Kang J, Yang J, Varlotto J, Saw C, Ma C
Fox Chase Cancer Center, Harrisburg, PA.
Hershey Medical Center, Hershey, PA.
Med Phys. 2012 Jun;39(6Part18):3823. doi: 10.1118/1.4735600.
To investigate the tumor geometric relationship to the dose variations of Anisotropic Analytical Algorithm (AAA), pencil beam convolution algorithm with/without modified Bath Power Law(PBMPL)/PB in stereotactic body radiation therapy(SBRT) treatment plans of patients presenting with a solitary primary lung cancer.
MATERIALS/METHODS: Treatment plans of 14 patients (7 upper lobe, 7 lower lobe) were used for this study. The planning target volume (PTV) size ranges from 3.9c.c. to 156.7c.c. The SBRT treatment plans were composed of 10-12 non- coplanar photon beams as per RTOG guidelines. The prescription dose for this study were (i) 4×12Gy, (ii) 5×10Gy, and (iii) 5×11Gy. The Varian Eclipse treatment planning system Eclipse v. 8.9 (Palo Alto, CA) was used for this study. Four-dimensional CT (4D CT) data were used to define the integral target volume (ITV) on maximum intensity projection. An 5mm circumferential margin was used to create PTV from ITV. Plans were generated with three algorithms.
a). For small lesions (PTV occupy less than 1% of the ipsilateral lung volume), the PBMPL plans had overestimated the dose by average 10% compared to AAA. But the PB without any heterogeneity correction agrees well with AAA. b). For big lesions (PTV occupy more than 1% of the ipsilateral lung volume), the PBMPL plans had agreed well with AAA. But the PB without any heterogeneity correction underestimate the dose by average 15% compared to AAA. c). The tumor location (Group1: within 1cm from the lung wall;Group2: 2cm away from the lung wall Group3: in between zone of 1 and 2cm from the lung wall; Group 4:Spread from the lung wall to the 2cm away zone) seems to relate with dose calculation variations among different algorithms.
Prescription adjustment is not necessary for PTV less than 1% of ipsilateral lung volume as the recent suggestion by the quality assurance working group of phase III Rosel study of prescription dose reduction of 10% from 60Gy to 54Gy when utilizing AAA instead of PBC.
探讨在立体定向体部放射治疗（SBRT）治疗计划中，孤立性原发性肺癌患者的肿瘤几何形状与各向异性分析算法（AAA）、带/不带修正巴斯幂律（PBMPL）/铅笔束卷积算法（PB）剂量变化之间的关系。
材料/方法：本研究使用了14例患者（7例上叶，7例下叶）的治疗计划。计划靶体积（PTV）大小范围为3.9立方厘米至156.7立方厘米。根据美国放射肿瘤学会（RTOG）指南，SBRT治疗计划由10 - 12个非共面光子束组成。本研究的处方剂量为：（i）4×12Gy，（ii）5×10Gy，以及（iii）5×11Gy。本研究使用瓦里安Eclipse治疗计划系统Eclipse v. 8.9（加利福尼亚州帕洛阿尔托）。使用四维CT（4D CT）数据在最大强度投影上定义整体靶体积（ITV）。使用5毫米的周向边界从ITV创建PTV。使用三种算法生成计划。
a）. 对于小病灶（PTV占同侧肺体积的比例小于1%），与AAA相比，PBMPL计划平均高估剂量10%。但未进行任何不均匀性校正的PB与AAA吻合良好。b）. 对于大病灶（PTV占同侧肺体积的比例大于1%），PBMPL计划与AAA吻合良好。但未进行任何不均匀性校正的PB与AAA相比平均低估剂量15%。c）. 肿瘤位置（第1组：距肺壁1厘米以内；第2组：距肺壁2厘米；第3组：在距肺壁1至2厘米区域之间；第4组：从肺壁扩散至距肺壁2厘米区域）似乎与不同算法之间剂量计算的差异有关。
对于PTV小于同侧肺体积1%的情况，无需像III期Rosel研究质量保证工作组最近所建议的那样进行处方调整，即当使用AAA而非铅笔束卷积算法（PBC）时，将处方剂量从60Gy降低10%至54Gy。
