ProCure Proton Therapy Center.
J Appl Clin Med Phys. 2014 May 8;15(3):4611. doi: 10.1120/jacmp.v15i3.4611.
The main purposes of this study were to 1) investigate the dosimetric quality of uniform scanning proton therapy planning (USPT) for prostate cancer patients with a metal hip prosthesis, and 2) compare the dosimetric results of USPT with that of volumetric-modulated arc therapy (VMAT). Proton plans for prostate cancer (four cases) were generated in XiO treatment planning system (TPS). The beam arrangement in each proton plan consisted of three fields (two oblique fields and one lateral or slightly angled field), and the proton beams passing through a metal hip prosthesis was avoided. Dose calculations in proton plans were performed using the pencil beam algorithm. From each proton plan, planning target volume (PTV) coverage value (i.e., relative volume of the PTV receiving the prescription dose of 79.2 CGE) was recorded. The VMAT prostate planning was done using two arcs in the Eclipse TPS utilizing 6 MV X-rays, and beam entrance through metallic hip prosthesis was avoided. Dose computation in the VMAT plans was done using anisotropic analytical algorithm, and calculated VMAT plans were then normalized such that the PTV coverage in the VMAT plan was the same as in the proton plan of the corresponding case. The dose-volume histograms of calculated treatment plans were used to evaluate the dosimetric quality of USPT and VMAT. In comparison to the proton plans, on average, the maximum and mean doses to the PTV were higher in the VMAT plans by 1.4% and 0.5%, respectively, whereas the minimum PTV dose was lower in the VMAT plans by 3.4%. The proton plans had lower (or better) average homogeneity index (HI) of 0.03 compared to the one for VMAT (HI = 0.04). The relative rectal volume exposed to radiation was lower in the proton plan, with an average absolute difference ranging from 0.1% to 32.6%. In contrast, using proton planning, the relative bladder volume exposed to radiation was higher at high-dose region with an average absolute difference ranging from 0.4% to 0.8%, and lower at low- and medium-dose regions with an average absolute difference ranging from 2.7% to 10.1%. The average mean dose to the rectum and bladder was lower in the proton plans by 45.1% and 22.0%, respectively, whereas the mean dose to femoral head was lower in VMAT plans by an average difference of 79.6%. In comparison to the VMAT, the proton planning produced lower equivalent uniform dose (EUD) for the rectum (43.7 CGE vs. 51.4 Gy) and higher EUD for the femoral head (16.7 CGE vs. 9.5 Gy), whereas both the VMAT and proton planning produced comparable EUDs for the prostate tumor (76.2 CGE vs. 76.8 Gy) and bladder (50.3 CGE vs. 51.1 Gy). The results presented in this study show that the combination of lateral and oblique fields in USPT planning could potentially provide dosimetric advantage over the VMAT for prostate cancer involving a metallic hip prosthesis.
1）研究前列腺癌伴金属髋关节假体患者的均匀扫描质子治疗计划（USPT）的剂量学质量，2）比较 USPT 与容积调制弧形治疗（VMAT）的剂量学结果。在 XiO 治疗计划系统（TPS）中生成了前列腺癌的质子计划（四个病例）。每个质子计划中的光束排列包括三个射野（两个斜野和一个外侧或稍微倾斜的射野），并避免质子束穿过金属髋关节假体。质子计划中的剂量计算使用铅笔束算法进行。从每个质子计划中记录了计划靶区（PTV）覆盖值（即，PTV 接收 79.2CGE 处方剂量的相对体积）。在 Eclipse TPS 中使用两个弧进行 VMAT 前列腺计划，同时避免了金属髋关节假体的射束进入。VMAT 计划中的剂量计算使用各向异性分析算法进行，并且计算的 VMAT 计划随后进行归一化，使得 VMAT 计划的 PTV 覆盖与相应病例的质子计划相同。计算治疗计划的剂量-体积直方图用于评估 USPT 和 VMAT 的剂量学质量。与质子计划相比，VMAT 计划的 PTV 的最大和平均剂量分别高 1.4%和 0.5%，而 PTV 的最小剂量低 3.4%。质子计划的平均均匀性指数（HI）较低，为 0.03，而 VMAT 的 HI 为 0.04。质子计划中暴露于辐射的直肠相对体积较低，平均绝对差异范围为 0.1%至 32.6%。相反，使用质子计划，暴露于高剂量区域的膀胱相对体积较高，平均绝对差异范围为 0.4%至 0.8%，而在低剂量和中剂量区域较低，平均绝对差异范围为 2.7%至 10.1%。质子计划中直肠和膀胱的平均剂量分别低 45.1%和 22.0%，而 VMAT 计划中股骨头的平均剂量低 79.6%。与 VMAT 相比，质子计划为直肠（43.7CGE 比 51.4Gy）和股骨头（16.7CGE 比 9.5Gy）产生了更低的等效均匀剂量（EUD），而 VMAT 和质子计划为前列腺肿瘤（76.2CGE 比 76.8Gy）和膀胱（50.3CGE 比 51.1Gy）产生了可比的 EUD。本研究结果表明，在涉及金属髋关节假体的前列腺癌中，USPT 计划中侧向和斜向射野的组合可能比 VMAT 具有更好的剂量学优势。
