Spectral performance of dual source flash mode on the emerging photon counting CT: Comparison with dual energy CT for...

To evaluate the spectral performance of dual-source (DS) compared to single-source (SS) mode on the photon counting CT (PCCT), and conventional dual-energy CT (DECT).

Multi-Energy CT phantoms (20, 40 cm) were configured with solid-iodine (2-15mgI/cc) and solid-water rods to simulate pediatric and adult-sized abdomens. PCCT scans were acquired with SS (pitch-1.5) and DS (pitch-3.0). DECT scans were performed using 80/Sn140 and 100/Sn140kV with a maximum-pitch 1.2. At the clinical dose setting, CTDI values were 0.63 mGy (20-cm) and 4.30 mGy (40-cm). Dose and reconstruction parameters were matched across all scan modes. Virtual monoenergetic images (VMI) between 40 and 80 keV and iodine maps (IM) were generated. Noise, noise power spectra and section sensitive profiles of VMIs were then calculated. HU accuracy was evaluated using absolute percent error (APE) between measured and reference attenuation values, while iodine quantification accuracy was assessed by linear regression and root-mean-square-error (RMSE) comparing measured and reference concentrations.

PCCT DS and SS modes showed comparable noise levels across keV. Both PCCT modes had lower noise than DECT across all conditions, although discrepancies diminished in larger phantoms and higher VMI keV. At the 20-cm phantom, median APEs for iodine CT numbers were lower for PCCT SS (0.53%) and DS (0.55%) than for DECT (0.98%, 1.06%). RMSE values of iodine quantification are 0.50mgI/cc for PCCT DS and 0.53mgI/cc for PCCT SS.

Ultra-fast PCCT dual-source mode yields spectral image quality comparable to PCCT single-source and DECT, supporting its use when fast scanning is critical for pediatric and cardiac applications.