title: Vascular enhancement in early dynamic liver MR imaging in an animal model: comparison of two injection regimen and two different doses Gd-EOB-DTPA (gadoxetic acid) with standard Gd-DTPA.
abstract: OBJECTIVE
  To investigate the influence of 2 different doses and injection rates on the enhancement of liver vasculature in Gd-EOB-DTPA enhanced liver MRI compared with the standard dose Gd-DTPA.
  
  
  METHODS
  This animal experimental study has been approved by the local authorities. In 5 pigs, a time-resolved T1w 3D GRE sequence, and in a second experiment, a single-slice turbo FLASH T1w sequence with 3 frames/s were started each with contrast agent application of Gd-EOB-DTPA and Gd-DTPA. Three sets with different doses were performed with an injection rate of 1 and 2 mL/s which are as follows: A, Standard dose: 25 [mu]mol Gd-EOB-DTPA/kg body-weight (bw); B, Double dose: 50 [mu]mol Gd-EOB-DTPA/kg bw; and C, Standard dose: 100 [mu]mol Gd-DTPA/kg bw. Signal intensities were measured in aorta, vena cava inferior, portal vein, and liver parenchyma, and time-signal-to-noise (SNR)-curves were generated. The increase in SNR from baseline and several perfusion parameters were calculated. Statistical significance was tested with the Wilcoxon rank test at a significance level of P = 0.05.
  
  
  RESULTS
  Mean peak enhancement (SNR) in the aorta was not significantly different for set A, B, and C with the same injection rate. Mean peak enhancement in the aorta was significantly higher for set A at 1 mL/s than at 2 mL/s (159.1 vs. 144.4, P = 0.043). Mean peak enhancement in the PV, the vena cava inferior, and the liver parenchyma was significantly lower for set A compared with set B and set C, at both injection speeds. The full width at half max was significantly longer for injection protocols with 1 as compared with 2 mL/s for sets A and set B. Set A with 1 mL/s reached similar values as compared with set C with 2 mL/s for the full width at half max (8.92 vs. 9.40; P = 0.35), for the area-under-the curve (1736.64 vs. 1912.74; P = 0.69) and the maximal signal-to-noise ratio (25.21 vs. 25.37; P = 0.69).
  
  
  CONCLUSIONS
  Despite the lower amount of gadolinium in the standard dose of Gd-EOB-DTPA, the results showed that the arterial enhancement in Gd-EOB-DTPA-enhanced dynamic liver MRI was comparable to Gd-DTPA. This result can be explained mainly by the higher relaxivity. Choosing a lower injection rate additionally supported to compensate for the lower injection volume by stretching the bolus without decreasing the peak. In this respect, an injection rate of 1 mL/s showed better results with regard to the arterial enhancement compared with 2 mL/s.
authors.affiliation: Institute of Clinical Radiology, University Hospitals-Grosshadern, Ludwig-Maximilians-University Munich, Germany. Christoph.Zech@med.uni-muenchen.de
authors.forename: Christoph J
authors.initials: CJ
authors.lastname: Zech
authors.forename: Bernhard
authors.initials: B
authors.lastname: Vos
authors.forename: Anders
authors.initials: A
authors.lastname: Nordell
authors.forename: Matthias
authors.initials: M
authors.lastname: Urich
authors.forename: Lennart
authors.initials: L
authors.lastname: Blomqvist
authors.forename: Josy
authors.initials: J
authors.lastname: Breuer
authors.forename: Maximilian F
authors.initials: MF
authors.lastname: Reiser
authors.forename: Hanns-Joachim
authors.initials: HJ
authors.lastname: Weinmann
mesh_terms: D000818:Animals; D003287:Contrast Media / Q000008:administration & dosage; D004305:Dose-Response Relationship, Drug; D019786:Gadolinium DTPA; D006499:Hepatic Artery / Q000033:anatomy & histology*; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007267:Injections; D023421:Models, Animal; D011169:Portal Vein / Q000033:anatomy & histology*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013552:Swine
chemical_list: D003287:Contrast Media; C073590:gadolinium ethoxybenzyl DTPA; D019786:Gadolinium DTPA