Estimating kinetic parameters from dynamic contrast-enhanced t1-weighted MRI of a diffusable tracer: Standardized quantities and symbols

Abstract

We describe a standard set of quantity names and symbols related to the estimation of kinetic parameters from dynamic contrast-enhanced T 1 -weighted magnetic resonance imaging data, using diffusable agents such as gadopentetate dimeglumine (Gd-DTPA). These include a) the volume transfer constant K trans (min ؊1 ); b) the volume of extravascular extracellular space (EES) per unit volume of tissue v e (0 F v e F 1); and c) the flux rate constant between EES and plasma k ep (min ؊1 ). The rate constant is the ratio of the transfer constant to the EES (k ep ‫؍‬ K trans / v e ). Under flow-limited conditions K trans equals the blood plasma flow per unit volume of tissue; under permeability-limited conditions K trans equals the permeability surface area product per unit volume of tissue. We relate these quantities to previously published work from our groups; our future publications will refer to these standardized terms, and we propose that these be adopted as international standards.

Correlation of quantitative dynamic contrast‐enhanced MRI with microvascular density in necrotic, partial necrotic, and viable liver tumors in a rabbit model

“…This exchange rate between ${\mathrm{normalv}}_{\mathrm{normalp}}$ and ${\mathrm{normalv}}_{\mathrm{normale}}$ spaces depends on vascular perfusion factors such as blood flow and permeability surface area product. Thus, ${\mathrm{normalK}}^{\text{trans}}$ may be interpreted as tumor blood flow or vascular permeability, depending on whether the underlying tumor condition is flow‐limited or permeability‐limited (18) . In this study, the increased numbers of blood vessels counted from CD31 stain images indicate increased blood flow of contrast agent or increased permeability surface area in the PNA and the VTA of VX2 tumors, reflecting increased ${\mathrm{normalK}}^{\text{trans}}$ value in DCE‐MRI data, in turn showing positive correlations between MVD and ${\mathrm{normalK}}^{\text{trans}}$ values.…”

DCE‐MRI pixel‐by‐pixel quantitative curve pattern analysis and its application to osteosarcoma

“…Compartmental model-based methods have variations in compartment number (two or three) and flow as- sumptions (perfusion-or permeability-limited models or mixed models) (24). To use these models, many assumptions have to be made, including a uniform AIF for a selected region, the physiological meaning of derived parameters, and idealized tissue structure.…”

“…Assuming a uniform AIF across the whole tumor is one source of error in pharmacokinetic modeling, in addi-tion to the actual selection of the AIF. A baseline T 1 measurement is usually required for generating the concentration curve from the signal curve (24). The accuracy of the T 1 measurement is problematic, especially for 3D acquisition, and is another source of error.…”

Transvascular and interstitial transport in rat hepatocellular carcinomas: Dynamic contrast‐enhanced MRI assessment with low‐ and high‐molecular weight agents

“…Recently, Leach et al (5), on behalf of the Pharmacodynamic/Pharmacokinetic Technologies Advisory Committee of the Cancer Research UK, recommended using K trans with the simple Kety model as the primary endpoint of antiangiogenesis therapeutics. The authors considered that K trans was the most widely accepted kinetic parameter, describing the transendothelial transport into the extravascular extracellular space by diffusion (20). However, K trans may not be well suited for this assessment because it is a lumped parameter that equals the product of the tissue plasma flow F and the extraction fraction E. Because of this formulation, K trans reflects blood flow, endothelial permeability, or both, depending on whether the model is flow-or permeability-limited (20).…”