45 research outputs found
Statistical Sinogram Restoration in Dual-Energy CT for PET Attenuation Correction
Dual-energy (DE) X-ray computed tomography (CT)
has been found useful in various applications. In medical imaging,
one promising application is using low-dose DECT for attenuation
correction in positron emission tomography (PET). Existing approaches
to sinogram material decomposition ignore noise characteristics
and are based on logarithmic transforms, producing noisy
component sinogram estimates for low-dose DECT. In this paper,
we propose two novel sinogram restoration methods based on statistical
models: penalized weighted least square (PWLS) and penalized
likelihood (PL), yielding less noisy component sinogram estimates
for low-dose DECT than classical methods. The proposed
methods consequently provide more precise attenuation correction
of the PET emission images than do previous methods for sinogram
material decomposition with DECT. We report simulations
that compare the proposed techniques and existing approaches.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/85900/1/Fessler11.pd
A Detailed Hydrodynamic Study of the Split-Plate Airlift Reactor by using Non-Invasive Gamma-Ray Techniques
This study focused on detailed investigations of selected local hydrodynamics in split airlift reactor by using an unconventional measurements facility: computed tomography (CT) and radioactive particle tracking (RPT). The local distribution in a cross-sectional manner with its radial\u27s profiles for gas holdup, liquid velocity flow field, shear stresses, and turbulent kinetic energy were studied under various gas velocity 1, 2 and 3 cm/s with various six axial level z = 12, 20, 40, 60, 90 and 112 cm. The distribution in gas-liquid phases in the whole split reactor column, the riser and downcomer sides, including their behavior at the top and bottom sections of the split plate was also described. The outcomes of this study displayed an exemplary gas-liquid phases dispersion approximately in all reactor\u27s zones and had large magnitude over the ring of the sparger as well as upper the split plate. Furthermore, the outcomes pointed out that the distribution of this flow may significantly impacts the performance of the split reactor, which may have essential influence on its performance particularly for microorganisms culturing applications. These outcomes are dependable as benchmark information to validate computational fluid dynamics (CFD) simulations and other models
A Detailed Hydrodynamic Study of the Split-Plate Airlift Reactor by using Non-Invasive Gamma-Ray Techniques
This study focused on detailed investigations of selected local hydrodynamics in split airlift reactor by using an unconventional measurements facility: computed tomography (CT) and radioactive particle tracking (RPT). The local distribution in a cross-sectional manner with its radial\u27s profiles for gas holdup, liquid velocity flow field, shear stresses, and turbulent kinetic energy were studied under various gas velocity 1, 2 and 3 cm/s with various six axial level z = 12, 20, 40, 60, 90 and 112 cm. The distribution in gas–liquid phases in the whole split reactor column, the riser and downcomer sides, including their behavior at the top and bottom sections of the split plate was also described. The outcomes of this study displayed an exemplary gas–liquid phases dispersion approximately in all reactor\u27s zones and had large magnitude over the ring of the sparger as well as upper the split plate. Furthermore, the outcomes pointed out that the distribution of this flow may significantly impacts the performance of the split reactor, which may have essential influence on its performance particularly for microorganisms culturing applications. These outcomes are dependable as benchmark information to validate computational fluid dynamics (CFD) simulations and other models