To establish optical in situ detection of mitochondrial malfunction, nonradiative energy transfer from the coenzyme NADH to the mitochondrial marker rhodamine 123 (R123) was examined. Dual excitation of R123 via energy transfer from excited NADH molecules as well as by direct absorption of light results in two fluorescence signals whose ratio is a measure of mitochondrial NADH. A screening system was developed in which these signals are detected simultaneously using a time-gated (nanosecond) technique for energy transfer measurements and a frequency selective technique for direct excitation and fluorescence monitoring of R123. Optical and electronic components of the apparatus are described, and results obtained from cultivated endothelial cells are reported. The ratio of fluorescence intensities excited in the near ultraviolet and blue–green spectral ranges increased by a factor 1.5 or 1.35 after inhibition of the mitochondrial respiratory chain by rotenone at cytotoxic or noncytotoxic concentrations, respectively. Concomitantly the amount of mitochondrial NADH increased. Excellent linearity between the number of cells incubated with R123 and fluorescence intensity was found in suspension.

Optical coherence tomography (OCT) was used to image the internal structure of a rat cochlea (ex vivo). Immediately following sacrifice, the temporal bone of a Sprague–Dawley rat was harvested. Axial OCT cross sectional images (over regions of interest, 1x1 mm– 2x8 mm) were obtained with a spatial resolution of 10–15 µm. The osseous borders of the lateral membranous labyrinth overlying the cochlea and the scala vestibuli, media, and tympani, which were well demarcated by the modiolus, Reissner’s and the basilar membranes, were clearly identified. OCT can be used to image internal structures in the cochlea without violating the osseous labyrinth using simple surgical exposure of the promontory, and may potentially be used to diagnose inner ear pathology in vivo in both animal and human subjects labyrinth.

Several optical techniques that investigate blood contained within the retinal vessels are available or under development. We present a mechanical model that simulates the optical properties of the eye, the retinal vessels, and the ocular fundus. A micropipette is chosen as the retinal vessel model, and a mechanical housing is constructed to simulate the eyeball. Spectralon is used to simulate the retinal layers. Filling the eye with fluid index matched to the glass pipette eliminates reflection and refraction effects from the pipette. An apparatus is constructed and used to set the oxygen, nitrogen, and carbon dioxide concentrations in whole human blood. These whole blood samples are pumped through the pipette at 34 µL/min. Measurements made in the model eye closely resemble measurements made in the human eye. This apparatus is useful for developing the science and testing the systems that optically investigate blood and blood flow in the large retinal vessels.

To improve the effectiveness of microsurgical techniques, we are developing a semi-autonomous robotic surgical tool (called the ‘‘Smart Scalpel’’) as an alternate approach to treatment of vascular lesions. The device employs optical reflectance spectroscopy as part of a line scan imaging system to identify and selectively target blood vessels in a vascular lesion for thermal treatment with a focused laser beam. Our proof-of-concept reported here presents the design and construction of a prototype instrument, initial quantification of imaging system resolution and contrast, and preliminary verification of the imaging and targeting strategies with standard targets and live dermal tissue.

Near infrared spectroscopy is an increasingly important tool for the investigation of human brain function, however, to date there have been few systematic evaluations of accompanying thermal effects due to absorption. We have measured the spatial distribution of temperature changes during near infrared irradiation (789 nm) as a function of laser power, in both excised tissue (chicken meat and skin) and in the forearm of an awake human volunteer. Light was applied using a 1 mm optical fiber which is characteristic of the topographic system. The temperature of excised chicken tissue increased linearly with power level as 0.097 and 0.042°C/mW at depths of 0 and 1 mm, respectively. Human forearm studies yielded temperature changes of 0.101, 0.038, and 0.030°C/mW at depths of 0.5, 1.0, and 1.5 mm, respectively. Due to direct irradiation of the thermocouple all measurements represent the maximum temperature increase from the laser. In all cases the estimated heating effects from continuous wave optical topography systems were small and well below levels which would endanger tissue cells. The close similarity between ex vivo and in vivo measurements suggests negligible contributions from blood flow in the skin which was further supported by measurements during cuff ischemia. Heating effects decreased sharply with both depth and lateral position; thus, for optode spacings greater than a few millimeters, fibers can be treated independently. Finite element analysis confirms that the experimental results are consistent with a simple heat conduction model.

Pulse oximetry (oxygen saturation monitoring) has markedly improved medical care in many fields, including anesthesiology, intensive care, and newborn intensive care. In obstetrics, fetal heart rate monitoring remains the standard for intrapartum assessment of fetal well being. Fetal oxygen saturation monitoring is a new technique currently under development. It is potentially superior to electronic fetal heart rate monitoring (cardiotocography) because it allows direct assessment of both the fetal oxygen status and fetal tissue perfusion. Here we present the analysis for determining the most optimal wavelength selection for pulse oximetry. The wavelengths we chose as the most optimal are the first in the range of 670–720 nm and the second in the range of 825–925 nm. Further, we discuss the possible systematic errors during our measurements and their contribution to the obtained saturation results. We present feasibility studies for fetal pulse oximetry, monitored noninvasively through the maternal abdomen. Our preliminary experiments show that the fetal pulse can be discriminated from the maternal pulse and thus, in principle, the fetal arterial oxygen saturation can be obtained. We present the methodology for obtaining these data, and discuss the dependence of our measurements on the fetal position with respect to the optode assembly.

The purpose of this study was to measure O2 consumption of nonexercising skeletal muscles (VO2nonex) at rest and after aerobic exercise and to investigate the stimulant factors of O2 consumption. In experiment 1, we measured the resting metabolic rate of the finger flexor muscles in seven healthy males by 31P-magnetic resonance spectroscopy during a 15 min arterial occlusion. In experiment 2, the VO2nonex of the finger flexor muscles was measured using near infrared continuous wave spectroscopy at rest, immediate postexercise, and 3, 5, 10, 15, and 20 min following a cycling exercise at a workload corresponding to 50% of peak pulmonary O2 uptake for 20 min. We also monitored deep tissue temperature in the VO2nonex measurement area and determined catecholamines and lactate concentrations in the blood at rest and immediate postexercise. VO2nonex at rest was 1.1±0.1µMO2 /s (mean6standard error) and VO2nonex after exercise increased 59.6±7.2% (p<0.001) from the resting values. There were significant correlations between the increase in VO2nonex and the increase in epinephrine concentration (p<0.01), and between the increase in VO2nonex and the increase in lactate concentration (p<0.05). These results suggest that epinephrine and lactate concentrations are important VO2nonex stimulant factors.

A cDNA microarray is a complex biochemical-optical system whose purpose is the simultaneous measurement of gene expression for thousands of genes. In this paper we propose a general statistical approach to finding associations between the expression patterns of genes via the coefficient of determination. This coefficient measures the degree to which the transcriptional levels of an observed gene set can be used to improve the prediction of the transcriptional state of a target gene relative to the best possible prediction in the absence of observations. The method allows incorporation of knowledge of other conditions relevant to the prediction, such as the application of particular stimuli or the presence of inactivating gene mutations, as predictive elements affecting the expression level of a given gene. Various aspects of the method are discussed: prediction quantification, unconstrained prediction, constrained prediction using ternary perceptrons, and design of predictors given small numbers of replicated microarrays. The method is applied to a set of genes undergoing genotoxic stress for validation according to the manner in which it points toward previously known and unknown relationships. The entire procedure is supported by software that can be applied to large gene sets, has a number of facilities to simplify data analysis, and provides graphics for visualizing experimental data, multiple gene interaction, and prediction logic.

This paper presents an effective two-step scheme for automatic object detection in computed radiography (CR) images. First, various structure elements of the morphological filters, designed by incorporating available morphological features of the objects of interest including their sizes and rough shape descriptions, are used to effectively distinguish the foreign object candidates from the complex background structures. Second, since the boundaries of the objects are the key features in reflecting object characteristics, active contour models are employed to accurately outline the morphological shapes of the suspicious foreign objects to further reduce the rate of false alarms. The actual detection scheme is accomplished by jointly using these two steps. The proposed methods are tested with a database of 50 hand–wrist computed radiographic images containing various types of foreign objects. Our experimental results demonstrate that the combined use of morphological filters and active contour models can provide an effective automatic detection of foreign objects in CR images achieving good sensitivity and specificity, and the accurate descriptions of the object morphological characteristics.