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Indian J Nucl Med. 2019 Jan-Mar;34(1):24-26. doi: 10.4103/ijnm.IJNM_109_18.

Evaluation of Acceptance Angle in Iodine-131 Single Photon Emission Computed Tomography Imaging with Monte Carlo Simulation.

Author information

Department of Physics, LPHE, Modeling and Simulations, Faculty of Science, Mohammed V University, Rabat, Morocco.
Department of Medical Physics, Academic Hospital of Udine, Udine, Italy.



In iodine-131 (I-131) imaging, the image quality is degraded by scatter and penetration in a collimator. In this work, we assessed the penetrated and the scattered photon fractions in the photopeak energy window using Monte Carlo Simulation code.

Materials and Methods:

The Siemens Medical System equipped with high-energy collimator was simulated. We evaluated the acceptance angle values on geometric, penetration, and scatter components in a separate file. Binary images in a data file are obtained and each one of them was imported in software ImageJ. Full-width at half-maximum (FWHM) and sensitivity were calculated and compared.


The simulation data show that for the acceptance angle value equal to 4.845°, the geometric, scatter, and penetration components were 93.20%, 4.13%, and 2.67%, respectively. Moreover, the resolution is improved (FWHM = 7.21 mm, full width at tenth maximum = 12.36 mm) for a point source at 12 cm from the detector.


The small acceptance angle has a major impact on the image quality in I-131 single photon emission computed tomography.


Acceptance angle; I-131; geometrical; penetration; scatter; simulation Monte Carlo imaging nuclear detector

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