Carbon- (¹²C-) ion radiotherapy exhibits enhanced biological effectiveness compared to photon radiotherapy, however, the contribution of its interaction with the vasculature remains debatable. The effect of high-dose ¹²C-ion and photon irradiation on vascular permeability in moderately differentiated rat prostate tumors was compared using dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI). Syngeneic R3327-HI rat prostate tumors were irradiated with a single dose of either 18 or 37 Gy ¹²C ions, or 37 or 75 Gy 6-MV photons (sub-curative and curative dose levels, respectively). DCE-MRI was performed one day prior to and 3, 7, 14 and 21 days postirradiation. Voxel-based tumor concentration-time curves were clustered based on their curve shape and treatment response was assessed as the longitudinal changes in the relative abundance per cluster. Radiation-induced vascular damage and increased permeability occurred at day 7 postirradiation for all treatment groups except for the 75 Gy photon-irradiated group, where the onset of vascular damage was delayed until day 14. No differences between irradiation modalities were found. Therefore, early vascular damage cannot explain the higher effectiveness of ¹²C ions relative to photons in terms of local tumor control for this moderately differentiated prostate tumor and the applied single high doses.

碳（¹² C-）离子放射疗法与光子放射疗法相比具有增强的生物学功效，但是，其与脉管系统相互作用的作用仍有待商bat。使用动态对比增强磁共振成像（DCE-MRI），比较了大剂量¹² C离子和光子辐照对中分化大鼠前列腺肿瘤血管通透性的影响。用单一剂量的18或37 Gy ¹²照射同基因的R3327-HI大鼠前列腺肿瘤C离子或37或75 Gy 6-MV光子（分别为亚治疗剂量和治疗剂量）。DCE-MRI在照射前一天，照射后3、7、14和21天进行。基于体素的肿瘤浓度-时间曲线基于其曲线形状进行聚类，并根据每个聚类的相对丰度的纵向变化来评估治疗反应。除75 Gy光子照射组外，所有治疗组在辐射后第7天均发生了辐射诱导的血管损伤和通透性增加，其中血管损伤的发作延迟至第14天。未发现照射方式之间存在差异。因此，早期血管损伤不能解释¹²的更高疗效。就该中度分化的前列腺肿瘤和所施加的单个高剂量而言，就局部肿瘤控制而言，相对于光子的C离子。