Improvement of reproducibility in quantitative susceptibility mapping (QSM) and transverse relaxation rates () after physiological noise correction

BACKGROUND: Numerous studies have suggested that quantitative susceptibility mapping (QSM) and transverse relaxation rates ( R2* ) are useful to monitor neurological diseases. For clinical use of QSM and R2* , reproducibility is an important feature. However, respiration-induced local magnetic field variation makes artifacts in gradient echo-based images and reduces the reproducibility of QSM and R2* . PURPOSE: To investigate the improvement of reproducibility of QSM and R2* after the correction of respiration-induced field variation, and to assess the effect of varying types of the region of interest (ROI) analysis on reproducibility. STUDY TYPE: Reproducibility study. POPULATION: Ten controls. FIELD STRENGTH/SEQUENCE: 3T/multiecho gradient echo sequence. ASSESSMENT: Intrascan reproducibility of QSM and R2* was investigated in ROIs before and after the respiration correction. STATISTICAL TESTS: Reproducibility was obtained by the square of voxel-wise correlation coefficients between scans. A paired t-test was performed for comparison between before and after the respiration correction and between QSM and R2* . RESULTS: Based on the ROI analysis, reproducibility increased after the respiration correction. Reproducibility in the white matter (11.89% increased in QSM and 23.38% in R2* , P = 0.009 and 0.024, respectively) and deep gray matter (5.50% increased in QSM and 13.96% in R2* , P = 0.024 and 0.019, respectively) increased significantly after the respiration correction. Reproducibility of R2* was higher than that of QSM in the whole brain and cortical gray matter, while QSM maps showed higher reproducibility than R2* in the white matter and deep gray matter. DATA CONCLUSION: Respiration-induced error correction significantly improved reproducibility in QSM and R2* mapping. QSM and R2* mapping showed a different level of reproducibility depending on the types of ROI analysis. LEVEL OF EVIDENCE: 4 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2018.