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CC BY 4.0 · World J Nucl Med
DOI: 10.1055/s-0044-1786165
Original Article

Evaluation of Improved Imaging Properties with Tungsten-Based Parallel-Hole Collimators: A Monte Carlo Study

Jalil Pirayesh Islamian 
1   Department of Medical Physics, Faculty of Medicine, Tabriz University of Medical Sciences, Tabriz, Iran
,
Michael Ljungberg
2   Department of Medical Radiation Physics, Lund, Lund University, Lund, Sweden
› Author Affiliations Funding This work was partly supported by funding from Science Faculty, Lund University, Lund, Sweden.
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Abstract

Objectives The purpose of a parallel-hole collimator in a scintillation camera system is to transmit only those photons that have an emission angle close to the direction of the hole. This makes it possible to receive spatial information about the origin of the emission, that is, radioactivity decay. The dimension, shape, and intrahole thickness determine the spatial resolution and, by a tradeoff, sensitivity. The composition of the collimator material also plays an important role in determining a proper collimator. In this study, we compared tungsten alloys as a potential collimator material replacement for the conventional lead antimony material used in most of the current camera systems.

Materials and Methods Monte Carlo simulations of a commercial scintillation camera system with low energy high resolution (LEHR), medium-energy (ME), and high-energy (HE) collimators of lead, tungsten, and tungsten-based alloy were simulated for different I-131, Lu-177, I-123, and Tc-99m sources, and a Deluxe rod phantom using the SIMIND Monte Carlo code. Planar images were analyzed regarding spatial resolution, image contrast in a cold source case, and system sensitivity for each collimator configuration. The hole dimensions for the three collimators were those specified in the vendor's datasheet.

Results Using Pb, W, and tungsten alloy (Wolfmet) as collimator materials, the full width at half maximum (FWHM) measures for total counts (T) for LEHR with Tc-99m source (6.9, 6.8, and 6.8 mm), for ME with Lu-177 source (11.7, 11.5, and 11.6 mm), and for HE with I-131 (6.2, 13.1, and 13.1 mm) were obtained, and the system sensitivities were calculated as 89.9, 86.1, and 89.8 cpsT/MBq with Tc-99m source; 42.7, 17.4, and 20.9 cpsT/MBq with Lu-177 source; and 40.1, 69.7, and 77.4 cpsT/MBq with I-131 source. The collimators of tungsten and tungsten alloy (97.0% W, 1.5% Fe, 1.5% Ni) provided better spatial resolution and improved image contrast when compared with conventional lead-based collimators. This was due to lower septal penetration.

Conclusion The results suggest that development of a new set of ME and HE tungsten and tungsten alloy collimators could improve imaging of I-131, Lu-177, and I-123.

Keywords

collimator - gamma camera - planar imaging - SIMIND - tungsten - spatial resolution - Wolfmet

Authors' Contribution

J.P.I. contributed to conceptualization, methodology, data curation, software, and writing the original draft. M.L. was responsible for supervision, funding acquisition, providing materials for SIMIND simulation, and review and editing of the manuscript.




Publication History

Article published online:
12 April 2024

© 2024. The Author(s). This is an open access article published by Thieme under the terms of the Creative Commons Attribution License, permitting unrestricted use, distribution, and reproduction so long as the original work is properly cited. (https://creativecommons.org/licenses/by/4.0/)

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