著作: [松元 友暉]/[金澤 裕樹]/Sasaki Toshiaki/Ikemitsu Natsuki/[林 裕晃]/Miyoshi Mitsuharu/[原田 雅史]/[大塚 秀樹]/Phase Correction for Quantitative Susceptibility Mapping (QSM) using T2* Mapping/The 5th International Congress on Magnetic Resonance Imaging
(英) Phase Correction for Quantitative Susceptibility Mapping (QSM) using T2* Mapping
(英) Objectives : The purpose of this study is to develop a phase correction method focusing on the SNR of phase and to improve the quantitative measurement of QSM. Methods : On a 3.0 T MRI system (Discovery MR750; GE Healthcare), using three-dimensional spoiled gradient-echo (3D-SPGR) sequence with multiple TEs were used in this study. The imaging parameters were TE, 12 echoes from 3.1 to 51.7 ms (ΔTE = 4.4 ms); repetition time, 55.5 ms; spatial resolution, 1.0 × 1.0 × 1.0 mm; and pixel bandwidth, 244.1 Hz. We conducted a phantom experiment in this study. Five tubes were filled with different concentrations (100, 150, 200, 250, and 300 mg/mL) of calcium hydroxyapatite samples. In this study, we focused on the computation of off-set frequency of each voxel (i.e., field map estimation). At first, we calculate the TE having the maximum for our setting number of echo from the measured T2* map. Second, the ``appropriate TE dataset'' was defined as the maximum SNR dataset with appropriate TE and two datasets with neighboring TE. Third, after estimating the field map using the appropriate TE dataset, a corrected phase angle at each phase angle of the appropriate TE dataset was calculated from a mean resultant length which is the length of the average vectors calculated from all phase angles. Then, the corrected phase angle was defined from mean resultant length. Finally, all phase angles in FOV were corrected for each appropriate TE dataset. Results : The linearity of the relationship between the measured susceptibility and the concentration of hydroxyapatite in the corrected phase dataset was significantly higher than other methods (R = 0.30 VS 0.97). Conclusions : The correction method in QSM using phase correction method makes it possible to more accurately obtain susceptibility information of tissue having a short T2*.
(英) The 5th International Congress on Magnetic Resonance Imaging
|年月日||必須||2017年 3月 初日|