Quantification of Manganese Enhanced Magnetic Resonance Imaging based on Spatially Resolved Elemental Mass Spectrometry

Niehoff AC , Wachsmuth L , Schmid F , Sperling M, Faber C , Karst U

Abstract

Laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) is proposed as a method to calibrate manganese enhanced magnetic resonance imaging (MEMRI) for the quantitative analysis of manganese accumulation in rat brain. T-1 maps of the brain of rats, either naive or after systemic fractionated manganese chloride administration were recorded in vivo and brain slices were subsequently investigated by LA-ICP-MS. Based on the proportional relationship between R-1, the rate constant of T-1 relaxation, and the concentration of manganese, a conversion function for retrospective quantification was generated, using a region of interest (ROI) analysis of corresponding MEMRI and LA-ICP-MS images. This conversion function was used to transform in vivo T-1 maps directly into local manganese concentrations, thus allowing an externally validated quantification of MEMRI in vivo experiments for the first time.