Improvement of the Point Spread Function by Collimators’ New Configuration in Nuclear Medicine

Mapping Intimacies ◽

10.21203/rs.3.rs-595223/v1 ◽

2021 ◽

Author(s):

Mansour Ashoor ◽

Abdollah Khorshidi

Keyword(s):

Nuclear Medicine ◽

Point Source ◽

Point Spread Function ◽

Parametric Method ◽

Delta Function ◽

Mcnpx Code ◽

Point Spread ◽

Spread Function ◽

Cylindrical Volume ◽

Theoretical Results

Abstract Objective: The collimators in which the various geometrical configurations have been suggested to optimize the sensitivity and resolution have a key role in acquiring the qualified images in nuclear medicine towards a better recognition of some diseases. Methods: In this study, a new configuration as a geometrical combination of the conical, cylindrical and spherical (CCS) volumes for parallel hole collimators which is assessed by using the volumetric-parametric method has been introduced to improve point spread function (PSF) being the collimators response on the radioactive point source. It has been simulated by the MCNPX code at the various energies values of the point source along with the traditional collimator in which included the cylindrical volume only. Results: The PSF will transmogrify from a delta function to a distribution which can correlate with a Gaussian distribution, while the scattered gamma rays were increased. The simulation results have indicated that the PSF in the CCS configuration is narrower than that of the cylindrical one at all the energies, leading the improvement of the resolution. Also, the theoretical results are agreement with the simulated ones. The more the energy value of the source, the more broaden the PSF will be due the more penetration strength. The narrower the PSF, the better the qualified image will be. Conclusion: This method may be employed to determine the accurate attenuation coefficient of absorbers as well.

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Nonconvex Optimization for 3-Dimensional Point Source Localization Using a Rotating Point Spread Function

SIAM Journal on Imaging Sciences ◽

10.1137/18m1178566 ◽

2019 ◽

Vol 12 (1) ◽

pp. 259-286 ◽

Cited By ~ 1

Author(s):

Chao Wang ◽

Raymond Chan ◽

Mila Nikolova ◽

Robert Plemmons ◽

Sudhakar Prasad

Keyword(s):

Point Source ◽

Source Localization ◽

Nonconvex Optimization ◽

Point Spread Function ◽

3 Dimensional ◽

Point Spread ◽

Spread Function

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Point source detection based on point spread function symmetry

Optical Engineering ◽

10.1117/12.145055 ◽

1993 ◽

Vol 32 (9) ◽

pp. 2156 ◽

Cited By ~ 11

Author(s):

Jean-Pierre Ardouin

Keyword(s):

Point Source ◽

Point Spread Function ◽

Source Detection ◽

Point Spread ◽

Spread Function

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The nature of point source fringes in mid-infrared spectra acquired with the James Webb Space Telescope

Astronomy and Astrophysics ◽

10.1051/0004-6361/202037535 ◽

2020 ◽

Vol 641 ◽

pp. A150 ◽

Cited By ~ 1

Author(s):

Ioannis Argyriou ◽

Martyn Wells ◽

Alistair Glasse ◽

David Lee ◽

Pierre Royer ◽

...

Keyword(s):

Point Source ◽

Point Spread Function ◽

Point Sources ◽

Systematic Variation ◽

Multiple Point ◽

Mid Infrared ◽

Space Telescope ◽

Point Spread ◽

Spread Function ◽

Extended Sources

Context. As is common for infrared spectrometers, the constructive and destructive interference in different layers of the James Webb Space Telescope (JWST) Mid-Infrared Instrument (MIRI) detector arrays modulate the detected signal as a function of wavelength. The resulting “fringing” in the Medium-Resolution Spectrometer (MRS) spectra varies in amplitude between 10% and 30% of the spectral baseline. A common method for correcting for fringes relies on dividing the data by a fringe flat. In the case of MIRI MRS, the fringe flat is derived from measurements of an extended, spatially homogeneous source acquired during the thermal-vacuum ground verification of the instrument. While this approach reduces fringe amplitudes of extended sources below the percent level, at the detector level, point source fringe residuals vary in a systematic way across the point spread function. The effect could hamper the scientific interpretation of MRS observations of unresolved sources, semi-extended sources, and point sources in crowded fields. Aims. We find MIRI MRS point source fringes to be reproducible under similar observing conditions. We want to investigate whether a generic and accurate correction can be determined. Therefore, we want to identify the variables, if they exist, that would allow for a parametrization of the signal variations induced by point source fringe modulations. Methods. We determine the point source fringe properties by analyzing MRS detector plane images acquired on the ground. We extracted the fringe profile of multiple point source observations and studied the amplitude and phase of the fringes as a function of field position and pixel sampling of the point spread function of the optical chain. Results. A systematic variation in the amplitude and phase of the point source fringes is found over the wavelength range covered by the test sources (4.9 − 5.8 μm). The variation depends on the fraction of the point spread function seen by the detector pixel. We identify the non-uniform pixel illumination as the root cause of the reported systematic variation. This new finding allows us to reconcile the point source and extended source fringe patterns observed in test data during ground verification. We report an improvement after correction of 50% on the 1σ standard deviation of the spectral continuum. A 50% improvement is also reported in line sensitivity for a benchmark test with a spectral continuum of 100 mJy. The improvement in the shape of weak lines is illustrated using a T Tauri model spectrum. Consequently, we verify that fringes of extended sources and potentially semi-extended sources and crowded fields can be simulated by combining multiple point source fringe transmissions. Furthermore, we discuss the applicability of this novel fringe-correction method to the MRS data (and the data of other instruments).

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