Photoacoustic correlation signal-to-noise ratio enhancement by coherent averaging and optical waveform optimization.

Photoacoustic (PA) imaging of biological tissues using laser diodes instead of conventional Q-switched pulsed systems provides an attractive alternative for biomedical applications. However, the relatively low energy of laser diodes operating in the pulsed regime, results in generation of very weak acoustic waves, and low signal-to-noise ratio (SNR) of the detected signals. This problem can be addressed if optical excitation is modulated using custom waveforms and correlation processing is employed to increase SNR through signal compression.

Photothermoacoustic imaging of biological tissues: maximum depth characterization comparison of time and frequency-domain measurements.

The photothermoacoustic (PTA) or photoacoustic (PA) effect induced in light-absorbing materials can be observed either as a transient signal in time domain or as a periodic response to modulated optical excitation. Both techniques can be utilized for creating an image of subsurface light-absorbing structures (chromophores). In biological materials, the optical contrast information can be related to physiological activity and chemical composition of a test specimen.

Fourier-domain biophotoacoustic subsurface depth selective amplitude and phase imaging of turbid phantoms and biological tissue.

A novel photothermoacoustic imaging modality utilizing a frequency-swept (chirped) intensity-modulated laser source and coherent frequency domain signal processing ("biophotoacoustics") was introduced for noninvasive imaging of biological tissues. The developed frequency-domain imaging system takes advantage of linear frequency modulation waveforms to relate depth of tissue chromophores to the frequency spectrum of the detected acoustic response and of a narrow signal detection bandwidth to improve signal-to-noise ratio (SNR). Application of frequency-domain photothermoacoustic (FD-PTA) imaging was demonstrated using turbid phantoms and ex-vivo specimens of chicken breast with embedded absorbing inclusions simulating tumors.

Differential phase optical coherence probe for depth-resolved detection of photothermal response in tissue.

We describe a differential phase low-coherence interferometric probe for non-invasive, quantitative imaging of photothermal phenomena in biological materials. Our detection method utilizes principles of optical coherence tomography with differential phase measurement of interference fringe signals. A dual-channel optical low-coherence probe is used to analyse laser-induced thermoelastic and thermorefractive effects in tissue with micrometre axial resolution and nanometre sensitivity.

Imaging tissue response to electrical and photothermal stimulation with nanometer sensitivity.

Background And Objectives: Tissue response to thermal, electrical, or chemical stimuli are important in the health and survival of tissue. We report experimental results to assess tissue response to various stimuli using a low coherence differential phase interferometer.

Study Design/materials And Methods: The optical system utilized to measure tissue response is a novel fiber-based phase sensitive optical low coherence reflectometer (PS-OLCR).

Radiofrequency cartilage reshaping: efficacy, biophysical measurements, and tissue viability.

Objectives: To assess the feasibility of reshaping cartilage using radiofrequency (RF) heating, and to examine the effects of this process on tissue biophysical properties (optical and thermal) and cellular viability.

Methods: Mechanically deformed porcine septal cartilage was reshaped using 2 RF-generating devices. We performed dynamic measurements of tissue thermal and optical properties while heating cartilage with one of these devices.