Acquisitions of mass-per-charge (m/z) spectrometry data from tissue samples, at high spatial resolutions, using Mass Spectrometry Imaging (MSI), require hours to days of time. The Deep Learning Approach for Dynamic Sampling (DLADS) and Supervised Learning Approach for Dynamic Sampling with Least-Squares (SLADS-LS) algorithms follow compressed sensing principles to minimize the number of physical measurements performed, generating low-error reconstructions from spatially sparse data. Measurement locations are actively determined during scanning, according to which are estimated, by a machine learning model, to provide the most relevant information to an intended reconstruction process. Preliminary results for DLADS and SLADS-LS simulations with Matrix-Assisted Laser Desorption/Ionization (MALDI) MSI match prior 70% throughput improvements, achieved in nanoscale Desorption Electro-Spray Ionization (nano-DESI) MSI. A new multimodal DLADS variant incorporates optical imaging for a 5% improvement to final reconstruction quality, with DLADS holding a 4% advantage over SLADS-LS regression performance. Further, a Forward Feature Selection (FFS) algorithm replaces expert-based determination of m/z channels targeted during scans, with negligible impact to location selection and reconstruction quality.
A Supervised Learning Approach for Dynamic Sampling (SLADS) addresses traditional issues with the incorporation o stochastic processes into a compressed sensing method. Statistical features, extracted from a sample reconstruction, estimate entropy reduction with regression models, in order to dynamically determine optimal sampling locations. This work introduces an enhanced SLADS method, in the form of a Deep Learning Approach for Dynamic Sampling (DLADS), showing reductions in sample acquisition times for high-fidelity reconstructions between ˜ 70–80% over traditional rectilinear scanning. These improvements are demonstrated for dimensionally asymmetric, high-resolution molecular images of mouse uterine and kidney tissues, as obtained using Nanospray Desorption Electro- Spray Ionization (nano-DESI) Mass Spectrometry Imaging (MSI). The methodology for training set creation is adjusted to mitigate stretching artifacts generated when using prior SLADS approaches. Transitioning to DLADS removes the need for feature extraction, further advanced with the employment of convolutional layers to leverage inter-pixel spatial relationships. Additionally, DLADS demonstrates effective generalization, despite dissimilar training and testing data. Overall, DLADS is shown to maximize potential experimental throughput for nano-DESI MSI.