Measurements of the 82Sr half-life.

Half-life of (82)Sr was measured at the National Institute of Standards and Technology (NIST) using gamma-ray spectrometry and a 4pigamma pressurized ionization chamber. The (82)Sr half-life was found to be 25.36+/-0.03 days (k=1) according to gamma-ray spectrometry and 25.34+/-0.02 days (k=1) according to the 4pigamma pressurized ionization chamber measurements.

Establishment of transfer standard for holmium-166-DOTMP.

The measurement of 166Ho, both as a chloride solution and as [166Ho]-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetramethylenephoonic acid (DOTMP), was examined for four models of radionuclide calibrators: Capintec CRC-35R (two chambers), Capintec 712MX, AtomLab 100 (two chambers), and a Capintec CRC-12. Holmium-166 chloride was measured as 16 ml in 20-ml glass dose vials. Diagnostic imaging level [166Ho]DOTMP solutions, nominally 400 MBqg(-1), were measured as 12 ml in 20-ml dose vials. Finally, therapeutic level [166Ho]DOTMP solutions, nominally 9GBqg(-1), were measured as aliquots of 100-500 microl in sealed plastic vials of 10-ml saline. Single calibration factors for each instrument manufacturer are recommended for 12-16-ml of either solution in 20-ml glass dose vials, (673+/-9) x 10 and 72.7+/-0.7, for the Capintec and AtomLab models, respectively. Calibration factors recommended for the therapeutic dose geometry are (706+/-6) x 10 and 68.7+/-1.3, for the Capintec and AtomLab models, respectively. The calibration factors recommended for an NIST 5-ml ampoule are (686+/-5) x 10 and 70.9+/-0.4 for the Capintec and AtomLab models, respectively.

National radioactivity standards for beta-emitting radionuclides used in intravascular brachytherapy.

The uses of beta-particle emitting radionuclides in therapeutic medicine are rapidly expanding. To ensure the accurate assays of these nuclides prior to administration, radioactivity standards are needed. The National Institute of Standards and Technology (NIST), the national metrological standards laboratory for the United States, uses high-efficiency liquid scintillation counting to standardize solutions of such beta emitters, including 32P, 90Sr/90Y, and 188Re. Additional measurements are made on radionuclidic impurities, half lives, and other decay-scheme parameters (such as branching decay ratios or gamma-ray abundances) using HPGe detectors and reentrant ionization chambers. Following such measurements at NIST, standards are disseminated in three ways: Standard Reference Materials (SRMs), calibrations for source manufacturers, and calibration factors for commercial instruments. Uncertainties in the activity calibrations for these nuclides are of the order of +/-0.5% (at approximately 1-standard deviation confidence intervals).

Measurement standards for strontium-89 for use in bone palliation.

Strontium-89 standards have been prepared for use in calibrating instruments in the measurement chain from production in reactors to administration in the clinic or radiopharmacy. Alternate reactor production schemes were evaluated to yield high purity 89Sr with minimum 85Sr impurity. Following purification to remove radionuclidic impurities, samples of 89Sr were standardized by high-efficiency liquid-scintillation counting with a relative expanded uncertainty (intended to approximate two standard deviations) of 0.48%. A Standard Reference Material, SRM 4426A, was prepared and distributed to radiopharmaceutical manufacturers and other customers. The standard sources of 89Sr were used in different geometries to calibrate high purity Ge semiconductor detectors, re-entrant ionization chambers and commercial radionuclide calibrators. The latter included Capintec dose calibrators and the Capintec beta C NaI(Tl) scintillation counter.

Effects of varying geometry on dose calibrator response: cobalt-57 and technetium-99m.

A joint project between the National Bureau of Standards (NBS) and Biomedical Products Department, E.I. du Pont de Nemours and Company, Inc. compared the indicated activity of (a) cobalt-57 samples in NBS 5-ml ampoules, plastic syringes, Du Pont 27-ml Vial E epoxy- and solution-filled containers, and (b) technetium-99m solutions in NBS 5-ml ampoules, elution vials, and syringes. The measurements were made in ionization chambers from two manufacturers, Capintec and Radcal. The main objective was to examine the use of radionuclides in NBS ampoules and Du Pont Vial E containers as suitable reference sources for ionization chambers used to assay radiopharmaceuticals in elution vials and syringes. The exercise illustrated that regardless of the brand of dose calibrator used, a calibration factor for each geometry should be determined to ensure the highest accuracy. The data show that as much as a 9% difference from the correct activity can be observed for these radionuclides, even when the ampoule reference source gives the appropriate reading.

U.S. National Bureau of Standards/Atomic Industrial Forum radioactivity measurements assurance program.

With the above exceptions, the participants as a whole have done very well during the past 8 years and their measurements should continue to show improvement. Since mid-1981, the agreement between AIF and NBS has been modified to recover the cost of an SRM production program over the next two or three years in order for the program to eventually become self-supporting. This will benefit not only the current sponsors of the program, but also hospitals and other users of NBS radiopharmaceutical SRMs by having these standards available to the public on a regular continuing basis. The participants in this program have derived many benefits since its inception in 1975. Through the measurement of blind samples which demonstrate traceability to NBS, the companies have made it easier to comply with some of the regulatory requirements of the FDA and NRC when applying for new drug applications. They also receive monthly feedback on their measurement procedures so that they can promptly determine if their measurement procedures or instruments have gone awry. If the results are satisfactory, they receive reassurance and confidence that they are making good measurements and providing accurately dispensed products.