Minimum Clinically Achievable Dose for Detecting Liver Lesions Using Deep Learning Image Reconstruction: A Phantom
Zhijie Pan1, Min Xu1, Tingting Qu1
1Radiology Department, Shanghai General Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China (Z.P., M.X., T.Q, Y.Z., L.Z., Q.L., X.X).
Rationale And Objectives:
To investigate the performance of deep learning image reconstruction (DLIR) at an ultra-low dose of approximately 4.5 mGy for detecting focal liver lesions (FLLs), in comparison with adaptive statistical iterative reconstruction-V (ASIR-V) at standard doses (10-15 mGy), through both phantom and prospective patient studies.
Materials And Methods:
A Gammex CT phantom (simulating FLLs with iodine concentrations 2.0-20 mg/mL and normal liver density 1.06 g/cm3) was scanned using DLIR (4.5 mGy) and ASIR-V (10 and 15 mGy). Quantitative metrics included image noise, signal-to-noise ratio, contrast-to-noise ratio, noise power spectrum peak (NPSpeak), and detectability index. In a prospective single-center study, 84 participants (mean age 64 ± 12 years, IQR 60-69 years; 48 males) underwent triple-phase upper-abdominal CT (target dose: 4.5 mGy/phase). Images were reconstructed with DLIR and ASIR-V. Two radiologists blindly evaluated image quality (5-point scale), FLL detectability, sensitivity, and specificity. The reference standard for detectability included histopathology, 3-month standard-dose CT, or MRI.
Results:
In the phantom study, DLIR at 4.5 mGy outperformed ASIR-V at 10 mGy across all quantitative metrics (P < 0.001) and exceeded ASIR-V at 15 mGy in noise and NPSpeak (P < 0.05). Clinically, 71 FLLs (mean size 12.8 ± 10 mm; 55 benign, 16 malignant) were identified. The median CTDIvol was 4.64 mGy (50% to 70% lower than standard doses). DLIR showed superior qualitative image quality vs. ASIR-V (1.25 mm slices: 3.9 ± 0.6 vs. 2.2 ± 0.4, P < 0.001) and higher FLL detection rate (93.0% vs. 77.5%, P < 0.001), with sensitivity 90.1% and specificity 75.0% (both higher than ASIR-V, P < 0.001).
Conclusion:
DLIR at 4.5 mGy achieves substantial radiation dose reduction while providing superior FLL detection performance compared to ASIR-V at 10-15 mGy. This protocol offers a safe and accurate option for FLL screening and follow-up.
