Measurement of brain activity with bolus administration of contrast agent and gradient-echo MR imaging

This study was performed to measure changes in cerebral blood volume (CBV) associated with visual activation by use of bolus administration of contrast agent and conventional, clinically configured magnetic resonance (MR) hardware and software. Fast gradient-recalled acquisition in the steady state technique was used to study five healthy subjects during visual activation and a control dark state. MR images were obtained every 2.048 seconds for 2 minutes. A bolus of gadopentetate dimeglumine was injected during visual stimulation and darkness. Cine images produced from the series of rapid images clearly depicted arterial, capillary, and venous phases. Analysis of serial concentration maps derived from the rapid images revealed expected differences between the relative CBV of gray matter and that of white matter, as well as significantly increased relative CBV in calcarine cortex during visual activation versus the control state (mean increase, 15.24%; range, 6.41%-27.78%; P < .05). These results confirm those reported in echo-planar imaging studies and demonstrate that brain function can be assessed with the bolus method by means of MR imaging hardware and software with conventional clinical configurations.