Monte Carlo modelling of cyclotron and radioisotope center (CYRIC) at Tohoku University: a radiation protection study.

Protection against ionizing radiations is important in laboratories with radioactive materials and high energy cyclotron beams. The Cyclotron and Radioisotope Center (CYRIC) located in Tohoku University in Miyagi prefecture, Japan and is a well-known nuclear science laboratory with cyclotron beams and substantial number of high activity radioactive materials. Considering this, it is important to perform complete radiation transport computations to ensure the safety of non-occupational and occupational workers. In the present work, we have developed a complete 3-dimensional model of the main cyclotron building and radiation labs using Monte Carlo method. We have found that the dispersed photons and neutrons inside and in the surrounding of the CYRIC building pose no significant risk to occupational and non-occupational workers. The present work and the developed models would be useful in the field of radiation protection.

Application of a Machine Learning Method for Prediction of Urban Neighborhood-Scale Air Pollution.

Urban air pollution has aroused growing attention due to its associated adverse health effects. A model which could promptly predict urban air quality with considerable accuracy is, therefore, important and will benefit the development of smart cities. However, only a computational fluid dynamics (CFD) model could better resolve the dispersion behavior within an urban canyon layer. A machine learning (ML) model using the Artificial Neural Network (ANN) approach was formulated in the current study to investigate vehicle-derived airborne particulate (PM10) dispersion within a compact high-rise-built environment. Various measured meteorological parameters and PM10 concentrations were adopted as the model inputs to train the ANN model. A building-resolved CFD model under the same environmental settings was also set up to compare its model performance with the ANN model. Our results showed that the ANN model exhibited promising performance (r = 0.82, fractional bias = 0.002) when comparing the > 1000 h PM10 measurements. When comparing the diurnal hourly measured PM10 variations in a clear-sky day, both the ANN and CFD models performed well (r > 0.8). The good performance of the CFD model relied on the knowledge of the in situ diurnal traffic profile, the adoption of suitable mobile source emission factor(s) (e.g., from MOBILE 6 and COPERT4), and the use of urban thermal and dynamical variables to capture PM10 variations in both neutral and unstable atmospheric conditions. These requirements/constraints make it impractical for daily operation. On the contrary, the ML (ANN) model adopted here is free from these constraints and is fast (less than 0.1% computational time relative to the CFD model). These results demonstrate that the ANN model is a superior option for a smart city application.

Properties and gene expression profiling of acquired radioresistance in mouse breast cancer cells.

BACKGROUND: Acquired radioresistant cells exhibit many characteristic changes which may influence cancer progression and further treatment options. The purpose of this study is to investigate the changes of radioresistant human epidermal growth factor receptor 2 (HER2)-positive breast cancer cells on both phenotypic and molecular levels. METHODS: We established an acquired radioresistant cell line from its parental NF639 cell line (HER2-positive) by fractionated radiation and assessed changes in cellular morphology, proliferation, migration, anti-apoptosis activity, basal reactive oxygen species (ROS) level and energy metabolism. RNA-sequencing (RNA-seq) was also used to reveal the potential regulating genes and molecular mechanisms associated with the acquired changed phenotypes. Real-time PCR was used to validate the results of RNA-seq. RESULTS: The NF639R cells exhibited increased radioresistance and enhanced activity of proliferation, migration and anti-apoptosis, but decreased basal ROS. Two main energy metabolism pathways, mitochondrial respiration and glycolytic, were also upregulated. Furthermore, 490 differentially expressed genes were identified by RNA-seq. Enrichment analysis based on Gene Ontology and Kyoto Encyclopedia of Genes and Genomes showed many differently expressed genes were significantly enriched in cell morphology, proliferation, migration, anti-apoptosis, antioxidation, tumor stem cells and energy metabolism and the signaling cascades such as the transforming growth factor-ß, Wnt, Hedgehog, vascular endothelial growth factor, retinoic acid-inducible gene I (RIG-I)-like receptor, Toll-like receptor and nucleotide oligomerization domain (NOD)-like receptor were significantly altered in NF639R cells. CONCLUSIONS: In clinical radiotherapy, repeat radiotherapy for short-term recurrence of breast cancer may result in enhanced radioresistance and promote malignant progression. Our research provided hints to understand the tumor resistance to radiotherapy de novo and recurrence with a worse prognosis following radiotherapy.

Highly Sensitive and Cost-Effective Portable Sensor for Early Gastric Carcinoma Diagnosis.

Facile and efficient early detection of cancer is a major challenge in healthcare. Herein we developed a novel sensor made from a polycarbonate (PC) membrane with nanopores, followed by sequence-specific Oligo RNA modification for early gastric carcinoma diagnosis. In this design, the gastric cancer antigen CA72-4 is specifically conjugated to the Oligo RNA, thereby inhibiting the electrical current through the PC membrane in a concentration-dependent manner. The device can determine the concentration of cancer antigen CA72-4 in the range from 4 to 14 U/mL, possessing a sensitivity of 7.029 µAU-1mLcm-2 with a linear regression (R2) of 0.965 and a lower detection limit of 4 U/mL. This device has integrated advantages including high specificity and sensitivity and being simple, portable, and cost effective, which collectively enables a giant leap for cancer screening technologies towards clinical use. This is the first report to use RNA aptamers to detect CA72-4 for gastric carcinoma diagnosis.

External Cesium-137 doses to humans from soil influenced by the Fukushima and Chernobyl nuclear power plants accidents: a comparative study.

External exposure to gamma-photon irradiation from soil contamination due to nuclear power plant (NPP) accidents has significant contribution to human radiation exposure in the proximity of the NPP. Detailed absorbed doses in human organs are rarely reported in the literature. We applied the Monte Carlo Neutron Particle (MCNP) transport code to calculate and compare the absorbed doses in different human organs. The absorbed doses by gamma-photon radiation were from cesium-137 (137Cs) in soil contaminated by the two major NPP accidents. More serious and wide-spread impacts of the Chernobyl NPP accident on soil contamination in Ukraine, Belarus, Russia and countries as far as Sweden and Greece were due to the inland location, radiative plume transport pathway and high 137Cs emission strength (9 times the Fukushima emission). Based on our MCNP calculations, the largest absorbed dose was found in skin. The maximum calculated external 137Cs annual effective dose received from the Chernobyl accident was 10 times higher relative to the Fukushima accident. Our calculated effective doses at various influenced areas were comparable to those available in the literature. The calculated annual effective doses at areas near the Fukushima and Chernobyl NPPs exceeded the ICRP recommendation of 1 mSv yr-1.

Gating a Single Cell: A Label-Free and Real-Time Measurement Method for Cellular Progression.

There is an ever-growing need for more advanced methods to study the response of cancer cells to new therapies. To determine cancer cells' response from a cell-mortality perspective to various cancer therapies, we report a label-free and real time method to monitor the in situ response of individual HeLa cells using a single cell gated transistor (SCGT). As a cell undergoes apoptotic cell death, it experiences changes in morphology and ion concentrations. This change is well in line with the threshold voltage of the SCGT, which has been verified by correlating the data with the cell morphologies by scanning electron microscopy and the ion-concentration analysis by inductively-coupled plasma mass spectrometry (ICPMS). This SCGT could replace patch clamps to study single cell activity via direct measurement in real time. Importantly, this SCGT can be used to study the electrical response of a single cell to stimuli that leaves the membrane intact.

Relationship between pedestrian-level outdoor thermal comfort and building morphology in a high-density city.

Urban compact buildings impose large frictional drag on boundary-layer air flow and create stagnant air within the building environment. It results in exacerbating the street-level outdoor thermal comfort (OTC). It is common to perform in-situ measurements of the OTC in different urban forms and to study their relationship. However, it is impossible to do so from a planning perspective because of the absence of physical planned urban forms. Our objective was to quantify the thermal environment and OTC in different planned complex urban forms by well-validated numerical models. We coupled a computational fluid dynamics (CFD) model to an OTC (Rayman) model to study the OTC. The κ-ω SST turbulent model was adopted for the CFD simulations, with accuracy of the turbulent model validated by wind tunnel measurements. The highest calculated air temperature within the street canyon of a planned bulky urban form could reach more than 5 °C higher than the surrounding environment. Within the tested urban forms, our coupled model predicted mean radiant temperature comparable with measurements in the literature. The model also produced sensible street-level physiologically equivalent temperatures (PETs) when comparing with those listed in the human thermal sensation categories. In the morning, the predicted PETs within all the urban forms were lower than that in open areas, which indicated that the shading of buildings effectively reduced the PET increase due to solar irradiance. At noon, increases in PETs by more than 10 °C relative to the morning situation indicated that when the buildings acted as heat sources after insolation absorption, increase in the air temperature at the street intersection and in the street canyon made an important contribution to the receiver PETs. The reduction in building lengths and increase in the low-level porosity were the most effective ways to reduce the heat stress at the pedestrian-level.

Size Controllable and Surface Tunable Zeolitic Imidazolate Framework-8-Poly(acrylic acid sodium salt) Nanocomposites for pH Responsive Drug Release and Enhanced in Vivo Cancer Treatment.

Nanoscale size controllable and surface modifiable zeolitic imidazolate framework-8-poly(acrylic acid sodium salt) (ZIF-8-PAAS) nanocomposites are fabricated by employing PAAS nanospheres as a soft template. These ZIF-8-PAAS nanocomposites have different sizes ranging from 30 to 200 nm and exhibit different crystallinity, and pH sensitivity. These nanocomposites can be employed as vectors to deliver doxorubicin for anticancer therapy, leading to greatly enhanced drug therapeutic efficacy when tested in cell lines and mice model. Systematic toxicity investigation including hematoxylin and eosin staining analysis of tumor and major organs, hematology analysis, and blood chemistry analysis indicates that the nanocomposites possess high biocompatibility. This work provides a strategy to make metal-organic frameworks (MOFs) nanocomposites with size tunability in nanoscale and flexible surface modification for various applications.

Public health risk of mercury in China through consumption of vegetables, a modelling study.

Sample measurement of mercury (Hg) contents is a common method for health risk assessment of Hg through vegetable consumption in China. In the present work, we undertook the first modelling study which produced consistent health-risk maps for the whole eastern China. Regional maps of Probable Daily Intake (PDI) of Total mercury (THg) and Methylmercury (MeHg) over the studied area were produced, which were important for the researchers and policy-makers to evaluate the risk and to propose mitigation measures if necessary. The model predictions of air-borne Hg(0) concentrations agreed well with the observations and simulated Hg distribution over China as reported elsewhere. Our calculated PDIs of THg in vegetables were also comparable to those reported in the literature. There was 19% of the studied area with PDIs > 0.08µgkg-1 bw d-1 [half of the reference dose (RfD)]. The PDI for THg (MeHg) varied from 0.034 (0.007) to 0.162 (0.035)µgkg-1 bw d-1 with an average of 0.058 (0.013)µgkg-1 bw d-1. The highest calculated PDIs of THg over China was equal to the RfD, while the calculated PDIs of MeHg were well below the RfD of 0.1µgkg-1 bw d-1. The health risk was of concern through consumption of THg in leafy vegetables, rice/wheat and fish in Liaoning Provinces, Hunan, Zhejiang and Guizhou Provinces, with the associated PDIs exceeding the RfD. Despite this, the heath risk of MeHg exposure for the general population in southern China from the same foodstuff consumption was not a concern. The contribution of consumption through leafy vegetation should be considered when THg and MeHg exposures to the population are evaluated. The results improve our understanding in managing public health risk in China especially in large cities with high population, and thus have important contribution to enhance sustainable urbanization as one of the principle goals under the framework of the Nature-Based Solution (NBS).

Intracellular Delivery: Diamond-Nanoneedle-Array-Facilitated Intracellular Delivery and the Potential Influence on Cell Physiology (Adv. Healthcare Mater. 10/2016).

G. Zhu, W. Zhang, X. Chen, and co-workers show on page 1157 that diamond needle arrays can efficiently deliver biomolecules into living cells. The study paves the way to a wide application of the nanonneedle treatment by systematically investigating the influence of the treatment on metabolic signal pathways.

Self-Assembly of Electron Donor-Acceptor-Based Carbazole Derivatives: Novel Fluorescent Organic Nanoprobes for Both One- and Two-Photon Cellular Imaging.

In this study, we report fluorescent organic nanoprobes with intense blue, green, and orange-red emissions prepared by self-assembling three carbazole derivatives into nanorods/nanoparticles. The three compounds consist of two or four electron-donating carbazole groups linked to a central dicyanobenzene electron acceptor. Steric hindrance from the carbazole groups leads to noncoplanar 3D molecular structures favorable to fluorescence in the solid state, while the donor-acceptor structures endow the molecules with good two-photon excited emission properties. The fluorescent organic nanoprobes exhibit good water dispersibility, low cytotoxicity, superior resistance against photodegradation and photobleaching. Both one- and two-photon fluorescent imaging were shown in the A549 cell line. Two-photon fluorescence imaging with the fluorescent probes was demonstrated to be more effective in visualizing and distinguishing cellular details compared to conventional one-photon fluorescence imaging.

Diamond-Nanoneedle-Array-Facilitated Intracellular Delivery and the Potential Influence on Cell Physiology.

Vertical arrays of nanostructures can provide access to the cell cytoplasma and probe intracellular molecules. Here, the simple combination of diamond nanoneedle arrays with centrifugation-induced supergravity is shown to efficiently deliver drugs and biomaterials into the cytosol within several minutes, negotiating the endocytososomal system. The potential influence of the technique on cell metabolism is thoroughly studied. By detecting the phosphorylated histone variant H2AX (pH2AX) in the nucleus, it is proved that the operating process will not lead to DNA double-strand breaks. However, the mechanical disruption can temporarily improve the permeability of the cell membranes. Nanoneedle treatment affects cell metabolism at multiple points. The treatment can slightly elevate the apoptotic signal in A549 cells and can significantly increase the production of reactive oxygen species (ROS) in cells, particularly if combined with anticancer drugs. Meanwhile, the activity of cytosolic glucose 6-phosphate dehydrogenase (G6PD) is also raised to counterbalance the elevated ROS content. A detected depolarization of the mitochondrial membrane potential suggests mitochondrial involvement in the intracellular redox reactions and cell apoptosis which are induced by diamond nanoneedle treatment. Overall this study provides a novel understanding on the intracellular delivery mediated by nanoneedles, especially the impact on cell physiology.

Self-Monitoring and Self-Delivery of Photosensitizer-Doped Nanoparticles for Highly Effective Combination Cancer Therapy in Vitro and in Vivo.

Theranostic nanomedicine is capable of diagnosis, therapy, and monitoring the delivery and distribution of drug molecules and has received growing interest. Herein, a self-monitored and self-delivered photosensitizer-doped FRET nanoparticle (NP) drug delivery system (DDS) is designed for this purpose. During preparation, a donor/acceptor pair of perylene and 5,10,15,20-tetro (4-pyridyl) porphyrin (H2TPyP) is co-doped into a chemotherapeutic anticancer drug curcumin (Cur) matrix. In the system, Cur works as a chemotherapeutic agent. In the meantime, the green fluorescence of Cur molecules is quenched (OFF) in the form of NPs and can be subsequently recovered (ON) upon release in tumor cells, which enables additional imaging and real-time self-monitoring capabilities. H2TPyP is employed as a photodynamic therapeutic drug, but it also emits efficient NIR fluorescence for diagnosis via FRET from perylene. By exploiting the emission characteristics of these two emitters, the combinatorial drugs provide a real-time dual-fluorescent imaging/tracking system in vitro and in vivo, and this has not been reported before in self-delivered DDS which simultaneously shows a high drug loading capacity (77.6%Cur). Overall, our carrier-free DDS is able to achieve chemotherapy (Cur), photodynamic therapy (H2TPyP), and real-time self-monitoring of the release and distribution of the nanomedicine (Cur and H2TPyP). More importantly, the as-prepared NPs show high cancer therapeutic efficiency both in vitro and in vivo. We expect that the present real-time self-monitored and self-delivered DDS with multiple-therapeutic and multiple-fluorescent ability will have broad applications in future cancer therapy.

Induction of Non-Targeted Stress Responses in Mammary Tissues by Heavy Ions.

PURPOSE: Side effects related to radiation exposures are based primarily on the assumption that the detrimental effects of radiation occur in directly irradiated cells. However, several studies have reported over the years of radiation-induced non-targeted/ abscopal effects in vivo that challenge this paradigm. There is evidence that Cyclooxygenase-2 (COX2) plays an important role in modulating non-targeted effects, including DNA damages in vitro and mutagenesis in vivo. While most reports on radiation-induced non-targeted response utilize x-rays, there is little information available for heavy ions. METHODS AND MATERIALS: Adult female transgenic gpt delta mice were exposed to an equitoxic dose of either carbon or argon particles using the Heavy Ion Medical Accelerator in Chiba (HIMAC) at the National Institute of Radiological Sciences (NIRS) in Japan. The mice were stratified into 4 groups of 5 animals each: Control; animals irradiated under full shielding (Sham-irradiated); animals receiving whole body irradiation (WBIR); and animals receiving partial body irradiation (PBIR) to the lower abdomen with a 1 x 1 cm2 field. The doses used in the carbon ion group (4.5 Gy) and in argon particle group (1.5 Gy) have a relative biological effectiveness equivalent to a 5 Gy dose of x-rays. 24 hours after irradiation, breast tissues in and out of the irradiated field were harvested for analysis. Induction of COX2, 8-hydroxydeoxyguanosine (8-OHdG), phosphorylated histone H2AX (γ-H2AX), and apoptosis-related cysteine protease-3 (Caspase-3) antibodies were examined in the four categories of breast tissues using immunohistochemical techniques. Analysis was performed by measuring the intensity of more than 20 individual microscopic fields and comparing the relative fold difference. RESULTS: In the carbon ion group, the relative fold increase in COX2 expression was 1.01 in sham-irradiated group (p > 0.05), 3.07 in PBIR (p < 0.05) and 2.50 in WBIR (p < 0.05), respectively, when compared with controls. The relative fold increase in 8-OHdG expression was 1.29 in sham-irradiated (p > 0.05), 11.31 in PBIR (p < 0.05) and 11.79 in WBIR (p < 0.05), respectively, when compared with controls. A similar increase in γ-H2AX expression was found in that, compared to controls, the increase was 1.41 fold in sham-irradiated (p > 0.05), 8.41 in PBIR (p < 0.05) and 10.59 in WBIR (p < 0.05). Results for the argon particle therapy group showed a similar magnitude of changes in the various biological endpoints examined. There was no statistical significance observed in Caspase-3 expression among the 4 groups. CONCLUSIONS: Our data show that both carbon and argon ions induced non-targeted, out of field induction of COX2 and DNA damages in breast tissues. These effects may pose new challenges to evaluate the risks associated with radiation exposure and understanding radiation-induced side effects.

Reduction of Solar UV Radiation Due to Urban High-Rise Buildings--A Coupled Modelling Study.

Solar UV radiation has both adverse and beneficial effects to human health. Using models (a radiative transfer model coupled to a building shading model), together with satellite and surface measurements, we studied the un-obstructed and obstructed UV environments in a sub-tropical urban environment featured with relatively high pollution (aerosol) loadings and high-rise buildings. Seasonal patterns of the erythemal UV exposure rates were governed by solar zenith angles, seasonal variations of aerosol loadings and cloud effects. The radiative transfer modelling results agreed with measurements of erythemal UV exposure rates and spectral irradiances in UVA and UVB ranges. High-rise buildings and narrow road width (height to width, H/W, ratios up to 15) reduced the modelled total UV (UVA+UVB) radiation and leave 10% of the un-obstructed exposure rate at ground-level at noon. No more than 80% of the un-obstructed exposure rate was received in the open area surrounded by 20-storey buildings. Our modelled reduction of UVB radiation in the urban environment was consistent with similar measurements obtained for Australia. However, our results in more extreme environments (higher H/W ratios) were for the first time reported, with 18% of the un-obstructed exposure rate remained at the ground-level center of the street canyon.

Gene profiling characteristics of radioadaptive response in AG01522 normal human fibroblasts.

Radioadaptive response (RAR) in mammalian cells refers to the phenomenon where a low-dose ionizing irradiation alters the gene expression profiles, and protects the cells from the detrimental effects of a subsequent high dose exposure. Despite the completion of numerous experimental studies on RAR, the underlying mechanism has remained unclear. In this study, we aimed to have a comprehensive investigation on the RAR induced in the AG01522 human fibroblasts first exposed to 5 cGy (priming dose) and then followed by 2 Gy (challenge dose) of X-ray through comparisons to those cells that had only received a single 2 Gy dose. We studied how the priming dose affected the expression of gene transcripts, and to identify transcripts or pathways that were associated with the reduced chromosomal damages (in terms of the number of micronuclei) after application of the challenging dose. Through the mRNA and microRNA microarray analyses, the transcriptome alteration in AG01522 cells was examined, and the significantly altered genes were identified for different irradiation procedures using bioinformatics approaches. We observed that a low-dose X-ray exposure produced an alert, triggering and altering cellular responses to defend against subsequent high dose-induced damages, and accelerating the cell repair process. Moreover, the p53 signaling pathway was found to play critial roles in regulating DNA damage responses at the early stage after application of the challenging dose, particularly in the RAR group. Furthermore, microRNA analyses also revealed that cell communication and intercellular signaling transduction played important roles after low-dose irradiation. We conclude that RAR benefits from the alarm mechanisms triggered by a low-dose priming radation dose.

Trans-oceanic transport of 137Cs from the Fukushima nuclear accident and impact of hypothetical Fukushima-like events of future nuclear plants in Southern China.

A Lagrangian model was adopted to assess the potential impact of (137)Cs released from hypothetical Fukushima-like accidents occurring on three potential nuclear power plant sites in Southern China in the near future (planned within 10 years) in four different seasons. The maximum surface (0-500 m) (137)Cs air concentrations would be reached 10 Bq m(-3) near the source, comparable to the Fukushima case. In January, Southeast Asian countries would be mostly affected by the radioactive plume due to the effects of winter monsoon. In April, the impact would be mainly on Southern and Northern China. Debris of radioactive plume (~1 mBq m(-3)) would carry out long-range transport to North America. The area of influence would be the smallest in July due to the frequent and intense wet removal events by trough of low pressure and tropical cyclone. The maximum worst-case areas of influence were 2382000, 2327000, 517000 and 1395000 km(2) in January, April, July and October, respectively. Prior to the above calculations, the model was employed to simulate the trans-oceanic transport of (137)Cs from the Fukushima nuclear accident. Observed and modeled (137)Cs concentrations were comparable. Sensitivity runs were performed to optimize the wet scavenging parameterization. The adoption of higher-resolution (1° × 1°) meteorological fields improved the prediction. The computed large-scale plume transport pattern over the Pacific Ocean was compared with that reported in the literature.

The use of biologically related model (Eclipse) for the intensity-modulated radiation therapy planning of nasopharyngeal carcinomas.

PURPOSE: Intensity-modulated radiation therapy (IMRT) is the most common treatment technique for nasopharyngeal carcinoma (NPC). Physical quantities such as dose/dose-volume parameters are used conventionally for IMRT optimization. The use of biological related models has been proposed and can be a new trend. This work was to assess the performance of the biologically based IMRT optimization model installed in a popular commercial treatment planning system (Eclipse) as compared to its dose/dose volume optimization model when employed in the clinical environment for NPC cases. METHODS: Ten patients of early stage NPC and ten of advanced stage NPC were selected for this study. IMRT plans optimized using biological related approach (BBTP) were compared to their corresponding plans optimized using the dose/dose volume based approach (DVTP). Plan evaluation was performed using both biological indices and physical dose indices such as tumor control probability (TCP), normal tissue complication probability (NTCP), target coverage, conformity, dose homogeneity and doses to organs at risk. The comparison results of the more complex advanced stage cases were reported separately from those of the simpler early stage cases. RESULTS: The target coverage and conformity were comparable between the two approaches, with BBTP plans producing more hot spots. For the primary targets, BBTP plans produced comparable TCP for the early stage cases and higher TCP for the advanced stage cases. BBTP plans reduced the volume of parotid glands receiving doses of above 40 Gy compared to DVTP plans. The NTCP of parotid glands produced by BBTP were 8.0 ± 5.8 and 7.9 ± 8.7 for early and advanced stage cases, respectively, while those of DVTP were 21.3 ± 8.3 and 24.4 ± 12.8, respectively. There were no significant differences in the NTCP values between the two approaches for the serial organs. CONCLUSIONS: Our results showed that the BBTP approach could be a potential alternative approach to the DVTP approach for NPC.

The performance of the progressive resolution optimizer (PRO) for RapidArc planning in targets with low-density media.

A new version of progressive resolution optimizer (PRO) with an option of air cavity correction has been implemented for RapidArc volumetric-modulated arc therapy (RA). The purpose of this study was to compare the performance of this new PRO with the use of air cavity correction option (PRO10_air) against the one without the use of the air cavity correction option (PRO10_no-air) for RapidArc planning in targets with low-density media of different sizes and complexities. The performance of PRO10_no-air and PRO10_air was initially compared using single-arc plans created for four different simple heterogeneous phantoms with virtual targets and organs at risk. Multiple-arc planning of 12 real patients having nasopharyngeal carcinomas (NPC) and ten patients having non-small cell lung cancer (NSCLC) were then performed using the above two options for further comparison. Dose calculations were performed using both the Acuros XB (AXB) algorithm with the dose to medium option and the analytical anisotropic algorithm (AAA). The effect of using intermediate dose option after the first optimization cycle in PRO10_air and PRO10_no-air was also investigated and compared. Plans were evaluated and compared using target dose coverage, critical organ sparing, conformity index, and dose homogeneity index. For NSCLC cases or cases for which large volumes of low-density media were present in or adjacent to the target volume, the use of the air cavity correction option in PRO10 was shown to be beneficial. For NPC cases or cases for which small volumes of both low- and high-density media existed in the target volume, the use of air cavity correction in PRO10 did not improve the plan quality. Based on the AXB dose calculation results, the use of PRO10_air could produce up to 18% less coverage to the bony structures of the planning target volumes for NPC cases. When the intermediate dose option in PRO10 was used, there was negligible difference observed in plan quality between optimizations with and without using the air cavity correction option.

Solar ultraviolet radiation response of EBT2 Gafchromic, radiochromic film.

Measurement of solar ultraviolet (UV) radiation is an important aspect of dosimetry for the improved knowledge of UV exposure and its associated health related issues. EBT2 Gafchromic film has been designed by its manufacturers as an improved tool for ionizing radiation dosimetry. The film is stated as exhibiting a significant reduction in UV response. However, results have shown that when exposed to UV from the 'bottom side' i.e. from the thick laminate side, the film exhibits a sensitivity to solar UV radiation which is both measurable and accurate for UV dosimetry. Films were irradiated in this position to known solar UV exposures and results are quantified showing a reproducibility of measurement to within ±7% (1 SD) when compared to calibrated UV meters. With an exposure of 20 J cm(-2) broad spectrum solar UV, the films net OD change was found to be 0.248 OD ± 0.021 OD when analysing the results using the red channel region of an Epson V700 desktop scanner. This was compared to 0.0294 OD ± 0.0053 OD change with exposure to the same UV exposure from the top side. This means that solar UV dosimetry can be performed using EBT2 Gafchromic film utilizing the underside of the film for dosimetry. The main advantages of this film type for measurement of UV exposure is the visible colour change and thus easy analysis using a desktop scanner as well as its uniformity in response and its robust physical strength for use in outside exposure situations.