4.2 Inter-slice and sequence HAN
Our inter-slice and sequence HAN (hereafter sequence-HAN) was designed for abnormality detection using a collection of image slices from multiple MRI sequences. Like the intra- and inter-slice network, it built up a hierarchical data representation for abnormality classification, but this time at the series level. This was achieved by first building up individual sequence representations using separate LSTM units, CNNs, and slice-level attention modules. A sequence-level attention module then weighed the importance of each sequence representation, and the resulting series-level representation was again sent to a single layer classifier (Fig. 3).