Acoustic Radiation Force Impulse Optical Coherence Elastography for Measuring Elasticity of Cerebral Cortex

Abstract

Elasticity change in brain tissues has been applicable to diagnosis and study of brain diseases including meningitis or stroke. Elastography modality has been developed to measure the elasticity of biological organ and tissue. Although various elastography techniques, such as magnetic resonance elastography (MRE) and ultrasound elastography (UE) are introduced to date, these approaches are limited in their spatial resolution to measure the elasticity in micron level of tissue or single cell. Due to intrinsic higher resolution power, optical coherence elastography (OCE) may shows a better chance to provide better outcomes compared to other techniques. Here, we established acoustic radiation force impulse optical coherence elastography (ARFI-OCE) to measure the elasticity of a soft tissue. Acoustic radiation force generated by an ultrasound transducer is in-troduced to stimulate the sample. The displacement of a sample is measured by home-made spectral domain optical coherence tomography (OCT) system that uses a spectrometer to detect interference signal and thus can achieve much longer penetration depth than that of other optical imaging systems. To estimate the stiff-ness of samples, we calculate its displacement by using cross-correlation algorithm and phase resolve meth-od. The implemented system composes of a spectrometer-based OCT system, an ARFI system, and a linear stage set. The ARFI triggering signal is synchronized with a camera acquisition time. In this study, ex-vivo tests on the cerebral cortex of mouse and the cerebral cortex of stroke rat model were conducted to evaluate strength of ARFI-OCE system. The system could distinguish the elasticity of dif-ferent cortex samples with better spatial resolution. Our results show that the ARFI-SD-OCE system is appli-cable to draw high-resolution elastogram in soft tissues as exemplified here using the brain and thus has a diagnostic potential to detect any abnormal changes in brain diseases.