Photon Counting Micro-CT for Imaging Cisplatin

The photon-counting (PC) detector technology promises to enhance the number of CT applications due to the spectral information. Of high interest for the cancer research community is imaging the tumor delivery of Cisplatin (CisPt), a chemotherapeutic agent utilized for treatment of numerous malignancies. CisPt contains platinum (Pt), a high-Z element material with a K-edge (78.4 keV) in the diagnostic spectrum. Our group has developed a preclinical prototype photon counting (PC) CT and applied it in cancer studies using nanoparticles. This study aims to investigate if CisPt can be imaged by K-edge spectral PCCT. Simulations and phantom experiments were performed to investigate CisPt detection using PCCT. We have selected scanning parameters (125 kVp) and energy thresholds (28, 34, 70, 78 keV) to enable K-edge separation of Pt and iodine (I) from calcium (Ca). The simulations include modeling of the polychromatic spectrum, and the PC detector response with spectral distortions. Two digital phantoms were used with maximum concentrations corresponding to low (2 mg/mL) and high (10 mg/mL) concentrations of I and Pt. A physical phantom with CisPt, I and Ca solutions was imaged both on our PC micro-CT and a novel clinical PCCT system. Material decompositions confirm the separation of Pt, Ca and I. However, low concentrations (<1 mg/mL) of CisPt are unlikely to be separated. Nevertheless, a liposomal nanoparticle-based CisPt formulation can enhance tumor delivery, via enhanced permeability and retention (EPR) and benefit from PCCT monitoring. Thus, depending on the levels of tumor accumulation, PCCT imaging of nanoparticles containing CisPt may become possible.