Intravoxel incoherent motion diffusion-weighted imaging (IVIM-DWI) of the major salivary glands: an assessment of the optimal number and combination of b-values

PURPOSE: To examine the optimal number and combination of b-values in intravoxel incoherent motion (IVIM) diffusionweighted imaging (DWI) of the major salivary glands. MATERIAL AND METHODS: IVIM-DWI was performed on 10 healthy volunteers using 13 b-values (low b-values: 0-100 s/mm(2); high b-values: 200-1000 s/mm(2)). The IVIM parameters and apparent diffusion coefficient of the bilateral major salivary glands were calculated using 13 b-values and were considered the standard values. We sequentially reduced the number of b-values to 10, 8, 6, and 5. The parameters in each combination were calculated. The standard values were compared with the parameters from each reduced b-value in IVIM-DWI. The Wilcoxon signed-rank test was used to determine whether there were any differences between the parameters in each combination. Bonferroni correction was conducted for multiple comparisons. RESULTS: There were no significant differences between the standard values and parameters from the 2 combinations of 6 b-values. However, significant differences were observed between the standard values and parameters from some combinations of only 2 low or only 2 high b-values. CONCLUSIONS: IVIM-DWI of the major salivary glands could be performed using a minimum of 6 b-values. However, they should contain 3 low and 3 high b-values.