[The effect of Gd-DTPA on magnetic resonance imaging: a potential blood-brain barrier indicator]

Magnetic resonance image (MRI) has been applied on central nervous system to evaluate the anatomical and functional aspects. On the other hand, gadolinium-diethylenetriamine-pentaacetic acid (Gd-DTPA) is considered to be a valuable contrast agent on MRI. This paramagnetic compound shortens the magnetic relaxation times of surrounding hydrogen nuclei by altering local magnetic environments. A molecular weight of this compound was 590, therefore this does not pass through the normal blood-brain barrier (BBB), and it may possible to detect a breakdown of BBB in vivo. In order to investigate the effect of Gd-DTPA as an indicator of BBB disruption on MRI, we measured T1 value of hemisphere of rat in osmotic BBB disruption model and experimental global cerebral ischemic model with and without Gd-DTPA. The MRI system employed was JNM-SMR 270 (JEOL) and the superconducting magnet was operated at a field strength of 6.34 tesla. Gd-DTPA was injected intra-venously through femoral vein and its dose was 0.5 mmol/kg. Osmotic BBB disruption model was made by intra-arterial injection of 25% mannitol through an internal carotid artery. Calculated T1 value of the ipsilateral hemisphere decreased with Gd-DTPA to 43.3 +/- 10.2% (n = 4) of control value immediately after BBB disruption with mannitol administration but no change of T1 value was recognized with Gd-DTPA in rats which Gd-DTPA was injected 4 hours after BBB disruption. Global ischemic insult was made by 3 vessel occlusion permanently and temporarily (30 or 120 minutes).(ABSTRACT TRUNCATED AT 250 WORDS)