Double low-dose abdominopelvic CT for acute appendicitis: early exploratory analysis on image quality and diagnostic performance

Abstract

Objective: To evaluate the feasibility of a standardized double low-dose CT (DLCT) protocol that simultaneously reduces both iodine contrast media (CM) dose and tube voltage, and to compare its image quality and diagnostic performance with a single low-dose CT (SLCT) protocol using fixed iodine dose and reduced tube voltage, representative of institutional low-radiation dose imaging practice in suspected acute appendicitis.

Methods: In this exploratory analysis of a prospective single-arm study, 49 participants aged 18-44 years presenting to the emergency department (ED) with suspected acute appendicitis underwent DLCT using automated kVp selection and a kVp- and weight-adjusted CM dosing protocol. This protocol targeted a 10% iodine dose reduction for every 10 kVp decrease from a reference standard of 0.521 g I/kg at 120 kVp. A historical control group of 53 patients with the same inclusion criteria, who had undergone SLCT using a fixed CM dose and low-kVp protocol (80-100 kVp) prior to study initiation, was retrospectively included. Quantitative (signal-to-noise ratio [SNR] and contrast-to-noise ratio [CNR]) and qualitative (subjective image quality and appendiceal visibility) assessments were compared. Diagnostic performance was evaluated using positive predictive value (PPV) for acute appendicitis and alternative diagnoses, based on surgical findings, clinical follow-up, or an Alvarado score ≥ 7.

Results: DLCT significantly reduced iodine dose (0.383 ± 0.049 g I/kg vs. 0.589 ± 0.085 g I/kg; P < 0.001) while maintaining comparable image noise and appendiceal visibility. Although SNR and CNR were lower in the DLCT group, diagnostic performance including PPVs for acute appendicitis (63.6% vs. 72.7%) and alternative diagnoses (100% vs. 86.7%) did not significantly differ between groups.

Conclusion: An iodine dose-reducing DLCT protocol tailored to tube voltage and body weight is feasible in the ED setting and offers substantial CM dose saving without compromising diagnostic performance for acute appendicitis or alternative diagnoses.

Keywords: Appendicitis; Computed tomography; Contrast media; Iodine; Radiation dosage.