title: Intraoperative ultrasound using phase inversion harmonic imaging: first experiences.
abstract: OBJECTIVE
  To study the feasibility of intraoperative ultrasound using the phase inversion harmonic imaging (PIHI) technique.
  
  
  METHODS
  Eight patients with intracranial middle cerebral artery aneurysms and five patients with arteriovenous malformations were studied after written informed consent. A first ultrasound study was performed through the intact dura mater after cranial trepanation to assess the pathology, its feeding artery, and downstream segments. A second ultrasound study was performed immediately after intervention to monitor the success of the procedure. All patients were studied using a Siemens Sonoline Antares ultrasound machine (Siemens Medical Solutions USA, Inc., Malvern, PA) before and after intravenous administration of an ultrasound contrast agent (Optison; GE Healthcare, Milwaukee, WI). Other than conventional brightness mode, PIHI is sensitive to the nonlinear acoustic response of tissue, and especially to ultrasound contrast agent microbubbles. The latter enables contrast-specific vascular imaging.
  
  
  RESULTS
  PIHI provided anatomically detailed information. In combination with an ultrasound contrast agent, angiography-like views of the vascular pathologies, including their surrounding vessels, could be obtained. Flow velocities in afferent and downstream vascular segments, as well as inside the pathology, could be assessed. Flow dynamics inside the aneurysm sac or the arteriovenous malformation could be studied in real-time. Postintervention, contrast-enhanced PIHI could be used to immediately monitor the success of the surgical procedure.
  
  
  CONCLUSIONS
  PIHI enables intraoperative visualization and morphological assessment of neurovascular pathologies, such as middle cerebral artery aneurysms or arteriovenous malformations. In combination with an ultrasound contrast agent, the flow dynamics of these lesions can be displayed in real-time.
authors.affiliation: Department of Radiology, University of California, San Diego, California 92103-8756, USA. thoelscher@ucsd.edu
authors.forename: Thilo
authors.initials: T
authors.lastname: Hölscher
authors.forename: Burak
authors.initials: B
authors.lastname: Ozgur
authors.forename: Soren
authors.initials: S
authors.lastname: Singel
authors.forename: Wilko G
authors.initials: WG
authors.lastname: Wilkening
authors.forename: Robert F
authors.initials: RF
authors.lastname: Mattrey
authors.forename: Hoi
authors.initials: H
authors.lastname: Sang
mesh_terms: D001783:Blood Flow Velocity; D002560:Cerebrovascular Circulation; D003287:Contrast Media / Q000008:administration & dosage; D005240:Feasibility Studies; D006801:Humans; D020407:Internet; D002532:Intracranial Aneurysm / Q000000981:diagnostic imaging* / Q000601:surgery; D002538:Intracranial Arteriovenous Malformations / Q000000981:diagnostic imaging* / Q000601:surgery; D007432:Intraoperative Period; D018615:Ultrasonography, Doppler, Color / Q000295:instrumentation* / Q000379:methods; D018084:Ultrasonography, Interventional / Q000295:instrumentation* / Q000379:methods; D014741:Video Recording
chemical_list: D003287:Contrast Media