The Journal of Biomedical Optics started in January 1996, with the goal of becoming the leading journal in the biomedical applications of optics technology.

Optical imaging of cardiac transmembrane potential in dye-stained tissue is an emerging technique in cardiac electrophysiology. Despite its widespread application to studies of isolated hearts, it has been applied traditionally to recording only a single view that presents the potential distribution of a fraction of the cardiac surface. This poses a significant limitation in studying whole heart electrophysiology, particularly when large-scale phenomena such as fibrillation and defibrillation are of interest. We have developed a panoramic imaging system based on a high-speed charge-coupled device camera with a maximum imaging speed of 335 frames/s at 128x64 pixels/frame. Our system provides one front view and two back mirror views of isolated hearts, thus extending optical imaging capabilities to record from the entire three dimensional heart surface with only one camera.

Controversy remains about which tissue is primarily responsible for light attenuation of near infrared spectroscopy (NIRS) in the adult, the spatial resolution provided and the preferred algorithm for quantification. Until recently, changes in NIRS have not been fully quantified and have been difficult to interpret without sophisticated computation. A new development by Hamamatsu Photonics, the spatially resolved spectrometer (SRS), may be able to give a quantitative measure of oxygen saturation. We have incorporated the SRS into a multimodality monitoring system for the purpose of direct validation against jugular bulb oxygen saturation (SjO2) in patients undergoing routine cardiopulmonary bypass (CPB). The importance of this investigation is in the development of the SRS machine which shows potential as a useful clinical tool. The results demonstrated good correlation between SRS and SjO2 in 12 out of the 24 patients studied. Although these results are encouraging, this study suggests that the SRS, in its present form, is not a reliable clinical monitor of cerebral oxygen saturation during CPB.

We have used a tunable, infrared, free-electron laser with a Pockels cell controlled pulse duration to generate photoacoustic pulses with separate variable rise times (from 15 to 100 ns), durations (100–400 ns), and amplitudes (0.005–0.1 MPa). The tunability of the free-electron laser across water absorption bands allows the rise time of the thermal-elastically generated acoustical pulsed to be varied, while a Pockels cell controls the duration and cross polarizers control the pressure amplitude. The mechanical effects of pressure transients on biological tissue can have dramatic consequences. In addition to cell necrosis, carefully controlled pressure transients can also be used for therapeutic applications, such as drug delivery and gene therapy. This technique permits systemic probing of how biological tissue is affected by stress transients.

A fiber optic sensor for the measurement of the respiratory depth has been developed. The sensor is composed of a bent optic fiber which is connected to an elastic section of a chest belt so that its radius of curvature changes during respiration due to respiratory chest circumference changes (RCCC). The measurement of light transmission through the bent fiber provides information on its changes in curvature since a higher fraction of light escapes through the core-cladding surface of a fiber bent to a lower radius of curvature. The sensor can quantitatively measure the RCCC, although in relative terms, and it is sensitive enough to detect changes of the chest circumference due to the heart beat. Measurements of the RCCC were simultaneously performed with photoplethysmography (PPG)—the measurement by light absorption of the cardiac induced blood volume changes in the tissue—and a significant correlation was found between the RCCC and some parameters of the PPG signal. The fiber optic respiratory depth sensor enables a quantitative assessment of the respiratory induced changes in the cardiovascular parameters.

Studies on the phenomena of light scattered multiply from strongly absorbent media have been of benefit to metrology in biophysics, chemistry, and other areas. In this article, a temporal autocorrelation function of time-varying light backscattered multiply from a fractal aggregate of particles under Brownian motion suspended in an absorbent medium is investigated by means of Monte Carlo simulation. Temporal statistics of the backscattered light in time regions longer and shorter than the relaxation time depend on the fractal dimension and agree with the case of the homogeneously random media, respectively. The angular dependence of light backscattered multiply from fractal media varies dramatically depending on the fractal dimension in comparison with that from homogeneously random media. The influence of absorption generates the time shift in the temporal autocorrelation function in such a way that they vary approximately in accordance with a square root of the absorption coefficient but are independent of the fractal dimension.

This paper explains the term low-coherence interferometry, reviews the early development of optical low-coherence reflectometry, and shows some of the paths that led to the field of biomedical optics. This paper demonstrates that early technical developments in the telecommunications industry resulted in a myriad of technical implementations and applications in biology, medicine, and the explosion of the field in noninvasive biomedical optical techniques. Recent examples of innovative applications of this proliferating technology into the fields of ophthalmology, developmental biology, and endoscopy are described.

When heated, living tissue exhibits random nonuniformities in temperature that are due to the discreteness of vessel arrangement. Because of the strong temperature dependence of the thermal coagulation rate these nonuniformities should substantially affect the necrosis growth induced by local heating. In the present work we study the effect of vessel discreteness on the form of a necrosis domain when its growth is limited by heat diffusion into the surrounding tissue. Namely, we analyze the characteristics of the necrosis boundary that are due to vessel discreteness. In particular, we find the mean amplitude ?? and the correlation length l? of the necrosis boundary perturbations depending on the main tissue parameters. In addition, it is shown that there are universal relations between the mean size R of the necrosis domain and the characteristics ?? , l? of the boundary perturbations, which are due to the fractal structure of the vascular network.

Cell viability and DNA denaturation are measured through two-photon fluorescence excitation using a single diode laser beam as the trapping and exciting source simultaneously. Two-photon fluorescence emission spectra are presented for CHO cells and T lymphocytes loaded with various fluorescent probes. This single beam method is demonstrated to be a safe tool to monitor the viability of optically trapped cells, even under intense 809 nm diode laser illumination (~106 W/cm2). The dynamics of cellular necrosis is monitored by adding ethanol to the cell suspension during trapping. Thermal damage to heat-treated samples is assessed by recording shifts in the emission spectra from trapped cells loaded with the nucleic acid probe, acridine orange.