Department of Medical Physics, Tampere University Hospital, 33521 Tampere, Finland; Department of Oncology, Tampere University Hospital, 33521 Tampere, Finland.
Center of Oncology, Kuopio University Hospital, 70210 Kuopio, Finland.
Med Dosim. 2021;46(1):86-93. doi: 10.1016/j.meddos.2020.09.005. Epub 2020 Sep 29.
To investigate the near-surface doses and target coverage in modulated arc radiotherapy (RT) of the breast or chest wall in two treatment planning systems (TPS) in the presence of soft tissue deformations. This retrospective study consisted of 10 breast cancer patients with axillary lymph node inclusion. For each case, five RT plans were created: (1) tangential 3D conformal field-in-field (FinF) technique; (2) 200° to 240° arcs with optimization bolus (OB) in Eclipse (EB); (3) 243° to 250° arcs with an 8-mm OB in Monaco (MB); (4) 243° to 250° arcs with automatic skin flash tool (ASF) in Monaco TPS (MA); (5) 243° to 250° arcs with both ASF and OB in Monaco (MAB). Soft tissue deformation was simulated by editing CT-images with 4-, 8-, and 12-mm swelling and recalculating the dose. The increasing swelling from 0 to 12 mm caused the coverage (V95%) in clinical target volume to decrease from 96% ± 2% to 90% ± 6% for the FinF plans. For volumetric-modulated arc therapy (VMAT), the coverage decreased from 99% ± 1% to 92% ± 4% in the EB plans, and from 97% ± 1% to 68% ± 8%, 85% ± 6%, and 86% ± 5% for MA, MB, and MAB, respectively. The mean dose in the surface extending from 0 to 3 mm from the skin decreased on average 5%, 17%, 20%, 15%, and 8% in FinF, EB, MA, MB, and MAB, respectively. In the Monaco plans, the use of an OB(+ASF) provided better target coverage and lower dose maxima despite of tissue swelling than the ASF alone. With modulated arc therapy, we recommend the use of an OB instead of or in addition to the ASF. The use of 8 mm OB with VMAT plans is robust to account deformations extending outside up to 8mm. If soft tissue deformation is larger than 8 mm, the need for replanning should be evaluated.
为了研究在存在软组织变形的情况下，两种治疗计划系统（TPS）中调制弧放射治疗（RT）对乳房或胸壁的近表面剂量和靶区覆盖情况。本回顾性研究包括 10 例腋窝淋巴结受累的乳腺癌患者。对于每个病例，创建了五个 RT 计划：（1）切线 3D 适形场中野（FinF）技术；（2）在 Eclipse（EB）中使用优化敷贴（OB）进行 200°至 240°弧形照射；（3）在 Monaco（MB）中使用 8mm OB 进行 243°至 250°弧形照射；（4）在 Monaco TPS（MA）中使用自动皮肤闪光工具（ASF）进行 243°至 250°弧形照射；（5）在 Monaco 中同时使用 ASF 和 OB 进行 243°至 250°弧形照射（MAB）。通过编辑 CT 图像来模拟软组织变形，模拟肿胀程度为 4mm、8mm 和 12mm，并重新计算剂量。从 0 到 12mm 的肿胀程度增加导致 FinF 计划中临床靶区的覆盖率（V95%）从 96%±2%下降到 90%±6%。对于容积调强弧形治疗（VMAT），EB 计划中的覆盖率从 99%±1%下降到 92%±4%，而 MA、MB 和 MAB 的覆盖率分别下降到 68%±8%、85%±6%和 86%±5%。从皮肤表面向 0 到 3mm 延伸的平均剂量分别下降了 5%、17%、20%、15%和 8%，在 FinF、EB、MA、MB 和 MAB 中。在 Monaco 计划中，与单独使用 ASF 相比，使用 OB（+ASF）可以提供更好的靶区覆盖和更低的剂量最大值，尽管存在组织肿胀。对于调强弧形治疗，我们建议使用 OB 代替或附加使用 ASF。使用 8mm OB 与 VMAT 计划结合，可以稳健地应对向外延伸至 8mm 的变形。如果软组织变形大于 8mm，则需要评估重新计划的必要性。
