Three-Dimensional Reconstruction of the Tissue-Specific Multielemental Distribution within Ceriodaphnia dubia via Multimodal Registration Using Laser Ablation ICP-Mass Spectrometry and X-ray Spectroscopic Techniques

In this work, the three-dimensional elemental distribution profile within the freshwater crustacean Ceriodaphnia dubia was constructed at a spatial resolution down to 5 μm via a data fusion approach employing state-of-the-art laser ablation-inductively coupled plasma-time-of-flight mass spectrometry (LA-ICP-TOFMS) and laboratory-based absorption microcomputed tomography (μ-CT). C. dubia was exposed to elevated Cu, Ni, and Zn concentrations, chemically fixed, dehydrated, stained, and embedded, prior to μ-CT analysis. Subsequently, the sample was cut into 5 μm thin sections that were subjected to LA-ICP-TOFMS imaging. Multimodal image registration was performed to spatially align the 2D LA-ICP-TOFMS images relative to the corresponding slices of the 3D μ-CT reconstruction. Mass channels corresponding to the isotopes of a single element were merged to improve the signal-to-noise ratios within the elemental images. In order to aid the visual interpretation of the data, LA-ICP-TOFMS data were projected onto the μ-CT voxels representing tissue. Additionally, the image resolution and elemental sensitivity were compared to those obtained with synchrotron radiation based 3D confocal μ-X-ray fluorescence imaging upon a chemically fixed and air-dried C. dubia specimen.