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B E Zimmerman

Publications and source records attributed to B E Zimmerman.

At least 19 recordsLinked to original sources
PubMed2006

International guidance on the establishment of quality assurance programmes for radioactivity measurement in nuclear medicine.

A new guidance document for the implementation of quality assurance (QA) programmes for nuclear medicine radioactivity measurement, produced by the International Atomic Energy Agency, is described. The proposed programme is based on the principles of ISO 17025 and will enable laboratories, particularly in developing countries, to provide consistent, safe and effective radioactivity measurement services to the nuclear medicine community.

Guidelines as Topic↗
PubMed2006

Radionuclide metrology in the life sciences: recent advances and future trends.

This paper reviews activities in the field of radionuclide metrology applied to the life sciences between the years 2000 and 2005. The requirements for accuracy and consistency in making radioactivity measurements in radiation medicine, coupled with an increased awareness of the role of measurement standards in quality assurance programmes, has prompted a great deal of research in this area. During the past 5 years, particular emphasis has been on: (1) the development of primary standards for radionuclides, (2) development of secondary/transfer standards, (3) development of radionuclide standards for brachytherapy, and (4) inter-laboratory comparisons at the end-user level. Activities carried out by National Metrology Institutions in these areas are reviewed and a look at future trends is presented.

Biological Science Disciplines↗
PubMed2006

Comparison of calculated spectra for the interaction of photons in a liquid scintillator. Example of 54Mn 835 keV emission.

The CIEMAT/NIST and TDCR methods in liquid scintillation counting, initially developed for the activity standardization of pure-beta radionuclides, have been extended to the standardization of electron capture and beta-gamma radionuclides. Both methods require the calculation of the energy spectrum absorbed by the liquid scintillator. For radionuclides emitting X-rays or gamma-rays, when the energy is greater than a few tens of keV the Compton interaction is important and the absorption is not total. In this case, the spectrum absorbed by the scintillator must be calculated using analytical or stochastic models. An illustration of this problem is the standardization of 54Mn, which is a radionuclide decaying by electron capture. The gamma transition, very weakly converted, leads to the emission of an 835 keV photon. The calculation of the detection efficiency of this radionuclide requires the calculation of the energy spectrum transferred to the scintillator after the absorption of the gamma ray and the associated probability of absorption. The validity of the method is thus dependent on the correct calculation of the energy transferred to the scintillator. In order to compare the calculation results obtained using various calculation tools, and to provide the metrology community with some information on the choice of these tools, the LS working group of the ICRM organised a comparison of the calculated absorbed spectra for the 835 keV photon of 54Mn. The result is the spectrum of the energy absorbed by the scintillator per emission of an 835 keV gamma ray. This exercise was proposed for a standard 20 ml LS glass vial and for LS cocktail volumes of 10 and 15 ml. The calculation was done for two different cocktails: toluene and a widely used commercial cocktail, Ultima Gold. The paper describes the results obtained by nine participants using a total of 12 calculation codes.

Algorithms↗
PubMed2006

Monte Carlo calculations of spectra and interaction probabilities for photons in liquid scintillators for use in the standardization of radionuclides.

The probabilities for the interaction of photons, Pint, in three different liquid scintillators (toluene, Ultima Gold, and Hionic Fluor) were calculated as a function of energy for three different geometries using the Monte Carlo codes PENELOPE and EGSnrcMP. The agreement in Pint values between the two codes in all of the geometries and scintillators for energies above 100 keV was within +/-0.5%. The agreement was better than +/-4% for energies between 20 and 100 keV. No substantive differences in the normalized absorbed energy spectra were observed for initial photon energies in the range of 20-1000 keV. The influence of scintillator composition on the simulation results was investigated in the context of a possible conflict in the published composition data for Hionic Fluor. A difference in interaction probability of about 27% was observed at 20 keV when an alternate composition having lower amounts of S and P is used. At 100 keV, the differences were within the calculational uncertainties.

Algorithms↗
PubMed2002

Experimental investigation of dose calibrator response for 125I brachytherapy solutions contained in 5 mL plastic syringes and 2 mL conical glass v-vials as a function of filling mass.

The effect of measurement geometry on the determination of the activity of solutions containing 125I for use in brachytherapy applications has been investigated for 5 mL plastic syringes and 2 mL conical glass dose vials as a function of filling mass. New dial settings for the syringes over a filling mass range of 1 to 3 g have been determined to be 497+/-8 and 469+/-8 (expanded, k = 2, uncertainties) for the NIST Capintec CRC- 12 and Capintec CRC-35R, respectively, with any effect due to the filling mass lying within the uncertainty in the activity calibration. A filling mass effect was observed in the dose vials, causing a 10.5% reduction in the chamber response from a 2 g filling mass to 1 g. Dial settings at 2 g were experimentally found to be 143+/-2 and 135+/-2 (expanded uncertainties) for the NIST Capintec CRC-12 and Capintec CRC-35R, respectively. The appropriate dial settings for the same vials with a 1 g filling mass were found to be 120+/-2 and 114+/-2 for CRC-12 and CRC-35R, respectively. Differences of up to +/-45% in the activity determination were observed between values obtained with the manufacturer's recommended setting and the settings obtained experimentally for each specific geometry. Calibration factors were also determined for a Vinten 671 Radionuclide Calibrator, giving values of 0.226+/-0.009 pA x MBq(-1) and 0.231+/-0.004 pA x MBq(-1) (expanded uncertainties), respectively, for the 1 and 2 g dispensings. This study demonstrates that experimentally determined calibration factors for the exact measurement geometry are necessary when measuring radionuclides in configurations other than the manufacturer's standard geometry, especially when nuclides that emit low-energy radiations are involved.

Brachytherapy↗
PubMed2001

The standardization of 177Lu by 4pibeta liquid scintillation spectrometry with 3H-standard efficiency tracing.

Solutions containing the potential radiotherapy radionuclide 177Lu have been standardized at the National Institute of Standards and Technology (NIST) by 4pibeta liquid scintillation (LS) counting with 3H-standard efficiency tracing using the CIEMAT/NIST method. Confirmatory measurements were made with 4pi NaI(TI) gamma-ray spectrometry. Activity determinations were made on 4 solutions over the course of 10 months with an expanded (k = 2) uncertainty on the activity of 0.8%. Half-life measurements were carried out using the NIST "4pi" gamma ionization chamber (IC) and LS counting and gave a new value of 6.65+/-0.01 d, which is shorter than the current ENSDF-recommended value by 1.3%. Impurity analyses were performed by high-purity germanium (HPGe) gamma-ray spectrometry and indicated only the presence of 177mLu at a level of 0.02% that of the 177Lu as of the respective reference times for the four solutions. Calibration factors for the NIST IC and Vinten 671 ionization chambers were developed, as were dial settings for the NIST-maintained Capintec CRC-12.

Calibration↗
PubMed2001

Radioassays and experimental evaluation of dose calibrator settings for 18F.

The positron emitter 18F continues to be one of the most important imaging radionuclides in diagnostic nuclear medicine. Assays of radiopharmaceuticals containing this nuclide are often performed in the clinic using commercial reentrant ionization chambers, or "dose calibrators". Meaningful quantitative clinical studies require accurate knowledge of the injected activity which requires proper calibration of these instruments. Radioassays were performed at the National Institute of Standards and Technology (NIST) on a solution of 18F produced at the National Institutes of Health (NIH) using 4pibeta liquid scintillation (fS) counting with 3H-standard efficiency tracing. Cocktails containing water fractions of approximately 0.9 and 9% (both as saline) were used. The massic activity values were measured to be 2.52+/-0.06 and 2.50+/-0.03 MBq g(-1), respectively, for the 0.9 and 9% water cocktails as of the reference time. The uncertainties on the activity measurements are expanded (k = 2) uncertainties. The largest uncertainty component was found to be the repeatability on a single LS source, with the cocktails containing 0.9% water fraction exhibiting a larger variability by nearly a factor of two. Reproducibility between LS cocktails with the same water fraction was also found to be a large uncertainty component, but with a value less than half that due to measurement repeatability. Radionuclidic impurities consisted of 48V and 46Sc, at levels of 0.11+/-0.08% (expanded uncertainties) and approximately 2 x 10(-3)% (upper limit) relative to the activity of the 18F, as of the reference time. Dose calibrator dial settings for measuring solutions of 18F were experimentally determined for Capintec CRC-12 and CRC-35R dose calibrators in three measurement geometries: a 5-ml standard NIST ampoule (two ampoules measured), a 12-ml plastic syringe containing 9 ml of solution and a 10-ml Mallinckrodt molded dose vial filled with 5 ml of solution. The experimental dial settings (and the corresponding expanded uncertainties) for these geometries were found to be 477+/-7, 474+/-6, 482+/-6 and 463+/-7 for the two ampoules, the syringe and the dose vial, respectively, in the CRC-12. The dial settings determined for the CRC-35R were 472+/-7, 470+/-7, 464+/-6 and 456+/-6 for the two ampoules, the syringe, and the dose vial, respectively. The uncertainties in the dial settings are expanded uncertainties. Comparisons between the empirically determined dial settings and the manufacturer's recommended setting of "439" indicate that use of the manufacturer's setting overestimates the activity by between 3 and 6%, depending upon the geometry used.

Calibration↗
PubMed2000

Experimental determinations of commercial 'dose calibrator' settings for nuclides used in nuclear medicine.

Commercial reentrant ionization chambers ('dose calibrators') have become the de facto standard instrument for making radioactivity measurements in the radiopharmaceutical industry. Accurate activity measurements, however, depend on the application of the correct calibration factor (dial setting) for the radionuclide in the exact measurement geometry for that particular instrument. Two methods are described for the experimental determination of dial settings for the Capintec CRC-12 dose calibrator. Using these methods, we have determined new calibration factors for 18F, 62Cu, 186Re and 188Re in several geometries. These new factors are presented, along with previously determined settings, for nuclides commonly used in nuclear medicine. The differences between the calibration factors for the different geometries, as well as the differences between the manufacturer's recommended setting underscore the need for empirically determined dose calibrator settings.

Radioisotopes↗
PubMed2000

Well-ionization chamber response relative to NIST air-kerma strength standard for prostate brachytherapy seeds.

The response of well-ionization chambers to the emissions of 103Pd and 125I radioactive seed sources used in prostate cancer brachytherapy has been measured. Calibration factors relating chamber response (current or dial setting) to measured air-kerma strength have been determined for seeds from nine manufacturers, each with different designs. Variations in well-ionization chamber response relative to measured air-kerma strength have been observed because of differences in the emitted energy spectrum due to both the radionuclide support material (125I seeds) and the mass ratio of 103Pd to 102Pd (103Pd seeds). Obtaining accurate results from quality assurance measurements using well-ionization chambers at a therapy clinic requires knowledge of such differences in chamber response as a function of seed design.

Air↗
PubMed2000

Experimental determination of dose calibrator settings and study of associated volume dependence in v-vials for rhenium-186 perrhenate solution sources.

OBJECTIVE: Accurate activity measurements of glass conical v-vials are only possible if dose calibrator dial settings are experimentally determined for the specific vial and volume range over which the measurements of a particular radionuclide is to be made. V-vials are used to transport and store unit doses of radiopharmaceuticals containing high-energy beta-emitters, such as 186Re. We have determined the correct dose calibrator dial settings for measuring 186Re in 3-mL glass conical v-vials from 2 manufacturers. METHODS: The 186Re solutions used were calibrated for radioactivity content at the National Institute of Standards and Technology (NIST) using liquid scintillation counting with 3H-standard efficiency with a maximum expanded (k = 2) uncertainty of 1.2% on the activity. Volumes of the solutions then were accurately dispensed into a set of v-vials from each of the 2 manufacturers and assayed in the dose calibrator maintained at NIST. RESULTS: For filling volumes above 1 mL, the dose calibrator response was found to be constant for both of the vials studied, enabling a single dial setting to be used for each vial type. The expanded uncertainties on the activity from uncertainty in the dial setting in that volume range were 0.4%-0.7%. Variability in vial construction contributed another 0.2%-0.3% in the uncertainty in the activity determination. CONCLUSION: These studies indicate a strong volume dependence on the response of the dose calibrator and highlight the need for experimental verification of dose calibrator settings for nonstandard geometries.

Calibration↗
PubMed1999

Determination of a calibration factor for the nondestructive assay of Guidant 32P brachytherapy sources.

A calibration factor ('dial setting') for the nondestructive assay of Guidant TiNi-encapsulated 32P intravascular brachytherapy wire sources has been determined for measurements with the Capintec CRC-12 (sic. 'dose calibrator') ionization chamber. The calibration factor was derived from ionization current measurements with the CRC-12 followed by very quantitative, destructive assays of the 32P content in two sources.

Brachytherapy↗
PubMed1999

The standardization of 62Cu and experimental determinations of dose calibrator settings for generator-produced 62CuPTSM.

The Positron Emission Tomography agent 62Cu Pyruvaldehyde Bis(N4-methyl)thiosemicarbazone (PTSM) has been standardized by the National Institute of Standards and Technology (NIST) using 4 pi beta liquid scintillation counting with 3H-standard efficiency tracing. Using a measurement model developed at NIST for the determination of experimental dose calibrator dial settings for short-lived radionuclides, the correct dial settings for 62CuPTSM in a clinically useful geometry (a 35 ml plastic syringe containing 33 ml of solution) as well as the standard NIST 5 ml glass ampoule have been elucidated. This measurement model is fully described, as is the treatment of associated uncertainties. The correct instrument settings for the NIST Capintec CRC-12 re-entrant ionization chamber ('dose calibrator') were found to be '499 +/- 6' and '489 +/- 8', respectively, for the syringe and ampoule geometries. The stated uncertainties are expanded (k = 2) uncertainties. The expanded uncertainties in the measured activity arising from these new dial settings are +/- 0.8% and +/- 1.4%, respectively, for the syringe and ampoule. The measured activities using these settings are lower than those obtained from the manufacture's recommended setting of '448' by 9.7% for the syringe and 7.7% for the ampoule, and underscore the need for experimental verification of the dose calibrator settings for each radionuclide and each geometry used in the clinic.

Calibration↗
PubMed1999

A new experimental determination of the dose calibrator setting for 188Re.

UNLABELLED: Accurate activity measurements of radionuclides using commercial dose calibrators requires that the correct dial setting (or calibration factor) be applied. The dose calibrator setting for the medical radionuclide 188Re (as 188ReO4-) has been determined experimentally using solution sources prepared and calibrated at the National Institute of Standards and Technology (NIST). METHODS: The specific activity of two sources (in units of MBq/g) in the standard 5-mL NIST ampoule and in a 5-mL SoloPak dose vial were calibrated using 4pibeta liquid scintillation counting with 3H-standard efficiency tracing and gamma-ray/bremmstrahlung counting in the NIST "4pi" gamma ionization chamber on gravimetrically related sources. RESULTS: The newly determined settings for the NIST Capintec CRC-12 dose calibrator are (631+/-4) x 10 and (621+/-3) x 10 for the respective ampoule and dose vial geometries with an expanded (at a presumed 95% confidence level) uncertainty of 0.4%-0.5% in the activity determination. The setting for the dose vial geometry was independently confirmed using a Capintec CRC-15R at Cedars-Sinai Medical Center using sources calibrated against a NIST standard. CONCLUSION: These new settings result in activity readings 28%-30% lower than those obtained using the previously recommended setting of 496 x 10. This discrepancy most likely results from underestimating the total radiation yield from 188Re decay when calculating the dose calibrator response. This study emphasizes the need for experimental determinations of dose calibrator settings in the geometry in which the measurements will be performed.

Calibration↗
PubMed1998

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).

Academies and Institutes↗
PubMed1998

The standardization of the potential bone palliation radiopharmaceutical 117mSn(+4)DTPA.

Solutions containing the potential bone pain palliation radionuclide 117mSn, in chloride form and as a diethylenetriaminepentaacetate (DTPA) complex, have been standardized by 4 pi beta liquid scintillation (LS) spectrometry and 4 pi gamma-ray spectrometry. Massic activities of the stock solutions were measured in order to determine dose calibrator settings for the solutions using commercial dose calibrators. Excellent agreement in the measurement of solution massic activity between the two techniques was achieved. The massic activity of 117mSnCl4 stock solution was found to be 38.62 +/- 0.23 MBq g-1 and 38.81 +/- 0.94 MBq g-1 with LS spectrometry and 4 pi gamma-ray spectrometry respectively. The respective values of the massic activity of the 117mSnDTPA stock solution with LS spectrometry and 4 pi gamma-ray spectrometry were 39.35 +/- 0.23 MBq g-1 and 39.70 +/- 0.96 MBq g-1. Impurities were analyzed in several solutions and found to have emission rates on the order of 10(-4) to 10(-6) of the rate of the 117mSn emission at the end-of-bombardment. The largest impurities came from 113Sn and 125Sn, the activation products of isotopic impurities present in the 117Sn target. The relative proportions of the various impurities were found to be highly dependent upon the source of 117Sn target material. The implications of choice of half-life used in the decay correction of 117mSn are discussed.

Bone Diseases↗
PubMed1997

Comparison of the French and U.S. national 3H (tritiated H2O) standards by 4 pi beta liquid scintillation spectrometry.

Radioactivity standards of tritiated water (3H2O)-disseminated by the Laboratoire Primaire des Rayonnements Ionisants (LPRI) and the National Institute of Standards and Technology (NIST), the national radionuclidic metrology and standardization laboratories of France and U.S.A., respectively-have been intercompared by liquid scintillation (LS) spectrometry. The ratio of the certified massic activities for the two standards was compared to that obtained from direct measurements on matched sets of LS cocktails prepared from the standards. Seven experimental trials (involving a total of 21 counting sources for each standard) were performed for the comparison. The trials were performed under a wide range of experimental conditions, including use of two different LS spectrometers and three series of LS cocktail compositions (with systematically varied 3H detection efficiencies). The results exhibited an apparent mean disagreement between standards of < 0.4% on a relative basis. For contrast, the relative combined standard uncertainty on the massic activity ratio for the two standards, as obtained from their respective certified uncertainty assessments, is about 0.7%.

France↗
PubMed1983

Primary cysts of the mastoid process.

Two patients with primary mastoid cysts are presented. These examples stress the importance of regular follow-up of patients with chronic serous otitis media so that the complications or associated abnormalities may be treated early prior to extensive destructive erosion. The formation of these cysts may be due to changes brought about by chronic serous otitis media, or they may be of congenital origin with middle ear effusion as a sequela.

Adolescent↗