Twin beam dual-energy vs single-energy on a novel PET-dual energy CT: Phantom study and clinical validation.

1767 Objectives: To assess the quantitative image quality and radiation dose of twin beam dual-energy (TBDE) and single-energy technique at different kV levels on a novel PET-DECT scanner. Methods and Materials A chest phantom was scanned with a PET-DECT scanner (Biograph mCT Flow, Siemens Healthineers) in single-energy (SE) and dual-energy (DE) mode [slice thickness 3 mm, pitch 0.6 (SE) and 0.3 (DE)]. Phantom SE acquisitions from 70kV to 140kV and 120kV DE acquisition were performed. 13 patients underwent TBDE protocol (120 kV/140mAs, slice thickness 3mm, pitch 0.3) for primary lung cancer staging. TBDE dataset was used to generate linearly-blended (TB-LB) and noise-optimized virtual monoenergetic images at 50keV (TB-50keV) using filtered-back projection (FBP) and iterative reconstruction (IR). Contrast-to-noise ratio (CNR) was calculated and iodine CNR was normalized by radiation dose (CTDI) for all protocols using a figure-of-merit (FOM). Results TB-50keV datasets achieved the highest CNR and FOM compared to other datasets at each reconstruction. TB-50keV dataset reconstructed with IR 5 obtained the highest CNR, accounting for a 2-fold increase compared to FBP. TB-DE acquisition showed a CTDI of 6.7mGy, lower than 100kV (8.3mGy) and 120kV (14.2mGy). Patient data matched phantom result, TB-50keV achieved the highest CNR (5.39±1.61), yet with a 40% reduction in CTDI (9.7±1.8 mGy) compared with SE120kV protocol. Conclusion TB-50keV achieved higher CNR and FOM values compared to SE dataset ≥100 kV at a lower radiation dose. IR technique significantly improves DE and SE datasets CNR. Thus, TB-50keV dataset with IR reconstruction can significantly improve the objective image quality of a PET-DECT acquisition.