Schneider Uwe, Pemler Peter, Besserer Jürgen, Pedroni Eros, Lomax Antony, Kaser-Hotz Barbara
Department of Radiation Oncology and Nuclear Medicine, City Hospital Triemli, 8063 Zürich, Switzerland.
Med Phys. 2005 Jan;32(1):195-9. doi: 10.1118/1.1833041.
The purpose of this work is to show the feasibility of using in vivo proton radiography of a radiotherapy patient for the patient individual optimization of the calibration from CT-Hounsfield units to relative proton stopping power. Water equivalent tissue (WET) calibrated proton radiographs of a dog patient treated for a nasal tumor were used as baseline in comparison with integrated proton stopping power through the calibrated CT of the dog. In an optimization procedure starting with a stoichiometric calibration curve, the calibration was modified randomly. The result of this iteration is an optimized calibration curve which was used to recalculate the dose distribution of the patient. One result of this experiment was that the mean value of the deviations between WET calculations based on the stoichiometric calibration curve and the measurements was shifted systematically away from zero. The calibration produced by the optimization procedure reduced this shift to around 0.4 mm. Another result was that the precision of the calibration, reflected as the standard deviation of the normally distributed deviations between WET calculation and measurement, could be reduced from 7.9 to 6.7 mm with the optimized calibration. The dose distributions based on the two calibration curves showed major deviations at the distal end of the target volume.
这项工作的目的是展示对放疗患者进行体内质子射线照相，以实现从CT亨氏单位到相对质子阻止本领的校准的患者个体化优化的可行性。将一只接受鼻肿瘤治疗的犬类患者的水等效组织（WET）校准质子射线照片用作基线，并与通过该犬类校准CT得到的积分质子阻止本领进行比较。在一个从化学计量校准曲线开始的优化过程中，校准被随机修改。该迭代的结果是一条优化的校准曲线，用于重新计算患者的剂量分布。该实验的一个结果是，基于化学计量校准曲线的WET计算值与测量值之间偏差的平均值系统性地偏离了零。优化过程产生的校准将这种偏差减小到了约0.4毫米。另一个结果是，校准的精度（以WET计算值与测量值之间正态分布偏差的标准差表示）通过优化校准从7.9毫米降低到了6.7毫米。基于两条校准曲线的剂量分布在靶区远端显示出较大偏差。
