Abstract 15552: Optimal Virtual Monoenergetic Settings in Spectral Ct With a Dual Layer Detector: Breakthrough in Achieving Best Contrast Between Non Calcified and Calcified Plaques and Lumen in Coronary Arteries

Abstract

Introduction: Non calcified plaque (NCP) in coronary arteries on CT is correlated with occurrence of acute coronary syndromes and coronary artery calcification (CAC) may occasionally be co-existed. CAC induces a blooming artifact, which magnifies the calcification versus its actual size. The CT values of NCP and CAC are influenced by tube kilovoltage (kV). Recent spectral CT with a dual-layer detector can generate CT images at any kiloelectron voltage (keV) (range: 40-200) after ordinary acquisition using virtual monoenergetic settings (VMS). Hypothesis: Using a new spectral CT, we can determine the optimal VMS settings for achieving best contrast between NCP, CAC and the lumen in coronary arteries. Methods: We performed enhanced 128 slice Spectral CT 7500 scans using a dual-layer detector in 42 patients with NCP and CAC on CT (tube voltage: 120 kV). After scanning, VMS images at various keV values were created from the spectral-based images. We measured the mean CT values of NCP and CAC, lumen in left main artery (LMA), and fat tissue around coronary arteries within a 1.0 mm2 circle in the axial images at each keV in early phase with a contrast. Results: Lower keV values were linked to only slightly increased mean CT values of NCP, but markedly increased mean CT values of CAC. The CT values of the lumen in the LMA were markedly increased. Conversely, the CT values of fat tissue were slightly decreased. The greatest differences in mean CT values between NCP and the LMA were observed at 40 keV. However, considering blooming artifact of CAC at 40 keV, the optimal keV for achieving the best contrast between the CT values of NCP and the lumen in the LMA was influenced by age, male sex. Conclusions: The NCP in coronary arteries, CAC, lumen of the LMA, and fat tissue exhibit unique characteristics. When conventional CT rather than spectral CT is used to evaluate the occurrence of NCP, it is necessary to determine the optimal tube voltage based on the age and male sex of the patient, CAC, and lumen of the LMA.