Article Figures & Data
Figures
- FIG 1.
A schematic of the GAN (generator network, upper image; discriminator network, lower image) used in this work and its input and output channels. The arrows denote computational operations, and the tensors are denoted by boxes, with the number of channels indicated above each box. BN indicates batch normalization; Conv, convolution; Max, maximum; ReLU, rectified linear unit; tanh, hyperbolic tangent.
- FIG 2.
Representative τ PET images and their corresponding T1-weighted MR image in 2 individuals positive for amyloid. The enhanced PET image shows greatly reduced noise compared with the ultra-low-dose PET image. Arrows correspond to regions of abnormal elevated τ uptake. MCI indicates mild cognitive impairment.
- FIG 3.
Image-quality metrics comparing the ultra-low-dose PET (LD) and the ultra-low-dose enhanced PET (E) images with the ground truth full-dose PET image. PSNR indicates peak signal-to-noise ratio; SSIM, structural similarity; RMSE, root mean square error.
- FIG 4.
Mean (SD) of SUVR coefficient of variation in selected brain regions. E indicates enhanced images; FD, full-dose images; Inf. Cerebel, inferior cerebellum; MTL, medial temporal lobe; LD, ultra-low-dose image; Inf. Temporal, inferior temporal cortex
- FIG 5.
Bland-Altman plots comparing mean SUVRs in the ultra-low-dose PET and the enhanced PET with the full-dose PET images. The red dots denote healthy controls positive for amyloid, and the regions selected are the FreeSurfer labels, which make up the bilateral medial temporal lobe (entorhinal, amygdala) and the bilateral inferior temporal cortex.
- FIG 6.
Quality scores of different image types as rated by 3 expert readers. Image quality scores: 1, uninterpretable; 2, bad; 3, adequate; 4, good; 5, excellent. FD indicates full-dose; LD, ultra-low-dose; E, enhanced.
Tables
Healthy Control AD CBS MCI PSP svPPA No. 31 5 1 4 1 2 Age (mean) (yr) 70.13 (SD, 6.43) 67.8 (SD, 13.48) 76 71.5 (SD, 10.54) 71 66, 78 Sex (female) 12 3 0 2 0 1 Amyloid status 7 P, 21 N 4 P 3 P, 1 N Note:—CBS indicates cortical basal syndrome; MCI, mild cognitive impairment; N, negative; P, positive; PSP, progressive supranuclear palsy; svPPA, semantic variant primary-progressive aphasia.
- Table 2:
Gwet's AC1 between and within readers of 10 randomly selected full-dose images on the tracer uptake in relevant brain regions and on the subjective image quality
Gwet's AC1 Interreader Reproducibility (Reader 1) Reproducibility (Reader 2) Reproducibility (Reader 3) Normal 0.677 0.727 0.628 1 Entorhinal cortex 0.813 1 1 0.883 Hipp./Amyg./Parahipp. 0.677 0.771 1 1 Inferior/mesial temporal 0.901 1 1 1 Other cortex 0.830 0.872 0.669 1 Primary eloquent cortex 0.967 1 1 1 Quality (high vs low) 0.797 1 0.599 0.760 Note:—Normal indicates no abnormal uptake in any of the selected regions; Hipp., hippocampus; Amyg., amygdala; Parahipp., parahippocampal gyrus.
- Table 3:
Accuracy, sensitivity, and specificity of ultra-low-dose images and enhanced images compared with the full-dose images
Metric Full-Dose vs Ultra-Low-Dose Full-Dose vs Enhanced Accuracy (%) Sensitivity (%) Specificity (%) Accuracy (%) Sensitivity (%) Specificity (%) Normal 86.4 89.7 77.1 84.8 87.6 77.1 Entorhinal cortex 92.4 50.0 97.5 93.9 42.9 98.3 Hipp./Amyg./Parahipp. 87.9 54.2 95.4 88.6 66.7 93.5 Inferior/mesial temporal 95.5 83.3 97.4 93.2 77.8 95.6 Other cortex 87.9 73.9 90.8 88.6 87.0 89.0 Primary eloquent cortex 95.5 80.0 96.1 99.2 80.0 100 Note:— Normal indicates no abnormal uptake in any of the selected regions; Hipp., hippocampus; Amyg., amygdala; Parahipp., parahippocampal gyrus.
