Detecting strontium-89 removable contamination using a sodium iodide well counter.

UNLABELLED: Monitoring for 89Sr removable contamination is required for incoming DOT-labeled packages and work areas containing radioactivity. However, few nuclear medicine departments are equipped for liquid scintillation counting, which is the preferred method for detecting beta emitters. We investigated using a sodium iodide well counter to detect 89Sr through its bremsstrahlung photon production. METHODS: We used a manufacturer's 89Sr-chloride solution of known concentration and tested various parameters: type of tube, access of tube contents to air, volume of sample, type of wipe material and counting geometry. Liquid scintillation samples also were obtained. RESULTS: Initial counting efficiencies were 0.10-0.14 cpm/dpm for small volume (10-microliter) samples. The various parameters tested had either positive or negative effects on the system's efficiency to detect 89Sr. One set of samples, counted over time, demonstrated a calculated mean half-life of 50.8 days, which is similar to the 89Sr reported half-life of 50.5 days. Liquid scintillation samples demonstrated efficiencies of almost 1.0 cpm/dpm and a calculated mean half-life of 50.8 days, both as expected. CONCLUSION: This study demonstrates that 89Sr removable contamination can be detected sensitively using a sodium iodide well counter, but special considerations must be made when determining the system's counting efficiency.

Determinants of diagnostic accuracy in pulmonary scintigraphy for pulmonary capillary protein leak associated with adult respiratory distress syndrome (ARDS): a technical note.

Radionuclide assessment of pulmonary capillary protein leak using [99mTc] human serum albumin (99mTc-HSA) was first reported from our laboratory. In this study we investigated the impact of 1) sampling time post tracer injection, and 2) lung region assignment, on diagnostic accuracy between 2 groups (control n = 20 and ARDS n = 20). Each patient received 370 MBq 99mTc-HSA i.v. and was imaged for 45 min. The slope index (SI) [change in lung: heart activity ratio/min] was calculated from 11 computer assigned lung regions for intervals of 5-15 (early [E]) and 15-45 (late [L]) min. The diagnostic accuracy of E vs L SI calculations for the 11 regions was evaluated by stepwise logistic regression. E SI data and L SI data from the lower 1/3 of the lung did not achieve significance for inclusion in the discriminant model (P less than 0.05). In the nine remaining regions L SI was significant. Optimal discrimination was achieved from L SI data obtained from a region confined to the lateral half of the mid 3rd of the lung field (sensitivity 81%, specificity 85%, accuracy 83%). The results confirm that: 1) a late (15-45 min) sampling period and 2) proper region assignment are necessary to maximize accuracy of this technique.