Suitability of Pharmacokinetic Models for Dynamic Contrast-Enhanced MRI of Abdominal Aortic Aneurysm Vessel Wall: A Comparison

Abstract

PurposeIncreased microvascularization of the abdominal aortic aneurysm (AAA) vessel wall has been related to AAA progression and rupture. The aim of this study was to compare the suitability of three pharmacokinetic models to describe AAA vessel wall enhancement using dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI).Materials and MethodsPatients with AAA underwent DCE-MRI at 1.5 Tesla. The volume transfer constant (Ktrans), which reflects microvascular flow, permeability and surface area, was calculated by fitting the blood and aneurysm vessel wall gadolinium concentration curves. The relative fit errors, parameter uncertainties and parameter reproducibilities for the Patlak, Tofts and Extended Tofts model were compared to find the most suitable model. Scan-rescan reproducibility was assessed using the interclass correlation coefficient and coefficient of variation (CV). Further, the relationship between Ktrans and AAA size was investigated.ResultsDCE-MRI examinations from thirty-nine patients (mean age±SD: 72±6 years; M/F: 35/4) with an mean AAA maximal diameter of 49±6 mm could be included for pharmacokinetic analysis. Relative fit uncertainties for Ktrans based on the Patlak model (17%) were significantly lower compared to the Tofts (37%) and Extended Tofts model (42%) (p<0.001). Ktrans scan-rescan reproducibility for the Patlak model (ICC = 0.61 and CV = 22%) was comparable with the Tofts (ICC = 0.61, CV = 23%) and Extended Tofts model (ICC = 0.76, CV = 22%). Ktrans was positively correlated with maximal AAA diameter (Spearman’s ρ = 0.38, p = 0.02) using the Patlak model.ConclusionUsing the presented imaging protocol, the Patlak model is most suited to describe DCE-MRI data of the AAA vessel wall with good Ktrans scan-rescan reproducibility.

Three-dimensional dynamic contrast-enhanced MRI for the accurate, extensive quantification of microvascular permeability in atherosclerotic plaques

“…AUC is a non‐model‐based parameter and a validated measure of plaque microvasculature/permeability in rabbits . Furthermore, ROI curves were analyzed to calculate kinetic parameters according to the following modified Tofts–Kermode model , under Patlak assumption , as validated previously : where C VW ( T ) and C p ( T ) are the contrast agent concentrations in the vessel wall and in the blood plasma compartment, respectively, at time T , v p is the fractional microvascular volume and K trans is a measure of the extravasation of contrast agent from the plasma to the tissue compartment (in this case indicating endothelial permeability). Fitting to the kinetic model was implemented using the function lsqnonneg (linear least‐squares with non‐negativity constraints) in Matlab.…”

“…AUC is a non-model-based parameter and a validated measure of plaque microvasculature/ permeability in rabbits (4,(8)(9)(10)23). Furthermore, ROI curves were analyzed to calculate kinetic parameters according to the following modified Tofts-Kermode model (15), under Patlak assumption (3,44), as validated previously (3,21,22):…”

Models and methods for analyzing DCE‐MRI: A review

“…The Patlak plot is the simplest PK technique having been widely used in the dynamic MRI data analysis. The slope of the Patlak plot is a useful quantitative index for characterizing the CA kinetic properties in certain applications, such as quantifying the MBF, 294,316,317 assessing the kidney function, 9,[187][188][189] predicting the blood-brain barrier disruption after an embolic stroke in rats, 318 measuring the blood-brain barrier permeability, 175 and studying the abdominal aortic aneurysm 319 and carotid stenosis. 193 The 2CXM model 6,127,194 and the more general multicompartment models 135,195,[197][198][199] resolve the ambiguity in interpreting the K trans -estimates from the TK and ETK models.…”

Aneurysm Wall Enhancement Detected by Contrast Computed Tomography Scan Is Associated With Aneurysm Shrinkage After Endovascular Aneurysm Repair for Abdominal Aortic Aneurysm

“…The stent-graft blocks blood flow from the intravascular space to the aneurysm wall, and blood flow of the aneurysm wall depends solely on vasa vasorum. 24, 25 Therefore, in type II endoleaks the aneurysm wall receives blood flow directly from the type II endoleak as well as from the vasa vasorum. In the absence of a type II endoleak, however, the aneurysm wall receives blood flow through the vasa vasorum only.…”