High-throughput gadobutrol-enhanced CMR: a time and dose optimization study

Abstract

Background: Reducing time and contrast agent doses are important goals to provide cost-efficient cardiovascular magnetic resonance (CMR) imaging. Limited information is available regarding the feasibility of evaluating left ventricular (LV) function after gadobutrol injection as well as defining the lowest dose for high quality scar imaging. We sought to evaluate both aspects separately and systematically to provide an optimized protocol for contrast-enhanced CMR (CE-CMR) using gadobutrol.

Methods: This is a prospective, randomized, single-blind cross-over study performed in two different populations. The first population consisted of 30 patients with general indications for a rest CE-CMR who underwent cine-imaging before and immediately after intravenous administration of 0.1 mmol/kg body-weight of gadobutrol. Quantitative assessment of LV volumes and function was performed by the same reader in a randomized and blinded fashion. The second population was composed of 30 patients with indication to late gadolinium enhancement (LGE) imaging, which was performed twice at different gadobutrol doses (0.1 mmol/kg vs. 0.2 mmol/kg) and at different time delays (5 and 10 min vs. 5, 10, 15 and 20 min), within a maximal interval of 21 days. LGE images were analysed qualitatively (contrast-to-noise ratio) and quantitatively (LGE%-of-mass).

Results: Excellent correlation between pre- and post-contrast cine-imaging was found, with no difference of LV stroke volume and ejection fraction (p = 0.538 and p = 0.095, respectively). End-diastolic-volume and end-systolic-volume were measured significantly larger after contrast injection (p = 0.008 and p = 0.001, respectively), with a mean difference of 3.7 ml and 2.9 ml, respectively. LGE imaging resulted in optimal contrast-to-noise ratios 10 min post-injection for a gadobutrol dose of 0.1 mmol/kg body-weight and 20 min for a dose of 0.2 mmol/kg body-weight. At these time points LGE quantification did not significantly differ (0.1 mmol/kg: 11% (16.4); 0.2 mmol/kg: 12% (14.5); p = 0.059), showing excellent correlation (ICC = 0.957; p < 0.001).

Conclusion: A standardized CE-CMR rest protocol giving a dose of 0.1 mmol/kg of gadobutrol before cine-imaging and performing LGE 10 min after injection represents a fast low-dose protocol without significant loss of information in comparison to a longer protocol with cine-imaging before contrast injection and a higher dose of gadobutrol. This approach allows to reduce examination time and costs as well as minimize contrast-agent exposure.

Keywords: Cardiovascular magnetic resonance; Dose optimization; Gadobutrol; Time optimization.

Fig. 1

Balanced steady state free precession short-axis images obtained at the mid ventricular level before (a) and after (b) injection of gadobutrol 0.1 mmol/kg body-weight

Fig. 2

Graphs showing contrast-to-noise-ratio (CNR) between late gadolinium enhancement (LGE) scar and left ventricular cavity (LVC) and between LGE scar and remote myocardium (MYO) measured at different time delays for 0.1 mmol/kg (yellow) and for 0.2 mmol/kg body-weight protocol (purple)

Fig. 3

2D turbo-field-echo inversion recovery T1-weighted basal short-axis images showing a subendocardial scar in inferoseptal segment. Good contrast between subendocardial border and LV blood pool is obtained after intravenous injection of gadobutrol 0.1 mmol/kg with a time delay of 10 min (a) as well as after injection of a 0.2 mmol/kg dose with a time delay of 20 min (b)

Fig. 4

Illustration showing the advantages in terms of time-saving of our recommended high-throughput CE-CMR protocol (gadobutrol 0.1 mmol/kg body-weight) over a conventional CE-CMR protocol performed using a gadobutrol dose of 0.2 mmol/kg body-weight