Vaniqui Ana, van der Heyden Brent, Almeida Isabel P, Schyns Lotte Ejr, van Hoof Stefan J, Verhaegen Frank
1 Department of Radiation Oncology (MAASTRO), GROW-School for Oncology and Developmental Biology, Maastricht University Medical Centre , Maastricht , The Netherlands.
2 SmART Scientific Solutions BV , Maastricht , The Netherlands.
Br J Radiol. 2019 Mar;92(1095):20180445. doi: 10.1259/bjr.20180445. Epub 2018 Jul 20.
: This work aims to analyse the effect of respiratory motion on optimal irradiation margins for murine lung tumour models.
: Four-dimensional mathematical phantoms with different lung tumour locations affected by respiratory motion were created. Two extreme breathing curves were adopted and divided into time-points. Each time-point was loaded in a treatment planning system and Monte Carlo (MC) dose calculations were performed for a 360° arc plan. A time-resolved dose was derived, considering the gantry rotation and the breathing motion. Radiotherapy metrics were derived to assess the final treatment plans. An interpolation function was investigated to reduce calculation cost.
: The effect of respiratory motion on the treatment plan quality is strongly dependent on the breathing pattern and the tumour position. Tumours located closer to the diaphragm required a compromise between tumour conformity and healthy tissue damage. A recipe, which considers collimator size, was proposed to derive tumour margins and spare the organs at risk (OARs) by respecting constraints on user-defined metrics.
: It is recommended to add a target margin, especially on sites where movement is substantial. A simple recipe to derive tumour margins was developed.
: This work is a first step towards a standard planning target volume concept in pre-clinical radiotherapy.
本研究旨在分析呼吸运动对小鼠肺癌模型最佳照射边界的影响。
创建了受呼吸运动影响的不同肺肿瘤位置的四维数学模型。采用两条极端呼吸曲线并将其划分为多个时间点。将每个时间点加载到治疗计划系统中，并对360°弧形计划进行蒙特卡罗（MC）剂量计算。考虑到机架旋转和呼吸运动，得出时间分辨剂量。推导放射治疗指标以评估最终治疗计划。研究了一种插值函数以降低计算成本。
呼吸运动对治疗计划质量的影响很大程度上取决于呼吸模式和肿瘤位置。位于靠近膈肌处的肿瘤需要在肿瘤适形性和健康组织损伤之间进行权衡。提出了一种考虑准直器尺寸的方法，以得出肿瘤边界并通过遵守对用户定义指标的限制来保护危及器官（OARs）。
建议增加靶区边界，尤其是在运动幅度较大的部位。开发了一种得出肿瘤边界的简单方法。
本研究是迈向临床前放射治疗中标准计划靶区体积概念的第一步。
