Detection Capability of 89Sr and 90Sr Using Liquid Scintillation Counting.

ABSTRACT: We developed a new method for simultaneous determination of 89Sr and 90Sr with an emphasis on detectability. The samples were digested, and Sr was chemically purified followed by a single count on a liquid scintillation counter in three windows overlapping the 90Sr, 89Sr, and 90Y peaks. Gamma spectrometry was used to measure 85Sr, added for chemical recovery. The method was tested on 18 water samples spiked at levels from 9 to 242 Bq of 89Sr and 90Sr, with either single radionuclides or their mixtures. In addition, eight method blanks were measured. The data were analyzed numerically by solving a system of linear equations for 89Sr and 90Sr activities as analytes and 90Y activity as a participating component. The total uncertainties of the results were calculated numerically using variances and covariances. The average bias from the known activities was -0.3% (range from -3.6 to 3.1%) for 90Sr and - 1.5% (range from -10.1 to 5.1%) for 89Sr. The En-scores were within -1.0 and 1.0 at 95% confidence level. The detection capabilities of this method were determined by means of the decision threshold LC and the limit of detection referred to as the minimum detectable activity. All relevant uncertainties were propagated into the LC and minimum detectable activity. In addition, detection limits were calculated for the purpose of Safe Drinking Water Act monitoring. The detection capabilities were compared with the regulatory requirements in the US and EU for food and water. For samples spiked with either pure 89Sr or 90Sr, false positives were observed for the opposite radionuclide exceeding the above LC values. This was attributed to interference by the spiked activity. A new method was developed to calculate decision and detectability curves in the presence of interference.

Gamma Radioactivity Detection Limits and Associated Radionuclide Intakes Study in Artificial Human Urine Using Sodium-iodide and High-purity Germanium Detectors.

ABSTRACT: The performance of several gamma detectors was investigated for emergency urine bioassay screening of two radionuclides of concern: 131 I and 137 Cs. Unspiked artificial urine samples were measured for 10 min each on four different gamma detectors: 80% relative efficiency high-purity Ge detector in standard shielding, 102% low-background high-purity Ge detector equipped with top muon shield, 78% high-purity Ge well detector in standard shielding, and 4″ × 4″ NaI well detector in standard shielding. The measured gamma spectra were analyzed in two ways: (1) for the 364-keV peak region of 131 I and 662-keV peak region of 137 Cs and (2) for the total counts in the full energy spectrum (50-2,048 keV). The results were analyzed using the principles of signal detection theory according to the Currie's formalism extended by a complete uncertainty propagation. This enabled calculation of the detection capability in terms of detection limit (Bq L -1 ) of urine, the latter referred to as minimum detectable activity. The NaI well detector had the lowest minimum detectable activities for total spectra, whereas the high-purity Ge well detector had the lowest peak minimum detectable activity values. Minimum detectable inhalation and ingestion intakes from urine bioassay were calculated from the minimum detectable activity values for urine collection 1 d, 1 wk, and 1 mo past the initial intake. The calculated intakes were compared with annual limits on intake. The results are interpreted with respect to a large-scale radiological emergency response.

Current evidence and future perspectives on the effective practice of patient-centered laboratory medicine.

BACKGROUND: Systematic evidence of the contribution made by laboratory medicine to patient outcomes and the overall process of healthcare is difficult to find. An understanding of the value of laboratory medicine, how it can be determined, and the various factors that influence it is vital to ensuring that the service is provided and used optimally. CONTENT: This review summarizes existing evidence supporting the impact of laboratory medicine in healthcare and indicates the gaps in our understanding. It also identifies deficiencies in current utilization, suggests potential solutions, and offers a vision of a future in which laboratory medicine is used optimally to support patient care. SUMMARY: To maximize the value of laboratory medicine, work is required in 5 areas: (a) improved utilization of existing and new tests; (b) definition of new roles for laboratory professionals that are focused on optimizing patient outcomes by adding value at all points of the diagnostic brain-to-brain cycle; (c) development of standardized protocols for prospective patient-centered studies of biomarker clinical effectiveness or extraanalytical process effectiveness; (d) benchmarking of existing and new tests in specified situations with commonly accepted measures of effectiveness; (e) agreed definition and validation of effectiveness measures and use of checklists for articles submitted for publication. Progress in these areas is essential if we are to demonstrate and enhance the value of laboratory medicine and prevent valuable information being lost in meaningless data. This requires effective collaboration with clinicians, and a determination to accept patient outcome and patient experience as the primary measure of laboratory effectiveness.