低剂量迭代重建技术在放疗定位图像中的应用

Application of low-dose iterative reconstruction technique for radiotherapy localization images

目的:探讨新型低剂量迭代重建技术应用于放疗定位图像的可行性。方法:基于体模的实验数据,对CT辐射剂量进行分析。对CT值、低对比度分辨率、噪声、均匀性以及几何畸变各项质量评价参数进行定量的分析。对仿真体模进行迭代重建技术扫描重建,并在放射治疗计划系统中对仿真体模进行模拟剂量计算,分析感兴趣体积的绝对剂量和平面内剂量的Gamma通过率。结果:低剂量迭代重建技术能够在保证图像质量的同时减少约60%的CT扫描辐射剂量。当管电压保持不变时,低剂量迭代重建技术对TPS剂量计算的准确性的影响可以忽略不计,感兴趣体积剂量最大差异0.6%,面剂量的Gamma通过率优于99.82%。低剂量迭代重建技术对图像低对比度分辨率有一定影响,需要进一步结合临床影像进行分析。结论:低剂量迭代重建技术可以应用于放疗定位图像中,但是需要注意图像特性和某些图像质量的改变,建议与PET-CT、超声、核磁等检查手段结合综合考虑确定靶区范围。

Objective To discuss the feasibility of a new low-dose iterative reconstruction(IR)technique for radiotherapy localization images.Methods Computed tomography(CT)radiation doses were analyzed based on the experimental data of a phantom.The quality evaluation parameters such as CT value,low-contrast resolution,noise,uniformity and geometric distortion of IR images were quantitatively analyzed.Additionally,an anthropomorphic phantom was scanned and reconstructed with IR technique,and then simulated dose calculations for the anthropomorphic phantom were conducted in the treatment planning system.The absolute dose of the volume of interest and the Gamma passing rates of the plane doses were analyzed.Results Low-dose IR technique ensured image quality while reducing CT radiation dose by about 60%.When the tube voltage remains constant,the effect of IR on the accuracy of TPS calculations was negligible;the maximum dose difference of the volume of interest was 0.6%;and the Gamma passing rates of the plane doses were higher than 99.82%.Low-dose IR technique had a certain effect on the low-contrast resolution of images,and the effects needed to be further analyzed based on clinical images.Conclusion Low-dose IR technique can be applied to radiotherapy localization images,but the changes in image features and some image quality indexes need to be paid attention to.The target areas should be determined by low-dose IR technique combined with PET-CT,ultrasound,magnetic resonance imaging and other examinations.