Image-guided Intracranial Endosonography

Background: Although the skull limits applicability of sonography, bedside intracranial endosonography might be an alternative to computed tomography scans to detect adverse events in sedated patients. However, the usefulness of intracranial endosonography for potential clinical application has not been evaluated. The present study was designed to investigate the suitability of an image-guided intracranial endosonography (IGIE) catheter for intracranial ultrasound imaging in an ex vivo phantom model and in a large animal model.Materials and Methods: IGIE was evaluated in a cranial phantom and a porcine intracranial hemorrhage (ICH) model. Two anesthetized animals underwent an initial magnetic resonance imaging (MRI) scan, followed by placement of an endosonography catheter in the frontal lobe. After anatomic imaging, an experimental ICH was placed in the contralateral hemisphere. B-scan imaging, duplex, Doppler sonography, and a second MRI were performed. A standard image-guiding device tracked the ultrasound catheter.Results: Endosonography provided high-definition imaging of intracranial structures. Image guidance allowed direction of the catheter to and intuitive identification of anatomic structures. Doppler imaging allowed analysis of blood flow in intracranial vessels. Ultrasound imaging was used to monitor evolution of ICH and the resulting brain edema in real time. Coregistration of ultrasound and MRI images acquired after ICH placement demonstrated the high accuracy of the spatial resolution of IGIE (largest mismatch <5 mm).Conclusions: IGIE provides high-definition images of intracranial structures, Doppler analysis of blood flow, and real-time monitoring of intracranial structural lesions. We suggest that IGIE might prove a valuable tool for intracranial monitoring of sedated patients over extended time periods.