Photon-counting computed tomography of lanthanide contrast agents with a high-flux 330- μ m-pitch cadmium zinc telluride detector in a table-top system

Abstract

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 $330\text{-}\mu m$ -pitch CZT detector of size $8\mathrm{mm}\times 24{\mathrm{mm}}^2$ 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.

Keywords: contrast agents; image reconstruction; lanthanides; multienergy computed tomography; photon-counting detectors.