Peripheral MR Lymphangiography: Integration into Clinical Workflow in a Hybrid Interventional US/MR Suite

Learning Objectives:

1. To review lower extremity lymphatic anatomy and variations


2. To review procedural and imaging techniques of transpedal interstitial gadolinium enhanced MR lymphangiography 


3. To provide a case-based review of peripheral MR lymphangiography utility

Background:

MR Lymphangiography (MRL) is a useful diagnostic imaging adjunct to conventional lymphangiography (CL). Abdominopelvic and thoracic MRL can be performed via ultrasound-guided nodal access, transhepatic, trans-mesenteric, retrograde thoracic duct or via transdermal injection via the feet. When suitable inguinal lymph nodes are not present or in patients with prior CL via nodal access, peripheral MRL is a favored diagnostic approach. Peripheral MRL also enables assessment of thigh and calf lymphatics in suspected lower extremity lymphedema. This educational exhibit will detail the experience to date integrating peripheral MRL into the hybrid procedural suite with a 1.5T magnet.

Clinical Findings/Procedure Details:

1. Review the anatomy of the lower extremity lymphatic channels (1).


2. Review the method for injection of dilute gadolinium contrast into different regions of the feet to achieve opacification of unique calf and thigh lymphatic channels: a) Webspaces: Anteromedial; b) Medial foot to medial malleolus: Posteromedial; c) Lateral forefoot: Anterolateral; d) Posterior (heel) and posterior lateral foot: Posterolateral


3. Review imaging techniques to optimize visualization of lymphatic channels in the lower extremities: a) High-resolution Dixon imaging; b) Time-Resolved MR Angiography; c) T2-weighted non-contrast peripheral MRL; d) Dual-agent relaxation contrast MRL using Ferumoxytol (intravenous) for venous suppression (2)


4. Case-based review of peripheral MRL Utility: a) Unilateral limb lymphedema in a patient with a lymphatic malformation; b) Unilateral limb lymphedema in a patient with a lymphatic malformation of the thigh and pelvic soft tissues; c) Localizing source of post-operative lymphatic leak in patients with limited nodal access: i) Post EVAR explant with graft placement for infection, continued peritoneal leak; post CL without visualization of thoracic duct; ii) Post soft tissue mass resection with ongoing lymphatic leak.


5. Challenges in peripheral MRL: a) Distinguishing normal lymph channels from enhancing veins with “intravasation” of intradermal contrast; b) Diffuse venous shunting with long-standing lymphedema

Conclusion and/or Teaching Points: Integrating contrast-enhanced peripheral MR lymphangiography (MRL) into a hybrid interventional suite with a 1.5T magnet is feasible but requires dedicated resources and team