Lewis D, Chan M, Micke A, Yu X
Ashland Specialty Ingredients, Wayne, NJ.
Memorial Sloan-Kettering Cancer Center, Basking Ridge, NJ.
Med Phys. 2012 Jun;39(6Part12):3741. doi: 10.1118/1.4735223.
Radiochromic film provides dose measurement at high spatial resolution, but often is not selected for routine evaluation of patient-specific IMRT plans owing to ease-of-use factors. We have developed a simplified protocol that avoids complications encountered in commonly used methods.
We evaluated the simplified protocol by collecting dose-response data from six production lots of EBT3 film at doses up to 480 cGy. In this work, we used eight different scanners of two different models - Epson 10000XL and V700; post-exposure times before scanning from 30 minutes to 9 days; ambient temperatures for scanning spanning 23°F and two film orientations. Scanning was in 48-bit rgb format at 72 dpi resolution. Dose evaluation was conducted using a triple-channel dosimetry method. To validate the simplified protocol, patient specific IMRT QA was performed using a Varian Trilogy Linac to expose EBT3 films. Scanning and film analysis was done following the protocol.
The results indicated that the dose-response data could be fit by a set of related rational functions leading to the description of a universal calibration curve. A simplified protocol was established where dose-response data for a specific film lot, scanner, and scanning conditions could be derived from no more than two films exposed to known doses. In most cases only one calibrated exposure was required. Using the Gamma test criterion of 2%/2mm to evaluate the measurements, passing rates ranged between 95% and 99%.
We have demonstrated a simplified protocol to measure doses delivered by an IMRT treatment plan using only the patient film, one calibration film, one unexposed film, and applying a single scan to acquire a digital image for calculation and analysis. The simplification and time-savings provide a practical solution for using radiochromic film for routine IMRT QA without sacrificing spatial resolution for convenience. David Lewis, Andre Micke and Xiang Yu are all employed by Ashland Specialty Ingredients the manufacturer of GAFCHROMIC EBT3 radiochromic film that is the subject of the work presented in the Abstract.
放射变色薄膜可在高空间分辨率下进行剂量测量，但由于使用便利性因素，通常不被选用于患者特异性调强放疗（IMRT）计划的常规评估。我们开发了一种简化方案，避免了常用方法中遇到的复杂情况。
我们通过收集六个生产批次的EBT3薄膜在高达480 cGy剂量下的剂量响应数据，对简化方案进行了评估。在这项工作中，我们使用了两种不同型号的八种不同扫描仪——爱普生10000XL和V700；扫描前的曝光后时间从30分钟到9天；扫描时的环境温度跨度为23°F，以及两种薄膜方向。扫描采用72 dpi分辨率的48位rgb格式。使用三通道剂量测定法进行剂量评估。为了验证简化方案，使用瓦里安Trilogy直线加速器对EBT3薄膜进行患者特异性IMRT质量保证（QA）。按照方案进行扫描和薄膜分析。
结果表明，剂量响应数据可以用一组相关的有理函数拟合，从而得出通用校准曲线的描述。建立了一种简化方案，其中特定薄膜批次、扫描仪和扫描条件的剂量响应数据可以从不超过两张暴露于已知剂量的薄膜中得出。在大多数情况下，只需要一次校准曝光。使用2%/2mm的伽马测试标准来评估测量结果，通过率在95%至99%之间。
我们展示了一种简化方案，仅使用患者薄膜、一张校准薄膜、一张未曝光薄膜，并通过单次扫描获取数字图像进行计算和分析，来测量IMRT治疗计划所交付的剂量。这种简化和节省时间为在不牺牲空间分辨率以换取便利性的情况下，将放射变色薄膜用于常规IMRT QA提供了一种切实可行的解决方案。大卫·刘易斯、安德烈·米克和向宇均受雇于亚什兰特种成分公司，该公司是GAFCHROMIC EBT3放射变色薄膜的制造商，也是本摘要中所呈现工作的主题。
