Optimization of image quality and accuracy of low iodine concentration quantification as function of kVp pairs for abdominal imaging using dual-source CT: A phantom study

Purpose: To determine the suitable kVp pair for optimal image quality of the virtual monochromatic images (VMIs) and iodine quantification accuracy at low concentration, using a third generation dual-source CT (DSCT). Materials and methods: Multi-energy CT phantoms with and without body rings were scanned with a DSCT using four kVp pairs (tube "A"/"B" voltage): 100/Sn150, 90/Sn150, 80/Sn150 and 70/Sn150 kVp. The reference mAs was adjusted to obtain a CTDIvol close to 11 mGy. HU values accuracy (RMSDHU), noise (SD) and contrast-tonoise ratio (CNR) of iodine inserts of 0.5, 1, 2 and 5 mg/mL concentrations were assessed on VMIs at 40/50/ 60/70 keV. Iodine quantification accuracy was assessed using the RMSDiodine and iodine bias (IBiodine). Results: The RMSDHU decreased when the tube "A" voltage increased. The mean noise value increased significantly with tube "A" voltage (p < 0.001) but decreased between 80/Sn150 and 90/Sn150 kVp for the small phantom (1.1 +/- 0.1%; p = 0.047). The CNR significantly decreased with tube "A" voltage (p < 0.001), except between 80/Sn150 and 90/Sn150 kVp for all inserts and between 90/Sn150 kVp and 100/Sn150 kVp for the 1.0 and 0.5 mg/mL inserts in the large phantom. In the small phantom, no significant difference was found between 80/Sn150 kVp and 90/Sn150 kVp for all inserts and between 80/Sn150, 90/Sn150 and 100/Sn150 kVp for the 1 and 0.5 mg/mL inserts. The RMSDiodine and IBiodine decreased as the tube "A" voltage of the kVp pair increased. Conclusion: The kVp pair of 70/Sn150 led to better image quality in VMIs and sufficient iodine accuracy.