Abstract
Objective
To obtain attenuation-corrected PET images directly from non-attenuation-corrected images using a convolutional encoder-decoder network.
Methods
Brain PET images from 129 patients were evaluated. The network was designed to map non-attenuation-corrected (NAC) images to pixel-wise continuously valued measured attenuation-corrected (MAC) PET images via an encoder-decoder architecture. Image quality was evaluated using various evaluation metrics. Image quantification was assessed for 19 radiomic features in 83 brain regions as delineated using the Hammersmith atlas (n30r83). Reliability of measurements was determined using pixel-wise relative errors (RE; %) for radiomic feature values in reference MAC PET images.
Results
Peak signal-to-noise ratio (PSNR) and structural similarity index metric (SSIM) values were 39.2 ± 3.65 and 0.989 ± 0.006 for the external validation set, respectively. RE (%) of SUVmean was − 0.10 ± 2.14 for all regions, and only 3 of 83 regions depicted significant differences. However, the mean RE (%) of this region was 0.02 (range, − 0.83 to 1.18). SUVmax had mean RE (%) of − 3.87 ± 2.84 for all brain regions, and 17 regions in the brain depicted significant differences with respect to MAC images with a mean RE of − 3.99 ± 2.11 (range, − 8.46 to 0.76). Homogeneity amongst Haralick-based radiomic features had the highest number (20) of regions with significant differences with a mean RE (%) of 7.22 ± 2.99.
Conclusions
Direct AC of PET images using deep convolutional encoder-decoder networks is a promising technique for brain PET images. The proposed deep learning method shows significant potential for emission-based AC in PET images with applications in PET/MRI and dedicated brain PET scanners.
Key Points
• We demonstrate direct emission-based attenuation correction of PET images without using anatomical information.
• We performed radiomics analysis of 83 brain regions to show robustness of direct attenuation correction of PET images.
• Deep learning methods have significant promise for emission-based attenuation correction in PET images with potential applications in PET/MRI and dedicated brain PET scanners.
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Abbreviations
- AC:
-
Attenuation correction
- CGAN :
-
Conditional generative adversarial networks
- CNN :
-
Convolutional neural network
- Deep-DAC:
-
Deep direct attenuation correction
- FOV :
-
Field of view
- GLCM :
-
Gray-level co-occurrence matrix
- GLRLM:
-
Gray-level run length matrix
- GLZLM:
-
Gray-level size zone matrix
- GPU:
-
Graphics processing unit
- LRE:
-
Long-run emphasis
- MAC :
-
Measured attenuation corrected
- MAE :
-
Mean absolute error
- MLAA :
-
Maximum likelihood reconstruction of activity and attenuation
- MRI:
-
Magnetic resonance imaging
- MSE :
-
Mean squared error
- NAC :
-
Non-attenuation corrected
- OSEM:
-
Ordered subset expectation maximization
- PET:
-
Positron emission tomography
- PSNR :
-
Peak signal-to-noise ratio
- RBM :
-
Restricted Boltzmann machine
- RE:
-
Relative errors
- ReLU :
-
Rectified linear unit
- RFV :
-
Radiomic feature values
- RMSE :
-
Root mean squared error
- RP:
-
Run percentage
- SRE:
-
Short-run emphasis
- SSIM :
-
Structural similarity index metrics
- SUV:
-
Standard uptake value
- SZE :
-
Size zone emphasis
- TLG:
-
Total lesion glycolysis
- TOF:
-
Time of flight
- UTE :
-
Ultra-short echo time
- VOI :
-
Volumes of interest
- ZP:
-
Zone percentage
- ZTE :
-
Zero echo time
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Funding
This study has received funding the Tehran University of Medical Sciences under grant number 97-01-30-38001.
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The scientific guarantor of this publication is Mohammad Reza Ay, PhD, Professor of Medical Physics.
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Shiri, I., Ghafarian, P., Geramifar, P. et al. Direct attenuation correction of brain PET images using only emission data via a deep convolutional encoder-decoder (Deep-DAC). Eur Radiol 29, 6867–6879 (2019). https://doi.org/10.1007/s00330-019-06229-1
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DOI: https://doi.org/10.1007/s00330-019-06229-1