In vivo relaxometry of three brain tumors in the rat: Effect of Mn‐TPPS, a tumor‐selective contrast agent

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Abstract
T1 and T2 were determined simultaneously in vivo at 4.7 T in implanted rat brain tumors. Three different tumor cell lines were implanted in the right caudate nucleus: the F98 glioma, the E367 neuro-blastoma, and the RN6 schwannoma. Their T1 and T2 values (mean ± standard deviation [msec]), respectively, were 1,312 ± 107 and 89 ± 3 (gli-oma), 1,284 ± 86 and 87 ± 7 (neuroblastoma), and 1,338 ± 85 and 86 ± 9 (schwannoma). The T1 values (msec) of normal brain and muscle were 1,090 ± 59 and 1,139 ± 77, respectively, and the T2 values (msec) were 76 ± 3 and 36 ± 2, respectively. After injection of the contrast agent manganese (III) tet-raphenylporphine sulfonate (TPPS) the T1 of all three tumors decreased by 30% and the T2 by 10%, whereas no such change in relaxivity was noted in normal brain. As a result, strong contrast enhancement of the three tumor types was seen on T1-weighted images. The tumor was clearly delineated and correlated with findings at histologic examination. This tumor enhancement was followed up for 4 days with quantitative relaxation time measurements, and the strong, selective reduction in T1 for all three tumor types after Mn-TPPS injection was preserved over the entire observation period.