Image Quality, Motion Artifacts, and Reconstruction Timing of 64-Slice Coronary Computed Tomography Angiography With 0.33-Second Rotation Speed

Abstract

Objectives: We sought to evaluate the impact of patients’ heart rate (HR) on coronary CTA image quality (IQ) and motion artifacts using a 64-slice scanner with 0.33/360° rotation. Materials and Methods: Coronary CTA data sets of 32 patients (HR ≤ 65 beats per minute [bpm], n = 15; HR > 65 bpm to ≤75 bpm, n = 10; HR > 75 bpm, n = 7) examined on a 64-slice scanner (Sensation 64, Siemens Medical Solutions, Forchheim, Germany) with 0.33s/360° gantry rotation speed were analyzed. All patients had suspicion of coronary artery disease. Data acquisition was performed using 64 × 0.6-mm collimation, and contrast enhancement was provided by injection of 80 mL of iopromide (5 mL/s + NaCl). Images were reconstructed throughout the RR interval using half-scan and dual-segment reconstruction. IQ was rated by 2 observers using a 3-point scale from excellent (1) to nondiagnostic (3) for coronary segments. Quality was correlated to the HR, time point of optimal IQ analyzed, and the benefit of dual-segment reconstruction evaluated. Results: Overall mean IQ was 1.31 ± 0.32 for all HR, with IQ being 1.08 ± 0.12 for HR ≤ 65 bpm, 1.62 ± 0.27 for HR > 65 bpm ≤ 75 bpm and 1.36 ± 0.31 for HR > 75 bpm (P = 0.0003). Dual-segment reconstruction did not significantly improve IQ in any HR group (P = NS). Mean IQ was significantly better for LAD than for RCA (P < 0.0001) and LCX (P < 0.01). A total of 3.5% (11/318) of coronary artery segments were rated nondiagnostic by at least one reader based on motion artifacts. Although in HR < 65 bpm, the best IQ was predominately in diastole (93%), in HR > 75 bpm, the best IQ shifted to systole in most cases (86%). Conclusions: Temporal resolution at 0.33-second rotation allows for diagnostic IQ within a wide range of HR using half-scan reconstruction. With increasing HR the time point of best IQ shifts from mid-diastole to systole.