  Weakly supervised disease classification of CT imaging suffers from poor
localization owing to case-level annotations, where even a positive scan can
hold hundreds to thousands of negative slices along multiple planes.
Furthermore, although deep learning segmentation and classification models
extract distinctly unique combinations of anatomical features from the same
target class(es), they are typically seen as two independent processes in a
computer-aided diagnosis (CAD) pipeline, with little to no feature reuse. In
this research, we propose a medical classifier that leverages the semantic
structural concepts learned via multi-resolution segmentation feature maps, to
guide weakly supervised 3D classification of chest CT volumes. Additionally, a
comparative analysis is drawn across two different types of feature aggregation
to explore the vast possibilities surrounding feature fusion. Using a dataset
of 1593 scans labeled on a case-level basis via rule-based model, we train a
dual-stage convolutional neural network (CNN) to perform organ segmentation and
binary classification of four representative diseases (emphysema,
pneumonia/atelectasis, mass and nodules) in lungs. The baseline model, with
separate stages for segmentation and classification, results in AUC of 0.791.
Using identical hyperparameters, the connected architecture using static and
dynamic feature aggregation improves performance to AUC of 0.832 and 0.851,
respectively. This study advances the field in two key ways. First, case-level
report data is used to weakly supervise a 3D CT classifier of multiple,
simultaneous diseases for an organ. Second, segmentation and classification
models are connected with two different feature aggregation strategies to
enhance the classification performance.
