Parsai E Ishmael, Jahadakbar Ahmadreza, Lavvafi Hossein, Elahinia Mohammad
Department of Radiation Oncology, University of Toledo Medical Center, Toledo, OH, USA.
Department of Mechanical, Industrial and Manufacturing Engineering, University of Toledo, Toledo, OH, USA.
J Appl Clin Med Phys. 2019 Jan;20(1):194-199. doi: 10.1002/acm2.12517. Epub 2018 Dec 26.
An effective radiotherapy treatment entails maximizing radiation dose to the tumor while sparing the surrounding and normal tissues. With the advent of SBRT with extreme hypo-fractionation in treating tumors including prostate where ablative dose is delivered in smaller number of fractions, rectum remains a dose-limiting organ and at the risk of rectal toxicity or secondary cancer. The same limitation of rectal toxicity exists for high-dose rate (HDR) treatments of cervical, endometrial, or prostate cancer when creating even a short distance between the anterior rectal wall and field of radiation is ideal in delivering ablative dose to the target. An effective solution to such problem is to physically displace rectum as the organ at risk. This research presents an organ retractor device that is designed to displace the rectum away from the path of radiation beam employing a Nitinol shape memory alloy that is designed for displacing the rectum upon actuation. A control system regulates the motion in a reproducible and safe manner by creating the desirable shape in moving the anterior rectal wall. The study finds the novel organ retractor device to be a promising tool that can be applied in a clinical setting for minimizing dose to the rectum during treatment of pelvic tumors, and creating the potential to deliver an ablative dose to tumor volume or to escalate the dose when needed.
有效的放射治疗需要在使周围正常组织免受辐射的同时，将肿瘤的辐射剂量最大化。随着立体定向体部放疗（SBRT）的出现，其采用极端低分割方式治疗包括前列腺癌在内的肿瘤，即通过较少的分次给予消融剂量，直肠仍然是剂量限制器官，存在直肠毒性或继发性癌症的风险。当在直肠前壁和辐射野之间形成哪怕很短的距离对于向靶区给予消融剂量很理想时，对于宫颈癌、子宫内膜癌或前列腺癌的高剂量率（HDR）治疗，同样存在直肠毒性的限制。解决此类问题的一个有效方法是将直肠作为危险器官进行物理移位。本研究提出了一种器官牵开器装置，该装置采用镍钛诺形状记忆合金设计，旨在将直肠从辐射束路径移开，这种合金经设计可在激活时移位直肠。一个控制系统通过在前直肠壁移动时形成所需形状，以可重复且安全的方式调节运动。该研究发现这种新型器官牵开器装置是一种有前景的工具，可应用于临床环境，在盆腔肿瘤治疗期间使直肠剂量最小化，并有可能向肿瘤体积给予消融剂量或在需要时提高剂量。
