Sritharan Kobika, Dunlop Alex, Mohajer Jonathan, Adair-Smith Gillian, Barnes Helen, Brand Douglas, Greenlay Emily, Hijab Adham, Oelfke Uwe, Pathmanathan Angela, Mitchell Adam, Murray Julia, Nill Simeon, Parker Chris, Sundahl Nora, Tree Alison C
The Royal Marsden NHS Foundation Trust, United Kingdom.
The Institute of Cancer Research, United Kingdom.
Clin Transl Radiat Oncol. 2022 Aug 6;37:25-32. doi: 10.1016/j.ctro.2022.08.004. eCollection 2022 Nov.
The prostate demonstrates inter- and intra- fractional changes and thus adaptive radiotherapy would be required to ensure optimal coverage. Daily adaptive radiotherapy for MRI-guided radiotherapy can be both time and resource intensive when structure delineation is completed manually. Contours can be auto-generated on the MR-Linac via a deformable image registration (DIR) based mapping process from the reference image. This study evaluates the performance of automatically generated target structure contours against manually delineated contours by radiation oncologists for prostate radiotherapy on the Elekta Unity MR-Linac.
Plans were generated from prostate contours propagated by DIR and rigid image registration (RIR) for forty fractions from ten patients. A two-dose level SIB (simultaneous integrated boost) IMRT plan is used to treat localised prostate cancer; 6000 cGy to the prostate and 4860 cGy to the seminal vesicles. The dose coverage of the PTV 6000 and PTV 4860 created from the manually drawn target structures was evaluated with each plan. If the dose objectives were met, the plan was considered successful in covering the gold standard (clinician-delineated) volume.
The mandatory PTV 6000 dose objective (D98% > 5580 cGy) was met in 81 % of DIR plans and 45 % of RIR plans. The SV were mapped by DIR only and for all the plans, the PTV 4860 dose objective met the optimal target (D98% > 4617 cGy). The plans created by RIR led to under-coverage of the clinician-delineated prostate, predominantly at the apex or the bladder-prostate interface.
Plans created from DIR propagation of prostate contours outperform those created from RIR propagation. In approximately 1 in 5 DIR plans, dosimetric coverage of the gold standard PTV was not clinically acceptable. Thus, at our institution, we use a combination of DIR propagation of contours alongside manual editing of contours where deemed necessary for online treatments.
前列腺在分次放疗期间及分次放疗之间会发生变化，因此需要采用自适应放疗以确保最佳覆盖范围。当手动完成结构勾画时，用于磁共振成像引导放疗的每日自适应放疗在时间和资源方面都较为密集。通过基于可变形图像配准（DIR）的映射过程，可从参考图像在磁共振直线加速器上自动生成轮廓。本研究评估了在医科达Unity磁共振直线加速器上，针对前列腺放疗，自动生成的靶区结构轮廓相对于放射肿瘤学家手动勾画轮廓的性能。
从10例患者的前列腺轮廓通过DIR和刚性图像配准（RIR）传播生成40次分割的计划。采用两剂量水平同步整合加量（SIB）调强放疗计划治疗局限性前列腺癌；前列腺剂量为6000 cGy，精囊剂量为4860 cGy。用每个计划评估由手动绘制的靶区结构创建的PTV 6000和PTV 4860的剂量覆盖情况。如果达到剂量目标，则认为该计划成功覆盖了金标准（临床医生勾画）体积。
81%的DIR计划和45%的RIR计划达到了强制性PTV 6000剂量目标（D98%>5580 cGy）。精囊仅通过DIR映射，对于所有计划，PTV 4860剂量目标达到了最佳靶区（D98%>4617 cGy）。由RIR创建的计划导致临床医生勾画的前列腺覆盖不足，主要在前列腺尖部或膀胱 - 前列腺界面。
由前列腺轮廓的DIR传播创建的计划优于由RIR传播创建的计划。在大约五分之一的DIR计划中，金标准PTV的剂量学覆盖在临床上不可接受。因此，在我们机构，对于在线治疗，我们在必要时将轮廓的DIR传播与轮廓的手动编辑相结合使用。
