Biomedical subjects

B E Zimmerman

Publications and source records attributed to B E Zimmerman.

22 records · Page 2Linked to original sources

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↗

PubMedDate not supplied

A dual-compensated cryogenic microcalorimeter for radioactivity standardizations.

Efforts are underway by our laboratory to develop a microcalorimeter that can be routinely used for radioactivity standardizations of nuclides that decay by pure beta-emission or by low-Z electron capture. The prototype calorimeter consists of a cryostat with two temperature-controlled stages and a base stage that are operated at nominal temperatures of 8 K. A unique aspect of the calorimeter's design is the ability to repeatedly engage and disengage the radioactive source from the second stage heat path using a magnetically activated elevator. The measurement of the total power from a radioactive sample is obtained from the difference in the second stage power with and without the source in place. As a result of extensive performance evaluations using 90Sr-90Y and 32P brachytherapy seeds as well as with an internal calibration heater, many initial design flaws have been identified and are being addressed.

Journal Article↗