Design and evaluation of two multi-pinhole collimators for brain SPECT
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ORIGINAL ARTICLE
Design and evaluation of two multi-pinhole collimators for brain SPECT Ling Chen1 • Benjamin M. W. Tsui3 • Greta S. P. Mok1,2
Received: 12 April 2017 / Accepted: 7 July 2017 The Japanese Society of Nuclear Medicine 2017
1
Biomedical Imaging Laboratory (BIG), Department of Electrical and Computer Engineering, Faculty of Science and Technology, University of Macau, Avenida da Universidade, Taipa, Macau SAR, China
2
Faculty of Health Sciences, University of Macau, Avenida da Universidade, Taipa, Macau SAR, China
standard low-energy high-resolution (LEHR) collimators using analytical simulations of a digital NCAT brain phantom with 99mTc-HMPAO/99mTc-TRODAT-1 distributions; Monte Carlo simulations of a hot-rod phantom; and a Defrise phantom using GATE v6.1. Projections were generated over 360 and reconstructed using the 3D MPH/ LEHR OS-EM methods with up to 720 updates. The normalized mean square error (NMSE) was calculated over the cerebral and striatal regions extracted from the reconstructed images for 99mTc-HMPAO and 99mTc-TRODAT-1 simulations, respectively, and average normalized standard deviation (NSD) based on 20 noise realizations was assessed on selected uniform 3D regions as the noise index. Visual assessment and image profiles were applied to the results of Monte Carlo simulations. Results The optimized design parameters of the MPH collimators were 9 pinholes with 4.7 and 2.8 mm pinhole diameter, 73 acceptance angle, 127 mm focal length, 167 mm ROR for 12 mm and 8 mm target resolution, respectively. According to the optimization results, the detection efficiencies of the proposed collimators were 270 and 40% more as compared to LEHR. The Monte Carlo simulations showed that 7.9 and 6.4 mm rods can be discriminated for the MPH collimators with target resolutions of 12 and 8 mm, respectively. The eight 12 mm-thick discs of the Defrise phantom can also be resolved clearly in the axial plane as demonstrated by the image profiles generated with the MPH collimators. Conclusion The two collimator designs provide superior image quality as compared to the conventional LEHR, and shows potential to improve current brain SPECT imaging based on a conventional SPECT scanner.
3
Division of Medical Imaging Physics, The Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University, Baltimore, MD 21287, USA
Keywords Brain SPECT Multi-pinhole Alzheimer’s disease (AD) Parkinson’s disease (PD)
Abstract Objective SPECT is a powerful tool for diagnosing or staging brain diseases such as Alzheimer’s disease (AD) and Parkinson’s disease (PD) but is limited by its inferior resolution and sensitivity. At the same time, pinhole SPECT provides superior resolution and detection efficiency tradeoff as compared to the conventional parallel-hole collimator for imaging small field-of-view (FOV), which fits for the case of brain imaging. In this study, we propose to develop and evaluate two multi-pinhole (MPH) collimator designs to improve the imaging of cerebral blood flow a
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