Cilla Savino, Ianiro Anna, Craus Maurizio, Viola Pietro, Deodato Francesco, Macchia Gabriella, Buwenge Milly, Morganti Alessio G, Valentini Vincenzo, Piermattei Angelo
Medical Physics Unit, Fondazione di Ricerca e Cura Giovanni Paolo II - Università Cattolica del Sacro Cuore, Campobasso, Italy.
Radiation Oncology Unit, Fondazione di Ricerca e Cura Giovanni Paolo II - Università Cattolica del Sacro Cuore, Campobasso, Italy.
J Appl Clin Med Phys. 2019 Mar;20(3):37-44. doi: 10.1002/acm2.12538. Epub 2019 Feb 20.
We evaluated an EPID-based in-vivo dosimetry (IVD) method for the dose verification and the treatment reproducibility of lung SBRT-VMAT treatments in clinical routine. Ten patients with lung metastases treated with Elekta VMAT technique were enrolled. All patients were irradiated in five consecutive fractions, with total doses of 50 Gy. Set-up was carried out with the Elekta stereotactic body frame. Eight patients were simulated and treated using the Active Breath Control (ABC) system, a spirometer enabling patients to maintain a breath-hold at a predetermined lung volume. Two patients were simulated and treated in free-breathing using an abdominal compressor. IVD was performed using the SOFTDISO software. IVD tests were evaluated by means of (a) ratio R between daily in-vivo isocenter dose and planned dose and (b) γ-analysis between EPID integral portal images in terms of percentage of points with γ-value smaller than one (γ ) and mean γ-values (γ ) using a 3%(global)/3 mm criteria. Alert criteria of ±5% for R ratio, γ < 90%, and γ > 0.67 were chosen. 50 transit EPID images were acquired. For the patients treated with ABC spirometer, the results reported a high level of accuracy in dose delivery with 100% of tests within ±5%. The γ-analysis showed a mean value of γ equal to 0.21 (range: 0.04-0.56) and a mean γ equal to 96.9 (range: 78-100). Relevant discrepancies were observed only for the two patients treated without ABC, mainly due to a blurring dose effect due to residual respiratory motion. Our method provided a fast and accurate procedure in clinical routine for verifying delivered dose as well as for detecting errors.
我们评估了一种基于电子射野影像装置（EPID）的体内剂量测定（IVD）方法，用于临床常规肺立体定向体部放疗容积调强弧形治疗（SBRT-VMAT）的剂量验证和治疗可重复性。纳入了10例接受医科达VMAT技术治疗的肺转移瘤患者。所有患者均连续分5次照射，总剂量为50 Gy。使用医科达立体定向体架进行摆位。8例患者使用主动呼吸控制（ABC）系统进行模拟和治疗，该系统是一种肺活量计，可使患者在预定肺容积下屏气。2例患者使用腹部压迫器在自由呼吸状态下进行模拟和治疗。使用SOFTDISO软件进行IVD。通过以下方式评估IVD测试：（a）每日体内等中心剂量与计划剂量之间的比值R；（b）根据γ值小于1（γ）的点的百分比和平均γ值（γ），使用3%（全局）/3 mm标准对EPID积分门静脉图像进行γ分析。选择R比值的警戒标准为±5%，γ<90%，γ>0.67。采集了50幅传输EPID图像。对于使用ABC肺活量计治疗的患者，结果显示剂量传递的准确性很高，100%的测试在±5%范围内。γ分析显示γ的平均值为0.21（范围：0.04 - 0.56），平均γ为96.9（范围：78 - 100）。仅在2例未使用ABC治疗的患者中观察到相关差异，主要是由于残余呼吸运动导致的剂量模糊效应。我们的方法在临床常规中提供了一种快速准确的程序，用于验证 delivered dose以及检测误差。 （注：原文中“delivered dose”未翻译完整，可能存在信息遗漏，推测完整应为“已交付剂量”之类，但按照要求未添加其他解释，仅按原文翻译）
