RESULTS OF FREQUENT QUALITY CONTROLS FOR QUANTITATIVE CLINICAL H-1-MR-SPECTROSCOPY

Different methods exist for an absolute quantification of in vivo prot on MR spectra. According to the principle of reciprocity a simple meth od has been suggested previously, comprising the multiplication of the spectral signals with the unlocalised reference amplitude of the meas urement as a correction for the different coil load. Afterwards, the r esult can be compared to measurements on phantoms in order to obtain i n vivo metabolite concentrations. Thus, only one calibration would be sufficient in principle for all measured spectra. However, during a pr evious serial study on humans and phantoms we observed significant cha nges in transmitter amplitudes over time, although metabolite peak are as remained quite constant. Hence, the method led to incorrect metabol ite concentrations. Since these effects are mostly underestimated or e ven neglected in clinical spectroscopy, the purpose of the present stu dy was to investigate these instabilities over time in order to find a new correction method for quantitative MRS. According to this new met hod, the spectra corrected by the coil load have to be modified additi onally by dividing by the reference amplitude of a phantom.