title: In vivo measurement of gadolinium diffusivity by dynamic contrast-enhanced MRI: a preclinical study of human xenografts.
abstract: Compartmental tracer kinetic models currently used for analysis of dynamic contrast-enhanced MRI data yield poor fittings or parameter values that are unphysiological in necrotic regions of the tumor, as these models only describe microcirculation in perfused tissue. In this study, we explore the use of Fick's law of diffusion as an alternative method for analysis of dynamic contrast-enhanced MRI data in the necrotic regions. Xenografts of various human cancer cell lines were implanted in 14 mice that were subjected to dynamic contrast-enhanced MRI performed using a spoiled gradient recalled sequence. Tracer concentration was estimated using the variable flip angle technique. Poorly perfused and necrotic tumor regions exhibiting delayed and slow enhancement were identified using a k-means clustering algorithm. Tracer behavior in necrotic regions was shown to be consistent with Fick's diffusion equation and the in vivo gadolinium diffusivity was estimated to be 2.08 (±0.88) × 10(-4) mm(2)/s. This study proposes the use of gadolinium diffusivity as an alternative parameter for quantifying tracer transport within necrotic tumor regions.
authors.affiliation: Department of Oncologic Imaging, National Cancer Center, Singapore, Singapore. etskoh@ntu.edu.sg
authors.forename: T S
authors.initials: TS
authors.lastname: Koh
authors.forename: S
authors.initials: S
authors.lastname: Hartono
authors.forename: C H
authors.initials: CH
authors.lastname: Thng
authors.forename: T K H
authors.initials: TK
authors.lastname: Lim
authors.forename: L
authors.initials: L
authors.lastname: Martarello
authors.forename: Q S
authors.initials: QS
authors.lastname: Ng
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D003287:Contrast Media / Q000493:pharmacokinetics; D004058:Diffusion; D019786:Gadolinium DTPA; D006801:Humans; D008114:Liver Neoplasms, Experimental / Q000473:pathology*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009368:Neoplasm Transplantation
chemical_list: D003287:Contrast Media; D019786:Gadolinium DTPA