title: First order correction for T2*-relaxation in determining contrast agent concentration from spoiled gradient echo pulse sequence signal intensity.
abstract: OBJECTIVE
  To investigate the accuracy of a method neglecting T(2)*-relaxation, for the conversion of spoiled gradient echo pulse sequence signal intensity to contrast agent (CA) concentration, in dynamic contrast enhanced MRI studies. In addition a new closed form conversion expression is proposed that accounts for a first order approximation of T(2)*-relaxation.
  
  
  METHODS
  The accuracy of both conversion methods is compared theoretically by means of simulations for four pulse sequences from literature. Both methods are tested in vivo against the numerical conversion method for measuring the arterial input function in mice.
  
  
  RESULTS
  Simulations show that the T(2)*-neglecting method underestimates typical tissue CA concentrations (0 mM to 2 mM) up to 6%, while the errors for arterial concentrations (0 mM to 10 mM) range up to 43%. The results from our first order method are numerically indistinguishable from the simulation input values in tumor tissue, while for arterial concentrations the error is reduced up to a factor 10. In vivo, peak Gd-DOTA concentration is underestimated up to 14% with the T(2)*-neglecting method and up to 0.9% with our first order method.
  
  
  CONCLUSIONS
  Our conversion method reduces the underestimation of CA concentration severely in a broad physiological concentration range and is easy to perform in any clinical setting.
authors.affiliation: Institute Biomedical Technology (IBiTech), Department of Civil Engineering, Ghent University, Belgium. dieter.denaeyer@ugent.be
authors.forename: Dieter
authors.initials: D
authors.lastname: De Naeyer
authors.forename: Isabelle
authors.initials: I
authors.lastname: Debergh
authors.forename: Yves
authors.initials: Y
authors.lastname: De Deene
authors.forename: Wim P
authors.initials: WP
authors.lastname: Ceelen
authors.forename: Patrick
authors.initials: P
authors.lastname: Segers
authors.forename: Pascal
authors.initials: P
authors.lastname: Verdonck
mesh_terms: D000465:Algorithms; D000818:Animals; D016477:Artifacts; D003287:Contrast Media / Q000493:pharmacokinetics; D017352:Echo-Planar Imaging / Q000379:methods*; D006571:Heterocyclic Compounds / Q000493:pharmacokinetics*; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D051379:Mice; D008819:Mice, Nude; D009942:Organometallic Compounds / Q000493:pharmacokinetics*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
chemical_list: D003287:Contrast Media; D006571:Heterocyclic Compounds; D009942:Organometallic Compounds; C050823:gadolinium 1,4,7,10-tetraazacyclododecane-N,N',N'',N'''-tetraacetate