Wireless array for small animal imaging

Abstract

The invention relates to a wireless array for small animal imaging, which comprises at least a plurality of passive resonance coils, any one passive resonance coil and two adjacent passive resonance coils are partially overlapped to form two first areas, and the two first areas are partially overlapped to form a second area. The three passive resonance coils are mutually combined and overlapped, so that the wireless array can be decoupled, and the influence of coupling on an excitation process and a receiving process is prevented. 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 obtain magnetic resonance imaging of the small animal, and special equipment for the small animal does not need to be matched for use, so that extra cable interfaces which have ultrahigh field intensity and are compatible and adaptive to different manufacturers do not need to be applied; the purpose of improving the signal-to-noise ratio of small animal imaging can be achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of magnetic resonance imaging equipment, and in particular to a wireless array for small animal imaging. Background Art

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

[0003] However, the existing small animal high-resolution MRI technology still faces the following problems: the scanning sequence of the dedicated ultra-high field animal MRI system cannot correspond to the clinical sequence and cannot fully simulate the actual situation of human imaging. At the same time, the dedicated coils for small animal imaging on the clinical MRI system have the disadvantages of requiring special customization and being expensive, requiring additional cable interfaces and being incompatible with MRI systems from different suppliers.

[0004] In summary, how to improve the signal-to-noise ratio of small animal imaging is an urgent problem to be solved in the existing technology. Summary of the invention

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

[0006] The technical solution adopted by the present invention is a wireless array for small animal imaging, including multiple passive resonant coils with detuned circuits, any one passive resonant coil partially overlaps with two adjacent passive resonant coils with detuned circuits to form two first areas, and the two first areas partially overlap to form a second area.

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

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

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

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

[0011] Preferably, the second region is in the shape of a triangle, and the long side of the parallelogram of the first region is a 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 measured.

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

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

[0015] Preferably, the detuning 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] The present application discloses a wireless array for small animal imaging, including a plurality of passive resonant coils, wherein any one 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. The composite overlapping manner of the three passive resonant coils can decouple the wireless array, thereby preventing the occurrence of coupling and affecting the excitation process and the receiving process. At the same time, when the passive resonant coils are of the same size, the composite overlapping manner can make the wireless array have a smaller volume to meet the use for small animals. When the small animal is loaded with the wireless array for use, it can be directly applied to a clinical whole body scanner to obtain magnetic resonance imaging of the small animal, without the need to be used with special equipment for small animals, but with different wired receiving coils, so that there is no need to apply ultra-high field strength and be compatible with additional cable interfaces produced by different manufacturers.

[0018] Compared with the prior art, the wireless array for small animal imaging disclosed in the present application can achieve the purpose of improving the signal-to-noise ratio of small animal imaging. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

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

[0022] Figure 3 A structural diagram showing a wireless array for small animal imaging provided by an embodiment of the present invention in combination with a commercial knee coil is shown;

[0023] Figure 4 A diagram showing high-resolution imaging results of a rat brain using a wireless array for small animal imaging provided by an embodiment of the present invention is shown;

[0024] Figure 5 The results of a water phantom imaging experiment using a wireless array for small animal imaging provided by an embodiment of the present invention in combination with different commercial matching coils are shown. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical scheme and advantages of the present invention clearer, the embodiments of the present invention will be further described in detail below in conjunction with the accompanying drawings. Examples of embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar components or components with the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be interpreted as limiting the present invention.

[0026] The invention discloses a wireless array for small animal imaging, comprising a plurality of passive resonant coils, wherein any passive resonant coil partially overlaps with two adjacent passive resonant coils to form two first areas, and the two first areas partially overlap to form a second area.

[0027] The composite overlapping of the three passive resonant coils can decouple the wireless array, thereby preventing the occurrence of coupling and affecting the excitation process and the receiving process. At the same time, when the passive resonant coils are of the same size, the composite overlapping can make the wireless array have a smaller volume to meet the use of small animals. When the small animal is loaded with the wireless array for use, it can be directly used in a clinical whole-body scanner to obtain magnetic resonance imaging of the small animal without the need for use with special equipment for small animals, thereby eliminating the need for applying ultra-high field strength and compatibility with additional cable interfaces produced by different manufacturers. Compared with the prior art, the wireless array for small animal imaging disclosed in the present application can achieve the purpose of improving the signal-to-noise ratio of small animal imaging.

[0028] The present invention proposes a wireless array with a simple structure and compatible with commercial magnetic resonance systems. The wireless array is passive, without cables, baluns and a series of connecting devices. It has a simple structure and can be easily placed on any test part of the scanned animal. It can be used close to the body surface of small animals, avoiding the surgical risks and biocompatibility issues of implanting coils. It can be directly placed on the scanned part of the test animal and is universal for commercial radio frequency receiving coils. At the same time, it can enhance the image signal-to-noise ratio of small animal imaging and improve the image spatial resolution. At the same time, the wireless array is composed of multiple resonant loops, and these passive resonant coils are decoupled from each other by overlapping. The wireless array does not require cables and a series of connectors, and can be directly attached to the place where the signal needs to be enhanced. It is compatible with MRI equipment from different suppliers and can achieve imaging signal-to-noise ratio enhancement when used in conjunction with different radio frequency receiving coils.

[0029] A wireless array for small animal imaging mainly adopts a loop structure, which locally enhances the received signal without changing the transmitting field B1+; it can be used with any RF receiving coil during use. The size of the wireless array affects both the imaging depth and the imaging range, and the size and the size of a single passive resonant coil can be changed according to the part that needs to be enhanced. The passive resonant coil of the wireless array ensures transparency to the RF transmitting field by controlling the on-off of the passive resonant coil by a pair of opposing PIN diodes. The decoupling method is to achieve decoupling between units by partially overlapping the passive resonant coils of the wireless array and canceling the magnetic flux between the passive resonant coils.

[0030] The wireless array provided by the present invention has been tested to prove its feasibility. Figure 4 and Figure 5 During the experiment, it was shown that for the wireless array used in conjunction with the knee coil, the wireless array significantly improved the signal-to-noise ratio of the rat brain tissue near the wireless array. Compared with the rat coil, the wireless array used in conjunction with the knee coil can improve the signal-to-noise ratio in the rat brain area by more than 4 times, which can meet the requirements of high-resolution imaging, high signal-to-noise ratio and image quality for rat brain imaging. The wireless array has no restrictions on the receiving coil and can be used in conjunction with the commercial coils of conventional clinical magnetic resonance imaging systems to enhance the signal-to-noise ratio of imaging, such as Figure 5 shown.

[0031] Among them, when adding a passive resonant coil, since any passive resonant coil has only two first areas and a second area, there is no overlapping area between any two adjacent decoupling modules, and the decoupling of each decoupling module is achieved only by the overlapping of the three passive resonant coils it has.

[0032] The passive resonant coil has a detuned state and a resonant state. The detuned state is used for detuning in the radio frequency transmission stage, and the resonant state is used for resonating in the reception stage to enhance the signal.

[0033] The working process of the wireless array is as follows: in the RF transmission stage of the magnetic resonance imaging system, the PIN-type diode of the detuned circuit in the unit resonant loop of the wireless array is turned on, so that the entire loop is in a detuned state, and the response of the wireless array to the RF transmission field is attenuated, thereby reducing the impact on the RF transmission field to a minimum; when the wireless array is working in the receiving stage, the PIN-type diode of the detuned circuit in the unit resonant loop of the wireless array is not turned on, and the detuned circuit is not working, so that the signal can pass. Under Faraday's law of electromagnetic induction, the change in magnetic flux passing through the wireless array causes the wireless array to induce an electromotive force, and the wireless array amplifies the voltage signal by Q (the quality factor of the wireless array) times and then is received by the RF receiving coil, thereby achieving an enhancement in the signal-to-noise ratio of the imaging signal. The present invention provides an implementation example: a 3-channel wireless array used in conjunction with a commercial knee coil, and its placement diagram is shown in the figure below. Figure 3 shown.

[0034] The relative positions of the knee coil and the wireless array are as follows Figure 3 As shown. The role of the wireless resonant ring is to increase the size of the magnetic resonance signal without changing the distribution of the RF transmission field to enhance the signal-to-noise ratio, thereby improving the image signal-to-noise ratio and improving image quality. The commercial knee coil is a hollow cylinder that can accommodate a human leg and has 24 receiving channels.

[0035] The commissioning of wireless arrays includes tuning, detuning, and decoupling; e.g. Figure 2 As shown, the passive resonant coil of the wireless array adopts a loop structure, and its tuning is achieved by the adjustable capacitor Tune in the passive resonant coil, wherein the frequency of the detuned loop in the loop is achieved by adjusting C1 and L1. The wireless array is decoupled by overlapping to reduce the coupling between the passive resonant coils. The decoupling method is as follows Figure 1 As shown, Figure 1 Reference numeral 101 is an overlapping area portion for overlapping decoupling, reference numeral 102 is a passive resonant coil, and 102 has a detuned state and a tuned state, and is tuned to a desired Larmor frequency. Figure 3 shows a 3-channel wireless array used in conjunction with a commercial knee coil. Figure 3 Reference numeral 101 is a schematic diagram of a commercial knee coil, which is in the shape of a hollow cylinder and has 24 receiving channels. Reference numeral 102 is a wireless array, which has three passive resonant coils.

[0036] The present invention does not limit the use of receiving coils, and conventional coils can be used. The present invention is not limited to the type, size and dimensions of the wireless array unit coils, the number of channels of the wireless array, and the detuning method. It is also not limited to the distribution plane of the wireless array, that is, it can be distributed on a plane or on a cylindrical surface. In addition, the placement of the RF receiving coil and the wireless array can be directly placed close 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. In order to ensure that the imaging quality in the area where the gap is located is lower than that in other areas due to the appearance of the gap between the two decoupling modules, and to avoid the situation where the size of the wireless array is greatly increased due to the appearance of the gap, the number of passive resonant coils is selected to be three.

[0039] In some embodiments, the passive resonant coil is in the shape of a regular octagon.

[0040] Specifically, the shape of the passive resonant coil is a regular octagon. In the high frequency band, the regular octagonal coil exhibits lower parasitic capacitance than other shapes (such as square). This means that at high frequencies, the regular octagonal coil can transmit signals more effectively and reduce energy losses. At the same time, the Q value is an important parameter to measure the performance of the inductor, which reflects the loss of the inductor. The transition between each metal wire of the regular octagonal inductor is smoother (the two adjacent metal wires are at an angle of 120 degrees), and the loss to the RF signal is smaller than that of the square inductor (the two adjacent metal wires are at an angle of 90 degrees). Therefore, the Q value of the regular octagonal inductor is usually higher. In addition, the regular octagon can have three side lengths in both the length and width directions, so that the stacking between the passive resonant coils can be selected and controlled, and the overlapping area can be calculated more conveniently.

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

[0042] It should be noted that, in order to ensure that the area of ​​the overlapping region is more convenient and quick to calculate, the shapes of the two first regions are both parallelograms, or one is a parallelogram and a hexagon. In the process of overlapping the regular octagons, only one of the three passive resonant coils has two first regions that are two parallelograms, and the two first regions of the other two detuned resonant passive coils are a parallelogram and a hexagon, respectively.

[0043] In some more specific embodiments, the parallelogram and the hexagon have the same area.

[0044] Specifically, in order to achieve the best decoupling effect, the areas of the parallelepiped and the hexagon should be the same, so as to ensure that the influences caused by different passive resonant coils on each other tend to be consistent.

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

[0046] It should be noted that, in order to further improve the decoupling effect, it has been verified by experimenters that when the shape of the second area is a triangle and the long side of the parallelogram of the first area is the side of the regular octagon of the passive resonant coil, the decoupling effect reaches a peak.

[0047] In some embodiments, please refer to Figure 3 , the size of the wireless array matches the size of the area to be measured.

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

[0049] The flexible structure may be a flexible structure such as cloth or felt, and the wireless array may be more convenient to use by setting the flexible structure.

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

[0051] In order to further optimize the passive resonant coil structure and reduce the manufacturing cost of the wireless array, the present application connects an adjustable capacitor in series in the tuning loop to achieve a tuning state. It should be noted that the detuning loop and the tuning loop do not emphasize having two different loops. In some embodiments, the detuning loop and the tuning loop have a common circuit.

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

[0053] This embodiment uses a parallel LC circuit controlled by two pairs of bidirectional diodes to achieve detuning. Other methods can also be used to achieve detuning in the detuning circuit, such as introducing a new detuning circuit.

[0054] In the description of this specification, if the terms "embodiment one", "this embodiment", "in an embodiment" and the like appear, it means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in the invention or at least one embodiment or example of the invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example; moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in an appropriate manner.

[0055] In the description of this specification, the terms "connect", "install", "fix", "set", "have", etc. are all understood in a broad sense. 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 it can be an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0056] In the description of this specification, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "comprises", "comprising" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the statement "comprising a ..." does not exclude the presence of other identical elements in the process, method, article or device including the element.

[0057] The above description of the embodiments is to facilitate ordinary technicians in the technical field to understand and apply the technology of this case. People familiar with the technology in this field can obviously easily make various modifications to these examples and apply the general principles described here to other embodiments without creative work. Therefore, this case is not limited to the above embodiments. Modifications to the following situations should all be within the scope of protection of this case: ① A new technical solution implemented based on the technical solution of the present invention and combined with existing common knowledge, the technical effect produced by the new technical solution does not exceed the technical effect of the present invention; ② The equivalent replacement of some features of the technical solution of the present invention by using known technology, the technical effect produced is the same as the technical effect of the present invention; ③ The technical solution of the present invention can be expanded, and the substantive content of the expanded technical solution does not exceed the technical solution of the present invention; ④ The equivalent transformation made by using the contents of the description and drawings of the present invention is directly or indirectly applied to other related technical fields.

Claims

1. A wireless array for small animal imaging, characterized in that: It comprises a plurality of passive resonant coils with detuned circuits, wherein any one of the passive resonant coils 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.

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

3. A wireless array for small animal imaging according to claim 1, characterized in that: The passive resonant coil is in a regular octagonal shape.

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

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

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

7. A wireless array for small animal imaging according to any one of claims 1 to 6, characterized in that: The size of the wireless array matches the size of the area to be measured.

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

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

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