Intra-individual comparison of coronary calcium scoring between photon counting detector- and energy integrating detector-CT: Effects on risk reclassification
Elias V. Wolf, Moritz C. Halfmann, U. Joseph Schoepf, Emese Zsarnóczay, Nicola Fink, Joseph P. Griffith, Gilberto J. Aquino, Martin J. Willemink, Jim O’Doherty, Michaela M. Hell, Pál Surányi, Ismael M. Kabakus, Dhiraj Baruah, Ákos Varga‐Szemes, Tilman Emrich
Abstract
Purpose To compare coronary artery calcium volume and score (CACS) between photon-counting detector (PCD) and conventional energy integrating detector (EID) computed tomography (CT) in a phantom and prospective patient study. Methods A commercially available CACS phantom was scanned with a standard CACS protocol (120 kVp, slice thickness/increment 3/1.5 mm, and a quantitative Qr36 kernel), with filtered back projection on the EID-CT, and with monoenergetic reconstruction at 70 keV and quantum iterative reconstruction off on the PCD-CT. The same settings were used to prospectively acquire data in patients ( n = 23, 65 ± 12.1 years), who underwent PCD- and EID-CT scans with a median of 5.5 (3.0–12.5) days between the two scans in the period from August 2021 to March 2022. CACS was quantified using a commercially available software solution. A regression formula was obtained from the aforementioned comparison and applied to simulate risk reclassification in a pre-existing cohort of 514 patients who underwent a cardiac EID-CT between January and December 2021. Results Based on the phantom experiment, CACS PCD–CT showed a more accurate measurement of the reference CAC volumes (overestimation of physical volumes: PCD-CT 66.1 ± 1.6% vs. EID-CT: 77.2 ± 0.5%). CACS EID–CT and CACS PCD–CT were strongly correlated, however, the latter measured significantly lower values in the phantom (CACS PCD–CT : 60.5 (30.2–170.3) vs CACS EID–CT 74.7 (34.6–180.8), p = 0.0015, r = 0.99, mean bias –9.7, Limits of Agreement (LoA) –36.6/17.3) and in patients (non-significant) (CACS PCD–CT : 174.3 (11.1–872.7) vs CACS EID–CT 218.2 (18.5–876.4), p = 0.10, r = 0.94, mean bias –41.1, LoA –315.3/232.5). The systematic lower measurements of Agatston score on PCD-CT system led to reclassification of 5.25% of our simulated patient cohort to a lower classification class. Conclusion CACS PCD–CT is feasible and correlates strongly with CACS EID–CT , however, leads to lower CACS values. PCD-CT may provide results that are more accurate for CACS than EID-CT.