WHAT IS THE OPTIMAL DOSE OF GADOBUTROL FOR LATE GADOLINIUM ENHANCEMENT IMAGING: A DOSE AND TIME OPTIMIZATION STUDY

Objectives: Gadolinium chelates represent the cornerstone of contemporary contrast-enhanced cardiac magnetic resonance (CMR) imaging. Despite use in routine clinical practice generally considered safe, there is an increasing concern about dose reduction, due to their possible retention in human tissues, especially brain and kidneys. The purpose of our study was to compare different doses of gadobutrol (0.1 mmol/kg versus 0.2 mmol/kg) for the detection of myocardial late gadolinium enhancement (LGE) in the same group of patients. Methods: This was a single-cohort parallel group study comparing gadobutrol at a concentration of 0.1 mmol/kg ("low-dose" protocol) and 0.2 mmol/kg ("full-dose" protocol). Thirty consecutive patients (23 men and 7 women; median age: 61 years; range: 27-80 years) scheduled for LGE cardiac imaging were prospectively enrolled. The median interval between two protocols was 7 days (range: 6-11). Short-axis images were acquired after 5 and 10 minutes of peripheral administration of gadobutrol for "low-dose" protocol, and after 5, 10, 15, and 20 minutes for "full-dose" protocol, by using a 3D turbo field echo inversion recovery T1-weighted sequence. Volume, pattern and localization of LGE were assessed. LGE signal-to-noise ratio (SNR) and contrast-to-noise ratio between scar and myocardium (CNRs-m), and scar and blood (CNRs-b) were compared in both protocols and at different time points Results: "Low-dose" protocol showed optimal CNRs-m and CNRs-b 10 minutes after gadobutrol administration (median ± interquartile range: 16,57±31,89 and 3,06±4,81). "Full-dose" protocol, reached optimal CNRs-m 15 minutes after contrast injection (16,33±9,46), showing no significant differences with "low-dose" protocol either at 15 minutes (p=0,790) and 20 minutes (14,93±15,28; p=0,668). "Full-dose" CNRs-b was significantly inferior compared to "low-dose" protocol at 15 minutes (0,26±6,31; p<0,01). Optimal CNRs-b was reached after 20 minutes, with no significant differences with "low-dose" protocol (1,68±4,55; p=0,525) (Figure 1) <FILE IMAGE='246_20170203094442.jpg'> Conclusion: "Low-dose" gadobutrol may represent a safer, faster and cost-effective alternative to "full-dose" LGE imaging, especially if performed within 10 minutes from intravenous injection. Moreover, higher doses of gadobutrol may significantly affect CNRs-b of LGE images if these are acquired earlier than 20 minutes after the contrast administration.