Mechano-Vibrational Spectroscopy of Tissues and Materials Using Vibrational Optical Coherence Tomography: A New Non-Invasive and Non-Destructive Technique

Abstract

Elastic moduli of tissues and synthetic polymeric materials are important design properties needed to develop new implants. In this paper we report the use of vibrational optical coherence tomography (VOCT) to measure the resonant frequency and calculate the modulus of tissues and synthetic polymers non-invasively and non-destructively in vitro and in vivo.Values of tissue and polymer moduli were obtained by applying an audible sinusoidal sound wave to the surface of each specimen. The sound wave travels to the interior of the material and is reflected back to the surface from underlying layers. A spectrum of resonant frequencies and moduli are then obtained. By analyzing the frequencies at which the maximum displacements are observed the resonant frequencies are determined of the material components and the moduli can then be calculated from calibration equations. The characteristic spectrum of resonant frequencies measured is a finger print by which the composition of the underlying tissue components can be determined using VOCT. The resonant frequencies of cells and tissues range from about 40 Hz for fat to about 990 Hz for

Virtual biopsies and vibrational-mechanical analysis of skin rejuvenation: comparison of results obtained with micro-needling and topical treatments

“…VOCT is a non-invasive and non-destructive method that uses infrared light and audible sound to create a displacement of skin as described in detail previously. [17][18][19] The measured resonant frequencies are converted into modulus values using a calibration equation (equation 1) developed based on in vitro uniaxial mechanical tensile testing and VOCT measurements. 20,21 Experimentally, the VOCT hand piece uses infrared light to image the specimen as described previously.…”

“…20,21 Experimentally, the VOCT hand piece uses infrared light to image the specimen as described previously. [17][18][19][20][21] The infrared beam is focused on a fixed position on the area of skin above the tissue to be studied. A frequency generating app is downloaded onto the i5 processor within the VOCT device.…”

“…This app is capable of driving the speaker between 30 and 20,000Hz. [17][18][19][20][21] The speaker is placed near but not touching areas of the skin. During in vivo measurements, no sensation of the light or sound is felt impinging on the skin.…”

“…[18][19][20][21] The spectral-domain optical coherence tomography (SD-OCT) system uses a fiber-coupled super luminescent diode light source with an 810nm center wavelength and 100nm bandwidth (full-width at half maximum). [17][18][19][20][21] For measurement of the resonant frequency of a material, the VOCT system is operated in the B mode with the beam focused on one point with an area of about 14 m as previously indicated. [17][18][19][20][21] The resonant frequency of each sample is determined by measuring the displacement of skin resulting from sinusoidal driving frequencies ranging from 30 to 200Hz, in steps of 10Hz.…”

“…[17][18][19][20][21] For measurement of the resonant frequency of a material, the VOCT system is operated in the B mode with the beam focused on one point with an area of about 14 m as previously indicated. [17][18][19][20][21] The resonant frequency of each sample is determined by measuring the displacement of skin resulting from sinusoidal driving frequencies ranging from 30 to 200Hz, in steps of 10Hz. The peak frequency (the resonant frequency), f n , is defined as the frequency at which the displacement is maximized as discussed previously.…”