Use of Model-Based Iterative Reconstruction (MBIR) in reduced-dose CT for routine follow-up of patients with malignant lymphoma: dose savings, image quality and phantom study.

Objectives: To evaluate both in vivo and in phantom studies, dose reduction, and image quality of body CT reconstructed with model-based iterative reconstruction (MBIR), performed during patient follow-ups for lymphoma.

Methods: This study included 40 patients (mean age 49 years) with lymphoma. All underwent reduced-dose CT during follow-up, reconstructed using MBIR or 50 % advanced statistical iterative reconstruction (ASIR). All had previously undergone a standard dose CT with filtered back projection (FBP) reconstruction. The volume CT dose index (CTDIvol), the density measures in liver, spleen, fat, air, and muscle, and the image quality (noise and signal to noise ratio, SNR) (ANOVA) observed using standard or reduced-dose CT were compared both in patients and a phantom study (Catphan 600) (Kruskal Wallis).

Results: The CTDIvol was decreased on reduced-dose body CT (4.06 mGy vs. 15.64 mGy p < 0.0001). SNR was higher in reduced-dose CT reconstructed with MBIR than in 50 % ASIR or than standard dose CT with FBP (patients, p ≤ 0.01; phantoms, p = 0.003). Low contrast detectability and spatial resolution in phantoms were not altered on MBIR-reconstructed CT (p ≥ 0.11).

Conclusion: Reduced-dose CT with MBIR reconstruction can decrease radiation dose delivered to patients with lymphoma, while keeping an image quality similar to that obtained on standard-dose CT.

Key Points: • In lymphoma patients, CT dose reduction is a major concern. • Reduced-dose body CT provides a fourfold radiation dose reduction. • Optimized CT reconstruction techniques (MBIR) can maintain image quality.