title: Transcranial perfusion sonography using a low mechanical index and pulse inversion harmonic imaging: reliability, inter-/intraobserver variability.
abstract: OBJECTIVE
  Transcranial perfusion sonography (TPS) is an emerging noninvasive bedside method for evaluating brain perfusion. The purpose was to assess the feasibility of a low MI/almost real-time frame rate approach and to test its intra-/interobserver variability.
  
  
  METHODS
  10 healthy volunteers were investigated 3 times with TPS at a low MI (1.0) and a high frame rate (8.3 Hz). Investigations were performed by 2 sonographers in a cross-over design: 1.) twofold measurements each with 5 volunteers (intraobserver test), and 2.) single measurements of the other 5 volunteers (interobserver test). From 8 established regions of interest (ROI), time-intensity curves (TIC) with the following parameters were calculated: peak intensity (PI), time-to-PI (TTP), area-under-curve (AUC), and cerebral transit time (CTT). The TIC quality was described by the coefficient of determination. TIC parameters were presented descriptively. Intra- and interobserver variability was tested by Spearman's correlation.
  
  
  RESULTS
  The overall quality of the TIC was very good (mean r(2) = 0.92, 0.87 - 0.97). TTP (25.7 - 28.1 sec; mean 26.8 sec) and CTT (8.2 - 10.7 sec; mean 9.9 sec) were the most robust parameters. The intraobserver variability was lower with the more experienced sonographer (r = 0.70 vs. r = 0.29). The interobserver reliability was r = 0.34 (p < 0.05).
  
  
  CONCLUSIONS
  Low MI TPS allows for nearly real-time imaging facilitating probe control. Sound sonographer experience allows for a high reliability and makes TPS an interesting tool for the diagnosis and follow-up of perfusion changes, e. g. in stroke or anti-angiogenic brain tumor therapy.
authors.affiliation: Neurology, MVZ at Caritas Klinik St. Theresia, Saarbrücken, Germany. judith.harrer@web.de
authors.forename: J U
authors.initials: JU
authors.lastname: Harrer
authors.forename: J
authors.initials: J
authors.lastname: Valaikiene
authors.forename: H
authors.initials: H
authors.lastname: Koch
authors.forename: R
authors.initials: R
authors.lastname: Knorr
authors.forename: M
authors.initials: M
authors.lastname: Horn
authors.forename: G
authors.initials: G
authors.lastname: Ickenstein
authors.forename: U
authors.initials: U
authors.lastname: Bogdahn
authors.forename: F
authors.initials: F
authors.lastname: Schlachetzki
mesh_terms: D000328:Adult; D001783:Blood Flow Velocity / Q000502:physiology; D001921:Brain / Q000098:blood supply*; D003287:Contrast Media / Q000008:administration & dosage; D004292:Dominance, Cerebral / Q000502:physiology; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D016014:Linear Models; D008297:Male; D015588:Observer Variation; D010743:Phospholipids; D012016:Reference Values; D012039:Regional Blood Flow / Q000502:physiology; D012984:Software; D013459:Sulfur Hexafluoride; D018615:Ultrasonography, Doppler, Color / Q000379:methods*; D017585:Ultrasonography, Doppler, Transcranial / Q000379:methods*
chemical_list: D003287:Contrast Media; D010743:Phospholipids; C420843:contrast agent BR1; D013459:Sulfur Hexafluoride