较快和较低剂量的成像:在快速低剂量4D形光束CT成像中评估自适应性,恒定的门架速度和角度分离
Benjamin K F Lau1, Owen Dillon1, Shalini K Vinod2,3
1Faculty of Medicine and Health, Image X Institute, University of Sydney, Sydney, NSW, Australia.
Medical physics
|July 10, 2023
概括
肺癌放射治疗的快速四维圆束计算断层扫描 (4DCBCT) 成像是可行的,通过自适应采样和运动补偿重建. 图像质量保持不变,即使在快速旋转道和不同投影角度的情况下.
科学领域:
- 医学物理 医学物理
- 放射治疗技术 放射治疗技术
- 图像重建 图像的重建
背景情况:
- 四维圆束计算断层扫描 (4DCBCT) 越来越多地用于肺癌放射治疗,特别是用于低分离治疗.
- 目前的4DCBCT系统面临的挑战包括漫长的扫描时间,可变的图像质量,高成像剂量和文物.
- 新兴的线性加速器提供了明显更快的4DCBCT采集 (9.2s),需要对其对图像质量的影响进行评估.
研究的目的:
- 为了研究廊速度和X射线投射角度分离如何影响快速,低剂量4DCBCT的图像质量.
- 为了评估恒定与自适应式门架速度对图像质量的影响.
- 通过使用先进的重建技术,确定角度差距降低4DCBCT图像质量的值.
主要方法:
- 模拟的快速低剂量4DCBCT采集 (60-80s,200投影) 使用4D扩展心脏体 (XCAT) 数字幻影.
- 从临床试验中分析了患者的角度差距,并引入了可变/静态的角度差距 (20°,30°,40°) 来评估影响.
- 模拟快速门架旋转 (9.2s-240s) 和使用费尔德坎普-戴维斯-克雷斯 (FDK),麦金农-贝茨 (MKB) 和运动补偿-MKB (MCMKB) 算法重建图像.
- 通过使用SSIM,CNR,SNR,TIW-D和TIW-T指标评估图像质量.
主要成果:
- 用患者的角度间隙和可变角度间隙进行的重建显示,图像质量与理想的角度分离相当.
- 静态角间隙重建导致图像质量指标明显降低 (例如,SSIM 0.92,CNR 6.8与40°间隙).
- 运动补偿重建 (MCMKB) 产生了最高的对比度和最低的条纹文物,即使在高速门架速度下也保持了高图像质量.
结论:
- 通过自适应采样和运动补偿重建,可以实现非常快的4DCBCT扫描,从而保持图像质量.
- 呼吸器容器内投射之间的角分离对快速,低剂量4DCBCT图像质量产生最小的影响.
- 这些发现支持开发优化协议,以在新兴线性加速器上快速获得4DCBCT.
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