A hybrid reconstruction algorithm for fast and accurate 4D cone-beam CT imaginga)
A hybrid reconstruction algorithm for fast and accurate 4D cone-beam CT imaginga)
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DOI：
10.1118/1.4881326
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发表时间：
2014-07-01
期刊：
影响因子：
3.8
通讯作者：
Jia, Xun
中科院分区：
文献类型：
--
作者：
Yan, Hao;Zhen, Xin;Jia, Xun
目的：四维锥束CT(4D-CBCT)已被应用于放射治疗，为肺部和上腹部提供4D图像指导。然而，目前4D-CBCT扫描时间长、图像质量低，限制了其临床应用。本文的目的是开发一种新的4D-CBCT重建方法，该方法基于标准3D-CBCT协议获取的1分钟扫描数据来恢复体积图像。方法：该模型优化变形矢量场，使患者特定的计划CT(p-CT)变形，从而使计算的4D-CBCT投影与测量值相匹配。为了解决这一优化问题，提出了一种前后向分裂(FBS)方法。它将原问题分解为两个研究较好的子问题，即图像重建和可变形图像配准。通过迭代求解这两个子问题，FBS在保持高图像质量的同时，逐渐产生正确的变形信息。整个工作流程在一个图形处理单元上实现，提高了效率。对一个运动模型和三个真实病例进行了重建图像的准确性和质量以及算法的稳健性和效率的综合评估。结果：该算法从1min扫描获得的高欠采样投影数据中重建出4D-CBCT图像。在解剖结构定位精度方面，体模的平均差值为0.204 mm，最大差值为0.484 mm，患者1~3的最大差值为0.3~0.5 mm。在图像质量方面，体模和病人的强度误差分别小于5HU和20HU。与使用1分钟数据和4分钟数据的FDK算法相比，信噪比分别提高了12.74倍和5.12倍。该算法在NVIDIA GTX590卡上的计算时间为每相1~1.5min。结论：基于临床标准1min三维CBCT扫描协议的高质量4D-CBCT成像是可行的。(C)2014年美国医学物理学家协会。
Purpose: 4D cone beam CT (4D-CBCT) has been utilized in radiation therapy to provide 4D image guidance in lung and upper abdomen area. However, clinical application of 4D-CBCT is currently limited due to the long scan time and low image quality. The purpose of this paper is to develop a new 4D-CBCT reconstruction method that restores volumetric images based on the 1-min scan data acquired with a standard 3D-CBCT protocol.Methods: The model optimizes a deformation vector field that deforms a patient-specific planning CT (p-CT), so that the calculated 4D-CBCT projections match measurements. A forward-backward splitting (FBS) method is invented to solve the optimization problem. It splits the original problem into two well-studied subproblems, i.e., image reconstruction and deformable image registration. By iteratively solving the two subproblems, FBS gradually yields correct deformation information, while maintaining high image quality. The whole workflow is implemented on a graphic-processing-unit to improve efficiency. Comprehensive evaluations have been conducted on a moving phantom and three real patient cases regarding the accuracy and quality of the reconstructed images, as well as the algorithm robustness and efficiency.Results: The proposed algorithm reconstructs 4D-CBCT images from highly under-sampled projection data acquired with 1-min scans. Regarding the anatomical structure location accuracy, 0.204 mm average differences and 0.484 mm maximum difference are found for the phantom case, and the maximum differences of 0.3-0.5 mm for patients 1-3 are observed. As for the image quality, intensity errors below 5 and 20 HU compared to the planning CT are achieved for the phantom and the patient cases, respectively. Signal-noise-ratio values are improved by 12.74 and 5.12 times compared to results from FDK algorithm using the 1-min data and 4-min data, respectively. The computation time of the algorithm on a NVIDIA GTX590 card is 1-1.5 min per phase.Conclusions: High-quality 4D-CBCT imaging based on the clinically standard 1-min 3D CBCT scanning protocol is feasible via the proposed hybrid reconstruction algorithm. (C) 2014 American Association of Physicists in Medicine.