Purpose: A recently FDA-approved dual-source photon-counting-detector (DS-PCD) CT enables multi-energy cardiac imaging in high-pitch (>3) mode. The current study evaluates its multi-energy performance using phantom and patient studies, and how it compares with conventional low-pitch dual-energy mode on dual-source energy-integrating-detector (DS-EID) CT.
Methods: A cardiac motion phantom consisting of a 3 mm diameter iodinated rod mimicking motion of right coronary artery was scanned 25 times on DS-PCD in high-pitch multi-energy mode (120 kV, 65% R-R phase start, 66 ms temporal resolution) and DS-EID in low-pitch dual-energy mode (90/Sn150 kV, 65%-65% phase, 125 ms temporal resolution). Iodine maps were reconstructed, and the circularity, diameter, and iodine concentration of the rod were compared between the two scanners. Patients scanned using the DS-PCD high-pitch mode and DS-EID dual-energy mode with matched heartbeat rates were included in this study by qualitatively comparing the generated iodine maps.
Results: The volume CT dose index was 3 mGy with DS-PCD high-pitch mode and 11 mGy with DS-EID low-pitch dual-energy mode. In the iodine maps, the average circularity of the iodinated rod was 0.97 ± 0.02 with DS-PCD and 0.95 ± 0.06 with DS-EID (higher is better). The average diameter was 2.9 ± 0.2 mm with DS-PCD and 3.1 ± 0.2 mm with DS-EID, both of which are close to the 3 mm ground truth. For DS-PCD, the average iodine concentration was 9.6 ± 0.8 mg/ml which was consistent with the reference value of 9.4 mg/ml obtained with the cardiac motion disabled. On patient images, there were substantial motion artifacts in iodine maps obtained with DS-EID whereas DS-PCD provided well-defined coronaries even at a heart rate of 86 beats per minute.
Conclusion: DS-PCD CT can perform material decomposition in low-dose, high-pitch mode and provided accurate iodine quantification and excellent geometric accuracy despite the presence of cardiac motion.
Funding Support, Disclosures, and Conflict of Interest: This study was supported by the National Institutes of Health under award numbers R01 EB028590 and supported in kind by Siemens Healthineers GmbH, who own the evaluated system under the terms of a sponsored research agreement with the Mayo Clinic.