engleski

ACTIVITY QUANTIFICATION OF 133Ba SOURCES IN WATER PHANTOM

Quantitative information about spatial and temporal distribution of radioisotope in nuclear medicine procedures is important for dosimetric studies. 133Ba is suitable isotope (E=356 keV, T1/2=10.5 y) for simulation of 131I (E=364 keV, T1/2=8 d) imaging in radioiodine and radionuclide therapy. We imaged 4 cylindrical 133Ba sources in a cylindrical water phantom. Activity of each source was < 1.5 MBq. The sources were produced at the National Institute of Standards and Technology (NIST, USA). Planar and SPECT measurements were done on a dual head gamma camera. Triple-energy window (TEW) acquisition was performed for scatter correction. In planar measurements, transmission flood source (57Co) was used for attenuation correction (AC). In SPECT imaging, CT-based AC was applied. From measurements in air of calibration source the sensitivity factor was obtained in cps/MBq. Three consecutive acquisitions were performed in order to evaluate the reproducibility of the measurements. The results of activity measurements for the calibration source, A0=0.91 MBq, showed that Aplanar= 0.730.03 MBq ; ASPECT=0.920.01 MBq. SPECT measurements with CT-based AC produced result accurate within 2%, while planar measurements underestimated activity by 20%. Therefore SPECT/CT imaging should be used for accurate dosimetry. Acknowledgement: This work is a part of the collaboration with the International Atomic Energy Agency (IAEA, Vienna) under the Coordinated Research Project E2.10.07.

nuclear medicine procedures; dosimetric studies

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