International Journal of Radiation Research
Volume:14 Issue: 4, Oct 2016

Dose calculation algorithms play a very important role in predicting the explicit dose distribution. We evaluated the percent depth dose (PDD), lateral depth dose profile, and surface dose volume histogram in inhomogeneous media using calculation algorithms and inhomogeneity correction methods.
The homogeneous and inhomogeneous virtual slab phantoms used in this study were manufactured in the radiation treatment planning system to represent the air, lung, and bone density with planned radiation treatment of 6 MV photons, a field size of 10 × 10 cm2, and a source-to-surface distance of 100 cm.
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 relatively large differences (over 30%) in the field. There were large differences (20.0%–26.1%) at the second homogeneous–inhomogeneous junction (depth of 10 cm) in the field for all calculation 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.
The dose calculation uncertainties were shown to change at the interface between different densities and in varied densities using the dose calculation methods. In particular, the AXB algorithm showed large differences in and out of the field in inhomogeneous media.

This study assessed the optimal timing of computed tomography for detection of metastatic disease in locoregional lymph nodes in patients with rectal cancer who have undergone chemoradiotherapy.
This observational retrospective study was performed in a single institution. All patients 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 preoperative computed tomography were compared with postoperative pathologic lymph node status.
The study population consisted of 108 patients: Group A (nodal negative on preoperative computed tomography, n = 52) and Group B (nodal positive on preoperative computed tomography, n = 56). Analysis of the computed tomography scans in Group A revealed a high ability (98.07%) to predict negative lymph nodes, compared to 58.92% for predicting positive lymph nodes in Group B.
The results of this study suggest that the optimal timing of computed tomography for assessing lymph nodes after neoadjuvant chemoradiotherapy for rectal cancer is after 6 weeks; this timing might be key for prediction of complete clinical responses.

This study describes the possibility of implementing three-dimensional printing technology to create a precise construction of a planned bolus, based on computed tomography information stored in the Digital Imaging and Communications in Medicine (DICOM) format file.
To create the bolus with a 3D printer, we converted data in the DICOM format to the stereolithography (STL) format. In addition, we produced a paraffin bolus that, traditionally, is manually placed directly on the patient. CT scans were acquired for both boluses, and the images were superimposed onto the patient CT scans that were used to design the bolus. The superimposition 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 traditional way. In addition, for both models, the dose distribution was simulated. To quantify 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.
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%.
A bolus printed on a three-dimensional 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

stereotactic body radiotherapy (SBRT) has emerged as an effective treatment for localized prostate cancer. However, prostate-specific antigen (PSA) kinetics after SBRT has not been well characterized. The objective of the current study is to analyze the rate of PSA decline and PSA nadir following hypofractonated SBRT in localized prostate cancer.
From 2008 to 2014, thirty-nine patients 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 fractions of 7.25 Gy were administered. No one received androgen deprivation therapy (ADT). PSA nadir and rate of change in PSA (slope) were calculated and compared.
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, respectively, for durations of 1, 2 and 3 years after radiotherapy, respectively. The decline of PSA was maximal in the first year and continuously decreased for durations of 2 and 3 year. The median PSA nadir was 0.28 ng/mL after a median 33 months. There was one biochemical failure, occurring in a high risk patient. 5-year actuarial biochemical failure (BCF) free survival was 94.2%.
In this report of localized prostate cancer, continuous decrease of PSA level for duration 1, 2 and 3 year following SBRT using Cyberknife resulted in lower PSA nadir. Also, SBRT leaded to long-term favorable BCF-free survival.

An effective polymer gel dosimeter can be fabricated by varying the composition of its chemical components.
The MAGAT gel dosimeter formulations that used different compositions of Methacrylic acid (MAA) and gelatin were extensively investigated in the present study according to the R2–dose response and R2–dose sensitivity. The irradiation of MAGAT gel was performed by 6-MV photon beam at a dose range 1 to 10 Gy and was imaged by 1.5T Magnetic Resonance Imaging (MRI). The dose response of MAGAT gel dosimeter was obtained from spin-spin relaxation rate (R2) of MRI signal.
The MAGAT gel dosimeter composed of 5% gelatin and 6% MAA gave the highest sensitivity (1.1180 s-1Gy-1).
Understanding the effects of the compositional changes will help to clarify the mechanisms involved in the dose response of the MAGAT gel dosimeter.

This study presents patient specific and organ dose estimation in computed tomography (CT) imaging of thorax directly from patient CT image using Monte Carlo simulation. Patient's CT image is considered as the patient specific phantom and the best representative of patient physical index in order to calculate specific organ dose.
EGSnrc /BEAMnrc Monte Carlo (MC) System was used for CT scanner simulation and DOSXYZnrc was used in order to produce patient specific phantom and irradiation of photons to phantom in step and shoot mode (axial mode). In order to calculate patient thorax organ dose, patient 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/particle were converted to absorbed dose in unit of mGy by a conversion factor (CF). We calculated patient thorax organ dose in MC simulation from all irradiated slices, in 120 kV and 80 kV photon energies.
Effective dose was obtained from organ dose and organ weighting factor. Esophagus and spinal cord received the lowest, and bone received the highest dose. In our study, effective dose in CT of thorax was 7.4 mSV and 1.8 mSv in 120 and 80 kV, respectively.
The results of this study might be used to provide the actual patient organ dose in CT imaging and calculation of real effective dose based on organ dose.

Natural background radiation of a particular region is one of the distinctive 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 evaluating the annual effective dose to the population residing in this area.
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 locations. The activity concentration of 232Th, 238U and 40K in the samples were analyzed using gamma spectrometry. The outdoor external gamma ray dose rates were evaluated from the activity concentration of 40K, 238U and 232Th in the soil samples collected from the study area.
The average indoor gamma dose measured using TLDs were found to be 1219 µGy y-1. The measured activity 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 effective dose equivalent to population residing in the island has been estimated and is found to be 0.68 mSv y-1 for indoors and 0.32 mSv y-1 for outdoors.
The annual effective dose equivalent to population estimated 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.

Inhalation of radon and its short-lived decay products is one of the ýmost significant sources of exposure to natural radiation. Radon is the second cause ýof lung cancer in the populations. The present study was carried out under the projects of ýnational radon, with the aim of determining the concentration of indoor in the city of Qom ýlocated in the central semi-arid region of Iran.ý
Radon measurements were carried out in 123 dwellings ýusing passive sampling with CR-39 detectors for 90 days. The map of radon ýconcentration distribution was prepared using Arc GIS software and the statistical ýanalysis was performed with SPSS version 20.
Indoor radon concentrations in Qom dwellings ranged from 15–259 Bq ým-ýý3ý. The arithmetic mean of indoor radon concentrations on basement, ground floors, ýfirst floors and second and upper floors were ý123.43, 87.94, 63.72 and 40.69ýþ þBq m-3, ýrespectively.
A correlation was found between the distances from fault zones and measured ýindoor radon concentration. In most of cases, radon values were lower in well- ýventilated dwellings in comparison with poorly-ventilated ones. Moreover, high radon ýconcentration levels were observed in basements. The results indicated that in 30 ýplaces (24.3% of cases), the radon concentrations were higher than the reference levels ýrecommended by the World Health Organization (100 Bq m-3).

To suggest South India CT diagnostic reference levels (DRLs) by collecting radiation doses for the most commonly performed CT examinations.
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.
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.
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.

In this study a series of basic dosimetric properties of a low-density (LD) gel dosimeter are investigated. The dose response is studied regarding to linearity, sensitivity, dose-rate and energy dependence as well as lung tissue equivalence.
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. Investigation 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 identical preparation, irradiation and imaging procedure at three different days. Moreover the linearity and sensitivity were investigated up to 30Gy.
The results showed that the dose response was reproducible. The gel response was found linear up to 22Gy with r2=0.981 and sensitivity 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 tissue equivalent with mass density 0.37 to 0.4g/cm3 and relative electron density 0.41.
MAGAT LD gel dosimeter appears to be a promising dosimeter in all aspects of dosimetric properties evaluated in this study. In addition, its high linearity together with no dose rate dependence in different level of absorbed doses makes it a suitable dosimeter to measure 3D-dose distributions inside a non-homogeneous media.

Although it is one of the most toxic nonradioactive 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 electromagnetic fields including laptop computers, mobile phones, MRI and mobile phone jammers have been evaluated by our laboratory in our previous investigations. In this study, we aimed to evaluate the effect of X ray exposure on microleakage of amalgam restoration.
Standardized class V cavities 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 filtration. The absorbed dose was 245.0 ± 0.5 µGy. All specimens were placed in 2 % basic fuchsin solution for 24 hours. Then the specimens were sectioned and microleakage was assessed according to dye penetration using a stereomicroscope. Statistical analysis was performed with the Mann-Whitney U-test.
Microleakage was significantly higher in the X-ray exposed teeth compared to those of the non-irradiated samples.
The results of the present study suggest that X-ray exposure increased microleakage of amalgam restorations

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 potentially cause a series of health problems including cancers of the digestive 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 potentially cause a series of health problems including cancers of the digestive system.
226Ra has been determined in drinking water samples collected from various locations of Guilan province of Iran. The water samples are taken from public water and urban tap water sources. For evolution of gross a and b exposure precipitation method and proportional scintillator system was used. The radon emanation method was used to measure the radium concentration in drinking water.
The measurements showed the gross α and β concentration ranges were between The average concentration of 226Ra was found (7.6 mBq l-1) in drinking water samples and the average annual effective dose, from the digestion of 226Ra in water samples was calculated to be 1.5 µSv y-1. According to UNSCEAR, the annual effective dose value by ingestion is report to be 0.12 mSv y-1.

Radon concentration was measured in the soil and indoor of Amman and Al- Rusaifa cities in Jordan during summer season.
The measurement was performed using time-integrated passive radon dosimeters, containing a solid state nuclear track plastic detector, commercially known as CR-39.
Radon concentration 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 concentration in the first floor in Amman was 44.8± 5.3 (Bq/m3); while the average concentration 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 ratio reaches to 56% of the soil.
The average indoor radon concentration indoor in Al-Rusaifa exceeds the action radon level recommend by WHO (100 Bq/m3). The potential 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 correlation between the radon concentration 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 (Iγr). 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.

Polyethylene composites including boron can be used as an effective neutron shield. Our investigation focuses on manufacturing borated polyethylene nano-composite. The purpose of this study is to design a radiation shield for use in both neutron and gamma fields.
Borated polyethylene shields containing 2%, and 5% weight percentage of Boron nano-particles were constructed and their neutron attenuation was compared with pure polyethylene. Polycarbonate films were used to find the attenuation of Am-Be neutrons after passing the shields. Mechanical properties of the shields were finally compared.
Mean (± SD) number of α tracks induced by neutrons passing through the shields, were found to be 1.0488×103±128.98, 1.1972×103±289.56and 1.5340×103±206.52 for polyethylene with 5% by weight, polyethylene with 2% by weight boron nano-particles, and pure polyethylene, respectively. The neutron spectrum after each shield was also obtained by MCNP4C Monte Carlo simulations. On the other hand, borated polyethylene nano-composites showed higher tensile strength compared to that of pure polyethylene. Attenuation of neutrons measured in experiments and the result of MCNP simulation were in good agreement.
A statistically significant difference was found between neutron attenuation 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 statistically significant.