Learning from irregularly sampled data for endomicroscopy super-resolution: a comparative study of sparse and dense approaches

Agnieszka Barbara Szczotka, Dzhoshkun Ismail Shakir, Daniele Ravì, Matthew J. Clarkson, Stephen P. Pereira, Tom Vercauteren

Research output: Contribution to journalArticlepeer-review

3 Citations (Scopus)


Purpose: Probe-based confocal laser endomicroscopy (pCLE) enables performing an optical biopsy via a probe. pCLE probes consist of multiple optical fibres arranged in a bundle, which taken together generate signals in an irregularly sampled pattern. Current pCLE reconstruction is based on interpolating irregular signals onto an over-sampled Cartesian grid, using a naive linear interpolation. It was shown that convolutional neural networks (CNNs) could improve pCLE image quality. Yet classical CNNs may be suboptimal in regard to irregular data. Methods: We compare pCLE reconstruction and super-resolution (SR) methods taking irregularly sampled or reconstructed pCLE images as input. We also propose to embed a Nadaraya–Watson (NW) kernel regression into the CNN framework as a novel trainable CNN layer. We design deep learning architectures allowing for reconstructing high-quality pCLE images directly from the irregularly sampled input data. We created synthetic sparse pCLE images to evaluate our methodology. Results: The results were validated through an image quality assessment based on a combination of the following metrics: peak signal-to-noise ratio and the structural similarity index. Our analysis indicates that both dense and sparse CNNs outperform the reconstruction method currently used in the clinic. Conclusion: The main contributions of our study are a comparison of sparse and dense approach in pCLE image reconstruction. We also implement trainable generalised NW kernel regression as a novel sparse approach. We also generated synthetic data for training pCLE SR.

Original languageEnglish
Pages (from-to)1167-1175
Number of pages9
JournalInternational Journal of Computer Assisted Radiology and Surgery (IJCARS)
Issue number7
Publication statusPublished - 1 Jul 2020


  • CNN
  • Nadaraya–Watson kernel regression
  • pCLE reconstruction
  • Super-resolution


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