International Journal of Radiation Research
Volume:16 Issue: 3, Jul 2018

Using high energy X-rays (>10 MV) as a radiotherapy boost in treating oropharyngeal cancers (OPC) to reduce mandible radiation exposure may result in deterioration of disease control rates due to re-build-up of X-rays at the tumor surface. Therefore, we retrospectively compared the treatment outcomes and toxicities in OPC patients treated with radiotherapy using 15 MV and/or 4–6 MV X-rays as a boost. Between 2008 and 2014, 63 OPC patients received definitive 3-dimensional conformal radiotherapy. The median total dose was 70.2 (range, 46.8–75.6) Gy. The median follow-up period for surviving patients was 48 (range, 9–88) months. Twenty-one patients (33.3%) received a boost employing 15 MV X-ray in at least one beam during treatment, and 42 patients (66.7%) received only 4–6 MV X-rays. Local control (LC), locoregional control (LRC), disease-free survival (DFS), overall survival (OS) rates and the incidence of osteoradionecrosis (ORN) in the mandible for the two cohorts were estimated using the Kaplan-Meier method and compared using the log-rank test. There were no statistically significant differences between the two cohorts in either treatment outcomes (3-year LC, 81% versus 75% [p=0.742]; 3-year LRC, 71% versus 71% [p=0.925]; 3-year DFS, 66% versus 66% [p=0.934]; 3-year OS, 65% versus 78% [p=0.321]) or incidence of grade >2 ORN in the mandible (9.5% versus 11.9% [p=0.883]). Employing 15 MV X-rays in a boost may provide comparable treatment outcomes to 4–6 MV X-rays. However, reduction in the incidence of ORN in the mandible was not demonstrated.

To compare the following techniques for hypofractionated whole-breast irradiation (WBI) with simultaneous integrated boost (SIB) after breast-conserving surgery (BCS): three-dimensional conformal radiation therapy plus electron boost (3DCRT-EB), intensity-modulated radiation therapy (IMRT) plus EB (IMRT-EB), field-in-field IMRT plus EB (FIF-IMRT-EB), FIF-IMRT plus IMRT boost (FIF-IMRT-IB), IMRT plus IMRT boost (IMRT-IB), and volumetric-modulated arc therapy (VMAT) plus VMAT boost (VMAT-VB). Twenty patients with left breast cancer were enrolled. The prescribed dose was 40.05 Gy in 15 fractions to the whole breast and an SIB to the tumor bed of 3.2 Gy/fraction (total, 48 Gy). Target-volume coverage, dose-conformity index, homogeneity index (HI), doses to organs at risk (OAR), and costs were compared. FIF-IMRT-EB performed the best, while FIF-IMRT-IB, IMRT-IB, and VMAT-VB performed the worst. The mean dose to the planning target volume for breast evaluation (PTV Eval-breast) was significantly lower for IMRT-EB and FIF-IMRT-EB than for the other plans. For both PTV Eval-breast and PTV Eval-boost, VMAT-VB had the lowest target-volume coverage for 95% of the prescription dose and the highest target-volume coverage for >105% of the prescription dose. Among the six plans, VMAT-VB had the best HI for PTV Eval-boost and the highest doses to all OAR, except the coronary artery. Plans with EBs had lower mean doses for the contralateral lung and contralateral breast than plans with IMRT boosts. FIF-IMRT-EB had a low cost; plans with IMRT boosts had the highest costs. FIF-IMRT-EB may be the most suitable irradiation technique for hypofractionated WBI with SIB after BCS.

The purpose of this study was to evaluate the feasibility of a multi-purpose quality assurance (QA) phantom for pretreatment verification of volumetric modulated arc therapy (VMAT). The QA phantom was constructed with polymethyl methacrylate (PMMA) to perform relative dosimetry using EBT3 film and MapCHECK, as well as absolute dosimetry using an ionization chamber. The QA phantom was constructed to perform relative dosimetry using EBT3 film and MapCHECK, as well as the absolute dosimetry using ionization chamber. In order to verify the pretreatment plans, 25 patients treated with VMAT were selected. The pretreatment plans were calculated in the Eclipse treatment planning system using the Acuros XB dose calculation algorithm and CT images for the QA phantom, with the same beam setup and monitor units (MUs) as those for patient treatment. All plans were delivered to the Varian TrueBeam accelerator equipped with a high-definition multi-leaf collimator. The multi-purpose QA phantom is developed for convenient VMAT dose verification. By using the QA phantom, all 25 cases passed ±3% acceptability criteria in absolute dosimetry with an ionization chamber for pretreatment verification. The relative dosimetry using EBT3 film and MapCHECK system also showed high agreement of more than 90% for 2%/2-mm and 3%/3-mm criteria. The results of this study demonstrated the good multi-purpose capabilities of the phantom for the absolute and relative dosimetry. Therefore, the developed multi-purpose QA phantom was applied in our institution for routine VMRT dose verification.

In the tube current modulation (TCM) technique, tube current is changed dynamically during the scanning process. To quantify the effect of a dynamic tube current, a distinct calculator is needed to estimate the CT output radiation dose in terms of volume CT dose index (CTDIvol) and individual patient dose in terms of size-specific dose estimate (SSDE). This study developed a specific calculator for CT scanning using the TCM technique. The tube current was extracted from the DICOM header for every slice, and averaged over the scan length. The water equivalent diameter (Dw) and SSDE values were calculated for each tube rotation. The software was retrospectively applied to 57 patients who had undergone abdominal and thoracic CT examinations using a multi-detector CT, the Somatom Emotion 6. The differences between the calculated CTDIvol and the CTDIvol reported by the CT scanner were 4.4 ± 1.2% and 6.0 ± 2.0% for abdominal and thoracic examinations, respectively. The average tube current was found to be linearly correlated with Dw with R2 values of 0.707 and 0.696 for abdominal and thoracic examinations, respectively. The average tube current was also linearly and strongly correlated with the SSDE with R2 values of 0.941 and 0.887 for abdominal and thoracic examinations, respectively. Calculator for estimating CTDIvol and SSDE specifically for TCM in CT scanning has been successfully developed. The difference between calculated CTDIvol values using this calculator and reported CTDIvol values were less than 10%.

To study attenuation and increased skin dose for the iBEAM Standard couchtop, and attenuation of the BreastSTEP board, for an Elekta Compact 6 MV accelerator. Couchtop attenuation were measured for the range of gantry angles 125°-180° and field sizes 5×5-20×8 cm2. H&N extension and the BreastSTEP attenuations measured in an 8×8 cm2 field. The couchtop effect on percentage depth-dose (PDD) measured by an EFD diode for field sizes 5×5-20×20 cm2 and compared with that produced by a Co-60 beam passing through a ‘tennis-racket’ couch insert. A Monte Carlo (MC) model of the couchtop produced to provide more superficial PDDs. (PDDs that are more superficial) Maximum couchtop attenuation (7.6%) measured for the 135° gantry and 5×5 cm2 field. Couch extension attenuation was 1.5% lower. Adding BreastSTEP increased attenuation by 2.4%. MC attenuation results agreed with measurements to within 0.2%. The couchtop removed the dose buildup effect almost completely and increased the PDD at 0.4 mm depth by 60.6%-74.6%. MC-calculated PDDs at the depth range of skin basal cell layer (0.1-0.4 mm) increased by 55.3%-63.2%. The couch insert in the Co-60 beam increased the dose at 0.4 mm depth by 18.1%. For the same dose prescription at 10 cm depth, the insert in the Co-60 beam produced a skin dose 49.7% lower than the couchtop at 6 MV. These results provide useful practical data on attenuation and skin dose increase applicable to many centres. The accelerator-couchtop combination creates a greater skin dose increase than a tennis-racket insert on a Co-60 unit.

Modern radiation therapy such as intensity modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT) has resulted in using small therapeutic photon beams. The scope of this work is to investigate the variation in efficiency of different ionization chambers and semiconductor diodes in small multi-leaf collimator (MLC) defined fields of ARTISTE linear accelerator. Dose distributions measurements was done in field sizes ranging from 0.5×0.5 to 10×10 cm2 combining with Monte Carlo (MC) simulation. The treatment head of linac and the detectors were simulated by means of BEAMnrc/DOSXYZnrc of EGSnrc MC. The parameters such as output ratio (OR), penumbral width, dosimetric field size and the percentage surface dose in small radiation fields was evaluated using ionization chambers and semiconductor dosimeters. ORs and beam profiles resulting from various measurements showed significant difference between ionization chambers and diodes in small fields. Derivation of less than 2% was observed between EDGE and Diode P. ORs vary by more than 30% for 1×1 cm2 field size but, in larger field sizes differences was less than 1%. Penumbra underestimation was seen in Semiflex relative to pinpoint ionization chamber. No difference was seen in the pattern of surface dose among the applied detectors. Dosimetric characteristics of different detectors showed significant differences in small photon beams. Profiles and ORs analysis with different dosimeters showed that not only water equivalency of detectors, but also dosimeter active volume is important factors for determination of dosimetric behavior in small photon beams.

Calcium sennosides are the main active metabolites of sennas, which have a powerful interest to phytochemical and pharmacological research, due to their brilliant medicinal values. It is well known in folk medicine for their laxative and purgative uses. This experiment aimed to assess cytogenetic (micronucleus assay and chromosomal aberration study) and biochemical effects of calcium sennosides at a working dose (24 or 48 mg/ ml) on suppressing radiation hazards in human blood cultures. Biochemical investigations include superoxide dismutase (SOD), catalase (CAT), tumor necrosis factor-α (TNF-α), interleukin-8 (IL-8), cyclooxygenase-2 (COX-2) and lactate dehydrogenase (LDH) levels. The treatment periods were 48 and 72 hrs post-irradiation at a dose of 3 Gy. Triple blood cultures for each blood sample were set up. Ionizing radiation exposure induced significant increase in micronuclei (MN) frequencies in both mono- and bi- nucleated cells, and all types of chromosome aberrations, beside significant decrease in SOD and CAT activities. While TNF-α, IL-8, COX-2 and LDH levels were significantly increased after irradiation. Treatment with calcium sennosides exhibited decreased of micronuclei and chromosome aberration numbers and enhancement in the level of SOD and CAT activities. In addition, a significant amelioration in IL-8, TNF-α, COX-2 levels and LDH activity were scored. Present results revealed the antimutagenic and the anti-inflammatory effects of sennosides against oxidative stress induced by γ- irradiation.

Radioiodine I131 therapy (RAI) is an efficient method to decrease the functioning of very active thyroid tissues and to ablate the remnant thyroidal tissue after surgery and its metastases in differentiated thyroid carcinomas. Several cytoprotective, anti-oxidant or radioprotective mediators have been used in trials for RAI-induced damage in other organ systems. The hypothesis of this study was that zinc would ameliorate RAI-induced histopathological parameters in the rat gastrointestinal system. A total of 30 female Wistar albino rats were separated into 3 groups of 10. First group received only 0.003 mCi/g of I131, second group received 0.003 mCi/g of I131 and 0.01 mg/g of zinc and the control group (Sham Group) were given neither I131 nor zinc. Zinc was started via gastric gavage two days before I131 administration and continued for five days after RAI. At 24 hours after the last dosage of zinc, all the animals were sacrificed and the gastrointestinal tissues, including stomach, duodenum, ileum and colon were removed for histopathological examination. All the histopathological parameters were diminished in the I131-zinc group compared to the I131 group. The histopathological differences were statistically significant in respect of inflammation and fibrosis between the I131-zinc group and the I131 group in all the evaluated gastrointestinal organs (p< 0.05). The co-administration of zinc was observed to significantly prevent RAI-induced histopathological alterations in rats.

The presence of heavy metals and radon in water are considered as a potential threat to public health. Modern day industrialization has led to increase pollutants in ecosystem whilst the main source of public radiation exposure, especially exposure from radon, is caused by portable water. This study aimed to estimate the health risk related to radon concentration and heavy metals in drinking and irrigated water. Water samples, from different sources, were collected from Kulim, Malaysia and analyzed for radon and heavy metals using RAD7 and Atomic Absorption Spectrometry. Results showed that the maximum average value of radon concentration (16.06±1.7) Bq/l was found in well water used for drinking and irrigation. Minimum average value of radon concentration (2.65±0.33) Bq/l was found in tap water used for drinking purpose. From the measured radon concentrations, age dependent associated annual effective doses and contribution of radon in drinking water to indoor air was calculated which were found below the lower limit of recommended action level. Metal concentrations were found higher in stream and lake waters used for irrigation, compared to well and tap waters. The average daily intake of drinking water and health risk indices were found higher for infants and lower for children and adults. Radon concentrations in well, stream and lake waters were found higher than EPA recommended level and lower than WHO action level while the annual effective doses and level of heavy metals in water reported in this study were found lower than recommended levels.

Oil exploration is known to have great impact on the environment due the presence of natural radionuclides in crude oil and bitumen. In this study, high purity germanium (HpGe) detector was used to determine the activity concentrations of 40K, 226Ra and 232Th in bituminous soil and viscous bitumen samples collected from 5 different locations within the tar-sand belt of southwest Nigeria. Soil samples were collected also from a non tar-sand area to serve as control. The average concentrations of 40K, 226Ra and 232Th in the bituminous-soil samples were 139.32, 28.21 and 27.13 Bq kg-1, respectively for Agbabu, 16.09, 18.71 and 17.99 Bq kg-1, respectively for Ilubirin, 33.98, 38.90 and 29.82 Bq kg-1, respectively for Iju Oke, 35.01, 30.06 and 21.52 Bq kg-1, respectively for Ode Aye, 7.99, 4.77 and 4.08 Bq kg-1, respectively for Ode Irele. Their respective values were 306.82, 23.52 and 23.14 Bq kg-1 for the non bituminous-soil. The natural radioactivity levels of 40K, 226Ra and 232Th in the viscous bitumen samples ranged from below detection level (BDL)-30.74, 2.02-36.33 and 3.38-33.71 Bq kg-1, respectively. The estimated gamma dose rate was higher in the non-bituminous soil than that of bituminous soil. All the radiation hazard indices estimated in this study are lower than the acceptable limits. It can therefore be concluded that the soil and bitumen samples are safe for use as materials for building and road constructions.

Indoor and outdoor gamma radiation exposure levels were measured in a total of 360 randomly selected dwellings categorized as local, semi-modern and modern buildings across Ondo State, Nigeria to determine the annual effective doses. All radiation measurements were taken using a calibrated Kindenoo PG-15 Geiger Muller detector and a GPS for geographical coordinates of sample points. Equal number (360) sample point measurements were carried out for indoor and outdoor measurements. Measurements at each location point were performed holding the survey meter at 1 m above ground surface or floor to avoid unwanted effects of radiation from soil or building floor. The detector was also held at least six to seven meters away from buildings nearby in order to avoid unwanted effects of the building materials on outdoor measurements. Each measurement was repeated six times and the average was taken to represent the value for a sample point. The average outdoor and indoor dose rates were determined as 263 ± 32 μSvh-1 and 213 ± 64 μSvh-1 respectively. The highest contribution to the total indoor dose was from the local buildings followed by semi modern buildings and the modern buildings contributed the least dose. The average annual effective dose was calculated as 1.56 ± 0.33 mSv, which is higher than the world average value (0.48 mSv). In view of the potential radiation resulting from building materials, comprehensive assessment of natural radiations in such materials is required.

Total α- and β- as well as radium isotopes (226Ra, 228Ra) and uranium isotopes (234U, 238U) activity concentrations were determined in six most popular Tunisian bottled mineral waters samples. Total alpha/beta activity was measured by background gas-flow proportional counting system, and the activity concentrations of uranium were studied by radiochemical separation procedures followed by alpha spectrometry and that of radium isotopes by gamma-ray spectrometry. The total-a activity ranged from 48 to 94 mBq L−1 and the total-b activity between 45 and 430 mBq L−1. The activity concentrations of 238U, 234U, 226Ra and 228Ra in water samples varied in range 3.3 - 22.5 mBq.L−1, 4.0 - 34.2 mBq L−1, 2.0 - 67.0 mBq L−1 and 2.0 - 30.2 mBq L−1, respectively. These values are comparable with those reported for many other countries in the world for different types of water. The 234U/238U activity ratio were found to be higher than 1 in all cases. Based on the activity concentration results obtained in this study, the estimated annual ingestion dose rates for three different age groups (< 1 year, 7-12 years, and > 17 years) due to the ingestion of radium and uranium isotopes through drinking water are lower than the limit of intake prescribed by WHO. The annual doses exceed the recommended value of 0.1 mSv y-1 in one case for age group < 1 year. According Based on the activity concentration results obtained in this study, the estimated annual ingestion dose rates for three different age groups (< 1 year, 7-12 years, and > 17 years) due to the ingestion of radium and uranium isotopes through drinking water are lower than the limit of intake prescribed by WHO. The annual doses exceed the recommended value of 0.1 mSv y-1 in one case for age group < 1 year.

The expression alterations of specific miRNAs were analysed in response to gamma-irradiation in two breast cancer cell lines MCF-7 and MDA-MB-231 with low and high BCSCs content to design probable strategies for sensitizing breast cancer stem-like cells MDA-MB-231 to radiation. The expression levels of hsa-miR-34a, hsa-let-7i and hsa-miR-21 were assessed by QRT-PCR in MCF-7 and MDA-MB-231 breast cancer cells at three time points after gamma irradiation using three different doses. The results showed that the over-expression of hsa-miR-34a in MCF-7 cells was much more significant than MDA-MB-231 cells. Furthermore, there was a considerable over-expression of hsa-miR-21 in MDA-MB-231 cells following exposure to ionizing radiation (IR). The hsa-let-7i expression changes were different, depending on radiation dose, time post irradiation and cell type. According to the results, we may be able to sensitize stem-like MDA-MB-231 breast cancer cells to radiation by increasing miR-34a and decreasing miR-21 expression levels simultaneously.

The aim of this study was to compare the radiation dose to ipsilateral lung and heart for different radiotherapy (RT) techniques including; two tangential photon beams, electron therapy and combined photon-electron. Treatment planning of the mentioned techniques on the CT images of a chest phantom was done using treatment planning system (TiGRT, Lina Tech, China). According to the plans, the phantom was irradiated with 6 MV photon and 10 MeV electron beams of Siemens Primus linac. Radiation dose was also measured using LiF Thermo Luminescence Dosimeter (TLD) which was placed inside 3 mm depth holes of ipsilateral lung and heart on the phantom. The mean (± SD) radiation dose to the ipsilateral lung of the combined photon-electron was 66.12 ± 5.16% of prescribed dose. Whereas for the heart, it was 64.05 ± 2.62%. Mean (± SD) dose of ipsilateral lung and heart for electron irradiation was 54.51 ± 3.88 % and 34.21 ± 3.41%, respectively. The mean (± SD) radiation dose to ipsilateral lung and heart of the tangential was 50.73 ± 3.01 % and 31.36 ± 3.13%, respectively. The mean (± SD) radiation dose to the chest wall-lung interface for electron therapy (72.44 ± 2.01 %) was significantly different in comparison with tangential (65.23± 4.20%; p = 0.045) and combined photon-electron (68.14± 3.53 %; p = 0.032). Tangential beams is more suitable for treating mastectomy patients compared to the other techniques such as electron therapy and combined photon-electron, due to lower radiation dose to patient's ipsilateral lung and heart.