Guebert Alexandra, Conroy Leigh, Weppler Sarah, Alghamdi Majed, Conway Jessica, Harper Lindsay, Phan Tien, Olivotto Ivo A, Smith Wendy L, Quirk Sarah
Department of Physics and Astronomy, University of Calgary, Calgary, AB, Canada.
Division of Medical Physics, Tom Baker Cancer Centre, Calgary, AB, Canada.
J Appl Clin Med Phys. 2018 May;19(3):243-250. doi: 10.1002/acm2.12329. Epub 2018 Apr 25.
Two dose calculation algorithms are available in Varian Eclipse software: Anisotropic Analytical Algorithm (AAA) and Acuros External Beam (AXB). Many Varian Eclipse-based centers have access to AXB; however, a thorough understanding of how it will affect plan characteristics and, subsequently, clinical practice is necessary prior to implementation. We characterized the difference in breast plan quality between AXB and AAA for dissemination to clinicians during implementation.
Locoregional irradiation plans were created with AAA for 30 breast cancer patients with a prescription dose of 50 Gy to the breast and 45 Gy to the regional node, in 25 fractions. The internal mammary chain (IMC ) nodes were covered by 80% of the breast dose. AXB, both dose-to-water and dose-to-medium reporting, was used to recalculate plans while maintaining constant monitor units. Target coverage and organ-at-risk doses were compared between the two algorithms using dose-volume parameters. An analysis to assess location-specific changes was performed by dividing the breast into nine subvolumes in the superior-inferior and left-right directions.
There were minimal differences found between the AXB and AAA calculated plans. The median difference between AXB and AAA for breast V , was <2.5%. For IMC , the median differences V , and V were <5% and 0%, respectively; indicating IMC coverage only decreased when marginally covered. Mean superficial dose increased by a median of 3.2 Gy. In the subvolume analysis, the medial subvolumes were "hotter" when recalculated with AXB and the lateral subvolumes "cooler" with AXB; however, all differences were within 2 Gy.
We observed minimal difference in magnitude and spatial distribution of dose when comparing the two algorithms. The largest observable differences occurred in superficial dose regions. Therefore, clinical implementation of AXB from AAA for breast radiotherapy is not expected to result in changes in clinical practice for prescribing or planning breast radiotherapy.
瓦里安Eclipse软件中有两种剂量计算算法：各向异性分析算法（AAA）和Acuros外照射束算法（AXB）。许多基于瓦里安Eclipse的中心都可以使用AXB；然而，在实施之前，有必要全面了解它将如何影响计划特征以及随后的临床实践。我们对AXB和AAA之间乳腺计划质量的差异进行了表征，以便在实施过程中向临床医生进行传播。
为30例乳腺癌患者创建局部区域照射计划，乳腺处方剂量为50 Gy，分25次给予，区域淋巴结处方剂量为45 Gy。内乳链（IMC）淋巴结接受80%的乳腺剂量。使用AXB重新计算计划，同时保持监测单位不变，包括剂量到水和剂量到介质报告。使用剂量体积参数比较两种算法之间的靶区覆盖和危及器官剂量。通过将乳腺在上下和左右方向上划分为九个亚体积来进行评估位置特异性变化的分析。
AXB和AAA计算的计划之间差异极小。AXB和AAA之间乳腺V的中位数差异<2.5%。对于IMC，V和V的中位数差异分别<5%和0%；表明仅在边缘覆盖时IMC覆盖率才会降低。平均表面剂量中位数增加了3.2 Gy。在亚体积分析中，用AXB重新计算时内侧亚体积“更热”，外侧亚体积“更冷”；然而，所有差异均在2 Gy以内。
比较这两种算法时，我们观察到剂量大小和空间分布的差异极小。最大的可观察到的差异发生在表面剂量区域。因此，预计从AAA转换为AXB用于乳腺放疗的临床实施不会导致乳腺放疗处方或计划的临床实践发生变化。
