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J T Cessna

Publications and source records attributed to J T Cessna.

13 recordsLinked to original sources
PubMed2005

Development of activity standard for 90 Y microspheres.

(90)Y microspheres are important therapeutic radiopharmaceuticals used in the treatment of liver cancer through a process known as selective internal radiation therapy. SIR-spheres is a radiopharmaceutical product that is comprised of (90)Y microspheres suspended in sterile, pyrogen-free water for injection into patients. It is necessary to establish for the SIR-spheres production the capability of accurately measuring the activity of this product to a traceable national measurement standard. An activity standard for SIR-spheres was developed from a standard for (90)Y solution, employing a highly quantifiable chemical digestion process. Calibration factors for the manufacturer's ionisation chambers were determined for 1 and 5 ml of the SIR-spheres product placed in Wheaton vials, for both 34% and 44% of (90)Y microsphere concentration.

Australia↗
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

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↗
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↗
PubMed1993

Radioassays of yttrium-90 used in nuclear medicine.

Yttrium-90 radioassays are required in nuclear medicine at the gigabecquerel activity level (GBq) for measuring injected activity, and at the becquerel level for measuring individual tissue samples in biodistribution studies. A method of standardizing 90Y for activity using high-efficiency liquid-scintillation counting is described. Solution standards were used to establish the calibration factors for commercial radionuclide calibrators. Detection efficiencies are also presented for liquid-scintillation counting, NaI(T1) bremsstrahlung counting and Cerenkov counting.

Nuclear Medicine↗
PubMedDate not supplied

Construction and implementation of the NIST triple-to-double coincidence ratio (TDCR) spectrometer.

A description of the triple-to-double coincidence ratio (TDCR) spectrometer recently constructed at NIST and results of tests to assess its operating characteristics are presented. Measured activities for previously calibrated solutions of 3H (tritiated water) and 63Ni agreed with certified activity values to within 0.04% and 0.2%, respectively. Agreement between measurements of solutions containing 90Y using the TDCR and the CIEMAT/NIST efficiency tracing method was achieved to within 0.7% and within the respective experimental uncertainties. A difference of 5.3% was observed between TDCR measurements and the certified massic activity value for a calibrated solution containing 54Mn, but because of the large uncertainty on the TDCR result (3.6% relative standard uncertainty), the values agree to within the experimental uncertainties. Agreement to within experimental uncertainties (2%) for 103Pd was achieved with the TDCR and CIEMAT/NIST methods, but not between TDCR and isothermal calorimetric measurements. TDCR results for a 204Tl solution were in excellent agreement (maximum difference of 0.2% with any other method, with combined standard uncertainty of 0.45% on TDCR result) with results obtained using three other methods.

Beta Particles↗
PubMedDate not supplied

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.

Calibration↗
PubMedDate not supplied

Experimental determination of calibration settings for plastic syringes containing solutions of 90Y using commercial radionuclide calibrators.

Calibration factors for several makes (Capintec, AtomLab, and PTW) and models of commercially available re-entrant ionization chambers ("dose calibrators") were determined for solutions of 90Y using 10 ml plastic syringes that are used in the administration of the recently approved radioimmunotherapy drug Zevalin. Effects of filling volume on chamber response were studied for the anticipated prescription volume range of 3-9 ml in those syringes. A series of syringes were prepared over that range with accurately known volumes using a "standard" solution containing 90YCl3 in 1 moll(-1) HCl and approximately 50 microg of nonradioactive YCl3 per gram of solution. The respective calibration factors for the Capintec and AtomLab chambers required to give the correct activity reading were found to be "55+/-2 x 10" and 393+/-6, where the uncertainties are expanded (k = 2) uncertainties. The results indicated no significant effect of filling volume on the calibration setting to within the uncertainty on the activity measurement for all but the PTW chamber. In that case, a variation of about 5% was observed over the filling range. A direct comparison was also made between the actual 90Y Zevalin drug and the "standard" solution, with no differences in determined calibration settings observed within the uncertainties on the activity calibration.

Calibration↗