Diffusion-Weighted Imaging of Upper Abdominal Organs Acquired with Multiple B-Value Combinations: Value of Normalization Using Spleen as the Reference Organ

Objective: To compare apparent diffusion coefficient (ADC) of the upper abdominal organs acquired with multiple b-value combinations and to investigate usefulness of normalization. Materials and Methods: We retrospectively analyzed data, including 3T diffusion-weighted images, of 100 patients (56 men, 44 women; mean age, 63.9) that underwent liver magnetic resonance imaging. An ADC map was derived with the following six b-value combinations: b(1) = 0, 50, 400, 800; b(2) = 0, 800; b(3) = 0, 50, 800; b(4) = 0, 400, 800; b(5) = 50, 800; and b(6) = 50, 400, 800 s/mm(2). ADC values of the right liver lobe, left liver lobe, spleen, pancreas, right kidney, and left kidney were measured. ADC values of the spleen were used for normalization. Intraclass correlation coefficients (ICCs), comparison of dependent ICCs, and repeated-measures analysis of variance were used for statistical analysis. Results: Intraclass correlation coefficients of the original ADC revealed moderate to substantial agreement (0.5145-0.6509), while normalized ADCs revealed almost perfect agreement (0.8014-0.8569). ICC of normalized ADC for all anatomical regions revealed significantly less variability than that of the original ADC (p < 0.05). Coefficient of variance for normalized ADC was significantly lower than that for the original ADC (3.0-3.8% vs. 4.8-8.8%, p < 0.05). Conclusion: Normalization of the ADC values of the upper abdominal organs using the spleen as the reference organ significantly decreased variability in ADC measurement acquired with multiple b-value combinations.