Low-dose CT imaging of the acute abdomen using model-based iterative reconstruction: a prospective study.

Abstract

Performance of a modified abdominopelvic CT protocol reconstructed using full iterative reconstruction (IR) was assessed for imaging patients presenting with acute abdominal symptoms. Fifty-seven patients (17 male, 40 female; mean age of 56.5 ± 8years) were prospectively studied. Low-dose (LD) and conventional-dose (CD) CTs were contemporaneously acquired between November 2015 and March 2016. The LD and CD protocols imparted radiation exposures approximating 10-20% and 80-90% those of routine abdominopelvic CT, respectively. The LD images were reconstructed with model-based iterative reconstruction (MBIR), and CD images with hybrid IR (40% adaptive statistical iterative reconstruction (ASIR)). Image quality was assessed quantitatively and qualitatively. Independent clinical interpretations were performed with a 6-week delay between reviews. A 74.7% mean radiation dose reduction was achieved: LD effective dose (ED) 2.38 ± 1.78mSv (size-specific dose estimate (SSDE) 3.77 ± 1.97mGy); CD ED 7.04 ± 4.89mSv (SSDE 10.74 ± 5.5mGy). LD-MBIR images had significantly lower objective and subjective image noise compared with CD-ASIR (p < 0.0001). Noise reduction for LD-MBIR studies was greater for patients with BMI < 25kg/m2 than those with BMI ≥ 25kg/m2 (5.36 ± 3.2Hounsfield units (HU) vs. 4.05 ± 3.1HU, p < 0.0001). CD-ASIR studies had significantly better contrast resolution, and diagnostic acceptability (p < 0.0001 for all). LD-MBIR studies had significantly lower streak artifact (p < 0.0001). There was no difference in sensitivity for primary findings between the low-dose and conventional protocols with the exception of one case of enteritis. Low-dose abdominopelvic CT performed with MBIR is a feasible radiation dose reduction strategy for imaging patients presenting with acute abdominal pain.