The Christie NHSFT, Manchester, United Kingdom.
The University of Liverpool, Liverpool, United Kingdom.
J Med Imaging Radiat Sci. 2021 Mar;52(1):147-151. doi: 10.1016/j.jmir.2020.11.019. Epub 2020 Dec 17.
The integration of magnetic resonance (MR) imaging into radiotherapy through new technology, including the MR -linear accelerator (MRL), has allowed further advancements into image guided radiotherapy (IGRT). Better soft tissue visualisation has led to some unusual findings.
A patient with T1c N0 M0 prostate adenocarcinoma received 60Gy in 20# radiotherapy on the MRL. Radiotherapy planning (RTP) scans were completed on both CT and MR (using T2 and T1 weighted three-dimensional turbo spin echo sequences, reconstructed transaxially (TRA). The MR scans revealed atypical oedema in the right peripheral zone, visualised on T2-weighted (T2w) MR Images as an accumulation of high signal intensity fluid. Daily MRL treatment includes a (T2w 3D Tra) sequence with which oedematous changes could be monitored. The images demonstrated an increase in oedematous volume over fractions 1-10 causing the prostate contour variations from the initial planning scans. Despite the prostate volume variations PTV coverage was never breached and dose constraints were always met for both PTV and surrounding organs at risk (OAR's), excluding the need for oncologist input. A single Therapeutic Radiographer (RTT) experienced in MRL delivery, contoured the prostate and oedematous volumes on the radiotherapy plan (RTP) MR and all on-treatment MR images to assess change over the radiotherapy course. The initial volumes were 53.4 cm and 8.3 cm for the prostate plus oedema and oedema alone respectively. The most significant change was seen for both the prostate and oedema on fraction nine (68.0 cm and 10.1 cm, respectively). Reductions were noted after this with final (fraction 20) volumes of 55.2 cm and 0.58 cm respectively.
The ability to visualise prostatic oedema was new to the radiotherapy treatment team due to better soft tissue visualisation than standard radiotherapy. The results from contouring the prostate and oedema volumes confirmed radiographer observations and demonstrated how oedema impacted the overall prostate volume by quantifying the oedematous variations over time. The changes in oedema volume are presumed to be in response to radiotherapy.
Further adaptive radiotherapy work-flow developments, utilising an "Adapt to Shape" model will allow real-time re-contouring of the prostate to ensure tumour control is not compromised. Further work investigating the frequency and impact of oedemotous changes to external beam prostate patients will help to inform practice.
通过新技术，包括磁共振-直线加速器（MRL），将磁共振成像整合到放射治疗中，使得图像引导放射治疗（IGRT）有了进一步的发展。更好的软组织可视化导致了一些不寻常的发现。
一名 T1c N0 M0 前列腺腺癌患者在 MRL 上接受了 60Gy 的 20#放疗。在 CT 和 MR 上完成了放射治疗计划（RTP）扫描（使用 T2 和 T1 加权三维涡轮自旋回波序列，经轴位重建（TRA）。MR 扫描显示右侧外周带出现异常水肿，在 T2 加权（T2w）MR 图像上表现为高信号强度液体的积聚。每日 MRL 治疗包括一个（T2w 3D Tra）序列，可以监测水肿变化。图像显示水肿体积在分数 1-10 期间增加，导致前列腺轮廓从初始计划扫描中发生变化。尽管前列腺体积发生了变化，但 PTV 覆盖率从未突破，PTV 和周围危及器官（OAR）的剂量限制始终得到满足，无需肿瘤学家的参与。一名经验丰富的 MRL 治疗的治疗放射技师（RTT）在放射治疗计划（RTP）MR 和所有治疗中的 MR 图像上对前列腺和水肿体积进行了轮廓勾画，以评估放射治疗过程中的变化。初始体积分别为前列腺加水肿 53.4cm 和 8.3cm，单纯水肿 53.4cm 和 8.3cm。第 9 个分数（分别为 68.0cm 和 10.1cm）观察到最大变化。在此之后，体积分别减少到最后一次（第 20 次）的 55.2cm 和 0.58cm。
由于比标准放射治疗有更好的软组织可视化，因此治疗团队能够观察到前列腺水肿，这是放射治疗的新发现。对前列腺和水肿体积进行轮廓勾画的结果证实了放射技师的观察结果，并通过量化水肿随时间的变化，显示了水肿如何影响整体前列腺体积。水肿体积的变化据推测是对放射治疗的反应。
进一步利用“适应形状”模型的自适应放射治疗工作流程开发将允许实时重新轮廓化前列腺，以确保肿瘤控制不受影响。进一步研究外部束前列腺患者水肿变化的频率和影响将有助于为实践提供信息。
