Proceedings of the meeting - Department of Physics - University of ...

Spectroscopy BasicsWhat is MRSpectroscopy ?A Method fordetecting andquantifying biologicalcompounds otherthan water.How does it differfrom normal MRI ?AmplitudeLess electrondensity aroundnucleusFrequencyMore electrondensity aroundnucleusSpectroscopy uses a standard MRI scanner but instead of frequencyencoding a spatial image it encodes chemical information.How does the scanner frequency encode chemical information ?Hydrogen (or other) Nuclei in different molecules resonate at differentfrequenciesWhy ?The resonant frequency is proportional to the magnetic fieldDoes the magnetic vary for different nuclei in different molecules?Yes it is dependent on the local climate.What is an MR Spectrum?It’s a graph of signal amplitude versus frequency.Frequency is expressed Hz or “Parts per Million” ppm .The Frequencyshift due to the differences in the chemical environment is called“Chemical Shift”.Generally the spectrum consists of water, fat and metabolites. Theconcentration ratio of water: Metabolites is greater than 10,000:1.Therefore water suppression is applied globally.1) Frequencies arespecific to thelocal chemicalenvironment2) Amplitudes areproportional tothe concentrationConcentrationdeterminesheightCompositiondeterminesposition (ppm)Which application areas are important ?Head, Body: Prostate, muscle, bone marrow, breast & liver, lungs & many otherdeveloping areas of interest. The real strength is that it allows clinicians to performdiagnostic biochemistry in vivo and define (new) features in the pathophysiology ofdisease. The key to achieving this is that we acquire accurate, reproducible spectra inshort acquisition times, compatible across all field strengthsand platforms and integrated into the routine clinicalarchitecture of the systems.