جستجوی مقالات مرتبط با کلیدواژه "coincidence counting" در نشریات گروه "علوم پایه"

Photon-photon coincidence counting is a primary standardization technique used for the absolute activity measurement of short half-life radionuclides. In this study, a coincidence spectrometer based on digital signal processing was developed for the absolute standardization of 125I seed Brachytherapy. The spectrometer includes a waveform digitizer that samples at the preamplifier signals directly from two similar 2ʺ × 2ʺ NaI (Tl) detectors. The sampled signals were shaped into trapezoidal signals for pulse height analysis. These detected signals were then recorded in a list file and the software was used to recognize coincidence events. Detailed discussions were included on the formulas for determining absolute activity measurement. The activity of a 125I seed was measured and showed good agreement with the reference values. This presented technique is a quick method for measuring the activity of 125I at nuclear hospitals. The standardized source can also serve as a tracer for measuring the activity of the 109Cd source

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.