Department of Radiation Oncology, Leo Jenkins Cancer Center, East Carolina University, Greenville, NC 27834, USA.
Med Phys. 2012 Apr;39(4):1887-92. doi: 10.1118/1.3694110.
A new technique called "curvilinear approach" for prostate seed implantation has been proposed. The purpose of this study is to evaluate the dosimetric benefit of curvilinear distribution of seeds for low-dose-rate (LDR) prostate brachytherapy.
Twenty LDR prostate brachytherapy cases planned intraoperatively with VariSeed planning system and I-125 seeds were randomly selected as reference rectilinear cases. All the cases were replanned by using curved-needle approach keeping the same individual source strength and the volume receiving 100% of prescribed dose 145 Gy (V(100)). Parameters such as number of needles, seeds, and the dose coverage of the prostate (D(90), V(150), V(200)), urethra (D(30), D(10)) and rectum (D(5), V(100)) were compared for the rectilinear and the curvilinear methods. Statistical significance was assessed using two-tailed student's t-test.
Reduction of the required number of needles and seeds in curvilinear method were 30.5% (p < 0.001) and 11.8% (p < 0.49), respectively. Dose to the urethra was reduced significantly; D(30) reduced by 10.1% (p < 0.01) and D(10) reduced by 9.9% (p < 0.02). Reduction in rectum dose D(5) was 18.5% (p < 0.03) and V(100) was also reduced from 0.93 cc in rectilinear to 0.21 cc in curvilinear (p < 0.001). Also the V(150) and V(200) coverage of prostate reduced by 18.8% (p < 0.01) and 33.9% (p < 0.001), respectively.
Significant improvement in the relevant dosimetric parameters was observed in curvilinear needle approach. Prostate dose homogeneity (V(150), V(200)) improved while urethral dose was reduced, which might potentially result in better treatment outcome. Reduction in rectal dose could potentially reduce rectal toxicity and complications. Reduction in number of needles would minimize edema and thereby could improve postimplant urinary incontinence. This study indicates that the curvilinear implantation approach is dosimetrically superior to conventional rectilinear implantation technique.
提出了一种称为“曲线方法”的前列腺种子植入新方法。本研究旨在评估低剂量率（LDR）前列腺近距离放射治疗中种子曲线分布的剂量学优势。
随机选择 20 例采用 VariSeed 计划系统和 I-125 种子进行术中计划的 LDR 前列腺近距离放射治疗病例作为参考直线病例。所有病例均采用曲线针方法重新计划，保持相同的个体源强度和接受 145 Gy 处方剂量 100%的体积 V(100)。比较直线和曲线方法的参数，如针数、种子数以及前列腺（D(90)、V(150)、V(200)）、尿道（D(30)、D(10)）和直肠（D(5)、V(100)）的剂量覆盖情况。使用双尾学生 t 检验评估统计学意义。
曲线方法中所需的针数和种子数分别减少了 30.5%（p<0.001）和 11.8%（p<0.49）。尿道剂量显著降低；D(30)降低了 10.1%（p<0.01），D(10)降低了 9.9%（p<0.02）。直肠剂量 D(5)降低了 18.5%（p<0.03），曲线中的 V(100)也从直线中的 0.93 cc 降低到 0.21 cc（p<0.001）。前列腺的 V(150)和 V(200)覆盖范围也分别降低了 18.8%（p<0.01）和 33.9%（p<0.001）。
在曲线针方法中观察到相关剂量学参数的显著改善。前列腺剂量均匀性（V(150)、V(200)）得到改善，同时尿道剂量降低，这可能会带来更好的治疗效果。直肠剂量的降低可能会降低直肠毒性和并发症的风险。针数的减少将最大限度地减少水肿，从而可能改善植入后的尿失禁。本研究表明，曲线植入方法在剂量学上优于传统的直线植入技术。
