Panel Disdussion

3rd International Congress 3rd International of Nuclear Congress Medicine of Nuclear & 15th Medicine Iranian Annual & 15th Iranian Congress Annual of
Nuclear Congress Medicine of Nuclear Medicine
Shahid Beheshti Shahid Beheshti University University of Medical Sciences of Medical 19-21 Sciences May 201119-21 May 2011
Estimation of Fan Beam Parameters by Parallel Beam
Collimator in Wire Mesh Design
Abdollah Khorshidi 1 , Mansour Ashoor 2
1 Department of Physics
2 Nuclear Science & Technology Research Institute
Introduction: Collimation of the low energy photons, allowing
detection of only those photons propagating in the appropriate
direction, plays a key role to obtain a suitable map in the Single
Photon Emission Computed Tomography (SPECT) imaging.
Methods: In this study, for assessment of Fan Beam (FB) and
Parallel Beam (PB) collimators responses various parameters have
been compared based on the Geometric Efficiency (G), Geometric
Resolution (Rc), Full Width at Half Maximum (FWHM) and Scatter and
Penetration (S+P) components. Monte Carlo (MC) simulations were
used for estimate the response of cubic hole collimators.
Results: Calculations demonstrated FB Geometry efficiency was
raised when angle of slant hole increased. In FB collimator, while
distance between point source and collimator surface (z) became
larger for a special angle, the Rc increased. But when hole angles
were enlarged for a special distance, the Rc reduced. Simulations in
wire mesh design indicated FB had the better resolution rather than
PB with cubic holes. Simulated point source responses are relatively
close to ADAC Company data. Moreover, whereas z increased the
S+P amounts decreased for both collimators.
Conclusion: The FB had the highest S+P and PB specified the lowest
amount with 1.04 ratio in air at 10 cm distance. The closeness of the
FB collimator responses demonstrated the cubic holes approximation
is applicable to the MC modeling of converging collimators.
Keywords: Fan Beam, Cube, FWHM, Penetration, Phantom
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