An international journal published by K. N. Toosi University of Technology

Document Type : Research Article


1 Nuclear Engineering School, Shahid Beheshti University, Tehran, Iran

2 Physics and Accelerators Research School, Nuclear Science and Technology Research Institute, P.O. Box 14395-836, Tehran, Iran


Primary standardization of radioactivity is related to the direct measurement of activity in radioactive decay. A large variety of primary standardization techniques have been developed in the past years. The photon-photon coincidence counting is one of the methods for activity determination. This method is particularly applied for the standardization of I-125 using the detection of X-ray and gamma-ray coincident counting. In this paper, a 2D photon-photon coincidence digital system with two similar ‎‎2'' × 2''‎‎ NaI(Tl) detectors for absolute activity measurement is developed. The system is established based on a 100 MHz CAEN waveform digitizer (DT5724) which directly records the pre-amplifier output signals of the two NaI(Tl) detectors. The sampled signals was transformed to trapezoidal signals using pulse height analyzer firmware and coincidence events were recorded in a list file. The list file was analyzed offline using a Matlab code to realize correlated gama lines of Co-60 source.  The Volkovitsky formulas were used for the activity calculation and the details of the experimental setup were also discussed. Standardization of  the two Co-60 standard sources was performed using this system. Results are in good agreement with the reference activity of Co-60 sources. The presented formula can be modified for absolute calibration of the other medical radioisotopes. The technique can be generalized for absolute activity measurement of I-125 which uses for ophthalmic plaque radiation therapy.


  • A 2D photon-photon coincidence digital system is designed using for the primary standardization of radionuclides.
  • 2D energy spectrum of Co-60 was measured.
  • The application of list mode data acquisition for absolute calibration was described.
  • Formulas for the activity measurement of cascade gamma-ray emitter radioisotopes were presented.


Main Subjects

Adelstein, S. J., Kassis, A. I., Bodei, L., et al. (2003). Radiotoxicity of iodine-125 and other auger-electron-emitting radionuclides: background to therapy. Cancer Biotherapy and Radiopharmaceuticals, 18(3):301–316.
Barnothy, J. and Forro, M. (1951). Coincidence methods of measuring disintegration rates of radioactive sources. Review of Scientific Instruments, 22(6):415–423.
Biganeh, A. and Kakuee, O. (2021). Identification and measurement of muon cosmic radiation using digital spectroscopy system. Journal of Nuclear Science and Technology (JonSat).
Biganeh, A. and Shakeri Jooybari, B. (2022). Design of a two-dimensional pseudo coincidence compton suppressor system for neutron activation analysis. Radiation Physics and Engineering.
Bikit, I., Nemes, T., and Mrda, D. (2009). Simple method for absolute activity measurement of Co-60 source. Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 603(3):333–336.
Bodei, L., Kassis, A. I., Adelstein, S. J., et al. (2003). Radionuclide therapy with iodine-125 and other auger-electron-emitting radionuclides: Experimental models and clinical applications. Cancer Biotherapy and Radiopharmaceuticals, 18(6):861–877.
Brinkman, G., Aten Jr, A., and Veenboer, J. T. (1963). Absolute standardization with a NaI (Tl) crystalI: calibration by means of a single nuclide. The International Journal of Applied Radiation and Isotopes, 14(3):153–157.
Caen (2022). Caen Electronic Instrumentation, compass multi-parameter DAQ software for physics applications, revision 2.0.1, February 15th2022. Technical report. Caen Electronic Instrumentation.
Colle, R. (2009). Radionuclidic standardization by primary methods: an overview. Journal of Radioanalytical and Nuclear Chemistry, 280(2):265–273.
Eldridge, J. S. and Crowther, P. (1964). Absolute determination of I-125 in clinical applications. Nucleonics, 22(6):56.
Horrocks, D. L. and Klein, P. R. (1975). Theoretical considerations for standardization of I-125 by the coincidence method. Nuclear Instruments and Methods, 124(2):585–589.
Jordanov, V. T. and Knoll, G. F. (1994). Digital synthesis of pulse shapes in real time for high resolution radiation spectroscopy. Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 345(2):337–345.
Lagoutine, F., Coursol, N., and Legrand, J. (1984). Table de radionucléides: table présentée dans le cadre d’une collection de monographies et de documents métrologiques. LMRI.
Martin, R. and Taylor, J. (1992). The standardization of I-125: a comparison of three methods. Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 312(1-2):64–66.
Mart´ınez-Monge, R., Pagola, M., Vivas, I., et al. (2008). CT-guided permanent brachytherapy for patients with medically inoperable early-stage non-small cell lung cancer (NSCLC). Lung cancer, 61(2):209–213.
ORTEC (2000). Gamma Vision, Gamma-ray Spectrum Analysis and MCA Emulation for MS Windows, Software User’s Manual, Version 32, V5.10. Oak Ridge, USA.
Pommé, S. (2007). Methods for primary standardization of activity. Metrologia, 44(4):S17.
Quinn, T. (1997). Primary methods of measurement and primary standards. Metrologia, 34(1):61.
Schrader, H. (2006). Photon–photon coincidences for activity determination: I-125 and other radionuclides. Applied Radiation and Isotopes, 64(10-11):1179–1185.
Schrader, H. and Walz, K. (1987). Standardization of I-125 by photon-photon coincidence counting and efficiency extrapolation. International Journal of Radiation Applications and Instrumentation. Part A. Applied Radiation and Isotopes, 38(10):763–766.
Taylor, J. (1967). X-ray-x-ray coincidence counting methods for the standardization of I-125 and Hg-197. In Standardization of Radionuclides. Proceedings of a Symposium on Standardization of Radionuclides.
Volkovitsky, P. and Naudus, P. (2009). Absolute Co-60 characterization based on gamma–gamma coincident detection by two NaI(Tl) detectors. Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 607(3):568–572.
Wang, Z., Lu, J., Liu, L., et al. (2011a). Clinical application of CT-guided I-125 seed interstitial implantation for local re-current rectal carcinoma. Radiation Oncology, 6(1):1–7.
Wang, Z.-M., Lu, J., Liu, T., et al. (2011b). Ct-guided interstitial brachytherapy of inoperable non-small cell lung cancer. Lung Cancer, 74(2):253–257.
Zhongmin, W., Yu, L., Fenju, L., et al. (2010). Clinical efficacy of CT-guided iodine-125 seed implantation therapy in patients with advanced pancreatic cancer. European Radiology, 20(7):1786–1791.