Lymphoscintigraphic identification of sentinel lymph nodes:: Clinical evaluation of 0.22-μm filtration of Tc-99m sulfur colloid

PURPOSE: To evaluate the use of 0.22-mu m filtration of technetium-99m sulfur colloid particles in the optimization of lymphoscintigraphy. MATERIALS AND METHODS: Forty-one consecutive lymphoscintigraphic studies obtained with 0.22-mu m filtration of Tc-99m sulfur colloid in 41 patients (26 men, 15 women; average age, 55.4 years) and 41 consecutive studies obtained with 5.0-mu m filtration in 41 patients (20 men, 21 women; average age, 54.5 years) were retrospectively, randomly reviewed. Studies were evaluated for lymphatic channel depiction and sentinel lymph node depiction. Studies included immediate flow images (obtained at 10 seconds per frame) and multiview static images obtained up to 2 hours after intradermal Tc-99m sulfur colloid injection. RESULTS: The number of drainage beds visualized was 52 with 5.0-mu m filtration and 51 with 0.22-mu m filtration (P = .570). The number of lymphatic channels visualized was 45 with 5.0-mu m filtration and 75 with 0.22-mu m filtration (P = .006). The number of lymph nodes visualized was 102 with 5.0-mu m filtration and 123 with 0.22-mu m filtration (P = .123). The number of studies judged as optimal (ie, depicted lymphatic channels leading to sentinel nodes) was 10 with 5.0-mu m filtration and 19 with 0.22-mu m filtration (P = .038). The number of studies with depicted lymph nodes but no depicted lymphatic channel was 15 with 5.0-mu m filtration and six with 0.22-mu m filtration (P = .023). CONCLUSION: The use of 0.22-mu m filtration in the preparation of Tc-99m sulfur colloid substantially improves study quality and increases the diagnostic certainty in the identification of sentinel lymph nodes.