Radiation dose and image quality with new protocol in lower extremity computed tomography angiography

PurposeTo compare radiation dose and image quality of lower extremity computed tomography angiography (CTA) between cranio-caudal acquisition with single-source CT (SSCT) and flash caudo-cranial acquisition with dual-source CT (DSCT). Materials and methodsIn this prospective study, 60 patients were randomly assigned to Group A (control) or Group B (experimental) to undergo lower extremity CTA for peripheral obliterative arterial disease. Group A received protocol 1 (P1) with SSCT cranio-caudal acquisition. Group B received protocol (P2) with DSCT flash caudo-cranial acquisition. Intravascular attenuation (IVA), signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR) and image noise were compared. Two radiologists assessed the image quality. Computed tomography volume dose index (CTDIvol) and dose-length product (DLP) were also compared.ResultsIVA with P2 was higher than with P1 (586.8140.3 vs. 496.1 +/- 129.3 HU, p=0.011), as was SNR (33.0 +/- 11.3 vs. 27.4 +/- 12.3; p=0.042), CNR (30.1 +/- 13.3 vs. 24.2 +/- 10.3; p=0.029) and image quality score of small arteries below the knee (3.8 +/- 0.2 vs. 3.1 +/- 0.2; p=0.001). Radiation dose was significantly lower in P2 than in P1 with CTDIvol reduction of 40.9% (1.3 +/- 0.1 vs. 2.2 +/- 0.3mGy; p=0.006) and DLP reduction of 42.8% (148.7 +/- 21.9 vs 260.2 +/- 59.1mGy*cm; p=0.018).Conclusion Lower extremity CTA with DSCT flash caudo-cranial acquisition allows lower radiation dose with higher IVA, SNR, CNR and better image quality for small arteries below the knee than SSCT cranio-caudal acquisition.