Showing papers in "Iranian Journal of Radiation Research in 2008"

Radon level in dwellings basement of Yazd-Iran

Abstract: *Corresponding author: Dr. Fathollah Bouzarjomehri, Department of Medical Physics and Environment Health, Shahid Sadoghi University of Medical Sciences, Yazd, Iran Fax: +98 351 7244078 E-mail: Bouzarj_44@ssu.ac.ir Background: Indoor radon gas (222Rn) has been recognized as one of the health hazards for human. Air radon comes mainly from basement soil and construction materials. Saghand region with rich uranium mines lies 180 km from Yazd, so the indoor radon concentration can be high. Yazd, with population of about 457000, is the biggest city near Saghand, thus, indoor gamma background radiation of Yazd could be more than the other cities of Yazd province. Materials and Methods: In this study the air radon level of 84 dwellings basement from various regions of Yazd were measured during the year 2007. To do so, a portable radon gas surveyor was used which is an active measurement method. Using this device, α radiation of each basement was measured by a solid state detector for 24 hours. Results: Radon concentrations of the basements were between 5.55 to 747.4 Bq/m3 with mean of 137.36 Bq/m3. The mean radon concentration wasn't significantly different from the EPA guide line that is mitigation recommendations level (148 Bq/m3). However, more than 30% of the basements had radon concentration more than EPA guide line. Conclusion: Using good air conditioning system in the dwelling basements is suggested. Iran. J. Radiat. Res., 2008; 6 (3): 141­144

Migration of radionuclide in soil and plants in the Western Ghats environment

Abstract: U, 210 Po, 232 Th and 40 K within the soil to the wild plants in the Western Ghats were carried out. Materials and Methods: Concentrations of these radionuclides were measured in different depths of soil and from different species by employing gamma ray spectrometer and alpha counter. Results: The activity concentration of these radionuclides varied faintly within the soil but widely varied within the plant and between the species. Conclusion: The CR (Concentration ratio) showed wide variation in different species, while a few species of wild plants such as Evodia roxburghiana, Eleaocarpus oblangus and Glochidion neilgherense indicated preferential uptake of these radionuclides. Iran. J. Radiat. Res., 2008; 6 (1): 7-12

Radial dose functions of GZP6 intracavitary brachytherapy 60Co sources: treatment planning system versus Monte Carlo calculations

Abstract: The aim of brachytherapy is the placement of radioactive sources near the tumor volume in order to maximize the dose delivered to the tumor and minimize the dose delivered to the surrounding normal tissues. Several factors affect the purpose including the rapid dose fall-off near the sources, difficulties in localizing the tumor and normal organs, and inconsistencies in the methods employed for dose calculation. Nowadays, high dose rate Co and Ir sources of various designs are currently used in brachytherapy (1, 2). Dose calculation accuracy plays a vital role in the outcome of brachytherpay treatment due to steep dose gradient around the source which makes it susceptible for dosimetric errors, and over or under-dosage of target volume consequently. The Sievert integral is applied as a dose calculation algorithm in many commercially available treatment planning systems (3, 4). Although, algorithms implementation and simplifications may vary among different manufacturers, quality assurance of treatment planning system prior to clinical use is one of the tasks of medical physicists. The establishment of a quality assurance protocol to guarantee the desired treatment accuracy is mandatory at present, and it is an important task to verify the accuracy in the dose calculation of the treatment planning programs. The methods implemented to test these programs often make use of standard data sets and phantoms and compare the programs results with the values expected for those standards. Several calculation methods, especially Monte Carlo (MC) method have been employed to assess the absorbed dose near brachytherapy sources (5-7). In contrast to measurements, the Monte Carlo dose estimates are not affected by errors in detector positioning, detector energy, angular dependence, and steep dose gradients near the sources. In current study, the Co sources of a new high dose rate after loading system were simulated using MCNP4C MC Code. One of the important dosimetric properties of sources, radial dose function was calculated using MC method to compare the results of dedicated TPS of the brachytherapy system.

An evaluation of the equivalent dose due to natural radioactivity in the soil around the consolidated tin mine in baukuru-jos, plateau state of nigeria

Abstract: Background: The equivalent dose in the human body due to the natural gamma-emitting radionucides ( 238 U, 232 Th and 40 K) in the surface soil surrounding the Consolidated Tin mine site in Bukuru-Jos, Nigeria has been determined in this study. Materials and Methods: Measurements of the soil natural radioactivity were made using a multi-channel pulseheight analyzer (Canberra Series 10 plus) coupled to a 76 mm×76 mm Nal (Tl) scintillation detector. Results: The mean concentrations obtained for each of the radionuclides is 35.4±17.6 Bq/kg for 40 K; 776.0± 158.0 Bq/kg for 238 U and 2.72±0.58 kBq/kg for 232 Th. The mean absorbed dose rate due to natural radioactivity calculated at a height of 1.0 m above the ground is 2.16 ||which converts to an equivalent dose of 3.0 mSv/y. Conclusion: The results obtained in this study are far above the world average equivalent dose of 0.41 mSv/y but lower than the annual limit of 20 mSv/y for radiation workers but still represents a health risk to workers on the site. Iran. J. Radiat. Res., 2008; 5 (4): 203-206

Indoor radon entry: 30 years later

Abstract: Indoor radon entry (IRE) is a great public health concern. During the last three decades, intensive research has been done to clarify the mechanism of IRE. Numerous papers and scientific reports were devoted to these problems. US Environmental Protection Agency (EPA) and US Department of Energy (DOE) spent millions of dollars on researching the transport of radon into houses. Finally, US EPA declared that the pressure driven radon transport through cracks and openings in a concrete slab is the dominant mechanism of IRE. Since the pressure driven mechanism has been recognized as the dominant mechanism of IRE, US EPA and US DOE ceased sponsoring research on this topic. However, the understanding of the problem has not progressed much beyond the initial stage (1, 2). Numerous misconceptions about radon transport in homes retard progress in creating reliable, passive mitigation methods intended to reduce radon concentrations in homes. Active soil depressurization, as recommended by the EPA USA, is energy consuming, costly, and is not based on understanding of radon transport. Recognition of this fact would stimulate research on indoor radon transport and create effective and reliable radon prevention and mitigation techniques.

Proton beam dosimetry by CR-39 track-etched detector

Abstract: Background: High and intermediate energy protons are not able to form a track in a solid state nuclear track detector (SSNTD) directly. However, such tracks can be formed through secondary particles created during primary radiation nuclear reactions in a SSNTD. Materials and Methods: The protons with primary energies of 9.6 and 30 MeV available at the cyclotron accelerator with corresponding low LETs of 5.87 and 2.40 keV/µm were taken into consideration. The nuclear tracks etch rate ratio V in CR-39 were measured and transformed into LET spectra for the absorbed and equivalent dose measurements. Results: The optimum etching condition of 6 N NaOH solutions at 65 to 70 oC over a 6-hour period for the CR-39 were found initially. The corresponding bulk etching rate reached a steady rate of about 0.62 to 1.3 um/h after nine hours for an optimum etching condition. Although the LET was low, but the energy range seemed sufficient enough to create secondary particles with much higher LET through the nuclear reactions in CR-39. The relative absorbed dose contribution of the created secondary particles to the primary particles for the 9.6 and 30 MeV protons in CR-39 at 1 Gy entrance dose were 7.5 and 29.6%, respectively. Conclusion: The contribution of the secondary particle increased relatively with the proton energy decrease. This phenomenon could modify the characteristics of the energy transfer process due to secondary particles when such particles are used for radiobiological studies and/or for radiotherapy. Iran. J. Radiat. Res., 2008; 6 (3): 113­120

Verification of dose rate and energy dependence of MAGICA polymer gel dosimeter with electron beams

Abstract: Background: The purpose of this study was to evaluate the dependency of MAGICA polymer gel dosimeter response (R2) on different electron energies as well as on different mean dose rate for a standard clinically used linear accelerator. Materials and Methods: The sensitivity of the dosimeter was represented by the slope of calibration curve in the linear region measured for each modality. A calibration curve (in the linear region) based on 12 dosimeters (11 irradiated and one blank) was obtained for 6 MeV electron beam. Dosimeter energy dependence was studied for electron energies of 4,6,12 and 18 MeV. Dose rate dependence was studied in 10 MeV electron beam with the use of dose rates 80,160,240,320,400 and 480 cGymin 1 . Evaluations of dosimeters were performed on Siemens Symphony, Germany, 1.5T Scanner in the head coil. A multiecho sequence with 32 equidistant echoes was used for the evaluation of irradiated polymer gel dosimeters. The parameters of the sequence were as follows: TR 3000ms, TE 20ms, Slice Thickness 4mm and FOV 256mm. Results: Polymer gel dosimeter response R2 was increased with increasing electron energy. No trend in polymergel dosimeter R2 dependence was found on mean dose rate for electron beams. Conclusion: In MAGICA polymer gel, the sensitivity is dependant on electron energy increase, but no dependence was observed on response to dose rate. The presence of antioxidant and oxygen scavengers in the MAGICA polymer gel is believed to cause different results. Iran. J. Radiat. Res., 2008; 6 (1): 31-36

Effect of cimetidine and famotidine on survival of lethally gamma irradiated mice

Abstract: Background: Currently available radioprotectors are poorly tolerated in man and the general use of aminothiols is compromised by their side effects. This study was carried out to test and compare the radioprotective potential of cimetidine and famotidine against lethally gamma irradiated NMRI mice. Materials and Methods: Adult male NMRI mice in groups of 10 were exposed to various doses of gamma rays at a dose rate of 93.3 cGy generated from a Co60 source. Mortality was examined daily for 30 days after irradiation. Various doses of gamma rays were used to calculate LD50/30. Different doses of cimetidine and famotidine were used in combination with 8 Gy gamma rays to find out the optimum protecting concentration of either drug. Finally the optimum protecting concentration of either drug was used in combination with various doses of gamma rays. Each experiment was repeated for three times. Results: Results show that mean LD50/30 for radiation alone was found to be 723.7 cGy. When using different doses of cimetidine in combination with 801 cGy gamma rays, the dose of 15 mg/kg cimetidine produced optimum protection, while optimum dose of famotidine was found to be 10 mg/kg. However, LD50/30 obtained with optimum dose of either cimetidine or famotidine led to a DRF of 1.11 and 1.05 respectively. Conclusion: Cimetidine compared to famotidine was found to be more protective against mortality induced by radiation in mice. This effect of cimetidine might be due to its immunomodulatory role and thus protecting bone marrow and lymphoid tissue injuries following whole body gamma irradiation. Iran. J. Radiat. Res., 2008; 5 (4): 187-194

A comparative study of radioprotection by four Indian medicinal herbs against genotoxicity induced by sub-lethal gamma irradiation in Swiss albino mice

Abstract: The development of radio protective agents has been the subject of intense research in view of their potential utility in a radiation environment like space exploration, radiotherapy units, nuclear power plants reactor accidents like Chernobyl in1986 and even nuclear warfare (1). Up to eighty percent of cancer patients need radiotherapy either for curative or palliative purpose. In order to obtain better tumor control with a higher dose, the normal tissues should be protected and this could be achieved by various techniques as well as radioprotective agents. Thus the role of radioprotective compounds is very important in clinical radiotherapy. Aqueous free radicals are generated by radiation energy in the cells and their reactions with DNA, RNA, and organelle cause cell dysfunction, mortality, mutagenesis or carcinogenesis (2). This process of cell damage is modulated by various factors like presence of oxygen, sulfhydril compounds and level of cellular protective enzymes like superoxide dismutase (SOD), glutathione peroxidise (Gpx) and catalase (3, 4). Evidently, rapidly dividing cells like epithelial and hemopoietic system are prone to early and marked damage to chromosomes as well as other organelle due to higher content of oxygen and water with a higher level of free radical Background: Synthetic radio-protective agents like aminothiols are toxic and FDA approved agent amifostine is no exception. Some Ayurvedic herbs have shown radioprotective potential. This study was carried out to test and compare the radioprotective potential of Curcuma longa (CL) Tinospora cordifolia (TC), Zizyphus mauritiana (ZM) and Ocimum sanctum (OS) against 2Gy gamma irradiation in Swiss albino mice. Materials and Methods: Adult Swiss albino mice from random breed colony were divided in to 6 groups (n=9), sham-control (SCT), radiation control (RACT), and four herb + radiation groups respectively. All except SCT were exposed to whole body 2 Gy of gamma radiation in a teletherapy unit and SCT was sham exposed on day 7 of herb pretreatment (200mg/kg-bw orally by gavage). Chromosomal studies from the bone marrow of femur by routine metaphase preparation after colchicine treatment were done in 3 animals from each group at 24, 72 and 168 hours after exposure. Results: All four herbs showed significant radio-protective effects at 24 hrs. OS, TC and ZM showed nearly similar activity while CL showing the lowest activity. However the effects at 72 and 168 hrs showed highest protection by CL followed by ZM ||“|| TC > OS respectively suggesting that the well studied OS was less effective at 72 and 168 hrs. Conclusion: All the four herbs showed radioprotective potential with different efficacies at different time interval. Iran. J. Radiat. Res., 2008; 6 (1): 1930

The effect of electronic disequilibrium on the received dose by lung in small fields with photon beams: Measurements and Monte Carlo study

Abstract: Background: Prediction of the absorbed dose in irradiated volume plays an important role in the outcome of radiotherapy. Application of small fields for radiotherapy of thorax makes the dose calculation process inaccurate due to the existence of electronic disequilibrium and intrinsic deficiencies in dose calculation algorithms. To study the lung absorbed dose in radiotherapy with small fields, the central axis absorbed dose in heterogeneous thorax phantom was measured by ionization chamber and calculated for small fields by Monte Carlo (MC) method. Materials and Methods: A solid slab phantom consisting of unit and low density materials was used for dose measurements. The 6 and 18 MV photon beams of Elekta SL25 linac were simulated using MCNP4C MC Code. The model was validated by comparing the calculated depth dose and beam profiles with measurements in a water phantom. The MC model was used to calculate the depth doses in unit density and low density materials resembling the soft tissue and lung, respectively. Two small field sizes including 5×5 and 2×2 cm2 were used in this study. Results: The measured depth dose values were in good agreement with MC results and the difference less than 2% was observed. A large dose reduction was seen in lung for field size of 2×2 cm 2 due to the lateral electronic disequilibrium and it reached up to 16.2% and 33.3% for 6 and 18 MV beams, respectively. Dose build up and down at material interfaces was predicted by MC method. Conclusion: Our study showed that the dose reductions with small fields in lung and dose variations at interfaces was very considerable, and inaccurate prediction of absorbed dose in lung using small fields and photon beams may lead to critical consequences for patients. Iran. J. Radiat. Res., 2008; 6 (2): 70­76

Monte Carlo and experimental relative dose determination for an Iridium-192 source in water phantom

Abstract: Ir source is presented for real energy spectrum and monochromatic at 356 keV. Materials and Methods: The dose distribution has been calculated around the 192 Ir located in the center of 30 cm ×30 cm ×30 cm water phantom using MCNP4C code by Monte Carlo method. Relative dose variation has been measured by using Gafchromic Rtqa along X and Y axis, as well. Percentage depth dose (PDD) variation along the different axis parallel and perpendicular the source were calculated. Finally, F (5cm, θ|) dosimetry parameters of TG-43 protocol were determined. Results: The results showed that the Monte Carlo method could calculate dose deposition in high gradient region, near the source, accurately. The isodose curves and dosimetric characteristics obtained for 192

Assessment of bone mineral density with dual energy X-ray absorptiometry in pre- and post-menopausal women

Abstract: *Corresponding author: Nima Rostampour, Medical Physics , Isfahan University of Medical Sciences, Isfahan, Iran. Fax: +98 831 8238710 E-mail: nrostampour@yahoo.com Background: Osteoporosis is a chronic disease that contributes substantially to decrease physical activity and decline in the quality of life. Osteoporosis can be diagnosed easily with the use of dual-energy X-ray absorptiometry (DXA) equipment. The aim of this study was to investigate the magnitude of bone loss on proximal femur and lumbar spine LS in preand post-menopausal women from Isfahan Osteoporosis Diagnosis Center (IODC) since 2005. Materials and Methods: Bone mineral density (BMD) measurements using DXA have been performed at IODC. 185 pre-menopausal and 174 early post-menopausal women were selected randomly. A Norland XR46 system was used for the investigations. The student t-test was done to find the difference between the T-scores of the femoral neck (FN) and lumbar spine (LS) in preand post-menopausal women. Results: Mean BMDs for the FN and LS in pre-menopausal women were 0.859 ± 0.136 and 1.012 ± 0.161 and in post-menopausal women were 0.816 ± 0.119 and 0.919 ± 0.140, respectively. Long-term BMD CVs of 1.0% and 1.2% for the LS and FN were found, respectively. The differences between the FN and LS for preand post-menopausal women were t = 9.02, p < 0.05 and t = -3.50, p < 0.05, respectively. Conclusion: In spite of, the reported lower BMD T-scores for the LS compared with the FN for women, we found that the FN had significantly lower T-score than LS for both preand post-menopausal women. Iran. J. Radiat. Res., 2008; 6 (2): 103­107

Development of [201Tl](III)oxinate complex for in vitro cell labeling

Abstract: Background: The incorporation of thallium-201 into 8-hydroxyquinoline was targeted for cell labeling due to interesting physical properties and wide availability of this nuclide as a single photon emission computed tomography (SPECT) radionuclide. Materials and Methods: Thallium-201 (T1/2=3.04 d) in Tl+ form was converted to Tl3+ cation in presence of O3/6M HCl and di-isopropyl ether, controlled by radiothin layer chromatography (RTLC) /gel electrophoresis methods. The final evaporated activity reacted with ethanolic 8-hydroxy-quinoline (oxine) solution in normal saline to yield [ 201 Tl](III)oxinate at room temperature after 0.5 h, followed by solid phase extraction/purification using C18 Sep-Pak column and partition coefficient determination for water/lipid solubility. In vitro red blood cell (RBC) labeling was also performed. Results: A radiochemical yield of more than 95% was obtained. Radiochemical purity of 92% was obtained using RTLC (>90% using HPLC) with specific activity of about 820 GBq/mmol. The tracer was stable in the final product and in presence of human serum at 37°C up to 6h. The partition coefficient of lopP=5.5 was obtained. The labeled compound was used in RBC labeling. The cell uptake ratio was 0.47 after 240 min. Conclusion: [201Tl](III) oxinate used in this study is a widely available agent for use in RBC labeling studies in biology, medicine and various other research areas. Iran. J. Radiat. Res., 2008; 6 (3): 145­150

Dosimetric evaluation of a treatment planning system using pencil beam convolution algorithm for enhanced dynamic wedges with symmetric and asymmetric fields

Abstract: Background: The dosimetric performance of Eclipse 6.5 three dimensional treatment planning system (3DTPS) is evaluated by comparing the calculated and measured dose in two dimensions following the guide lines of American Association for Physicists in Medicine Task Group 53. Materials and Methods: The calculations were performed by the 3DTPS for symmetric as well as asymmetric fields for standard source to surface distance (SSD) at dmax, 5, 10 and 20cm depths in water phantom using 45° and 60° enhanced dynamic wedges (EDWs) in a field of 15 cm×15 cm size for 6 MV photon beams. Measurements were carried out for 6 MV photon beams produced by a linear accelerator, Clinac EX 2100, equipped with EDWs using 0.125cc volume PTW ionization chamber and PTW UNIDOS electrometer for beam axis and two off axis points. Results: The deviations between the calculated dose (Dcalc) and the measured dose (Dmeas) at toe, centre and heel at different depths for symmetric as well as asymmetric fields for both the wedge angles is less than 2% at all the points and in all geometries. For 45° EDW the deviation was maximum at 20 cm depth and in asymmetric geometry. For 60° EDW the deviation was maximum at 20 cm depth but in symmetric geometry. Conclusion: The results indicate that the accuracy of Eclipse 6.5 (version 7.3.10) three dimensional treatment planning system used with the EDWs in symmetric as well asymmetric fields is adequate in clinical applications under the studied experimental conditions. Iran. J. Radiat. Res., 2008; 5 (4): 169-174

A new approach to contrast enhancement in magica gel dosimeter image with mri technique

Abstract: Background: Sensitivity and resolution are two main parameters that have to be measured in gel dosimetry. However, the resolution in gel is strongly dependant on gel composition. Selection of optimum method in dose response readout and proper values of parameters can result in noise reduction as well as improvement of contrast, and spatial resolution considerably. Materials and Methods: MAGICA polymer gel dosimeters were manufactured and irradiated to different doses using a 60 Co therapy unit. Imaging was performed in a 0.5T MRI with 8 echoes in air and water as a hydrogenous environment. Imaging condition was kept constant, as much as possible, in both imaging modalities. Results: Images obtained from these two procedures were compared quantitatively. R2- dose curves have three different sections, sensitivity obtained in these three sections were 1.039, 1.671, 1.260 Gy-1S-1 and 1.032, 1.729, 1.37 Gy -1 S -1 for water and air respectively. Calibration errors were investigated and graphically were compared in two different methods. Conclusion: Imaging in water medium for doses lower than 17 Gy led to a small reduction in spatial resolution was exchanged to a considerable increase of contrast in R2 map. For doses higher than17 Gy, imaging in water or air was preferred depending on the importance of contrast or spatial resolution. Iran. J. Radiat. Res., 2008; 6 (3): 151­156

Computer simulation techniques to design Xenon- 124 solid target for iodine-123 production

Abstract: I in the form of sodium iodide is used most commonly for the measurement of thyroid uptake and thyroid imaging. In addition, radioiodinated compounds have been widely employed in the detection of cardiological, neurological and oncological diseases (1). Among the various types of nuclear reactions for producing I, the following reactions are favored due to the absence of I and I impurities: I production system via Xe gas target technology has been constructed and installed in Cyclotron and Nuclear Medicine Department of Nuclear Research Centre for Agriculture and Medicine (NRCAM). One of the major problems in this system is the highly expensive cost of the enriched Xe gas. Therefore, saving this gas inside the system is very important. Unfortunately, by accidental rupture of the window foil or bad function of O-rings, the whole Xenon gas will escape from the system immediately. In this paper, by using computer codes, Alice91, SRIM and doing some calculations, it has been tried to demonstrate the latest effort for feasibility study of producing I with the above mentioned reactions, but using Xe solid target instead.

Study of gamma exposure rate in Mysore and Chamaraj Nagar district, Karnataka, India

Abstract: Background: Humans beings are continuously exposed to ionizing radiation from natural sources. The main contributors to natural radiation are high-energy cosmic radiation and radioactive nuclides that originates in the earth’s crust. Exposure to high levels of radiation can cause serious health effects. In this study an attempt has been made to monitor the levels of environmental background radiation (gamma) in temples, historical monuments, schools and colleges, hostels, wedding halls and theaters in Mysore and Chamaraj Nagar districts and assess the possible effects on environment and human health. Materials and Methods: Environmental radiation dosimeter is used to measure the outdoor and indoor radiation absorbed dose levels. The measurements were made 1 m above the ground level. Results: Inside the temples it varies from 122.7 to 231.4 nGy.h–1 with a median of 130.1 nGy.h–1 outside the temples it varies from 141.8 to 340.2 nGy.h–1 with a median of 216.2 nGy.h–1. In different types of buildings in indoor atmosphere it varies from 112.2 to 197.5 nGy.h–1 with a median of 127.0 nGy.h–1 and in outdoor atmosphere it varies from 140.9 to 298.4 nGy.h–1 with a median of 216.2 nGy.h–1. Conclusion: The indoor absorbed dose rate is higher than outdoors in all types of constructions. Indoor and outdoor environment of the temples has higher levels of radiation than the historical monuments and other public and private building in Mysore and Chamaraj Nagar districts. Use of additional granite materials inside or outside the building will enhance the absorbed radiation dose levels. The values observed in the study area are comparable with other values observed in different parts of the world.

Historical review of interstitial prostate brachytherapy

Abstract: In the recent years, interstitial brachytherapy implantation has become the treatment of choice for early stage prostate cancer patients (1, 2, 3). Popularity of this modality is most likely due to the fact that five-and ten-year disease control rates of brachytherapy are equal to those of the surgical and external radiation therapy, whereas, the toxicity and side-effects are perceived to be lower (4,5). It has been estimated that up to 50% of patients with early stage prostate cancer are now treated with ultrasound-guided transperineal interstitial brachytherapy (3-7) with I-125 or Pd-103 radioactive seeds. The principal advantage of this technique is that the seeds can deliver a substantially higher radiation dose to the prostate and less radiation dose to the surrounding tissue compared with external beam irradiation (8, 9). Iodine-125, Pladium-103, and most recently introduced Cs-131 are the most suitable radiation sources for this treatment modality. These sources emit low energy photons and the dose falls quickly with the distance and therefore, seeds deliver low dose to the adjacent rectum and bladder (10-14).

Performance of Sife - Eldeen dosimeter over broad absorbed dose and dose rate ranges of γ – radiation and at different temperatures

Abstract: *Corresponding author: Dr. Kh. A. Sife-Eldeen, National Center for Radiation Research and Technology, P.O. Box 29, Nasr City, Cairo, Egypt E-mail: sifekhdr@hotmail.com Background: Results are presented on some dosimetric characteristics of Sife – Eldeen dosimeter based on the radiation induced conductivity (RIC) of 3.5 M aqueous urea solutions. The studied characteristics were the response (RIC) of Sife – Eldeen dosimeter in broad ranges of absorbed dose, dose rates and at different irradiation temperature. Materials and Methods: Kent EIL5007 conductivity meter (Kent industrial measurements–Brown Boveri) was used for the measurement of samples RIC. Results: RIC of 3.5M urea aqueous was studied at low (0 – 462 Gy), as well as, at high (0 2592 kGy) absorbed radiation dose ranges. The coefficient of variation CV%, associated with RIC measurement of 3.5 M urea solution as a function of absorbed radiation dose, was found to be not more than 3.5% for both high and low absorbed radiation dose ranges. The effect of dose rate on RIC was studied in the range 0.035 5.969 kGy/h. The temperature effect on this system, at different doses, was also studied. Conclusion: The obtained results show the importance of using this dosimeter for dose evaluation in industrial gamma radiation processes , as well as in medical fields. Iran. J. Radiat. Res., 2008; 6 (3):

Verification of the PAGAT polymer gel dosimeter by photon beams using magnetic resonance imaging

Abstract: Background: In this work investigation of the normoxic PAGAT polymer gel dosimeter such as sensitivity, the R2-dose response with post time and the percentage depth dose (PDD) of PAGAT polymer gel dosimeter have been undertaken. Materials and Methods: Using MRI, the formulation to give the maximum change in the transverse relaxation rate R2 was determined to be 4.5% N,N'-methylenbis-acrylamide ©(bis), 4.5% acrylamid(AA), 5% gelatin, 5 mM tetrakis (hydroxymethyl)phosphonium chloride (THPC), 0.01 mM hydroquinone (HQ) and 86% HPLC (Water). Irradiation of vials was performed using photon beams by Co-60 therapy unit and an Electa linear accelerator. Gel dosimeters were imaged in a Siemens Symphony 1.5 Tesla clinical MRI scanner using a head coil. Gel dosimeters were irradiated 1 day post-manufacture, and imaged 1 day post irradiation. Results: The R2dose response was linear up to 30 Gy. The response of the PAGAT gel is very similar in the lower dose region and the R2-dose response for doses less than 2 Gy is not exact. The R2-dose response of the PAGAT polymer gel dosimeters varies between 10 to 30 Gy with R2-dose sensitivities of 0.0905, 0.1037, 0.1023, 0.0907 and 0.123 S-1Gy-1 when imaged at 1, 8, 15, 29 and 38 days post-irradiation respectively. The percentage depth dose (PDD) of PAGAT gel dosimeter was determined and at depth of 21cm, the percentage depth dose for 1.25, 4, 6 and 18 MV photons were determined to be, 48%, 52%, 57.3% and 59.73% respectively. Conclusion: Calibration curve of the PAGAT polymer gel dosimeter, were found to be linear between 2-10 Gy and 10-30 Gy with different slopes of the R2-dose sensitivity also showed stability with post time imaging after 38 days. In this study, the percentage depth dose (PDD) of the PAGAT gel dosimeter was measured. It can be concluded that in case of higher energy of photon beams, higher doses can be delivered to deep-seated tumors. Iran. J. Radiat. Res., 2008; 6 (2): 83­87

Diode calibration for dose determination in total body irradiation

Abstract: Total body irradiation (TBI) differs in many aspects from standard irradiation procedures, since the whole body including the skin is the target volume, so, it is difficult to predict the actual dose delivered to the patients under TBI treatment (1). In spite of this difference, the accuracy in the determination of an administrated dose in TBI, as well as, standard radiotherapy has to be high (preferably below ±5%). In this presentation the type of the detectors used, and the procedure of their calibration are considered as important conditions in the whole chain of dose determination procedure (2). In recent years the use of diode dosimeters has become very common in the practice of radiation therapy. Early researches concentrated on understanding the intrinsic physical characteristics of p-type silicon diodes and determining how the diodes can be applied to accelerator or Co beam dosimetry. Diodes were shown to be useful for scanning beam symmetry, flatness profiles and measuring percentage depth dose curves (1). Several investigators have presented methods for measuring entrance and exit doses with diode detectors in order to determine midplane dose (2-6). Diodes were implemented to replace the TLD because they provide immediate results, and labor intense TLD often depend on operator skills (1). The primary aim of this work was to present how diodes could be implemented as dosimeters for TBI and to evaluate the methods of determination midplane dose in patients irradiated by Co for TBI.

Bone mineral densities in normal Bangladeshi women

Abstract: Background: Low bone mass may increase risk of fracture. Several chronic medical conditions, medications, and life style factors affect bone mineral accrual. This study aims to evaluate the bone mineral densities and hip axis lengths in the local population. Materials and Methods: 336 normal Bangladeshi women age ranges 20 to 70 years had evaluation of their bone mineral densities (BMDs) by means of dual X-ray absorptiometry (DXA). Results: The trend of BMD at the left femoral neck and the lumber spine remains fairly constant with increasing age until the 45-49 years age range, beyond which there is a consistent decline. The mean hip axis length is 10.27 cm. Conclusion: Bone mineral densities in femoral neck and lumber spine as measured by DXA and the hip axis length of the local population is lower than corresponding figures reported in the western population. Iran. J. Radiat. Res., 2008; 6 (3): 157­160

Determining rectal dose through cervical cancer radiotherapy by 9 mv photon beam using tld and xr type t gafchromic® film

Abstract: Background: The goals of the present research were to investigate the rectal dose during four chosen techniques of cervical cancer radiotherapy and to examine how accurately the treatment planning represents dose measurements, and it’s practicality for routine use as well as, to determine the homogeneity of dose in tumor volume. Materials and Methods: The study was carried out using a Nepton 10-PC unit and a Rando phantom. The equipments which were used for dose determination were a Radiochromic densitometer with GAFCHROMIC ® film (XR type T), and a thermo-luminescent dosimeter (TLD) reader system with TLD chips for rectal and target volume dose determination. Several techniques of external beam radiation therapy such as two-field (AP-PA), three-field and four-field with equal tumor dose and with equal applied dose were planned. Results: The maximum dose received by rectum was caused by two-field technique. The results of two dosimetry types were compared with each other as well as with the treatment planning, however, no statistically significant difference was observed between them (p > 0.05). In three-field, four -field with equal tumor dose and four-field with equal applied dose, rectal dose was lower, respectively 26.17%, 33.75% and 16.47%, than tumor dose. Conclusion: This study showed that dosimetry using TLD and film during radiotherapy could have a useful role as a predictor of choosing appropriate technique for preventing future rectal complications. Dose limitation to the rectum could possibly be achieved by using three-field and four-field techniques with equal tumor dose while maintaining a high dose to the tumor. Iran. J. Radiat. Res., 2008; 6 (3): 129­134

Bio-indicators in the tropical forest of Western Ghats environment

Abstract: 210 Po in the prominent plants species of Western Ghats tropical forest near Kotagiri have been carried out as a part of baseline background radiation studies in the forest environment. Materials and Methods: The prominent plants species of the region Evodia roxburghiana and Eleaocarpus oblangus were chosen and concentrations of 238 U, 232 Th, 40 K and 210 Po were measured by employing gamma ray spectrometer and alpha counter. Results: The radioactivity concentrations in plants and soils reflect the impact of the existence of igneous nature of rock in the area of study. Concentration ratios (CR) of these radionuclides, between plants and underlying soil, have been studied and results shows that the concentration ratios (CR) seem to be depend on radionuclides in soil. Conclusion: From careful analysis of the results, these Plants could be used as an indicator to monitor these radionuclides. Iran. J. Radiat. Res., 2008; 5 (4): 195-202

Staff exposure rate in Mahallat hot spring region

Abstract: 226 Ra concentration measurements as emanation method and Alfa guard detector for 222 Rn concentration measurements. Results: Considering stay period of the studied groups in indoor and outdoor environment, calculated annual external effective dose for staff has been 514.8 ± 22.7 µSv. Annual internal effective doses for staff in outdoor and indoor environment has been 21.1 mSv. Annual internal effective dose for staff due to drinking water has been 32 µSv. Conclusion: Measurements showed that more than 90% of the received dose in the studied groups was due to inhalation of Radon gas. External and internal effective dose for the staff was 21.6 mSv. Considering these results Mahallat hot spring region is a high level natural radiation area (HLNRA). Iran. J. Radiat. Res., 2008; 6 (1): 13-18

Preparation of prostate specific antigen standards for immunoradiometric assay

Abstract: Prostate cancer is the sixth most common cancer in the world, the third most common cancer in men. In 2000, the number of new cases of prostate cancer was estimated at 513000 worldwide and this disease accounts for 9.7% of all cancers in men (1, 2). Thus early detection and local treatment have been advocated in an effort to influence the significant morbidity and mortality associated with the disease. Prostate specific antigen (PSA) is a glycoprotein of 30 KDa found mainly in prostatic tissue and specific for prostatic tissue normal or malignant. It has been identified to be present in normal, benign hyperplastic and malignant prostatic tissue, in metastatic prostate carcinoma, and also in prostatic fluid and seminal plasma. Pathologically increased production of PSA is a characteristic for malignant prostatic tissues. Considerably increased PSA levels in patients with bone metastases demonstrate their prostatic origin. The determination of PSA is based on the biochemistry and immunoassay methods, such as: radioimmunoassay (RIA) and enzyme-linked immunosorbent assay (ELISA) (5, 6). Today, one of the most common methods for analysis of PSA is immunoradiometric assay (IRMA) which is one of the RIA methods. In this method two monoclonal antibodies against two different epitopes of PSA molecule are used. An IRMA kit used in clinical laboratories is consisted of four main components including, Background: Immunoradiometric assay is one of the most common and precise methods for determination of prostate specific antigen (PSA) in clinical laboratories. Usual use of human serum in routine assays has many disadvantages; such as easy contamination and precipitation, instability and unavailability. Thus in order to avoid these problems the artificial matrix was used which acts similar to human serum. Materials and Methods: In order to design immunoradiometric assay for prostate specific antigen, series of standards in different concentrations were needed for special artificial matrix preparation. The influence of artificial matrix in standards was studied to determine prostate specific antigen in comparison with human serum. Some different factors, such as the amount of non-specific bonding (NSB), precision, and accuracy, conditions of storage and stability of these standards prepared by artificial matrix were investigated. Results: The most appropriate artificial matrix (Tris-glycine (25.0 mmol/L) + NaCl (75.0 mmol/L) + Tris (12.5 mmol/L) +Triton X100 (0.5 ml/L) + HSA (1.2 g/L) + Urea (0.5 mol/L)) for preparing the standards was selected in comparison with human serum (HSA) and a commercial kit standards. HSA and Urea concentration have more critical influences on the properties of the standards. The amount of NSB of the selected matrix was the lowest one, so the selected matrix was the most suitable for preparing the standards. The results show the optimum condition of storage duration of our standards for one year was in refrigerator (2-8°C). It was observed that preparation of standards with selected matrix had acceptable accuracy and precision. Conclusion: According to the results, standards which were prepared with this matrix had suitable and appropriate properties and it could be utilized to prepare PSA standards in immunoradiometric assay. Iran. J. Radiat. Res., 2008; 6 (1): 51-58

A survey on stimulatory effects of topical application of radioactive lantern mantle powder on wound healing

Abstract: Some people in different parts of Iran use burned mantles as a wound healing medicine. To perform surface area measurement, twenty rats were divided randomly into two groups of 10 animals each. The 1st group received topical burned radioactive lantern mantle powder at 1st-3rd day after making excision wounds. The 2nd group received nonradioactive lantern mantle powder. For histological study, 36 male rats randomly divided into two groups of 18 animals each. Full thickness excision wound (314±31.4 mm 2 ) was made on the dorsal neck in all animals after inducing general anesthesia. For the first 3 days, cases received topical application of the radioactive lantern mantle powder. Finally, to measure the tensile strength, an incision was made on the dorsal neck of the rats. Surface area measurement of the wounds showed a progressive surface reduction in both groups. Histological study showed a significant statistically difference between cases and controls with respect to fibrinoid necrosis and neutrophilic exudate at the days 3 and 14. Considering the existence of granulation tissue, a significant difference was observed between case and control groups at days 3 and 7. Tensile strength study showed no significant difference between the cases and controls until 30 days after excision.

Evaluation of the relation between breast glandular absorbed dose and radiographic quality in mammography

Abstract: *Corresponding Author: Dr. Mohammad Bagher Tavakoli, Department of Medical Physics and Medical Engineering, Isfahan University of Medical Sciences, Isfahan, Iran. Fax: +98 311 7922412 E-mail: mbtavakoli@mui.ac.ir Background: Breast is one of the main radiological sensitive organs, hence it is important to evaluate absorbed dose to this organ especially to the glandular parts. It is the aim of this study to measure mean glandular dose and image contrast in terms of different mammographic parameters. Materials and Methods: In this study two mammography machines located at Said-al Shohada (Giotto) and Shahid Behesti (GE) hospitals were used. According to the recommendations of ACR and MQSA, breast phantoms were constructed and used for this study. For dose evaluation TLD dosimetry method was used. The TLD dosimeters were of LiF type and the reader was a Solaro TLD reader. Results: To obtain a constant contrast when increasing kVp from 22 to 24, it was necessary to reduce mAs by 12 percent. The obtained relation between these two parameters is: contrast=0.2829D-0.2427. It was also found that there is a linear relationship between contrast and image quality. The relation between these two parameters is: Image quality = 28.117 Contarst + 20.134. Increasing kVp and hence decreasing mAs results a reduction to the glandular dose, especially in patients with large breast. Increasing kVp from 28 to 30 results in reduction of dose from 6.8mGy to 5mGy. Conclusions: It was found that there has been a linear relationship between contrast and image quality. It was also found that increasing kVp necessitate to reduce mAs for a constant contrast and hence reduction of glandular dose. Iran. J. Radiat. Res., 2008; 6 (2): 77­82

Innovation of a method to decrease interruption time during treatment of pelvic area carcinomas

Abstract: Background: The presence of small intestine in the radiation field during pelvic cancers treatment causes an interruption in radiotherapy. A non-invasive method was developed to exclude small intestine during conventional radiotherapy. Materials and Methods: The incidence of the radiation therapy interruption is highly dependent upon the area of the small intestine included in the portals and its absorbed dose. In order to investigate the radiation therapy interruption and the resulting elongation of the total treatment time, 35 patients suffering from pelvic cancers were selected and randomly assigned to control and study groups. All the patients were treated in prone position. In the 18 patients in the study group, a commercially available water bag was inserted between patient abdomen and treatment couch. Other 17 patients in the control group underwent similar therapy without water bag. Results: The total treatment time was shown to be 1.52 days shorter in the study group with a statistically significant difference (p<0.003). Conclusion: Due to the lack of the early morbidities during radiotherapy, it is concluded that the current method helps to optimize total treatment time by preventing interruption of radiation therapy. Iran. J. Radiat. Res., 2008; 5 (4): 175180

An investigation on the performance of dose calibrators in nuclear medicine centers in Iran

Abstract: Background: To investigate the status of the nuclear medicine (NM) centers in Iran for the performance of dose calibrators, 18 out of 54 centers providing NM services in Iran were randomly selected and inspected in 1997. In the first phase of the study the selected centers were inspected for performing of quality control (QC) tests of dose calibrators. The linearity of the activity response, precision, accuracy, and the physical functions of the instruments, were studied. In the second phase of the study, carried out in 2006, 28 out of 75 NM centers were investigated for QC tests performance. Materials and Methods: The QC tests were performed by using standardized radio nuclides of Tc-99m and Cs-137 in the first phase, and Tc-99m and I-131 in the second phase of the studies. Standard procedures were used for carrying out the tests. Results: According to the obtained results in the first phase of the study, 10 centers were found to be in unacceptable situation. Following this study, all the concerned NM centers were informed about the results, and at the same time the repair and adjustment of the dose calibrators were requested. In addition, the appropriate training courses along with the QC testing manuals were provided to the centers. Based on the data of the second phase of the study, only 6 NM centers were in unacceptable situation. The results indicated the effectiveness of the improvements carried out in the working procedures of the centers during interval between the two phases of investigation. Iran. J. Radiat. Res., 2008; 6 (2): 64­69