An illustrative example of image classification by an expert veterinary observer and an artificial neural network (ANN). In the case of a human observer, light photons trigger nerves in the retina, some of which activate and send signals to the brain. Within the brain, networks of neurons are selectively activated (green) or deactivated (red). This in turn triggers a response by a person with training and experience to classify the image as having pulmonary nodules on the basis of its similarity to other images seen previously. In an ANN, pixel data from the images enter at the level of the input layer before progressing through a series of hidden layers. Depending on the degree of activation or deactivation in the hidden layer, the ANN would classify the image, in this case correctly as a patient with pulmonary nodules.
Citation: Journal of the American Veterinary Medical Association 2022; 10.2460/javma.22.03.0093