Department of Radiotherapy, UMC Utrecht, Heidelberglaan 100, 3508 GA Utrecht, The Netherlands.
Imaging Division, UMC Utrecht, Heidelberglaan 100, 3508 GA Utrecht, The Netherlands.
Phys Med Biol. 2021 Mar 2;66(6):065002. doi: 10.1088/1361-6560/abe02a.
Accurate spatial dose delivery in radiotherapy is frequently complicated due to changes in the patient's internal anatomy during and in-between therapy segments. The recent introduction of hybrid MRI radiotherapy systems allows unequaled soft-tissue visualization during radiation delivery and can be used for dose reconstruction to quantify the impact of motion. To this end, knowledge of anatomical deformations obtained from continuous monitoring during treatment has to be combined with information on the spatio-temporal dose delivery to perform motion-compensated dose accumulation (MCDA). Here, the influence of the choice of deformable image registration algorithm, dose warping strategy, and magnetic resonance image resolution and signal-to-noise-ratio on the resulting MCDA is investigated. For a quantitative investigation, four 4D MRI-datasets representing typical patient observed motion patterns are generated using finite element modeling and serve as a gold standard. Energy delivery is simulated intra-fractionally in the deformed image space and, subsequently, MCDA-processed. Finally, the results are substantiated by comparing MCDA strategies on clinically acquired patient data. It is shown that MCDA is needed for correct quantitative dose reconstruction. For prostate treatments, using the energy per mass transfer dose warping strategy has the largest influence on decreasing dose estimation errors.
在放疗中，由于患者内部解剖结构在治疗过程中和治疗段之间的变化，精确的空间剂量传递常常变得复杂。最近引入的混合 MRI 放疗系统允许在放射治疗过程中进行无与伦比的软组织可视化，并可用于剂量重建以量化运动的影响。为此，必须将在治疗过程中连续监测获得的解剖变形知识与关于时空剂量传递的信息结合起来，以进行运动补偿剂量积累（MCDA）。在这里，研究了可变形图像配准算法、剂量变形策略以及磁共振图像分辨率和信噪比对所得 MCDA 的影响。为了进行定量研究，使用有限元建模生成了四个代表典型患者观察到的运动模式的 4D MRI 数据集，作为金标准。在变形图像空间中进行了分次内能量传递模拟，随后进行了 MCDA 处理。最后，通过比较临床采集的患者数据上的 MCDA 策略来证实结果。结果表明，MCDA 对于正确的定量剂量重建是必要的。对于前列腺治疗，使用每质量传递剂量变形策略对降低剂量估计误差的影响最大。
