Method for multimodal tissue imaging based on resonance Raman effect on metal based MRI contrast agents and method for ionizing laser plumes

Disclosed herein is a method for multimodal imaging during a medical procedure using magnetic resonance imaging (MRI) and Raman optical imaging which involves administering an MRI imaging contrast agent that a chemical structure having charge-transfer electronic transitions. The tissue is imaged using and MRI device and the tissue is illuminated with excitation light that has spectral components that are approximately tuned close to one of the charge-transfer electronic transitions thereby producing enhanced Raman optical signals which are analyzed to produce Raman imaging data followed by registering the MRI and Raman imaging data. The present disclosure also provides a method for ionizing laser plumes through atmospheric pressure chemical ionization.