摘要：We performed dynamic MRI to reveal the characteristic gadopentetate dimeglumine (Gd-DTPA) uptake in carbon-ion irradiated tumor and compare it with photon irradiation. Fibrosarcomas in C3H mice legs were irradiated with either 16 Gy of carbon ions (74 keV/mm) or an equivalent dose (30 Gy) of Cs-137 γ-rays. Dynamic MRI was performed 1 or 6 days after irradiation when the tumors showed an initial growth delay or incipient regrowth, respectively. The enhancement pattern was visualized by mapping the maximum enhanced time ( Tmax ), relative signal intensity maximum ( SImax ), and time delay of starting enhancement ( Td ). Significantly larger Tmax and Td values were observed in the tumors 1 day after carbon-ion irradiation than in the nonradiated tumors ( No-R ) and tumors 1 day after γ-ray irradiation. Among the selected pixels in the tumors 6 days after carbon irradiation, 77% had Tmax values of less than 120 sec, significantly more than in the No-R group. The Tmax maps for the tumors irradiated with γ-rays showed a similar tendency to the carbon-irradiated ones, and only a significant difference was obtained between tumors 1 and 6 days after irradiation. Tmax and Td in the carbon-ion irradiated tumors were different from those in the γ-ray-irradiated tumors. These treatment-specific kinetics may be useful in predicting the therapeutic efficacy of carbon-ion treatment.
