title: Gadolinium-enhanced MR images of the growing piglet skeleton: ionic versus nonionic contrast agent.
abstract: OBJECTIVE
  To determine whether there are differences in the distribution of ionic and nonionic gadolinium-based contrast agents by evaluating contrast enhancement of the physis, epiphyseal cartilage, secondary ossification center, and metaphysis in the knees of normal piglets.
  
  
  METHODS
  Following approval from the Subcommittee on Research Animal Care, knees of 12 3-week-old piglets were imaged at 3-T magnetic resonance (MR) imaging after intravenous injection of gadoteridol (nonionic contrast agent; n = 6) or gadopentetate dimeglumine (ionic contrast agent; n = 6). Early enhancement evaluation with gradient-echo MR imaging was quantified and compared (Student t test) by means of enhancement ratios. Distribution of contrast material was assessed and compared (Student t test) by means of T1 measurements obtained before and at three 15-minute intervals after contrast agent administration. The relative visibility of the physis, epiphyseal cartilage, secondary ossification center, and metaphysis was qualitatively assessed by two observers and compared (Wilcoxon signed rank test). Differences in matrix content and cellularity that might explain the imaging findings were studied at histologic evaluation.
  
  
  RESULTS
  Enhancement ratios were significantly higher for gadoteridol than for gadopentetate dimeglumine in the physis, epiphyseal cartilage, and secondary ossification center (P < .05). After contrast agent administration, T1 values decreased sharply for both agents-but more so for gadoteridol. Additionally, there was less variability in T1 values across structures with this contrast agent. Gadoteridol resulted in greater visibility of the physis, while gadopentetate dimeglumine resulted in greater contrast between the physis and metaphysis (P < .05).
  
  
  CONCLUSIONS
  The results suggest different roles for the two gadolinium-based contrast agents: The nonionic contrast medium is better suited for evaluating perfusion and anatomic definition in the immature skeleton, while the ionic contrast medium is better for evaluating cartilage fixed-charge density.
authors.affiliation: Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Boston, Mass, USA. nmenezes@nmr.harvard.edu
authors.forename: Nina M
authors.initials: NM
authors.lastname: Menezes
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Olear
authors.forename: Xiaoming
authors.initials: X
authors.lastname: Li
authors.forename: Susan A
authors.initials: SA
authors.lastname: Connolly
authors.forename: David
authors.initials: D
authors.lastname: Zurakowski
authors.forename: Mary
authors.initials: M
authors.lastname: Foley
authors.forename: Frederic
authors.initials: F
authors.lastname: Shapiro
authors.forename: Diego
authors.initials: D
authors.lastname: Jaramillo
mesh_terms: D000818:Animals; D001846:Bone Development; D001842:Bone and Bones / Q000033:anatomy & histology* / Q000378:metabolism; D003287:Contrast Media / Q000493:pharmacokinetics; D005682:Gadolinium; D019786:Gadolinium DTPA / Q000493:pharmacokinetics; D006571:Heterocyclic Compounds / Q000493:pharmacokinetics; D008279:Magnetic Resonance Imaging / Q000379:methods; D009942:Organometallic Compounds / Q000493:pharmacokinetics; D013552:Swine; D014018:Tissue Distribution
chemical_list: D003287:Contrast Media; D006571:Heterocyclic Compounds; D009942:Organometallic Compounds; C062402:gadoteridol; D005682:Gadolinium; D019786:Gadolinium DTPA