Abstract
ObjectivesThe purpose of this study was to assess image quality and radiation dose of lower extremity CT angiography (CTA) with 70 kVp, high pitch acquisition and sinogram-affirmed iterative reconstruction (SAFIRE).MethodsLower extremity CTAs were performed on 44 patients: 22 patients were examined using protocol A (120 kVp, pitch of 0.85 and 120 ml of contrast agent on a first-generation dual-source CT) (120 kVp group) and 22 patients were evaluated with protocol B (70 kVp, pitch of 2.2 and 80 ml of contrast agent on a second-generation dual-source CT) (70 kVp group). Images from the 120 kVp group were reconstructed with filtered back projection (FBP) and images from the 70 kVp group with SAFIRE. The attenuation, image noise, signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were calculated. Two radiologists subjectively assessed image quality of lower extremity arteries, plantar arterial enhancement and venous contamination of all patients. Radiation dose was compared between the two groups.ResultsHigher mean intravascular attenuation was obtained in the 70 kVp group (70 vs. 120 kVp group, 555.4±83.4 HU vs. 300.9±81.4 HU, P<0.001), as well as image noise (20.0±2.8 HU vs. 17.5±3.2 HU, P = 0.010), SNR (32.0±7.0 vs. 19.1±6.9, P<0.001) and CNR (28.1±6.6 vs 15.9±6.3, P<0.001). No difference in subjective image quality and plantar arterial enhancement was found between 120 kVp group and 70 kVp group (all P>0.05). The venous contamination score was 1.5±0.8 for 120 kVp group while no venous contamination was found in 70 kVp group. The inter-observer agreement was moderate to good for both groups (0.515∼1, P<0.001). The effective dose was lower in 70 kVp group (0.3±0.1 mSv) than in 120 kVp group (1.6±0.7 mSv)(P<0.001).ConclusionsLower extremity CTA using 70 kVp, high pitch acquisition and SAFIRE, except increasing imaging noise, allows for lower radiation dose and contrast material volume without compromising image quality.
Highlights
Peripheral arterial disease (PAD) is a common, chronic and progressive health problem
It is reported that the overall prevalence of PAD was 16.7% in Chinese patients with type 2 diabetes and 27.5% in Chinese patients with hypertension [1,2]
A previous study has shown that the weighted CT dose index (CTDIw) of lower extremity CT angiography (CTA) could be as high as 12.2 mGy and the volume of contrast material could be as much as 140 ml [5]
Summary
Peripheral arterial disease (PAD) is a common, chronic and progressive health problem. The tube voltage of 80 kVp has been verified to be feasible for lower extremity CTA with substantial reduction of radiation dose [9,10]. Duan et al have reduced radiation dose to 1.94 mSv and contrast medium volume to 1.2 mL/kg when a tube voltage of 70 kVp was used in lower extremity CTA [11]. The combination of 70 kVp and high-pitch acquisition technique holds potential to further reduce radiation dose. To the best of our knowledge, no study has been performed on lower extremity CTA using 70 kVp combined with high pitch acquisition and iterative reconstruction. The aim of our study was to investigate the feasibility, image quality and radiation dose of lower extremity CTA using 70 kVp combined with dual-source high pitch acquisition and iterative reconstruction
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