Modeling optical coherence tomography (OCT) images is highly beneficial
for various image processing applications as well as assisting
ophthalmologists in the early detection of macular abnormalities. Sparse
representation-based models, particularly dictionary learning (DL), play
an important role in image modeling. Traditionally, DL transforms
higher-order tensors into vectors and aggregates them into matrices,
disregarding the multi-dimensional inherent structure of data. To
overcome this problem, tensor-based DL approaches have been developed.
In this study, we propose a tensor-based DL algorithm named CircWaveDL
for OCT classification where both the training data and the dictionary
are higher-order tensors. Instead of random initialization of the
dictionary, we suggested initializing it with CircWave atoms, which has
previously demonstrated its effectiveness in OCT classification. This
algorithm employs CANDECOMP/PARAFAC (CP) decomposition to factorize each
tensor into lower dimensions. Subsequently, we learn a sub-dictionary
for each class using the training tensor of that class. A test tensor is
reconstructed using each sub-dictionary individually and every test
B-scan is assigned to the class with the minimal residual error. To
assess the generalizability of the model, we have tested it on three
different databases. Furthermore, we introduce a new heatmap generation
approach based on averaging the most significant atoms of the learned
sub-dictionaries, demonstrating that selecting an appropriate
sub-dictionary for test B-scan restoration can lead to better
reconstructions, emphasizing distinctive features of different classes.
CircWaveDL demonstrates a high level of generalizability according to
external validation conducted on three different databases and it
outperforms previous classification methods designed for similar
datasets.