Showing papers in "Iranian Journal of Radiation Research in 2006"

Assessment of radionuclides in imported foodstuffs in Iran

Abstract: Background: Knowledge of radioactivity levels in human diet is of particular concern for the estimation of possible radiological hazards to human health. However, very few surveys of radioactivity in food have been conducted in Iran; therefore the baseline values of the natural radionuclides concentration (40K, 226Ra and 232 Th), and man made radionuclide, 137Cs, were determined in twenty six samples of imported foodstuff in Iran. Materials and Methods: Twenty six samples of different kinds of imported foodstuff were selected for analysis. These samples, after pretreatment and washing (if necessary), were measured by a low level gamma spectrometry system. Results: All samples were found to contain detectable 40K content in range 6.4 to 778.4 Bq.kg -1 fresh weights (fw). 137Cs, 226Ra and 232Th were detectable in most of the samples. The maximum concentration of 40K, 226Ra and 232Th were found in tea sample, equal to 778.4±23.4, 2.9±0.1 and 5.4±0.2 Bq.kg -1 (fw), respectively, where as for 137Cs it was 3.2±0.1 Bq.kg -1 (fw) in milk powder. Conclusion: The concentrations of 40K and 137Cs in different imported foodstuff are comparable with those from the other countries yet 232Th concentration is higher than the reported values. Also, 226Ra results appear to be higher than the reported values in some cases. Iran. J. Radiat. Res., 2006; 4 (3): 149-153

Radiological risk assessment of use of phosphate fertilizers in soil

Abstract: We live in a milieu of radiation and exposed to ionizing radiation from natural sources. Natural radioactivity is wide spread in the earth's environment and it exists in various geological formations in soils, rocks, plants, water and air (1-3). Naturally occurring radioactive materials (NORM) became the focus of regulatory interest with the publication of International Atomic Energy Agency SS115 and the subsequent publishing of European Council Directive 96/29/EURATOM. It has changed the profile of radiation protection completely, increasing the regulatory awareness of natural radiation and the industries involved. Three major industries have been identified in terms of their scope and the materials handled as industries requiring further attention. They are the Oil & Gas Industry, the Zircon Industry and the Phosphate & Fertilizer Industry. The Phosphate and associated Fertilizer industry has an added complication, because it has two distinct sources of raw material, e.g. being of igneous or sedimentary origin. The source material contains isotopes from the natural uranium and thorium decay chains that may or may not follow the gypsum in the process. The weathering of the parent igneous rock released the radionuclides by the process of leaching and finally they entered the appetite structure by adsorption and co-precipitation 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 Ra, Th and K 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 Ra, Th and K 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 to 119.71 nGyh, 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, 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. Iran. J. Radiat. Res., 2006; 4 (2): 63-70

Free hydroxyl radical dosimetry by using 1 MHz low level ultrasound waves

Abstract: Background: In order to quantify effects of ultrasound irradiation parameters under therapeutic condition, especially sonodynamic therapy, it is initially necessary to evaluate inertial cavitation activity in vitro conditions; therefore, in this study, the effect of 1 MHz low level ultrasound based on °OH radicals generated by acoustic inertial cavitation in aqueous solution was monitored by their reaction with terephthalic acid (TA) to produce fluorescent 2-Hydroxyterephthalate acid (HTA) by spectrofluorometry method (Terephtalic acid dosimetry). Materials and Methods: The study was designed to measure hydroxyl radicals in a field near to 1 MHz sonotherapy probe in progressive mode and low level intensity. The effect of ultrasound irradiation parameters (1MHz) containing duty factor, mode, intensity ultrasound and, time sonication in hydroxyl radical production have been considered. After preparation of solution of dosimetry and plotting calibration curve of spectrofluorescence, the effect of mode of sonication (continuous and pulsating), duty factor (20-80%), intensity (0-2 W/cm2, with step of 0.5 W/cm2), and sonication time (0-60min with step time of 10min) without increasing temperature to more than 3°C to determine the effective exposure in low level ultrasound were evaluated. The fluorescence intensity of TA solution before and after irradiation, in all cases was measured, and the results were reported as Mean ± Standard Deviation (SD). Results: The result of experiments related to sonication mode for 1MHz ultrasound irradiation (2 W/cm2) show that continuous mode of sonication is 29% higher fluorescence intensity than the pulse mode in 80% duty cycle for sonodynamic therapy. With compensation of irradiation time for 1MHz sonication in different duty cycles, fluorescence intensity in continuous mode is 22% higher than the pulse mode in average. The amount of hydroxyl radicals production versus ultrasound intensity, and sonication time show with increasing intensity or sonication time in continuous mode, the hydroxyl radical production is linearity increased (R=0.99). Conclusion: The results show that the terephthalic acid dosimetry is suitable for detecting and quantifying free hydroxyl radical as a criterion of inertial cavitation production over a range of condition in medical ultrasound fields. Iran. J. Radiat. Res., 2006; 3 (4): 163-169

Alpha radioactivity in Indian cement samples

Abstract: Background: The essential constituents of cements like lime, silica and alumina are derived from earth's crust in which radioactive elements like uranium, thorium etc are also present in varying amounts almost everywhere. These two elements are considered as the parent elements of uranium and thorium radioactive decay series in which radon and thoron are produced respectively as decay products. In the present study the samples of ordinary Portland cement (OPC), Portland pozzolana cement (PPC) and some other cementious finishing materials like white cement, Plaster of Paris (POP), cement putty etc were collected and analysed for radium and radon concentrations along with radon exhalation rates. Materials and Methods: Alpha sensitive LR-115 Type II plastic track detectors commonly known as "Solid State Nuclear Track Detectors" were used to measure the radium and radon concentration. The alpha particles emitted from the radon causes the radiation damaged tracks. The Chemical etching in NaOH at 60 °C for about 90 minutes was done to reveal these latent tracks, which were then scanned and counted by an optical microscope of suitable magnification. By calculating the track density of registered tracks, the radon and radium concentrations along with exhalation rate of radon, were determined using required formulae. Results: The radon and radium concentration in various brands of cements found to vary from 333 ±9.9 to 506 ±13.3 Bq m-3 and from 3.7 ± 0.1 to 5.6 ± 0.2 Bq kg-1 while in various cementious finishing materials used in the construction, these were found to vary from 378 ±19.7 to 550 ± 9.8 Bq m-3 and from 4.2 ± 0.2 to 6.1 ± 0.1 Bq Kg-1, respectively. Based on the data the mass and surface exhalation rates were also calculated. Conclusion: The measurements indicate that there is marginal variation of the concentration of radium and radon in various brands of cements in India with lower levels in the cement samples having red oxide and higher levels in fly ash based cement samples but overall concentration levels of radon and radium are lower than that of average global values. Iran. J. Radiat. Res., 2006; 3 (4): 171-176

Development a simple point source model for Elekta SL-25 linear accelerator using MCNP4C Monte Carlo code

Abstract: Background: Monte Carlo (MC) modeling of a linear accelerator is a prerequisite for Monte Carlo dose calculations in external beam radiotherapy. In this study, a simple and efficient model was developed for Elekta SL-25 linear accelerator using MCNP4C Monte Carlo code. Materials and Methods: The head of Elekta SL-25 linac was simulated for 6 and 18 MV photon beams using MCNP4C MC code. Energy spectra and fluence distribution of photons crossing the phase space plane were calculated. A simple point source model was developed based on calculated photon spectra and spatial distribution. Using this model, percent depth doses (PDDs), and beam profiles were calculated for different field sizes. The results of MC calculations were compared with measurements. Results: There was a good agreement between MC calculations and measurement for descending part of PDD curves. However, comparing calculated PDDs with measurement showed up to 10% differences for build up region of PDD curves for both energies. For beam profiles, there was 2% difference in flat region and up to 15% difference was seen for out of field region. These results were acceptable according to the recommended criteria. Using this model, the run time was decreased 24 times in comparison to original full Monte Carlo method. Conclusion: Our study showed the presented model to be accurate and effective for MC calculations in radiotherapy treatment planning. Also, it substantially lowers MC runtime for radiotherapy purposes. Iran. J. Radiat. Res., 2006; 4 (1): 7-14

Entrance surface dose measurements for routine X-ray examinations in Chaharmahal and Bakhtiari hospitals

Abstract: Over the past hundred years or so, X-rays have been used for diagnostic purposes. The use of X-rays for imaging purposes, however, exposes patients to ionizing radiation. The increasing use of X-ray in hospitals has made medical exposure an important source of radiation in the population collective dose (1, 2). Ionizing radiation has the ability to break apart biologically important molecules such as DNA in exposed cells and can cause harm. As a result, the amount of radiation received by patients undergoing X-ray examinations needs to be quantified to estimate the possibility of harm. Patient doses in radiography primarily depend on the entrance surface dose and the sensitivity of the organs and tissues that are irradiated during the radiographic examination (3). The patient effective dose is proportional to the entrance surface exposure, and also depends on the X-ray penetrating power. The body region being examined is another important factor for determining the patient dose. The effective dose is a radiation dose parameter, which takes into account the absorbed dose received by each irradiated organ and the organ's relative sensitivity. Since the effective dose may be taken as an approximate measure of the stochastic radiation risk, it may be used to quantify the amount of radiation received by patients undergoing diagnostic examinations (4). Radiation protection is concerned with the control of the manner in which sources of ionizing radiation are used so that the user of the sources and also members of the public are not irradiated above acceptable levels recommended by the International Commission on Radiological Protection (2). Many studies have been proposed to measure entrance surface dose in different countries and their results were compared with dose levels recommended by relevant organizations. Also, organizations such as the National Radiological Protection Board and International Atomic Energy Agency (1, 5) recommended the use of dose constraints or *Corresponding author: Dr. Daryoush Shahbazi-Gahrouei, Department of Medical Physics and Medical Engineering, Isfahan University of Medical Sciences, Isfahan, Iran. Fax: +98 311 6688597 E-mail: shahbazi24@yahoo.com Background: There is not any report on the radiation doses received by patients in diagnostic radiology sections in hospitals under control of Chaharmahal and Bakhtiari Medical Sciences University, in the south west of Iran. The aim of this study is measurement of entrance surface doses (ESD) for the most routine types of X-ray procedures in radiology centers as part of ongoing dose reduction program. Materials and Methods: Geiger-Muller and thermoluminescence dosimeters (TLD), were used to measure entrance surface doses for four common radiographic views in six hospitals (7 X-ray machines). The entrance surface dose was measured on 20 randomly selected patients (male and female) for each X-ray examination. Patients were not exposed to any additional radiation and the radiographs were used for diagnostic purposes. Results: The entrance surface doses for the PA and lateral chest X-ray examinations were found to be in the range of 0.22-1.45 and 0.344.90 mGy, respectively. The ESD values for the AP or PA skull and LAT skull were in the range of 2.55-8.45 and 2.85-9.12 mGy, respectively. Most of the ESD measured doses were slightly greater than the ICRP and NRPB reference doses. Conclusion: The results of the present study indicate a need for quality assurance (QA) programs to be undertaken to avert considerable cost and high patient doses. The recommendations to avoid unnecessary radiation exposure are also given without lose of image quality. Iran. J. Radiat. Res., 2006; 4 (1): 29-33

Application of dose-area product compared with three other dosimetric quantities used to estimate patient effective dose in diagnostic radiology

Abstract: Background: Application of dose-area product (DAP) quantity has been increased in the clinical practice. DAP is relatively easy to measure, and has been shown to correlate well with the total energy to the effective dose imparted to the patient correlated. Materials and Methods: Measurements of DAP were carried out with 421 adult patients who underwent conventional radiological examinations. Then, some useful dosimetric quantities such as exposure area product (EAP), air kerma and entrance surface dose (ESD) were estimated. Furthermore, effective doses were computed by the measurement of DAP and corresponding conversion factors. Results: The effective dose values derived from various methods are in good agreement. The mean effective dose estimated from DAP measurements were 0.13, 0.42, 0.05, 0.59, 0.54 and 0.03 mSv/projection for chest, abdomen, cervical spine, lumbar spine, pelvis and skull examinations, respectively. Conclusion: Indirect effective dose determination using the NRPB dosimetric data and the measured value of DAP or ESD allows for reliable estimates of effective dose. The ODS-60 software was used in this study as to it’s flexibility to manipulate the technical parameters of an examination and patient’s parameters. Iran. J. Radiat.

Conventional and spiral CT dose indices in Yazd general hospitals, Iran

Abstract: Background: While the benefits of Computed Tomography (CT) are well known in accurate diagnosis, those benefits are not risk free. CT is a device with higher patient dose in comparison with other conventional radiological procedures. Is the reduction of exposures by requiring optimization of CT procedures [a principle concern in radiological protection]? In this study, the radiation dose of conventional and spiral CT were investigated and compared with European Commission Reference Dose Levels (EC RDLs) Materials and Methods: The dosimetric quantities proposed in the European Guidelines (EG) for CT are Weighted Computed Tomography Dose Index (CTDIW) for a single slice for axial scanning or per rotation for helical scanning and Dose-Length Product (DLP) for a complete examination. The patient-related data were collected for brain, neck, chest, abdomen and pelvis examinations in each scanner. For each type of examination, 10 typical patients were randomly included. CTDI with an active length of 10cm was measured in two CT scanners by using UNFORS (MultO-Meter 601) in head and body phantom (PMMA) with 16 cm and 32 cm in diameter; respectively. Mean values of CTDIW, DLP and Effective Dose(ED) were estimated for those examinations. Results: CTDIW had a range of 15.8-24.7 mGy for brain, 16.1-30.6mGy for neck, 6.8-9.2 mGy for chest, 6.8-9.8 mGy for abdomen and pelvis. DLP had a range of 246.4-397.7 mGy.cm for brain, 104.6-262.2 mGy.cm for neck, 135248.4 mGy.cm for chest, 187-298.9 mGy.cm for abdomen and 197.2-319.4 mGy.cm for pelvis. The mean values of effective dose were 0.70 mSv for brain, 1 mSv for neck, 3.2 mSv for chest, 3.3 mSv for abdomen and 5.1 mSv for pelvis. Conclusion: The obtained results in this study have shown that CTDIW and DLP are lower than EC RDLs and other studies, in other words, the performance of all scanners has been satisfactory as far as CTDIw and DLP are concerned. The CTDIW and DLP in the conventional CT are higher than the spiral CT values. With regard to ALARA principle, for the establishment of reference dose levels, the radiation dose with spiral CT scanners should be taken into account. Iran. J. Radiat. Res., 2006; 3 (4): 183-189

Achievable accuracy in brain tumors by in vivo dosimetry with diode detectors

Abstract: Background: In vivo measurements of applied dose during radiotherapy treatment, is important to ensure accurate dose delivery to patients. Uncertainty in dose delivery should fall within ±5% of the prescribed dose as recommended by ICRU. Assessment of dose for radiotherapy applications performed with various types of detectors. In this study, semiconductor diodes were used which have some advantages for clinical dosimetry. Materials and Methods: The brain tumors have generally treated with two fields using SSD technique. Entrance and exit dose were measured for each patient with diodes during treatment. Entrance and exit dose measurements have converted to midline dose. Measured entrance and exit doses have compared with calculated ones and large deviations (more than 5%) have observed. A farmer ionization chamber (0.6 cm) was used as the reference dose detector and a Perspex water phantom (30|| 2 area and thickness ranging from 5 cm to 30 cm) were used to determine calibration and correction factors. Results: Correction factors were determined and variations more than 1% have used to obtain correct doses. Large deviations between measured and calculated for entrance (5.3%), exit (42%) and midline (47%) were detected. The difference was not found to be significant when comparing the measured entrance dose with the calculated one (p=0.696) and the measured exit dose with calculated one (p=0.643) and measured midline dose with calculated one (p=0.104). Conclusion: In vivo dosimetry is very useful to check the dose delivered to the patient. A high precision obtained when the calibration and correction factors for each parameter of influence on the diode response are carefully determined and applied to convert the diode signal in the adsorbed dose. In this study, the target-absorbed doses were estimated from the measured entrance dose and the measured transmission. Iran. J. Radiat. Res., 2006; 3 (4): 153-161

A study of densitometry comparison among three radiographic processing solutions

Abstract: The radiographic image accuracy depends on the X-ray film information visibility. Good visibility is found by good contrast. The image information is a pattern of the X-ray beam intensities caused by the subject as its different attenuating materials. For example bone and soft tissues pass different beam intensities which results in an image contrast (1). It was shown that the energy of the X-ray beam may be used to produce a visible pattern of black metallic silver on the X-ray film (2-4). The measurement of film blackness is called "photographic density" defined by:

Impact of quality control on radiation doses received by patients undergoing abdomen X-ray examination in ten hospitals

Abstract: Background: The X-ray machines used for radiodiagnosis should meet certain quality assurance (QA) programmes. These are necessary to have good quality radiographs at reasonably low exposure to patients. Materials and Methods: Dose reduction methods in abdomen X-ray examination were carried out in 10 hospitals in Tehran. This paper presents the work, which was implemented on 200 patients and evaluated using the entrance skin dose (ESD) in the Anterior-Posterior (AP) abdomen projection measured directly at the center of the X-ray field. In addition, the machine room, and dark room parameters, as well as work practices and repeat rates were studied. Results: The quality control (QC) parameters and the ESD were evaluated utilizing an anthropologic phantom to define the optimal exposure condition at all hospitals before and after QC. Results show that after using the QC parameters and optimization of the exposure conditions, the mean of mAs and ESD can be decreased by 62% and 65% respectively. Conclusion: The quality of the radiographs generally increased. The reported method is easily implemented in any clinical situation where optimization of abdomen radiography is necessary. Iran. J. Radiat. Res., 2006; 3 (4): 177-182

Radiotherapy techniques for intracranial tumours

Abstract: The central nervous system (CNS) consists of the brain and the spinal cord. CNS tumours are relatively rare ( 50 years where it increases with age. They can be malignant or benign. Even benign tumours can be critical due to their location in brain tissue (e.g., compressing the surrounding tissue) and possibly fatal. Radiosensitivity differs among CNS tumours, e.g., high-grade gliomas are generally radioresistant while medulloblastoma is more radiosensitive. Radiotherapy (RT) is usually given following surgery and can be radical (with curative intent) or palliative (to relieve symptoms). For instance, treatment of CNS germinomas and medulloblastoma is likely to be curative while only short-term palliation is achieved with high-grade astrocytomas. The majority of CNS tumours develop within the brain. Figure 1 shows a schematic classification of intracranial tumours according to site. However, some tumours, e.g., medulloblastoma, ependymoma, germinoma and CNS lymphoma can spread to the spine via the cerebrospinal fluid pathways. In this paper, RT of intracranial tumours will be reviewed briefly with more emphasis on the methods that have been developed and/or used at the Royal Marsden Hospital, UK.

Patient dose resulting from CT examinations in Yazd, Iran

Abstract: Background: With the introduction of computed tomography in diagnostic radiology a new and fundamentally different imaging modality has become available. Meanwhile, it is clear that the absorbed doses by the patients during CT were relatively high in comparison with those of other diagnostic radiology techniques. The aim of this survey was to determine the average absorbed dose in Yazd province by CT examinations, and to evaluate the potential risks per year by these examinations. Materials and Methods: This study was conducted in Yazd CT centers during 2005-2006. The examination frequencies from 3 CT scanners were collected from all types of examinations. The effective dose was determined by CT Dose program (ImPACT CT patient dosimetry calculator). To use of this software, CTDI air , mAs and the thickness and number of slices in each type of CT examinations should have been measured. CTDI air was measured by pencil diode detector. Results: The annual collective dose and caput dose were 32.48 Person-Sv and 0.038 mSv, respectively for the Yazd population, which is lower than that reported for other populations. The frequency of examinations per 1000 people of Yazd was 18 which were equal to many other populations such as UK and New Zealand. The mean effective dose of each CT examinations was also lower than that of other countries. Conclusion: According to the ICRP risk factors, radiation dose from CT examinations could lead to about 1.3 fatal cancer per year. Therefore request for CT examinations should be more justified. Iran. J. Radiat. Res., 2006; 4 (3): 121-127

Prospective evaluation of endo venous laser therapy for varicose vein complications. The first report from Iran

Abstract: Lower limb varicose veins are common, with a prevalence of %15 in men, and %25 in women in the United States (1). Many patients are a symptomatic, but their complaints may vary from subjective symptoms such as aching, leg heaviness, pruritus, and muscle cramps, to more objective features of edema, eczema, lipodermatosclerosis and ulceration (2). Several treatment options are available when there is no reflux, including sclerotherapy, hand-held lasers applied externally and ambulatory phlebectomy for varicose veins (3). The vast majority (60-80%) of varicose veins arise from incompetence of the saphenofemoral junction (SFJ) and great saphenous vein (GSV) reflux (4). When reflux is present, the standard intervention is SFJ ligation with GSV stripping. Surgery usually requires general anesthesia, and it is associated with significant perioperative morbidity, increased cost of hospitalization and delayed return to normal activities and work (5). Endovenous laser therapy (EVLT) is a new and minimally invasive therapeutic option for treating primary varicose veins which provides an effective and safe alternative to conventional surgical management and it may be done in an outpatient setting using local anesthesia (2, 6). Several wavelengths have been proposed, 810, 940, and 980 respectively. At these wavelengths, the power is usually set between 10 and 15 Watts. The energy is administered endovenously, either in a pulsed fashion or continuously with a constant pullback of the laser fiber. At all the mentioned parameters, doses applied will range from 20 J/cm to 140 J/cm. These doses induce a heating of the vein wall which is necessary to cause collagen contraction and destruction of endothelium. Blood vaporization was found to be the main vehicle for vein wall damage (7, 8). 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 paresthesias 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. Iran. J. Radiat. Res., 2006; 4 (2): 87-91

A New Approach for Quantitative Evaluation of Reconstruction Algorithms in SPECT

Abstract: 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. Iran. J. Radiat. Res., 2006; 4 (2): 77-80

Relative measurement of heavy elements in the bile, gallbladder and gallstone

Abstract: The extra hepatic biliary system begins with the hepatic ducts and ends at the stoma of the common bile duct in the duodenum. The common bile duct is approximately 811.5 cm in length and 6-10 mm in diameter. The gallbladder, which is located in the bed of the liver, contains most of the smooth muscle of the organ, in contrast to the body, which is the major strong area and contains most of the elastic tissue. The main constituent of bile is water, electrolytes, bile salt, proteins, lipid, and bile pigments. Sodium, potassium, calcium and chloride have the same concentration in the bile. The major elements involved in the formation of the gallstones are cholesterol, bile pigment, and calcium(1). The suitability of PIXE spectroscopy for trace elements analysis in human tissues lies in the simultaneous analysis of wide range of light and heavy elements. This method is extremely sensitive and multielemental analysis. Absorption of necessary amount of elements for biological organs is from the surroundings or blood. Therefore, a breakdown of the homostatisis is indeed one of the most important indications of diseases (2, 3). The role of trace elements in the biological samples is very important in some diseases. The aim of this study was to compare the relative values of Fe/K, Cu/K and Zn/K for gallstones, gallbladder and bile of specific patient for studying the origin formation of gallstones. In contrast to conventional methods, the shell and center of the sands have been analyzed separately (4).

Preparation and evaluation of [201tl] (iii)-dtpa-higg for inflammation detection

Abstract: Background: Radiolabeled polyclonal human immunoglubins are useful in the detection of inflammations. In this work a novel approach has been presented to use thallium-201 as a complexing nuclide for the development of radioimmunoconjugates. Materials and Methods: Thallium-201 (T1/2=3.04 d) in Tl+ form was converted to Tl3+ cation in presence of O3 in 6M HCl, controlled by RTLC/gel electrophoresis methods and used in the labeling of human polyclonal antibody (HIgG) after residulation with freshly prepared cyclic DTPA-dianhydride. The best results of the conjugation were obtained by the addition of 1 ml of a HIgG pharmaceutical solution (5 mg/ml, in phosphate buffer, pH=7) to a glass tube, which was pre-coated with DTPA-dianhydride (0.01 mg) at 25| | continuous mild stirring for 30 min. Results: The final isotonic [ 201 Tl](III)-DTPA-HIgG complex was checked by radio-TLC using several solvent systems to ensure the formation of only one species, and it was followed by filtration through a 0.22 µm filter (specific activity= 33.7 TBq/mM, radiochemical purity|||||||95%). Preliminary bio-distribution studies in normal and inflammationbearing rats were performed. The target/skin and target/blood ratios were 4 and 6 after 28h, respectively, showing the selectivity of the radiopharmaceutical for the inflammatory lesions. Conclusion: The incorporation of Tl(III) cation into a immunoconjugate was performed using the known methods. The biodistribution of the immunocomplex was shown to be consistent with a stable complex for the detection of inflammations. Significant inflammation detection was observed for the final complex in rats with turpentine oil-induced inflammation. Iran. J. Radiat. Res., 2006; 4 (3): 105-114

Dose distribution and dosimetry parameters calculation of MED3633 palladium-103 source in water phantom using MCNP

Abstract: 3water phantom cube was calculated using MCNP code by the Monte Carlo method. The percentage depth dose (PDD) variation along the different axis parallel and perpendicular to the source was also calculated. Then, the isodose curves for 100%, 75%, 50% and 25% PDD and dosimetry parameters of TG43 protocol were determined. Results: The results show 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 MED3633 103 Pd source are in good agreement with published results. Conclusion: The isodose curves of the MED3633 103 Pd source have been derived form dose calculation by MCNP code. The calculated dosimetry parameters for the source agree quite well with their Monte Carlo calculated and experimental measurement values. Iran. J. Radiat. Res., 2006; 4 (1): 15-19

Simulation of gamma irradiation system for a ballast water treatment

Abstract: Another method is heating. The use of waste heat from the ship's main engine 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 60 Co in a triangle implant arranged in a 1||1|| 3 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, proves that this novel method not only can be used for ballast water treatment, but is also effective for drinking water purification. Iran. J. Radiat. Res., 2006; 4 (2): 93-97

Measurement of the immobilisation efficacy of a head fixation system

Abstract: Background: In order to assign appropriate planning target volume (PTV) margins, each centre should measure the patient positioning deviations for their set-up techniques. At the Royal Marsden Hospital, UK, a conformal shell (cast) system is used when a stereotactic frame is not suitable. In this paper, we report on a series of measurements with the aim of obtaining the systematic and random components of positioning error when using the above-mentioned shell system. Materials and Methods: The verification protocol was based on orthogonal pairs of anterior-posterior and lateral electronic portal images (EPIs) used to check the isocentre position. The isocentre verification results of paediatric patients were analysed. A practical 'off-line' patient set-up correction strategy had been used with the aim of reducing systematic errors. The verification protocol involved EPI acquisition on the first three fractions and then on a weekly basis. Additional images were taken if an isocentre movement was applied based on a 3 mm tolerance for a consistent 1D discrepancy. Results: Four patients required isocentre corrections ranging between 2 mm and 4 mm. Following the offline corrections, the residual systematic errors in each direction were within 0.5 mm while the 1D random variation was about 1.0 mm. Conclusion: The head fixation system in conjunction with the correction strategy successfully kept the random and systematic positioning errors within an acceptable level well within the 3 mm tolerance. The measured components of positioning error can be used to define appropriate PTV margins. Iran. J. Radiat. Res., 2006; 4 (1): 1-6

Transfer of 226Ra and 137Cs from tea leaves to drinking tea

Abstract: The sources of radioactivity in the environment have both natural and man made origins. The UNSCEAR has reported that the human exposure to radiation is mainly from natural sources(1). These sources may in turn be grouped into two distinct components, namely the sources of both terrestrial and extraterrestrial origins responsible for the external exposure, and the radionuclides taken into the human body through food, water and air particulate which give rise to the internal exposure. Radium is one of the most important alpha emitting radionuclides in the uranium-238 decay chain, and is retained primarily in bone, due to metabolic similarities to calcium. The effective dose resulting from radium intake in normal area is found to be 3.8 |μ |Sv y-1 for 226Ra(2). Also, there is increasingly significant contribution from man-made sources. Two obvious examples are the Windsclae and the Chernobyl reactor accidents on 1957 and 1986. The release of radionuclides into the environment can result in contamination of food. Cs is intercepted directly on vegetation surfaces during dry and wet deposition in the early stage after an accident. Cs is then transferred in to the soil with the highest soil to plant uptake in areas with high organic or sandy soils (3). The present study was carried out to measure Ra and Cs activity levels in tea leave samples and drinking tea due the fact that acknowledge of the contribution of the contamination of tea leaves and process of food transfer can improve the understanding of exposure through ingestion of radionuclides.

Unusual presentation of gestational trophoblastic neoplasm: report of two cases

Abstract: Gestational Trophoblastic Neoplasm originates from placental tissue and it is one of the rare human tumors that can be observed with wide spread metastasis (1). It is known that about 80% of Gestational Trophoblastic Neoplasms have remote metastatic lesions, and brain is the second metastatic site which occurs in only 10% of GTN patients (2). Virtually, all patients with brain metastasis have concurrent pulmonary, and or vaginal involvement. Vaginal bleeding usually precedes neurological symptoms. Prognosis in patients with brain metastasis is worse than vaginal or pulmonary metastasis and almost exclusively are seen in patients who have had a non molar pregnancy with a long delay in the diagnosis (1) Prodromal symptoms of brain metastases are defined as those neurologic symptoms which are mild and transient in nature, and may be present for several weeks before the onset of the classical symptoms. The classical symptoms of brain metastases are defined as those neurologic symptoms having a fulminate onset and are associated with progressive deterioration of the patient's neurologic status (4). The initial presence of brain metastasis can be confirmed by CT scan, magnetic resonance imaging (MRI), or serum / CSF | | human chorionic gonadotropin (| hCG) ratio. Imaging studies may not be able to show micrometastasis in very early stage of brain metastases (4). Cases have been reported with brain metastasis without evidence on imaging studies. Measurement of plasma / CSF (| hCG) ratio should be considered in deferential diagnosis (2). GTN should be considered in any woman of reproductive age who presents with neurologic symptoms. Observation of these two patients was supported the concept that some patients with central nervous system involvement have minimal gynecologic symptoms.

Depleted Uranium in the food chain at south of Iraq

Abstract: As a result of uranium enrichments to use 235U as fuel in the reactors or nuclear weapons, 0.5 million tones of DU are left in the environment. Some of these amounts of DU are used to balance of Buoying aircraft, aircraft wings, shield and fast breeder reactors to produce plutonium. Many options have been suggested for disposal of DU inside the earth or to send it outside into the space. These suggestions cost a lot. Some researches were conducted in 1972 to find a way to get rid of DU by using it as bolts or as shield for tanks; because of its high density and its high penetration power when bombarding solid targets and being fired strongly, causes high pressure and temperature of about 70% of DU transfer to aerosol of 238U which reacts with oxygen at high temperature producing uranium oxides. DU is alpha emitter with radioactivity of 12500 Bq/gm which is about half the activity of natural uranium (25160 Bq/gm) (1). The inhalation of DU aerosol is hazardous to human being (2). During the second Gulf war in 1991, DU ammunition was used by USA and British army to destroy the Iraqi tanks near Kuwaiti border. Farms of Basra province, south of Iraq were contaminated by DU. The Iraqi environmental scientists in the ex-Iraqi atomic energy commotion discovered this contamination in 1994, and in some parts of Iraq especially near Basra, where the tanks battles took place near the border. These areas were heavily contaminated with DU and some health risk began to appear on people living in Basra. The most important health effects of DU is Background: Depleted Uranium (DU) is uranium with low content of 235U produced as a result of uranium enrichment. DU has high density (19.05 g/cm3), which is 2.54 more than Iron, so it's high penetrating power makes it preferable as emanations with high penetration power. It was used in second Gulf ware in 1991 for first time. The radioactivity of soil, plants, fruit, meat, milk and water is measured using gamma ray spectroscopy. Materials and Methods: One hundred samples of soil, plants and tomato fruit were selected from the tomato farms near Basra city south of Iraq and 6 control samples from other farms not contaminated with depleted uranium (DU). Also samples of meats, milk and water were collected in January 2003. Radioactivity of these samples was measured using Gamma-ray spectrograph system with high purity Germanium detector with resolution of 2.2 keV at the energy of 1332.3 keV of Co-60. The system is connected to PC Pentium 111 with PCA program. Results: The measurements show that radiation equilibrium between 234Th and 226R existed with the range between (0.86-1.16) in uncontaminated soil samples. For contaminated soil samples radiation equilibrium between 234Th and Pa-234m existed with the range between (0.9280.956). The mathematical equations of Kosovo team were used. Results show that the soils of two farms were contaminated with (DU). The radioactivity of 226R for plants ranging from 5.97 to 7.26 and for tomato fruits samples between 9.16 to 12.4Bq/kg. Comparing these values with the control radioactivity which range between 6.25 to 7.34 for fruits and 13.3 to 13.9 Bq/kg for plants indicate that these samples were not contaminated with DU. Conclusion: The soil samples of two farms were contaminated with DU but the fruit of these farms was not contaminated with DU may be due to its high molecular weight and not being water soluble. The radioactivity of 226Ra for different kinds of meat and milk for animal grazing near destroyed tanks contaminated with DU, ranges between (0.02-1.1) and (0.01-.0.2) Bq/kg respectively. These values indicated that meat and milk are uncontaminated with DU. The water samples collected from wells in the same region are below the detection limit of the system. All these results indicated that the food chain was not contaminated with DU at the time of measurements. Iran. J. Radiat. Res., 2006; 4 (3): 143-148

Radiosynthesis of [103Pd]-di-actyl-bis (N4-methylthiosemicarbazone): a potential therapeutic agent

Abstract: Pd]labeled compounds. Chemical purity of the final product was confirmed to be below the accepted limits by polarography. The labeled compound was purified by reverse phase column chromatography using C18 plus Sep-Pak. The partition co-efficient of the final complex was determined. The initial physico-chemical properties of the labeled compound was compared to those of their copper homologues. Results: Radiochemical purity of more than 99% using RTLC was obtained (specific activity of about 12500-13000 Ci/mol). The stability of the tracer was checked in final product and human serum, at 37°C up to 48h. Conclusion: The labeled compound prepared in this study is probably one of the few new 103

Effect of vitamin e on preovulatory stage irradiated female mouse expressed as chromosomal abnormalities in generated embryos

Abstract: Background: The present study has been carried out to investigate the effects of preovulatory stage gamma-irradiation of female mice in the absence or presence of vitamin E on numerical chromosome abnormalities in 8-cell embryos after mating with nonirradiated males. Materials and Methods: The 8-11 weeks adult female NMRI mice were whole body irradiated at preovulatory stage (post PMSG injection and about 12-18 hours before injecting HCG) with 4 Gy gamma-rays generated from a cobalt-60 source alone or in combination with 200 IU/kg vitamin E, intraperitoneally administered one hour prior to irradiation. Soon after HCG injection super ovulated irradiated females were mated with non-irradiated males. About 68-h post coitus (p.c), 8-cell embryos were flushed from the oviducts of pregnant mice and were fixed on slides using standard methods in order to screen for metaphase spreads and numerical chromosome abnormalities. Results: In control embryos, 8% of metaphase plates were aneuploid, whereas in preovulatory stage irradiated female mice, about 50% of metaphase plates of embryos showed numerical chromosome aberrations (P<0.001). Administration of vitamin E one hour before the irradiation reduced chromosomal aberrations significantly (P=0.005). Conclusion: Results show that the effects of gamma-irradiation on preovulatory stage oocytes led to chromosomal abnormalities in subsequent embryos generated by these oocytes. Increase the frequency of numerical chromosome abnormalities -mostly aneuploidy- may be due to abnormal chromosomal non disjunctions during 2 nd

Chronological response of prostacyclin changes to moderately low doses of radiation in Rat cervical spinal cord

Abstract: Recent advances reported the probable priority of vascular and its secretory profile changes in pathogenesis of radiation myelopathy (RM). Vascular hypothesis states that vascular changes occur prior to any alterations in the white matter parenchyma possibly due to low dose radiosensitivity of vascular endothelium (1, 2). Modern enzymatic and/or immunohistochemical techniques have been applied to animal models for studying the radiation-induced changes in the various biochemical mediators produced by different cells within the irradiated medium (2). Prostacyclin in vitro measurement has shown its alteration shortly after low dose irradiation. Prostaglandins (PGs) have applications in diagnosis of different spinal cord disorders in a range from cerebrospinal fluid to intra spinal antibody microprobes or spinal cord homogenates. A basal level of PGs may exist in many laboratory samples and it is believed that injury to tissue induces release of prostaglandins (3). The possibility of the eicosanoids role in development of radiation toxicities have been reported by other investigations (3-7). More recent studies have also shown that some prostaglandins are responsive to irradiation and their early changes can induce the late reactions of spinal cord so called radiation myelopathy (3, 8, 9). Purpose of this article is to study the model of prostaglandin I2 (PGI2) or prostacyclin concentration changes in response to the low doses of X-irradiation after a short period of time. Background: Study of vascular and its secretory profile changes is an important issue in pathogenesis of radiation myelopathy. This paper reports the prostacyclin concentration changes after lowmoderate doses of X-irradiation within a short period of time. Materials and Methods: Cervical cords of Wistar rats were irradiated to doses of 0.5, 1, 2, 4 and 6 Gy X-rays. After 24 hours, 2 and 13 weeks postirradiation, prostacyclin contents were quantified and cords specimens were also stained routinely for histological studies. Results: Twenty four hours postirradiation, showed a decrease in the content of prostacyclin after doses of 0.5 and 1 Gy 91.67±1.47% 96.80±2.17% of respectively age-matched control group. After 2 weeks the concentration of prostacyclin showed significant decreases after 6 Gy. After 13 weeks irradiation shows marked differences even after a small dose of 2 Gy (p<0.001), and after doses of the low dose group. The differences between concentration values at doses of 4 Gy and 6 Gy were significant in comparison with the control (p<0.001 and p<0.002, respectively). Conclusion: Results suggested that the response of the vascular tissues to low and moderate doses of radiation occurs prior to that of the nervous tissue of the spinal cord. It means that the asymptomatic interval after radiation is characterized by sequential physiological changes which are imperfectly reflected in routine histological study and that even in the histologically unaffected spinal cord; severe impairment is present in substructures and biochemistry of irradiated spinal cord. Iran. J. Radiat. Res., 2006; 4 (3): 129-136

Derived intervention levels for mostly consumed foodstuffs in iran

Abstract: 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 90 Sr, 131 I, 134 Cs + 137 Cs, 238 Pu + 239 Pu + 241 Am and 103 Ru + 106 Ru radionuclide groups were calculated for infants ( 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

Track detection on the cells exposed to high LET heavy-ions by CR-39 plastic and terminal deoxynucleotidyl transferase (TdT)

Abstract: Background: The fatal effect of ionizing radiation on cells depends on Linear Energy Transfer (LET) level. The distribution of ionizing radiation is sparse and homogeneous for low LET radiations such as X or |, but it is dense and concentrated for high LET radiation such as heavy-ions radiation. Materials and Methods: Chinese hamster ovary cells (CHO-K1) were exposed to 4 Gy Fe-ion 2000 keV/||m. The CR-39 is a special and sensitive plastic used to verify exact position of heavy-ions traversal. Terminal deoxynucleotidyl transferase (TdT) is an enzyme labeled with [ 3 H] dATP for detection of cellular DNA damage by autoradiography assay. Results: The track of heavy ions traversals presented by pit size was almost similar for all different doses of radiation. No pits to show the track of traversal were found in 20% of the cell nuclei of the irradiation. Apparently these fractions of cells wave not hit by heavy ions. Conclusion: This study indicated the possible usefulness of both the CR-39 plastics and DNA labeling with TdT method for evaluating the biological effect of heavy-ions in comparison with low LET ionizing radiation. Iran. J. Radiat. Res., 2006; 4 (3): 137141

Monte carlo computation of dose deposited by carbon ions in radiation therapy

Abstract: Heavy charged particles interact with matter predominantly through inelastic collisions with atomic electrons. Slower particles give more energy to the electrons in comparison with faster particles; therefore, the delivered dose increases while the particle energy decreases. The point at which the particles deposit most of their energy is called the Bragg peak. The presence of a Bragg peak makes heavy charged particles very useful to treat deep-seated tumors. By varying the energy of a charged particle beam, radiation oncologists can spread this peak to match the contours of tumors or other targets. The advantages of heavy ion therapy over the conventional photon, and proton therapies are due to the better physical dose distributions achievable, tumor-conform treatment (1), and the radiobiological characteristics of heavy ions. Carbon ion beams appear to have the most optimal characteristics in physical and biological efficiencies comparing with other heavy ions. On the other hand, the relative biological effectiveness (RBE) of carbon ions widely varies as a function of depth in a medium, whereas it is similar to the RBE of neutrons only around the Bragg peak. Beams of high-velocity carbon ions provide an excellent physical depth-dose profile with an increased RBE (2) in the target volume. Millimeter precision at any depth is another additional advantage of carbon ion beam therapy of deep-seated tumors. Hence, radiation therapy with carbon ion beam is recommended when an advanced physical precision is of great importance, such as treating a solid tumor close to sensitive organs, as well as tumors in the head and neck region (3). At present, for therapeutic purposes, carbon ions are accelerated up to 430 MeV/u (4). The study of ion trajectories in tissue is essential in the fields of radiation dosimetry, health physics, radiation biology, and ion beam therapy. The precision of a Monte Carlo technique for computation of ion trajectories in matter depends mainly on the precision of the calculation of the stopping power properties of the matter (5). Stopping powers of charged particles in elements can be Background: High-velocity carbon ion beams represent the most advanced tool for radiotherapy of deep-seated tumors. Currently, the superiority of carbon ion therapy is more prominent on lung cancer or hepatomas. Materials and Methods: The data for lateral straggling and projected range of monoenergetic 290 MeV/u (3.48 GeV) carbon ions in muscle tissue were obtained from the stopping and range of ions in matter (SRIM) computer code. The data were transformed to determine the carbon ion trajectories in tissue by means of the Monte Carlo method. Consequently, the lateral dose distributions in the Bragg peak as well as the thickness of a thin discshaped tumor in the lateral direction were computed. The absorbed dose in the tissue was obtained as a function of the diameter of a carbon ion pencil beam. Results: More than 90% of the radiation dose in the lateral direction is deposited in the Bragg peak. The simulation results are in agreement with the existing data. Conclusion: It was confirmed that this method is reliable for estimation of dose deposited in human tissue by carbon ion beams. Iran. J. Radiat. Res., 2006; 4 (3): 115-120