The Experts below are selected from a list of 4155 Experts worldwide ranked by ideXlab platform
David R Burton - One of the best experts on this subject based on the ideXlab platform.
-
spatiotemporal phase unwrapping and its application in fringe Projection Fiber optic phase shifting profilometry
Optical Engineering, 2000Co-Authors: Hong Zhang, Michael J Lalor, David R BurtonAbstract:A spatiotemporal phase unwrapping method is proposed that combines the dynamic optic Fiber interferometric fringe Projection method and the phase-shifting technique. A fringe Projection Fiber optic phase- shifting interferometer was set up, in which the fringe spacing and rotation can be easily adjusted. In the first step of the spatiotemporal phase unwrapping method, a large effective wavelength can be chosen so that the phase jump at the discontinuous profile is less than ?, then the spatial phase unwrapping method can be applied. Several intermediate phase maps can be obtained by changing fringe pitch and fringe orientation, reducing the effective wavelength step by step, and unwrapping each pixel along the time axis. In the final step, a high precision result can be obtained. A minimum number of steps can be chosen to obtain the required accuracy according to the conclusion presented. An experimental result is presented for the measurement of a discontinuous object and shows the validity of the proposed method.
-
spatiotemporal phase unwrapping and its application in fringe Projection Fiber optic phase shifting profilometry
International Conference on Optical Metrology, 1999Co-Authors: Hong Zhang, Michael J Lalor, David R BurtonAbstract:In this paper, a spatiotemporal phase unwrapping method is proposed, which combines the dynamic optic Fiber interferometric fringe Projection method and the phase- shifting technique. A fringe Projection Fiber optic phase- shifting interferometer was set up, in which the fringe spacing and rotation can be easily adjusted. In the first step of the spatiotemporal phase unwrapping method, a large effective wavelength can be chosen so that the phase jump at the discontinuous profile is less than (pi) , then the spatial phase unwrapping method can be applied. Several intermediate phase maps can be obtained by changing fringe pitch and fringe orientation, reducing the effective wavelength step by step, and unwrapping each pixel along the time axis. In the final step, a high precision result can be obtained. A minimum number of steps may be chosen for obtaining the required accuracy according to the conclusion presented in this paper. An experimental result is presented for the measurement of a discontinuous object and shows the validity of the proposed method.© (1999) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
David E Vaillancourt - One of the best experts on this subject based on the ideXlab platform.
-
thalamic Projection Fiber integrity in de novo parkinson disease
American Journal of Neuroradiology, 2013Co-Authors: Peggy J Planetta, Evan T Schulze, Elizabeth K Geary, Daniel M Corcos, Jennifer G Goldman, Deborah M Little, David E VaillancourtAbstract:BACKGROUND AND PURPOSE: Postmortem studies of advanced PD have revealed disease-related pathology in the thalamus with an apparent predilection for specific thalamic nuclei. In the present study, we used DTI to investigate in vivo the microstructural integrity of 6 thalamic regions in de novo patients with PD relative to healthy controls. MATERIALS AND METHODS: Forty subjects (20 with early stage untreated PD and 20 age- and sex-matched controls) were studied with a high-resolution DTI protocol at 3T to investigate the integrity of thalamic nuclei Projection Fibers. Two blinded, independent raters drew ROIs in the following 6 thalamic regions: AN, VA, VL, DM, VPL/VPM, and PU. FA values were then calculated from the Projection Fibers in each region. RESULTS: FA values were reduced significantly in the Fibers projecting from the AN, VA, and DM, but not the VPL/VPM and PU, in the PD group compared with the control group. In addition, there was a reduction in FA values that approached significance in the VL of patients with PD. These findings were consistent across both raters. CONCLUSIONS: The present study provides preliminary in vivo evidence of thalamic Projection Fiber degeneration in de novo PD and sheds light on the extent of disrupted thalamic circuitry as a result of the disease itself.
Deborah M Little - One of the best experts on this subject based on the ideXlab platform.
-
thalamic Projection Fiber integrity in de novo parkinson disease
American Journal of Neuroradiology, 2013Co-Authors: Peggy J Planetta, Evan T Schulze, Elizabeth K Geary, Daniel M Corcos, Jennifer G Goldman, Deborah M Little, David E VaillancourtAbstract:BACKGROUND AND PURPOSE: Postmortem studies of advanced PD have revealed disease-related pathology in the thalamus with an apparent predilection for specific thalamic nuclei. In the present study, we used DTI to investigate in vivo the microstructural integrity of 6 thalamic regions in de novo patients with PD relative to healthy controls. MATERIALS AND METHODS: Forty subjects (20 with early stage untreated PD and 20 age- and sex-matched controls) were studied with a high-resolution DTI protocol at 3T to investigate the integrity of thalamic nuclei Projection Fibers. Two blinded, independent raters drew ROIs in the following 6 thalamic regions: AN, VA, VL, DM, VPL/VPM, and PU. FA values were then calculated from the Projection Fibers in each region. RESULTS: FA values were reduced significantly in the Fibers projecting from the AN, VA, and DM, but not the VPL/VPM and PU, in the PD group compared with the control group. In addition, there was a reduction in FA values that approached significance in the VL of patients with PD. These findings were consistent across both raters. CONCLUSIONS: The present study provides preliminary in vivo evidence of thalamic Projection Fiber degeneration in de novo PD and sheds light on the extent of disrupted thalamic circuitry as a result of the disease itself.
Hong Zhang - One of the best experts on this subject based on the ideXlab platform.
-
spatiotemporal phase unwrapping and its application in fringe Projection Fiber optic phase shifting profilometry
Optical Engineering, 2000Co-Authors: Hong Zhang, Michael J Lalor, David R BurtonAbstract:A spatiotemporal phase unwrapping method is proposed that combines the dynamic optic Fiber interferometric fringe Projection method and the phase-shifting technique. A fringe Projection Fiber optic phase- shifting interferometer was set up, in which the fringe spacing and rotation can be easily adjusted. In the first step of the spatiotemporal phase unwrapping method, a large effective wavelength can be chosen so that the phase jump at the discontinuous profile is less than ?, then the spatial phase unwrapping method can be applied. Several intermediate phase maps can be obtained by changing fringe pitch and fringe orientation, reducing the effective wavelength step by step, and unwrapping each pixel along the time axis. In the final step, a high precision result can be obtained. A minimum number of steps can be chosen to obtain the required accuracy according to the conclusion presented. An experimental result is presented for the measurement of a discontinuous object and shows the validity of the proposed method.
-
spatiotemporal phase unwrapping and its application in fringe Projection Fiber optic phase shifting profilometry
International Conference on Optical Metrology, 1999Co-Authors: Hong Zhang, Michael J Lalor, David R BurtonAbstract:In this paper, a spatiotemporal phase unwrapping method is proposed, which combines the dynamic optic Fiber interferometric fringe Projection method and the phase- shifting technique. A fringe Projection Fiber optic phase- shifting interferometer was set up, in which the fringe spacing and rotation can be easily adjusted. In the first step of the spatiotemporal phase unwrapping method, a large effective wavelength can be chosen so that the phase jump at the discontinuous profile is less than (pi) , then the spatial phase unwrapping method can be applied. Several intermediate phase maps can be obtained by changing fringe pitch and fringe orientation, reducing the effective wavelength step by step, and unwrapping each pixel along the time axis. In the final step, a high precision result can be obtained. A minimum number of steps may be chosen for obtaining the required accuracy according to the conclusion presented in this paper. An experimental result is presented for the measurement of a discontinuous object and shows the validity of the proposed method.© (1999) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
Changwoo Ryu - One of the best experts on this subject based on the ideXlab platform.
-
differential associations between systemic markers of disease and white matter tissue health in middle aged and older adults
Journal of Cerebral Blood Flow and Metabolism, 2017Co-Authors: Changwoo Ryu, Jeanphilippe Coutu, Anna Greka, Diana H Rosas, Geonho Jahng, Bruce R Rosen, David H SalatAbstract:Age-associated cerebrovascular disease impacts brain tissue integrity, but other factors, including normal variation in blood markers of systemic health, may also influence the structural integrity of the brain. This cross-sectional study included 139 individuals between 40 to 86 years old who were physically healthy and cognitively intact. Eleven markers (total-cholesterol, high-density lipoprotein, low-density lipoprotein, triglyceride, insulin, fasting glucose, glycated hemoglobin, creatinine, blood urea nitrogen, albumin, total protein) and five derived indicators (estimated glomerular filtration rate, creatinine clearance rate, insulin-resistance, average glucose, and cholesterol/high-density lipoprotein ratio) were obtained from blood sampling. Diffusion tensor imaging was used to evaluate white matter tissue health. Blood markers were clustered into five factors. The first factor (defined as insulin/high-density lipoprotein factor) was associated with markers of integrity in the deep white matter and Projection Fiber systems, while the third factor (defined as kidney function factor) was associated with different markers of integrity in the periventricular and watershed white matter regions. Differential segregated associations for insulin and high-density lipoprotein levels and serum markers of kidney function may provide information about distinct mechanisms of brain changes across the lifespan. These results emphasize the need to determine whether therapeutic modulation of systemic health and organ function may prevent decline in brain structural integrity.
