Biomedical subjects

Maria Sahagia

Publications and source records attributed to Maria Sahagia.

5 recordsLinked to original sources

PubMed2006

Standardization of 99mTc.

The radioactivity of 99mTc was standardized by the 4piPC-gamma coincidence method with two different modes. One is using coincidences between (119.5-142.6)keV conversion electrons and K X-rays, and the other is coincidences between the 2.13 keV conversion electrons and 140.5 keVgamma-rays. The background of the K X-ray peak and the sensitivity of the proportional counter (PC) to 140 keV gamma-rays were the main sources of uncertainties in the first case and low detection efficiency for conversion electrons in the second case. General coincidence equations were written, with specific forms, for the three measurement variants, including literature variant. Comparison with the ionization chamber calibration is reported.

Algorithms↗

PubMedDate not supplied

Standardization of 65Zn by 4piPC-gamma coincidence counting method with efficiency extrapolation.

A 65Zn solution was standardized by the 4piPC-gamma efficiency-extrapolation coincidence counting method. Theoretical aspects of coincidence equations, efficiency equations and linearity conditions are reviewed. Experimental measurements were performed for two low level discrimination thresholds for the PC channel (counting K+L or K X-rays or Auger electrons from EC decay) and for three different settings of the gamma window. Requirements on gamma channel set-up for linear extrapolation were established by using a Pb absorber or by proper gamma window setting. The measured activity values were discussed and found in good agreement with those obtained with a calibrated ionization chamber.

Algorithms↗

PubMedDate not supplied

Precise measurement of the activity of 186Re, 188Re radiopharmaceuticals.

The paper presents the results obtained in the assurance of traceability along the whole chain: production, distribution, use in hospitals, for the activity measurement of radiopharmaceuticals containing 186Re, 188Re and 186Re + 188Re mixtures. Standardization of the solutions, 4piPC-beta-efficiency relations and responses of a Centronic IG 12/20A ionization chamber and other radioisotope calibrators are presented. Gamma-ray and bremsstrahlung radiation contributions in the total response were evaluated. Some of the relevant results were compared with literature data.

Gamma Rays↗

PubMedDate not supplied

Standardization of 152Eu.

152Eu was standardized within the frame of a BIPM international comparison. The solution was prepared and bottled by PTB. The ampoules were measured at BIPM in the SIR ionization chambers and then dispatched to the participating laboratories. In the Radionuclide Metrology Laboratory of IFIN-HH, the solution was standardized using a coincidence method with "beta-efficiency extrapolation" by foil absorption. A simple 4pi beta-gamma-coincidence system was used, with NaI(Tl) and 4piPC detectors. No significant impurities were found apart for 0.5% 154Eu. To obtain linear extrapolation plots, a "gamma-window" of 180-1500 keV was chosen. Dead-times of 10 micros were used. A combined uncertainty of 0.24% was obtained, mainly from the extrapolation procedure component.

Journal Article↗

PubMedDate not supplied

Standardization of 89Sr.

Two methods were used for the standardization of the pure beta-emitter 59Sr solution received in the framework of the 2000 BIPM comparison of activity measurements. The first method was by scintillation counting using the triple to double coincidence ratio (TDCR) technique. The existing three detector-system was improved by the inclusion of a MAC-3 module produced by LNHB-Saclay. This module contains the circuits for the coincidence, dead time and gate functions. This was the first use of this equipment in an international comparison. The DETECSZ program (LNHB) was used to obtain the activity concentration, at the reference time, as 26.09+/-0.21 kBq g(-1). The second method was the efficiency tracer technique, using a 60Co standard solution and a 4pi beta-gamma-coincidence system. The radioactivity concentration was calculated from a general extrapolation curve, by using data from several sources. The value was 26.58+/-0.28 kBq g(-1) on the reference date 01.10.2000, 00 h UTC. The two results are in agreement within the limits of their combined uncertainties.

Journal Article↗