Objective.评估一种用于放射治疗剂量学的新胶片,GafchrochromeEBT4,与当前EBT3相比。评估剂量反应并验证MV外波束和HDR近距离放射治疗的测试案例。方法。三批(批次)EBT4和三批EBT3薄膜在0-1200cGy范围内以6MV校准,使用FilmQAPro软件。像素值的信噪比,报告剂量(RD),并评估了影响剂量测定准确性的因素(扫描时胶片的旋转,能量响应和曝光后变暗)。两片都暴露于临床治疗计划(VMAT前列腺,SABR肺,单个HDR源驻留,和“伪”3通道HDR子宫颈近距离放射治疗)。将膜-RD与TPS计算的剂量进行比较。主要结果。EBT4校准曲线具有比EBT3更有利的辐射剂量测定特性,与EBT3相比,EBT4的胶片RD具有改善的信噪比(在500cGy时,红色和绿色通道平均增加了46%)。对于两个膜,在扫描和曝光后变暗时的膜旋转是相似的。EBT4的能量响应类似于EBT3。对于所有临床案例研究,与EBT3相比,EBT4与TPS计划的剂量具有更好的一致性。VMAT前列腺gamma3%/3mm通过率,EBT4100.0%,EBT397.9%;SABR肺gamma2%/2mm,EBT499.6%和EBT397.9%;HDR子宫颈伽玛3%/2mm,EBT497.7%和EBT395.0%。意义。这些成果显示EBT4优于EBT3用于TPS计划递送的放疗剂量学验证。报告了EBT4的噪声分布和校准曲线的基本改善。所有临床测试案例显示,与EBT3相比,EBT4提供了与TPS计算剂量相当或更小的测量剂量差异。使用新的GafchrorEBT4胶片,提供了有关放射治疗中胶片剂量测定可达到的准确性的基线数据。
Objective.To evaluate a new film for radiotherapy dosimetry, Gafchromic EBT4, compared to the current
EBT3. To evaluate dose-response and verify test cases in MV external beam and HDR brachytherapy.Approach. Three lots (batches) of EBT4 and three lots of
EBT3 films were calibrated at 6 MV over 0-1200 cGy range, using FilmQAPro software. Signal-to-noise of pixel value, reported dose (RD), and factors affecting dosimetry accuracy were evaluated (rotation of the film at scanning, energy response and post-exposure darkening). Both films were exposed to clinical treatment plans (VMAT prostate, SABR lung, single HDR source dwell, and \'pseudo\' 3-channel HDR cervix brachytherapy). Film-RD was compared to TPS-calculated dose.Main results.EBT4 calibration curves had characteristics more favourable than EBT3 for radiation dosimetry, with improved signal to noise in film-RD of EBT4 compared to EBT3 (increase of average 46% in red and green channels at 500 cGy). Film rotation at scanning and post-exposure darkening was similar for the two films. The energy response of EBT4 is similar to
EBT3. For all clinical case studies, EBT4 provided better agreement with the TPS-planned doses than EBT3. VMAT prostate gamma 3%/3 mm passing rate, EBT4 100.0% compared to EBT3 97.9%; SABR lung gamma 2%/2 mm, EBT4 99.6% and
EBT3 97.9%; HDR cervix gamma 3%/2 mm, EBT4 97.7% and
EBT3 95.0%.Significance.These results show EBT4 is superior to
EBT3 for radiotherapy dosimetry validation of TPS plan delivery. Fundamental improvements in noise profile and calibration curve are reported for EBT4. All clinical test cases showed EBT4 provided equivalent or smaller difference in measured dose to TPS calculated dose than EBT3. Baseline data is presented on the achievable accuracy of film dosimetry in radiotherapy using the new Gafchromic EBT4 film.