Normal values for native T1 at 1.5T in the pericardial fluid of healthy volunteers

Abstract

T1 mapping cardiovascular magnetic resonance (CMR) imaging has been used to characterize pericardial effusions, and shown that routinely administered gadolinium-based contrast agents (GBCA) are excreted into effusion fluid.AimsTo measure pericardial fluid T1 before and after contrast administration in healthy volunteers to establish normal values and compare them to patients with pericardial effusion. Volunteers (n=30) were compared to retrospectively included patients with at least 5 mm of pericardial effusion (n=69). T1 maps were acquired at 1.5T CMR. A volume of pericardial fluid was imaged in a short-axis slice and in a slice perpendicular to the short-axis orientation. A reliable measurement had a region of interest size >10mm2, coefficient of variation <10%, and a relative difference <5% between the two slice orientations. In 26/30 (87%) of volunteers, there was a sufficient amount of pericardial fluid to enable reliable measurement. Native T1 did not differ between slice orientations (3262±163 vs 3267±173 ms, p=0.75). In patients, native T1 was normal in 41%, above normal in 3%, below normal in 56%, and GBCA concentration, estimated using the specific relaxivity of the GBCA used, was normal in 65% and above normal in 35%. More than half of effusions in patients had a native T1 below normal, consistent with higher protein content, and a third had an above normal GBCA excretion despite dilution effects, suggesting an inflammatory and exudative etiology. The use of T1 mapping and contrast dynamics to characterize pericardial fluid merits prospective evaluation.