Detuning circuit and method for radio frequency transmitting coil in nuclear magnetic resonance system

Abstract

The invention discloses a detuning circuit and a detuning method for a radio frequency transmitting coil in a nuclear magnetic resonance system. The radio frequency transmitting coil is in a birdcage type; antenna masts are circularly distributed at the connecting nodes of two end rings at equal intervals; the end ring between the nodes is broken and connected with an end ring capacitor; the detuning circuit is uniformly distributed on the end ring and connected in parallel with the end ring capacitor; and the detuning circuit comprises a current-limiting resistor, a choking inductor, a detuning capacitor and a PIN diode. The invention also discloses a method for detuning the radio frequency transmitting coil, which comprises the following steps that: the inductor of the antenna mast is matched with the end ring capacitor to make the transmitting coil produce resonance; a detuning power supply driving circuit applies a positive DC voltage at the input end, the PIN diode is turned off to show high impedance, the choking inductor has high impedance to the radio frequency signal, and the transmitting coil resonates; and a negative DC voltage is applied at the input end, the PIN diode is turned on to show low impedance, the detuning capacitor is connected in parallel with the end ring capacitor, and the transmitting coil is detuned. The detuning circuit and the detuning method protect the transmitting coil from being influenced at the transmission stage and deviate from the resonant frequency at the receiving stage so as to prevent the coupling between the coils.

Description

technical field [0001] The invention relates to a circuit and a method for detuning a radio frequency transmitting coil in a receiving phase in a nuclear magnetic resonance system. Background technique [0002] Magnetic resonance imaging (MRI) equipment is a medical diagnostic equipment developed since the 1980s. It can obtain images of arbitrary sections of various parts of the human body without trauma, and can obtain clear soft tissue images and human anatomical information. And the most advanced clinical diagnostic equipment for diagnosing early cancer and various other diseases are valued in the international medical and technical circles. [0003] There are usually two fields in the NMR system, one is the main magnetic field B0 generated by the superconducting magnet, and the other is the radio frequency field B1 generated by the radio frequency coil. The radio frequency coil that generates the radio frequency field is a very important part in the nuclear magnetic res...

AI Technical Summary

Problems solved by technology

The main performance of the radio frequency coil is the inductance performance. There is an inductive coupling phenomenon between the radio frequency coils, and when the mutual magnetic flux changes, it can affect the magnetic flux change of the nearby radio frequency coils. When they are close to each other, they will affect each other, resulting in the radio frequency coil Deviating from the original resonance point, the desired resonance signal cannot be received

Images