Innovative Technology Of Radiotherapy Computation and Hardware (iTORCH) Laboratory, Department of Radiation Oncology, University of Texas Southwestern Medical Center, Dallas, TX 75390, United States of America.
Department of Radiation Oncology, University of Texas Southwestern Medical Center, Dallas, TX 75287, United States of America.
Phys Med Biol. 2021 Mar 1;66(5):055028. doi: 10.1088/1361-6560/abd00e.
Needle catheter positions critically affect the quality of treatment plans in prostate cancer high-dose-rate (HDR) brachytherapy. The current standard needle positioning approach is based on human intuition, which cannot guarantee a high-quality plan. This study proposed a method to simultaneously select needle catheter positions and determine dwell time for preplanning of HDR brachytherapy of prostate cancer.
We formulated the needle catheter selection problem and inverse dwell time optimization problem in a unified framework. In addition to the dose objectives of the planning target volume (PTV) and organs at risk (OARs), the objective function incorporated a group-sparsity term with a needle-specific adaptive weighting scheme to generate high-quality plans with the minimal number of needle catheters. The optimization problem was solved by a fast-iterative shrinkage-thresholding algorithm. For validation purposes, we tested the proposed algorithm on 10 patient cases previously treated at our institution and compared the resulting plans with plans generated using needle catheters selected manually.
Compared to the plan with manually selected needle catheters, when normalizing both plans to the same PTV coverage V = 95%, the plans generated by the proposed algorithm reduced median V from 65% to 64%, but increased median V from 35% to 38%, and V from 14% to 16%. All planning objectives were met. All clinically important dosimetric parameters of OARs were reduced. D of bladder and rectum were reduced from 8.57 Gy to 8.50 Gy and from 7.24 Gy to 6.80 Gy, respectively. D of urethra was reduced from 15.85 Gy to 15.77 Gy. The median number of selected needle catheters was reduced by two. The computational time for solving the proposed optimization problem was ∼90 s using MATLAB.
The proposed algorithm was able to generate plans for prostate cancer HDR brachytherapy preplanning with increased median conformity index (0.73-0.77) and slightly lower median homogeneity index (0.64-0.62) with the number of selected needles reduced by two compared to the manual needle selection approach.
在前列腺癌高剂量率（HDR）近距离放射治疗中，针导管的位置对治疗计划的质量有重要影响。目前的标准针定位方法基于人体直觉，不能保证高质量的计划。本研究提出了一种方法，用于同时选择针导管位置并确定驻留时间，以进行前列腺癌 HDR 近距离放射治疗的预规划。
我们将针导管选择问题和逆驻留时间优化问题统一在一个框架中。除了计划靶区（PTV）和危及器官（OARs）的剂量目标外，目标函数还包含一个组稀疏项，并采用针特异性自适应加权方案，以最少的针导管数量生成高质量的计划。优化问题通过快速迭代收缩阈值算法求解。为了验证目的，我们在本机构之前治疗的 10 个患者病例上测试了所提出的算法，并将生成的计划与手动选择针导管生成的计划进行了比较。
与手动选择针导管的计划相比，当将两个计划归一化为相同的 PTV 覆盖率 V = 95%时，所提出的算法生成的计划将中位数 V 从 65%降低到 64%，但将中位数 V 从 35%提高到 38%，将 V 从 14%提高到 16%。所有计划目标都得到了满足。所有 OAR 的重要临床剂量学参数都有所降低。膀胱和直肠的 D 分别从 8.57 Gy 降低到 8.50 Gy 和从 7.24 Gy 降低到 6.80 Gy，尿道的 D 从 15.85 Gy 降低到 15.77 Gy。所选针导管的中位数数量减少了两个。使用 MATLAB 求解所提出的优化问题的计算时间约为 90 s。
与手动针选择方法相比，所提出的算法能够生成前列腺癌 HDR 近距离放射治疗预规划的计划，与中位数一致性指数（0.73-0.77）略有增加，所选针数量减少两个，而中位数均匀性指数（0.64-0.62）略有降低。
