MR angiography with a new rapid‐clearance blood pool agent: Initial experience in rabbits

Abstract

The purpose of this study was to assess a new Gd-based macromolecular intravascular contrast agent (P792, Vistarem®; Laboratoire Guerbet, Aulnay sous Bois, France) for MR angiography (MRA). P792 is a macrocyclic gadolinium compound based on a gadoterate meglumine structure substituted by hydrophilic arms. In vitro imaging of phantoms containing varying concentrations of P792 and gadoterate meglumine (Gd-DOTA) was performed. In rabbits (N ‫؍‬ 5), arterial concentrations for P792 and Gd-DOTA were determined, and in vivo 3D MRA was performed. For gadolinium concentrations ranging from 200 to 3000 mol/l, in vitro imaging showed higher SNR values for P792 compared to Gd-DOTA. Determination of arterial Gd concentration showed comparable bolus phase curves for P792 and Gd-DOTA. With P792, higher concentrations were obtained due to a restricted diffusion into the interstitial space. P792 allowed acquisition of high-quality MR angiograms. Image quality was rated as superior for P792 in the post-bolus phase images. In conclusion, P792 appears to be well suited for highquality first-pass and equilibrium-phase MRA. The intravascular properties lead to an excellent signal in the vasculature, with limited background enhancement. Since the agent is rapidly renally excreted, it should be well suited for perfusion and permeability imaging. Contrast-enhanced MR angiography (MRA) has evolved into an accurate technique for the assessment of most vascular territories (1-7). The technique is based on the availability of high-performance gradient systems, and is capable of reducing data acquisition times sufficiently to collect an entire 3D data set during the arterial phase of intravenously administered extracellular contrast agents (8). The T 1 -shortening effect of gadolinium chelates allows select enhancement of the arterial lumen without depending on time-of-flight effects. This assures maximal contrast between the arterial lumen and surrounding tissues, and renders the technique less susceptible to flow-dependent artifacts.The extracellular nature of the paramagnetic gadolinium chelates leads to rapid diffusion into the extracellular fluid compartment, resulting in decreasing arterial signal intensity and concomitant enhancement within surrounding tissues. The short intravascular halflife requires optimal timing of the contrast bolus, and provides only a very limited time window for data collection during the arterial phase of the intravenously administered contrast bolus. Timing errors may render the examination suboptimal or nondiagnostic. Thus high contrast doses and fast injection rates are required to induce adequate T 1

Effects of AZD2171 and vandetanib (ZD6474, Zactima) on haemodynamic variables in an SW620 human colon tumour model: an investigation using dynamic contrast‐enhanced MRI and the rapid clearance blood pool contrast agent, P792 (gadomelitol)

“…s À1 Gd at 60 MHz in saline). This contrast agent has slow physiological extravasation from the intravascular space and has been used in angiographic applications (26). It has been used previously in a tumour xenograft model in nude mice, to resolve tumour blood flow per unit of volume of tissue (F/V T , mL/s/mL), fractional plasma volume (V p , %), and permeability surface area product per unit volume of tissue (PSr, s À1 ) (27).…”

Determination of the maturity and functionality of tumor vasculature by MRI: Correlation between BOLD‐MRI and DCE‐MRI using P792 in experimental fibrosarcoma tumors

“…Errors in V p estimation could have accounted for the lack of correlation with VF. However, the Gd contrast agent we used (P792) can provide reliable assessment of blood plasma volume due to lower transendothelial diffusion (compared to Gd-DTPA) (31,36). Intrinsically, VF and V p are related to blood volume.…”

In vitro Relaxometric and Luminescence Characterization of P792 (Gadomelitol, Vistarem®), an Efficient and Rapid Clearance Blood Pool MRI Contrast Agent

“…(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) to be a rapid clearance blood pool agent (RCBPA) (Figure 1) with a limited diffusion across the normal endothelium. [6,8] It is mainly excreted by glomerular filtration and has been reported to be well suited for high-quality firstpass and equilibrium-phase MR angiography, [10] visualization of the coronary arteries and their branches, [11] assessment of viability of infarcted myocardium, [12] differentiation of tumor-bearing lymph nodes from reactive inflammatory and normal nodes, [13] and for the distinction between metastatic and relatively benign cancers. [14] A phase I clinical trial has established its safety in humans.…”