Inversion-recovery MR elastography of the human brain for improved stiffness quantification near fluid-solid...

Area of Science:

• Biomedical Engineering
• Neuroimaging
• Medical Physics

Background:

• In vivo MR elastography (MRE) is a promising neuroimaging technique for assessing tissue stiffness.
• Cerebral MRE is challenged by cerebrospinal fluid (CSF) vibrations, causing blurring and inaccurate stiffness values near brain surfaces.

Purpose of the Study:

• To introduce and evaluate inversion-recovery MRE (IR-MRE) for suppressing CSF signal.
• To improve stiffness quantification in brain surface areas using IR-MRE.

Main Methods:

• IR-MRE was applied to agar phantoms and 11 healthy volunteers.
• Standard single-shot, spin-echo EPI MRE was used with 2800-ms IR preparation and 31.25-Hz harmonic vibrations.
• Wave fields were acquired in 10 axial slices and analyzed for shear wave speed (SWS) using wavenumber-based multicomponent inversion.

Main Results:

• Phantom SWS near fluid interfaces was 7.5% higher with IR-MRE than MRE (P = .01).
• Brain IR-MRE showed 17% lower SNR but similar parenchymal SWS (1.39 m/s vs 1.38 m/s).
• IR-MRE yielded sharper tissue-CSF interfaces with 10% higher SWS (P < .001) and 39% smaller ventricle sizes (P < .001).

Conclusions:

• IR-MRE effectively suppresses fluid oscillations in brain MRE, enhancing anatomical depiction and surface stiffness quantification.
• Similar parenchymal stiffness values with and without fluid suppression validate the technique.
• IR-MRE improves the accuracy of MRE for neuroimaging applications.