The objective of this study is to investigate the dose perturbations introduced by the implanted gold fiducial markers in the prostate cancer intensity modulated proton therapy (IMPT) and the impacts of different plan...The objective of this study is to investigate the dose perturbations introduced by the implanted gold fiducial markers in the prostate cancer intensity modulated proton therapy (IMPT) and the impacts of different plan designs on the pertur-bations. Five proton plans: a single lateral field 3D-modulation (3D-mod) plan, 2 fields laterally opposing 3D-mod plan, 6-, 9-, and 18-field distal edge tracking (DET) plans were designed on the CT images of a prostate patient. The dose distributions were first generated for the plans free of fiducial markers with 78 Gy prescribed to 95% of the PTV. To derive the dose perturbations of the gold fiducial markers, three cylindrical shaped gold fiducial markers (3 mm long and 1 mm in diameter) were artificially inserted into the prostate, and the dose distributions were re-computed. Monte Carlo method was used for dose computation. It was found that the gold fiducial markers perturbed the dose distribu-tions, especially along the beam paths. The markers caused a shadowing effect reducing the doses in the areas beyond the markers. Overall, due to the presence of the fiducial markers, D99% of prostate were reduced by 2.96 Gy, 4.21 Gy, 0.16 Gy, 0.34 Gy, 0.15 Gy for the plans of single field 3D-mod, 2-field parallel opposed 3D-mod, 6-, 9-, and 18-field DET respectively. Our study showed these dose perturbation effects decreased with the increase of number of beam angles. Up to 6 beam angles may be required to reduce the dose perturbations from the gold fiducial markers to a clini- cally acceptable level in IMPT.展开更多
文摘The objective of this study is to investigate the dose perturbations introduced by the implanted gold fiducial markers in the prostate cancer intensity modulated proton therapy (IMPT) and the impacts of different plan designs on the pertur-bations. Five proton plans: a single lateral field 3D-modulation (3D-mod) plan, 2 fields laterally opposing 3D-mod plan, 6-, 9-, and 18-field distal edge tracking (DET) plans were designed on the CT images of a prostate patient. The dose distributions were first generated for the plans free of fiducial markers with 78 Gy prescribed to 95% of the PTV. To derive the dose perturbations of the gold fiducial markers, three cylindrical shaped gold fiducial markers (3 mm long and 1 mm in diameter) were artificially inserted into the prostate, and the dose distributions were re-computed. Monte Carlo method was used for dose computation. It was found that the gold fiducial markers perturbed the dose distribu-tions, especially along the beam paths. The markers caused a shadowing effect reducing the doses in the areas beyond the markers. Overall, due to the presence of the fiducial markers, D99% of prostate were reduced by 2.96 Gy, 4.21 Gy, 0.16 Gy, 0.34 Gy, 0.15 Gy for the plans of single field 3D-mod, 2-field parallel opposed 3D-mod, 6-, 9-, and 18-field DET respectively. Our study showed these dose perturbation effects decreased with the increase of number of beam angles. Up to 6 beam angles may be required to reduce the dose perturbations from the gold fiducial markers to a clini- cally acceptable level in IMPT.
文摘目的:评价前列腺癌图像引导放疗中经直肠超声引导下经会阴途径穿刺置入黄金基准标志物(gold fiducial marker,GFM)时会阴神经阻滞的疼痛控制效果并分析其风险因素。方法:筛选符合纳入标准的前列腺癌患者176例,将其分为接受会阴神经阻滞的试验组(n=92)和前列腺周围神经阻滞的对照组(n=84)。使用视觉模拟评分(VAS)评价并比较两组患者GFM置入术中和术后6 h、12 h、24 h的疼痛。对试验组行Logistic回归分析置入术中VAS≥4分的风险因素。结果:试验组GFM置入术中VAS为(2.61±1.32)分,显著低于对照组的(4.82±1.93)分(P<0.001);试验组置入术后6 h VAS为(1.95±0.94)分,显著低于对照组的(3.24±1.53)分(P<0.001);术后12 h、24 h VAS两组间比较差异无统计学意义。回归分析结果显示,前列腺体积、会阴神经选择和GFM置入部位分别是导致VAS≥4分的独立影响因素(均P<0.01),前列腺体积每增加1 cm 3、选择会阴神经浅支(以深支为对照)和置入部位为底部(以顶部为对照)时相对风险分别升高约1.308倍、2.446倍和2.602倍。结论:与前列腺周围神经阻滞相比,GFM置入术6 h内会阴神经阻滞疼痛控制效果更好。GFM置入术中应尽量规避风险因素,从而进一步降低患者疼痛。
