DYNAMIC OPTICAL COHERENCE ELASTOGRAPHY: A REVIEW

Abstract

With the development of optical coherence tomography, the application optical coherence elastography (OCE) has gained more and more attention in biomechanics for its unique features including micron-scale resolution, real-time processing, and non-invasive imaging. In this review, one group of OCE techniques, namely dynamic OCE, are introduced and discussed including external dynamic OCE mapping and imaging of ex vivo breast tumor, external dynamic OCE measurement of in vivo human skin, and internal dynamic OCE including acoustomotive OCE and magnetomotive OCE. These techniques overcame some of the major drawbacks of traditional static OCE, and broadened the OCE application fields. Driven by scientific needs to engineer new quantitative methods that utilize the high micron-scale resolution achievable with optics, results of biomechanical properties were obtained from biological tissues. The results suggest potential diagnostic and therapeutic clinical applications. Results from these studies also help our understanding of the relationship between biomechanical variations and functional tissue changes in biological systems.

Fig. 1

Classification and examples of OCE techniques.

Fig. 2

Schematic diagram of the SD-OCT system used in the dynamic OCE studies.

Fig. 3

Phase-resolved OCE map of human breast tissue elasticity. (a) B-mode OCT image of breast tissue. The left side of this image represents adipose tissue while the right side of the image represents tumor tissue. (b) Histology image corresponding to (a). (c) Map of elasticity by sinusoidally driven phase-resolved OCE. (d) Error map of elasticity by sinusoidally driven phase-resolved OCE. Unit for color bar is kPa. Reprinted from Ref. with permission.

Fig. 4

OCE results of ex vivo rat tumor tissue. (a) OCE image under 45 Hz mechanical excitation. (b) OCT structural image of the tissue. (c) OCE image under 313 Hz mechanical excitation. (d) Corresponding histological image. Scale bar applies to all the images. Orange arrows denote adipose cells and connective tissues within tumor, and blue arrows denote invading tumor tissues in fat. Reprinted from Ref. with permission.

Fig. 5

Young’s moduli measured by OCE under different driving frequencies and skin hydration conditions. Blue line denotes results from dehydrated skin, brown line denotes results on hydrated skin, and red line denotes results on normal untreated skin. Reprinted from Ref. with permission.

Fig. 6

AM-OCE results on gelatin phantoms. (a) AM-OCE shear modulus. (b) AM-OCE shear damping parameter. The asterisk (*) denotes no statistical or calculation error estimations. Reprinted from Ref. with permission.

Fig. 7

Normalized measured displacements from samples of different elastic moduli following a step waveform of the applied magnetic field.

Fig. 8

Normalized MM-OCE measured tissue displacements (step responses) from the application of a switched (off-to-on) magnetic field in biological samples of (a) lung tissue, (c) liver tissue, and (e) muscle tissue from a rat model, and their corresponding MM-OCT images (b, d, and f, respectively). Scale bar applies to all MM-OCT images.