4.7 Article

True ultra-low-dose amyloid PET/MRI enhanced with deep learning for clinical interpretation

Journal

Publisher

SPRINGER
DOI: 10.1007/s00259-020-05151-9

Keywords

PET/MRI; Deep learning; Amyloid PET; Ultra-low-dose PET

Funding

  1. NIH [P41-EB015891, P50-AG047366]
  2. GE Healthcare
  3. Michael J. Fox Foundation for Parkinson's Disease Research
  4. Foundation of the ASNR
  5. Life Molecular Imaging

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This study demonstrated that deep learning methods can enhance PET images from ultra-low injected dose PET/MRI data, showing significant improvement in image quality metrics and high accuracy in clinical diagnosis. The enhanced images were comparable to standard-dose images in terms of regional coefficient of variation, indicating the potential for dose reduction in amyloid imaging.
Purpose While sampled or short-frame realizations have shown the potential power of deep learning to reduce radiation dose for PET images, evidence in true injected ultra-low-dose cases is lacking. Therefore, we evaluated deep learning enhancement using a significantly reduced injected radiotracer protocol for amyloid PET/MRI. Methods Eighteen participants underwent two separate F-18-florbetaben PET/MRI studies in which an ultra-low-dose (6.64 +/- 3.57 MBq, 2.2 +/- 1.3% of standard) or a standard-dose (300 +/- 14 MBq) was injected. The PET counts from the standard-dose list-mode data were also undersampled to approximate an ultra-low-dose session. A pre-trained convolutional neural network was fine-tuned using MR images and either the injected or sampled ultra-low-dose PET as inputs. Image quality of the enhanced images was evaluated using three metrics (peak signal-to-noise ratio, structural similarity, and root mean square error), as well as the coefficient of variation (CV) for regional standard uptake value ratios (SUVRs). Mean cerebral uptake was correlated across image types to assess the validity of the sampled realizations. To judge clinical performance, four trained readers scored image quality on a five-point scale (using 15% non-inferiority limits for proportion of studies rated 3 or better) and classified cases into amyloid-positive and negative studies. Results The deep learning-enhanced PET images showed marked improvement on all quality metrics compared with the low-dose images as well as having generally similar regional CVs as the standard-dose. All enhanced images were non-inferior to their standard-dose counterparts. Accuracy for amyloid status was high (97.2% and 91.7% for images enhanced from injected and sampled ultra-low-dose data, respectively) which was similar to intra-reader reproducibility of standard-dose images (98.6%). Conclusion Deep learning methods can synthesize diagnostic-quality PET images from ultra-low injected dose simultaneous PET/MRI data, demonstrating the general validity of sampled realizations and the potential to reduce dose significantly for amyloid imaging.

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