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

CHANG Rui; FAN Jing; ZHANG Xu; YANG Wenjie

doi:10.19300/j.2024.L21655

Abstract：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.