The effects of a gadolinium-based contrast agent on cardiac diffusion tensor imaging

Purpose Cardiac diffusion tensor imaging (cDTI) is a novel technique which allows the non-invasive estimation of the magnitude and direction of water diffusion within the myocardium. Although cDTI is currently a research tool, it is a rapidly emerging technique that allows in vivo assessment of the microstructure of the myocardium without the need for contrast agents. This technique allows us to infer the orientations of cardiomyocytes and sheetlets from the anisotropic diffusion of water molecules within the myocardium. Microstructural changes in the myocardium can be quantified by mean diffusivity (MD), fractional anisotropy (FA), secondary eigenvector angle (E2A) and helix angle gradient (HAg). MD is a measure of the magnitude of diffusion of water molecules and FA is a measure of the preference of diffusion towards a particular direction. E2A is a marker of sheetlet orientation through units of myocytes and HAg describes the angle or twist of the myocytes as they wrap around the heart. Recent studies have demonstrated the ability of cDTI to detect abnormalities in cardiac disease such as acute myocardial injury, hypertrophic cardiomyopathy and dilated cardiomyopathy(1). As cDTI is approaching the transition from a research method to a diagnostic clinical tool, it needs to be integrated into routine clinical protocols, which routinely includes the administration of gadolinium-based contrast agent (GBCA). To date, studies using cDTI have mostly been performed without prior GBCA administration and it is unknown whether an acquisition following the administration of contrast affects cDTI measurements. Determining the effects of GBCA on cDTI read-outs will be helpful to streamlining clinical protocols and enhance clinical applicability of the method. Aim To investigate the effect of GBCA administration on cDTI markers MD, FA, E2A and HAg. Methods In this single centre study, 17 healthy adult subjects (mean age 60 years, range 24-73 years, M:F= 10:7) underwent free breathing, motion compensated (M2) single shot spin echo (SE) cDTI on a Siemens Prisma 3T scanner as reported previously(2). Each subject underwent pre-GBCA cDTI imaging. Once completed, 0.15ml/kg GBCA was routinely administered through a cannula. A timer was set and exactly 20 mins later, post-GBCA cDTI imaging was performed with scanning parameters copied from the first cDTI imaging. Results Baseline patient characteristics and CMR metrics are given in Table 1 and are within normal ranges as established by the SCMR cDTI consensus document. There were no significant differences between any of the cDTI metrics pre-GBCA and post-GBCA; MD (p=0.970), FA (p=0.162), E2A (p=0.113) and HAg (p=0.171) (Table 2). Conclusion cDTI measurements are not significantly affected by the administration of GBCA contrast agents. This allows for more flexible inclusion of cDTI into clinical protocols, and therefore facilitate the transition of cDTI scanning to clinical practice.