Stephens T C, Peacock J H, Shipley W U, Steel G G
Br J Cancer Suppl. 1984;6:271-4.
In vivo ultra low dose rate continuous irradiation (CI, 15 cGy h-1) was used in an attempt to accurately quantify low dose radiation response (less than 2 Gy) of both tumour and normal tissue, a parameter which is clinically relevant but difficult to assess using conventional acute radiation survival curves. Dorsally placed tumours were irradiated by housing tumour bearing mice for up to three weeks in a dedicated 137Cs unit taking care to shield the lower body. Response to CI was monitored by an excision cell survival assay. For bone marrow treatment whole body irradiation was used and BM-CFUc were assessed. In all 4 tissues studied (Lewis lung carcinoma, B16 melanoma, carcinoma MT and C57B1/6 bone marrow) cell survival decreased exponentially with dose; the three tumours had similar D0 (approximately 6 Gy), bone marrow was more sensitive (D0 1.5 Gy). Acute in vitro radiation survival curves were analysed using both the multi-target plus single hit and the linear quadratic models of radiation cell kill. Comparison of CI results with acute radiation survival curve parameters derived from each model suggest that CI offers a useful means of assessing the low dose radiosensitivity of tumours and may therefore be useful in the prediction of tumour response to clinically relevant fractionated treatments.
为了准确量化肿瘤组织和正常组织的低剂量辐射反应（小于2 Gy），采用了体内超低剂量率连续照射（CI，15 cGy h-1），这一参数在临床上具有相关性，但使用传统的急性辐射存活曲线很难评估。将荷瘤小鼠饲养在专用的137Cs照射装置中长达三周，对背部的肿瘤进行照射，注意保护小鼠下半身。通过切除细胞存活试验监测对CI的反应。对于骨髓治疗，采用全身照射并评估骨髓集落形成单位（BM-CFUc）。在所研究的所有4种组织（Lewis肺癌、B16黑色素瘤、MT癌和C57B1/6骨髓）中，细胞存活率随剂量呈指数下降；三种肿瘤的D0相似（约6 Gy），骨髓更敏感（D0为1.5 Gy）。使用多靶加单击模型和线性二次模型分析急性体外辐射存活曲线。将CI结果与从每个模型得出的急性辐射存活曲线参数进行比较，结果表明CI为评估肿瘤的低剂量放射敏感性提供了一种有用的方法，因此可能有助于预测肿瘤对临床相关分割治疗的反应。
