Spectral quantification in different lumen diameters for cardiovascular applications

The first clinical dual-source photon-counting CT couples high spatial resolution with spectral imaging that is advantageous to imaging of small vessels, such as the coronary arteries, in cardiovascular disease. While both the high spatial resolution and quantification accuracy have been established in PCCT, the effect of lumen size on spectral quantification has not been evaluated. Phantoms with an internal tube diameter ranging from 4 to 12 mm were printed with calcium-based polylactic acid filament to mimic a coronary artery. These diameter phantoms were filled with solutions with iodine concentrations of 2, 5, and 10 mg/mL and scanned with phantoms of varying sizes on a PCCT. Virtual monoenergetic images (VMI) at 70 keV, iodine density maps, and virtual non-contrast maps were measured to determine the effect of lumen diameter on spectral quantification at different iodine concentrations, radiation doses, and phantom sizes. Each evaluated spectral result exhibited consistent quantification at lumen diameters greater than 6 mm with all phantom sizes. VMI 70 keV were within ±15, ±12, and ±4 of VMI 70 keV at a lumen diameter of 12 mm and the small phantom for iodine concentrations of 2, 5, and 10 mg/mL. At a lumen diameter of 4 mm, significant deviations were present in VMI 70 keV, iodine density maps, and VNC with large phantoms, which averaged 55 HU, 1.4 mg/mL, and 61 HU at an iodine concentration of 5 mg/mL, respectively. The consistent spectral results across lumen diameters demonstrated the synergy between high spatial resolution and quantification that will spur the use of quantitative metrics and development of new applications in diagnostic cardiac imaging.