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During orthodontic treatment, the early diagnosis of microscopic changes in soft and hard tissues, including periodontal tissue, is very important to prevent iatrogenic side effects like root resorption and periodontal diseases. Cervical periodontal tissue is the most critical area that reacts first to mal-habits or orthodontic forces, and it is also the place where bacteria deposits in the early stage of periodontal diseases. The early diagnosis of hard tissue changes, such as demineralization, is also very important in maintaining a patient's health during orthodontic treatment. Many diagnostic devices, including radiographic equipment and intra-oral scanners, are helpful in diagnosing these problems, but have certain limitations in invasiveness and precision. The purpose of this study is to verify the possible utilities of non-invasive diagnostic devices in the orthodontic field that can compensate for these limitations. For this, non-invasive optical diagnostic devices, including optical coherence tomography and optical Doppler tomography, were used in vivo with animal and human examination for hard and soft tissues. These devices can provide real-time three-dimensional images at the histological scale. The results of this study verified these devices can be used in clinical practice during orthodontic treatment and introduced a new diagnostic paradigm differentiating microstructural changes in tissues in orthodontic diagnosis. [ABSTRACT FROM AUTHOR]

In otology, visualization and vibratory analysis have been crucial to enhance the success of diagnosis and surgical operation. Optical coherence tomography (OCT) has been employed in otology to obtain morphological structure of tissues non-invasively, owing to the ability of measuring the entire region of tympanic membrane, which compensates the limitations of conventional methods. As a functional extension of OCT, Doppler OCT, which enables the measurement of the motion information with structural data of tissue, has been applied in otology. Over the years, Doppler OCT systems have been evolved in various forms to enhance the measuring sensitivity of phase difference. In this review, we provide representative algorithms of Doppler OCT and various applications in otology from preclinical analysis to clinical experiments and discuss future developments. [ABSTRACT FROM AUTHOR]

Different types and sizes of micro- and nanoparticles have been synthesized and developed for numerous applications. It is crucial to characterize the particle sizes. Traditional dynamic light scattering, a predominant method used to characterize particle size, is unable to provide depth resolved information or imaging functions. Doppler variance optical coherence tomography (OCT) measures the spectral bandwidth of the Doppler frequency shift due to the Brownian motion of the particles utilizing the phase-resolved approach and can provide quantitative information about particle size. Spectral bandwidths of Doppler frequency shifts for various sized particles were quantified and were demonstrated to be inversely proportional to the diameter of the particles. The study demonstrates the phase-resolved Doppler variance spectral domain OCT technique has the potential to be used to investigate the properties of particles in highly scattering media.

We demonstrate the use of Doppler variance (standard deviation) imaging for 3-D in vivo angiography in the human eye. In addition to the regular optical Doppler tomography velocity and structural images, we use the variance of blood flow velocity to map the retina and choroid vessels. Variance imaging is subject to bulk motion artifacts as in phase-resolved Doppler imaging, and a histogram-based method is proposed for bulk-motion correction in variance imaging. Experiments were performed to demonstrate the effectiveness of the proposed method for 3-D vasculature imaging of human retina and choroid.

An abnormal level of red blood cell (RBC) aggregation is a clinical condition associated with many pathologies. Our purpose is to investigate the feasibility of spectral domain phase-resolved optical Doppler tomography incorporated with Doppler variance imaging to characterize RBC aggregation in flowing blood. Variance/standard deviation (SD) of the Doppler frequency spectrum of porcine blood flowing through a glass tube (diameter 300 microm) at 4.7 mms is measured. For nonaggregating RBCs with hematocrits of 20, 40, and 60%, the mean centerline SD values were 34.2+/-1.2, 47.8+/-1.0, and 47.2+/-0.5, respectively. After dextran 500 induction, the SD value decreased significantly to 29.9+/-0.7, 37.9+/-3.0, and 40.1+/-0.6 (P

Early detection of cancer and its precursors remains the best way to ensure patient survival and quality of life. Our specific aim is to test a multimodality approach to noninvasive diagnostics of oral premalignancy and malignancy. In the hamster cheek pouch model (120 hamsters), in vivo optical coherence tomography (OCT) and optical Doppler tomography (ODT) map epithelial, subepithelial, and vascular change throughout carcinogenesis. In vivo multiwavelength multiphoton (MPM) and second-harmonic generated (SHG) fluorescence techniques provided parallel data on surface and subsurface tissue structure, specifically collagen presence and structure, cellular presence, and vasculature. Images are diagnosed by two blinded, prestandardized investigators using a scale from 0 to 6 for all modalities. After sacrifice, histopathology is evaluated on a scale of 0 to 6. Imaging data are reproducibly obtained with good accuracy. Carcinogenesis-related structural and vascular changes are clearly visible to tissue depths of 2 mm. Sensitivity (OCT/ODT alone, 71 to 88%; OCT+MPMSHG, 79 to 91%) and specificity (OCT alone, 62 to 83%; OCT+MPMSHG, 67 to 90%) compare well with conventional techniques. Our conclusions are that OCT/ODT and MPM/SHG are promising noninvasive in vivo diagnostic modalities for oral dysplasia and malignancy.

Frequency domain phase-resolved optical Doppler tomography (ODT) was developed with Doppler variance imaging capability. It is shown that utilizing the frequency domain method, phase-resolved ODT can achieve much higher imaging speed and velocity dynamic range than the time domain method. Structural, Doppler and Doppler variance images of fluid flow through glass channels were quantified and blood flow through vessels were demonstrated in vivo. © 2004 Elsevier B.V. All rights reserved.

We present a phase-resolved optical Doppler tomography (ODT) sys tern at 1310 nm using frequency domain method. Frequency domain phase-resolved ODT potentially allows for an increased longitudinal imaging range, signal-to-noise ratio and imaging acquisition rates, which can dramatically increase the measurable velocity dynamic range. A detailed derivation of phase-resolved frequency domain ODT and a measurement of flow through micro channel are presented. This technique can be used to quantify flow in integrated microfluidic devices in which complex three-dimensional structures and a wide velocity range are present.

We report on application of pulsed photothermal radiometry (PPTR) to determine the depth of port wine stain (PWS) blood vessels in human skin. When blood vessels are deep in the PWS skin (>100 microm), conventional PPTR depth profiling can be used to determine PWS depth with sufficient accuracy. When blood vessels are close or partially overlap the epidermal melanin layer, a modified PPTR technique using two-wavelength (585 and 600 nm) excitation is a superior method to determine PWS depth. A direct difference approach in which PWS depth is determined from a weighted difference of temperature profiles reconstructed independently from two-wavelength excitation is demonstrated to be appropriate for a wider range of PWS patients with various blood volume fractions, blood vessel sizes, and depth distribution. The most superficial PWS depths determined in vivo by PPTR are in good agreement with those measured using optical Doppler tomography (ODT).

We present a phase-resolved optical Doppler tomography (ODT) sys tern at 1310 nm using frequency domain method. Frequency domain phase-resolved ODT potentially allows for an increased longitudinal imaging range, signal-to-noise ratio and imaging acquisition rates, which can dramatically increase the measurable velocity dynamic range. A detailed derivation of phase-resolved frequency domain ODT and a measurement of flow through micro channel are presented. This technique can be used to quantify flow in integrated microfluidic devices in which complex three-dimensional structures and a wide velocity range are present.

Phase-resolved optical Doppler tomography (ODT), an imaging technique based on low coherence interferometry, is presented as a new tool to determine electroosmotic flow (EOF) in microfluidic channel. This is a non-contact technique that not only can image cross-sectional EOF profile but also can determine electroosmotic mobility. The electroosmotic coefficient measured by ODT was verified by conventional current monitor method. Since phase-resolved ODT provides cross-sectional imaging of flow velocity, complicated flow dynamics caused by microscale effects such as electrokinetic effects, can be investigated and quantified using this tool, particularly for turbid media such as biofluids, which cannot be readily investigated using other techniques. © 2003 Published by Elsevier B.V.

In otology, visualization and vibratory analysis have been crucial to enhance the success of diagnosis and surgical operation. Optical coherence tomography (OCT) has been employed in otology to obtain morphological structure of tissues non-invasively, owing to the ability of measuring the entire region of tympanic membrane, which compensates the limitations of conventional methods. As a functional extension of OCT, Doppler OCT, which enables the measurement of the motion information with structural data of tissue, has been applied in otology. Over the years, Doppler OCT systems have been evolved in various forms to enhance the measuring sensitivity of phase difference. In this review, we provide representative algorithms of Doppler OCT and various applications in otology from preclinical analysis to clinical experiments and discuss future developments.

Background: The purpose of our study is to use a noninvasive tomographic imaging technique with high spatial resolution to characterize and monitor biological tissue responses associated with laser thermal injury. Methods: Optical doppler tomography (ODT) combines laser doppler flowmetry (LDF) with optical coherence tomography (OCT) to obtain high resolution tomographic velocity and structural images of static and moving constituents in highly scattering biological tissues. A SurgiLase XJ150 carbon dioxide (CO2) laser using a continuous mode of 3 watts (W) was used to create first, second or third degree burns on anesthetized Sprague–Dawley rats. Additional parameters for laser thermal injury were assessed as well. Results: The rationale for using ODT in the evaluation of laser thermal injury offers a means of constructing a high resolution tomographic image of the structure and perfusion of laser damaged skin. In the velocity images, the blood flow is coded at 1300 μm/s and 0 velocity, 1000 μm/s and 0 velocity, 700 μm/s and 0 velocity adjacent to the first, second, and third degree injuries, respectively. Conclusion: ODT produces exceptional spatial resolution while having a non-invasive way of measurement, therefore, ODT is an accurate measuring method for high-resolution fluid flow velocity and structural images for biological tissue with laser thermal injury.

Phase-resolved optical Doppler tomography (ODT) has very high sensitivity while maintaining a fast axial scanning rate, making it possible to reconstruct blood flow in three dimensions. Here we demonstrate an ODT system that employed novel signal-processing techniques to remove aliasing effects and artifacts caused by lateral scanning and target movement. The results show that these techniques not only simplified ODT, but also improved lateral scanning speed. Using these signal-processing techniques, three-dimensional images of in vivo blood vessels in human skin were then reconstructed.

A novel phase resolved optical coherence tomographic (OCT) and optical Doppler tomographic (ODT) system is developed for simultaneous imaging of tissue structure and physiology with high imaging speed and high spatial resolution.

A novel phase resolved optical coherence tomographic (OCT) and optical Doppler tomographic (ODT) system is developed for simultaneous imaging of tissue structure and physiology with high imaging speed and high spatial resolution.

Optical Doppler tomography (ODT) is an imaging modality that takes advantage of the short coherence length of a broad-band light sources to perform micrometer-scale, cross-sectional imaging of tissue structure and blood flow dynamics simultaneously. We review in this paper the principal of ODT and its applications. Results from in vitro and in vivo model studies demonstrated that ODT can map the blood flow velocity profile with high spatial resolution in scattering medium. ODT detection mechanisms are illustrated using Monte Carlo simulations. The application of ODT to image brain hemodynamics is demonstrated. Finally, we discuss the limitations of the current technology and application of a phase resolved technique to improve image speed and quality.

We report the development of an optical technique for noninvasive in vivo imaging of tissue structure and blood flow dynamics with high spatial resolution (2 - 15 micrometer) in biological systems. The technique is based on coherence optical Doppler tomography (ODT), which combines Doppler velocimetry with optical coherence tomography to measure blood flow velocity at discrete spatial locations. The exceptionally high resolution of ODT allows noninvasive in vivo imaging of both blood microcirculation and tissue structures surrounding the vessel, which has significance for biomedical research and clinical applications. Tomographic velocity imaging of in vivo blood flow in a rat mesentery is demonstrated. ©2004 Copyright SPIE - The International Society for Optical Engineering.

We report the development of an optical technique for noninvasive in vivo imaging of tissue structure and blood flow dynamics with high spatial resolution (2 - 15 micrometer) in biological systems. The technique is based on coherence optical Doppler tomography (ODT), which combines Doppler velocimetry with optical coherence tomography to measure blood flow velocity at discrete spatial locations. The exceptionally high resolution of ODT allows noninvasive in vivo imaging of both blood microcirculation and tissue structures surrounding the vessel, which has significance for biomedical research and clinical applications. Tomographic velocity imaging of in vivo blood flow in a rat mesentery is demonstrated. ©2004 Copyright SPIE - The International Society for Optical Engineering.

Optical Doppler tomography is demonstrated to be a simple, accurate, and noncontact method for measuring the fluid velocity of laminar flow in small-diameter (~0.5-mm) ducts. Studies are described that utilize circular (square) plastic (glass) ducts infused with a moving suspension of polymer microspheres in air and buried in an optically turbid medium. The measurement of Doppler-shifted frequencies of backscattered light from moving microspheres is used to construct a high-resolution spatial profile of fluid-flow velocity in the ducts.

Retinal oxygen metabolic rate can be effectively measured by visible-light optical coherence tomography (vis-OCT), which simultaneously quantifies oxygen saturation and blood flow rate in retinal vessels through spectroscopic analysis and Doppler measurement, respectively. Doppler OCT relates phase variation between sequential A-lines to the axial flow velocity of the scattering medium. The detectable phase shift is between −π and π due to its periodicity, which limits the maximum measurable unambiguous velocity without phase unwrapping. Using shorter wavelengths, vis-OCT is more vulnerable to phase ambiguity since flow induced phase variation is linearly related to the center wavenumber of the probing light. We eliminated the need for phase unwrapping using spectroscopic Doppler analysis. We split the whole vis-OCT spectrum into a series of narrow subbands and reconstructed vis-OCT images to extract corresponding Doppler phase shifts in all the subbands. Then, we quantified flow velocity by analyzing subband-dependent phase shift using linear regression. In the phantom experiment, we showed that spectroscopic Doppler analysis extended the measurable absolute phase shift range without conducting phase unwrapping. We also tested this method to quantify retinal blood flow in rodents in vivo. [ABSTRACT FROM AUTHOR]

A method of layer-by-layer heterodyne analysis of volume optical media is described. The results of a theoretical evaluation, computer modeling, and experimental investigation of the dependence of the maximum speed of the analysis on the parameters of the optical circuit and medium are given. The effect of the analysis speed on the resolution of the method along the thickness of the optical medium and on the pattern of the dependence of the output signal on the depth of the studied layer is evaluated. A method for increasing the maximum scanning speed is proposed. The obtained results are confirmed experimentally.. [ABSTRACT FROM AUTHOR]

We conducted an initial feasibility study using real-time magneto-motive optical Doppler tomography (MM-ODT) with enhanced contrast to investigate the detection of superparamagnetic iron oxide (SPIO) magnetic nanoparticles implanted into in vivo melanoma tissue. The MM-ODT signals were detected owing to the phase shift of the implanted magnetic nanoparticles, which occurred due to the action of an applied magnetic field. An amplifier circuit-based solenoid was utilized for generating high-intensity oscillating magnetic fields. The MM-ODT system was confirmed as an effective in vivo imaging method for detecting melanoma tissue, with the performance comparable to those of conventional optical coherence tomography and optical Doppler tomography methods. Moreover, the optimal values of the SPIO nanoparticles concentration and solenoid voltage for obtaining the uppermost Doppler velocity were derived as well. To improve the signal processing speed for real-time imaging, we adopted multithread programming techniques and optimized the signal path. The results suggest that this imaging modality can be used as a powerful tool to identify the intracellular and extracellular SPIO nanoparticles in melanoma tissues in vivo. [ABSTRACT FROM AUTHOR]

Optical Doppler Tomography (ODT) provides a novel method to measure the blood flow velocity in vessels with the diameter at micrometer scale. Rats with cranial window are used as a model, and the changes in the blood flow velocity of cerebral arterioles in sensory cortex are measured in real time with an established ODT system, under electrical stimulation and drug administration. The results show significant differences in the blood flow velocity between experimental groups and control groups, demonstrating the feasibility of ODT in the cerebral microcirculation study. Compared with the conventional Doppler ultrasound, ODT provides much higher spatial resolution, and thus holds a promising future in the application of the cerebral microcirculation study, especially in the observation of the blood flow velocity in micrometer scale vessels. [ABSTRACT FROM AUTHOR]

Vascular responses were monitored to understand the role of the microvasculature in tumor destruction as a result of photodynamic therapy (PDT). Rats received an intravenous dose of 2 mg/kg Benzoporphyrin Derivative (BPD), at 20 min, 4 h, or 7 h before laser irradiation. With Photofrin (10 mg/kg), drug-light intervals were 20 min or 8 h. Jejunal blood vessels were exposed to 12 J/cm2 at 690 nm (with BPD) or at 630 nm (with Photofrin). Optical Doppler tomography (ODT) was used to evaluate PDT-induced changes in vessel diameter and blood flow. At the shortest drug-light time interval (20 min), BPD-mediated PDT caused transient constriction of arteries, accompanied by decreased blood flow, followed by vasodilation until baseline was reached or overshoot occurred. Veins became occluded with no restoration of the vessel lumen. At longer drug-light intervals, vasoconstriction diminished and venodilation was observed. With Photofrin, vasoconstriction and venodilation increased with the drug-light interval. Application of a higher light dose (48 J/cm2) resulted in irreversible hemostasis. ODT can be used to study changes in lumen diameter and blood flow, which are important diagnostic parameters of PDT [ABSTRACT FROM PUBLISHER]

Optical Doppler tomography (ODT) is an imaging modality that takes advantage of the short coherence length of a broad-band light sources to perform micrometer-scale, cross-sectional imaging of tissue structure and blood flow dynamics simultaneously. The authors review in this paper the principal of ODT and its applications. Results from in vitro and in vivo model studies demonstrated that ODT can map the blood flow velocity profile with high spatial resolution in scattering medium. ODT detection mechanisms are illustrated using Monte Carlo simulations. The application of ODT to image brain hemodynamics is demonstrated. Finally, the authors discuss the limitations of the current technology and application of a phase resolved technique to improve image speed and quality [ABSTRACT FROM PUBLISHER]