Mohr Peter, Brieger Sabrina, Stahl Jürgen, Witucki Gerlo
Strahlentherapie, Diakoniekrankenhaus Schwäbisch Hall, Diakoniestrasse 10, 74523 Schwäbisch Hall, Germany.
Strahlenther Onkol. 2007 Jun;183(6):327-31. doi: 10.1007/s00066-007-1596-2.
The accuracy of the dose monitor system of a medical electron accelerator is of crucial importance for the precise delivery of the prescribed dose. Special attention is given to the case of low monitor units (MU). The long-term stability of the dose monitor system is analyzed.
Photon and electron fields with monitor units between 1 and 500 MU were measured with field sizes of 10 x 10 cm(2) and 20 x 20 cm(2) at source-skin distances (SSDs) of 100 cm and 95 cm, respectively. The relative dose per MU [see text] was determined for an Elekta linear accelerator.
The relative dose per MU was measured to be constant within about 1% down to fields with only 2 MU. The deviation remained below 2% down to 1 MU which is the minimum setting of the accelerator. The long-term stability is better than 0.2% per month.
No therapeutically relevant deviation of the prescribed dose could be detected for the Elekta linear accelerator. This is a prerequisite for the implementation of intensity-modulated radiotherapy (IMRT) techniques.
医用电子加速器剂量监测系统的准确性对于精确给予规定剂量至关重要。特别关注低监测单位 （MU） 的情况。分析了剂量监测系统的长期稳定性。
分别在源皮距离 （SSD） 为 100 cm 和 95 cm 时，对监测单位在 1 至 500 MU 之间、射野尺寸为 10×10 cm² 和 20×20 cm² 的光子和电子射野进行测量。针对一台医科达直线加速器，测定了每 MU 的相对剂量 [见正文]。
测量得出，每 MU 的相对剂量在约 1% 以内保持恒定，直至射野仅为 2 MU 时亦是如此。偏差在加速器的最小设置即 1 MU 时仍低于 2%。长期稳定性优于每月 0.2%。
对于医科达直线加速器，未检测到与治疗相关的规定剂量偏差。这是实施调强放射治疗 （IMRT） 技术的一个前提条件。
