Accelerated model-based quantitative diffusion MRI A feasibility study for musculoskeletal application

Purpose: To develop a model-based reconstruction technique for diffusion quantification based on accelerated twodimensional echo planar data, obtained with multiple b-weightings. In combination with a dedicated undersampling pattern, acceleration factors above three were proven feasible in a clinical setting. Methods: The proposed model-based method minimizes a cost function considering the l2-norm of the difference between the Fourier transformation of a synthetic diffusion-model-generated k-space and the measured k-space data. Further regularization is performed by introduction of a total variation (TV) constraint to the cost function. Acceleration is achieved by a non-random undersampling pattern using acceleration factors that correspond to the total number of b-values. A rectangular region of variable size, centered in k-space, remains fully sampled for correction of phase variations, introduced by the different diffusion-encoding strengths. Results: Qualitative analysis of the resulting images (S0 and ADC) demonstrates the potential of the suggested undersampling pattern in combination with a model-based iterative reconstruction. An edge analysis highlights the preservation of high-frequency information for all investigated undersampling factors. In comparison to a conventional SENSE-accelerated reconstruction, the quantitative analysis of the ADC maps revealed a significantly (P < 0.05) superior performance of the suggested technique, enabling acceleration factors of R = 3.65 without compromising diffusion data fidelity. Conclusion: The presented work shows the potential of model-based ADC quantification, which, in combination with a suited undersampling pattern for multiple b-values, enables more than three-fold acceleration using two-dimensional EPI without sacrificing ADC fidelity.

Automated summary

The purpose of this study is to develop a model-based reconstruction technique for diffusion quantification using accelerated two-dimensional echo planar data with multiple b-values. The study proves the feasibility of achieving acceleration factors above three in a clinical setting by introducing a suitable undersampling pattern and acceleration factors. The results demonstrate the potential of the suggested undersampling pattern in combination with a model-based iterative reconstruction, showing a superior performance compared to conventional SENSE-accelerated reconstruction.