title: Validation of injection parameters for catheter-directed intraarterial gadolinium-enhanced MR angiography.
abstract: OBJECTIVE
  Catheter-directed intraarterial (IA) injections of gadolinium contrast agents may be used during endovascular interventions with magnetic resonance (MR) imaging guidance. Injection protocols require further validation. Using a flow phantom and swine, the authors aimed to (a) measure the optimal arterial gadolinium concentration ([Gd]) required for MR angiography and (b) validate a proposed IA injection protocol for gadolinium-enhanced MR angiography.
  
  
  METHODS
  For in vitro experiments, the authors placed a catheter in the aorta of an aorto-renal-iliac flow phantom. Injected [Gd], injection rates, and aortic blood flow rates were varied independently for 36 separate IA gadolinium injections. The authors performed 2D and 3D MR angiography with a fast spoiled gradient-recalled echo sequence. For subsequent in vivo experiments, they selectively placed catheters within the aorta, renal artery, or common iliac artery of three pigs. Injection rate and injected [Gd] were varied. The authors performed 32 separate IA gadolinium injections for 2D MR angiography. Signal-to-noise ratios (SNRs) were compared for the various combinations of injection rate and injected [Gd].
  
  
  RESULTS
  In vitro, an arterial [Gd] of 2%-4% produced an optimal SNR for 2D MR angiography, and 3%-5% was best for 3D MR angiography. In swine, an arterial [Gd] of 1%-4% produced an optimal SNR. In the phantom and swine experiments, SNR was maintained at higher injection rates by inversely varying the injected [Gd].
  
  
  CONCLUSIONS
  Dilute arterial [Gd] is required for optimal IA gadolinium-enhanced MR angiography. To maintain an optimal SNR, injection rates and injected [Gd] should be varied inversely. The postulated injection protocol was validated.
authors.affiliation: Department of Radiology, Northwestern University Medical School, Chicago, IL 60611, USA.
authors.forename: Reed A
authors.initials: RA
authors.lastname: Omary
authors.forename: Kevin P
authors.initials: KP
authors.lastname: Henseler
authors.forename: Orhan
authors.initials: O
authors.lastname: Unal
authors.forename: Randall J
authors.initials: RJ
authors.lastname: Smith
authors.forename: Robert K
authors.initials: RK
authors.lastname: Ryu
authors.forename: Scott A
authors.initials: SA
authors.lastname: Resnick
authors.forename: Mark B
authors.initials: MB
authors.lastname: Saker
authors.forename: Howard B
authors.initials: HB
authors.lastname: Chrisman
authors.forename: Richard
authors.initials: R
authors.lastname: Frayne
authors.forename: J Paul
authors.initials: JP
authors.lastname: Finn
authors.forename: Debiao
authors.initials: D
authors.lastname: Li
authors.forename: Thomas M
authors.initials: TM
authors.lastname: Grist
mesh_terms: D000818:Animals; D001783:Blood Flow Velocity; D003287:Contrast Media / Q000008:administration & dosage*; D019786:Gadolinium DTPA / Q000008:administration & dosage* / Q000097:blood*; D007089:Image Enhancement; D007269:Injections, Intra-Arterial; D018810:Magnetic Resonance Angiography; D023421:Models, Animal; D019047:Phantoms, Imaging; D013552:Swine
chemical_list: D003287:Contrast Media; C064925:gadodiamide; D019786:Gadolinium DTPA