| Summary: | 碩士 === 長庚大學 === 醫學物理暨影像科學研究所 === 96 === Microvascular dimensions can be estimated by vessel size imaging (VSI) based on the measurements of transverse relaxation rates of gradient-echo and spin-echo signals following bolus injection of contrast agents. VSI has been successfully applied in humans using a dual-echo echo-planar imaging sequence. Such sequence is not commonly available in clinical scanners and may be limited in spatial resolution. The purpose of this study was to investigate the use of separate injections for VSI on a clinical 3T scanner with higher resolution. Eight patients with brain tumors participated in the study (six with acquisition matrix = 64×64, two with 128×128). From the datasets with the 64 matrix, the estimated vessel caliber of normal tissues were 37.4±12.9, 20.7±8.8, and 15.0±5.1 μm for occipital gray matter, thalamus and deep white matter, respectively, which were in good agreement with previous studies. The datasets with higher resolution gave vessel sizes within the ranges of the lower resolution results for normal brain tissues but demonstrated more detailed heterogeneity in tumors. This study suggested the dual injections method as a feasible technique for estimating microvessel sizes with high spatial resolution in clinical scanners.
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