Measurement of sound intensity of MRI driving sound in near field of MRI equipment

Magnetic resonance imaging (MRI) equipment of high magnetic field generates loud sound of around 100 dB. The purpose of this study is sound source search of MRI driving sound for hearing protection. We reported sound source search on the patient's table of MRI equipment. This paper shows the result of sound source search of the driving sound in near field of MRI equipment. Target of MRI equipment is Signa Horizon LX 1.5T for the whole body of magnetostatic field 1.5T of GE Yokogawa Medical Systems. The objects of analysis sound are auto tuning pulses and continuous driving sound of slice positioning. Auto tuning pulses are generated at the initial of imaging sequence. Slice positioning is utilized to get an image for decide the region of diagnosis. Measurement conditions are follows. Sampling frequency is 48000 Hz, analysis by sound intensity is cross-spectral method with Fast Fourier Transform (FFT), window function is Hanning window, analysis data length by FFT is 4096 points, and analysis frequency is from 176 to 1414 Hz. The result shows that maximum of sound intensity level of the driving sound was 89.3 dB and characteristic of the vector radiated from side surface of MRI gantry. It is clear that sound source of the driving sound is radiated from side shell and bore of MRI equipment.