Extracting a quality spectrum from the signal involves several processing steps:
- Zero-filling or apodization filtering to complete the digitized FID signal
- Phase correction to obtain the real part of the spectrum (absorption spectrum)
- Baseline correction
In vivo metabolite quantification
- Relative quantification: The results of the MRS are generally expressed as concentration ratios. Creatine peak or comparison with the healthy controlateral zone often serve as the reference values.
- Absolute quantification: Measuring the true concentration of metabolites by MRS comes up against several technical difficulties: the peak area has to be determined accurately then converted into concentration after calibration.