image quality of the rat brain. The wireless array is not limited to any particular receiving coil and can be used in conjunction with commercially available coils compatible with conventional clinical MRI systems to enhance the SNR of imaging, as shown in Figure 5.

[0031] When adding passive resonant coils, since any passive resonant coil only has two first regions and a second region, there is no overlapping region between any two adjacent decoupling modules. The decoupling of each decoupling module is achieved by the overlapping of its three passive resonant coils.

[0032] A passive resonant coil has a detuned state and a resonant state. The detuned state is used to detune during the radio frequency transmission phase, and the resonant state is used to resonate during the reception phase to enhance the signal.

[0033] The wireless array operates as follows: During the radio frequency (RF) transmission phase of the magnetic resonance imaging (MRI) system, the PIN diode in the detuned loop of the wireless array's unit resonant loop is turned on, putting the entire loop in a detuned state. This attenuates the wireless array's response to the RF transmission field, minimizing its impact. When the wireless array operates in the receiving phase, the PIN diode in the detuned loop of the unit resonant loop is not turned on, and the detuned loop is inactive, allowing the signal to pass through. Under Faraday's law of electromagnetic induction, the change in magnetic flux passing through the wireless array induces an electromotive force. The wireless array amplifies this voltage signal by a factor of Q (the wireless array's quality factor) before it is received by the RF receiving coil, thereby enhancing the signal-to-noise ratio of the imaging signal. This invention provides an implementation example: a 3-channel wireless array used in conjunction with a commercial knee coil, as shown in Figure 3.

[0034] The relative positions of the knee coil and the wireless array are shown in Figure 3. The wireless resonant loop enhances the signal-to-noise ratio (SNR) by increasing the magnitude of the magnetic resonance signal without altering the RF transmission field distribution, thereby improving image quality. The commercial knee coil is a hollow cylinder, large enough to accommodate a human leg, and has 24 receiving channels.

[0035] The commissioning of the wireless array includes tuning, detuning, and decoupling. As shown in Figure 2, the passive resonant coils of the wireless array adopt a loop structure. Tuning is achieved through the adjustable capacitor Tune in the passive resonant coils. The frequency of the detuning loop in the loop is achieved by adjusting C1 and L1. The wireless array uses overlapping decoupling to reduce the coupling between the individual passive resonant coils. The decoupling method is shown in Figure 1. In Figure 1, label 101 represents the overlapping area of ​​the overlapping decoupling, and label 102 represents the passive resonant coil, which has both detuned and tuned states, tuned to the desired Larmor frequency. Figure 3 shows a 3-channel wireless array used in conjunction with a commercial knee coil. Label 101 in Figure 3 is a schematic diagram of a commercial knee coil, which is a hollow cylinder with 24 receiving channels. Label 102 represents the wireless array with three passive resonant coils.

[0036] This invention does not limit the use of the receiving coil; any conventional coil can be used. It is not limited by the type, size, or dimensions of the wireless array unit coils, nor by the number of channels in the wireless array, nor by the detuning method. It is also not limited by the distribution plane of the wireless array; it can be distributed on a plane or a cylindrical surface. Furthermore, the RF receiving coil and the wireless array can be placed directly adjacent to each other or at a certain distance.

[0037] In some embodiments, the number of passive resonant coils is three.

[0038] It should be noted that the number of passive resonant coils is preferably three. This is to prevent the imaging quality in the area where the gap between the two decoupling modules is located from being lower than that in other areas, and to avoid the situation where the size of the wireless array is greatly increased due to the presence of the gap. Therefore, the number of passive resonant coils is selected as three.

[0039] In some embodiments, the passive resonant coil is octagonal in shape.

[0040] Specifically, the passive resonant coil is octagonal in shape. At high frequencies, octagonal coils exhibit lower parasitic capacitance compared to other shapes (such as square coils). This means that at high frequencies, octagonal coils can transmit signals more efficiently and reduce energy loss. Meanwhile, the Q value is an important parameter for evaluating inductor performance, reflecting its losses. The transitions between each metal segment of an octagonal inductor are smoother (adjacent metal segments form a 120-degree angle), resulting in less loss to radio frequency signals compared to a square inductor (adjacent metal segments form a 90-degree angle). Therefore, octagonal inductors typically have a higher Q value. Furthermore, the octagonal shape allows for the selection and control of the stacking of passive resonant coils, and also makes it easier to calculate the area of ​​the overlapping region.

[0041] In some specific embodiments, the two first regions on a passive resonant coil are both parallelograms, or the two first regions are parallelograms and hexagons, respectively.

[0042] It should be noted that, to facilitate the calculation of the overlapping area, both first regions are made to be parallelograms, or one is a parallelogram and a hexagon. During the overlapping of the regular octagons, only one of the three passive resonant coils, which is detuned, has two first regions that are both parallelograms; the other two detuned passive resonant coils have two first regions that are one parallelogram and one hexagon, respectively.

[0043] In some more specific embodiments, the parallelograms and hexagons have the same area.

[0044] Specifically, to achieve the best decoupling effect, the areas of the parallelogram and the hexagon should be the same, so as to ensure that the influence between different passive resonant coils tends to be consistent.

[0045] In some more specific embodiments, the second region is triangular in shape, and the long side of the parallelogram of the first region is the side of the regular octagon of the passive resonant coil.

[0046] It should be noted that, in order to further improve the decoupling effect, the experimenters verified that the decoupling effect reached its peak when the shape of the second region was a triangle and the long side of the parallelogram in the first region was the side of the regular octagon of the passive resonant coil.

[0047] In some embodiments, referring to Figure 3, the size of the wireless array is matched with the size of the area to be tested.

[0048] In some embodiments, the passive resonant coils are all disposed on a flexible structure.

[0049] The flexible structure can be made of flexible materials such as cloth or felt, which makes the wireless array easier to use.

[0050] In some embodiments, an adjustable capacitor is connected in series in the passive resonant coil.

[0051] To further optimize the passive resonant coil structure and reduce the manufacturing cost of the wireless array, this application incorporates an adjustable capacitor in series in the tuning circuit to achieve the tuning state. It should be noted that the detuning circuit and the tuning circuit are not necessarily two separate circuits; in some embodiments, the detuning circuit and the tuning circuit share a common line.

[0052] In some embodiments, the detuned circuit is a parallel LC circuit controlled by two pairs of bidirectional diodes.

[0053] This implementation example uses a parallel LC circuit controlled by two pairs of bidirectional diodes to achieve detuning. Detuning can also be achieved in other ways, such as introducing a new detuning circuit.

[0054] In the description of this specification, the use of terms such as "Embodiment 1," "this embodiment," or "in one embodiment" indicates that the specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example; moreover, the specific features, structures, materials, or characteristics described may be combined in any appropriate manner in one or more embodiments or examples.

[0055] In the description of this specification, the terms "connection," "installation," "fixing," "setting," and "having" are interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be a connection within two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0056] In the description of this specification, relational terms such as “first” and “second” are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase “comprising one…” does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0057] The above description of the embodiments is intended to enable those skilled in the art to understand and apply the technology of this invention. Those skilled in the art can easily make various modifications to these examples and apply the general principles described herein to other embodiments without creative effort. Therefore, this invention is not limited to the above embodiments. Modifications in the following situations should be within the scope of protection of this invention: ① New technical solutions implemented based on the technical solution of this invention and combined with existing common knowledge, where the technical effects of the new technical solution do not exceed the technical effects of this invention; ② Equivalent substitutions of some features of the technical solution of this invention using known technology, resulting in the same technical effects as those of this invention; ③ Extendable technical solutions based on the technical solution of this invention, where the substantive content of the extended technical solution does not exceed the technical solution of this invention; ④ Equivalent transformations made using the content of this specification and drawings, directly or indirectly applied to other related technical fields.

Claims

1. A wireless array for imaging small animals, characterized in that, It includes multiple passive resonant coils with detuned circuits, wherein any one of the passive resonant coils and two adjacent passive resonant coils partially overlap to form two first regions, and the two first regions partially overlap to form a second region.

2. The wireless array for small animal imaging according to claim 1, characterized in that, The number of passive resonant coils is three.

3. A wireless array for imaging small animals according to claim 1, characterized in that, The passive resonant coil is in the shape of a regular octagon.

4. A wireless array for imaging small animals according to claim 3, characterized in that, The two first regions on one of the passive resonant coils are both parallelograms, or the two first regions are parallelograms and hexagons, respectively.

5. A wireless array for imaging small animals according to claim 4, characterized in that, The parallelogram and the hexagon have the same area.

6. A wireless array for imaging small animals according to claim 4, characterized in that, The second region is triangular in shape, and the long side of the parallelogram in the first region is the side of the regular octagon of the passive resonant coil.

7. A wireless array for imaging small animals according to any one of claims 1 to 6, characterized in that, The size of the wireless array is matched to the size of the area to be tested.

8. A wireless array for imaging small animals according to any one of claims 1 to 6, characterized in that, The passive resonant coils are all mounted on a flexible structure.

9. A wireless array for imaging small animals according to any one of claims 1 to 6, characterized in that, An adjustable capacitor is connected in series in the passive resonant coil.

10. A wireless array for imaging small animals according to any one of claims 1 to 6, characterized in that, The detuned circuit is a parallel LC circuit controlled by two pairs of bidirectional diodes.

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