Laser-induced fluorescence (LIF) can be used for noninvasive spectroscopic identification of biological tissue and is of special interest in early tumor detection. The basis for this optical biopsy method is the interaction of the laser light with tissue chromophores, such as tryptophan, collagen, elastin, NADH, beta-carotene and hemoglobin. The UV-excited fluorescence that arises from the native chromophores, the autofluorescence, has a broad distribution, peaking at about 490 nm with a lower intensity in tumor compared to normal tissue. The tumor detection potential is enhanced with exogenously administrated tumor- marking agents, such as hematoporphyrin (HPD, commercial name Photofrin), with two fluorescence peaks at about 630 and 690 nm. We have developed clinical instrumentation both for tissue point monitoring and for full real-time image processing. Seventy-one patients were investigated in vivo and surgical samples from additional 20 patients. In 46 patients the autofluorescence only was monitored. In 45 patients low-dose Photofrin injection was used. The in vivo investigations included different kinds of lung tumors, urinary bladder tumors, and malignant gliomas. The in vitro measurements were performed in breast tumors and prostatic tumors. Invasive and early tumors and also precancerous lesions can be revealed utilizing LIF in low-dose Photofrin injected patients.

We report on the in vivo fluorescence spectroscopy of ten oral tongue cancers in previously untreated patients. Spectral profiles of the tongue tumor in each patient were compared to those of the corresponding normal contralateral oral tongue mucosa. Spectral characteristics were generated using a xenon lamp as a light source and the results described herein were restricted to one excitation scan obtained using a Mediscience-CD Scanner. The ratio of the main peak at 320-350 nm to the secondary peak at 373-376 nm and the area under the curve between 300 and 400 nm in the excitation scan were used as measurements to calculate differences between the normal versus oral tongue cancer. Significance was determined using the paired t-st. The ratio of the main peak to the secondary peak was higher in the tumor scans when compared to the corresponding contralateral mucosa. When the area under the curves was analyzed, the tumor tissue had reproducible lower values as compared to the contralateral normal sites.

We have developed and are testing early prototypes of an optical biopsy system (OBS) for detection of cancer and other tissue pathologies. The OBS invokes a unique approach to optical diagnosis of tissue pathologies based on the elastic scattering properties, over a wide range of wavelengths, of the microscopic structure of the tissue. Absorption bands in the tissue also add useful complexity to the spectral data collected. The data acquisition and storage/display time with the OBS instrument is approximately 1 second. Thus, in addition to the reduced invasiveness of this technique compared with current state-of- the-art methods, the OBS offers the possibility of impressively faster diagnostic assessment. The OBS employs a small fiber-optic probe that is amendable to use with any endoscope, catheter or hypodermic, or to direct surface examination (e.g., as in skin cancer or cervical cancer). We report here specifically on its potential application in the detection of bladder cancer.

The fluorescence and excitation spectra of cancer and normal colon mucosa were measured to establish a suitable criterion for colon cancer diagnosis.

Emission and excitation fluorescence spectra have been measured for gynecological (GYN) tissues. Statistics have been established to evaluate the state of tissues and to distinguish cancerous from normal specimens.

An ultrasensitive fiberoptic sensor using a near-IR fluorescence drug was developed for early cancer detection. Due to the use of long wavelength excitation at 670 nm with a diode laser, no measurable background fluorescence was observed. The system was built and successfully demonstrated in-vitro with a great drug sensitivity and tumor size resolution. The system, consisting of fiber probe, grating, and CCD optoelectronic components, is highly integrated. Based on fluorescence signature, tumors can be detected in real time. The flexible fiber with excellent light collection efficiency could be inserted into a human body through the working channel of an endoscope to map the metastatic region.

This study aimed to develop a spectroscopic imaging method to visualize superficial pH of tumor and normal tissues after injection of 5,6-carboxyfluorescein as pH marker. In vivo experiments were performed on CDF mice bearing a lymphoid leukemia P388 grafted tumor. Tissue pH were controlled by microelectrodes. Metabolic depression of tumor pH was induced by prior injection of glucose (6g/kg). Images show lower fluorescence intensity in tumor. Both fluorescence kinetic show an increase followed by a plateau phase. Calculated ratio were 1.72+/- 0.07 and 2.03+/- 0.04 in tumor and normal tissues respectively. These ratios based on a calibration curve correspond to 6.21+/- 0.12 and 6.99+/- 0.16. Controlled pH by microelectrodes show similar values (6.2+/- 0.3 and 7.0+/- 0.2 respectively). This imaging technique can be a new tool to study metabolic and functional event in tumor like the relation between pH and hypoxia.

This project investigates the use of fluorescence to discriminate cancerous margins from surrounding normal tissues during neurosurgery. This paper presents a study of the excitation/emission matrix for in vivo rat brain tissue and ex vivo human brain tissue. Measurements were made with an optical fiber fluorimeter, consisting of excitation with a nitrogen/dye laser and detection with a spectrograph and optical multichannel analyzer. The ex/em pair of wavelengths (nm) for excitation and emission of fluorescence are summarized for three types fluorophores. Measurements of these fluorophores types were measured in ex vivo human normal and cancerous tissues, in vivo rat normal brain and glioma, and cell culture aggregates (GBM cells). In general, the magnitude of fluorescence decreases in cancerous tissues. The ratio F_{`flavin'</sub>/F<sub>`NADH'} is an indicator of metabolic activity and a potential assay for normal vs cancerous tissues. Pilot studies with in vivo rat glioma model and with ex vivo human samples tested the use of this ratio for discriminating tissue types. The results did not show obvious trends but more work is still needed.

The ability of laser-induced fluorescence (LIF) to detect flat dysplasia has not been carefully studied. A multiexcitation wavelength LIF system was used to develop an algorithm to detect chemically-induced dysplasia in the rat urinary bladder.

The present work has modeled fluorophore detection in optically turbid (absorbing and scattering) media by Monte Carlo simulation to determine the response functions for the single source/single detector case. This included application of the 'adjoint' Monte Carlo technique, as well as equivalent cylindrical models for noncylindrically symmetric geometries, which have reduced the computation time significantly. The case of fluorescent layer at depth in an optically homogeneous medium was then modeled and an image backprojection algorithm applied to estimate the depth of the fluorescent layer. The influence of tissue albedo, source- detector spacing, and detector numerical aperture on the depth accuracy and resolution have been examined. Possible improvements in multifiber detection for fluorescence quantification and localization within tissue are discussed.

The major objective of this theoretical modeling was to examine the quantitative relationships between the microscopic properties of tissue and the macroscopic in vivo autofluorescence measurements. The modeling was carried out using skin tissue as an example. Monte Carlo simulation was used to model the excitation laser light distribution in and the autofluorescence escape process from skin tissue. The processes of fluorescence escape was modeled as the escape process from an isotropic point source embedded inside the tissue. The fractional contributions of different skin layers to the measured total in vivo autofluorescence signal were calculated and demonstrate good agreements with the results estimated from our laser induced autofluorescence decay experiments. This modeling also yielded the spatial resolution resolvable using tissue autofluorescence imaging. It was found to be worse than diffraction effect limited spatial resolution (equals the wavelength of light) and became significantly degraded for fluorescence sources deep inside the tissue.

Biological tissues produce high levels of optical scattering in the visible and near-infrared. A phase function is often used to characterize the scattering properties of the media. Henyey- Greenstein's phase function has been widely adopted by researchers in the biomedical optics field. A new scattering phase function is proposed to approximate phase functions strictly derived from Mie scattering theory. The new phase function demonstrates much better agreement with Mie theory than Henyey-Greenstein's phase function. In calculation of light propagation within biological media using the radiative transport equation, the phase function plays an even more important role. Using the new phase function as the integral kernel in the radiative transport equation, an analytical expression for the integral term of the equation is obtained for highly aligned beams. This may lead to a semi-analytical solution to the time- dependent radiative transport equation for time-resolved spectroscopy.

We describe an instrument which will permit simultaneous collection of radial resolved reflectance over the spectral range 600-1000 nm and a neural network algorithm which permits real- time analysis of the data. The in vivo performance of the instrument is presently under investigation. Data will be presented illustrating the performance of the instrument over the useful optical spectrum for certain tissues of interest. In addition the derived tissue concentrations of photosensitizers will be compared with those obtained using chemical extraction techniques on excised tissue samples.

Certain bacteria are able to synthesize metal-free fluorescent porphyrins and can therefore be detected by sensitive autofluorescence measurements in the red spectral region. The porphyrin-producing bacterium Propionibacterium acnes, which is involved in the pathogenesis of acne vulgaris, was localized in human skin. Spectrally resolved fluorescence images of bacteria distribution in the face were obtained by a slow-scan CCD camera combined with a tunable liquid crystal filter. The structured autofluorescence of dental caries and dental plaque in the red is caused by oral bacteria, like Bacteroides or Actinomyces odontolyticus. `Caries images' were created by time-gated imaging in the ns-region after ultrashort laser excitation. Time-gated measurements allow the suppression of backscattered light and non-porphyrin autofluorescence. Biopsies of oral squamous cell carcinoma exhibited red autofluorescence in necrotic regions and high concentrations of the porphyrin-producing bacterium Pseudomonas aerigunosa. These studies suggest that the temporal and spectral characteristics of bacterial autofluorescence can be used in the diagnosis and treatment of a variety of diseases.

Near-IR spectroscopy was used to quantify blood content and oxygenation dynamics in abdominal organs and skeletal muscle of 18 anesthetized rabbits during hypoxic hypoxia. Liver, kidney, and hindlimb muscle were exposed surgically. Laser diode pulses transmitted across the tissues were detected by means of a photomultiplier. The amount and redox level of tissue hemoglobin were estimated from the near-IR signals and monitored during 5- min-long hypoxic challenges and subsequent recovery periods. In the kidney, exposure to 10% FiO₂ resulted in rapid and symmetrical changes in oxygenated and reduced hemoglobin with 50% of the variations occurring within 1 min and a plateau after 3 min. Total hemoglobin did not change and hemoglobin oxygenation returned to baseline within 1 min of hypoxia cessation. Exposure to 6% FiO₂ doubled the decrease in oxygenated hemoglobin and induced a sustained vasoconstriction which decreased total hemoglobin content 2 min after initiation of hypoxia. Comparable patterns were observed in the liver and skeletal muscle with the following exceptions: local vasoconstriction was generally not observed at 6% FiO₂, return to baseline oxygen availability was much slower in skeletal muscle than in the other organs.

Information about surface state of different regions of biological objects diagnoses and properties can be very important for some decease treatment. The large majority special measurements methods either need to pick out the pattern from object what is sometime is difficult, or loose the precision and reproducibility of the results to a considerable extent in comparison with standard method application in practice. We offer the method of the spectrum reflactence coefficient measurements from the small part of the nonpiane surface(less than 1 square mm) using the technique is based on optical high precision matching the probe radiation field of research able pattern and photo detectors window. The device is portable enough (full weight less than 0.2 kg.), let us to measure spectrum characteristics of al;most unaccessible surface region, wich has area one square mm with standard deviation about 2%.

Photon migration theory is employed to calculate the line spread function of time-resolved photons as they cross different planes inside a finite slab. Results are used to determine the spatial resolution for objects imbedded at each depth, shown to be proportional to the square root of the excess transit time (Delta) t. However, the light intensities available at small excess transit times, required to obtain finer resolutions, are severely reduced as tissue thickness is increased. Optical parameters of breast tissues are used in our theoretical findings in order to analyze the feasibility of breast screening. For 5- cm-thick tissues that mimic targets of interest in clinical mammography, were predict vanishingly small detectable intensity at the small values of (Delta) t needed in order to achieve 2-mm resolution. Additionally, because normal breast is a spatially heterogeneous mixture of glandular and adipose tissues, which have significantly different optical scattering parameters, the analysis indicates large-amplitude background variations, particularly at short delay times.

A method is presented for simulating the paths traced by photons traveling through a homogenous isotropically scattering medium. An initial photon path is defined with a string of characters that represent the most direct path between a source pixel and a detection pixel. This string then is expanded systematically in unit increments using well-defined rules. In two dimensions using a hexagonal lattice, these rules assume that only six possible directions of scatter are allowed. In three dimensions using a Cartesian lattice, there also are only six directions. The method is tractable and lends itself to computational implementation. Because the method is deterministic, it is more efficient than Monte Carlo methods when investigating paths between specific source and detection pixels. When boundaries are imposed on an object, it is possible to investigate millions of photon paths of a given specified length and to determine probabilistically the pixels visited by the photons within the object.

We report the detection of an object inside a phantom tissue using a spatial filter and a 5-mW He-Ne Laser. The phantom tissue is composed of 8% scattering polystyrene spheres and is diluted to different concentrations in water. The solution is placed inside of a cuvette of length 5 cm and width 5 cm. The spatial filter, composed of a 4-cm plano-convex lens and a 10-micrometers pinhole, is able to extract ballistic and quasi-ballistic photons from the transmitted light. A photomultiplier tube is used for detection, and a lock-in amplifier is used to reduce the amount of noise in the signal. We are able to detect the object in a phantom tissue of 20 mean free paths [mfp] with a contrast of 99.0%. The contrast in a tissue with 30 mfp is 22.7%.

Images of objects hidden behind random intralipid media were greatly improved using a Fourier spatial filter system and NIR laser wavelengths of 670 nm, 830 nm, and 1300 nm in the therapeutic window. It was found that the decrease in scattering and the increase in absorption at longer wavelengths also improve the image quality and contrast.

A mathematical model is proposed describing time-resolved output measurements obtained on the surface of a diffusely scattering body due to an input pulse of near-IR light at a different location also on the surface. Such measurements can be obtained using a pulsed near-IR laser coupled with a CCD streak camera. The scattering body is assumed to exhibit homogenous scattering and spatially varying absorption. Using this model, an iterative algorithm is derived using maximum likelihood methods that allows the reconstruction of the spatial absorption pattern from a set of time-resolved tomographic measurements. The methodology places no restrictions upon the time-of-arrival of the detected photons, thus permitting the entire time-resolved signal to be used in the reconstruction process. The reconstruction algorithm is easily initialized and preliminary results indicate that stable reconstructions can be performed.

This article proposes a new approach to the `forward problem' by directly solving the radiative transport equation. A new phase function introduced by the authors' previous work has been used in the new approach in a simplified form. A function modeling the spatial, directional and temporal distributions of the incident laser pulse is proposed. For every small time increment, analytical approximation solutions to the time-dependent radiative transport equation are formulated. Preliminary results of computer simulation of the approach are provided.

We describe a new optical low-coherence reflectometer (interferometer) for depth profiling and lateral scanning without moving parts which can also be employed as a stationary FT-IR spectrometer. The reflectometer covers a range of 0.45 mm and 1 mm in the depth and lateral dimensions, respectively. The entire depth range is recorded simultaneously in one scan using a cooled 16-bit CCD camera; the lateral dimension is covered by scanning the probe beam sequentially across the sample with an acousto- optic deflector. The frequency shift generated by this deflector and an additional one placed in the reference arm creates an AC heterodyne signal with a frequency of 2kHz. Since the CCD camera cannot record the AC signal directly, a special readout scheme is employed. Stationary imaging was demonstrated using an artificial phantom. Using the same interferometer configured as a stationary FT-IR spectrometer, we measured the emission spectrum of a LED with a resolution of 0.74 nm at a central wavelength of 820 nm. We discuss the performance of the stationary CCD imaging system and compare it to that of a single-detector system employing moving parts.

In this paper we compare the performance of confocal and optical- coherence (OC) microscopes designed for imaging structures in a dense biological tissue, like skin, to depths greater than several hundred micrometers. Simple theoretical models, supplemented by Monte-Carlo simulations, are developed for evaluating the optical-sectioning capabilities of the two types of microscopes. The OC microscope is shown to exhibit superior rejection of undesired scattered light when the available angular field of view is restricted. Results of experimental studies with tissue phantoms show a progressive degradation with optical depth in the contrast of objects viewed by a confocal microscope compared to that achieved with the heterodyne technique. We conclude by making a few observations and generalizations regarding the suitability of OC and confocal techniques for potential in-vivo applications.

Laser Raman scattering has been used to monitor glucose and lactate metabolites within aqueous humor specimens obtained from nine human eyes during cataract surgery. Nine postmortem rabbit eyes were also investigated. Raman measurements were obtained using a single grating Raman spectrometer with a liquid nitrogen cooled CCD. A 514.5 nm line from an argon laser was used to illuminate capillaries containing several microliters of aqueous humor. A water background was subtracted from each of the aqueous humor Raman spectra. This experimental system was calibrated so that each metabolite in water could be measured down to 0.1 weight percent. Raman peaks indicative of the stretching vibrations of methylene and methyl groups associated with glucose and lactate, respectively, were observed in the human specimens. A second stretching mode characteristic of lactate between the carbon atom and either the carboxylic acid group or carboxylate ion group was also observed providing a distinguishing feature between the glucose and lactate Raman peaks. Similar structure was observed from the rabbit specimens, but these samples have recently been found to have been contaminated during euthanasia.

The potential of a rapid noninvasive diagnostic system to detect tissue abnormalities on the surface of the eye has been investigated. The optical scatter signal from lesions and normal areas on the conjunctival sclera of the human eye were measured in vivo. It is possible to distinguish nonpigmented pingueculas from other lesions. The ability of the system to detect malignancies could not be tested because none of the measured and biopsied lesions were malignant. Optical scatter and fluorescence spectra of bacterial and fungal suspensions, and corneal irritations were also collected. Both scattering and fluorescence show potential for diagnosing corneal infections.

Numerical solutions to the diffusion equation describing light propagation in tissues are presented. The results show that time- dependent measurements of light propagation can be used to monitor the fluorescent lifetimes of a fluorophore uniformly distrusted in tissues. With proper referencing, frequency-domain measurements of phase-shift, (Theta) , may allow quantitation of fluorescent lifetimes, (tau) , independent of changes in the local absorption and scattering properties. These results point to a new approach for noninvasive diagnostic monitoring through quantitation of fluorescent lifetimes, (tau) .

Light spectroscopy in the frequency-domain has been used to study the optical properties of biological tissues. We have analyzed the possibility of using LEDs as intensity modulated light sources for frequency-domain spectroscopy. The use of LEDs presents several advantages: one LED's output covers a spectral region of about 80 nm, and commercially available LEDs allow for the coverage of the spectral range from 550 to 900 nm, which is a region of interest in near-IR medical applications; the light output of an LED is stable with respect to that of lasers and lamps; the wide angular distribution make LEDs safe for in vivo studies. Furthermore, LED frequency-domain spectroscopy is a relatively inexpensive technique. We describe some circuits we used to modulate the intensity of LEDs at radio frequency, and point out the possibility of building a multisource spectrometer. Some applications of LED frequency-domain spectroscopy, both in vitro and in vivo, are shown.

As a new treatment model for endometriosis, photodynamic therapy (PDT) was applied to endometrium cultures. Endometriosis is a benign disease. Therefore primary cultures were used instead of cell lines. Endometrium is composed of epithelial and stromal cells which can also be found in primary culture. While stromal cells take a polygonal shape in culture, epithelial cells form cell colonies. PSIII (Photasan III), which is similar to hematorporphyrin derivate (HpD), meso-tetra (4-sulfonatophenyl) porphyrin (TPPS₄), which posses a high fluorescence quantum yield and may be useful in fluorescence diagnosis of subtle endometriotic spots, and methylene blue (MB), a vital dye with phototoxic properties, were used as photosensitizers. Different sensitizer concentrations and incubation times were applied. The highest phototoxicity was observed for PSIII; TPPS₄ and MB were less phototoxic. We compared our results with the sensitivity of cell lines described in the literature. The necessary irradiation to destroy stromal cells was relatively high but still in the same dimension as for cell lines. However they were even more sensitive than epithelial cells. This was true for all sensitizers used.

A study in order to investigate the uptake of porphyrins in neoplasias in the female breast tissue and to evaluate the potential of fluorescence diagnostics for tumor demarcation was performed. Six women with positive mammography and cytological biopsies took part in the study. The patients were given Photofrin intravenously in a low dose of 0.35 mg/kg b.w. 24 hours before the planned surgical procedure. Immediately after surgery the pathological specimen were investigated with fluorescence spectroscopy following 405 nm laser excitation. Afterwards the investigated tissue sample was taken for histological preparation. The spectroscopic results were correlated with the histopathological diagnoses. The study shows a good demarcation between invasive or in situ cancerous tissue and the surrounding breast tissue, based on fluorescence data.

The intrinsic NADH autofluorescence intensity of biological tissue depends on the local, cellular concentration of this coenzyme. It plays a dominant role in the Krebs-Cycle and therefore serves as indicator for the vitality of the observed cells. Due to individually and locally varying boundary conditions and optical tissue properties, which are scattering coefficients, absorption coefficients and g-factors the fluorescence signal needs to be rescaled. One possible rescaling method is the theoretical derived Photon Migration Theory. Our new rescaling method is partly based on measurements and partly theoretical derived. By using the 4 information channels: LIF time-resolved signal, biochemical concentration measurements, Monte Carlo simulations with optical parameters and microscopic investigations we demonstrate that simultaneous detection of the fluorescence and the backscattering signal can easily and accurately provide rescaled, quantitative values for the NADH concentrations.