Convolutional neural network based attenuation correction for 123I-FP-CIT SPECT with focused striatum imaging

Journal Article (2021)
Author(s)

Yuan Chen (TU Delft - RST/Biomedical Imaging)

M.C. Goorden (TU Delft - RST/Biomedical Imaging)

Freek J. Beekman (TU Delft - RST/Biomedical Imaging, University Medical Center Utrecht, MILabs B.V.)

Research Group
RST/Biomedical Imaging
Copyright
© 2021 Y. Chen, M.C. Goorden, F.J. Beekman
DOI related publication
https://doi.org/10.1088/1361-6560/ac2470
More Info
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Publication Year
2021
Language
English
Copyright
© 2021 Y. Chen, M.C. Goorden, F.J. Beekman
Research Group
RST/Biomedical Imaging
Issue number
19
Volume number
66
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Abstract

SPECT imaging with 123I-FP-CIT is used for diagnosis of neurodegenerative disorders like Parkinson's disease. Attenuation correction (AC) can be useful for quantitative analysis of 123I-FP-CIT SPECT. Ideally, AC would be performed based on attenuation maps (μ-maps) derived from perfectly registered CT scans. Such μ-maps, however, are most times not available and possible errors in image registration can induce quantitative inaccuracies in AC corrected SPECT images. Earlier, we showed that a convolutional neural network (CNN) based approach allows to estimate SPECT-aligned μ-maps for full brain perfusion imaging using only emission data. Here we investigate the feasibility of similar CNN methods for axially focused 123I-FP-CIT scans. We tested our approach on a high-resolution multi-pinhole prototype clinical SPECT system in a Monte Carlo simulation study. Three CNNs that estimate μ-maps in a voxel-wise, patch-wise and image-wise manner were investigated. As the added value of AC on clinical 123I-FP-CIT scans is still debatable, the impact of AC was also reported to check in which cases CNN based AC could be beneficial. AC using the ground truth μ-maps (GT-AC) and CNN estimated μ-maps (CNN-AC) were compared with the case when no AC was done (No-AC). Results show that the effect of using GT-AC versus CNN-AC or No-AC on striatal shape and symmetry is minimal. Specific binding ratios (SBRs) from localized regions show a deviation from GT-AC ≤ 2.5% for all three CNN-ACs while No-AC systematically underestimates SBRs by 13.1%. A strong correlation (r ≥ 0.99) was obtained between GT-AC based SBRs and SBRs from CNN-ACs and No-AC. Absolute quantification (in kBq ml-1) shows a deviation from GT-AC within 2.2% for all three CNN-ACs and of 71.7% for No-AC. To conclude, all three CNNs show comparable performance in accurate μ-map estimation and 123I-FP-CIT quantification. CNN-estimated μ-map can be a promising substitute for CT-based μ-map.