In vivo assessment of macrophage CNS infiltration during disruption of the blood-brain barrier with focused ultrasound: a magnetic resonance imaging study.

Focused ultrasound has been discovered to locally and reversibly increase permeability of the blood-brain barrier (BBB). However, inappropriate sonication of the BBB may cause complications, such as hemorrhage and brain tissue damage. Tissue damage may be controlled by selecting optimal sonication parameters. In this study, we sought to investigate the feasibility of labeling cells with superparamagnetic iron oxide particles to assess the inflammatory response during focused-ultrasound-induced BBB opening. We show that infiltration of phagocytes does not occur using optimal parameters of sonication. Taken together, the results of our study support the usefulness and safety of focused-ultrasound-induced BBB opening for enhancing drug delivery to the brain. These findings may have implications for the optimization of sonication parameters.

Novel diffusion anisotropy indices: an evaluation.

PURPOSE: To systematically evaluate diffusion anisotropy (DA) using newly defined indices based on the diffusion deviation and mean diffusivity approach. MATERIALS AND METHODS: Measures of amplitude, area, and volume of the DA index (DAI) were measured and compared with regard to their sensitivity to changes in DA, susceptibility to noise in the original diffusion-weighted (DW) images, and contrast-to-noise ratio (CNR) in homogenous regions. Simulations were performed under different levels of noise and DA. Human DTI data were acquired from eight normal volunteers. RESULTS: Indices of area and volume measures provided improved resolution for characterizing the DA compared to the eigenvalue ratio. The amplitude measure showed consistent performances with good CNR and less susceptibility to noise in the original data. CONCLUSION: These indices are rotationally invariant without the requirement of eigenvalue sorting. At low anisotropy, all indices have a similar CNR. For larger DA, the first index (the deviation tensor divided by the DT) shows improved sensitivity, contrast-to-noise ratio (CNR), and noise immunity compared to the other indices.