Iterative model reconstruction (IMR) algorithm for reduced radiation dose renal artery CT angiography with different tube voltage protocols.

Purpose: To investigate the image quality (IQ) of reduced radiation dose (RRD) renal artery CT angiography (CTA) using iterative model reconstruction (IMR) algorithm at different tube voltage.

Methods: Renal artery CTA scans were acquired with a 256-MDCT scanner on 84 patients assigned into four groups. Group 4 was scanned as standard radiation dose (SRD) group: 120 kVp, automatic tube current modulation (ATCM) technique with an Image Quality Index of 20, and filtered back projection (FBP) algorithm. Tube voltage for three RRD groups was 80 kVp in group 1, 100 kVp in group 2, and 120 kVp in group 3, and all three groups were with image quality index of 18 and IMR algorithm. Image noise, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) were measured. Subjective evaluation including diagnostic confidence, vessel artifact and intravascular contrast were performed. The effective radiation dose was recorded.

Results: Effective radiation dose was reduced in three RRD groups compared to group 4. Intravascular contrast was significantly better in group 1 and 2 than in group 3, and artifacts decreased in group 2 than in group 3 (P < 0.05). Vascular SNR, CNR and image noise improved in three IMR groups than those in FBP group (P < 0.05). Furthermore, among three IMR groups, group 1 and 2 achieved better objective evaluation than group 3 (P < 0.05).

Conclusions: IMR along with RRD for renal artery CTA improved image quality compared to SRD protocol using FBP. On top of that, lower tube voltage tended to be more optimal.