TISSUE CHARACTERIZATION BY MAGNETIC-RESONANCE SPECTROSCOPY AND IMAGING - RESULTS OF A CONCERTED RESEARCH-PROJECT OF THE EUROPEAN-ECONOMIC-COMMUNITY .5. IN-VIVO FIELD-DEPENDENCE OF PROTON RELAXATION-TIMES IN HUMAN BRAIN, LIVER AND SKELETAL-MUSCLE - A MULTICENTER STUDY

T1 and T2 relaxation times are fundamental parameters for signal contrast behaviour in MRI. A number of ex vivo relaxometry studies have dealt with the magnetic field dispersion of T1. By means of a multicenter study within the frame of the COMAC BME Concerted Action on Tissue Characterization by MRI and MRS, the in vivo field dispersion of T1 and T2 has been measured in order to evaluate whether ex vivo data are representative for the in vivo situation. Brain, skeletal muscle, and liver of healthy human volunteers were studied. Fifteen MR units with a field strength ranging from 0.08 T to 1.5 T took part in the trial, which comprised 218 volunteers. All the MR systems were tested for measurement accuracy using the Eurospin TO5 test object. The measured relaxation data were subsequently corrected according to the obtained calibration curves. The results showed a clear field dispersion of T1, whereas no significant variations were seen for T2. Our in vivo data were generally in reasonable agreement with proposed models based on ex vivo measurements.