Optimal b-values for diffusion kurtosis imaging in invasive ductal carcinoma versus ductal carcinoma in situ breast lesions.

Diffusion kurtosis imaging (DKI) is a diffusion-weighted MRI technique that probes the non-Gaussian diffusion of water molecules within biological tissues. The purpose of this study was to investigate the DKI model optimal b-values combinations in invasive ductal carcinoma (IDC) versus ductal carcinoma in situ (DCIS) breast lesions. The study included 114 malignant breast lesions (64 IDC and 50 DCIS). Patients underwent a breast MRI examination which included a diffusion-weighted sequence (b = 0-3000 s/mm2). For each lesion, the b-values were combined among each other (109 combinations) and each mean kurtosis (MK) parameter was obtained. Differences between the lesion groups and b-values combinations were assessed. Also, the diagnostic performance of the combinations was determined through receiver operating characteristic (ROC) curve analysis, and compared. Root mean square error (RMSE) was also obtained. All the b-values combinations showed significant differences between the lesion groups (p < 0.05). The combination 0, 50, 200, 750, 1000, 2000 s/mm2 showed the best performance (AUC = 0.930, sensitivity = 95.3%, specificity = 82.0%, accuracy = 89.5%), with a RMSE of 17.65. The b-values combinations with the worst performance were composed of only high or ultra-high b-values, or with b = 1000 s/mm2 as the maximum b-value. Better results were obtained when zero b-value was included in the DKI model fitting with at least one b-value below 1000 s/mm2 and one b-value above 1000 s/mm2 (conserving b = 1000 s/mm2). Six was the optimal number of b-values, nonetheless other combinations with less b-values may be considered, but with a consequent diagnostic performance loss.