Effect of High-Pitch Dual-Source CT to Compensate Motion Artifacts: A Phantom Study

摘要

Rationale and Objectives: To evaluate the potential of high-pitch, dual-source computed tomography (DSCT) for compensation of motion artifacts. Materials and Methods: Motion artifacts were created using a moving chest/cardiac phantom with integrated stents at different velocities (from 0 to 4-6cm/s) parallel (z direction), transverse (x direction), and diagonal (x and z direction combined) to the scanning direction using standard-pitch (SP) (pitch=1) and high-pitch (HP) (pitch=3.2) 128-detector DSCT (Siemens, Healthcare, Forchheim, Germany). The scanning parameters were (SP/HP): tube voltage, 120 kV/120 kV; effective tube current time product, 300mAs/500mAs; and a pitch of 1/3.2. Motion artifacts were analyzed in terms of subjective image quality and object distortion. Image quality was rated by two blinded, independent observers using a 4-point scoring system (1, excellent; 2, good with minor object distortion or blurring; 3, diagnostically partially not acceptable; and 4, diagnostically not acceptable image quality). Object distortion was assessed by the measured changes of the object's outer diameter (x) and length (z) and a corresponding calculated distortion vector (d) (d=√(x2 + z2)). Results: The interobserver agreement was excellent (. k = 0.91). Image quality using SP was diagnostically not acceptable with any motion in x direction (scores 3 and 4), in contrast to HP DSCT where it remained diagnostic up to 2cm/s (scores 1 and 2). For motion in the z direction only, image quality remained diagnostic for SP and HP DSCT (scores 1 and 2). Changes of the object's diameter (x), length (z), and distortion vectors (d) were significantly greater with SP (overall: x = 1.9cm ± 1.7cm, z = 0.6cm ± 0.8cm, and d = 1.4cm ± 1.5cm) compared to HP DSCT (overall: x = 0.1cm ± 0.1cm, z = 0.0cm ± 0.1cm, and d = 0.1cm ± 0.1cm; each P .05). Conclusion: High-pitch DSCT significantly decreases motion artifacts in various directions and improves image quality.