Visualization of blood-brain barrier disruption on MR images of cats with acute cerebral infarction: value of administering a high dose of contrast material.

Abstract

The detection of blood-brain barrier disruption in patients with cerebral infarction by means of contrast-enhanced MR images improves the specificity of diagnosis, enables lesion dating, and on occasion improves lesion detection. Accordingly, we performed a study to determine the extent of visualization of disruption of the blood-brain barrier on contrast-enhanced MR images, with specific attention to contrast dose, in a cat model of acute cerebral infarction. We used doses of 0.1 and 0.3 mmol/kg of a gadolinium chelate, gadoteridol, which is characterized by extracellular distribution and renal excretion, and was approved by the Food and Drug Administration for clinical use at these doses. Blood flow in the middle cerebral artery was occluded unilaterally in seven cats for 1 hr, followed by 4 hr of reperfusion. T2- and T1-weighted MR images were obtained before the injection of contrast material. After injection, the time course of enhancement was observed for 1 hr by repeated sequential acquisition of T1-weighted images. Five cats received an initial injection of 0.1 mmol/kg of contrast material, supplemented 33 min later by 0.2 mmol/kg (cumulative dose, 0.3 mmol/kg). Two cats received a single injection of contrast material, either 0.1 or 0.3 mmol/kg. The images were reviewed in a prospective fashion by a single observer, who was blinded to the dose of contrast material and the timing of image acquisition, in order to detect abnormal contrast enhancement. Changes in single intensity were quantified by region-of-interest measurements. Enhancement at 4 and 13 min, respectively, after injection of contrast material was 25 +/- 10% and 38 +/- 7% with 0.1 mmol/kg, vs 80 +/- 12% and 100 +/- 15% with 0.3 mmol/kg (n = 5). The difference between doses was statistically significant (p < .002) for all time points. Abnormal contrast enhancement was visible in three of six cats that received 0.1 mmol/kg and in all cats that received 0.3 mmol/kg. By 13 min after injection, enhancement had peaked with a dose of 0.1 mmol/kg and was within 20% of maximum with a dose of 0.3 mmol/kg. Detection of disruption of the blood-brain barrier in acute cerebral infarction in cats is improved when high doses (0.3 mmol/kg) of contrast material are used. Disruption may not be visualized when 0.1 mmol/kg, the currently accepted standard dose, is used.