Evaluation of RF noise shielding effectiveness for the improvement of MR image in hybrid PET/MRI

The hybrid PET and MRI which could provide information on functional and structural images was required to improve the mutual compatibility. The purpose of this study is to propose a new electromagnetic shielding material; Au plated conductive fabric (Au PCF) tape, and evaluated shielding effectiveness of Au PCF tape and Cu foil for insertable PET in hybrid PET/MRI. The PET consisted of 18 detector blocks arranged in a ring of 390 mm diameter and 60 mm axial FOV. Each detector block was constituted of 4 × 4 matrix of detector module, each of which consisted of a 4 × 4 array LSO coupled to a 4 × 4 GAPD array. The PET gantry was positioned in center of two 3T Human MRIs and shielded with Au PCF tape or Cu foil. The PET readout electronics were enclosed in an aluminum shielding box behind MRI. RF head coil was also shielded with Au PCF tape or Cu foil to improve shielding effects. The MR image of cylindrical water phantom was acquired to evaluate MR image homogeneity and signal-to-noise ratio (SNR) with various MR sequences. The homogeneity of MR Images was similar without and with PET gantry shielded with Au PCF tape and Cu foil. SNRs measured without and with PET gantry shielded with Au PCF tape have small differences (<;4%). SNR was decreased <;~9% with PET gantry shielded with Cu foil. Experimental results indicate that Au PCF tape have good performance of electromagnetic shielding to reduce the effect of RF noise on the MR image in hybrid PET-MR.