[en] Destructive assays of stainless-steel stents containing ³²P were performed. Prior to assay, 24 stents were intercompared on a NaI(Tl) well-type crystal. A subset of stents were then digested in a suitable carrier solution by the addition of concentrated hydrofluoric acid. The final solution was measured by the CIEMAT/NIST tritium efficiency tracing method for liquid scintillation counting. A separate experiment was performed which indicated no loss of activity during stent digestion. Expanded (k=2) uncertainties on stent activity ranged from 1.0% to 2.6%

[en] Dose calibrator dial settings reported by NIST in 2010 (ARI, v. 68, p. 1367) are now known to give erroneously low (by 10%) activity readings. The original determinations were based on a chain of calibrations; a broken link in this chain was recently discovered. New calibration factors (i.e., dial settings), directly linked to updated NIST primary standards, are reported here. In addition, the raw data used to derive the factors reported in 2010 are revisited. The validity of the reevaluation is established via comparison with the new experiments and revised calibration factors for numerous clinical geometries are reported. The main conclusions of the 2010 report regarding geometry effects remain valid. - Highlights: • The new NIST primary standard for Ra-223 is transferred to secondary measurements. • Dose calibrator calibration factors first reported in 2010 are revised. • New experiments confirm the validity of the data reevaluations

[en] Calibration factors for commercial ionization chambers (i.e. dose calibrators) were determined for a solution of ¹²³I; the activity was based on the 1976 NBS standard. A link between the NIST standard and the International Reference System (SIR) was established. The two major U.S. dose calibrator manufacturers recommend oppositely biased calibration factors, giving a spread of 11.3% in measured activities. With modern quantitative imaging techniques capable of ≤10% accuracy, this bias for a SPECT nuclide is highly significant. - Highlights: • Dose calibrator calibration factors were determined for ¹²³I. • The NIST standard was indirectly linked to the SIR. • Manufacturer-dependent biases result in a spread of 11.3 % in measured activity

[en] Highlights: • The half-life of Ge-68 is determined by two methods. • Ionization chamber measurements give a value of 271.07(12) d. • NaI(Tl) well counter measurements give a value of 271.14(15) d. • Both values are consistent with the DDEP recommended value and other recent determinations. • Our value would change the DDEP recommended half-life from 270.95(26) d to 271.05(8) d. - Abstract: In nuclear medicine, ⁶⁸Ge is used to generate ⁶⁸Ga for imaging by positron emission tomography (PET) and sealed sources containing ⁶⁸Ge/⁶⁸Ga in equilibrium have been adopted as long-lived calibration surrogates for the more common PET nuclide, ¹⁸F. We prepared several ⁶⁸Ge sources for measurement on a NaI(Tl) well counter and a pressurized ionization chamber, following their decay for 110 weeks (≈ 2.8 half-lives). We determined values for the ⁶⁸Ge half-life of T_1/2 = 271.14(15) d and T_1/2 = 271.07(12) d from the NaI(Tl) well counter and ionization chamber measurements, respectively. These are in accord with the current Decay Data Evaluation Project (DDEP) recommended value of T_1/2 = 270.95(26) d and we discuss the expected impact of our measurements on this value.

[en] Ra-223 is a bone-seeking alpha emitter currently being evaluated as a radiopharmaceutical. Concurrent with the primary standardization, NIST established that calibration factors currently used for radionuclide calibrators in the clinical setting give readings 5.7-8.7% higher than the NIST calibrated activity. This work describes the determination of calibration factors specific to dose vials and syringes. Using the calibration factors derived with standard ampoules to measure syringe activities can give readings up to 3.6% too high.

[en] In the triple-to-double coincidence ratio (TDCR) method of liquid scintillation counting, unaccounted or improperly accounted impurities can result in lower-than-expected or higher-than-expected recovered activities, depending on the counting efficiency of the nuclide of interest, the counting efficiency of the radionuclidic impurity, and the amount of impurity present. We describe these general dependences using a simple model. The trends predicted by the model are tested experimentally using a series of mixed ²⁴¹Am/³H and ⁶³Ni/³H sources. An “impurity surface” is derived to facilitate an intuitive grasp of impurity phenomena in TDCR. - Highlights: ► Improperly accounting for impurities can have counterintuitive effects in TDCR LS counting. ► We model the variation of the ratio of recovered and actual activities with impurity fraction. ► Our model reproduces trends observed in experiments with mixed ²⁴¹Am/³H and ⁶³Ni/³H sources. ► A 3D surface is derived to promote a more intuitive grasp of impurity effects in TDCR counting.

[en] The National Institute of Standards and Technology (NIST) maintains a program for the establishment and dissemination of activity measurement standards in nuclear medicine. These standards are disseminated through Standard Reference Materials (SRMs), Calibration Services, radionuclide calibrator settings, and the NIST Radioactivity Measurement Assurance Program (NRMAP, formerly the NEI/NIST MAP). The MAP for the radiopharmaceutical industry is described here. Consolidated results show that, for over 3600 comparisons, 96% of the participants' results differed from that of NIST by less than 10%, with 98% being less than 20%. Individual radionuclide results are presented from 214 to 439 comparisons, per radionuclide, for ⁶⁷Ga, ⁹⁰Y, ^99mTc, ⁹⁹Mo, ¹¹¹In, ¹²⁵I, ¹³¹I, and ²⁰¹Tl. The percentage of participants results within 10% of NIST ranges from 88% to 98%. - Research highlights: ► NIST has maintained an MAP for the radiopharmaceutical industry since 1975. ► Participants measure sources with known, but blinded, activity and submit results. ► The schedule is chosen by a steering committee made up of participants and NIST. ► Participants submit calibrated sources for measurement by NIST during open months. ► Results are presented for over 3600 measurements of distributed sources.

[en] Source self-attenuation for solutions of "5"7Co of varying density and carrier concentration was measured in nine re-entrant ionization chambers maintained at NIST. The magnitude of the attenuation must be investigated to determine whether a correction is necessary in the determination of the activity of a source that differs in composition from the source used to calibrate the ionization chamber. At our institute, corrections are currently made in the measurement of "1"4"4Ce, "1"0"9Cd, "6"7Ga, "1"9"5Au, "1"6"6Ho, "1"7"7Lu, and "1"5"3Sm. This work presents the methods used as recently applied to "5"7Co. A range of corrections up to 1% were calculated for dilute to concentrated HCl at routinely used carrier concentrations. - Highlights: • The effect was studied in nine ionization chambers. • A variation due to solution density of between −1.0% and +0.6% was observed. • Uncertainties on an example correction are evaluated. • Correction can be necessary for secondary standard ionization chambers. • A limit for the effect can be placed on radionuclide “dose” calibrator measurements.

[en] Highlights: • NIST and NPL activity standards for ²²⁴Ra are demonstrated to be in accord. • The absolute emission intensity for the 241 keV γ ray is evaluated as I_γ = 4.011(16) per 100 disintegrations of ²²⁴Ra. • The ²²⁴Ra half-life is evaluated as T_1/2 = 3.6313(14) d. The national metrology institutes for the United Kingdom (UK) and the United States of America (USA) have compared activity standards for ²²⁴Ra, an α-particle emitter of interest as the basis for therapeutic radiopharmaceuticals. Solutions of ²²⁴RaCl₂ were assayed by absolute methods, including digital coincidence counting and triple-to-double coincidence ratio liquid scintillation counting. Ionization chamber and high-purity germanium (HPGe) γ-ray spectrometry calibrations were compared; further, a solution was shipped between laboratories for a direct comparison by HPGe spectrometry. New determinations of the absolute emission intensity for the 241 keV γ ray (I_γ = 4.011(16) per 100 disintegrations of ²²⁴Ra) and of the ²²⁴Ra half-life (T_1/2 = 3.6313(14) d) are presented and discussed in the context of previous measurements and evaluations.

[en] A method for assessing the impurity ²¹⁰At in cyclotron-produced ²¹¹At via isotope dilution alpha spectrometry is presented. The activity of ²¹⁰At is quantified by measuring the activity of daughter nuclide ²¹⁰Po. Counting sources are prepared by spontaneous deposition of Po on a silver disc. Activity of ²¹⁰At (at the time of ²¹⁰Po maximum activity) is found to be 83.5+/-9.0Bq, corresponding to an atom ratio (²¹⁰At:²¹¹At at the time of distillation) of 0.010+/-0.007% (k=2). The method produces high-quality alpha spectra, with baseline alpha-peak resolution and chemical yields of greater than 85%