Showing papers in "Journal of Biomedical Optics in 1999"

Ratio-based decisions and the quantitative analysis of cDNA micro-array images

Abstract: Gene expression can be quantitatively analyzed by hybridizing fluor-tagged mRNA to targets on a cDNA micro-array. Comparison of gene expression levels arising from co-hybridized samples is achieved by taking ratios of average expression levels for individual genes. In an image-processing phase, a method of image segmentation identifies cDNA target sites in a cDNA micro-array image. The resulting cDNA target sites are analyzed based on a hypothesis test and confidence interval to quantify the significance of observed differences in expression ratios. In particular, the probability density of the ratio and the maximum-likelihood estimator for the distribution are derived, and an iterative procedure for signal calibration is developed.

Speckle in Optical Coherence Tomography

Abstract: Speckle arises as a natural consequence of the limited spatial-frequency bandwidth of the interference signals measured in optical coherence tomography (OCT). In images of highly scattering biological tissues, speckle has a dual role as a source of noise and as a carrier of information about tissue microstructure. The first half of this paper provides an overview of the origin, statistical properties, and classification of speckle in OCT. The concepts of signal-carrying and signal-degrading speckle are defined in terms of the phase and amplitude disturbances of the sample beam. In the remaining half of the paper, four speckle-reduction methods-polarization diversity, spatial compounding, frequency compounding, and digital signal processing-are discussed and the potential effectiveness of each method is analyzed briefly with the aid of examples. Finally, remaining problems that merit further research are suggested. © 1999 Society of Photo-Optical Instrumentation Engineers.

Optical Properties of Circulating Human Blood in the Wavelength Range 400-2500 nm.

Abstract: Knowledge about the optical properties μa,μs, and g of human blood plays an important role for many diagnostic and therapeutic applications in laser medicine and medical diagnostics. They strongly depend on physiological parameters such as oxygen saturation, osmolarity, flow conditions, haematocrit, etc. The integrating sphere technique and inverse Monte Carlo simulations were applied to measure μa,μs, and g of circulating human blood. At 633 nm the optical properties of human blood with a haematocrit of 10% and an oxygen saturation of 98% were found to be 0.210±0.002 mm-1 for μa,77.3±0.5 mm-1 for μs, and 0.994±0.001 for the g factor. An increase of the haematocrit up to 50% lead to a linear increase of absorption and reduced scattering. Variations in osmolarity and wall shear rate led to changes of all three parameters while variations in the oxygen saturation only led to a significant change of the absorption coefficient. A spectrum of all three parameters was measured in the wavelength range 400-2500 nm for oxygenated and deoxygenated blood, showing that blood absorption followed the absorption behavior of haemoglobin and water. The scattering coefficient decreased for wavelengths above 500 nm with approximately λ-1.7; the g factor was higher than 0.9 over the whole wavelength range. © 1999 Society of Photo-Optical Instrumentation Engineers.

Capillary Blood Flow Monitoring Using Laser Speckle Contrast Analysis (LASCA)

Abstract: Coherent light scattered from an ensemble of moving scatterers produces a time-varying speckle pattern. The intensity fluctuations observed in a single speckle can be regarded either as a time-varying interference effect or as a Doppler beating effect. Techniques based on each of these approaches have been developed to analyze the fluctuations in an attempt to measure the velocities of the scatterers. Most of these methods measure the temporal statistics of the intensity fluctuations in a single speckle, i.e., at a single point. If a map of the velocity distribution is required, some form of scanning must be introduced. One way of avoiding the need to scan is to make use of the spatial statistics of time-integrated speckle. This is the basis of a technique, already described in the literature, called laser speckle contrast analysis (LASCA). In this article, we present a brief review of the theory linking the intensity fluctuations to the velocity and of the various techniques that have been proposed to measure them. We then describe the present configuration of our LASCA technique and describe some recent developments in our search for a real-time, noninvasive, full-field technique for visualizing capillary blood flow. © 1999 Society of Photo-Optical Instrumentation Engineers.

Dispersion effects in partial coherence interferometry: implications for intraocular ranging

Abstract: In nondispersive media, the minimum distance that can be resolved by partial coherence interferometry (PCI) and optical coherence tomography (OCT) is inversely proportional to the source spectral bandwidth. Dispersion tends to increase the signal width and to degrade the resolution. We analyze the situation for PCI ranging and OCT imaging of ocular structures. It can be shown that for each ocular segment an optimum source bandwidth yielding optimum resolution exists. If the resolution is to be improved beyond this point, the group dispersion of the ocular media has to be compensated. With the use of a dispersion compensating element, and employing a broadband superluminescent diode, we demonstrate a resolution of 5 μm in the retina of both a model eye and a human eye in vivo. This is an improvement by a factor of 2-3 as compared to currently used instruments. © 1999 Society of Photo-Optical Instrumentation Engineers.

Higher-Order Brain Function Analysis by Trans-Cranial Dynamic Near-Infrared Spectroscopy Imaging

Abstract: Near-infrared spectroscopy is discussed from the viewpoint of human higher-order brain function analysis. Pioneering work in this field is reviewed; then we describe our concept of noninvasive trans-cranial dynamic optical topography and its instrumentation. Also, the validity of its functional images is assessed from both physical and physiological viewpoints. After confirming the validity of this method, we have applied it to a wide variety of fields such as clinical medicine, cognitive science, and linguistics in collaboration with researchers at several other institutes. Further application possibilities and the future of trans-cranial dynamic optical topography are also discussed. © 1999 Society of Photo-Optical Instrumentation Engineers.

Coherent optical techniques for the analysis of tissue structure and dynamics.

Abstract: This paper summarizes the description of the speckle-correlation, speckle-interferometric, and polarimetric methods and instruments designed for various tissue structure imaging and their optical and dynamical parameter monitoring. © 1999 Society of Photo-Optical Instrumentation Engineers. [S1083-3668(99)01201-0]

Phase-Domain Processing of Optical Coherence Tomography Images

Abstract: In optical coherence tomography (OCT), images are usually formed from the envelope of the measured interference signal. Computation of the absolute magnitude of the signal for measurement of the envelope is a nonlinear process that destroys phase information. This study explores the idea of recording and processing the phase of the OCT interference signal before calculation of the magnitudes for display. Processing the partially coherent OCT signals in the complex domain provides the opportunity to correct phase aberrations responsible for speckle noise in OCT images. We describe an OCT system that incorporates a quadraturedemodulation scheme for accurate recording of the phase and amplitude of OCT signals from single or multiple detectors. A speckle-reduction technique that works in the complex domain, called the zeroadjustment procedure (ZAP), is investigated as an example of complex-domain processing. After demonstrating its speckle-correction properties mathematically and in numerical simulations, we apply ZAP to OCT images of living skin. The results show that ZAP reduces speckle contrast in regions where scatterer density is high and expands the range of gray values in the image. However, as presently implemented, ZAP tends to blur sharp boundaries between image features. © 1999 Society of Photo-Optical Instrumentation Engineers. [S1083-3668(99)01501-4]

Infrared spectroscopy, microscopy, and microscopic imaging of mineralizing tissues: spectra-structure correlations from human iliac crest biopsies.

Abstract: Infrared microscopic images of the cortical region of human iliac crest biopsies have been obtained at ;7 mm spatial resolution and 8 cm ˛1 spectral resolution with a 64364 mercury‐cadmium‐telluride focal plane array detector coupled to a Fourier transform infrared microscope and a step scanning interferometer. Images of several spectral parameters provide information about the spatial distribution of the mineral (apatite) and protein (mostly collagen) components of the tissue. In addition, the image of a parameter known to reflect the crystallinity/perfection of the mineral phase, namely, the intensity ratio of bands at 1030 and 1020 cm ˛1 within the phosphate n 1 ,n 3 contour, revealed a progressive increase in the apatite crystal size/perfection from the osteonal center to the periphery. Finally, a detailed comparison of the spatial distribution of the I(1020)/I(1030) ratio for the same osteon obtained by array detection and by conventional point-by-point microspectroscopy revealed statistically identical behavior, thereby providing a validation of infrared imaging for structural analysis of apatite forming tissues. © 1999 Society of Photo-Optical Instrumentation Engineers. [S1083-3668(99)00101-X]

Influence of the scattering phase function approximation on the optical properties of blood determined from the integrating sphere measurements

Abstract: We investigated the impact of the scattering phase function approximation on the optical properties of whole human blood determined from integrating sphere measurements using an inverse Monte Carlo technique. The diffuse reflectance R d and the total transmittance T t (l5633 nm) of whole blood samples (Hct538%) were measured with double-integrating sphere equipment. The scattering phase functions of highly diluted blood samples (Hct50.1%) were measured using a goniophotometer. We approximated the experimentally determined scattering phase functions with either Henyey‐Greenstein (HGPF), Gegenbauer kernel (GKPF), or

Comparison of optical coherence tomography imaging of cataracts with histopathology.

Abstract: This paper presents a comparison of in vivo optical coherence tomography (OCT) captured cataract images to subsequent histopathological examination of the lenticular opacities. OCT imaging was performed on anesthetized Rhesus monkeys, known as the delayed effects colony (DEC), with documented cataracts. These monkeys were exposed to several types of radiation during the mid and late 1960s. The radiation and age related cataracts in these animals were closely monitored using a unique grading system developed specifically for the DEC. In addition to this system, a modified version of a common cataract grading scheme for use in humans was applied. Of the original 18 monkeys imaged, lenses were collected at necropsy from seven of these animals, processed, and compared to OCT images. Results showed a direct correlation between the vertical OCT images and the cataractous lesions seen on corresponding histopathologic sections of the lenses. Based on the images obtained and their corresponding documented comparison to histopathology, OCT showed tremendous potential to aid identification and characterization of cataracts. There can be artifactual problems with the images related to movement and shadows produced by opacities. However, with the advent of increased speed in imaging and multiplanar imaging, these disadvantages may easily be overcome. © 1999 Society of Photo-Optical Instrumentation Engineers.

Spatial distribution of phosphate species in mature and newly generated mammalian bone by hyperspectral Raman imaging

Abstract: Hyperspectral Raman images of mineral components of trabecular and cortical bone at 3 μm spatial resolution are presented. Contrast is generated from Raman spectra acquired over the 600-1400 cm-1 Raman shift range. Factor analysis on the ensemble of Raman spectra is used to generate descriptors of mineral components. In trabecular bone independent phosphate (PO4-3) and monohydrogen phosphate (HPO4-2) factors are observed. Phosphate and monohydrogen phosphate gradients extend from trabecular packets into the interior of a rod. The gradients are sharply defined in newly regenerated bone. There, HPO4-2 content maximizes near a trabecular packet and decreases to a minimum value over as little as a 20 μm distance. Incomplete mineralization is clearly visible. In cortical bone, factor analysis yields only a single mineral factor containing both PO4-3 and HPO4-2 signatures and this implies uniform distribution of these ions in the region imaged. Uniform PO4-3 and HPO4-2 distribution is verified by spectral band integration. © 1999 Society of Photo-Optical Instrumentation Engineers.

Discovery of the near-infrared window into the body and the early development of near-infrared spectroscopy

Abstract: Extension of optical monitoring of intact tissues from the visible and ultraviolet to the near-infrared (NIR) range (700‐1300 nm) was first undertaken in 1977 for the purpose of monitoring the redox behavior of Cytochrome c oxidase ( cyt co x) in vivo. Soon it became evident that the much greater NIR translucency of skin and bone made it possible to reach brain and muscle tissue without surgical intervention. The presence of hemoglobin absorption led to complications forcing the construction of algorithms to separate the signals of the two molecular entities. It was also realized, however, that the hemoglobin signals provide information regarding the source of oxygen in the tissue, while the cyt co xsignals indicate the intracellular availability of oxygen for oxidative phosphorylation. This ability of recognizing the source/sink relationship greatly enhances the value of NIR spectrophotometry (NIRS) for research and clinical purposes. © 1999 Society of PhotoOptical Instrumentation Engineers. [S1083-3668(99)01404-5]

Aggregation and disaggregation of erythrocytes in whole blood: study by backscattering technique

Abstract: The aggregation phenomenon is of great importance for the evaluation of performance of the microcirculation system because of its influence on the blood viscosity at low shear stresses. Some important features and consequences of this phenomenon in vivo can be predicted in the in vitro experiments using optical methods. These methods are considered to be the most informative and applicable not only for the basic study of the aggregation phenomenon, but also for the diagnosis of a number of diseases and for the monitoring of therapeutic treatment in clinics. Results presented in this paper prove that the backscattering technique allows one to detect different changes of aggregational ability and deformability of erythrocytes and to get reliable and reproducible results distinguishing normal blood and blood with different pathologies. © 1999 Society of Photo-Optical Instrumentation Engineers.

Effect of pulse shape on the efficiency of multiphoton processes: implications for biological microscopy.

Abstract: The effects of spectral shape on two photon fluorescence excitation are investigated experimentally using an acousto-optic pulse shaper to modify femtosecond pulses from a Ti:sapphire laser. By using different spectral window shapes, we find that the measured two photon efficiency can vary by a factor of 2 for differently shaped spectra with the same full width at half maximum. We find that these effects are described well by a simple model assuming transform-limited pulses. The fact that even small changes in the spectral wings can significantly affect the efficiency of nonlinear processes has implications for biological multiphoton imaging, where it may be desirable to minimize sample exposure to radiation and maximize fluorescence or harmonic efficiency. © 1999 Society of Photo-Optical Instrumentation Engineers.

Compact laser Doppler choroidal flowmeter.

Abstract: A compact instrument is described that allows the measurement of the laser Doppler flow parameters, i.e., the velocity, the volume, and flow of blood in the foveal region of the human choroidal vascular system. This new device uses the optical principle of confocality for the delivery of the laser light to the site of measurement and heterodyne detection of the Doppler frequency shifted scattered light. Power of the incident light (785 nm) at the cornea is 90 mW. Measurements were obtained in both eyes of a group of 21 normal volunteers without pupil dilatation. We determined the intrasubject reproducibility and the minimum statistically significant detectable changes in the flow parameters for a group of 21 eyes (one in each subject). Linear correlations were also established between the flow parameters in the right and left eyes. © 1999 Society of Photo-Optical Instrumentation Engineers. [S1083-3668(99)00704-2]

Measurement system for noninvasive dynamic optical topography.

Abstract: We have developed a 24-channel simultaneous measurement system for optical topography that noninvasively obtains dynamic images of brain activity using near-infrared light. To evaluate the system performance, we utilized a dynamic phantom containing a rotating absorber in a cylindrical scattering medium. In this system, eight incident and eight detecting optical fibers are arranged alternately at square lattice points on the phantom. The phantom is illuminated with light of two wavelengths (780 and 830 nm) from each incident fiber. Reflected light is received by the detecting fibers, each of which is connected to an avalanche photodiode. Multiple light intensity modulation and lock-in detection are used to enable highly sensitive measurement with negligible cross talk for multichannel measurement. In the phantom measurement, we obtained topographic dynamic images of the absorber rotating in the medium with a temporal resolution of 0.5 s over a measurement area of 90 mm×90 mm. © 1999 Society of Photo-Optical Instrumentation Engineers.

Visible-near infrared multispectral imaging of the rat dorsal skin flap.

Abstract: Visible-near infrared multispectral reflectance image sets were acquired from the dorsal surface of rats both before and after elevation of reversed McFarlane skin flaps. Raw images were dominated by uneven surface illumination and shadowing along with the variation associated with instrument response. These interfering features obscured variation associated with a change in tissue reflectance, which is related to the degree of flap perfusion. Logarithmic residual preprocessing followed by principal component analysis of multispectral images could clearly detect a difference in the optical properties between the base and distal section of the flap. The difference in the reflectance properties correlates with the varying degree of tissue perfusion. Principal component analysis detected this optical difference between the well-perfused base of the skin flap and the compromised distal section of the flap immediately following surgery. The first visual signs of compromised tissue perfusion appeared only 6 or more hours after surgery. The results from this study indicate that the application of principal component analysis to discrete wavelength near infrared multispectral reflectance images of skin flaps can effectively distinguish reflectance changes related to the degree of tissue perfusion immediately following surgical elevation of the reversed McFarlane skin flap. © 1999 Society of Photo-Optical Instrumentation Engineers.

Fiber optic sensor for the measurement of respiratory chest circumference changes.

Abstract: 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. © 1999 Society of Photo-Optical Instrumentation Engineers.

Coherent Optical Techniques for Diagnostics of Retinal Blood Flow

Abstract: Up to now, a variety of coherent optical techniques have been proposed and extensively studied for diagnostics of the retinal blood flow. These techniques are mainly based on dynamic laser light-scattering phenomena such as the laser Doppler effect and the laser speckle fluctuation. This paper reviews, first, spectral reflectance properties of the ocular fundus tissue layers and, then, principles of the techniques with the comparison of the Doppler and the speckle methods. Some physical phenomena are also discussed in the origin of the techniques such as heterodyne and homodyne beatings, and time-varying speckles. Developing processes of each technique are briefly outlined. Peculiarities of blood flow measurements at the retina are finally examined from the methodological point of view. © 1999 Society of Photo-Optical Instrumentation Engineers.

Panoramic optical imaging of electrical propagation in isolated heart

Abstract: 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 128×64 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. © 1999 Society of Photo-Optical Instrumentation Engineers.

Tetrapyrrolic glycosylated macrocycles for an application in pdt

Abstract: The synthesis and characterization of amphiphilic glycoconjugated porphyrins, benzochlorin, and azaporphyrins were reported Among these molecules, several were found to be efficient photosensitizers in an in vitro assay using the human tumoral cell line HT29 Moreover, glycosylated benzochlorin and azaporphyrins, whose absorption bands in the red region of the visible spectrum are substantially increased as compared to porphyrins, display a good photocytotoxicity on tumor cells after irradiation with wavelength above 590 nm © 1999 Society of Photo-Optical Instrumentation Engineers [S1083-3668(99)00703-0]

Inverse Problems of Spectroturbidimetry of Biological Disperse Systems: An Overview

Abstract: The obtainment of stable solutions of inverse problems for studying the disperse composition of suspensions using effects of elastic light scattering was discussed. Versions of a regularization of solving the inverse problems of the spectroturbidimetric method were considered, taking into account unavoidable restrictions on the scope of the necessary prior data for particles and on the width of the spectral interval for real biological disperse systems. Possibilities for increasing the number of particle parameters determined in a single optical experiment were analyzed. They were shown to be provided by the use of effects of the orientation ordering of a system on combination of capabilities of the methods of spectroturbidimetry and electro-optics, using bacterial cell suspensions as an example. © 1999 Society of Photo-Optical Instrumentation Engineers.

Infrared Spectroscopic Imaging of the Biochemical Modifications Induced in the Cerebellum of the Niemann-Pick type C Mouse.

Abstract: We have applied Fourier transform infrared (IR) spectroscopic imaging to the investigation of the neuropathologic effects of a genetic lipid storage disease, Niemann-Pick type C (NPC). Tissue sections both from the cerebella of a strain of BALB/c mice that demonstrated morphology and pathology of the human disease and from control animals were used. These samples were analyzed by standard histopathological procedures as well as this new IR imaging approach. The IR absorbance images exhibit contrast based on biochemical variations and allow for the identification of the cellular layers within the tissue samples. Furthermore, these images provide a qualitative description of the localized biochemical differences existing between the diseased and control tissue in the absence of histological staining. Statistical analyses of the IR spectra extracted from individual cell layers of the imaging data sets provide concise quantitative descriptions of these biochemical changes. The results indicate that lipid is depleted specifically in the white matter of the NPC mouse in comparison to the control samples. Minor differences were noted for the granular layers, but no significant differences were observed in the molecular layers of the cerebellar tissue. These changes are consistent with significant demyelination within the cerebellum of the NPC mouse. © 1999 Society of Photo-Optical Instrumentation Engineers.

In situ monitoring of laser modification process in human cataractous lens and porcine cornea using coherence tomography

Abstract: We demonstrate that optical coherence tomography (OCT) is a convenient diagnostic tool to monitor pulse-to-pulse kinetics in laser interactions with biological tissue. In experiments on laser modification and ablation of the cataractous human lens and the porcine cornea we have applied this technique in situ to investigate different modes of preablation tissue swelling, crater formation and thermally affected zone development. The cataractous lens is an example of highly scattering media whereas the cornea is initially low scattering. The radiation with different wavelengths has been employed including that of a YAG:Er laser (λ=2.94 μm), a glass:Er laser (λ=1.54 μm), YAG:Nd lasers (λ=1.32 μm and λ=1.44 μm), as well as of the fifth harmonic of a Nd:YAP laser (λ=0.216 μm). Pulse-to-pulse OCT monitoring has been accompanied by the probe beam shielding diagnostics to provide the time-resolved observation of the interaction dynamics. © 1999 Society of Photo-Optical Instrumentation Engineers.

Precision and reproducibility of measurements of human corneal thickness with rapid optical low-coherence reflectometry (OLCR)

Abstract: Reference LOA-ARTICLE-1999-002doi:10.1117/1.429901View record in Web of Science Record created on 2009-01-20, modified on 2017-05-10

Application of Twyman–Green Interferometer for Evaluation of In Vivo Breakup Characteristic of the Human Tear Film

Abstract: The paper presents an interferometric method of assessing the in vivo stability of the precorneal tear film. To observe dynamic effects on a human cornea the Twyman‐Green interferometer with television frame speed digital registration synchronized with a laser flash was used. The instrument was applied to the human cornea in vivo. The results of the experiment, both tear film distribution and its dynamics, are presented. The proposed interferometric setup can be used to evaluate the breakup characteristics of the tear film, its distribution, and to examine its dynamic changes. The breakup profiles and their cross sections calculated from the interferogram analysis are presented. The depth of recorded breakup, calculated on the basis of interferogram analysis, amounts to about 1.5 mm. The proposed method has the advantage of being noncontact and applies only a low-energy laser beam to the eye. This provides noninvasive viewing of human cornea in vivo and makes it possible to observe the kinetics of its tear film deterioration. © 1999 Society of Photo-Optical Instrumentation Engineers. [S1083-3668(99)01601-9]

Early development of optical low-coherence reflectometry and some recent biomedical applications.

Abstract: This paper explains the term low-coherence interferometry, reviews the early development of optical lowcoherence 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. © 1999 Society of PhotoOptical Instrumentation Engineers. [S1083-3668(99)00602-4]

Naphthalocyanine complexes as potential photosensitizers for photodynamic therapy of tumors

Abstract: In the present paper information about the synthesis and results on the pharmacokinetic and experimental photodynamic therapy (PDT) of naphthalocyanines are given. The photodynamic activity of differently substituted zinc(II)- and silicon(IV)-naphthalocyanines using liposomes or Cremophor EL as drug-delivery systems is shown on different tumor models. For the evaluation of the phototherapeutic effect different assessment criteria were used, including light and electron microscopy observations. The main conclusions which can be arrived at on the basis of our findings are the following: silicon(IV)-naphthalocyanine seems to be not a very effective tumor sensitizer, especially in the treatment of pigmented melanoma, while zinc(II)naphthalocyanines appear to be very promising for PDT of tumors. Their selective targeting and slow clearance from tumor tissue, fast clearance from skin and pronounced phototherapeutic effect on different tumor models and especially at melanotic tumors, even after application of low drug doses, make this group of photosensitizers very attractive for successful PDT of cancer. © 1999 Society of Photo-Optical Instrumentation Engineers. [S1083-3668(99)01203-4]

Spectroscopic and Morphologic Characterization of the Dentin/ Adhesive Interface

Abstract: The potential environmental risks associated with mercury release have forced many European countries to ban the use of dental amalgam. Alternative materials such as composite resins do not provide the clinical function for the length of time characteristically associated with dental amalgam. The weak link in the composite restoration is the dentin/adhesive bond. The purpose of this study was to correlate morphologic characterization of the dentin/adhesive bond with chemical analyses using micro-Fourier transform infrared and micro-Raman spectroscopy. A commercial dental adhesive was placed on dentin substrates cut from extracted, unerupted human third molars. Sections of the dentin/adhesive interface were investigated using infrared radiation produced at the Aladdin synchrotron source; visible radiation from a Kr + laser was used for the micro-Raman spectroscopy. Sections of the dentin/adhesive interface, differentially stained to identify protein, mineral, and adhesive, were examined using light microscopy. Due to its limited spatial resolution and the unknown sample thickness the infrared results cannot be used quantitatively in determining the extent of diffusion. The results from the micro-Raman spectroscopy and light microscopy indicate exposed protein at the dentin/adhesive interface. Using a laser that reduces background fluorescence, the microRaman spectroscopy provides quantitative chemical and morphologic information on the dentin/adhesive interface. The staining procedure is sensitive to sites of pure protein and thus, complements the Raman results. © 1999 Society of Photo-Optical Instrumentation Engineers. [S1083-3668(99)00201-4]