OFC/NFOEC 2007 - 2007 Conference on Optical Fiber Communication and the National Fiber Optic Engineers Conference, 2007
We describe the implementation of a wavelength-tunable polarization-dependent-loss element on pol... more We describe the implementation of a wavelength-tunable polarization-dependent-loss element on polarization-maintaining fiber using two independently-controlled acoustic gratings. Continuous attenuation in both fast and slow axes at the same wavelength is demonstrated.
Medical Imaging 2011: Physics of Medical Imaging, 2011
Preclinical SPECT offers a powerful means to understand the molecular pathways of metabolic activ... more Preclinical SPECT offers a powerful means to understand the molecular pathways of metabolic activity in animals. SPECT cameras using pinhole collimators offer high resolution that is needed for visualizing small structures in laboratory animals. One of the limitations of pinhole geometries is that increased magnification causes some rays to travel through the scintillator detector at steep angles, introducing parallax errors
We have developed an ultrafast statistical iterative reconstruction method for multipinhole singl... more We have developed an ultrafast statistical iterative reconstruction method for multipinhole single photon emission computed tomography using high performance graphics processing unit computing and have demonstrated a significant performance improvement in reconstruction using computer-generated and experimental sinogram data.
We demonstrate dynamic strain sensing using a fiber acousto-optic tunable filter (AOTF). The sens... more We demonstrate dynamic strain sensing using a fiber acousto-optic tunable filter (AOTF). The sensing mechanism is based on the shift of resonant wavelength of the AOTF filter in the presence of mechanical strain on the fiber. An input laser signal can thus be modulated by a dynamic strain. The modulation due to a low-frequency (~10 Hz) dynamic strain applied to
OFC/NFOEC 2007 - 2007 Conference on Optical Fiber Communication and the National Fiber Optic Engineers Conference, 2007
Page 1. Ultra-Compact Long-Period Fiber Grating and Grating Pair Fabrication using a Modulation-S... more Page 1. Ultra-Compact Long-Period Fiber Grating and Grating Pair Fabrication using a Modulation-Scanned CO2 Laser Hon M. Chan, Eric Perez, Fares Alhassen, Ivan V. Tomov, and Henry P. Lee Department of Electrical Engineering ...
American journal of nuclear medicine and molecular imaging, 2013
Cardiac single photon emission computed tomography (SPECT) cameras typically rotate too slowly ar... more Cardiac single photon emission computed tomography (SPECT) cameras typically rotate too slowly around a patient to capture changes in the blood pool activity distribution and provide accurate kinetic parameters. A spatiotemporal iterative reconstruction method to overcome these limitations was investigated. Dynamic rest/stress (99m)Tc-methoxyisobutylisonitrile ((99m)Tc-MIBI) SPECT/CT was performed along with reference standard rest/stress dynamic positron emission tomography (PET/CT) (13)N-NH3 in five patients. The SPECT data were reconstructed using conventional and spatiotemporal iterative reconstruction methods. The spatiotemporal reconstruction yielded improved image quality, defined here as a statistically significant (p<0.01) 50% contrast enhancement. We did not observe a statistically significant difference between the correlations of the conventional and spatiotemporal SPECT myocardial uptake K 1 values with PET K 1 values (r=0.25, 0.88, respectively) (p<0.17). These r...
Acousto-optic interaction in optical fiber is examined from the perspective of copropagating opti... more Acousto-optic interaction in optical fiber is examined from the perspective of copropagating optical and acoustic vortex modes. Calculation of the acousto-optic coupling coefficient between different optical modes leads to independent conservation of spin and orbital angular momentum of the interacting photons and phonons. We show that the orbital angular momentum of the acoustic vortex can be transferred to a circularly polarized fundamental optical mode to form a stable optical vortex in the fiber carrying orbital angular momentum. The technique provides a useful way of generating stable optical vortices in the fiber medium.
We describe the operational principle of and experimentally demonstrate a narrowband, wavelength-... more We describe the operational principle of and experimentally demonstrate a narrowband, wavelength-tunable polarization monitor based on a fiber acousto-optic tunable filter. Two orthogonally vibrating acoustic waves are used to create a variable polarizer that can be used to measure the state of polarization of an incident narrowband light source. The accuracy of the polarization monitor is measured at two different wavelengths in reference to a commercial polarimeter and is shown to be within 5%.
We investigated the dependence of image quality on the temperature of a position sensitive avalan... more We investigated the dependence of image quality on the temperature of a position sensitive avalanche photodiode (PSAPD)-based small animal single photon emission computed tomography (SPECT) gamma camera with a CsI:Tl scintillator. Currently, nitrogen gas cooling is preferred to operate PSAPDs in order to minimize the dark current shot noise. Being able to operate a PSAPD at a relatively high temperature (e.g., 5 °C) would allow a more compact and simple cooling system for the PSAPD. In our investigation, the temperature of the PSAPD was controlled by varying the flow of cold nitrogen gas through the PSAPD module and varied from -40 °C to 20 °C. Three experiments were performed to demonstrate the performance variation over this temperature range. The point spread function (PSF) of the gamma camera was measured at various temperatures, showing variation of full-width-half-maximum (FWHM) of the PSF. In addition, a (99m)Tc-pertechnetate (140 keV) flood source was imaged and the visibility of the scintillator segmentation (16×16 array, 8 mm × 8 mm area, 400 μm pixel size) at different temperatures was evaluated. Comparison of image quality was made at -25 °C and 5 °C using a mouse heart phantom filled with an aqueous solution of (99m)Tc-pertechnetate and imaged using a 0.5 mm pinhole collimator made of tungsten. The reconstructed image quality of the mouse heart phantom at 5 °C degraded in comparision to the reconstructed image quality at -25 °C. However, the defect and structure of the mouse heart phantom were clearly observed, showing the feasibility of operating PSAPDs for SPECT imaging at 5 °C, a temperature that would not need the nitrogen cooling. All PSAPD evaluations were conducted with an applied bias voltage that allowed the highest gain at a given temperature.
ABSTRACT A dual-wavelength erbium-doped fiber (EDF) variable ring laser using a fiber acousto-opt... more ABSTRACT A dual-wavelength erbium-doped fiber (EDF) variable ring laser using a fiber acousto-optic tunable filter (AOTF) and highly nonlinear fiber (HNLF) is demonstrated. Stable and variable lasing wavelengths were achieved by electronically adjusting the AOTF settings.
OFC/NFOEC 2007 - 2007 Conference on Optical Fiber Communication and the National Fiber Optic Engineers Conference, 2007
We describe the implementation of a wavelength-tunable polarization-dependent-loss element on pol... more We describe the implementation of a wavelength-tunable polarization-dependent-loss element on polarization-maintaining fiber using two independently-controlled acoustic gratings. Continuous attenuation in both fast and slow axes at the same wavelength is demonstrated.
Medical Imaging 2011: Physics of Medical Imaging, 2011
Preclinical SPECT offers a powerful means to understand the molecular pathways of metabolic activ... more Preclinical SPECT offers a powerful means to understand the molecular pathways of metabolic activity in animals. SPECT cameras using pinhole collimators offer high resolution that is needed for visualizing small structures in laboratory animals. One of the limitations of pinhole geometries is that increased magnification causes some rays to travel through the scintillator detector at steep angles, introducing parallax errors
We have developed an ultrafast statistical iterative reconstruction method for multipinhole singl... more We have developed an ultrafast statistical iterative reconstruction method for multipinhole single photon emission computed tomography using high performance graphics processing unit computing and have demonstrated a significant performance improvement in reconstruction using computer-generated and experimental sinogram data.
We demonstrate dynamic strain sensing using a fiber acousto-optic tunable filter (AOTF). The sens... more We demonstrate dynamic strain sensing using a fiber acousto-optic tunable filter (AOTF). The sensing mechanism is based on the shift of resonant wavelength of the AOTF filter in the presence of mechanical strain on the fiber. An input laser signal can thus be modulated by a dynamic strain. The modulation due to a low-frequency (~10 Hz) dynamic strain applied to
OFC/NFOEC 2007 - 2007 Conference on Optical Fiber Communication and the National Fiber Optic Engineers Conference, 2007
Page 1. Ultra-Compact Long-Period Fiber Grating and Grating Pair Fabrication using a Modulation-S... more Page 1. Ultra-Compact Long-Period Fiber Grating and Grating Pair Fabrication using a Modulation-Scanned CO2 Laser Hon M. Chan, Eric Perez, Fares Alhassen, Ivan V. Tomov, and Henry P. Lee Department of Electrical Engineering ...
American journal of nuclear medicine and molecular imaging, 2013
Cardiac single photon emission computed tomography (SPECT) cameras typically rotate too slowly ar... more Cardiac single photon emission computed tomography (SPECT) cameras typically rotate too slowly around a patient to capture changes in the blood pool activity distribution and provide accurate kinetic parameters. A spatiotemporal iterative reconstruction method to overcome these limitations was investigated. Dynamic rest/stress (99m)Tc-methoxyisobutylisonitrile ((99m)Tc-MIBI) SPECT/CT was performed along with reference standard rest/stress dynamic positron emission tomography (PET/CT) (13)N-NH3 in five patients. The SPECT data were reconstructed using conventional and spatiotemporal iterative reconstruction methods. The spatiotemporal reconstruction yielded improved image quality, defined here as a statistically significant (p<0.01) 50% contrast enhancement. We did not observe a statistically significant difference between the correlations of the conventional and spatiotemporal SPECT myocardial uptake K 1 values with PET K 1 values (r=0.25, 0.88, respectively) (p<0.17). These r...
Acousto-optic interaction in optical fiber is examined from the perspective of copropagating opti... more Acousto-optic interaction in optical fiber is examined from the perspective of copropagating optical and acoustic vortex modes. Calculation of the acousto-optic coupling coefficient between different optical modes leads to independent conservation of spin and orbital angular momentum of the interacting photons and phonons. We show that the orbital angular momentum of the acoustic vortex can be transferred to a circularly polarized fundamental optical mode to form a stable optical vortex in the fiber carrying orbital angular momentum. The technique provides a useful way of generating stable optical vortices in the fiber medium.
We describe the operational principle of and experimentally demonstrate a narrowband, wavelength-... more We describe the operational principle of and experimentally demonstrate a narrowband, wavelength-tunable polarization monitor based on a fiber acousto-optic tunable filter. Two orthogonally vibrating acoustic waves are used to create a variable polarizer that can be used to measure the state of polarization of an incident narrowband light source. The accuracy of the polarization monitor is measured at two different wavelengths in reference to a commercial polarimeter and is shown to be within 5%.
We investigated the dependence of image quality on the temperature of a position sensitive avalan... more We investigated the dependence of image quality on the temperature of a position sensitive avalanche photodiode (PSAPD)-based small animal single photon emission computed tomography (SPECT) gamma camera with a CsI:Tl scintillator. Currently, nitrogen gas cooling is preferred to operate PSAPDs in order to minimize the dark current shot noise. Being able to operate a PSAPD at a relatively high temperature (e.g., 5 °C) would allow a more compact and simple cooling system for the PSAPD. In our investigation, the temperature of the PSAPD was controlled by varying the flow of cold nitrogen gas through the PSAPD module and varied from -40 °C to 20 °C. Three experiments were performed to demonstrate the performance variation over this temperature range. The point spread function (PSF) of the gamma camera was measured at various temperatures, showing variation of full-width-half-maximum (FWHM) of the PSF. In addition, a (99m)Tc-pertechnetate (140 keV) flood source was imaged and the visibility of the scintillator segmentation (16×16 array, 8 mm × 8 mm area, 400 μm pixel size) at different temperatures was evaluated. Comparison of image quality was made at -25 °C and 5 °C using a mouse heart phantom filled with an aqueous solution of (99m)Tc-pertechnetate and imaged using a 0.5 mm pinhole collimator made of tungsten. The reconstructed image quality of the mouse heart phantom at 5 °C degraded in comparision to the reconstructed image quality at -25 °C. However, the defect and structure of the mouse heart phantom were clearly observed, showing the feasibility of operating PSAPDs for SPECT imaging at 5 °C, a temperature that would not need the nitrogen cooling. All PSAPD evaluations were conducted with an applied bias voltage that allowed the highest gain at a given temperature.
ABSTRACT A dual-wavelength erbium-doped fiber (EDF) variable ring laser using a fiber acousto-opt... more ABSTRACT A dual-wavelength erbium-doped fiber (EDF) variable ring laser using a fiber acousto-optic tunable filter (AOTF) and highly nonlinear fiber (HNLF) is demonstrated. Stable and variable lasing wavelengths were achieved by electronically adjusting the AOTF settings.
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