Single-Breathhold 3D MR Elastography in the Liver, With Simultaneous R2* and PDFF Mapping.

Area of Science:

• Medical Imaging
• Biophysics
• Radiology

Background:

• Multiparametric assessment of liver disease requires accurate measurement of viscoelastic properties, fat fraction, and iron content.
• Current MR elastography (MRE) techniques often involve lengthy acquisition times, limiting their clinical applicability.
• Simultaneous acquisition of MRE, proton-density fat fraction (PDFF), and R2* can provide comprehensive liver status evaluation.

Purpose of the Study:

• To develop a novel 3D MR elastography (MRE) sequence for rapid parameter acquisition.
• To enable simultaneous measurement of PDFF and R2* alongside MRE parameters for multiparametric liver assessment.
• To achieve a time-efficient MRE protocol suitable for single breathhold acquisition.

Main Methods:

• An interleaved motion-encoding scheme was employed for efficient 3D volume acquisition.
• A constant repetition time and incoherent k-space undersampling facilitated single breathhold acquisition.
• Compressed sensing with model-based temporal regularization was used for reconstructing undersampled volumes.
• A multi-echo readout allowed for simultaneous 3D PDFF and R2* map reconstruction.

Main Results:

• Phantom measurements demonstrated close agreement for viscoelastic parameters, PDFF, and R2* compared to reference values.
• In vivo liver measurements at 3T yielded average values for shear-wave speed, complex shear modulus, loss modulus, PDFF, and R2*.
• The sequence successfully acquired comprehensive multiparametric data within a single breathhold.

Conclusions:

• A novel acquisition ordering enabled single-breathhold 3D MRE of the liver.
• The developed sequence provides 3D elastograms within a 16-second breathhold.
• Integration with PDFF and R2* mapping is achievable within a 21-second breathhold, offering a powerful tool for liver disease evaluation.