The use of iterative reconstruction technique in low-dose CT angiography of renal artery

Objective: To assess the feasibility of computed tomography angiography (CTA) in renal artery using the iterative reconstruction technique(iDose⁴) in Brilliance iCT (Philips Ltd.). Methods: 90 patients (body weight 60-70 kg) supposed to undergo renal artery CTA were selected and randomly divided into three groups: A(120 kV, 120 mAs), B(120 kV, 60 mAs) and C(100 kV, 100 mAs). CTA images from Group A were obtained using filtered back projection and those from the rest groups were generated by iDose⁴. Then CT number of renal artery, noise (denoted as standard deviation SD), signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) of images for each group were measured and recorded. Images were post-processed using volume reformation (VR) 3D imaging and image quality were assessed in five-level grade (1-5). Results: The five parameters (CT number of renal artery, SD value, SNR, CNR and VR grade) of group A and group B were statistically insignificant (P > 0.05). While SD values of group C were comparable to those of group A and B, the rest four parameters of group C were apparently larger, which was statistically significant (t_{CT value} = -12.326, t_SNR = -7.136, t_CNR = -7.649, Z_VR = -2.690, P_VR < 0.05). Conclusions: Image quality could still fit the diagnosis requirements using iDose⁴ when mAs decreased lower than 50%. The image quality increases when radiation dose is halved at 100 kVp kV. (authors)