International Journal of Radiation Research
Volume:10 Issue: 3, Jan-Oct 2012

Although there are substantial experimental, epidemiological and clinical evidences that high doses of ionizing radiation cause cancer and other detrimental biological effects, the health effects of human exposure to chronic low dose radiation exposures are still poorly known. People in some areas around the world live in dwellings with radiation and radon levels as much as more than 200 times the global average. Inhabited areas with high levels of natural radiation are found in different areas around the world including Yangjiang, China; Kerala, India; Guarapari, Brazil and Ramsar, Iran. Ramsar in northern Iran is among the world’s well-known areas with highest levels of natural radiation. Annual exposure levels in areas with elevated levels of natural radiation in Ramsar are up to 260 mGy y-1 and average exposure rates are about 10 mGy y-1 for a population of about 2000 residents. Due to the local geology, which includes high levels of radium in rocks, soils, and groundwater, Ramsar residents are also exposed to high levels of alpha activity in the form of ingested radium and radium decay progeny as well as very high radon levels in their dwellings. Based on the findings obtained by studies on the health effect of high levels of natural radiation in Ramsar, as well as other high background radiation areas, no consistent detrimental effect has been detected so far. Further research is needed to clarify if the regulatory authorities should set limiting regulations to protect the inhabitants against such extraordinary elevated levels of natural radiation

Breakfast cereal is a nutritious type of food that is widely consumed by various age groups in Kuwait. This study investigates the presence of long-lived gamma emitters in breakfast cereal, and estimates annual effective doses to various age groups. Breakfast cereal samples were collected from the Kuwaiti local market. The samples originated from different countries. After proper lab treatment, the samples underwent gamma spectroscopy, where the targeted radionuclides were 226Ra, 232Th, and 40K. While 40K was detected in all samples, 226Ra and 232Th were detected in most samples. The activity concentration of each targeted radionuclide varied from one sample to another. The annual effective dose from consumption of breakfast cereal is estimated to be 129, 185, and 351 μSv for the adult, child, and infant age groups respectively. The obtained activity concentrations are found to agree with those reported in the literature. Moreover, the estimated annual effective doses are found to be safe.

To reduce uncertainties of patient positioning, the Computerized Tomography (CT) images acquired at the treatment planning time can be compared with those images obtained during radiation dose delivery. This can be followed during dose delivery procedure as Image Guided radiotherapy (IGRT) to verify the prescribed radiation dose delivery to the target as well as to monitor radiation dose constraints for organ at risks located in the vicinity of tumour region. A method was developed to compare registered rigid CT images with those acquired during treatment procedure. Several CT images were acquired for a typical Rando phantom at head and neck region. Selecting the CT images as reference, they were then manipulated in transitional and rotational directions. The differences in transited and rotated images were evaluated by edge detection algorithms and conventional automatic contouring used in most of current treatment planning systems. Setting of standard edge detection algorithms was investigated and the appropriate one was selected. Applying the selected optimized standard edge detection algorithm and conventional auto-contouring on CT image differences, the characteristics of methods were evaluated. Results show that 1 pixel difference in transition and 1 degree in rotation can be recognized for inhomogeneous regions. A significant variation was detected at the bony-soft tissue and air-soft tissue conjunction regions. The results obtained from the current study are comparable with those reported using Chamfer algorithm. It is concluded that the current method, can be used to control patient positioning in radiotherapy sessions as a part of Image guided radiotherapy protocols.

We aimed to compare field-in-field technique (FIF) with conformal tangential field radiotherapy (CRT) in terms of dosimetric benefits for early stage breast cancer radiotherapy. Twenty consecutive left-side breast cancer patients who underwent breast-conserving surgery were included to the study. For each patient, two different treatment plans were created for the entire breast. FIF plans and CRT plans were compared for doses in the planning target volume (PTV), the organ at risk (OAR) volume including ipsilateral lung, heart, left ascending coronary artery (LAD) and the contralateral breast, the homogeneity index (HI), and the monitor unit (MU) counts required for the treatment. Paired samples t-test was used for statistical analysis. The FIF technique significantly reduced the maximum dose of the PTV as well as the mean doses of the heart, LAD, ipsilateral lung and the contralateral breast (p values were <0.001 for each). When the OAR volumes irradiated with 2, 5, 10, 20, 30 and 40 Gy were compared, the results were in favor of the FIF technique. The volume receiving <20 Gy of the prescription dose for the ipsilateral lung was significantly decreased using FIF technique (p<0.001). FIF technique allowed us more homogenous dose distribution with lower MUs. The FIF technique provided better dose distribution in the PTV and significantly reduced the doses in the OAR. Considering the lower MUs required for treatment the FIF technique seems to be more advantageous than CRT during whole breast irradiation.

The radiation doses resulting from diagnostic X-ray examinations are routinely measured in terms of entrance surface dose (ESD) and effective dose (ED). In this study, for the purpose of radiation protection, the radiation doses received from Digital chest X-ray examination were evaluated in terms of ESD and ED. The ED was calculated by using the MCNP Monte Carlo code and an adult hermaphrodite mathematical phantom. The effects of both operating high voltage and projection geometry on the effective dose were investigated. The absolute values of the ED were calculated for digital and conventional Posterior-Anterior (PA) and Lateral (LAT) projections of chest radiography. The results show ED for PA projection in digital chest radiography in some major hospitals is higher than National Diagnostic Reference Level (NDRL). Therefore optimization process should be considered seriously at national level to reduce patient exposure in digital chest radiography in Iran.

To evaluate the dosimetric difference between conventional and three-dimensional conformal Radiotherapy (3D-CRT) using 6 and 18 MV X-ray photons. Computed tomography scans of 26 pelvic patients were acquired and transferred to the 3D treatment planning system. For each patient, 8 Conventional plans (3, 4, 5 and 6 Fields) and one 3D-CRT plan were prepared using 6 and 18 MV photon energies. The minimum dose (Dmin), maximum dose (Dmax) and mean dose (Dmean) to target (PTV) and organs at risk (OAR), Integral dose, Homogeneity Index and Conformity Index were compared for each plan. Also, Experimental measurements were performed using farmer ionization chamber on a patient based pelvic phantom. On Average, six-field (6F1) plans, offer minimum dose to critical organs and sufficient dose to prostate. Increasing the beam energy lead to a decrease in Dmean of the bladder and femoral heads, as well as Dmax of PTV. The CI and ID were decreased by 4% and 11% respectively with increasing the energy and the number of beams. Experimental measurements were also in good agreement with calculations. 3D-CRT reduced Dmean of bladder, rectum and femoral heads and also CI and ID were significantly improved by 44.6% and 30.8%, respectively. Increasing the photon energy and number of beams, improve the treatment parameters of bladder, femoral heads and PTV, except the rectum. 3D-CRT offered the most conformity in the delivery doses to the prostate while sparing dose to OARs, uninvolved structures with lower integral dose.

In most cancer cases, the treatment choice for a pregnant patient is radiotherapy. In these patients, the abdomen is usually not exposed; therefore fetus exposure is due to peripheral dose (PD). The purpose of this study was to estimate the fetal dose (the maximum PD in each pregnancy stage) for modalities available and to fabricate and evaluate a generally applicable fetal shield. PD values were measured for brain, breast and mediastinum irradiation in a whole body anthropomorphic phantom using a NE 2571 ionization chamber. An external shield was then designed to reduce the fetal dose to the standard dose limit, 5 mSv. The range of PD values as a function of distance from the field’s edge were as follows 1) 9.4-259 cGy for Mantel field; 2) 6.5-95 cGy for chest wall irradiation with 10 MeV electrons, 3) 8.5- 52.5 cGy for tangential field with Co-60 and 4) 4.8-7.8 cGy for brain radiotherapy with 9 MV photon. PD values for the same setups using the fetal shield were as follows: 1) 1.4-22 cGy, 2) 0.5-4 cGy, 3) 1.5-5 cGy and 4) under 1 cGy. The measured PD data sets can be used to estimate fetal dose for specific treatment setups and pregnancy stages. The use of external shield designed in this research reduced the fetal dose effectively to under the threshold (a 70-90% reduction), except for the final stages of pregnancy in Hodgkin’s patients.

Advances in radiation dosimetry concepts and the development of primary measurement standards based on absorbed dose to water over the last decades offer the possibility to calibrate ionisation chambers directly in terms of absorbed dose to water. The aim of this study is the investigation on utility of artificial body fluid (ABF) instead of water by comparing dosimetric measurements for radiotherapy between water and ABF which is more close to human tissue. The measurements were done using 60Co gamma source with a radiation field sizes of 5×5, 10×10, 15×15, 20×20 and 25×25 cm2 at PTW Freiburg MP3 water phantom front surface. The comparisons of the dose measurements were obtained by using IAEA TRS-398 dosimetry protocols and Mephysto mc2 dose analyzer program. Percent depth dose (PDD), dose profiles and penumbras are compared for water and ABF. When the results of the PDD for water and ABF were compared, the maximum difference was observed in big field sizes. The difference in penumbras was found 2.3 mm averagely for depth of maximum dose (dmax). In addition same differences were observed between water and ABF when the dose profiles were compared. It is found that PDD values taken for water are good agreed with PDD values published in British Journal of Radiology (BJR) Supplement 25. Since the ABF is more equivalent to human tissue than water, it is suggested that advanced dosimetric studies should be performed with ABF instead of water.

In some areas of Ramsar, a city in northern Iran, residents receive a much higher annual radiation exposure than is permitted for radiation workers. Induction of adaptive response in residents of Ramsar has been reported previously. In this study induction of such a response in short term exposure to high background levels of gamma radiation is investigated. Fifty male NMRI mice were randomly divided into four groups of 10-17 animals and 53 Wistar rats were randomly divided into five groups of 10-12 animals were studied. Animals in the 1st group were kept for 7 days in an outdoor area with normal background radiation while the 2nd, 3rd, 4th and 5th (in case of rats) groups were kept in 3 different outdoor areas with naturally elevated levels of gamma radiation. Animals were then exposed to a lethal dose of 8 Gy gamma radiation. For mice, 30 days after exposure to lethal dose, the survival fraction for the control group was 40% while the 2nd, 3rd, and 4th groups had survival rates of 20%, 33.30%, and 35.20%, respectively. For rats, 30 days after exposure to the lethal dose, the survival fraction for the control group was 40% while the 2nd, 3rd, 4th and 5th groups had survival rates of 20%, 41.6%, 60.0% and 35.7%, respectively. Results indicate that shortterm exposure to extremely high levels of natural gamma radiation (up to 196 times higher than the normal background) do not lead to induction of survival adaptive response.

Radiotherapy is an established therapeutic modality for prostate cancer. Resveratrol, a natural antioxidant, has been shown to inhibit carcinogenesis and to block the process of tumor initiation and progression. No data is available on the response of cellular spheroid to Reseveratol. In this study we have examined the effect of Resveratol on the radiation response of human prostate cell line DU145 in monolayer and spheroid cultures. Radiosensitivity was assessed using viability and colony formation assay. Apoptosis and necrosis were assessed using acridine orange/ ethidium bromide double staining. The colony formation assay did not show any significant radio-sensitizing effect, but apoptosis assay showed significant radio-sensitizing effect of Resveratol on DU145 cells grown as monolayer. In the spheroid cells the results of apoptosis test were not significant and corresponded closely to the result of survival curve. While Resveratol could sensitize DU145 cells in monolayer to ionizing radiation, it did not have any effect on sensitivity of cells cultured in spheroid cultures.

Radiotherapy is an established therapeutic modality for prostate cancer. Resveratrol, a natural antioxidant, has been shown to inhibit carcinogenesis and to block the process of tumor initiation and progression. No data is available on the response of cellular spheroid to Reseveratol. In this study we have examined the effect of Resveratol on the radiation response of human prostate cell line DU145 in monolayer and spheroid cultures. Radiosensitivity was assessed using viability and colony formation assay. Apoptosis and necrosis were assessed using acridine orange/ ethidium bromide double staining. The colony formation assay did not show any significant radio-sensitizing effect, but apoptosis assay showed significant radio-sensitizing effect of Resveratol on DU145 cells grown as monolayer. In the spheroid cells the results of apoptosis test were not significant and corresponded closely to the result of survival curve. While Resveratol could sensitize DU145 cells in monolayer to ionizing radiation, it did not have any effect on sensitivity of cells cultured in spheroid cultures.

Gold nanoparticles (GNPs) have been shown as a good radiosensitizer. In combination with radiotherapy, several studies with orthovoltage X-rays have shown considerable dose enhancement effects. This paper reports the dose enhancement factor (DEF) due to GNPs in 18 megavoltage (MV) beams. Different geometrical 50-nm GNPs configurations at a concentration of 5 mg/ml were used by both experimental and Monte Carlo (MC) simulation in a deep-seated tumor-like insertion within a phantom. Using MCNP repeated structure capability; a large number of gold nanospheres with a semi-random distribution were applied to simulate this phantom based study. Thermoluminescence dosimetries were used to verify the process of irradiation and MC simulation. Under geometries with different probable combinations of water and GNPs distribution in the tumor, the percentage depth dose and DEF were calculated. Incorporation of GNPs into the radiation field in our set-ups showed a 12% DEF. We show that the method of nanoparticles, distribution, and orientation can effectively change the DEF value.

Ultraviolet (UV) radiation is divided into three regions: UVA, UVB, and UVC. Both the quality and quantity of solar UV radiation vary with various factors including the elevation of the sun above the horizon, as well as absorption and scattering of UV photons by molecules in the atmosphere, notably ozone and clouds. It is clear that whereas a moderate amount of UV exposure is beneficial, too much is detrimental, so there is a need to quantify variations of solar UV on the earth surface, at different time intervals. The measurement of solar UV radiation in Yazd city was achieved by two radiometers: 1) a special UVA light meter with maximum sensitivity to 365nm in the range of 320- 390nm and 2) a radiometer with a probe for 280-320 nm in UVB radiation. Measurement duration was from 1st January to the end of December 2008 and from sunrise to sunset, every one hour. Daily integral UVA radiation in December with the lowest (0.38×105Jm-2) and July with the highest intensity (5.26×105Jm-2) were found. The minimum and maximum monthly UVA radiation on the ground level of Yazd city were 25.8×105Jm-2 in December and 128.7×105Jm-2 in July, respectively. Based on UVB /UVA ratio the UVB intensity at 12 oclock is 25 times lower than the UVA. Therefore, the integrated hourly UVB in this time is equal to 3.13 kjm-2 and almost the effective UVB is 1.56 kJm-2 so the minimum required exposure time of UVB radiation for one SDD and MED by hands and head are about 22 and 110 minutes respectively.

More than 50% of the total dose received by human beings from all sources of radiation (both from natural and manmade) comes from radon and its progeny which is responsible for lung cancer in many cases. In the present study, the measurements have been carried out by using twin chamber dosimeter cups with LR-115 type-II detectors. The value of track density of detectors gives the concentration of radon, thoron and their progeny in different modes. The average value of radon and thoron concentration was found 59 and 28 Bq/m3, respectively. The inhalation dose was found to vary from 1.6 to 2.9 mSv/y. The average value of PAEC for radon and thoron was found 6.4 mWL and 0.75 mWL, respectively. Total annual exposure and annual effective dose varies from 0.23 to 0.39 WLM and 0.87 to 1.51 mSv/y respectively. The values of life time fatality risk was found to vary from 0.68 x 10-4 to 1.18 x 10-4. These measurements show that the radon/thoron concentrations and annual effective dose received by the population of the area are well below the action level recommended by the International Commission on Radiological Protection (ICRP).

Osteoid osteoma (OO) is a relatively common skeletal neoplasm, frequently involves long bones. OO of rib is extremely rare, including 0.23-2% of OO cases. Most of them arose in posterior arc, frequently in its head or neck and might lead to painful scoliosis. Involvement of anterior aspect of a rib is extremely rare. Skeletal scintigraphy is highly sensitive for detection of OO. “Double density sign"; a typical pattern in bone scintigraphy is usually seen in OO of cortical bones. The current study presents a case of 22-year-old man with OO in anterior arc of a rib, revealed double density sign on 99mTc-MDP scan.

I would like to discuss about some important aspects regarding the article published in, "Iran. J. Radiat. Res., 2012; 10(2): 89-94“with title of “Patient doses from X-ray computed tomography examinations by a single-array detector unit: Axial versus spiral mode" by Ghavami et al. (1), so according to journal policy and in suitable manner please ask the authors to reply to the comments.