Carrasco Pablo, Jornet Núria, Latorre Artur, Eudaldo Teresa, Ruiz Agustí, Ribas Montserrat
Servei de Radiofísica i Radioprotecció, Hospital de la Santa Creu i Sant Pau, Sant Antoni Maria Claret, 167, 08025 Barcelona, Spain.
Med Phys. 2012 Aug;39(8):5040-9. doi: 10.1118/1.4736949.
To evaluate methods of pretreatment IMRT analysis, using real measurements performed with a commercial 2D detector array, for clinical relevance and accuracy by comparing clinical DVH parameters.
We divided the work into two parts. The first part consisted of six in-phantom tests aimed to study the sensitivity of the different analysis methods. Beam fluences, 3D dose distribution, and DVH of an unaltered original plan were compared to those of the delivered plan, in which an error had been intentionally introduced. The second part consisted of comparing gamma analysis with DVH metrics for 17 patient plans from various sites. Beam fluences were measured with the MapCHECK 2 detector, per-beam planar analysis was performed with the MapCHECK software, and 3D gamma analysis and the DVH evaluation were performed using 3DVH software.
In a per-beam gamma analysis some of the tests yielded false positives or false negatives. However, the 3DVH software correctly described the DVH of the plan which included the error. The measured DVH from the plan with controlled error agreed with the planned DVH within 2% dose or 2% volume. We also found that a gamma criterion of 3%∕3 mm was too lax to detect some of the forced errors. Global analysis masked some problems, while local analysis magnified irrelevant errors at low doses. Small hotspots were missed for all metrics due to the spatial resolution of the detector panel. DVH analysis for patient plans revealed small differences between treatment plan calculations and 3DVH results, with the exception of very small volume structures such as the eyes and the lenses. Target coverage (D(98) and D(95)) of the measured plan was systematically lower than that predicted by the treatment planning system, while other DVH characteristics varied depending on the parameter and organ.
We found no correlation between the gamma index and the clinical impact of a discrepancy for any of the gamma index evaluation possibilities (global, local, 2D, or 3D). Some of the tests yielded false positives or false negatives in a per-beam gamma analysis. However, they were correctly accounted for in a DVH analysis. We also showed that 3DVH software is reliable for our tests, and is a viable method for correlating planar discrepancies with clinical relevance by comparing the measured DVH of target and OAR's with clinical tolerance.
通过比较临床剂量体积直方图（DVH）参数，评估使用商业二维探测器阵列进行的实际测量的预处理调强放射治疗（IMRT）分析方法的临床相关性和准确性。
我们将工作分为两部分。第一部分包括六个模体测试，旨在研究不同分析方法的敏感性。将未改变的原始计划的射束注量、三维剂量分布和DVH与故意引入误差的实际交付计划的进行比较。第二部分包括对来自不同部位的17个患者计划的伽马分析与DVH指标进行比较。使用MapCHECK 2探测器测量射束注量，使用MapCHECK软件进行逐束平面分析，并使用3DVH软件进行三维伽马分析和DVH评估。
在逐束伽马分析中，一些测试产生了假阳性或假阴性。然而，3DVH软件正确地描述了包含误差的计划的DVH。来自具有可控误差的计划的测量DVH与计划DVH在剂量的2%或体积的2%范围内一致。我们还发现3%∕3毫米的伽马标准对于检测一些人为引入的误差过于宽松。全局分析掩盖了一些问题，而局部分析在低剂量时放大了无关的误差。由于探测器面板的空间分辨率，所有指标都遗漏了小的热点区域。对患者计划的DVH分析显示，治疗计划计算与3DVH结果之间存在小的差异，但眼睛和晶状体等非常小的体积结构除外。测量计划的靶区覆盖度（D(98)和D(95)）系统地低于治疗计划系统预测的值，而其他DVH特征则根据参数和器官而有所不同。
对于任何伽马指数评估可能性（全局、局部、二维或三维），我们发现伽马指数与差异的临床影响之间没有相关性。在逐束伽马分析中，一些测试产生了假阳性或假阴性。然而，它们在DVH分析中得到了正确的处理。我们还表明，3DVH软件对于我们的测试是可靠的，并且通过将靶区和危及器官的测量DVH与临床耐受性进行比较，是一种将平面差异与临床相关性相关联的可行方法。
