Cumulative Irradiation Research Articles

Development of TRAIL Resistance by Radiation-Induced Hypermethylation of DR4 CpG Island in Recurrent Laryngeal Squamous Cell Carcinoma

There are limited therapeutic options for patients with recurrent head and neck cancer after radiation therapy failure. To assess the use of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) as a salvage chemotherapeutic agent for recurrent cancer after radiation failure, we investigated the effect of clinically relevant cumulative irradiation on TRAIL-induced apoptosis. Using a previously established HN3 cell line from a laryngeal carcinoma patient, we generated a chronically irradiated HN3R isogenic cell line. Viability and apoptosis in HN3 and HN3R cells treated with TRAIL were analyzed with MTS and PI/annexin V-FITC assays. Western blotting and flow cytometry were used to determine the underlying mechanism of TRAIL resistance. DR4 expression was semiquantitatively scored in a tissue microarray with 107 laryngeal cancer specimens. Methylation-specific polymerase chain reaction and bisulfite sequencing for DR4 were performed for genomic DNA isolated from each cell line. HN3R cells were more resistant than HN3 cells to TRAIL-induced apoptosis because of significantly reduced levels of the DR4 receptor. The DR4 staining score in 37 salvage surgical specimens after radiation failure was lower in 70 surgical specimens without radiation treatment (3.03 ± 2.75 vs 5.46 ± 3.30, respectively; P<.001). HN3R cells had a methylated DR4 CpG island that was partially demethylated by the DNA demethylating agent 5-aza-2'-deoxycytidine. Epigenetic silencing of the TRAIL receptor by hypermethylation of a DR4 CpG island might be an underlying mechanism for TRAIL resistance in recurrent laryngeal carcinoma treated with radiation.

Factors affecting photoreactivation in UVB-irradiated herbivorous spider mite (Tetranychus urticae)

Ambient ultraviolet-B (UVB) radiation causes lethal damage to spider mites, and the extent of photochemical effects is determined by cumulative irradiance in the two-spotted spider mite, Tetranychus urticae. However, the LD50 values obtained using a UVB lamp were much lower than those elicited by solar UVB radiation. As solar radiation includes intense visible light and UVA, we assumed that a photoreactivation mechanism would play a role to survive under solar radiation. We assessed the capacity for photoreactivation in T. urticae eggs and larvae, and found that the efficacy of photoreactivation was determined by the cumulative irradiance of visible light (VIS) after exposure to UVB radiation. The wavelength range effective for photoreactivation went from UVA to green. Next, we found that an increased time lag between UVB and VIS radiation reduced the photoreactivation efficacy in eggs. In contrast, a time lag ≤4h did not affect that in larvae. We discussed the possibility that the timing of photoreactivation occurs related with phase-specific UVB vulnerability and outbreak symptoms due to UVB-induced DNA damage. Our results suggest that T. urticae depends on a photoreactivation mechanism, and that the photoreactivation efficiency probably caused the divergence in UVB impact between UV lamp and solar radiation.

Electrical characterization of 60Co gamma radiation-exposed InAlN/GaN high electron mobility transistors

In0.17Al0.83N/GaN high electron mobility transistors (HEMTs) were cumulatively subjected to 60Co gamma-ray irradiation doses up to 500 Mrad. Source–drain current–voltage characteristics (IDS-VDS) showed little change after lower dose gamma-ray irradiations (&amp;lt;200 Mrad). However, the electrical properties were significantly degraded after 500 Mrad irradiations, indicating that the radiation-induced damage near the active region of the devices was severe. The saturation current level at VGS = 0 V was degraded by 48% after 500 Mrad irradiation. The effective carrier removal rate was not linear with dose, but was 0.54 × 1010 cm−2 Mrad−1 in the range from 200 to 500 Mrad. The cumulative gamma-ray irradiation of In0.17Al0.83N/GaN HEMTs caused much larger reductions in drain–source current compared to AlGaN/GaN devices exposed under the same conditions.

Singlet Oxygen Generation by the Genetically Encoded Tag miniSOG

The genetically encodable fluorescent tag miniSOG is expected to revolutionize correlative light- and electron microscopy due to its ability to produce singlet oxygen upon light irradiation. The quantum yield of this process was reported as ΦΔ = 0.47 ± 0.05, as derived from miniSOG's ability to photooxidize the fluorescent probe anthracene dipropionic acid (ADPA). In this report, a significantly smaller value of ΦΔ = 0.03 ± 0.01 is obtained by two methods: direct measurement of its phosphorescence at 1275 nm and chemical trapping using uric acid as an alternative probe. We present insight into the photochemistry of miniSOG and ascertain the reasons for the discrepancy in ΦΔ values. We find that miniSOG oxidizes ADPA by both singlet oxygen-dependent and -independent processes. We also find that cumulative irradiation of miniSOG increases its ΦΔ value ~10-fold due to a photoinduced transformation of the protein. This may be the reason why miniSOG outperforms other fluorescent proteins reported to date as singlet oxygen generators.

Estimation of solar direct beam transmittance of conifer canopies from airborne LiDAR

The utility of airborne scanning LiDAR data to estimate solar direct beam canopy transmittance in complex, forested terrain was evaluated. Twenty-four hemispherical photos were used to produce ground-based estimates of solar direct beam canopy transmittance. The photo estimates were used to develop and evaluate two spatially distributed canopy transmittance models: 1) a Beer's Law-type transmittance model based on LiDAR-derived canopy metrics, and 2) a solar raytrace model applied to a three-dimensional canopy model. The models were used to estimate solar direct beam canopy transmittance at five-minute resolution for all days between the winter and summer solstices over an 800m by 700m domain at 1m horizontal grid spacing. When compared to estimates from hemispherical photos, the raytrace model resolved the complex seasonal and diurnal variability of solar direct beam canopy transmittance resulting from individual trees and localized canopy structure. The Beer's-type model was unable to resolve these detailed factors. The two models exhibited similar and relatively low normalized daily mean error values from December to early March. Later in the season (01 March–21 June), the model differences were pronounced; the daily mean and standard deviation of the error values for the Beer's-type and raytrace models were 13%±10% and 8%±6%, respectively. The results confirm previously known limitations of Beer's Law when used to estimate sub-canopy solar beam irradiance under heterogeneous canopy conditions. Averaged over the spatial domain, the Beer's-type model estimated 21% and 48% lower canopy transmittance than the raytrace model on 01 March and 03 May, respectively. The Beer's-type model was unable to represent the seasonal increase in areal average canopy transmission contributed from small canopy gaps. Finally, both distributed models were used to simulate the cumulative solar beam irradiance during the 2010 snowmelt season. The raytrace model was shown to capture a high level of variability necessary to simulate explicit stand-scale solar irradiance that strongly influences spatiotemporal patterns of snowmelt, soil water availability, and the partition and exchange of energy within heterogeneous forest ecosystems.

SU-E-T-49: Implementation of Optically Stimulated Luminescent Detectors in the Clinical Setting

Purpose: To perform experiments to determine how Optically Stimulated Luminescent Detectors (OSLDs) can be used for in vivo dosimetry in the clinical environment. For clinical use, OSLDs should have stable, reproducible behavior in measuring dose and be easy to use. Methods: OSLDs were placed in solid water at dmax, with 12cm of solid water below for backscatter, and were irradiated with a TG51 calibrated linac at 10MV, 100SSD and with a 10x10 cm2 field. The OSLDs were of the Nanodot type from Landauer; the Landauer microStar reader was used to measure photomultiplier counts. No modifications were made to the reader, e.g., use of special filters. OSLDs were irradiated to a variety of dose levels which could be encountered in the clinic, as well as levels of 200Gy or more. OSLDs were bleached after each irradiation with a compact fluorescent light source. Results: Without preirradiation to relatively high doses, OSLDs displayed non-stabilized supralinear behavior in plots of counts versus dose; dosing histories where cumulative dose is acquired solely in amounts comparable to clinical levels, e.g., <10Gy per irradiation, do not yield useful detectors; the counts versus dose curve continues to change significantly with acquired cumulative irradiation until cumulative dose reaches 250Gy or more. However, irradiation of OSLDs to as little as 200Gy before use yields stable detectors that followed supralinear behavior characterized with a quadratic polynomial fit. Pre-irradiation of 1kGy or more, as reported by Jursinic*, is not needed to yield stable detector performance. Conclusion: Nanodot OSLDs can be used in a clinical setting after receiving one shot preirradiations of ∼200Gy. Dose measuring performance is stable after the preirradiation treatment. One shot irradiations of 1kGy or more are not needed to obtain stable counts versus dose performance.* P. Jursinic, Med. Phys. 37, p. 132 to 140 (2010)

Molecular dynamics simulation of erosion and surface evolution of tungsten due to bombardment with deuterium and carbon in Tokamak fusion environments

The behavior of tungsten as plasma facing material in fusion environment is investigated using molecular dynamics simulation. Tungsten erosion and surface evolution is simulated during irradiation by carbon and deuterium ions. Non-cumulative pure carbon bombardment on crystal tungsten shows that substrate temperature does not affect carbon trapping rate, implantation depth, and tungsten sputtering yield. Carbon induced tungsten physical sputtering yield threshold is predicted to be around ∼25eV. Cumulative carbon irradiation on crystal tungsten reveals that tungsten erosion is enhanced at high substrate temperatures. Cumulative carbon induced tungsten sputtering yield matches experimental data as well as Monte Carlo results. Carbon pre-irradiated tungsten tends to trap more hydrogen and facilitates gas bubble formation. Simultaneous deuterium and carbon bombardment on crystal tungsten indicates that carbon induced tungsten sputtering yield exhibits a maximum value when carbon ratio is around 20%. Higher carbon ratio reduces both the carbon and deuterium trapping rates.

Temporal Variations in Metabolic and Autotrophic Indices for Acropora digitifera and Acropora spicifera – Implications for Monitoring Projects

Coral health indices are important components of the management assessments of coral reefs, providing insight into local variation in reef condition, as well as tools for comparisons between reefs and across various time scales. Understanding how such health indices vary in space and time is critical to their successful implementation as management tools. Here we compare autotrophic and heterotrophic coral health indices, examining specifically the temporal variation driven by the local environmental variation, at three scales (diel, daily and seasonal). We compared metabolic indices (RNA/DNA ratio, protein concentration) and autotrophic indices (Chlorophyll a (Chl a), zooxanthellae density, effective quantum yield (yield) and relative electron transport rate (rETR)) for two dominant Acropora species, A. digitifera and A. spicifera at Ningaloo Reef (north-western Australia) in August 2010 (austral winter) and February 2011 (austral summer). Clear seasonal patterns were documented for metabolic indices, zooxanthellae density and rETR, while cyclic diel patterns only occurred for yield and rETR, and RNA/DNA ratio. Significant daily variation was observed for RNA/DNA ratio, Chl a concentration, yield and rETR. Results suggest that zooxanthellae density and protein concentrations are good long-term indicators of coral health whose variance is largely seasonal, while RNA/DNA ratio and rETR can be used for both long-term (seasonal) and short-term (diel) coral monitoring. Chl a can be used to describe changes between days and yield for both diel and daily variations. Correlations between health indices and light history showed that short-term changes in irradiance had the strongest impact on all health indices except zooxanthellae density for A. digitifera; for A. spicifera no correlation was observed at all. However, cumulative irradiance over the several days before sampling showed significant correlations with most health indices suggesting that a time-lag effect has to be taken into account when interpreting diel variations in coral condition.

Large Area Uniform Microstructures on Silicon Surface Created with a Picosecond Laser Beam Scanning

We present the experimental results of picosecond pulse laser microstructuring of silicon in the SF6 atmosphere using the galvanometer scanning technique. With appropriate irradiation conditions, a large variety of surface microstructures even nanostructures were produced. By rapidly scanning, a uniform array of micro-crater structure with 10nm in depth is generated on the crystal silicon surface. At low scanning speed, large area uniform self-organizing micro-grating, micro-hole, or micro-cone structure can be produced by cumulative pulses irradiation. These results suggest that picosecond laser scanning technique is a flexible method to produce uniform surface micro-nanostructures, which exhibits great potential for applications in photoelectron devices, special surface marking and surface modification.

A study on comparison of Gafchromic EBT2 film response under single and cumulative exposure conditions.

Gafchromic films are used as dosimeter for in vivo and in phantom dose measurements. The dose response of Gafchromic EBT2 film under single and repeated exposure conditions is compared in this study to analyze the usability of Gafchromic EBT2 films in cumulative dose measurements. The post-irradiation change in response of the film is studied for up to 4 days after irradiation. The effect of repeated exposure to scanner light on the response of the film is also studied. To check usability of Gafchromic EBT2 films in cumulative dose measurements, three EBT2 films were exposed to a daily fraction dose of 100 cGy, 150 cGy and 200 cGy, respectively, for 4 days. The dose response of the films exposed to cumulative irradiation was compared with the dose measured from films exposed to the same dose but in a single exposure. It is observed that the post-irradiation darkening of the film does not saturate and continue to take place even 4 days after irradiation. The dose measured from the EBT2 films after 4 days from irradiation was around 2% higher than the dose measured from the same films at 24 hours post-irradiation. It was also observed that the repeated exposure to scanner light does not produce any significant change in the film response. The dose response of films exposed to cumulative irradiation agrees with the dose response of films exposed to the same dose in a single irradiation with less than 3% difference. Gafchromic EBT2 films can be used to measure the cumulative dose delivered over multiple fractions, when the delivered dose is uniform across the film.

The Bunsen–Roscoe reciprocity law in ultraviolet-B-induced mortality of the two-spotted spider mite Tetranychus urticae

To determine whether the Bunsen–Roscoe reciprocity law (i.e., the extent of photochemical effects is determined by cumulative irradiance) is applicable to ultraviolet-B (UVB) damage in the twospotted spider mite Tetranychus urticae, egg hatchability and survival of individuals were assessed after irradiation with a UVB lamp using various combinations of intensity and time length. A positive linear correlation between probit mortality and cumulative UVB irradiance was detected in eggs, larvae, teleiochrysalis females, and adult females, regardless of UVB intensity (0.19–0.58Wm−2). LD50 values were clearly higher in adult females, followed by teleiochrysalis females, larvae, and eggs. In eggs, reciprocity was obeyed not only at the UVB intensities listed above, but also at very low UVB intensity (0.014–0.023Wm−2). Such reciprocity in the negative effects of UVB radiation was also observed for the developmental rate of juveniles and egg production of adult females. However, the LD50 value of eggs obtained using the UVB lamp (0.58kJm−2) was lower than that elicited by solar UVB radiation in a previous outdoor experiment (about 50kJm−2). These results suggest that a photoreactivation mechanism plays an important role in the survival of this mite under solar radiation.

Synergistic Effects of Incubation in Rotating Bioreactors and Cumulative Low Dose 60Co γ-ray Irradiation on Human Immortal Lymphoblastoid Cells

The complex space environments can influence cell structure and function. The research results on space biology have shown that the major mutagenic factors in space are microgravity and ionizing radiation. In addition, possible synergistic effects of radiation and microgravity on human cells are not well understood. In this study, human immortal lymphoblastoid cells were established from human peripheral blood lymphocytes and the cells were treated with low dose (0.1, 0.15 and 0.2 Gy) cumulative 60Co γ-irradiation and simulated weightlessness [obtained by culturing cells in the Rotating Cell Culture System (RCCS)]. The commonly used indexes of cell damage such as micronucleus rate, cell cycle and mitotic index were studied. Previous work has proved that Gadd45 (growth arrest and DNA-damage-inducible protein 45) gene increases with a dose-effect relationship, and will possibly be a new biological dosimeter to show irradiation damage. So Gadd45 expression is also detected in this study. The micronucleus rate and the expression of Gadd45α gene increased with irradiation dose and were much higher after incubation in the rotating bioreactor than that in the static irradiation group, while the cell proliferation after incubation in the rotating bioreactor decreased at the same time. These results indicate synergetic effects of simulated weightlessness and low dose irradiation in human cells. The cell damage inflicted by γ-irradiation increased under simulated weightlessness. Our results suggest that during medium- and long-term flight, the human body can be damaged by cumulative low dose radiation, and the damage will even be increased by microgravity in space.

Evaluation of the antifouling and photocatalytic properties of poly(vinylidene fluoride) plasma-grafted poly(acrylic acid) membrane with self-assembled TiO2

Immobilization of TiO2 is a promising approach that produces antifouling and photocatalytic membranes that could help advance wastewater treatment and re-use processes. In this study, poly(acrylic acid) (PAA) was plasma-grafted on commercial poly(vinylidene fluoride) (PVDF) to introduce functional groups on the membrane surface that can support the nanoparticles. It was found that plasma treatment at 100W for 120s followed by liquid grafting with 70% aqueous AA at 60°C for 2h maximized the number of TiO2 binding sites. Membrane hydrophilicity was tremendously enhanced by the self-assembly of TiO2, following a direct proportionality to TiO2 loading. The membrane with 0.5% TiO2 loading maintained the highest pure water flux and the best protein antifouling property. UV irradiation triggered the photodegradation of strongly bound foulants, but at least 1.5% TiO2 and 30min cumulative irradiation were necessary to completely recover the membrane's original performance. The TiO2-modified membranes removed 30–42% of 50mg/l aqueous Reactive Black 5 (RB5) dye. The fabricated membranes demonstrate huge potential for use in membrane reactors with high hydrophilicity, fouling mitigation, and photocatalytic capability.

Outgassing and photochemical studies of photosensitive films upon irradiation at 13.5 nm

Neutral outgassed species from polymethylmethacrylate (PMMA), a model resist (denoted RRR), and three underlayer thin films have been characterized and their absolute outgassing rates determined using a quadrupole mass spectrometer following irradiation at 13.5 nm. The radiation, which was in the extreme ultraviolet (EUV) energy range at 13.5 nm, was delivered from the 08A1-beamline at the National Synchrotron Radiation Research Center in Taiwan. The side chains of acryl-type polymers that are vulnerable to fragmentation and outgassing upon EUV irradiation were characterized and the important outgassed species (H2O and H3O+) were identified from the Si-containing photosensitive materials. The authors propose that the Si-OH formed on the Si-containing surfaces upon EUV irradiation likely undergoes subsequent incremental H2O and H3O+ outgassing upon cumulative EUV irradiation. A benchmark comparison revealed that the absolute outgassing rates of PMMA, RRR, and a Si-containing underlayer sample determined in this work were consistent with values previously reported in the literature. Thus, we have effectively demonstrated that the Taiwanese facility is capable of evaluating absolute resist outgassing rates, making it one of a limited number of EUV resist evaluation sites worldwide. The authors have provided direct evidence that the extent of ionic and neutral outgassing from 80, 100, and 125 nm PMMA and RRR films is not thickness-dependent. The authors have further demonstrated that the absolute outgassing rates of PMMA and RRR films of various thickness and two oxy-hydrocarbon underlayer samples correlated strongly with the 13.5 nm photoabsorption (σabs) and the structural toughness [double-bond-equivalence-per-backbone (DBEPB)] of the polymers. The authors revealed that the formula σabs/DBEPB could be used as a generic metric to predict the resistance of photosensitive films to EUV irradiation for the oxy-hydrocarbons in this work and four previously studied photoresists.

A phenomenological approach shows a high coherence of warming patterns in dimictic aquatic systems across latitude

To predict the coherence in local responses to large-scale climatic forcing among aquatic systems, we developed a generalized approach to compare long-term data of dimictic water bodies based on phenomenologically defined hydrographic events. These climate-sensitive phases (inverse stratification, spring overturn, early thermal stratification, summer stagnation) were classified in a dual code (cold/warm) based on threshold temperatures. Accounting for a latitudinal gradient in seasonal timing of phases derived from gradients in cumulative irradiation (2.2 days per degree latitude), we found a high spatial and temporal coherence in warm–cold patterns for six lakes (84 %) and the Baltic Sea (78 %), even when using the same thresholds for all sites. Similarity to CW-codes for the North Sea still was up to 72 %. The approach allows prediction of phase-specific warming trends and resulting instantaneous or time-delayed ecological responses. Exemplarily, we show that warming during early thermal stratification controls food-web-mediated effects on key species during summer.

Influence of canopy structure and direct beam solar irradiance on snowmelt rates in a mixed conifer forest

Sub-canopy snow ablation rates were measured for three years at forested research plots in the Sierra Nevada, California with a network of 24 automated snow depth sensors and monthly snow density surveys. Snow ablation rates, in mm SWE day−1, specific to each depth sensor location were estimated as the seasonal maximum SWE divided by the number of days from peak SWE to snow disappearance. Estimates of sub-canopy direct beam solar irradiance and sky view factor (SVFθ) derived from hemispherical photographs were used to explain the spatial distribution of snow ablation rates. Cumulative direct beam irradiance during the observed snowmelt periods explained the most variability in snow ablation rates for the most cloud-free melt season (58% in 2008; 4 cloudy days; at 15 sensor locations snowmelt duration ranged from 39 days to 88 days and direct irradiance ranged from 96MJm−2 to 603MJm−2) and explained the least ablation variability for the cloudiest melt season of the study (29% in 2009; 23 cloudy days; at 12 sensor locations snowmelt duration ranged from 45 days to 79 days and direct irradiance ranged from 121MJm−2 to 410MJm−2). Conversely, sky view factor (SVFθ) explained the most variability in snow ablation rates under cloudier conditions (i.e. 87% in 2009) and the relationships were strongest when developed over the entire hemisphere (i.e. SVF90°, which ranged from 0.17 to 0.31). Combined, the two metrics studied here (sub-canopy direct beam irradiance and SVFθ) may be used to explain much of the observed plot-scale variability in SWE ablation at finer time scales relevant to snow and hydrological model applications.

Multimodal treatment, including interferon beta, of nasopharyngeal carcinoma in children and young adults

The authors report preliminary results from a prospective multicenter study (Nasopharyngeal Carcinoma [NPC] 2003 German Society of Pediatric Oncology and Hematology/German Children's Oncology Group [NPC-2003-GPOH/DCOG]). From 2003 to 2010, 45 patients (ages 8-20 years), including 1 patient with stage II NPC and 44 patients with stage III/IV NPC, were recruited to the study. The patient with stage II disease received radiotherapy (59.4 grays [Gy]). The patients with stage III/IV disease received 3 courses of neoadjuvant chemotherapy with cisplatin, 5-fluorouracil, and folinic acid. The cumulative irradiation dose was 54 Gy in 5 patients, who achieved complete remission after neoadjuvant chemotherapy, and 59.4 Gy in the remaining 40 patients. All patients received concomitant cisplatin during the first week and last week of irradiation. After irradiation, all patients received interferon beta for 6 months. Tumor response was evaluated by magnetic resonance imaging studies and positron emission tomography scans. After the completion of treatment, 43 of 45 patients were in complete remission. In 2 patients, only a partial response was achieved, followed by distant metastases (1 patient) or local progression and distant metastases (1 patient), 6 months and 10 months after diagnosis, respectively. Another patient developed a solitary pelvic bone metastasis 21 months after diagnosis. After a median follow-up of 30 months (range, 6-95 months), the event-free survival rate was 92.4%, and the overall survival was 97.1%. Acute toxicity consisted mainly of leucopenia, mucositis, and nausea; and late toxicity consisted of hearing loss and hypothyroidism. Combined therapy with neoadjuvant chemotherapy, radiochemotherapy, and interferon beta was well tolerated and resulted in a very good outcome that was superior to the outcomes of published results from all other pediatric NPC study groups.

Seasonal changes in the deleterious effects of solar ultraviolet-B radiation on eggs of the twospotted spider mite, Tetranychus urticae (Acari: Tetranychidae)

Solar ultraviolet-B (UVB) radiation has deleterious effects on plant-dwelling mites. We assessed the biological effects of UVB radiation on the eggs of the twospotted spider mite, Tetranychus urticae Koch, under both near ambient (UV+) and UV-attenuated (UV−) conditions from spring to autumn and compared them to the effects of temperature and humidity. The ambient daily UVB irradiance increased from January to August and then decreased rapidly until December, whereas egg hatchability under UV+ was lowest in April (10.7%) and increased almost linearly until October (74.9–92.3%). In contrast, hatchability under UV− was consistently high (96.2–99.8%) through all seasons. For UV+, the stepwise multiple linear regression analysis supported the negative correlation of hatchability with cumulative UVB irradiance during egg periods (cumulative dose), but did not support that with the mean daily UVB irradiance (dose rate), suggesting that UVB-induced mortality in T. urticae eggs is cumulative dose dependent rather than dose rate dependent. The high mortality in April may have reflected the slower development caused by the relatively lower temperature and higher UVB radiation, increasing the cumulative dose, while the low mortality in October may have reflected the faster development caused by the relatively higher temperature and lower UVB radiation, decreasing the cumulative dose.

Enhanced photocatalytic activity of TiO2 thin film coating on microstructured silicon substrate

Photocatalytic TiO2 thin film is prepared by sol-gel technique on microstructured silicon substrate produced by femtosecond laser cumulative irradiation. The photocatalytic activity is evaluated by the degradation of methylene blue (MB) solution under ultraviolet (UV) irradiation. For 6-ml MB solution with initial concentration of 3.0 \times 10^{-5} mol/L, the degradation rate caused by TiO2 thin film of 2-cm2 area is higher than 70% after 10-h UV irradiation. Microstructured silicon substrate is found to enhance photocatalytic activity of the TiO2 thin film remarkably. The femtosecond laser microstructured silicon substrate is suitable to support TiO2 thin film photocatalysts.

Reirradiation of brain metastases with radiosurgery

PurposeTo assess the outcome of reirradiation with stereotactic radiosurgery (SRS) of brain metastases (BM) recurring after whole brain radiotherapy (WBRT). Methods and materialsBetween September 2001 and October 2008, 69 patients who recurred after WBRT were re-irradiated with SRS using a linear accelerator. The dose prescription was generally chosen according to maximum diameter of the tumor as suggested by Radiation Therapy Oncology Group (RTOG) 90-05 protocol. Patients were stratified by Karnofsky Performance Status (KPS), Neurologic Functional Score (NFS), RTOG Recursive Partitioning Analysis (RPA), Score Index for Radiosurgery (SIR), primary disease, dimension and number of BM, and time to first brain recurrence after WBRT. Response, survival, and toxicity were analyzed. ResultsAt time of this retrospective analysis all patients had died. The 69 patients reirradiated with SRS had 150 metastases. Median interval between prior WBRT and SRS was 11months and median SRS prescribed dose was 20Gy. Response was obtained in 91% of lesions with 1-year local control rate of 74±4%. Significantly longer duration of response was associated with higher doses (⩾23Gy) and response achieved after SRS (complete and partial response better than stable disease). Cause of death was brain failure only in 36 (52%) patients. Median overall survival after reirradiation was 10months. Variables which significantly conditioned survival were KPS and NFS. Four (6%) patients had asymptomatic radionecrosis that developed prevalently when lesion diameters were larger and cumulative doses exceeded the values recommended by RTOG 90-05 protocol. About three-fourth of the patients had a good KPS and NFS after reirradiation. ConclusionsReirradiation of BM with SRS resulted feasible and effective. A correct patient selection and an accurate evaluation of the cumulative irradiation dose were suggested.