Intravenous MR Lymphangiography: Feasibility in a Swine Model and Proof-of-Concept in Patients.

Abstract

Background Visualization of the hepatic and mesenteric lymphatics remains challenging despite recent advances in lymphatic imaging, including dynamic contrast-enhanced MR lymphangiography (DCMRL). Purpose To assess the feasibility of intravenous contrast-enhanced MR lymphangiography (IV-MRL) in a swine model and a pilot patient group. Materials and Methods Systemic and portal venous and lymph samples were collected from two swine after intravenous administration of gadolinium (Gd)-based contrast agents (Gd tetraazacyclododecane tetraacetic acid and Gd ethoxybenzyl diethylenetriamine pentaacetic acid; <i>n</i> = 1 each), and Gd quantification was performed. IV-MRL and DCMRL were performed in a separate animal, and the signal intensity (SI) of the lymphatic and vascular structures was measured. In a pilot human study, conducted between September 2024 and August 2025, lymphatic enhancement was assessed by comparing the SI ratios of the thoracic duct (TD) to the inferior vena cava at 1 and 20 minutes after the contrast agent administration. Within-subject differences between time points were analyzed using paired <i>t</i> tests. Results The body fluid sampling study showed that the Gd concentration in the lymph peaked at 20-30 minutes and exceeded those of the portal and systemic veins, indicating the presence of the "lymphatic phase." IV-MRL revealed enhancement of not only the TD and cisterna chyli but also the hepatic and mesenteric lymphatics during the phase. The human pilot study (<i>n</i> = 16; mean age of 56.6 years ± 24.7 [SD]; 11 men) showed a substantial increase in TD/inferior vena cava SI ratio from 0.49 ± 0.21 at 1 minute to 1.47 ± 0.32 at 20 minutes (all values are means ± SDs; <i>P</i> < .001). Conclusion IV-MRL had potential as a noninvasive technique for comprehensive visualization of the lymphatics, including hepatic and mesenteric ones, which are often incompletely assessed by conventional lymphatic studies such as DCMRL. © RSNA, 2026 <i>Supplemental material is available for this article.</i>