Zhu Jingeng, Yin Fang-Fang, Kim Jae Ho
Department of Radiation Oncology, Henry Ford Hospital, Detroit, Michigan 48202, USA.
Med Phys. 2003 Aug;30(8):2218-21. doi: 10.1118/1.1589495.
In clinical radiation physics chart checking, the dose calculation results generated by computer treatment planning software are usually verified by an independent computerized monitor unit calculation routine, or by "hand calculation" using percent depth dose (PDD), tissue phantom ratio (TPR), scatter factors, and the machine calibration factors. For intensity-modulated radiosurgery (IMRS) or intensity-modulated radiation therapy (IMRT), the "hand calculation" becomes not feasible due to the sophisticated multileaf collimator (MLC) segments created for intensity-modulated dose delivery. Therefore, an independent computerized dose calculation routine is needed for fast and reliable dose verification. In this work, a point dose calculation routine for IMRS/IMRT plan verification is developed by directly applying Clarkson's method. The method includes preparing data table by measuring TPRs for circular fields with diameters ranging 6 to 98 mm, extrapolating TPR for the zero field size (TPR0) from measured data and generating scatter phantom ratio (SPR) for each individual circular field. The segmented MLC sequences created by IMRS/IMRT inverse planning are converted into irregular fields for Clarkson's calculation. This method has been tested using 29 IMRS/IMRT cases. The results indicate that it is reliable, fast, and accurate. The average time to calculate one field is about 2 s with a 300 Mhz CPU.
在临床放射物理计划审核中，计算机治疗计划软件生成的剂量计算结果通常通过独立的计算机监测单元计算程序进行验证，或者使用百分深度剂量（PDD）、组织体模比（TPR）、散射因子和机器校准因子进行“手工计算”来验证。对于调强放射外科（IMRS）或调强放射治疗（IMRT），由于为调强剂量输送而创建的复杂多叶准直器（MLC）段，“手工计算”变得不可行。因此，需要一个独立的计算机剂量计算程序来进行快速可靠的剂量验证。在这项工作中，通过直接应用克拉克森方法开发了一种用于IMRS/IMRT计划验证的点剂量计算程序。该方法包括通过测量直径范围为6至98mm的圆形射野的TPR来准备数据表，从测量数据中外推零射野尺寸的TPR（TPR0），并为每个单独的圆形射野生成散射体模比（SPR）。将IMRS/IMRT逆向计划创建的分段MLC序列转换为不规则射野以进行克拉克森计算。该方法已使用29个IMRS/IMRT病例进行了测试。结果表明它可靠、快速且准确。使用300MHz的CPU时，计算一个射野的平均时间约为2秒。
