Purpose: We present photon-counting computed tomography (PCCT) imaging of contrast agent triplets similar in atomic number (Z) achieved with a high-flux cadmium zinc telluride (CZT) detector.

Approach: The table-top PCCT imaging system included a 330-μm-pitch CZT detector of size 8  mm  ×  24  mm² capable of using six energy bins. Four 3D-printed 3-cm-diameter phantoms each contained seven 6-mm-diameter vials with water and low and high concentration solutions of various contrast agents. Lanthanum (Z  =  57), gadolinium (Gd) (Z  =  64), and lutetium (Z  =  71) were imaged together and so were iodine (Z  =  53), Gd, and holmium (Z  =  67). Each phantom was imaged with 1-mm aluminum-filtered 120-kVp cone beam x rays to produce six energy-binned computed tomography (CT) images.

Results: K-edge images were reconstructed using a weighted sum of six CT images, which distinguished each contrast agent with a root-mean-square error (RMSE) of <0.29  %   and 0.51% for the 0.5% and 5% concentrations, respectively. Minimal cross-contamination in each K-edge image was seen, with RMSE values <0.27  %   in vials with no contrast.

Conclusion: This is the first preliminary demonstration of simultaneously imaging three similar Z contrast agents with a difference in Z as low as 3.