Matching Items (5)
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- All Subjects: Imaging
- Creators: Kodibagkar, Vikram
- Creators: Aberle, James
Description
Magnetic Resonance Imaging using spiral trajectories has many advantages in speed, efficiency in data-acquistion and robustness to motion and flow related artifacts. The increase in sampling speed, however, requires high performance of the gradient system. Hardware inaccuracies from system delays and eddy currents can cause spatial and temporal distortions in the encoding gradient waveforms. This causes sampling discrepancies between the actual and the ideal k-space trajectory. Reconstruction assuming an ideal trajectory can result in shading and blurring artifacts in spiral images. Current methods to estimate such hardware errors require many modifications to the pulse sequence, phantom measurements or specialized hardware. This work presents a new method to estimate time-varying system delays for spiral-based trajectories. It requires a minor modification of a conventional stack-of-spirals sequence and analyzes data collected on three orthogonal cylinders. The method is fast, robust to off-resonance effects, requires no phantom measurements or specialized hardware and estimate variable system delays for the three gradient channels over the data-sampling period. The initial results are presented for acquired phantom and in-vivo data, which show a substantial reduction in the artifacts and improvement in the image quality.
ContributorsBhavsar, Payal (Author) / Pipe, James G (Thesis advisor) / Frakes, David (Committee member) / Kodibagkar, Vikram (Committee member) / Arizona State University (Publisher)
Created2013
Description
Oxygen delivery is crucial for the development of healthy, functional tissue. Low tissue oxygenation, or hypoxia, is a characteristic that is common in many tumors. Hypoxia contributes to tumor malignancy and can reduce the success of chemotherapy and radiation treatment. There is a current need to noninvasively measure tumor oxygenation or pO2 in patients to determine a personalized treatment method. This project focuses on creating and characterizing nanoemulsions using a pO2 reporter molecule hexamethyldisiloxane (HMDSO) and its longer chain variants as well as assessing their cytotoxicity. We also explored creating multi-modal (MRI/Fluorescence) nanoemulsions.
ContributorsGrucky, Marian Louise (Author) / Kodibagkar, Vikram (Thesis director) / Rege, Kaushal (Committee member) / Stabenfeldt, Sarah (Committee member) / Barrett, The Honors College (Contributor) / Harrington Bioengineering Program (Contributor)
Created2013-05
Description
Readout Integrated Circuits(ROICs) are important components of infrared(IR) imag
ing systems. Performance of ROICs affect the quality of images obtained from IR
imaging systems. Contemporary infrared imaging applications demand ROICs that
can support large dynamic range, high frame rate, high output data rate, at low
cost, size and power. Some of these applications are military surveillance, remote
sensing in space and earth science missions and medical diagnosis. This work focuses
on developing a ROIC unit cell prototype for National Aeronautics and Space Ad
ministration(NASA), Jet Propulsion Laboratory’s(JPL’s) space applications. These
space applications also demand high sensitivity, longer integration times(large well
capacity), wide operating temperature range, wide input current range and immunity
to radiation events such as Single Event Latchup(SEL).
This work proposes a digital ROIC(DROIC) unit cell prototype of 30ux30u size,
to be used mainly with NASA JPL’s High Operating Temperature Barrier Infrared
Detectors(HOT BIRDs). Current state of the art DROICs achieve a dynamic range
of 16 bits using advanced 65-90nm CMOS processes which adds a lot of cost overhead.
The DROIC pixel proposed in this work uses a low cost 180nm CMOS process and
supports a dynamic range of 20 bits operating at a low frame rate of 100 frames per
second(fps), and a dynamic range of 12 bits operating at a high frame rate of 5kfps.
The total electron well capacity of this DROIC pixel is 1.27 billion electrons, enabling
integration times as long as 10ms, to achieve better dynamic range. The DROIC unit
cell uses an in-pixel 12-bit coarse ADC and an external 8-bit DAC based fine ADC.
The proposed DROIC uses layout techniques that make it immune to radiation up to
300krad(Si) of total ionizing dose(TID) and single event latch-up(SEL). It also has a
wide input current range from 10pA to 1uA and supports detectors operating from
Short-wave infrared (SWIR) to longwave infrared (LWIR) regions.
ing systems. Performance of ROICs affect the quality of images obtained from IR
imaging systems. Contemporary infrared imaging applications demand ROICs that
can support large dynamic range, high frame rate, high output data rate, at low
cost, size and power. Some of these applications are military surveillance, remote
sensing in space and earth science missions and medical diagnosis. This work focuses
on developing a ROIC unit cell prototype for National Aeronautics and Space Ad
ministration(NASA), Jet Propulsion Laboratory’s(JPL’s) space applications. These
space applications also demand high sensitivity, longer integration times(large well
capacity), wide operating temperature range, wide input current range and immunity
to radiation events such as Single Event Latchup(SEL).
This work proposes a digital ROIC(DROIC) unit cell prototype of 30ux30u size,
to be used mainly with NASA JPL’s High Operating Temperature Barrier Infrared
Detectors(HOT BIRDs). Current state of the art DROICs achieve a dynamic range
of 16 bits using advanced 65-90nm CMOS processes which adds a lot of cost overhead.
The DROIC pixel proposed in this work uses a low cost 180nm CMOS process and
supports a dynamic range of 20 bits operating at a low frame rate of 100 frames per
second(fps), and a dynamic range of 12 bits operating at a high frame rate of 5kfps.
The total electron well capacity of this DROIC pixel is 1.27 billion electrons, enabling
integration times as long as 10ms, to achieve better dynamic range. The DROIC unit
cell uses an in-pixel 12-bit coarse ADC and an external 8-bit DAC based fine ADC.
The proposed DROIC uses layout techniques that make it immune to radiation up to
300krad(Si) of total ionizing dose(TID) and single event latch-up(SEL). It also has a
wide input current range from 10pA to 1uA and supports detectors operating from
Short-wave infrared (SWIR) to longwave infrared (LWIR) regions.
ContributorsPraveen, Subramanya Chilukuri (Author) / Bakkaloglu, Bertan (Thesis advisor) / Kitchen, Jennifer (Committee member) / Long, Yu (Committee member) / Arizona State University (Publisher)
Created2019
Description
This work focuses on the analysis and design of large-scale millimeter-wave andterahertz (mmWave/THz) beamforming apertures (e.g., reconfigurable reflective surfaces–
RRSs). As such, the small wavelengths and ample bandwidths of these frequencies enable
the development of high-spatial-resolution imaging and high-throughput wireless
communication systems that leverage electrically large apertures to form high-gain
steerable beams.
For the rigorous evaluation of these systems’ performance in realistic application
scenarios, full-wave simulations are needed to capture all the exhibited electromagnetic
phenomena. However, the small wavelengths of mmWave/THz bands lead to enormous
meshes in conventional full-wave simulators. Thus, a novel numerical decomposition
technique is presented, which decomposes the full-wave models in smaller domains with
less meshed elements, enabling their computationally efficient analysis. Thereafter, this
method is leveraged to study a novel radar configuration that employs a rotating linear
antenna with beam steering capabilities to form 3D images. This imaging process requires
fewer elements to carry out high-spatial-resolution imaging compared to traditional 2D
phased arrays, constituting a perfect candidate in low-profile, low-cost applications.
Afterward, a high-yield nanofabrication technique for mmWave/THz graphene
switches is presented. The measured graphene sheet impedances are incorporated into
equivalent circuit models of coplanar switches to identify the optimum mmWave/THz
switch topology that would enable the development of large-scale RRSs.ii
Thereon, the process of integrating the optimized graphene switches into largescale mmWave/THz RRSs is detailed. The resulting RRSs enable dynamic beam steering
achieving 4-bits of phase quantization –for the first time in the known literature–
eliminating the parasitic lobes and increasing the aperture efficiency. Furthermore, the
devised multi-bit configurations use a single switch-per-bit topology retaining low system
complexity and RF losses. Finally, single-bit RRSs are modified to offer single-lobe
patterns by employing a surface randomization technique. This approach allows for the use
of low-complexity single-bit configurations to suppress the undesired quantization lobes
without residing to the use of sophisticated multi-bit topologies.
The presented concepts pave the road toward the implementation and proliferation
of large-scale reconfigurable beamforming apertures that can serve both as mmWave/THz
imagers and as relays or base stations in future wireless communication applications.
ContributorsTheofanopoulos, Panagiotis (Author) / Trichopoulos, Georgios (Thesis advisor) / Balanis, Constantine (Committee member) / Aberle, James (Committee member) / Bliss, Dan (Committee member) / Groppi, Christopher (Committee member) / Arizona State University (Publisher)
Created2021
Description
This thesis describes the development, characterization, and application of new biomedical technologies developed around the photoacoustic effect. The photoacoustic effect is defined as optical absorption-based generation of ultrasound and provides the foundation for a unique method of imaging and molecular detection. The range of applications of the photoacoustic effect have not yet been fully explored. Photoacoustic endoscopy (PAE) has emerged as a minimally invasive tool for imaging internal organs and tissues. One of the main themes of this dissertation involves the first reported dual-intrauterine photoacoustic and ultrasound deep-tissue imaging endoscope. This device was designed to enable physicians at the point-of-care to better elucidate overall gynecological health, by imaging the lining of the human uterus. Intrauterine photoacoustic endoscopy is made possible due to the small diameter of the endoscope (3mm), which allows for complete, 360-degree organ analysis from within the uterine cavity. In certain biomedical applications, however, further minimization is necessary. Sufficiently small diameter endoscopes may allow for the possibility of applying PAE in new areas. To further miniaturize the diameter of our endoscopes, alternative imaging probe designs were investigated. The proposed PAE architecture utilizes a hollow optical waveguide to allow for concentric guiding of both light and sound. This enables imaging depths of up to several millimeters into animal tissue while maintaining an outer diameter of roughly 1mm. In the final focus of this dissertation, these waveguides are further investigated for use in micropipette electrodes, common in the field of single cell electrophysiology. Pulsed light is coupled with these electrodes providing real-time photoacoustic feedback, useful in navigation towards intended targets. Lastly, fluorescence can be generated and collected at the micropipette aperture by utilizing an intra-electrode tapered optical fiber. This allows for a targeted robotic approach to labeled neurons that is independent of microscopy.
ContributorsMiranda, Christopher (Author) / Smith, Barbara S. (Thesis advisor) / Kodibagkar, Vikram (Committee member) / LaBaer, Joshua (Committee member) / Frakes, David (Committee member) / Barkley, Joel (Committee member) / Arizona State University (Publisher)
Created2021