Showing papers in "Journal of Biomedical Optics in 2004"
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TL;DR: The results of clinical tests in colonoscopy and esophagoscopy indicated that NBI will be useful as a supporting method for observation of the endoscopic findings of early cancer.
Abstract: This study was performed to examine the usefulness of medical endoscopic imaging utilizing narrow-band illumination. The contrast between the vascular pattern and the adjacent mucosa of the underside of the human tongue was measured using five narrow-band illuminations and three broadband illuminations. The results demon- strate that the pathological features of a vascular pattern are depen- dent on the center wavelength and the bandwidth of illumination. By utilizing narrow-band illumination of 415630 nm, the contrast of the capillary pattern in the superficial layer was markedly improved. This is an important benefit that is difficult to obtain with ordinary broad- band illumination. The appearances of capillary patterns on color im- ages were evaluated for three sets of filters. The narrow, band imaging (NBI) filter set (415630 nm, 445630 nm, 500630 nm) was selected to achieve the preferred appearance of the vascular patterns for clini- cal tests. The results of clinical tests in colonoscopy and esophagos- copy indicated that NBI will be useful as a supporting method for observation of the endoscopic findings of early cancer. © 2004 Society of
858 citations
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TL;DR: The rapid development of ultrabroad bandwidth light sources has recently enabled a significant improvement in OCT imaging resolution, demonstrating the potential of OCT to accomplish its original goal of performing noninvasive optical biopsies, i.e., the in vivo visualization of microstructural morphology in situ, which had previously only been possible with histopathology.
Abstract: In the past two decades, optical coherence tomography (OCT) has been established as an adjunct diagnostic technique for noninvasive, high-resolution, cross-sectional imaging in a variety of medical fields. The rapid development of ultrabroad bandwidth light sources has recently enabled a significant improvement in OCT imaging resolution, demonstrating the potential of OCT to accomplish its original goal of performing noninvasive optical biopsies, i.e., the in vivo visualization of microstructural morphology in situ, which had previously only been possible with histopathology. In addition, these novel light sources might also enable the use of spectroscopic OCT, an extension of ultrahigh-resolution OCT, for enhancing image contrast as well as detecting spatially resolved functional, biochemical tissue information. State-of-the-art-light sources that now permit ultrahigh-resolution OCT covering the whole wavelength region from 500 to 1600 nm are reviewed and fundamental limitations of OCT image resolution are discussed. Ex vivo ultrahigh-resolution OCT tomograms are compared with histological results; first clinical in vivo ultrahigh-resolution OCT and preliminary spectroscopic OCT results are presented and their impact for future clinical and research applications is discussed.
701 citations
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TL;DR: Comparison of CLSM and OCT suggests that the same fibrous layer is imaged by the two techniques, and this layer might be due to the transition between the papillary and reticular dermis.
Abstract: Skin structure and age-related changes in human skin were characterized in vivo by applying confocal laser scanning microscopy (CLSM) and optical coherence tomography (OCT). The overall effect of aging skin, derived from studies of volunteers belonging to two age groups, was found to be a significant decrease in the maximum thickness of the epidermis and flattening of the dermo-epidermal junction. At a certain depth in the dermis, well below the basal layer, a reflecting layer of fibrous structure is observed in CLSM images. The location of this layer strongly depends on age and is situated much deeper below the skin surface in younger than in older skin. In addition, large structural changes were observed with age. The OCT images show two bright reflecting layers. The first one is due to scattering at the skin surface. The second band appears to be caused by a layer of fibrous structure in the dermis. Direct comparison of CLSM and OCT suggests that the same fibrous layer is imaged by the two techniques. This layer might be due to the transition between the papillary and reticular dermis. A comparison of CLSM and OCT enables a better understanding of the images.
260 citations
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TL;DR: In this paper, the angular compounding by path length encoding (ACPE) algorithm is proposed to reduce speckle in OCT images by averaging images obtained at different incident angles, with each image encoded by the path length.
Abstract: Speckle, a factor reducing image quality in optical coherence tomography ('OCT'), can limit the ability to identify cellular structures that are important for the diagnosis of a variety of diseases. The present invention allows for an implementation of an angular compounding, angular compounding by path length encoding ('ACPE') for reducing speckle in OCT images. By averaging images obtained at different incident angles, with each image encoded by path length, ACPE maintains high-speed image acquisition and implements minimal modifications to OCT probe optics. ACPE images obtained from tissue phantoms and human skin in vivo demonstrate a qualitative improvement over traditional OCT and an increased signal-to-noise ratio ('SNR'). Accordingly, apparatus probe catheter, and method are provided for irradiating a sample. In particular, an interferometer (5) may forward forwarding an electromagnetic radiation (10). In addition, a sample arm may receive the electromagnetic radiation, and can include an arrangement (20) which facilitates a production of at least two radiations (30, 40) from the electromagnetic radiation so as to irradiate the sample. Such arrangement can be configured to delay a first radiation of the at least two radiations with respect to a second radiation of the at least two radiations.
258 citations
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TL;DR: Examination of several tumors examined indicate that PS-OCT can identify features that distinguish normal skin from tumor and may have the potential to guide surgeons in the treatment of aggressive skin cancer.
Abstract: Skin cancer is the most common human malignancy, with basal cell carcinoma (BCC) the most frequent type. Aggressive forms of BCC are associated with extensive dermal invasion and destruction of collagen. Surgery is the most common treatment, but identification of tumor borders is a challenge. Polarization-sensitive optical coher- ence tomography (PS-OCT) is an optical method to examine collagen birefringence. To date, it has not been exploited for cancer manage- ment. As part of a pilot exploratory study to examine the use of OCT in skin cancer, we examined several tumors that pose a challenge to the surgeon due to their large size and histological subtype. In normal perilesional skin, OCT identifies epidermal and dermal structure; PS- OCT identified dermal birefringence. In BCC, tumors lost normal structure and gained the appearance of lobular impressions. PS-OCT identified an alteration of dermal birefringence. Examination of a bor- der area revealed a gradual transition from more normal appearing image to frank tumor. These results indicate that PS-OCT can identify features that distinguish normal skin from tumor and may have the potential to guide surgeons in the treatment of aggressive skin cancer.
239 citations
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TL;DR: P polarization-sensitive optical coherence tomography (OCT) images of human skin in vivo are presented, demonstrating the ability of the technique to visualize and quantify the birefringent properties of skin.
Abstract: Optical coherence tomography enables cross-sectional imaging of tissue structure to depths of around 1.5 mm, at high-resolution and in real time. Incorporation of polarization sensitivity (PS) provides an additional contrast mechanism which is complementary to images mapping backscattered intensity only. We present here polarization-sensitive optical coherence tomography (OCT) images of human skin in vivo, demonstrating the ability of the technique to visualize and quantify the birefringent properties of skin. Variation in normal skin birefringence according to anatomical location is demonstrated, and discussed in relation to collagen distribution at each location. From measurements on a sample of five human volunteers, mean double-pass phase retardation rates of 0.340+/-0.143, 0.250+/-0.076, and 0.592+/-0.142 deg/microm were obtained for the dorsal hand, temple, and lower back regions, respectively. We demonstrate how averaging the Stokes parameters of backscattered light over a range of axial and lateral dimensions results in a reduction of speckle-induced noise. Examples of PS-OCT images from skin sites following wound healing and repair are also presented and discussed.
235 citations
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TL;DR: Near-infrared imaging was used to quantify typical values of hemoglobin concentration, oxygen saturation, water fraction, scattering power, and scattering amplitude within the breast tissue of volunteer subjects, and it may be important to use hemoglobin contrast values relative to the background for a given breast, rather than absolute hemoglobin Contrast when trying to compare the features of breast lesions among subjects.
Abstract: Near-infrared imaging was used to quantify typical values of hemoglobin concentration, oxygen saturation, water fraction, scat- tering power, and scattering amplitude within the breast tissue of vol- unteer subjects. A systematic study of the menstrual variations in these parameters was carried out by measuring a group of seven premeno- pausal normal women (aged 41 to 47 years) in the follicular (days 7 to 14 of the cycle) and secretory phases (days 21 to 28) of the cycle, for two complete menstrual cycles. An average increase in hemoglobin concentration of 2.6 mM or 13% of the background breast values was observed in the secretory phase relative to the follicular phase (p ,0.0001), but no other average near-infrared parameter changes were significant. While repeatable and systematic changes were ob- served in all parameters for individual subjects, large intersubject variations were present in all parameters. In a survey of thirty-nine normal subjects, the total hemoglobin varied from 9 to 45 mM, with a systematic correlation observed between total hemoglobin concentra- tion and breast radiographic density. Scattering power and scattering amplitude were also correlated with radiographic density, but oxygen saturation and water fraction were not. Images of breast lesions indi- cate that total hemoglobin-based contrast can be up to 200% relative to the background in the same breast. Yet, since the background he- moglobin values vary considerably among breasts, the maximum he- moglobin concentrations observed in cancer tumors may vary consid- erably as well. In light of these observations, it may be important to use hemoglobin contrast values relative to the background for a given breast, rather than absolute hemoglobin contrast when trying to com- pare the features of breast lesions among subjects. © 2004 Society of Photo-
218 citations
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TL;DR: The data suggest that noninvasive, quantitative optical methods that characterize tumor physiology may be useful in assessing and optimizing individual response to neoadjuvant chemotherapy.
Abstract: Presurgical chemotherapy is widely used in the treatment of locally advanced breast cancer. Monitoring the response to therapy can improve survival and reduce morbidity. We employ a noninvasive, near-infrared method based on diffuse optical spectroscopy (DOS) to quantitatively monitor tumor response to neoadjuvant chemotherapy. DOS was used to monitor tumor response in one patient with locally advanced breast cancer throughout the course of her therapy. Measurements were performed prior to doxorubicin-cyclophosphamide therapy and at several time points over the course of three treatment cycles (68 days). Our results show strong tumor to normal (T/N) tissue contrast in total hemoglobin concentration (T/N=2.4), water fraction (T/N=6.9), tissue hemoglobin oxygen saturation, S(t)O(2) (T/N=0.9), and lipid fraction (T/N=0.7) prior to treatment. Over a 10-week period, the peak total hemoglobin and water dropped 56 and 67%, respectively. Lipid content nearly returned to baseline (T/N =0.9) while S(t)O(2) exceeded pretreatment levels (T/N =1.5). Approximately half of the hemoglobin and water changes occurred within 5 days of treatment (26 and 37%, respectively). These data suggest that noninvasive, quantitative optical methods that characterize tumor physiology may be useful in assessing and optimizing individual response to neoadjuvant chemotherapy.
210 citations
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TL;DR: It is found that as the optode distance increased, the absorption coefficients increased and the scattering coefficients decreased, retrieving the optical values of scalp and brain for shorter and longer optode distances, respectively.
Abstract: The basic parameters for physiological measurements provided by near-infrared spectroscopy are the local absorption and scattering coefficients. For the adult human head, they have been difficult to measure noninvasively because of the layered structure of the head. The results of measurements of absorption and reduced scattering coefficients through the forehead on 30 adult volunteers using a multidistance frequency domain method are reported. The optode separation distance ranged from 10 to 80 mm and measurements were recorded at 758 and 830 nm. The measured absorption and reduced scattering coefficients of the forehead were used to evaluate the hemoglobin content in the scalp and brain as well as cerebral oxygen saturation. We found that cerebral oxygenation was relatively narrowly distributed within the subject group (the standard deviation was about 3% for scalp and 6% for brain, respectively), whereas hemoglobin concentrations had a relatively broader distribution. We found that as the optode distance increased, the absorption coefficients increased and the scattering coefficients decreased, retrieving the optical values of scalp and brain for shorter and longer optode distances, respectively. We present the transition curves of the absorption and reduced scattering coefficients as functions of the optode distance. In order to verify the values for each layer, a comparison between the experimental data and a prediction based on the two-layer model of the adult head was carried out. The thicknesses of scalp and skull for the two-layer model were obtained by magnetic resonance imaging of a subject's head. The optical parameters obtained from the two-layer model agreed very well with those measured by the multidistance method.
205 citations
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TL;DR: Polarization-sensitive optical coherence tomography (PS-OCT) is a noninvasive technique with potential to give the physician the information needed to formulate an optimal treatment plan for burn patients.
Abstract: An assessment of burn depth is a key step in guiding the treatment of patients who have sustained thermal injuries. Polarization-sensitive optical coherence tomography (PS-OCT) might eventually provide the physician with a quantitative estimate of actual burn depth. Burns of various depths were induced by contacting rat skin with a brass rod preheated to 75 degrees C for 5, 15, or 30 s. Thermal injury denatured the collagen in the skin, and PS-OCT imaged the resulting reduction of birefringence through the depth-resolved changes in the polarization state of light propagated and reflected from the sample. Stokes vectors were calculated for each point in the PS-OCT images and the reduction in the rate of phase retardation between two orthogonal polarizations of light (deg/microm) was found to show a consistent trend with burn exposure time. PS-OCT is a noninvasive technique with potential to give the physician the information needed to formulate an optimal treatment plan for burn patients.
205 citations
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TL;DR: Knowing of the retardation and the slow axis distribution of the cornea might improve nerve fiber polarimetry for glaucoma diagnostics and could be useful for diagnosing different types of pathologies of the Cornea.
Abstract: Optical coherence tomography (OCT) is an emerging technology for high-resolution, noncontact imaging of transparent and scattering media. Polarization-sensitive optical coherence tomography (PS-OCT) is a functional extension of OCT that can image birefringent properties of a biological sample. PS-OCT was used to measure and image retardation and birefringent axis orientation of in vitro human cornea. We used a two-channel PS-OCT system employing a phase-sensitive recording of the interferometric signals in two orthogonal polarization channels. Using an algorithm based on a Hilbert transform, it is possible to calculate the retardation and the slow axis orientation of the sample with only a single A-scan per transversal measurement location. While the retardation information is encoded in the amplitude ratio of the two interferometric signals, the axis orientation is encoded entirely in their phase difference. We present maps of retardation and the distribution of slow axis orientation of the human cornea in longitudinal cross-sections and en face images obtained at the back surface of the cornea. The retardation increases in a radial direction and with depth; the slow axis varies in the transversal direction. Knowledge of the retardation and the slow axis distribution of the cornea might improve nerve fiber polarimetry for glaucoma diagnostics and could be useful for diagnosing different types of pathologies of the cornea.
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TL;DR: The ability to acquire these unique in vivo melanin signals suggests that Raman spectroscopy may be a useful clinical method for noninvasive in situ analysis and diagnosis of the skin.
Abstract: We successfully acquire the in vivo Raman spectrum of melanin from human skin using a rapid near-infrared (NIR) Raman spectrometer. The Raman signals of in vivo cutaneous melanin are similar to those observed from natural and synthetic eumelanins. The melanin Raman spectrum is dominated by two intense and broad peaks at about 1580 and 1380 cm ˛1 , which can be interpreted as originating from the in-plane stretching of the aromatic rings and the linear stretching of the C-C bonds within the rings, along with some contributions from the C-H vibrations in the methyl and methylene groups. Variations in the peak frequencies and bandwidths of these two Raman signals due to differing biological environments have been observed in melanin from different sources. The ability to ac- quire these unique in vivo melanin signals suggests that Raman spec- troscopy may be a useful clinical method for noninvasive in situ analysis and diagnosis of the skin. © 2004 Society of Photo-Optical Instrumenta-
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TL;DR: Digital image correlation (DIC) is a versatile optical method that shows tremendous promise for applications involving biological tissues and biomaterials and should serve as a valuable tool for biomedical research.
Abstract: Optical methods are becoming commonplace in investiga- tions of the physical and mechanical behavior of biological tissues. Digital image correlation (DIC) is a versatile optical method that shows tremendous promise for applications involving biological tis- sues and biomaterials. We present the fundamentals of DIC with an emphasis on the application to biological materials. An approach for surface preparation is described that facilitates its application to hy- drated substrates. Three examples are presented that highlight the use of DIC for biomedical research. The first example describes the use of DIC to study the mechanical behavior of arterial tissues up to 40% elongation. The second example describes an evaluation of the me- chanical properties of bovine hoof horn in the dehydrated and fully hydrated states. Uniaxial tension experiments are performed to deter- mine the elastic modulus (E) and Poisson's ratio (n) of both the arterial and dermal tissues. Spatial variations in the mechanical properties are evident from the full-field characterization of both tissues. Finally, an application of DIC to study the evolution of loosening in cemented total hip replacements is described. The noncontact analysis enables measurement of the relative displacement between the bone/bone ce- ment and bone cement/prosthesis interfaces. Based on the elementary optical arrangement, the simple surface preparation, and the ability to acquire displacement/strain measurements over a large range of de- formation, DIC should serve as a valuable tool for biomedical re- search. Further developments will enable the use of DIC for in vivo
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TL;DR: A fiber-based PS-OCT setup that produces real-time images of the human retina in vivo, coregistered with retinal video images of a healthy volunteer's location, shows that the nerve fiber layer located inferior and superior to the optic nerve head is more birefringent than the thinner layer of nerve fiber tissue in the temporal and nasal regions.
Abstract: Glaucoma causes damage of the nerve fiber layer, which may cause loss of retinal birefringence. Therefore, PS-OCT is a poten- tially useful technique for the early detection of glaucoma. We built a fiber-based PS-OCT setup that produces real-time images of the hu- man retina in vivo, coregistered with retinal video images of the lo- cation of PS-OCT scans. Preliminary measurements of a healthy vol- unteer show that the double-pass phase retardation per unit of depth of the RNFL is not constant and varies with location, with values between 0.18 and 0.37 deg/mm. A trend in the preliminary measure- ments shows that the nerve fiber layer located inferior and superior to the optic nerve head is more birefringent than the thinner layer of nerve fiber tissue in the temporal and nasal regions. © 2004 Society of Photo-Optical Instrumentation Engineers. (DOI: 10.1117/1.1627774)
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TL;DR: A laboratory version of a photoacoustic mammoscope, based on a parallel plate geometry, built around a flat high-density ultrasound detector matrix, is presented, and various recommendations that will guide the evolving of the prototype into a clinical version are discussed.
Abstract: We present a laboratory version of a photoacoustic mammoscope, based on a parallel plate geometry. The instrument is built around a flat high-density ultrasound detector matrix. The light source is a Q-switched Nd:YAG laser with a pulse duration of 5 ns. To test the instrument, a novel photoacoustic phantom is developed using poly(vinyl alcohol) gel, prepared by a simple procedure that imparts optical scattering suggestive of breast tissue to it without the requirement for extraneous scattering particles. Tumor simulating poly(vinyl alcohol) gel spheres appropriately dyed at the time of preparation are characterized for optical absorption coefficients. These are then embedded in the phantom to serve as tumors with absorption contrasts ranging from 2 to 7, with respect to the background. Photoacoustic studies in transmission mode are performed, by acquiring the laser-induced ultrasound signals from regions of interest in the phantom. Image reconstruction is based on a delay-and-sum beamforming algorithm. The results of these studies provide an insight into the capabilities of the prototype. Various recommendations that will guide the evolving of our laboratory prototype into a clinical version are also discussed.
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TL;DR: The results of a clinical study about optical properties and bulk composition of the female breast suggest that optical measurements on breasts can be exploited to obtain relevant information on breast tissue composition.
Abstract: We present the results of a clinical study about optical properties and bulk composition of the female breast. The clinical study involved more than 150 subjects that underwent optical mammography. A multiwavelength time-resolved mammograph designed to collect time-resolved transmittance images of the breast at different wavelengths in the range 637 to 980 nm is used to this purpose. From the absorption spectrum of the breast, the concentrations of the main tissue constituents, i.e., oxygenated and deoxygenated hemoglobin, lipid, and water, are obtained for a subset of 113 breasts. The lipid content of breast is estimated for the first time on such a large number of subjects. The total hemoglobin concentration, blood oxygen saturation, lipid, and water content of breast is correlated to demographic information collected during the trial. As expected, breast optical properties and components undergo huge variations among different subjects. Different constituents, however, show interesting correlation with clinical parameters such as age, breast size, body mass index, and mammographic parenchymal pattern. These results suggest that optical measurements on breasts can be exploited to obtain relevant information on breast tissue composition.
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TL;DR: An experimental setup for measurement of time-resolved autofluorescence of the human eye fundus is demonstrated, and diagrams of lifetime tau2 versus tau1 are well suited for comparison of substances.
Abstract: An experimental setup for measurement of time-resolved autofluorescence of the human eye fundus is demonstrated. The method combines laser scanning technique and time-correlated single photon counting. The light source is a laser diode, delivering pulses of about 100 ps duration at a repetition rate of 40 MHz. The excitation wavelength is 446 nm and the cutoff wavelength of fluorescence detection is at 475 nm. The autofluorescence can be determined with a spatial resolution of 80×80 µm2 and 25 ps time resolution. The fluorescence decay is optimally approximated by a biexponential model. The dominating lifetime 1 is shortest in the macula (320 to 380 ps) and reaches 1500 ps in the optic disk. The lifetime 2 varies between 2 ns and 5 ns, but the spatial distribution is more homogeneous. Respiration of 100% oxygen for 6 min leads to changes in the fluorescence lifetime pointing to detection of coenzymes. Diagrams of lifetime 2 versus 1 are well suited for comparison of substances. Such lifetime clusters of a 20 deg macular field of a young healthy subject and of a patient suffering from dry age-related macular degeneration overlap only partially with 2-1 clusters of lipofuscin.
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TL;DR: Results imply that the reticular dermis posses a tangled structure of collagen fibers, which is highly consistent with the result of the anatomical examination of the skin.
Abstract: We have proposed an optical probe that can be used to characterize the orientation of collagen fibers in human dermis. A specific probing ability for collagen results from the use of second- harmonic-generation (SHG) light induced by collagen molecules in the tissue. Based on the concept of collagen SHG light, a reflection- type polarization measurement system (named SHG polarimetry) with a probe light spot of 15 mm in diameter has been constructed, and the human reticular dermis has been measured using this system. Result- ant data exhibit that the reticular dermis possesses approximately uniaxial orientation of the collagen fibers. Furthermore, we demon- strated a nondestructive measurement of the collagen orientation in the papillary dermis across an epidermis layer. For distribution mea- surement of the collagen fiber orientation in the reticular dermis, we have extended the SHG polarimetry to one- (1-D) and two- dimensional (2-D) measurement. By the macroscopic 2-D SHG polar- imetry, we have observed that the orientation angle and organization degree of collagen fibers vary widely depending on the discrete prob- ing positions in the reticular dermis. Furthermore, microscopic 1-D SHG polarimetry indicated a swell of the orientation angle and a large variance of the organization degree in the collagen fibers in the mi- croscopic region. These results imply that the reticular dermis posses a tangled structure of collagen fibers, which is highly consistent with the result of the anatomical examination of the skin. The proposed method will be a powerful tool for monitoring the microscopic distri- bution of the collagen fiber orientation in the human dermis. © 2004
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TL;DR: A fast fluorescence lifetime imaging (FLIM) system is developed that can acquire images at a rate of hundreds of frames per second and its performance is evaluated in calcium imaging experiments on beating neonatal rat myocytes.
Abstract: A fast fluorescence lifetime imaging (FLIM) system is developed that can acquire images at a rate of hundreds of frames per second. The FLIM system is based on a wide-field microscope equipped with a time-gated intensified CCD detector and a pulsed laser. The time-gated detector acquires the signals from two time gates simultaneously and is therefore insensitive to movements of the specimen and photo-bleaching. The system is well suited for quantitative biological FLIM experiments and its performance is evaluated in calcium imaging experiments on beating neonatal rat myocytes. Several calcium sensitive dyes are characterized and tested for their suitability for fast FLIM experiments: Oregon Green Bapta-1 (OGB1), Oregon Green Bapta-2 (OGB2), and Oregon Green Bapta-5N (OGB5N). Overall the sensitivity range of these dyes is shifted to low calcium concentrations when used as lifetime dyes. OGB1 and OGB2 behave very similarly and can be used for FLIM-based calcium imaging in the range 1 to ~500 nM and OGB5N can be used up to 3 µM. The fast FLIM experiments on the myocytes could be carried out at a 100-Hz frame rate. During the beating of the myocytes a lifetime change of about 20% is observed. From the lifetime images a rest calcium level of about 65 nM is found.
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TL;DR: The complementary features of linear and nonlinear light-tissue interaction in intrinsic signal optical imaging and their use for noninvasive, serial monitoring of wound healing processes in biological tissues are illustrated.
Abstract: Laser thermal injury and subsequent wound healing in or- ganotypic, skin-equivalent tissue models were monitored using opti- cal coherence tomography (OCT), multiphoton microscopy (MPM), and histopathology. The in vitro skin-equivalent raft tissue model was composed of dermis with type I collagen and fibroblast cells and epi- dermis of differentiated keratinocytes. Noninvasive optical imaging techniques were used for time-dependent, serial measurements of ma- trix destruction and reconstruction and compared with histopathol- ogy. The region of laser thermal injury was clearly delineated in OCT images by low signal intensity. High resolution MPM imaging using second-harmonic generation revealed alterations in collagen micro- structure organization with subsequent matrix reconstruction. Fibro- blast cell migration in response to injury was monitored by MPM using two-photon excited fluorescence. This study illustrates the complementary features of linear and nonlinear light-tissue interac- tion in intrinsic signal optical imaging and their use for noninvasive, serial monitoring of wound healing processes in biological tissues.
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TL;DR: Although no consistent right-left differences are observed in the study population, relative differences between symmetric positions ranged from 18 to 30% for THC, 10 to 40% for adipose,10 to 25% for water, and 4 to 9% for scattering within an individual.
Abstract: Near-infrared (NIR) diffuse optical spectroscopy (DOS) and diffuse optical imaging (DOI) show promise as noninvasive clinical techniques for breast cancer screening and diagnosis. Since NIR methods are based on optical contrast between healthy and diseased tissue, it is essential to characterize the sources of endogenous con- trast in normal subjects. We report intra- and inter-subject variation and bilateral asymmetry of the optical and physiological parameters of 31 women using a seven-wavelength NIR frequency-domain pho- ton migration (FDPM) instrument. Wavelength-dependent absorption and reduced scattering parameters (m a and m s8 , respectively) were measured in four major quadrants and the areolar regions of left and right breasts. These values were used to determine tissue concentra- tions of oxy-(HbO2) and deoxy-(Hb-R) hemoglobin, lipid content, water concentration, and tissue ''scatter power.'' Mean total hemoglo- bin for premenopausal (PRE) women (20 to 30 mM) is approximately two-fold higher than for postmenopausal (POST) subjects at all posi- tions. POST women have approximately 50% higher lipid content (50 to 60%) than PRE at all positions. Water concentration on average is 1.8-fold higher for PRE subjects (30 to 40%) than POST. These differ- ences are most pronounced when comparing the areolar complex to the other regions of the breast. In premenopausal women, the areolar regions have 40 to 45% increased total hemoglobin concentration (THC), 20 to 25% lower lipid content, and 30 to 60% higher scatter power versus the quadrants. Small-scale (3 cm) changes in optical properties are negligible compared to large-scale variations over all quadrants, where the intrinsic spatial heterogeneity of healthy breast tissue is 20 to 40% for m a and 5 to 12% for m s8 . Although no con- sistent right-left differences are observed in the study population, rela- tive differences between symmetric positions ranged from 18 to 30% for THC, 10 to 40% for adipose, 10 to 25% for water, and 4 to 9% for scattering (674 nm) within an individual. © 2004 Society of Photo-Optical In-
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TL;DR: A so-called "inner-cell-effect" and re-absorption of emission photons are found to contribute to the decay of emission strength.
Abstract: Emission and absorption properties of indocyanine green (ICG) in Intralipid solution have been investigated. The study is focused on relatively low ICG concentration at a range of 0 to 20 μM. A diffusion model was used to analyze the emission properties of ICG solution at different concentrations. In the low-concentration region, the emission strength increases with the concentration of ICG, while in the high-concentration region, the emission decreases with the concentration. In general, a maximum of emission strength exists and its position (concentration) depends on the wavelength of the excitation light, the distance between the source and the detector, and the sample geometry and size. A so-called “inner-cell-effect” and re-absorption of emission photons are found to contribute to the decay of emission strength. Also, in the concentration range of 0 to 2 μM, ICG solution always has a higher absorption coefficient at wavelength 830 nm than that at 660 nm, which is quite different from the ICG in water case.
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TL;DR: The capability to noninvasively quantify bone tissue composition suggests a possible use of optical biopsy for the diagnosis of bone pathologies such as osteoporosis, which are characterized by a progressive reduction and transformation of the mineral in the bone matrix.
Abstract: In vivo absorption and reduced scattering spectra of the human calcaneous from 650 to 1000 nm were assessed using a laboratory system for time-resolved transmittance spectroscopy. Measurements were performed on the calcaneous of seven female volunteers ranging from 26 to 82 years of age. The analysis of the absorption spectra, using a linear combination of the key tissue absorbers (bone mineral, water, lipids, oxy- and deoxyhemoglobin), revealed a general decrease in bone mineral content and an increase in lipids with age, which is in agreement with the aging transformations that occur in bone tissues. The scattering spectra were less effective in detecting such changes in older subjects, showing only a minor decrease in the coefficient for these subjects. The capability to noninvasively quantify bone tissue composition suggests a possible use of optical biopsy for the diagnosis of bone pathologies such as osteoporosis, which are characterized by a progressive reduction and transformation of the mineral in the bone matrix.
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TL;DR: The first time-resolved optical mammograph operating beyond 900 nm (683, 785, 913, and 975 nm) is presently being used in a clinical trial to test the diagnostic potential of the technique in detecting and characterizing breast lesions.
Abstract: The first time-resolved optical mammograph operating beyond 900 nm (683, 785, 913, and 975 nm) is presently being used in a clinical trial to test the diagnostic potential of the technique in detecting and characterizing breast lesions. Between November 2001 and October 2002, 101 patients with malignant and benign lesions were analyzed retrospectively. Scattering plots, as derived from a homogeneous model, and late gated intensity images, to monitor spatial changes in the absorption properties, are routinely used. The intensity images available at four wavelengths provide sensitivity to the main tissue constituents (oxy- and deoxyhemoglobin, water, and lipids), in agreement with expected tissue composition and physiology, while the scattering plots mirror structural changes. Briefly, tumors are usually identified due to the strong blood absorption at short wavelengths, cysts to the low scattering, and fibroadenomas to low absorption at 913 nm and high at 975 nm, even though the optical features of fibroadenomas seem not to be uniquely defined. The effectiveness of the technique in localizing and discriminating different lesion types is analyzed as a function of various parameters (lesion size, compressed breast thickness, and breast parenchymal pattern).
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TL;DR: The clinical application of a multiplanar imaging system that simultaneously acquires en face (C-scan) optical coherence tomography and the corresponding confocal ophthalmoscopic images, along with cross-sectional OCT at specifiable locations on the confocal image is demonstrated.
Abstract: We demonstrate the clinical application of a multiplanar imaging system that simultaneously acquires en face (C-scan) optical coherence tomography (OCT) and the corresponding confocal ophthalmoscopic images, along with cross-sectional (B-scan) OCT at specifiable locations on the confocal image The advantages of the simultaneous OCT and confocal acquisition as well as the challenges of interpreting the C-scan OCT images are discussed Variations in tissue inclination with respect to the coherence wave surface alter the sampling of structures within the depth of the retina, producing novel slice orientations that are often challenging to interpret We have evaluated for the first time the utility of C-scan OCT for a variety of pathologies, including melanocytoma, diabetic retinopathy, choroidal neovascular membrane, and macular pucker Several remarkable new aspects of clinical anatomy were revealed using this new technique The versatility of selective capture of C-scan OCT images and B-scan OCT images at precise points on the confocal image affords the clinician a more complete and interactive tool for 3-D imaging of retinal pathology
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TL;DR: A systematic approach for interpreting protein subcellular distributions using various sets of sub cellular location features (SLF) in combination with supervised classification and unsupervised clustering methods is described.
Abstract: Quantitative microscopy has been extensively used in biomedical research and has provided significant insights into structure and dynamics at the cell and tissue level. The entire procedure of quantitative microscopy is comprised of specimen preparation, light absorption/reflection/emission from the specimen, microscope optical processing, optical/electrical conversion by a camera or detector, and computational processing of digitized images. Although many of the latest digital signal processing techniques have been successfully applied to compress, restore, and register digital microscope images, automated approaches for recognition and understanding of complex subcellular patterns in light microscope images have been far less widely used. We describe a systematic approach for interpreting protein subcellular distributions using various sets of subcellular location features (SLF), in combination with supervised classification and unsupervised clustering methods. These methods can handle complex patterns in digital microscope images, and the features can be applied for other purposes such as objectively choosing a representative image from a collection and performing statistical comparisons of image sets.
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TL;DR: It is demonstrated experimentally that both agents can largely improve the OCT imaging depth for porcine stomach tissue and that glycerol causes a higher degree of dehydration of the tissue than DMSO does, and the two-stage diffusion of the chemicals is suggested.
Abstract: The depth of light penetration into highly scattering tissues can be improved by the application of biocompatible and osmotically active chemical agents. We compare the dynamics of optical clearing of tissue by the topical application of glycerol and dimethyl sulfoxide (DMSO) using optical coherence tomography (OCT). It is demonstrated experimentally that both agents can largely improve the OCT imaging depth for porcine stomach tissue. During a period of approximately 20 to 30 min after the application of glycerol image contrast is also enhanced. This enhancement disappears over time. Such enhancement of image contrast is not observed with DMSO. Glycerol causes a higher degree of dehydration of the tissue than DMSO does. We suggest that these phenomena are caused by a two-stage diffusion of the chemicals. The first stage of diffusion is from the top tissue to the intercellular space, and the second is into the cell matrix. During the first stage, the imaging contrast could be improved by dehydration.
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TL;DR: An analytical model of the fluorescence spectrum of a two-layer medium such as epithelial tissue is presented and the use of this model to extract information about changes in epithelial and stromal optical properties from clinical measurements and the diagnostic value of these parameters is explored.
Abstract: Fluorescence spectroscopy has shown promise for the de- tection of precancerous changes in vivo. The epithelial and stromal layers of tissue have very different optical properties; the albedo is relatively low in the epithelium and approaches one in the stroma. As precancer develops, the optical properties of the epithelium and stroma are altered in markedly different ways: epithelial scattering and fluorescence increase, and stromal scattering and fluorescence de- crease. We present an analytical model of the fluorescence spectrum of a two-layer medium such as epithelial tissue. Our hypothesis is that accounting for the two different tissue layers will provide increased diagnostic information when used to analyze tissue fluorescence spectra measured in vivo. The Beer-Lambert law is used to describe light propagation in the epithelial layer, while light propagation in the highly scattering stromal layer is described with diffusion theory. Pre- dictions of the analytical model are compared to results from Monte Carlo simulations of light propagation under a range of optical prop- erties reported for normal and precancerous epithelial tissue. In all cases, the mean square error between the Monte Carlo simulations and the analytical model are within 15%. Finally, model predictions are compared to fluorescence spectra of normal and precancerous cervical tissue measured in vivo; the lineshape of fluorescence agrees well in both cases, and the decrease in fluorescence intensity from normal to precancerous tissue is correctly predicted to within 5%. Future work will explore the use of this model to extract information about changes in epithelial and stromal optical properties from clini- cal measurements and the diagnostic value of these parameters.
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TL;DR: These studies represent the first 3-D tomographic images from physiologically relevant geometries for breast imaging from 2-D boundary surface measurements using the modified truncated Newton's method.
Abstract: Molecular targeting with exogenous near-infrared excitable fluorescent agents using time-dependent imaging techniques may enable diagnostic imaging of breast cancer and prognostic imaging of sentinel lymph nodes within the breast. However, prior to the administration of unproven contrast agents, phantom studies on clinically relevant volumes are essential to assess the benefits of fluorescence-enhanced optical imaging in humans. Diagnostic 3-D fluorescence-enhanced optical tomography is demonstrated using 0.5 to 1 cm(3) single and multiple targets differentiated from their surroundings by indocyanine green (micromolar) in a breast-shaped phantom (10-cm diameter). Fluorescence measurements of referenced ac intensity and phase shift were acquired in response to point illumination measurement geometry using a homodyned intensified charge-coupled device system modulated at 100 MHz. Bayesian reconstructions show artifact-free 3-D images (3857 unknowns) from 3-D boundary surface measurements (126 to 439). In a reflectance geometry appropriate for prognostic imaging of lymph node involvement, fluorescence measurements were likewise acquired from the surface of a semi-infinite phantom (8x8x8 cm(3)) in response to area illumination (12 cm(2)) by excitation light. Tomographic 3-D reconstructions (24,123 unknowns) were recovered from 2-D boundary surface measurements (3194) using the modified truncated Newton's method. These studies represent the first 3-D tomographic images from physiologically relevant geometries for breast imaging.
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TL;DR: Second harmonic generation (SHG) imaging is used to study and quantify a strong intrinsic SHG signal in skeletal muscle fiber preparations and single isolated myofibrils and may allow the study of dynamic interactions between the contractile proteins actin and myosin during force production and muscle shortening.
Abstract: We use second harmonic generation (SHG) imaging to study and quantify a strong intrinsic SHG signal in skeletal muscle fiber preparations and single isolated myofibrils. The intrinsic signal follows the striation pattern of the muscle cells and is positioned at the sarcomeric location of the myosin filaments. Interestingly, the signal is enhanced at the region where the myosin heads are located on the myosin filaments. As the intrinsic signal reflects the subcellular structure in an accurate way, SHG can be used for noninvasive high resolution structural imaging without exogenous labels in living muscle cells. This may be very important for detecting changes in myofibrillar organization occurring under pathophysiological conditions, e.g., in cardiac and skeletal myopathies. Due to the strong dependency of SHG on orientation and symmetries of the tissue, it may allow the study of dynamic interactions between the contractile proteins actin and myosin during force production and muscle shortening. Furthermore, SHG imaging can be combined with other nonlinear microscopical techniques, such as laser scanning multiphoton fluorescence microscopy, to simultaneously measure other dynamic cellular processes, representing a complementary method and extending the range of nonlinear microscopical methods.