Dosimetry in thyroid follicles due to low-energy electrons of iodine using the Monte Carlo method

اختصاصی از فی فوو Dosimetry in thyroid follicles due to low-energy electrons of iodine using the Monte Carlo method دانلود با لینک مستقیم و پر سرعت .

OBJECTIVE: To evaluate the absorbed dose in thyroid follicles due to low-energy electrons such as Auger and internal conversion electrons, besides beta particles, for iodine radioisotopes ( 131 I, 132 I, 133 I, 134 I and 135 I) utilizing the Monte Carlo method. MATERIALS AND METHODS: The dose calculation was performed at follicular level, simulating Auger, internal conversion electrons and beta particles, with the MCNP4C code. The follicles (colloid and follicular cells) were modeled as spheres with colloid diameter ranging from 30 to 500 µ µ µm, and with the same density of water (1.0 g.cm – ³). RESULTS: Considering low-energy particles, the contribution of 131 I for total absorbed dose to the colloid is about 25%, while the contribution due to short-lived isotopes is 75%. For follicular cells, this contribution is still higher achieving 87% due to short-lived iodine and 13% due to 131 I. CONCLUSION: The results of the present study demonstrate the importance of considering low-energy particles in the contribution for the total absorbed dose at follicular level (colloid and follicular cells) due to iodine radioisotopes ( 131 I, 132 I, 133 I, 134 I and 135 I)

Response Function of the BGO and NaI(Tl) Detectors Using Monte Carlo Simulations

اختصاصی از فی فوو Response Function of the BGO and NaI(Tl) Detectors Using Monte Carlo Simulations دانلود با لینک مستقیم و پر سرعت .

The high efficiency of the BGO detectors makes them a very attractive candidates to
replace NaI(Tl) detectors, which are widely used in studies of body composition. In this work,
the response functions of the BGO and NaI(Tl) detectors were determined at 0.662, 4.4, and 10.0
MeV using three different Monte Carlo codes; EGS4 1 , MCNP 2 , and PHOTON 3 . These codes
differ in their input files and transport calculations, and were used to verify the internal
consistency of the set-up and of the input data. The energy range of 0.662-10 MeV was chosen to
cover energies of interest in body-composition studies. The superior efficiency of the BGO
detectors has to be weighed against their inferior resolution, and their higher price than that of
the NaI detectors. Since the price of the BGO detectors strongly depends on the crystal’s size, its
optimization is an important component in the design of the entire system.