Ultrafast non-ECG-gated cardiac spectral CT scanning for myocardial late iodine enhancement assessment: a feasibility study

Purpose: Evaluate Late Iodine Enhancement (LIE) using the new Philips Spectral CT 7500 scanner without ECG-gating. Material and Methods: Fifty-one contrast-enhanced cardiac Computed Tomography (CT) scans with LIE phase (LIE-CT) acquired using the Philips Spectral CT 7500 scanner (8 cm, 256 reconstructed slices) were retrospectively reviewed. LIE-CT was acquired 6–7 min after the administration of contrast agent, using ultra-short scanning time without ECG-gating. LIE-CT technical and dosimetry data were compared with data from 17 cardiac CT scans acquired with Philips Brilliance iCT (4 cm, 128 reconstructed slices). On Spectral CT images, LIE was assessed using "Iodine no water" spectral maps and Extracellular Volume (ECV) quantification. CT findings were compared with the gold standard (Cardiac Magnetic Resonance, CMR) when available. Results: Spectral CT images without ECG-gating exhibited high visual quality with minimal motion artifacts. Technical data significantly differed (p <.001) between Spectral CT and iCT: median scan time 0.69 s (interquartile range (IQR) 0.66–0.72) vs 8.02 s (IQR 7.32–8.49), median Table speed 433.2 mm/s vs 23.5 mm/s (IQR 21.8–26.5), median CTDIvol 7.2 mGy vs 29.6 mGy (IQR 27.8–33.3), median DLP 211 mGy*cm (IQR 199–222) vs 477.6 mGy*cm (IQR 430.9–551.7), current 812 mA vs 924 mA (IQR 924–925), voltage 100 kV (min 100–max 140) vs 80 kV. Interobserver reproducibility of ECV quantification on Spectral CT images was good in myocardium without LIE and excellent in LIE areas, with negligible bias between observers. Where available, LIE and ECV findings showed good concordance with CMR LGE and ECV. Conclusion: Ultrafast non-ECG-gated cardiac Spectral CT provides high-quality images for evaluating LIE, 76% reduction of radiation dose, 50% increase in signal-to-noise ratio, and 91% reduction of acquisition time. ECV measurements demonstrate high interobserver reproducibility. Preliminary findings show good agreement with CMR; while based on a limited validation cohort with selective ECV use.