Semaniak Anna, Jodkiewicz Zbigniew, Skowrońska-Gardas Anna
Department of Medical Physics, Maria Skłodowska Curie Memorial Cancer Centre-Institute, Wawelska 15, 00-973 Warsaw, Poland.
Department of Radiotherapy, Maria Skłodowska Curie Memorial Cancer Centre-Institute, Wawelska 15, 00-973 Warsaw, Poland.
Rep Pract Oncol Radiother. 2012 Mar 8;17(2):85-92. doi: 10.1016/j.rpor.2012.01.008. eCollection 2012.
To present the segmented photon beams technique (SPBT) for irradiation of postmastectomy patients.
In majority of techniques for irradiation of posmastectomy patients, a few adjacent photon or electron beams were usually implemented in order to encompass different parts of the target. In the presented SPBT technique, the radiotherapy plan consists of 6 isocentric photon beams and the area CTV includes both the chest wall and the supraclavicular area. This makes it possible to provide a uniform dose to the CTV with no hot and cold points and enables the determination of doses for the entire volume of critical organs.
The treatment forward-IMRT plan comprises six isocentric 4 and 15 MV photon beams. Modulation of the dose distribution for each field was obtained by applying three segments on average. The total dose of 45 Gy was administered in 20 fractions. Dose distributions in target volume and organs at risk were evaluated for 70 randomly chosen patients.
On average, 94.8% of the CTV volume received doses within 95-107% of the prescribed dose. The average volume of the heart receiving a dose of 30 Gy and lager was 2% for patients with left breast cancer. The average dose to the lung on the irradiation side was always lower than 15.5 Gy and the average V20 Gy was below 35.5%.
The SPBT complies with requirements for high dose homogeneity within the target volume and satisfactory level of sparing of organs at risk.
介绍用于乳房切除术后患者放疗的分段光子束技术（SPBT）。
在大多数乳房切除术后患者的放疗技术中，通常采用少数相邻的光子束或电子束来覆盖靶区的不同部位。在所介绍的SPBT技术中，放疗计划由6个等中心光子束组成，临床靶区（CTV）包括胸壁和锁骨上区。这使得能够为CTV提供均匀剂量，无热点和冷点，并能确定关键器官整个体积的剂量。
正向调强放疗（IMRT）计划包括6个等中心4兆伏和15兆伏光子束。每个射野的剂量分布调制平均通过应用三段来实现。总剂量45Gy分20次给予。对70例随机选择的患者评估靶区体积和危及器官的剂量分布。
平均而言，94.8%的CTV体积接受的剂量在处方剂量的95%至107%范围内。左乳腺癌患者接受30Gy及以上剂量的心脏平均体积为2%。照射侧肺的平均剂量始终低于15.5Gy，平均V20Gy低于35.5%。
SPBT符合靶区内高剂量均匀性的要求以及危及器官满意的 sparing 水平。
