Measuring natural radioactivity of bricks used in the constructions of Tehran

        Naturally occurring radionuclides have different amount of activity concentration for 226 Ra, 232Th and 40K in building materials. In this study, natural radioactivity has been measured for bricks used in Tehran. For this work, 9 samples of three types of bricks, clay brick (CB), making the facade brick (MFB) and firebrick (FB) has been selected from different regions and factories in Tehran. Gamma rays analyzed by high purity germanium (HPGe) detector and spectroscopy system. As the results show, the maximum value of the mean 226 Ra, 232Th and 40K for clay brick has been 17, 9 and 422Bq/kg respectively. Maximum of radium equivalent activities (Raeq) were calculated 62.81Bq/kg that less than the level has been determined 370Bq/kg for building materials. Other type of bricks had low amounts compared to clay bricks. The calculation results show that the bricks are safe for inhabitants because hazard indexes for gamma were below the standard was been introduced. The results of this research compared with other studies in different countrie

Radiolabeling and Bio-distribution study of ICD-85 with Technetium-99m as a cancer treatment agent in mice

     ICD-85 is a combination of three poly-peptides, ranging from 10,000 to 30,000 Dalton, derived from the venoms of an Iranian brown snake (Agkistrodon halys) and a yellow scorpion (Hemiscorpius lepturus). Labeling of this ICD-85 was successfully achieved with 99mTc, through direct method using SnF2 as reducing agent. Labeled ICD-85 was injected into mice to determine the excretion pathway. The results show that the maximum labeling yield (>75%) was obtained by using 30 μg of ICD-85 in phosphate buffer (60 μl, pH 7.1) at room temperature. Bio-distribution studies with radiolabeled ICD-85 shows moderate clearance of the complex from blood. The improvement of the immunotherapeutic treatment of cancer requires a better knowledge of the biological actions of the ICD-85 since tissue distribution studies are very important for clinical purpose

A case study of energy absorption buildup factors in some human bones for gamma energies 30 keV to 1.5 MeV

Human body consists of some tissues among which bone is one of the important living and growing tissue. In this research, energy absorption buildup factor (EABF) values of 27 types of bone have been computed for photon energy 0.03 to 1.5 MeV up to 40 mean free path (40mfp) penetration depths. The Inner bone tissue, Spongiosa and Male sternum had the largest values of EABF in low photon energies, and great differences below 150 keV photon energy were noted relative to the other bones. This study would be of utmost  importance for estimation of the effective dose to the human bones, radiation therapy and various medical applications.

131I-Chlorotoxin dosimetry in liver using MCNP simulation code

     Chlorotoxin is a 36 amino acids peptide, which is able to block chloride channels isolated from mouse brain. A derivative of chlorotoxin is synthesized and it is labeled by iodine 131; then animal experiments carry out on rats. Multiple organ doses may be calculated with biological distribution results in rats with labeled compounds using simulated MCNP4C code. Human dose can be calculated using the dose distribution in rats with a conversion ratio for dose distribution. Chloramine T is our method for marking, and electrophilic substitution reactions are methods for iodize of peptides. Simulation of a human phantom to evaluate dose distribution was done using simulation code MCNP4C. To evaluate the dose distribution in the human body, using this code and the accumulated activity in each organ tissue dose is calculated. To study the biological distribution of the radiotracer 131I, 0.37 MBq radiotracer was injected into rat via the tail vein. The accumulated activity in each organ with the agent “ID / g” is determined. Biological distribution of 131I-chlorotoxine in the normal rats is obtained. Its Decay constant in the liver is 0.07h and the effective half-life of the radiotracer is 10h in rat liver. The total number of particles found in the leak from liver tissue was reported 67600. Liver tissue dosimetries originating from other sources (thyroid tissue, stomach, kidney, right & left lung, spleen, and pancreas) were examined. Then, the overall dose to the target tissue will be calculated. Leaked beta particles in liver itself (self-dose) are the most delivered dose to the liver (98%); it is for gamma rays 1.1%, while its source is adjacent tissues in addition to liver (cross-dose); Because of low atomic number of the tissue, delivered dose originated from Bremsstrahlung (braking radiation) is low (0.9%). Radiation dose to the liver in intravenous injection of 0.37 MBq  131I-chlorotoxine radiotracer is 3.44 * 10-6.

Investigation of the Effect of Proton Energy on the Depth-dose Distribution in the Proton Therapy of the Eye Tumor Using MCNPX Code

Introduction: Depth-dose distribution curve of protons in the matter has a maximum is called Bragg peak. Bragg peak of a monoenergetic proton beam is too narrow. The spread out Bragg peak should be created for full coverage of the tumor. The spread out Bragg peak is obtained in the depth of the tumor with superposition of the several Bragg peaks. The aim of this study was coverage of an eye tumor in the proton therapy while healthy eye tissue absorbs less radiation. Methods: In this analytical study, the simulations were performed using MCNPX code. A tumor in the eye phantom was considered. The eye phantom has been irradiated with different proton beam energy. A Polystyrene modulator wheel was used for creating the spread out Bragg peak in the tumor region. Results: Bragg peaks were created in different depths of the tumor, by varying the proton beam energies from 20 MeV to 38 MeV. Bragg peak of the 32.85 MeV proton beam energy was precisely placed at the end of the tumor. Different pristine Bragg peaks were produced using a Polystyrene modulator wheel with different thicknesses and 32.85 MeV proton beam energy. The spread out Bragg peak was created in the tumor region by modulation of the pristine Bragg peaks. Neutrons and photons are produced by the inelastic nuclear interactions of protons with the nuclei of different tissues of eyes. The flux and absorbed dose of secondary neutrons and photons were considerably small compared to the depth-dose distribution of protons and the total absorbed dose in the tumor was more than other tissues of eyes. Conclusion: Using a modulator wheel the tumor can be treated, so that the minimal damage reaches the surrounding tissues. The results show that more than 92% of the total dose of secondary particles and protons is absorbed in the tumor

Estimation of human absorbed dose of 99mTc-MAA using MIRD method based on animal data and comparison with MCNP simulation code: Estimation of absorbed dose of 99mTc-MAA using MIRD and MCNP method

Introduction: 99mTc-Macro Aggregated-Albumin (99mTc-MAA) has been evaluated as a useful perfusion study agent. In this study, the human absorbed dose of 99mTc-MAA was estimated with MIRD and MCNP methods based on animal biodistribution data and finally compared with ICRP publication data. Materials and Methods: In this study, for investigating the biodistribution of 99mTc-MAA, after radiolabeling of MAA with Technetium-99m, it was injected to mice via the tail vein. After 1-120 min post injection, the mice were sacrificed and some of their tissues dissected and counted for calculating the percentage of the injected dose per gram (% ID/g) and the absorbed dose. Then, the obtained data was converted to equivalent data in human for each tissue. Results: Dose prediction shows that the highest absorbed dose is observed in the lungs (MIRD: 6.8E-2 mGy/MBq, MCNP: 6.32E-2 mGy/MBq). There is good agreement between the results obtained from MIRD and MCNP simulation for lungs. Conclusion: According to the present results and comparison with ICRP publication data, animal dissection model and simulation MCNP code can be useful tools for internally-absorbed dose estimation of pulmonary radiopharmaceuticals