title: An intraoperative brain shift monitor using shear mode transcranial ultrasound: preliminary results.
abstract: OBJECTIVE
  Various methods of intraoperative structural monitoring during neurosurgery are used to localize lesions after brain shift and to guide surgically introduced probes such as biopsy needles or stimulation electrodes. With its high temporal resolution, portability, and nonionizing mode of radiation, ultrasound has potential advantages over other existing imaging modalities for intraoperative monitoring, yet ultrasound is rarely used during neurosurgery largely because of the craniotomy requirement to achieve sufficiently useful signals.
  
  
  METHODS
  Prompted by results from recent studies on transcranial ultrasound, a prototype device that aims to use the shear mode of transcranial ultrasound transmission for intraoperative monitoring was designed, constructed, and tested with 10 human participants. Magnetic resonance images were then obtained with the device spatially registered to the magnetic resonance imaging (MRI) reference coordinates. Peaks in both the ultrasound and MRI signals were identified and analyzed for both spatial localization and signal-to-noise ratio (SNR).
  
  
  RESULTS
  The first results aimed toward validating the prototype device with MRI showed an excellent correlation (n = 38; R(2) = 0.9962) between the structural localization abilities of the two modalities. In addition, the overall SNR of the ultrasound backscatter signals (n = 38; SNR = 25.4 +/- 5.2 dB, mean +/- SD) was statistically equivalent to that of the MRI data (n = 38; SNR = 22.5 +/- 4.8 dB).
  
  
  CONCLUSIONS
  A statistically significant correlation of localized intracranial structures between intraoperative transcranial ultrasound monitoring and MRI data was achieved with 10 human participants. We have shown and validated a prototype device incorporating transcranial shear mode ultrasound for clinical monitoring applications.
authors.affiliation: Department of Radiology, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts 02115, USA. white@bwh.harvard.edu
authors.forename: P Jason
authors.initials: PJ
authors.lastname: White
authors.forename: Stephen
authors.initials: S
authors.lastname: Whalen
authors.forename: Sai Chun
authors.initials: SC
authors.lastname: Tang
authors.forename: Greg T
authors.initials: GT
authors.lastname: Clement
authors.forename: Ferenc
authors.initials: F
authors.lastname: Jolesz
authors.forename: Alexandra J
authors.initials: AJ
authors.lastname: Golby
mesh_terms: D001921:Brain / Q000601:surgery*; D004453:Echoencephalography / Q000295:instrumentation* / Q000379:methods; D004867:Equipment Design; D019544:Equipment Failure Analysis; D006801:Humans; D007089:Image Enhancement / Q000295:instrumentation* / Q000379:methods; D010865:Pilot Projects; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014159:Transducers; D018084:Ultrasonography, Interventional / Q000295:instrumentation* / Q000379:methods