Changes in the pharmacokinetics of Gd-DTPA in experimental tumors after charged particle radiation: comparison with gamma-ray radiation.
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 gamma-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 gamma-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 gamma-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 gamma-ray-irradiated tumors. These treatment-specific kinetics may be useful in predicting the therapeutic efficacy of carbon-ion treatment.
Department of Medical Imaging, National Institute of Radiological Sciences, Chiba, Japan. t_obata@nirs.go.jp
Takayuki
T
Obata
Koichi
K
Ando
Sachiko
S
Koike
Chisa
C
Oohira
Hiroshi
H
Yasuda
Hiroo
H
Ikehira
Shuji
S
Tanada
Hirohiko
H
Tsujii
D000818:Animals; D002244:Carbon / Q000627:therapeutic use; D003287:Contrast Media / Q000493:pharmacokinetics; D005354:Fibrosarcoma / Q000175:diagnosis* / Q000378:metabolism* / Q000532:radiotherapy; D019786:Gadolinium DTPA / Q000493:pharmacokinetics*; D005720:Gamma Rays / Q000627:therapeutic use*; D063193:Heavy Ion Radiotherapy; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008657:Metabolic Clearance Rate; D051379:Mice; D008809:Mice, Inbred C3H; D009374:Neoplasms, Experimental / Q000175:diagnosis / Q000378:metabolism; D012062:Relative Biological Effectiveness
D003287:Contrast Media; D002244:Carbon; D019786:Gadolinium DTPA