Linearity between CT number and iodine concentration and application to improving accuracy of CT number in slow kV-switching dual energy CT

Abstract

The linearity between CT numbers and iodine concentrations is proved analytically provided the correlations between the atoms are negligible. This relationship is applied to correct the CT numbers in the ICA regions in monochromatic images of dual energy CT with the slow kV-switching technique where one scan with a low/high tube voltage follows by another scan with a high/low voltage. The iodine concentration may change significantly during the kV-switching. The resultant CT numbers in ICA regions may not be meaningful in the monochromatic images from pre-reconstruction decompositions because the data with the low/high voltages are not consistent. Using the linearity between CT numbers and iodine concentrations, the CT numbers in ICA regions can be corrected by referring to the CT numbers in the polychromatic images with the low/high voltages. A numerical simulation and a phantom study are performed to examine the linearity between CT numbers and iodine concentrations. The CT number correction by use of the linearity is tested in the numerical simulation study in slow kV-switching dual energy CT. The results show that the corrected CT numbers by use of the linearity are accurate.