Medical Physics, Radiotherapy Hirslanden, Witellikerstrasse 40, Zürich, CH-8032, Switzerland.
Radiat Oncol. 2013 Nov 16;8:270. doi: 10.1186/1748-717X-8-270.
For patients with high risk breast cancer and mastectomy, radiotherapy is the treatment of choice to improve survival and local control. Target dose is mainly limited due to skin reactions. The feasibility of using 4 MV beams for chest wall treatment was studied and compared to standard 6 MV bolus radiotherapy.
Post-mastectomy IMRT was planned on an Alderson-phantom using 4 and 6 MV photon beams without/with a 0.5 cm thick bolus. Dose was measured using TLDs placed at 8 locations in 1 and 3 mm depth to represent skin and superficial target dose, respectively.
4 MV and 6 MV beams with bolus perform equally regarding target coverage. The minimum and mean superficial target dose for the 6 MV and 4 MV were 93.0% and 94.7%, and 93.1% and 94.4%, respectively. Regarding skin dose the 4 MV photon beam was advantageous. The minimum and mean skin dose for the 6 MV and 4 MV was 76.7% and 81.6%, and 69.4% and 72.9%, respectively. The TPS was able to predict dose in the build-up region with a precision of around 5%.
The use of 4 MV photon beams are a good alternative for treating the thoracic wall without the need to place a bolus on the patient. The main limitation of 4 MV beams is the limited dose rate.
对于高危乳腺癌和乳房切除术患者，放射治疗是提高生存率和局部控制率的首选治疗方法。靶剂量主要受到皮肤反应的限制。本研究旨在探讨和比较使用 4MV 射线治疗胸壁的可行性，并与标准的 6MV 加速超分割放疗进行比较。
在 Alderson 体模上对乳房切除术后的患者进行调强放疗计划，使用 4MV 和 6MV 光子束，不使用/使用 0.5cm 厚的填充物。使用 TLD 在 1mm 和 3mm 深度的 8 个位置测量剂量，分别代表皮肤和浅层靶区剂量。
4MV 和 6MV 射线束加填充物在靶区覆盖方面表现相当。6MV 和 4MV 的最小和平均浅层靶区剂量分别为 93.0%和 94.7%，93.1%和 94.4%。对于皮肤剂量，4MV 光子束具有优势。6MV 和 4MV 的最小和平均皮肤剂量分别为 76.7%和 81.6%，69.4%和 72.9%。TPS 能够以 5%左右的精度预测建成区的剂量。
不使用填充物即可使用 4MV 光子束治疗胸壁，是一种很好的替代方法。4MV 射线束的主要限制是剂量率有限。
