Intravoxel incoherent motion diffusion-weighted MR imaging of breast cancer at 3.0 tesla: Comparison of different curve-fitting methods.

Background: To compare three different curve-fitting methods for intravoxel incoherent motion (IVIM) analysis in breast cancer.

Methods: Diffusion-weighted imaging was acquired in 30 patients with breast cancer using seven b-values (0-800 s/mm(2) ). Three curve-fitting methods were used for biexponential IVIM analysis: a. Direct estimation of D (diffusion coefficient), D* (pseudodiffusion coefficient) and f (perfusion fraction) (Method 1), b. Estimation of D first and then D* and f (Method 2), c. Estimation of D and f first and then D* (Method 3). Goodness-of-fit, parameter precision (coefficient of variance [CV]), parameter difference and correlation with relative enhancement ratio (RER) and initial area under the curve (IAUC) from dynamic contrast-enhanced (DCE) MRI of the three methods were determined and compared.

Results: Among the three biexponential methods, Method 1 best described most of the pixels (63.20% based on R(2) ; 44.52% based on Akaike Information Criteria). The CV of D calculated from Method 2/3 (14.95%/13.90%), the CV of D* from Method 2 (77.04%) and the CV of f from Method 3 (80.87%) were the lowest among the three methods. Significant difference was observed for each IVIM-derived parameter calculated from all the three methods (P = 0.000-0.005). Only the perfusion-related f value calculated from Method 2 was correlated with RER (r = 0.548; P = 0.002) or IAUC (r = 0.561; P = 0.001).

Conclusion: IVIM-derived parameters differ depending on the calculation methods. The two-step fitting method with D value estimation first was correlated with DCE MRI perfusion.