Prospective Evaluation of Reduced Dose Computed Tomography for the Detection of Low-Contrast Liver Lesions: Direct Comparison with Concurrent Standard Dose Imaging.

OBJECTIVES: To prospectively compare the diagnostic performance of reduced-dose (RD) contrast-enhanced CT (CECT) with standard-dose (SD) CECT for detection of low-contrast liver lesions.

METHODS: Seventy adults with non-liver primary malignancies underwent abdominal SD-CECT immediately followed by RD-CECT, aggressively targeted at 60-70 % dose reduction. SD series were reconstructed using FBP. RD series were reconstructed with FBP, ASIR, and MBIR (Veo). Three readers-blinded to clinical history and comparison studies-reviewed all series, identifying liver lesions ≥4 mm. Non-blinded review by two experienced abdominal radiologists-assessing SD against available clinical and radiologic information-established the reference standard.

RESULTS: RD-CECT mean effective dose was 2.01 ± 1.36 mSv (median, 1.71), a 64.1 ± 8.8 % reduction. Pooled per-patient performance data were (sensitivity/specificity/PPV/NPV/accuracy) 0.91/0.78/0.60/0.96/0.81 for SD-FBP compared with RD-FBP 0.79/0.75/0.54/0.91/0.76; RD-ASIR 0.84/0.75/0.56/0.93/0.78; and RD-MBIR 0.84/0.68/0.49/0.92/0.72. ROC AUC values were 0.896/0.834/0.858/0.854 for SD-FBP/RD-FBP/RD-ASIR/RD-MBIR, respectively. RD-FBP (P = 0.002) and RD-MBIR (P = 0.032) AUCs were significantly lower than those of SD-FBP; RD-ASIR was not (P = 0.052). Reader confidence was lower for all RD series (P < 0.001) compared with SD-FBP, especially when calling patients entirely negative.

CONCLUSIONS: Aggressive CT dose reduction resulted in inferior diagnostic performance and reader confidence for detection of low-contrast liver lesions compared to SD. Relative to RD-ASIR, RD-FBP showed decreased sensitivity and RD-MBIR showed decreased specificity.

KEY POINTS: • Reduced-dose CECT demonstrates inferior diagnostic performance for detecting low-contrast liver lesions. • Reader confidence is lower with reduced-dose CECT compared to standard-dose CECT. • Overly aggressive dose reduction may result in misdiagnosis, regardless of reconstruction algorithm. • Careful consideration of perceived risks versus benefits of dose reduction is crucial.