A magnetic resonance open wireless birdcage coil

Abstract

The present invention discloses a magnetic resonance open wireless birdcage coil, which relates to the technical field of magnetic resonance coils, and specifically includes a transverse channel and a vertical channel located at the upper and lower ends thereof, and a vertical channel is evenly arranged between the two transverse channels, and the transverse channel and the vertical channel form a sheet-shaped open wireless birdcage coil, and the distance between two adjacent vertical channels is equal, and the vertical channel includes an upper part and a lower part, and the upper part and the lower part are connected by a capacitor; the number of the vertical channels is four, six or eight. The magnetic resonance open wireless birdcage coil has a simple and clear design, high cost-effectiveness, does not require cable connection, and does not require decoupling. Its adjustable function does not require changing the system settings of the original instrument, and can adapt to most magnetic resonance imaging platforms, thereby improving its adaptability.

Description

Technical Field

[0001] The invention relates to the technical field of magnetic resonance coils, in particular to an open wireless birdcage coil for magnetic resonance. Background Art

[0002] Magnetic resonance imaging (MRI) provides a non-invasive method for producing high-resolution images with excellent soft tissue contrast. MRI not only provides detailed anatomical images, but also provides functional and physiological information, such as blood flow and tissue perfusion. This unique feature of MRI allows it to fully evaluate a variety of medical conditions with great precision and accuracy.

[0003] The most important and fundamental parameter of MRI is the signal-to-noise ratio (SNR), which directly affects the spatial resolution and imaging quality. From a hardware perspective, a mainstream approach to improving SNR is to optimize the radio frequency (RF) detector, also known as the RF receive coil. In modern scanners, receive arrays with multiple elements have become mainstream because they provide superior SNR and encoding capabilities for fast MRI. In head imaging, the most popular receive coils are 12-channel / 32-channel arrays at 1.5T / 3T. In addition to optimizing the RF receive coil, passive plugs placed between the tissue and the coil are also used to enhance the SNR. One type of passive plug is a dielectric pad made of a high dielectric constant material, such as water, barium titanate (BaTiO3), etc. Another is to use inductively coupled wireless / passive resonators, such as ring resonators, volume resonators, dipole antennas, and the recently proposed metamaterials.

[0004] High-permittivity dielectric pads and conventional metamaterials often self-deactivate during RF transmission, a process known as detuning. They remain active during the transmit phase, even though their primary design is to enhance receive performance. This property can be advantageous when the original transmit field (B1+) needs to be improved. For example, at 7T, the original B1+ field from the head transmit coil is non-uniform, and properly designed dielectrics and metamaterials can help shape the B1+ field, improving its uniformity and efficiency. However, for most applications in clinical scanners operating at 1.5T or 3T, the B1+ field from the body transmit coil is sufficiently uniform. There is no need to modify the original B1+. In this case, it is a better option to maintain the original field of the body coil to alleviate RF safety concerns, prevent RF artifacts, and avoid changing the scanner's coil settings. This is critical in clinical MRI scanners where such modifications may not be feasible.

[0005] In contrast, wireless resonators using lumped capacitors can be easily detuned by adding a shunt inductor and a pair of anti-parallel diodes to the capacitor, forming a passive detuned circuit. Detunable wireless birdcage resonators (i.e., closed ladder resonators) and detunable ring resonators (i.e., Figure 5 However, the closed structure of the birdcage resonator limits its application to the head and limbs, and the high-power RF signal of the ring-shaped birdcage coil causes a voltage drop on each capacitor in the wireless birdcage coil during the transmission phase, activating the cross diode. Subsequently, the additional inductor and capacitor form a parallel resonant circuit, which exhibits high impedance and effectively disables the wireless resonator. However, in actual use, the scanner's default body coil is used for RF transmission without changing the B1+ field (RF field) or specific absorption rate (SAR) of human tissue. The wireless birdcage coil will act as a new local transmitter if it is not sufficiently detuned. In this case, a lot of effort is required to ensure the safety of the subject, including electromagnetic modeling, SAR calculation, B1 (magnetic field perpendicular to the main magnetic field direction) calibration, and adjustment of scanner coil parameters (such as reference voltage and safety factor). Therefore, the present invention introduces a non-enclosed trapezoidal resonator as a wireless insert to enhance MRI. The non-enclosed structural design makes it suitable for more general medical scenarios.

[0006] Compared with traditional wired birdcage coils, wireless birdcage coils do not require long cables to connect imaging equipment, greatly improving the flexibility and convenience of operation. They also provide patients with more freedom in position adjustment, greatly improving the comfort of the examination process. In addition, the use of wireless birdcage coils reduces potential safety risks associated with cables and improves the safety of the imaging process. The main challenge facing wireless birdcage coils is the need to further improve the signal-to-noise ratio. This requires continuous optimization of coil design to improve the signal-to-noise ratio. In previous studies, the stacked wireless birdcage coil design has a signal-to-noise ratio comparable to that of traditional single-loop coils of the same size, but the decoupling of stacked coils remains a challenge. Summary of the invention

[0007] The present invention provides a magnetic resonance open wireless birdcage coil, which has an open structure and maintains the high signal-to-noise ratio advantage of the birdcage coil while eliminating the coupling effect, thereby solving the problems in the above-mentioned background technology that the wireless birdcage coil is difficult to decouple and the closed structure of the birdcage resonator limits its adaptability.

[0008] The present invention provides the following technical solutions: a magnetic resonance open wireless bird cage coil, comprising a transverse channel and a vertical channel located at the upper end and the lower end thereof, the upper end and the lower end of the open wireless bird cage coil are both provided with a transverse channel, a vertical channel is evenly provided between the two transverse channels, the size of the transverse channel is the same as the size of the vertical channel, the transverse channel and the vertical channel are both rod-shaped, the transverse channel and the vertical channel form a sheet-shaped open wireless bird cage coil, which is applied to the head and limbs, the distance between two adjacent vertical channels is equal, and the vertical channel includes an upper part and a lower part, and the upper part and the lower part are connected through a capacitor;

[0009] The number of the vertical channels is four, six or eight, two transverse channels and four vertical channels form a four-step open wireless birdcage coil; two transverse channels and six vertical channels form a six-step open wireless birdcage coil; two transverse channels and eight vertical channels form an eight-step open wireless birdcage coil;

[0010] The open wireless birdcage coil adopts a low-pass birdcage design, and when used in practice, a detuning circuit needs to be added;

[0011] A detuning current is applied to seven steps of the eight-step open wireless birdcage coil; a detuning current is applied to three steps of the four-step open wireless birdcage coil; and a detuning current is applied to five steps of the six-step open wireless birdcage coil.

[0012] Preferably, the size of the sheet-like open wireless birdcage coil formed by the transverse channel and the vertical channel is 10*10 square centimeters.

[0013] Preferably, the capacitors fixed on two adjacent vertical channels are the same, but the capacitors installed on the four-step open wireless birdcage coil, the six-step open wireless birdcage coil and the eight-step open wireless birdcage coil are all different.

[0014] Preferably, the capacitance value of the capacitor installed on the four-step open wireless birdcage coil is 45.2pF; the capacitance value of the capacitor installed on the six-step open wireless birdcage coil is 34.6pF; the capacitance value of the capacitor installed on the eight-step open wireless birdcage coil is 27pF.

[0015] Preferably, the capacitor is located in the middle of the vertical channel.

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

[0017] 1. The MRI open wireless birdcage coil has a simple and clear design, is cost-effective, does not require cable connection, and does not require decoupling. Its adjustable function does not require changing the system settings of the original instrument and can adapt to most MRI platforms, improving its adaptability.

[0018] 2. The MRI open wireless birdcage coil maintains the high signal-to-noise ratio advantage of the birdcage coil while eliminating the coupling effect. When in use, it avoids the need to adjust system settings, making it adaptable to most MRI platforms at any time, thereby improving the quality of MRI imaging. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic diagram of the structure of a four-stage magnetic resonance open wireless birdcage coil;

[0020] Figure 2 It is a schematic diagram of the structure of a six-step magnetic resonance open wireless birdcage coil;

[0021] Figure 3 The schematic diagram of the structure of an eight-step magnetic resonance open wireless birdcage coil;

[0022] Figure 4 It is a schematic diagram of relative positions when the structure of the present invention is used;

[0023] Figure 5 The figure is a schematic diagram of a birdcage coil in the prior art.

[0024] In the figure: 1, horizontal channel; 2, vertical channel; 3, capacitor; 4, upper part; 5, lower part. DETAILED DESCRIPTION

[0025] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] The present invention provides a magnetic resonance open wireless birdcage coil, comprising a transverse channel 1 and a vertical channel 2, wherein there are two transverse channels 1, the upper end and the lower end of the open wireless birdcage coil are both provided with the transverse channels 1, the vertical channels 2 are evenly provided between the two transverse channels 1, the transverse channels 1 and the vertical channels 2 form a sheet-like open wireless birdcage coil, and the sheet-like open wireless birdcage coil formed by the transverse channels 1 and the vertical channels 2 has a size of 10*10 square centimeters.

[0027] The size of the transverse channel 1 is the same as that of the vertical channel 2. Both the transverse channel 1 and the vertical channel 2 are rod-shaped. In some embodiments of the present application, the diameter of both the transverse channel 1 and the vertical channel 2 is 5 mm.

[0028] The number of vertical channels 2 can be four, six or eight. Two transverse channels 1 and four vertical channels 2 can form a four-step open wireless birdcage coil; two transverse channels 1 and six vertical channels 2 can form a six-step open wireless birdcage coil; two transverse channels 1 and eight vertical channels 2 can form an eight-step open wireless birdcage coil.

[0029] The vertical channel 2 includes an upper portion 4 and a lower portion 5 . The upper portion 4 and the lower portion 5 are connected via a capacitor 3 , and the capacitor 3 is located in the middle of the vertical channel 2 .

[0030] The capacitors 3 fixed on two adjacent vertical channels 2 are the same, but the capacitors installed on the four-step open wireless birdcage coil, the six-step open wireless birdcage coil and the eight-step open wireless birdcage coil are all different. The capacitance value of the capacitor installed on the four-step open wireless birdcage coil is 45.2pF; the capacitance value of the capacitor installed on the six-step open wireless birdcage coil is 34.6pF; the capacitance value of the capacitor installed on the eight-step open wireless birdcage coil is 27pF.

[0031] The above-mentioned open wireless birdcage coil adopts a low-pass birdcage design, and in actual use, a detuning circuit needs to be added. Detuning current is applied to seven steps of the eight-step open wireless birdcage coil; three steps of the four-step open wireless birdcage coil; and five steps of the six-step open wireless birdcage coil. The purpose is to de-resonate all resonant modes during RF transmission. During RF transmission, the body coil produces a uniform transmission field, and the head array and all wireless resonators are detuned. During RF reception, the head array is used as the main coil instead of the body coil.

[0032] The present invention has conducted an extensive analysis of different levels of open birdcage wireless coils in 1.5T magnetic resonance imaging. Among them, the eight-level wireless open birdcage coil has the highest signal-to-noise ratio. Compared with the wireless single coil, the signal-to-noise ratio of the eight-level wireless open birdcage coil is significantly improved. The design proposed by the present invention is simple and cost-effective, does not require cable connection, and does not require decoupling. The adjustable function of the wireless open birdcage coil does not require changing the system settings of the original instrument, which is easy to adapt to most magnetic resonance imaging platforms, thereby improving the performance of magnetic resonance imaging. Compared with the single-loop wireless coil, the eight-loop configuration significantly improves the signal-to-noise ratio. The design proposed in this application is simple and cost-effective, does not require cable connection, thereby bypassing the need for decoupling. Its adjustable characteristics avoid the requirement to adjust the system settings, making it adaptable to most magnetic resonance imaging platforms at any time, thereby improving the quality of magnetic resonance imaging.

[0033] From the above description, it can be seen that the wireless birdcage coil proposed in the present invention is an open structure and can be applied to the head and limbs. Compared with the closed birdcage coil structure, the present invention is suitable for more general medical scenarios.

[0034] In summary: The relative position of the magnetic resonance open wireless birdcage coil when in use is as shown in the attached manual. Figure 3 As shown in the instruction manual (see Figure 3 The four-channel array shown is designed based on Siemens' 12-channel commercial head coil, and it is necessary to apply detuning currents on seven steps of the eight-step open wireless birdcage coil. During RF transmission, the body coil produces a uniform transmission field, and the head array and all wireless resonators are detuned. During RF reception, the head array is used as the main coil instead of the body coil, which eliminates the coupling effect while maintaining the advantage of high signal-to-noise ratio, making it easy to use.

[0035] The contents not described in detail in this specification belong to the prior art known to professional and technical personnel in the field. Although the embodiments of the present invention have been shown and described, it is understood by ordinary technicians in the field that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principle and spirit of the present invention. The scope of the present invention is defined by the attached claims and their equivalents.

Claims

1. A magnetic resonance open wireless birdcage coil, comprising a transverse channel (1) and a vertical channel (2) located at the upper and lower ends thereof, characterized in that: The upper and lower ends of the open wireless birdcage coil are both provided with a transverse channel (1), and a vertical channel (2) is evenly provided between the two transverse channels (1). The size of the transverse channel (1) is the same as the size of the vertical channel (2). Both the transverse channel (1) and the vertical channel (2) are rod-shaped bodies. The transverse channel (1) and the vertical channel (2) form a sheet-like open wireless birdcage coil, which is applied to the head and limbs. The distance between two adjacent vertical channels (2) is equal, and the vertical channel (2) includes an upper part (4) and a lower part (5), and the upper part (4) and the lower part (5) are connected through a capacitor (3); The number of the vertical channels (2) is four, six or eight; the two transverse channels (1) and the four vertical channels (2) form a four-step open wireless birdcage coil; the two transverse channels (1) and the six vertical channels (2) form a six-step open wireless birdcage coil; the two transverse channels (1) and the eight vertical channels (2) form an eight-step open wireless birdcage coil; The open wireless birdcage coil adopts a low-pass birdcage design, and when used in practice, a detuning circuit needs to be added; A detuning current is applied to seven steps of the eight-step open wireless birdcage coil; a detuning current is applied to three steps of the four-step open wireless birdcage coil; and a detuning current is applied to five steps of the six-step open wireless birdcage coil.

2. The magnetic resonance open wireless birdcage coil according to claim 1, characterized in that: The size of the sheet-like open wireless birdcage coil formed by the transverse channel (1) and the vertical channel (2) is 10*10 square centimeters.

3. The magnetic resonance open wireless birdcage coil according to claim 1, characterized in that: The capacitors (3) fixed on two adjacent vertical channels (2) are the same, but the capacitors installed on the four-step open wireless birdcage coil, the six-step open wireless birdcage coil and the eight-step open wireless birdcage coil are all different.

4. The magnetic resonance open wireless birdcage coil according to claim 3, characterized in that: The capacitance value of the capacitor installed on the four-step open wireless birdcage coil is 45.2pF; the capacitance value of the capacitor installed on the six-step open wireless birdcage coil is 34.6pF; the capacitance value of the capacitor installed on the eight-step open wireless birdcage coil is 27pF.

5. The magnetic resonance open wireless birdcage coil according to claim 1, characterized in that: The capacitor (3) is located in the middle of the vertical channel (2).

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