Количественные снимки компонентов Т2 в мозге с использованием переменного угла поворота, сбалансированного свободного состояния с ультракоротким эхом МРТ.
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Shen Xin, Green Ari, Henry Roland G, Deveshwar Nikhil, Emir Uzay, Larson Peder E Z
Аннотация
Оригинал публикации
Quantitative ultrashort T2 components imaging in the brain using variable flip angle balanced steady state free precession ultrashort echo time MRI.
PURPOSE: This study aimed to develop a new method for quantitative measurement of ultrashort T2 (uT2) components in the brain that are associated with myelin, providing reliable and high-quality fitting results of uT2 fraction.
METHODS: Four healthy volunteers and four multiple sclerosis (MS) patients were recruited. A modified dual-echo balanced steady state free precession (bSSFP) ultrashort echo time (UTE) sequence was applied for acquisitions at six flip angles. The signals originating from uT2 components (e.g., myelin) were extracted and fitted by analyzing the differences between TE1 = 50 μs and TE2 = 2.2 ms signal curves along flip angles. A two-sample t-test was used for statistical comparison between uT2 fractions in white matter (WM), gray matter (GM), and MS lesions.
RESULTS: The differences between two TEs' signal curves along flip angles showed clear evidence of a uT2 component with a shape that matched the simulated results. Significantly higher uT2 fraction values were found in total WM than total GM for all individuals (around 6 %-7 % vs. 2 %, P < 0.001). In healthy volunteers, the uT2 fraction was consistent between repeated scans. In addition, the uT2 fraction in MS lesions was quantified with significantly reduced values than surrounding normal appearing WM by this method (4.84 %±0.49 % vs. 7.96 %±0.94 %, P < 0.001).
CONCLUSION: An isotropic sub-millimeter resolution uT2 fraction map was achieved with a simplified fitting model, and corresponded to expected patterns of myelination. There was a significant uT2 fraction reduction in MS patients' lesions. The repeatability of the quantification was verified by the consistency between two separate scans.