Determination of [99]Mo contamination in [99m]Tc elute obtained from [99]Mo / [99m]Tc- generator

[99m]Tc is a widely used radioisotope in nuclear medicine centers which is obtained by elution from Mo-[99]/Tc-[99m] generators. Usually the generators are either supplied by the Iran Atomic Energy Agency or by private companies from foreign countries. In this study we have measured [99]Mo contamination in [99m]Tc elute from different generators in a period of one year. The radionuclide impurity of the [99m]Tc elute were studied in two types of radionuclide generators [A: produced in Iran and B: imported from other country]. In-vitro measurements were performed using dose calibrator. Direct measurements were made, using a standard canister at the time of milking of the generators and also in subsequent hours after milking. The results showed a mean of [99]Mo impurity in generators A and B to be 0.00932 +/- 0.0043 and 0.0170 +/- 0.0127 respectively. Although the results showed that the [99]Mo contamination in [99m]Tc elute was lesser than the maximum accepted activity limit of 0.015%, the difference in these two types may reflect different methods of productions of generator, as well as the quality control procedures. The mean of [99]Mo contamination in generators produced in Iran Atomic Energy Organization was lesser than generators imported from foreign origin

Monte Carlo simulation and dosimetric verification of physical wedges used in radiation therapy

The presence of a wedge filter in the beam trajectory can modify the beam quality and cause some changes in the dosimetry parameters which are usually difficult to be measured directly and accurately. In this study the MCNP-4C Monte Carlo code was used to simulate the 9 MV photon beam generated by a linear accelerator. Upon getting a good agreement between the Monte Carlo simulated and measured dose distribution in open fields, the model was used to simulate the physical wedges. The steel wedges with angles from 15°-60° were modeled and the primary and the secondary photon beams were calculated. The beam profiles and wedges factors were calculated for each wedge. The output factors were determined for 45 wedge. The calculated data were compared with the measured values of the same parameters. The results showed that the use of wedges reduced the fluencies of the primary and scattered photons and also increased the average energy of the primary and the scattered photons. The agreement between the calculated and the measured data was better than 2% for all wedges. The results also showed that as the wedge angle increased, the electron contamination of photon beam decreased. The presence of a wedge in a 9 MV photon beam alters the primary and the scattered components generated by a linear accelerator. The simulated linac machine and its associated data can be used to predict the dose distribution in other complex fields