Armour E P, White J R, DeWitt C C, Corry P M, Martinez A
Department of Radiation Oncology, William Beaumont Hospital, Royal Oak, Michigan 48073, USA.
Radiat Res. 1996 Apr;145(4):474-80.
The dose-limiting factor in essentially all curative radiotherapy is damage to normal tissue. In spite of this, our understanding of radiation-induced damage to normal tissue leaves much to be desired. Damage to the rectum is often observed after clinical brachytherapy of pelvic malignancies. A model in which the rectum of the rat is irradiated with a uniform and reproducible dose of brachytherapy irradiation was developed. This system consists of an intracavitary applicator, which is used in conjunction with methods that reduce fecal flow, a jacket that restrains rat movement and a lead-shielded chamber to contain rats during low-dose-rate brachytherapy. Irradiation was applied in 48-h intervals separated by 48-h breaks during which the applicator was removed. Methods to analyze the sequelae of brachytherapy irradiation of the rectum were also developed. The total dose of 0.75 Gy/h continuous low-dose-rate brachytherapy required to produce obstruction in the rat rectum has been measured. The ED50 was 70.6 +/- 4.2 Gy. The length of time between irradiation and obstruction was also correlated with total dose. Other effects on the rectum that were related to dose were diarrhea and rectovaginal fistula. This irradiation system can produce uniform and reliable brachytherapy doses to the rat rectum. The late effects in normal tissues observed in this model are similar to those observed in humans after irradiation of the rectum. The model should be appropriate for analyzing relative changes in the rectum resulting from different dose rates and fractionation schemes relevant to brachytherapy.
基本上所有根治性放射治疗中的剂量限制因素都是对正常组织的损伤。尽管如此，我们对辐射诱发的正常组织损伤的了解仍有很大欠缺。盆腔恶性肿瘤临床近距离放射治疗后常可观察到直肠损伤。我们开发了一种用均匀且可重复的近距离放射治疗剂量照射大鼠直肠的模型。该系统包括一个腔内施源器，它与减少粪便流动的方法联合使用，一个限制大鼠活动的外套以及一个在低剂量率近距离放射治疗期间容纳大鼠的铅屏蔽室。照射以48小时为间隔进行，每次照射后间隔48小时，在此期间取出施源器。我们还开发了分析直肠近距离放射治疗后遗症的方法。已测量出在大鼠直肠中产生梗阻所需的0.75 Gy/h连续低剂量率近距离放射治疗的总剂量。半数有效剂量为70.6±4.2 Gy。照射与梗阻之间的时间长度也与总剂量相关。与剂量相关的对直肠的其他影响包括腹泻和直肠阴道瘘。这种照射系统可为大鼠直肠产生均匀且可靠的近距离放射治疗剂量。在该模型中观察到的正常组织晚期效应与人类直肠照射后观察到的效应相似。该模型应适用于分析与近距离放射治疗相关的不同剂量率和分割方案导致的直肠相对变化。
