Abstract
BackgroundThe purpose of this study was to define an optimal injection protocol for 5–10 min duration navigator-based coronary MR angiography using an intravascular gadolinium-based contrast agent (GBCA), which is better suited for steady-state coronary MR angiography than conventional GBCAs.MethodsUsing projections from pharmacokinetic models of the intravascular concentration of gadofosveset, a dual-injection protocol was formulated and tested on 14 healthy human subjects. Modified Look-Locker inversion recovery (MOLLI) sequences were used for T1 mapping at 3 Tesla to evaluate the concentration of tracer in the aorta over the scanning interval.ResultsPharmacokinetic models for a bolus plus slow infusion technique at a 5, 10, and 15 min steady state intravascular concentration was compared to single bolus curves. The 70 %/30 % bolus/slow infusion technique resulted in the highest intravascular concentration over a 5 min scan duration. Similarly, the 60 %/40 % bolus/slow infusion technique was projected to be ideal for image acquisition duration of 5–10 min. These models were confirmed with T1 maps on normal volunteers. Arterial-venous mixing of contrast was achieved within 90 s of the beginning of the bolus.ConclusionsGadofosveset injection is optimized for the lowest intravascular T1 time for 5–10 min duration MR angiography by bolus injection of 60–70 % of the total dose followed by slow infusion of the remainder of the total dose. This protocol achieves rapid and prolonged steady state intravascular concentrations of the GBCA that may be useful for prolonged image acquisition, such as required for navigator-based coronary MR angiography at 3 Tesla. Trial registrationClinicalTrials.gov identifier: NCT01130545NCT01130545, registered as of May 25, 2010.
Highlights
The purpose of this study was to define an optimal injection protocol for 5–10 min duration navigator-based coronary magnetic resonance (MR) angiography using an intravascular gadolinium-based contrast agent (GBCA), which is better suited for steady-state coronary MR angiography than conventional GBCAs
Owing to work investigating alternate infusion techniques with GBCAs with low intravascular residence time [11], the same techniques have not been investigated with gadofosveset, which may be further optimized by a dual injection technique rather than with a single bolus infusion
Using the 100 % bolus approach, blood concentration of gadofosveset was predicted to drop rapidly to 40 % (Fig. 2, 1 min after equilibrium) of maximum after the initial peak vascular concentration. This was followed by a plateau phase beginning about 1 min after the beginning of the infusion (Fig. 2, “100 % bolus” curve), where T1 time increased to more than than 10 % of its baseline equilibrium value for a theoretical 5-minute scan duration
Summary
The purpose of this study was to define an optimal injection protocol for 5–10 min duration navigator-based coronary MR angiography using an intravascular gadolinium-based contrast agent (GBCA), which is better suited for steady-state coronary MR angiography than conventional GBCAs. The success of contrast enhanced coronary angiography at 3T had been demonstrated [3] and the addition of 3D non-Cartesian acquisition with 100 % imaging efficiency can reduce imaging time to less than 10 min [4,5,6]. Even this shorter acquisition time is much longer than the intravascular residence time of common GBCAs [7]. Owing to work investigating alternate infusion techniques with GBCAs with low intravascular residence time [11], the same techniques have not been investigated with gadofosveset, which may be further optimized by a dual injection technique rather than with a single bolus infusion
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