7T dynamic contrast-enhanced MRI for the detection of subtle blood-brain barrier leakage.

Background And Purpose: Dynamic contrast-enhanced MRI (DCE-MRI) can be employed to assess the blood-brain barrier (BBB) integrity. Detection of BBB leakage at lower field strengths (≤3T) is cumbersome as the signal is noisy, while leakage can be subtle. Utilizing the increased signal-to-noise ratio at higher field strengths, we explored the application of 7T DCE-MRI for assessing BBB leakage.

Methods: A dual-time resolution DCE-MRI method was implemented at 7T and a slow injection rate (0.3 ml/s) and low dose (3 mmol) served to obtain signal changes linearly related to the gadolinium concentration, that is, minimized for T degradation effects. With the Patlak graphical approach, the leakage rate (K ) and blood plasma volume fraction (v ) were calculated. The method was evaluated in 10 controls, an ischemic stroke patient, and a patient with a transient ischemic attack.

Results: K and v were significantly higher in gray matter compared to white matter of all participants. These K values were higher in both patients compared to the control subjects. Finally, for the lesion identified in the ischemic stroke patient, higher leakage values were observed compared to normal-appearing tissue.

Conclusion: We demonstrate how a dual-time resolution DCE-MRI protocol at 7T, with administration of half the clinically used contrast agent dose, can be used for assessing subtle BBB leakage. Although the feasibility of DCE-MRI for assessing the BBB integrity at 3T is well known, we showed that a continuous sampling DCE-MRI method tailored for 7T is also capable of assessing leakage with a high sensitivity over a range of K values.