4 research outputs found
Generalized-Equiangular Geometry CT: Concept and Shift-Invariant FBP Algorithms
With advanced X-ray source and detector technologies being continuously
developed, non-traditional CT geometries have been widely explored.
Generalized-Equiangular Geometry CT (GEGCT) architecture, in which an X-ray
source might be positioned radially far away from the focus of arced detector
array that is equiangularly spaced, is of importance in many novel CT systems
and designs. GEGCT, unfortunately, has no theoretically exact and
shift-invariant analytical image reconstruction algorithm in general. In this
study, to obtain fast and accurate reconstruction from GEGCT and to promote its
system design and optimization, an in-depth investigation on a group of
approximate Filtered BackProjection (FBP) algorithms with a variety of
weighting strategies has been conducted. The architecture of GEGCT is first
presented and characterized by using a normalized-radial-offset distance
(NROD). Next, shift-invariant weighted FBP-type algorithms are derived in a
unified framework, with pre-filtering, filtering, and post-filtering weights.
Three viable weighting strategies are then presented including a classic one
developed by Besson in the literature and two new ones generated from a
curvature fitting and from an empirical formula, where all of the three weights
can be expressed as certain functions of NROD. After that, an analysis of
reconstruction accuracy is conducted with a wide range of NROD. We further
stretch the weighted FBP-type algorithms to GEGCT with dynamic NROD. Finally,
the weighted FBP algorithm for GEGCT is extended to a three-dimensional form in
the case of cone-beam scan with a cylindrical detector array.Comment: 31 pages, 13 figure
Effects of lateral size, thickness, and stabilizer concentration on the cytotoxicity of defect-free graphene nanosheets: implicatioEffects of lateral size, thickness, and stabilizer concentration on the cytotoxicity of defect-free graphene nanosheets: implications for biological applicationsns for biological applications
In this work, we apply liquid cascade centrifugation
to highly
concentrated graphene dispersions produced by liquid-phase exfoliation
in water with an insoluble bis-pyrene stabilizer to obtain fractions
containing nanosheets with different lateral size distributions. The
concentration, stability, size, thickness, and the cytotoxicity profile
are studied as a function of the initial stabilizer concentration
for each fraction. Our results show that there is a critical initial
amount of stabilizer (0.4 mg/mL) above which the dispersions show
reduced concentration, stability, and biocompatibility, no matter
the lateral size of the flakes