title: Limitations of the permeability-limited compartment model in estimating vascular permeability and interstitial volume fraction in DCE-MRI.
abstract: Dynamic contrast-enhanced magnetic resonance imaging commonly uses compartment models to estimate tissue parameters in general and perfusion parameters in particular. Compartment models assume a homogeneous distribution of the injected tracer throughout the compartment volume. Since tracer distribution within a compartment cannot be assessed, the parameters obtained by means of a compartment model might differ from the actual physical values. This work systematically examines the widely used permeability-surface-limited one-compartment model to determine the reliability of the parameters obtained by comparing them with their actual values. A computer simulation was used to model spatial tracer distribution within the interstitial volume using diffusion of contrast agent in tissue. Vascular parameters were varied as well as tissue parameters. The vascular parameters used were capillary radius (4 and 12 μm), capillary permeability (from 0.03 to 3.3 μm/s) and intercapillary distances from 30 to 300 μm. The tissue parameters used were tortuosity (λ), porosity (α) and interstitial volume fraction (v(e)). Our results suggest that the permeability-surface-limited compartment model generally underestimates capillary permeability for capillaries with a radius of 4 μm by factors from ≈0.03 for α=0.04, to ≈ 0.1 for α=0.2, to ≈ 0.5 for α=1.0. An overestimation of actual capillary permeability for capillaries with a radius of 12 μm by a factor of ≥1.3 was found for α=1.0, while α=0.2 yielded an underestimation by a factor of ≈0.3 and α=0.04 by a factor of ≈ 0.03. The interstitial volume fraction, v(e), obtained by the compartment model differed with increasing intercapillary distances and for low vessel permeability, whereas v(e) was found to be estimated approximately accurately for P=0.3 μm/s and P=3.3 μm/s for vessel distances <100 μm.
authors.affiliation: Department of Neuroradiology and Radiology, Charité-Universitätsmedizin Berlin, 10117 Berlin, Germany.
authors.forename: Guido Correia
authors.initials: GC
authors.lastname: Carreira
authors.forename: Ole
authors.initials: O
authors.lastname: Gemeinhardt
authors.forename: Rudolf
authors.initials: R
authors.lastname: Gorenflo
authors.forename: Dirk
authors.initials: D
authors.lastname: Beyersdorff
authors.forename: Tobias
authors.initials: T
authors.lastname: Franiel
authors.forename: Johanna
authors.initials: J
authors.lastname: Plendl
authors.forename: Lutz
authors.initials: L
authors.lastname: Lüdemann
mesh_terms: D000758:Anesthesia; D000818:Animals; D002196:Capillaries / Q000473:pathology; D002199:Capillary Permeability; D003198:Computer Simulation; D004058:Diffusion; D004867:Equipment Design; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008962:Models, Theoretical; D010539:Permeability; D011467:Prostate / Q000473:pathology; D011471:Prostatic Neoplasms / Q000473:pathology; D051381:Rats; D012984:Software