Alzheimer's disease (AD) is an irreversible progressive cerebral disease with most of its symptoms appearing after 60 years of age. Alzheimer's disease has been largely attributed to accumulation of amyloid beta (Aβ), but a complete cure has remained elusive. 18F-Florbetaben amyloid positron emission tomography (PET) has been shown as a more powerful tool for understanding AD-related brain changes than magnetic resonance imaging and computed tomography. In this paper, we propose an accurate classification method for scoring brain amyloid plaque load (BAPL) based on deep convolutional neural networks. A joint discriminative loss function was formulated by adding a discriminative intra-loss function to the conventional (cross-entropy) loss function. The performance of the proposed joint loss function was compared with that of the conventional loss function in three state-of-the-art deep neural network architectures. The intra-loss function significantly improved the BAPL classification performance. In addition, we showed that the mix-up data augmentation method, originally proposed for natural image classification, was also useful for medical image classification.Appl. Sci. 2020, 10, 965 2 of 13 fluid) Aβ/tau or amyloid PET [4], but clinical trials of Aβ-targeting drugs have been unsuccessful in clinical trials. This failure might be attributable to the late application of the treatment, highlighting the need for early treatment after early diagnosis [5]. Amyloid markers are the fastest appearing biomarkers early in the disease [6][7][8].In recent years, AD in MRI or PET brain images has been identified by various machine learning methods including deep learning [3,[9][10][11][12][13]. Zhang [9] classified AD and normal control images by a combined kernel technique with a support vector machine. Sarraf [10] developed the program DeepAD for AD diagnosis which analyzes sMRI and fMRI brain scans separately on the slice and subject levels by two convolutional neural networks (CNNs) (LeNet and GoogleNet). Farooq [11] classified AD in MRI scans by a deep CNN-based multi-class classification algorithm based on GoogleNet and ResNet. In a related study of PET images, Kang [12] proposed a classification method for scoring brain amyloid plaque load (BAPL) in FBB PET images which is based on a deep CNN developed by the Visual Geometry Group. Liu [13] combined a CNN with recurrent neural networks (RNN) for classifying amyloids in fluorodeoxyglucose (FDG) PET images. Although Kang's method satisfactorily classified images as positive or negative for amyloids, it could not accurately identify BAPL2 in a ternary classification, because BAPL2 is a weaker amyloid load than BAPL1 [12]. In some cases, the interpreter cannot easily distinguish between BAPL1 and BAPL2. Liu [13] studied FDG PET images, which are more appropriate for identifying progression markers than diagnostic markers, and clinically classified them as normal, mild cognitive impairment (MCI), or AD. Choi [7] combined florbetapir (not FBB) amyloid PET and FDG PET image...