Tyagi Neelam, Zelefsky Michael J, Wibmer Andreas, Zakian Kristen, Burleson Sarah, Happersett Laura, Halkola Aleksi, Kadbi Mo, Hunt Margie
Department of Medical Physics, Memorial Sloan Kettering Cancer Center, 1275 York Avenue, NY, NY 10065.
Department of Radiation Oncology, Memorial Sloan Kettering Cancer Center, 1275 York Avenue, NY, NY 10065.
Phys Imaging Radiat Oncol. 2020 Oct;16:43-49. doi: 10.1016/j.phro.2020.09.009. Epub 2020 Oct 13.
Magnetic Resonance (MR)-only planning has been implemented clinically for radiotherapy of prostate cancer. However, fewer studies exist regarding the overall success rate of MR-only workflows. We report on successes and challenges of implementing MR-only workflows for prostate.
A total of 585 patients with prostate cancer underwent an MR-only simulation and planning between 06/2016-06/2018. MR simulation included images for contouring, synthetic-CT generation and fiducial identification. Workflow interruptions occurred that required a backup CT, a re-simulation or an update to our current quality assurance (QA) process. The challenges were prospectively evaluated and classified into syn-CT generation, motion/artifacts in the MRs, fiducial QA and bowel preparation guidelines.
MR-only simulation was successful in 544 (93.2 %) patients. . In seventeen patients (2.9%), reconstruction of synthetic-CT failed due to patient size, femur angulation, or failure to determine the body contour. Twenty-four patients (4.1%) underwent a repeat/backup CT scan because of artifacts on the MR such as image blur due to patient motion or biopsy/surgical artifacts that hampered identification of the implanted fiducial markers. In patients requiring large coverage due to nodal involvement, inhomogeneity artifacts were resolved by using a two-stack acquisition and adaptive inhomogeneity correction. Bowel preparation guidelines were modified to address frequent rectum/gas issues due to longer MR scan time.
MR-only simulation has been successfully implemented for a majority of patients in the clinic. However, MR-CT or CT-only pathway may still be needed for patients where MR-only solution fails or patients with MR contraindications.
磁共振（MR）仅用于计划的方式已在临床上用于前列腺癌的放射治疗。然而，关于仅使用MR流程的总体成功率的研究较少。我们报告了实施前列腺癌仅使用MR流程的成功经验和挑战。
2016年6月至2018年6月期间，共有585例前列腺癌患者接受了仅使用MR的模拟和计划。MR模拟包括用于轮廓勾画、合成CT生成和基准标记识别的图像。出现了工作流程中断的情况，需要备份CT、重新模拟或更新我们当前的质量保证（QA）流程。对这些挑战进行了前瞻性评估，并分为合成CT生成、MR中的运动/伪影、基准QA和肠道准备指南。
544例（93.2%）患者仅使用MR模拟成功。17例（2.9%）患者因患者体型、股骨角度或未能确定身体轮廓而导致合成CT重建失败。24例（4.1%）患者因MR上的伪影，如患者运动导致的图像模糊或活检/手术伪影妨碍了植入基准标记的识别，而接受了重复/备份CT扫描。对于因淋巴结受累而需要大覆盖范围的患者，通过使用双堆叠采集和自适应不均匀性校正解决了不均匀性伪影。由于MR扫描时间较长，对肠道准备指南进行了修改，以解决频繁出现的直肠/气体问题。
仅使用MR模拟已在临床上成功应用于大多数患者。然而，对于仅使用MR解决方案失败的患者或有MR禁忌证的患者，可能仍需要MR-CT或仅使用CT的途径。
