Kinhikar R A, Pandey V P, Jose Rojas K, Mahantshetty U, Dhote D S, Deshpande D D, Shrivastava S K
Department of Medical Physics, Tata Memorial Hospital, Mumbai, India.
J Med Phys. 2013 Jul;38(3):139-42. doi: 10.4103/0971-6203.116373.
The objective of this work was to investigate and quantify the effect of sharp edges of the phantom on the point dose measurement during patient-specific dosimetry with Rapid Arc (RA). Ten patients with carcinoma of prostate were randomly selected for this dosimetric study. Rapid Arc plans were generated with 6 MV X-rays in the Eclipse (v 8.6.14) with single arc (clockwise). Dosimetry verification plans were generated for two phantoms (cylindrical and rectangular). The cylindrical phantom was solid water (diameter 34 cm) and the rectangular phantom was a water phantom (25 cm × 25 cm × 10 cm). These phantoms were pre-scanned in computed tomography (CT) machine with cylindrical ionization chamber (FC65) in place. The plans were delivered with Novalis Tx linear accelerator with 6 MV X-rays for both the phantoms separately. The measured dose was compared with the planned dose for both the phantoms. Mean percentage deviation between measured and planned doses was found to be 4.19 (SD 0.82) and 3.63 (SD 0.89) for cylindrical and rectangular phantoms, respectively. No significant dosimetric variation was found due to the geometry (sharp edges) of the phantom. The sharp edges of the phantom do not perturb the patient specific Rapid Arc dosimetry significantly.
这项工作的目的是研究并量化在使用容积旋转调强放疗（RA）进行患者特异性剂量测定期间，模体锐利边缘对点剂量测量的影响。随机选择10例前列腺癌患者进行此项剂量学研究。在Eclipse（v 8.6.14）中使用6兆伏X射线生成单弧（顺时针）的容积旋转调强放疗计划。为两个模体（圆柱形和矩形）生成剂量学验证计划。圆柱形模体为固体水（直径34厘米），矩形模体为水体模（25厘米×25厘米×10厘米）。这些模体在计算机断层扫描（CT）机中进行预扫描，此时圆柱形电离室（FC65）已就位。分别使用诺瓦利斯Tx直线加速器和6兆伏X射线对两个模体进行计划照射。将测量剂量与两个模体的计划剂量进行比较。发现圆柱形和矩形模体测量剂量与计划剂量之间的平均百分比偏差分别为4.19（标准差0.82）和3.63（标准差0.89）。未发现由于模体的几何形状（锐利边缘）导致显著的剂量学差异。模体的锐利边缘不会对患者特异性容积旋转调强放疗剂量测定产生显著干扰。
