Phase-resolved Acoustic Radiation Force Optical Coherence Elastography.

摘要

Optical coherence tomography (OCT) is a noninvasive, high resolution and high speed imaging modality that provides cross-sectional depth resolved microstructure information of biological tissues based on their tissue scattering properties. However, subtle scattering property changes in diseased tissue are difficult to visualize solely by OCT structural imaging at the early stages of disease. Elastography has opened new horizons for medical imaging by characterizing the mechanical properties of biological tissues. However, current elastography imaging modalities such as ultrasound (US) elastography and magnetic resonant elastography (MRE) can only image mechanical properties at the organ level due to their limitations in resolution. Although current optical coherence elastography (OCE) technologies can achieve microscale imaging of tissue mechanical properties, they are still facing challenges for real time in vivo imaging.;My Ph.D. research focuses on the development of a novel phase-resolved acoustic radiation force optical coherence elastography technology (ARF-OCE). This technique combines the dynamic acoustic radiation force (ARF) excitation with phase-resolved OCT to achieve high resolution, high speed and high sensitivity for imaging and characterizing tissue biomechanical properties.;The ARF-OCE technique uses a localized amplitude modulated (AM) acoustic wave to apply dynamic "pushes" on the sample and phase-resolved OCT to evaluate the ARF-induced displacement of the sample by determining the phase shift of OCT interference fringe. Three generations of ARF-OCE configurations have been developed as a consequence of system optimization. The first generation ARF-OCE system utilizes a focused ultrasonic transducer and stimulates the object in "transmission" mode. Aiming for in vivo imaging, the second generation ARF-OCE system features a confocal OCT and ARF arrangement and a "reflection" excitation mode. A dual-element ring transducer is used for the third generation ARF-OCE system that makes use of the "beat" phenomenon in order to achieve highly localized ARF excitation. Imaging results from both tissue phantoms and ex vivo real tissue specimens have demonstrated the feasibility of the phase-resolved ARF-OCE technique for tissue elasticity imaging with superior performance. Finally, a frequency-dependent resonant ARF-OCE method has also been developed to characterize tissue biomechanical properties using the resonant frequency without the knowledge of ARF parameters.