Diffuse shear wave imaging: toward passive elastography using low-frame rate spectral-domain optical coherence tomography

Abstract

Optical coherence tomography (OCT) can map the stiffness of biological tissue by imaging mechanical perturbations (shear waves) propagating in the tissue. Most shear wave elastography (SWE) techniques rely on active shear sources to generate controlled displacements that are tracked at ultrafast imaging rates. Here, we propose a noise-correlation approach to retrieve stiffness information from the imaging of diffuse displacement fields using low-frame rate spectral-domain OCT. We demonstrated the method on tissue-mimicking phantoms and validated the results by comparison with classic ultrafast SWE. Then we investigated the in vivo feasibility on the eye of an anesthetized rat by applying noise correlation to naturally occurring displacements. The results suggest a great potential for passive elastography based on the detection of natural pulsatile motions using conventional spectral-domain OCT systems. This would facilitate the transfer of OCT-elastography to clinical practice, in particular, in ophthalmology or dermatology.

Spatial resolution in dynamic optical coherence elastography

“…In dynamic OCE, the typical assumption of an infinite, homogeneous, nearly incompressible elastic material would suggest that the elastographic resolution can be described by the OCT image resolution alone, yet, spatial resolution has been reported to range from the micron scale to multiple millimeters for similar reconstruction methods based on elastic wave propagation. [20][21][22][23][24][25][26][27][28] Recently, it was suggested that the mechanical model of the medium is directly related to resolution in the closely related field of compression OCE, 17 thus indicating that spatial resolution is not always defined by the resolution of the imaging method (OCT).…”

Translational optical coherence elastography for assessment of systemic sclerosis

“…In the clinic, diagnosis of skin tethering relies on the palpation experience of the physician, and the mRSS does not score tethering. Therefore, future work will focus on developing a Quadrate Swept Source OCT system that incorporates a booster optical amplifier and piezoelectric transducer‐based elastography system to image up to 2 mm deep in the skin and to measure the stiffness within the dermis by exciting elastic waves up to 5 kHz . We hypothesize that the combination of an improved OCT structural imaging that can capture the entire reticular dermis with the OCE‐based stiffness assessment will improve our ability to accurately and reliably measure skin fibrosis in SSc.…”

L'OCT plein champ

“…Toujours à la recherche de nouvelles formes de contraste qui puissent enrichir les images morphologiques fournies par l'OCT plein champ, mentionnons les mesures des propriétés élastiques des tissus : la carte d'élasticité peut être obtenue en statique par corrélation 3D [17] en dynamique en mesurant la vitesse des ondes de cisaillement [18] avec une caméra ultrarapide ou par des méthodes de corrélation liées à l'utilisation de l'opérateur de renversement temporel [19].…”