Image acquisition and analysis

Lymphoscintigraphy was acquired using a dual-head gamma camera (E.CAM; Siemens Medical Systems, Hoffman Estates, IL) equipped with a low-energy high-resolution collimator. The acquisition speed was 15 cm/min. After the patient was laid in the supine position, 0.4 mL of ^99mTc-phytate 37 MBq (1 mCi) was subcutaneously injected into the first and second web spaces of both feet using a 27-gauge syringe. Patients were asked to exercise between each image acquisition. Early images were obtained at 5 minutes post-injection and delayed images were obtained at 30 minutes and 1 hour. Two board-certified nuclear medicine physicians (M.Y.Y. and H.-J.Y. with more than 9 and 14 years of experience, respectively) analyzed the images in consensus and were blind to the clinical information.

Patterns of main lymphatics (trunk pattern, thigh-restricted, and lower leg-restricted), and visualization of regional lymph nodes were evaluated, according to previous reports [18]. According to the presence and extent of dermal backflow (DBF), DBF patterns were classified into the absence, small extent (dermal back flow on the thigh or lower leg only), and large extent (dermal back flow on both the thigh and lower leg) [17].