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Shielding requirements of a SPECT insert for installation in a PET/MRI system

Salvado, D; Erlandsson, K; Hutton, BF; (2016) Shielding requirements of a SPECT insert for installation in a PET/MRI system. In: 2015 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC). IEEE Green open access

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Abstract

The objective of this work is to evaluate the shielding requirements of a SPECT insert for installation in the Siemens Biograph mMR in order to perform simultaneous SPECT/MR imaging of the human brain. We intend to use the radionuclides 99mTc, 123I and 111In. The main photopeaks of these radionuclides have the following energies: 140.5, 159.0, 171.3 and 245.4 keV. There is also about ∼3% of emission probability of high energy gamma photons for 123I in the range of 248-784 keV. The main constraints to the design of the gamma shielding are the presence of high energy photons, the weight, the MR compatibility and the PET LSO crystals intrinsic activity. We used GATE to simulate a SPECT acquisition, defining an MRI system with LSO crystals, a partial SPECT ring and a NEMA phantom. We also defined a lead (Pb) base plate (BP) to simulate the support system and three Pb shielding volumes with variable thickness: front and end (FE), back (B), and lateral (L) shield. These volumes reduce interference from out-of-field activity, LSO intrinsic activity and edge effects, respectively. We performed 4 sets of simulations, with variable FE, variable B, variable L and variable BP thickness, respectively, with a NEMA phantom filled with 185 MBq of 123I or 111In. For all simulations, we compared the different energy spectra and count-distribution plots. Results show that a Pb shielding configuration with a thickness of 6 mm-F, 2 mm-E, 3 mm-B, and 5 mm-L is appropriate for the insert. For 123I there is still a high contribution from high energy photons, as the amount of shielding is limited by weight, however this contribution is likely to be overestimated in the simulations as compared to practice. The effect of the LSO intrinsic activity is negligible at the energies of interest.

Type: Proceedings paper
Title: Shielding requirements of a SPECT insert for installation in a PET/MRI system
Event: 2015 IEEE Nuclear Science Symposium and Medical Imaging Conference: 22nd International Symposium on Room-Temperature Semiconductor X-Ray and Gamma-ray Detectors
Location: San Diego, California, United States
Dates: 31 October 2015 - 07 November 2015
ISBN-13: 9781467398626
Open access status: An open access version is available from UCL Discovery
DOI: 10.1109/NSSMIC.2015.7582068
Publisher version: http://ieeexplore.ieee.org/document/7582068/
Language: English
Additional information: © 2015 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.
Keywords: Single photon emission computed tomography, Detectors, Iron, Photonics, Lead, Crystals, Phantoms, technetium, biomedical MRI, brain, indium, iodine, phantoms, positron emission tomography, single photon emission computed tomography, 111In, PET imaging, SPECT imaging, MR imaging, human brain, radionuclides, high energy gamma photon emission probability, high energy photons, electron volt energy 140.5 keV, electron volt energy 159.0 keV, electron volt energy 171.3 keV, gamma shielding, SPECT/MR, SPECT insert, multi-modality
UCL classification: UCL
UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Medical Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Medical Sciences > Div of Medicine
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Medical Sciences > Div of Medicine > Metabolism and Experi Therapeutics
URI: https://discovery.ucl.ac.uk/id/eprint/1529759
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