Prospective evaluation of an optimized low-dose CT enterography protocol for patients with Crohn's disease

To evaluate an optimized CT enterography (CTE) strategy combining reduced radiation exposure and iodine administration in patients with Crohn's disease (CD), with subjective image quality as the primary endpoint.

This prospective single-center randomized study enrolled 102 patients with CD who underwent CTE between February and October 2025. Participants were randomly assigned in a 1:1:1 ratio using a computer-generated random sequence, with allocation concealed in sequentially numbered, opaque, sealed envelopes opened by a research nurse not involved in patient enrollment, image evaluation, or clinical data collection. No stratification or blocking was used. The three protocols were: a standard-dose protocol (Group A), a low-dose protocol using 100 kVp and 70% adaptive statistical iterative reconstruction-V (ASIR-V) (Group B), and a combined low-dose, low-contrast protocol using the same acquisition settings with a reduced iodine dose (320 mgI/kg, corresponding to 1.0 mL/kg of contrast medium) (Group C). The primary endpoint was subjective image quality assessed using a 5-point Likert scale. Secondary endpoints included objective image quality, bowel wall enhancement, and radiation dose metrics. Diagnostic performance for disease activity and luminal stenosis was evaluated as an exploratory analysis in patients with an eligible endoscopic reference standard; the study was not designed or powered for diagnostic non-inferiority or equivalence testing.

No statistically significant between-group differences were detected in baseline characteristics (all p > 0.05). For the primary endpoint, mean subjective image quality scores were 4.3 ± 0.5, 4.5 ± 0.6, and 4.5 ± 0.5 in Groups A, B, and C, respectively, with no significant between-group difference (p = 0.27); the between-group differences were 0.2 points (95% CI, -0.1 to 0.5) for Group B versus A, 0.2 points (95% CI, -0.1 to 0.5) for Group C versus A, and 0.0 points (95% CI, -0.3 to 0.3) for Group C versus B. Compared with the standard protocol, the estimated effective radiation dose was reduced by 53.2% in Group B and 50.0% in Group C (both p < 0.001), with no significant difference between the two optimized protocols. Both optimized protocols showed lower image noise and higher signal-to-noise and contrast-to-noise ratios than the standard protocol (all p < 0.05), whereas no statistically significant between-group differences were detected in bowel wall attenuation (all p > 0.05). For the exploratory diagnostic analysis, 76/102 patients had an eligible endoscopic reference standard (Group A, 25/31; Group B, 28/38; Group C, 23/33). Diagnostic accuracy for disease activity was 88.0% (95% CI, 70.0-95.8%) in Group A, 89.3% (95% CI, 72.8-96.3%) in Group B, and 87.0% (95% CI, 67.9-95.5%) in Group C; the corresponding between-group differences were 1.3 percentage points (95% CI, -16.8 to 19.4) for B versus A, -1.0 percentage points (95% CI, -19.4 to 17.4) for C versus A, and 2.3 percentage points (95% CI, -16.6 to 21.2) for B versus C. For luminal stenosis, diagnostic accuracy was 84.0% (95% CI, 65.3-94.1%), 89.3% (95% CI, 72.8-96.3%), and 87.0% (95% CI, 67.9-95.5%), respectively; the absolute differences were 5.3 percentage points (95% CI, -12.1 to 22.7) for B versus A, 3.0 percentage points (95% CI, -15.2 to 21.2) for C versus A, and 2.3 percentage points (95% CI, -16.6 to 21.2) for B versus C. The confidence intervals for between-group differences were wide and included values that could be clinically relevant; because the study was not powered to establish diagnostic non-inferiority or equivalence, the absence of statistically significant differences should not be interpreted as evidence of diagnostic equivalence or non-inferiority.

On the GE Revolution 256-detector-row CT platform, the optimized CTE protocols reduced radiation exposure by approximately 50%, while Group C additionally achieved a protocol-defined 33.3% reduction in weight-normalized iodine dose. Based on the observed dose and image-quality findings, Group B can reasonably be recommended when radiation reduction is the primary goal, whereas Group C may be considered when both radiation and iodine reduction are desired. These findings do not establish equivalence or non-inferiority in image quality or diagnostic performance.