Papers Published

1. Kristin Frinkley Bing and Gabriel P Howles and Yi Qi and Mark L Palmeri and Kathryn R Nightingale, Blood-brain barrier (BBB) disruption using a diagnostic ultrasound scanner and Definity in Mice., Ultrasound Med Biol, vol. 35 no. 8 (2009), pp. 1298–1308 [012] .
   (last updated on 2009/09/26)

   Abstract:
   The objective of this work was to determine whether diagnostic ultrasound and contrast agent could be used to transcranially and nondestructively disrupt the blood-brain barrier (BBB) in mice under ultrasound image guidance and to quantify that disruption using magnetic resonance imaging (MRI) and magnetic resonance (MR) contrast agent. Each mouse was placed under isoflurane anesthesia and the hair on top of its skull was removed before treatment. A diagnostic ultrasound transducer was placed in a water bag coupled with gel on the mouse skull. Definity (ultrasound [US] contrast) and Magnevist (MR contrast) were injected concurrent with the start of a custom ultrasound transmission sequence. The transducer was translated along the rostral-caudal axis to insonify three spatial locations (2mm apart) along one half of the brain for each sequence. T1-weighted MR images were used to quantify the volume of tissue over which the BBB disruption allowed Magnevist to enter the brain,based upon increases in MR contrast-to-noise ratio (CNR) compared with the noninsonified portions of the brain. Ultrasonic frequency,pressure and pulse duration,as well as Definity dose and injection time were varied. Preliminary results suggest that a threshold exists for BBB opening dependent upon both pressure and pulse duration (consistent with reports in the literature performed at lower frequencies). A range of typical diagnostic frequencies (e.g.,5.0-8.0 MHz) generated BBB disruption. Comparable BBB opening was noted with varied delays between Definity injection and insonification (0-2 min) for a range of Definity concentrations (400-2400 microL/kg). The low-pressure,custom sequences (mechanical index [MI]