Contrast-enhanced whole heart coronary MRI with a bolus infusion of gadobenate dimeglumine at 1.5 t

Introduction

The potential benefits of contrast agents have been studied for coronary MRI; however the contrast timing/injection rate and sequence remain to be optimized. We investigated three infusion schemes (bolus, hybrid, slow) of gadobenate dimeglumine ([Gd-BOPTA]^2-, MultiHance; Bracco Imaging SpA, Milan, Italy), a high relaxivity extracellular contrast agent, for improved whole-heart coronary MRI by measuring blood T₁ kinetics. Subsequently, we developed a contrast-enhanced whole-heart coronary MRI method at 1.5 T using an inversion-recovery SSFP sequence acquired after a bolus infusion.

Methods

Four healthy adult subjects were imaged three times each using three infusion schemes: a) bolus (0.2mmol/kg@2ml/s), b) hybrid (0.1mmol/kg@2ml/s plus 0.1mmol/kg@0.1ml/s), and c) slow (0.2mmol/kg@ 0.3ml/s). A Look-Locker sequence was used for quantitative T₁ measurements. Subsequently, seven healthy subjects were recruited for evaluation of a contrast-enhanced whole-heart coronary MRI with a bolus infusion. Free-breathing SSFP coronary MRI (TR/TE/α = 3.6/1.8/90°, FOV = 300 × 300 × 120 mm³, resolution = 1.3 × 1.3 × 1.3 mm³, T₂-Prep, ×2 accelerated) was performed before contrast injection. Gd-BOPTA (0.2mmol/kg@2ml/s) was injected intravenously, immediately followed by a Look-Locker sequence to visually determine the optimal inversion time. A contrast-enhanced whole-heart coronary was then acquired with identical imaging parameters with the exception of replacing the T₂-Prep with a non-selective inversion pulse. For both acquisitions, a noise scan was performed immediately after acquisition. The blood SNR and blood-myocardium CNR were measured.

Results

Figure 1 shows the blood T₁ during the first 10 min after contrast injection. The bolus injection yields the fastest and largest T₁ reduction in the initial 1-2 minutes. Slow infusion reduces the T₁ at a slower pace than bolus, but was similar to bolus ∼ 2-3 min after injection. A hybrid infusion results in the lowest decrease in T₁, but also the most stable. Figure 2 shows a comparison of contrast-enhanced and non-contrast coronary images. The coronary SNR and CNR were significantly improved by 36% (58.5 ± 18.7 vs. 79.5 ± 17.5) and 101% (27.3 ± 11.4 vs. 55.0 ± 12.1), respectively (p < 0.003 for both). Figure 3 shows reformatted examples of the LAD, which shows improved visualization of mid and distal LAD.

Figure 1

Time course of blood T ₁ up to 10 minutes after contrast injection using three infusion schemes.

Figure 2

Example coronary images acquired on a healthy subject using an SSFP sequence before (top row) and after (bottom row) a bolus injection of Gd-BOPTA.

Figure 3

Reformatted non-contrast (a) and contrast-enhanced (b) LAD images. The improved suppression of myocardial signal using Gd-BOPTA facilities depiction of mid and distal right coronary artery.

Conclusion

Contrast-enhanced whole heart coronary MRI with a bolus infusion of Gd-BOPTA using inversion-recovery SSFP at 1.5 T results in enhanced SNR and CNR.