Comparison of Image Quality According to Phantom Fluid Material in MR-based Attenuation Correction PET Imaging in PET/MR

Abstract

Integrated positron emission tomography (PET)/magnetic resonance (MR) imaging is gradually being used to improve the rate of cancer lesion detection in the medical field. To enhance the quality of PET/MR images, attenuation correction (AC) techniques are used by applying MR pulse sequences of the controlled aliasing in parallel imaging results in higher acceleration (CAIPI; MR ACSUBDixon-Caipi/SUB) and the generation autocalibrating partially parallel acquisition (GRAPPA; MR ACSUBDixon-Grappa/SUB), based on the T1-weighted two-point Dixon pulse sequence. In addition, quality control using a Jaszczak phantom filled with water and radioisotopes is frequently performed when scanning the patient. When acquiring MR-based AC PET images in the phantom study, artifacts are caused by high permittivity in water, and there is a limitation in the acquisition of uniform image quality. Therefore, the purpose of this study was to compare the image quality using phantom fluids with lower permittivity than water (sodium chloride (NaCl) NaCl+nickel sulfate (NiSO₄)) according to MR ACSUBDixon-Caipi/SUB and MR ACSUBDixon-Grappa/SUB pulse sequences using various quantitative analysis parameters: percent of non-uniformity (PNU), percent contrast recovery (PCR), signal to noise ratio (SNR), and coefficient of variation (COV). The results indicated that the image quality with NaCl+NiSO₄ fluid based on the results was 1.2-, 1.6-, 1.4-, and 1.1 times superior to that of NaCl fluid, respectively. In conclusion, NaCl+NiSO₄ fluid is suitable as a phantom fluid material in PET/MR images.