Iterative Model Reconstruction: Improved Image Quality of Low-Tube-Voltage Prospective ECG-Gated Coronary CT Angiography Images at 256-Slice CT
OBJECTIVES: To investigate the effects of a new model-based type of iterative reconstruction (M-IR) technique, the iterative model reconstruction, on image quality of prospectively gated coronary CT angiography (CTA) acquired at low-tube-voltage.
METHODS: Thirty patients (16 men, 14 women; mean age 52.2±13.2 years) underwent coronary CTA at 100-kVp on a 256-slice CT. Paired image sets were created using 3 types of reconstruction, i.e. filtered back projection (FBP), a hybrid type of iterative reconstruction (H-IR), and M-IR. Quantitative parameters including CT-attenuation, image noise, and contrast-to-noise ratio (CNR) were measured. The visual image quality, i.e. graininess, beam-hardening, vessel sharpness, and overall image quality, was scored on a 5-point scale. Lastly, coronary artery segments were evaluated using a 4-point scale to investigate the assessability of each segment.
RESULTS: There was no significant difference in coronary arterial CT attenuation among the 3 reconstruction methods. The mean image noise of FBP, H-IR, and M-IR images was 29.3±9.6, 19.3±6.9, and 12.9±3.3HU, respectively, there were significant differences for all comparison combinations among the 3 methods (p<0.01). The CNR of M-IR was significantly better than of FBP and H-IR images (13.5±5.0 [FBP], 20.9±8.9 [H-IR] and 39.3±13.9 [M-IR]; p<0.01). The visual scores were significantly higher for M-IR than the other images (p<0.01), and 95.3% of the coronary segments imaged with M-IR were of assessable quality compared with 76.7% of FBP- and 86.9% of H-IR images.
CONCLUSIONS: M-IR can provide significantly improved qualitative and quantitative image quality in prospectively gated coronary CTA using a low-tube-voltage.