Multicontrast Multiphase Intestinal Imaging Using Photon-Counting CT: A Feasibility Study in Rats

The aim of this study is to validate a 3-material decomposition algorithm for distinguishing between 2 contrast media (CM) (iodine-based and tungsten-based) and water in vivo using a commercial photon-counting CT (PCCT) unit, able to acquire 4 energy thresholds simultaneously.

Six healthy rats were imaged during different CM distribution phases with both iodine-based and tungsten-based CM present in the animals, one administered orally and one intravenously. Material decomposition was used to compute quantitative contrast maps, virtual noncontrast (VNC) maps, and virtual monoenergetic images (VMI). The mean enhancement in CM-filled regions and in CM-free muscle was measured. This prospective preclinical study was conducted in accordance with the German Animal Welfare Act guidelines and with the approval of the local state animal welfare committee.

Iodine-filled regions were exclusively enhanced (P<0.001) in the iodine map. Tungsten-filled regions were exclusively enhanced (P<0.001) in the tungsten map. VNC maps of a 3-material decomposition received no additional enhancement by CM. VMI, incorporating both iodine and tungsten CM, of different energy levels indicated the K-edge of tungsten.

This study successfully demonstrated the capability of PCCT combined with material decomposition to delineate 2 CM and water in rats. The contrast dynamics of the 2 CM in the vessels (aorta and vena cava) and intestines were successfully reproduced in the CM maps. VNC maps may omit the need for CT scans before contrast administration. VMI revealed distinct energy-dependent attenuation profiles of the given materials.