迭代重建可提高痛风诊断准确率：一项离体（生物）双能 CT 研究。

Iterative Reconstruction May Improve Diagnosis of Gout: An Ex Vivo (Bio)Phantom Dual-Energy Computed Tomography Study.

出版信息

Invest Radiol. 2018 Jan;53(1):6-12. doi: 10.1097/RLI.0000000000000402.

Abstract

OBJECTIVES

We hypothesize that, compared with filtered back projection (FBP), iterative reconstruction (IR) increases the detected volume of uric acid, which serves as a measure of the sensitivity of the method, and therefore allows examinations with lower radiation exposure. Thus, the aim of our study was to evaluate the role of IR in dual-energy computed tomography (DECT) for gout assessment and volumetry in an ex vivo gout model using an epoxy phantom and a biophantom.

MATERIALS AND METHODS

We prepared specimens with different concentrations of monosodium uric acid in ultrasound gel (30%-50%) and inserted them into an epoxy-based phantom and a porcine foreleg. Computed tomography scanning was performed on a 320-row single-source DECT scanner in volume mode with an ascending order of tube currents. Image data sets were reconstructed using FBP and IR with 2 iteration levels (IR1 and IR2). Measurements in regions of interest (ROIs) and volumetric measurements were performed using either fixed parameters for the analysis software (epoxy phantom) or parameters specifically adapted for each data set (porcine phantom). Seven retrospectively identified clinical data sets were used for validation in patients. Rm-ANOVA was used for statistical analysis. No institutional review board approval was required.

RESULTS

We found no differences in Hounsfield units between the different reconstruction algorithms (P = 0.09 and 0.05 for 80 and 135 kVp, respectively) and the calculated dual-energy gradient (P = 0.27). Filtered back projection detected less uric acid compared with IR (with fixed parameters: 6.0 ± 0.3 cm for FBP and 6.1 ± 0.2 for IR1 and IR2; with adapted thresholds: 1.2 ± 0.3 cm for FBP and 1.8 ± 0.1 and 2.0 ± 0.1 for IR1 and IR2, respectively). The differences were significant for all measurements (P = 0.0003). Also in the test cases, FBP detected significantly fewer tophi (mean volume, 1.38 ± 2.1 cm) compared with IR1 (1.86 ± 2.9) and IR2 (2.07 ± 3.1) (P = 0.04).

CONCLUSIONS

Iterative reconstruction has the potential to improve the sensitivity of a DECT scan for gouty tophi, to decrease radiation exposure, or to combine both options.

摘要

目的

我们假设与滤波反投影（filtered back projection，FBP）相比，迭代重建（iterative reconstruction，IR）可增加尿酸的检测体积，这可作为方法灵敏度的衡量指标，从而实现更低辐射剂量的检查。因此，我们的研究旨在评估 IR 在双能 CT（dual-energy computed tomography，DECT）用于痛风评估和容积测量中的作用，为此我们在环氧体模和生物体模中使用尿酸盐浓度不同的单钠尿酸盐在超声凝胶（30%-50%）中的样本进行实验。使用具有递增管电流的 320 排单源 DECT 扫描仪以容积模式进行 CT 扫描。使用 FBP 和 2 次迭代水平（IR1 和 IR2）的 IR 对图像数据集进行重建。使用分析软件的固定参数（环氧体模）或针对每个数据集专门调整的参数（猪前肢体模）在感兴趣区域（region of interest，ROI）中进行测量和容积测量。使用 7 个回顾性确定的临床数据集对患者数据进行验证。使用重复测量方差分析进行统计学分析。本研究无需机构审查委员会批准。

结果

我们发现不同重建算法之间的 CT 值（Hounsfield units，HU）没有差异（80 kVp 时 P = 0.09，135 kVp 时 P = 0.05）和计算出的双能梯度（P = 0.27）。与 IR 相比，FBP 检测到的尿酸较少（使用固定参数：FBP 为 6.0 ± 0.3 cm，IR1 和 IR2 分别为 6.1 ± 0.2 cm；使用自适应阈值：FBP 为 1.2 ± 0.3 cm，IR1 和 IR2 分别为 1.8 ± 0.1 和 2.0 ± 0.1 cm）。所有测量的差异均有统计学意义（P = 0.0003）。在测试病例中，与 IR1（1.86 ± 2.9 cm）和 IR2（2.07 ± 3.1 cm）相比，FBP 检测到的痛风石体积明显较小（平均体积，1.38 ± 2.1 cm）（P = 0.04）。