Research On The Magnetic Field Measurement Standards And Traceability Technology Of Magnetic Resonance Imaging

In recent years, a lot of medical equipment, especially high-tech medical diagnosticequipment entered into the hospital, provided more quantitative data to help doctors conductclinical diagnosis. At the same time, some medical diagnostic equipment caused endlessmedical misdiagnosis and disputes. If the hospital did not have the appropriate standards ofmeasuring and testing, it is difficult to regulate and real-time calibrate the medical diagnosticequipment, and it is difficult to ensure that the real test data is valid. Magnetic resonanceimaging devices are commonly used in large hospitals, and it is one of the most expensivemedical equipment for the hospital. With the increasing demands of image quality, the mainmagnetic field strength magnetic resonance equipment is also rising, up from1T,1.5T,3T to5T or7T. At present, in the national magnetic induction test system,the weak magnetic fieldrange of10-10~1×10-4T, the midfield magnetic field range of10-4~0.1T, and the magneticfield range of0.05~2T have the specific vertification regulation. However, it is still in theblank stage for the test of more than2T magnetic field, and there is not a national traceablestandard. In this case, the magnetic field of the existing traceability system can not meet thetest of medical MRI magnetic field calibration traceability requirements.This article cited the development and application of nuclear magnetic resonancetechnology, analyzed the status and current problems of the magnetic resonance imagingequipment. The detection device was established which can measure the uniformity ofmagnetic field, including nuclear magnetic resonance field measuring meter and the fieldsource, and the traceability system for measuring the magnetic resonance equipment fieldhomogeneity was initially established. According to the principles of nuclear magneticresonance measured the magnetic field, the paper analyzed the classical circuit design of theedge of the vibrator and designed nuclear magnetic resonance magnetometer which canautomatically search field. The instrument consists of an oscillator and a controller, and it canadjust the oscillation frequency by the reverse biased of the varactor diode. The oscillationfrequency can cover10-82MHz. The controller can automatically search the resonance signalthrough MCU control circuit,and find the resonance signal and locked on the resonance point. For different measured magnetic field, two probe were designed. The water probe isused to measure the field less than2T, and the heavy water probe is used to measure the fieldhiger than2T. Meanwhile, the display system based on Labview on PC were designed, and itcan automatically measure the magnetic field, and display the size and changes of themagnetic field. The measurement speed was fast and the measurement results were accurate.Finally, the development of automated searched nuclear magnetic resonance magnetometer,measuring the value of the uniform magnetic field zones of a permanent magnet, and theuncertainty of the measurement results were assessed, the ultimately measurement results is:B0=0.73932(1±1.4×10-5) T; k=2.