Comparison of technetium-99m-ll-EC isomers in rats and humans.

UNLABELLED: Technetium-99m-L,L-ethylenedicysteine (99mTc-LL-EC) is a new renal imaging agent with pharmacokinetic properties reported to be slightly superior to those of 99mTc-mercaptoacetyltriglycine (99mTc-MAG3); however, to better define the potential of the enantiomer 99mTc-DD-EC and the diastereomer 99mTc-DL-EC as renal imaging agents, we compared the three EC stereoisomers with 131I-orthoiodohippurate (OIH) in a series of rats and humans. METHODS: Each 99mTc-EC stereoisomer was coinjected with OIH in six Sprague-Dawley rats for measurements of clearance and extraction fraction. Each stereoisomer was also coinjected with OIH in three human volunteers followed by sequential imaging, plasma clearance measurements and timed urine collections. RESULTS: Technetium-99m-DD-EC had the highest clearance and extraction efficiency in rats (p < or = 0.02). In humans, image quality was good with all three agents. The clearance ratio (EC/OIH) was 82% +/- 8% for 99mTc-DD-EC compared to 70% +/- 3% and 40% +/- 5% for 99mTc-LL-EC and 99mTc-DL-EC, respectively. Technetium-99m-DD and 99mTc-LL-EC were excreted more rapidly than 99mTc-DL-EC. CONCLUSION: Technetium-99m-DD-EC has excellent imaging properties and the data suggest that its clearance may approach that of OIH more closely than any other 99mTc renal agent. A potential limitation is the fact that both 99mTc-DD and LL-EC exist in dianionic (80%) and monoanionic (20%) forms at physiological pH and it is unlikely that these two forms have the same clearance or protein binding affinity.

Early stage melanoma: lymphoscintigraphy, reproducibility of sentinel node detection, and effectiveness of the intraoperative gamma probe.

PURPOSE: To assess the influence of lymphoscintigraphic and intraoperative gamma probe findings on the surgical management of melanoma and to test reproducibility of lymphoscintigraphic findings. MATERIALS AND METHODS: After lymphoscintigraphic identification of the sentinel node, intraoperative gamma probe localization and sentinel lymph node excision were performed in 25 patients. To assess reproducibility, 13 patients underwent lymphoscintigraphy twice within 2-17 days. A modified preparation of technetium-99m sulfur colloid with smaller particles than routinely obtained was injected intradermally around the lesion. Dynamic flow images were obtained at 10 seconds per frame followed by a series of static images obtained every 5 minutes for 30 minutes. RESULTS: A sentinel node was identified in all patients. In eight patients, multiple drainage pathways were seen and surgical management was changed. In 11 of the 13 who underwent lymphoscintigraphy twice, sentinel node identification was reproducible. CONCLUSION: Lymphoscintigraphy is reproducible in detection of the sentinel node and with the surgical probe helps effectively guide surgical management.

Evaluation of the hepatobiliary excretion of technetium-99m-MAG3 and reconstitution factors affecting radiochemical purity.

UNLABELLED: Technetium-99-MAG3 is a renal tubular function agent. However, sporadic liver and gallbladder visualization have raised questions about kit stability, impurities and nonrenal routes of excretion. To address these issues, studies were conducted to optimize the labeling efficiency of the TechneScan MAG3 kit and to evaluate the hepatobiliary excretion of the MAG3 complex. METHODS: Thirty-six vials of the commercial formulation of 99mTc-MAG3 were prepared according to manufacturer's instructions and evaluated for radiochemical purity using two methods: a combination of high-performance liquid chromatography and paper chromatography (HPLC/PC); and the manufacturer's miniature chromatography system (Sep-Pak procedure). RESULTS: The labeling efficiency was significantly higher when the kit was reconstituted with 10 ml (96.6%) of saline versus 5 ml (91.4%) (p < 0.01). The radiochemical purity of the kits remained stable for up to 6 hr, but the purity determined by Sep-Pak averaged 2.5% higher than that determined by HPLC procedures (p < 0.01). Rat studies to evaluate renal and hepatobiliary elimination of MAG3 showed no difference in the %ID excreted into the urine by 60 min in all groups of animals studied. However, the %ID excreted into the bile was significantly higher for the kit formulation than the HPLC-purified MAG3, 9.9% versus 6.6% (p = 0.0475). CONCLUSION: The radiochemical purity of the TechneScan MAG3 kit can be improved by reconstituting with larger volumes. In addition, the studies in rats suggest that fasting or kit impurities may be a contributing factor to increased hepatobiliary visualization in patient studies.

Biological distribution of 99mTc-labeled YIGSR and IKVAV laminin peptides in rodents: 99mTc-IKVAV peptide localizes to the lung.

Two laminin-derived peptides containing either YIGSR or IKVAV (single amino acid code) sequences were radiolabeled with 99mTc and their biological distribution evaluated in rodents. Both 99mTc-peptides cleared rapidly from the circulation though the kidney, and to a lesser extent, through the liver. 99mTc-YIGSR peptide did not accumulate in any organ examined in normal, tumored, and emphysemic mice. The 99mTc-IKVAV peptide localized within 10 min to the lung of normal animals, resulting in lung-to-blood ratios of approximately 23:1. The 99mTc-IKVAV peptide localized to lung after submicron filtration and after intraperitoneal injection, suggesting that particulates do not major role in localization. Pre-incubation of 99mTc-IKVAV peptide in whole blood decreased lung localization, suggesting that margination of radiolabeled cells does not play a major role in the lung localization. When 99mTc-IKVAV was injected into mice with tumored lungs (melanoma), the lung uptake was markedly increased (up to 20% injected dose higher than control lungs) at all time points examined (10, 30, and 120 min). When 99mTc-IKVAV was injected into mice with genetic emphysema, the lung uptake was markedly decreased at all time points. The localization of the 99mTc-IKVAV-containing peptide to the lung is consistent with a receptor-based mechanism.

Sports-related injuries in school-aged children.

Most studies of sports-related injuries have been investigations of specific injuries resulting from specific, organized sports at the high school, college, or professional level. This study documented all types of sports-related injuries received by all school-aged children in a midwestern community of 100,000 for a 1-year period. Public and private schools, community sports programs, hospital emergency rooms, the schools' accident insurance company, and local physicians provided initial accident reports. Injuries were sustained by 3% of all elementary school students, 7% of all junior high school (grades 7 and 8) students, and 11% of all high school students. Nonorganized sports and physical education classes each produced nearly twice as many injuries as organized sports. One-fifth of the injuries were considered serious and one-fourth of all injuries could have been avoided had nominal safety precautions been observed.