Christie Medical Physics and Engineering (CMPE), The Christie NHS Foundation Trust, Wilmslow Road, Manchester, M20 4BX, United Kingdom.
Division of Cancer Sciences, School of Medical Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, M13 9PL, United Kingdom.
Phys Med Biol. 2023 Jan 11;68(2). doi: 10.1088/1361-6560/acae18.
Patients treated for cervical cancer exhibit large inter and intra-fraction anatomical changes. The Unity MR-Linac (MRL) can image these patients with MR prior to and during treatment which enables daily plan adaptation. However, the MRL has a limited treatment field in the sup/inf direction of 22 cm which can restrict the treatment of patients who require longer treatment fields. Here we explore potential adaptive workflows in combination with a dual isocentre approach, to widen the range of cervix patients that can benefit from this treatment.Ten cervical cancer patients were retrospectively planned with a dual isocentre technique to deliver 45 Gy in 25 fractions. 5 node-negative and 5 node-positive patients were planned using the EMBRACE II protocol. A 2 cm overlap region between the two isocentres was positioned entirely in the nodal region. A treatment workflow was simulated to account for inter-fraction anatomical change. Isocentre shifts of 3 and 6 mm were applied to investigate the effect of intra-fraction motion.Dual isocentre adapted plans ensured significantly better coverage than non-adapted (recalculated) plans with a larger benefit seen for the node-negative cases. The difference to the reference plan for the V4275 cGy to the ITV was -0.8 cGy and -8.2 cGy for the adapted and recalculated plans respectively. Movements superiorly did not affect the coverage of the ITV by more than 1%, but shifting it inferiorly caused the ITV coverage on the plan to reduce by ∼2.4% per mm.A dual isocentre technique for cervical cancer treatments and adaptive workflows have been demonstrated to recover the required plan quality for inter-fraction changes. This illustrates the feasibility of a dual isocentre technique for the MRL.
接受宫颈癌治疗的患者会表现出较大的分次内和分次间解剖变化。Unity MR-Linac（MRL）可以在治疗前后对这些患者进行 MR 成像，从而实现每日计划调整。然而，MRL 在上下方向的治疗野有限，只有 22cm，这可能会限制需要更长治疗野的患者的治疗。在这里，我们探索了与双等中心方法相结合的潜在自适应工作流程，以扩大受益于这种治疗的宫颈癌患者范围。
回顾性地为 10 名宫颈癌患者制定了双等中心技术计划，以 25 次分割方式给予 45Gy。5 名淋巴结阴性患者和 5 名淋巴结阳性患者按照 EMBRACE II 方案进行计划。将两个等中心之间的 2cm 重叠区域完全置于淋巴结区域内。模拟了一种治疗工作流程，以考虑分次间解剖变化。应用等中心偏移 3mm 和 6mm 来研究分次内运动的影响。
双等中心自适应计划确保了比非自适应（重新计算）计划更好的覆盖，对于淋巴结阴性病例，受益更大。与 ITV 的 V4275cGy 相比，适应计划和重新计算计划的参考计划的差异分别为-0.8cGy 和-8.2cGy。向上运动不会使 ITV 覆盖率增加超过 1%，但向下运动使 ITV 覆盖率在计划中减少约 2.4%/mm。
已经证明，宫颈癌治疗的双等中心技术和自适应工作流程可以恢复对分次间变化所需的计划质量。这说明了 MRL 双等中心技术的可行性。
