فهرست مطالب

Iranian Journal of Medical Physics
Volume:9 Issue: 2, Spring 2012

  • تاریخ انتشار: 1391/02/17
  • تعداد عناوین: 8
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  • Banafsheh Zeinali Rafsanjani, Mohammad Amin Mosleh Shirazi, Reza Faghihi, Ahmad Mosalaei, Shapoor Omidvari, Kamal Hadad, Sareh Karbasi Page 75
    Breast cancer is the most common cancer in women after skin cancer. In Iran, the presentation age of this cancer is younger than the global average. There are different therapeutic methods for treatment of breast cancer and the choice of treatment depends on the stage of the disease as well as its type and characteristics. Therapeutic methods include surgery, radiotherapy, and systemic therapies, each consisting of a variety of techniques. The two main surgical techniques are lumpectomy and mastectomy. The main systemic methods are biological therapy (immunotherapy), hormone therapy, and chemotherapy. Radiotherapy is mainly categorized into external-beam radiotherapy and brachytherapy. In this paper, we present a brief review of the different types of breast cancer and their treatments using conventional and modern radiotherapy methods, as well as the treatment efficacy and side effects of breast radiotherapy.
    Keywords: Breast Cancer, Radiotherapy, Review
  • Tayyeb Allahverdi Pourfallah, Hamed Babapour, Maryam Shahidi Page 87
    Introduction
    The exposure of human beings to ionizing radiation from natural sources is a continuing and inescapable feature of life on earth. For most individuals, this exposure exceeds that from all man-made sources combined.
    Materials And Methods
    In this study, the annual effective dose in high level environmental background radiation areas (HLEBRAs) of northern city of Ramsar in Iran was determined. For dosimetry, a gamma radiation dosimeter was used. Measurements were performed in more than 90 points in five districts with HLEBR around and near hot springs.
    Results
    In some areas, the annual effective dose from outdoor external gamma radiation in HLEBRAs (30 mSv/y) exceeded the annual effective dose limit for radiation workers. Our results are evident that the population dose from normal background radiation in HLEBRAs is 200 times higher than corresponding values in Ramsar sea shore. To estimate the cosmic ray contribution, dose measurements were performed on the sea surface one km off the sea shore.
    Conclusion
    The observed differences over locations and measured doses between this study and the others revealed the dynamic nature of this phenomenon, and necessitate performing the periodic studies in these areas. Moreover, cytogenetic and immunologic researches for studying the long term effects of these high level environmental radiations on the residents of these HLEBRAs are necessary.
    Keywords: Annual Effective Dose, External Environmental Radiation, Gamma Radiation, High Background Radiation, Ramsar
  • Shila Banari Bahnamiri, Reza Izadi Najafabadi, Seyed Hashem Miri Hakimabad Page 93
    Introduction
    The potential hazards posed by exposure to radiation from radon have been of great concern worldwide, since it is especially associated with increased risk of lung cancer. Some radioisotopes of radon progeny deposited in the human lungs emit β particles followed by the γ rays. While γ rays are comparatively less damaging to the respiratory system than α and β particles, it is the principal deposited energy in other organs.
    Materials And Methods
    In order to establish a quantitative estimate of hazards caused by the radiation, this paper studies the photon absorbed doses from radon progeny in all major organs of the human body through a simulation of the Oak Ridge National Laboratory (ORNL) adult phantom using MCNPX2.4.0 Monte Carlo code and calculations which were performed in photon/electron mode.
    Results
    Effective dose due to photons from radon progeny deposited in the human lungs was about 1.69 μSvWLM-1. Based on UNSCEAR2006 reports, the effective dose of these photons per year is about 5.7610-1mSv in for radon concentration of 31000 Bq/m3 (the maximum concentration of radon in Iran). Therefore, this value is comparable with 1mSv (The annual allowable effective dose).
    Conclusion
    The dosimetry of photons particularly in areas with high levels of exposure to radon and radon's decay products is important because all organs receive the photon absorbed dose from radon progeny.
    Keywords: Dosimetry, Lung Cancer, ORNL Phantom, Radon Progeny, MCNPX
  • Akram Fazli, Mojtaba Salouti, Gholamreza Ahmadi, Fatemeh Mirshojaei, Mohammad Mazidi, Zahra Heydari Page 103
    Introduction
    Bacterial infection is one of the major causes of morbidity and mortality especially in developing countries. Nuclear medicine has an important role in helping the diagnosis of deep-seated infections by developing more specific radiopharmaceuticals. The aim of this study was to evaluate 99mTc-labeling ceftriaxone as a new radiopharmaceutical for Staphylococcus aureus infection imaging in nuclear medicine.
    Materials And Methods
    Radiolabeling of ceftriaxone was carried out by adding 370 MBq of 99mTc to 10 mg of ceftriaxone in the presence of 50 μg of SnCl2.2H2O at pH=5. The radiochemical purity and stability tests at room temperature and human blood serum were evaluated with ITLC. Intramuscular infection was induced by injection of Staphylococcus aureus into the left thigh muscle of the mice. The biodistribution of 99mTc-ceftriaxone was studied in normal and infected mice at various times post-injection.
    Results
    Radiochemical purity of the product was 94.5±5.4% with a good stability at room temperature and human serum, 80.6% and 71.2% after 24 h, respectively. The biodistribution studies showed the localization of 99mTc-ceftriaxone at the site of infection with high sensitivity without any significant accumulation in vital organs.
    Conclusion
    Due to the ease of 99mTc-ceftriaxone conjugation method, high labeling efficiency, and high uptake in the infected muscle, it may provide a promising candidate as a targeting radiopharmaceutical for imaging infectious foci due to Staphylococcus aureus in nuclear medicine.
    Keywords: Ceftriaxone, Infection, Radiopharmaceutical, Staphylococcus Aureus, Targeting, 99mTcradiolabeling
  • Keyvan Jabbari, Alireza Amouheidari, Shadi Babazadeh Page 111
    Introduction
    Intensity Modulated Radiation Therapy (IMRT) has made a significant progress in radiation therapy centers in recent years. In this method, each radiation beam is divided into many subfields that create a field with a modulated intensity. Considering the complexity of this method, the quality control for IMRT is a topic of interest for researchers. This article is about the various steps of planning and quality control of Siemens linear accelerators for IMRT, using film dosimetry. This article in addition to review of the techniques, discusses the details of experiments and possible sources of errors which are not mentioned in the protocols and other references.
    Materials And Methods
    This project was carried out in Isfahan Milad hospital which has two Siemens ONCOR linear accelerators.Both accelerators are equipped with Multi-Leaf Collimators (MLC) which enables us to perform IMRT delivery in the step-and-shoot method. The quality control consists of various experiments related to the sections of radiation therapy. In these experiments, the accuracy of some components such as treatment planning system, imaging device (CT), MLC, control system of accelerator, and stability of the output are evaluated. The dose verification is performed using film dosimetry method. The films were KODAK-EDR2, which were calibrated before the experiments. One of the important steps is the comparison of the calculated dose with planning system and the measured dose in experiments.
    Results
    The results of the experiments in various steps have been acceptable according to the standard protocols. The calibration of MLC and evaluation of the leakage through the leaves of MLC was performed by using the film dosimetry and visual check. In comparison with calculated and measured dose, more that 80% of the points have to be in agreement within 3% of the value. In our experiments, between 85 and 90% of the points had such an agreement with IMRT delivery.
    Conclusion
    The EDR2 films are suitable for quality control of IMRT. According to complexity of the quality control for IMRT, the physicists of each center have to develop specific guidelines according to their equipments and limitations. An accurate treatment planning system with capability of inverse planning is an essential need for IMRT. The result of the planning system has to be compared with experiments in various situations.
    Keywords: Film Dosimetry, Intensity Modulated Radiation Therapy, Quality Control
  • Atousa Montaseri, Mohammadreza Alinaghizadeh, Seied Rabi Mahdavi Page 127
    Introduction
    Bolus is a soft and resilient material which is used for increasing skin dose or to even out the irregular patient contour. The main property of various materials used presently as bolus is the water-equivalent electron density. Ethyl methacrylate is used as a soft-liner in dentistry and its physical and chemical properties are proved to be nontoxic for human body. The goal of this study was to assess the feasibility of using this material as bolus in radiotherapy and also evaluating some parameters such as mass, electron densities, and transmission factors.
    Materials And Methods
    Computed tomography data from the sample material were acquired to assess mass and electron densities with various techniques (mA and kVp). Circular ROIs were delineated on CT DICOM images and densities were calculated using CT numbers. Transmission factors were calculated for 6 and 18 MV.
    Results
    Evaluation of our results are evident that showed that mass and electron densities of ethyl methacrylate are similar to those of water and soft tissue. Furthermore, transmission factors are close to those of water.
    Conclusion
    According to the results of this study and other properties such as flexibility and harmlessness, it seems that ethyl methacrylate is a suitable material to be used as bolus in radiotherapy.
    Keywords: Bolus, CT scan, Ethyl Methacrylate, Radiotherapy
  • Jalil Pirayesh Islamian, Mohammad Taghi Bahreyni Toossi, Mehdi Momennezhad, Shahrokh Naseri, M. Ljungberg Page 135
    Introduction
    Quality control is an important phenomenon in nuclear medicine imaging. A Jaszczak SPECT Phantom provides consistent performance information for any SPECT or PET system. This article describes the simulation of a Jaszczak phantom and creating an executable phantom file for comparing assessment of SPECT cameras using SIMIND Monte Carlo simulation program which is well-established for SPECT.
    Materials And Methods
    The simulation was based on a Deluxe model of Jaszczak Phantom with defined geometry. Quality control tests were provided together with initial imaging example and suggested use for the assessment of parameters such as spatial resolution, limits of lesion detection, and contrast comparing with a Siemens E.Cam SPECT system.
    Results
    The phantom simulation was verified by matching tomographic spatial resolution, image contrast, and also uniformity compared with the experiment SPECT of the phantom from filtered backprojection reconstructed images of the spheres and rods. The calculated contrasts of the rods were 0.774, 0.627, 0.575, 0.372, 0.191, and 0.132 for an experiment with the rods diameters of 31.8, 25.4, 19.1, 15.9, 12.7, and 9.5 mm, respectively. The calculated contrasts of simulated rods were 0.661, 0.527, 0.487, 0.400, 0.23, and 0.2 for cold rods and also 0.92, 0.91, 0.88, 0.81, 0.76, and 0.56 for hot rods. Reconstructed spatial tomographic resolution of both experiment and simulated SPECTs of the phantom obtained about 9.5 mm. An executable phantom file and an input phantom file were created for the SIMIND Monte Carlo program.
    Conclusion
    This phantom may be used for simulated SPECT systems and would be ideal for verification of the simulated systems with real ones by comparing the results of quality control and image evaluation. It is also envisaged that this phantom could be used with a range of radionuclide doses in simulation situations such as cold, hot, and background uptakes for the assessment of detection characteristics when a new similar clinical SPECT procedure is being simulated.
    Keywords: Jaszczak Phantom, Quality Control, SIMIND Monte Carlo, SPECT
  • Seyed Ali Shafiei, Seyed Mohammad Firoozabadi, Kazem Rasoulzadeh Tabatabaie, Mojdeh Ghabaee Page 141
    Introduction
    Increase in alpha band is observed when blood perfusion in frontal area of head decreases. The present study evaluated some changes in the alpha band particularly, alpha-1 of frontal and central areas of the head, when several areas were exposed simultaneously to magnetic field.
    Materials And Methods
    Five points of head (F3, F4, Cz, T3, and T4) of twenty healthy male participants were exposed to magnetic fields simultaneously by five separate coils at different frequencies of 45, 17, 10, 5, and 3 Hz, in five separate sessions. The magnetic field intensity was 100 μT at 1.5 cm distance from the coil. At the end, relative powers over these areas in common frequency and alpha-1 bands were evaluated by paired t-test.
    Results
    Significant reduction (p<0.05) in alpha-1 band was observed by exposure of local ELF magnetic field at frequencies of higher than 5 Hz in closed-eye. These reductive effects were enormous at 5 and 45 Hz frequency.
    Conclusion
    Observed reduction in alpha-1 band may be due to the influence of magnetic field exposure on production centers of alpha band, particularly the thalamus. Hence, increased blood perfusion in some areas is probably the cause of this reduction which requires more research.
    Keywords: Alpha Band, Brain Signal, EEG, Magnetic Field