光子计数探测器CT脂肪定量准确性和稳定性的体模研究

Accuracy and stability of fat quantification using photon-counting detector CT:a phantom study

目的 旨在探讨光子计数探测器(PCD)-CT在不同扫描方案下进行脂肪定量的准确性及辐射剂量水平。方法 构建11个不同脂肪浓度的体模[真实脂肪分数(FF)为0%、2.5%、5%、10%、15%、20%、25%、30%、40%、50%和100%]。采用3种扫描模式(横断面扫描、常规螺旋扫描和大螺距螺旋扫描)、4种管电压[90、120、140和锡过滤(Sn)100 kV]和3种水平的影像质量(IQ,20、40和80)的参数组合方式完成36种扫描方案的PCD-CT扫描。记录每种扫描方案重建影像的CT剂量指数(CTDIvol)。以120 kV-IQ80的常规螺旋扫描方案作为参考,将所有方案扫描获得的CT值通过线性回归方程转换为FF值。采用组内相关系数(ICC)和Bland-Altman分析进行准确性和一致性评估,使用单向重复测量方差分析对PCD-CT衍生的FF进行比较分析。结果 PCD-CT在所有扫描方案下获得的FF的一致性和准确性结果优异[ICC>0.9(范围:0.929~0.998,P<0.017)]。通过PCD-CT获得的FF与真实FF值之间的均方根误差(RMSE)范围为1.0%~5.0%,其中120 kV-IQ20大螺距扫描的RMSE值最低(1.0%)。120 kV-IQ20和120kV-IQ80常规螺旋扫描偏倚值最低(平均值分别为1.19%和1.23%)。36种扫描方案的辐射剂量范围为0.09~1.45m Gy。结论 PCD-CT在多种扫描方案下进行脂肪定量均具有较高的准确性。此外,PCD-CT具有在超低辐射剂量下进行准确脂肪定量的潜力。

Objective To evaluate the accuracy of fat quantification and radiation dose levels of photon-counting detector(PCD)CT under various scanning protocols.Methods Phantoms with 11 different fat concentrations[true fat fractions(FF):0%,2.5%,5%,10%,15%,20%,25%,30%,40%,50%,and 100%]were constructed.Scans were performed using PCD-CT with 3 scanning modes(axial scan,conventional helical scan,and high-pitch helical scan),4 tube voltages[90 kV,120 kV,140 kV,and tin-filtered(Sn)100 kV],and 3 image quality(IQ)levels(20,40,and 80),resulting in 36 scanning protocols.CT dose index(CTDIvol)for each protocol was recorded.Using the conventional helical scan with 120 kV and IQ 80 as the reference,CT values from all protocols were converted to FF values via linear regression.Accuracy and consistency were assessed using intraclass correlation coefficients(ICC)and Bland-Altman analysis.FF derived from PCD-CT across protocols was compared using one-way repeated measures ANOVA.Results PCD-CT demonstrated excellent accuracy and consistency for FF across all protocols[ICC>0.9(range:0.929-0.998,P<0.017)].The root mean square error(RMSE)between PCD-CT-derived FF and true FF ranged from 1.0%to 5.0%,with the lowest RMSE(1.0%)observed in the high-pitch helical scan at 120 kV and IQ 20.The conventional helical scans at 120 kV with IQ 20 and IQ 80 had the lowest bias values(mean biases of 1.19%and 1.23%,respectively).Radiation doses across the 36 protocols ranged from 0.09 to 1.45 mGy.Conclusion PCD-CT achieves high accuracy in fat quantification across various scanning protocols and has potential for accurate fat quantification at ultra-low radiation doses.