Gueorguiev Gueorgui, Cotter Christopher, Turcotte Julie Catherine, Crawford Bruce, Sharp Gregory, Mah'D Mufeed
University of Massachusetts; Massachusetts General Hospital.
J Appl Clin Med Phys. 2015 Sep 8;16(5):179–192. doi: 10.1120/jacmp.v16i5.5392.
This work aims at three goals: first, to define a set of statistical parameters and plan structures for a 3D pretreatment thoracic and prostate intensity-modulated radiation therapy (IMRT) quality assurance (QA) protocol; secondly, to test if the 3D QA protocol is able to detect certain clinical errors; and third, to compare the 3D QA method with QA performed with single ion chamber and 2D gamma test in detecting those errors. The 3D QA protocol measurements were performed on 13 prostate and 25 thoracic IMRT patients using IBA's COMPASS system. For each treatment planning structure included in the protocol, the following statistical parameters were evaluated: average absolute dose difference (AADD), percent structure volume with absolute dose difference greater than 6% (ADD6), and 3D gamma test. To test the 3D QA protocol error sensitivity, two prostate and two thoracic step-and-shoot IMRT patients were investigated. Errors introduced to each of the treatment plans included energy switched from 6 MV to 10 MV, multileaf collimator (MLC) leaf errors, linac jaws errors, monitor unit (MU) errors, MLC and gantry angle errors, and detector shift errors. QA was performed on each plan using a single ion chamber and 2D array of ion chambers for 2D and 3D QA. Based on the measurements performed, we established a uniform set of tolerance levels to determine if QA passes for each IMRT treatment plan structure: maximum allowed AADD is 6%; maximum 4% of any structure volume can be with ADD6 greater than 6%, and maximum 4% of any structure volume may fail 3D gamma test with test parameters 3%/3 mm DTA. Out of the three QA methods tested the single ion chamber performed the worst by detecting 4 out of 18 introduced errors, 2D QA detected 11 out of 18 errors, and 3D QA detected 14 out of 18 errors.
第一，为三维预处理胸部和前列腺调强放射治疗（IMRT）质量保证（QA）方案定义一组统计参数和计划结构；第二，测试三维QA方案是否能够检测出某些临床误差；第三，在检测这些误差方面，将三维QA方法与使用单电离室和二维伽马测试进行的QA进行比较。使用IBA的COMPASS系统对13例前列腺IMRT患者和25例胸部IMRT患者进行了三维QA方案测量。对于方案中包含的每个治疗计划结构，评估了以下统计参数：平均绝对剂量差（AADD）、绝对剂量差大于6%的结构体积百分比（ADD6）以及三维伽马测试。为了测试三维QA方案的误差敏感性，研究了两名前列腺和两名胸部静态调强放射治疗患者。引入到每个治疗计划中的误差包括能量从6兆伏切换到10兆伏、多叶准直器（MLC）叶片误差、直线加速器机头误差、监测单位（MU）误差、MLC和机架角度误差以及探测器移位误差。使用单电离室和电离室二维阵列对每个计划进行二维和三维QA。基于所进行的测量，我们建立了一套统一的公差水平，以确定每个IMRT治疗计划结构的QA是否通过：允许的最大AADD为6%；任何结构体积的最大4%可以具有大于6%的ADD6，并且任何结构体积的最大4%可能在测试参数为3%/3毫米剂量阈值分析（DTA）的三维伽马测试中失败。在所测试的三种QA方法中，单电离室表现最差，检测出18个引入误差中的4个，二维QA检测出18个误差中的11个，三维QA检测出18个误差中的14个。
