International Journal of Radiation Research
Year:2016 | Volume:14 | Issue:4|Papers Count:15

Background: Dose calcula on algorithms play a very important role in predic ng the explicit dose distribu on. We evaluated the percent depth dose (PDD), lateral depth dose profile, and surface dose volume histogram in inhomogeneous media using calcula on algorithms and inhomogeneity correc on methods. Materials and Methods: The homogeneous and inhomogeneous virtual slab phantoms used in this study were manufactured in the radia on treatment planning system to represent the air, lung, and bone density with planned radia on treatment of 6 MV photons, a field size of 10 × 10 cm2, and a source-to-surface distance of 100 cm. Results: The PDD of air density slab for the Acuros XB (AXB) algorithm was differed by an average of 20% in comparison with other algorithms. Rebuild up occurred in the region below the air density slab (10– 10. 6 cm) for the AXB algorithm. The lateral dose profiles for the air density slab showed rela vely large differences (over 30%) in the field. There were large differences (20. 0%– 26. 1%) at the second homogeneous– inhomogeneous junc on (depth of 10 cm) in the field for all calcula on methods. The surface dose volume histogram for the pencil beam algorithm showed a response that was approximately 4% lower than that for the AXB algorithm. Conclusion: The dose calcula on uncertain es were shown to change at the interface between different densi es and in varied densi es using the dose calcula on methods. In par cular, the AXB algorithm showed large differences in and out of the field in inhomogeneous media.

Background: This study assessed the op mal  ming of computed tomography for detec on of metasta c disease in locoregional lymph nodes in pa ents with rectal cancer who have undergone chemoradiotherapy. Materials and Methods: This observa onal retrospec ve study was performed in a single ins tu on. All pa ents with locally advanced rectal cancer treated with chemoradiotherapy, followed by a total mesorectum excision from January 1, 2003 to December 31, 2012, were included. Lymph node metastases evident on preopera ve computed tomography were compared with postopera ve pathologic lymph node status. Results: The study popula on consisted of 108 pa ents: Group A (nodal nega ve on preopera ve computed tomography, n = 52) and Group B (nodal posi ve on preopera ve computed tomography, n = 56). Analysis of the computed tomography scans in Group A revealed a high ability (98. 07%) to predict nega ve lymph nodes, compared to 58. 92% for predic ng posi ve lymph nodes in Group B. Conclusion: The results of this study suggest that the op mal  ming of computed tomography for assessing lymph nodes a0er neoadjuvant chemoradiotherapy for rectal cancer is a0er 6 weeks; this  ming might be key for predic on of complete clinical responses.

Background: This study describes the possibility of implemen ng threedimensional prin ng technology to create a precise construc on of a planned bolus, based on computed tomography informa on stored in the Digital Imaging and Communica ons in Medicine (DICOM) format file. Materials and Methods: To create the bolus with a 3D printer, we converted data in the DICOM format to the stereolithography (STL) format. In addi on, we produced a paraffin bolus that, tradi onally, is manually placed directly on the pa ent. CT scans were acquired for both boluses, and the images were superimposed onto the pa ent CT scans that were used to design the bolus. The superimposi on of images was performed to compare the fit of the bolus printed on a 3D printer to that of the paraffin bolus made in the tradi onal way. In addi on, for both models, the dose distribu on was simulated. To quan fy the level of matching ML, special formula was used. The ML parameter had a value between 0 and 100%, where 100% indicated a perfect fit between the model and the 3D printed bolus. Results: We verified that 100% of the volume of the 3D printed bolus was located within the contour of the designed model. The ML of the bolus was 94%. For the classical paraffin bolus the ML was only 28%. Conclusion: A bolus printed on a threedimensional printer can faithfully reproduce the structure specified in the project plan. Compared to the classical paraffin bolus, the three-dimensional printed bolus more closely matched the planned model and possessed greater material uniformity.

Background: stereotac c body radiotherapy (SBRT) has emerged as an effec ve treatment for localized prostate cancer. However, prostate-specific an gen (PSA) kine cs a'er SBRT has not been well characterized. The objec ve of the current study is to analyze the rate of PSA decline and PSA nadir following hypofractonated SBRT in localized prostate cancer. Materials and Methods: From 2008 to 2014, thirty-nine pa ents newly diagnosed, localized prostate (25. 6% low risk, 66. 7% intermediate risk and 7. 7% high risk) cancer were treated with SBRT using Cyberknife. Total dose of 36. 25 Gy in 5 frac ons of 7. 25 Gy were administered. No one received androgen depriva on therapy (ADT). PSA nadir and rate of change in PSA (slope) were calculated and compared. Results: With a median follow-up of 52 months (range, 13-71), the median rates of decline of PSA were-0. 372,-0. 211 and-0. 128 ng/mL/month, respec vely, for dura ons of 1, 2 and 3 years a'er radiotherapy, respec vely. The decline of PSA was maximal in the first year and con nuously decreased for dura ons of 2 and 3 year. The median PSA nadir was 0. 28 ng/mL a'er a median 33 months. There was one biochemical failure, occurring in a high risk pa ent. 5-year actuarial biochemical failure (BCF) free survival was 94. 2%. Conclusion: In this report of localized prostate cancer, con nuous decrease of PSA level for dura on 1, 2 and 3 year following SBRT using Cyberknife resulted in lower PSA nadir. Also, SBRT leaded to long-term favorable BCF-free survival.

Background: An effec ve polymer gel dosimeter can be fabricated by varying the composi on of its chemical components. Materials and Methods: The MAGAT gel dosimeter formula ons that used different composi ons of Methacrylic acid (MAA) and gela n were extensively inves gated in the present study according to the R2– dose response and R2– dose sensi vity. The irradia on of MAGAT gel was performed by 6-MV photon beam at a dose range 1 to 10 Gy and was imaged by 1. 5T Magne c Resonance Imaging (MRI). The dose response of MAGAT gel dosimeter was obtained from spin-spin relaxa on rate (R2) of MRI signal. Results: The MAGAT gel dosimeter composed of 5% gela n and 6% MAA gave the highest sensi vity (1. 1180 s-1Gy-1). Conclusion: Understanding the effects of the composi onal changes will help to clarify the mechanisms involved in the dose response of the MAGAT gel dosimeter.

Background: This study presents pa ent specific and organ dose es ma on in computed tomography (CT) imaging of thorax directly from pa ent CT image using Monte Carlo simula on. Pa ent's CT image is considered as the pa ent specific phantom and the best representa ve of pa ent physical index in order to calculate specific organ dose. Materials and Methods: EGSnrc / BEAMnrc Monte Carlo (MC) System was used for CT scanner simula on and DOSXYZnrc was used in order to produce pa ent specific phantom and irradia on of photons to phantom in step and shoot mode (axial mode). In order to calculate pa ent thorax organ dose, pa ent CT image of thorax as voxelized phantom was divided to a 64x64x20 matrix and 6. 25 x 6. 25 x 6. 25 mm3 voxel size and this phantom was imported to DOSXYZnrc code. MC results in unit of Gy/par cle were converted to absorbed dose in unit of mGy by a conversion factor (CF). We calculated pa ent thorax organ dose in MC simula on from all irradiated slices, in 120 kV and 80 kV photon energies. Results: Effec ve dose was obtained from organ dose and organ weigh ng factor. Esophagus and spinal cord received the lowest, and bone received the highest dose. In our study, effec ve dose in CT of thorax was 7. 4 mSV and 1. 8 mSv in 120 and 80 kV, respec vely. Conclusion: The results of this study might be used to provide the actual pa ent organ dose in CT imaging and calcula on of real effec ve dose based on organ dose.

Background: Natural background radia on of a par cular region is one of the dis nc ve factors defining the status of environment. Eloor Island is an industrial area in Ernakulum District of the state of Kerala, India. The indoor and outdoor gamma level measurements have been carried out for the region for evalua ng the annual effec ve dose to the popula on residing in this area. Materials and Methods: Measurements of indoor gamma dose were done for a whole year using Thermo Luminescent Dosimeters (TLDs) and GM tube based survey meters in forty five selected loca ons. The ac vity concentra on of 232Th, 238U and 40K in the samples were analyzed using gamma spectrometry. The outdoor external gamma ray dose rates were evaluated from the ac vity concentra on of 40K, 238U and 232Th in the soil samples collected from the study area. Results: The average indoor gamma dose measured using TLDs were found to be 1219 μ Gy y-1. The measured ac vity in the soil samples had range from 92. 5 Bq kg-1 to 792. 8 Bq kg-1 for 232Th, 9. 2 Bq kg-1 to 114. 6 Bq kg-1 for 238U and 265. 9 Bq kg-1 to 851. 9 Bq kg-1 for 40K. From the observed mean dose levels, the annual effec ve dose equivalent to popula on residing in the island has been es mated and is found to be 0. 68 mSv y-1 for indoors and 0. 32 mSv y-1 for outdoors. Conclusion: The annual effec ve dose equivalent to popula on es mated for indoor is found to be higher as compared to the global average the same for outdoor was found to be less when compared with the natural background gamma level reported by UNSCEAR for normal background areas.

Background: Inhalation of radon and its short-lived decay products is one of the most significant sources of exposure to natural radiation. Radon is the second cause of lung cancer in the populations. The present study was carried out under the projects of national radon, with the aim of determining the concentration of indoor in the city of Qom located in the central semi-arid region of Iran. Materials and Methods: Radon measurements were carried out in 123 dwellings using passive sampling with CR-39 detectors for 90 days. The map of radon concentration distribution was prepared using Arc GIS software and the statistical analysis was performed with SPSS version 20. Results: Indoor radon concentrations in Qom dwellings ranged from 15– 259 Bq m- 3. The arithmetic mean of indoor radon concentrations on basement, ground floors, first floors and second and upper floors were 123. 43, 87. 94, 63. 72 and 40. 69 Bq m-3, respectively. Conclusion: A correlation was found between the distances from fault zones and measured indoor radon concentration. In most of cases, radon values were lower in well- ventilated dwellings in comparison with poorly-ventilated ones. Moreover, high radon concentration levels were observed in basements. The results indicated that in 30 places (24. 3% of cases), the radon concentrations were higher than the reference levels recommended by the World Health Organization (100 Bq m-3).

Background: To suggest South India CT diagnostic reference levels (DRLs) by collecting radiation doses for the most commonly performed CT examinations. Materials and Methods: A pilot study investigated the most frequent CT examinations. 110 CT sites were asked to complete a survey booklet to allow the recording of CT parameters for each of 3 CT examinations during a 1 year time period. Dose data such Volumetric Computed Tomography Dose Index (CTDIv) and Dose length product (DLP) on a minimum of 50 average-sized patients in each category were recorded to calculate a mean site CTDIvol and DLP value. The rounded 75th percentile was used to calculate a DRL for each site and the region by compiling all results. Results are compared with international DRL data. Results: Data were collected for 16, 500 patients. All equipment had multislice capability (2-256 slices). DRLs are proposed using CTDIvol (mGy) and DLP (mGy. cm) for CT head (47 and 1041 respectively), CT chest (10 and 445 respectively), and CT abdomen (12 and 550 respectively). These values are lower than current DRLs and comparable to other international studies. Wide variations in mean doses are noted across the region. Conclusion: Baseline figures for South India CT DRLs are provided on the most frequently performed CT examinations. It was noted that there was a wide variation in mean doses among the CT scanners used during diagnosis. The differences in CT doses between CT scanner departments as well as identical scanners suggest a large potential for optimization of examinations.

Background: In this study a series of basic dosimetric proper es of a lowdensity (LD) gel dosimeter are inves gated. The dose response is studied regarding to linearity, sensi vity, dose-rate and energy dependence as well as lung  ssue equivalence. Materials and Methods: The LD gel was made by mixing the polymer gel with expanded polystyrene spheres. Energy dependence was studied at two different energies: 1. 25 MeV and 6 MV photon beams which were produced by 60Co and Linac machines. Inves ga on of dose rate dependence was performed in the low, medium, and high absorbed dose regions. Also reproducibility of dose response was studied in three sets of LD gel with iden cal prepara on, irradia on and imaging procedure at three different days. Moreover the linearity and sensi vity were inves gated up to 30Gy. Results: The results showed that the dose response was reproducible. The gel response was found linear up to 22Gy with r2=0. 981 and sensi vity of 0. 814S-1Gy-1. In the measured ranges, the dose response of LD gel was independent of beam energy within less than ± 0. 02 and dose rate had no effect on the gel response. LD gel was nearly lung  ssue equivalent with mass density 0. 37 to 0. 4g/cm3 and rela ve electron density 0. 41. Conclusion: MAGAT LD gel dosimeter appears to be a promising dosimeter in all aspects of dosimetric proper es evaluated in this study. In addi on, its high linearity together with no dose rate dependence in different level of absorbed doses makes it a suitable dosimeter to measure 3D-dose distribu ons inside a non-homogeneous media.

Background: Although it is one of the most toxic nonradioac ve elements, mercury is widely used in dental amalgam. Mercury is a toxic element which can damage various organs such as central nervous system, renal, respiratory and hematologic systems. The adverse health impacts associated to exposure to some common sources of electromagne c fields including laptop computers, mobile phones, MRI and mobile phone jammers have been evaluated by our laboratory in our previous inves ga ons. In this study, we aimed to evaluate the effect of X ray exposure on microleakage of amalgam restora on. Materials and Methods: Standardized class V cavi es were prepared on the buccal surfaces of 46 non-carious freshly extracted human premolars. The teeth were randomly divided into experimental and control groups. Experimental group were exposed to X-ray using an intraoral radiography machine at 60 kVp, 0. 1 s, 7 mA with 2. 5 mm Al total filtra on. The absorbed dose was 245. 0 ± 0. 5 μ Gy. All specimens were placed in 2 % basic fuchsin solu on for 24 hours. Then the specimens were sec oned and microleakage was assessed according to dye penetra on using a stereomicroscope. Sta s cal analysis was performed with the Mann-Whitney U-test. Results: Microleakage was significantly higher in the X-ray exposed teeth compared to those of the non-irradiated samples. Conclusion: The results of the present study suggest that X-ray exposure increased microleakage of amalgam restora ons.

Background: Radium-226 (226Ra) is a product of the 238U radionuclide decay series that significantly incorporated into the human body through water intake. It can also poten#ally cause a series of health problems including cancers of the diges#ve system. Radium-226 (226Ra) is a product of the 238U radionuclide decay series that significantly incorporated into the human body through water intake. It can also poten#ally cause a series of health problems including cancers of the diges#ve system. Materials and Methods: 226Ra has been determined in drinking water samples collected from various loca#ons of Guilan province of Iran. The water samples are taken from public water and urban tap water sources. For evolu#on of gross a and b exposure precipita#on method and propor#onal scin#llator system was used. The radon emana#on method was used to measure the radium concentra#on in drinking water. Results: The measurements showed the gross α and β concentra#on ranges were between <38 mBql-1 to 92 mBql-1 and <41 mBql-1 to 328 mBql-1, respec#vely. The radium concentra#on range was between 2 mBq l-1 to 38. 2 mBq l-1. The resul#ng contribu#on to the annual effec#ve dose due to the diges#on of 226R in water was calculated to be between <0. 4 μ Sv y-1 to 7. 8 μ Sv y-1, respec#vely. Conclusion: The average concentra#on of 226Ra was found (7. 6 mBq l-1) in drinking water samples and the average annual effec#ve dose, from the diges#on of 226Ra in water samples was calculated to be 1. 5 μ Sv y-1. According to UNSCEAR, the annual effec#ve dose value by inges#on is report to be 0. 12 mSv y-1.

Background: Radon concentra on was measured in the soil and indoor of Amman and Al-Rusaifa ci es in Jordan during summer season. Materials and Methods: The measurement was performed using  me-integrated passive radon dosimeters, containing a solid state nuclear track plas c detector, commercially known as CR-39. Results: Radon concentra on levels in the soil ranged from 2. 8 ± 1. 2 to 6. 9 ± 1. 5 (kBq/m3) with an average 4. 0 ± 1. 6 (kBq/ m3) in Amman and from and 6. 5± 1. 1 to 22. 4 ± 5. 2 kBq/m3 in Al-Rusaifa with average 14. 2 ± 2. 5 (kBq/m3). The average indoor radon concentra on in the first floor in Amman was 44. 8± 5. 3 (Bq/m3); while the average concentra on in Al-Rusaifa, in the first floor, was 187± 16. 35 (Bq/m3). In Al-Rusaifa, our results in the ground floor and the first floor were about 11%-26 % higher than the reported values, while this ra o reaches to 56% of the soil. Conclusion: The average indoor radon concentra on indoor in Al-Rusaifa exceeds the ac on radon level recommend by WHO (100 Bq/m3). The poten al health impact in this city is considered high. High radon level in Al-Rusaifa may be due to the phosphate content in its soil. A correla on between the radon concentra on in the soil and indoor was observed.

To assess the environmental radioactivity levels and hence to determine the population exposure in Kutubdia Island, Bangladesh the sediment samples were analyzed by using gamma ray spectrometry. In those sediment samples the average activity concentration of natural radionuclides 238U, 232Th and 40K were found 15. 39± 1. 67, 38. 35± 0. 76 and 475. 51± 21. 15 Bq/kg respectively. The activity concentration of 238U and 232Th were less than the world average. But the activity concentration of 40K was higher than the world average values. These results were used to calculate the radiological hazard parameters like radium equivalent activities (Raeq), representative level index (Iγ r). Due to natural radionuclides in sediment, the effective annual outdoor dose in the study area was 0. 07 mSv; which is within the accepted range of 0. 07 mSv. The average value of radium equivalent activities (Raeq) and representative level index (Igr) were found to be 128. 03± 12. 08 Bq/Kg and 0. 96± 0. 09 Bq/Kg which were greater than the world average. The anthropogenic radionuclide 137Cs was also found in few samples. The average activity concentration of 137Cs was 1. 64± 0. 20 Bq/kg which is lower than the world average. The obtained experimental data of this research work would be useful to assess the population exposure from radionuclides in sediment as well as base line data of natural radioactivity in this island.

Background: Polyethylene composites including boron can be used as an effec ve neutron shield. Our inves ga on focuses on manufacturing borated polyethylene nano-composite. The purpose of this study is to design a radia on shield for use in both neutron and gamma fields. Materials and Methods: Borated polyethylene shields containing 2%, and 5% weight percentage of Boron nano-par cles were constructed and their neutron a$enua on was compared with pure polyethylene. Polycarbonate films were used to find the a$enua on of Am-Be neutrons a&er passing the shields. Mechanical proper es of the shields were finally compared. Results: Mean (± SD) number of α tracks induced by neutrons passing through the shields, were found to be 1. 0488×103± 128. 98, 289. 56± 103×1. 1972 and 1. 5340×103± 206. 52 for polyethylene with 5% by weight, polyethylene with 2% by weight boron nano-par cles, and pure polyethylene, respec vely. The neutron spectrum a&er each shield was also obtained by MCNP4C Monte Carlo simula ons. On the other hand, borated polyethylene nano-composites showed higher tensile strength compared to that of pure polyethylene. A$enua on of neutrons measured in experiments and the result of MCNP simula on were in good agreement. Conclusion: A sta s cally significant difference was found between neutron a$enua on by borated polyethylene nanocomposite made of 5% by weight boron and pure polyethylene. However, the difference between borated polyethylene nano-composite with 5% weight and 2% wt boron was not sta s cally significant.