Unrealistic Data Augmentation Improves the Robustness of Deep Learning–Based Classification of Dopamine Transporter SPECT Against Variability Between Sites and Between Cameras

Abstract

We propose strongly unrealistic data augmentation to improve the robustness of convolutional neural networks (CNNs) for automatic classification of dopamine transporter SPECT against the variability between sites and between cameras. Methods: A CNN was trained on a homogeneous dataset comprising 1,100 ¹²³I-labeled 2β-carbomethoxy-3β-(4-iodophenyl)-N-(3-fluoropropyl)nortropane SPECT images using strongly unrealistic data augmentation based on gaussian blurring and additive noise. Strongly unrealistic data augmentation was compared with no augmentation and intensity-based nnU-Net augmentation on 2 independent datasets with lower (n = 645) and considerably higher (n = 640) spatial resolution. Results: The CNN trained with strongly unrealistic augmentation achieved an overall accuracy of 0.989 (95% CI, 0.978–0.996) and 0.975 (95% CI, 0.960–0.986) in the independent test datasets, which was better than that without (0.960, 95% CI, 0.942–0.974; 0.953, 95% CI, 0.934–0.968) and with nnU-Net augmentation (0.972, 95% CI, 0.956–0.983; 0.950, 95% CI, 0.930–0.966) (all McNemar P < 0.001). Conclusion: Strongly unrealistic data augmentation results in better generalization of CNN-based classification of ¹²³I-labeled 2β-carbomethoxy-3β-(4-iodophenyl)-N-(3-fluoropropyl)nortropane SPECT images to unseen acquisition settings. We hypothesize that this can be transferred to other nuclear imaging applications.