On the b-value Derivation for diffusion-weighted Double-Echo Steady-State (dwDESS) Magnetic Resonance Imaging

To determine the degree of observed diffusion weighting and to calculate the diagnostically valuable “Apparent Diffusion Coefficient” (ADC) in MR-based “Diffusion-Weighted Imaging” (DWI), a standardized b-value is typically used. To overcome geometrical distortions in standard DWI, diffusion-weighted double-echo steady-state (dwDESS) sequences have been proposed. Balanced bipolar dwDESS, in particular, provides high SNR and is robust against motion. However, a proper definition of the b-value equivalent to standard DWI is not yet well addressed for this bipolar dwDESS. Therefore, this study investigated an estimation for effective b-values in bipolar dwDESS based on approximation of the underlying signal model in the framework of configuration theory. The obtained effective b-values have been validated in phantom as well as in vivo breast studies of a healthy human subject, yielding good agreement with the corresponding b-values of standard DWI. Thus, this study enables the quantitative comparison of dwDESS with diffusion-weighted images obtained from different sequences, different measurements, and different scanners, which helps a wide clinical adaption in studies of, for example, cartilage impairments or breast cancer lesions.