Ikeguchi Hiroaki, Shonai Takaharu, Watanabe Tomohito, Nawate Mitsuru, Yano Ryutaro
Department of Radiological Technology, KKR Sapporo Medical Center.
Department of Diagnostic Radiology, Sapporo Teishinkai Hospital.
Nihon Hoshasen Gijutsu Gakkai Zasshi. 2020;76(12):1256-1265. doi: 10.6009/jjrt.2020_JSRT_76.12.1256.
T fluid-attenuated inversion recovery (FLAIR) using inversion recovery pulse to suppress cerebrospinal fluid signal needs adequate T recovery time after data acquisition, otherwise, the T-weighted contrast in brain tissue will get lower. Over 10000 ms of repetition time (TR) is recommended for the 1.5 T MR scanner, so it is difficult to shorten the imaging time. We verified whether T FLAIR combined with the magnetization transfer contrast (MTC) pulse shows better gray-to-white matter (GM/WM) and lesion-to-normal tissue contrasts even when the TR is shortened compared to the conventional T FLAIR. Optimal parameters of the MTC pulse were determined with a self-produced phantom, which modeled on cerebral cortical gray and white matters. GM/WM contrasts of the phantom were measured in T FLAIR with the MTC pulse while decreasing TR gradually from 10000 ms to 6500 ms. Although GM/WM contrast of the phantom in T FLAIR with the MTC pulse gradually decreased as the TR got shortened, the T FLAIR with the MTC pulse of 6500 ms of TR still showed 27% higher contrast than the conventional T FLAIR (TR 10000 ms). GM/WM contrast in T FLAIR with the MTC pulse was improved also in healthy volunteers, but improvement in thalamo-medullary contrast was less than that of cerebral cortico-medullary and putamino-medullary contrasts. It seems to be because thalamus, which is a deep gray matter, shows a higher MTC effect than other gray matters. Thus, it is necessary to note that the tissue contrast might differ between T FLAIR with the MTC pulse and the conventional T FLAIR. Because general lesions with an elongated T value show lower MTC effect compared to the normal brain tissue, a clinical case with thalamic lesion showed that the lesion-to-normal tissue contrast improved in T FLAIR with the MTC pulse of 6500 ms of TR. Although it is necessary to note the difference in contrast between some tissues, T FLAIR with the MTC pulse improves GM/WM and lesion-to-normal tissue contrasts even when the TR is shortened compared to the conventional T FLAIR, and it enables to shorten the imaging time.
使用反转恢复脉冲抑制脑脊液信号的液体衰减反转恢复（FLAIR）序列在数据采集后需要足够的T恢复时间，否则，脑组织中的T加权对比度会降低。对于1.5T MR扫描仪，建议重复时间（TR）超过10000ms，因此难以缩短成像时间。我们验证了即使与传统T FLAIR相比缩短了TR，T FLAIR与磁化传递对比（MTC）脉冲相结合是否能显示出更好的灰质与白质（GM/WM）以及病变与正常组织的对比度。使用一个模拟大脑皮质灰质和白质的自制体模确定了MTC脉冲的最佳参数。在T FLAIR序列中使用MTC脉冲测量体模的GM/WM对比度，同时将TR从10000ms逐渐降低到6500ms。尽管随着TR缩短，T FLAIR序列中使用MTC脉冲的体模的GM/WM对比度逐渐降低，但TR为6500ms的T FLAIR序列中使用MTC脉冲的对比度仍比传统T FLAIR（TR 10000ms）高27%。在健康志愿者中，T FLAIR序列中使用MTC脉冲时GM/WM对比度也有所改善，但丘脑-髓质对比度的改善小于大脑皮质-髓质和壳核-髓质对比度的改善。这似乎是因为作为深部灰质的丘脑比其他灰质显示出更高的MTC效应。因此，有必要注意使用MTC脉冲的T FLAIR序列与传统T FLAIR序列之间的组织对比度可能存在差异。由于T值延长的一般病变与正常脑组织相比显示出较低的MTC效应，一个丘脑病变的临床病例表明，TR为6500ms的T FLAIR序列中使用MTC脉冲时病变与正常组织的对比度有所改善。尽管有必要注意某些组织之间对比度的差异，但与传统T FLAIR相比，即使缩短了TR，使用MTC脉冲的T FLAIR序列仍能改善GM/WM以及病变与正常组织的对比度，并且能够缩短成像时间。
