Abstract： Objective To assess the feasibility of intestitial MR lymphangiography (MRL) with subcutaneous injection of a commercially available,non-ionic,extracellular paramagnetic contrast agent,to visualize lymphatic vessels in patients with primary lymphedema.Methods Forty lower extremities in 31 patients with clinically advanced stages of primary lymphedema were examined with magnetic resonance lymphangiography.A 1 ml mixed liquor of gadobenate dimeglumine and mepivacainhydrochloride were injected subcutaneously into the dorsal aspect of both feet For MRL,a 3D fast spoiled gradient-recalled echo T1-weighted images with a fat saturation technique (T1 high resolution isotropic volume excitation,THRIVE) were performed after subcutaneous application of the contrast material To outline lymphatic vessels,source images were used to reconstruct images of MIP.The SNR and CNR of enhanced lymphatic vessels and veins were measured and calculated respectively.The significance of the differences of the data comparisons was assessed using an unpaired student t teat.Results Of the 40 lower extremities,the beaded appearance of dilated lymphatic vessels was detected in 36 lower legs (90.0%) and 17 upper legs (42.5%).The numbers of the dilated lymphatic vessels displayed in all segments of lower extremities added up to 365 and its mean diameter was (3.4 ± 0.1) mm on MRL MIP image.The average SNR and CNR were 257 ±130,207 ± 113 in the dilated lymphatic vessels and 218 ± 129,152 ± 113 in the vein respectively,which was statistically significant (SNR t = -2.649,CNR t = -3.404,P <0.01).Contrast enhancement was observed in 30/40 inguinal lymph node groups (75.0%).In 26 lower extremities (65.0%) collateral vessels with dermal back-flow areas between lymphatic vessels were seen.Conclusions As a novel tool to image the pathologically modified lymphatic vessels in patients with clinically advanced stage of primary lymphedema,magnetic resonance lymphangiography is a safe,useful technique.