Department of Biomedical Engineering, University of Iowa, Iowa City, Iowa.
Department of Radiation Oncology, University of Iowa, Iowa City, Iowa.
Int J Radiat Oncol Biol Phys. 2017 Nov 1;99(3):719-728. doi: 10.1016/j.ijrobp.2017.06.008. Epub 2017 Jun 20.
Our purpose is to present a novel multisource rotating shield brachytherapy (RSBT) apparatus for the simultaneous precise angular and linear positioning of partially shielded Gd brachytherapy sources in interstitial needles for the treatment of locally advanced prostate cancer. It is designed to lower the dose to nearby healthy tissues, the urethra in particular, relative to conventional high-dose-rate brachytherapy techniques.
Following needle implantation through the patient template, an angular drive mechanism is docked to the patient template. Each needle is coupled to a multisource afterloader catheter by a connector passing through a shaft. The shafts are rotated about their axes by translating a moving template between 2 stationary templates. The shafts' surfaces and moving template holes are helically threaded with the same pattern such that translation of the moving template causes simultaneous rotation of the shafts. The rotation of each shaft is mechanically transmitted to the catheter-source-shield combination, inside the needles, via several key-keyway pairs. The catheter angles are simultaneously incremented throughout treatment, and only a single 360° rotation of all catheters is needed for a full treatment. For each rotation angle, source depth in each needle is controlled by a multisource afterloader, which is proposed as an array of belt-driven linear actuators, each of which drives a wire that controls catheter depth in a needle.
Treatment plans demonstrated that RSBT with the proposed apparatus reduced urethral D (the minimum dose delivered to the hottest 0.1cm of the urethra) below that of conventional high-dose-rate brachytherapy by 31% for urethral dose gradient volume within 3 mm of the urethra surface. Treatment time to deliver 20 Gy with the proposed multisource RSBT apparatus by use of nineteen 62.4-GBq Gd sources was 122 minutes.
The proposed RSBT delivery apparatus enables a mechanically feasible urethra-sparing treatment technique for prostate cancer in a clinically reasonable time frame.
本研究旨在介绍一种新型多源旋转屏蔽近距离放射治疗（RSBT）设备，用于将部分屏蔽的 Gd 近距离放射治疗源在间质针中进行精确的角度和线性定位，以治疗局部晚期前列腺癌。该设备旨在降低对附近健康组织（特别是尿道）的剂量，相对于传统的高剂量率近距离放射治疗技术。
在通过患者模板植入针后，将角度驱动机构对接至患者模板。每个针都通过一个穿过轴的连接器与多源后装机导管相连。通过在两个固定模板之间平移移动模板，使轴围绕其轴旋转。轴的表面和移动模板孔采用相同的螺旋螺纹，使移动模板的平移导致轴的同时旋转。每个轴的旋转通过几个键-键槽对机械传递到针内的导管-源-屏蔽组合。在整个治疗过程中，导管角度同时递增，并且仅需对所有导管进行一次 360°旋转即可完成整个治疗。对于每个旋转角度，通过多源后装机控制每个针中的源深度，该多源后装机被提议为一系列带驱动线性执行器的阵列，每个执行器驱动一根线，控制针中的导管深度。
治疗计划表明，使用所提出的设备进行 RSBT 可将尿道 D（尿道表面 3mm 范围内最热点 0.1cm 处的最小剂量）降低 31%，比传统高剂量率近距离放射治疗低，对于尿道剂量梯度体积。使用所提出的多源 RSBT 设备，通过使用 19 个 62.4GBq Gd 源，在 122 分钟内可提供 20Gy 的治疗。
所提出的 RSBT 输送设备可实现一种机械可行的前列腺癌尿道保护治疗技术，在临床合理的时间框架内完成。
