Roberts S A, Hendry J H, Potten C S
Cancer Research Campaign, Biomathematics and Computing Unit, Paterson Institute for Cancer Research, Christie Hospital (NHS) Trust, Manchester, United Kingdom.
Radiat Res. 1995 Mar;141(3):303-8.
A microcolony assay was used in conjunction with fractionated gamma irradiation to determine the number of clonogens in murine intestinal crypts with varying doses of irradiation used in the determination. The experimental design allows direct comparison between two-dose methodologies, employing one and two (or two or four) equal dose fractions, and multiple-dose methodologies involving determination of the crypt survival curves for a number of fractionation regimens using equal doses per fraction. The two-dose methodology yielded estimates of clonogen number of between 3 and 4 at low delivered dose (single and double fractions each of 6.5-7.5 Gy), rising to around 40 at high biological doses (two and four fractions each of 5.75 or 6.5 Gy). The multifraction methodology yielded estimates of clonogen number which increased from 13 after a single fraction to values of 26 and 22 after three and four fractions. However, the latter values were reduced to 11 and 9, and showed little evidence of any dependence on fraction number, when data pertaining to high biologically effective doses were excluded. Hence it is concluded that the high values for clonogen number typically deduced from such multiple-dose protocols, compared with the generally lower (but dose-dependent) values obtained from two-dose protocols, may be explained at least partially by the higher biological doses generally employed in the multiple-dose protocols.
微集落试验与分次γ射线照射相结合，以确定在测定中使用不同照射剂量时小鼠肠道隐窝中的克隆原细胞数量。该实验设计允许在两种剂量方法之间进行直接比较，一种是采用一个和两个（或两个或四个）相等剂量分次的单剂量方法，另一种是多剂量方法，涉及使用每个分次相等剂量确定多种分次方案的隐窝存活曲线。在低给予剂量（单次和两次分次，每次6.5 - 7.5 Gy）时，单剂量方法得出的克隆原细胞数量估计值在3到4之间，在高生物剂量（两次和四次分次，每次5.75或6.5 Gy）时升至约40。多分次方法得出的克隆原细胞数量估计值从单次分次后的13增加到三次和四次分次后的26和22。然而，当排除与高生物等效剂量相关的数据时，后两个值降至11和9，几乎没有显示出对分次次数的任何依赖性。因此得出结论，与通常从单剂量方案获得的较低（但与剂量相关）值相比，通常从此类多剂量方案推断出的克隆原细胞数量的高值，至少部分可以由多剂量方案中通常采用的较高生物剂量来解释。
