Kapatoes J M, Olivera G H, Balog J P, Keller H, Reckwerdt P J, Mackie T R
University of Wisconsin-Madison, 53706, USA.
Phys Med Biol. 2001 Apr;46(4):943-66. doi: 10.1088/0031-9155/46/4/303.
Dose reconstruction is a process that re-creates the treatment-time dose deposited in a patient provided there is knowledge of the delivered energy fluence and the patient's anatomy at the time of treatment. A method for reconstructing dose is presented. The process starts with delivery verification, in which the incident energy fluence from a treatment is computed using the exit detector signal and a transfer matrix to convert the detector signal to energy fluence. With the verified energy fluence and a CT image of the patient in the treatment position, the treatment-time dose distribution is computed using any model-based algorithm such as convolution/superposition or Monte Carlo. The accuracy of dose reconstruction and the ability of the process to reveal delivery errors are presented. Regarding accuracy, a reconstructed dose distribution was compared with a measured film distribution for a simulated breast treatment carried out on a thorax phantom. It was found that the reconstructed dose distribution agreed well with the dose distribution measured using film: the majority of the voxels were within the low and high dose-gradient tolerances of 3% and 3 mm respectively. Concerning delivery errors, it was found that errors associated with the accelerator, the multileaf collimator and patient positioning might be detected in the verified energy fluence and are readily apparent in the reconstructed dose. For the cases in which errors appear in the reconstructed dose, the possibility for adaptive radiotherapy is discussed.
剂量重建是一个在已知治疗时传递的能量注量和患者解剖结构的情况下，重新创建患者体内治疗时间剂量沉积的过程。本文提出了一种剂量重建方法。该过程从剂量传递验证开始，在剂量传递验证中，利用出射探测器信号和一个将探测器信号转换为能量注量的转移矩阵来计算治疗的入射能量注量。利用验证后的能量注量和处于治疗位置的患者的CT图像，使用基于模型的算法（如卷积/叠加法或蒙特卡罗法）计算治疗时间剂量分布。本文给出了剂量重建的准确性以及该过程揭示剂量传递误差的能力。关于准确性，将重建的剂量分布与在胸部体模上进行的模拟乳腺治疗的测量胶片剂量分布进行了比较。结果发现，重建的剂量分布与使用胶片测量的剂量分布吻合良好：大多数体素分别在3%和3毫米的低剂量梯度和高剂量梯度容差范围内。关于剂量传递误差，发现在验证后的能量注量中可能检测到与加速器、多叶准直器和患者定位相关的误差，并且在重建的剂量中很明显。对于重建剂量中出现误差的情况，讨论了自适应放射治疗的可能性。
