Development of a spatial-spectral phantom for evaluation of vascular CT imaging

Abstract

Cardiovascular disease diagnosis relies heavily on diagnostic imaging. Advancement in computed tomography (CT) technology has particularly improved diagnosis in patients with coronary artery disease. In particular, the improved spatial resolution and iodine quantification capabilities of photon-counting CT (PCCT) have the potential to further improve the diagnostic workflow. Since iodine quantification has become a critical aspect of clinical diagnosis, several studies have been conducted to evaluate its effectiveness and the parameters that may affect it. An additional relationship, the effect of spatial resolution and vessel size on iodine quantification, was examined with a designed phantom. A phantom consisted of six different tubes of changing diameters (2 to 12 mm), along with a cone and an hourglass-shaped tube with diameters from 3 to 8 mm. It was scanned on a PCCT after being filled with an iodine solution. Iodine density maps, VNC, and VMI 70keV were then reconstructed with different fields of view (250 mm, 350 mm, 450 mm). Regions of interest were placed on spectral results along the length of the hourglass. Spectral results were highly accurate for vessels larger than 4 mm in diameter and regions of interest larger than 3 mm. The bias in iodine quantification increases with smaller diameters. Conversely, VNC increased, illustrating a directly proportional relationship between VNC and iodine density. The proposed phantom design allows for future studies that further investigate the relationship between spatial resolution and iodine quantification, especially in clinical workflow for optimizing protocols, implementing new CT technologies, and harmonizing protocols between different CT platforms.