title: Multi-Channel Optical Coherence Elastography Using Relative and Absolute Shear-Wave Time of Flight.
abstract: Elastography, the imaging of elastic properties of soft tissues, is well developed for macroscopic clinical imaging of soft tissues and can provide useful information about various pathological processes which is complementary to that provided by the original modality. Scaling down of this technique should ply the field of cellular biology with valuable information with regard to elastic properties of cells and their environment. This paper evaluates the potential to develop such a tool by modifying a commercial optical coherence tomography (OCT) device to measure the speed of shear waves propagating in a three-dimensional (3D) medium. A needle, embedded in the gel, was excited to vibrate along its long axis and the displacement as a function of time and distance from the needle associated with the resulting shear waves was detected using four M-mode images acquired simultaneously using a commercial four-channel swept-source OCT system. Shear-wave time of arrival (TOA) was detected by tracking the axial OCT-speckle motion using cross-correlation methods. Shear-wave speed was then calculated from inter-channel differences of TOA for a single burst (the relative TOA method) and compared with the shear-wave speed determined from positional differences of TOA for a single channel over multiple bursts (the absolute TOA method). For homogeneous gels the relative method provided shear-wave speed with acceptable precision and accuracy when judged against the expected linear dependence of shear modulus on gelatine concentration (R2 = 0.95) and ultimate resolution capabilities limited by 184μm inter-channel distance. This overall approach shows promise for its eventual provision as a research tool in cancer cell biology. Further work is required to optimize parameters such as vibration frequency, burst length and amplitude, and to assess the lateral and axial resolutions of this type of device as well as to create 3D elastograms.
authors.affiliation: CRUK Imaging Centre, Division of Radiotherapy and Imaging, Institute of Cancer Research, Sutton, Surrey, United Kingdom.|Joint Department of Physics, Institute of Cancer Research and Royal Marsden NHS Foundation Trust, Sutton, Surrey, United Kingdom.
authors.forename: Eli
authors.initials: E
authors.lastname: Elyas
authors.affiliation: Department of Medical Physics, Royal Surrey County Hospital, Guildford, Surrey, United Kingdom.
authors.forename: Alex
authors.initials: A
authors.lastname: Grimwood
authors.affiliation: Biotech Research & Innovation Centre, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Janine T
authors.initials: JT
authors.lastname: Erler
authors.affiliation: CRUK Imaging Centre, Division of Radiotherapy and Imaging, Institute of Cancer Research, Sutton, Surrey, United Kingdom.
authors.forename: Simon P
authors.initials: SP
authors.lastname: Robinson
authors.affiliation: Biotech Research & Innovation Centre, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Thomas R
authors.initials: TR
authors.lastname: Cox
authors.affiliation: Michelson Diagnostics, 1 Grays Farm Production Village, Orpington, Kent, United Kingdom.
authors.forename: Daniel
authors.initials: D
authors.lastname: Woods
authors.affiliation: Joint Department of Physics, Institute of Cancer Research and Royal Marsden NHS Foundation Trust, Sutton, Surrey, United Kingdom.
authors.forename: Peter
authors.initials: P
authors.lastname: Clowes
authors.affiliation: CRUK Imaging Centre, Division of Radiotherapy and Imaging, Institute of Cancer Research, Sutton, Surrey, United Kingdom.|Joint Department of Physics, Institute of Cancer Research and Royal Marsden NHS Foundation Trust, Sutton, Surrey, United Kingdom.|Department of Mechanical and Aerospace Engineering, Sapienza University of Rome, Rome, Italy.
authors.forename: Ramona
authors.initials: R
authors.lastname: De Luca
authors.affiliation: Department of Mechanical and Aerospace Engineering, Sapienza University of Rome, Rome, Italy.
authors.forename: Franco
authors.initials: F
authors.lastname: Marinozzi
authors.affiliation: CRUK Imaging Centre, Division of Radiotherapy and Imaging, Institute of Cancer Research, Sutton, Surrey, United Kingdom.|Joint Department of Physics, Institute of Cancer Research and Royal Marsden NHS Foundation Trust, Sutton, Surrey, United Kingdom.
authors.forename: Jérémie
authors.initials: J
authors.lastname: Fromageau
authors.affiliation: CRUK Imaging Centre, Division of Radiotherapy and Imaging, Institute of Cancer Research, Sutton, Surrey, United Kingdom.|Joint Department of Physics, Institute of Cancer Research and Royal Marsden NHS Foundation Trust, Sutton, Surrey, United Kingdom.
authors.forename: Jeffrey C
authors.initials: JC
authors.lastname: Bamber
mesh_terms: D054459:Elasticity Imaging Techniques / Q000379:methods*; D019047:Phantoms, Imaging; D041623:Tomography, Optical Coherence / Q000379:methods*