Hydrogen and fluorine double-resonance radio-frequency coil for rectum

Abstract

A hydrogen and fluorine double-resonance radio-frequency coil for a rectum. The radio-frequency coil comprises a supporting column (1), wherein four electrically conductive strips are uniformly distributed at intervals on the supporting column (1) in the circumferential direction, and the four electrically conductive strips are respectively an electrically conductive strip I (2), an electrically conductive strip II (3), an electrically conductive strip III (4) and an electrically conductive strip IV (5) in sequence; at one end of the supporting column (1), the electrically conductive strip I (2) is connected to the electrically conductive strip II (3) via a resistor R1 (6), and the electrically conductive strip III (4) is connected to the electrically conductive strip IV (5) via a capacitor C1 (7); an excitation port (12) is provided at the capacitor C1 (7), and the excitation port (12) is connected to a double-tuned matching circuit (13); at the other end of the supporting column (1), the electrically conductive strip I (2) is connected to the electrically conductive strip III (4) via a resistor R2 (8), and the electrically conductive strip II (3) is connected to the electrically conductive strip IV (5) via a resistor R3 (9); and each of the electrically conductive strips is provided with an opening (10) in the middle thereof, and is connected via a capacitor C0 (11) at the opening (10), and a differential port is provided at the capacitor C0 (11). The coil is suitable for rectums with an inner diameter of 5 mm or above and supports synchronous imaging of 1H and 19F in the rectum.

Description

A hydrogen and fluorine double resonance radiofrequency coil for rectal use Technical Field

[0001] The present invention relates to the technical field of magnetic resonance imaging, in particular to a hydrogen and fluorine double resonance radio frequency coil for rectum. Background Art

[0002] It is very important to accurately assess the staging of rectal cancer before surgery. Staging mainly relies on medical imaging examinations. Magnetic resonance imaging (MRI), as the preferred method for local assessment of rectal cancer recommended by the European Society of Medical Oncology (ESMO), can provide important information for rectal cancer staging and plays a vital role in the diagnosis and treatment of rectal cancer.

[0003] MRI technology uses a radio frequency transmitter coil to transmit a radio frequency signal of a specific frequency to a subject within a main magnetic field. This pulse excites the resonant nuclei in the subject, causing nuclear magnetic resonance (NMR). The resulting magnetic resonance signals are captured by a radio frequency receiver coil, which then undergoes a Fourier transform to reconstruct the NMR image.

[0004] The Q value is a measure of the efficiency of the coil loop in detecting MR signals and is closely related to the strength of the magnetic resonance signal received by the receiving coil. There are many ways to increase the Q value (i.e., reduce loss), but the most common method is to increase the resistance of the sample. The resistance of the sample can be increased by placing the coil closer to the sample. In other words, selecting a coil closer to the ROI (region of interest) can produce higher-quality images, covering the imaging area while not picking up noise from distant areas of the subject. Compared to ordinary surface coils, endorectal coils are smaller and closer to the ROI, allowing for clearer visualization of the structure of rectal cancer lesions and better facilitating accurate diagnosis and staging.

[0005] However, the existing rectal MRI radiofrequency coils are mostly ordinary surface coils, which have lower imaging signal-to-noise ratios than the insertable rectal radiofrequency coils. 1 H single-nuclide coils make it difficult to analyze information in organisms at the molecular level and determine the occurrence and development of diseases.

[0006] Patent document CN114415090A discloses a four-channel MRI rectal coil with multiple layers of circuitry stacked on the surface of a support column. These layers require overlapping and decoupling, otherwise coupling between channels can severely impact image quality. Reducing the size of this structure prevents the layers from stacking. Therefore, this rectal coil is suitable for rectal examinations with larger inner diameters, but not for those with smaller diameters of 5-7 mm, such as those in rabbits.

[0007] Patent document CN109725273B discloses a magnetic resonance dual-mode tuned hydrogen-fluorine deformable birdcage RF coil. The birdcage RF coil has a complex structure and a large volume. It cannot be used as an in-vivo coil that can provide high signal-to-noise ratio images and can only be used as an in-vitro coil.

[0008] Patent document CN111812568B discloses a hydrogen and fluorine dual-resonance radio frequency surface coil that transmits and receives signals in one. The radio frequency coil involved in this document is a surface coil, and the imaging signal-to-noise ratio of the surface coil is relatively low. However, the above document does not address how to design an in-vivo coil to make it suitable for a thin rectum of 5-7 mm while receiving higher-quality nuclear magnetic resonance signals. Summary of the Invention

[0009] The present invention proposes a hydrogen and fluorine double resonance radio frequency coil for rectum, which is suitable for rectums with an inner diameter of 5mm or more, such as rectums with an inner diameter of 6mm, and supports rectal intraoperative radiofrequency ablation. 1 H. 19 F synchronous imaging can reconstruct higher signal-to-noise ratio and higher quality MRI images.

[0010] The technical solution of the present invention is achieved as follows: a hydrogen and fluorine dual-resonance radio frequency coil for rectal use, comprising a support column, on which a coil loop is provided, the coil loop comprising four conductive strips, the four conductive strips being evenly spaced circumferentially on the sidewall of the support column, the four conductive strips being sequentially conductive strip one, conductive strip two, conductive strip three, and conductive strip four. Conductive strip one and conductive strip two at one end of the support column are connected via a resistor R1, conductive strip three and conductive strip four are connected via a capacitor C1, capacitor C1 and resistor R1 are parallel to each other, an excitation port is provided at capacitor C1, and the excitation port is connected to a double-tuned matching circuit, conductive strip one and conductive strip three at the other end of the support column are connected via a resistor R2, and conductive strip two and conductive strip four are connected via a resistor R3, resistors R2 and R3 have different axial heights, and resistors R2 and R3 form an orthogonal structure, each conductive strip is provided with an opening in the middle, and the openings are connected via a capacitor C0, and a differential port is provided at capacitor C0.

[0011] Furthermore, the double-tuned matching circuit is connected to a low-noise preamplifier, and the low-noise preamplifier is connected to a back end of a radio frequency receiving system.

[0012] Furthermore, a hole groove corresponding to the conductive strip is provided on the side wall of the support column, and the conductive strip is embedded in the hole groove.

[0013] Furthermore, the ends of conductive strip 1 and conductive strip 3 connected to resistor R2 are at the same height and are both higher than the support column; the ends of conductive strip 2 and conductive strip 4 connected to resistor R3 are at the same height and are both flush with the end of the support column.

[0014] Furthermore, each conductive strip is arranged along the axial direction of the supporting column.

[0015] Furthermore, the support column is a circular support column or a prismatic support column.

[0016] Beneficial effects of the present invention:

[0017] The hydrogen and fluorine double resonance radio frequency coil for rectum of the present invention is a coil structure with simple structure and small volume, which is suitable for rectum with inner diameter of 5mm and above, such as rectum with inner diameter of 6mm, and supports rectal internal resonant radiofrequency coil. 1 H. 19 F synchronous imaging can reconstruct higher signal-to-noise ratio and higher quality nuclear magnetic resonance images; by the different axial heights of resistors R2 and R3, the small coil space is utilized and the 1 H. 19 F is the coupling between two signals of different frequencies.

[0018] The hydrogen and fluorine dual-resonance radio frequency coil for rectal use of the present invention is not limited to the rabbit rectum, but is applicable to any situation requiring a coil structure such as a circular support cylinder or a prismatic support cylinder, especially a small-sized coil. The present structure can achieve performance comparable to that of a single-tuning dual-tuning coil and is portable.

[0019] The present invention supports rectal 1 H. 19 F synchronous imaging solves the problem that most of the MRI radiofrequency coils currently used for rectal examinations are ordinary surface coils, while most of the inserted rectal coils are 1 The technical difficulty of the H single-nuclide coil is to achieve multi-dimensional analysis of information in the organism at the molecular level while improving imaging quality, and to judge the occurrence and development of the disease.

[0020] Traditional methods 1 H image and 19 The F image needs to be scanned twice, and the present invention can obtain the F image through only one scan. 1 H image and 19 F image, greatly shortening the imaging time and avoiding the motion artifacts caused by the movement of the measured object during the two scanning processes. 1 H image and19 Accurate registration and fusion of F images.

[0021] With the aid of the rectal hydrogen and fluorine double resonance radio frequency coil of the present invention, exogenous 19 F probe for drug delivery, in situ oxygen partial pressure positioning measurement (pO2), tumor targeting and other application analyses. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] FIG1 is a schematic structural diagram of a support column;

[0023] Figure 2 is a schematic structural diagram of one end of a support column;

[0024] FIG3 is a schematic structural diagram of the other end of the support column;

[0025] FIG4 is a planar circuit diagram of the coil loop and the double-tuned matching circuit;

[0026] FIG5 is a schematic diagram of the structural modules of the back-end of the radio frequency receiving system;

[0027] FIG6 is a diagram showing the simulation results of the magnetic field distribution of the RF coil without the water model;

[0028] FIG7 is a diagram showing the simulation results of the magnetic field distribution of the RF coil with a water model;

[0029] Figure 8 shows the coil 1 H / 19 F double-tuned S-parameter simulation results diagram;

[0030] Figure 9 shows the coil 1 H single-tuned S-parameter simulation results diagram;

[0031] Figure 10 shows the coil 19 F single-tuned S-parameter simulation results.

[0032] Support column 1, conductive strip 1 2, conductive strip 2 3, conductive strip 3 4, conductive strip 4 5, resistor R16, capacitor C17, resistor R28, resistor R39, opening 10, capacitor C011, excitation port 12, double-tuned matching circuit 13. DETAILED DESCRIPTION

[0033] As shown in Figure 1, a hydrogen and fluorine double-resonance radiofrequency coil for rectal examination includes a support column 1. The support column 1 is a solid circular support column made of flexible material, which effectively avoids wear and tear on the rectal wall during actual examination and insertion into the rectum, effectively improving the examination experience and enhancing the comfort level. A coil loop is provided on the support column 1. The coil loop includes four conductive strips made of copper strips, which are evenly distributed on the side wall of the support column 1 along the circumferential direction. Each conductive strip is arranged along the axial direction of the support column 1. The side wall of the support column 1 is provided with a hole slot corresponding to the conductive strip. The conductive strip is embedded in the hole slot. The arrangement of the hole slot saves coil space. For small areas such as the rectum, it is necessary to reduce the coil space as much as possible without affecting performance.

[0034] As shown in Figure 1-3, the four conductive strips are, in order, conductive strip 1 2, conductive strip 2 3, conductive strip 3 4, and conductive strip 4 5. At one end of support column 1, conductive strip 1 2 and conductive strip 2 3 are connected via resistor R16, while conductive strip 3 4 and conductive strip 4 5 are connected via capacitor C17. Capacitor C17 and resistor R16 are parallel to each other. At the other end of support column 1, conductive strip 1 2 and conductive strip 3 4 are connected via resistor R28, while conductive strip 2 3 and conductive strip 4 5 are connected via resistor R39. Resistors R28 and R39 form an orthogonal structure. Furthermore, the ends of conductive strip 1 2 and conductive strip 3 4 connected to resistor R28 are at the same height and are both higher than support column 1. The ends of conductive strip 2 3 and conductive strip 4 5 connected to resistor R39 are at the same height and are both flush with the end of support column 1. This structural arrangement ensures that resistors R28 and R39 have different axial heights, preventing coupling.

[0035] An opening 10 is provided in the middle of each conductive strip, and a capacitor C011 is welded at the opening 10 , and a differential port is provided at the capacitor C011 .

[0036] As shown in FIG4 , an excitation port 12 is provided at the capacitor C17, and the excitation port 12 is connected to a double-tuned matching circuit 13. The coil is tuned and matched by the double-tuned matching circuit 13 so that the coil 1 H. 19 Resonance occurs at the F resonant frequency. Taking the 3T platform as an example, 1 H. 19 F resonates at 128.2MHz and 120.6MHz respectively: the inductor L and the capacitor C2 form an LC parallel resonant circuit. When the signal frequency in the coil is too low, the signal mainly passes through the inductor L. At this time, the circuit is inductive and the phase angle is positive. When the signal frequency in the coil is too high, the signal mainly passes through the capacitor C2. At this time, the circuit is capacitive and the phase angle is negative. When the signal is at a certain frequency, the circuit is only purely resistive, that is, sinusoidal oscillation will occur.

[0037] As shown in FIG5 , the double-tuned matching circuit 13 is connected to the low-noise preamplifier, which is connected to the back end of the RF receiving system. The back end of the RF receiving system includes a power splitter, 1 H bandpass filter and 19 F bandpass filter, the power divider divides the RF signal output by the low noise preamplifier into two paths, outputting them to 1 H bandpass filter and 19 F band-pass filter, after filtering, outputs to the corresponding receivers.

[0038] To verify the imaging performance of the RF coil, the 3D electromagnetic simulation software CST Studio Suite was used to simulate the RF coil's S parameters and magnetic field distribution. The S-parameter simulation ensured that the designed coil could resonate at the target resonant frequency and that the magnetic resonance signal received by the coil would be minimally lost at that frequency. The magnetic field distribution simulation ensured that the designed coil could receive a sufficiently high magnetic field.

[0039] The simulation of S parameters takes the 3T platform as an example. 1 H. 19 F needs to resonate at 128.2MHz and 120.6MHz respectively. Theoretically, the signal loss of the dual-tuned RF coil will inevitably increase compared to the single-tuned one. However, only by achieving dual tuning can synchronous imaging be achieved, which is a technical difficulty. As shown in Figures 8-10, from the S-parameter simulation results of the RF coil, it can be seen that the RF coil of this embodiment can resonate at 128.2MHz and 120.6MHz, and 1 H / 19 The gain of F double tuning at the target resonant frequency is about -15dB, while 1 The gain of H single tuning at the target resonant frequency is -25dB. 19 The gain of F single tuning at the target resonant frequency is -17dB, which shows that the coil has less signal loss at the target resonant frequency, and 1 H / 19 The performance of F dual tuning is similar to that of single tuning. The vast majority of nuclear magnetic resonance signals are transmitted from the transmitter to the receiver instead of being reflected along the transmission line, which ensures the acquisition of high signal-to-noise ratio images.

[0040] Because the RF coil is ultimately inserted into the rectum of a living organism for scanning and imaging, the unique electromagnetic environment within the organism will have a certain impact on the magnetic field distribution of the RF coil. In order to more realistically simulate the situation when the RF coil is actually inserted into the organism for imaging, a hollow cylinder is designed according to the RF coil structure of this embodiment. This hollow cylinder is used as a water phantom. The hollow part of the water phantom is used for inserting the RF coil of this embodiment, and the material properties of the solid part of the water phantom are set to match the dielectric constant of the organism during simulation to simulate the electromagnetic physiological environment in the real organism.

[0041] When simulating the magnetic field distribution of the RF coil, the individual RF coils were first simulated, with the results shown in Figure 6. The RF coils and water phantom were then simulated together, with the results shown in Figure 7. Finally, the two simulation results were compared. The simulation results for the magnetic field distribution of the RF coils show that the results for the coils and water phantoms are similar to those for the individual coils, demonstrating that the RF coils prepared in this embodiment perform well when inserted into a living organism for imaging. Furthermore, Figures 6 and 7 show that the received field strength of the RF coils in and around the coils is sufficiently high. This demonstrates that the designed coils can reconstruct higher signal-to-noise ratios and higher-quality MRI images.

Claims

1. A rectal hydrogen and fluorine double resonance radiofrequency coil, comprising a support column, characterized in that: A coil loop is provided on the support column, which includes 4 conductive strips. The 4 conductive strips are evenly distributed on the side wall of the support column along the circumferential direction. The 4 conductive strips are conductive strip one, conductive strip two, conductive strip three and conductive strip four respectively. The conductive strip one and conductive strip two at one end of the support column are connected through a resistor R1, and the conductive strip three and conductive strip four are connected through a capacitor C1. The capacitor C1 and the resistor R1 are parallel to each other. An excitation port is provided at the capacitor C1, and the excitation port is connected to the double-tuned matching circuit. The conductive strip one and conductive strip three at the other end of the support column are connected through a resistor R2, and the conductive strip two and conductive strip four are connected through a resistor R3. The axial heights of the resistor R2 and the resistor R3 are different, and the resistor R2 and the resistor R3 form an orthogonal structure. An opening is provided in the middle of each conductive strip, and the opening is connected through a capacitor C0. A differential port is provided at the capacitor C0.

2. The hydrogen and fluorine double resonance radio frequency coil for rectal use according to claim 1, characterized in that: The double-tuned matching circuit is connected to a low-noise preamplifier, and the low-noise preamplifier is connected to a rear end of a radio frequency receiving system.

3. The hydrogen and fluorine double resonance radio frequency coil for rectal use according to claim 1, characterized in that: A hole groove corresponding to the conductive strip is provided on the side wall of the supporting column, and the conductive strip is embedded in the hole groove.

4. The hydrogen and fluorine double resonance radio frequency coil for rectal use according to claim 1, characterized in that: The ends of conductive strips 1 and 3 connected to resistor R2 are at the same height and are both higher than the support column; the ends of conductive strips 2 and 4 connected to resistor R3 are at the same height and are both flush with the end of the support column.

5. The hydrogen and fluorine double resonance radio frequency coil for rectal use according to claim 1, characterized in that: Each conductive belt is arranged along the axial direction of the supporting column.

6. The hydrogen and fluorine double resonance radio frequency coil for rectal use according to claim 1, characterized in that: The supporting column is a circular supporting column or a prismatic supporting column.

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