Branco Daniela, Taylor Paige, Zhang Xiaodong, Li Heng, Guindani Michele, Followill David
Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, TX, USA.
Department of Biostatistics, The University of Texas MD Anderson Cancer Center, Houston, TX, USA.
Int J Part Ther. 2018 Winter;4(3):40-47. doi: 10.14338/IJPT-17-00005.1. Epub 2018 Mar 21.
To design and commission a head and neck (H&N) anthropomorphic phantom that the Imaging and Radiation Oncology Core Houston (IROC-H) can use to verify the quality of intensity-modulated proton therapy H&N treatments for institutions participating in National Cancer Institute-sponsored clinical trials.
The phantom design was based on a generalized oropharyngeal tumor, including critical H&N structures (parotid glands and spinal cord). Radiochromic film and thermoluminescent dosimeter (TLD)-100 capsules were embedded in the phantom and used to evaluate dose delivery. A spot-scanning treatment plan with typical clinical constraints for H&N cancer was created by using the Eclipse analytic algorithm. The treatment plan was approved by a radiation oncologist and the phantom was irradiated 4 times. The measured dose distribution using a ±7%/4 mm gamma analysis (85% of pixels passing) and point doses were compared with the treatment planning system calculations. The prescribed target dose was 6 Gy (RBE) with 646.2 cGy (RBE) and 648.6 cGy (RBE) planned to the superior and inferior TLD, respectively.
For point dosimetry, the average measured-to-calculated dose ratios were 0.984 and 0.986 for the superior and inferior target TLD, respectively. Dose values for the superior and inferior target TLDs were 636.1 cGy and 639.6 cGy, respectively. For the relative dose comparison, the pixel passing rates for the axial and sagittal films, respectively, were 95.5% and 94.2% for trial 1, 97.3% and 93.2% for trial 2, 93.4% and 90.0% for trial 3, and 96.2% and 92.7% for trial 4.
The anthropomorphic H&N phantom was successfully designed so that TLD measured-to-calculated ratios were within IROC-H's 7% acceptance criteria, 1.6% and 1.4% lower than expected for the superior and inferior target TLDs, respectively. All trials passed the 85% pixel passing criteria established at IROC-H for the relative dose comparison performed when using a gamma index of ±7%/4 mm.
设计并调试一个头颈（H&N）拟人化体模，休斯顿影像与放射肿瘤学核心（IROC-H）可利用该体模，为参与美国国立癌症研究所资助的临床试验的机构，验证调强质子治疗H&N疾病治疗的质量。
体模设计基于一个广义的口咽肿瘤，包括关键的H&N结构（腮腺和脊髓）。将放射变色胶片和热释光剂量计（TLD）-100胶囊嵌入体模中，并用于评估剂量传递。使用Eclipse解析算法创建了一个具有典型H&N癌症临床约束条件的点扫描治疗计划。该治疗计划经放射肿瘤学家批准，体模接受了4次照射。使用±7%/4 mm伽马分析（85%的像素通过）测量的剂量分布和点剂量与治疗计划系统的计算结果进行了比较。规定的靶剂量为6 Gy（相对生物效应），计划分别给予上、下TLD 646.2 cGy（相对生物效应）和648.6 cGy（相对生物效应）。
对于点剂量测定，上、下靶TLD的平均测量剂量与计算剂量之比分别为0.984和0.986。上、下靶TLD的剂量值分别为636.1 cGy和639.6 cGy。对于相对剂量比较，第1次试验轴向和矢状面胶片的像素通过率分别为95.5%和94.2%，第2次试验为97.3%和93.2%，第3次试验为93.4%和90.0%，第4次试验为96.2%和92.7%。
成功设计了拟人化的H&N体模，使得TLD测量剂量与计算剂量之比在IROC-H的7%验收标准范围内，分别比上、下靶TLD的预期值低1.6%和1.4%。所有试验均通过了IROC-H在使用±7%/4 mm伽马指数进行相对剂量比较时所设定的85%像素通过率标准。
