Improvement of functional magnetic resonance images by pretreatment of data.

Functional magnetic resonance images of the brains of subjects performing the finger-tapping paradigm were made using a conventional technique. Two threshold values for the pixels were obtained by analysing pixel by pixel the distributions of the means and variances of each subject's images for 20 consecutive scans, both while performing the task and while at rest. Considerable signal improvement in the final images was achieved by removing from our data all pixels beyond these threshold values (mean < or = 16 and variance > or = 7).