Lymphoscintigraphic identification of sentinel lymph nodes: clinical evaluation of 0.22-micron filtration of Tc-99m sulfur colloid.

PURPOSE: To evaluate the use of 0.22-micron filtration of technetium-99m sulfur colloid particles in the optimization of lymphoscintigraphy. MATERIALS AND METHODS: Forty-one consecutive lymphoscintigraphic studies obtained with 0.22-micron 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-micron 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-micron filtration and 51 with 0.22-micron filtration (P = .570). The number of lymphatic channels visualized was 45 with 5.0-micron filtration and 75 with 0.22-micron filtration (P = .006). The number of lymph nodes visualized was 102 with 5.0-micron filtration and 123 with 0.22-micron filtration (P = .123). The number of studies judged as optimal (i.e., depicted lymphatic channels leading to sentinel nodes) was 10 with 5.0-micron filtration and 19 with 0.22-micron filtration (P = .038). The number of studies with depicted lymph nodes but no depicted lymphatic channel was 15 with 5.0-micron filtration and six with 0.22-micron filtration (P = .023). CONCLUSION: The use of 0.22-micron 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.

Lymphoscintigraphy, the sentinel node concept, and the intraoperative gamma probe in melanoma, breast cancer, and other potential cancers.

There is a resurgence of interest in lymphoscintigraphy because of attention to the sentinel node concept and the availability of the surgical gamma probe that can be used in the operating room to localize radiolabeled sentinel nodes. Conventional surgical management of melanoma has been altered for intermediate thickness tumors such that lymph node dissection is performed for a lymph node bed only if the sentinel node is tumor positive on histological exam after gamma probe-guided excision. This approach is cost effective, saving about 80% of these patients (sentinel node tumor negative) the cost and morbidity of unnecessary "elective lymph node dissection." In addition, a biopsy can be performed on all lymph node beds that receive lymphatic drainage from the tumor site thereby improving staging and perhaps survival by providing the most appropriate therapy. Substantial work has been done to develop optimum imaging techniques and the best radiopharmaceutical preparation to achieve accurate, reproducible lymphatic drainage images. Our methodology includes the following intradermal injections of a technetium 99m sulfur colloid (modified preparation) are followed by dynamic imaging (10 seconds per frame); static imaging up to 30 minutes and late imaging at 1 to 2 hours. Images show lymphatic channels that lead to sentinel nodes in 1, 2, 3, or more anatomic locations. Surgical management is altered to include sampling sentinel nodes of nodal beds, many of which would not have been sampled by previous conventional surgical estimates of lymphatic drainage. While clinical success of lymphoscintigraphy and intraoperative probe localization of the sentinel node in melanoma is evident, use of lymphoscintigraphy and the sentinel node concept in breast cancer is investigative, but promising. The radiopharmaceutical is injected around the tumor in the breast followed by imaging to delineate lymphatic drainage to the sentinel node(s). Optimum methodologies for radiopharmaceutical, volume and/or activity of injectate, and imaging have yet to be determined. Breast lymphatic drainage can be to axilla, internal mammary, and/or supraclavicular nodes in any combination.

Technetium-99m-sulfur colloid for lymphoscintigraphy: effects of preparation parameters.

UNLABELLED: There has been a resurgence in the use of lymphoscintigraphy for the external detection of lymph nodes for metastatic melanoma and breast tumors. Technetium-99m-antimony trisulfide colloid was the radiopharmaceutical developed for this procedure and was found to have a narrow distribution of small particles, 0.003-0.03 microns, but it was never approved by the FDA. Technetium-99m-sulfur colloid also forms particles and this article reports on the effects different preparation parameters have on its particle size distribution and stability. METHODS: Four groups of kits were evaluated, kits which utilized: (a) a reduced heating protocol with a new 99mTc-elution, (b) a reduced heating protocol with an old 99mTc-elution, (c) a prolonged heating protocol with a new 99mTc-elution and (d) a prolonged heating protocol with an old 99mTc-elution. The particle size distribution and the stability of the different 99mTc-sulfur colloid kit preparations were evaluated over 6 hr utilizing polycarbonate filters ranging from 0.03 to 10 microns. RESULTS: In vitro studies demonstrated no significant change in the particle size distribution over a 6-hr period and all 99mTc-sulfur colloid preparations had a bimodal particle size distribution pattern. Importantly, heating the kit for shorter periods of times utilizing [99mTc]pertechnetate, which had a longer ingrowth of [99mTc]pertechnetate, produced a formulation which had the largest percentage of particles smaller than 0.03 microns. CONCLUSION: In our clinical setting, 99mTc-sulfur colloid prepared with the reduced heating protocol and utilizing [99mTc]pertechnetate, which has the highest ingrowth of [99mTc]pertechnetate has proved to be an excellent agent for lymphoscintigraphy studies. This preparation has demonstrated rapid movement of the particles from the primary site to the lymph nodes in over 97% (106/109) of the patients we have studied.