Intraluminal laser speckle rheology using an omni-directional viewing catheter

Abstract

A number of disease conditions in luminal organs are associated with alterations in tissue mechanical properties. Here, we report a new omni-directional viewing Laser Speckle Rheology (LSR) catheter for mapping the mechanical properties of luminal organs without the need for rotational motion. The LSR catheter incorporates multiple illumination fibers, an optical fiber bundle and a multi-faceted mirror to permit omni-directional viewing of the luminal wall. By retracting the catheter using a motor-drive assembly, cylindrical maps of tissue mechanical properties are reconstructed. Evaluation conducted in a test phantom with circumferentially-varying mechanical properties demonstrates the capability of the LSR catheter for the accurate mechanical assessment of luminal organs.

Optical elastography and tissue biomechanics

“…They also developed an improved algorithm for enhancing the resolution of laser speckle microrheology, which they applied for the stiffness assessment of the extracellular matrix as a key regulator of cancer cell proliferation and migration and demonstrated the capability of their technique to address important questions related to mechanobiology. 17,18 Dr. Ruikang Wang and Dr. Matthew O'Donnell, from the University of Washington (Seattle), USA, suggested to replace optical trapping with acoustic microtapping (AuT). 19 By employing focused, air-coupled US to induce mechanical displacement at the boundary of a soft material and combining it with high-speed phase-sensitive OCT, it is possible to achieve high-resolution quantitative elastography of soft tissues.…”

Tutorial on laser speckle rheology: technology, applications, and opportunities

“…59,60 3 Laser Speckle Rheology: Technology Platform LSR is an optical technique that evaluates the viscoelastic properties of biological tissues and biomaterials, without applying an external force, physically contacting the specimen, or using exogenous particles, in a passive, noninvasive approach. [30][31][32][33][34][35][37][38][39][40][41][42][43][44][45][46][61][62][63][64] Laser speckle [ Fig. 1(a)] is a random granular pattern of dark and bright spots that emerges when a highly coherent beam of light, e.g., laser, is backscattered from a particulate material, such as the biological tissue.…”

“…These fluctuations are highly sensitive to particle displacements, and in-turn to the viscoelastic properties of the microenvironment surrounding the particles. [30][31][32][33][34][35][37][38][39][40][41][42][43][44][45][46]64 The optical layout of a bench-top LSR system is shown in Fig. 1(b).…”

“…45 This design featured multiple single-mode fibers (SMF), a customized multifaceted pyramidal mirror (MFPM) to guide light to various circumferential locations on the lumen wall, and an OFB to simultaneously collect multiple laser speckle patterns. 45 By retracting the catheter using a motor-drive assembly, cylindrical maps of tissue mechanical properties are reconstructed without the need for mechanical rotation. The accuracy of the new omnidirectional LSR catheter measurements was confirmed in gel phantoms and human coronary arteries, using conventional mechanical rheometry as a reference standard.…”

“…The accuracy of the new omnidirectional LSR catheter measurements was confirmed in gel phantoms and human coronary arteries, using conventional mechanical rheometry as a reference standard. 45 The rigorous development and preclinical testing in animal models, outlined above, pave the path for translating the LSR endoscopy systems to clinical setting, opening existing avenues for directly evaluating the viscoelastic properties of luminal organ in deep, inaccessible, uncharted fields.…”