Distortion‐free water‐fat separated diffusion‐weighted imaging using spatiotemporal joint reconstruction

• Published in: Magnetic resonance in medicine Vol. 92; no. 6; pp. 2343 - 2357
• Main Authors: Zhou, Xuetong, Daniel, Bruce L., Hargreaves, Brian A., Lee, Philip K.
• Format: Journal Article
• Language: English
• Published: United States Wiley Subscription Services, Inc 25.07.2024
• Subjects: body imaging; Chemical equilibrium; chemical‐shift encoding; Coding; Diffusion coefficient; Diffusion rate; diffusion‐weighted MRI; Distortion; Image acquisition; Image contrast; Image reconstruction; In vivo methods and tests; Medical imaging; Neuroimaging; Separation; water‐fat separation; diffusion‐weighted MRI; body imaging; chemical‐shift encoding; water‐fat separation
• ISSN: 0740-3194; 1522-2594; 1522-2594
• DOI: 10.1002/mrm.30221

Purpose Diffusion‐weighted imaging (DWI) suffers from geometric distortion and chemical shift artifacts due to the commonly used Echo Planar Imaging (EPI) trajectory. Even with fat suppression in DWI, severe B0 and B1 variations can result in residual fat, which becomes both a source of image artifacts and a confounding factor in diffusion‐weighted contrast in distinguishing benign and malignant tissues. This work presents a method for acquiring distortion‐free diffusion‐weighted images using spatiotemporal acquisition and joint reconstruction. Water‐fat separation is performed by chemical‐shift encoding. Methods Spatiotemporal acquisition is employed to obtain distortion‐free images at a series of echo times. Chemical‐shift encoding is used for water‐fat separation. Reconstruction and separation are performed jointly in the spat‐spectral domain. To address the shot‐to‐shot motion‐induced phase in DWI, an Fast Spin Echo (FSE)‐based phase navigator is incorporated into the sequence to obtain distortion‐free phase information. The proposed method was validated in phantoms and in vivo for the brain, head and neck, and breast. Results The proposed method enables the acquisition of distortion‐free diffusion‐weighted images in the presence of B0 field inhomogenieties commonly observed in the body. Water and fat components are separated with no obvious spectral leakage artifacts. The estimated Apparent Diffusion Coefficient (ADC) is comparable to that of multishot DW‐EPI. Conclusion Distortion‐free, water‐fat separated diffusion‐weighted images in body can be obtained through the utilization of spatiotemporal acquisition and joint reconstruction methods.