Quantitative stress lymphoscintigraphy in patients with suspected lymphedema

Learning Objectives 1. Highlight the role of nuclear medicine techniques in evaluation of lymphedema. 2. Describe the lymphoscintigraphic examination of the lower and upper extremities. 3. Highlight the major challenges of this procedure, present image examples and discuss study interpretation 4. Gain an understanding of the clinical utility of this technique.

Lymphedema is a serious and a difficult-to-treat condition that may have many causes. It has also a deleterious psychological effect especially in young women. It may be useful to differentiate lymphatic drainage disorder as the cause of lymphedema. Lymphoscintigraphy could help in this regard. In this procedure, the capability of lymphatic vessels to drain lymph from the extremities at rest and after stress is evaluated. Radiocolloids are injected subcutaneously in the web spaces of the feet or hands and static images for 1 minute are performed immediately post injection, 30 minutes post injection at rest and after 30 minutes of walking (3 hours after 30 minutes exercising in upper extremities). The percentage of the injected dose is then calculated. ROIs around the injection sites and the regional lymph node basins are drawn and the fraction of the injected counts in the lymph nodes is calculated. No decay correction is necessary. Different image patterns are also evaluated (asymmetry, collaterals, dermal backflow). Lymph node accumulation >1% of injected activity at rest and >5% after stress is considered normal. Quantitative parameters characterizing the capability of lymphatic vessels to drain lymph from the extremities can help the clinician to establish the cause of lymphedema in order to treat patients appropriately