Objective:To compare the effect of different reconstruction algorithms of gemstone spectral imaging(GSI)parameters,and to explore the feasibility and value of deep learning image reconstruction(DLIR)in quantifying iodine concentration(IC)and effective atomic number(Zeff).Methods:GSI mode was used to scan the QSP phantom which containing 9 test tubes,including 1 tube of pure water and 5 tubes of iodine solution with the iodine concentrations of 3.75,7.5,15,30 and 30 mg/mL.The original scanning data were reconstructed using the standard algorithm ASIR-V(ranged from 0%to 100%with the interval of 10%)and the high/middle/low-strength DLIR(DLIR-L/M/H)with a layer thickness of 0.625 mm for IC and Zeff images.ROIs were placed at the center of the test tubes at 9 fixed layers.The values of IC,Zeff and their average value and standard deviation(SD)of images from different reconstruction algorithms were measured and compared.The values of IC and Zeff under different algorithmic conditions of two tubes of iodine solution with iodine concentration of 30 mg/mL located at the center and edge of the phantom were compared.Results:Different algorithms images were able to be used for the measurements of iodine concentration in pure water and various solutions using IC,and there were no statistically significant differences(all P>0.05).In terms of the SD values of IC,there were no statistically significant differences between DLIR-L and ASIR-V(ranged from 40%to 70%)or between DLIR-M and ASIR-V(ranged from 70%to 100%)of pure water or different iodine solution(all P>0.05),while the remaining SD values showed statistical differences(all P<0.05).The center position IC of the phantom was slightly lower than the edge position,reducing by about 0.63%.Zeff values had no statistically significant differences of different reconstruction algorithms(all P>0.05).In terms of the SD values of Zeff in pure water and iodine solution with iodine concentration of 3.75 mg/mL,there were no statistically significant differences between DLIR-L and ASIR-V(ranged from 40%to 70%)or between DLIR-M and ASIR-V(ranged from 50%to 90%),DLIR-L,DLIR-H(all P>0.05),while the remaining SD values showed statistical differences(all P<0.05).There were no statistically significant differences in the SD values of Zeff of iodine solution with iodine concentration of 7.5,15 or 30 mg/mL in different reconstruction algorithms(all P>0.05).The center position Zeff of the phantom was slightly lower than the edge position,reducing by about 0.13%.Conclusions:Compared to ASIR-V,DLIR algorithm does not change IC and Zeff,but can reduce the noise to some extent,and DLIR-H has the lowest degree of noise.The position change has little effect on IC and Zeff in ASIR-V and DLIR.
Tomography,X-ray computedGemstone spectral imagingIodine concentrationEffective atomic number
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