Delayed Myocardial Ehnancement using Gadobutrol: A Time and Dose Optimization Study

Purpose: Gadolinium chelates are the cornerstone of cardiac magnetic resonance (CMR). Despite considered safe, there is an increasing concern about dose reduction. Aim of this study is to compare 0.1mmol/kg versus 0.2mmol/kg dose of gadobutrol for detection of late gadolinium enhancement (LGE). Methods & Materials: This is a single­cohort parallel­group study comparing gadobutrol at a concentration of 0.1mmol/kg (“low­dose” protocol) and 0.2mmol/kg (“full­dose” protocol). 30 consecutive patients (23 men) scheduled for LGE cardiac imaging were prospectively enrolled and classified as ischemic or non­ischemic LGE. The median interval between two protocols was 7 days. Short­axis images were acquired 5 and 10 minutes after peripheral injection of gadobutrol for “low­dose” protocol, and at 5,10,15, and 20 minutes for “full­dose” protocol, by using a 3D­turbo­field­-echo inversion­recovery T1­weighted sequence. LGE mass, contrast­to­noise ratio between scar/myocardium (CNRs/m), and scar/blood (CNRs/b) were compared in both protocols at different time points. Results: “Low­dose” protocol showed optimal CNRs/m and CNRs/b 10 minutes after injection. “Full­dose” protocol, reached optimal CNRs/m 15 minutes after contrast injection, preserving it up to 20 minutes with no significant differences compared to “low­dose” protocol. CNRs/b of the “full­dose” protocol was significantly inferior until a time delay of 20 minutes (p<0.001 and p=0.525 respectively at 15 and 20 minutes). No significant differences in LGE mass were seen between the two protocols, either for ischemic and non­ischemic LGE groups. Conclusion: 0.1mmol/kg dose of gadobutrol may represent a safer/faster/cost­effective alternative for LGE imaging if performed within 10 minutes from injection. Higher doses may significantly affect CNRs/b of images if acquired too early.