Clark R A, Watanabe A T, Bradley W G, Roberts J D
Gates Laboratory of Chemistry, California Institute of Technology, Pasadena 91126.
Radiology. 1990 Apr;175(1):201-6. doi: 10.1148/radiology.175.1.2315481.
Acute hematomas can appear hypointense on T2-weighted magnetic resonance (MR) images at field strengths as low as 0.35 T. Using Raman spectroscopy to measure blood oxygenation and taking T2 measurements at 2.1 and 9.4 T, the authors examined the relaxation mechanisms acting during deoxygenation, increases in hematocrit, and fibrin-clot formation and retraction. Individual contributions to overall T2 from deoxyhemoglobin and the interactions of water with protein hydration layers in hemoglobin, plasma proteins, and fibrin were measured. Overall T2 values estimated by summing individual relaxation rates were in reasonable agreement with the T2 values of clotted blood. Results suggest that deoxygenation may be most important in T2 shortening, followed by increased hematocrit. T2 shortening from fibrin polymerization was minimal at the field strengths used. Effects of deoxygenation and increasing hematocrit are more sensitive to field strength than fibrin T2 shortening. Effects of fibrin may be more significant at middle and low field strengths.
急性血肿在低至0.35T的场强下，于T2加权磁共振（MR）图像上可呈现低信号。作者利用拉曼光谱法测量血液氧合情况，并在2.1T和9.4T下进行T2测量，研究了脱氧过程、血细胞比容增加以及纤维蛋白凝块形成和收缩过程中的弛豫机制。测量了脱氧血红蛋白对整体T2的单独贡献以及水与血红蛋白、血浆蛋白和纤维蛋白中蛋白质水化层的相互作用。通过将各个弛豫率相加估算出的整体T2值与凝血的T2值具有合理的一致性。结果表明，脱氧在T2缩短中可能最为重要，其次是血细胞比容增加。在所使用的场强下，纤维蛋白聚合导致的T2缩短最小。脱氧和血细胞比容增加对T2的影响比纤维蛋白T2缩短对场强更为敏感。在中低场强下，纤维蛋白的影响可能更为显著。
