Abstract
OBJECTIVE: Lymphatic scintigraphy using radioisotope agents is a good method for evaluating the lymph flow status of patients with lower-limb lymphedema. To depict wide regions of lower-limb lymphatic vessels, at our institution, we administer radioisotopes at four locations in each limb when lymphatic scintigraphy images are to be obtained. Herein, we evaluated the correlation of lymphatic scintigraphy with lymphedema staging and investigated the usefulness of this four-point dermal-injection lymphatic scintigraphy (LyS4). MATERIALS AND METHODS: The 52 lower limbs of 26 patients (23 females, three males, aged 20-85 years, median 65 years) underwent a LyS4 examination of their lower limbs. The stage of lower-limb lymphedema was diagnosed by plastic surgeons at our institution using the International Society of Lymphology (ISL) staging system. The patients' ISL stages were stage 0 (n=20), stage 1 (n=7), and stage 2 (n=25). No patient was stage 3. For each LyS4 examination, technetium-99m human serum albumin diethylenetriamine pentaacetic acid (99mTc-HSA) was injected. The four injection points were the first interdigital web, slightly below the area of the lateral malleolus, slightly below the area of the medial malleolus, and the lateral side of the feet near the fifth digit of both feet. Using the planar LyS4 images, we investigated the positive/negative appearance of the four lymphatic vessel regions, i.e., anteromedial (AM), anterolateral (AL), posteromedial (PM), and posterolateral (PL) and the dermal backflow (DB). We then examined the correlations of these parameters with the ISL stage. RESULTS: The absence of AM, the absence of PM, the appearance of DB, and the number of lymphatic vessels depicted were each significant factors for distinguishing lymphedema. The appearance of DB and the number of lymphatic vessels depicted can distinguish moderate lymphedema (ISL stage 0 or 1) from severe lymphedema (ISL stage 2e or 2d). Regarding the diagnostic performance of the LyS4 parameters, high accuracy was observed for the appearance of PM (0.71), that of DB (0.79), and the number of depicted lymphatic vessels (0.77). CONCLUSION: LyS4 is a useful method with good correlation with the ISL stage in patients with lower-limb lymphedema.