Final colloquium Melissa Molenaars

Deep Non-Negative Matrix Factorization to Improve Interpretability of Imaging Mass Spectrometry Data

Supervisor: R. Van de plas

Abstract:

In medical research, Imaging Mass Spectrometry (IMS) is a powerful tool that facilitates the spatial mapping of biomolecules in tissue samples, contributing to the identification of disease biomarkers and the analysis of drug effects. While offering valuable insights, IMS data is often large and complex, presenting challenges in data interpretation. Traditional techniques such as principal component analysis (PCA) and non-negative matrix factorization (NMF) have been employed to address these issues, but they fall short due to their inability to fully capture the complex, mixed nature of IMS data. Deep non-negative matrix factorization (deep NMF) offers a promising solution by employing a multi-layer architecture, allowing for dimensionality reduction while improving interpretability.

Deep NMF can decompose IMS data into multiple structures, helping to uncover complex biochemical interactions. This thesis explores the application of deep NMF to IMS data, deriving update algorithms for both the Frobenius norm and generalized Kullback-Leibler (gKL) divergence, and testing these methods on MALDI-TOF IMS data. Results show that the deep multiplicative update rule (MUR) outperforms non-deep methods in terms of interpretability and surpasses multi-layer structures in both reconstruction error and interpretability. Computational challenges remain in tuning algorithm parameters and achieving convergence in deep Alternating Direction Method of Multipliers (ADMM) NMF.