@article { author = {Niroomand-Rad, A.}, title = {An Overview of Technological Developments in Medical Applications of X-Rays and Radioactivity}, journal = {Journal of Biomedical Physics and Engineering}, volume = {1}, number = {1}, pages = {-}, year = {2011}, publisher = {Shiraz University of Medical Sciences}, issn = {2251-7200}, eissn = {2251-7200}, doi = {}, abstract = {The years 1895 to 1898 were momentous for their impact on health and human well beings. First, Wilhelm Roentgen noted a glowing fluorescent screen, caused by invisible rays. This event subsequently led to the discovery of X-rays in 1895, and thus the birth of the “atomic age”. Next Becquerel’s investigations of these mysterious rays led to his experiments with uranium salt crystals. He thought that when these crystals are exposed to sunlight they could emit rays and cause exposure on photographic plates. This led to the discovery of radioactivity in 1896, with its full significance appreciated when the Curies discovered radium in 1897. The term “radioactivity” was first used by Marie Curie to describe this phenomenon that led to the birth of the “nuclear age”.  Shortly after, the medical applications of x-rays and radioactivity were recognized and widely disseminated. In the past 100 years, the technological developments in the production of x-ray beams along with the impact of the discovery of artificial radioactivity by Irene Curie and Frederic Joliot in 1930s have revolutionized the practice of medicine. Currently x-ray imaging is being used, more than any other imaging modality, in diagnosis of diseases and abnormalities. In addition, over 50% of all cancer patients receive radiation treatments as part of their treatment plan(s).  Despite significant advances in imaging technology and in production and delivery of x-rays and radioactivity, about half of these patients are successfully cured with 5 to 10 years local control. Reasons for treatment failure with radiation may be several including physical, biological, or both. For example, because of the imaging limitations, the exact extent of disease for many tumors is often unknown. Moreover, some tumors are able to “repair” radiation damage very effectively and some are radio resistant due to relative hypoxia.  In recent years, the major “challenge” of radiation treatment is to deliver large enough doses to the most resistant cancer cells to provide a high probability of local control while minimizing the dose to normal tissues and hence reducing complications.  With recent developments in “imaging” the metabolic or functional status of cancers, the position of tumors relative to surrounding normal tissue can be more clearly delineated.  The therapeutic dosage of radiation to the tumors can be escalated without exceeding normal tissues tolerances. These special techniques include: 3D  “conformal” radiation treatment where the shape of the high dose region “conforms” to the shape of the tumor (“target”), intensity modulated radiation therapy (IMRT) that uses combinations of radiation beams with varying spatial intensity across the fields (“intensity modulated”) in order to achieve an “ideal” dose distribution, image guided radiation treatment, and heavy charged particle radiotherapy. As such, it is expected to increase the success rate of cancer treatment significantly with this radiation treatment modality.}, keywords = {Medical Applications,X-Rays and Radioactivities,Conformal Therapy}, url = {https://jbpe.sums.ac.ir/article_43018.html}, eprint = {https://jbpe.sums.ac.ir/article_43018_880af2c97b8e06695a0ca813ff67cca9.pdf} } @article { author = {Parsai, E. I. and Gautam, B. and Shvydka, D.}, title = {Evaluation of a Novel Thermobrachytherapy Seed for Concurrent Administration of Brachytherapy and Magnetically Mediated Hyperthermia in Treatment of Solid Tumors}, journal = {Journal of Biomedical Physics and Engineering}, volume = {1}, number = {1}, pages = {-}, year = {2011}, publisher = {Shiraz University of Medical Sciences}, issn = {2251-7200}, eissn = {2251-7200}, doi = {}, abstract = {Concurrent hyperthermia and radiation therapy in treatment of cancer show a strong evidence of a synergistic enhancement. We designed a new self-regulating Thermo-Brachytherapy seed, which serves as a source of both radiation and heat for concurrent administration of brachytherapy and hyperthermia. The Thermo-Brachytherapy seed has a core of ferromagnetic material which produces heat when subjected to alternating electro-magnetic (EM) field and effectively shuts off after reaching the Curie temperature (TC) of the ferromagnetic material thus realizing the temperature self-regulation. For the thermal characteristics, we considered a model consisting of one seed as well as an array of 16 seeds placed in the central region of a cylindrical water phantom. Isodose distributions of these models were computed using MCNP5 Monte Carlo simulation technique. The modeling for the isothermal distribution computations performed using a finite-element partial differential equation solver package COMSOL Multiphysics. It is shown that by changing frequency and intensity of the alternating applied magnetic field, we can obtain desired isothermal distribution within the target volume. Adjustment of these two parameters allows one to match the desired isosurface dose distribution with an optimized isothermal distribution achieving optimal treatment in both modalities. We also demonstrate that the effect of tissue cooling down due to the blood perfusion could be compensated by adjusting the externally applied magnetic field parameters. In this paper, parameters effecting radiation and thermal distribution on this proposed new seed will be presented.}, keywords = {Hyperthermia,Brachytherapy,Ferromagnetic Induction Heating,Blood Perfusion}, url = {https://jbpe.sums.ac.ir/article_43019.html}, eprint = {https://jbpe.sums.ac.ir/article_43019_46a2c139f805b3e0e9142b49ed8f4621.pdf} } @article { author = {Aghamiri, M. R. and Mortazavi, S. M. J. and Tayebi, M. and Mosleh-Shirazi, M. A. and Baharvand, H. and Tavakkoli-Golpayegani, A. and Zeinali-Rafsanjani, B.}, title = {A Novel Design for Production of Efficient Flexible Lead-Free Shields against X-ray Photons in Diagnostic Energy Range}, journal = {Journal of Biomedical Physics and Engineering}, volume = {1}, number = {1}, pages = {-}, year = {2011}, publisher = {Shiraz University of Medical Sciences}, issn = {2251-7200}, eissn = {2251-7200}, doi = {}, abstract = {Background: Lead-based radiation shields are widely used in radiology departments to protect both workers and patients from any unnecessary exposure to ionizing radiation. Recently there has been a great deal of concern expressed about the toxicity of lead. Human lead toxicity is well documented. In that light, production of environmentally-friendly lead-free radiation shields with less weight compared to conventional lead-based shields is a challenging issue. The aim of this study was to design lead free flexible radiation shields for protection against X and gamma rays.Methods: In this investigation, a wide variety of metallic compounds which potentially could be appropriate radiation shields, were studied. The Monte Carlo code, MCNP4C, was used to model the attenuation of X-ray photons in shields with different designs. Besides simulation, experimental measurements were carried out to assess the attenuation properties of each shielding design. On the other hand, major mechanical properties of this shield such as tensile strength, modulus and elongation at break were investigated.Results: Among different metals, tungsten and tin were the two most appropriate candidates for making radiation shields in diagnostic photon energy range. A combination of tungsten (45%) and tin (55%) provided the best protection in both simulation and experiments. In the next stage, attempts were made to produce appropriate Tungsten-tin-filled polymers which could be used for production of shielding garments. The density of this tungsten-tin-filled polymer was 4.4 g/cm3. The MCNP simulation and experimental measurements for HVL values of this shield at 100 kVp were 0.26 and 0.24 mm, respectively. On the other hand, this novel shield provides considerable mechanical properties and is highly resistant to chemicals.Conclusions: The cost-effective lead-free flexible radiation shield produced in this study offers effective radiation protection in a diagnostic energy range. This environmentally-friendly shield may replace the traditional lead-based shielding garments.}, keywords = {Radiation protection,Lead-free Shields,Non-Lead Shielding Garments,Tungsten,Tin,X-rays,Diagnostic Energy}, url = {https://jbpe.sums.ac.ir/article_43020.html}, eprint = {https://jbpe.sums.ac.ir/article_43020_55587eb85118804b14ce230cde5c19c0.pdf} } @article { author = {Chatterjee, S. and Vyas, A. and Ravanfar Haghighi, R. and Kumar, P.}, title = {The Energy Dependence of the Photoelectric Attenuation Coefficient of Substances}, journal = {Journal of Biomedical Physics and Engineering}, volume = {1}, number = {1}, pages = {-}, year = {2011}, publisher = {Shiraz University of Medical Sciences}, issn = {2251-7200}, eissn = {2251-7200}, doi = {}, abstract = {Introduction: The photoelectric attenuation coefficient of substances is known to depend upon the energy E of the photon and the effective atomic number of substances (Zeff) as (Zeffx/Ey).  No definitive values about these indices x, y are given in the literature. The index x is said to lie between, 3.0 and 4.0, while for ‘y’ different values have been assigned, between 3.0 and 4.0. Methodology: We followed a methodology to find both the exponent y explicitly, from a formula which does not contain x. Through this way, the risk of one parameter leading to an estimation error for the other is automatically eliminated. With the value of y being unmistakably established, we determined the exponent x for different elements. Results: It was found from the NIST data that ‘y’ = 3.0669 for most substances with low atomic number but no single value can be assigned for the exponent ‘x’.Conclusions: These results help us to perform model calculations for the attenuation coefficients of different substances. They can also provide important inputs for the diagnostic purposes in the DECT method.}, keywords = {X-ray,Photoelectric effect,Attenuation coefficient,Photon energy}, url = {https://jbpe.sums.ac.ir/article_43021.html}, eprint = {https://jbpe.sums.ac.ir/article_43021_04a2466ea0c66f8b3813e4b2301bc3da.pdf} } @article { author = {Bouzarjomehri, F. and Tsapaki, V.}, title = {Active Personal Dosimeter in a Nuclear Medicine Center in Yazd City, Iran}, journal = {Journal of Biomedical Physics and Engineering}, volume = {1}, number = {1}, pages = {-}, year = {2011}, publisher = {Shiraz University of Medical Sciences}, issn = {2251-7200}, eissn = {2251-7200}, doi = {}, abstract = {Introduction: Active personal dosimeters (APDs) are well accepted as useful and reliable instruments for individual dosimetry measurements. APDs have many advantages compared with passive dosimeters for individual external radiation dose assessments. In routine monitoring, occupational exposure is carried out for verification and demonstration of compliance with the regulatory dose limits. So, it is one of the most important tools in order to achieve or demonstrate the level of radiation protection.Methods: Yazd province has only one private nuclear medicine (NM) center. In this center, two NM technologists exposed to radioactive patients during radiopharmacuticals preparation were monitored. NM technologists have to be close to the patient during radiopharmaceutical injection and patient positioning on the gamma camera table. An electronic personal dosimeter DKG-21 Ecotest made in Ukraine which records the ambient dose equivalent rate and equivalent dose was used to monitor the radiation exposure to the technologists and to record the accumulation dose in mSv throughout a working day. This study was accomplished between the time period of January to June 2011. The dosimeter is designed to measure individual equivalent dose Hp(10). The dose range of gamma radiation was 0.01 mSv to 1 Sv and the energy range 0.05 to 6 MeV which was suitable for NM procedures. The planar and tomography NM images were performed by the 2 technologists in the morning and afternoon shifts.Results: The average monthly occupational dose of each technologist was approximately 0.6 mSv. Their annual doses were 6.6 and 8.8 mSv, respectively. They were lower than the maximum permissible dose of 20 mSv/y. Total number of NM procedures performed in this NM center during June 2010 to June 2011 was 3265.Conclusion: The use of APD for monitoring the NM technologists is a useful tool to check compliance with regulatory dose limits and radiation protection principals.}, keywords = {Active personal dosimeter,Occupational dose,Nuclear medicine,Yazd,Radiation protection}, url = {https://jbpe.sums.ac.ir/article_43022.html}, eprint = {https://jbpe.sums.ac.ir/article_43022_51ab54372d61c004b0c8f993793354d4.pdf} }