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Convolutional neural networks are known to require large amounts of data to achieve optimal performance. In addition, data is commonly computationally augmented using a variety of geometric and intensity transformations to further extent the set of training samples. In medical imaging, annotated data is often scarce or costly to obtain, and there is considerable interest in methods to reduce the amount of data needed. In this work, we investigate the relative benefit of increasing the amount of original data, with respect to computationally augmenting the amount of training samples, for the case of false positive reduction of lung nodules candidates. To this end, we have implemented a previously published topology for classification, shown to achieve state of the art results on the publicly available Luna16 dataset. Numerous models were trained using different amounts of unique training samples and different degrees of data augmentation involving rotations and translations, and the performance was compared. Results indicate that in general, better performance is achieved when increasing the amount of data, or augmenting the data more extensively, as expected. Surprisingly however, we observed that after reaching a certain amount of unique training samples, data augmentation leads to significantly better performance compared to adding the same number of new samples to the training dataset. We hypothesize that the augmentation has aided in learning more general {rotation and translation invariant-features, leading to improved performance on unseen data. Future experiments include more detailed characterization of this behavior, and relating this to the topology and amount of parameters to be trained.

Computer aided diagnosis systems are used to assist radiologists in their decision making. The sensitivity of these systems is hindered by the complexity of the structures inside the lungs. Several systems and methods have been proposed to detect and classify lung nodules, but all of them have their strengths and weaknesses. One way to overcome the weaknesses is to combine multiple systems. Systems based on handcrafted features capture a limited set of characteristics from the image, while deep learning based classifiers can deal with a wider range of structures. In this work, several ways to combine a handcrafted feature based classifier with four convolutional neural network are explored. The systems were combined merging the probabilities assigned to the detections in several ways. Support-vector machine, multilayer perceptron and random forest classifiers were used to combine the selected classifiers. The LUNA16 Challenge was used to evaluate the performance of the resulting hybrid systems. In all cases, the hybrid systems outperformed the individual systems. Although the average of sensitivities are similar for most of the combinations, the best hybrid system achieves a gain of 35 extra nodules at 4 FP per scan.

Recently, efficient image descriptors have shown promise for image classification tasks. Moreover, methods based on the combination of multiple image features provide better performance compared to methods based on a single feature. This work presents a simple and efficient approach for combining multiple image descriptors. We first employ a Naive-Bayes Nearest-Neighbor scheme to evaluate four widely used descriptors. For all features, “Image-to-Class” distances are directly computed without descriptor quantization. Since distances measured by different metrics can be of different nature and they may not be on the same numerical scale, a normalization step is essential to transform these distances into a common domain prior to combining them. Our experiments conducted on a challenging database indicate that z-score normalization followed by a simple sum of distances fusion technique can significantly improve the performance compared to applications in which individual features are used. It was also observed that our experimental results on the Caltech 101 dataset outperform other previous results.

This paper provides an overview of the medical scales which are currently in practice at the geriatrics department of the hospital for assessing independence and mobility of elderly patients. Several shortcomings and issues related to the scales are identified. It is shown how a 3D camera system could be used for the automatic assessment of several items of the scales. this automated assessment is overcoming many of the issues with the existing methods. An analysis of the automatically identified activity features of a typical patient is used to compare the data derived from our system with data obtained with accelerometer readings.