Kordolaimi Sofia D, Saradeas Ioannis, Ploussi Agapi, Pantos Ioannis, Argentos Stylianos, Efstathopoulos Efstathios P
1 Second Department of Radiology, Medical School, University of Athens, 1 Rimini Str, 12462 Haidari, Athens, Greece.
AJR Am J Roentgenol. 2014 Oct;203(4):W434-9. doi: 10.2214/AJR.13.11973.
The purpose of this study is to introduce an efficient method for the optimization of iterative reconstruction CT protocols based on phantom image analysis and the comparison of obtained results with actual patient data.
We considered chest, abdomen, and pelvis CT examinations before the installation of an iterative reconstruction algorithm (iDose4) to define the exposure parameters used in clinical routine with filtered back projection (FBP). The body area of a CT phantom was subsequently scanned with various tube voltages and tube currents-exposure time products, and acquired data were reconstructed with FBP and different levels of iDose4. The contrast-to-noise ratio (CNR) for FBP with the original exposure parameters was calculated to define the minimum acceptable CNR value for each tube voltage. Then, an optimum tube current-exposure time products for each tube voltage and level of iterative reconstruction was estimated. We also compared findings derived by the phantom with real patient data by assessing dosimetric and image quality indexes from a patient cohort scanned with exposure parameters gradually adjusted during 1 year of adoption of iDose4.
By use of the proposed phantom method, dose reduction up to 75% was achievable, whereas for an intermediate level of iteration (level 4), the dose reduction ranged between 50% and 60%, depending on the tube voltage. For comparison, with the gradual adjustment of exposure settings, the corresponding dose reduction for the same level of iteration was about 35%.
The proposed method provides rapid and efficient optimization of CT protocols and could be used as the first step in the optimization process.
本研究旨在介绍一种基于体模图像分析优化迭代重建CT协议的有效方法，并将所得结果与实际患者数据进行比较。
我们考虑了在安装迭代重建算法（iDose4）之前的胸部、腹部和骨盆CT检查，以确定临床常规中使用滤波反投影（FBP）时的曝光参数。随后，使用不同的管电压和管电流-曝光时间乘积扫描CT体模的身体区域，采集的数据用FBP和不同水平的iDose4进行重建。计算原始曝光参数下FBP的对比噪声比（CNR），以确定每个管电压的最低可接受CNR值。然后，估计每个管电压和迭代重建水平的最佳管电流-曝光时间乘积。我们还通过评估在采用iDose4的1年期间逐渐调整曝光参数扫描的患者队列的剂量学和图像质量指标，将体模得出的结果与真实患者数据进行比较。
使用所提出的体模方法，剂量降低可达75%，而对于中等迭代水平（4级），剂量降低范围在50%至60%之间，具体取决于管电压。相比之下，随着曝光设置的逐渐调整，相同迭代水平下的相应剂量降低约为35%。
所提出的方法可快速有效地优化CT协议，可作为优化过程的第一步。
