Low Doses of Ethanol Enhance LTD-like Plasticity in Human Motor Cortex.

Science.gov (United States)

Fuhl, Anna; Müller-Dahlhaus, Florian; Lücke, Caroline; Toennes, Stefan W; Ziemann, Ulf

2015-12-01

Humans liberally use ethanol for its facilitating effects on social interactions but its effects on central nervous system function remain underexplored. We have recently described that very low doses of ethanol abolish long-term potentiation (LTP)-like plasticity in human cortex, most likely through enhancement of tonic inhibition [Lücke et al, 2014, Neuropsychopharmacology 39:1508-18]. Here, we studied the effects of low-dose ethanol on long-term depression (LTD)-like plasticity. LTD-like plasticity was induced in human motor cortex by paired associative transcranial magnetic stimulation (PASLTD), and measured as decreases of motor evoked potential input-output curve (IO-curve). In addition, sedation was measured by decreases in saccade peak velocity (SPV). Ethanol in two low doses (EtOH<10mM, EtOH<20mM) was compared to single oral doses of alprazolam (APZ, 1mg) a classical benzodiazepine, and zolpidem (ZLP, 10 mg), a non-benzodiazepine hypnotic, in a double-blinded randomized placebo-controlled crossover design in ten healthy human subjects. EtOH<10mM and EtOH<20mM but not APZ or ZLP enhanced the PASLTD-induced LTD-like plasticity, while APZ and ZLP but not EtOH<10mM or EtOH<20mM decreased SPV. Non-sedating low doses of ethanol, easily reached during social drinking, enhance LTD-like plasticity in human cortex. This effect is most likely explained by the activation of extrasynaptic α4-subunit containing gamma-aminobutyric type A receptors by low-dose EtOH, resulting in increased tonic inhibition. Findings may stimulate cellular research on the role of tonic inhibition in regulating excitability and plasticity of cortical neuronal networks.

Cocaine and Pavlovian fear conditioning: dose-effect analysis.

Science.gov (United States)

Wood, Suzanne C; Fay, Jonathan; Sage, Jennifer R; Anagnostaras, Stephan G

2007-01-25

Emerging evidence suggests that cocaine and other drugs of abuse can interfere with many aspects of cognitive functioning. The authors examined the effects of 0.1-15mg/kg of cocaine on Pavlovian contextual and cued fear conditioning in mice. As expected, pre-training cocaine dose-dependently produced hyperactivity and disrupted freezing. Surprisingly, when the mice were tested off-drug later, the group pre-treated with a moderate dose of cocaine (15mg/kg) displayed significantly less contextual and cued memory, compared to saline control animals. Conversely, mice pre-treated with a very low dose of cocaine (0.1mg/kg) showed significantly enhanced fear memory for both context and tone, compared to controls. These results were not due to cocaine's anesthetic effects, as shock reactivity was unaffected by cocaine. The data suggest that despite cocaine's reputation as a performance-enhancing and anxiogenic drug, this effect is seen only at very low doses, whereas a moderate dose disrupts hippocampus and amygdala-dependent fear conditioning.

Mechanisms of Enhanced Cell Killing at Low Doses: Implications for Radiation Risk

International Nuclear Information System (INIS)

Johnston, Peter J.; Wilson, George D.

2003-01-01

We have shown that cell lethality actually measured after exposure to low-doses of low-LET radiation, is markedly enhanced relative to the cell lethality previously expected by extrapolation of the high-dose cell-killing response. Net cancer risk is a balance between cell transformation and cell kill and such enhanced lethality may more than compensate for transformation at low radiation doses over a least the first 10 cGy of low-LET exposure. This would lead to a non-linear, threshold, dose-risk relationship. Therefore our data imply the possibility that the adverse effects of small radiation doses (<10 cGy) could be overestimated in specific cases. It is now important to research the mechanisms underlying the phenomenon of low-dose hypersensitivity to cell killing, in order to determine whether this can be generalized to safely allow an increase in radiation exposure limits. This would have major cost-reduction implications for the whole EM program

Radiation dose of aircrews during a solar proton event without ground-level enhancement

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R. Kataoka

2015-01-01

Full Text Available A significant enhancement of radiation doses is expected for aircrews during ground-level enhancement (GLE events, while the possible radiation hazard remains an open question during non-GLE solar energetic particle (SEP events. Using a new air-shower simulation driven by the proton flux data obtained from GOES satellites, we show the possibility of significant enhancement of the effective dose rate of up to 4.5 μSv h−1 at a conventional flight altitude of 12 km during the largest SEP event that did not cause a GLE. As a result, a new GOES-driven model is proposed to give an estimate of the contribution from the isotropic component of the radiation dose in the stratosphere during non-GLE SEP events.

Dose enhancement effects to the nucleus and mitochondria from gold nanoparticles in the cytosol

Science.gov (United States)

McNamara, AL; Kam, WW-Y; Scales, N; McMahon, SJ; Bennett, JW; Byrne, HL; Schuemann, J; Paganetti, H; Banati, R; Kuncic, Z

2016-01-01

Gold nanoparticles (GNPs) have shown potential as dose enhancers for radiation therapy. Since damage to the genome affects the viability of a cell, it is generally assumed that GNPs have to localise within the cell nucleus. In practice, however, GNPs tend to localise in the cytoplasm yet still appear to have a dose enhancing effect on the cell. Whether this effect can be attributed to stress-induced biological mechanisms or to physical damage to extra-nuclear cellular targets is still unclear. There is however growing evidence to suggest that the cellular response to radiation can also be influenced by indirect processes induced when the nucleus is not directly targeted by radiation. The mitochondrion in particular may be an effective extra-nuclear radiation target given its many important functional roles in the cell. To more accurately predict the physical effect of radiation within different cell organelles, we measured the full chemical composition of a whole human lymphocytic JURKAT cell as well as two separate organelles; the cell nucleus and the mitochondrion. The experimental measurements found that all three biological materials had similar ionisation energies ~ 70 eV, substantially lower than that of liquid water ~ 78 eV. Monte Carlo simulations for 10 – 50 keV incident photons showed higher energy deposition and ionisation numbers in the cell and organelle materials compared to liquid water. Adding a 1% mass fraction of gold to each material increased the energy deposition by a factor of ~ 1.8 when averaged over all incident photon energies. Simulations of a realistic compartmentalised cell show that the presence of gold in the cytosol increases the energy deposition in the mitochondrial volume more than within the nuclear volume. We find this is due to sub-micron delocalisation of energy by photoelectrons, making the mitochondria a potentially viable indirect radiation target for GNPs that localise to the cytosol. PMID:27435339

Gadodiamide injection for enhancement of MRI in the CNS. Applications, dose, field and time dependence

Energy Technology Data Exchange (ETDEWEB)

Aakeson, P

1996-10-01

Gadodiamide injection was comparable to Gd-DTPA with regard to both safety and diagnostic efficiency in the central nervous system. The contrast effect of Gd contrast agents is higher at 1.5 T than at 0.3 T both in phantoms and patients with a maximum ratio (signal lesion/signal grey matter) more than 50% higher at 1.5 T. To achieve high contrast effect, heavily T1-weighted images are important. Prolonging the TR from 400 ms to 600 ms reduced the ratio by 15-45% depending on concentration. The effective time window for imaging of BBB (Blood-Brain Barrier) damage is between 2-5 and 25-30 minutes after injection and several scans can be performed without loss of enhancement. To provide maximum detectability of BBB damage in patients, higher doses of Gd contrast media should be useful, especially at low field strengths, as the doses used clinically today do not utilize the maximum contrast effect. High-dose (0.3 mmol/kg b.w.) contrast enhanced MRI (0.3 T) with Gadodiamide injection allowed detection of significantly more and smaller metastases (i.e. BBB damage) than standard dose (0.1 mmol/kg b.w.) High dose contrast-enhanced MRI (0.3 T) did not increase the diagnostic information for the evaluation of patients with failed back surgery syndrome compared to standard dose MRI. 55 refs, 9 figs, 10 tabs.

Gadodiamide injection for enhancement of MRI in the CNS. Applications, dose, field and time dependence

International Nuclear Information System (INIS)

Aakeson, P.

1996-01-01

Gadodiamide injection was comparable to Gd-DTPA with regard to both safety and diagnostic efficiency in the central nervous system. The contrast effect of Gd contrast agents is higher at 1.5 T than at 0.3 T both in phantoms and patients with a maximum ratio (signal lesion/signal grey matter) more than 50% higher at 1.5 T. To achieve high contrast effect, heavily T1-weighted images are important. Prolonging the TR from 400 ms to 600 ms reduced the ratio by 15-45% depending on concentration. The effective time window for imaging of BBB (Blood-Brain Barrier) damage is between 2-5 and 25-30 minutes after injection and several scans can be performed without loss of enhancement. To provide maximum detectability of BBB damage in patients, higher doses of Gd contrast media should be useful, especially at low field strengths, as the doses used clinically today do not utilize the maximum contrast effect. High-dose (0.3 mmol/kg b.w.) contrast enhanced MRI (0.3 T) with Gadodiamide injection allowed detection of significantly more and smaller metastases (i.e. BBB damage) than standard dose (0.1 mmol/kg b.w.) High dose contrast-enhanced MRI (0.3 T) did not increase the diagnostic information for the evaluation of patients with failed back surgery syndrome compared to standard dose MRI. 55 refs, 9 figs, 10 tabs

Dose of radiation enhancement, using silver nanoparticles in a human tissue equivalent gel dosimeter.

Science.gov (United States)

Hassan, Muhammad; Waheed, Muhammad Mohsin; Anjum, Muhammad Naeem

2016-01-01

To quantify the radiation dose enhancement in a human tissue-equivalent polymer gel impregnated with silver nanoparticles. The case-control study was conducted at the Bahawalpur Institute of Nuclear Medicine and Oncology, Bahawalpur, Pakistan, in January 2014. Silver nanoparticles used in this study were prepared by wet chemical method. Polymer gel was prepared by known quantity of gelatine, methacrylic acid, ascorbic acid, copper sulphate pentahydrate, hydroquinone and water. Different concentrations of silver nanoparticles were added to the gel during its cooling process. The gel was cooled in six plastic vials of 50ml each. Two vials were used as a control sample while four vials were impregnated with silver nanoparticles. After 22 hours, the vials were irradiated with gamma rays by aCobalt-60 unit. Radiation enhancement was assessed by taking magnetic resonance images of the vials. The images were analysed using Image J software. The dose enhancement factor was 24.17% and 40.49% for 5Gy and 10Gy dose respectively. The dose enhancement factor for the gel impregnated with 0.10mM silver nanoparticles was 32.88% and 51.98% for 5Gy and 10Gy dose respectively. The impregnation of a tissue-equivalent gel with silver nanoparticles resulted in dose enhancement and this effect was magnified up to a certain level with the increase in concentration of silver nanoparticles.

Low dose gamma irradiation enhances defined signaling components of intercellular reactive oxygen-mediated apoptosis induction

International Nuclear Information System (INIS)

Bauer, G

2011-01-01

Transformed cells are selectively removed by intercellular ROS-mediated induction of apoptosis. Signaling is based on the HOCl and the NO/peroxynitrite pathway (major pathways) and the nitryl chloride and the metal-catalyzed Haber-Weiss pathway (minor pathways). During tumor progression, resistance against intercellular induction of apoptosis is acquired through expression of membrane-associated catalase. Low dose radiation of nontransformed cells has been shown to enhance intercellular induction of apoptosis. The present study was performed to define the signaling components which are modulated by low dose gamma irradiation. Low dose radiation induced the release of peroxidase from nontransformed, transformed and tumor cells. Extracellular superoxide anion generation was strongly enhanced in the case of transformed cells and tumor cells, but not in nontransformed cells. Enhancement of peroxidase release and superoxide anion generation either increased intercellular induction of apoptosis of transformed cells, or caused a partial protection under specific signaling conditions. In tumor cells, low dose radiation enhanced the production of major signaling components, but this had no effect on apoptosis induction, due to the strong resistance mechanism of tumor cells. Our data specify the nature of low dose radiation-induced effects on specific signaling components of intercellular induction of apoptosis at defined stages of multistep carcinogenesis.

Dose Rate Effects in Linear Bipolar Transistors

Science.gov (United States)

Johnston, Allan; Swimm, Randall; Harris, R. D.; Thorbourn, Dennis

2011-01-01

Dose rate effects are examined in linear bipolar transistors at high and low dose rates. At high dose rates, approximately 50% of the damage anneals at room temperature, even though these devices exhibit enhanced damage at low dose rate. The unexpected recovery of a significant fraction of the damage after tests at high dose rate requires changes in existing test standards. Tests at low temperature with a one-second radiation pulse width show that damage continues to increase for more than 3000 seconds afterward, consistent with predictions of the CTRW model for oxides with a thickness of 700 nm.

Monte Carlo simulation study on dose enhancement by gold nanoparticles in brachytherapy

International Nuclear Information System (INIS)

Cho, Sungkoo; Jeong, Jonghwi; Kim, Chanhyeong; Yoon, Myonggeun

2010-01-01

Radiation dose enhancement by injection of a high atomic number (Z) material into tumor volumes has been studied for various radiation sources and different concentrations of gold nanoparticles. Brachytherapy employs low energy photons of less than ∼0.5 MeV, which indeed is the optimal energy range for radiation dose enhancement by introduction of high-Z material. The present study uses the MCNPX TM code to estimate the dose enhancement by gold nanoparticles for the four common brachytherapy sources ( 137 Cs, 192 Ir, 125 I, and 103 Pd). Additionally, cisplatin (H 6 Cl 2 N 2 Pt), a platinum-based chemotherapeutic drug, was used to evaluate the dose enhancement. The simulated source models were evaluated with reference to the calculated TG-43 parameter values. The dose enhancement in the tumor region due to the gold nanoparticles and cisplatin was evaluated according to the dose enhancement factor (DEF). The maximum values of the average DEFs were found to be 1.03, 1.11, 3.43, and 2.17 for the 137 Cs, 192 Ir, 125 I, and 103 Pd sources, respectively. The dose enhancement values for the low-energy sources were significantly higher than those for the high-energy sources. The dose enhancement due to cisplatin was calculated by using the same approach and was found to be comparable to that of the gold nanoparticles. The maximum value of the average DEF for cisplatin was 1.12 for the 5% concentration level in water and a 192 Ir source. We confirmed that cisplatin could be applied to cancer therapy that combines chemotherapeutic drugs with radiation therapy. The results presented herein will be used to study dose enhancement in tumor regions using various radiation modalities with high atomic number materials.

Low doses of glyphosate enhance growth, CO2 assimilation, stomatal conductance and transpiration in sugarcane and eucalyptus.

Science.gov (United States)

Nascentes, Renan F; Carbonari, Caio A; Simões, Plinio S; Brunelli, Marcela C; Velini, Edivaldo D; Duke, Stephen O

2018-05-01

Sublethal doses of herbicides can enhance plant growth and stimulate other process, an effect known as hormesis. The magnitude of hormesis is dependent on the plant species, the herbicide and its dose, plant development stage and environmental parameters. Glyphosate hormesis is well established, but relatively little is known of the mechanism of this phenomenon. The objective of this study was to determine if low doses of glyphosate that cause growth stimulation in sugarcane and eucalyptus concomitantly stimulate CO 2 assimilation. Shoot dry weight in both species increased at both 40 and 60 days after application of 6.2 to 20.2 g a.e. ha -1 glyphosate. The level of enhanced shoot dry weight was 11 to 37%, depending on the time after treatment and the species. Concomitantly, CO 2 assimilation, stomatal conductance and transpiration were increased by glyphosate doses similar to those that caused growth increases. Glyphosate applied at low doses increased the dry weight of sugarcane and eucalyptus plants in all experiments. This hormetic effect was related to low dose effects on CO 2 assimilation rate, stomatal conductance and transpiration rate, indicating that low glyphosate doses enhance photosynthesis of plants. © 2017 Society of Chemical Industry. © 2017 Society of Chemical Industry.

SU-F-T-426: Measurement of Dose Enhancement Due to Backscatter From Modern Dental Materials

International Nuclear Information System (INIS)

Hurwitz, M; Margalit, D; Williams, C; Tso, T; Lee, S; Rosen, E

2016-01-01

Purpose: High-density materials used in dental restoration can cause significant localized dose enhancement due to electron backscatter in head-and-neck radiotherapy, increasing the risk of mucositis. The materials used in prosthetic dentistry have evolved in the last decades from metal alloys to ceramics. We aim to determine the dose enhancement caused by backscatter from currently-used dental materials. Methods: Measurements were performed for three different dental materials: lithium disilicate (Li 2 Si 2 O 5 ), zirconium dioxide (ZrO 2 ), and gold alloy. Small thin squares (2×2×0.15 cm 3 ) of the material were fabricated, and placed into a phantom composed of tissue-equivalent material. The phantom was irradiated with a single 6 MV photon field. A thin-window parallel-plate ion chamber was used to measure the dose at varying distances from the proximal interface between the material and the plastic. Results: The dose enhancement at the interface between the high-density and tissue-equivalent materials, relative to a homogeneous phantom, was 54% for the gold alloy, 31% for ZrO 2 , and 9% for Li 2 Si 2 O 5 . This enhancement decreased rapidly with distance from the interface, falling to 11%, 5%, and 0.5%, respectively, 2 mm from the interface. Comparisons with the modeling of this effect in treatment planning systems are performed. Conclusion: While dose enhancement due to dental restoration is smaller with ceramic materials than with metal alloys, it can still be significant. A spacer of about 2–3 mm would be effective in reducing this enhancement, even for metal alloys.

SU-F-T-426: Measurement of Dose Enhancement Due to Backscatter From Modern Dental Materials

Energy Technology Data Exchange (ETDEWEB)

Hurwitz, M; Margalit, D; Williams, C [Brigham and Women’s Hospital / Harvard Medical School, Boston, MA (United States); Tso, T; Lee, S; Rosen, E [Harvard School of Dental Medicine, Boston, MA (United States)

2016-06-15

Purpose: High-density materials used in dental restoration can cause significant localized dose enhancement due to electron backscatter in head-and-neck radiotherapy, increasing the risk of mucositis. The materials used in prosthetic dentistry have evolved in the last decades from metal alloys to ceramics. We aim to determine the dose enhancement caused by backscatter from currently-used dental materials. Methods: Measurements were performed for three different dental materials: lithium disilicate (Li{sub 2}Si{sub 2}O{sub 5}), zirconium dioxide (ZrO{sub 2}), and gold alloy. Small thin squares (2×2×0.15 cm{sup 3}) of the material were fabricated, and placed into a phantom composed of tissue-equivalent material. The phantom was irradiated with a single 6 MV photon field. A thin-window parallel-plate ion chamber was used to measure the dose at varying distances from the proximal interface between the material and the plastic. Results: The dose enhancement at the interface between the high-density and tissue-equivalent materials, relative to a homogeneous phantom, was 54% for the gold alloy, 31% for ZrO{sub 2}, and 9% for Li{sub 2}Si{sub 2}O{sub 5}. This enhancement decreased rapidly with distance from the interface, falling to 11%, 5%, and 0.5%, respectively, 2 mm from the interface. Comparisons with the modeling of this effect in treatment planning systems are performed. Conclusion: While dose enhancement due to dental restoration is smaller with ceramic materials than with metal alloys, it can still be significant. A spacer of about 2–3 mm would be effective in reducing this enhancement, even for metal alloys.

SU-E-T-279: Dose Enhancement Effect Due to Cerium Oxide Nanoparticles Employed as Radiation Protectants

Energy Technology Data Exchange (ETDEWEB)

Ouyang, Z; Altundal, Y; Sajo, E [Univ Massachusetts Lowell, Lowell, MA (United States); Ngwa, W [Univ Massachusetts Lowell, Lowell, MA (United States); Brigham and Women’s Hospital, Dana Farber Cancer Institute, Harvard Medical, Boston, MA (United States)

2015-06-15

Purpose: The goal of radiotherapy is to maximize radiation dose to diseased cells while minimizing radiation damage to normal tissues. In order to minimize damage to normal tissues, cerium oxide nanoparticles (nanoceria) are currently considered as a radioprotectant. However, some studies have reported concerns that nanoceria can also lead to radiotherapy dose enhancement due to the high atomic number of cerium, especially when used in conjunction with kV energy and brachytherapy sources. In this study, this concern is investigated to determine if the concentrations of nanoceria employed in in-vivo studies to confer radioprotection can engender a significant dose enhancement. Methods: Radiation with energies ranging from 50kVp to 140kVp is investigated in this work along with brachytherapy sources Pd-103 and I-125. A previously established theoretical model is used to calculate the dose enhancement factor (DEF). In this model, each cell is assumed to be a voxel of size (10 µm, 10 µm, 10 µm) with nanoceria homogeneously distributed among them. Electron energy loss formula of Cole is used to calculate energy (and hence dose) deposited by photoelectrons and Auger electrons in each tissue voxel due to irradiation of nanoceria. The DEF is defined as the ratio of the dose with and without nanoparticles. Results: DEF calculation results are smaller than 1.02 with dosages of nanoceria smaller than 0.645 mg/g, which is shown to be sufficiently protective by some previous in-vitro and in-vivo experiments. The brachytherapy sources show higher DEF’s than kVp radiations. DEF peaks are consistent with K shell and L shell energies of cerium, 40 keV and 6 keV, respectively. Conclusion: The results show that for sufficiently radioprotective concentrations of nanoceria, there will be minimal DEF when used in conjunction with clinically applicable kV energy radiotherapy sources or brachytherapy sources.

Dose perturbation effect of metallic spinal implants in proton beam therapy.

Science.gov (United States)

Jia, Yingcui; Zhao, Li; Cheng, Chee-Wai; McDonald, Mark W; Das, Indra J

2015-09-08

The purpose of this study was to investigate the effect of dose perturbations for two metallic spinal screw implants in proton beam therapy in the perpendicular and parallel beam geometry. A 5.5 mm (diameter) by 45 mm (length) stainless steel (SS) screw and a 5.5 mm by 35 mm titanium (Ti) screw commonly used for spinal fixation were CT-scanned in a hybrid phantom of water and solid water. The CT data were processed with an orthopedic metal artifact reduction (O-MAR) algorithm. Treatment plans were generated for each metal screw with a proton beam oriented, first parallel and then perpendicular, to the longitudinal axis of the screw. The calculated dose profiles were compared with measured results from a plane-parallel ion chamber and Gafchromic EBT2 films. For the perpendicular setup, the measured dose immediately downstream from the screw exhibited dose enhancement up to 12% for SS and 8% for Ti, respectively, but such dose perturbation was not observed outside the lateral edges of the screws. The TPS showed 5% and 2% dose reductions immediately at the interface for the SS nd Ti screws, respectively, and up to 9% dose enhancements within 1 cm outside of the lateral edges of the screws. The measured dose enhancement was only observed within 5 mm from the interface along the beam path. At deeper depths, the lateral dose profiles appeared to be similar between the measurement and TPS, with dose reduction in the screw shadow region and dose enhancement within 1-2 cm outside of the lateral edges of the metals. For the parallel setup, no significant dose perturbation was detected at lateral distance beyond 3 mm away from both screws. Significant dose discrepancies exist between TPS calculations and ion chamber and film measurements in close proximity of high-Z inhomogeneities. The observed dose enhancement effect with proton therapy is not correctly modeled by TPS. An extra measure of caution should be taken when evaluating dosimetry with spinal metallic implants.

Measurement bias dependence of enhanced bipolar gain degradation at low dose rates

International Nuclear Information System (INIS)

Witczak, S.C.; Lacoe, R.C.; Mayer, D.C.; Fleetwood, D.M.

1998-03-01

Oxide trapped charge, field effects from emitter metallization, and high level injection phenomena moderate enhanced gain degradation of lateral pnp transistors at low dose rates. Hardness assurance tests at elevated irradiation temperatures require larger design margins for low power measurement biases

TU-H-CAMPUS-TeP3-05: Evaluation of the Microscopic Dose Enhancement in the Nanoparticle-Enhanced Auger Therapy

International Nuclear Information System (INIS)

Sung, W; Jung, S; Ye, S

2016-01-01

Purpose: The aim of this study is to apply Monte Carlo simulations to investigate the nanoparticle dose enhancement for Auger therapy. Methods: Two nanoparticle fabrications were considered: nanoshell and nanosphere. In the first step, a single nanoparticle was irradiated with Auger emitters. The electrons were scored in a phase space at the outer surface of the nanoparticle with Geant4-Penelope. In the second step, the previously recorded phase space was used as a source and placed at the center of a cell-size water phantom. The nanoscale dose was evaluated in water around the nanoparticle with Geant4-DNA. The dose enhancement factor (DEF) is defined as the ratio of doses with and without nanoparticles. The nanoparticles were replaced by corresponding water nanoparticle with the same size and volume source which represents typical situation of Auger emitters without nanoparticle. Various sizes/materials of nanoparticles and isotopes were considered. Results: Nanoshell - Microscopic dose was increased up to 130% at 20 – 100 nm distances from the surface of Au- 125 I nanoshell. However, dose at less than 20 nm distance was reduced due to absorbed low energy electrons in gold nanoshell. The amounts and regions of the dose enhancement were dependent on nanoshell size, materials, and isotopes. Nanosphere - The increased amounts of electrons up to 300% and reduced average energy with nanosphere were observed compared with water nanoparticle. We observed localized dose enhancement (up to a factor 3.6) in the immediate vicinity (< 50 nm) of Au- 125 I nanosphere. The dose enhancement patterns vary according to nanosphere sizes and isotopes. Conclusion: We conclude that Auger therapy with nanoparticles can lead to change of electron energy spectrum and dose enhancements at certain range. The dose enhancement patterns vary according to nanoparticle sizes, materials, and isotopes. This work was supported by the National Research Foundation of Korea (NRF) grant funded by the

Deep learning enables reduced gadolinium dose for contrast-enhanced brain MRI.

Science.gov (United States)

Gong, Enhao; Pauly, John M; Wintermark, Max; Zaharchuk, Greg

2018-02-13

There are concerns over gadolinium deposition from gadolinium-based contrast agents (GBCA) administration. To reduce gadolinium dose in contrast-enhanced brain MRI using a deep learning method. Retrospective, crossover. Sixty patients receiving clinically indicated contrast-enhanced brain MRI. 3D T 1 -weighted inversion-recovery prepped fast-spoiled-gradient-echo (IR-FSPGR) imaging was acquired at both 1.5T and 3T. In 60 brain MRI exams, the IR-FSPGR sequence was obtained under three conditions: precontrast, postcontrast images with 10% low-dose (0.01mmol/kg) and 100% full-dose (0.1 mmol/kg) of gadobenate dimeglumine. We trained a deep learning model using the first 10 cases (with mixed indications) to approximate full-dose images from the precontrast and low-dose images. Synthesized full-dose images were created using the trained model in two test sets: 20 patients with mixed indications and 30 patients with glioma. For both test sets, low-dose, true full-dose, and the synthesized full-dose postcontrast image sets were compared quantitatively using peak-signal-to-noise-ratios (PSNR) and structural-similarity-index (SSIM). For the test set comprised of 20 patients with mixed indications, two neuroradiologists scored blindly and independently for the three postcontrast image sets, evaluating image quality, motion-artifact suppression, and contrast enhancement compared with precontrast images. Results were assessed using paired t-tests and noninferiority tests. The proposed deep learning method yielded significant (n = 50, P 5 dB PSNR gains and >11.0% SSIM). Ratings on image quality (n = 20, P = 0.003) and contrast enhancement (n = 20, P deep learning method, gadolinium dose can be reduced 10-fold while preserving contrast information and avoiding significant image quality degradation. 3 Technical Efficacy: Stage 5 J. Magn. Reson. Imaging 2018. © 2018 International Society for Magnetic Resonance in Medicine.

SU-G-TeP3-15: Radiation Dose Enhancement by Anatase TiO2NPs

Energy Technology Data Exchange (ETDEWEB)

Youkhana, E; Geso, M; Feltis, B [RMIT University, Melbourne, VIC (Australia)

2016-06-15

Purpose: This work investigates radiation dose enhancement caused by TiO2 nanoparticles covering entire X-ray energy ranges used in radiation therapy. Methods: Anatase TiO2NPs crystal were synthesised and modified as hydrophilic and hydrophobic to disperse in culture-medium and halocarbons (PRESAGE chemical composition) respectively. TiO2NPs were characterised using TEM, XPS, XRD, TGA and FTIR. Various Concentrations have been utilised for determination of radiation-dose enhancement. This investigation is carried out in two ways; one using PRESAGE dosimeter/phantom and the other is radiobiological and based on in vitro study using two types of cell lines, Human Keratinocyte (HaCaT) and prostate cancer cell lines. The x-ray used are both kilovoltage and megavoltage separately. The prepared PRESAGE dosimeters were scanned using optical CT scanner. Clonogenic and MTS assays were employed for cell cytotoxicity and viability measurements for determination of the levels of dose enhancement. Results: Significant about (50%, 45%) dose enhancement by TiO2-NPs for kV x-rays is measured in both ways (Presage and Cells study). Slightly more is detected with the cells. However, the dose enhancement with megavoltage beams was insignificant using Presage and under same conditions the cells survival curves indicates around 20% which is relatively high. This difference can only be attributed to some biochemical effects. Such as generation of reactive oxygen species (ROS), this can affect the cells while it can’t be detected by Presage. Elevation of hydroxyl radicals (•OH) of many orders is observed with the inclusion of TiO2-NPs in cells-medium. Conclusion: Dose enhancement inflicted by TiO2-NPs is proven to be significant with megavoltage beams and minimal with kV. The high dose enhancements obtained can be attributed to higher levels of ROS generated. Since MV beams are most commonly used, this research proves potential value for more efficient beam delivery. This has

Quantitative investigation of physical factors contributing to gold nanoparticle-mediated proton dose enhancement

International Nuclear Information System (INIS)

Cho, Jongmin; Manohar, Nivedh; Kerr, Matthew; Cho, Sang Hyun; Gonzalez-Lepera, Carlos; Krishnan, Sunil

2016-01-01

Some investigators have shown tumor cell killing enhancement in vitro and tumor regression in mice associated with the loading of gold nanoparticles (GNPs) before proton treatments. Several Monte Carlo (MC) investigations have also demonstrated GNP-mediated proton dose enhancement. However, further studies need to be done to quantify the individual physical factors that contribute to the dose enhancement or cell-kill enhancement (or radiosensitization). Thus, the current study investigated the contributions of particle-induced x-ray emission (PIXE), particle-induced gamma-ray emission (PIGE), Auger and secondary electrons, and activation products towards the total dose enhancement. Specifically, GNP-mediated dose enhancement was measured using strips of radiochromic film that were inserted into vials of cylindrical GNPs, i.e. gold nanorods (GNRs), dispersed in a saline solution (0.3 mg of GNRs/g or 0.03% of GNRs by weight), as well as vials containing water only, before proton irradiation. MC simulations were also performed with the tool for particle simulation code using the film measurement setup. Additionally, a high-purity germanium detector system was used to measure the photon spectrum originating from activation products created from the interaction of protons and spherical GNPs present in a saline solution (20 mg of GNPs/g or 2% of GNPs by weight). The dose enhancement due to PIXE/PIGE recorded on the films in the GNR-loaded saline solution was less than the experimental uncertainty of the film dosimetry (<2%). MC simulations showed highly localized dose enhancement (up to a factor 17) in the immediate vicinity (<100 nm) of GNRs, compared with hypothetical water nanorods (WNRs), mostly due to GNR-originated Auger/secondary electrons; however, the average dose enhancement over the entire GNR-loaded vial was found to be minimal (0.1%). The dose enhancement due to the activation products from GNPs was minimal (<0.1%) as well. In conclusion, under the

Reduced oxygen enhancement ratio at low doses

International Nuclear Information System (INIS)

Palcic, B.; Skarsgard, L.D.

1984-01-01

The oxygen depletion rate in cell suspensions was measured using a Clark electrode. It was found that under experimental conditions used in this laboratory for hypoxic irradiations, the oxygen levels before the start of irradiation are always below 0.1μm, the levels which could give any significant enhancement to radiation inactivation by x-rays. The measured O/sub 2/ depletion rates were comparable to those reported in the literature. Chinese hamster cells (CHO) were made hypoxic by gas exchange, combined with metabolic consumption of oxygen by cells at 37 0 C. Full survival curves were determined in the dose range 0 to 3Gy using the low dose survival assay. The results confirmed the authors' earlier finding that the OER decreases at low doses. The authors therefore believe that the dose-dependent OER is a true radiobiological phenomenon and not an artifact of the experimental method used in the low dose survival assay

Applications of tissue heterogeneity corrections and biologically effective dose volume histograms in assessing the doses for accelerated partial breast irradiation using an electronic brachytherapy source

Science.gov (United States)

Shi, Chengyu; Guo, Bingqi; Cheng, Chih-Yao; Eng, Tony; Papanikolaou, Nikos

2010-09-01

A low-energy electronic brachytherapy source (EBS), the model S700 Axxent™ x-ray device developed by Xoft Inc., has been used in high dose rate (HDR) intracavitary accelerated partial breast irradiation (APBI) as an alternative to an Ir-192 source. The prescription dose and delivery schema of the electronic brachytherapy APBI plan are the same as the Ir-192 plan. However, due to its lower mean energy than the Ir-192 source, an EBS plan has dosimetric and biological features different from an Ir-192 source plan. Current brachytherapy treatment planning methods may have large errors in treatment outcome prediction for an EBS plan. Two main factors contribute to the errors: the dosimetric influence of tissue heterogeneities and the enhancement of relative biological effectiveness (RBE) of electronic brachytherapy. This study quantified the effects of these two factors and revisited the plan quality of electronic brachytherapy APBI. The influence of tissue heterogeneities is studied by a Monte Carlo method and heterogeneous 'virtual patient' phantoms created from CT images and structure contours; the effect of RBE enhancement in the treatment outcome was estimated by biologically effective dose (BED) distribution. Ten electronic brachytherapy APBI cases were studied. The results showed that, for electronic brachytherapy cases, tissue heterogeneities and patient boundary effect decreased dose to the target and skin but increased dose to the bones. On average, the target dose coverage PTV V100 reduced from 95.0% in water phantoms (planned) to only 66.7% in virtual patient phantoms (actual). The actual maximum dose to the ribs is 3.3 times higher than the planned dose; the actual mean dose to the ipsilateral breast and maximum dose to the skin were reduced by 22% and 17%, respectively. Combining the effect of tissue heterogeneities and RBE enhancement, BED coverage of the target was 89.9% in virtual patient phantoms with RBE enhancement (actual BED) as compared to 95

Applications of tissue heterogeneity corrections and biologically effective dose volume histograms in assessing the doses for accelerated partial breast irradiation using an electronic brachytherapy source

Energy Technology Data Exchange (ETDEWEB)

Shi Chengyu; Guo Bingqi; Eng, Tony; Papanikolaou, Nikos [Cancer Therapy and Research Center, University of Texas Health Science Center at San Antonio, TX 78229 (United States); Cheng, Chih-Yao, E-mail: shic@uthscsa.ed [Radiation Oncology Department, Oklahoma University Health Science Center, Oklahoma, OK 73104 (United States)

2010-09-21

A low-energy electronic brachytherapy source (EBS), the model S700 Axxent(TM) x-ray device developed by Xoft Inc., has been used in high dose rate (HDR) intracavitary accelerated partial breast irradiation (APBI) as an alternative to an Ir-192 source. The prescription dose and delivery schema of the electronic brachytherapy APBI plan are the same as the Ir-192 plan. However, due to its lower mean energy than the Ir-192 source, an EBS plan has dosimetric and biological features different from an Ir-192 source plan. Current brachytherapy treatment planning methods may have large errors in treatment outcome prediction for an EBS plan. Two main factors contribute to the errors: the dosimetric influence of tissue heterogeneities and the enhancement of relative biological effectiveness (RBE) of electronic brachytherapy. This study quantified the effects of these two factors and revisited the plan quality of electronic brachytherapy APBI. The influence of tissue heterogeneities is studied by a Monte Carlo method and heterogeneous 'virtual patient' phantoms created from CT images and structure contours; the effect of RBE enhancement in the treatment outcome was estimated by biologically effective dose (BED) distribution. Ten electronic brachytherapy APBI cases were studied. The results showed that, for electronic brachytherapy cases, tissue heterogeneities and patient boundary effect decreased dose to the target and skin but increased dose to the bones. On average, the target dose coverage PTV V{sub 100} reduced from 95.0% in water phantoms (planned) to only 66.7% in virtual patient phantoms (actual). The actual maximum dose to the ribs is 3.3 times higher than the planned dose; the actual mean dose to the ipsilateral breast and maximum dose to the skin were reduced by 22% and 17%, respectively. Combining the effect of tissue heterogeneities and RBE enhancement, BED coverage of the target was 89.9% in virtual patient phantoms with RBE enhancement (actual BED) as

Applications of tissue heterogeneity corrections and biologically effective dose volume histograms in assessing the doses for accelerated partial breast irradiation using an electronic brachytherapy source

International Nuclear Information System (INIS)

Shi Chengyu; Guo Bingqi; Eng, Tony; Papanikolaou, Nikos; Cheng, Chih-Yao

2010-01-01

A low-energy electronic brachytherapy source (EBS), the model S700 Axxent(TM) x-ray device developed by Xoft Inc., has been used in high dose rate (HDR) intracavitary accelerated partial breast irradiation (APBI) as an alternative to an Ir-192 source. The prescription dose and delivery schema of the electronic brachytherapy APBI plan are the same as the Ir-192 plan. However, due to its lower mean energy than the Ir-192 source, an EBS plan has dosimetric and biological features different from an Ir-192 source plan. Current brachytherapy treatment planning methods may have large errors in treatment outcome prediction for an EBS plan. Two main factors contribute to the errors: the dosimetric influence of tissue heterogeneities and the enhancement of relative biological effectiveness (RBE) of electronic brachytherapy. This study quantified the effects of these two factors and revisited the plan quality of electronic brachytherapy APBI. The influence of tissue heterogeneities is studied by a Monte Carlo method and heterogeneous 'virtual patient' phantoms created from CT images and structure contours; the effect of RBE enhancement in the treatment outcome was estimated by biologically effective dose (BED) distribution. Ten electronic brachytherapy APBI cases were studied. The results showed that, for electronic brachytherapy cases, tissue heterogeneities and patient boundary effect decreased dose to the target and skin but increased dose to the bones. On average, the target dose coverage PTV V 100 reduced from 95.0% in water phantoms (planned) to only 66.7% in virtual patient phantoms (actual). The actual maximum dose to the ribs is 3.3 times higher than the planned dose; the actual mean dose to the ipsilateral breast and maximum dose to the skin were reduced by 22% and 17%, respectively. Combining the effect of tissue heterogeneities and RBE enhancement, BED coverage of the target was 89.9% in virtual patient phantoms with RBE enhancement (actual BED) as compared to 95

Biological effective dose studies in carcinoma of uterine cervix

International Nuclear Information System (INIS)

Yadav, Poonam; Ramasubramanian, V.

2008-01-01

Cancer of cervix is the second most common cancer worldwide among women. Several treatments related protocols of radiotherapy have been followed over few decades in its treatment for evaluating the response. These physical doses varying on the basics of fractionation size, dose rate and total dose needed to be indicated as biological effective dose (BED) to rationalize these treatments. The curative potential of radiation therapy in the management of carcinoma of the cervix is greatly enhanced by the use of intracavitary brachytherapy. Successful brachytherapy requires the high radiation dose to be delivered to the tumor where as minimum radiation dose reach to surrounding normal tissue. Present study is aimed to evaluate biologically effective dose in patients receiving high dose-rate brachytherapy plus external beam radiotherapy based on tumor cell proliferation values in cancer of the cervix patients. The study includes 30 patients' data as a retrospective analysis. In addition determine extent of a dose-response relationship existing between the biological effective dose at Point A and the bladder and rectum and the clinical outcomes

Polymer gel dosimetry for synchrotron stereotactic radiotherapy and iodine dose-enhancement measurements

International Nuclear Information System (INIS)

Boudou, C; Tropres, I; Rousseau, J; Lamalle, L; Adam, J F; Esteve, F; Elleaume, H

2007-01-01

Synchrotron stereotactic radiotherapy (SSR) is a radiotherapy technique that makes use of the interactions of monochromatic low energy x-rays with high atomic number (Z) elements. An important dose-enhancement can be obtained if the target volume has been loaded with a sufficient amount of a high-Z element, such as iodine. In this study, we compare experimental dose measurements, obtained with normoxic polymer gel (nPAG), with Monte Carlo computations. Gels were irradiated within an anthropomorphic head phantom and were read out by magnetic resonance imaging. The dose-enhancement due to the presence of iodine in the gel (iodine concentration: 5 and 10 mg ml -1 ) was measured at two radiation energies (35 and 80 keV) and was compared to the calculated factors. nPAG dosimetry was shown to be efficient for measuring the sharp dose gradients produced by SSR. The agreement between 3D gel dosimetry and calculated dose distributions was found to be within 4% of the dose difference criterion and a distance to agreement of 2.1 mm for 80% of the voxels. Polymer gel doped with iodine exhibited higher sensitivity, in good agreement with the calculated iodine-dose enhancement. We demonstrate in this preliminary study that iodine-doped nPAG could be used for measuring in situ dose distributions for iodine-enhanced SSR treatment

Edge enhancement algorithm for low-dose X-ray fluoroscopic imaging.

Science.gov (United States)

Lee, Min Seok; Park, Chul Hee; Kang, Moon Gi

2017-12-01

Low-dose X-ray fluoroscopy has continually evolved to reduce radiation risk to patients during clinical diagnosis and surgery. However, the reduction in dose exposure causes quality degradation of the acquired images. In general, an X-ray device has a time-average pre-processor to remove the generated quantum noise. However, this pre-processor causes blurring and artifacts within the moving edge regions, and noise remains in the image. During high-pass filtering (HPF) to enhance edge detail, this noise in the image is amplified. In this study, a 2D edge enhancement algorithm comprising region adaptive HPF with the transient improvement (TI) method, as well as artifacts and noise reduction (ANR), was developed for degraded X-ray fluoroscopic images. The proposed method was applied in a static scene pre-processed by a low-dose X-ray fluoroscopy device. First, the sharpness of the X-ray image was improved using region adaptive HPF with the TI method, which facilitates sharpening of edge details without overshoot problems. Then, an ANR filter that uses an edge directional kernel was developed to remove the artifacts and noise that can occur during sharpening, while preserving edge details. The quantitative and qualitative results obtained by applying the developed method to low-dose X-ray fluoroscopic images and visually and numerically comparing the final images with images improved using conventional edge enhancement techniques indicate that the proposed method outperforms existing edge enhancement methods in terms of objective criteria and subjective visual perception of the actual X-ray fluoroscopic image. The developed edge enhancement algorithm performed well when applied to actual low-dose X-ray fluoroscopic images, not only by improving the sharpness, but also by removing artifacts and noise, including overshoot. Copyright © 2017 Elsevier B.V. All rights reserved.

The relative biological effectiveness of out-of-field dose

International Nuclear Information System (INIS)

Balderson, Michael; Koger, Brandon; Kirkby, Charles

2016-01-01

Purpose: using simulations and models derived from existing literature, this work investigates relative biological effectiveness (RBE) for out-of-field radiation and attempts to quantify the relative magnitudes of different contributing phenomena (spectral, bystander, and low dose hypersensitivity effects). Specific attention is paid to external beam radiotherapy treatments for prostate cancer. Materials and methods: using different biological models that account for spectral, bystander, and low dose hypersensitivity effects, the RBE was calculated for different points moving radially out from isocentre for a typical single arc VMAT prostate case. The RBE was found by taking the ratio of the equivalent dose with the physical dose. Equivalent doses were calculated by determining what physical dose would be necessary to produce the same overall biological effect as that predicted using the different biological models. Results: spectral effects changed the RBE out-of-field less than 2%, whereas response models incorporating low dose hypersensitivity and bystander effects resulted in a much more profound change of the RBE for out-of-field doses. The bystander effect had the largest RBE for points located just outside the edge of the primary radiation beam in the cranial caudal (z-direction) compared to low dose hypersensitivity and spectral effects. In the coplanar direction, bystander effect played the largest role in enhancing the RBE for points up to 8.75 cm from isocentre. Conclusions: spectral, bystander, and low dose hypersensitivity effects can all increase the RBE for out-of-field radiation doses. In most cases, bystander effects seem to play the largest role followed by low dose hypersensitivity. Spectral effects were unlikely to be of any clinical significance. Bystander, low dose hypersensitivity, and spectral effect increased the RBE much more in the cranial caudal direction (z-direction) compared with the coplanar directions. (paper)

Organ or tissue doses, effective dose and collective effective dose from X-ray diagnosis, in Japan

International Nuclear Information System (INIS)

Murayama, Takashi; Nishizawa, Kanae; Noda, Yutaka; Kumamoto, Yoshikazu; Iwai, Kazuo.

1996-01-01

Effective doses and collective effective doses from X-ray diagnostic examinations were calculated on the basis of the frequency of examinations estimated by a nationwide survey and the organ or tissue doses experimentally determined. The average organ or tissue doses were determined with thermoluminescence dosimeters put at various sites of organs or tissues in an adult and a child phantom. Effective doses (effective dose equivalents) were calculated as the sum of the weighted equivalent doses in all the organs or tissues of the body. As the examples of results, the effective doses per radiographic examination were approximately 7 mGy for male, and 9 mGy for female angiocardiography, and about 3 mGy for barium meal. Annual collective effective dose from X-ray diagnostic examinations in 1986 were about 104 x 10 3 person Sv from radiography and 118 x 10 3 person Sv from fluoroscopy, with the total of 222 x 10 3 person Sv. (author)

Low doses of glyphosate enhance growth, CO2 assimilation, stomatal conductance and transpiration in sugarcane and eucalyptus

Science.gov (United States)

Sublethal doses of herbicides can enhance plant growth and stimulate other process, an effect known as hormesis. The magnitude of hormesis is dependent on the plant species, the herbicide and its dose, plant development stage, and environmental parameters. Glyphosate hormesis is well established, bu...

CT findings of pancreatic carcinoma. Evaluation with the combined method of early enhancement CT and high dose enhancement CT

International Nuclear Information System (INIS)

Itoh, Shigeki; Endo, Tokiko; Isomura, Takayuki; Ishigaki, Takeo; Ikeda, Mitsuru; Senda, Kouhei.

1995-01-01

Computed tomographic (CT) findings of pancreatic ductal adenocarcinoma were studied with the combined method of early enhancement CT and high dose enhancement CT in 72 carcinomas. Common Findings were change in pancreatic contour, abnormal attenuation in a tumor and dilatation of the main pancreatic duct. The incidence of abnormal attenuation and dilatation of the main pancreatic duct and bile duct was constant regardless of tumor size. The finding of hypoattenuation at early enhancement CT was most useful for demonstrating a carcinoma. However, this finding was negative in ten cases, five of which showed inhomogenous hyperattenuation at high dose enhancement CT. The detection of change in pancreatic contour and dilatation of the main pancreatic duct was most frequent at high dose enhancement CT. The finding of change in pancreatic contour and/or abnormal attenuation in a tumor could be detected in 47 cases at plain CT, 66 at early enhancement CT and 65 at high dose enhancement CT. Since the four cases in which neither finding was detected by any CT method showed dilatated main pancreatic duct, there was no case without abnormal CT findings. This combined CT method will be a reliable diagnostic technique in the imaging of pancreatic carcinoma. (author)

Low-dose cyclophosphamide administered as daily or single dose enhances the antitumor effects of a therapeutic HPV vaccine

Science.gov (United States)

Peng, Shiwen; Lyford-Pike, Sofia; Akpeng, Belinda; Wu, Annie; Hung, Chien-Fu; Hannaman, Drew; Saunders, John R.; Wu, T.-C.

2012-01-01

Although therapeutic HPV vaccines are able to elicit systemic HPV-specific immunity, clinical responses have not always correlated with levels of vaccine-induced CD8+ T cells in human clinical trials. This observed discrepancy may be attributable to an immunosuppressive tumor microenvironment in which the CD8+ T cells are recruited. Regulatory T cells (Tregs) are cells that can dampen cytotoxic CD8+ T-cell function. Cyclophosphamide (CTX) is a systemic chemotherapeutic agent, which can eradicate immune cells, including inhibitory Tregs. The optimal dose and schedule of CTX administration in combination with immunotherapy to eliminate the Treg population without adversely affecting vaccine-induced T-cell responses is unknown. Therefore, we investigated various dosing and administration schedules of CTX in combination with a therapeutic HPV vaccine in a preclinical tumor model. HPV tumor-bearing mice received either a single preconditioning dose or a daily dose of CTX in combination with the pNGVL4a-CRT/E7(detox) DNA vaccine. Both single and daily dosing of CTX in combination with vaccine had a synergistic anti-tumor effect as compared to monotherapy alone. The potent antitumor responses were attributed to the reduction in Treg frequency and increased infiltration of HPV16 E7-specific CD8+ T cells, which led to higher ratios of CD8+/Treg and CD8+/CD11b+Gr-1+ myeloid-derived suppressor cells (MDSCs). There was an observed trend toward decreased vaccine-induced CD8+ T-cell frequency with daily dosing of CTX. We recommend a single, preconditioning dose of CTX prior to vaccination due to its efficacy, ease of administration, and reduced cumulative adverse effect on vaccine-induced T cells. PMID:23011589

Bile duct evaluation of potential living liver donors with Gd-EOB-DTPA enhanced MR cholangiography: Single-dose, double dose or half-dose contrast enhanced imaging

Energy Technology Data Exchange (ETDEWEB)

Kinner, Sonja, E-mail: Sonja.Kinner@uni-due.de [Department of Diagnostic and Interventional Radiology and Neuroradiology, University Hospital Essen (Germany); Steinweg, Verena [Department of Diagnostic and Interventional Radiology and Neuroradiology, University Hospital Essen (Germany); Maderwald, Stefan [Department of Diagnostic and Interventional Radiology and Neuroradiology, University Hospital Essen (Germany); Erwin L. Hahn Institute for Magnetic Resonance Imaging, Essen (Germany); Radtke, Arnold; Sotiropoulos, Georgios [Department of General Surgery, University Hospital Essen (Germany); Forsting, Michael; Schroeder, Tobias [Department of Diagnostic and Interventional Radiology and Neuroradiology, University Hospital Essen (Germany)

2014-05-15

Introduction: Detailed knowledge of the biliary anatomy is essential to avoid complications in living donor liver transplantation. The aim of this study was to determine the optimal dosage of Gd-EOB-DTPA for contrast-enhanced magnetic resonance cholangiography (ce-MRC) with reference to contrast-enhanced CT cholangiography (ce-CTC). Materials and methods: 30 potential living liver donors (PLLD) underwent both ce-CTC and ce-MRC. Ten candidates each received single, double or half-dose Gd-EOB-DTPA. Ce-MRC images with and without inversion recovery pulses (T1w ± IR) were acquired 20–30 min after intravenous contrast injection. Image data was quantitatively and qualitatively reviewed by two radiologists based on a on a 5-point scale. Data sets were compared using a Mann–Whitney-U-test or Wilcoxon-rank-sum-test. Kappa values were also calculated. Results: All image series provided sufficient diagnostic information both showing normal biliary anatomy and variant bile ducts. Ce-CTC showed statistically significant better results compared to all ce-MRC data sets. T1w MRC with single dose Gd-EOB-DTPA proved to be superior to half and double dose in subjective and objective evaluation without a statistically significant difference. Conclusions: Ce-MRC is at any dosage inferior to ce-CTC. As far as preoperative planning of bile duct surgery is focused on the central biliary anatomy, ce-MRC can replace harmful ce-CTC strategies, anyway. Best results were seen with single dose GD-EOB-DTPA on T1w MRC+IR.

Comparison of triple dose versus standard dose gadolinium-DTPA for detection of MRI enhancing lesions in patients with primary progressive multiple sclerosis.

Science.gov (United States)

Filippi, M; Campi, A; Martinelli, V; Colombo, B; Yousry, T; Canal, N; Scotti, G; Comi, G

1995-01-01

This study was performed to evaluate whether a triple dose of gadolinium-DTPA (Gd-DTPA) increases the sensitivity of brain MRI for detecting enhancing lesions in patients with primary progressive multiple sclerosis (PPMS). T1 weighted brain MRI was obtained for 10 patients with PPMS in two sessions. In the first session, one scan was obtained five to seven minutes after the injection of 0.1 mmol/kg Gd-DTPA (standard dose). In the second session, six to 24 hours later, one scan before and two scans five to seven minutes and one hour after the injection of 0.3 mmol/kg Gd-DTPA (triple dose) were obtained. Four enhancing lesions were detected in two patients when the standard dose of Gd-DTPA was used. The numbers of enhancing lesions increased to 13 and the numbers of patients with such lesions to five when the triple dose of Gd-DTPA was used and to 14 and six in the one hour delayed scans. The mean contrast ratio for enhancing lesions detected with the triple dose of Gd-DTPA was higher than those for lesions present in both the standard dose (P DTPA many more enhancing lesions can be detected in patients with PPMS. This is important both for planning clinical trials and for detecting the presence of inflammation in vivo in the lesions of such patients. Images PMID:8530944

Dose dependent effect of progesterone on hypoxic ventilatory response in newborn rats.

Science.gov (United States)

Hichri, Oubeidallah; Laurin, Jean-C; Julien, Cécile A; Joseph, Vincent; Bairam, Aida

2012-01-01

The effect of progesterone as a respiratory stimulant in newborn subjects is less known than that in adults. This study investigated the dose-response curve (0, 2, 4, and 8 mg/kg, ip) of progesterone on ventilation in non-anesthetized newborn rats at 4- and 12-days old using plethysmography. Progesterone had no effects in the regulation of normoxic ventilation. However, it enhanced the response to moderate hypoxia (FiO(2) 12%, 20 min) in 4- but not in 12-days old pups. This response was similar between the dose of 4 and 8 mg/kg. These observations suggested that progesterone enhances in age- and dose-dependent manner the hypoxic ventilatory response in newborn rats.

Supraphysiological Doses of Performance Enhancing Anabolic-Androgenic Steroids Exert Direct Toxic Effects on Neuron-like Cells

Directory of Open Access Journals (Sweden)

John Robert Basile

2013-05-01

Full Text Available Anabolic-androgenic steroids (AAS are lipophilic hormones often taken in excessive quantities by athletes and bodybuilders to enhance performance and increase muscle mass. AAS exert well known toxic effects on specific cell and tissue types and organ systems. The attention that androgen abuse has received lately should be used as an opportunity to educate both athletes and the general population regarding their adverse effects. Among numerous commercially available steroid hormones, very few have been specifically tested for direct neurotoxicity. We evaluated the effects of supraphysiological doses of methandienone and 17-α-methyltestosterone on sympathetic-like neuron cells. Vitality and apoptotic effects were analyzed, and immunofluorescence staining and western blot performed. In this study, we demonstrate that exposure of supraphysiological doses of methandienone and 17-α-methyltestosterone are toxic to the neuron-like differentiated pheochromocytoma cell line PC12, as confirmed by toxicity on neurite networks responding to nerve growth factor and the modulation of the survival and apoptosis-related proteins ERK, caspase-3, poly (ADP-ribose polymerase and heat-shock protein 90. We observe, in contrast to some previous reports but in accordance with others, expression of the androgen receptor (AR in neuron-like cells, which when inhibited mitigated the toxic effects of AAS tested, suggesting that the AR could be binding these steroid hormones to induce genomic effects. We also note elevated transcription of neuritin in treated cells, a neurotropic factor likely expressed in an attempt to resist neurotoxicity. Taken together, these results demonstrate that supraphysiological exposure to the AAS methandienone and 17-α-methyltestosterone exert neurotoxic effects by an increase in the activity of the intrinsic apoptotic pathway and alterations in neurite networks.

Measurement of dose enhancement close to high atomic number media using optical fibre thermoluminescence dosimeters

International Nuclear Information System (INIS)

Alalawi, Amani I.; Hugtenburg, R.P.; Abdul Rahman, A.T.; Barry, M.A.; Nisbet, A.; Alzimami, Khalid S.; Bradley, D.A.

2014-01-01

Present interest concerns development of a system to measure photoelectron-enhanced dose close to a tissue interface using analogue gold-coated doped silica-fibre thermoluminescence detectors and an X-ray set operating at 250 kVp. Study is made of the dose enhancement factor for various thicknesses of gold; measurements at a total gold thickness of 160 nm (accounting for incident and exiting photons) produces a mean measured dose enhancement factor of 1.33±0.01 To verify results, simulations of the experimental setup have been performed. - Highlights: • Dose enhancement • Thermoluminescence dosimeter • Monte Carlo simulation

Effect of edema, relative biological effectiveness, and dose heterogeneity on prostate brachytherapy

International Nuclear Information System (INIS)

Wang, Jian Z.; Mayr, Nina A.; Nag, Subir; Montebello, Joseph; Gupta, Nilendu; Samsami, Nina; Kanellitsas, Christos

2006-01-01

Many factors influence response in low-dose-rate (LDR) brachytherapy of prostate cancer. Among them, edema, relative biological effectiveness (RBE), and dose heterogeneity have not been fully modeled previously. In this work, the generalized linear-quadratic (LQ) model, extended to account for the effects of edema, RBE, and dose heterogeneity, was used to assess these factors and their combination effect. Published clinical data have shown that prostate edema after seed implant has a magnitude (ratio of post- to preimplant volume) of 1.3-2.0 and resolves exponentially with a half-life of 4-25 days over the duration of the implant dose delivery. Based on these parameters and a representative dose-volume histogram (DVH), we investigated the influence of edema on the implant dose distribution. The LQ parameters (α=0.15 Gy -1 and α/β=3.1 Gy) determined in earlier studies were used to calculate the equivalent uniform dose in 2 Gy fractions (EUD 2 ) with respect to three effects: edema, RBE, and dose heterogeneity for 125 I and 103 Pd implants. The EUD 2 analysis shows a negative effect of edema and dose heterogeneity on tumor cell killing because the prostate edema degrades the dose coverage to tumor target. For the representative DVH, the V 100 (volume covered by 100% of prescription dose) decreases from 93% to 91% and 86%, and the D 90 (dose covering 90% of target volume) decrease from 107% to 102% and 94% of prescription dose for 125 I and 103 Pd implants, respectively. Conversely, the RBE effect of LDR brachytherapy [versus external-beam radiotherapy (EBRT) and high-dose-rate (HDR) brachytherapy] enhances dose effect on tumor cell kill. In order to balance the negative effects of edema and dose heterogeneity, the RBE of prostate brachytherapy was determined to be approximately 1.2-1.4 for 125 I and 1.3-1.6 for 103 Pd implants. These RBE values are consistent with the RBE data published in the literature. These results may explain why in earlier modeling studies

Enchanced total dose damage in junction field effect transistors and related linear integrated circuits

International Nuclear Information System (INIS)

Flament, O.; Autran, J.L.; Roche, P.; Leray, J.L.; Musseau, O.

1996-01-01

Enhanced total dose damage of Junction Field-effect Transistors (JFETs) due to low dose rate and/or elevated temperature has been investigated for elementary p-channel structures fabricated on bulk and SOI substrates as well as for related linear integrated circuits. All these devices were fabricated with conventional junction isolation (field oxide). Large increases in damage have been revealed by performing high temperature and/or low dose rate irradiations. These results are consistent with previous studies concerning bipolar field oxides under low-field conditions. They suggest that the transport of radiation-induced holes through the oxide is the underlying mechanism. Such an enhanced degradation must be taken into account for low dose rate effects on linear integrated circuits

Field strength and dose dependence of contrast enhancement by gadolinium-based MR contrast agents

International Nuclear Information System (INIS)

Rinck, P.A.; Muller, R.N.

1999-01-01

The relaxivities r 1 and r 2 of magnetic resonance contrast agents and the T 1 relaxation time values of tissues are strongly field dependent. We present quantitative data and simulations of different gadolinium-based extracellular fluid contrast agents and the modulation of their contrast enhancement by the magnetic field to be able to answer the following questions: How are the dose and field dependences of their contrast enhancement? Is there an interrelationship between dose and field dependence? Should one increase or decrease doses at specific fields? Nuclear magnetic relaxation dispersion data were acquired for the following contrast agents: gadopentetate dimeglumine, gadoterate meglumine, gadodiamide injection, and gadoteridol injection, as well as for several normal and pathological human tissue samples. The magnetic field range stretched from 0.0002 to 4.7 T, including the entire clinical imaging range. The data acquired were then fitted with the appropriate theoretical models. The combination of the diamagnetic relaxation rates (R 1 = 1/T 1 and R 2 = 1/T 2 ) of tissues with the respective paramagnetic contributions of the contrast agents allowed the prediction of image contrast at any magnetic field. The results revealed a nearly identical field and dose-dependent increase of contrast enhancement induced by these contrast agents within a certain dose range. The target tissue concentration (TTC) was an important though nonlinear factor for enhancement. The currently recommended dose of 0.1 mmol/kg body weight seems to be a compromise close to the lower limits of diagnostically sufficient contrast enhancement for clinical imaging at all field strengths. At low field contrast enhancement might be insufficient. Adjustment of dose or concentration, or a new class of contrast agents with optimized relaxivity, would be a valuable contribution to a better diagnostic yield of contrast enhancement at all fields. (orig.)

TU-H-CAMPUS-TeP3-03: Dose Enhancement by Gold Nanoparticles Around the Bragg Peak of Proton Beams

Energy Technology Data Exchange (ETDEWEB)

Kwon, J; Sutherland, K [Department of Medical Physics, Hokkaido University Graduate School of Medicine (Japan); Hashimoto, T [Department of Radiation Medicine, Hokkaido University Graduate School of Medicine (Japan); Peng, H; Xing, L [Department of Radiation Oncology, Stanford University and Global Station for Quantum Medical Science and Engineering, Global Institution for Collaborative Research and Education (GI-CoRE), Hokkaido University (Japan); Shirato, H [Department of Radiation Medicine, Hokkaido University Graduate School of Medicine and Global Station for Quantum Medical Science and Engineering, Global Institution for Collaborative Research and Education (GI-CoRE), Hokkaido University (Japan); Date, H [Faculty of Health Sciences, Hokkaido University (Japan)

2016-06-15

Purpose: To make clear the spatial distribution of dose enhancement around gold nanoparticles (GNPs) located near the proton Bragg peak, and to evaluate the potential of GNPs as a radio sensitizer. Methods: The dose enhancement by electrons emitted from GNPs under proton irradiation was estimated by Geant4 Monte Carlo simulation toolkit in two steps. In an initial macroscopic step, 100 and 195 MeV proton beams were incident on a water cube, 30 cm on a side. Energy distributions of protons were calculated at four depths, 50% and 75% proximal to the Bragg peak, 100% peak, and 75% distal to the peak (P50, P75, Peak, and D75, respectively). In a subsequent microscopic step, protons with the energy distribution calculated above were incident on a 20 nm diameter GNP in a nanometer-size water box and the spatial distribution of dose around the GNP was determined for each energy distribution. The dose enhancement factor (DEF) was also deduced. Results: The dose enhancement effect was spread to several tens of nanometers in the both depth and radial directions. The enhancement area increased in the order of P50, P75, Peak, and D75 for both cases with 100 and 195 MeV protons. In every position around the Bragg peak, the 100 MeV beam resulted in a higher dose enhancement than the 195 MeV beam. At P75, the average and maximum DEF were 3.9 and 17.0 for 100 MeV, and 3.5 and 16.2 for 195 MeV, respectively. These results indicate that lower energy protons caused higher dose enhancement in this incident proton energy range. Conclusion: The dose enhancement around GNPs spread as the position in the Bragg peak region becomes deeper and depends on proton energy. It is expected that GNPs can be used as a radio sensitizer with consideration of the location and proton beam energy.

Effects of low dose rate irradiation on life span prolongation of human premature-aging syndrome model mice

International Nuclear Information System (INIS)

Nomura, Takaharu

2006-01-01

We previously showed that Type II diabetes model mice prolonged of their life span by life long low dose rate irradiation. We also found that antioxidant function in variety tissues of some strain of mice were enhancement after low dose/low dose rate irradiation. The prolongation of life span might depend on certain damaged level of reactive oxygen species. We thought the effect of the prolongation was due to the enhancement of the antioxidant activities after irradiation. We investigated whether the enhancement of antioxidant activities after low dose rate irradiation had an effect on life span prolongation. Four-week-old female human premature-aging syndrome model mice, kl/kl (klotho) mice, which the life span of this model mouse is about 65 days, were irradiated with gamma rays at 0.35, 0.70 or 1.2 mGy/hr. The 0.70 mGy/hr-irradiated group remarkably effected on the prolongation of their life span. Some mice of the group were extremely survived for about and more 100 days. Antioxidant activities in the irradiated groups were enhancement by low dose rate irradiation, however the dependence of the dose rates were not clearly difference. These results suggest that the antioxidant activities in this model mouse were enhanced by the low dose rate irradiation, and may make it possible to prolong the life span of this mouse. (author)

Development and validation of Monte Carlo dose computations for contrast-enhanced stereotactic synchrotron radiation therapy

International Nuclear Information System (INIS)

Vautrin, M.

2011-01-01

Contrast-enhanced stereotactic synchrotron radiation therapy (SSRT) is an innovative technique based on localized dose-enhancement effects obtained by reinforced photoelectric absorption in the tumor. Medium energy monochromatic X-rays (50 - 100 keV) are used for irradiating tumors previously loaded with a high-Z element. Clinical trials of SSRT are being prepared at the European Synchrotron Radiation Facility (ESRF), an iodinated contrast agent will be used. In order to compute the energy deposited in the patient (dose), a dedicated treatment planning system (TPS) has been developed for the clinical trials, based on the ISOgray TPS. This work focuses on the SSRT specific modifications of the TPS, especially to the PENELOPE-based Monte Carlo dose engine. The TPS uses a dedicated Monte Carlo simulation of medium energy polarized photons to compute the deposited energy in the patient. Simulations are performed considering the synchrotron source, the modeled beamline geometry and finally the patient. Specific materials were also implemented in the voxelized geometry of the patient, to consider iodine concentrations in the tumor. The computation process has been optimized and parallelized. Finally a specific computation of absolute doses and associated irradiation times (instead of monitor units) was implemented. The dedicated TPS was validated with depth dose curves, dose profiles and absolute dose measurements performed at the ESRF in a water tank and solid water phantoms with or without bone slabs. (author) [fr

Effects of low dose mitomycin C on experimental tumor radiotherapy

International Nuclear Information System (INIS)

Yang Jianzheng; Liang Shuo; Qu Yaqin; Pu Chunji; Zhang Haiying; Wu Zhenfeng; Wang Xianli

2001-01-01

Objective: To evaluate the possibility of low dose mitomycin C(MMC) as an adjunct therapy for radiotherapy. Methods: Change in tumor size tumor-bearing mice was measured. Radioimmunoassay was used to determine immune function of mice. Results: Low dose Mac's pretreatment reduced tumor size more markedly than did radiotherapy only. The immune function in mice given with low dose MMC 12h before radiotherapy was obviously higher than that in mice subjected to radiotherapy only (P<0.05), and was close to that in the tumor-bearing mice before radiotherapy. Conclusion: Low dose MMC could improve the radiotherapy effect. Pretreatment with low dose MMC could obviously improve the immune suppression state in mice caused by radiotherapy. The mechanism of its improvement of radiotherapeutic effect by low dose of MMC might be due to its enhancement of immune function and induction of adaptive response in tumor-bearing mice

Estimation of the collective effective dose to the population from medical X-ray examinations in Finland

International Nuclear Information System (INIS)

Tenkanen-Rautakoskia, Petra; Jaervinen, Hannu; Bly, Ritva

2008-01-01

The collective effective dose to the population from all X-ray examinations in Finland in 2005 was estimated. The numbers of X-ray examinations were collected by a questionnaire to the health care units (response rate 100 %). The effective doses in plain radiography were calculated using a Monte Carlo based program (PCXMC), as average values for selected health care units. For computed tomography (CT), weighted dose length product (DLP w ) in a standard phantom was measured for routine CT protocols of four body regions, for 80 % of CT scanners including all types. The effective doses were calculated from DPL w values using published conversion factors. For contrast-enhanced radiology and interventional radiology, the effective dose was estimated mainly by using published DAP values and conversion factors for given body regions. About 733 examinations per 1000 inhabitants (excluding dental) were made in 2005, slightly less than in 2000. The proportions of plain radiography, computed tomography, contrast-enhanced radiography and interventional procedures were about 92, 7, 1 and 1 %, respectively. From 2000, the frequencies (number of examinations per 1000 inhabitants) of plain radiography and contrast-enhanced radiography have decreased about 8 and 33 %, respectively, while the frequencies of CT and interventional radiology have increased about 28 and 38 %, respectively. The population dose from all X-ray examinations is about 0.43 mSv per person (in 1997 0.5 mSv). About half of this is caused by CT (in 1997 only 20 %) although the relative number of CT examinations is only 7 %. The contribution by plain radiography is 19 %, interventional radiology 17 %, and contrast-enhanced radiology 14 %. It is concluded that CT examinations are the major source of the population dose, while interventional radiology gives about the same population dose as plain radiography. For plain radiography, body examinations cause the highest effective dose. (author)

Dose enhancement in radiotherapy of small lung tumors using inline magnetic fields: A Monte Carlo based planning study

Energy Technology Data Exchange (ETDEWEB)

Oborn, B. M., E-mail: brad.oborn@gmail.com [Illawarra Cancer Care Centre (ICCC), Wollongong, NSW 2500, Australia and Centre for Medical Radiation Physics (CMRP), University of Wollongong, Wollongong, NSW 2500 (Australia); Ge, Y. [Sydney Medical School, University of Sydney, NSW 2006 (Australia); Hardcastle, N. [Northern Sydney Cancer Centre, Royal North Shore Hospital, Sydney, NSW 2065 (Australia); Metcalfe, P. E. [Centre for Medical Radiation Physics (CMRP), University of Wollongong, Wollongong NSW 2500, Australia and Ingham Institute for Applied Medical Research, Liverpool, NSW 2170 (Australia); Keall, P. J. [Sydney Medical School, University of Sydney, NSW 2006, Australia and Ingham Institute for Applied Medical Research, Liverpool, NSW 2170 (Australia)

2016-01-15

Purpose: To report on significant dose enhancement effects caused by magnetic fields aligned parallel to 6 MV photon beam radiotherapy of small lung tumors. Findings are applicable to future inline MRI-guided radiotherapy systems. Methods: A total of eight clinical lung tumor cases were recalculated using Monte Carlo methods, and external magnetic fields of 0.5, 1.0, and 3 T were included to observe the impact on dose to the planning target volume (PTV) and gross tumor volume (GTV). Three plans were 6 MV 3D-CRT plans while 6 were 6 MV IMRT. The GTV’s ranged from 0.8 to 16 cm{sup 3}, while the PTV’s ranged from 1 to 59 cm{sup 3}. In addition, the dose changes in a 30 cm diameter cylindrical water phantom were investigated for small beams. The central 20 cm of this phantom contained either water or lung density insert. Results: For single beams, an inline magnetic field of 1 T has a small impact in lung dose distributions by reducing the lateral scatter of secondary electrons, resulting in a small dose increase along the beam. Superposition of multiple small beams leads to significant dose enhancements. Clinically, this process occurs in the lung tissue typically surrounding the GTV, resulting in increases to the D{sub 98%} (PTV). Two isolated tumors with very small PTVs (3 and 6 cm{sup 3}) showed increases in D{sub 98%} of 23% and 22%. Larger PTVs of 13, 26, and 59 cm{sup 3} had increases of 9%, 6%, and 4%, describing a natural fall-off in enhancement with increasing PTV size. However, three PTVs bounded to the lung wall showed no significant increase, due to lack of dose enhancement in the denser PTV volume. In general, at 0.5 T, the GTV mean dose enhancement is around 60% lower than that at 1 T, while at 3 T, it is 5%–60% higher than 1 T. Conclusions: Monte Carlo methods have described significant and predictable dose enhancement effects in small lung tumor plans for 6 MV radiotherapy when an external inline magnetic field is included. Results of this study

The radiosensitizing effect of doranidazole on human colorectal cancer cells exposed to high doses of irradiation

International Nuclear Information System (INIS)

Zhang, Li; Gong, Aimin; Ji, Jun; Wu, Yuanyuan; Zhu, Xiaoyu; Lv, Suqing; Lv, Hongzhu; Sun, Xizhuo

2007-01-01

This paper investigates the effects of a new radiosensitizer, doranidazole, and enhancing irradiation on colorectal cancer cells. The radiosensitizing effect of doranidazole was determined using colony formation and propidium iodide (PI) assays to measure cell growth inhibition and the cell killing effect of human colorectal cancer cell lines exposed to high doses of γ-ray irradiation under hypoxic conditions in vitro. Fluorescence staining and cell migration assays were also used to assess the radiosensitizing effect. Cell proliferation evaluated by clonogenic survival curves was significantly inhibited by 5 mmol/L doranidazole, particularly at doses ranging from 10 to 30 Gy of irradiation. The radiosensitizing effect of doranidazole on colorectal cancer cells occurs in a time- and dose-dependent manner. Doranidazole also inhibited the mobility of cell invasion and migration. Doranidazole can enhance the killing effect and the cell growth inhibition of colorectal cancer after high-dose irradiation in a time and dose-dependent manner

Plutonium dose-effect relationship

International Nuclear Information System (INIS)

Matsuoka, Osamu

1976-01-01

Dose in internal exposure to Pu was investigated, and dose-effect relationship was discussed. Dose-effect relationship in internal exposure was investigated by means of two methods, which were relationship between dose and its effect (relationship between μ Ci/Kg and its effect), and exposure dose and its effects (rad-effect), and merits and demerits of two methods were mentioned. Problems in a indication method such as mean dose were discussed with respect to the dose in skeleton, the liver and the lung. Pu-induced osteosarcoma in mice rats, and beagles was described, and differences in its induction between animals were discussed. Pulmonary neoplasma induced by 239 PuO 2 inhalation in beagles was reported, and description was made as to differences in induction of lung cancer between animals when Pu was inhaled and was taken into the lung. A theoretical and experimental study of a extrapolation of the results of the animal experiment using Pu to human cases is necessary. (Serizawa, K.)

SU-F-T-661: Dependence of Gold Nano Particles Cluster Morphology On Dose Enhancement of Photon Radiation Therapy Apply for Radiation Biology Effect

Energy Technology Data Exchange (ETDEWEB)

Ahn, S [Department of Health Sciences and Technology, Samsung Advanced Institute for Health Sciences and Technology, Sungkyunkwan University (Korea, Republic of); Chung, K; Han, Y; Park, H [Samsung Medical Center, Sungkyunkwan University School of Medicine radiation oncology (Korea, Republic of)

2016-06-15

Purpose: Injected gold nano particles (GNPs) to a body for dose enhancement are known to form in the tumorcell cluster morphology. We investigated the dependence of dose enhancement on the morphology characteristic with an approximated morphology model by using Monte Carlo simulations. Methods: For MC simulation, TOPAS version 2.0P-03 was used. GNP cluster morphology was approximated as a body center cubic(BCC) model by placing 8 GNPs at the corner and one at the center of cube with length from 2.59 µm to 0.25 µm located in a 4 µm length water filled cube phantom. 4 µm length square shaped beams of poly-energetic 50, 260 kVp photons were irradiated to the water filled cube phantom with 100 nm diameter GNPs in it. Dose enhancement ratio(DER) was computed as a function of distance from the surface of the GNP at the cube center for 18 cubes geometries. For scoring particles, 10 nm width of concentric shell shaped detector was constructed up to 100 nm from the center. Total dose in a sphere of 100 nm radius of detector were normalized to 2.59 µm length cube morphology. To verified biological effect of BCC model applied to cell survival curve fitting. Results: DER increase as the distance of the GNPs reduces. DER was largest for 0.25 µm length cube. Dependence of GNP distance DER increment was 1.73, 1.60 for 50 kVp, 260 kVp photons, respectively. Also, Using BCC model applied to cell survival curve was well prediction. Conclusion: DER with GNPs was larger when they are closely packed in the phantom. Therefore, better therapeutic effects can be expected with close-packed GNPs. This research was supported by the NRF funded by the Ministry of Science, ICT & Future Planning (2012M3A9B6055201 and 2012R1A1A2042414), Samsung Medical Center grant[GFO1130081].

Spatial distributions of dose enhancement around a gold nanoparticle at several depths of proton Bragg peak

Energy Technology Data Exchange (ETDEWEB)

Kwon, Jihun [Department of Radiation Oncology, Hokkaido University Graduate School of Medicine, Hokkaido University (Japan); Sutherland, Kenneth [Department of Medical Physics, Hokkaido University Graduate School of Medicine, Hokkaido University (Japan); Hashimoto, Takayuki [Department of Radiation Medicine, Hokkaido University Graduate School of Medicine (Japan); Shirato, Hiroki [Department of Radiation Medicine, Hokkaido University Graduate School of Medicine and Global Station for Quantum Medical Science and Engineering, Global Institution for Collaborative Research and Education (GI-CoRE), Hokkaido University (Japan); Date, Hiroyuki, E-mail: date@hs.hokudai.ac.jp [Faculty of Health Sciences, Hokkaido University (Japan)

2016-10-01

Gold nanoparticles (GNPs) have been recognized as a promising candidate for a radiation sensitizer. A proton beam incident on a GNP can produce secondary electrons, resulting in an enhancement of the dose around the GNP. However, little is known about the spatial distribution of dose enhancement around the GNP, especially in the direction along the incident proton. The purpose of this study is to determine the spatial distribution of dose enhancement by taking the incident direction into account. Two steps of calculation were conducted using the Geant4 Monte Carlo simulation toolkit. First, the energy spectra of 100 and 195 MeV protons colliding with a GNP were calculated at the Bragg peak and three other depths around the peak in liquid water. Second, the GNP was bombarded by protons with the obtained energy spectra. Radial dose distributions were computed along the incident beam direction. The spatial distributions of the dose enhancement factor (DEF) and subtracted dose (D{sub sub}) were then evaluated. The spatial DEF distributions showed hot spots in the distal radial region from the proton beam axis. The spatial D{sub sub} distribution isotropically spread out around the GNP. Low energy protons caused higher and wider dose enhancement. The macroscopic dose enhancement in clinical applications was also evaluated. The results suggest that the consideration of the spatial distribution of GNPs in treatment planning will maximize the potential of GNPs.

Quantitative MR changes in Gd-DTPA enhancement after high dose intravenous methylprednisolone in multiple sclerosis

International Nuclear Information System (INIS)

Barkhof, F.; Valk, J.; Hommes, O.R.; Scheltens, P.

1991-01-01

The purpose of this study was to investigate the effect of high dose intravenous methylprednisolone (MP) on gadolinium-DTPA enhancement in MS-lesions. By means of this the influence of MP on the permeability of the blood-brain barrier can be studied. (author). 19 refs.; 1 fig

Determination of organ doses and effective doses in radiooncology

International Nuclear Information System (INIS)

Roth, J.; Martinez, A.E.

2007-01-01

Background and Purpose: With an increasing chance of success in radiooncology, it is necessary to estimate the risk from radiation scatter to areas outside the target volume. The cancer risk from a radiation treatment can be estimated from the organ doses, allowing a somewhat limited effective dose to be estimated and compared. Material and Methods: The doses of the radiation-sensitive organs outside the target volume can be estimated with the aid of the PC program PERIDOSE developed by van der Giessen. The effective doses are determined according to the concept of ICRP, whereby the target volume and the associated organs related to it are not taken into consideration. Results: Organ doses outside the target volume are generally < 1% of the dose in the target volume. In some cases, however, they can be as high as 3%. The effective doses during radiotherapy are between 60 and 900 mSv, depending upon the specific target volume, the applied treatment technique, and the given dose in the ICRU point. Conclusion: For the estimation of the radiation risk, organ doses in radiooncology can be calculated with the aid of the PC program PERIDOSE. While evaluating the radiation risk after ICRP, for the calculation of the effective dose, the advanced age of many patients has to be considered to prevent that, e.g., the high gonad doses do not overestimate the effective dose. (orig.)

Normal tissue dose-effect models in biological dose optimisation

International Nuclear Information System (INIS)

Alber, M.

2008-01-01

Sophisticated radiotherapy techniques like intensity modulated radiotherapy with photons and protons rely on numerical dose optimisation. The evaluation of normal tissue dose distributions that deviate significantly from the common clinical routine and also the mathematical expression of desirable properties of a dose distribution is difficult. In essence, a dose evaluation model for normal tissues has to express the tissue specific volume effect. A formalism of local dose effect measures is presented, which can be applied to serial and parallel responding tissues as well as target volumes and physical dose penalties. These models allow a transparent description of the volume effect and an efficient control over the optimum dose distribution. They can be linked to normal tissue complication probability models and the equivalent uniform dose concept. In clinical applications, they provide a means to standardize normal tissue doses in the face of inevitable anatomical differences between patients and a vastly increased freedom to shape the dose, without being overly limiting like sets of dose-volume constraints. (orig.)

Enhanced natural radiation exposure enhanced by human activity: the largest contributor to the Chinese population dose

International Nuclear Information System (INIS)

Pan Ziqiang; Liu Yanyang

2011-01-01

For the radiation exposure caused by human activities, the enhanced natural radiation exposure is the largest contributor to Chinese population dose. This problem has attracted social attention in recent years. Efforts have been made in several fields, such as radon indoors and in workplace, environmental problems associated with NORMs, occupational radiation hazards of non-uranium mine, and radiation dose evaluation for energy chain, but there are still many problems to be solved. In order to protect the health of workers and the public, while ensuring industrial production and economic development, it is also necessary to continue to strengthen research in all aspects above mentioned, and gradually promote the control of natural radiation exposure enhanced by human activities. (authors)

Low dose radiation enhancing inhibitory effect of tumor-associated antigen peptide extract on H-22 hepatocarcinoma

Energy Technology Data Exchange (ETDEWEB)

Zuyue, Sun; Jingyi, Fu; Yong, Zhao [Transplantation Biology Research Division, State Key Laboratory of Biomembrane and Membrane Biotechnology, Inst. of Zoology, Chinese Academy of Sciences, Beijing (China); Jianxiang, Liu; Zhibo, Fu; Xiuyi, Li; Shuzheng, Liu; Shouliang, Gong

2005-06-15

Objective: To determine whether there is synergically inhibitory effect of low dose radiation (LDR) and tumor-associated antigen peptides (TAP) on tumor growth in vivo, which may provide experimental basis for potential clinical co-application of these two approaches to treat cancers. Methods: TAP extract (MW {<=}3x10{sup 6}) from tumor cell membrane was prepared with mild acid elution method , as reported. The mice were whole-bodily irradiated with 75 mGy X-rays 12 h before immunization with TAP extract. After immunization , the levels of CD3, CD69, TCR{alpha}{beta} cells and T cell subsets in the spleen were detected with FACS. The tumor growth rate was estimated, and the responses to Con A, the cytokine productions and CTL activities of splenocytes were also analyzed 7 d after immunization with TAP. Results: The present experimental results showed that the TAP extract significantly reduced the incidence of the transplanted tumor, delayed the average appearing time and decreased the growth speed of the tumor. The response of splenocytes from mice immunized with TAP extract to Con A increased significantly compared with that in the control group. Irradiation with 75 mGy X-rays 12 h before immunization further enhanced the inhibitory effect of TAP extract on tumor growth, and increased the percentage of CD8{sup +} splenocytes. Conclusion: These results suggest that whole-body irradiation with LDR exerts a synergic inhibitory effect with TAP on tumor growth in vivo, in which enhanced cellular immune responses may be involved. (authors)

Effects of low dose radiation on tumor-bearing mice

International Nuclear Information System (INIS)

Feng Li; Hou Dianjun; Huang Shanying; Deng Daping; Wang Linchao; Cheng Yufeng

2007-01-01

Objective: To explore the effects of low-dose radiation on tumor-bearing mice and radiotherapy induced by low-dose radiation. Methods: Male Wistar mice were implanted with Walker-256 sarcoma cells in the right armpit. On day 4, the mice were given 75 mGy whole-body X-ray radiation. From the fifth day, tumor volume was measured, allowing for the creation of a graph depicting tumor growth. Lymphocytes activity in mice after whole-body X-ray radiation with LDR was determinned by FCM. Cytokines level were also determined by ELISA. Results: Compared with the radiotherapy group, tumor growth was significantly slower in the mice pre-exposed to low-dose radiation (P<0.05), after 15 days, the average tumor weight in the mice pre- exposed to low-dose radiation was also significantly lower (P<0.05). Lymphocytes activity and the expression of the CK in mice after whole-body y-ray radiation with LDR increased significantly. Conclusions: Low-dose radiation can markedly improve the immune function of the lymphocyte, inhibit the tumor growth, increase the resistant of the high-dose radiotherapy and enhance the effect of radiotherapy. (authors)

Optimal gadolinium dose level for magnetic resonance imaging (MRI) contrast enhancement of U87-derived tumors in athymic nude rats for the assessment of photodynamic therapy

Science.gov (United States)

Cross, Nathan; Varghai, Davood; Flask, Chris A.; Feyes, Denise K.; Oleinick, Nancy L.; Dean, David

2009-02-01

This study aims to determine the effect of varying gadopentetate dimeglumine (Gd-DTPA) dose on Dynamic Contrast Enhanced-Magnetic Resonance Imaging (DCE-MRI) tracking of brain tumor photodynamic therapy (PDT) outcome. Methods: We injected 2.5 x 105 U87 cells (derived from human malignant glioma) into the brains of six athymic nude rats. After 9, 12, and 13 days DCE-MRI images were acquired on a 9.4 T micro-MRI scanner before and after administration of 100, 150, or 200 μL of Gd-DTPA. Results: Tumor region normalized DCE-MRI scan enhancement at peak was: 1.217 over baseline (0.018 Standard Error [SE]) at the 100 μL dose, 1.339 (0.013 SE) at the 150 μL dose, and 1.287 (0.014 SE) at the 200 μL dose. DCE-MRI peak tumor enhancement at the 150 μL dose was significantly greater than both the 100 μL dose (p DTPA dose provided the greatest T1 weighted contrast enhancement, while minimizing negative T2* effects, in DCE-MRI scans of U87-derived tumors. Maximizing Gd-DTPA enhancement in DCE-MRI scans may assist development of a clinically robust (i.e., unambiguous) technique for PDT outcome assessment.

Oesteosarcomagenic doses of radium (224Ra) and infectious endogenous retroviruses enhance proliferation and osteogenic differentiation of skeletal tissue dofferentiating in vitro

International Nuclear Information System (INIS)

Schmidt, J.; Heermeier, K.; Linzner, U.; Luz, A.; Silbermann, M.; Livne, E.; Erfle, V.

1994-01-01

Cartilage tissue from embryonic mice which undergoes osteogenic differentiation during in vitro cultivation was used to study the effect of osteosarcomagenic doses of α-irradiation and bone-tumor-inducing retroviruses on proliferation and phenotypic differentiation of skeletal cells in a defined tissue culture model. Irradiated mandibular condyles showed dose-dependent enhancement of cell proliferation at day 7 of the culture and increased osteogenic differentiation at day 14. Maximal effects were found with 7.4 Bq/ml of 224 Ra-labeled medium. Doses of 740 and 7400 Bq/ml of 224 Ra-labeled medium induced increasing cell death. Retrovirus infection enhanced osteogenic differentiation and extended the viability of irradiated cells. After transplantation none of the treated tissues developed tumors in syngeneic mice. (orig.)

A comparison of the angular dependence of effective dose and effective dose equivalent

International Nuclear Information System (INIS)

Sitek, M.A.; Gierga, D.P.; Xu, X.G.

1996-01-01

In ICRP (International Commission on Radiological Protection) Publication 60, the set of critical organs and their weighing factors were changed, defining the quantity effective dose, E. This quantity replaced the effective dose equivalent, H E , as defined by ICRP 26. Most notably, the esophagus was added to the list of critical organs. The Monte Carlo neutron/photon transport code MCNP was used to determine the effective dose to sex-specific anthropomorphic phantoms. The phantoms, developed in previous research, were modified to include the esophagus. Monte Carlo simulations were performed for monoenergetic photon beams of energies 0.08 MeV, 0.3 MeV, and 1.0 MeV for various azimuthal and polar angles. Separate organ equivalent doses were determined for male and female phantoms. The resulting organ equivalent doses were calculated from arithmetic mean averages. The angular dependence of effective dose was compared with that of effective dose equivalent reported in previous research. The differences between the two definitions and possible implications to regulatory agencies were summarized

Cognitive enhancement and antipsychotic-like activity following repeated dosing with the selective M4 PAM VU0467154.

Science.gov (United States)

Gould, Robert W; Grannan, Michael D; Gunter, Barak W; Ball, Jacob; Bubser, Michael; Bridges, Thomas M; Wess, Jurgen; Wood, Michael W; Brandon, Nicholas J; Duggan, Mark E; Niswender, Colleen M; Lindsley, Craig W; Conn, P Jeffrey; Jones, Carrie K

2018-01-01

Although selective activation of the M 1 muscarinic acetylcholine receptor (mAChR) subtype has been shown to improve cognitive function in animal models of neuropsychiatric disorders, recent evidence suggests that enhancing M 4 mAChR function can also improve memory performance. Positive allosteric modulators (PAMs) targeting the M 4 mAChR subtype have shown therapeutic potential for the treatment of multiple symptoms observed in schizophrenia, including positive and cognitive symptoms when assessed in acute preclinical dosing paradigms. Since the cholinergic system has been implicated in multiple stages of learning and memory, we evaluated the effects of repeated dosing with the highly selective M 4 PAM VU0467154 on either acquisition and/or consolidation of learning and memory when dosed alone or after pharmacologic challenge with the N-methyl-d-aspartate subtype of glutamate receptors (NMDAR) antagonist MK-801. MK-801 challenge represents a well-documented preclinical model of NMDAR hypofunction that is thought to underlie some of the positive and cognitive symptoms observed in schizophrenia. In wildtype mice, 10-day, once-daily dosing of VU0467154 either prior to, or immediately after daily testing enhanced the rate of learning in a touchscreen visual pairwise discrimination task; these effects were absent in M 4 mAChR knockout mice. Following a similar 10-day, once-daily dosing regimen of VU0467154, we also observed 1) improved acquisition of memory in a cue-mediated conditioned freezing paradigm, 2) attenuation of MK-801-induced disruptions in the acquisition of memory in a context-mediated conditioned freezing paradigm and 3) reversal of MK-801-induced hyperlocomotion. Comparable efficacy and plasma and brain concentrations of VU0467154 were observed after repeated dosing as those previously reported with an acute, single dose administration of this M 4 PAM. Together, these studies are the first to demonstrate that cognitive enhancing and antipsychotic

Effects of low dose gamma radiation on the early growth of red pepper and the resistance to subsquent high dose of radiation

Energy Technology Data Exchange (ETDEWEB)

Kim, J. S.; Baek, M. H.; Kim, D. H.; Lee, Y. K. [KAERI, Taejon (Korea, Republic of); Lee, Y. B. [Chungnam National Univ., Taejon (Korea, Republic of)

2001-05-01

Red pepper (capsicum annuum L. cv. Jokwang and cv. Johong) seeds were irradiated with the dose of 0{approx}50 Gy to investigated the effect of the low dose gamma radiation on the early growth and resistance to subsequent high dose of radiation. The effect of the low dose gamma radiation on the early growth and resistance to subsequenct high dose of radiation were enhanced in Johong cultivar but not in Jokwang cultivar. Germination rate and early growth of Johong cultivar were noticeably increased at 4 Gy-, 8 Gy- and 20 Gy irradiation group. Resistance to subsequent high dose of radiation of Johong cultivar were increased at almost all of the low dose irradiation group. Especially it was highest at 4 Gy irradiation group. The carotenoid contents and enzyme activity on the resistance to subsequent high dose of radiation of Johong cultivar were increased at the 4 Gy and 8 Gy irradiation group.

Health effect of low dose/low dose rate radiation

International Nuclear Information System (INIS)

Kodama, Seiji

2012-01-01

The clarified and non-clarified scientific knowledge is discussed to consider the cause of confusion of explanation of the title subject. The low dose is defined roughly lower than 200 mGy and low dose rate, 0.05 mGy/min. The health effect is evaluated from 2 aspects of clinical symptom/radiation hazard protection. In the clinical aspect, the effect is classified in physical (early and late) and genetic ones, and is classified in stochastic (no threshold value, TV) and deterministic (with TV) ones from the radioprotection aspect. Although the absence of TV in the carcinogenic and genetic effects has not been proved, ICRP employs the stochastic standpoint from the safety aspect for radioprotection. The lowest human TV known now is 100 mGy, meaning that human deterministic effect would not be generated below this dose. Genetic deterministic effect can be observable only in animal experiments. These facts suggest that the practical risk of exposure to <100 mGy in human is the carcinogenesis. The relationship between carcinogenic risk in A-bomb survivors and their exposed dose are found fitted to the linear no TV model, but the epidemiologic data, because of restriction of subject number analyzed, do not always mean that the model is applicable even below the dose <100 mGy. This would be one of confusing causes in explanation: no carcinogenic risk at <100 mGy or risk linear to dose even at <100 mGy, neither of which is scientifically conclusive at present. Also mentioned is the scarce risk of cancer in residents living in the high background radiation regions in the world in comparison with that in the A-bomb survivors exposed to the chronic or acute low dose/dose rate. Molecular events are explained for the low-dose radiation-induced DNA damage and its repair, gene mutation and chromosome aberration, hypothesis of carcinogenesis by mutation, and non-targeting effect of radiation (bystander effect and gene instability). Further researches to elucidate the low dose

Modeling low-dose-rate effects in irradiated bipolar-base oxides

International Nuclear Information System (INIS)

Graves, R.J.; Cirba, C.R.; Schrimpf, R.D.; Milanowski, R.J.; Saigne, F.; Michez, A.; Fleetwood, D.M.; Witczak, S.C.

1997-02-01

A physical model is developed to quantify the contribution of oxide-trapped charge to enhanced low-dose-rate gain degradation in BJTs. Simulations show that space charge limited transport is partially responsible for the low-dose-rate enhancement

Low doses effects

International Nuclear Information System (INIS)

Tubiana, M.

1997-01-01

In this article is asked the question about a possible carcinogens effect of low dose irradiation. With epidemiological data, knowledge about the carcinogenesis, the professor Tubiana explains that in spite of experiments made on thousand or hundred of thousands animals it has not been possible to bring to the fore a carcinogens effect for low doses and then it is not reasonable to believe and let the population believe that low dose irradiation could lead to an increase of neoplasms and from this point of view any hardening of radiation protection standards could in fact, increase anguish about ionizing radiations. (N.C.)

Effective dose equivalent

International Nuclear Information System (INIS)

Huyskens, C.J.; Passchier, W.F.

1988-01-01

The effective dose equivalent is a quantity which is used in the daily practice of radiation protection as well as in the radiation hygienic rules as measure for the health risks. In this contribution it is worked out upon which assumptions this quantity is based and in which cases the effective dose equivalent can be used more or less well. (H.W.)

Gold nanoparticle-aided brachytherapy with vascular dose painting: estimation of dose enhancement to the tumor endothelial cell nucleus.

Science.gov (United States)

Ngwa, Wilfred; Makrigiorgos, G Mike; Berbeco, Ross I

2012-01-01

Theoretical microdosimetry at the subcellular level is employed in this study to estimate the dose enhancement to tumor endothelial cell nuclei, caused by radiation-induced photo/Auger electrons originating from gold nanoparticles (AuNPs) targeting the tumor endothelium, during brachytherapy. A tumor vascular endothelial cell (EC) is modeled as a slab of 2 μm (thickness) × 10 μm (length) × 10 μm (width). The EC contains a nucleus of 5 μm diameter and thickness of 0.5-1 μm, corresponding to nucleus size 5%-10% of cellular volume, respectively. Analytic calculations based on the electron energy loss formula of Cole were carried out to estimate the dose enhancement to the nucleus caused by photo/Auger electrons from AuNPs attached to the exterior surface of the EC. The nucleus dose enhancement factor (nDEF), representing the ratio of the dose to the nucleus with and without the presence of gold nanoparticles was calculated for different AuNP local concentrations. The investigated concentration range considers the potential for significantly higher local concentration near the EC due to preferential accumulation of AuNP in the tumor vasculature. Four brachytherapy sources: I-125, Pd-103, Yb-169, and 50 kVp x-rays were investigated. For nucleus size of 10% of the cellular volume and AuNP concentrations ranging from 7 to 140 mg/g, brachytherapy sources Pd-103, I-125, 50 kVp, and Yb-169 yielded nDEF values of 5.6-73, 4.8-58.3, 4.7-56.6, and 3.2-25.8, respectively. Meanwhile, for nucleus size 5% of the cellular volume in the same concentration range, Pd-103, I-125, 50 kVp, and Yb-169 yielded nDEF values of 6.9-79.2, 5.1-63.2, 5.0-61.5, and 3.3-28.3, respectively. The results predict that a substantial dose boost to the nucleus of endothelial cells can be achieved by applying tumor vasculature-targeted AuNPs in combination with brachytherapy. Such vascular dose boosts could induce tumor vascular shutdown, prompting extensive tumor cell death.

Gold nanoparticle-aided brachytherapy with vascular dose painting: Estimation of dose enhancement to the tumor endothelial cell nucleus

Energy Technology Data Exchange (ETDEWEB)

Ngwa, Wilfred; Makrigiorgos, G. Mike; Berbeco, Ross I. [Department of Radiation Oncology, Division of Medical Physics and Biophysics, Brigham and Women' s Hospital, Dana-Farber Cancer Institute and Harvard Medical School, Boston, Massachusetts 02115 (United States)

2012-01-15

Purpose: Theoretical microdosimetry at the subcellular level is employed in this study to estimate the dose enhancement to tumor endothelial cell nuclei, caused by radiation-induced photo/Auger electrons originating from gold nanoparticles (AuNPs) targeting the tumor endothelium, during brachytherapy. Methods: A tumor vascular endothelial cell (EC) is modeled as a slab of 2 {mu}m (thickness) x 10 {mu}m (length) x 10 {mu}m (width). The EC contains a nucleus of 5 {mu}m diameter and thickness of 0.5-1 {mu}m, corresponding to nucleus size 5%-10% of cellular volume, respectively. Analytic calculations based on the electron energy loss formula of Cole were carried out to estimate the dose enhancement to the nucleus caused by photo/Auger electrons from AuNPs attached to the exterior surface of the EC. The nucleus dose enhancement factor (nDEF), representing the ratio of the dose to the nucleus with and without the presence of gold nanoparticles was calculated for different AuNP local concentrations. The investigated concentration range considers the potential for significantly higher local concentration near the EC due to preferential accumulation of AuNP in the tumor vasculature. Four brachytherapy sources: I-125, Pd-103, Yb-169, and 50 kVp x-rays were investigated. Results: For nucleus size of 10% of the cellular volume and AuNP concentrations ranging from 7 to 140 mg/g, brachytherapy sources Pd-103, I-125, 50 kVp, and Yb-169 yielded nDEF values of 5.6-73, 4.8-58.3, 4.7-56.6, and 3.2-25.8, respectively. Meanwhile, for nucleus size 5% of the cellular volume in the same concentration range, Pd-103, I-125, 50 kVp, and Yb-169 yielded nDEF values of 6.9-79.2, 5.1-63.2, 5.0-61.5, and 3.3-28.3, respectively. Conclusions: The results predict that a substantial dose boost to the nucleus of endothelial cells can be achieved by applying tumor vasculature-targeted AuNPs in combination with brachytherapy. Such vascular dose boosts could induce tumor vascular shutdown, prompting

Evaluation of Enhanced Low Dose Rate Sensitivity in Discrete Bipolar Junction Transistors

Science.gov (United States)

Chen, Dakai; Ladbury Raymond; LaBel, Kenneth; Topper, Alyson; Ladbury, Raymond; Triggs, Brian; Kazmakites, Tony

2012-01-01

We evaluate the low dose rate sensitivity in several families of discrete bipolar transistors across device parameter, quality assurance level, and irradiation bias configuration. The 2N2222 showed the most significant low dose rate sensitivity, with low dose rate enhancement factor of 3.91 after 100 krad(Si). The 2N2907 also showed critical degradation levels. The devices irradiated at 10 mrad(Si)/s exceeded specifications after 40 and 50 krad(Si) for the 2N2222 and 2N2907 devices, respectively.

Photon activation therapy with 127I-deoxyuridine: measurement of dose enhancement in cultured mammalian cells

International Nuclear Information System (INIS)

Fairchild, R.G.; Laster, B.H.; Commerford, S.L.; Furcinitti, P.S.; Sylvester, B.; Gabel, D.; Popenoe, E.; Foster, S.

1985-01-01

A technique for radiation enhancement of conventional photon radiotherapy is outlined which has been called photon activation therapy (PAT) (6). High linear energy transfer (LET) radiations in the form of Auger electron distributions are generated by photons of appropriate energies, through photon activation of stable iodine incorporated as an analog of thymidine (Tyd) in DNA. Of the several halogenated deoxyribonucleosides evaluated, iodinated deoxyuridine (IdUrd) has been chosen as the only Tyd analog providing effective photon activation. This mechanism is combined with radiation sensitization produced by IdUrd to produce an overall radiation enhancement. Calculations show that at 5% replacement (IdUrd for Tyd) therapeutic (TG) will vary from ∼2 (single acute dose) to ∼17 (low dose rates associated with permanent implant brachytherapy). Parameters used in the calculation of TG have been evaluated in cell culture; dose enhancements obtained with x-rays (including photon activation) were found to be significantly higher than values measured with γ-rays (no photon activation). Comparison is made between theoretical and measured values. Because of the evident lack of repair of damage produced by both sensitization and photon activation, significant gains are expected to be realized following protracted irradiations. Exchanges (IdUrd for Tyd) for 105 have been obtained in vivo (murine tumors). The authors believe that the application of PAT would be most advantageous in the treatment of brain tumors (grade IV astrocytomas) with implanted 145 Sm sources

The effect of low-dose X-irradiation on immune system

International Nuclear Information System (INIS)

Ishii, Keiichiro

1996-01-01

The hypothesis of radiation hormesis has been proposed. To elucidate the hormetic effect on the immune system, we studied the mitogen-induced proliferation of splenocytes of F344/NSlc rat and BALB/c mouse after low-dose X-irradiation. Con A, PHA or LPS-induced proliferation of rat splenocytes prepared at 4 hr after irradiation was augmented with 5 cGy. This augmentation was observed within a few hours after irradiation, being a temporary effect. In case of mice, the proliferation of splenocytes induced by Con A, PHA or LPS was augmented by irradiation with 2.5 cGy. Thus, some phenomena of hormetic effect on the immune system were observed. However, the mechanism of augmentation of immune splenocytes is uncertainty. Therefore, we examined changes in production of LTB 4 and IL-1 being inflammatory mediators. After 5 cGy irradiation the production of LTB 4 of rat splenocyte showed a significant increase. Furthermore, 2.5 cGy irradiation also enhanced, the biological activity of intracellular IL-1 of LPS-stimulated mouse splenocytes. Additionally, to elucidate the stimulative effect on the antitumor immunity by low-dose X-irradiation, we studied the changes in the incidence of thymic lymphoma using AKR mice and of spontaneous metastasis to lung using tumor bearing mice. The incidence of thymic lymphoma was significantly decreased and the life span was significantly prolonged by periodical low-dose X-irradiation in terms of breeding of AKR mice. By an irradiation with 15 cGy, numbers of lung colony in the tumor bearing mice were decreased by 57% relative to the sham-irradiated controls. Then, IL-6 and TNF-α production of tumor bearing mice splenocytes were enhanced. These findings suggest that the low-dose X-irradiation might have caused a light inflammation and might have induced an augmentation of immune splenocytes. Furthermore, these results indicate that an augmentation of the antitumor immunity was induced by low-dose X-irradiation. (author). 127 refs

The effect of low-dose X-irradiation on immune system

Energy Technology Data Exchange (ETDEWEB)

Ishii, Keiichiro [Central Research Inst. of Electric Power Industry, Komae, Tokyo (Japan). Komae Research Lab.

1996-06-01

The hypothesis of radiation hormesis has been proposed. To elucidate the hormetic effect on the immune system, we studied the mitogen-induced proliferation of splenocytes of F344/NSlc rat and BALB/c mouse after low-dose X-irradiation. Con A, PHA or LPS-induced proliferation of rat splenocytes prepared at 4 hr after irradiation was augmented with 5 cGy. This augmentation was observed within a few hours after irradiation, being a temporary effect. In case of mice, the proliferation of splenocytes induced by Con A, PHA or LPS was augmented by irradiation with 2.5 cGy. Thus, some phenomena of hormetic effect on the immune system were observed. However, the mechanism of augmentation of immune splenocytes is uncertainty. Therefore, we examined changes in production of LTB{sub 4} and IL-1 being inflammatory mediators. After 5 cGy irradiation the production of LTB{sub 4} of rat splenocyte showed a significant increase. Furthermore, 2.5 cGy irradiation also enhanced, the biological activity of intracellular IL-1 of LPS-stimulated mouse splenocytes. Additionally, to elucidate the stimulative effect on the antitumor immunity by low-dose X-irradiation, we studied the changes in the incidence of thymic lymphoma using AKR mice and of spontaneous metastasis to lung using tumor bearing mice. The incidence of thymic lymphoma was significantly decreased and the life span was significantly prolonged by periodical low-dose X-irradiation in terms of breeding of AKR mice. By an irradiation with 15 cGy, numbers of lung colony in the tumor bearing mice were decreased by 57% relative to the sham-irradiated controls. Then, IL-6 and TNF-{alpha} production of tumor bearing mice splenocytes were enhanced. These findings suggest that the low-dose X-irradiation might have caused a light inflammation and might have induced an augmentation of immune splenocytes. Furthermore, these results indicate that an augmentation of the antitumor immunity was induced by low-dose X-irradiation. 127 refs.

Caffeine Markedly Enhanced Radiation-Induced Bystander Effects

International Nuclear Information System (INIS)

Jiang Erkang; Wu Lijun

2009-01-01

In this paper it is shown that incubation with 2 mM caffeine enhanced significantly the MN (micronucleus) formation in both the 1 cGy α-particle irradiated and non-irradiated bystander regions. Moreover, caffeine treatment made the non-irradiated bystander cells more sensitive to damage signals. Treated by c-PTIO(2-(4-carboxy-phenyl)- 4,4,5,5-tetramethyl-imidazoline-1-oxyl-3-oxide), a nitric oxide (NO) scavenger, the MN frequencies were effectively inhibited, showing that nitric oxide might be very important in mediating the enhanced damage. These results indicated that caffeine enhanced the low dose α-particle radiation-induced damage in irradiated and non-irradiated bystander regions, and therefore it is important to investigate the relationship between the radiosensitizer and radiation-induced bystander effects (RIBE). (ion beam bioengineering)

Effects of an acute therapeutic or rewarding dose of amphetamine on acquisition of Pavlovian autoshaping and ventral striatal dopamine signaling.

Science.gov (United States)

Schuweiler, D R; Athens, J M; Thompson, J M; Vazhayil, S T; Garris, P A

2018-01-15

Rewarding doses of amphetamine increase the amplitude, duration, and frequency of dopamine transients in the ventral striatum. Debate continues at the behavioral level about which component of reward, learning or incentive salience, is signaled by these dopamine transients and thus altered in addiction. The learning hypothesis proposes that rewarding drugs result in pathological overlearning of drug-predictive cues, while the incentive sensitization hypothesis suggests that rewarding drugs result in sensitized attribution of incentive salience to drug-predictive cues. Therapeutic doses of amphetamine, such as those used to treat attention-deficit hyperactivity disorder, are hypothesized to enhance the ventral striatal dopamine transients that are critical for reward-related learning and to enhance Pavlovian learning. However, the effects of therapeutic doses of amphetamine on Pavlovian learning are poorly understood, and the effects on dopamine transients are completely unknown. We determined the effects of an acute pre-training therapeutic or rewarding amphetamine injection on the acquisition of Pavlovian autoshaping in the intact rat. We also determined the effects of these doses on electrically evoked transient-like dopamine signals using fast-scan cyclic voltammetry in the anesthetized rat. The rewarding dose enhanced the amplitude and duration of DA signals, caused acute task disengagement, impaired learning for several days, and triggered incentive sensitization. The therapeutic dose produced smaller enhancements in DA signals but did not have similar behavioral effects. These results underscore the necessity of more studies using therapeutic doses, and suggest a hybrid learning/incentive sensitization model may be required to explain the development of addiction. Copyright © 2017 Elsevier B.V. All rights reserved.

Effects of proton radiation dose, dose rate and dose fractionation on hematopoietic cells in mice

International Nuclear Information System (INIS)

Ware, J.H.; Rusek, A.; Sanzari, J.; Avery, S.; Sayers, C.; Krigsfeld, G.; Nuth, M.; Wan, X.S.; Kennedy, A.R.

2010-01-01

The present study evaluated the acute effects of radiation dose, dose rate and fractionation as well as the energy of protons in hematopoietic cells of irradiated mice. The mice were irradiated with a single dose of 51.24 MeV protons at a dose of 2 Gy and a dose rate of 0.05-0.07 Gy/min or 1 GeV protons at doses of 0.1, 0.2, 0.5, 1, 1.5 and 2 Gy delivered in a single dose at dose rates of 0.05 or 0.5 Gy/min or in five daily dose fractions at a dose rate of 0.05 Gy/min. Sham-irradiated animals were used as controls. The results demonstrate a dose-dependent loss of white blood cells (WBCs) and lymphocytes by up to 61% and 72%, respectively, in mice irradiated with protons at doses up to 2 Gy. The results also demonstrate that the dose rate, fractionation pattern and energy of the proton radiation did not have significant effects on WBC and lymphocyte counts in the irradiated animals. These results suggest that the acute effects of proton radiation on WBC and lymphocyte counts are determined mainly by the radiation dose, with very little contribution from the dose rate (over the range of dose rates evaluated), fractionation and energy of the protons.

Effects of proton radiation dose, dose rate and dose fractionation on hematopoietic cells in mice.

Science.gov (United States)

Ware, J H; Sanzari, J; Avery, S; Sayers, C; Krigsfeld, G; Nuth, M; Wan, X S; Rusek, A; Kennedy, A R

2010-09-01

The present study evaluated the acute effects of radiation dose, dose rate and fractionation as well as the energy of protons in hematopoietic cells of irradiated mice. The mice were irradiated with a single dose of 51.24 MeV protons at a dose of 2 Gy and a dose rate of 0.05-0.07 Gy/min or 1 GeV protons at doses of 0.1, 0.2, 0.5, 1, 1.5 and 2 Gy delivered in a single dose at dose rates of 0.05 or 0.5 Gy/min or in five daily dose fractions at a dose rate of 0.05 Gy/min. Sham-irradiated animals were used as controls. The results demonstrate a dose-dependent loss of white blood cells (WBCs) and lymphocytes by up to 61% and 72%, respectively, in mice irradiated with protons at doses up to 2 Gy. The results also demonstrate that the dose rate, fractionation pattern and energy of the proton radiation did not have significant effects on WBC and lymphocyte counts in the irradiated animals. These results suggest that the acute effects of proton radiation on WBC and lymphocyte counts are determined mainly by the radiation dose, with very little contribution from the dose rate (over the range of dose rates evaluated), fractionation and energy of the protons.

Anti-tumor effect of low dose radiation in mice

International Nuclear Information System (INIS)

Fan Zhengping; Lu Jiaben; Zhu Bingchai

1997-01-01

The author reports the effects of the total body irradiation of low dose radiation (LDR) and/or the local irradiation of large dose on average tumor weights and tumor inhibitory rates in 170 mice inoculated S 180 sarcoma cell, and the influence of LDR on average longevity in 40 tumor-bearing animals. Results show (1) LDR in the range of 75∼250 mGy can inhibit tumor growth to some extent; (2) fractionated irradiation of 75 mGy and local irradiation of 10 Gy may produce a synergism in tumor growth inhibition; and (3)LDR may enhance average longevity in ascitic tumor-bearing mice

Maximizing the biological effect of proton dose delivered with scanned beams via inhomogeneous daily dose distributions

Energy Technology Data Exchange (ETDEWEB)

Zeng Chuan; Giantsoudi, Drosoula; Grassberger, Clemens; Goldberg, Saveli; Niemierko, Andrzej; Paganetti, Harald; Efstathiou, Jason A.; Trofimov, Alexei [Department of Radiation Oncology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114 (United States)

2013-05-15

Purpose: Biological effect of radiation can be enhanced with hypofractionation, localized dose escalation, and, in particle therapy, with optimized distribution of linear energy transfer (LET). The authors describe a method to construct inhomogeneous fractional dose (IFD) distributions, and evaluate the potential gain in the therapeutic effect from their delivery in proton therapy delivered by pencil beam scanning. Methods: For 13 cases of prostate cancer, the authors considered hypofractionated courses of 60 Gy delivered in 20 fractions. (All doses denoted in Gy include the proton's mean relative biological effectiveness (RBE) of 1.1.) Two types of plans were optimized using two opposed lateral beams to deliver a uniform dose of 3 Gy per fraction to the target by scanning: (1) in conventional full-target plans (FTP), each beam irradiated the entire gland, (2) in split-target plans (STP), beams irradiated only the respective proximal hemispheres (prostate split sagittally). Inverse planning yielded intensity maps, in which discrete position control points of the scanned beam (spots) were assigned optimized intensity values. FTP plans preferentially required a higher intensity of spots in the distal part of the target, while STP, by design, employed proximal spots. To evaluate the utility of IFD delivery, IFD plans were generated by rearranging the spot intensities from FTP or STP intensity maps, separately as well as combined using a variety of mixing weights. IFD courses were designed so that, in alternating fractions, one of the hemispheres of the prostate would receive a dose boost and the other receive a lower dose, while the total physical dose from the IFD course was roughly uniform across the prostate. IFD plans were normalized so that the equivalent uniform dose (EUD) of rectum and bladder did not increase, compared to the baseline FTP plan, which irradiated the prostate uniformly in every fraction. An EUD-based model was then applied to estimate tumor

Maximizing the biological effect of proton dose delivered with scanned beams via inhomogeneous daily dose distributions

International Nuclear Information System (INIS)

Zeng Chuan; Giantsoudi, Drosoula; Grassberger, Clemens; Goldberg, Saveli; Niemierko, Andrzej; Paganetti, Harald; Efstathiou, Jason A.; Trofimov, Alexei

2013-01-01

Purpose: Biological effect of radiation can be enhanced with hypofractionation, localized dose escalation, and, in particle therapy, with optimized distribution of linear energy transfer (LET). The authors describe a method to construct inhomogeneous fractional dose (IFD) distributions, and evaluate the potential gain in the therapeutic effect from their delivery in proton therapy delivered by pencil beam scanning. Methods: For 13 cases of prostate cancer, the authors considered hypofractionated courses of 60 Gy delivered in 20 fractions. (All doses denoted in Gy include the proton's mean relative biological effectiveness (RBE) of 1.1.) Two types of plans were optimized using two opposed lateral beams to deliver a uniform dose of 3 Gy per fraction to the target by scanning: (1) in conventional full-target plans (FTP), each beam irradiated the entire gland, (2) in split-target plans (STP), beams irradiated only the respective proximal hemispheres (prostate split sagittally). Inverse planning yielded intensity maps, in which discrete position control points of the scanned beam (spots) were assigned optimized intensity values. FTP plans preferentially required a higher intensity of spots in the distal part of the target, while STP, by design, employed proximal spots. To evaluate the utility of IFD delivery, IFD plans were generated by rearranging the spot intensities from FTP or STP intensity maps, separately as well as combined using a variety of mixing weights. IFD courses were designed so that, in alternating fractions, one of the hemispheres of the prostate would receive a dose boost and the other receive a lower dose, while the total physical dose from the IFD course was roughly uniform across the prostate. IFD plans were normalized so that the equivalent uniform dose (EUD) of rectum and bladder did not increase, compared to the baseline FTP plan, which irradiated the prostate uniformly in every fraction. An EUD-based model was then applied to estimate tumor

Maximizing the biological effect of proton dose delivered with scanned beams via inhomogeneous daily dose distributions.

Science.gov (United States)

Zeng, Chuan; Giantsoudi, Drosoula; Grassberger, Clemens; Goldberg, Saveli; Niemierko, Andrzej; Paganetti, Harald; Efstathiou, Jason A; Trofimov, Alexei

2013-05-01

Biological effect of radiation can be enhanced with hypofractionation, localized dose escalation, and, in particle therapy, with optimized distribution of linear energy transfer (LET). The authors describe a method to construct inhomogeneous fractional dose (IFD) distributions, and evaluate the potential gain in the therapeutic effect from their delivery in proton therapy delivered by pencil beam scanning. For 13 cases of prostate cancer, the authors considered hypofractionated courses of 60 Gy delivered in 20 fractions. (All doses denoted in Gy include the proton's mean relative biological effectiveness (RBE) of 1.1.) Two types of plans were optimized using two opposed lateral beams to deliver a uniform dose of 3 Gy per fraction to the target by scanning: (1) in conventional full-target plans (FTP), each beam irradiated the entire gland, (2) in split-target plans (STP), beams irradiated only the respective proximal hemispheres (prostate split sagittally). Inverse planning yielded intensity maps, in which discrete position control points of the scanned beam (spots) were assigned optimized intensity values. FTP plans preferentially required a higher intensity of spots in the distal part of the target, while STP, by design, employed proximal spots. To evaluate the utility of IFD delivery, IFD plans were generated by rearranging the spot intensities from FTP or STP intensity maps, separately as well as combined using a variety of mixing weights. IFD courses were designed so that, in alternating fractions, one of the hemispheres of the prostate would receive a dose boost and the other receive a lower dose, while the total physical dose from the IFD course was roughly uniform across the prostate. IFD plans were normalized so that the equivalent uniform dose (EUD) of rectum and bladder did not increase, compared to the baseline FTP plan, which irradiated the prostate uniformly in every fraction. An EUD-based model was then applied to estimate tumor control probability

Low doses effects and gamma radiations low dose rates

International Nuclear Information System (INIS)

Averbeck, D.

1999-01-01

This expose wishes for bringing some definitions and base facts relative to the problematics of low doses effects and low dose rates effects. It shows some already used methods and some actual experimental approaches by focusing on the effects of ionizing radiations with a low linear energy transfer. (N.C.)

Radiomodifying effect of hyperglycemia: correlation between a glucose dose and a tumor size

International Nuclear Information System (INIS)

Ul'yanenko, S.E.; Polityukova, N.A.

1991-01-01

Experiments were made on rats with trasplantable sarcoma-45 and sarcoma M-1. Dose correlation was established during a study of hyperglycemic radiomodifying action. Glucose injection at a dose of 6-17.5 g/kg was shown to enhance irradiation action. Glucose injection below or above these doses might cause worse radiotherapy results or even the death of animals. The best effect was obtained with small-size tumors. Large tumors(over 2 cm 3 ) were less sensitive to hyperglycemia combined with irradiation. Skin radioprotective action of hyperglycemia before irradiation increased with an increase in a dose

Effects of low dose radiation and epigenetic regulation

International Nuclear Information System (INIS)

Jiao Benzheng; Ma Shumei; Yi Heqing; Kong Dejuan; Zhao Guangtong; Gao Lin; Liu Xiaodong

2010-01-01

Purpose: To conclude the relationship between epigenetics regulation and radiation responses, especially in low-dose area. Methods: The literature was examined for papers related to the topics of DNA methylation, histone modifications, chromatin remodeling and non-coding RNA modulation in low-dose radiation responses. Results: DNA methylation and radiation can regulate reciprocally, especially in low-dose radiation responses. The relationship between histone methylation and radiation mainly exists in the high-dose radiation area; histone deacetylase (HDAC) inhibitors show a promising application to enhance radiation sensitivity, no matter whether in low-dose or high-dose areas; the connection between γ-H2AX and LDR has been remained unknown, although γ-H2AX has been shown no radiation sensitivities with 1-15 Gy irradiation; histone ubiquitination play an important role in DNA damage repair mechanism. Moreover, chromatin remodeling has an integral role in DSB repair and the chromatin response, in general, may be precede DNA end resection. Finally, the effect of radiation on miRNA expression seems to vary according to cell type, radiation dose, and post-irradiation time point. Conclusion: Although the advance of epigenetic regulation on radiation responses, which we are managing to elucidate in this review, has been concluded, there are many questions and blind blots deserved to investigated, especially in low-dose radiation area. However, as progress on epigenetics, we believe that many new elements will be identified in the low-dose radiation responses which may put new sights into the mechanisms of radiation responses and radiotherapy. (authors)

Three-dimensional dose distribution in contrast-enhanced digital mammography using Gafchromic XR-QA2 films: Feasibility study

International Nuclear Information System (INIS)

Hwang, Yi-Shuan; Lin, Yu-Ying; Cheung, Yun-Chung; Tsai, Hui-Yu

2014-01-01

This study was aimed to establish three-dimensional dose distributions for contrast-enhanced digital mammography (CEDM) using self-developed Gafchromic XR-QA2 films. Dose calibration and distribution evaluations were performed on a full-field digital mammography unit with dual energy (DE) contrast-enhanced option. Strategy for dose calibration of films in the DE mode was based on the data obtained from common target/filter/kVp combinations used clinically and the dose response model modified from Rampado's model. Dose derived from films were also verified by measured data from an ionization chamber. The average difference of dose was 8.9% in the dose range for clinical uses. Three-dimensional dose distributions were estimated using triangular acrylic phantom equipped with the mammography system. Five pieces of film sheets were separately placed between the acrylic slabs to evaluate the dose distribution at different depths. After normalizing the dose in each pixel to the maximum dose at the top-center position of the acrylic, normalized dose distribution for transverse, coronal and sagittal planes, could thus be obtained. The depth dose distribution evaluated in this study may further serve as a reference for evaluating the patient glandular dose at different depths based on the entrance exposure information. - Highlights: • CEDM techniques can enhance contrast uptake areas and suppress background tissue. • Dose for the dual-energy acquisition is about 20% higher than standard mode. • A new method is proposed to estimate the 3D dose distribution in dual-energy CEDM. • Depth of normalized dose ratio of 0.5 is less than but near 1 cm in the DE mode

Contrast-enhanced spectral mammography based on a photon-counting detector: quantitative accuracy and radiation dose

Science.gov (United States)

Lee, Seungwan; Kang, Sooncheol; Eom, Jisoo

2017-03-01

Contrast-enhanced mammography has been used to demonstrate functional information about a breast tumor by injecting contrast agents. However, a conventional technique with a single exposure degrades the efficiency of tumor detection due to structure overlapping. Dual-energy techniques with energy-integrating detectors (EIDs) also cause an increase of radiation dose and an inaccuracy of material decomposition due to the limitations of EIDs. On the other hands, spectral mammography with photon-counting detectors (PCDs) is able to resolve the issues induced by the conventional technique and EIDs using their energy-discrimination capabilities. In this study, the contrast-enhanced spectral mammography based on a PCD was implemented by using a polychromatic dual-energy model, and the proposed technique was compared with the dual-energy technique with an EID in terms of quantitative accuracy and radiation dose. The results showed that the proposed technique improved the quantitative accuracy as well as reduced radiation dose comparing to the dual-energy technique with an EID. The quantitative accuracy of the contrast-enhanced spectral mammography based on a PCD was slightly improved as a function of radiation dose. Therefore, the contrast-enhanced spectral mammography based on a PCD is able to provide useful information for detecting breast tumors and improving diagnostic accuracy.

An experimental study on the alteration of thermal enhancement ratio by combination of split dose hyperthermia irradiation

Energy Technology Data Exchange (ETDEWEB)

Park, Sun Ok; Kim, Hee Seup [Ewha Womens University College of Medicine, Seoul (Korea, Republic of)

1983-06-15

The study was undertaken to evaluate the alteration of thermal enhancement ratio as a function of time intervals between two split dose hyperthermias followed by irradiation. For the experiments, 330 mice were divided into 3 groups; the first, 72 mice were used to evaluate the heat reaction by single dose hyperthermia and heat resistance by split dose hyperthermia, the second, 36 mice were used to evaluate the radiation reaction by irradiation only, and the third, 222 mice were used for TER observation by combination of single dose hyperthermia and irradiation, and TER alteration by combination of split dose hyperthermia and irradiation. For each group the skin reaction score of mouse tail was used for observation and evaluation of the result of heat and irradiation. The results obtained are summarized as follows: 1. The heating time resulting 50% necrosis (ND{sub 5}0) Was 101 minutes in 43 .deg. C and 24 minutes in 45 .deg. C hyperthermia, which indicated that three is reciprocal proportion between temperature and heating time. 2. Development of heat resistance was observed by split dose hyperthermia. 3. The degree of skin reaction by irradiation only was increased proportionally as a function of radiation dose, and calculated radiation dose corresponding to skin score 1.5 (D{sub 1}.5) was 4,137 rads. 4. Obtained thermal enhancement ratio by combination of single dose hyperthermia and irradiation was increased proportionally as a function of heating time. 5. Thermal enhancement ratio was decreased by combination of split dose hyperthermia and irradiation, which was less intense and lasted longer than development of heat resistance. In summary, these studies indicate that the alteration of thermal enhancement ratio has influence on heat resistance by split dose hyperthermia and irradiation.

Enhanced aflatoxin production by aspergillus parasiticus and aspergillus flavus after low dose gamma irradiation

International Nuclear Information System (INIS)

Ito, Hitoshi

1992-01-01

Spores of Aspergillus parasiticus IFO 30179 and A. flavus var. columnaris S46 were irradiated at 0.05, 0.2 and 0.4 kGy in the synthetic low salts (SL) broth, and the effect on aflatoxin production was examined after 10 days incubation at 30 or 25degC. In these two strains, irradiation of spores at 0.05 kGy resulted in higher B1 or G1 production than the non-irradiated controles. However, spores of the both strains irradiated at 0.2 or 0.4 kGy produced less aflatoxins than non-irradiated controles. In the SL broth, apparent stimulation by low dose irradiation was slight, and these enhanced effects were not observed after reinfection to fresh SL broth. In the case of food samples, the levels of aflatoxin B 1 and G 1 with A. parasiticus were increased from 15 to 90% by incubation of irradiated spores at 1 kGy in autoclaved polished rice, black pepper, white pepper and red pepper. These enhancement would be induced by change of composition in each substrates. Mutations of fungi induced by irradiation is not effective for enhancement of aflatoxin production. (author)

Riboflavin at high doses enhances lung cancer cell proliferation, invasion, and migration.

Science.gov (United States)

Yang, Hui-ting; Chao, Pei-chun; Yin, Mei-chin

2013-02-01

The influence of riboflavin (vitamin B(2) ) upon growth, invasion, and migration in non-small cell lung cancer cell lines was evaluated. Riboflavin at 1, 10, 25, 50, 100, 200, or 400 μmol/L was added into A549, H3255, or Calu-6 cells. The effects of this compound upon level and/or expression of reactive oxygen species (ROS), inflammatory cytokines, intercellular adhesion molecule (ICAM)-1, fibronectin, matrix metalloproteinase (MMP)-9, MMP-2, focal adhesion kinase (FAK), nuclear factor kappa B (NF-κB), and mitogen-activated protein kinase (MAPK) were examined. Results showed that riboflavin at test doses did not affect the level of ROS and glutathione. Riboflavin at 200 and 400 μmol/L significantly enhanced cell growth in test lung cancer cell lines, and at 400 μmol/L significantly increased the release of interleukin-6, tumor necrosis factor-alpha, and vascular endothelial growth factor. This agent at 200 and 400 μmol/L also upregulated protein production of ICAM-1, fibronectin, MMP-9, MMP-2, NF-κB p50, p-p38 MAPK, and FAK; and at 400 μmol/L enhanced invasion and migration in test cell lines. These findings suggested that riboflavin at high doses might promote lung cancer progression. © 2013 Institute of Food Technologists®

Effective doses in paediatric radiology

International Nuclear Information System (INIS)

Iacob, Olga; Diaconescu, Cornelia; Roca, Antoaneta

2001-01-01

Because of their longer life expectancy, the risk of late manifestations of detrimental radiation effects is greater in children than in adults and, consequently, paediatric radiology gives ground for more concern regarding radiation protection than radiology of adults. The purpose of our study is to assess in terms of effective doses the magnitude of paediatric patient exposure during conventional X-ray examinations, selected for their high frequency or their relatively high doses to the patient. Effective doses have been derived from measurements of dose-area product (DAP) carried out on over 900 patients undergoing X-ray examinations, in five paediatric units. The conversion coefficients for estimating effective doses are those calculated by the NRPB using Monte-Carlo technique on a series of 5 mathematical phantoms representing 0, 1, 5, 10 and 15 year old children. The annual frequency of X-ray examinations necessary for collective dose calculation are those reported in our last national study on medical exposure, conducted in 1995. The annual effective doses from all medical examinations for the average paediatric patient are as follows: 1.05 mSv for 0 year old, 0.98 mSv for 1 year old, 0.53 mSv for 5 year old, 0.65 mSv for 10 year old and 0.70 mSv for 15 year old. The resulting annual collective effective dose was evaluated at 625 man Sv with the largest contribution of pelvis and hip examinations (34%). The annual collective effective associated with paediatric radiology in Romania represent 5% of the annual value resulting from all diagnostic radiology. Examination of the chest is by far the most frequent procedure for children, accounting for about 60 per cent of all annually performed X-ray conventional examinations. Knowledge of real level of patient dose is an essential component of quality assurance programs in paediatric radiology. (authors)

SU-E-T-44: Angular Dependence of Surface Dose Enhancement Measured On Several Inhomogeneities Using Radiochromic EBT3 Films

International Nuclear Information System (INIS)

Jansen, A; Schoenfeld, A; Poppinga, D; Chofor, N; Poppe, B

2014-01-01

Purpose: The quantification of the relative surface dose enhancement in dependence on the angle of incidence and the atomic number Z of the surface material. Methods: Experiments were performed with slabs made of aluminum, titanium, copper, silver, dental gold and lead. The metal slabs with equal sizes of 1.0×8.0×8.8mm 3 were embedded in an Octavius 4D phantom (PTW Freiburg, Germany). Radiochromic EBT3 films were used to measure the surface dose for angles of incidence ranging from 0° to 90°. The setup with the metals slabs at the isocenter was irradiated with acceleration voltages of 6MV and 10MV. Water reference measurements were taken under equal conditions. Results: The surface dose enhancement is highest for angles of incidence below 30° and drops significantly for higher. The surface dose enhancement produced by lead and dental gold at 6MV showed a peak of 65%. At 90°, the surface dose enhancement dropped to 15% for both materials. The surface dose enhancements for silver, copper, titanium and aluminum were 45%, 32%, 22% and 12% at 0°, respectively. At an angle of incidence of 80°, the values dropped to 22%, 18%, 12% und 6%. The values for 10MV were very similar. Lead and dental gold showed peaks of 65% und 60%. Their values dropped to 18% at an angle of 90°. The surface dose enhancements for silver, copper, titanium and aluminum were 45%, 30%, 20% and 8% at 0°. At 80° the values dropped to 30%, 20%, 12% and 5%. A dependence of the magnitude of the surface dose enhancement on the atomic number of the surface material can be seen, which is in consistence with literature. Conclusion: The results show that the surface dose enhancements near implant materials with high Z-values should be taken into consideration in radio therapy, even when the angle of incidence is flat

CTA-enhanced perfusion CT: an original method to perform ultra-low-dose CTA-enhanced perfusion CT

Energy Technology Data Exchange (ETDEWEB)

Tong, Elizabeth; Wintermark, Max [University of Virginia, Department of Radiology, Neuroradiology Division, Charlottesville, VA (United States)

2014-11-15

Utilizing CT angiography enhances image quality in PCT, thereby permitting acquisition at ultra-low dose. Dynamic CT acquisitions were obtained at 80 kVp with decreasing tube current-time product [milliamperes x seconds (mAs)] in patients suspected of ischemic stroke, with concurrent CTA of the cervical and intracranial arteries. By utilizing fast Fourier transformation, high spatial frequencies of CTA were combined with low spatial frequencies of PCT to create a virtual PCT dataset. The real and virtual PCT datasets with decreasing mAs were compared by assessing contrast-to-noise ratio (CNR), signal-to-noise ratio (SNR), and noise and PCT values and by visual inspection of PCT parametric maps. Virtual PCT attained CNR and SNR three- to sevenfold superior to real PCT and noise reduction by a factor of 4-6 (p < 0.05). At 20 mAs, virtual PCT achieved diagnostic parametric maps, while the quality of real PCT maps was inadequate. At 10 mAs, both real and virtual PCT maps were nondiagnostic. Virtual PCT (but not real PCT) maps regained diagnostic quality at 10 mAs by applying 40 % adaptive statistical iterative reconstruction (ASIR) and improved further with 80 % ASIR. Our new method of creating virtual PCT by combining ultra-low-dose PCT with CTA information yields diagnostic perfusion parametric maps from PCT acquired at 20 or 10 mAs with 80 % ASIR. Effective dose is approximately 0.20 mSv, equivalent to two chest radiographs. (orig.)

Estimation of tumour dose enhancement due to gold nanoparticles during typical radiation treatments: a preliminary Monte Carlo study

International Nuclear Information System (INIS)

Cho, S H

2005-01-01

A recent mice study demonstrated that gold nanoparticles could be safely administered and used to enhance the tumour dose during radiation therapy. The use of gold nanoparticles seems more promising than earlier methods because of the high atomic number of gold and because nanoparticles can more easily penetrate the tumour vasculature. However, to date, possible dose enhancement due to the use of gold nanoparticles has not been well quantified, especially for common radiation treatment situations. Therefore, the current preliminary study estimated this dose enhancement by Monte Carlo calculations for several phantom test cases representing radiation treatments with the following modalities: 140 kVp x-rays, 4 and 6 MV photon beams, and 192 Ir gamma rays. The current study considered three levels of gold concentration within the tumour, two of which are based on the aforementioned mice study, and assumed either no gold or a single gold concentration level outside the tumour. The dose enhancement over the tumour volume considered for the 140 kVp x-ray case can be at least a factor of 2 at an achievable gold concentration of 7 mg Au/g tumour assuming no gold outside the tumour. The tumour dose enhancement for the cases involving the 4 and 6 MV photon beams based on the same assumption ranged from about 1% to 7%, depending on the amount of gold within the tumour and photon beam qualities. For the 192 Ir cases, the dose enhancement within the tumour region ranged from 5% to 31%, depending on radial distance and gold concentration level within the tumour. For the 7 mg Au/g tumour cases, the loading of gold into surrounding normal tissue at 2 mg Au/g resulted in an increase in the normal tissue dose, up to 30%, negligible, and about 2% for the 140 kVp x-rays, 6 MV photon beam, and 192 Ir gamma rays, respectively, while the magnitude of dose enhancement within the tumour was essentially unchanged. (note)

Investigation of the effects of cell model and subcellular location of gold nanoparticles on nuclear dose enhancement factors using Monte Carlo simulation

Energy Technology Data Exchange (ETDEWEB)

Cai, Zhongli; Chattopadhyay, Niladri; Kwon, Yongkyu Luke [Department of Pharmaceutical Sciences, University of Toronto, Toronto, Ontario M5S 3M2 (Canada); Pignol, Jean-Philippe [Department of Radiation Oncology, University of Toronto, Toronto, Ontario M4N 3M5, Canada and Department of Medical Biophysics, University of Toronto, Toronto, Ontario M4N 3M5 (Canada); Lechtman, Eli [Department of Medical Biophysics, University of Toronto, Toronto, Ontario M4N 3M5 (Canada); Reilly, Raymond M. [Department of Pharmaceutical Sciences, University of Toronto, Toronto, Ontario M5S 3M2 (Canada); Department of Medical Imaging, University of Toronto, Toronto, Ontario M5S 3E2 (Canada); Toronto General Research Institute, University Health Network, Toronto, Ontario M5G 2C4 (Canada)

2013-11-15

Purpose: The authors’ aims were to model how various factors influence radiation dose enhancement by gold nanoparticles (AuNPs) and to propose a new modeling approach to the dose enhancement factor (DEF).Methods: The authors used Monte Carlo N-particle (MCNP 5) computer code to simulate photon and electron transport in cells. The authors modeled human breast cancer cells as a single cell, a monolayer, or a cluster of cells. Different numbers of 5, 30, or 50 nm AuNPs were placed in the extracellular space, on the cell surface, in the cytoplasm, or in the nucleus. Photon sources examined in the simulation included nine monoenergetic x-rays (10–100 keV), an x-ray beam (100 kVp), and {sup 125}I and {sup 103}Pd brachytherapy seeds. Both nuclear and cellular dose enhancement factors (NDEFs, CDEFs) were calculated. The ability of these metrics to predict the experimental DEF based on the clonogenic survival of MDA-MB-361 human breast cancer cells exposed to AuNPs and x-rays were compared.Results: NDEFs show a strong dependence on photon energies with peaks at 15, 30/40, and 90 keV. Cell model and subcellular location of AuNPs influence the peak position and value of NDEF. NDEFs decrease in the order of AuNPs in the nucleus, cytoplasm, cell membrane, and extracellular space. NDEFs also decrease in the order of AuNPs in a cell cluster, monolayer, and single cell if the photon energy is larger than 20 keV. NDEFs depend linearly on the number of AuNPs per cell. Similar trends were observed for CDEFs. NDEFs using the monolayer cell model were more predictive than either single cell or cluster cell models of the DEFs experimentally derived from the clonogenic survival of cells cultured as a monolayer. The amount of AuNPs required to double the prescribed dose in terms of mg Au/g tissue decreases as the size of AuNPs increases, especially when AuNPs are in the nucleus and the cytoplasm. For 40 keV x-rays and a cluster of cells, to double the prescribed x-ray dose (NDEF = 2

Local dose enhancement in radiation therapy: Monte Carlo simulation study

International Nuclear Information System (INIS)

Silva, Laura E. da; Nicolucci, Patricia

2014-01-01

The development of nanotechnology has boosted the use of nanoparticles in radiation therapy in order to achieve greater therapeutic ratio between tumor and healthy tissues. Gold has been shown to be most suitable to this task due to the high biocompatibility and high atomic number, which contributes to a better in vivo distribution and for the local energy deposition. As a result, this study proposes to study, nanoparticle in the tumor cell. At a range of 11 nm from the nanoparticle surface, results have shown an absorbed dose 141 times higher for the medium with the gold nanoparticle compared to the water for an incident energy spectrum with maximum photon energy of 50 keV. It was also noted that when only scattered radiation is interacting with the gold nanoparticles, the dose was 134 times higher compared to enhanced local dose that remained significant even for scattered radiation. (author)

Nanoscale radiation transport and clinical beam modeling for gold nanoparticle dose enhanced radiotherapy (GNPT) using X-rays.

Science.gov (United States)

Zygmanski, Piotr; Sajo, Erno

2016-01-01

We review radiation transport and clinical beam modelling for gold nanoparticle dose-enhanced radiotherapy using X-rays. We focus on the nanoscale radiation transport and its relation to macroscopic dosimetry for monoenergetic and clinical beams. Among other aspects, we discuss Monte Carlo and deterministic methods and their applications to predicting dose enhancement using various metrics.

SU-G-TeP3-05: In Vitro Demonstration of Endothelial Dose Enhancement Due to Gold Nanoparticles During Low-Voltage Radiotherapy

Energy Technology Data Exchange (ETDEWEB)

Yasmin-Karim, S; Makrigiorgos, GM [Brigham and Women’s Hospital, Dana-Farber Cancer Institute and Harvard Medical School, Boston, MA (United States); Moreau, M; Ngwa, W [Brigham and Women’s Hospital, Dana-Farber Cancer Institute and Harvard Medical School, Boston, MA (United States); University of Massachusetts Lowell, Lowell, MA (United States); Kumar, R [Brigham and Women’s Hospital, Dana-Farber Cancer Institute and Harvard Medical School, Boston, MA (United States); Northeastern University, Boston, MA (United States); Hanlon, J; Arnoldussen, M [Oraya Therapeutics Inc., Newark, CA (United States); Hempstead, J; Celli, J [University of Massachusetts Boston, Boston, MA (United States)

2016-06-15

Purpose: Oraya Therapy uses low-voltage, stereotactic, highly targeted X-rays for the treatment of wet age-related macular degeneration (AMD) — offering a new option for patients worldwide. Neovascular endothelial cells play a crucial role in the pathogenesis of this disease. This in-vitro study investigates the potential of gold nanoparticles (GNP) to enhance endothelial cell damage during low-voltage radiotherapy towards potential applications in the treatment of wet-AMD. Methods: Primary human umbilical cord vein endothelium cells (HUVEC) were treated with 1.4 nm sized GNPs for 24 hrs and then irradiated with variable X-ray doses using an Oraya therapy system (100 kVp) or a Small Animal Radiation and Research platform (SARRP) at other beam qualities (up to 220 kVp). Radio-sensitization was assessed by clonogenic assays. Variable concentrations of GNPs (0.05 mg/ml, 0.1 mg/ml, 0.25 mg/ml, 0.5 mg/ml, and 1 mg/ml) where employed. The dose enhancement factor (DEF) was calculated as the ratio of radiation doses required to give the same biological effect (survival factor, SF) with and without GNPs. Results: Preliminary results show DEFs of up to 2.62 for the different combinations of x-ray doses and GNP concentrations and beam qualities. In general the DEF increased with increase in GNP concentration. However, for high doses the effect of GNP becomes less apparent likely due to already high cell kill by the radiation alone. Conclusion: The findings suggest that targeted GNPs can play a significant synergistic role in enhancing stereotactic radiosurgery for wet AMD. The results also provide impetus for ongoing studies to find the optimal synergy between the doses or beam energies and GNPs concentration. This will benefit in-vivo studies towards development of nanoparticle-aided radiotherapy for treatment of wet-AMD and potentially ocular cancers.

Radiation dose in cardiac SPECT/CT: An estimation of SSDE and effective dose

International Nuclear Information System (INIS)

Abdollahi, Hamid; Shiri, Isaac; Salimi, Yazdan; Sarebani, Maghsoud; Mehdinia, Reza; Deevband, Mohammad Reza; Mahdavi, Seied Rabi; Sohrabi, Ahmad; Bitarafan-Rajabi, Ahmad

2016-01-01

Aims: The dose levels for Computed Tomography (CT) localization and attenuation correction of Single Photon Emission Computed Tomography (SPECT) are limited and reported as Volume Computed Tomography Dose Index (CTDIvol) and Dose-Length Product (DLP). This work presents CT dose estimation from Cardiac SPECT/CT based on new American Association of Physicists in Medicine (AAPM) Size Specific Dose Estimation (SSDE) parameter, effective dose, organ doses and also emission dose from nuclear issue. Material and methods: Myocardial perfusion SPECT/CT for 509 patients was included in the study. SSDE, effective dose and organ dose were calculated using AAPM guideline and Impact-Dose software. Data were analyzed using R and SPSS statistical software. Spearman-Pearson correlation test and linear regression models were used for finding correlations and relationships among parameters. Results: The mean CTDIvol was 1.34 mGy ± 0.19 and the mean SSDE was 1.7 mGy ± 0.16. The mean ± SD of effective dose from emission, CT and total dose were 11.5 ± 1.4, 0.49 ± 0.11 and 12.67 ± 1.73 (mSv) respectively. The mean ± SD of effective dose from emission, CT and total dose were 11.5 ± 1.4, 0.49 ± 0.11 and 12.67 ± 1.73 (mSv) respectively. The spearman test showed that correlation between body size and organ doses is significant except thyroid and red bone marrow. CTDIvol was strongly dependent on patient size, but SSDE was not. Emission dose was strongly dependent on patient weight, but its dependency was lower to effective diameter. Conclusion: The dose parameters including CTDIvol, DLP, SSDE, effective dose values reported here are very low and below the reference level. This data suggest that appropriate CT acquisition parameters in SPECT/CT localization and attenuation correction are very beneficial for patients and lowering cancer risks.

Radiation dose in cardiac SPECT/CT: An estimation of SSDE and effective dose

Energy Technology Data Exchange (ETDEWEB)

Abdollahi, Hamid, E-mail: Hamid_rbp@yahoo.com [Department of Medical Physics, School of Medicine, Iran University of Medical Sciences, Tehran (Iran, Islamic Republic of); Shiri, Isaac [Department of Medical Physics, School of Medicine, Iran University of Medical Sciences, Tehran (Iran, Islamic Republic of); Salimi, Yazdan [Biomedical Engineering and Medical Physics Department, Faculty of Medicine, Shahid Beheshti University of Medical Sciences, Tehran (Iran, Islamic Republic of); Sarebani, Maghsoud; Mehdinia, Reza [Department of Medical Physics, School of Medicine, Iran University of Medical Sciences, Tehran (Iran, Islamic Republic of); Deevband, Mohammad Reza [Biomedical Engineering and Medical Physics Department, Faculty of Medicine, Shahid Beheshti University of Medical Sciences, Tehran (Iran, Islamic Republic of); Mahdavi, Seied Rabi [Department of Medical Physics, School of Medicine, Iran University of Medical Sciences, Tehran (Iran, Islamic Republic of); Radiation Biology Research Center, Iran University of Medical Sciences, Tehran (Iran, Islamic Republic of); Sohrabi, Ahmad [Department of Biostatistics, School of Public Health, Iran University of Medical Sciences, Tehran (Iran, Islamic Republic of); Bitarafan-Rajabi, Ahmad, E-mail: bitarafan@hotmail.com [Department of Medical Physics, School of Medicine, Iran University of Medical Sciences, Tehran (Iran, Islamic Republic of); Department of Nuclear Medicine, Rajaei Cardiovascular, Medical and Research Center, Iran University of Medical Sciences, Tehran (Iran, Islamic Republic of)

2016-12-15

Aims: The dose levels for Computed Tomography (CT) localization and attenuation correction of Single Photon Emission Computed Tomography (SPECT) are limited and reported as Volume Computed Tomography Dose Index (CTDIvol) and Dose-Length Product (DLP). This work presents CT dose estimation from Cardiac SPECT/CT based on new American Association of Physicists in Medicine (AAPM) Size Specific Dose Estimation (SSDE) parameter, effective dose, organ doses and also emission dose from nuclear issue. Material and methods: Myocardial perfusion SPECT/CT for 509 patients was included in the study. SSDE, effective dose and organ dose were calculated using AAPM guideline and Impact-Dose software. Data were analyzed using R and SPSS statistical software. Spearman-Pearson correlation test and linear regression models were used for finding correlations and relationships among parameters. Results: The mean CTDIvol was 1.34 mGy ± 0.19 and the mean SSDE was 1.7 mGy ± 0.16. The mean ± SD of effective dose from emission, CT and total dose were 11.5 ± 1.4, 0.49 ± 0.11 and 12.67 ± 1.73 (mSv) respectively. The mean ± SD of effective dose from emission, CT and total dose were 11.5 ± 1.4, 0.49 ± 0.11 and 12.67 ± 1.73 (mSv) respectively. The spearman test showed that correlation between body size and organ doses is significant except thyroid and red bone marrow. CTDIvol was strongly dependent on patient size, but SSDE was not. Emission dose was strongly dependent on patient weight, but its dependency was lower to effective diameter. Conclusion: The dose parameters including CTDIvol, DLP, SSDE, effective dose values reported here are very low and below the reference level. This data suggest that appropriate CT acquisition parameters in SPECT/CT localization and attenuation correction are very beneficial for patients and lowering cancer risks.

Effect of low doses of cannabidiolic acid and ondansetron on LiCl-induced conditioned gaping (a model of nausea-induced behaviour) in rats.

Science.gov (United States)

Rock, E M; Parker, L A

2013-06-01

To determine the minimally effective dose of cannabidiolic acid (CBDA) that effectively reduces lithium chloride (LiCl)-induced conditioned gaping reactions (nausea-induced behaviour) in rats and to determine if these low systemic doses of CBDA (5-0.1 μg·kg⁻¹) relative to those of CBD could potentiate the anti-nausea effects of the classic 5-hydroxytryptamine 3 (5-HT₃) receptor antagonist, ondansetron (OND). We investigated the efficacy of low doses of CBDA to suppress acute nausea, assessed by the establishment of conditioned gaping to a LiCl-paired flavour in rats. The potential of threshold and subthreshold doses of CBDA to enhance the reduction of nausea-induced conditioned gaping by OND were then determined. CBDA (at doses as low as 0.5 μg·kg⁻¹) suppressed nausea-induced conditioned gaping to a flavour. A low dose of OND (1.0 μg·kg⁻¹) alone reduced nausea-induced conditioned gaping, but when it was combined with a subthreshold dose of CBDA (0.1 μg·kg⁻¹) there was an enhancement in the suppression of LiCl-induced conditioned gaping. CBDA potently reduced conditioned gaping in rats, even at low doses and enhanced the anti-nausea effect of a low dose of OND. These findings suggest that combining low doses of CBDA and OND will more effectively treat acute nausea in chemotherapy patients. © 2013 The Authors. British Journal of Pharmacology © 2013 The British Pharmacological Society.

SU-E-T-235: Monte Carlo Analysis of the Dose Enhancement in the Scalp of Patients Due to Titanium Plate Backscatter During Post-Operative Radiotherapy

International Nuclear Information System (INIS)

Hardin, M; Elson, H; Lamba, M; Wolf, E; Warnick, R

2014-01-01

Purpose: To quantify the clinically observed dose enhancement adjacent to cranial titanium fixation plates during post-operative radiotherapy. Methods: Irradiation of a titanium burr hole cover was simulated using Monte Carlo code MCNPX for a 6 MV photon spectrum to investigate backscatter dose enhancement due to increased production of secondary electrons within the titanium plate. The simulated plate was placed 3 mm deep in a water phantom, and dose deposition was tallied for 0.2 mm thick cells adjacent to the entrance and exit sides of the plate. These results were compared to a simulation excluding the presence of the titanium to calculate relative dose enhancement on the entrance and exit sides of the plate. To verify simulated results, two titanium burr hole covers (Synthes, Inc. and Biomet, Inc.) were irradiated with 6 MV photons in a solid water phantom containing GafChromic MD-55 film. The phantom was irradiated on a Varian 21EX linear accelerator at multiple gantry angles (0–180 degrees) to analyze the angular dependence of the backscattered radiation. Relative dose enhancement was quantified using computer software. Results: Monte Carlo simulations indicate a relative difference of 26.4% and 7.1% on the entrance and exit sides of the plate respectively. Film dosimetry results using a similar geometry indicate a relative difference of 13% and -10% on the entrance and exit sides of the plate respectively. Relative dose enhancement on the entrance side of the plate decreased with increasing gantry angle from 0 to 180 degrees. Conclusion: Film and simulation results demonstrate an increase in dose to structures immediately adjacent to cranial titanium fixation plates. Increased beam obliquity has shown to alleviate dose enhancement to some extent. These results are consistent with clinically observed effects

Reboxetine Enhances the Olanzapine-Induced Antipsychotic-Like Effect, Cortical Dopamine Outflow and NMDA Receptor-Mediated Transmission

Science.gov (United States)

Marcus, Monica M; Jardemark, Kent; Malmerfelt, Anna; Björkholm, Carl; Svensson, Torgny H

2010-01-01

Preclinical data have shown that addition of the selective norepinephrine transporter (NET) inhibitor reboxetine increases the antipsychotic-like effect of the D2/3 antagonist raclopride and, in parallel, enhances cortical dopamine output. Subsequent clinical results suggested that adding reboxetine to stable treatments with various antipsychotic drugs (APDs) may improve positive, negative and depressive symptoms in schizophrenia. In this study, we investigated in rats the effects of adding reboxetine to the second-generation APD olanzapine on: (i) antipsychotic efficacy, using the conditioned avoidance response (CAR) test, (ii) extrapyramidal side effect (EPS) liability, using a catalepsy test, (iii) dopamine efflux in the medial prefrontal cortex and the nucleus accumbens, using in vivo microdialysis in freely moving animals and (iv) cortical N-methyl--aspartate (NMDA) receptor-mediated transmission, using intracellular electrophysiological recording in vitro. Reboxetine (6 mg/kg) enhanced the suppression of CAR induced by a suboptimal dose (1.25 mg/kg), but not an optimal (2.5 mg/kg) dose of olanzapine without any concomitant catalepsy. Addition of reboxetine to the low dose of olanzapine also markedly increased cortical dopamine outflow and facilitated prefrontal NMDA receptor-mediated transmission. Our data suggest that adjunctive treatment with a NET inhibitor may enhance the therapeutic effect of low-dose olanzapine in schizophrenia without increasing EPS liability and add an antidepressant action, thus in principle allowing for a dose reduction of olanzapine with a concomitant reduction of dose-related side effects, such as EPS and weight gain. PMID:20463659

Epidemiological methods for assessing dose-response and dose-effect relationships

DEFF Research Database (Denmark)

Kjellström, Tord; Grandjean, Philippe

2007-01-01

Selected Molecular Mechanisms of Metal Toxicity and Carcinogenicity General Considerations of Dose-Effect and Dose-Response Relationships Interactions in Metal Toxicology Epidemiological Methods for Assessing Dose-Response and Dose-Effect Relationships Essential Metals: Assessing Risks from Deficiency......Description Handbook of the Toxicology of Metals is the standard reference work for physicians, toxicologists and engineers in the field of environmental and occupational health. This new edition is a comprehensive review of the effects on biological systems from metallic elements...... access to a broad range of basic toxicological data and also gives a general introduction to the toxicology of metallic compounds. Audience Toxicologists, physicians, and engineers in the fields of environmental and occupational health as well as libraries in these disciplines. Will also be a useful...

Bayesian estimation of dose rate effectiveness

International Nuclear Information System (INIS)

Arnish, J.J.; Groer, P.G.

2000-01-01

A Bayesian statistical method was used to quantify the effectiveness of high dose rate 137 Cs gamma radiation at inducing fatal mammary tumours and increasing the overall mortality rate in BALB/c female mice. The Bayesian approach considers both the temporal and dose dependence of radiation carcinogenesis and total mortality. This paper provides the first direct estimation of dose rate effectiveness using Bayesian statistics. This statistical approach provides a quantitative description of the uncertainty of the factor characterising the dose rate in terms of a probability density function. The results show that a fixed dose from 137 Cs gamma radiation delivered at a high dose rate is more effective at inducing fatal mammary tumours and increasing the overall mortality rate in BALB/c female mice than the same dose delivered at a low dose rate. (author)

The fitting parameters extraction of conversion model of the low dose rate effect in bipolar devices

International Nuclear Information System (INIS)

Bakerenkov, Alexander

2011-01-01

The Enhanced Low Dose Rate Sensitivity (ELDRS) in bipolar devices consists of in base current degradation of NPN and PNP transistors increase as the dose rate is decreased. As a result of almost 20-year studying, the some physical models of effect are developed, being described in detail. Accelerated test methods, based on these models use in standards. The conversion model of the effect, that allows to describe the inverse S-shaped excess base current dependence versus dose rate, was proposed. This paper presents the problem of conversion model fitting parameters extraction.

Cytogenetic effects of low-dose radiation

International Nuclear Information System (INIS)

Metalli, P.

1983-01-01

The effects of ionizing radiation on chromosomes have been known for several decades and dose-effect relationships are also fairly well established in the mid- and high-dose and dose-rate range for chromosomes of mammalian cells. In the range of low doses and dose rates of different types of radiation few data are available for direct analysis of the dose-effect relationships, and extrapolation from high to low doses is still the unavoidable approach in many cases of interest for risk assessment. A review is presented of the data actually available and of the attempts that have been made to obtain possible generalizations. Attention is focused on some specific chromosomal anomalies experimentally induced by radiation (such as reciprocal translocations and aneuploidies in germinal cells) and on their relevance for the human situation. (author)

Radioprotective effect of low doses of 2-(1-naphthylmethyl)-2-imidazoline alone or associated with phosphorothioates

International Nuclear Information System (INIS)

Laval, J.D.; Roman, V.; Fatome, M.; Laduranty, J.; Miginiac, L.; Lion, C.; Sentenac-Roumanou, H.

1993-01-01

In the mouse, the intraperitoneal injection of 2-(1-naphthylmethyl)-2-imidazoline has a radioprotective effect even at low doses. Its association with S-[2-(3-aminopropyl)aminoethyl] phosphorothioate (WR 2721) or S-[3-(3-methylaminopropyl)-aminopropyl]phosphorothioate (WR 151327) at low doses led to an enhancement of their respective radioprotective activities without any apparent side effects. These results strengthen the interest of this non-sulphur compound as a radioprotector

Supra-aortic low-dose contrast-enhanced time-resolved magnetic resonance (MR) angiography at 3 T: comparison with time-of-flight MR angiography and high-resolution contrast-enhanced MR angiography.

Science.gov (United States)

Lee, Youn-Joo; Kim, Bum-soo; Koo, Ja-Sung; Kim, Bom-Yi; Jang, Jinhee; Choi, Hyun Seok; Jung, So-Lyung; Ahn, Kook-Jin

2015-06-01

Low-dose, time-resolved, contrast-enhanced, magnetic resonance angiography (TR-CEMRA) has been described previously; however, a comparative study between low dose TR-CEMRA and time-of-flight MRA (TOF-MRA) in the diagnosis of supra-aortic arterial stenosis has not yet been published. To demonstrate the feasibility and effectiveness of low-dose TR-CEMRA compared with TOF-MRA, using high-resolution contrast-enhanced MRA (HR-CEMRA) as the reference standard. This prospective study consisted of 30 consecutive patients. All patients underwent TOF-MRA of the neck and circle of Willis and supra-aortic HR-CEMRA, followed by supra-aortic low-dose TR-CEMRA. Gadoterate meglumine (Gd-DOTA, Dotarem(®), Guerbet, Roissy CdG Cedex, France) was injected at a dose of 0.1 mmol/kg for HR-CEMRA, followed by a 0.03 mmol/kg bolus for low-dose TR-CEMRA. Three readers evaluated the assessibility and image quality, and then two readers classified each stenosis into the following categories: normal (0-30%), mild stenosis (31-50%), moderate (51-70%), severe (71-99%), and occlusion. TR-CEMRA and HR-CEMRA showed a greater number of assessable arterial segments than TOF-MRA (P supra-aortic arterial stenosis, and could be more useful option than TOF-MRA. © The Foundation Acta Radiologica 2014 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav.

Applying gold nanoparticles as tumor-vascular disrupting agents during brachytherapy: estimation of endothelial dose enhancement

International Nuclear Information System (INIS)

Ngwa, Wilfred; Makrigiorgos, G Mike; Berbeco, Ross I

2010-01-01

Tumor vascular disrupting agents (VDAs) represent a promising approach to the treatment of cancer, in view of the tumor vasculature's pivotal role in tumor survival, growth and metastasis. VDAs targeting the tumor's dysmorphic endothelial cells can cause selective and rapid occlusion of the tumor vasculature, leading to tumor cell death from ischemia and extensive hemorrhagic necrosis. In this study, the potential for applying gold nanoparticles (AuNPs) as VDAs, during brachytherapy, is examined. Analytic calculations based on the electron energy loss formula of Cole were carried out to estimate the endothelial dose enhancement caused by radiation-induced photo/Auger electrons originating from AuNPs targeting the tumor endothelium. The endothelial dose enhancement factor (EDEF), representing the ratio of the dose to the endothelium with and without gold nanoparticles was calculated for different AuNP local concentrations, and endothelial cell thicknesses. Four brachytherapy sources were investigated, I-125, Pd-103, Yb-169, as well as 50 kVp x-rays. The results reveal that, even at relatively low intra-vascular AuNP concentrations, ablative dose enhancement to tumor endothelial cells due to photo/Auger electrons from the AuNPs can be achieved. Pd-103 registered the highest EDEF values of 7.4-271.5 for local AuNP concentrations ranging from 7 to 350 mg g -1 , respectively. Over the same concentration range, I-125, 50 kVp and Yb-169 yielded values of 6.4-219.9, 6.3-214.5 and 4.0-99.7, respectively. Calculations of the EDEF as a function of endothelial cell thickness showed that lower energy sources like Pd-103 reach the maximum EDEF at smaller thicknesses. The results also reveal that the highest contribution to the EDEF comes from Auger electrons, apparently due to their shorter range. Overall, the data suggest that ablative dose enhancement to tumor endothelial cells can be achieved by applying tumor vasculature-targeted AuNPs as adjuvants to brachytherapy, with

Applying gold nanoparticles as tumor-vascular disrupting agents during brachytherapy: estimation of endothelial dose enhancement

Science.gov (United States)

Ngwa, Wilfred; Makrigiorgos, G. Mike; Berbeco, Ross I.

2010-11-01

Tumor vascular disrupting agents (VDAs) represent a promising approach to the treatment of cancer, in view of the tumor vasculature's pivotal role in tumor survival, growth and metastasis. VDAs targeting the tumor's dysmorphic endothelial cells can cause selective and rapid occlusion of the tumor vasculature, leading to tumor cell death from ischemia and extensive hemorrhagic necrosis. In this study, the potential for applying gold nanoparticles (AuNPs) as VDAs, during brachytherapy, is examined. Analytic calculations based on the electron energy loss formula of Cole were carried out to estimate the endothelial dose enhancement caused by radiation-induced photo/Auger electrons originating from AuNPs targeting the tumor endothelium. The endothelial dose enhancement factor (EDEF), representing the ratio of the dose to the endothelium with and without gold nanoparticles was calculated for different AuNP local concentrations, and endothelial cell thicknesses. Four brachytherapy sources were investigated, I-125, Pd-103, Yb-169, as well as 50 kVp x-rays. The results reveal that, even at relatively low intra-vascular AuNP concentrations, ablative dose enhancement to tumor endothelial cells due to photo/Auger electrons from the AuNPs can be achieved. Pd-103 registered the highest EDEF values of 7.4-271.5 for local AuNP concentrations ranging from 7 to 350 mg g-1, respectively. Over the same concentration range, I-125, 50 kVp and Yb-169 yielded values of 6.4-219.9, 6.3-214.5 and 4.0-99.7, respectively. Calculations of the EDEF as a function of endothelial cell thickness showed that lower energy sources like Pd-103 reach the maximum EDEF at smaller thicknesses. The results also reveal that the highest contribution to the EDEF comes from Auger electrons, apparently due to their shorter range. Overall, the data suggest that ablative dose enhancement to tumor endothelial cells can be achieved by applying tumor vasculature-targeted AuNPs as adjuvants to brachytherapy, with lower

Low-tube-voltage selection for non-contrast-enhanced CT: Comparison of the radiation dose in pediatric and adult phantoms.

Science.gov (United States)

Shimonobo, Toshiaki; Funama, Yoshinori; Utsunomiya, Daisuke; Nakaura, Takeshi; Oda, Seitaro; Kiguchi, Masao; Masuda, Takanori; Sakabe, Daisuke; Yamashita, Yasuyuki; Awai, Kazuo

2016-01-01

We used pediatric and adult anthropomorphic phantoms to compare the radiation dose of low- and standard tube voltage chest and abdominal non-contrast-enhanced computed tomography (CT) scans. We also discuss the optimal low tube voltage for non-contrast-enhanced CT. Using a female adult- and three differently-sized pediatric anthropomorphic phantoms we acquired chest and abdominal non-contrast-enhanced scans on a 320-multidetector CT volume scanner. The tube voltage was set at 80-, 100-, and 120 kVp. The tube current was automatically assigned on the CT scanner in response to the set image noise level. On each phantom and at each tube voltage we measured the surface and center dose using high-sensitivity metal-oxide-semiconductor field-effect transistor detectors. The mean surface dose of chest and abdominal CT scans in 5-year olds was 4.4 and 5.3 mGy at 80 kVp, 4.5 and 5.4 mGy at 100 kV, and 4.0 and 5.0 mGy at 120 kVp, respectively. These values were similar in our 3-pediatric phantoms (p > 0.05). The mean surface dose in the adult phantom increased from 14.7 to 19.4 mGy for chest- and from 18.7 to 24.8 mGy for abdominal CT as the tube voltage decreased from 120 to 80 kVp (p voltage and the low tube voltage technique can be used for non-contrast-enhanced chest- and abdominal scanning. Copyright © 2015 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.

SU-E-T-231: Measurements of Gold Nanoparticle-Mediated Proton Dose Enhancement Due to Particle-Induced X-Ray Emission and Activation Products Using Radiochromic Films and CdTe Detector

International Nuclear Information System (INIS)

Cho, J; Cho, S; Manohar, N; Krishnan, S

2014-01-01

Purpose: There have been several reports of enhanced cell-killing and tumor regression when tumor cells and mouse tumors were loaded with gold nanoparticles (GNPs) prior to proton irradiation. While particle-induced xray emission (PIXE), Auger electrons, secondary electrons, free radicals, and biological effects have been suggested as potential mechanisms responsible for the observed GNP-mediated dose enhancement/radiosensitization, there is a lack of quantitative analysis regarding the contribution from each mechanism. Here, we report our experimental effort to quantify some of these effects. Methods: 5-cm-long cylindrical plastic vials were filled with 1.8 mL of either water or water mixed with cylindrical GNPs at the same gold concentration (0.3 mg Au/g) as used in previous animal studies. A piece of EBT2 radiochromic film (30-µm active-layer sandwiched between 80/175-µm outer-layers) was inserted along the long axis of each vial and used to measure dose enhancement due to PIXE from GNPs. Vials were placed at center-of-modulation (COM) and 3-cm up-/down-stream from COM and irradiated with 5 different doses (2–10 Gy) using 10-cm-SOBP 160-MeV protons. After irradiation, films were cleaned and read to determine the delivered dose. A vial containing spherical GNPs (20 mg Au/g) was also irradiated, and gamma-rays from activation products were measured using a cadmium-telluride (CdTe) detector. Results: Film measurements showed no significant dose enhancement beyond the experimental uncertainty (∼2%). There was a detectable activation product from GNPs, but it appeared to contribute to dose enhancement minimally (<0.01%). Conclusion: Considering the composition of EBT2 film, it can be inferred that gold characteristic x-rays from PIXE and their secondary electrons make insignificant contribution to dose enhancement. The current investigation also suggests negligible dose enhancement due to activation products. Thus, previously-reported GNP-mediated proton dose

Double Dose: High Family Conflict Enhances the Effect of Media Violence Exposure on Adolescents’ Aggression

Directory of Open Access Journals (Sweden)

Patti M. Valkenburg

2013-07-01

Full Text Available We investigated how exposure to media violence and family conflict affects adolescents’ subsequent aggressive behavior. We expected a double dose effect, meaning that high media violence exposure would lead to higher levels of aggression for adolescents in high conflict families compared to low conflict families. A total of 499 adolescents (aged 10 to 14, 48% girls participated in a two-wave longitudinal survey (4-month interval. Survey questions assessed their exposure to violence on television and in electronic games, family conflict, and aggressive behavior. Analyses revealed a significant interaction between media violence and family conflict. In families with higher conflict, higher media violence exposure was related to increased subsequent aggression. This study is the first to show a double dose effect of media violence and family conflict on adolescents’ aggression. These findings underscore the important role of the family in shaping the effects of adolescents’ media use on their social development.

Aortic and hepatic enhancement at multidetector CT: Evaluation of optimal iodine dose determined by lean body weight

International Nuclear Information System (INIS)

Kondo, Hiroshi; Kanematsu, Masayuki; Goshima, Satoshi; Watanabe, Haruo; Onozuka, Minoru; Moriyama, Noriyuki; Bae, Kyongtae T.

2011-01-01

Purpose: To determine the optimal iodine dose for aortic and hepatic enhancement at MDCT by comparing lean body weight (LBW) with total body weight (TBW). Materials and methods: This study was approved by our institutional review committee. One hundred and thirty-six patients were randomized into four groups: 550, 650, 750 mg iodine/(kg of LBW) and 600 mgI/(kg of TBW). The aortic and hepatic contrast enhancements (ΔHUs) during the portal venous-phase and variances of ΔHUs were compared. Results: Mean ΔHUs for 550, 650, 750 mgI/kg LBW and 600 mgI/kg TBW were: 95.1, 109.9, 122.4, and 131.2 HU, respectively, for the aorta. For the liver, 43.1, 55.4, 60.8, and 63.5 HU. Mean ΔHUs increased with iodine dose per kg LBW (p < 0.01), but no significant difference between 750 mgI/kg LBW and 600 mgI/kg TBW groups. Hepatic enhancement increased by ≥50 HU in 94% of patients with 750 mg/kg LBW. Variance of hepatic enhancement was marginally greater in the 600 mgI/kg TBW than in the 550 and 750 mgI/kg LBW. Conclusion: Hepatic enhancement variation was reduced with iodine doses based on LBW. Iodine dose of 750 mg iodine/kg LBW was appropriate to achieve hepatic enhancement ≥50 HU in 94% of patients.

Reducing radiation dose in liver enhanced CT scan by setting mAs according to plain scan noise

International Nuclear Information System (INIS)

Yang Shangwen; He Jian; Yang Xianfeng; Zhou Kefeng; Xin Xiaoyan; Hu Anning; Zhu Bin

2013-01-01

Objective: To investigate the feasibility of setting mAs in liver enhanced CT scan according to plain scan noise with fixed mA CT scanner, in order to reduce the radiation dose. Methods: One hundred continuous patients underwent liver enhanced CT scan (group A) prospectively. Two hundred and fifty mAs was used in plain and enhanced CT scans. Noises of plain and venous phase CT images were measured, and the image quality was evaluated. The equation between mAs of enhanced scan and noise of plain scan image was derived. Another 100 continuous patients underwent liver enhanced CT scan (group B). Enhanced scan mAs was calculated from noise on plain scan by using the equation above. Noises on venous phase images were measured and the image quality was measured. Based on body mass index (BMI), patients in groups A and B were divided into three subgroups respectively: BMI < 18.5 kg/m 2 , 18.5 kg/m 2 ≤ BMI < 25.0 kg/m 2 and BMI ≥ 25.0 kg/m 2 . Image quality score was compared with nonparametric rank sum test, CT dose index (CTDI) and effective dose (ED) were measured and compared between each subgroup with 2 independent samples t or t' test. Results: The equation between enhanced scan mAs (mAsX) and plain scan noise (SDp) was as follows: mAsX = mAs1 × [(0.989 × SDp + 1.06) /SDx] 2 , mAs1 = 250 mAs, SDx = 13. In patients with BMI < 18.5 kg/m 2 , ED of group A [(6.86 ± 0.38) mSv, n = 12] was significantly higher than group B [(2.66 ± 0.46) mSv, n = 10)] (t = 18.52, P < 0.01). In patients with 18.5 kg/m 2 ≤ BMI < 25.0 kg/m 2 , ED of group A [(7.08 ± 0.91) mSv, n = 66] was significantly higher than group B [(4.50 ± 1.41) mSv, n = 73] (t' = 10.57, P < 0.01). In patients with BMI ≥ 25.0 kg/m 2 , there was no significant difference between EDs of group A (7.54 ± 0.62 mSv, n = 22) and group B [(8.19 ± 3.16) mSv, n = 17] (t' = 0.89, P = 0.39). Image quality of 5 patients in group A and none in group B did not meet the diagnostic requirement

Juvenile Hormone Analogues, Methoprene and Fenoxycarb Dose-Dependently Enhance Certain Enzyme Activities in the Silkworm Bombyx Mori (L

Directory of Open Access Journals (Sweden)

M. Rajeswara Rao

2008-06-01

Full Text Available Use of Juvenile Hormone Analogues (JHA in sericulture practices has been shown to boost good cocoon yield; their effect has been determined to be dose-dependent. We studied the impact of low doses of JHA compounds such as methoprene and fenoxycarb on selected key enzymatic activities of the silkworm Bombyx mori. Methoprene and fenoxycarb at doses of 1.0 μg and 3.0fg/larvae/48 hours showed enhancement of the 5th instar B. mori larval muscle and silkgland protease, aspartate aminotransaminase (AAT and alanine aminotransaminase (ALAT, adenosine triphosphate synthase (ATPase and cytochrome-c-oxidase (CCO activity levels, indicating an upsurge in the overall oxidative metabolism of the B.mori larval tissues.

Low-dose effect on blood chromosomes

International Nuclear Information System (INIS)

Pohl-Rueling, J.

1992-01-01

Linear dose response relationships of biological effects at low doses are experimentally and theoretically disputed. Structural chromosome aberration rates at doses ranging from normal background exposures up to about 30 mGy/yr in vivo and up to 50 mGy in vitro were investigated by the author and other scientists. Results are comparable and dose effect curves reveal following shapes; within the normal burden and up to 2-10 mGy/yr in vivo rates they increase sharply to about 3-6 times the lowest values; subsequent doses either from natural, occupational or accidental exposures up to about 30 mGy/yr yield either constant aberration rates, assuming a plateau, or perhaps even a decrease. In vitro experiments show comparable results up to 50 mGy. Other biological effects seem to have similar dose dependencies. The non-linearity of low-dose effects can be explained by induction of repair enzymes at certain damage to the DNA. This hypothesis is sustained experimentally and theoretically by several papers in literature. (author). 14 refs., 5 figs

Study on dependence of dose enhancement on cluster morphology of gold nanoparticles in radiation therapy using a body-centred cubic model

Science.gov (United States)

Ahn, Sang Hee; Chung, Kwangzoo; Shin, Jung Wook; Cheon, Wonjoong; Han, Youngyih; Park, Hee Chul; Choi, Doo Ho

2017-10-01

Gold nanoparticles (GNPs) injected in a body for dose enhancement in radiation therapy are known to form clusters. We investigated the dependence of dose enhancement on the GNP morphology using Monte-Carlo simulations and compared the model predictions with experimental data. The cluster morphology was approximated as a body-centred cubic (BCC) structure by placing GNPs at the 8 corners and the centre of a cube with an edge length of 0.22-1.03 µm in a 4  ×  4  ×  4 µm3 water-filled phantom. We computed the dose enhancement ratio (DER) for 50 and 260 kVp photons as a function of the distance from the cube centre for 12 different cube sizes. A 10 nm-wide concentric shell shaped detector was placed up to 100 nm away from a GNP at the cube centre. For model validation, simulations based on BCC and nanoparticle random distribution (NRD) models were performed using parameters that corresponded to the experimental conditions, which measured increases in the relative biological effect due to GNPs. We employed the linear quadratic model to compute cell surviving fraction (SF) and sensitizer enhancement ratio (SER). The DER is inversely proportional to the distance to the GNPs. The largest DERs were 1.97 and 1.80 for 50 kVp and 260 kVp photons, respectively. The SF predicted by the BCC model agreed with the experimental value within 10%, up to a 5 Gy dose, while the NRD model showed a deviation larger than 10%. The SERs were 1.21  ±  0.13, 1.16  ±  0.11, and 1.08  ±  0.11 according to the experiment, BCC, and NRD models, respectively. We most accurately predicted the GNP radiosensitization effect using the BCC approximation and suggest that the BCC model is effective for use in nanoparticle dosimetry.

Effective dose and dose to crystalline lens during angiographic procedures

International Nuclear Information System (INIS)

Pages, J.

1998-01-01

The highest radiation doses levels received by radiologists are observed during interventional procedures. Doses to forehead and neck received by a radiologist executing angiographic examinations at the department of radiology at the academic hospital (AZ-VUB) have been measured for a group of 34 examinations. The doses to crystalline lens and the effective doses for a period of one year have been estimated. For the crystalline lens the maximum dose approaches the ICRP limit, that indicates the necessity for the radiologist to use leaded glasses. (N.C.)

Ranitidine Can Potentiate The Prokinetic Effect Of Itopride At Low Doses- An In Vitro Study.

Science.gov (United States)

Butt, Aroosa Ishtiaq; Khan, Bushra Tayyaba; Khan, Asma; Khan, Qamar-Uz-Zaman

2017-01-01

Gastroparesis and GERD occur concomitantly in 40 percent of the cases. Prokinetic drugs and acid blockers are employed as the main treatment modality. Ranitidine is an acid blocker with additional prokinetic activity and Itopride is a known prokinetic drug. This study was designed to observe the synergistic potentiating prokinetic effect of Ranitidine on itopride on isolated duodenum of rabbits. Ranitidine (10-5-10-3) and itopride (10-6-10-5) were added in increasing concentrations to isolated duodenum of rabbits and contractions were recorded on PowerLab Data acquisition unit AHK/214. Cumulative dose response curves were constructed. The potentiating prokinetic effect of Ranitidine on itopride was seen by using a fixed dose of ranitidine and cumulatively enhancing doses of itopride on iWorx. Ranitidine and itopride produced a dose dependent reversible contraction of the isolated tissue of rabbits with ranitidine showing a max response of 0.124mV and itopride showing a maximum response of 0.131mV. Ranitidine was able to potentiate the prokinetic effect of itopride at low doses but at high dose the effect began to wane off. Ranitidine and itopride produce a statistically significant synergistic potentiating prokinetic effect at low doses in vitro.

Gamma dose rate effect on JFET transistors

International Nuclear Information System (INIS)

Assaf, J.

2011-04-01

The effect of Gamma dose rate on JFET transistors is presented. The irradiation was accomplished at the following available dose rates: 1, 2.38, 5, 10 , 17 and 19 kGy/h at a constant dose of 600 kGy. A non proportional relationship between the noise and dose rate in the medium range (between 2.38 and 5 kGy/h) was observed. While in the low and high ranges, the noise was proportional to the dose rate as the case of the dose effect. This may be explained as follows: the obtained result is considered as the yield of a competition between many reactions and events which are dependent on the dose rate. At a given values of that events parameters, a proportional or a non proportional dose rate effects are generated. No dependence effects between the dose rate and thermal annealing recovery after irradiation was observed . (author)

Radiosurgery for brain metastases: relationship of dose and pattern of enhancement to local control

International Nuclear Information System (INIS)

Shiau, C.-Y.; Sneed, Penny K.; Shu, H.-K.G.; Lamborn, Kathleen R.; McDermott, Michael W.; Chang, Susan; Nowak, Peter; Petti, Paula L.; Smith, Vernon; Verhey, Lynn J.; Ho, Maria; Park, Elaine; Wara, William M.; Gutin, Philip H.; Larson, David A.

1997-01-01

Purpose: This study aimed to analyze dose, initial pattern of enhancement, and other factors associated with freedom from progression (FFP) of brain metastases after radiosurgery (RS). Methods and Materials: All brain metastases treated with gamma-knife RS at the University of California, San Francisco, from 1991 to 1994 were reviewed. Evaluable lesions were those with follow-up magnetic resonance or computed tomographic imaging. Actuarial FFP was calculated using the Kaplan-Meier method, measuring FFP from the date of RS to the first imaging study showing tumor progression. Controlled lesions were censored at the time of the last imaging study. Multivariate analyses were performed using a stepwise Cox proportional hazards model. Results: Of 261 lesions treated in 119 patients, 219 lesions in 100 patients were evaluable. Major histologies included adenocarcinoma (86 lesions), melanoma (77), renal cell carcinoma (21), and carcinoma not otherwise specified (17). The median prescribed RS dose was 18.5 Gy (range, 10-22) and the median tumor volume was 1.3 ml (range, 0.02-30.9). The initial pattern of contrast enhancement was homogeneous in 68% of lesions, heterogeneous in 12%, and ring-enhancing in 19%. The actuarial FFP was 82% at 6 months and 77% at 1 year for all lesions, and 93 and 90%, respectively, for 145 lesions receiving ≥ 18 Gy. Multivariate analysis showed that longer FFP was significantly associated with higher prescribed RS dose, a homogeneous pattern of contrast enhancement, and a longer interval between primary diagnosis and RS. Adjusted for these factors, adenocarcinomas had longer FFP than melanomas. No significant differences in FFP were noted among lesions undergoing RS for recurrence after prior radiotherapy (119 lesions), RS alone as initial treatment (45), or RS boost (55). Conclusion: A minimum prescribed radiosurgical dose ≥ 18 Gy yields excellent local control of brain metastases. The influence of pattern of enhancement on local control, a

The effect of low-dose total body irradiation on tumor control

International Nuclear Information System (INIS)

Sakamoto, Kiyohiko; Miyamoto, Miyako; Watabe, Nobuyuki.

1987-01-01

Total body irradiation (TBI) is considered to bring about an immunosuppressive effect on an organism, on the basis of data obtained from sublethal doses of TBI. However, there are no data on how low-dose TBI affects an organism. Over the last five years, we have been studying the effects of low-dose TBI on normal or tumor-bearing mice and the immunological background of these effects. In experimental studies, an increase in the TD50 value (the number of cells required for a tumor incidence of 50 %) in mice exposed to 10 rad was recognized and showed a remarkable increase at 6 hours to 15 hours after irradiation. TBI of 10 rad also showed an enhancement effect on tumor cell killing when given 12 hours before local tumor irradiation. In order to clarify the mechanism of this kind of effect, some immunological studies were performed using several immunological procedures, and the results suggested that 10 rad of TBI caused increasing tumor immunity in irradiated mice. Clinical trials in some patients with advanced tumors are now being undertaken on the basis of these experimental data, and the effect of TBI on tumor control appears promising, although it is too early to draw conclusions. (author)

Model predictions and analysis of enhanced biological effectiveness at low dose rates

International Nuclear Information System (INIS)

Watt, D.E.; Sykes, C.E.; Younis, A.-R.S.

1988-01-01

A severe challenge to all models purporting to describe the biological effects of ionizing radiation has arisen with the discovery of two phenomena: the anomalous trend with dose rate of the frequency of neoplastic transformation of mammalian cells and the apparent excessive damaging power of electron-capture radionuclides when incorporated into cell nuclei. A new model is proposed which predicts and enables interpretation of these phenomena. Radiation effectiveness is found to be expressible absolutely in terms of the geometrical cross-sectional area of the radiosensitive sites. The duration of the irradiation, the mean free path for ionization, the influence of particles in the slowing-down spectrum perrtaining in the medium and two collective time factors determining the mean repair rate and the mean lifetime of unidentified reactive chemical species [pt

Dose and Dose-Rate Effectiveness Factor (DDREF); Der Dosis- und Dosisleistungs-Effektivitaetsfaktor (DDREF)

Energy Technology Data Exchange (ETDEWEB)

Breckow, Joachim [Fachhochschule Giessen-Friedberg, Giessen (Germany). Inst. fuer Medizinische Physik und Strahlenschutz

2016-08-01

For practical radiation protection purposes it is supposed that stochastic radiation effects a determined by a proportional dose relation (LNT). Radiobiological and radiation epidemiological studies indicated that in the low dose range a dependence on dose rates might exist. This would trigger an overestimation of radiation risks based on the LNT model. OCRP had recommended a concept to combine all effects in a single factor DDREF (dose and dose-Rate effectiveness factor). There is still too low information on cellular mechanisms of low dose irradiation including possible repair and other processes. The Strahlenschutzkommission cannot identify a sufficient scientific justification for DDREF and recommends an adaption to the actual state of science.

Organ dose and effective dose with the EOS scanner in spine deformity surgery

DEFF Research Database (Denmark)

Heide Pedersen, Peter; Petersen, Asger Greval; Eiskjær, Søren Peter

2016-01-01

Organ dose and effective dose with the EOS scanner in spine deformity surgery. A study on anthropomorphic phantoms describing patient radiation exposure in full spine examinations. Authors: Peter Heide Pedersen, Asger Greval Petersen, Søren Peter Eiskjær. Background: Ionizing radiation potentially...... quality images while at the same time reducing radiation dose. At our institution we use the EOS for pre- and postoperative full spine examinations. Purpose: The purpose of the study is to make first time organ dose and effective dose evaluations with micro-dose settings in full spine examinations. Our...... hypothesis is that organ dose and effective doses can be reduced 5-10 times compared to standard settings, without too high image-quality trade off, resulting in a theoretical reduction of radiation induced cancer. Methods: Patient dosimetry is performed on anthropomorphic child phantoms, representing a 5...

Response of rat spinal cord to very small doses per fraction: lack of enhanced radiosensitivity

International Nuclear Information System (INIS)

Shun, Wong C.; Yong, Hao; Hill, Richard P.

1995-01-01

Our previous work with rat spinal cord demonstrated that the linear quadratic (LQ) model based on data for large fraction sizes ((α(β)) of 2.4 Gy) failed to predict isoeffective doses between 1 and 2 Gy per fraction, and under-estimated the sparing effect of small doses per fraction given once daily. In contrast, data from mouse skin and kidney, and recent in vitro results revealed a paradoxical increase in radiosensitivity at below 1 Gy per fraction. To assess whether enhanced radiosensitivity is present in the spinal cord below 1 Gy per fraction, the rat spinal cord (C2-T2) was irradiated initially with three daily doses of 10.25 Gy (top-up doses representing 90% of tolerance), followed by graded single doses or fractionated doses in 1.5, 1.0, 0.8, 0.6 or 0.4 Gy fractions given once daily. To limit the overall treatment time to ≤ 8 weeks, a small number of the 0.6- and 0.4-Gy fractions were given twice daily with an interfraction interval of 16 h. The end-point was forelimb paralysis secondary to white matter necrosis, confirmed histologically. The ED 50 values, excluding the top-up doses, were 5.8, 10.6, 14.8, 15.2, 15.9 and 19.1 Gy for a single dose and doses in 1.5-, 1.0-, 0.8-, 0.6- and 0.4-Gy fractions, respectively. The data gave an (α(β)) of 2.1 Gy (95% CI, 1.4, 2.7 Gy). Pooling the data separately, the (α(β)) value was 2.3 Gy (95% CI, 0.82, 3.7 Gy) for fraction sizes ≥ 1 Gy, and 1.2 Gy (95% CI, 0.16, 2.3 Gy) for the 0.8-, 0.6- and 0.4-Gy experiments. These results in which top-up doses were given initially are consistent with a large sparing effect of very small fraction sizes in rat spinal cord provided sufficient time is allowed for repair of sublethal damage between fractions, and provide no evidence for a paradoxical increase in radiosensitivity in the rat spinal cord below 1 Gy down to 0.4 Gy per fraction

Use of low-dose irradiation to enhance the safety and quality of chilled ready meals

Energy Technology Data Exchange (ETDEWEB)

Stewart, E M [Department of Food Science, Queen' s University Belfast (QUB) (United Kingdom); Patterson, M F [Food Science Division, Department of Agriculture and Rural Development (DARD), Belfast (United Kingdom)

2002-07-01

The market for 'cook-chill' ready meals has expanded significantly during the past ten years. This specific category of food has been defined as a catering system based on the full cooking of food followed by fast chilling and storage in controlled temperature conditions (0-3 deg. C) and subsequent thorough re-heating before consumption. Such meals cover a wide range of commodities including meat, poultry, fish, vegetables, pasta and desserts and are used at home by consumers and by the catering industry for use, for example, as hospital meals or meals-on-wheels. These products have a relatively short shelf-life with a recommended maximum shelf-life of 5 days at 0-3 deg. C including the day of cooking. In addition, there are other concerns with regard to microbiological quality, reduced sensory quality and decreased nutritive value. It has been suggested that low-dose irradiation could be used to extend the shelf-life of these products while at the same time reducing the risk of food poisoning. Research carried out at QUB and DARD has readily demonstrated that the safety and shelf-life of chilled ready meals consisting of meat (chicken, beef or pork) and certain vegetables (e.g. broccoli, carrots and roast potatoes) can be enhanced by irradiation doses of 2 or 3 kGy without having a detrimental effect on sensory or nutritional quality. To date, investigations have been limited to such traditional meals with no research being carried out on the more popular ready meals such as lasagna, cottage pies, curries, etc. which have a relatively short shelf-life upon purchase. It is therefore the objective of this work program to investigate the effect of low-dose irradiation (1-5 kGy) on the microbiological, sensory and nutritional quality of these meals and to determine if their overall quality can be enhanced.

The benefits of folic acid-modified gold nanoparticles in CT-based molecular imaging: radiation dose reduction and image contrast enhancement.

Science.gov (United States)

Beik, Jaber; Jafariyan, Maryam; Montazerabadi, Alireza; Ghadimi-Daresajini, Ali; Tarighi, Parastoo; Mahmoudabadi, Alireza; Ghaznavi, Habib; Shakeri-Zadeh, Ali

2017-12-12

X-ray computed tomography (CT) requires an optimal compromise between image quality and patient dose. While high image quality is an important requirement in CT, the radiation dose must be kept minimal to protect the patients from ionizing radiation-associated risks. The use of probes based on gold nanoparticles (AuNPs) along with active targeting ligands for specific recognition of cancer cells may be one of the balanced solutions. Herein, we report the effect of folic acid (FA)-modified AuNP as a targeted nanoprobe on the contrast enhancement of CT images as well as its potential for patient dose reduction. For this purpose, nasopharyngeal KB cancer cells overexpressing FA receptors were incubated with AuNPs with and without FA modification and imaged in a CT scanner with the following X-ray tube parameters: peak tube voltage of 130 KVp, and tube current-time products of 60, 90, 120, 160 and 250 mAs. Moreover, in order to estimate the radiation dose to which the patient was exposed during a head CT protocol, the CT dose index (CTDI) value was measured by an X-ray electrometer by changing the tube current-time product. Raising the tube current-time product from 60 to 250 mAs significantly increased the absorbed dose from 18 mGy to 75 mGy. This increase was not associated with a significant enhancement of the image quality of the KB cells. However, an obvious increase in image brightness and CT signal intensity (quantified by Hounsfield units [HU]) were observed in cells exposed to nanoparticles without any increase in the mAs product or radiation dose. Under the same Au concentration, KB cells exposed to FA-modified AuNPs had significantly higher HU and brighter CT images than those of the cells exposed to AuNPs without FA modification. In conclusion, FA-modified AuNP can be considered as a targeted CT nanoprobe with the potential for dose reduction by keeping the required mAs product as low as possible while enhancing image contrast.

Effective dose in abdominal digital radiography: Patient factor

Energy Technology Data Exchange (ETDEWEB)

Jang, Ji Sung; Koo, Hyun Jung; Park, Jung Hoon; Cho, Young Chul; Do, Kyung Hyun [Dept. of Radiology, and Research Institute of Radiology, Asan Medical Center, University of Ulsan College of Medicine, Seoul(Korea, Republic of); Yang, Hyung Jin [Dept. of Medical Physics, Korea University, Seoul (Korea, Republic of)

2017-08-15

To identify independent patient factors associated with an increased radiation dose, and to evaluate the effect of patient position on the effective dose in abdominal digital radiography. We retrospectively evaluated the effective dose for abdominal digital radiography in 222 patients. The patients were divided into two groups based on the cut-off dose value of 0.311 mSv (the upper third quartile of dose distribution): group A (n = 166) and group B (n = 56). Through logistic regression, independent factors associated with a larger effective dose were identified. The effect of patient position on the effective dose was evaluated using a paired t-test. High body mass index (BMI) (≥ 23 kg/m2), presence of ascites, and spinal metallic instrumentation were significantly associated with a larger effective dose. Multivariate logistic regression analysis revealed that high BMI [odds ratio (OR), 25.201; p < 0.001] and ascites (OR, 25.132; p < 0.001) were significantly associated with a larger effective dose. The effective dose was significantly lesser (22.6%) in the supine position than in the standing position (p < 0.001). High BMI and ascites were independent factors associated with a larger effective dose in abdominal digital radiography. Significant dose reduction in patients with these factors may be achieved by placing the patient in the supine position during abdominal digital radiography.

Applying gold nanoparticles as tumor-vascular disrupting agents during brachytherapy: estimation of endothelial dose enhancement

Energy Technology Data Exchange (ETDEWEB)

Ngwa, Wilfred; Makrigiorgos, G Mike; Berbeco, Ross I, E-mail: mmakrigiorgos@lroc.harvard.ed [Department of Radiation Oncology, Division of Medical Physics and Biophysics, Brigham and Women' s Hospital, Dana-Farber Cancer Institute and Harvard Medical School, Boston, MA 02115 (United States)

2010-11-07

Tumor vascular disrupting agents (VDAs) represent a promising approach to the treatment of cancer, in view of the tumor vasculature's pivotal role in tumor survival, growth and metastasis. VDAs targeting the tumor's dysmorphic endothelial cells can cause selective and rapid occlusion of the tumor vasculature, leading to tumor cell death from ischemia and extensive hemorrhagic necrosis. In this study, the potential for applying gold nanoparticles (AuNPs) as VDAs, during brachytherapy, is examined. Analytic calculations based on the electron energy loss formula of Cole were carried out to estimate the endothelial dose enhancement caused by radiation-induced photo/Auger electrons originating from AuNPs targeting the tumor endothelium. The endothelial dose enhancement factor (EDEF), representing the ratio of the dose to the endothelium with and without gold nanoparticles was calculated for different AuNP local concentrations, and endothelial cell thicknesses. Four brachytherapy sources were investigated, I-125, Pd-103, Yb-169, as well as 50 kVp x-rays. The results reveal that, even at relatively low intra-vascular AuNP concentrations, ablative dose enhancement to tumor endothelial cells due to photo/Auger electrons from the AuNPs can be achieved. Pd-103 registered the highest EDEF values of 7.4-271.5 for local AuNP concentrations ranging from 7 to 350 mg g{sup -1}, respectively. Over the same concentration range, I-125, 50 kVp and Yb-169 yielded values of 6.4-219.9, 6.3-214.5 and 4.0-99.7, respectively. Calculations of the EDEF as a function of endothelial cell thickness showed that lower energy sources like Pd-103 reach the maximum EDEF at smaller thicknesses. The results also reveal that the highest contribution to the EDEF comes from Auger electrons, apparently due to their shorter range. Overall, the data suggest that ablative dose enhancement to tumor endothelial cells can be achieved by applying tumor vasculature-targeted AuNPs as adjuvants to

Double dose: High family conflict enhances the effect of media violence exposure on adolescents’ aggression

NARCIS (Netherlands)

Fikkers, K.M.; Piotrowski, J.T.; Weeda, W.D.; Vossen, H.G.M.; Valkenburg, P.M.

2013-01-01

We investigated how exposure to media violence and family conflict affects adolescents’ subsequent aggressive behavior. We expected a double dose effect, meaning that high media violence exposure would lead to higher levels of aggression for adolescents in high conflict families compared to low

Late effects of low doses and dose rates

International Nuclear Information System (INIS)

Paretzke, H.G.

1980-01-01

This paper outlines the spectrum of problems and approaches used in work on the derivation of quantitative prognoses of late effects in man of low doses and dose rates. The origins of principal problems encountered in radiation risks assessments, definitions and explanations of useful quantities, methods of deriving risk factors from biological and epidemiological data, and concepts of risk evaluation and problems of acceptance are individually discussed

Low-dose effects in the sputtering of evaporated films

Energy Technology Data Exchange (ETDEWEB)

Florio, A.R.O.; Alonso, E.V.; Baragiola, R.A.; Ferron, J. (Comision Nacional de Energia Atomica, San Carlos de Bariloche (Argentina). Centro Atomico Bariloche)

1983-05-01

We report measurements of the dose dependence of the sputtering of evaporated films by 30 keV ions under UHV. An initial (sub-monolayer) enhanced sputtering is attributed to the removal of weakly bound atoms; this enhancement does not depend on the incidence angle of the projectile.

Aortic and hepatic enhancement at multidetector CT: evaluation of optimal iodine dose determined by lean body weight.

Science.gov (United States)

Kondo, Hiroshi; Kanematsu, Masayuki; Goshima, Satoshi; Watanabe, Haruo; Onozuka, Minoru; Moriyama, Noriyuki; Bae, Kyongtae T

2011-12-01

To determine the optimal iodine dose for aortic and hepatic enhancement at MDCT by comparing lean body weight (LBW) with total body weight (TBW). This study was approved by our institutional review committee. One hundred and thirty-six patients were randomized into four groups: 550, 650, 750 mg iodine/(kg of LBW) and 600 mgI/(kg of TBW). The aortic and hepatic contrast enhancements (Δ HUs) during the portal venous-phase and variances of ΔHUs were compared. Mean ΔHUs for 550, 650, 750 mgI/kg LBW and 600 mgI/kg TBW were: 95.1, 109.9, 122.4, and 131.2HU, respectively, for the aorta. For the liver, 43.1, 55.4, 60.8, and 63.5 HU. Mean Δ HUs increased with iodine dose per kg LBW (p<0.01), but no significant difference between 750 mgI/kg LBW and 600 mgI/kg TBW groups. Hepatic enhancement increased by ≥50 HU in 94% of patients with 750 mg/kg LBW. Variance of hepatic enhancement was marginally greater in the 600 mgI/kg TBW than in the 550 and 750 mgI/kg LBW. Hepatic enhancement variation was reduced with iodine doses based on LBW. Iodine dose of 750 mg iodine/kg LBW was appropriate to achieve hepatic enhancement≥50 HU in 94% of patients. Copyright © 2010 Elsevier Ireland Ltd. All rights reserved.

Brain tumours at 7T MRI compared to 3T - contrast effect after half and full standard contrast agent dose: initial results

International Nuclear Information System (INIS)

Noebauer-Huhmann, Iris-Melanie; Weber, M.; Szomolanyi, P.; Juras, V.; Kronnerwetter, C.; Widhalm, G.; Nemec, S.; Prayer, D.; Ladd, M.E.; Trattnig, S.

2015-01-01

To compare the contrast agent effect of a full dose and half the dose of gadobenate dimeglumine in brain tumours at 7 Tesla (7T) MR versus 3 Tesla (3T). Ten patients with primary brain tumours or metastases were examined. Signal intensities were assessed in the lesion and normal brain. Tumour-to-brain contrast and lesion enhancement were calculated. Additionally, two independent readers subjectively graded the image quality and artefacts. The enhanced mean tumour-to-brain contrast and lesion enhancement were significantly higher at 7T than at 3T for both half the dose (91.8 ± 45.8 vs. 43.9 ± 25.3 [p = 0.010], 128.1 ± 53.7 vs. 75.5 ± 32.4 [p = 0.004]) and the full dose (129.2 ± 50.9 vs. 66.6 ± 33.1 [p = 0.002], 165.4 ± 54.2 vs. 102.6 ± 45.4 [p = 0.004]). Differences between dosages at each field strength were also significant. Lesion enhancement was higher with half the dose at 7T than with the full dose at 3T (p =.037), while the tumour-to-brain contrast was not significantly different. Subjectively, contrast enhancement, visibility, and lesion delineation were better at 7T and with the full dose. All parameters were rated as good, at the least. Half the routine contrast agent dose at 7T provided higher lesion enhancement than the full dose at 3T which indicates the possibility of dose reduction at 7T. (orig.)

Brain tumours at 7T MRI compared to 3T - contrast effect after half and full standard contrast agent dose: initial results

Energy Technology Data Exchange (ETDEWEB)

Noebauer-Huhmann, Iris-Melanie; Weber, M. [Medical University of Vienna, High Field MR Centre, Department of Biomedical Imaging and Image-guided Therapy, Vienna (Austria); Medical University of Vienna, Division of Neuroradiology and Musculoskeletal Radiology, Department of Biomedical Imaging and Image-guided Therapy, Vienna (Austria); Szomolanyi, P.; Juras, V. [Medical University of Vienna, High Field MR Centre, Department of Biomedical Imaging and Image-guided Therapy, Vienna (Austria); Slovak Academy of Sciences, Department of Imaging Methods, Institute of Measurement Science, Bratislava (Slovakia); Kronnerwetter, C. [Medical University of Vienna, High Field MR Centre, Department of Biomedical Imaging and Image-guided Therapy, Vienna (Austria); Widhalm, G. [Medical University of Vienna, Department of Neurosurgery, Vienna (Austria); Nemec, S.; Prayer, D. [Medical University of Vienna, Division of Neuroradiology and Musculoskeletal Radiology, Department of Biomedical Imaging and Image-guided Therapy, Vienna (Austria); Ladd, M.E. [University Duisburg-Essen, Erwin L. Hahn Institute for Magnetic Resonance Imaging, Essen (Germany); German Cancer Research Center (DKFZ), Division of Medical Physics in Radiology, Heidelberg (Germany); Trattnig, S. [Medical University of Vienna, High Field MR Centre, Department of Biomedical Imaging and Image-guided Therapy, Vienna (Austria); Ludwig Boltzmann Institute for Experimental and Clinical Traumatology, Austrian Cluster for Tissue Regeneration, Vienna (Austria)

2015-01-15

To compare the contrast agent effect of a full dose and half the dose of gadobenate dimeglumine in brain tumours at 7 Tesla (7T) MR versus 3 Tesla (3T). Ten patients with primary brain tumours or metastases were examined. Signal intensities were assessed in the lesion and normal brain. Tumour-to-brain contrast and lesion enhancement were calculated. Additionally, two independent readers subjectively graded the image quality and artefacts. The enhanced mean tumour-to-brain contrast and lesion enhancement were significantly higher at 7T than at 3T for both half the dose (91.8 ± 45.8 vs. 43.9 ± 25.3 [p = 0.010], 128.1 ± 53.7 vs. 75.5 ± 32.4 [p = 0.004]) and the full dose (129.2 ± 50.9 vs. 66.6 ± 33.1 [p = 0.002], 165.4 ± 54.2 vs. 102.6 ± 45.4 [p = 0.004]). Differences between dosages at each field strength were also significant. Lesion enhancement was higher with half the dose at 7T than with the full dose at 3T (p =.037), while the tumour-to-brain contrast was not significantly different. Subjectively, contrast enhancement, visibility, and lesion delineation were better at 7T and with the full dose. All parameters were rated as good, at the least. Half the routine contrast agent dose at 7T provided higher lesion enhancement than the full dose at 3T which indicates the possibility of dose reduction at 7T. (orig.)

SU-F-T-648: Sharpening Dose Fall-Off Via Beam Number Enhancements For Stereotactic Brain Radiosurgery

Energy Technology Data Exchange (ETDEWEB)

Chiu, J; Braunstein, S; McDermott, M; Sneed, P; Ma, L [University of California San Francisco, San Francisco, CA (United States); Pierce, M [Indiana University, Bloomington, IN (United States)

2016-06-15

Purpose: Sharp dose fall-off is the hallmark of brain radiosurgery to deliver a high dose of radiation to the target while minimizing dose to normal brain tissue. In this study, we developed a technique for the purpose of enhancing the peripheral dose gradient by magnifying the total number of beams focused toward each isocenter via patient head tilt and simultaneous beam intensity modulations. Methods: Computer scripting for the proposed beam number enhancement (BNE) technique was developed. The technique was tested and then implemented on a clinical treatment planning system for a dedicated brain radiosurgical system (GK Perfexion, Elekta Oncology). To study technical feasibility and dosimetric advantages of the technique, we compared treatment planning quality and delivery efficiency for 20 radiosurgical cases previously treated at our institution. These cases included relatively complex treatments such as acoustic schwannoma, meningioma, brain metastasis and mesial temporal lobe epilepsy. Results: The BNE treatment plans were found to produce nearly identical target volume coverage (absolute value < 0.5%, P > 0.2) and dose conformity (BNE CI= 1.41±0.15 versus 1.41±0.20, P>0.9) as the original treatment plans. The total beam-on time for theBNE treatment plans were comparable (within 1.0 min or 1.8%) with those of the original treatment plans for all the cases. However, BNE treatment plans significantly improved the mean gradient index (BNE GI = 2.9±0.3 versus original GI =3.0±0.3 p<0.0001) and low-level isodose volumes, e.g. 20-50% prescribed isodose volumes, by 2.0% to 5.0% (p<0.02). Furthermore, with 4 to 5-fold increase in the total number of beams, the GI decreased by as much as 20% or 0.5 in absolute values. Conclusion: BNE via head tilt and simultaneous beam intensity modulation is an effective and efficient technique that physically sharpens the peripheral dose gradient for brain radiosurgery.

Low dose creatine supplementation enhances sprint phase of 400 meters swimming performance.

Science.gov (United States)

Anomasiri, Wilai; Sanguanrungsirikul, Sompol; Saichandee, Pisut

2004-09-01

This study demonstrated the effect of low dose creatine supplement (10 g. per day) on the sprinting time in the last 50 meters of 400 meters swimming competition, as well as the effect on exertion. Nineteen swimmers in the experimental group received creatine monohydrate 5 g with orange solution 15 g, twice per day for 7 days and nineteen swimmers in the control group received the same quantity of orange solution. The results showed that the swimmers who received creatine supplement lessened the sprinting time in the last 50 meters of 400 meters swimming competition than the control group. (p<0.05). The results of Wingate test (anaerobic power, anaerobic capacity and fatigue index) compared between pre and post supplementation. There was significant difference at p<0.05 in the control group from training effect whereas there was significant difference at p<0.000 from training effect and creatine supplement in the experiment group. Therefore, the creatine supplement in amateur swimmers in the present study enhanced the physical performance up to the maximum capacity.

Low-dose effects in the sputtering of evaporated films

International Nuclear Information System (INIS)

Florio, A.R.O.; Alonso, E.V.; Baragiola, R.A.; Ferron, J.

1983-01-01

We report measurements of the dose dependence of the sputtering of evaporated films by 30 keV ions under UHV. An initial (sub-monolayer) enhanced sputtering is attributed to the removal of weakly bound atoms; this enhancement does not depend on the incidence angle of the projectile. (author)

In vivo tumor targeting of gold nanoparticles: effect of particle type and dosing strategy.

Science.gov (United States)

Puvanakrishnan, Priyaveena; Park, Jaesook; Chatterjee, Deyali; Krishnan, Sunil; Tunnell, James W

2012-01-01

Gold nanoparticles (GNPs) have gained significant interest as nanovectors for combined imaging and photothermal therapy of tumors. Delivered systemically, GNPs preferentially accumulate at the tumor site via the enhanced permeability and retention effect, and when irradiated with near infrared light, produce sufficient heat to treat tumor tissue. The efficacy of this process strongly depends on the targeting ability of the GNPs, which is a function of the particle's geometric properties (eg, size) and dosing strategy (eg, number and amount of injections). The purpose of this study was to investigate the effect of GNP type and dosing strategy on in vivo tumor targeting. Specifically, we investigated the in vivo tumor-targeting efficiency of pegylated gold nanoshells (GNSs) and gold nanorods (GNRs) for single and multiple dosing. We used Swiss nu/nu mice with a subcutaneous tumor xenograft model that received intravenous administration for a single and multiple doses of GNS and GNR. We performed neutron activation analysis to quantify the gold present in the tumor and liver. We performed histology to determine if there was acute toxicity as a result of multiple dosing. Neutron activation analysis results showed that the smaller GNRs accumulated in higher concentrations in the tumor compared to the larger GNSs. We observed a significant increase in GNS and GNR accumulation in the liver for higher doses. However, multiple doses increased targeting efficiency with minimal effect beyond three doses of GNPs. These results suggest a significant effect of particle type and multiple doses on increasing particle accumulation and on tumor targeting ability.

Biological Effects of Low-Dose Exposure

CERN Document Server

Komochkov, M M

2000-01-01

On the basis of the two-protection reaction model an analysis of stochastic radiobiological effects of low-dose exposure of different biological objects has been carried out. The stochastic effects are the results published in the last decade: epidemiological studies of human cancer mortality, the yield of thymocyte apoptosis of mice and different types of chromosomal aberrations. The results of the analysis show that as dependent upon the nature of biological object, spontanous effect, exposure conditions and radiation type one or another form dose - effect relationship is realized: downwards concave, near to linear and upwards concave with the effect of hormesis included. This result testifies to the incomplete conformity of studied effects of 1990 ICRP recomendations based on the linear no-threshold hypothesis about dose - effect relationship. Because of this the methodology of radiation risk estimation recomended by ICRP needs more precisian and such quantity as collective dose ought to be classified into...

We can do better than effective dose for estimating or comparing low-dose radiation risks

International Nuclear Information System (INIS)

Brenner, D.J.

2012-01-01

The effective dose concept was designed to compare the generic risks of exposure to different radiation fields. More commonly these days, it is used to estimate or compare radiation-induced cancer risks. For various reasons, effective dose represents flawed science: for instance, the tissue-specific weighting factors used to calculate effective dose are a subjective mix of different endpoints; and the marked and differing age and gender dependencies for different health detriment endpoints are not taken into account. This paper suggests that effective dose could be replaced with a new quantity, ‘effective risk’, which, like effective dose, is a weighted sum of equivalent doses to different tissues. Unlike effective dose, where the tissue-dependent weighting factors are a set of generic, subjective committee-defined numbers, the weighting factors for effective risk are simply evaluated tissue-specific lifetime cancer risks per unit equivalent dose. Effective risk, which has the potential to be age and gender specific if desired, would perform the same comparative role as effective dose, be just as easy to estimate, be less prone to misuse, be more directly understandable, and would be based on solid science. An added major advantage is that it gives the users some feel for the actual numerical values of the radiation risks they are trying to control.

Biochemical and cellular mechanisms of low-dose effects

International Nuclear Information System (INIS)

Feinendegen, L.E.; Booz, J.; Muehlensiepen, H.

1988-01-01

The question of health effects from small radiation doses remains open. Individual cells, when being hit by single elemental doses - in low-dose irradiation - react acutely and temporarily by altering control of enzyme activity, as is demonstrated for the case of thymidine kinase. This response is not constant in that it provides a temporary protection of enzyme activity against a second irradiation, by a mechanism likely to be via improved detoxification of intracellular radicals. It must be considered that in the low-dose region radiation may also exert protection against other challenges involving radicals, causing a net beneficial effect by temporarily shielding the hit cell against radicals produced by metabolism. Since molecular alterations leading to late effects are considered a consequence of the initial cellular response, late effects from small radiation doses do not necessarily adhere to a linear dose-effect relationship. The reality of the linear relationship between the risk of late effects from high doses to small doses is an assumption, for setting dose limits, but it must not be taken for predicting health detriment from low doses. (author)

Effect of temporal distribution of dose on oncogenic transformation

International Nuclear Information System (INIS)

Miller, R.C.; Brenner, D.J.; Geard, C.R.; Marino, S.A.; Hall, E.J.

1988-01-01

Risk estimates for neutron hazards are of considerable social and economic importance. Effectiveness per unit dose of X or γ rays (low-LET radiations) has been consistently observed to be dependent on the temporal distribution of dose. In a series of comparisons, 0.5 Gy of single or fractionated (five fractions in 8 h), neutrons of 0.23, 0.35, 0.45, 5.9, or 13.7 MeV were delivered to a synchronous C3H 10T1/2 cells. Transformation frequencies per surviving cell are shown. Cells exposed to one energy (5.9 MeV) show a significant enhancement at the 95% level due to fractionated exposures, and at the 85% confidence level the 0.35- and 0.45-MeV fractionated exposures additionally result in significantly greater transformation frequencies. The frequencies of surviving cells per dish between a single or fractionated exposure vary by less than 10%. In three of five pairwise comparisons, fractionated exposures result in statistically greater frequencies of transformants per dish, and are in complete agreement with the results when induction is expressed as transformants per surviving cell. However, after 0.23-MeV neutron irradiation, the single dose resulted in a greater incidence of transformed foci than the fractionated dose

Minimising activity and dose with enhanced image quality by radiopharmaceutical administrations

International Nuclear Information System (INIS)

Hoeschen, C.; Mattsson, S.; Cantone, M. C.; Mikuz, M.; Lacasta, C.; Ebel, G.; Clinthorne, N.; Giussani, A.

2010-01-01

Owing to the introduction of new diagnostic procedures, such as computed tomography (CT), positron emission tomography (PET) and single photon emission computed tomography (SPECT), the individual dose caused by medical exposures has grown rapidly in the last years. This is especially a subject to radiation protection for nuclear medical diagnosis, since in this case radiopharmaceuticals are administered to the patient, meaning not only a radiation exposure to the diseased tissue but also to the healthy tissues of large parts of the body. 'Minimizing Activity and Dose with Enhanced Image quality by Radiopharmaceutical Administrations' (MADEIRA) is a project co-funded by the European Commission within the Seventh Euratom Framework Programme that aims to improve three-dimensional (3D) nuclear medical imaging technologies significantly. MADEIRA is aiming to improve the efficacy and safety of 3D PET and SPECT functional imaging by optimising the spatial resolution and the signal-to-noise ratio, improving the knowledge of the temporal variation of the radiopharmaceuticals' uptake in and clearance from tumorous and healthy tissues, and evaluation of the corresponding patient dose. Using an optimised imaging procedure that improves the information gained per unit administered dose, MADEIRA aims especially to reduce the dose to healthy tissues of the patient. In this paper, an overall summary of the current achievements will be presented. (authors)

A Monte Carlo Study on the Effect of Various Neutron Capturers on Dose Distribution in Brachytherapy with 252Cf Source

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Firoozabadi M. M.

2017-03-01

Full Text Available Background: In neutron interaction with matter and reduction of neutron energy due to multiple scatterings to the thermal energy range, increasing the probability of thermal neutron capture by neutron captures makes dose enhancement in the tumors loaded with these materials. Objective: The purpose of this study is to evaluate dose distribution in the presence of 10B, 157Gd and 33S neutron capturers and to determine the effect of these materials on dose enhancement rate for 252Cf brachytherapy source. Methods: Neutron-ray flux and energy spectra, neutron and gamma dose rates and dose enhancement factor (DEF are determined in the absence and presence of 10B, 157Gd and 33S using Monte Carlo simulation. Results: The difference in the thermal neutron flux rate in the presence of 10B and 157Gd is significant, while the flux changes in the fast and epithermal energy ranges are insensible. The dose enhancement factor has increased with increasing distance from the source and reached its maximum amount equal to 258.3 and 476.1 cGy/h/µg for 157Gd and 10B, respectively at about 8 cm distance from the source center. DEF for 33S is equal to one. Conclusion: Results show that the magnitude of dose augmentation in tumors containing 10B and 157Gd in brachytherapy with 252Cf source will depend not only on the capture product dose level, but also on the tumor distance from the source. 33S makes dose enhancement under specific conditions that these conditions depend on the neutron energy spectra of source, the 33S concentration in tumor and tumor distance from the source.

Effects of cytotoxic chemotherapeutic agents on split-dose repair in intestinal crypt cells

International Nuclear Information System (INIS)

Phillips, Theodore L.; Ross, Glenda Y.

1997-01-01

Purpose: Many cancer chemotherapeutic agents interact with radiation to enhance the amount of radiation damage observed in both tumor and normal tissues. It is important to predict this interaction and to determine the effect of drug on sublethal damage repair. To evaluate for effects in rapid renewing normal tissues, the intestinal crypt cell in vivo assay is an excellent one to employ. These studies investigate the effect of eleven cancer chemotherapeutic drugs on split-dose repair in the intestinal crypt cell of the mouse. Methods and Materials: LAF1 male mice, age 10-12 weeks, were exposed to whole-body irradiation with orthovoltage x-rays delivered as a single dose or as equally divided doses delivered with intervals between the two exposures of 2 to 24 h. In the experimental group, the cancer chemotherapeutic agent was administered intraperitoneally 2 h before the first radiation dose. At 3.6 days after the second irradiation, the mice were sacrificed; the jejunum was removed, fixed, and sectioned for light microscopy. The number of regenerating crypts were counted and corrected to represent the number of surviving cells per circumference. Results: Of the eleven drugs tested, only carmustine eliminated split-dose repair. Cisplatin delayed repair, and methotrexate caused marked synchronization obliterating the observation of split-dose repair. Conclusions: Most cytotoxic chemotherapeutic agents do not inhibit sublethal damage repair in intestinal crypt cells when given 2 h before the first radiation exposure. Absence of the initial increase in survival seen with split-dose radiation is noted with carmustine and high-dose methotrexate

Physical mechanisms contributing to enhanced bipolar gain degradation at low dose rates

International Nuclear Information System (INIS)

Fleetwood, D.M.; Reber, R.A. Jr.; Winokur, P.S.; Kosier, S.L.; Schrimpf, R.D.; Wei, A.; DeLaus, M.; Combs, W.E.; Pease, R.L.

1994-01-01

The authors have performed capacitance-voltage (C-V) and thermally-stimulated-current (TSC) measurements on non-radiation-hard MOS capacitors simulating screen oxides of modern bipolar technologies. For 0-V irradiation of ∼25 C, the net trapped-positive-charge density (N ox ) inferred from midgap C-V shifts is ∼25--40% greater for low-dose-rate ( 2 )/s) than for high-dose-rate (> 100 rad(SiO 2 )/s) exposure. Device modeling shows that such a difference in screen-oxide N ox is enough to account for the enhanced low-rate gain degradation often observed in bipolar devices, due to the ∼ exp(N ox 2 ) dependence of the excess base current. At the higher rates, TSC measurements reveal a ∼10% decrease in trapped-hole density over low rates. Also, at high rates, up to ∼2.5-times as many trapped holes are compensated by electrons in border traps than at low rates for these devices and irradiation conditions. Both the reduction in trapped-hole density and increased charge compensation reduce the high-rate midgap shift. A physical model is developed which suggests that both effects are caused by time-dependent space charge in the bulk of these soft oxides associated with slowly transporting and/or metastably trapped holes (e.g., in Eδ' centers). On the basis of this model, bipolar transistors and screen-oxide capacitors were irradiated at 60 C at 200 rad(SiO 2 )/s in a successful effort to match low-rate damage. these surprising results provide insight into enhanced low-rate bipolar gain degradation and suggest potentially promising new approaches to bipolar and BiCMOS hardness assurance for space applications

Age-dependent conversion coefficients for organ doses and effective doses for external neutron irradiation

International Nuclear Information System (INIS)

Nishizaki, Chihiro; Endo, Akira; Takahashi, Fumiaki

2006-06-01

To utilize dose assessment of the public for external neutron irradiation, conversion coefficients of absorbed doses of organs and effective doses were calculated using the numerical simulation technique for six different ages (adult, 15, 10, 5 and 1 years and newborn), which represent the member of the public. Calculations were performed using six age-specific anthropomorphic phantoms and a Monte Carlo radiation transport code for two irradiation geometries, anterior-posterior and rotational geometries, for 20 incident energies from thermal to 20 MeV. Effective doses defined by the 1990 Recommendation of ICRP were calculated from the absorbed doses in 21 organs. The calculated results were tabulated in the form of absorbed doses and effective doses per unit neutron fluence. The calculated conversion coefficients are used for dose assessment of the public around nuclear facilities and accelerator facilities. (author)

The Primary Origin of Dose Rate Effects on Microstructural Evolution of Austenitic Alloys During Neutron Irradiation

International Nuclear Information System (INIS)

Okita, Taira; Sato, Toshihiko; Sekimura, Naoto; Garner, Francis A.; Greenwood, Lawrence R.

2002-01-01

The effect of dose rate on neutron-induced microstructural evolution was experimentally estimated. Solution-annealed austenitic model alloys were irradiated at approximately 400 degrees C with fast neutrons at seven different dose rates that vary more than two orders difference in magnitude, and two different doses were achieved at each dose rate. Both cavity nucleation and growth were found to be enhanced at lower dose rate. The net vacancy flux is calculated from the growth rate of cavities that had already nucleated during the first cycle of irradiation and grown during the second cycle. The net vacancy flux was found to be proportional to (dpa/sec) exp (1/2) up to 28.8 dpa and 8.4 x 10 exp (-7) dpa/sec. This implies that mutual recombination dominates point defect annihilation, in this experiment even though point defect sinks such as cavities and dislocations were well developed. Thus, mutual recombination is thought to be the primary origin of the effect of dose rate on microstructural evolution

The concept of the effective dose

International Nuclear Information System (INIS)

Jacobi, W.

1975-01-01

Irradiation of the human body by external or internal sources leads mostly to a simultaneous exposure of several organs. However, so far no clear and consistent recommendations for the combination of organ doses and the assessment of an exposure limit under such irradiation conditions are available. Following a proposal described in ICRP-publication 14 one possible concept for the combination of organ doses is discussed in this paper. This concept is based on the assumption that at low doses the total radiation detriment to the exposed person is given by the sum of radiation detriments to the single organs. Taking into account a linear dose-risk relationship, the sum of weighted organ doses leads to the definition of an 'Effective Dose'. The applicability and consequences of this 'Effective Dose Concept' are discussed especially with regard to the assessment of the maximum permissible intake of radionuclides into the human body and the combination of external and internal exposure. (orig.) [de

Effective radiation dose and eye lens dose in dental cone beam CT: effect of field of view and angle of rotation.

Science.gov (United States)

Pauwels, R; Zhang, G; Theodorakou, C; Walker, A; Bosmans, H; Jacobs, R; Bogaerts, R; Horner, K

2014-10-01

To quantify the effect of field of view (FOV) and angle of rotation on radiation dose in dental cone beam CT (CBCT) and to define a preliminary volume-dose model. Organ and effective doses were estimated using 148 thermoluminescent dosemeters placed in an anthropomorphic phantom. Dose measurements were undertaken on a 3D Accuitomo 170 dental CBCT unit (J. Morita, Kyoto, Japan) using six FOVs as well as full-rotation (360°) and half-rotation (180°) protocols. For the 360° rotation protocols, effective dose ranged between 54 µSv (4 × 4 cm, upper canine) and 303 µSv (17 × 12 cm, maxillofacial). An empirical relationship between FOV dimension and effective dose was derived. The use of a 180° rotation resulted in an average dose reduction of 45% compared with a 360° rotation. Eye lens doses ranged between 95 and 6861 µGy. Significant dose reduction can be achieved by reducing the FOV size, particularly the FOV height, of CBCT examinations to the actual region of interest. In some cases, a 180° rotation can be preferred, as it has the added value of reducing the scan time. Eye lens doses should be reduced by decreasing the height of the FOV rather than using inferior FOV positioning, as the latter would increase the effective dose considerably. The effect of the FOV and rotation angle on the effective dose in dental CBCT was quantified. The dominant effect of FOV height was demonstrated. A preliminary model has been proposed, which could be used to predict effective dose as a function of FOV size and position.

Dexmedetomidine Dose Dependently Enhances the Local Anesthetic Action of Lidocaine in Inferior Alveolar Nerve Block: A Randomized Double-Blind Study.

Science.gov (United States)

Ouchi, Kentaro; Sugiyama, Kazuna

2016-01-01

Dexmedetomidine (DEX) dose dependently enhances the local anesthetic action of lidocaine in rats. We hypothesized that the effect might also be dose dependent in humans. We evaluated the effect of various concentrations of DEX with a local anesthetic in humans. Eighteen healthy volunteers were randomly assigned by a computer to receive 1.8 mL of 1 of 4 drug combinations: (1) 1% lidocaine with 2.5 ppm (parts per million) (4.5 μg) DEX, (2) lidocaine with 5.0 ppm (9.0 μg) DEX, (3) lidocaine with 7.5 ppm (13.5μg) DEX, or (4) lidocaine with 1:80,000 (22.5 μg) adrenaline (AD), to produce inferior alveolar nerve block. Pulp latency and lower lip numbness (for assessing onset and duration of anesthesia) were tested, and sedation level, blood pressure, and heart rate were recorded every 5 minutes for 20 minutes, and every 10 minutes from 20 to 60 minutes. Pulp latency of each tooth increased compared with baseline, from 5 to 15 minutes until 60 minutes. There were no significant intergroup differences at any time point. Anesthesia onset was not different between groups. Anesthesia duration was different between groups (that with DEX 7.5 ppm was significantly longer than that with DEX 2.5 ppm and AD; there was no difference between DEX 2.5 ppm and AD). Blood pressure decreased from baseline in the 5.0 and 7.5 ppm DEX groups at 30 to 60 minutes, although there was no hypotension; moreover, heart rate did not change in any group. Sedation score did not indicate deep sedation in any of the groups. Dexmedetomidine dose dependently enhances the local anesthetic action of lidocaine in humans. Dexmedetomidine at 2.5 ppm produces similar enhancement of local anesthesia effect as addition of 1:80,000 AD.

Effects of low doses; Effet des faibles doses

Energy Technology Data Exchange (ETDEWEB)

Le Guen, B. [Electricite de France (EDF-LAM-SCAST), 93 - Saint-Denis (France)

2001-07-01

Actually, even though it is comfortable for the risk management, the hypothesis of the dose-effect relationship linearity is not confirmed for any model. In particular, in the area of low dose rate delivered by low let emitters. this hypothesis is debated at the light of recent observations, notably these ones relative to the mechanisms leading to genetic instability and induction eventuality of DNA repair. The problem of strong let emitters is still to solve. (N.C.)

Therapeutic effects of low radiation doses

Energy Technology Data Exchange (ETDEWEB)

Trott, K.R. (Dept. of Radiation Biology, St. Bartholomew' s Medical College, London (United Kingdom))

1994-01-01

This editorial explores the scientific basis of radiotherapy with doses of < 1 Gy for various non-malignant conditions, in particular dose-effect relationships, risk-benefit considerations and biological mechanisms. A review of the literature, particularly clinical and experimental reports published more than 50 years ago was conducted to clarify the following problems. 1. The dose-response relationships for the therapeutic effects on three groups of conditions: non-malignant skin disease, arthrosis and other painful degenerative joint disorders and anti-inflammatory radiotherapy; 2. risks after radiotherapy and after the best alternative treatments; 3. the biological mechanisms of the different therapeutic effects. Radiotherapy is very effective in all three groups of disease. Few dose-finding studies have been performed, all demonstrating that the optimal doses are considerable lower than the generally recommended doses. In different conditions, risk-benefit analysis of radiotherapy versus the best alternative treatment yields very different results: whereas radiotherapy for acute postpartum mastitis may not be justified any more, the risk-benefit ratio of radiotherapy of other conditions and particularly so in dermatology and some anti-inflammatory radiotherapy appears to be more favourable than the risk-benefit ratio of the best alternative treatments. Radiotherapy can be very effective treatment for various non-malignant conditions such as eczema, psoriasis, periarthritis humeroscapularis, epicondylitis, knee arthrosis, hydradenitis, parotitis and panaritium and probably be associated with less acute and long-term side effects than similarly effective other treatments. Randomized clinical studies are required to find the optimal dosage which, at present, may be unnecessarily high.

Monte Carlo simulations for dose enhancement in cancer treatment using bismuth oxide nanoparticles implanted in brain soft tissue.

Science.gov (United States)

Taha, Eslam; Djouider, Fathi; Banoqitah, Essam

2018-03-26

The objective of this work is to study the dosimetric performances of bismuth oxide nanoparticles implanted in tumors in cancer radiotherapy. GEANT4 based Monte Carlo numerical simulations were performed to assess dose enhancement distributions in and around a 1 × 1 × 1 cm 3 tumor implanted with different concentrations of bismuth oxide and irradiated with low energies 125 I, 131 Cs, and 103 Pd radioactive sources. Dose contributions were considered from photoelectrons, Auger electrons, and characteristic X-rays. Our results show the dose enhancement increased with increasing both bismuth oxide concentration in the target and photon energy. A dose enhancement factor up to 18.55 was obtained for a concentration of 70 mg/g of bismuth oxide in the tumor when irradiated with 131 Cs source. This study showed that bismuth oxide nanoparticles are innovative agents that could be potentially applicable to in vivo cancer radiotherapy due to the fact that they induce a highly localized energy deposition within the tumor.

Effects of small doses of ionising radiation

International Nuclear Information System (INIS)

Doll, R.

1998-01-01

Uncertainty remains about the quantitative effects of doses of ionising radiation less than 0.2 Sv. Estimates of hereditary effects, based on the atomic bomb survivors, suggest that the mutation doubling dose is about 2 Sv for acute low LET radiation, but the confidence limits are wide. The idea that paternal gonadal irradiation might explain the Seascale cluster of childhood leukaemia has been disproved. Fetal irradiation may lead to a reduction in IQ and an increase in seizures in childhood proportional to dose. Estimates that doses to a whole population cause a risk of cancer proportional to dose, with 0.1 Sv given acutely causing a risk of 1%, will need to be modified as more information is obtained, but the idea that there is a threshold for risk above this level is not supported by observations on the irradiated fetus or the effect of fallout. The idea, based on ecological observations, that small doses protect against the development of cancer is refuted by the effect of radon in houses. New observations on the atomic bomb survivors have raised afresh the possibility that small doses may also have other somatic effects. (author)

Dose enhancement in the neighborhood of foreign bodies of the skin due to electron irradiation. A Monte-Carlo study using MCNP

Energy Technology Data Exchange (ETDEWEB)

Heide, Bernd [Karlsruhe Institute of Technology (KIT), Eggenstein-Leopoldshafen (DE). Inst. of Radiation Research (ISF)

2011-07-01

Foreign bodies penetrate into the skin in the region of the hand very frequently. If they are amicrobic, they can get stuck in the skin and do no harm to the body in normal case. However, when handling with a radioactive material, like an Sr-90/Y-90 syringe for example, a stuck foreign body in a finger can lead to an enhanced absorbed dose in the neighbourhood of a few hundredths of millimetre of a foreign body, which just is in magnitude of a body cell. In the following, we shall investigate the dose enhancement effect of graphite, lead, and gold when embedded in soft tissue and irradiated with electrons. This case study focusses on the region close to the piece of metal (foreign body) without consideration for the depth in which the foreign body is located. It holds some other idealised assumptions (concerning vacuum, shape and size of foreign bodies, tissue composition, and direction of the radiation field) but still is near to real situations. Among others, this case study served to estimate the dose enhancement in the neighbourhood of a pike of lead located at the right forefinger of a member of our Institute of Radiation Research after an Sr-90/Y-90 irradiation. (orig.)

Beneficial effects of low dose Musa paradisiaca on the semen quality of male Wistar rats.

Science.gov (United States)

Alabi, A S; Omotoso, Gabriel O; Enaibe, B U; Akinola, O B; Tagoe, C N B

2013-03-01

This study aimed at determining the effects of administration of mature green fruits of Musa paradisiaca on the semen quality of adult male Wistar rats. THE ANIMALS USED FOR THE STUDY WERE GROUPED INTO THREE: the control group, given 2 ml of double distilled water, a low dose group given 500 mg/kg/day and a high dose group given 1000 mg/kg/day of the plantain fruits, which was made into flour, and dissolved in 2 ml of double distilled water for easy oral administration. Significant increment in the semen parameters was noticed in animals that received a lower dose of the plantain flour, but those animals who received the high dose had marked and very significant reduction in sperm cell concentration and percentage of morphologically normal spermatozoa. Musa paradisiaca should be consumed in moderate quantities in order to derive its beneficial effects of enhancing male reproductive functions.

Relation between dose of bendrofluazide, antihypertensive effect, and adverse biochemical effects

DEFF Research Database (Denmark)

Carlsen, J E; Køber, L; Torp-Pedersen, C

1990-01-01

OBJECTIVE--To determine the relevant dose of bendrofluazide for treating mild to moderate hypertension. DESIGN--Double blind parallel group trial of patients who were given placebo for six weeks and then randomly allocated to various doses of bendrofluazide (1.25, 2.5, 5, or 10 mg daily) or place...... of bendrofluazide to treat mild to moderate hypertension is 1.25-2.5 mg a day. Higher doses caused more pronounced adverse biochemical effects including adverse lipid effects. Previous trials with bendrofluazide have used too high doses....... relations between dose and effect were shown for potassium, urate, glucose, total cholesterol, and apolipoprotein B concentrations. The 1.25 mg dose increased only urate concentrations, whereas the 10 mg dose affected all the above biochemical variables. CONCLUSION--The relevant range of doses...

Enhanced low dose rate sensitivity (ELDRS) in a voltage comparator which only utilizes complementary vertical NPN and PNP transistors

International Nuclear Information System (INIS)

Krieg, J.F.; Titus, J.L.; Emily, D.; Gehlhausen, M.; Swonger, J.; Platteter, D.

1999-01-01

For the first time, enhanced low dose rate sensitivity (ELDRS) is reported in a vertical bipolar process. A radiation hardness assurance (RHA) test method was successfully demonstrated on a linear circuit, the HS139RH quad comparator, and its discrete transistor elements. This circuit only uses vertical NPN and PNP transistors. Radiation tests on the HS139RH were performed at 25 C using dose rates of 50 rd(Si)/s, 100 mrd(Si)/s and 10 mrd(Si)/s, and at 100 C using a dose rate of 10 rd(Si)/s. Tests at dose rates of 50 rd(Si)/s at 25 C and 10 rd(Si)/s at 100 C were performed on discrete vertical NPN and PNP transistor elements which comprise the HS139RH. Transistor and circuit responses were evaluated. The die's passivation overcoat layers were varied to examine the effect of removing a nitride layer and thinning a deposited SiO 2 (silox) layer

Dosimetry in Interventional Radiology - Effective Dose Estimation

International Nuclear Information System (INIS)

Miljanic, S.; Buls, N.; Clerinx, P.; Jarvinen, H.; Nikodemova, D.; Ranogajec-Komor, M; D'Errico, F.

2008-01-01

Interventional radiological procedures can lead to significant radiation doses to patients and to staff members. In order to evaluate the personal doses with respect to the regulatory dose limits, doses measured by dosimeters have to be converted to effective doses (E). Measurement of personal dose equivalent Hp(10) using a single unshielded dosimeter above the lead apron can lead to significant overestimation of the effective dose, while the measurement with dosimeter under the apron can lead to underestimation. To improve the accuracy, measurements with two dosimeters, one above and the other under the apron have been suggested ( d ouble dosimetry ) . The ICRP has recommended that interventional radiology departments develop a policy that staff should wear two dosimeters. The aim of this study was to review the double dosimetry algorithms for the calculation of effective dose in high dose interventional radiology procedures. The results will be used to develop general guidelines for personal dosimetry in interventional radiology procedures. This work has been carried out by Working Group 9 (Radiation protection dosimetry of medical staff) of the CONRAD project, which is a Coordination Action supported by the European Commission within its 6th Framework Program.(author)

Equivalent dose, effective dose and risk assessment from cephalometric radiography to critical organs

International Nuclear Information System (INIS)

Kang, Seong Sook; Cho, Bon Hae; Kim, Hyun Ja

1995-01-01

In head and neck region, the critical organ and tissue doses were determined, and the risks were estimated from lateral, posteroanterial and basilar cephalometric radiography. For each cephalometric radiography, 31 TLDs were placed in selected sites (18 internal and 13 external sites) in a tissue-equivalent phantom and exposed, then read-out in the TLD reader. The following results were obtained; 1. From lateral cephalometric radiography, the highest effective dose recorded was that delivered to the salivary gland (3.6 μSv) and the next highest dose was that received by the bone marrow (3 μSv). 2. From posteroanterial cephalometric radiography, the highest effective dose recorded was that delivered to the salivary gland (2 μSv) and the next highest dose was that received by the bone marrow (1.8 μSv). 3. From basilar cephalometric radiography, the highest effective dose recorded was that delivered to the thyroid gland (31.4 μSv) and the next highest dose was that received by the salivary gland (13.3 μSv). 4. The probabilities of stochastic effect from lateral, posteroanterial and basilar cephalometric radiography were 0.72 X 10 -6 , 0.49 X 10 -6 and 3.51 X 10 -6 , respectively.

Contrast Dose and Radiation Dose Reduction in Abdominal Enhanced Computerized Tomography Scans with Single-phase Dual-energy Spectral Computerized Tomography Mode for Children with Solid Tumors.

Science.gov (United States)

Yu, Tong; Gao, Jun; Liu, Zhi-Min; Zhang, Qi-Feng; Liu, Yong; Jiang, Ling; Peng, Yun

2017-04-05

Contrast dose and radiation dose reduction in computerized tomography (CT) scan for adult has been explored successfully, but there have been few studies on the application of low-concentration contrast in pediatric abdominal CT examinations. This was a feasibility study on the use of dual-energy spectral imaging and adaptive statistical iterative reconstruction (ASiR) for the reduction of radiation dose and iodine contrast dose in pediatric abdominal CT patients with solid tumors. Forty-five patients with solid tumors who had initial CT (Group B) and follow-up CT (Group A) after chemotherapy were enrolled. The initial diagnostic CT scan (Group B) was performed using the standard two-phase enhanced CT with 320 mgI/ml concentration contrast, and the follow-up scan (Group A) was performed using a single-phase enhanced CT at 45 s after the beginning of the 270 mgI/ml contrast injection using spectral mode. Forty percent ASiR was used for the images in Group B and monochromatic images with energy levels ≥60 keV in Group A. In addition, filtered back-projection (FBP) reconstruction was used for monochromatic images hounsfield unit (HU). The abdominal organs of Groups A and B had similar degrees of absolute and relative enhancement (t = 0.36 and -1.716 for liver, -0.153 and -1.546 for pancreas, and 2.427 and 0.866 for renal cortex, all P> 0.05). Signal-to-noise ratio of the abdominal organs was significantly lower in Group A than in Group B (t = -8.11 for liver, -7.83 for pancreas, and -5.38 for renal cortex, all P 3, indicating clinically acceptable image quality. Single-phase, dual-energy spectral CT used for children with solid abdominal tumors can reduce contrast dose and radiation dose and can also maintain clinically acceptable image quality.

Combination of nitric oxide stimulation with high-dose 18F-FDG promotes apoptosis and enhances radiation therapy of endothelial cells

International Nuclear Information System (INIS)

Paik, Jin-Young; Park, Jin-Won; Jung, Kyung-Ho; Lee, Eun Jeong; Lee, Kyung-Han

2012-01-01

Introduction: High-dose 18 F-FDG can provide targeted nuclear therapy of cancer. Endothelial cell injury is a key determinant of tumor response to radiotherapy. Here, we tested the hypothesis that activation of endothelial cell glycolytic metabolism with nitric oxide can enhance the therapeutic effect of high-dose 18 F-FDG. Methods: Calf pulmonary artery endothelial (CPAE) cells were treated with graded doses of 18 F-FDG. Glycolysis was stimulated by 24 h of exposure to the nitric oxide donor, sodium nitroprusside (SNP). Cell viability was assessed by MTT and clonogenic assays. Apoptosis was evaluated by ELISA of cytosolic DNA fragments and Western blots of cleaved caspase-3. Results: SNP stimulation (0.1 and 1 mM) augmented CPAE cell 18 F-FDG uptake to 2.6- and 4.6-fold of controls without adverse effects. Treatment with 333 μCi/ml 18 F-FDG alone reduced viable cell number to 35.4% of controls by Day 3. Combining 0.1 mM SNP stimulation significantly enhanced the killing effect, reducing cell numbers to 19.2% and 39.2% of controls by 333 and 167 μCi/ml of 18 F-FDG, respectively. 18 F-FDG also suppressed clonogenic survival to 80.8% and 43.2% of controls by 83 and 167 μCi/ml, which was again intensified by SNP to 59.7% and 21.1% of controls. The cytotoxic effect of 18 F-FDG was attributed to induction of apoptosis as shown by increased cytosolic fragmented DNA and cleaved caspase-3 levels (26.4% and 30.7% increases by 167 μCi/ml). Combining SNP stimulation significantly increased both of these levels to 1.8-fold of control cells. Conclusion: High-dose 18 F-FDG combined with nitric oxide-stimulated glycolysis is an effective method to inhibit endothelial cell survival and promote apoptosis. These results suggest a potential role of this strategy for targeted radiotherapy of angiogenic vasculature.

Effective dose: a radiation protection quantity

CERN Document Server

Menzel, H G

2012-01-01

Modern radiation protection is based on the principles of justification, limitation, and optimisation. Assessment of radiation risks for individuals or groups of individuals is, however, not a primary objective of radiological protection. The implementation of the principles of limitation and optimisation requires an appropriate quantification of radiation exposure. The International Commission on Radiological Protection (ICRP) has introduced effective dose as the principal radiological protection quantity to be used for setting and controlling dose limits for stochastic effects in the regulatory context, and for the practical implementation of the optimisation principle. Effective dose is the tissue weighted sum of radiation weighted organ and tissue doses of a reference person from exposure to external irradiations and internal emitters. The specific normalised values of tissue weighting factors are defined by ICRP for individual tissues, and used as an approximate age- and sex-averaged representation of th...

Estimation of dose enhancement to soft tissue due to backscatter radiation near metal interfaces during head and neck radiothearpy - A phantom dosimetric study with radiochromic film

Directory of Open Access Journals (Sweden)

Rajesh Ashok Kinhikar

2014-01-01

Full Text Available The objective of this study was to investigate the dose enhancement to soft tissue due to backscatter radiation near metal interfaces during head and neck radiotherapy. The influence of titanium-mandibular plate with the screws on radiation dose was tested on four real bones from mandible with the metal and screws fixed. Radiochromic films were used for dosimetry. The bone and metal were inserted through the film at the center symmetrically. This was then placed in a small jig (7 cm × 7 cm × 10 cm to hold the film vertically straight. The polymer granules (tissue-equivalent were placed around the film for homogeneous scatter medium. The film was irradiated with 6 MV X-rays for 200 monitor units in Trilogy linear accelerator for 10 cm × 10 cm field size with source to axis distance of 100 cm at 5 cm. A single film was also irradiated without any bone and metal interface for reference data. The absolute dose and the vertical dose profile were measured from the film. There was 10% dose enhancement due to the backscatter radiation just adjacent to the metal-bone interface for all the materials. The extent of the backscatter effect was up to 4 mm. There is significant higher dose enhancement in the soft tissue/skin due to the backscatter radiation from the metallic components in the treatment region.

Low-dose effects of hormones and endocrine disruptors.

Science.gov (United States)

Vandenberg, Laura N

2014-01-01

Endogenous hormones have effects on tissue morphology, cell physiology, and behaviors at low doses. In fact, hormones are known to circulate in the part-per-trillion and part-per-billion concentrations, making them highly effective and potent signaling molecules. Many endocrine-disrupting chemicals (EDCs) mimic hormones, yet there is strong debate over whether these chemicals can also have effects at low doses. In the 1990s, scientists proposed the "low-dose hypothesis," which postulated that EDCs affect humans and animals at environmentally relevant doses. This chapter focuses on data that support and refute the low-dose hypothesis. A case study examining the highly controversial example of bisphenol A and its low-dose effects on the prostate is examined through the lens of endocrinology. Finally, the chapter concludes with a discussion of factors that can influence the ability of a study to detect and interpret low-dose effects appropriately. © 2014 Elsevier Inc. All rights reserved.

UV-radiation and skin cancer dose effect curves

International Nuclear Information System (INIS)

Henriksen, T.; Dahlback, A.; Larsen, S.H.

1988-08-01

Norwegian skin cancer data were used in an attempt to arrive at the dose effect relationship for UV-carcinogenesis. The Norwegian population is relatively homogenous with regard to skin type and live in a country where the annual effective UV-dose varies by approximately 40 percent. Four different regions of the country, each with a broadness of 1 o in latitude (approximately 111 km), were selected . The annual effective UV-doses for these regions were calculated assuming normal ozone conditions throughout the year. The incidence of malignant melanoma and non-melanoma skin cancer (mainly basal cell carcinoma) in these regions were considered and compared to the annual UV-doses. For both these types of cancer a quadratic dose effect curve seems to be valid. Depletions of the ozone layer results in larger UV-doses which in turn may yield more skin cancer. The dose effect curves suggest that the incidence rate will increase by an ''amplification factor'' of approximately 2

Investigation of absorbed radiation dose in refraction-enhanced breast tomosynthesis by a Laue case analyser

International Nuclear Information System (INIS)

Sato, H.; Ando, M.; Shimao, D.

2011-01-01

An early diagnosis system for breast cancer using refraction-enhanced breast tomosynthesis is under development. Tomograms of breast specimens based on refraction-contrast were demonstrated using the simplest shift-and-add tomosynthesis algorithm. Raw projection image data of breast specimens for tomosynthesis were acquired for a total of 51 views over an angle of 50 deg., in increments of 1 deg., by rotating the object. The incident X ray was monochromatic synchrotron radiation with 20 keV. The purpose of this study was to estimate the absorbed dose of a new X-ray imaging method. As breast cancer almost always arises in glandular breast tissue, the average absorbed dose in such glandular tissue should be measured to estimate the radiation risk associated with mammography. The absorbed dose of the mammary gland due to monochromatic X rays was calculated by the Monte Carlo method, and the optimal X ray energy range for refraction-enhanced breast tomosynthesis was investigated through actual measurements. Compared with the conventional method, it was found to be below one-sixth per inspection. (authors)

Health Effects of Exposure to Low Dose of Radiation

International Nuclear Information System (INIS)

Alatas, Zubaidah

2003-01-01

Human beings are exposed to natural radiation from external sources include radionuclides in the earth and cosmic radiation, and by internal radiation from radionuclides, mainly uranium and thorium series, incorporated into the body. Living systems have adapted to the natural levels of radiation and radioactivity. But some industrial practices involving natural resources enhance these radionuclides to a degree that they may pose risk to humans and the environment if they are not controlled. Biological effects of ionizing radiation are the outcomes of physical and chemical processes that occur immediately after the exposure, then followed by biological process in the body. These processes will involve successive changes in the molecular, cellular, tissue and whole organism levels. Any dose of radiation, no matter how small, may produce health effects since even a single ionizing event can result in DNA damage. The damage to DNA in the nucleus is considered to be the main initiating event by which radiation causes damage to cells that results in the development of cancer and hereditary disease. It has also been indicated that cytogenetic damage can occur in cells that receive no direct radiation exposure, known as bystander effects. This paper reviews health risks of low dose radiation exposure to human body causing stochastic effects, i.e. cancer induction in somatic cells and hereditary disease in genetic cells. (author)

Effects of low doses

International Nuclear Information System (INIS)

Le Guen, B.

2001-01-01

Actually, even though it is comfortable for the risk management, the hypothesis of the dose-effect relationship linearity is not confirmed for any model. In particular, in the area of low dose rate delivered by low let emitters. this hypothesis is debated at the light of recent observations, notably these ones relative to the mechanisms leading to genetic instability and induction eventuality of DNA repair. The problem of strong let emitters is still to solve. (N.C.)

Dose and dose-rate effects of ionizing radiation: a discussion in the light of radiological protection

Energy Technology Data Exchange (ETDEWEB)

Ruehm, Werner [Helmholtz Zentrum Muenchen, German Research Center for Environmental Health, Institute of Radiation Protection, Neuherberg (Germany); Woloschak, Gayle E. [Northwestern University, Department of Radiation Oncology, Feinberg School of Medicine, Chicago, IL (United States); Shore, Roy E. [Radiation Effects Research Foundation (RERF), Hiroshima City (Japan); Azizova, Tamara V. [Southern Urals Biophysics Institute (SUBI), Ozyorsk, Chelyabinsk Region (Russian Federation); Grosche, Bernd [Federal Office for Radiation Protection, Oberschleissheim (Germany); Niwa, Ohtsura [Fukushima Medical University, Fukushima (Japan); Akiba, Suminori [Kagoshima University Graduate School of Medical and Dental Sciences, Department of Epidemiology and Preventive Medicine, Kagoshima City (Japan); Ono, Tetsuya [Institute for Environmental Sciences, Rokkasho, Aomori-ken (Japan); Suzuki, Keiji [Nagasaki University, Department of Radiation Medical Sciences, Atomic Bomb Disease Institute, Nagasaki (Japan); Iwasaki, Toshiyasu [Central Research Institute of Electric Power Industry (CRIEPI), Radiation Safety Research Center, Nuclear Technology Research Laboratory, Tokyo (Japan); Ban, Nobuhiko [Tokyo Healthcare University, Faculty of Nursing, Tokyo (Japan); Kai, Michiaki [Oita University of Nursing and Health Sciences, Department of Environmental Health Science, Oita (Japan); Clement, Christopher H.; Hamada, Nobuyuki [International Commission on Radiological Protection (ICRP), PO Box 1046, Ottawa, ON (Canada); Bouffler, Simon [Public Health England (PHE), Centre for Radiation, Chemical and Environmental Hazards, Chilton, Didcot (United Kingdom); Toma, Hideki [JAPAN NUS Co., Ltd. (JANUS), Tokyo (Japan)

2015-11-15

The biological effects on humans of low-dose and low-dose-rate exposures to ionizing radiation have always been of major interest. The most recent concept as suggested by the International Commission on Radiological Protection (ICRP) is to extrapolate existing epidemiological data at high doses and dose rates down to low doses and low dose rates relevant to radiological protection, using the so-called dose and dose-rate effectiveness factor (DDREF). The present paper summarizes what was presented and discussed by experts from ICRP and Japan at a dedicated workshop on this topic held in May 2015 in Kyoto, Japan. This paper describes the historical development of the DDREF concept in light of emerging scientific evidence on dose and dose-rate effects, summarizes the conclusions recently drawn by a number of international organizations (e.g., BEIR VII, ICRP, SSK, UNSCEAR, and WHO), mentions current scientific efforts to obtain more data on low-dose and low-dose-rate effects at molecular, cellular, animal and human levels, and discusses future options that could be useful to improve and optimize the DDREF concept for the purpose of radiological protection. (orig.)

A sub-threshold dose of pilocarpine increases glutamine synthetase in reactive astrocytes and enhances the progression of amygdaloid-kindling epilepsy in rats.

Science.gov (United States)

Sun, Hong-Liu; Deng, Da-Ping; Pan, Xiao-Hong; Wang, Chao-Yun; Zhang, Xiu-Li; Chen, Xiang-Ming; Wang, Chun-Hua; Liu, Yu-Xia; Li, Shu-Cui; Bai, Xian-Yong; Zhu, Wei

2016-03-02

The prognosis of patients exposed to a sub-threshold dose of a proconvulsant is difficult to establish. In this study, we investigated the effect of a single sub-threshold dose of the proconvulsant pilocarpine (PILO) on the progression of seizures that were subsequently induced by daily electrical stimulation (kindling) of the amygdaloid formation. Male Sprague–Dawley rats were each implanted with an electrode in the right basolateral amygdala and an indwelling cannula in the right ventricle. The animals were randomized into groups and were administered one of the following treatments: saline, PILO, saline+L-α-aminoadipic acid (L-AAA; one dosage tested), PILO+L-AAA, or PILO+L-methionine sulfoximine (three dosages tested). Amygdaloid stimulation and electroencephalography were performed once daily. We performed immunohistochemistry and western blot for glial fibrillary acidic protein and glutamine synthetase (GS). We also assayed the enzymic activity of GS in discrete brain regions. An intraperitoneal injection of a sub-threshold PILO dose enhanced the progression of amygdaloid-kindling seizures and was accompanied by an increase in reactive-astrocyte and GS (content and activity) in the hippocampus and piriform cortex. L-AAA and L-methionine sulfoximine, inhibitors of astrocytic and GS function, respectively, abolished the effect of PILO on amygdaloid-kindling seizures. We conclude that one sub-threshold dose of a proconvulsant may enhance the progression of subsequent epilepsy and astrocytic GS may play a role in this phenomenon. Thus, a future therapy for epilepsy could be inhibition of astrocytes and/or GS.

Lateral topography for reducing effective dose in low-dose chest CT.

Science.gov (United States)

Bang, Dong-Ho; Lim, Daekeon; Hwang, Wi-Sub; Park, Seong-Hoon; Jeong, Ok-man; Kang, Kyung Wook; Kang, Hohyung

2013-06-01

The purposes of this study were to assess radiation exposure during low-dose chest CT by using lateral topography and to compare the lateral topographic findings with findings obtained with anteroposterior topography alone and anteroposterior and lateral topography combined. From November 2011 to February 2012, 210 male subjects were enrolled in the study. Age, weight, and height of the men were recorded. All subjects were placed into one of three subgroups based on the type of topographic image obtained: anteroposterior topography, lateral topography, and both anteroposterior and lateral topography. Imaging was performed with a 128-MDCT scanner. CT, except for topography, was the same for all subjects. A radiologist analyzed each image, recorded scan length, checked for any insufficiencies in the FOV, and calculated the effective radiation dose. One-way analysis of variance and multiple comparisons were used to compare the effective radiation exposure and scan length between groups. The mean scan length in the anteroposterior topography group was significantly greater than that of the lateral topography group and the combined anteroposterior and lateral topography group (p topography group (0.735 ± 0.033 mSv) was significantly lower than that for the anteroposterior topography group (0.763 ± 0.038 mSv) and the combined anteroposterior and lateral topography group (0.773 ± 0.038) (p < 0.001). Lateral topographic low-dose CT was associated with a lower effective radiation dose and scan length than either anteroposterior topographic low-dose chest CT or low-dose chest CT with both anteroposterior and lateral topograms.

Low-Dose Dextromethorphan, a NADPH Oxidase Inhibitor, Reduces Blood Pressure and Enhances Vascular Protection in Experimental Hypertension

Science.gov (United States)

Wu, Tao-Cheng; Chao, Chih-Yu; Lin, Shing-Jong; Chen, Jaw-Wen

2012-01-01

Background Vascular oxidative stress may be increased with age and aggravate endothelial dysfunction and vascular injury in hypertension. This study aimed to investigate the effects of dextromethorphan (DM), a NADPH oxidase inhibitor, either alone or in combination treatment, on blood pressure (BP) and vascular protection in aged spontaneous hypertensive rats (SHRs). Methodology/Principal Findings Eighteen-week-old WKY rats and SHRs were housed for 2 weeks. SHRs were randomly assigned to one of the 12 groups: untreated; DM monotherapy with 1, 5 or 25 mg/kg/day; amlodipine (AM, a calcium channel blocker) monotherapy with 1 or 5 mg/kg/day; and combination therapy of DM 1, 5 or 25 mg/kg/day with AM 1 or 5 mg/kg/day individually for 4 weeks. The in vitro effects of DM were also examined. In SHRs, AM monotherapy dose-dependently reduced arterial systolic BP. DM in various doses significantly and similarly reduced arterial systolic BP. Combination of DM with AM gave additive effects on BP reduction. DM, either alone or in combination with AM, improved aortic endothelial function indicated by ex vivo acetylcholine-induced relaxation. The combination of low-dose DM with AM gave most significant inhibition on aortic wall thickness in SHRs. Plasma total antioxidant status was significantly increased by all the therapies except for the combination of high-dose DM with high-dose AM. Serum nitrite and nitrate level was significantly reduced by AM but not by DM or the combination of DM with AM. Furthermore, in vitro treatment with DM reduced angiotensin II-induced reactive oxygen species and NADPH oxidase activation in human aortic endothelial cells. Conclusions/Significance Treatment of DM reduced BP and enhanced vascular protection probably by inhibiting vascular NADPH oxidase in aged hypertensive animals with or without AM treatment. It provides the potential rationale to a novel combination treatment with low-dose DM and AM in clinical hypertension. PMID:23049937

Low-dose dextromethorphan, a NADPH oxidase inhibitor, reduces blood pressure and enhances vascular protection in experimental hypertension.

Directory of Open Access Journals (Sweden)

Tao-Cheng Wu

Full Text Available BACKGROUND: Vascular oxidative stress may be increased with age and aggravate endothelial dysfunction and vascular injury in hypertension. This study aimed to investigate the effects of dextromethorphan (DM, a NADPH oxidase inhibitor, either alone or in combination treatment, on blood pressure (BP and vascular protection in aged spontaneous hypertensive rats (SHRs. METHODOLOGY/PRINCIPAL FINDINGS: Eighteen-week-old WKY rats and SHRs were housed for 2 weeks. SHRs were randomly assigned to one of the 12 groups: untreated; DM monotherapy with 1, 5 or 25 mg/kg/day; amlodipine (AM, a calcium channel blocker monotherapy with 1 or 5 mg/kg/day; and combination therapy of DM 1, 5 or 25 mg/kg/day with AM 1 or 5 mg/kg/day individually for 4 weeks. The in vitro effects of DM were also examined. In SHRs, AM monotherapy dose-dependently reduced arterial systolic BP. DM in various doses significantly and similarly reduced arterial systolic BP. Combination of DM with AM gave additive effects on BP reduction. DM, either alone or in combination with AM, improved aortic endothelial function indicated by ex vivo acetylcholine-induced relaxation. The combination of low-dose DM with AM gave most significant inhibition on aortic wall thickness in SHRs. Plasma total antioxidant status was significantly increased by all the therapies except for the combination of high-dose DM with high-dose AM. Serum nitrite and nitrate level was significantly reduced by AM but not by DM or the combination of DM with AM. Furthermore, in vitro treatment with DM reduced angiotensin II-induced reactive oxygen species and NADPH oxidase activation in human aortic endothelial cells. CONCLUSIONS/SIGNIFICANCE: Treatment of DM reduced BP and enhanced vascular protection probably by inhibiting vascular NADPH oxidase in aged hypertensive animals with or without AM treatment. It provides the potential rationale to a novel combination treatment with low-dose DM and AM in clinical hypertension.

Biological effects of low doses of radiation at low dose rate

International Nuclear Information System (INIS)

1996-05-01

The purpose of this report was to examine available scientific data and models relevant to the hypothesis that induction of genetic changes and cancers by low doses of ionizing radiation at low dose rate is a stochastic process with no threshold or apparent threshold. Assessment of the effects of higher doses of radiation is based on a wealth of data from both humans and other organisms. 234 refs., 26 figs., 14 tabs

Low doses effects and gamma radiations low dose rates; Les effets des faibles doses et des faibles debits de doses de rayons gamma

Energy Technology Data Exchange (ETDEWEB)

Averbeck, D [Institut Curie, CNRS UMR 2027, 75 - Paris (France)

1999-07-01

This expose wishes for bringing some definitions and base facts relative to the problematics of low doses effects and low dose rates effects. It shows some already used methods and some actual experimental approaches by focusing on the effects of ionizing radiations with a low linear energy transfer. (N.C.)

Effects of different doses of glucose and insulin on morphine state-dependent memory of passive avoidance in mice.

Science.gov (United States)

Jafari, M R; Zarrindast, M R; Djahanguiri, B

2004-10-01

Behavioral effects of morphine, including its effect on memory, have been demonstrated to be influenced by glucose pretreatment. The measurement of step-down latency in passive avoidance has been used to study memory in laboratory animals. The pre-training injection of 5 mg/kg morphine impaired memory, which was restored when 24 h later the same dose of the drug was administered. To investigate the effects of glucose and insulin alone or in combination with morphine, on pre-test day, on memory recall in mice. The effects of different doses of glucose (50, 100, and 200 mg/kg, IP) and insulin (5, 10, and 20 IU/kg, IP) alone or in combination with morphine, have been studied in mice. The blood glucose level and locomotor activity of the animals were also measured. Although the administration of glucose alone showed no effect on morphine-induced memory impairment, its co-administration with morphine resulted in a significant and dose-dependent memory enhancement compared with the effects of morphine administration alone. Like glucose, the administration of different doses of insulin alone produced no change in the memory, but when the drug was co-administered with morphine, it significantly reduced morphine-induced memory retrieval. The effect of insulin was the opposite of glucose. None of the animals subjected to insulin treatment showed convulsions. Glucose is suggested to increase, on the test day, the morphine-induced memory enhancement by three different mechanisms: cholinergic or opioidergic modulations, or regulation of the ATP-dependent potassium channels.

SU-C-BRC-05: Monte Carlo Calculations to Establish a Simple Relation of Backscatter Dose Enhancement Around High-Z Dental Alloy to Its Atomic Number

Energy Technology Data Exchange (ETDEWEB)

Utsunomiya, S; Kushima, N; Katsura, K; Tanabe, S; Hayakawa, T; Sakai, H; Yamada, T; Takahashi, H; Abe, E; Wada, S; Aoyama, H [Niigata University, Niigata (Japan)

2016-06-15

Purpose: To establish a simple relation of backscatter dose enhancement around a high-Z dental alloy in head and neck radiation therapy to its average atomic number based on Monte Carlo calculations. Methods: The PHITS Monte Carlo code was used to calculate dose enhancement, which is quantified by the backscatter dose factor (BSDF). The accuracy of the beam modeling with PHITS was verified by comparing with basic measured data namely PDDs and dose profiles. In the simulation, a high-Z alloy of 1 cm cube was embedded into a tough water phantom irradiated by a 6-MV (nominal) X-ray beam of 10 cm × 10 cm field size of Novalis TX (Brainlab). The ten different materials of high-Z alloys (Al, Ti, Cu, Ag, Au-Pd-Ag, I, Ba, W, Au, Pb) were considered. The accuracy of calculated BSDF was verified by comparing with measured data by Gafchromic EBT3 films placed at from 0 to 10 mm away from a high-Z alloy (Au-Pd-Ag). We derived an approximate equation to determine the relation of BSDF and range of backscatter to average atomic number of high-Z alloy. Results: The calculated BSDF showed excellent agreement with measured one by Gafchromic EBT3 films at from 0 to 10 mm away from the high-Z alloy. We found the simple linear relation of BSDF and range of backscatter to average atomic number of dental alloys. The latter relation was proven by the fact that energy spectrum of backscatter electrons strongly depend on average atomic number. Conclusion: We found a simple relation of backscatter dose enhancement around high-Z alloys to its average atomic number based on Monte Carlo calculations. This work provides a simple and useful method to estimate backscatter dose enhancement from dental alloys and corresponding optimal thickness of dental spacer to prevent mucositis effectively.

Notes on the effect of dose uncertainty

International Nuclear Information System (INIS)

Morris, M.D.

1987-01-01

The apparent dose-response relationship between amount of exposure to acute radiation and level of mortality in humans is affected by uncertainties in the dose values. It is apparent that one of the greatest concerns regarding the human data from Hiroshima and Nagasaki is the unexpectedly shallow slope of the dose response curve. This may be partially explained by uncertainty in the dose estimates. Some potential effects of dose uncertainty on the apparent dose-response relationship are demonstrated

Low-dose non-enhanced CT versus full-dose contrast-enhanced CT in integrated PET/CT studies for the diagnosis of uterine cancer recurrence

Energy Technology Data Exchange (ETDEWEB)

Kitajima, Kazuhiro [Institute of Biomedical Research and Innovation, Department of PET Diagnosis, Kobe (Japan); Kobe University Graduate School of Medicine, Department of Radiology, Kobe (Japan); Suzuki, Kayo [Institute of Biomedical Research and Innovation, Department of PET Diagnosis, Kobe (Japan); Nakamoto, Yuji [Kyoto University Hospital, Department of Diagnostic Radiology, Kyoto (Japan); Onishi, Yumiko; Sakamoto, Setsu; Sugimura, Kazuro [Kobe University Graduate School of Medicine, Department of Radiology, Kobe (Japan); Senda, Michio [Institute of Biomedical Research and Innovation, Department of Molecular Imaging, Kobe (Japan); Kita, Masato [Kobe City Medical Center General Hospital, Department of Obstetrics and Gynecology, Kobe (Japan)

2010-08-15

To evaluate low-dose non-enhanced CT (ldCT) and full-dose contrast-enhanced CT (ceCT) in integrated {sup 18}F-fluorodeoxyglucose (FDG) PET/CT studies for restaging of uterine cancer. A group of 100 women who had undergone treatment for uterine cervical (n=55) or endometrial cancer (n=45) underwent a conventional PET/CT scans with ldCT, and then a ceCT scan. Two observers retrospectively reviewed and interpreted the PET/ldCT and PET/ceCT images in consensus using a three-point grading scale (negative, equivocal, or positive) per patient and per lesion. Final diagnoses were obtained by histopathological examination, or clinical follow-up for at least 6 months. Patient-based analysis showed that the sensitivity, specificity and accuracy of PET/ceCT were 90% (27/30), 97% (68/70) and 95% (95/100), respectively, whereas those of PET/ldCT were 83% (25/30), 94% (66/70) and 91% (91/100), respectively. Sensitivity, specificity and accuracy did not significantly differ between two methods (McNemar test, p=0.48, p=0.48, and p=0.13, respectively). There were 52 sites of lesion recurrence: 12 pelvic lymph node (LN), 11 local recurrence, 8 peritoneum, 7 abdominal LN, 5 lung, 3 supraclavicular LN, 3 liver, 2 mediastinal LN, and 1 muscle and bone. The grading results for the 52 sites of recurrence were: negative 5, equivocal 0 and positive 47 for PET/ceCT, and negative 5, equivocal 4 and positive 43 for PET/ldCT, respectively. Four equivocal regions by PET/ldCT (local recurrence, pelvic LN metastasis, liver metastasis and muscle metastasis) were correctly interpreted as positive by PET/ceCT. PET/ceCT is an accurate imaging modality for the assessment of uterine cancer recurrence. Its use reduces the frequency of equivocal interpretations. (orig.)

Topics on study of low dose-effect relationship

Energy Technology Data Exchange (ETDEWEB)

Yamada, Takeshi [Toho Univ., School of Medicine, Tokyo (Japan); Ohyama, Harumi

1999-09-01

It is not exceptional but usually observed that a dose-effect relationship in biosystem is not linear. Sometimes, the low dose-effect relationship appears entirely contrary to the expectation from high dose-effect. This is called a 'hormesis' phenomena. A high dose irradiation inflicts certainly an injury on biosystem. No matter how low the dose may be, an irradiation might inflict some injury on biosystem according to Linear Non-Threshold hypothesis(LNT). On the contrary to the expectation, a low dose irradiation stimulates immune system, and promotes cell proliferation. This is called 'radiation hormesis'. The studies of the radiation hormesis are made on from four points of view as follows: (1) radiation adaptive response, (2) revitalization caused by a low dose stimulation, (3) a low dose response unexpected from the LNT hypothesis, (4) negation of the LNT hypothesis. The various empirical proofs of radiation hormesis are introduced in the report. (M . Suetake)

Topics on study of low dose-effect relationship

International Nuclear Information System (INIS)

Yamada, Takeshi; Ohyama, Harumi

1999-01-01

It is not exceptional but usually observed that a dose-effect relationship in biosystem is not linear. Sometimes, the low dose-effect relationship appears entirely contrary to the expectation from high dose-effect. This is called a 'hormesis' phenomena. A high dose irradiation inflicts certainly an injury on biosystem. No matter how low the dose may be, an irradiation might inflict some injury on biosystem according to Linear Non-Threshold hypothesis(LNT). On the contrary to the expectation, a low dose irradiation stimulates immune system, and promotes cell proliferation. This is called 'radiation hormesis'. The studies of the radiation hormesis are made on from four points of view as follows: (1) radiation adaptive response, (2) revitalization caused by a low dose stimulation, (3) a low dose response unexpected from the LNT hypothesis, (4) negation of the LNT hypothesis. The various empirical proofs of radiation hormesis are introduced in the report. (M . Suetake)

Determination of dose enhancement caused by gold-nanoparticles irradiated with proton, X-rays (kV and MV) and electron beams, using alanine/EPR dosimeters

International Nuclear Information System (INIS)

Smith, Clare L.; Ackerly, Trevor; Best, Stephen P.; Gagliardi, Frank; Kie, Katahira; Little, Peter J.; McCorkell, Giulia; Sale, Charlotte A.; Tsunei, Yusuke; Tominaga, Takahiro; Volaric, Sioe See; Geso, Moshi

2015-01-01

The main aims of this research was to employ alanine doped with gold-nanoparticles “AuNPs” to determine the levels of dose enhancement caused by these particles when irradiated with proton beams, low and high energy X-rays and electrons. DL-alanine was impregnated with 5 nm gold-nanoparticles (3% by weight) and added as a uniform layer within a wax pellet of dimensions 10 × 5 × 5 mm. Control pellets, containing DL-Alanine were also produced, and placed within a phantom, and exposed to various types of radiations: low energy (kV ranges) X-rays were obtained from a superficial machine, high energy (MV) X-rays and electrons derived from a linear accelerator, and protons were produced by the Hyogo Ion Beam Centre in Japan. Nominal doses received ranged from 2 to 20 Gy (within clinical range). The Electron Paramagnetic Resonance (EPR) spectra of the irradiated samples were recorded on a BRUKER Elexsys 9.5 MHz. The dose enhancement caused by gold nanoparticles for 80 kV x-rays was found to be more than 60% at about 5 Gy. Smaller dose enhancements (under the same measurement conditions) were observed for megavoltage x-ray beams (up to 10%). Dose enhancement caused by charged particles indicated minimal values for 6 MeV electrons (approximately 5%) whilst less than that is obtained with protons of 150 MeV. The proton results validate the latest simulation results based on Monte Carlo calculations but the dose enhancement is significantly less than that reported in cell and animal model systems, (about 20%). We attribute this difference to the fact that alanine only measures the levels of free radicals generated by the inclusion of nanoparticles and not the redox type radicals (such as reactive oxygen species) generated from aqueous media in cells. Dose enhancement caused by 5 nm gold-nanoparticles with radiotherapy type proton beams has been found to be less than 5% as determined when using alanine/wax as both a phantom and dosimeter. This agrees well

A graphical review of radiogenic animal cancer data using the 'dose and dose-rate map'

International Nuclear Information System (INIS)

Yoshida, Kazuo; Hoshi, Yuko; Sakai, Kazuo

2008-01-01

We have been investigating the effects of low dose or low dose rate irradiation on mice, using our low dose-rate irradiation facilities. In these studies, we found that the effects were highly dependent on both total dose and dose rate. To show this visually, we proposed the 'dose/dose rate map', and plotted the results of our laboratory and our co-workers. The map demonstrated that dose/dose rate plane could be divided into three areas; 1) An area where harmful effects are observed, 2) An area where no harmful effects are observed, and 3) Another area, between previous two areas, where certain protective functions are enhanced. As this map would be a powerful tool to find some trend among the vast numbers of data relating the biological effects of ionizing radiation, we have developed a computer program which plots the collected data on the dose/dose rate map sorting by experimental conditions. In this study, we graphically reviewed and analyzed the data relating to the lifespan studies of animals with a view to determining the relationships between doses and dose rates of ionizing radiation and cancer incidence. The data contains about 800 sets of experiments, which concerns 187,000 animals exposed to gamma ray or X-ray and their 112,000 controls, and total of about 30,000 cancers in exposed animals and 14,000 cancers in controls. About 800 points of data were plotted on the dose/dose rate map. The plot showed that 1) The divided three areas in the dose/dose rate map were generally confirmed by these 800 points of data, and 2) In some particular conditions, e.g. sarcoma by X-rays, the biologically effective area is extended to relatively high dose/dose rate area. (author)

Low-dose radiation enhances therapeutic HPV DNA vaccination in tumor-bearing hosts.

Science.gov (United States)

Tseng, Chih-Wen; Trimble, Cornelia; Zeng, Qi; Monie, Archana; Alvarez, Ronald D; Huh, Warner K; Hoory, Talia; Wang, Mei-Cheng; Hung, Chien-Fu; Wu, T-C

2009-05-01

Current therapeutic approaches to treatment of patients with bulky cervical cancer are based on conventional in situ ablative modalities including cisplatin-based chemotherapy and radiation therapy. The 5-year survival of patients with nonresectable disease is dismal. Because over 99% of squamous cervical cancer is caused by persistent infection with an oncogenic strain of human papillomavirus (HPV), particularly type 16 and viral oncoproteins E6 and E7 are functionally required for disease initiation and persistence, HPV-targeted immune strategies present a compelling opportunity in which to demonstrate proof of principle. Sublethal doses of radiation and chemotherapeutic agents have been shown to have synergistic effect in combination with either vaccination against cancer-specific antigens, or with passive transfer of tumor-specific cytotoxic T lymphocytes (CTLs). Here, we explored the combination of low-dose radiation therapy with DNA vaccination with calreticulin (CRT) linked to the mutated form of HPV-16 E7 antigen (E7(detox)), CRT/E7(detox) in the treatment of E7-expressing TC-1 tumors. We observed that TC-1 tumor-bearing mice treated with radiotherapy combined with CRT/E7(detox) DNA vaccination generated significant therapeutic antitumor effects and the highest frequency of E7-specific CD8(+) T cells in the tumors and spleens of treated mice. Furthermore, treatment with radiotherapy was shown to render the TC-1 tumor cells more susceptible to lysis by E7-specific CTLs. In addition, we observed that treatment with radiotherapy during the second DNA vaccination generated the highest frequency of E7-specific CD8(+) T cells in the tumors and spleens of TC-1 tumor-bearing mice. Finally, TC-1 tumor-bearing mice treated with the chemotherapy in combination with radiation and CRT/E7(detox) DNA vaccination generate significantly enhanced therapeutic antitumor effects. The clinical implications of the study are discussed.

Total dose and dose-rate effects on start-up current in anti-fuse FPGA

International Nuclear Information System (INIS)

Wang, J.; Wong, W.; McCollum, J.; Cronquist, B.; Katz, R.; Kleyner, I.; Kleyner, F.

1999-01-01

Radiation enhanced start-up current (RESC) in an anti-fuse FPGA, A1280A, is thoroughly investigated and a comprehensive transistor-level mechanism is proposed. Low dose-rate testing, appropriate for civilian space applications, and annealing at room temperature shows RESC to be negligible for the lot of parts tested with a fixed power supply slew rate. (authors)

Radiobiological modelling of dose-gradient effects in low dose rate, high dose rate and pulsed brachytherapy

International Nuclear Information System (INIS)

Armpilia, C; Dale, R G; Sandilos, P; Vlachos, L

2006-01-01

This paper presents a generalization of a previously published methodology which quantified the radiobiological consequences of dose-gradient effects in brachytherapy applications. The methodology uses the linear-quadratic (LQ) formulation to identify an equivalent biologically effective dose (BED eq ) which, if applied uniformly to a specified tissue volume, would produce the same net cell survival as that achieved by a given non-uniform brachytherapy application. Multiplying factors (MFs), which enable the equivalent BED for an enclosed volume to be estimated from the BED calculated at the dose reference surface, have been calculated and tabulated for both spherical and cylindrical geometries. The main types of brachytherapy (high dose rate (HDR), low dose rate (LDR) and pulsed (PB)) have been examined for a range of radiobiological parameters/dimensions. Equivalent BEDs are consistently higher than the BEDs calculated at the reference surface by an amount which depends on the treatment prescription (magnitude of the prescribed dose) at the reference point. MFs are closely related to the numerical BED values, irrespective of how the original BED was attained (e.g., via HDR, LDR or PB). Thus, an average MF can be used for a given prescribed BED as it will be largely independent of the assumed radiobiological parameters (radiosensitivity and α/β) and standardized look-up tables may be applicable to all types of brachytherapy treatment. This analysis opens the way to more systematic approaches for correlating physical and biological effects in several types of brachytherapy and for the improved quantitative assessment and ranking of clinical treatments which involve a brachytherapy component

Theoretical analysis of the dose dependence of the oxygen enhancement ratio and its relevance for clinical applications

International Nuclear Information System (INIS)

Wenzl, Tatiana; Wilkens, Jan J

2011-01-01

The increased resistance of hypoxic cells to ionizing radiation is usually believed to be the primary reason for treatment failure in tumors with oxygen-deficient areas. This oxygen effect can be expressed quantitatively by the oxygen enhancement ratio (OER). Here we investigate theoretically the dependence of the OER on the applied local dose for different types of ionizing irradiation and discuss its importance for clinical applications in radiotherapy for two scenarios: small dose variations during hypoxia-based dose painting and larger dose changes introduced by altered fractionation schemes. Using the widespread Alper-Howard-Flanders and standard linear-quadratic (LQ) models, OER calculations are performed for T1 human kidney and V79 Chinese hamster cells for various dose levels and various hypoxic oxygen partial pressures (pO2) between 0.01 and 20 mmHg as present in clinical situations in vivo. Our work comprises the analysis for both low linear energy transfer (LET) treatment with photons or protons and high-LET treatment with heavy ions. A detailed analysis of experimental data from the literature with respect to the dose dependence of the oxygen effect is performed, revealing controversial opinions whether the OER increases, decreases or stays constant with dose. The behavior of the OER with dose per fraction depends primarily on the ratios of the LQ parameters alpha and beta under hypoxic and aerobic conditions, which themselves depend on LET, pO2 and the cell or tissue type. According to our calculations, the OER variations with dose in vivo for low-LET treatments are moderate, with changes in the OER up to 11% for dose painting (1 or 3 Gy per fraction compared to 2 Gy) and up to 22% in hyper-/hypofractionation (0.5 or 20 Gy per fraction compared to 2 Gy) for oxygen tensions between 0.2 and 20 mmHg typically measured clinically in hypoxic tumors. For extremely hypoxic cells (0.01 mmHg), the dose dependence of the OER becomes more pronounced (up to 36

Augmentation by escitalopram, but not citalopram or R-citalopram, of the effects of low-dose risperidone: behavioral, biochemical, and electrophysiological evidence.

Science.gov (United States)

Marcus, Monica M; Jardemark, Kent; Malmerfelt, Anna; Gertow, Jens; Konradsson-Geuken, Asa; Svensson, Torgny H

2012-04-01

Antidepressant drugs are frequently used to treat affective symptoms in schizophrenia. We have recently shown that escitalopram, but not citalopram or R-citalopram, increases firing rate and burst firing of midbrain dopamine neurons, potentiates cortical N-methyl-D-aspartate (NMDA) receptor-mediated transmission and enhances cognition, effects that might influence the outcome of concomitant antipsychotic medication. Here, we studied, in rats, the behavioral and neurobiological effects of adding escitalopram, citalopram, or R-citalopram to the second-generation antipsychotic drug risperidone. We examined antipsychotic efficacy using the conditioned avoidance response (CAR) test, extrapyramidal side effect (EPS) liability using a catalepsy test, dopamine outflow in the medial prefrontal cortex (mPFC) and nucleus accumbens using in vivo microdialysis in freely moving animals, and NMDA receptor-mediated transmission in the mPFC using intracellular electrophysiological recording in vitro. Only escitalopram (5 mg/kg), but not citalopram (10 mg/kg), or R-citalopram (10 mg/kg), dramatically enhanced the antipsychotic-like effect of a low dose of risperidone (0.25 mg/kg), without increasing catalepsy. Given alone, escitalopram, but not citalopram or R-citalopram, markedly enhanced both cortical dopamine output and NMDA receptor-mediated transmission. Addition of escitalopram and to some extent R-citalopram, but not citalopram, significantly enhanced both cortical dopamine output and cortical NMDA receptor-mediated transmission induced by a suboptimal dose/concentration of risperidone. These results suggest that adjunct treatment with escitalopram, but not citalopram, may enhance the effect of a subtherapeutic dose of risperidone on positive, negative, cognitive, and depressive symptoms in schizophrenia, yet without increased EPS liability. Copyright © 2011 Wiley Periodicals, Inc.

Photon activation therapy: a Monte Carlo study on dose enhancement by various sources and activation media

International Nuclear Information System (INIS)

Bakhshabadi, Mahdi; Ghorbani, Mahdi; Meigooni, Ali Soleimani

2013-01-01

In the present study, a number of brachytherapy sources and activation media were simulated using MCNPX code and the results were analyzed based on the dose enhancement factor values. Furthermore, two new brachytherapy sources ( 131 Cs and a hypothetical 170 Tm) were evaluated for their application in photon activation therapy (PAT). 125 I, 103 Pd, 131 Cs and hypothetical 170 Tm brachytherapy sources were simulated in water and their dose rate constant and the radial dose functions were compared with previously published data. The sources were then simulated in a soft tissue phantom which was composed of Ag, I, Pt or Au as activation media uniformly distributed in the tumour volume. These simulations were performed using the MCNPX code, and dose enhancement factor (DEF) was obtained for 7, 18 and 30 mg/ml concentrations of the activation media. Each source, activation medium and concentration was evaluated separately in a separate simulation. The calculated dose rate constant and radial dose functions were in agreement with the published data for the aforementioned sources. The maximum DEF was found to be 5.58 for a combination of the 170 Tm source with 30 mg/ml concentration of I. The DEFs for 131 Cs and 170 Tm sources for all the four activation media were higher than those for other sources and activation media. From this point of view, these two sources can be more useful in photon activation therapy with photon emitter sources. Furthermore, 131 Cs and 170 Tm brachytherapy sources can be proposed as new options for use in the field of PAT.

High-Dose Estradiol-Replacement Therapy Enhances the Renal Vascular Response to Angiotensin II via an AT2-Receptor Dependent Mechanism

Directory of Open Access Journals (Sweden)

Tahereh Safari

2015-01-01

Full Text Available Physiological levels of estrogen appear to enhance angiotensin type 2 receptor- (AT2R- mediated vasodilatation. However, the effects of supraphysiological levels of estrogen, analogous to those achieved with high-dose estrogen replacement therapy in postmenopausal women, remain unknown. Therefore, we pretreated ovariectomized rats with a relatively high dose of estrogen (0.5 mg/kg/week for two weeks. Subsequently, renal hemodynamic responses to intravenous angiotensin II (Ang II, 30–300 ng/kg/min were tested under anesthesia, while renal perfusion pressure was held constant. The role of AT2R was examined by pretreating groups of rats with PD123319 or its vehicle. Renal blood flow (RBF decreased in a dose-related manner in response to Ang II. Responses to Ang II were enhanced by pretreatment with estradiol. For example, at 300 ng kg−1 min−1, Ang II reduced RBF by 45.7±1.9% in estradiol-treated rats but only by 27.3±5.1% in vehicle-treated rats. Pretreatment with PD123319 blunted the response of RBF to Ang II in estradiol-treated rats, so that reductions in RBF were similar to those in rats not treated with estradiol. We conclude that supraphysiological levels of estrogen promote AT2R-mediated renal vasoconstriction. This mechanism could potentially contribute to the increased risk of cardiovascular disease associated with hormone replacement therapy using high-dose estrogen.

Development of low-dose photon-counting contrast-enhanced tomosynthesis with spectral imaging.

Science.gov (United States)

Schmitzberger, Florian F; Fallenberg, Eva Maria; Lawaczeck, Rüdiger; Hemmendorff, Magnus; Moa, Elin; Danielsson, Mats; Bick, Ulrich; Diekmann, Susanne; Pöllinger, Alexander; Engelken, Florian J; Diekmann, Felix

2011-05-01

To demonstrate the feasibility of low-dose photon-counting tomosynthesis in combination with a contrast agent (contrast material-enhanced tomographic mammography) for the differentiation of breast cancer. All studies were approved by the institutional review board, and all patients provided written informed consent. A phantom model with wells of iodinated contrast material (3 mg of iodine per milliliter) 1, 2, 5, 10, and 15 mm in diameter was assessed. Nine patients with malignant lesions and one with a high-risk lesion (atypical papilloma) were included (all women; mean age, 60.7 years). A multislit photon-counting tomosynthesis system was utilized (spectral imaging) to produce both low- and high-energy tomographic data (below and above the k edge of iodine, respectively) in a single scan, which allowed for dual-energy visualization of iodine. Images were obtained prior to contrast material administration and 120 and 480 seconds after contrast material administration. Four readers independently assessed the images along with conventional mammograms, ultrasonographic images, and magnetic resonance images. Glandular dose was estimated. Contrast agent was visible in the phantom model with simulated spherical tumor diameters as small as 5 mm. The average glandular dose was measured as 0.42 mGy per complete spectral imaging tomosynthesis scan of one breast. Because there were three time points (prior to contrast medium administration and 120 and 480 seconds after contrast medium administration), this resulted in a total dose of 1.26 mGy for the whole procedure in the breast with the abnormality. Seven of 10 cases were categorized as Breast Imaging Reporting and Data System score of 4 or higher by all four readers when reviewing spectral images in combination with mammograms. One lesion near the chest wall was not captured on the spectral image because of a positioning problem. The use of contrast-enhanced tomographic mammography has been demonstrated successfully in

Dose distribution close to metal implants in Gamma Knife Radiosurgery: A Monte Carlo study

International Nuclear Information System (INIS)

Cheung, Joel Y.C.; Yu, K.N.; Chan, Josie F.K.; Ho, Robert T.K.; Yu, C.P.

2003-01-01

Materials with high atomic numbers favor the occurrence of the photoelectric effect when they are irradiated with gamma rays. Therefore, the photoelectric effects of metal implants within the target regions in Gamma Knife Radiosurgery are worth studying. In the present work, Monte Carlo simulations using EGS4 were employed to investigate the resulting dose enhancements. A dose enhancement as high as 10% was observed close to a platinum implant along the x and y axes, while no significant dose enhancements were observed for silver, stainless steel 301, and titanium ones. A dose enhancement as high as 20% was observed close to the platinum implant along the z axis at the superior position of the metal-phantom interface and was 10% higher for other metal implants

Exercise and Sport Performance with Low Doses of Caffeine

OpenAIRE

Spriet, Lawrence L.

2014-01-01

Caffeine is a popular work-enhancing supplement that has been actively researched since the 1970s. The majority of research has examined the effects of moderate to high caffeine doses (5–13 mg/kg body mass) on exercise and sport. These caffeine doses have profound effects on the responses to exercise at the whole-body level and are associated with variable results and some undesirable side effects. Low doses of caffeine (

The effect of Low-dose Gamma Radiation on the Bio-chemical ...

African Journals Online (AJOL)

Low-dose gamma radiation has been applied to intravenous fluids to enhance the sterility assurance levels. This study was undertaken to determine the stability of gamma irradiated 2.5 % dextrose, 2.5 % dextrose in saline, Ringers lactate and Gastrointestinal replacement fluid at doses of 0, 2, 4, 6, 8, 10 and 20 kGy.

Assessment of organ equivalent doses and effective doses from diagnostic X-ray examinations

International Nuclear Information System (INIS)

Park, Sang Hyun

2003-02-01

The MIRD-type adult male, female and age 10 phantoms were constructed to evaluate organ equivalent dose and effective dose of patient due to typical diagnostic X-ray examination. These phantoms were constructed with external and internal dimensions of Korean. The X-ray energy spectra were generated with SPEC78. MCNP4B ,the general-purposed Monte Carlo code, was used. Information of chest PA , chest LAT, and abdomen AP diagnostic X-ray procedures was collected on the protocol of domestic hospitals. The results showed that patients pick up approximate 0.02 to 0.18 mSv of effective dose from a single chest PA examination, and 0.01 to 0.19 mSv from a chest LAT examination depending on the ages. From an abdomen AP examination, patients pick up 0.17 to 1.40 mSv of effective dose. Exposure time, organ depth from the entrance surface and X-ray beam field coverage considerably affect the resulting doses. Deviation among medical institutions is somewhat high, and this indicated that medical institutions should interchange their information and the need of education for medical staff. The methodology and the established system can be applied, with some expansion, to dose assessment for other medical procedures accompanying radiation exposure of patients like nuclear medicine or therapeutic radiology

Radioprotection by murine and human tumor-necrosis factor; Dose-dependent effects on hematopoiesis in the mouse

Energy Technology Data Exchange (ETDEWEB)

Sloerdal, L; Muench, M O; Warren, D J; Moore, M A.S. [James Ewing Laboratory of Developmental Hematopoiesis, Memorial Sloan-Kettering Cancer Center, New York (USA)

1989-01-01

Tumor-necrosis factor (TNF) has been shown to confer significant radioprotection in murine models. Herein, we demonstrate a dose-dependent enhancement of hematological recovery when single doses of either murine or human recombinant TNF are administered prior to irradiation. In addition to its action upon leukocytes and erythocytes, TNF also alleviates radiation-induced thrombocytopenia in the mouse. These effects on circulating blood constituents are further reflected in increased numbers of both primitive (CFU-S) and more differentiated (CFU-GM, CFU-Mega) hematopoietic progenitors in TNF-treated animals. This suggests that TNF exerts it radioprotective effects on a pool of primitive multi-potential hematopoietic cells. (author).

Anti-tumor effect of total body irradiation of low doses on WHT/Ht mice

International Nuclear Information System (INIS)

Miyamoto, Miyako; Sakamoto, Kiyohiko

1987-01-01

The effect of low dose (0.05 - 1.0 Gy) of total body irradiation (TBI) on non-tumor bearing and tumor bearing mice were investigated. Mice received TBI of 0.1 Gy during 6 - 12 hours before tumor cell inoculation demonstrated to need larger number of tumor cells (approximately 2.5 times) for 50 per cent tumor incidence, compared to recipient mice not to receive TBI. On the other hand, in tumor bearing mice given 0.1 Gy of TBI only tumor cell killing effect was not detected, however enhancement of tumor cell killing effect and prolonged growth delay were observed when tumor bearing mice were treated with 0.1 Gy of TBI in combined with local irradiation on tumors, especially cell killing effect was remarkable in dose range over 6 Gy of local exposure. The mechanism of the effect of 0.1 Gy TBI is considered to be host mediated reactions from the other our experimental results. (author)

Consumption of high-dose vitamin C (1250 mg per day) enhances functional and structural properties of serum lipoprotein to improve anti-oxidant, anti-atherosclerotic, and anti-aging effects via regulation of anti-inflammatory microRNA.

Science.gov (United States)

Kim, Seong-Min; Lim, So-Mang; Yoo, Jeong-Ah; Woo, Moon-Jea; Cho, Kyung-Hyun

2015-11-01

Background Although the health effects of vitamin C are well known, its physiological effect on serum lipoproteins and microRNA still remain to be investigated, especially daily consumption of a high dosage. Objectives To investigate the physiological effect of vitamin C on serum lipoprotein metabolism in terms of its anti-oxidant and anti-glycation activities, and gene expression via microRNA regulation. Methods We analyzed blood parameters and lipoprotein parameters in young subjects (n = 46, 22 ± 2 years old) including smokers who consumed a high dose of vitamin C (1250 mg) daily for 8 weeks. Results Antioxidant activity of serum was enhanced with the elevation of Vit C content in plasma during 8 weeks consumption. In the LDL fraction, the apo-B48 band disappeared at 8 weeks post-consumption in all subjects. In the HDL fraction, apoA-I expression was enhanced by 20% at 8 weeks, especially in male smokers. In the lipoprotein fraction, all subjects showed significantly reduced contents of advanced glycated end products and reactive oxygen species (ROS). Triglyceride (TG) contents in each LDL and HDL fraction were significantly reduced in all groups following the Vit C consumption, suggesting that the lipoprotein was changed to be more anti-inflammatory and atherogenic properties. Phagocytosis of LDL, which was purified from each individual, into macrophages was significantly reduced at 8-weeks post-consumption of vitamin C. Anti-inflammatory and anti-senescence effects of HDL from all subjects were enhanced after the 8-weeks consumption. The expression level of microRNA 155 in HDL3 was reduced by 49% and 75% in non-smokers and smokers, respectively. Conclusion The daily consumption of a high dose of vitamin C for 8 weeks resulted in enhanced anti-senescence and anti-atherosclerotic effects via an improvement of lipoprotein parameters and microRNA expression through anti-oxidation and anti-glycation, especially in smokers.

MO-F-CAMPUS-J-01: Effect of Iodine Contrast Agent Concentration On Cerebrovascular Dose for Synchrotron Radiation Microangiography Based On a Simple Mouse Head Model and a Voxel Mouse Head Phantom

Energy Technology Data Exchange (ETDEWEB)

Lin, H; Jing, J; Xie, C [Hefei University of Technology, Hefei (China); Lu, Y [Shanghai Jiao Tong University, Shanghai (China)

2015-06-15

Purpose: To find effective setting methods to mitigate the irradiation injure in synchrotron radiation microangiography(SRA) by Monte Carlo simulation. Methods: A mouse 1-D head model and a segmented voxel mouse head phantom were simulated by EGSnrc/Dosxyznrc code to investigate the dose enhancement effect of the iodine contrast agent irradiated by a monochromatic synchrotron radiation(SR) source. The influence of, like iodine concentration (IC), vessel width and depth, with and without skull layer protection and the various incident X ray energies, were simulated. The dose enhancement effect and the absolute dose based on the segmented voxel mouse head phantom were evaluated. Results: The dose enhancement ratio depends little on the irradiation depth, but strongly on the IC, which is linearly increases with IC. The skull layer protection cannot be ignored in SRA, the 700µm thick skull could decrease 10% of the dose. The incident X-ray energy can significantly affact the dose. E.g. compared to the dose of 33.2keV for 50mgI/ml, the 32.7keV dose decreases 38%, whereas the dose of 33.7 keV increases 69.2%, and the variation will strengthen more with enhanced IC. The segmented voxel mouse head phantom also showed that the average dose enhancement effect and the maximal voxel dose per photon depends little on the iodine voxel volume ratio, but strongly on IC. Conclusion: To decrease dose damage in SRA, the high-Z contrast agent should be used as little as possible, and try to avoid radiating locally the injected position immediately after the contrast agent injection. The fragile vessel containing iodine should avoid closely irradiating. Avoiding irradiating through the no or thin skull region, or appending thin equivalent material from outside to protect is also a better method. As long as SRA image quality is ensured, using incident X-ray energy as low as possible.

Basic study on low dose radiation effect: SOD activity of immune organs and hemogram in rats

International Nuclear Information System (INIS)

Yamaoka, Kiyonori; Kaneko, Ichiro; Mizutani, Takeo; Nakano, Kazushiro; Edamatsu, Rei; Mori, Akitane.

1989-01-01

We examined the effect of low dose radiation on SOD activities of immune organs such as thymus, spleen, bone marrow in rats and hematological findings changes. Animals were exposed to radiation in a wholebody fashion, 4 hours before sacrifice. SOD activities in thymus and bone marrow cells from the rats X-ray irradiated at doses of 0.25∼0.50 Gy/10 min were enhanced in comparison with those of non-irradiated rats. The enhancement was also observed in spleen cells obtained from group of rats irradiated at 0.05 Gy/10 min. Radiation exposure with over 0.50 Gy/10 min gave rats inhibitory responses in those immune organs. The changes in homogram were not observed with γ-ray exposure of less than 0.10 Gy/10 min. (author)

Health effects of daily airborne particle dose in children: Direct association between personal dose and respiratory health effects

International Nuclear Information System (INIS)

Buonanno, Giorgio; Marks, Guy B.; Morawska, Lidia

2013-01-01

Air pollution is a widespread health problem associated with respiratory symptoms. Continuous exposure monitoring was performed to estimate alveolar and tracheobronchial dose, measured as deposited surface area, for 103 children and to evaluate the long-term effects of exposure to airborne particles through spirometry, skin prick tests and measurement of exhaled nitric oxide (eNO). The mean daily alveolar deposited surface area dose received by children was 1.35 × 10 3 mm 2 . The lowest and highest particle number concentrations were found during sleeping and eating time. A significant negative association was found between changes in pulmonary function tests and individual dose estimates. Significant differences were found for asthmatics, children with allergic rhinitis and sensitive to allergens compared to healthy subjects for eNO. Variation is a child's activity over time appeared to have a strong impact on respiratory outcomes, which indicates that personal monitoring is vital for assessing the expected health effects of exposure to particles. -- Highlights: •Particle dose was estimated through personal monitoring on more than 100 children. •We focused on real-time daily dose of particle alveolar deposited surface area. •Spirometry, skin prick and exhaled Nitric Oxide tests were performed. •Negative link was found between changes in pulmonary functions and individual doses. •A child's lifestyle appeared to have a strong impact on health respiratory outcomes. -- The respiratory health effects of daily airborne particle dose on children through personal monitoring

Hormesis of Low Doses of Ionizing Radiation Exposure on Immune System

International Nuclear Information System (INIS)

Ragab, M.H.; Abbas, M.O.; El-Asady, R.S.; Amer, H.A.; El-Khouly, W.A.; Shabon, M.H.

2015-01-01

The effect of low doses of ionizing radiation on the immune system has been a controversial subject. To evaluate the effect of low-doses γ-irradiation exposure on immune system. An animal model, using Rattus Rattus rats was used. The rats were divided into groups exposed to either continuous or fractionated 100, 200, 300, 400 and 500 mSv of radiation and compared to control rats that did not receive radiation. All groups were exposed to a total white blood count (Wcs), lymphocyte count and serum IgG level measurement, as indicators of the function of the cell-mediated (T lymphocytes) and the humoral (B lymphocytes) immune system. The results of the current study revealed that the counts of total leukocytes (WBCs) and lymphocytes, as well as the serum level of IgG were increased significantly in rats receiving low dose radiation, indicating enhancement of immune system. The data suggests that low-dose gamma-radiation improved hematological parameters and significantly enhances immune response indices of the exposed rats. These findings are similar to the radiation adaptive responses in which a small dose of pre irradiation would induce certain radiation resistance and enhances the cell response after exposure to further irradiation doses The applied low doses used in the present study may appear effective inducing the radio adaptive response. Farooqi and Kesavan (1993) and Bravard et al. (1999) reported that the adaptive response to ionizing radiation refers to the phenomenon by which cells irradiated with low (cGy) or sublethal doses (conditioning doses) become less susceptible to genotoxic effects of a subsequent high dose (challenge dose, several Gy).

Differential effect of prior heat treatment on the thermal enhancement of radiation damage in the ear of the mouse

International Nuclear Information System (INIS)

Law, M.P.; Ahier, R.G.

1982-01-01

The effect of prior heat treatment on thermal enhancement of radiodermatitis was investigated in the ear of the mouse. Ears were heated by immersion in hot water. A priming treatment of 43.5 0 C for 30 min (H) was given at various times before a second combined treatment of hypethermia at 43.5 0 C (h) given immediately before (hX) or after (Xh) a dose of X rays (X). The effect of H was measured in two ways. The heating time h, required to cause a given enhancement of radiodermatitis was estimated by fixing X and varying the duration of h. The thermal enhancement ratio, defined as the dose of X rays alone divided by the dose of X rays with heat required to cause a given reaction, was measured by fixing h and varying X. The priming treatment H reduced the skin response to hX. This effect was such that at 24 to 96 hr after H, the heating time h, had to be increased to about 1.5 times that required without prior hyperthermia. In contrast, the priming treatment had no effect on the response to Xh

Enhancement of radiation effect on cancer cells by gold-pHLIP

Science.gov (United States)

Antosh, Michael P.; Wijesinghe, Dayanjali D.; Shrestha, Samana; Lanou, Robert; Huang, Yun Hu; Hasselbacher, Thomas; Fox, David; Neretti, Nicola; Sun, Shouheng; Katenka, Natallia; Cooper, Leon N; Andreev, Oleg A.; Reshetnyak, Yana K.

2015-01-01

Previous research has shown that gold nanoparticles can increase the effectiveness of radiation on cancer cells. Improved radiation effectiveness would allow lower radiation doses given to patients, reducing adverse effects; alternatively, it would provide more cancer killing at current radiation doses. Damage from radiation and gold nanoparticles depends in part on the Auger effect, which is very localized; thus, it is important to place the gold nanoparticles on or in the cancer cells. In this work, we use the pH-sensitive, tumor-targeting agent, pH Low-Insertion Peptide (pHLIP), to tether 1.4-nm gold nanoparticles to cancer cells. We find that the conjugation of pHLIP to gold nanoparticles increases gold uptake in cells compared with gold nanoparticles without pHLIP, with the nanoparticles distributed mostly on the cellular membranes. We further find that gold nanoparticles conjugated to pHLIP produce a statistically significant decrease in cell survival with radiation compared with cells without gold nanoparticles and cells with gold alone. In the context of our previous findings demonstrating efficient pHLIP-mediated delivery of gold nanoparticles to tumors, the obtained results serve as a foundation for further preclinical evaluation of dose enhancement. PMID:25870296

Immunological low-dose radiation modulates the pediatric medulloblastoma antigens and enhances antibody-dependent cellular cytotoxicity.

Science.gov (United States)

Das, Arabinda; McDonald, Daniel; Lowe, Stephen; Bredlau, Amy-Lee; Vanek, Kenneth; Patel, Sunil J; Cheshier, Samuel; Eskandari, Ramin

2017-03-01

Immunotherapy can be an effective treatment for pediatric medulloblastoma (MB) patients. However, major subpopulations do not respond to immunotherapy, due to the lack of antigenic mutations or the immune-evasive properties of MB cells. Clinical observations suggest that radiation therapy (RT) may expand the therapeutic reach of immunotherapy. The aim of the present investigation is to study the effect of low-dose X-ray radiation (LDXR, 1 Gy) on the functional immunological responses of MB cells (DAOY, D283, and D341). Induction of MB cell death was examined using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Production of reactive oxygen species (ROS) was measured by fluorescent probes. Changes in the expression of  human leukocyte antigen (HLA) molecules and caspase-3 activities during treatment were analyzed using Western blotting and caspase-3 assay. Western blot analysis demonstrated that LDXR upregulated the expression of HLA class I and HLA II molecules by more than 20% compared with control and high-dose (12 Gy) groups in vitro. Several of these HLA subtypes, such as MAGE C1, CD137, and ICAM-1, have demonstrated upregulation. In addition, LDXR increases ROS production in association with phosphorylation of NF-κB and cell surface expression of mAb target molecules (HER2 and VEGF). These data suggest that a combined LDXR and mAb therapy can create a synergistic effect in vitro. These results suggest that LDXR modulates HLA molecules, leading to alterations in T-cell/tumor-cell interaction and enhancement of T-cell-mediated MB cell death. Also, low-dose radiotherapy combined with monoclonal antibody therapy may one day augment the standard treatment for MB, but more investigation is needed to prove its utility as a new therapeutic combination for MB patients.

Dose rate effect on low-dose hyper-radiosensitivity with cells in vitro

Energy Technology Data Exchange (ETDEWEB)

Kim, Geon-Min; Kim, Eun-Hee [Seoul National University, Seoul (Korea, Republic of)

2016-10-15

Low-dose hyper-radiosensitivity (HRS) is the phenomenon that mammalian cells exhibit higher sensitivity to radiation at low doses (< 0.5 Gy) than expected by the linear-quadratic model. At doses above 0.5Gy, the cellular response is recovered to the level expected by the linear-quadratic model. This transition is called the increased radio-resistance (IRR). HRS was first verified using Chinese hamster V79 cells in vitro by Marples and has been confirmed in studies with other cell lines including human normal and tumor cells. HRS is known to be induced by inactivation of ataxia telangiectasia-mutated (ATM), which plays a key role in repairing DNA damages. Considering the connection between ATM and HRS, one can infer that dose rate may affect cellular response regarding HRS at low doses. In this study, we quantitated the effect of dose rate on HRS by clonogenic assay with normal and tumor cells. The HRS of cells at low dose exposures is a phenomenon already known. In this study, we observed HRS of rat normal diencephalon cells and rat gliosarcoma cells at doses below 1 Gy. In addition, we found that dose rate mattered. HRS occurred at low doses, but only when total dose was delivered at a rate below certain level.

Collective effective dose equivalent, population doses and risk estimates from occupational exposures in Japan

International Nuclear Information System (INIS)

Maruyama, Takashi; Nishizawa, Kanae; Kumamoto, Yoshikazu; Iwai, Kazuo; Mase, Naomichi.

1993-01-01

Collective dose equivalent and population dose from occupational exposures in Japan, 1988 were estimated on the basis of a nationwide survey. The survey was conducted on annual collective dose equivalents by sex, age group and type of radiation work for about 0.21 million workers except for the workers in nuclear power stations. The data on the workers in nuclear power stations were obtained from the official report of the Japan Nuclear Safety Commission. The total number of workers including nuclear power stations was estimated to be about 0.26 million. Radiation works were subdivided as follows: medical works including dental; non-atomic energy industry; research and education; atomic energy industry and nuclear power station. For the determination of effective dose equivalent and population dose, organ or tissue doses were measured with a phantom experiment. The resultant doses were compared with the doses previously calculated using a chord length technique and with data from ICRP publications. The annual collective effective dose equivalent were estimated to be about 21.94 person·Sv for medical workers, 7.73 person·Sv for industrial workers, 0.75 person·Sv for research and educational workers, 2.48 person·Sv for atomic energy industry and 84.4 person ·Sv for workers in nuclear power station. The population doses were calculated to be about 1.07 Sv for genetically significant dose, 0.89 Sv for leukemia significant dose and 0.42 Sv for malignant significant dose. The population risks were estimated using these population doses. (author)

Estimates of effective dose in adult CT examinations

International Nuclear Information System (INIS)

Mohamed, Mustafa Awad Elhaj.

2015-12-01

The goal of study was to estimate effective dose (E) in adult CT examinations for Toshiba X64 slice using CT. Exp version 2.5 software in Sudan. Using of CT in medical diagnosis delivers radiation doses to patients that are higher than those from other radiological procedures. lack of optimized protocols could be an additional source of increased dose in developing countries. In order to achieve these objectives, data of CT-scanner has been collected from three hospitals ( ANH, ZSH and MMH). Data collected included equipment information and scan parameters for individual patients, who were used to asses. 300 adult patients underwent head, chest, abdomen-pelvis and peivis CT examinations. The CT1_w , CTD1_vol, DLP, patient effective dos and organ doses were estimated, using CT exposure parameters and CT Exp version 2.5 software. A large variation of mean effective dose and organ doses among hospitals was observed for similar CT examinations. These variations largely originated from different CT scanning protocols used in different hospitals and scan length. The mean effective dose in this study in the Brain, PNS, Chest, pulmonary, Abdomen-pelvis, Pelvis, KUB and CTU were 3.2 mSv, 2.6 mSv, 18.9 mSv 17.6 mSv 27.1 mSv, 11.2 mSv, 9.6 mSv and 23.7 mSv respectively, and organ equivalent, doses presented in this study in this study for the eye lens (for head), lungs and thymus ( for chest) , liver, kidney and small intest ( for abdomen t-pelvis), bladder, uterus and gonads ( for pelvis), were 62.9 mSv, 39.5 mSv, 34.1 mSv, 53.9 mSv, 52.6 mSv, 58.1 mSv, 37 mSv, and 34.6 mSv, respectively. These values were mostly comparable to and slightly higher than the values of effective doses reported from similar studies the United Kingdom, Tanzania, Australia, Canada and Sudan. It was concluded that patient effective dose and organ doses could be substantially minimized through careful selection of scanning parameters based on clinical indications of study, patient size, and body

Comparison of two dose and three dose human papillomavirus vaccine schedules: cost effectiveness analysis based on transmission model.

Science.gov (United States)

Jit, Mark; Brisson, Marc; Laprise, Jean-François; Choi, Yoon Hong

2015-01-06

To investigate the incremental cost effectiveness of two dose human papillomavirus vaccination and of additionally giving a third dose. Cost effectiveness study based on a transmission dynamic model of human papillomavirus vaccination. Two dose schedules for bivalent or quadrivalent human papillomavirus vaccines were assumed to provide 10, 20, or 30 years' vaccine type protection and cross protection or lifelong vaccine type protection without cross protection. Three dose schedules were assumed to give lifelong vaccine type and cross protection. United Kingdom. Males and females aged 12-74 years. No, two, or three doses of human papillomavirus vaccine given routinely to 12 year old girls, with an initial catch-up campaign to 18 years. Costs (from the healthcare provider's perspective), health related utilities, and incremental cost effectiveness ratios. Giving at least two doses of vaccine seems to be highly cost effective across the entire range of scenarios considered at the quadrivalent vaccine list price of £86.50 (€109.23; $136.00) per dose. If two doses give only 10 years' protection but adding a third dose extends this to lifetime protection, then the third dose also seems to be cost effective at £86.50 per dose (median incremental cost effectiveness ratio £17,000, interquartile range £11,700-£25,800). If two doses protect for more than 20 years, then the third dose will have to be priced substantially lower (median threshold price £31, interquartile range £28-£35) to be cost effective. Results are similar for a bivalent vaccine priced at £80.50 per dose and when the same scenarios are explored by parameterising a Canadian model (HPV-ADVISE) with economic data from the United Kingdom. Two dose human papillomavirus vaccine schedules are likely to be the most cost effective option provided protection lasts for at least 20 years. As the precise duration of two dose schedules may not be known for decades, cohorts given two doses should be closely

Resonant creep enhancement in austenitic stainless steels due to pulsed irradiation at low doses

International Nuclear Information System (INIS)

Kishimoto, N.; Amekura, H.; Saito, T.

1994-01-01

Steady-state irradiation creep of austenitic stainless steels has been extensively studied as one of the most important design parameters in fusion reactors. The steady-state irradiation creep has been evaluated using in-pile and light-ion experiments. Those creep compliances of various austenitic steels range in the vicinity of ε/Gσ = 10 -6 ∼10 -5 (dpa sm-bullet MPa) -1 , depending on chemical composition etc. The mechanism of steady-state irradiation creep has been elucidated, essentially in terms of stress-induced preferential absorption of point defects into dislocations, and their climb motion. From this standpoint, low doses such as 10 -3 ∼10 -1 dpa would not give rise to any serious creep, and the irradiation creep may not be a critical issue for the low-dose fusion devices including ITER. It is, however, possible that pulsed irradiation causes different creep behaviors from the steady-state one due to dynamic unbalance of interstitials and vacancies. The authors have actually observed anomalous creep enhancement due to pulsed irradiation in austenitic stainless steels. The resonant behavior of creep indicates that pulsed irradiation may cause significant deformation in austenitic steels even at such low doses and slow pulsing rates, especially for the SA-materials. The first-wall materials in plasma operation of ∼10 2 s may suffer from unexpected transient creep, even in the near-term fusion deices, such as ITER. Though this effect might be a transient effect for a relatively short period, it should be taken into account that the pulsed irradiation makes influences on stress relaxation of the fusion components and on the irradiation fatigue. The mechanism and the relevant behaviors of pulse-induced creep will be discussed in terms of a point-defect model based on the resonant interstitial enrichment

The effects of rat's sperm bioassay for low dose X-ray

International Nuclear Information System (INIS)

Jin, Gye Hwan; Min, Soo Young; Lee, Sang Bock; Lee, Sam Yul; Lee, Jun Haeng; Park, Jong Bae

2007-01-01

In order to investigate the enhancement effects of low dose radiation on biological activation, this study applied low dose X-ray to the whole body of male rats to find out whether hormesis is induced in male germ cells. Total 36 Sprague-Dawley (SD) rats as experimental animal were subdivided into 6 groups(in 6 rats per group) such as control, 10 mGy, 20 mGy, 50 mGy, 100 mGy and 200 mGy radiation group. All the groups showed slightly increasing number of sperms per 0.1 g semen (14.216 x 10 6 , 13.901 x 10 6 , 14.153 x 10 6 , 13.831 x 10 6 , 14.137 x 10 6 , 14.677 x 10 6 respectively), and the motility of sperms amounted to 50.9%, 49.5%, 55.1%, 54.3%, 48.0% and 52.2% respectively. Particularly, compared to the control, the other 5 groups showed higher male hormone level, and the microscopic observations of testicle tissues showed no vacuolization in seminiferous tubules and testis cells. In the results of this experiment, no harmful effect was observed on Sprague-Dawley (SD) rats for which the dose of radiation was controlled as regulated legally by the Ministry of Science and Technology and the Ministry of Health and Welfare. However, as these results were obtained from a limited number of animals, we cannot maintain that the same effect will be observed in the human body. Therefore, there should be further research on the effect on other animals and ultimately on the human body

Dose sculpting with generalized equivalent uniform dose

International Nuclear Information System (INIS)

Wu Qiuwen; Djajaputra, David; Liu, Helen H.; Dong Lei; Mohan, Radhe; Wu, Yan

2005-01-01

With intensity-modulated radiotherapy (IMRT), a variety of user-defined dose distribution can be produced using inverse planning. The generalized equivalent uniform dose (gEUD) has been used in IMRT optimization as an alternative objective function to the conventional dose-volume-based criteria. The purpose of this study was to investigate the effectiveness of gEUD optimization to fine tune the dose distributions of IMRT plans. We analyzed the effect of gEUD-based optimization parameters on plan quality. The objective was to determine whether dose distribution to selected structures could be improved using gEUD optimization without adversely altering the doses delivered to other structures, as in sculpting. We hypothesized that by carefully defining gEUD parameters (EUD 0 and n) based on the current dose distributions, the optimization system could be instructed to search for alternative solutions in the neighborhood, and we could maintain the dose distributions for structures already satisfactory and improve dose for structures that need enhancement. We started with an already acceptable IMRT plan optimized with any objective function. The dose distribution was analyzed first. For structures that dose should not be changed, a higher value of n was used and EUD 0 was set slightly higher/lower than the EUD value at the current dose distribution for critical structures/targets. For structures that needed improvement in dose, a higher to medium value of n was used, and EUD 0 was set to the EUD value or slightly lower/higher for the critical structure/target at the current dose distribution. We evaluated this method in one clinical case each of head and neck, lung and prostate cancer. Dose volume histograms, isodose distributions, and relevant tolerance doses for critical structures were used for the assessment. We found that by adjusting gEUD optimization parameters, the dose distribution could be improved with only a few iterations. A larger value of n could lead to

Effect of a mild dose of X-irradiation on rats under stress

International Nuclear Information System (INIS)

Khan, N.A.; Hasan, S.S.

1984-01-01

This investigation was apt at studying the effect of a mild dose of X-rays on the normal and shock administered rats. Administration of stress brought about a marked depression in the contents of DNA, RNA and protein in the brain. On the other hand, total body exposure to X-rays was found to increase the levels of DNA, RNA and protein in the brain. Thus, the use of a mild dose of X-rays in stressed animals seems to be stimulatory to the diminished levels of DNA, RNA and protein in the brain. There were rising levels of 5-hydroxy indol acetic acid and Vinyl mandelic acid in the urine of stress administered rats and the enhanced levels of these urinary metabolites appeared to be refractory to the application of X-rays. (orig.) [de

Effect of two doses of carbamylated allergoid extract of dust mite on nasal reactivity.

Science.gov (United States)

Scalone, G; Compalati, E; Bruno, M E; Mistrello, G

2013-11-01

Background and Objective. Single SLIT studies with native allergen extracts support a dose-response effect for clinical and immunological outcomes. Conversely for carbamylated allergoids this dose-response effects is less evident, likely because the threshold for efficacy is more easily reached through the enhanced bioavailability of the extract consequent to the selective chemical modification. Thus this pilot study investigates the dose-response effect on nasal specific reactivity and safety of two unusual doses of carbamylated allergoid in patients mono-sensitized to house dust mites. Methods. A prospective open randomized study involved 6-65 year-old Italian patients with clinically relevant sensitization to house dust mites and positive response to nasal provocation challenge. Monomeric carbamylated allergoid was delivered once daily at the dose of 1000 AU or 2000 AU from June to September 2009, during the lowest level of mites exposure. Primary outcomes were the change of the threshold of allergen concentration for a positive nasal provocation test (NPT) before and after the treatment and the product safety. Secondary outcome was the change  in the mean percentage fall of peak nasal inspiratory flow (PNIF) following nasal challenge. Results. Thirty-four patients were enrolled. Fifteen in group 1 and 14 in group 2 concluded the study. After 12 weeks all patients treated in group 1 and all but one in group 2 showed an increase in the threshold dose provoking a positive NPT. Those with no symptoms onset with the highest dose delivered were 80% in group 1 and 78.6% in group 2 (p=0.92). From first to second challenge, the mean percentage fall of PNIF  was reduced with no statistical difference between groups (p=0.95), and with no difference between the final mean percentage falls (p=0.65). No serious adverse reactions occurred and the frequency of events, all mild, was similar in the two groups. Conclusions. Twelve weeks of carbamylated sublingual allergoid

A PC program for estimating organ dose and effective dose values in computed tomography

International Nuclear Information System (INIS)

Kalender, W.A.; Schmidt, B.; Schmidt, M.; Zankl, M.

1999-01-01

Dose values in CT are specified by the manufacturers for all CT systems and operating conditions in phantoms. It is not trivial, however, to derive dose values in patients from this information. Therefore, we have developed a PC-based program which calculates organ dose and effective dose values for arbitrary scan parameters and anatomical ranges. Values for primary radiation are derived from measurements or manufacturer specifications; values for scattered radiation are derived from Monte Carlo calculations tabulated for standard anthropomorphic phantoms. Based on these values, organ doses can be computed by the program for arbitrary scan protocols in conventional and in spiral CT. Effective dose values are also provided, both with ICRP 26 and ICRP 60 tissue-weighting coefficients. Results for several standard CT protocols are presented in tabular form in this paper. In addition, potential for dose reduction is demonstrated, for example, in spiral CT and in quantitative CT. Providing realistic patient dose estimates for arbitrary CT protocols is relevant both for the physician and the patient, and it is particularly useful for educational and training purposes. The program, called WinDose, is now in use at the Erlangen University hospitals (Germany) as an information tool for radiologists and patients. Further extensions are planned. (orig.)

Absorbed dose thresholds and absorbed dose rate limitations for studies of electron radiation effects on polyetherimides

Science.gov (United States)

Long, Edward R., Jr.; Long, Sheila Ann T.; Gray, Stephanie L.; Collins, William D.

1989-01-01

The threshold values of total absorbed dose for causing changes in tensile properties of a polyetherimide film and the limitations of the absorbed dose rate for accelerated-exposure evaluation of the effects of electron radiation in geosynchronous orbit were studied. Total absorbed doses from 1 kGy to 100 MGy and absorbed dose rates from 0.01 MGy/hr to 100 MGy/hr were investigated, where 1 Gy equals 100 rads. Total doses less than 2.5 MGy did not significantly change the tensile properties of the film whereas doses higher than 2.5 MGy significantly reduced elongation-to-failure. There was no measurable effect of the dose rate on the tensile properties for accelerated electron exposures.

Study of gamma radiation induced damages and variation of oxygen enhancement ratio with radiation dose using Saccharomyces cerevisiae

International Nuclear Information System (INIS)

Nairy, R.K.; Yerol Narayana; Bhat, N.N.; Anjaria, K.B.; Sreedevi, B.; Sapra, B.K.

2014-01-01

In the present study, an attempt has been made to quantify Oxygen Enhancement Ratio (OER) and variation of OER as a function of dose with experimental and theoretical formulations using Saccharomyces cerevisiae D7, X2180 and rad 52. The study confirms that, the variation of OER with dose depends upon type of cell and repair proficiency of cells. A theoretical model has been formulated to estimate OER values. With the help of this model, OER value for any dose can be calculated in the exponential region of the survival curve without actually extending the experiment in that dose region. (author)

Towards a new dose and dose-rate effectiveness factor (DDREF)? Some comments.

Science.gov (United States)

Chadwick, K H

2017-06-26

The aim of this article is to offer a broader, mechanism-based, analytical tool than that used by (Rühm et al 2016 Ann. ICRP 45 262-79) for the interpretation of cancer induction relationships. The article explains the limitations of this broader analytical tool and the implications of its use in view of the publications by Leuraud et al 2015 (Lancet Haematol. 2 e276-81) and Richardson et al 2015 (Br. Med. J. 351 h5359). The publication by Rühm et al 2016 (Ann. ICRP 45 262-79), which is clearly work in progress, reviews the current status of the dose and dose-rate effectiveness factor (DDREF) as recommended by the ICRP. It also considers the issues which might influence a reassessment of both the value of the DDREF as well as its application in radiological protection. In this article, the problem is approached from a different perspective and starts by commenting on the limited scientific data used by Rühm et al 2016 (Ann. ICRP 45 262-79) to develop their analysis which ultimately leads them to use a linear-quadratic dose effect relationship to fit solid cancer mortality data from the Japanese life span study of atomic bomb survivors. The approach taken here includes more data on the induction of DNA double strand breaks and, using experimental data taken from the literature, directly relates the breaks to cell killing, chromosomal aberrations and somatic mutations. The relationships are expanded to describe the induction of cancer as arising from radiation induced cytological damage coupled to cell killing since the cancer mutated cell has to survive to express its malignant nature. Equations are derived for the induction of cancer after both acute and chronic exposure to sparsely ionising radiation. The equations are fitted to the induction of cancer in mice to illustrate a dose effect relationship over the total dose range. The 'DDREF' derived from the two equations varies with dose and the DDREF concept is called into question. Although the equation for

Effects of single cyanamide dose on free amino acid pool in rat brain

Energy Technology Data Exchange (ETDEWEB)

Ostrovskiy, S.Yu.

Outbred rats were employed in trials on the effects of cyanamide - an inhibitor of aldehyde dehydrogenase proposed for the treatment of alcoholism - on the brain pool of essential and nonessential amino acid. Cyanamide was administered intraperitoneally in a dose of 60 mg/kg, followed in some experiments by intraperitoneal ethanol in a dose of 0.5 g/kg. Following cyanamide administration, marked enhancement of the levels of taurine, cystine, and GABA was noted, whereas the increase in serine was less pronounced. Cyanamide administration also induced depression of alanine, valine, leucine, phenylalanine, and of ethanolamine levels. Administration of ethanol after priming with cyanamide had only the additional effect of diminishing the levels of cysteic acid and ornithine in the brain. However, the differences between the cyanamide animals and the cyanamide + ethanol animals were not significant. With currently available data, it is difficult to tell whether the effects of cyanamide are due to elevation in acetaldehyde levels, or to some direct effect of the drug on protein or amino acid metabolism. 24 references.

Biological effects of low-dose ionizing radiation exposure

International Nuclear Information System (INIS)

Reinoehl-Kompa, Sabine; Baldauf, Daniela; Heller, Horst

2009-01-01

The report on the meeting of the Strahlenschutzkommission 2007 concerning biological effects of low-dose ionizing radiation exposure includes the following contributions: Adaptive response. The importance of DNA damage mechanisms for the biological efficiency of low-energy photons. Radiation effects in mammography: the relative biological radiation effects of low-energy photons. Radiation-induced cataracts. Carcinomas following prenatal radiation exposure. Intercellular apoptosis induction and low-dose irradiation: possible consequences for the oncogenesis control. Mechanistic models for the carcinogenesis with radiation-induced cell inactivation: application to all solid tumors in the Japanese atomic bomb survivors. Microarrays at low radiation doses. Mouse models for the analysis of biological effects of low-dose ionizing radiation. The bystander effect: observations, mechanisms and implications. Lung carcinoma risk of Majak workers - modeling of carcinogenesis and the bystander effect. Microbeam studies in radiation biology - an overview. Carcinogenesis models with radiation-induced genomic instability. Application to two epidemiological cohorts.

Determination of effective dose of antimalarial from Cassia ...

African Journals Online (AJOL)

However, further investigation is required to determine an effective dose of the administered extract for a higher inhibitory effect and increasing effectiveness of the extract. Material and Methods: To determine the effective dose of ethanol extract of C. spectabilis leaves, a "4-day suppressive test"of Peter was performed with ...

Dose-rate effects in external beam radiotherapy redux

International Nuclear Information System (INIS)

Ling, C. Clifton; Gerweck, Leo E.; Zaider, Marco; Yorke, Ellen

2010-01-01

Recent developments in external beam radiotherapy, both in technical advances and in clinical approaches, have prompted renewed discussions on the potential influence of dose-rate on radio-response in certain treatment scenarios. We consider the multiple factors that influence the dose-rate effect, e.g. radical recombination, the kinetics of sublethal damage repair for tumors and normal tissues, the difference in α/β ratio for early and late reacting tissues, and perform a comprehensive literature review. Based on radiobiological considerations and the linear-quadratic (LQ) model we estimate the influence of overall treatment time on radio-response for specific clinical situations. As the influence of dose-rate applies to both the tumor and normal tissues, in oligo-fractionated treatment using large doses per fraction, the influence of delivery prolongation is likely important, with late reacting normal tissues being generally more sensitive to the dose-rate effect than tumors and early reacting tissues. In conventional fractionated treatment using 1.8-2 Gy per fraction and treatment times of 2-10 min, the influence of dose-rate is relatively small. Lastly, the dose-rate effect in external beam radiotherapy is governed by the overall beam-on-time, not by the average linac dose-rate, nor by the instantaneous dose-rate within individual linac pulses which could be as high as 3 x 10 6 MU/min.

Effective dose and cancer risk in PET/CT exams

International Nuclear Information System (INIS)

Pinto, Gabriella M.; Sa, Lidia Vasconcellos de

2013-01-01

Due to the use of radiopharmaceutical positron-emitting in PET exam and realization of tomography by x-ray transmission in CT examination, an increase of dose with hybrid PET/CT technology is expected. However, differences of doses have been reported in many countries for the same type of procedure. It is expected that the dose is an influent parameter to standardize the protocols of PET/CT. This study aimed to estimate the effective doses and absorbed in 65 patients submitted to oncological Protocol in a nuclear medicine clinic in Rio de Janeiro, considering the risk of induction of cancer from the scan. The CT exam-related doses were estimated with a simulator of PMMA and simulated on the lmPACT resistance, which for program effective dose, were considered the weight factors of the lCRP 103. The PET exam doses were estimated by multiplying the activity administered to the patient with the ICRP dose 80 factors. The radiological risk for cancer incidence were estimated according to the ICRP 103. The results showed that the effective dose from CT exam is responsible for 70% of the effective total in a PET/CT scan. values of effective dose for the PET/CT exam reached average values of up to 25 mSv leading to a risk of 2, 57 x 10 -4 . Considering that in staging of oncological diseases at least four tests are performed annually, the total risk comes to 1,03x 10 -3

Effective dose for patient in multimode panoramic radiography

International Nuclear Information System (INIS)

Yasaki, Shiro; Daibo, Motoji

1999-01-01

In recent years, multimode panoramic radiography has had various functions, such as the auto exposure function, auto focus function (auto function), TMJ radiography and tomogram radiography functions. The purpose of this study was to estimate the effective dose for patients in each mode of the new multimode panoramic radiography (J. MORITA MFG. CORP. Dental Panorama X-ray Apparatus: Veraview Scope X 600). The absorbed doses in important organs involved in the causation of stochastic effects were measured by a thermoluminescent dosimeter using RANDO phantom. The effective doses were calculated using modified tissue weighting factors recommended by the International Commission on Radiological Protection (ICRP) in 1999. The mean field size over skin in typical panoramic and tomographic examinations was about 3% and 0.4% of the total body surface area of 15000 cm 2 . Assuming that the incidence of skin cancer is proportional to the area of skin exposed to ionizing radiation, the tissue weighting factor of skin can be estimated to be about 0.0003 and 0.00004. The estimate in effective dose was lower (5.3 μSv) in the panoramic auto function mode (an average exposure condition of 69 kV 7 mA) than that (6.5-13.8 μSv) in the linear tomogram modes. Since the linear tomogram mode requires a scout view, such as standard panoramic radiography, the dose in the linear tomogram mode becomes higher than other modes. A percentage of gonad doses in effective doses was negligible. (author)

Effective dose to patients from thoracic spine examinations with tomosynthesis

International Nuclear Information System (INIS)

Svalkvist, Angelica; Baath, Magnus; Soederman, Christina

2016-01-01

The purposes of the present work were to calculate the average effective dose to patients from lateral tomosynthesis examinations of the thoracic spine, compare the results with the corresponding conventional examination and to determine a conversion factor between dose-area product (DAP) and effective dose for the tomosynthesis examination. Thoracic spine examinations from 17 patients were included in the study. The registered DAP and information about the field size for each projection radiograph were, together with patient height and mass, used to calculate the effective dose for each projection radiograph. The total effective doses for the tomosynthesis examinations were obtained by adding the effective doses from the 60 projection radiographs included in the examination. The mean effective dose was 0.47 mSv (range 0.24-0.81 mSv) for the tomosynthesis examinations and 0.20 mSv (range 0.07-0.29 mSv) for the corresponding conventional examinations (anteroposterior + left lateral projection). For the tomosynthesis examinations, a conversion factor between total DAP and effective dose of 0.092 mSv Gycm -2 was obtained. (authors)

Single event effects and total ionizing dose effects of typical VDMOSFET devices

International Nuclear Information System (INIS)

Lou Jianshe; Cai Nan; Liu Jiaxin; Wu Qinzhi; Wang Jia

2012-01-01

In this work, single event effects and total ionizing dose effects of typical VDMOSFET irradiated by 60 Co γ-rays and 252 Cf source were studied. The single event burnout and single event gate rupture (SEB/SEGR) effects were investigated, and the relationship between drain-source breakdown voltage and ionizing dose was obtained. The results showed that the VDMOSFET devices were sensitive to SEB and SEGR, and measures to improve their resistance to SEB and SEGR should be considered seriously for their space applications. The drain-source breakdown voltage was sensitive to total ionizing dose effects as the threshold voltage. In assessing the devices' resistance to the total ionizing dose effects, both the threshold voltage and the drain-source breakdown voltage should be taken into account. (authors)

Effect of three different doses of arginine enhanced enteral nutrition on nutritional status and outcomes in well nourished postsurgical cancer patients: a randomized single blinded prospective trial.

Science.gov (United States)

De Luis, D A; Izaola, O; Terroba, M C; Cuellar, L; Ventosa, M; Martin, T

2015-01-01

Patients with head and neck cancer undergoing surgery have a high occurrence of postoperative complications. The aim of our study was to investigate whether postoperative nutrition of head and neck cancer patients, using an enhanced enteral formula with three different doses of arginine could improve nutritional variables as well as clinical outcome, depending of arginine dose. A population of 84 patients with oral and laryngeal cancer was enrolled. At surgery patients were randomly assigned to three different treatment groups, each one containing at less 28 patients. Group I (28 patients) received an enteral diet supplements with a low physiological dose of arginine (5.7 g per day), group II (28 patients) received an isocaloric, isonitrogenous enteral formula with a medium dose of arginine (12.3 g per day) and group III (28 patients) received an isocaloric, isonitrogenous enteral formula with a high dose of arginine (18.9 g per day). The length of postoperative stay had a trend to be better with high dose of arginine received (31.9 ± 17.2 days in group I vs 27.8 ± 15.2 days in group II vs 24.8 ± 18.3 days in group III: p = 0.034). No differences were detected in postoperative infections complications and diarrhea. Fistula was less frequent in groups II and III than I (10.7% group I vs 3.6% group II vs 3.6% group III: p = 0.033), The length of postoperative stay had a trend to be better with high dose of arginine received (31.9 ± 17.2 days in group I vs 27.8 ± 15.2 days in group II vs 24.8 ± 18.3 days in group III: p = 0.034). Our results suggest that these patients could benefit from a high dose of arginine enhanced enteral formula to decrease length of hospital stay and fistula wound complications.

Effective dose from direct and indirect digital panoramic units

Energy Technology Data Exchange (ETDEWEB)

Lee, Gun Sun; Kim, Jin Soo; Seo, Yo Seob; Kim, Jae Duk [School of Dentistry, Oral Biology Research Institute, Chosun University, Gwangju (Korea, Republic of)

2013-06-15

This study aimed to provide comparative measurements of the effective dose from direct and indirect digital panoramic units according to phantoms and exposure parameters. Dose measurements were carried out using a head phantom representing an average man (175 cm tall, 73.5 kg male) and a limbless whole body phantom representing an average woman (155 cm tall, 50 kg female). Lithium fluoride thermoluminescent dosimeter (TLD) chips were used for the dosimeter. Two direct and 2 indirect digital panoramic units were evaluated in this study. Effective doses were derived using 2007 International Commission on Radiological Protection (ICRP) recommendations. The effective doses of the 4 digital panoramic units ranged between 8.9 {mu}Sv and 37.8 {mu}Sv. By using the head phantom, the effective doses from the direct digital panoramic units (37.8 {mu}Sv, 27.6 {mu}Sv) were higher than those from the indirect units (8.9 {mu}Sv, 15.9 {mu}Sv). The same panoramic unit showed the difference in effective doses according to the gender of the phantom, numbers and locations of TLDs, and kVp. To reasonably assess the radiation risk from various dental radiographic units, the effective doses should be obtained with the same numbers and locations of TLDs, and with standard hospital exposure. After that, it is necessary to survey the effective doses from various dental radiographic units according to the gender with the corresponding phantom.

Effect of gamma radiation dose and sensitizer on the physical properties of irradiated natural rubber latex

International Nuclear Information System (INIS)

Komgrit, R.; Thawat, C.; B, Tripob; Wirach, T.

2009-07-01

Full text: The vulcanization of natural rubber latex can be induced by gamma radiation, which enhances cross-linking within the rubber matrix. The purpose of this research is to investigate the effect of gamma radiation dose and sensitizers on the physical properties of irradiated natural rubber. Three sensitizers n-butyl acrylate (n-B A), tetrachloroethylene (C 2 Cl 4 ) and trichloromethane (CHCl 3 ) were mixed with natural rubber latex before irradiation with gamma ray dose varied from 14 to 22 kGy. Results showed that the mixture of three sensitizers with specific ratios effectively induced the cross-linking of natural rubber latex. The cross-linking ratio and improved physical properties increased with increasing gamma dose. Therefore, the mixture ratios of n-B A, C 2 Cl 4 and CHCl 3 have shown to be a critical parameter in the vulcanization of natural rubber latex by gamma radiation

Overexpression of caveolin-1 in lymphoblastoid TK6 cells enhances proliferation after irradiation with clinically relevant doses

International Nuclear Information System (INIS)

Barzan, David; Maier, Patrick; Wenz, Frederik; Herskind, Carsten; Zeller, W. Jens

2010-01-01

Background and Purpose: The transmembrane protein caveolin-1 (CAV1) is an essential component of caveolae, small membrane invaginations involved in vesicle formation. CAV1 plays a role in signal transduction, tumor suppression and oncogene transformation. Previous studies with CAV1 knockout mice and CAV1 knockdown in pancreatic tumor cells implicated CAV1 in mediating radioresistance. The aim of this work was to test the effect of CAV1 overexpression after irradiation in human cells lacking endogenous CAV1 expression. Material and Methods: Human CAV1 was overexpressed in lymphoblastoid TK6 cells (TK6-wt) using a eukaryotic expression plasmid, pCI-CAV1, or a lentiviral SIN (self-inactivating) vector, HR'SIN-CAV1. CAV1 expression was verified in TK6 cells with Western blot analysis or intracellular FACS (fluorescence-activated cell sorting) staining. The effect of CAV1 on proliferation kinetics after irradiation of TK6 cells was measured with a growth assay. Results: TK6-wt showed no detectable endogenous CAV1 expression. Lentivirally mediated transduction with HR'SIN-CAV1 (TK6-CAV1) resulted in a considerably stronger CAV1 expression in comparison to TK6 cells electroporated with pCI-CAV1. Intracellular FACS analysis showed that 90% of transduced cells expressed CAV1. CAV1 enhanced early proliferation of TK6 cells after irradiation with a dose of 2 Gy, whereas proliferation of unirradiated cells was not affected. CAV1 also protected cells after irradiation with 4 Gy. This radioprotective effect was supported by a reduction of radiation-induced apoptosis. Conclusion: A model system for expression of exogenous CAV1 by stable lentiviral transduction of TK6 cells was established. Functional assays demonstrated enhanced early proliferation by CAV1 expression in TK6 cells after irradiation with clinically relevant doses supporting the role of CAV1 as a prosurvival factor. (orig.)

Dose-rate effects on mammalian cells exposed to ionizing radiation

International Nuclear Information System (INIS)

Mitchell, J.B.

1978-01-01

The effect of irradiation on the life cycle and on cell survival was studied for a range of different dose rates. Log phase, plateau phase and synchronized cultures of different mammalian cells were used. Cell cycle redistribution during the radiation exposure was found to be a very important factor in determining the overall dose-rate effect for log phase and synchronized cells. In fact, cell cycle redistribution during the exposure, in some instances, resulted in a lower dose rate being more effective in cell killing per unit dose than a higher dose rate. For plateau phase cultures, where cell cycle times are greatly lengthened, the effects of redistribution in regard to cell killing was virtually eliminated. Both fed and unfed plateau phase cultures exhibited a dose-rate effect, but it was found that below dose rates of 154 rad/h there is no further loss in effectiveness

Estimation of effective dose equivalente from external irradiations

International Nuclear Information System (INIS)

Wakabayashi, T.

1985-07-01

A methodology for computing effective dose equivalent, derived from the computer code ALGAM: Monte Carlo Estimation of Internal Dose from Gamma-ray Sources in a Phantom Man, developed at Oak Ridge National Laboratory, is presented. The modified code was run for 12 different photon energy levels, from 0,010 Mev to 4.0 Mev, which provides computing the absorved dose, for these energy levels, in each one of the 97 organs of the original code. The code also was run for the principal energy levels used in the calibration of the dosimetric films. The results of the absorved doses per photon obtained for these levels of energy have been transformed in effective dose equivalents. (M.A.C.) [pt

Implications of effects ''adaptive response'', ''low-dose hypersensitivity'' und ''bystander effect'' for cancer risk at low doses and low dose rates

International Nuclear Information System (INIS)

Jacob, P

2006-01-01

A model for carcinogenesis (the TSCE model) was applied in order to examine the effects of ''Low-dose hypersensitivity (LDH)'' and the ''Bystander effect (BE)'' on the derivation of radiation related cancer mortality risks. LDH has been discovered to occur in the inactivation of cells after acute exposure to low LET radiation. A corresponding version of the TSCE model was applied to the mortality data on the Abomb survivors from Hiroshima and Nagasaki. The BE has been mainly observed in cells after exposure to high LET radiation. A Version of the TSCE model which included the BE was applied to the data on lung cancer mortality from the workers at the Mayak nuclear facilities who were exposed to Plutonium. In general an equally good description of the A-bomb survivor mortality data (for all solid, stomach and lung tumours) was found for the TSCE model and the (conventional) empirical models but fewer parameters were necessary for the TSCE model. The TSCE model which included the effects of radiation induced cell killing resulted in non-linear dose response curves with excess relative risks after exposure at young ages that were generally lower than in the models without cell killing. The main results from TSCE models which included cell killing described by either conventional survival curves or LDH were very similar. A sub multiplicative effect from the interaction of smoking and exposure to plutonium was found to result from the analysis of the Mayak lung cancer mortality data. All models examined resulted in the predominant number of Mayak lung cancer deaths being ascribed to smoking. The interaction between smoking and plutonium exposures was found to be the second largest effect. The TSCE model resulted in lower estimates for the lung cancer excess relative risk per unit plutonium dose than the empirical risk model, but this difference was not found to be statistically significant. The excess relative risk dose responses were linear in the empirical model and

Radiation doses during chest examinations using dose modulation techniques in multislice CT scanner

International Nuclear Information System (INIS)

Livingstone, Roshan S.; Pradip, Joe; Dinakran, Paul M.; Srikanth, B.

2010-01-01

Objectives: To evaluate the radiation dose and image quality using a manual protocol and dose modulation techniques in a 6-slice CT scanner. Materials and Methods: Two hundred and twenty-one patients who underwent contrast-enhanced CT of the chest were included in the study. For the manual protocol settings, constant tube potential (kV) and tube current-time product (mAs) of 140 kV and 120 mAs, respectively, were used. The angular and z-axis dose modulation techniques utilized a constant tube potential of 140 kV; mAs values were automatically selected by the machine. Effective doses were calculated using dose-length product (DLP) values and the image quality was assessed using the signal-to-noise (SNR) ratio values. Mean effective doses using manual protocol for patients of weights 40-60 kg, 61-80 kg, and 81 kg and above were 8.58 mSv, 8.54 mSv, and 9.07 mSv, respectively. Mean effective doses using z-axis dose modulation for patients of weights 40-60 kg, 61-80 kg, and 81 kg and above were 4.95 mSv, 6.87 mSv, and 10.24 mSv, respectively. The SNR at the region of the liver for patients of body weight of 40-60 kg was 5.1 H, 6.2 H, and 8.8 H for manual, angular, and z-axis dose modulation, respectively. Conclusion: Dose reduction of up to 15% was achieved using angular dose modulation and of up to 42% using z-axis dose modulation, with acceptable diagnostic image quality compared to the manual protocol. (author)

Subeffective doses of dexketoprofen trometamol enhance the potency and duration of fentanyl antinociception

Science.gov (United States)

Gaitán, Gema; Herrero, Juan F

2002-01-01

The combination of classic non-steroidal antiinflammatory drugs (NSAIDs) with opiates induces more analgesia than the summed effect of each drug given separately. No studies have been performed using new generation NSAIDs and fentanyl nor on the duration of this effect. We have studied the analgesic effect of fentanyl alone and after the administration of subeffective doses of dexketoprofen trometamol in rat nociceptive responses. The responses were evoked by noxious mechanical stimulation and were recorded as single motor units in male Wistar rats anaesthetized with α-chloralose. The effective dose 50 (ED50) observed with fentanyl was 22.4±1.5 μg kg−1 and full recovery was apparent 20 min later. The administration of a total dose of 40 μg kg−1 of dexketoprofen trometamol did not induce any significant effect on the nociceptive responses. In the presence of dexketoprofen trometamol, the ED50 for fentanyl was 5 fold lower than before: 3.8±1.1 μg kg−1 and no significant recovery was observed 45 min later. The opioid antagonist naloxone (200 μg kg−1) did not reverse the effect, although in control experiments the same dose was able to prevent any action of fentanyl given alone. We conclude that the combination of fentanyl and subeffective doses of dexketoprofen trometamol induces a more potent and longer lasting analgesic effect than that observed with fentanyl alone, and that this is not an opioid mediated action. PMID:11815374

Effect of combined oral doses of Δ(9)-tetrahydrocannabinol (THC) and cannabidiolic acid (CBDA) on acute and anticipatory nausea in rat models.

Science.gov (United States)

Rock, Erin M; Connolly, Cassidy; Limebeer, Cheryl L; Parker, Linda A

2016-09-01

The purpose of this study was to evaluate the potential of oral combined cannabis constituents to reduce nausea. The objective of this study was to determine the effect of combining subthreshold oral doses of Δ(9)-tetrahydrocannabinol (THC) and cannabidiolic acid (CBDA) on acute and anticipatory nausea in rat models of conditioned gaping. The potential of intragastric (i.g.) administration of THC, CBDA, or combined doses, to interfere with acute nausea-induced conditioned gaping (acute nausea) or the expression of contextually elicited conditioned gaping (anticipatory nausea), was evaluated. For acute nausea, i.g. administration of subthreshold doses of THC (0.5 and 1 mg/kg) or CBDA (0.5 and 1 μg/kg) significantly suppressed acute nausea-induced gaping, whereas higher individual doses of both THC and CBDA were maximally effective. Combined i.g. administration of higher doses of THC and CBDA (2.5 mg/kg THC-2.5 μg/kg CBDA; 10 mg/kg THC-10 μg/kg CBDA; 20 mg/kg THC-20 μg/kg CBDA) also enhanced positive hedonic reactions elicited by saccharin solution during conditioning. For anticipatory nausea, combined subthreshold i.g. doses of THC (0.1 mg/kg) and CBDA (0.1 μg/kg) suppressed contextually elicited conditioned gaping. When administered i.g., THC was effective on its own at doses ranging from 1 to 10 mg/kg, but CBDA was only effective at 10 μg/kg. THC alone was equally effective by intraperitoneal (i.p.) and i.g. administration, whereas CBDA alone was more effective by i.p. administration (Rock et al. in Psychopharmacol (Berl) 232:4445-4454, 2015) than by i.g. administration. Oral administration of subthreshold doses of THC and CBDA may be an effective new treatment for acute nausea and anticipatory nausea and appetite enhancement in chemotherapy patients.

Biologically effective dose distribution based on the linear quadratic model and its clinical relevance

International Nuclear Information System (INIS)

Lee, Steve P.; Leu, Min Y.; Smathers, James B.; McBride, William H.; Parker, Robert G.; Withers, H. Rodney

1995-01-01

Purpose: Radiotherapy plans based on physical dose distributions do not necessarily entirely reflect the biological effects under various fractionation schemes. Over the past decade, the linear-quadratic (LQ) model has emerged as a convenient tool to quantify biological effects for radiotherapy. In this work, we set out to construct a mechanism to display biologically oriented dose distribution based on the LQ model. Methods and Materials: A computer program that converts a physical dose distribution calculated by a commercially available treatment planning system to a biologically effective dose (BED) distribution has been developed and verified against theoretical calculations. This software accepts a user's input of biological parameters for each structure of interest (linear and quadratic dose-response and repopulation kinetic parameters), as well as treatment scheme factors (number of fractions, fractional dose, and treatment time). It then presents a two-dimensional BED display in conjunction with anatomical structures. Furthermore, to facilitate clinicians' intuitive comparison with conventional fractionation regimen, a conversion of BED to normalized isoeffective dose (NID) is also allowed. Results: Two sample cases serve to illustrate the application of our tool in clinical practice. (a) For an orthogonal wedged pair of x-ray beams treating a maxillary sinus tumor, the biological effect at the ipsilateral mandible can be quantified, thus illustrates the so-called 'double-trouble' effects very well. (b) For a typical four-field, evenly weighted prostate treatment using 10 MV x-rays, physical dosimetry predicts a comparable dose at the femoral necks between an alternate two-fields/day and four-fields/day schups. However, our BED display reveals an approximate 21% higher BED for the two-fields/day scheme. This excessive dose to the femoral necks can be eliminated if the treatment is delivered with a 3:2 (anterio-posterior/posterio-anterior (AP

Estimating effective doses to children from CT examinations

International Nuclear Information System (INIS)

Heron, J.C.L.

2000-01-01

Full text: Assessing doses to patients in diagnostic radiology is an integral part of implementing optimisation of radiation protection. Sources of normalised data are available for estimating doses to adults undergoing CT examinations, but for children this is not the case. This paper describes a simple method for estimating effective doses arising from paediatric CT examinations. First the effective dose to an adult is calculated, having anatomically matched the scanned regions of the child and the adult and also matched the irradiation conditions. A conversion factor is then applied to the adult effective dose, based on the region of the body being scanned - head, upper or lower trunk. This conversion factor is the child-to-adult ratio of the ratios of effective dose per entrance air kerma (in the absence of the patient) at the FAD. The values of these conversion factors were calculated by deriving effective dose per entrance air kerma at the FAD for new-born, 1, 5, 10, 15 and adult phantoms using four projections (AP, PA, left and right laterals) over a range of beam qualities and FADs.The program PCXMC was used for this purpose. Results to date suggest that the conversion factors to give effective doses for children undergoing CT examinations of the upper trunk are approximately 1.3, 1.2, 1.15, 1.1 and 1.05 for ages 0, 1, 5, 10 and 15 years respectively; CT of the lower trunk - 1.4, 1.3, 1.2, 1.2, 1.1; and CT of the head - 2.3, 2.0, 1.5, 1.3, 1.1. The dependence of these factors on beam quality (HVL from 4 to 10 mm Al) is less than 10%, with harder beams resulting in slightly smaller conversion factors. Dependence on FAD is also less than 10%. Major sources of uncertainties in the conversion factors include matching anatomical regions across the phantoms, and the presence of beam divergence in the z-direction when deriving the factors. The method described provides a simple means of estimating effective doses arising from paediatric CT examinations with

Effect of two doses of urea foliar application on leaves and grape nitrogen composition during two vintages.

Science.gov (United States)

Pérez-Álvarez, Eva P; Garde-Cerdán, Teresa; García-Escudero, Enrique; Martínez-Vidaurre, José María

2017-06-01

Nitrogen affects grapevine growth and also yeast metabolism, which have a direct influence on fermentation kinetics and the formation of different volatile compounds. Throughout the grapevine cycle, soil nitrogen availability and grape nitrogen composition can vary because of different factors. Nitrogen foliar applications can contribute toward enhancing grapevine nitrogen status and minimize the problem of leaching that traditional nitrogen-soil applications can provoke. The present study aimed to evaluate the influence of urea foliar applications on grapevine nitrogen status and grape amino acid content. Accordingly, two different doses of urea were applied over the leaves of a 'Tempranillo' vineyard. The highest urea doses affected nitrogen content on blade leaf tissues after veraison. Must amino acid profiles were modified by urea application and some of the compounds increased their concentrations. The effect of year on the increase of must total amino acid concentrations was more important than the effect of the doses applied. Urea foliar applications can be an interesting tool for decreasing grapevine nitrogen deficiencies. This method of nitrogen implementation in the vineyard could avoid sluggish fermentation problems during winemaking, enhance must nitrogen composition, and contribute to improving wine quality. © 2016 Society of Chemical Industry. © 2016 Society of Chemical Industry.

Quantifying the Combined Effect of Radiation Therapy and Hyperthermia in Terms of Equivalent Dose Distributions

International Nuclear Information System (INIS)

Kok, H. Petra; Crezee, Johannes; Franken, Nicolaas A.P.; Stalpers, Lukas J.A.; Barendsen, Gerrit W.; Bel, Arjan

2014-01-01

Purpose: To develop a method to quantify the therapeutic effect of radiosensitization by hyperthermia; to this end, a numerical method was proposed to convert radiation therapy dose distributions with hyperthermia to equivalent dose distributions without hyperthermia. Methods and Materials: Clinical intensity modulated radiation therapy plans were created for 15 prostate cancer cases. To simulate a clinically relevant heterogeneous temperature distribution, hyperthermia treatment planning was performed for heating with the AMC-8 system. The temperature-dependent parameters α (Gy −1 ) and β (Gy −2 ) of the linear–quadratic model for prostate cancer were estimated from the literature. No thermal enhancement was assumed for normal tissue. The intensity modulated radiation therapy plans and temperature distributions were exported to our in-house-developed radiation therapy treatment planning system, APlan, and equivalent dose distributions without hyperthermia were calculated voxel by voxel using the linear–quadratic model. Results: The planned average tumor temperatures T90, T50, and T10 in the planning target volume were 40.5°C, 41.6°C, and 42.4°C, respectively. The planned minimum, mean, and maximum radiation therapy doses were 62.9 Gy, 76.0 Gy, and 81.0 Gy, respectively. Adding hyperthermia yielded an equivalent dose distribution with an extended 95% isodose level. The equivalent minimum, mean, and maximum doses reflecting the radiosensitization by hyperthermia were 70.3 Gy, 86.3 Gy, and 93.6 Gy, respectively, for a linear increase of α with temperature. This can be considered similar to a dose escalation with a substantial increase in tumor control probability for high-risk prostate carcinoma. Conclusion: A model to quantify the effect of combined radiation therapy and hyperthermia in terms of equivalent dose distributions was presented. This model is particularly instructive to estimate the potential effects of interaction from different treatment

Mathematical model for evaluation of dose-rate effect on biological responses to low dose γ-radiation

International Nuclear Information System (INIS)

Ogata, H.; Kawakami, Y.; Magae, J.

2003-01-01

Full text: To evaluate quantitative dose-response relationship on the biological response to radiation, it is necessary to consider a model including cumulative dose, dose-rate and irradiation time. In this study, we measured micronucleus formation and [ 3 H] thymidine uptake in human cells as indices of biological response to gamma radiation, and analyzed mathematically and statistically the data for quantitative evaluation of radiation risk at low dose/low dose-rate. Effective dose (ED x ) was mathematically estimated by fitting a general function of logistic model to the dose-response relationship. Assuming that biological response depends on not only cumulative dose but also dose-rate and irradiation time, a multiple logistic function was applied to express the relationship of the three variables. Moreover, to estimate the effect of radiation at very low dose, we proposed a modified exponential model. From the results of fitting curves to the inhibition of [ 3 H] thymidine uptake and micronucleus formation, it was obvious that ED 50 in proportion of inhibition of [ 3 H] thymidine uptake increased with longer irradiation time. As for the micronuclei, ED 30 also increased with longer irradiation times. These results suggest that the biological response depends on not only total dose but also irradiation time. The estimated response surface using the three variables showed that the biological response declined sharply when the dose-rate was less than 0.01 Gy/h. These results suggest that the response does not depend on total cumulative dose at very low dose-rates. Further, to investigate the effect of dose-rate within a wider range, we analyzed the relationship between ED x and dose-rate. Fitted curves indicated that ED x increased sharply when dose-rate was less than 10 -2 Gy/h. The increase of ED x signifies the decline of the response or the risk and suggests that the risk approaches to 0 at infinitely low dose-rate

Low-Dose Contrast-Enhanced Breast CT Using Spectral Shaping Filters: An Experimental Study.

Science.gov (United States)

Makeev, Andrey; Glick, Stephen J

2017-12-01

Iodinated contrast-enhanced X-ray imaging of the breast has been studied with various modalities, including full-field digital mammography (FFDM), digital breast tomosynthesis (DBT), and dedicated breast CT. Contrast imaging with breast CT has a number of advantages over FFDM and DBT, including the lack of breast compression, and generation of fully isotropic 3-D reconstructions. Nonetheless, for breast CT to be considered as a viable tool for routine clinical use, it would be desirable to reduce radiation dose. One approach for dose reduction in breast CT is spectral shaping using X-ray filters. In this paper, two high atomic number filter materials are studied, namely, gadolinium (Gd) and erbium (Er), and compared with Al and Cu filters currently used in breast CT systems. Task-based performance is assessed by imaging a cylindrical poly(methyl methacrylate) phantom with iodine inserts on a benchtop breast CT system that emulates clinical breast CT. To evaluate detectability, a channelized hoteling observer (CHO) is used with sums of Laguerre-Gauss channels. It was observed that spectral shaping using Er and Gd filters substantially increased the dose efficiency (defined as signal-to-noise ratio of the CHO divided by mean glandular dose) as compared with kilovolt peak and filter settings used in commercial and prototype breast CT systems. These experimental phantom study results are encouraging for reducing dose of breast CT, however, further evaluation involving patients is needed.

EFFECTIVE DOSE TO PATIENTS FROM THORACIC SPINE EXAMINATIONS WITH TOMOSYNTHESIS.

Science.gov (United States)

Svalkvist, Angelica; Söderman, Christina; Båth, Magnus

2016-06-01

The purposes of the present work were to calculate the average effective dose to patients from lateral tomosynthesis examinations of the thoracic spine, compare the results with the corresponding conventional examination and to determine a conversion factor between dose-area product (DAP) and effective dose for the tomosynthesis examination. Thoracic spine examinations from 17 patients were included in the study. The registered DAP and information about the field size for each projection radiograph were, together with patient height and mass, used to calculate the effective dose for each projection radiograph. The total effective doses for the tomosynthesis examinations were obtained by adding the effective doses from the 60 projection radiographs included in the examination. The mean effective dose was 0.47 mSv (range 0.24-0.81 mSv) for the tomosynthesis examinations and 0.20 mSv (range 0.07-0.29 mSv) for the corresponding conventional examinations (anteroposterior + left lateral projection). For the tomosynthesis examinations, a conversion factor between total DAP and effective dose of 0.092 mSv Gycm(-2) was obtained. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Local dose enhancement in radiation therapy: Monte Carlo simulation study; Reforco local de dose em radioterapia utilizando nanoparticulas: estudo por simulacao Monte Carlo

Energy Technology Data Exchange (ETDEWEB)

Silva, Laura E. da; Nicolucci, Patricia, E-mail: laura.emilia.fm@gmail.com [Universidade de Sao Paulo (USP), Ribeirao Preto, SP (Brazil). Faculdade de Filosofia, Ciencias e Letras

2014-04-15

The development of nanotechnology has boosted the use of nanoparticles in radiation therapy in order to achieve greater therapeutic ratio between tumor and healthy tissues. Gold has been shown to be most suitable to this task due to the high biocompatibility and high atomic number, which contributes to a better in vivo distribution and for the local energy deposition. As a result, this study proposes to study, nanoparticle in the tumor cell. At a range of 11 nm from the nanoparticle surface, results have shown an absorbed dose 141 times higher for the medium with the gold nanoparticle compared to the water for an incident energy spectrum with maximum photon energy of 50 keV. It was also noted that when only scattered radiation is interacting with the gold nanoparticles, the dose was 134 times higher compared to enhanced local dose that remained significant even for scattered radiation. (author)

Investigation of repressive and enhancive effects of fruit extracts on the activity of glucose-6-phophatase.

Science.gov (United States)

Zahoor, Muhammad; Jan, Muhammad Rasul; Naz, Sumaira

2016-11-01

Glucose-6-phosphatase is a key enzyme of glucose metabolic pathways. Deficiency of this enzyme leads to glycogen storage disease. This enzyme also plays a negative role in diabetes mellitus disorder in which the catalytic activity of this enzyme increases. Thus there is need for activators to enhance the activity of glucose-6-phosphatase in glycogen storage disease of type 1b while in diabetes mellitus repressors are needed to reduce its activity. Crude extracts of apricot, fig, mulberry and apple fruits were investigated for their repressive/enhancive effects on glucose-6-phosphatase in vivo. Albino mice were used as experimental animal. All the selected extracts showed depressive effects on glucose-6-phosphatase, which shows that all these extracts can be used as antidiabetic supplement of food. The inhibitory pattern was competitive one, which was evident from the effect of increasing dose from 1g/Kg body weight to 3g/Kg body weight for all the selected fruit extracts. However fig and apple fruit extracts showed high repressive effects for high doses as compared to apricot and mulberry fruit extracts. None of these selected fruit extracts showed enhancive effect on glucose-6-phosphatase activity. All these fruits or their extracts can be used as antidiabetic dietary supplement for diabetes mellitus.

Low Z target switching to increase tumor endothelial cell dose enhancement during gold nanoparticle-aided radiation therapy

Energy Technology Data Exchange (ETDEWEB)

Berbeco, Ross I., E-mail: rberbeco@partners.org; Detappe, Alexandre [Department of Radiation Oncology, Brigham and Women’s Hospital, Dana-Farber Cancer Institute and Harvard Medical School, Boston, Massachusetts 02115 (United States); Tsiamas, Panogiotis [Department of Radiation Oncology, St. Jude Children’s Hospital, Memphis, Tennessee 38105 (United States); Parsons, David; Yewondwossen, Mammo; Robar, James [Department of Radiation Oncology and Department of Physics and Atmospheric Science, Dalhousie University, Halifax, Nova Scotia B3H 1V7 (Canada)

2016-01-15

Purpose: Previous studies have introduced gold nanoparticles as vascular-disrupting agents during radiation therapy. Crucial to this concept is the low energy photon content of the therapy radiation beam. The authors introduce a new mode of delivery including a linear accelerator target that can toggle between low Z and high Z targets during beam delivery. In this study, the authors examine the potential increase in tumor blood vessel endothelial cell radiation dose enhancement with the low Z target. Methods: The authors use Monte Carlo methods to simulate delivery of three different clinical photon beams: (1) a 6 MV standard (Cu/W) beam, (2) a 6 MV flattening filter free (Cu/W), and (3) a 6 MV (carbon) beam. The photon energy spectra for each scenario are generated for depths in tissue-equivalent material: 2, 10, and 20 cm. The endothelial dose enhancement for each target and depth is calculated using a previously published analytic method. Results: It is found that the carbon target increases the proportion of low energy (<150 keV) photons at 10 cm depth to 28% from 8% for the 6 MV standard (Cu/W) beam. This nearly quadrupling of the low energy photon content incident on a gold nanoparticle results in 7.7 times the endothelial dose enhancement as a 6 MV standard (Cu/W) beam at this depth. Increased surface dose from the low Z target can be mitigated by well-spaced beam arrangements. Conclusions: By using the fast-switching target, one can modulate the photon beam during delivery, producing a customized photon energy spectrum for each specific situation.

Protective Effect of Low Dose Gamma Irradiation against Oxidative Damage in Rats Administrated with Ferric- Nitrilotriacetate

International Nuclear Information System (INIS)

Mansonr, S.Z.

2009-01-01

Many studies have demonstrated the beneficial adaptive response of low dose gamma-irradiation. Low dose gamma-irradiation (LDR) might be effective for the prevention of various reactive oxygen species-related diseases. Ferric nitrilotriacetate (Fe-NTA) is a strong oxidant, which generates highly reactive hydroxyl radical and causes injuries of various organs including the kidney and liver. This study was designed to investigate the ability of low dose gamma-irradiation to restrain Fe-NT A induced oxidative stress. Sprague Dawley male albino rats were subjected to low dose gamma-irradiation (50 cGy). Animals were challenged with Fe-NT A (9 mg Fe/kg body weight, intraperitoneally). Results showed that Fe-NTA enhances lipid peroxidation (LPx) accompanied with reduction in glutathione (GSH) content, antioxidant enzymes, viz., glutathione peroxidase (GPX), glutathione reductase (GR), superoxide dismutase (SOD), catalase (CAT) and phase-U metabolizing enzyme glutathione-S-transferase (GST). Fe-NTA also enhances the concentration of blood urea nitrogen (BUN) and serum creatinine as well as alanine aminotransferase (ALT), aspartate aminotransferase (AST) and gamma-glutamyl transpeptidase (GGT) activities. Exposure to low dose gamma- irradiation (3 h after Fe-NTA administration) resulted in a significant decrease in LPx, BUN, serum creatinine contents as well as ALT, AST and GGT enzyme activities. GSH content; GST and antioxidant enzymes were also recovered to significant level. Thus, our data suggest that exposure to LDR might be a useful antioxidant mediator to suppress the Fe-NTA induced-oxidative damage in rats

Protective Effect of Low Dose Gamma Irradiation against Oxidative Damage in Rats Administrated with Ferric- Nitrilotriacetate

International Nuclear Information System (INIS)

Mansonr, S.Z.

2008-01-01

Many studies have demonstrated the beneficial adaptive response of low dose gamma-irradiation. Low dose gamma-irradiation (LDR) might be effective for the prevention of various reactive oxygen species-related diseases. Ferric nitrilotriacetate (Fe-NTA) is a strong oxidant, which generates highly reactive hydroxyl radical and causes injuries of various organs including the kidney and liver. This study was designed to investigate the ability of low dose gamma-irradiation to restrain Fe-NT A induced oxidative stress. Sprague Dawley male albino rats were subjected to low dose gamma-irradiation (50 cGy). Animals were challenged with Fe-NT A (9 mg Fe/kg body weight, intraperitoneally). Results showed that Fe-NTA enhances lipid peroxidation (LPx) accompanied with reduction in glutathione (GSH) content, antioxidant enzymes, viz., glutathione peroxidase (GPX), glutathione reductase (GR), superoxide dismutase (SOD), catalase (CAT) and phase-U metabolizing enzyme glutathione-S-transferase (GST). Fe-NTA also enhances the concentration of blood urea nitrogen (BUN) and serum creatinine as well as alanine aminotransferase (ALT), aspartate aminotransferase (AST) and gamma-glutamyl transpeptidase (GGT) activities. Exposure to low dose gamma- irradiation (3 h after Fe-NTA administration) resulted in a significant decrease in LPx, BUN, serum creatinine contents as well as ALT, AST and GGT enzyme activities. GSH content; GST and antioxidant enzymes were also recovered to significant level. Thus, our data suggest that exposure to LDR might be a useful antioxidant mediator to suppress the Fe-NTA induced-oxidative damage in rats

Radiation dose measurement in gastrointestinal studies

International Nuclear Information System (INIS)

Sulieman, A.; Elzaki, M.; Kappas, C.; Theodorou, K.

2011-01-01

Barium studies investigations (barium swallow, barium meal and barium enema) are the basic routine radiological examination, where barium sulphate suspension is introduced to enhance image contrast of gastrointestinal tracts. The aim of this study was to quantify the patients' radiation doses during barium studies and to estimate the organ equivalent dose and effective dose with those procedures. A total of 33 investigations of barium studies were measured by using thermoluminescence dosemeters. The result showed that the patient entrance surface doses were 12.6±10, 44.5±49 and 35.7±50 mGy for barium swallow, barium meal, follow through and enema, respectively. Effective doses were 0.2, 0.35 and 1.4 mSv per procedure for barium swallow, meal and enema respectively. Radiation doses were comparable with the previous studies. A written protocol for each procedure will reduce the inter-operator variations and will help to reduce unnecessary exposure. (authors)

Low dose of caffeine enhances the efficacy of antidepressants in major depressive disorder and the underlying neural substrates.

Science.gov (United States)

Liu, Qing-Shan; Deng, Ran; Fan, Yuyan; Li, Keqin; Meng, Fangang; Li, Xueli; Liu, Rui

2017-08-01

Caffeine is one of the most frequently used psychoactive substances ingested mainly via beverage or food products. Major depressive disorder is a serious and devastating psychiatric disorder. Emerging evidence indicates that caffeine enhances the antidepressant-like activity of common antidepressant drugs in rodents. However, whether joint administration of low dose of caffeine enhances the antidepressant actions in depressed patients remains unclear. A total of 95 male inpatients were assigned to three groups and were asked to take either caffeine (60, 120 mg) or placebo (soymilk powder) daily for 4 wk on the basis of their current antidepressant medications. Results showed that chronic supplementation with low dose of caffeine (60 mg) produced rapid antidepressant action by reduction of depressive scores. Furthermore, low dose of caffeine improved cognitive performance in depressed patients. However, caffeine did not affect sleep as measured by overnight polysomnography. Moreover, chronic caffeine consumption elicited inhibition of hypothalamic-pituitary-adrenal axis activation by normalization of salivary cortisol induced by Trier social stress test. These findings indicated the potential benefits of further implications of supplementary administration of caffeine to reverse the development of depression and enhance the outcome of antidepressants treatment in major depressive disorder. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Estimation and comparison of effective dose (E) in standard chest CT by organ dose measurements and dose-length-product methods and assessment of the influence of CT tube potential (energy dependency) on effective dose in a dual-source CT

International Nuclear Information System (INIS)

Paul, Jijo; Banckwitz, Rosemarie; Krauss, Bernhard; Vogl, Thomas J.; Maentele, Werner; Bauer, Ralf W.

2012-01-01

Highlights: ► The dual-energy protocol delivers the lowest effective dose of the investigated protocols for standard chest CT examinations, thus enabling functional imaging (like dual-energy perfusion) and can produce weighted images without dose penalty. ► The high-pitch protocol goes along with a 16% increase in dose compared to the standard 120 kV protocol and thus should preferably be used in pediatric, acute care settings (e.g. pulmonary embolism, aortic dissection and the like) or restless patients. ► The difference in effective dose estimates between ICRP 60 and 103 is minimal. ► Tube potential definitely has an effect on estimates of effective dose. - Abstract: Purpose: To determine effective dose (E) during standard chest CT using an organ dose-based and a dose-length-product-based (DLP) approach for four different scan protocols including high-pitch and dual-energy in a dual-source CT scanner of the second generation. Materials and methods: Organ doses were measured with thermo luminescence dosimeters (TLD) in an anthropomorphic male adult phantom. Further, DLP-based dose estimates were performed by using the standard 0.014 mSv/mGycm conversion coefficient k. Examinations were performed on a dual-source CT system (Somatom Definition Flash, Siemens). Four scan protocols were investigated: (1) single-source 120 kV, (2) single-source 100 kV, (3) high-pitch 120 kV, and (4) dual-energy with 100/Sn140 kV with equivalent CTDIvol and no automated tube current modulation. E was then determined following recommendations of ICRP publication 103 and 60 and specific k values were derived. Results: DLP-based estimates differed by 4.5–16.56% and 5.2–15.8% relatively to ICRP 60 and 103, respectively. The derived k factors calculated from TLD measurements were 0.0148, 0.015, 0.0166, and 0.0148 for protocol 1, 2, 3 and 4, respectively. Effective dose estimations by ICRP 103 and 60 for single-energy and dual-energy protocols show a difference of less than 0.04 m

Enhancement of antibiotic effect via gold:silver-alloy nanoparticles

International Nuclear Information System (INIS)

Moreira dos Santos, Margarida; Queiroz, Margarida João; Baptista, Pedro V.

2012-01-01

A strategy for the development of novel antimicrobials is to combine the stability and pleiotropic effects of inorganic compounds with the specificity and efficiency of organic compounds, such as antibiotics. Here we report on the use of gold:silver-alloy (Au:Ag-alloy) nanoparticles, obtained via a single-step citrate co-reduction method, combined to conventional antibiotics to enhance their antimicrobial effect on bacteria. Addition of the alloy nanoparticles considerably decreased the dose of antibiotic necessary to show antimicrobial effect, both for bacterial cells growing in rich medium in suspension and for bacterial cells resting in a physiological buffer on a humid cellulose surface. The observed effect was more pronounced than the sum of the individual effects of the nanoparticles and antibiotic. We demonstrate the enhancement effect of Au:Ag-alloy nanoparticles with a size distribution of 32.5 ± 7.5 nm mean diameter on the antimicrobial effect of (i) kanamycin on Escherichia coli (Gram-negative bacterium), and (ii) a β-lactam antibiotic on both a sensitive and resistant strain of Staphylococcus aureus (Gram-positive bacterium). Together, these results may pave the way for the combined use of nanoparticle–antibiotic conjugates towards decreasing antibiotic resistance currently observed for certain bacteria and conventional antibiotics.

Enhancement of antibiotic effect via gold:silver-alloy nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Moreira dos Santos, Margarida, E-mail: margarida.santos@fct.unl.pt; Queiroz, Margarida Joao; Baptista, Pedro V. [Universidade Nova de Lisboa, CIGMH, Departamento Ciencias da Vida, Faculdade de Ciencias e Tecnologia (Portugal)

2012-05-15

A strategy for the development of novel antimicrobials is to combine the stability and pleiotropic effects of inorganic compounds with the specificity and efficiency of organic compounds, such as antibiotics. Here we report on the use of gold:silver-alloy (Au:Ag-alloy) nanoparticles, obtained via a single-step citrate co-reduction method, combined to conventional antibiotics to enhance their antimicrobial effect on bacteria. Addition of the alloy nanoparticles considerably decreased the dose of antibiotic necessary to show antimicrobial effect, both for bacterial cells growing in rich medium in suspension and for bacterial cells resting in a physiological buffer on a humid cellulose surface. The observed effect was more pronounced than the sum of the individual effects of the nanoparticles and antibiotic. We demonstrate the enhancement effect of Au:Ag-alloy nanoparticles with a size distribution of 32.5 {+-} 7.5 nm mean diameter on the antimicrobial effect of (i) kanamycin on Escherichia coli (Gram-negative bacterium), and (ii) a {beta}-lactam antibiotic on both a sensitive and resistant strain of Staphylococcus aureus (Gram-positive bacterium). Together, these results may pave the way for the combined use of nanoparticle-antibiotic conjugates towards decreasing antibiotic resistance currently observed for certain bacteria and conventional antibiotics.

Adult head CT scans: the uncertainties of effective dose estimates

International Nuclear Information System (INIS)

Gregory, Kent J.; Bibbo, Giovanni; Pattison, John E.

2008-01-01

Full Text: CT scanning is a high dose imaging modality. Effective dose estimates from CT scans can provide important information to patients and medical professionals. For example, medical practitioners can use the dose to estimate the risk to the patient, and judge whether this risk is outweighed by the benefits of the CT examination, while radiographers can gauge the effect of different scanning protocols on the patient effective dose, and take this into consideration when establishing routine scan settings. Dose estimates also form an important part of epidemiological studies examining the health effects of medical radiation exposures on the wider population. Medical physicists have been devoting significant effort towards estimating patient radiation doses from diagnostic CT scans for some years. The question arises: How accurate are these effective dose estimates? The need for a greater understanding and improvement of the uncertainties in CT dose estimates is now gaining recognition as an important issue (BEIR VII 2006). This study is an attempt to analyse and quantify the uncertainty components relating to effective dose estimates from adult head CT examinations that are calculated with four commonly used methods. The dose estimation methods analysed are the Nagel method, the ImpaCT method, the Wellhoefer method and the Dose-Length Product (DLP) method. The analysis of the uncertainties was performed in accordance with the International Standards Organisation's Guide to the Expression of Uncertainty in Measurement as discussed in Gregory et al (Australas. Phys. Eng. Sci. Med., 28: 131-139, 2005). The uncertainty components vary, depending on the method used to derive the effective dose estimate. Uncertainty components in this study include the statistical and other errors from Monte Carlo simulations, uncertainties in the CT settings and positions of patients in the CT gantry, calibration errors from pencil ionization chambers, the variations in the organ

Dose and dose rate effects of whole-body gamma-irradiation: II. Hematological variables and cytokines

Science.gov (United States)

Gridley, D. S.; Pecaut, M. J.; Miller, G. M.; Moyers, M. F.; Nelson, G. A.

2001-01-01

The goal of part II of this study was to evaluate the effects of gamma-radiation on circulating blood cells, functional characteristics of splenocytes, and cytokine expression after whole-body irradiation at varying total doses and at low- and high-dose-rates (LDR, HDR). Young adult C57BL/6 mice (n = 75) were irradiated with either 1 cGy/min or 80 cGy/min photons from a 60Co source to cumulative doses of 0.5, 1.5, and 3.0 Gy. The animals were euthanized at 4 days post-exposure for in vitro assays. Significant dose- (but not dose-rate-) dependent decreases were observed in erythrocyte and blood leukocyte counts, hemoglobin, hematocrit, lipopolysaccharide (LPS)-induced 3H-thymidine incorporation, and interleukin-2 (IL-2) secretion by activated spleen cells when compared to sham-irradiated controls (p < 0.05). Basal proliferation of leukocytes in the blood and spleen increased significantly with increasing dose (p < 0.05). Significant dose rate effects were observed only in thrombocyte counts. Plasma levels of transforming growth factor-beta 1 (TGF-beta 1) and splenocyte secretion of tumor necrosis factor-alpha (TNF-alpha) were not affected by either the dose or dose rate of radiation. The data demonstrate that the responses of blood and spleen were largely dependent upon the total dose of radiation employed and that an 80-fold difference in the dose rate was not a significant factor in the great majority of measurements.

Effect of low-dose gamma-radiation upon hatchability and weight of chickens

International Nuclear Information System (INIS)

Vilic, M.; Kraljevic, P.; Simpraga, M.; Miljanic, S.

2006-01-01

Full text of publication follows: Although any dose of ionizing radiation has generally been recognized to be detrimental to living being, low dose ionizing radiation seems to invoke primary stimulative effects. Stimulatory effects of low dose ionizing radiation include many aspects such as growth, fecundity and longevity stimulation, accelerated development, enhance biological responses for immune systems, enzymatic repair, physiological functions, and the removal of cellular damage, including prevention and removal of cancers and other diseases. Low dose ionizing radiation might also cause changes in the concentration of some biochemical parameters in blood plasma of chickens such as changes in the concentration of total proteins, glucose and cholesterol. The objective of this study was to determine the effect of low doses of gamma irradiation before incubation and on the seventh day of incubation on hatchability of eggs and body weight of chickens. This study includes three independent experiments. In the first experiment, six-hundred eggs produced by a commercial flock of Avian-line 34, were irradiated by a dose of 0.15 Gy gamma radiation (60 Co) before incubation. In the second experiments also involving six-hundred-line 34 eggs were irradiated by dose of 0.15 Gy gamma radiation on the seventh day of incubation. In the third experiment three-hundred eggs produced by a commercial flock of Ross 308 were irradiated by dose 0.30 Gy gamma irradiation before incubation. Along with the chickens which were hatched from irradiated eggs, there was a control group of chickens hatched from nonirradiated eggs. All other conditions were the same for both groups. Hatchability was calculated in terms of all eggs divided with fertile eggs which hatched. The individual weights of the chickens were determined on the first and on the forty second day. Growth data were analyzed statistically by t-test. Irradiation of chicken eggs and embryos at rates o f 0.15 Gy increases

The MLC tongue-and-groove effect on IMRT dose distributions

Energy Technology Data Exchange (ETDEWEB)

Deng Jun [Department of Radiation Oncology, Stanford University School of Medicine, Stanford, CA 94305 (United States). E-mail: jun@reyes.stanford.edu; Pawlicki, Todd; Chen Yan; Li Jinsheng; Jiang, Steve B.; Ma, C.-M. [Department of Radiation Oncology, Stanford University School of Medicine, Stanford, CA 94305 (United States)

2001-04-01

We have investigated the tongue-and-groove effect on the IMRT dose distributions for a Varian MLC. We have compared the dose distributions calculated using the intensity maps with and without the tongue-and-groove effect. Our results showed that, for one intensity-modulated treatment field, the maximum tongue-and-groove effect could be up to 10% of the maximum dose in the dose distributions. For an IMRT treatment with multiple gantry angles ({>=} 5), the difference between the dose distributions with and without the tongue-and-groove effect was hardly visible, less than 1.6% for the two typical clinical cases studied. After considering the patient setup errors, the dose distributions were smoothed with reduced and insignificant differences between plans with and without the tongue-and-groove effect. Therefore, for a multiple-field IMRT plan ({>=} 5), the tongue-and-groove effect on the IMRT dose distributions will be generally clinically insignificant due to the smearing effect of individual fields. The tongue-and-groove effect on an IMRT plan with small number of fields (<5) will vary depending on the number of fields in a plan (coplanar or non-coplanar), the MLC leaf sequences and the patient setup uncertainty, and may be significant (>5% of maximum dose) in some cases, especially when the patient setup uncertainty is small ({<=} 2 mm). (author)

Indication-related dosing for magnetic resonance contrast media

International Nuclear Information System (INIS)

Yuh, W.T.C.; Parker, J.R.; Carvlin, M.J.

1997-01-01

This presentation reviews the issue of contrast media dosing and imaging protocols for the optimal MR imaging detection and characterization of pathology. The cumulative clinical experience gained in performing contrast-enhanced MR examinations with gadolinium chelates indicates that a dose of 0.1 mmol/kg body weight provides safe and effective enhancement of most CNS pathology. Doses lower than 0.1 mmol/kg have been shown to be inadequate for delineating all but selected types of CNS pathology, such as masses with a high lesion to background ratio on post-contrast images (acoustic neuromas) or lesions located in areas in which the normal tissue very rapidly takes up contrast agent (e. g. microadenomas in the pituitary gland). Recent clinical studies have suggested a role for high dose gadolinium administration (up to 0.3 mmol/kg) for the optimal detection and delineation of cerebral metastases or other small or poorly enhancing lesions. Differences in the histopathologic characteristics (capillary permeability, vascularity, location, size) of specific diseased tissues may require varying doses or even a different contrast agent to be used for optimal imaging results. As new MR contrast agents and new scanning techniques are introduced, the specific diagnostic question posed will likely determine the choice of pulse sequence, contrast agent and dose used. (orig.)

210Po, 210Pb, 226Ra in aquatic ecosystems and polders, anthropogenic sources, distribution and enhanced radiation doses in The Netherlands

International Nuclear Information System (INIS)

Koester, H.W.; Marwitz, P.A.; Berger, G.W.; Weers, A.W. van; Hagel, P.; Nieuwenhuize, J.

1992-01-01

Surveys of Dutch waters show that the Oosterschelde estuary and regular fresh waters have the lowest levels of 210 Po, 210 Pb and 226 Ra. Elsewhere effluents from phosphates and iron ore processing industries cause nearby enhancements. At a distance of 50-100 km, enhancements of 210 Po in edible parts of mussels and shrimps are of the order of 100 Bq.kg -1 dry weight. Estimates indicate that high consumption rates of seafood from specific waters may result in dose enhancements of 0.1-0.3 mSv.y -1 which probably affect a group of less than 1000 anglers and an unknown number of frequent mussel and shrimp consumers. Harbour sludge, with probably enhanced activity levels due to the phospho-gypsum effluents, has been used as landfill in polders around Rotterdam. Here enhanced doses of 0.3-1 mSv.y -1 may occur from consumption of local livestock produce and from inhalation of enhanced indoor radon. Further research is indicated to obtain information on effluent emissions, their associated environmental enhancements and risks. (author)

Effects of a single, oral 60 mg caffeine dose on attention in healthy adult subjects.

Science.gov (United States)

Wilhelmus, Micha Mm; Hay, Justin L; Zuiker, Rob Gja; Okkerse, Pieter; Perdrieu, Christelle; Sauser, Julien; Beaumont, Maurice; Schmitt, Jeroen; van Gerven, Joop Ma; Silber, Beata Y

2017-02-01

Caffeine induces positive effects on sustained attention, although studies assessing the acute effects of low caffeine dose (caffeine on sustained attention in tests lasting up to 45 minutes using 82 low or non-caffeine-consuming healthy male ( n=41) and female ( n=41) adults aged between 40 and 60 years. Vigilance was measured using Mackworth Clock test, Rapid Visual Information Processing Test, adaptive tracking test, saccadic eye movement and attention switch test. Effects on mood and fatigue were analysed using Bond and Lader and Caffeine Research visual analogue scales, and Samn-Perelli questionnaire. Saliva sampling was performed for both compliance and caffeine pharmacokinetic analysis. Administration of a 60 mg caffeine dose resulted in a significant improvement in sustained attention compared with the placebo. Also a significantly improved peak saccadic velocity and reaction time performance was found, and decreased error rate. Significantly increased feelings of alertness, contentment and overall mood after caffeine treatment compared with placebo were observed. This study demonstrated that in healthy adult subjects oral administration of a single 60 mg caffeine dose elicited a clear enhancement of sustained attention and alertness, measured both in multiple objective performances and in subjective scales.

Variation of oxygen enhancement ratio with radiation dose studies using 8 MeV electron beam

International Nuclear Information System (INIS)

Yerol, Narayana; Nairy, Rajesha K.; Sanjeev, Ganesh

2014-01-01

The radiobiological effects can be modified by physical, chemical and biological factors. Oxygen is one of the best known modifiers, and the biological effects are greater in the presence of oxygen. Failure to achieve complete response following radiotherapy of large tumors is attributed to the presence of radio-resistant hypoxic cells; therefore clarifying the mechanism of the oxygen effect is important. In the present study, an attempt was made to quantify Oxygen Enhancement Ratio (OER) and variation of OER as a function of dose with experimental and theoretical formulations using Saccharomyces cerevisiae D7, X2180 and rad 52 and 8 MeV electron beam from Microtron accelerator. The single cell stationary-phase cultures were obtained by growing the cells in Yeast extract: Peptone: Dextrose (YEPD) (1%:2%:2%) medium for several generations in stationary phase to a density of approximately 3 x 10 8 cells mL -1 . Cells were washed thrice by centrifugation and re-suspended to a cell concentration of 1 x 10 8 cells mL -1 in a sterile polypropylene vial for irradiation. Hypoxic conditions were achieved by incubating the samples in air tight vials at 30℃ for 30 min prior to irradiation. For euoxic samples, a cell suspension of 1 x 10 6 cells mL -1 was prepared and was thoroughly aerated by mixing before irradiation. Treated and untreated samples were suitably diluted and plated in quadruplicate on YEPD agar medium. Plates were incubated for 2-3 days at 30℃ in dark and normal atmospheric conditions and the colonies were counted. The study confirmed that, the variation of OER with dose depends upon type of cell and repair proficiency of cells. For repair proficient cells OER value has been found to increase with dose, while remain constant for repair deficient cell lines. A theoretical model has been formulated to estimate OER values. The OER value varies from 1.51 to 2.53 for D7, 2.02 to 2.98 for X2180, and 2.58 for rad 52. (author)

Organ doses and effective doses in some medical and industrial applications

International Nuclear Information System (INIS)

Keshavkumar, Biju

2000-01-01

The ICRP recommends radiation protection standards for the safe use of radiation and also prescribes the radiation protection quantities and periodically reviews them. In this context, the quantities like organ doses and effective doses are defined by ICRP. In this work we calculate these quantities and hence the conversion functions for the industrial radiation sources and those for CT and diagnostic X-ray exposures. Workers who are occupationally exposed to radiation are regularly monitored to evaluate the radiation dose received by them. It is quite possible that in an accident situation, the worker involved in the accident might not have worn a personal monitor, popularly known as the monitoring badge. In addition, even some non radiation workers (who are obviously not monitored) may also have received exposure. Under these circumstances, the persons involved are interviewed, the accident site inspected, and on the basis of realistic assumptions, the likely doses received by the exposed persons are estimated

The estimation of occupational effective dose in diagnostic radiology with two dosimeters

International Nuclear Information System (INIS)

Niklason, L.T.; Marx, M.V.; Chan, Heang-Ping

1994-01-01

Annual effective dose limits have been proposed by national and international radiation protection committees. Radiation protection agencies must decide upon a method of converting the radiation dose measured from dosimeters to an estimate of effective dose. A proposed method for the estimation of effective dose from the radiation dose to two dosimeters is presented. Correction factors are applied to an over-apron collar dose and an under-apron dose to estimate the effective dose. Correction factors are suggested for two cases, both with and without a thyroid shield. Effective dose may be estimated by the under-apron dose plus 6% of the over-collar dose if a thyroid shield is not worn or plus 2% of the over-collar dose if a thyroid shield is worn. This method provides a reasonable estimate of effective dose that is independent of lead apron thickness and accounts for the use of a thyroid shield. 17 refs., 3 tabs

[Dose rate-dependent cellular and molecular effects of ionizing radiation].

Science.gov (United States)

Przybyszewski, Waldemar M; Wideł, Maria; Szurko, Agnieszka; Maniakowski, Zbigniew

2008-09-11

The aim of radiation therapy is to kill tumor cells while minimizing damage to normal cells. The ultimate effect of radiation can be apoptotic or necrotic cell death as well as cytogenetic damage resulting in genetic instability and/or cell death. The destructive effects of radiation arise from direct and indirect ionization events leading to peroxidation of macromolecules, especially those present in lipid-rich membrane structures as well as chromatin lipids. Lipid peroxidative end-products may damage DNA and proteins. A characteristic feature of radiation-induced peroxidation is an inverse dose-rate effect (IDRE), defined as an increase in the degree of oxidation(at constant absorbed dose) accompanying a lower dose rate. On the other hand, a low dose rate can lead to the accumulation of cells in G2, the radiosensitive phase of the cell cycle since cell cycle control points are not sensitive to low dose rates. Radiation dose rate may potentially be the main factor improving radiotherapy efficacy as well as affecting the intensity of normal tissue and whole-body side effects. A better understanding of dose rate-dependent biological effects may lead to improved therapeutic intervention and limit normal tissue reaction. The study reviews basic biological effects that depend on the dose rate of ionizing radiation.

Study on mechanism of decreased lipid peroxide by low dose radiation

International Nuclear Information System (INIS)

Yamaoka, Kiyonori; Okazoe, Yoko; Akimaru, Kunihiro; Sato, E.F.; Utsumi, Kozo.

1991-01-01

We examined the effect of SOD on lipid peroxidation in biomembrane from V.E-deficient rats, in order to study the mechanism of increased SOD activities and decreased lipid peroxide by low dose irradiation. The following results were obtained. i. Active oxygen (O 2 - ) strongly enhances lipid peroxidations in biomembrane with the Fe 3+ as catalyst. ii. SOD evidently inhibits lipid peroxidations under above conditions. iii. We suggested that the effect of SOD enhanced by low dose irradiation results in inhibition of lipid peroxidation. (author)

Evaluation of two-dimensional bolus effect of immobilization/support devices on skin doses: A radiochromic EBT film dosimetry study in phantom

International Nuclear Information System (INIS)

Chiu-Tsao, Sou-Tung; Chan, Maria F.

2010-01-01

Purpose: In this study, the authors have quantified the two-dimensional (2D) perspective of skin dose increase using EBT film dosimetry in phantom in the presence of patient immobilization devices during conventional and IMRT treatments. Methods: For 6 MV conventional photon field, the authors evaluated and quantified the 2D bolus effect on skin doses for six different common patient immobilization/support devices, including carbon fiber grid with Mylar sheet, Orfit carbon fiber base plate, balsa wood board, Styrofoam, perforated AquaPlast sheet, and alpha-cradle. For 6 and 15 MV IMRT fields, a stack of two film layers positioned above a solid phantom was exposed at the air interface or in the presence of a patient alpha-cradle. All the films were scanned and the pixel values were converted to doses based on an established calibration curve. The authors determined the 2D skin dose distributions, isodose curves, and cross-sectional profiles at the surface layers with or without the immobilization/support device. The authors also generated and compared the dose area histograms (DAHs) and dose area products from the 2D skin dose distributions. Results: In contrast with 20% relative dose [(RD) dose relative to d max on central axis] at 0.0153 cm in the film layer for 6 MV 10x10 cm 2 open field, the average RDs at the same depth in the film layer were 71%, 69%, 55%, and 57% for Orfit, balsa wood, Styrofoam, and alpha-cradle, respectively. At the same depth, the RDs were 54% under a strut and 26% between neighboring struts of a carbon fiber grid with Mylar sheet, and between 34% and 56% for stretched perforated AquaPlast sheet. In the presence of the alpha-cradle for the 6 MV (15 MV) IMRT fields, the hot spot doses at the effective measurement depths of 0.0153 and 0.0459 cm were 140% and 150% (83% and 89%), respectively, of the isocenter dose. The enhancement factor was defined as the ratio of a given DAH parameter (minimum dose received in a given area) with and without

Dose and dose rate effects on coherent-to-incoherent transition of precipitates upon irradiation

Institute of Scientific and Technical Information of China (English)

LI Zhengchao

2006-01-01

A typical precipitation hardened alloy, Cu-Co dilute alloy was selected to study the precipitation behavior and irradiation effect on precipitates. It is found that the principal effect of ion irradiation on the coherent precipitates is loss of coherency, and TEM cross-section observations show that the fraction of the incoherent precipitates is dependent on dose but not on dose rate during heavy ion irradiation.

Effect of methylphenidate on enhancement of spatial learning by novel alternated dual task.

Science.gov (United States)

Veetil, Praveen Kottath; Mukkadan, Joseph Kurian

2011-01-01

The novel alternated dual task (ADT) arranged rats to learn T-maze spontaneous alternation task and radial arm maze (RAM) task alternatively, and by doing ADT, rats could acquire the tasks more easily than non alternated dual task (NADT) group. Also retention capacity of ADT group was significantly more and ADT help to learn a complex task faster than learning it in isolation from other tasks. In the present study effect of methylphenidate (MPD), a mood elevator, known to enhance learning and memory, on ADT procedure is assessed. Also effect of ADT procedure and MPD on spatial learning and memory are compared. Different groups were assigned by administering MPD (intraperitoneal injection at a dose of 3 mg/kg body weight) during different phases of behavioural experiments, and control groups received saline injection. MPD administration increased both acquisition and retention capacities. The amelioration attained for retention of complex task by ADT procedure, could be achieved by NADT rats only by administration of MPD. The influence of ADT procedure on acquisition and retention of TM and RAM tasks were similar to the effects of MPD, especially for the RAM task. MPD at low dose is found to enhance the learning and memory capacity in rats, than deteriorating it, supporting the use of MPD as a drug to treat attention deficit hyperactive disorder. The recent reports suggesting the effect of MPD only on retention and not on acquisition could not be confirmed, as enhancement for both acquisition and retention was found in this study.

Potential implications of the bystander effect on TCP and EUD when considering target volume dose heterogeneity.

Science.gov (United States)

Balderson, Michael J; Kirkby, Charles

2015-01-01

In light of in vitro evidence suggesting that radiation-induced bystander effects may enhance non-local cell killing, there is potential for impact on radiotherapy treatment planning paradigms such as the goal of delivering a uniform dose throughout the clinical target volume (CTV). This work applies a bystander effect model to calculate equivalent uniform dose (EUD) and tumor control probability (TCP) for external beam prostate treatment and compares the results with a more common model where local response is dictated exclusively by local absorbed dose. The broad assumptions applied in the bystander effect model are intended to place an upper limit on the extent of the results in a clinical context. EUD and TCP of a prostate cancer target volume under conditions of increasing dose heterogeneity were calculated using two models: One incorporating bystander effects derived from previously published in vitro bystander data ( McMahon et al. 2012 , 2013a); and one using a common linear-quadratic (LQ) response that relies exclusively on local absorbed dose. Dose through the CTV was modelled as a normal distribution, where the degree of heterogeneity was then dictated by changing the standard deviation (SD). Also, a representative clinical dose distribution was examined as cold (low dose) sub-volumes were systematically introduced. The bystander model suggests a moderate degree of dose heterogeneity throughout a target volume will yield as good or better outcome compared to a uniform dose in terms of EUD and TCP. For a typical intermediate risk prostate prescription of 78 Gy over 39 fractions maxima in EUD and TCP as a function of increasing SD occurred at SD ∼ 5 Gy. The plots only dropped below the uniform dose values for SD ∼ 10 Gy, almost 13% of the prescribed dose. Small, but potentially significant differences in the outcome metrics between the models were identified in the clinically-derived dose distribution as cold sub-volumes were introduced. In terms of

Nicotine, but not mecamylamine, enhances antidepressant-like effects of citalopram and reboxetine in the mouse forced swim and tail suspension tests

DEFF Research Database (Denmark)

Andreasen T., Jesper; Redrobe, John P

2009-01-01

and 10mg/kg citalopram and 3 and 10mg/kg reboxetine in the mTST. No concomitant locomotor stimulation was observed at the tested dose combinations. Mecamylamine was effective on its own in some tests, but did not augment the effects of citalopram or reboxetine at the doses tested. The data show...... activity and facilitates serotonin and noradrenaline release. Thus, we hypothesise that nicotine may enhance the behavioural effects of serotonin (e.g., citalopram) and/or noradrenaline (e.g., reboxetine) reuptake inhibitors. Here, we tested if nicotine enhanced the activity of citalopram or reboxetine...... in the mouse forced swim test (mFST) and the mouse tail suspension test (mTST). The potential for mecamylamine to augment antidepressant drug action was also investigated. Sub-threshold and threshold doses of citalopram (3 and 10mg/kg) or reboxetine (3, 10 and 20mg/kg) were tested alone and in combination...

Irradiation of gold nanoparticles by x-rays: Monte Carlo simulation of dose enhancements and the spatial properties of the secondary electrons production.

Science.gov (United States)

Leung, Michael K K; Chow, James C L; Chithrani, B Devika; Lee, Martin J G; Oms, Barbara; Jaffray, David A

2011-02-01

The aim of this study is to understand the characteristics of secondary electrons generated from the interaction of gold nanoparticles (GNPs) with x-rays as a function of nanoparticle size and beam energy and thereby further the understanding of GNP-enhanced radiotherapy. The effective range, deflection angle, dose deposition, energy, and interaction processes of electrons produced from the interaction of x-rays with a GNP were calculated by Monte Carlo simulations. The GEANT4 code was used to simulate and track electrons generated from a 2, 50, and 100 nm diameter GNP when it is irradiated with a 50 kVp, 250 kVp, cobalt-60, and 6 MV photon beam in water. When a GNP was present, depending on the beam energies used, secondary electron production was increased by 10- to 2000-fold compared to an absence of a GNP. Low-energy photon beams were much more efficient at interacting with the GNP by two to three orders of magnitude compared to MV energies and increased the deflection angle. GNPs with larger diameters also contributed more dose. The majority of the energy deposition was outside the GNP, rather than self-absorbed by the nanoparticle. The mean effective range of electron tracks for the beams tested ranged from approximately 3 microm to 1 mm. These simulated results yield important insights concerning the spatial distributions and elevated dose in GNP-enhanced radiotherapy. The authors conclude that the irradiation of GNP at lower photon energies will be more efficient for cell killing. This conclusion is consistent with published studies.

Attributability of health effects at low radiation doses

International Nuclear Information System (INIS)

Gonzalez, Abel

2008-01-01

Full text: A controversy still persists on whether health effects can be alleged from radiation exposure situations involving low radiation doses (e.g. below the international dose limits for the public). Arguments have evolved around the validity of the dose-response representation that is internationally used for radiation protection purposes, namely the so-called linear-non-threshold (LNT) model. The debate has been masked by the intrinsic randomness of radiation interaction at the cellular level and also by gaps in the relevant scientific knowledge on the development and expression of health effects. There has also been a vague use, abuse, and misuse of radiation-related risk concepts and quantities and their associated uncertainties. As a result, there is some ambiguity in the interpretation of the phenomena and a general lack of awareness of the implications for a number of risk-causation qualities, namely its attributes and characteristics. In particular, the LNT model has been used not only for protection purposes but also for blindly attributing actual effects to specific exposure situations. The latter has been discouraged as being a misuse of the model, but the supposed incorrectness has not been clearly proven. The paper will endeavour to demonstrate unambiguously the following thesis in relation to health effects due to low radiation doses: 1) Their existence is highly plausible. A number of epidemiological statistical assessments of sufficiently large exposed populations show that, under certain conditions, the prevalence of the effects increases with dose. From these assessments, it can be hypothesized that the occurrence of the effects at any dose, however small, appears decidedly worthy of belief. While strictly the evidence does not allow to conclude that a threshold dose level does not exist either. In fact, a formal quantitative uncertainty analysis, combining the different uncertain components of estimated radiation-related risk, with and

Attributability of Health Effects at Low Radiation Doses

International Nuclear Information System (INIS)

Gonzalez, A.J.

2011-01-01

Full text: A controversy still persists on whether health effects can be alleged from radiation exposure situations involving low radiation doses (e.g. below the international dose limits for the public). Arguments have evolved around the validity of the dose response representation that is internationally used for radiation protection purposes, namely the so-called linear-non-threshold (LNT) model. The debate has been masked by the intrinsic randomness of radiation interaction at the cellular level and also by gaps in the relevant scientific knowledge on the development and expression of health effects. There has also been a vague use, abuse, and misuse of radiation-related risk concepts and quantities and their associated uncertainties. As a result, there is some ambiguity in the interpretation of the phenomena and a general lack of awareness of the implications for a number of risk-causation qualities, namely its attributes and characteristics. In particular, the LNT model has been used not only for protection purposes but also for blindly attributing actual effects to specific exposure situations. The latter has been discouraged as being a misuse of the model, but the supposed incorrectness has not been clearly proven. The paper will endeavour to demonstrate unambiguously the following thesis in relation to health effects due to low radiation doses: (i) Their existence is highly plausible. A number of epidemiological statistical assessments of sufficiently large exposed populations show that, under certain conditions, the prevalence of the effects increases with dose. From these assessments, it can be hypothesized that the occurrence of the effects at any dose, however small, appears decidedly worthy of belief. While strictly the evidence does not allow to conclude that a threshold dose level does not exist either In fact, a formal quantitative uncertainty analysis, combining the different uncertain components of estimated radiation-related risk, with and

Influence of enhanced fluid intake on reduction of committed dose after acute intake of tritiated water vapour by occupational workers at Narora Atomic Power Station, India

International Nuclear Information System (INIS)

Pawar, S.K.; Mitra, S.R.; Chand, Lal

2001-01-01

The study of acute exposure cases of male radiation workers to tritiated water vapour (HTO) in Narora Atomic Power Station, using the bi-exponential function has provided direct practical evidence that the committed dose following an HTO exposure is directly proportional to effective half-life which in turn is inversely proportional to the fluid intake. Urine samples from these workers apparently in good health, were collected and measured for tritium concentration in urine up to maximum of 163 days after the exposure. They were advised to increase their fluid intakes to accelerate the elimination of tritium for dose mitigation. Their fluid intakes reverted to normal levels in the later stage of the post exposure period. The non-linear regression analysis of the data of tritium concentration in urine showed an effective half-life of 1.5 to 3.8 days during the period of enhanced fluid intake, 3.4 to 6.9 days during the period of normal and slightly above normal fluid intake and 23.6 to 52.3 days due to elimination of metabolized organically bound tritium. This increase in elimination rate due to enhanced fluid intake directly resulted in dose mitigation of 45.1 to 76.0 percent in different subjects. (author)

Biodegradation of an oil-hydrocarbon contaminated soil, enhanced by surfactants: Effect of the type and dose of surfactant

International Nuclear Information System (INIS)

Torres, L. G.; Galindo, C.; Rojas, N.; Iturbe, R.

2009-01-01

The aim of this work was to study the effect of different parameters, such as surfactant type an dose, soil initial hydrocarbons concentration, and soil granulometry, over the total petroleum hydrocarbons TPH degradation, as well as over the microbial count (as colony formation units CFU/g soil) along the process. (Author)

Medical irradiation and the use of the ''effective dose equivalent'' concept

International Nuclear Information System (INIS)

Persson, B.R.R.

1980-01-01

The aim of this paper is to demonstrate the use of the effective dose for all kinds of medical irradiation. In order to estimate the 'somatic effective dose' the weighting factors recommended by ICRP 26 have been separated into those for somatic effects and for genetic effects. Calculation of the effective dose in diagnostic radiology procedures must consider the various technical parameters which determine the absorbed dose in the various organs, i.e. beam quality, typical entrance dose and the number of films of each view. Knowledge about these parameters is not always well established and therefore the effective dose estimates are very uncertain. The average dose absorbed by various organs in the case of administration of radionuclides to the body depends to a much higher degree on biological parameters than in the case of external irradiation. In contrast to the variability and lack of reliability of biological data, the physical methods for internal dose calculation are quite elaborate. However, these methods have to be extended to involve the target dose from the radioactivity distributed within the remaining parts of the body. An attempt was made to estimate the somatic effective dose for the most common diagnostic X-ray and nuclear medicine procedures. This would make it possible to compare the risk of X-ray and nuclear medicine techniques on a more equitable basis. The collective effective dose from medical irradiation is estimated for various countries on the basis of reported statistical data. (H.K.)

Detection of brain metastasis. Comparison of Turbo-FLAIR imaging, T2-weighted imaging and double-dose gadolinium-enhanced MR imaging

International Nuclear Information System (INIS)

Okubo, Toshiyuki; Hayashi, Naoto; Shirouzu, Ichiro; Abe, Osamu; Ohtomo, Kuni; Sasaki, Yasuhito; Aoki, Shigeki; Wada, Akihiko

1998-01-01

The purpose of this study was to compare Turbo-FLAIR imaging, T 2 -weighted imaging, and double-dose gadolinium-enhanced MR imaging in the detection of brain metastasis. Using the three sequences, 20 consecutive patients with brain metastases were prospectively studied with a 1.5-Tesla system. Three independent, blinded readers assessed the images for the presence, size, number, and location of metastatic lesions. In the detection of large lesions (>0.5 cm), Turbo-FLAIR imaging (38/48, 79%) was not significantly different from gadolinium-enhanced imaging (42/48, 88%) (p=0.273). T 2 -weighted imaging (31/48, 65%), however, was inferior to gadolinium-enhanced imaging (p<0.05). There was no difference between Turbo-FLAIR imaging and gadolinium-enhanced imaging in the accuracy of detecting solitary brain metastasis (4/4, 100%). In conclusion, Turbo-FLAIR imaging is a useful, noninvasive screening modality for brain metastasis. Its use may lead to cost savings in the diagnosis of brain metastases and may impact positively the cost-effectiveness of treatment. (author)

Effects of low dose radiation on regulatory function between lymphocyte subsets

International Nuclear Information System (INIS)

Tian Hailin; Su Liaoyuan; Du Zeji; Zou Huawei; Wang Aiqing

1997-01-01

Four kinds of McAbs (anti CD 4 , CD 8 , CD 19 and CD 57 ) were used to separate CD 4 , CD 8 , CD 19 (B) and CD 57 (NK) lymphocyte subsets from human peripheral blood by 'Panning-direct' method. First the natural killing activity of each subsets and the regulatory functions between CD 57 and other subsets were studied. Then the effects of low dose radiation on the function of CD 57 cells and the regulatory functions between CD 57 and other subsets were studied. The results showed that the NK activity was found in all of the four subsets, with CD 57 cell having the strongest activity. When CD 4 and CD 57 cells were co-cultured, the total NK activity was higher than that of the sum of these two single subsets, i.e. there was synergistic effect between CD 4 and CD 57 cells. When CD 8 or CD 19 cells were co-cultured separately with CD 57 cells, no synergistic effect was found. Irradiation by gamma rays at doses of 50 cGy and 80 cGy was able to stimulate the function of CD 57 cells. After Cd 4 or CD 57 cells were irradiated, the total NK activity of their co-culture increased significantly. This phenomenon was not found in other subsets. This suggested that low dose radiation can enhance the synergistic action between CD 4 and CD 57 cells. So at least four subsets (CD 4 , CD 8 , CD 19 , CD 57 ) contribute to the total NK activity of peripheral blood mononuclear cells. (15 refs., 4 tabs.)

Identifying non-toxic doses of manganese for manganese-enhanced magnetic resonance imaging to map brain areas activated by operant behavior in trained rats.

Science.gov (United States)

Gálosi, Rita; Szalay, Csaba; Aradi, Mihály; Perlaki, Gábor; Pál, József; Steier, Roy; Lénárd, László; Karádi, Zoltán

2017-04-01

Manganese-enhanced magnetic resonance imaging (MEMRI) offers unique advantages such as studying brain activation in freely moving rats, but its usefulness has not been previously evaluated during operant behavior training. Manganese in a form of MnCl 2 , at a dose of 20mg/kg, was intraperitoneally infused. The administration was repeated and separated by 24h to reach the dose of 40mg/kg or 60mg/kg, respectively. Hepatotoxicity of the MnCl 2 was evaluated by determining serum aspartate aminotransferase, alanine aminotransferase, total bilirubin, albumin and protein levels. Neurological examination was also carried out. The animals were tested in visual cue discriminated operant task. Imaging was performed using a 3T clinical MR scanner. T1 values were determined before and after MnCl 2 administrations. Manganese-enhanced images of each animal were subtracted from their baseline images to calculate decrease in the T1 value (ΔT1) voxel by voxel. The subtracted T1 maps of trained animals performing visual cue discriminated operant task, and those of naive rats were compared. The dose of 60mg/kg MnCl 2 showed hepatotoxic effect, but even these animals did not exhibit neurological symptoms. The dose of 20 and 40mg/kg MnCl 2 increased the number of omissions and did not affect the accuracy of performing the visual cue discriminated operant task. Using the accumulated dose of 40mg/kg, voxels with a significant enhanced ΔT1 value were detected in the following brain areas of the visual cue discriminated operant behavior performed animals compared to those in the controls: the visual, somatosensory, motor and premotor cortices, the insula, cingulate, ectorhinal, entorhinal, perirhinal and piriform cortices, hippocampus, amygdala with amygdalohippocampal areas, dorsal striatum, nucleus accumbens core, substantia nigra, and retrorubral field. In conclusion, the MEMRI proved to be a reliable method to accomplish brain activity mapping in correlation with the operant behavior

Radio protective effects of calcium channel blockers (Deltiazem) on survival of Saccharomyces cerevisiae cells irradiated with different doses of gamma rays

Energy Technology Data Exchange (ETDEWEB)

Alya, G; Shamma, M; Sharabi, N [Atomic Energy Commission, Damascus (Syrian Arab Republic), Dept. of Molecular Biology and Biotechnology

2007-03-15

Investigations of radioprotective effects of Deltiazem (as one of the commonly used calcium channel blockers, which is used in the treatment of acute and chronic angina and spasmo angina, in addition to the treatment of different types of essential hypertension) has been carried on Saccharomyces Cerevisiae cells. Cells cultures of the most famous yeast Saccharomyces Cerevisiae (bakers yeast) were irradiated with different doses of gamma rays. Results revealed that the necessary dose of gamma rays that leads to 10% of survived cellular population (D10 value) was about 256 Gy. This irradiation dose was used then in all irradiation experiments on culture of S. Cerevisiae cells in which different concentrations of Deltiazem (55, 110, 165 mg/Kg medium) were added before and after irradiation in order to study the radio protective effect of Deltiazem. Results showed that Deltiazem enhances survival percentage of irradiated S. Cerevisiae cultures in a concentration dependent manner. This study confirmed our previous works, which had demonstrated that Deltiazem protects lethally and supralethally irradiated rats, and enhances survival of pre-irradiated Deltiazem treated animals.(author)

Radio protective effects of calcium channel blockers (Deltiazem) on survival of Saccharomyces cerevisiae cells irradiated with different doses of gamma rays

International Nuclear Information System (INIS)

Alya, G.; Shamma, M.; Sharabi, N.

2007-03-01

Investigations of radioprotective effects of Deltiazem (as one of the commonly used calcium channel blockers, which is used in the treatment of acute and chronic angina and spasmo angina, in addition to the treatment of different types of essential hypertension) has been carried on Saccharomyces Cerevisiae cells. Cells cultures of the most famous yeast Saccharomyces Cerevisiae (bakers yeast) were irradiated with different doses of gamma rays. Results revealed that the necessary dose of gamma rays that leads to 10% of survived cellular population (D10 value) was about 256 Gy. This irradiation dose was used then in all irradiation experiments on culture of S. Cerevisiae cells in which different concentrations of Deltiazem (55, 110, 165 mg/Kg medium) were added before and after irradiation in order to study the radio protective effect of Deltiazem. Results showed that Deltiazem enhances survival percentage of irradiated S. Cerevisiae cultures in a concentration dependent manner. This study confirmed our previous works, which had demonstrated that Deltiazem protects lethally and supralethally irradiated rats, and enhances survival of pre-irradiated Deltiazem treated animals.(author)

Effectance, committed effective dose equivalent and annual limits on intake: what are the changes?

International Nuclear Information System (INIS)

Kendall, G.M.; Stather, J.W.; Phipps, A.W.

1990-01-01

This paper outlines the concept of effectance, compares committed effectance with the old committed effective dose equivalent and goes on to discuss changes in the annual limits on intakes and the maximum organ doses which would result from an intake of an ALI (Annual Limit of Intake). It is shown that committed effectance is usually, but not always, higher than committed effective dose equivalent. ALIS are usually well below those resulting from the ICRP Publication 30 scheme. However, if the ALI were based only on a limit on effectance it would imply a high dose to specific organs for certain nuclides. In order to control maximum organ doses an explicit limit could be introduced. However, this would destroy some of the attractive features of the new scheme. An alternative would be a slight modification to some of the weighting factors. (author)

Collective effective dose in Europe from x-ray and nuclear medicine procedures

International Nuclear Information System (INIS)

Bly, R.; Jaervinen, H.; Jahnen, A.; Olerud, H.; Vassileva, J.; Vogiatzi, S.

2015-01-01

Population doses from radiodiagnostic (X-ray and nuclear medicine) procedures in Europe were estimated based on data collected from 36 European countries. For X-ray procedures in EU and EFTA countries (except Liechtenstein) the collective effective dose is 547 500 man Sv, resulting in a mean effective dose of 1.06 mSv per caput. For all European countries included in the survey the collective effective dose is 605 000 man Sv, resulting in a mean effective dose of 1.05 mSv per caput. For nuclear medicine procedures in EU countries and EFTA (except Liechtenstein) countries the collective effective dose is 30 700 man Sv, resulting in a mean effective dose of 0.06 mSv per caput. For all European countries included in the survey the collective effective dose is 31 100 man Sv, resulting in a mean effective dose of 0.05 mSv per caput. (authors)

Biological effect of Pulsed Dose Rate brachytherapy with stepping sources

International Nuclear Information System (INIS)

Limbergen, Erik F.M. van; Fowler, Jack F.

1996-01-01

Purpose: To explore the possible increase of radiation effect in tissues irradiated by pulsed brachytherapy (PDR), for local tissue dose-rates between those 'averaged over the whole pulse' and the instantaneous high dose rates close to the dwell positions. An earlier publication (Fowler and Mount 1992) had shown that, for dose rates (averaged for the duration of the pulse) up to 3 Gy/h, little change of isoeffect doses from continuous low dose rate (CLDR) are expected, unless larger doses per fraction than 1 Gy are used, and especially if components of very rapid repair are present with half-times of less than about 0.5 hours. However, local and transient dose rates close to stepping sources can be up to several Gy per minute. Methods: Calculations were done assuming the linear quadratic formula for radiation damage, in which only the dose-squared term is subject to repair, at a constant exponential rate. The formula developed by Dale for fractionated low-dose-rate radiotherapy was used. A constant overall time of 140 hours and constant total dose of 70 Gy were assumed throughout, the continuous low dose-rate of 0.5 Gy/h (CLDR) providing the unitary standard effects for each PDR condition. Effects of dose-rates ranging from 4 Gy/h to 120 Gy/h (HDR at 2 Gy/min) were studied, and T (1(2)) from 4 minutes to 1.5 hours. Results: Curves are presented relating the ratio of increased biological effect (proportional to log cell kill) calculated for PDR relative to CLDR. Ratios as high as 1.5 can be found for large doses per pulse (> 1 Gy) at high instantaneous dose-rates if T (1(2)) in tissues is as short as a few minutes. The major influences on effect are dose per pulse, half-time of repair in the tissue, and - when T (1(2)) is short - the instantaneous dose-rate. Maximum ratios of PDR/CLDR effect occur when the dose-rate is such that pulse duration is approximately equal to T (1(2)) of repair. Results are presented for late-responding tissues, the differences from CLDR

Fluence to Effective Dose and Effective Dose Equivalent Conversion Coefficients for Photons from 50 KeV to 10 GeV

International Nuclear Information System (INIS)

Ferrari, A.; Pelliccioni, M.; Pillon, M.

1996-07-01

Effective dose equivalent and effective dose per unit photon fluence have been calculated by the FLUKA code for various geometrical conditions of irradiation of an anthropomorphic phantom placed in a vacuum. Calculations have been performed for monoenergetic photons of energy ranging from 50 keV to 10 GeV. The agreement with the results of other authors, when existing, is generally very satisfactory

Cost-effectiveness of reduction of off-site dose

International Nuclear Information System (INIS)

McGrath, J.J.; Macphee, R.; Arbeau, N.; Miskin, J.; Scott, C.K.; Winters, E.

1988-03-01

Since the early 1970's, nuclear power plants have been designed and operated with a target of not releasing more than one percent of the licensed limits (derived emission limits) in liquid and gaseous effluents. The AECB initiated this study of the cost-effectiveness of the reduction of off-site doses as part of a review to determine if further measures to reduce off-site doses might be reasonably achievable. Atlantic Nuclear has estimated the cost of existing technology options that can be applied for a further reduction of radioactive effluents from future CANDU nuclear power plants. Detritiation, filtration, ion exchange and evaporation are included in the assessment. The costs are presented in 1987 Canadian dollars, and include capital and operating costs for a reference 50 year plant life. Darlington NGS and Point Lepreau NGS are the reference nuclear power plant types and locations. The effect resulting from the hypothetical application of each technology has been calculated as the resulting reduction in world collective radiation dose detriment. The CSA N288.1 procedure was used for local pathway analysis and the global dispersion model developed by the NEA (OECD) group of experts was used for dose calculations. The reduction in the 'collective effective dose equivalent commitment' was assumed to exist for 10,000 years, the expected life-span of solid waste repositories. No attempt was made to model world population dynamics. The collective dose reductions were calculated for a nominal world population of 10 billion persons. The estimated cost and effect of applying the technology options are summarized in a tabular form for input to further consideration of 'reasonably achievable off-site dose levels'

Chest X ray effective doses estimation in computed radiography

International Nuclear Information System (INIS)

Abdalla, Esra Abdalrhman Dfaalla

2013-06-01

Conventional chest radiography is technically difficult because of wide in tissue attenuations in the chest and limitations of screen-film systems. Computed radiography (CR) offers a different approach utilizing a photostimulable phosphor. photostimulable phosphors overcome some image quality limitations of chest imaging. The objective of this study was to estimate the effective dose in computed radiography at three hospitals in Khartoum. This study has been conducted in radiography departments in three centres Advanced Diagnostic Center, Nilain Diagnostic Center, Modern Diagnostic Center. The entrance surface dose (ESD) measurement was conducted for quality control of x-ray machines and survey of operators experimental techniques. The ESDs were measured by UNFORS dosimeter and mathematical equations to estimate patient doses during chest X rays. A total of 120 patients were examined in three centres, among them 62 were males and 58 were females. The overall mean and range of patient dosed was 0.073±0.037 (0.014-0.16) mGy per procedure while the effective dose was 3.4±01.7 (0.6-7.0) mSv per procedure. This study compared radiation doses to patients radiographic examinations of chest using computed radiology. The radiation dose was measured in three centres in Khartoum- Sudan. The results of the measured effective dose showed that the dose in chest radiography was lower in computed radiography compared to previous studies.(Author)

Does Caffeine Enhance Athletic Performance?

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Marcou Juliana

2016-04-01

Conclusion: Caffeine consumption may enhance athletic endurance, based on strong evidence, but further research needs to be conducted. High caffeine doses than the optimal, 3-6 mg/kg, before exercise does not confer any additional improvement in athletic performance. Additional, higher caffeine doses may cause side effects in athletes.

Review of time-dose effects in radiation therapy

International Nuclear Information System (INIS)

Peschel, R.E.; Fischer, J.J.

1980-01-01

A historical review of conventional fractionation offers little confidence that such treatment is optimal for all tumors. Thus manipulation of time-dose schedules may provide a relatively inexpensive yet potentially useful technique for improving therapeutic results in radiation therapy. Consideration of basic radiobiological principles and animal model data illustrates the complex and heterogeneous nature of normal tissue and tumor response to time-dose effects and supports the hypothesis that better time-dose prescriptions can be found in clinical practice. The number of possible time-dose prescriptions is very large, and a review of the clinical trials using nonconventional fractionation demonstrates that the sampled portion of the total three-dimensional space of time, fraction number, and dose has been very small. Only carefully designed clinical trials can establish the therapeutic advantage of a new treatment schedule, and methods for selecting the most promising schedules are discussed. The use of simple data reduction formulas for time-dose effects should be discarded since they ignore the very complexity and heterogeneity of tissues and tumors which may form the basis of improved clinical results

Effect of low dose radiation on apoptosis in mouse spleen

International Nuclear Information System (INIS)

Chen Dong; Liu Jiamei; Chen Aijun; Liu Shuzheng

1999-01-01

Objective: To study the effect of whole body irradiation (WBI) with different doses of X-ray on apoptosis in mouse spleen. Methods: Time course changes and dose-effect relationship of apoptosis in mouse spleen induced by WBI were observed with transmission electron microscopy (TEM) qualitatively and TUNEL method semi-quantitatively. Results: Many typical apoptotic lymphocytes were found by TEM in mouse spleen after WBI with 2 Gy. No marked alterations of ultrastructure were found following WBI with 0.075 Gy. It was observed by TUNEL that the apoptosis of splenocytes increased after high dose radiation and decreased following low dose radiation (LDR). The dose-effect relationship of radiation-induced apoptosis showed a J-shaped curve. Conclusion: The effect of different doses of ionizing radiation on apoptosis in mouse spleen was distinct. And the decrease of apoptosis after LDR is considered a manifestation of radiation hormesis

Evaluation of the effective dose and image quality of low-dose multi-detector CT for orthodontic treatment planning

International Nuclear Information System (INIS)

Chung, Gi Chung; Han, Won Jeong; Kim, Eun Kyung

2010-01-01

This study was designed to compare the effective doses from low-dose and standard-dose multi-detector CT (MDCT) scanning protocols and evaluate the image quality and the spatial resolution of the low-dose MDCT protocols for clinical use. 6-channel MDCT scanner (Siemens Medical System, Forschheim, Germany), was used for this study. Protocol of the standard-dose MDCT for the orthodontic analysis was 130 kV, 35 mAs, 1.25 mm slice width, 0.8 pitch. Those of the low-dose MDCT for orthodontic analysis and orthodontic surgery were 110 kV, 30 mAs, 1.25 mm slice width, 0.85 pitch and 110 kV, 45 mAs, 2.5 mm slice width, 0.85 pitch. Thermoluminescent dosimeters (TLDs) were placed at 31 sites throughout the levels of adult female ART head and neck phantom. Effective doses were calculated according to ICRP 1990 and 2007 recommendations. A formalin-fixed cadaver and AAPM CT performance phantom were scanned for the evaluation of subjective image quality and spatial resolution. Effective doses in μSv (E2007) were 699.1, 429.4 and 603.1 for standard-dose CT of orthodontic treatment, low-dose CT of orthodontic analysis, and low-dose CT of orthodontic surgery, respectively. The image quality from the low-dose protocol were not worse than those from the standard-dose protocol. The spatial resolutions of both standard-dose and low-dose CT images were acceptable. From the above results, it can be concluded that the low-dose MDCT protocol is preferable in obtaining CT images for orthodontic analysis and orthodontic surgery.

Evaluation of the effective dose and image quality of low-dose multi-detector CT for orthodontic treatment planning

Energy Technology Data Exchange (ETDEWEB)

Chung, Gi Chung; Han, Won Jeong; Kim, Eun Kyung [Department of Oral and Maxillofacial Radiology, School of Dentistry, Dankook University, Cheonan (Korea, Republic of)

2010-03-15

This study was designed to compare the effective doses from low-dose and standard-dose multi-detector CT (MDCT) scanning protocols and evaluate the image quality and the spatial resolution of the low-dose MDCT protocols for clinical use. 6-channel MDCT scanner (Siemens Medical System, Forschheim, Germany), was used for this study. Protocol of the standard-dose MDCT for the orthodontic analysis was 130 kV, 35 mAs, 1.25 mm slice width, 0.8 pitch. Those of the low-dose MDCT for orthodontic analysis and orthodontic surgery were 110 kV, 30 mAs, 1.25 mm slice width, 0.85 pitch and 110 kV, 45 mAs, 2.5 mm slice width, 0.85 pitch. Thermoluminescent dosimeters (TLDs) were placed at 31 sites throughout the levels of adult female ART head and neck phantom. Effective doses were calculated according to ICRP 1990 and 2007 recommendations. A formalin-fixed cadaver and AAPM CT performance phantom were scanned for the evaluation of subjective image quality and spatial resolution. Effective doses in {mu}Sv (E2007) were 699.1, 429.4 and 603.1 for standard-dose CT of orthodontic treatment, low-dose CT of orthodontic analysis, and low-dose CT of orthodontic surgery, respectively. The image quality from the low-dose protocol were not worse than those from the standard-dose protocol. The spatial resolutions of both standard-dose and low-dose CT images were acceptable. From the above results, it can be concluded that the low-dose MDCT protocol is preferable in obtaining CT images for orthodontic analysis and orthodontic surgery.

Medical effects of low doses of ionising radiation

International Nuclear Information System (INIS)

Coggle, J.E.

1990-01-01

Ionising radiation is genotoxic and causes biological effects via a chain of events involving DNA strand breaks and 'multiply damaged sites' as critical lesions that lead to cell death. The acute health effects of radiation after doses of a few gray, are due to such cell death and consequent disturbance of cell population kinetics. Because of cellular repair and repopulation there is generally a threshold dose of about 1-2 Gy below which such severe effects are not inducible. However, more subtle, sub-lethal mutational DNA damage in somatic cells of the body and the germ cells of the ovary and testis cause the two major low dose health risks -cancer induction and genetic (heritable) effects. This paper discusses some of the epidemiological and experimental evidence regarding radiation genetic effects, carcinogenesis and CNS teratogenesis. It concludes that current risk estimates imply that about 3% of all cancers; 1% of genetic disorders and between 0% and 0.3% of severe mental subnormality in the UK is attributable to the ubiquitous background radiation. The health risks associated with the medical uses of radiation are smaller, whilst the nuclear industry causes perhaps 1% of the health detriment attributable to background doses. (author)

A comparison of larval density and low dose rate irradiation effects on amphibian body size at metamorphosis

Energy Technology Data Exchange (ETDEWEB)

Stark, K.; Scott, D.E.; Tsyusko, O.; Coughlin, D.P.; Hinton, T.G.

2008-07-01

Amphibian larvae undergo substantial morphological and physiological changes as they metamorphose into adults. This period of rapid change and enhanced cell division could increase their sensitivity to external stressors. In this study, we were interested in possible differences between natural and anthropogenic stressor effects during the period just prior to metamorphosis. We studied this by exposing late-stage Scaphiopus holbrookii tadpoles in different larval densities to four irradiation dose rates (0.13, 2.4, 21, and 222 mGy d-1) from 137Cs. Life history traits important for population dynamics, such as body size at metamorphosis and development rate, were measured. Results suggest that the ecological factor larval density had a much more profound effect on juvenile body size at metamorphosis than low-dose rate radiation. The development rate measured as age at metamorphosis was not effected by the two stressors. Radiation had no impact on the endpoints we measured; giving credence to the IAEA guidance that a dose rate smaller than 10 mGy d-1 is protective of aquatic biota. (author)(tk)

A comparison of larval density and low dose rate irradiation effects on amphibian body size at metamorphosis

International Nuclear Information System (INIS)

Stark, K.; Scott, D.E.; Tsyusko, O.; Coughlin, D.P.; Hinton, T.G.

2008-01-01

Amphibian larvae undergo substantial morphological and physiological changes as they metamorphose into adults. This period of rapid change and enhanced cell division could increase their sensitivity to external stressors. In this study, we were interested in possible differences between natural and anthropogenic stressor effects during the period just prior to metamorphosis. We studied this by exposing late-stage Scaphiopus holbrookii tadpoles in different larval densities to four irradiation dose rates (0.13, 2.4, 21, and 222 mGy d -1 ) from 137 Cs. Life history traits important for population dynamics, such as body size at metamorphosis and development rate, were measured. Results suggest that the ecological factor larval density had a much more profound effect on juvenile body size at metamorphosis than low-dose rate radiation. The development rate measured as age at metamorphosis was not effected by the two stressors. Radiation had no impact on the endpoints we measured; giving credence to the IAEA guidance that a dose rate smaller than 10 mGy d -1 is protective of aquatic biota. (author)(tk)

Effects of low doses of ionizing radiation

International Nuclear Information System (INIS)

Masse, R.

2006-01-01

Several groups of human have been irradiated by accidental or medical exposure, if no gene defect has been associated to these exposures, some radioinduced cancers interesting several organs are observed among persons exposed over 100 to 200 mSv delivered at high dose rate. Numerous steps are now identified between the initial energy deposit in tissue and the aberrations of cell that lead to tumors but the sequence of events and the specific character of some of them are the subject of controversy. The stake of this controversy is the risk assessment. From the hypothesis called linear relationship without threshold is developed an approach that leads to predict cancers at any tiny dose without real scientific foundation. The nature and the intensity of biological effects depend on the quantity of energy absorbed in tissue and the modality of its distribution in space and time. The probability to reach a target (a gene) associated to the cancerating of tissue is directly proportional to the dose without any other threshold than the quantity of energy necessary to the effect, its probability of effect can be a more complex function and depends on the quality of the damage produced as well as the ability of the cell to repair the damage. These two parameters are influenced by the concentration of initial injuries in the target so by the quality of radiation and by the dose rate. The mechanisms of defence explain the low efficiency of radiation as carcinogen and then the linearity of effects in the area of low doses is certainly the least defensible scientific hypothesis for the prediction of the risks. (N.C.)

Dose reconstruction in deforming lung anatomy: Dose grid size effects and clinical implications

International Nuclear Information System (INIS)

Rosu, Mihaela; Chetty, Indrin J.; Balter, James M.; Kessler, Marc L.; McShan, Daniel L.; Ten Haken, Randall K.

2005-01-01

In this study we investigated the accumulation of dose to a deforming anatomy (such as lung) based on voxel tracking and by using time weighting factors derived from a breathing probability distribution function (p.d.f.). A mutual information registration scheme (using thin-plate spline warping) provided a transformation that allows the tracking of points between exhale and inhale treatment planning datasets (and/or intermediate state scans). The dose distributions were computed at the same resolution on each dataset using the Dose Planning Method (DPM) Monte Carlo code. Two accumulation/interpolation approaches were assessed. The first maps exhale dose grid points onto the inhale scan, estimates the doses at the 'tracked' locations by trilinear interpolation and scores the accumulated doses (via the p.d.f.) on the original exhale data set. In the second approach, the 'volume' associated with each exhale dose grid point (exhale dose voxel) is first subdivided into octants, the center of each octant is mapped to locations on the inhale dose grid and doses are estimated by trilinear interpolation. The octant doses are then averaged to form the inhale voxel dose and scored at the original exhale dose grid point location. Differences between the interpolation schemes are voxel size and tissue density dependent, but in general appear primarily only in regions with steep dose gradients (e.g., penumbra). Their magnitude (small regions of few percent differences) is less than the alterations in dose due to positional and shape changes from breathing in the first place. Thus, for sufficiently small dose grid point spacing, and relative to organ motion and deformation, differences due solely to the interpolation are unlikely to result in clinically significant differences to volume-based evaluation metrics such as mean lung dose (MLD) and tumor equivalent uniform dose (gEUD). The overall effects of deformation vary among patients. They depend on the tumor location, field

Radiation effects of high and low doses

International Nuclear Information System (INIS)

El-Naggar, A.M.

1998-01-01

The extensive proliferation of the uses and applications of atomic and nuclear energy resulted in possible repercussions on human health. The prominent features of the health hazards that may be incurred after exposure to high and low radiation doses are discussed. The physical and biological factors involved in the sequential development of radiation health effects and the different cellular responses to radiation injury are considered. The main criteria and features of radiation effects of high and low doses are comprehensively outlined

Low dose radiation enhances the Locomotor activity of D. melanogaster

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Seong, Ki Moon; Lee, Buyng Sub; Nam Seon Young; Kim, Ji Young; Yang, Kwang Hee; Choi, Tae In; Kim, Cha Soon [Radiation Effect Research Team, Radiation Health Research Institute, Korea Hydro and Nuclear Power Co., Ltd., Gyeongju (Korea, Republic of)

2013-04-15

Mild stresses at low level including radiation can induce the beneficial effects in many vertebrate and invertebrate species. However, a large amount of studies in radiation biology have focused on the detrimental effects of high dose radiation (HDR) such as the increased incidence of cancers and developmental diseases. Low dose radiation (LDR) induces biologically favorable effects in diverse fields, for example, cancer development, genomic instability, immune response, and longevity. Our previous data indicated that LDR promotes cells proliferation of which degree is not much but significant, and microarray data explained that LDR irradiated fruit flies showing the augmented immunity significantly changed the program for gene expression of many genes in Gene Ontology (GO) categories related to metabolic process. Metabolic process in development one of major contributors in organism growth, interbreeding, motility, and aging. Therefore, it is valuable to examine whether LDR change the physiological parameters related to metabolism, and how LDR regulates the metabolism in D. melanogaster. In this study, to investigate that LDR influences change of the metabolism, a representative parameter, locomotor activity. In addition, the activation of several cellular signal molecules was determined to investigate the specific molecular mechanism of LDR effects on the metabolism. We explored whether ionizing radiation affects the motility activity. We performed the RING assays to evaluate the locomotor activity, a representative parameter presenting motility of fruit flies. HDR dramatically decreased the motor activity of irradiated flies. Surprisingly, the irradiated flies at low dose radiation in both acute and chronic showed the significantly increased locomotor activity, compared to non-irradiated flies. Irradiation would induce change of the several signal pathways for flies to respond to it. The activation of some proteins involved in the cells proliferation and stress

Overexpression of caveolin-1 in lymphoblastoid TK6 cells enhances proliferation after irradiation with clinically relevant doses

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Barzan, David; Maier, Patrick; Wenz, Frederik; Herskind, Carsten [Dept. of Radiation Oncology, Univ. Medical Center Mannheim, Univ. of Heidelberg, Mannheim (Germany); Zeller, W. Jens [Pharmacology of Cancer Treatment, German Cancer Research Center, Heidelberg (Germany)

2010-02-15

Background and Purpose: The transmembrane protein caveolin-1 (CAV1) is an essential component of caveolae, small membrane invaginations involved in vesicle formation. CAV1 plays a role in signal transduction, tumor suppression and oncogene transformation. Previous studies with CAV1 knockout mice and CAV1 knockdown in pancreatic tumor cells implicated CAV1 in mediating radioresistance. The aim of this work was to test the effect of CAV1 overexpression after irradiation in human cells lacking endogenous CAV1 expression. Material and Methods: Human CAV1 was overexpressed in lymphoblastoid TK6 cells (TK6-wt) using a eukaryotic expression plasmid, pCI-CAV1, or a lentiviral SIN (self-inactivating) vector, HR'SIN-CAV1. CAV1 expression was verified in TK6 cells with Western blot analysis or intracellular FACS (fluorescence-activated cell sorting) staining. The effect of CAV1 on proliferation kinetics after irradiation of TK6 cells was measured with a growth assay. Results: TK6-wt showed no detectable endogenous CAV1 expression. Lentivirally mediated transduction with HR'SIN-CAV1 (TK6-CAV1) resulted in a considerably stronger CAV1 expression in comparison to TK6 cells electroporated with pCI-CAV1. Intracellular FACS analysis showed that 90% of transduced cells expressed CAV1. CAV1 enhanced early proliferation of TK6 cells after irradiation with a dose of 2 Gy, whereas proliferation of unirradiated cells was not affected. CAV1 also protected cells after irradiation with 4 Gy. This radioprotective effect was supported by a reduction of radiation-induced apoptosis. Conclusion: A model system for expression of exogenous CAV1 by stable lentiviral transduction of TK6 cells was established. Functional assays demonstrated enhanced early proliferation by CAV1 expression in TK6 cells after irradiation with clinically relevant doses supporting the role of CAV1 as a prosurvival factor. (orig.)

[Optimizing staff radiation protection in radiology by minimizing the effective dose].

Science.gov (United States)

von Boetticher, H; Lachmund, J; Hoffmann, W; Luska, G

2006-03-01

In the present study the optimization of radiation protection devices is achieved by minimizing the effective dose of the staff members since the stochastic radiation effects correlate to the effective dose. Radiation exposure dosimetry was performed with TLD measurements using one Alderson Phantom in the patient position and a second phantom in the typical position of the personnel. Various types of protective clothing as well as fixed shields were considered in the calculations. It was shown that the doses of the unshielded organs (thyroid, parts of the active bone marrow) contribute significantly to the effective dose of the staff. Therefore, there is no linear relationship between the shielding factors for protective garments and the effective dose. An additional thyroid protection collar reduces the effective dose by a factor of 1.7 - 3.0. X-ray protective clothing with a 0.35 mm lead equivalent and an additional thyroid protection collar provides better protection against radiation than an apron with a 0.5 mm lead equivalent but no collar. The use of thyroid protection collars is an effective preventive measure against exceeding occupational organ dose limits, and a thyroid shield also considerably reduces the effective dose. Therefore, thyroid protection collars should be a required component of anti-X protection.

Dose-rate effects of low-dropout voltage regulator at various biases

International Nuclear Information System (INIS)

Wang Yiyuan; Zheng Yuzhan; Gao Bo; Chen Rui; Fei Wuxiong; Lu Wu; Ren Diyuan

2010-01-01

A low-dropout voltage regulator, LM2941, was irradiated by 60 Co γ-rays at various dose rates and biases for investigating the total dose and dose rate effects. The radiation responses show that the key electrical parameters, including its output and dropout voltage, and the maximum output current, are sensitive to total dose and dose rates, and are significantly degraded at low dose rate and zero bias. The integrated circuits damage change with the dose rates and biases, and the dose-rate effects are relative to its electric field. (authors)

Elevated sodium chloride concentrations enhance the bystander effects induced by low dose alpha-particle irradiation

International Nuclear Information System (INIS)

Han Wei; Zhu Lingyan; Jiang Erkang; Wang Jun; Chen Shaopeng; Bao Linzhi; Zhao Ye; Xu An; Yu Zengliang; Wu Lijun

2007-01-01

Previous studies have shown that high NaCl can be genotoxic, either alone or combined with irradiation. However, little is known about the relationship between environmental NaCl at elevated conditions and radiation-induced bystander effects (RIBE). RIBE, which has been considered as non-targeted bystander responses, has been demonstrated to occur widely in various cell lines. In the present study, RIBE under the elevated NaCl culture condition was assessed in AG 1522 cells by both the induction of γ-H2AX, a reliable marker of DNA double-strand break (DSB) for the early process ( G -methyl-L-arginine, an inhibitor of nitric oxide synthase, the induced fraction of foci-positive cells was effectively inhibited both in 0.2 cGy α-particle irradiated and adjacent non-irradiated regions under either normal or elevated NaCl conditions. These results suggested that the cultures with elevated NaCl medium magnified the damage effects induced by the low dose α-particle irradiation and nitric oxide generated by irradiation was also very important in this process

Assessment of fusion facility dose rate map using mesh adaptivity enhancements of hybrid Monte Carlo/deterministic techniques

International Nuclear Information System (INIS)

Ibrahim, Ahmad M.; Wilson, Paul P.; Sawan, Mohamed E.; Mosher, Scott W.; Peplow, Douglas E.; Grove, Robert E.

2014-01-01

Highlights: •Calculate the prompt dose rate everywhere throughout the entire fusion energy facility. •Utilize FW-CADIS to accurately perform difficult neutronics calculations for fusion energy systems. •Develop three mesh adaptivity algorithms to enhance FW-CADIS efficiency in fusion-neutronics calculations. -- Abstract: Three mesh adaptivity algorithms were developed to facilitate and expedite the use of the CADIS and FW-CADIS hybrid Monte Carlo/deterministic techniques in accurate full-scale neutronics simulations of fusion energy systems with immense sizes and complicated geometries. First, a macromaterial approach enhances the fidelity of the deterministic models without changing the mesh. Second, a deterministic mesh refinement algorithm generates meshes that capture as much geometric detail as possible without exceeding a specified maximum number of mesh elements. Finally, a weight window coarsening algorithm decouples the weight window mesh and energy bins from the mesh and energy group structure of the deterministic calculations in order to remove the memory constraint of the weight window map from the deterministic mesh resolution. The three algorithms were used to enhance an FW-CADIS calculation of the prompt dose rate throughout the ITER experimental facility and resulted in a 23.3% increase in the number of mesh tally elements in which the dose rates were calculated in a 10-day Monte Carlo calculation. Additionally, because of the significant increase in the efficiency of FW-CADIS simulations, the three algorithms enabled this difficult calculation to be accurately solved on a regular computer cluster, eliminating the need for a world-class super computer

Radiation doses and correlated late effects in diagnostic radiology

International Nuclear Information System (INIS)

Gustafsson, M.

1980-04-01

Patient irradiation in diagnostic radiology was estimated from measurements of absorbed doses in different organs, assessment of the energy imparted and retrospective calculations based on literature data. Possible late biological effects, with special aspects on children, were surveyed. The dose to the lens of the eye and the possibility of shielding in carotid angiography was studied as was the absorbed dose to the thyroid gland at cardiac catheterization and angiocardiography in children. Calculations of the mean bone marrow dose and gonad doses were performed in children with chronic skeletal disease revealing large contributions from examinations of organs other than the skeleton. The dose distribution in the breast in mammography was investigated. Comparison of the energy imparted in common roentgen examinations in 1960 and 1975 showed an unexpected low decrease in spite of technical improvements. Reasons for the failing decrease are discussed. The energy imparted to children in urological examinations was reduced significantly due to introduction of high sensitivity screens and omission of dose demanding projections. Contributions to the possible late effects were estimated on the basis of the organ doses assessed. (author)

Effective doses to family members of patients treated with radioiodine-131

International Nuclear Information System (INIS)

Kocovska, M Zdraveska; Vaskova, O; Majstorov, V; Kuzmanovska, S; Gjorceva, D Pop; Jokic, V Spasic

2011-01-01

The purpose of this study was to evaluate the effective dose to family members of thyroid cancer and hyperthyroid patients treated with radioiodine-131, and also to compare the results with dose constraints proposed by the International Commission of Radiological Protection (ICRP) and the Basic Safety Standards (BSS) of the International Atomic Energy Agency (IAEA). For the estimation of the effective doses, sixty family members of sixty patients, treated with radioiodine-131, and thermoluminiscent dosimeters (Model TLD 100) were used. Thyroid cancer patients were hospitalized for three days, while hyperthyroid patients were treated on out-patient basis. The family members wore TLD in front of the torso for seven days. The radiation doses to family members of thyroid cancer patients were well below the recommended dose constraint of 1 mSv. The mean value of effective dose was 0.21 mSv (min 0.02 - max 0.51 mSv). Effective doses, higher than 1 mSv, were detected for 11 family members of hyperthyroid patients. The mean value of effective dose of family members of hyperthyroid patients was 0.87 mSv (min 0.12 - max 6.79). The estimated effective doses to family members of hyperthyroid patients were higher than the effective doses to family members of thyroid carcinoma patients. These findings may be considered when establishing new national guidelines concerning radiation protection and release of patients after a treatment with radioiodine therapy.

Nanoparticle enabled transdermal drug delivery systems for enhanced dose control and tissue targeting

Science.gov (United States)

Palmer, Brian C.; DeLouise, Lisa A.

2017-01-01

Transdermal drug delivery systems have been around for decades, and current technologies (e.g. patches, ointments, and creams) enhance the skin permeation of low molecular weight, lipophilic drugs that are efficacious at low doses. The objective of current transdermal drug delivery research is to discover ways to enhance skin penetration of larger, hydrophilic drugs and macromolecules for disease treatment and vaccination. Nanocarriers made of lipids, metals, or polymers have been successfully used to increase penetration of drugs or vaccines, control drug release, and target drugs to specific areas of skin in vivo. While more research is needed to identify the safety of nanocarriers, this technology has the potential to expand the use of transdermal routes of administration to a wide array of therapeutics. Here, we review the current state of nanoparticle skin delivery systems with special emphasis on targeting skin diseases. PMID:27983701

Nanoparticle-Enabled Transdermal Drug Delivery Systems for Enhanced Dose Control and Tissue Targeting.

Science.gov (United States)

Palmer, Brian C; DeLouise, Lisa A

2016-12-15

Transdermal drug delivery systems have been around for decades, and current technologies (e.g., patches, ointments, and creams) enhance the skin permeation of low molecular weight, lipophilic drugs that are efficacious at low doses. The objective of current transdermal drug delivery research is to discover ways to enhance skin penetration of larger, hydrophilic drugs and macromolecules for disease treatment and vaccination. Nanocarriers made of lipids, metals, or polymers have been successfully used to increase penetration of drugs or vaccines, control drug release, and target drugs to specific areas of skin in vivo. While more research is needed to identify the safety of nanocarriers, this technology has the potential to expand the use of transdermal routes of administration to a wide array of therapeutics. Here, we review the current state of nanoparticle skin delivery systems with special emphasis on targeting skin diseases.

Dose rate-dependent marrow toxicity of TBI in dogs and marrow sparing effect at high dose rate by dose fractionation.

Science.gov (United States)

Storb, R; Raff, R F; Graham, T; Appelbaum, F R; Deeg, H J; Schuening, F G; Sale, G; Seidel, K

1999-01-01

We evaluated the marrow toxicity of 200 and 300 cGy total-body irradiation (TBI) delivered at 10 and 60 cGy/min, respectively, in dogs not rescued by marrow transplant. Additionally, we compared toxicities after 300 cGy fractionated TBI (100 cGy fractions) to that after single-dose TBI at 10 and 60 cGy/min. Marrow toxicities were assessed on the basis of peripheral blood cell count changes and mortality from radiation-induced pancytopenia. TBI doses studied were just below the dose at which all dogs die despite optimal support. Specifically, 18 dogs were given single doses of 200 cGy TBI, delivered at either 10 (n=13) or 60 (n=5) cGy/min. Thirty-one dogs received 300 cGy TBI at 10 cGy/min, delivered as either single doses (n=21) or three fractions of 100 cGy each (n=10). Seventeen dogs were given 300 cGy TBI at 60 cGy/min, administered either as single doses (n=5) or three fractions of 100 cGy each (n=10). Within the limitations of the experimental design, three conclusions were drawn: 1) with 200 and 300 cGy single-dose TBI, an increase of dose rate from 10 to 60 cGy/min, respectively, caused significant increases in marrow toxicity; 2) at 60 cGy/min, dose fractionation resulted in a significant decrease in marrow toxicities, whereas such a protective effect was not seen at 10 cGy/min; and 3) with fractionated TBI, no significant differences in marrow toxicity were seen between dogs irradiated at 60 and 10 cGy/min. The reduced effectiveness of TBI when a dose of 300 cGy was divided into three fractions of 100 cGy or when dose rate was reduced from 60 cGy/min to 10 cGy/min was consistent with models of radiation toxicity that allow for repair of sublethal injury in DNA.

Radiation Therapy for Bone Metastases from Hepatocellular Carcinoma: Effect of Radiation Dose Escalation

International Nuclear Information System (INIS)

Kim, Tae Gyu; Park, Hee Chul; Lim, Do Hoon

2011-01-01

To evaluate the extent of pain response and objective response to palliative radiotherapy (RT) for bone metastases from hepatocellular carcinoma according to RT dose. From January 2007 to June 2010, palliative RT was conducted for 103 patients (223 sites) with bone metastases from hepatocellular carcinoma. Treatment sites were divided into the high RT dose and low RT dose groups by biologically effective dose (BED) of 39 Gy10. Pain responses were evaluated using the numeric rating scale. Pain scores before and after RT were compared and categorized into 'Decreased', 'No change' and 'increased'. Radiological objective responses were categorized into complete response, partial response, stable disease and progression using modified RECIST (Response Evaluation Criteria In Solid Tumors) criteria; the factors predicting patients' survival were analyzed. The median follow-up period was 6 months (range, 0 to 46 months), and the radiologic responses existed in 67 RT sites (66.3%) and 44 sites (89.8%) in the high and low RT dose group, respectively. A dose-response relationship was found in relation to RT dose (p=0.02). Pain responses were 75% and 65% in the high and low RT dose groups, respectively. However, no statistical difference in pain response was found between the two groups (p=0.24). There were no differences in the toxicity profiles between the high and low RT dose groups. Median survival from the time of bone metastases diagnosis was 11 months (range, 0 to 46 months). The Child-Pugh classification at the time of palliative RT was the only significant predictive factor for patient survival after RT. Median survival time was 14 months under Child-Pugh A and 2 months under Child-Pugh B and C. The rate of radiologic objective response was higher in the high RT dose group. Palliative RT with a high dose would provide an improvement in patient quality of life through enhanced tumor response, especially in patients with proper liver function.

Late effects of various dose-fractionation regimens

International Nuclear Information System (INIS)

Turesson, I.; Notter, G.

1983-01-01

These clinical investigations of various dose-fractionation regimens on human skin show that: The late reactions cannot be predicted from the early reactions; The dose-response curves for late reactions are much steeper than for early reactions; Equivalent doses for various fractionation schedules concerning late effects can be calculated by means of a corrected CRE (NSD) formula; the correction must be considered preliminary because further follow-up is needed. A clinical fractionation study of this type requires: Extremely careful dosimetry; Study of the same anatomical region; Very long follow-up; Studies at different effect levels; Skin reaction is the only end point we have studied systematically for different fractionation regimens. Experience with the CRE formula as a model for calculating isoeffect doses for different fractionation schedules in routine clinical use can be summarized as follows: The CRE formula has been used prospectively since 1972 in all patients; CRE-equivalent weekly doses to 5 x 2.0 Gy per week has been used. (Although the fractionation schedule is changed, the overall treatment time is still the same); The CRE range was 18 to 21 for curative radiotherapy on carcinomas; No irradiation was applied during pronounced acute reactions. No unexpected complications have been observed under these conditions

Compendium of Single Event Effects, Total Ionizing Dose, and Displacement Damage for Candidate Spacecraft Electronics for NASA

Science.gov (United States)

LaBel, Kenneth A.; OBryan, Martha V.; Chen, Dakai; Campola, Michael J.; Casey, Megan C.; Pellish, Jonathan A.; Lauenstein, Jean-Marie; Wilcox, Edward P.; Topper, Alyson D.; Ladbury, Raymond L.;