Miralbell R, Rouzaud M, Grob E, Nouet P, Bieri S, Majno S B, Botteron P, Montero M, Precoma J C
Division de Radio-Oncologie, Hôpital Cantonal Universitaire, Geneva, Switzerland.
Int J Radiat Oncol Biol Phys. 1994 Jul 30;29(5):1167-73. doi: 10.1016/0360-3016(94)90414-6.
Total body irradiation (TBI) is frequently a complex and time-consuming technique that significantly overloads Radiation Oncology departments. In an attempt to shorten TBI setup and treatment time we aimed to develop a system where the lung blocks are fixed with optimal precision to the build-up booster lucite screen while the patient is immobilized in a reproducible upright position.
Fifteen patients diagnosed with leukemia were conditioned before bone marrow transplant since March 1992. Patients were immobilized in a semistanding position in a special stand with arm bars and hand grips. Treatment was delivered with a 6 MV x-ray horizontal beam. Six fractions of 2.25 Gy (mean instantaneous dose rate of 13.8 +/- 3.8 cGy/min) were delivered twice a day over 3 days (total dose: 13.5 Gy). Each fraction was given in alternating AP (facing the beam) and PA (turning the back) projections. Customized lung blocks (35% transmission) were used to assure a maximum lung dose of 10 +/- 0.5 Gy. The blocks were taped to a 1 cm thick lucite screen interposed between the source and the patient. Lung shields were checked by port films before each fraction. The reproducibility of the patient's positioning (and lung shielding) was evaluated by measuring the horizontal and vertical deviations of the infero-external corners of the lung blocks in the port films in relation to the same point in the simulation films. In vivo dosimetry (thermoluminescence and diodes) was performed by placing dosimeters and probes in the central axis and in several off-axis sites.
The mean horizontal and vertical deviations were 3.5 +/- 4.1 mm and 7.5 +/- 5.9 mm for the anterior fields, and 4.1 +/- 4.1 mm and 6.9 +/- 6.4 mm for the posterior fields. An acceptable position of the blocks was considered when deviations were < 5 mm horizontally and/or < 10 mm vertically. The mean time per fraction (i.e., interval between the patient's entering and leaving the treatment room) was 35 +/- 5 min.
A satisfactory level of reproducibility can be reached with this technique. The reasonably short treatment time contributes to reproducibility and patient comfort.
全身照射（TBI）通常是一项复杂且耗时的技术，会使放射肿瘤学科室负担过重。为了缩短TBI的设置和治疗时间，我们旨在开发一种系统，在患者以可重复的直立姿势固定时，将肺部铅挡块以最佳精度固定在组织等效增能滤线板上。
自1992年3月起，对15例诊断为白血病的患者在进行骨髓移植前进行预处理。患者在带有臂杆和把手的特殊支架上以半站立姿势固定。使用6兆伏X射线水平束进行治疗。每天两次，每次给予2.25戈瑞的6个分次（平均瞬时剂量率为13.8±3.8厘戈瑞/分钟），持续3天（总剂量：13.5戈瑞）。每个分次在前后（面对射线）和后前（背对射线）投影中交替给予。使用定制的肺部铅挡块（透射率35%）以确保肺部最大剂量为10±0.5戈瑞。这些铅挡块用胶带固定在置于源和患者之间的1厘米厚的有机玻璃屏上。每次分次治疗前通过射野片检查肺部铅挡块。通过测量射野片中肺部铅挡块下外角相对于模拟片上同一点的水平和垂直偏差，评估患者定位（以及肺部铅挡）的可重复性。通过将剂量计和探头置于中心轴和几个离轴位置进行体内剂量测定（热释光和二极管）。
前野的平均水平和垂直偏差分别为3.5±4.1毫米和7.5±5.9毫米，后野为4.1±4.1毫米和6.9±6.4毫米。当水平偏差<5毫米和/或垂直偏差<10毫米时，认为铅挡块位置可接受。每个分次的平均时间（即患者进入和离开治疗室的间隔时间）为35±5分钟。
该技术可达到令人满意的可重复性水平。合理较短的治疗时间有助于提高可重复性并提升患者舒适度。
