title: Transcytolemmal water exchange in pharmacokinetic analysis of dynamic contrast-enhanced MRI data in squamous cell carcinoma of the head and neck.
abstract: OBJECTIVE
  To investigate the effect of transcytolemmal water exchange on the dynamic contrast-enhanced (DCE) T(1)-weighted MRI of human squamous cell carcinomas of the head and neck (HNSCC).
  
  
  METHODS
  Nine patients with HNSCC nodal metastasis underwent pretreatment DCE-MRI with a temporal resolution of 2.5 seconds and a spatial resolution of 1 mm x 1 mm x 5 mm at 1.5T. We used two pharmacokinetic models for data analysis: generalized kinetic model (GKM) without considering transcytolemmal water exchange and the shutter-speed model (SSM), based on a two-site exchange model for transcytolemmal water exchange. The results were compared in three subgroups of voxels in the tumor depending on the level of contrast enhancement.
  
  
  RESULTS
  SSM was found to be a better fit for more than 75% of pixels of all subjects (P < 0.01) in terms of residual size and Bayesian information criterion (BIC). For all three subgroups based on the contrast enhancement, the median K trans values of SSM were 42% to 55% higher than those of GKM and the median upsilon e values of SSM were 116% to 176% larger than those of GKM. The median K trans and upsilon e of two models were found significantly different (P < 0.01). The median tau i measured by SSM were from 211 to 364 msec.
  
  
  CONCLUSIONS
  The effect of transcytolemmal water exchange is an important factor that needs to be incorporated for adequate modeling of contrast enhancement dynamics measured by MRI of HNSCC.
authors.affiliation: Department of Radiology, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA. Sungheon.Kim@uphs.upenn.edu
authors.forename: Sungheon
authors.initials: S
authors.lastname: Kim
authors.forename: Harry
authors.initials: H
authors.lastname: Quon
authors.forename: Laurie A
authors.initials: LA
authors.lastname: Loevner
authors.forename: Mark A
authors.initials: MA
authors.lastname: Rosen
authors.forename: Lawrence
authors.initials: L
authors.lastname: Dougherty
authors.forename: Alex M
authors.initials: AM
authors.lastname: Kilger
authors.forename: Jerry D
authors.initials: JD
authors.lastname: Glickson
authors.forename: Harish
authors.initials: H
authors.lastname: Poptani
mesh_terms: D001499:Bayes Theorem; D001834:Body Water / Q000378:metabolism*; D002294:Carcinoma, Squamous Cell / Q000378:metabolism*; D016009:Chi-Square Distribution; D003287:Contrast Media / Q000493:pharmacokinetics*; D019786:Gadolinium DTPA / Q000493:pharmacokinetics*; D006258:Head and Neck Neoplasms / Q000378:metabolism*; D006801:Humans; D008207:Lymphatic Metastasis; D008279:Magnetic Resonance Imaging / Q000379:methods*; D009068:Movement
chemical_list: D003287:Contrast Media; C064925:gadodiamide; D019786:Gadolinium DTPA