Light scattering by a tissue has a wavelength dependence that depends on the size distribution of scatterers in the tissue. By measuring the wavelength dependence of scattering, one can deduce changes in the nanoscale architecture of cells and tissues. This report discusses the connection between nanoscale architecture and measurable light scattering. The significance of this work is to develop label-free optical imaging that describes tissue structure, to complement the absorption, fluorescence, and Raman scattering spectra that describe the chemical constituents of a tissue.

The development of optical methods in modern medicine in the areas of diagnostics, therapy, and surgery has stimulated the investigation of optical properties of various biological tissues, since the efficacy of laser treatment depends on the photon propagation and fluence rate distribution within irradiated tissues. In this work, an overview of published absorption and scattering properties of skin and subcutaneous tissues measured in wide wavelength range is presented. Basic principles of measurements of the tissue optical properties and techniques used for processing of the measured data are outlined.

Optoacoustics is a promising modality for biomedical imaging, sensing, and monitoring with high resolution and contrast. In this paper, we present an overview of our studies for the last two decades on optoacoustic effects in tissues and imaging capabilities of the optoacoustic technique. In our earlier optoacoustic works we studied laser ablation of tissues and tissue-like media and proposed to use optoacoustics for imaging in tissues. In mid-90s we demonstrated detection of optoacoustic signals from tissues at depths of up to several centimeters, well deeper than the optical diffusion limit. We then obtained optoacoustic images of tissues both in vitro and in vivo. In late 90s we studied optoacoustic monitoring of thermotherapy: hyperthermia, coagulation, and freezing. Then we proposed and studied optoacoustic monitoring of blood oxygenation, hemoglobin concentration, and other physiologic parameters.

In this paper, we studied portable blue and red light-emitting-diode (LED) light sources in phototherapy for mild to moderate acne vulgaris to evaluate the efficacy and tolerance of patients. Patients, randomly divided into blue and red groups, received either blue or red LED phototherapy twice a week for four weeks. After complete treatment, the number of lesions reduced by 71.4% in the blue group, in contrast to 19.5% in the red group. No obvious side effects were observed during and one month after the treatment, except for some mild dryness mentioned by several patients.

A novel broad tunable bandwidth and narrow instantaneous line-width linear swept laser source using combined tunable filters working at 1,300 nm center wavelength is proposed. The combined filters consist of a fiber Fabry Perot tunable filter and a tunable filter based on diffractive grating with scanning polygon mirror. In contrast to traditional method using single tunable filter, the trade-off between bandwidth and instantaneous line-width is alleviated. Parallel implementation of two semiconductor optical amplifiers with different wavelength range is adopted in the laser resonator for broadband light amplification. The Fourier domain mode locking swept laser source with combined tunable filters offers broadband tunable range with narrow instantaneous line-width, which is especially benefiting for high-quality optical frequency domain imaging. The proposed Fourier domain mode locking swept laser source provides a tuning range of 160 nm with instantaneous line-width of about 0.01nm at sweeping rate of 15 kHz, a finesse of 16,000 is thus achieved.

We report the results of a comparative study of Fourier domain analysis (FDA) and texture analysis (TA) of optical coherence tomography (OCT) images of resected human breast tissues for binary classification between normal-abnormal classes and benign-malignant classes. With the incorporation of Fisher linear discriminant analysis (FLDA) in TA for feature extraction, the TA-based algorithm provided improved diagnostic performance as compared to the FDAbased algorithm in discriminating OCT images corresponding to breast tissues with three different pathologies. The specificity and sensitivity values obtained for normal-abnormal classification were both 100%, whereas they were 90% and 85%, respectively for benign-malignant classification.

Scattering coefficients of human skin in vivo with and without vitiligo were measured with optical coherence tomography (OCT). The experimental results show that there exist significant difference between the scattering coefficient of the epidermis of in vivo human skin with and without vitiligo disease. The results may be helpful for quantitatively diagnosing or evaluating the treatment of the disease.

In this paper, an image processing method for improving the quality of optical coherence tomography (OCT) images is proposed. Wavelet denoising based on context modeling and contrast enhancement by means of the contrast measure in the wavelet domain is carried out on the OCT images in succession. Three parameters are selected to assess the effectiveness of the method. It is shown from the results that the proposed method can not only enhance the contrast of images, but also improve signal-to-noise ratio. Compared with two other typical algorithms, it has the best visual effect.

In swept-source optical coherence tomography (SSOCT), the swept-source stimulates system by a series of wavelengths in time sequence; a photo detector then collects all reflected/backscattered light from testing sample as the components of Fourier series. Due to the nature of the SSOCT, the processing in spectral domain can merge multiple swept-sources with different central wavelengths, which greatly increases the resolution of the OCT imaging. In the wavelength probing OCT, a standard broadband SSOCT system is used to extract the internal structure of the sample, and another narrow band light can be used to probe the spectral feature of the sample at the probing wavelength.

The signal processing speed of spectral domain optical coherence tomography (SD-OCT) has become a bottleneck in a lot of medical applications. Recently, a time-domain interpolation method was proposed. This method can get better signal-to-noise ratio (SNR) but much-reduced signal processing time in SD-OCT data processing as compared with the commonly used zeropadding interpolation method. Additionally, the resampled data can be obtained by a few data and coefficients in the cutoff window. Thus, a lot of interpolations can be performed simultaneously. So, this interpolation method is suitable for parallel computing. By using graphics processing unit (GPU) and the compute unified device architecture (CUDA) program model, time-domain interpolation can be accelerated significantly. The computing capability can be achieved more than 250,000 A-lines, 200,000 A-lines, and 160,000 A-lines in a second for 2,048 pixel OCT when the cutoff length is L = 11, L = 21, and L = 31, respectively. A frame SD-OCT data (400A-lines×2,048 pixel per line) is acquired and processed on GPU in real time. The results show that signal processing time of SD-OCT can be finished in 6.223 ms when the cutoff length L = 21, which is much faster than that on central processing unit (CPU). Real-time signal processing of acquired data can be realized.