Validation of an in-vivo proton beam range check method in an anthropomorphic pelvic phantom using dose measurements
Validation of an in-vivo proton beam range check method in an anthropomorphic pelvic phantom using dose measurements
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DOI：
10.1118/1.4915923
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发表时间：
2015-04-01
期刊：
影响因子：
3.8
通讯作者：
Lu, Hsiao-Ming
中科院分区：
文献类型：
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作者：
Bentefour, El H.;Tang, Shikui;Lu, Hsiao-Ming
目的：质子治疗中的体内剂量学和射束范围验证对质子治疗的验证和改进具有重要意义。具体地，体内射束范围验证可以实现新的治疗技术，其中之一可以是使用前列腺治疗的前部场而不是当前实践中的相对的横向场。本文报道了一种体内范围验证方法的验证研究，该方法可以将范围不确定性降低到亚毫米级，并可能允许在体内dosemetry.Methods：一个拟人骨盆体模用于验证的时间分辨剂量方法的临床潜力的范围验证的情况下，前列腺治疗使用范围调制前质子束。该方法使用安装在水球中的1 mm二极管的3x 4矩阵，其由ADC系统以100 kHz读取。该方法首先验证对光束范围测量的剂量消光测量。首先在水体模中完成确认，然后在开放野和治疗野配置的骨盆体模中完成确认。随后，将射束范围结果与治疗计划系统XIO计算的水等效路径长度（WEPL）值进行比较。结果：在水模中，时间分辨剂量法和剂量消光法的射束范围测量结果均达到亚毫米级精度。对于骨盆体模，当丢弃两个显示出显著范围混合迹象的二极管时，两种方法的结果均为+/- 1 mm。仅7 mGy的剂量就足以实现该结果。与治疗计划系统（XIO）计算的WEPL的比较表明，XIO低估了质子束范围。量化准确的XIO范围低估取决于用于评估WEPL结果的策略。结论：时间分辨剂量测量方法满足WEPL测量精度和最小剂量的两个基本要求，具有在体验证质子射程的潜力。需要进一步发展，即设计一个工作流程，考虑到质子射程混合所施加的限制以及测量和预期WEPL的比较对探测器位置误差的敏感性。该方法也可用于体内剂量测定，并可有益于各种质子治疗。(C)2015年美国医学物理学家协会。
Purpose: In-vivo dosimetry and beam range verification in proton therapy could play significant role in proton treatment validation and improvements. In-vivo beam range verification, in particular, could enable new treatment techniques one of which could be the use of anterior fields for prostate treatment instead of opposed lateral fields as in current practice. This paper reports validation study of an in-vivo range verification method which can reduce the range uncertainty to submillimeter levels and potentially allow for in-vivo dosimetry.Methods: An anthropomorphic pelvic phantom is used to validate the clinical potential of the time-resolved dose method for range verification in the case of prostrate treatment using range modulated anterior proton beams. The method uses a 3x4 matrix of 1 mm diodes mounted in water balloon which are read by an ADC system at 100 kHz. The method is first validated against beam range measurements by dose extinction measurements. The validation is first completed in water phantom and then in pelvic phantom for both open field and treatment field configurations. Later, the beam range results are compared with the water equivalent path length (WEPL) values computed from the treatment planning system XIO.Results: Beam range measurements from both time-resolved dose method and the dose extinction method agree with submillimeter precision in water phantom. For the pelvic phantom, when discarding two of the diodes that show sign of significant range mixing, the two methods agree with +/- 1 mm. Only a dose of 7 mGy is sufficient to achieve this result. The comparison to the computed WEPL by the treatment planning system (XIO) shows that XIO underestimates the protons beam range. Quantifying the exact XIO range underestimation depends on the strategy used to evaluate the WEPL results. To our best evaluation, XIO underestimates the treatment beam range between a minimum of 1.7% and maximum of 4.1%.Conclusions: Time-resolved dose measurement method satisfies the two basic requirements, WEPL accuracy and minimum dose, necessary for clinical use, thus, its potential for in-vivo protons range verification. Further development is needed, namely, devising a workflow that takes into account the limits imposed by proton range mixing and the susceptibility of the comparison of measured and expected WEPLs to errors on the detector positions. The methods may also be used for in-vivo dosimetry and could benefit various proton therapy treatments. (C) 2015 American Association of Physicists in Medicine.