Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Fully 3D Monte Carlo image reconstruction in SPECT using functional
  regions   Image reconstruction in Single Photon Emission Computed Tomography (SPECT) is
affected by physical effects such as photon attenuation, Compton scatter and
detector response. These effects can be compensated for by modeling the
corresponding spread of photons in 3D within the system matrix used for
tomographic reconstruction. The fully 3D Monte Carlo (F3DMC) reconstruction
technique consists in calculating this system matrix using Monte Carlo
simulations. The inverse problem of tomographic reconstruction is then solved
using conventional iterative algorithms such as maximum likelihood expectation
maximization (MLEM). Although F3DMC has already shown promising results, its
use is currently limited by two major issues: huge size of the fully 3D system
matrix and long computation time required for calculating a robust and accurate
system matrix. To address these two issues, we propose to calculate the F3DMC
system matrix using a spatial sampling matching the functional regions to be
reconstructed. In this approach, different regions of interest can be
reconstructed with different spatial sampling. For instance, a single value is
reconstructed for a functional region assumed to contain uniform activity. To
assess the value of this approach, Monte Carlo simulations have been performed
using GATE. Results suggest that F3DMC reconstruction using functional regions
improves quantitative accuracy compared to the F3DMC reconstruction method
proposed so far. In addition, it considerably reduces disk space requirement
and duration of the simulations needed to estimate the system matrix. The
concept of functional regions might therefore make F3DMC reconstruction
practically feasible.

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The categories of this paper are: acc-phys
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The categories of this paper are: q-fin
18
The categories of this paper are: econ
0
The categories of this paper are: hep-ph
7
The categories of this paper are: hep-th
12
The categories of this paper are: nucl-th
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The categories of this paper are: chao-dyn
32
The categories of this paper are: atom-ph
26
The categories of this paper are: bayes-an
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The categories of this paper are: supr-con
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The categories of this paper are: patt-sol
1
The categories of this paper are: cs
31
The categories of this paper are: ao-sci
27
The categories of this paper are: comp-gas
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The categories of this paper are: dg-ga
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The categories of this paper are: q-alg