CN-121995283-A - Double-layer magnetic resonance radio frequency receiving coil array

CN121995283ACN 121995283 ACN121995283 ACN 121995283ACN-121995283-A

Abstract

The invention discloses a double-layer magnetic resonance radio frequency receiving coil array, and belongs to the technical field of magnetic resonance imaging. The coil array solves the problem of signal attenuation caused by the fact that the existing single-layer receiving coil cannot be tightly attached to a human body, and potential safety hazards caused by the fact that the wireless coil is inserted into the single-layer receiving coil. The inner layer coil can be tightly attached to subjects of different sizes to directly receive signals, and the outer layer coil can efficiently receive signals from the inner layer through inductive coupling. The design ensures the safety during the radio frequency transmission through a detuning protection mechanism, and realizes the efficient transmission of magnetic resonance signals by optimizing the distance and the coupling state between the inner layer coil and the outer layer coil. By using the coil array, the image signal-to-noise ratio and the image signal-to-noise ratio after parallel imaging acceleration can be obviously improved under the condition of the same or fewer receiving channels, and particularly, the imaging effect of a small subject is obviously improved, and meanwhile, the good compatibility with the existing magnetic resonance system is maintained.

Inventors

ZHAO WEI
XUE RONG
ZHANG ZIHAO
WANG ZHE
FANG CHENG
ZHUO YAN

Assignees

中国科学院生物物理研究所

Dates

Publication Date: 20260508
Application Date: 20260226

Claims (8)

1. A dual layer magnetic resonance radio frequency receive coil array comprising: The inner layer coil array is arranged close to the subject and used for collecting and coupling magnetic resonance signals and comprises a coil array which is formed by a plurality of radio frequency coils with the same resonance frequency as the magnetic resonance frequency and covers a sample area; the outer layer coil array is arranged at a preset distance from the inner layer coil array and is connected with the receiving coil and the preamplifier, so that signals are amplified and then enter a receiving channel of the system spectrometer through the coaxial line.
2. The dual-layer magnetic resonance radio frequency receiving coil array as set forth in claim 1, wherein each of the resonant loops in the inner layer coil array and the outer layer coil array is provided with an active detuning circuit, a passive detuning circuit, and a fuse; the magnetic resonance signals are transmitted between the inner coil array and the outer coil array through inductive coupling; the outer coil array is a multichannel receiving coil covering the magnetic resonance sample area and the inner coil and comprises a plurality of receiving coils with the same frequency as the inner coil.
3. The dual layer magnetic resonance radio frequency receive coil array as set forth in claim 1, wherein the active detuning circuit comprises a first capacitor, a first inductance, and a first diode; the first capacitor and the first inductor are connected in series to form a first LC resonant circuit, and the resonant frequency of the first LC resonant circuit is the same as the magnetic resonance working frequency of the coil circuit; When the first diode is conducted under the direct current bias, the first LC resonant circuit causes the coil circuit to be detuned at the magnetic resonance working frequency; the passive detuning circuit comprises a second capacitor, a second inductor and a second diode; The second capacitor and the second inductor are connected in series to form a second LC resonant circuit; the second diode is connected with the second LC resonant circuit in parallel and is configured to realize self-bias conduction by energy generated by radio frequency emission pulse so as to detune the coil circuit; the fuse is connected in series in the coil loop.
4. The dual layer magnetic resonance radio frequency receive coil array of claim 1, further comprising a fixing bracket for fixing the inner layer coil array and the outer layer coil array to maintain the predetermined distance and the relative positions of the two layer coil arrays.
5. The dual layer magnetic resonance radio frequency receive coil array of claim 4, wherein the inner layer coil array further comprises a coil housing made of medical grade polyurethane rubber and configured to provide a plurality of size models for different sized subjects.
6. The dual layer magnetic resonance radio frequency receive coil array of claim 1, wherein the inner layer coil array receives magnetic resonance signals from the subject and transmits the magnetic resonance signals to the outer layer coil array via inductive coupling, and wherein the outer layer coil array receives the magnetic resonance signals coupled through the inner layer coil array and the magnetic resonance signals directly from the subject and transmits the combined signals to the preamplifier.
7. The dual layer magnetic resonance radio frequency receive coil array of claim 1, wherein the predetermined distance between the inner layer coil array and the outer layer coil array is adjusted to operate the two layer coil array in a near field strong coupling region and to have a frequency response measured at an input of the outer layer coil array within a transition distance from lorentz resonance to coupling cleavage to maximize signal transmission efficiency at the magnetic resonance frequency.
8. The dual-layer magnetic resonance radio frequency receive coil array as set forth in claim 7, wherein the process of adjusting the predetermined distance comprises: gradually approaching the outer coil array from a position far away from the inner coil array; monitoring the frequency response of the outer coil array input; When the frequency response changes from a single lorentz formant to a bimodal occurrence of cleavage, the predetermined distance is determined as a distance that maintains the frequency response at a transition state between the lorentz formant and the bimodal occurrence.

Description

Double-layer magnetic resonance radio frequency receiving coil array Technical Field The invention relates to the technical field of magnetic resonance imaging, in particular to a double-layer magnetic resonance radio frequency receiving coil array. Background A Magnetic Resonance Imaging (MRI) medical diagnostic device can obtain images of any faults of various parts of a human body in a non-invasive way, can obtain clear soft tissue images and obtain human anatomy information, and is the most advanced clinical diagnostic device for discovering and diagnosing early cancers and other various diseases at present. In a nuclear magnetic resonance system there are typically two fields, one being the main magnetic field B0 generated by the magnet and one being the radio frequency field B1 generated by the radio frequency transmit coil. In the B0 field, the nuclei excited by the radio frequency field B1 undergo energy level transitions. When the rf pulse is turned off, the nuclei gradually release energy, returning to the original equilibrium state, a process known as relaxation. The energy released by the nuclei during relaxation is detected by the receive coil and a magnetic resonance signal is formed. MRI pursues high quality images, relying on developments in radio frequency receive coil technology. The MRI radio frequency receiving coil now uses a single-layer multichannel receiving coil array, and the commercial coil is divided into a head coil, a body coil, a spine coil, an ankle coil, and the like for different parts of a human body. The number of head coil channels is 24 channels, 32 channels, 64 channels, etc. The coil units of the multichannel receiving coil array are arranged around the human body, and the distribution range and the size of the coil units are fixed. Because the size of the human body is large and small, the commercial coil cannot be closely attached to the human body, and MRI signals received by the coil attenuate along with the distance, so that the received signals cannot reach the optimal signal-to-noise ratio. Particularly for subjects with smaller body sizes, the distance between the receiving coil and the subject is larger, so that the signals acquired by the coil are weaker. In addition, the need to install a preamplifier and coaxial cable connection behind the receiving coil, a sturdy support structure is required, and placement close to the human body is difficult. At present, a wireless coil is designed to be placed close to a human body, and then through inductive coupling, magnetic resonance signals acquired by a receiving coil are enhanced, and the image signal-to-noise ratio and the parallel imaging image quality are improved. The technical defect is that the wireless coil can be placed at any part of the tested body, but has fewer protection measures on the tested body. The wireless coil has only one passive detuning circuit, and especially when a plurality of coils are conducted simultaneously and the coils are influenced by mutual coupling, the passive detuning circuit does not necessarily enter an ideal working state. In addition, if one of the bi-directional diodes of the circuit fails, this results in the coil itself not being able to detune well, resulting in excessive coupling of transmit energy into the coil. If the radio frequency emission energy is coupled to the wireless coil, local radio frequency radiation is likely to be excessive, and electromagnetic power (SAR) absorbed or consumed by human tissues with unit mass exceeds standard, so that safety has a hidden danger. In addition, there is no mention of inductive coupling with the receiver coil in the design of the wireless coil. The strong inductive coupling can lead to performance degradation of the wireless coil and the receiving coil, and the signal-to-noise ratio of the image can be improved only under the condition of higher energy transmission efficiency. Disclosure of Invention In order to solve the technical problems in the background, the active detuning, the passive detuning and the fuse are simultaneously applied to the two layers of coils, so that each coil in the double-layer receiving coil array can be fully detuned during radio frequency transmission, and the radio frequency transmitting signals are ensured not to be coupled into the receiving coils. Meanwhile, the invention also introduces a magnetic resonance wireless electric energy transmission theory, analyzes by utilizing an inductive coupling principle, and directly influences the signal received by the receiving coil by the transmission efficiency between the two layers of coils. The operating frequency is the first core factor affecting the transmission efficiency, and the transmission efficiency is highest when the two layers of coils are simultaneously operated at the larmor frequency of magnetic resonance. The second factor is the coupling coefficient, which is mainly determined by the placement positions of the inner and outer