International Journal of Radiation Research
Year:2006 | Volume:4 | Issue:2|Papers Count:8

Intracranial tumors often require radiotherapeutic approaches that differ from other sites. Their specific requirements merit a specialized discussion. A brief review of radiotherapy techniques to treat intracranial tumors is presented with emphasis on the author's own experience and work, where appropriate. A clinical introduction is presented first followed by a description of both conventional and modern techniques. Examples from clinical practice are also given. The issues discussed include direct simulation, 2D and 3D treatment planning, the use of CT and other imaging modalities, field shaping and noncoplanar techniques. While new technological advances have paved the way for many potential clinical benefits, in the modern radiotherapy era, simple conventional techniques still have a role to play in routine clinical practice. As new technologies are introduced into relatively under-resourced centres, they should be used judiciously and appropriately to maximize benefit to the whole patient population.

Background: The radiological impact of the use of phosphate fertilizers in soil is due to the internal irradiation of the lung by the alpha particles, short lived radon-thoron progeny and the external irradiation of the body by gamma rays emitted from radionuclides in situ. This paper describes the results of gamma spectrometric measurements of the concentration of the natural radionuclides namely 226Ra, 232Th and 40K in the soil samples collected from the fields where a variety of phosphate fertilizers are being used by the farmers to enhance the crop yield. Materials and Methods: The experimental work utilizes actual measurements of 226Ra, 232Th and 40K using gamma spectrometry and radon concentration and exhalation rates measurements using solid state nuclear track (LR-115, Type-II plastic) detectors to asses a first order exposure risk for the persons working in the fields where lot of fertilizers are being used to enhance crop yield in terms of occupational exposure. Results: The concentration of Radium, Thorium and Potassium in the mixed soil sample from crop fields is 16.2 ± 0.22, 68.1±1.44 and 875.0±9.68 Bq/kg, where as in barren soil sample is 9.1±0.13, 59.4±1.45 and 668.4±8.01 Bq/kg respectively. The radium equivalent activity (Raeq) in the mixed soil sample from crop fields is 225.9 Bq/kg, where as in barren soil sample is 193.1 Bq/kg. The values of absorbed dose and annual effective dose (indoors and outdoors) are found to vary from 90.87 nGyh-1 to 119.71 nGyh-1, 0.45 mSv/y to 0.59 mSv/y and 0.11 mSv/y to 0.15 mSv/y respectively in soil sample from crop fields, whereas the value of absorbed dose and annual effective dose (indoors and outdoors) is 92.29 nGyh-1, 0.45 mSv/y, 0.11 respectively in soil sample collected from barren land. The radon concentration and exhalation rates have also been reported. Conclusion: The activity concentration, exhalation rate and absorbed dose were found to increase substantially with the use of phosphate fertilizers and it varies from sample to sample. The radium equivalent activities in all the soil samples were found to be lower than the limit (370 Bq/kg) set in the Organization for Economic Cooperation and Development (OECD) report and the dose equivalent is within the safe limit of 1 mSv/y.

Background: Recently, the use of medium and high energy X-rays has increased in Iran, and radiotherapy centers along with a variety of accelerators have been installed in some provinces. Hence, there is not sufficient skill in designing and installing radiotherapy treatment rooms. This study was conducted to evaluate the efficacy of different mixtures of barite concrete for shielding the radiotherapy rooms. This way, we have emphasized on determining the size and amount of barite aggregations to achieve the maximum radiation attenuation which leads to minimizing wall thickness in treatment room. Materials and Methods: To increase concrete density, the barite aggregation was added to concrete. Different size variations of barite aggregates mixed with different water/cement ratio were examined. The dimension of cubic concrete specimens for compression strength test was 15×15×15 cm. The rectangular barite concrete blocks with different compressions as used for strength test with cross section of 10×10 cm, and thicknesses from 5 to 40 cm were used for radiation attenuation test. To do so, concrete specimens were irradiated by gamma beam of 60Co (Phoenix Theratron). The transmission radiation through the blocks was measured by a Farmer ionization chamber (FC65P). Results: Our findings showed that in all specimens the highest mean compression strength was related to the specimens with equal ratio of fine to coarse barite aggregates, but the lowest HVL was obtained from mixtures with fine to coarse ratio of 35/65. The concrete sample with a 0.45 water/cement ratio, 350 kg/m3 cement and equal amounts of fine and coarse barite sands had nearly minimum half value layer (HVL), and maximum compression strength, so the sample was considered as the best barite concrete sample. Conclusion: Since HVL of the barite concrete specimens with the same compression strength is markedly lower than the conventional concrete, and that there are quite a number of barite mines in our country, it is recommended to use barite concrete with the most suitable mixture condition based on our findings for shielding the radiotherapy rooms.

Background: In nuclear medicine, phantoms are mainly used to evaluate the overall performance of the imaging systems, and practically there is no phantom exclusively designed for the evaluation of the software performance. In this study the Hoffman brain phantom was used for quantitative evaluation of reconstruction techniques. The phantom is modified to acquire tomographic and planar image of the same structure. The planar image may be used as the reference image to evaluate the quality of reconstructed slices, using the companion software developed in MATLAB. Materials and Methods: The designed phantom was composed of 4 independent 2D slices that could have been placed juxtapose to the 3D phantom. Each slice was composed of objects of different size and shape (for example: circle, triangle, and rectangle). Each 2D slice was imaged at distances ranging from 0 to 15 cm from the collimator surface. The phantom in 3D configuration was imaged acquiring 128 views of 128×128 matrix size. Reconstruction was performed using different filtering condition and the reconstructed images were compared to the corresponding planar images. The modulation transfer function, scatter fraction and attenuation map were calculated for each reconstructed image. Results: Since all the parameters of the acquisition were identical for the 2D and the 3D imaging, it was assumed that the difference in the quality of the images has exclusively been due to the reconstruction condition. The planar images were assumed to be the most perfect images which could be obtained with the system. The comparison of the reconstructed slices with the corresponding planar images yielded the optimum reconstruction condition. The results clearly showed that Wiener filter yields superior quality image among the entire tested filters. The extent of the improvement has been quantified in terms of universal image quality index. Conclusion: The phantom and the accompanying software were evaluated and found to be quite useful in determining the optimum filtering condition and mathematical evaluation of the scatter and attenuation in tomographic images.

Background: The radiographic image accuracy depends on the X-ray film information visibility. Good visibility is found by good contrast. Radiation exposure parameters (kVp, mAs) and film processing conditions have impact on contrast. In dentistry radiography machines, exposure time and processing procedure are set by radiographer. No optimized exposure time and processing conditions may lead to incorrect diagnosis and re-exposure of the patient. Therefore, we studied the performance of the three different available processing solutions with dental X-ray film. Materials and Methods: Dental intraoral E-speed films, size 2 (Kodak company, USA) were used in this study. These films were developed in a manual processor using three different brands of processing solution: 1) Taifsaz (Iran), 2) Darutasvir (Iran) and 3) Agfa (Germany) for temperatures of 25°C, 28°C and 30°C at the three different exposure times, 0.2 s, 0.25 s and 0.35 s. Performance was evaluated with respect to base plus fog, relative contrast and relative speed. Results: Darutasvir processing solution as the cheapest one showed higher base plus fog density at 25°C and 30°C than that of Taifsaz and Agfa solutions. Also, Darutasvir solution was found to have better relative contrast than that of the others, except for 30°C at 0.25 s. Relative speed was higher in Darutsavir solution than Agfa for 25°C at three exposure times used in this study, for 28°C at 0.2 s and for 30°C at 0.35 s. Taifsaz Processing solution was in the second order with respect to tested conditions. Conclusion: Comparison among available X-ray film processing solutions for different temperatures at different exposure times can help to maintain image quality while patient exposure and film cost are kept considerably low. 

Background: In recent years, the endovenous laser therapy (EVLT) has been proposed to treat the incompetent greater saphenous veins (GSV) to increase patient comfort, and to reduce cost as well as risk. EVLT causes vein wall thickening, luminal contraction and vein fibrosis. The purpose of this article, as the first report from Iran, is to review our experience and outline the early results and complication of EVLT. Materials and Methods: 22 patients (13 females and 9 males, mean age: 40.6±11 years, range: 25-64) underwent EVLT of incompetent GSV segments with 810-nm diode laser with an average energy of 89.2 J/cm (range, 50-123 J/cm). Success rate was defined as absence of reflux throughout the entire treated segment on follow-up doppler ultrasound (DUS) and clinical resolution of symptoms. Results: Short-term results in the EVLT of 22 GSV indicate a 100% rate of closure. Self-limiting complication were occurred in 18% of patients and included moderate ecchymosis and parenthesis in 3 (13.5%), and 1 (4.5%) patients, respectively. No major complications such as deep vein thrombosis and pulmonary embolism were occurred. DUS demonstrated 21 (95%) and 19 (90.9%) occluded GSVs at 12 weeks, and 24 weeks respectively. Conclusion: The early results of our experiences are excellent. EVLT of the incompetent GSV with an 810 nm diode laser appears to be an extremely safe technique. EVLT is a very effective and safe with best cosmetic results and rare side effects.

Background: Invasion by different kinds of ballast water microorganisms is one of the most important marine environment problems around the world; therefore preventing the invasion of these unwanted and harmful stowaways is one of the main strategies of responsible agencies. Some of these methods such as ocean exchange, heating, filtration, hydro cyclones, UV irradiation and chemical treatment, have various problems such as technical deficiency, high costs, lack of safety and environmental side effects. Materials and Methods: A novel system of treatment by Gamma irradiation is designed to irradiate the blast water uniformly and effectively. To determine the dose distribution as a function of distance from the irradiation source, the MNCP code was used. The systems used for source implant in this simulation were Paterson-Parker, Paris and Network systems. In each system, Sivert-integral and inverse square law were used in MATLAB program to determine the dose distribution. Results: Results of initial laboratory tests on offshore water samples of Siri Island indicated that the appropriate dose for deactivation of organisms of water samples is approximately one kGy. It has been demonstrated that the dose can be provided by twenty five 100,000 Ci line sources of 60Co in a triangle implant arranged in a 1x1 x1 m3 cubic shape water pipe. In order to increase efficiency and radiation safety, water passed from two other coaxial and bigger cubes, after passing from the first cube. A one meter thick wall of concrete around the cubes was adequate to shield the system completely. Conclusion: The main advantages of this system such as high efficiency, safety, reliability, minimum environmental adverse effects, prove that this novel method not only can be used for ballast water treatment, but is also effective for drinking water purification.

Background: Measures to protect the public following an accidental release of radionuclides to the environment will depend on the circumstances including the extent of the potential hazards. The projected levels of risk are an important precondition in emergency planning. The levels can be expressed in terms of concentration levels in the environment or in foodstuffs. These derived intervention levels (DILs) can be determined for the range of important radionuclides that could be released to the environment in the event of a nuclear accident. Materials and Methods: Derived intervention levels for 90Sr, 131I, 134Cs + 137Cs, 238Pu + 239Pu + 241Am and 103Ru + 106Ru radionuclide groups were calculated for infants (<1 year) and adults (>17 years) for mostly consumed foodstuffs in Iran. Calculations of DILs were based on recommendations from international, national organizations and average food consumption rate data for Iran. Results: From our research it was found that DILs for foodstuffs consumed in Iran for above mentioned radionuclide groups except for Ruthenium group are equal to 387, 250, 1023 and 2.8 Bqkg-1 respectively. Conclusion: The comparison of DILs for foodstuffs consumed in Iran and DILs adopted in the new food and drug administration (FDA) Compliance Policy Guide (CPG) which are 160, 170, 1200, 2 Bq.kg-1 for 90Sr, 131I, 134/137Cs, 238/239Pu plus 241Am radionuclide groups respectively, shows agreement with cesium and plutonium group and higher values for strontium and Iodine group. In the case of nuclear accident or radiological events that might affect our country calculated DILs can be used to prevent or reduce exposure due to consumption of foodstuffs.