Reproducibility of magnetization transfer ratio histogram-derived measuresof the brain in healthy volunteers

Using two MR scanners, we evaluated the intraobserver, interobserver, image -reimage, and interimager variabilities in the assessment of magnetization transfer ratio (MTR) histograms obtained monthly on four occasions from fiv e healthy volunteers. With multiple observers, the mean coefficients of var iations ranged from 2.2% to 8.2% for "pure" image-reimage variability, from 1.2% to 4.9% for interobserver variability, and from 2.1% to 4.9% for imag e-reimage variability. The mean intraobserver coefficients of variations we re always lower than 1%, The mean coefficients of variations ranged from 10 .2% to 14.6% for pure interimager variability and from 8.6% to 14.3% for in terimager variability with multiple observers. Interimager variability acco unted for 96.0% of the overall variability of average MTR, for 96.7% of pea k location, and for 41.1% of the peak height. The use of different MR scann ers is the main source of variability when obtaining MTR histograms.