Diagnosis of Brain Tumor Using Chemical Shift Displacement Correction
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To account for the Chemical Shift Displacement (CSD) artifact in the framework of unsupervised brain tumor tissue differentiation methods based on 2Dmagnetic resonance spectroscopic imaging (MRSI) data. The CSD object is specific to the localization protocol used for selecting a certain volume of interest inside the brain. For vendorprovided point-resolved spectroscopy (PRESS) localization of MRSI on 3T clinical scanners, the CSD object implies that spectra corresponding to voxels within ~2cm of the borders of the selected volume are distorted, which means that the peaks at outer spectral regions are heavily suppressed. This effect may be wrongly interpreted as lower concentration or lack of some metabolites in the outer regions of the localized volume and may also hinder the methods for unsupervised tissue differentiation (e.g., non-negative matrix factorization). These methods can disentangle mixed tissue voxels in MRSI data acquired from brain tumors, and thus extract representative, tissue-specific spectra (called spectral sources), the spatial mixing coefficients and also the spectra assumed to be an approximate linear mixture of a few spectral sources. Here, we propose an approach to take the CSD artifact into account when evaluating the spatial distribution of tissue-specific spectral sources obtained from hierarchical non-negative matrix factorization.