International Journal of Radiation Research
Volume:2 Issue: 4, Oct 2004

An effective method for management of large and bulky malignant tumors. This treatment modality is also known as Specially Fractionated Radiation Therapy (SFRT). In this treatment technique a grid block converted the open radiation field into a series of pencil beams. Dosimetric characteristics of an external beam grid radiation field have been investigated using experimental and Monte Carlo simulation technique.Grid radiation therapy, using the megavoltage X-ray beam, has been proven to be radiation field have been determined using experimental and Monte Carlo simulation technique, for 6- and 18 MV X-ray beams from a Varian Clinics 2100C/D. The measurements were performed using LiF TLD and film in Solid Water phantom Material. Moreover, the MCNP Monte Carlo code was utilized to calculate the dose distribution in the grid radiation field in the same phantom material. The results of the experimental data were compared to the theoretical values, to validate this technique. Upon the agreement between the two techniques, dose distributions can be calculated for the grid field with different patterns and sizes of holes, in order to find an optimal design of the grid block.Dose distributions (%DD as well as the beam profiles) of a grid simulation technique was in good agreement with the measured data. In addition, the 3D dose distribution of the grid field generated by the Monte Carlo simulation gave more detailed information about the dose pattern of the grid.The results of dose profiles for 6 MV X-ray beams obtained with the Monte Carlo Carlo simulation technique can be utilized to optimize the pattern, size and spacing between the holes, for optimal clinical results. The grid block can be used as a boost for treatment of bulky tumors.

for treatment verification in radiation therapy. Several physical characteristics of ScanningLiquid filled Ionization Chamber EPID (SLIC-EPID) including: extra build-up layer,reproducibility and uniformity, and noise level were investigated.Electronic Portal Imaging Devices (EPIDs) have found an outstanding position equilibrium, 1-30 mm white water materials (RW3) were placed on the EPID cover and thevariation of pixel values were investigated. To assess the short term reproducibility, a series of10 consecutive Electronic Portal Images (EPIs) were acquired. The variation of pixel valueswere then determined in irradiated field using MATLAB software. For long term reproducibility,the described above experiment was then repeated seven times. To determine the noise levelin EPID images, 10 consecutive flood images were acquired. The measurement was repeatedafter two days during a fortnight.To determine the extra build-up layer to reach the electronic No significant variation was observed between the maximum thickness of build-up layerrequired for the central axis and peripheral points. For reproducibility measurements, no systematicvariation was observed between mean, maximum and minimum acquired pixel values.Both the long-term and short term reproducibility was found to be less than 1%. The noise levelwas generally less than 1% and this can be referred as an acceptable dose level5 mm of RW3 material was found to increase the pixel values to the maximum possible..can be used for dosimetry. However, for a particular linac energy and EPID image acquisitionmode, the extra build-up layer thickness must be known for the EPID to be used for dosimetricpurposesThe physical characteristics, measured in this work, suggest that the SLIC-EPID.

as fluoroscopy or different angiographies are usually evaluated using TL dosimeter. Thismethod is a time-consuming procedure; therefore, radiologists are usually worried and unawareof their exact radiation dose received during each fluoroscopy or angiography. In this study, anew trend for quick estimation of effective dose based on measuring air-absorbed dose of thescattered radiations at body surface of the radiologists has been introducedThe radiation effective dose received by the radiologists during procedures such fluoroscopy unit (Shimatsu, model SF5010MD), and a water phantom (spherical plastic bag 27cm in diameter filled with water up to 22.5 cm height). Radiation field was 20 × 20 cm on thebed and X-ray tube had 1.5 and 2 mm of Aluminum as an internal and external filtrationrespectively. A calibrated survey meter model RDS-110 was used to measure the scatteredradiation horizontally and vertically around the phantom at different angles and distances, infront and behind of an apron.Scattered radiations of abdominal viscera were simulated by a mA, was 451 µGy/h. This value reduced to 4.45 µGy/h by passing through lead ribbons ofserigraph and to 1.2 µSv/h behind an apron. The scattered dose rate at different angles above thebed was constant and varied by distance from the center of the radiation field. The effectivedose received by the radiologist is estimated to be about 174µGy/h, while wearing an apron andstaying 50 cm away from the patient during fluoroscopy or angiography of abdominal viscera.The scattered dose rate at 1 m from the phantom, during fluoroscopy at 83 kVp and 1.7 different angiographies of abdominal viscera, by determining scatter radiation dose at their bodysurface and applying factor 0.87 for shielding effect of the body. Equivalent organ dose can alsobe calculated from dose rate in air after applying factor 0.87 for deep organs or 1.1 (the massenergy absorption coefficient ratio of water/tissue to air) for organs near the surface. The radiologist can estimate his/her effective dose following a fluoroscopy orIran. J.

accurate methods of radiation therapy dose calculation. There are different Monte Carlo codesfor simulation of photons, electrons and the coupled transport of electrons and photons. MCNPis a general purpose Monte Carlo code that can be used for electron, photon and coupledphoton-electron transport.Monte Carlo simulation of radiation transport is considered to be one of the most calculating electron beam doses in water. For simulating, the geometry and other parameterswere the same for three codes. By choosing two energy indexing algorithm (ITS & MCNP),absorbed doses were scored in water. 10In this study the MCNP4A, 4B and 4C have been compared when6 Particles were followed in these three cases. used in 4B and 4C versions. There was a good agreement between versions 4B and 4C. For theenergy spectrum, there were significant differences between these three versions in two planes.MCNP4C and 4B gave different results compared to 4A when the ITS algorithm was for electron transport and also requires a shorter time than the two previous versions. Theseresults, in addition to the practical measurements acquired with MCNP4B by other investigators,suggest that in electron transport the user should use the ITS indexing energyalgorithm. Because of new improvements in electron transport in 4C, this version is reliableIran. J. Radiat. Res., 2005; 2 (4): 191-195

and soils with which it comes in contact. There is dual exposure from radon in water i.e. due toinhalation of the radon released from the water into the ambient air and through ingestion whenwater is used for drinking. As radon contaminated water adversely affects the health, it istherefore fundamental from health and hygiene point of view to measure radium concentrationand radon exhalation rates in waterDissolved radon is contained in natural water due to primordial uranium in rocksMaterials and Methodsradium concentration and radon exhalation rate in water samples collected from various thermalsprings. The alpha tracks registered were counted by optical microscope at suitable magnificationand converted into radium concentration and subsequently radon exhalation rates were measured.: LR-115, Type- II plastic track detectors were used to measure the mvaried from 5.65 Bq lexhalation rates varied from 2.37 mBq kg± 0.36 mBq kgThe radon concentration emanated from water samples (air borne) varied from 84 Bq-3 to 827 Bq m-3 with an average of 429 ± 12.72 Bqm-3 and the dissolved radon concentration-1 to 55.66 Bq l-1 with an average of 28.88± 0.85 Bq l-1. The radon mass-1 hr-1 to 23.39 mBq kg-1 hr-1 with an average of 12.14-1 hr-1 and surface exhalation rates from 52.34 mBq m-2 hr-1 to 515.29 mBq m-2 hr-1with an average of 267.36 ± 7.93 from different thermal spring water samples.concentration varied from 0.30 Bq l The radium-1 to 2.93 Bq l-1 with an average of 1.52 ± 0.045 Bq l-1. drinking, is safe as far as radium concentration is concerned with the exception of a few isolatedthermal spring sources.Results indicate that the thermal spring water, which is also being used forIran.

Coherent scattering leads to diffraction effects and especially constructive interferences. Theseinterferences carry some information about the molecular structure of the tissue. As breast cancer isthe most widespread cancer in women, this project evaluated the application of small angleX-ray scattering (SAXS) for differentiation between normal and cancerous breast tissues.Small angle X-ray scattering (to angles less than 10°) is predominantly coherent.primary collimator, sample holder, secondary collimator and HP Ge detector was used. The bestconstructive interference was found to be at 6.5at several angles of 4, 5, 6, 6.5 and 7.3 degrees. The total number of 99 breast tissue samples,including normal and tumor were studied at the 6.5transfer was obtained for each sample.The energy dispersive method with a set up including X-ray tube,° after doing experiments on adipose breast tissue°. The corrected intensity versus momentum adipose tissue and mixed tissue (adipose & fibroglandular) from tumor in peak positions (eachcoherent scattering spectrum has a peak that its position is determined by momentum transfer).Furthermore adipose tissue has shown significantly higher peaks than other breast tissues. Benignand malignant breast tissues were differentiated by both peak positions and peak heights (eachpeak has a height in coherent scattering spectrum). Preservation of samples nitrogen tank had noeffects on molecular structure of the breast tissue.Adipose tissue shows a sharp peak in low momentum transfer region. It is easy to separate between normal, benign and malignant breast tissues. By energy dispersive small angle X-ray scattering, it is possible to differentiateIran.

were made each week during year 2002 from samples of atmospheric aerosols filtered from theair at Tehran Nuclear Research CenterMeasurement of gross beta activities and cosmogenic Beryllium-7 concentrationsMaterials and Methodssampler at the Nuclear Research Center meteorological station in Tehran (40contents of samples were determined with semiconductor gamma spectrometry. The long-livedbeta activity, i.e. total beta activity measured four days after the end of sampling (after decay of: The aerosol samples were collected weekly with high-volume airo 35. N). The 7Be220The long-lived beta activity consists mainly of amount of artificial radionuclides in the air is negligible.Rn progeny and short-lived 220Rn progeny), was assessed with an automatic beta analyzer.210Bi, the daughter nuclide of 210Pb, as the lognormal distribution during the study period 2002. The arithmetic mean of annual concentrationsof The air concentrations of both the 7Be and the long-lived beta activity displayed a7Be and 210 Pb was 6.30 and 0.50 mBqm-3, respectively. beta activities are partially correlated. Both have maximum concentrations during warmmid-year months. Despite the different origins, the concentrations of both the 7Be and the long.livedIran.

Sarcomas are the most malignant tumors in the myocardium. Most common sarcoma is theangiosarcoma, classically located in the right atrium. Surgical resection is the primary treatmentof choice for these patients. In July 2003, an 18 years old man with chest pain and dyspnea,referred to the Imam Khomeini Hospital. Chest X-ray showed cardiac enlargement andtransthoracic echocardiography demonstrated a large lobulated tumoral mass in right atrium.Cytologic examination of the pericardial effusion reported as no evidence of malignancy andchest CT scan showed cardiac dilatation with blood density and pericardial effusion. The patientunderwent operation and tumor bulk was resected. Based on histological examination andimmunohistochemistry, diagnosis of cardiac angiosarcoma was made and the patient receivedpostoperative radiotherapy through parallel-opposed AP-PA cobalt beam technique. Aftercombined modality treatment with surgery and postoperative radiotherapy, symptoms weredisappeared and after 20 month follow up patient is symptom free. Despite of the ominousoutcome of this malignancy an multimodality approach is worthy of consideration.