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Measurement and Modeling of Brain Shift

An Intraoperative Brain-shift Monitor Using Shear-mode Transcranial Ultrasound: Preliminary Results. Left: Detail of an oblique MRI scan (SE T1, TR = 650 ms, TE = 10 ms, FOV = 12.0 cm × 12.0 cm, slice thickness = 3.0 mm) that has been registered with the ITUM's signal path (solid line) through the ICSF (arrow). Right: Results of the statistical analysis to validate the ability of the ITUM to localize intracranial structures against the "gold standard" of MR imaging. The location of intracranial structures as measured by the ITUM is plotted against the same measurement performed by MRI.

Several projects are ongoing within the NCIGT that focus on minimizing or compensating for shifts of organs during surgery. In neurosurgery, brain shift naturally happens; however, it must be accounted for to proceed with accuracy.

One project involving the NCIGT's neurosurgical researchers involves a collaboration with the focused ultrasound investigators to design and develop a prototype intraoperative transcranial ultrasound monitoring (ITUM) device that can be applied continuously during neurosurgery to monitor for brain shift.

The ITUM device incorporates five novel design aspects to achieve efficacy:

• a focused ultrasound transducer with a pressure field profile that selectively monitors specific intracranial regions,
• a lowered effective ultrasound frequency (fc = 0.96 MHz) to overcome attenuation stemming from the skull bone,
• a shear-mode transmission through the skull bone to enhance energy transmission and reduce beam aberration,
• a low ultrasound duty-cycle for time-extended application, and
• an echoic interface tracking algorithm.

To date, a prototype device has been designed, constructed, and validated against MRI with 10 human subjects. Results demonstrate a high level of correlation between the ultrasound data and T1-MRI imagery (n = 38, R^2 = 0.9962) for the localization of intracranial structures. In addition, the overall SNR of the ITUM signals (n = 38, SNR = 25.4±5.2 dB) was statistically equivalent to that of the MRI data (n = 38, SNR = 22.5±4.8 dB).

Back to Research Projects.

Publications

• White P, Whalen S, Tang S, Clement G, Jolesz F, Golby A. An Intraoperative Brain-shift Monitor Using Shear-mode Transcranial Ultrasound: Preliminary Results. J Ultrasound Med. 2009 Feb;28(2):191-203. PMID: 19168769. PMCID: PMC2631551.
• Neculai Archip, Olivier Clatz, Stephen Whalen, Simon P Dimaio, Peter M Black, Ferenc A Jolesz, Alexandra Golby, Simon K Warfield. Compensation of geometric distortion effects on intraoperative magnetic resonance imaging for enhanced visualization in image-guided neurosurgery. Neurosurgery. 2008 Mar;62(3 Suppl 1):209-15; discussion 215-6. PMID: 18424988.
• Archip N, Clatz O, Whalen S, Kacher D, Jolesz FA, Golby AJ, Black PM, Warfield SK. Non-rigid alignment of preoperative MRI, fMRI and DT-MRI with intraoperative MRI to enhance visualization and navigation in image-guided neurosurgery. Neuroimage. 2007; 35(2):609-624. PMID: 17289403.

Involved Investigators

• Alexandra Golby, PI
• Phillip Jason White, PhD, Focused Ultrasound Laboratory, BWH
• Greg Clement, PhD
• Sai-Chun Tang, PhD