High Spatial Resolution Ambient Ionization Mass Spectrometry Imaging Using Microscopy Image Fusion Determines Tumor Margins

Abstract

Mass spectrometry imaging (MSI) using ambient ionization technique enables a direct chemical investigation of biological samples with minimal sample pretreatment. However, detailed morphological information of the sample is often lost due to its limited spatial resolution. We demonstrated that the fusion of ambient ionization MSI with optical microscopy of routine hematoxylin and eosin (H&E) staining produces predictive, high-resolution molecular imaging. In this study, desorption electrospray ionization (DESI) and nanospray desorption electrospray ionization (nanoDESI) mass spectrometry were emplo yed to visualize lipid and protein species on mouse tissue sections. The resulting molecular distributions obtained by ambient ionization MSI-microscopy fusion were verified with matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) MSI and routine immunohistochemistry (IHC) staining on the adjacent sections. Label-free molecular imaging with 5-µm spatial resolution can be achieved using DESI and nanoDESI, whereas the typical spatial resolution of ambient ionization MSI is ~100 µm. In this regard, sharpened molecular histology of tissue sections was achieved, providing complementary references to the pathology. Such multi-modality integration enabled the discovery of potential tumor biomarkers. After image fusion, we identified about 70% more potential biomarkers that could be used to determine the tumor margins on a lung tissue section with metastatic tumors. spectrometry (SIMS) MSI, were reported to achieve sharpened molecular imaging with spatial resolution at cellular level on tissue sections 36,37 . approach for image fusion was reported to be broadly applicable to different tissue type. The distribution of ions was clear at the sub-cellular level. Sharped ion images of MALDI mass spectrometry fused with microscopy of mouse tissue sections were shown in their study 37 . In addition, fusion of SIMS and electron microscopy images were also reported 38 . Although high resolution molecular distribution were revealed, these mass spectrometry methods operated under high vacuum, which limits the compatibility with conventional imaging methods for pathological examinations.In our study, an optical microscope was applied to obtain images containing meticulous details of H&E stained tissue sections. Using multivariate regression algorithm, we fused MSI with optical microscopy and generated predictive fine-grained MSI. This method was applied in different tissue types and demonstrated as a tool for cancer diagnosis. By combining optical microscopy with ambient ionization methods, DESI, and nanoDESI, for tissue mapping with image fusion, both the image resolution and image quality were greatly improved. The workflow of our study is shown in Fig. 1. ResultsElevating spatial resolution of lipid species mapping in DESI MSI. The results for fusion of DESI MSI for mouse brain and cerebellum coronal sections were shown in Fig. 2, whereas the results for mouse kidney sections were shown in Fig. 3. In Fig. 2, the dis...

Multimodal Imaging Mass Spectrometry: Next Generation Molecular Mapping in Biology and Medicine

“…This is particularly difficult within an imaging regime because the various technologies can have dramatically different spatial resolutions, data structures, and chemical information. Different computation methods for addressing differences within spatial resolution include various methods of up sampling the data, performing more refined data fusion, as well as other experimental approaches. ,,− While these are capable of connecting modalities that are similar in resolution, significant experimental and technological capabilities are required to avoid the introduction of artifacts . While many imaging modalities are within an order of magnitude of one another, this will influence the capacity to combine lower spatial resolution IMS technologies like DESI with higher resolution molecular imaging approaches, like SEM.…”