title: The impact of imaging speed of MR-guided punctures and interventions in static organs--a phantom study.
abstract: OBJECTIVE
  Verification of MR-guidance with image acquisitions slower than 1 image per second as it is inevitable for some interventions. Therefore, we quantified solely the effect of acquisition-time on the efficiency of MR-guided interventions in a static phantom study.
  
  
  METHODS
  We measured the duration, accuracy and error rate of simulated interventions for different acquisition-times using a simplified interventional setup. All measurements were performed in a 1.0 T open MRI scanner. Imaging was performed with a gradient-echo sequence (flipangle=20°; TR/TE=12/6 ms; voxelsize=1 mm×1 mm; slicethickness=5 mm; FOV=230 mm×200 mm; acquisition-time=1 s). Variable acquisition times were simulated with intermediate pauses of 0, 1, 2, 3, 4 and 5 s. The interventions were performed by a total of 20 volunteers including 7 experienced interventionalists.
  
  
  RESULTS
  The mean duration of the intervention was 2 min. Significant differences between experienced and unexperienced volunteers were limited to the localization of the image plane and corrections made. The mean accuracy was 5.6 mm. The time to localize the image plane increased with deceleration of imaging from 24 s to 49 s. A similar increase was observed for the intervention time (55-108 s). A significant influence of the acquisition-time on durations and corrections was only found with acquisition-times greater than 4s per image.
  
  
  CONCLUSIONS
  Even image rates of several seconds per image are sufficient enough for efficient interventions in static organs. Thus, the main attention has to be turned on the visibility of the needle when sequences are optimized for MR-guidance. The minimization of imaging speed is rather of secondary interest.
authors.affiliation: Department of Radiology, Charité Campus Mitte, University Medicine Berlin, Charitéplatz 1, 10115 Berlin, Germany. jens.rump@charite.de
authors.forename: Jens C
authors.initials: JC
authors.lastname: Rump
authors.forename: Martin
authors.initials: M
authors.lastname: Jonczyk
authors.forename: Christian J
authors.initials: CJ
authors.lastname: Seebauer
authors.forename: Florian
authors.initials: F
authors.lastname: Streitparth
authors.forename: Felix V
authors.initials: FV
authors.lastname: Güttler
authors.forename: Thula
authors.initials: T
authors.lastname: Walter
authors.forename: Bernd
authors.initials: B
authors.lastname: Hamm
authors.forename: Ulf K M
authors.initials: UK
authors.lastname: Teichgräber
mesh_terms: D006801:Humans; D008279:Magnetic Resonance Imaging / Q000295:instrumentation / Q000379:methods*; D019047:Phantoms, Imaging; D011677:Punctures / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D025321:Surgery, Computer-Assisted / Q000379:methods*; D013997:Time Factors; D014781:Viscera / Q000033:anatomy & histology* / Q000601:surgery*