Line-field low coherence holography for ultra-fast assessment of tissue biomechanical properties

摘要

Changes in the biomechanical properties of tissues are often associated with disease etiology and can provide quantitative information for clinical diagnosis. Tissue elasticity is often assessed by analyzing the speed of an elastic wave, such as in supersonic shear wave imaging and magnetic resonance elastography techniques. However, insufficient spatial resolution and large stimulation forces limit their application in small samples (dimensions on the order of millimeters or micrometers). Optical coherence elastography (OCE) is an emerging technique that provides local biomechanical properties with micrometer scale resolution. However, conventional point-by-point scanning OCE methods require long acquisition times (tens of seconds) that are unfeasible for clinical use due to motion artifacts, and repeated external excitations. Here, we demonstrate a noncontact ultrafast line-field low coherent holography system (LF-LCH) integrated with spatial phase shifting algorithm for phase retrieval based on a single interferogram. The proposed method using the Hilbert transform outperforms the Fourier transform-based technique in LF-LCH. Spatio-temporal maps of elastic wave propagation were acquired using a single air-pulse excitation and the acquisition speed can be optimized to less than 10 ms. Results on homogenous, transversely heterogeneous agar phantoms and ex vivo chicken breast agreed well with mechanical testing, demonstrating that this method can accurately detect tissue stiffness with an ultrafast line imaging rate of 200 kHz using a robust phase retrieval algorithm, which is among the highest speed for lateral imaging of elastic wave propagation with optical elastography methods.