Brain-mimicking phantom for biomechanical validation of motion sensitive MR imaging techniques

Area of Science:

• Biomedical Engineering
• Medical Imaging
• Biomechanics

Background:

• Motion-sensitive MRI techniques non-invasively evaluate biological tissues using various excitation schemes.
• Mechanical biomarkers from MRI hold diagnostic value for neurological disorders.
• Existing techniques like amplified MRI (aMRI) and Magnetic Resonance Elastography (MRE) assess brain motion at different frequencies.

Purpose of the Study:

• To design and validate a novel phantom test setup capable of capturing both low and high frequency responses of a brain-mimicking phantom.
• To enable simultaneous application of aMRI and MRE on the same phantom model.
• To validate motion-sensitive MRI techniques for brain mechanics.

Main Methods:

• Developed a novel phantom test setup combining pneumatic (1 Hz for aMRI) and piezoelectric (30-60 Hz for MRE) actuators.
• Applied aMRI to track low-frequency intrinsic motion and MRE to measure high-frequency mechanical response.
• Validated aMRI's linear amplification up to a factor of 9 for visible and sub-voxel motion.
• Analyzed shear wave attenuation and actuator coupling effects in MRE experiments.

Main Results:

• In MRE, shear waves attenuated faster at higher driving frequencies (30-60 Hz).
• Actuator coupling significantly affected wave amplitude, with weaker coupling reducing it.
• aMRI demonstrated linear motion amplification up to a factor of 9 for both visible and sub-voxel motions.
• Pneumatic actuation power levels (40%-80%) and external video analysis validated aMRI results.

Conclusions:

• The novel phantom test setup effectively captures broadband mechanical responses of brain-mimicking phantoms.
• This setup allows for the validation of both aMRI and MRE techniques on a single platform.
• The findings support the use of these motion-sensitive MRI techniques for assessing brain mechanics and diagnosing neurological conditions.