Quantitative analysis of signal intensities and contrast after fat suppression in contrast-enhanced magnetic resonance imaging of the spine

We studied the effect of fat suppression on signal intensity and contrast on contrast-enhanced magnetic resonance (MR) images of the spine. Contrast-enhanced T1-weighted MR images were obtained at identical levels with and without fat suppression. Signal intensity and contrast were measured in regions of interest in fat, muscle, spinal bone marrow, and enhancing lesions. The differences in the mean values of these signal intensities and the mean values of contrast between enhanced tissues and bone marrow, fat, and muscle were subjected to statistical validation. Mean signal intensity of the extraspinal fat and bone marrow was lower after fat suppression (70% and 46% reduction, p < .001 and p < .05, respectively), whereas the signal intensity of muscle showed no significant change ( p < .9). Enhancing spinal lesions showed a difference in mean signal intensity after fat suppression (22% increase, p < .2). Contrast between enhanced lesions and bone marrow and fat was higher after fat suppression (78% increase, p < .01 for bone marrow; 8% increase, p < .001 for fat). In contrast-enhanced MR examinations of the spine, the use of fat suppression may increase the signal intensity of the enhancing lesion by expanding the dynamic gray scale of the image and increases the contrast between the lesion and adjacent bone marrow and suppressed fat.