International Journal of Radiation Research
Volume:9 Issue: 3, Jul 2011

We have validated the monitor unit calculations from a commercially available treatment planning system (TPS) for three intensity modulated radiotherapy (IMRT) planning techniques for tangential breast irradiation by using ionization chamber measurements. Treatment plans were generated for forty-two breast patients by a forward planned field in field technique, electronic tissue compensation (ETC), and an inverse planned sliding window technique. We also performed a reproducibility of delivery and dose linearity analysis for each technique. The treatments were delivered to a phantom using a Varian CL21EX linear accelerator. A 2571 0.6 cm3 Farmer type ionization chamber and Farmer 2570/1 electrometer from NE Technology was used to measure output of the linear accelerator and the dose at predefined point in the verification plan. The agreement between the measured and calculated dose was -0.87% ± 0.54% for field in field technique, -0.74% ± 0.23% for electronic tissue compensators, and -1.26% ± 0.48% for the inverse planning technique and. In terms of reproducibility the mean deviation was -1.10% ± 0.44% for the field in field technique, -0.38% ± 0.42% for electronic tissue compensators, -1.04% ± 0.42% for inverse planning technique. Dose linearity experiments showed no significant variations for clinical situations but a breakdown was observed in relative dose for very low monitor units. We have found that the monitor unit calculations for all three planning techniques are correct to the order of 1%, and that the plans can be delivered in a reproducible and accurate manner.

Craniospinal radiotherapy faces technical challenges which are due to the sensitivity of the location in which the gross tumor is, and to organs at risk around planning target volume. Using modern treatment planning systems causes a reduction in the complexities of the treatment techniques. The most effective method to assess the dosimetric accuracy and the validity of the software used for treatment planning is to investigate the radiotherapy and treatment planning by means of a anthropomorphic Rando phantom which was used here for treatment planning and practical dosimetry for craniospinal radiotherapy. Studying the absorbed dose by the organs at risk was the secondary objective discussed in this paper. Treatment planning in craniospinal radiotherapy was done using CorePlan 3D treatment planning software. Radiotherapy was administered on a anthropomorphic Rando phantom and practical dosimetry was done using GR-200 TLDs. Varian Clinac 2100C/D was used for radiotherapy. The absorbed dose by regions of interest was separately calculated for treatment planning and radiotherapy. Except the conjunction areas of the cranial and spinal radiation fields, the difference among the results was not more than 5%. Full comparison of the results for each part has been presented. The comparison the results of practical dosimetry and treatment planning software supports the validity of CorePlan treatment planning system. Also analysis of the absorbed dose through organs at risk showed that the absorbed dose by organs at risk have an acceptable value with respect to tolerance dose of these organs. The only unacceptable result was related to thyroid.

Radiotherapy Treatment Planning requires different dosimetric quantities as input in order to calculate a desired dose distribution. This study has been focused to evaluate the depth dose characteristics of superficial X-rays being used for radiotherapy treatment. Computerized 3-D water phantom of multi-data system was used. The measurements were made through PTW (Physikalirsch-Technische Werkstalten) farmer type NT-30006 waterproof ionization chamber of 0.6cc, and PTW electrometer for digital dose rate reading in Gy/min using five different diameter applicators and filters at five different values of accelerating potentials (kVps). The dose rate at various kVp X-ray beams was observed to decrease significantly with increasing depth in water phantom for all applicator diameters from 98% (at 0.1cm depth) down to 43% (at 2cm i.e. reference condition). The dose rate increases by increasing the value of kVp with a maximum at 150 kVp (1.6 and 0.93 Gy/ min for respective applicator diameters 2.5cm and 10cm). Applicator with 2.5cm diameter demonstrates better dose rate at 85kVp at different depths. PDD decreases lower than 50% for all combination of applicators and kVps at/or above 2cm depth so these measurements should not be considered for treatment planning. Higher energy X-rays are suggested to be used for applicators of higher diameters and smaller energy X-rays for applicators having smaller diameters.

Chromosomal alterations play an important role in carcinogenesis. Enhanced chromosomal radiosensitivity is shown for many cancer predisposition conditions including breast cancer. In this study chromosomal radiosensitivity and the frequency of background sister chromnatid exchanges (SCE) in lymphocytes of normal individuals and breast cancer patients was compared. G2 assay was performed on peripheral blood lymphocytes obtained from 60 breast cancer patients and 50 normal control. Blood culture was initiated and cells were irradiated with 1 Gy gammarays 4 h prior to harvesting. After metaphase preparations and slide making, chromatid aberrations were scored. For SCE studies, blood samples from 30 breast cancer patients and 30 normal control were studied. 24 hours after culture initiation, 5- bromodeoxy uridine (BrdU) was added and cells were harvested 48 hours after addition of BrdU. Slides were stained in Hoechst 33258 and exposed to UVA source, then stained in Giemsa. Results indicated that the frequency of radiation induced chromatid breaks was significantly higher in breast cancer patients compared to normal control (p<0.01). From radiosensitivity point of view, 12% of normal control and 47% of breast cancer patients showed elevated chromatid radiosensitivity. Frequency of background SCE was significantly higher in lymphocytes of breast cancer patients compared to lymphocytes of control (p<0.05). Elevated chromosomal radiosensitivity and higher frequency of SCE in lymphocytes of breast cancer patients might be indicative of genomic instability of these cells. Increased radiosensitivity could also be due to defects in DNA repair genes involved in breast cancer formation.

While in the open air the amount of radon gas is very small and does not pose a health risk, in confined spaces, radon can accumulate to relatively high levels and become a health hazard. Exposure to high levels of radon has been associated with an increased risk of lung cancer, depending on the time length of exposure. Radon level in dwelling of Shiraz with 1,200,000 populations has been sampled and analyzed in this study. Our study could be considered the largest radon study in Iran both time and area wise. In this study, radon (222Rn) concentration in residential dwellings in Shiraz-Iran was sampled and measured during two consecutive six month periods in 2009- 2010. We used Solid State Nuclear Track Detectors (SSNTD), CR-39 polycarbonate films. The survey parameters of radon concentrations were floor types, construction materials and dwelling’s age. Annual average indoor radon concentration for the survey period was 94±52 Bq/m3. The calculated mean annual effective doses in basements and different floors were less than the lowest limit recommended action level of 3 mSv by ICRP. High radon concentrations are measured in basements and old dwellings; however, due to rapidly changing housing structures and ventilation practices with no intervention, lower levels of radon concentration has been expected in Shiraz.

The effect of natural background radiation on health is still controversial. However, it is clear that it depends on the dose received by the population. The estimation of external natural background gamma rays received by the population of Caspian coastal provinces in the northern part of Iran was the main goal of this study. Gamma rays was measured using calibrated radiation survey meter in 51 urban and rural health centers randomly to estimate the exposure to population (Total population = 6888118 persons) in residential areas of Gilan, Mazandaran and Golestan (Total area 59240 Km2) as Caspian coastal provinces, North of Iran. Results showed that the average dose rate in the areas under study was about 60.37±14.88 nSv/h or 0.53 mSv/yr (Range 30 to 90 nSv/h or 0.26 to 0.79 mSv/yr). The data from Ramsar was excluded from the estimation because of its very high natural background radiation (Max. 240 mSv/yr). No significant difference was found among the doses of the provinces (P=0.237). The external natural background gamma ray dose to the population of Caspian coastal provinces, North of Iran, was found to be almost equal to the average value in the world (0.5 mSv/yr).

Natural radioactivity in materials under certain conditions can reach the hazardous radiological levels. So, it becomes necessary to study the natural radioactivity in different materials to assess the dose for the population in order to know the health risks and to have a baseline for future changes in the environmental radioactivity due to human activities. The present study deals with the measurement of radioactivity using “γ-ray spectrometry” from naturally occurring radionuclides in the soil, stone and sand samples used as building materials in North-Eastern Haryana state of India. The places are in the vicinity of Shivalik range of Himalayas. The activity concentrations for 226Ra, 232Th and 40K varied from 18±1.5 to 156±6Bqkg‑1, 23±1 to 300±5Bqkg‑1 and 32±0.5 to 1705±14 Bqkg‑1 respectively in various samples. The absorbed dose rate in soil, sand and stone samples is investigated at 1 m above ground level. Ra equivalents, Internal and external hazard indices have also been calculated. The natural radioactivity levels measured in the samples under present study are below the recommended limits except for black stone (SB) and red stone (SR). However, these samples satisfy the universal standards.

In previous investigations, it has been clarified that electromagnetic fields (ELF) can cause some changes in cellular behavior. The aim of this prospective study was to investigate the effect of magnetic field (MF) on human sperm parameters of motility, morphology, and viability. Semen samples were collected from 12 fertile men, and were allowed to liquefy for 15-30 min. Each sample was then divided into two aliquots. The experimental samples were placed in the ELF, while the control one was left intact. The applied fields were pulsed with distance of 6 m/ sec and effective intensity of 1mT and different frequencies of 10, 25 and 45 Hz at different time intervals. The constant field intensity was 1mT in all experiments. In frequency of 10Hz, an increase in quick motility of sperm (1.8 times) occurred after 4h; however, slow motility was decreased by 40% after 2h. Also, the quick motility increased by 1.6 times in frequency 25 Hz after 4 h, while the MF had no effect on other sperm parameters. MF had no effect on any of sperm parameters in frequency of 40 Hz in 4 h. The stimulation ratio on the sperm viability was only significant at frequency of 10 Hz after 2 h after incubation. The sperm morphology was not influenced in any of the fields. This study reports the existence of certain frequency windows for the resonance of the effects of the MF on human spermatozoa. Rapid motility was significantly affected by the exposure of spermatozoa to MF, but sperm structural parameter had remained intact.

Desmoplastic small round cell tumor is a rare malignant tumor that occurs primarily in young males. Here, a case of small round cell tumor in an adult male successfully treated with a curative concurrent chemoradiotherapy is presented. A 58-year-old man had an intrapelvic tumor. Surgical resection was attempted, but the tumor was unresectable. Needle biopsy was performed and the diagnosis was suggested to be desmoplastic small round cell tumor. Concurrent chemoradiotherapy was performed, and a complete response was obtained. This patient has been alive for 8 years after treatment with no evidence of disease. Concurrent chemoradiotherapy appears to be a useful treatment choice for unresectable desmoplastic small round cell tumor.

Sir, the big flooding in Thailand in 2011 is one of the problematic flooding in Asia. It causes several destroying to many things in the disaster areas. An important concern is on the effect on the setting with the radioactive elements usage. In Thailand, there are some places with radioactive elements including to the university, hospital as well as radioactive research center. Luckily, during the disaster period, there is no report on radioactive elements leakage. The interesting focus is on the way that each setting protect itself from flooding. In many places with small usage of radioactive elements, the replacing of the radioactive substances and machines is done. The cases of hospital is very interesting, some hospitals with radiotherapy unit were flooded but they previously replace the radioactive elements and machine to the safe place. The more problematic place as the radiation research center had to make more serious preventive means. The use of heavy big and high giant barrier to protect the building was used and the good first structural plan of the building helped a lot in prevention of the problem. However, there is the problem of transportation of the radioactive element for using in medical purposes. This caused the delay for treatment of many cancerous patients. Indeed, the flooding might be the cause of uncontrolled distribution of radioactive elements and can be serious public health problem (1, 2). Although there is no problem in this disaster, it is suggested that any site should have their own preventive protocol to correspond to the possible flooding and other disaster.