Towards genuine three-dimensional diffusion imaging with physiological motion compensation

Purpose: We aim to implement a 3D DWI sequence and show its usage on patients with new ischemic lesions. Materials and Methods: The proposed 3D DWI sequence was implemented by integrating second-order gradient moment nulling (M2) and cardiac motion synchronization (Sync). All data were acquired on a 3T MAGNETOM Prisma scanner (Siemens Healthcare, Erlangen, Germany) using a 64 channel head and neck coil. 21 healthy volunteers underwent 3D DWI scans at 0.9 mm isotropic resolution using four motion compensation methods for comparison: no compensation (M0), M2 only, Sync only and the proposed M2+Sync method. 2D phase variation maps with different motion compensation methods were also acquired for one subject to illustrate the mechanism of the proposed method. A ghost-to-signal ratio (GSR) and blurring index was defined and compared among the four methods with repeated measures ANOVA and Tukey's test. 3D DWI was compared with 2D DWI for ADC quantification. Image quality and ischemic lesion conspicuity were evaluated with 12 patients after endovascular treatment. Results: Whole brain 3D DWI was achieved at 0.9 mm isotropic resolution within 5 minutes using the proposed sequence. M2+Sync achieved the lowest level of GSR and blurring along the slice direction. ADC quantification showed no statistically significant difference between M2+Sync compared to 2D DWI. 3D DWI showed similar image quality, higher lesion conspicuity and counts compared to 2D DWI. Conclusion: Direct 3D DWI can be achieved by the combination of second order gradient moment nulling and cardiac synchronization.