Ultra-low radiation dose CT angiography of the lower extremity using the iterative model reconstruction (IMR) algorithm.

ABSTRACT

AIM: To investigate the image quality of lower-extremity computed tomography (CT) angiography (CTA) with ultra-low radiation dose using the iterative model reconstruction (IMR) algorithm. MATERIALS AND METHODS: Lower-extremity CTA was acquired using a 256-multidetector CT system from 90 patients assigned into three groups (1) the routine dose (RD) group 120 kVp, automatic tube current modulation (ACTM) with an image quality index of 12, and filtered back projection (FBP); (2) the low-dose (LD) group 80 kVp, ACTM with an image quality index of 1, and IMR; and (3) the ultra-low dose (ULD) group 80 kVp, 20 mAs, and IMR. CT attenuation, image noise, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) of the lower-extremity arteries were calculated. Subjective image quality of lower-extremity segments was assessed. Effective radiation dose was recorded. RESULTS: The radiation dose was reduced by 91.4% and 67.3% in the ULD group (0.15±0.02 mSv) compared to the RD group (1.86±0.51 mSv) and the LD group (0.49±0.08 mSv; both p<0.05). Higher CT attenuation, SNR, CNR, and lower image noise were obtained in the ULD group and the LD group compared to the RD group (all p<0.05). Better subjective image quality in lower leg segments was obtained in the ULD group and the LD group compared to the RD group (all p<0.05). No difference was found between the ULD and LD groups in both objective and subjective image quality (all p>0.05). CONCLUSION: By using IMR during lower-extremity CTA, the radiation dose is reduced by up to 91.4% without compromising image quality.