Pulse sequence and timing of contrast-enhanced MRI for assessing blood-brain barrier disruption after transcranial focused ultrasound in the presence of hemorrhage.

PURPOSE

To optimize the timing of contrast-enhanced magnetic resonance imaging (MRI) that best indicates blood-brain barrier (BBB) disruption induced by focused ultrasound (FUS) along with an ultrasound contrast agent (UCA) and to verify that the contrast-enhanced spin-echo MRI sequence can indicate the degree and location of BBB disruption in the presence of hemorrhage better than a gradient-echo sequence.

MATERIALS AND METHODS

Sonication was applied to 12 rat brains with four different doses of UCA to cause variable degrees of hemorrhage. Two imaging sequences were performed to acquire T1-weighted (T1W) images at two time-points after the administration of a T1-shortening contrast agent. The contrast enhancement at the sonicated regions was quantified and correlated against Evans blue (EB) staining.

RESULTS

The spin-echo T1W images at 10 minutes post-contrast enhancement showed the best correlation with EB staining in both quantity of EB extravasation (r = 0.812; P < 0.01) and spatial distribution (r = 0.528, P < 0.01). This capability was more robust than the gradient-echo sequence.

CONCLUSION

Our results suggest that contrast-enhanced T1W spin-echo sequence acquired in the early phase post-contrast enhancement should be considered to monitor the degree and location of BBB disruption under the possibility of hemorrhage induced by FUS.