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Sample records for average effective dose

  1. Effect of anode/filter combination on average glandular dose in mammography.

    PubMed

    Biegała, Michał; Jakubowska, Teresa; Markowska, Karolina

    2015-01-01

    A comparative analysis of the mean glandular doses was conducted in 100 female patients who underwent screening mammography in 2011 and 2013. Siemens Mammomat Novation with the application of the W/Rh anode/filter combination was used in 2011, whereas in 2013 anode/filter combination was Mo/Mo or Mo/Rh. The functioning of mammography was checked and the effectiveness of the automatic exposure control (AEC) system was verified by measuring compensation of changes in the phantom thickness and measuring tube voltage. On the base of exposure parameters, an average glandular dose for each of 100 female patients was estimated. The images obtained by using AEC system had the acceptable threshold contrast visibility irrespective of the applied anode/filter combination. Mean glandular doses in the females, examined with the application of the W/Rh anode/filter combination, were on average 23.6% lower than that of the Mo/Mo or Mo/Rh anode/filter combinations. It is recommended to use a combination of the W/Rh anode /filter which exhibited lower mean glandular doses.

  2. Effect of filter on average glandular dose and image quality in digital mammography

    NASA Astrophysics Data System (ADS)

    Songsaeng, C.; Krisanachinda, A.; Theerakul, K.

    2016-03-01

    To determine the average glandular dose and entrance surface air kerma in both phantoms and patients to assess image quality for different target-filters (W/Rh and W/Ag) in digital mammography system. The compressed breast thickness, compression force, average glandular dose, entrance surface air kerma, peak kilovoltage and tube current time were recorded and compared between W/Rh and W/Ag target filter. The CNR and the figure of merit were used to determine the effect of target filter on image quality. The mean AGD of the W/Rh target filter was 1.75 mGy, the mean ESAK was 6.67 mGy, the mean CBT was 54.1 mm, the mean CF was 14 1bs. The mean AGD of W/Ag target filter was 2.7 mGy, the mean ESAK was 12.6 mGy, the mean CBT was 75.5 mm, the mean CF was 15 1bs. In phantom study, the AGD was 1.2 mGy at 4 cm, 3.3 mGy at 6 cm and 3.83 mGy at 7 cm thickness. The FOM was 24.6, CNR was 9.02 at thickness 6 cm. The FOM was 18.4, CNR was 8.6 at thickness 7 cm. The AGD from Digital Mammogram system with W/Rh of thinner CBT was lower than the AGD from W/Ag target filter.

  3. Assessment of annual average effective dose status in the cohort of medical staff in Lithuania during 1991-2013.

    PubMed

    Samerdokiene, Vitalija; Mastauskas, Albinas; Atkocius, Vydmantas

    2015-12-01

    The use of radiation sources for various medical purposes is closely related to irradiation of the medical staff, which causes harmful effects to health and an increased risk of cancer. In total, 1463 medical staff who have been occupationally exposed to sources of ionising radiation (IR) had been monitored. Records with annual dose measurements (N = 19 157) were collected and regularly analysed for a 23-y period: from 01 January 1991 to 31 December 2013. The collected annual average effective dose (AAED) data have been analysed according to different socio-demographic parameters and will be used in future investigation in order to assess cancer risk among medical staff occupationally exposed to sources of IR. A thorough analysis of data extracted from medical staff's dose records allows one to conclude that the average annual effective dose of Lithuanian medical staff occupationally exposed to sources of IR was consistently decreased from 1991 (1.75 mSv) to 2013 (0.27 mSv) (p < 0.0001).

  4. Effect of low dose sotalol on the signal averaged P wave in patients with paroxysmal atrial fibrillation.

    PubMed Central

    Stafford, P. J.; Cooper, J.; de Bono, D. P.; Vincent, R.; Garratt, C. J.

    1995-01-01

    OBJECTIVE--To investigate the effects of low dose sotalol on the signal averaged surface P wave in patients with paroxysmal atrial fibrillation. DESIGN--A longitudinal within patient crossover study. SETTING--Cardiac departments of a regional cardiothoracic centre and a district general hospital. PATIENTS--Sixteen patients with documented paroxysmal atrial fibrillation. The median (range) age of the patients was 65.5 (36-70) years; 11 were men. MAIN OUTCOME MEASURES--Analysis of the signal averaged P wave recorded from patients not receiving antiarrhythmic medication and after 4-6 weeks' treatment with sotalol. P wave limits were defined automatically by a computer algorithm. Filtered P wave duration and energies contained in frequency bands from 20, 30, 40, 60, and 80 to 150 Hz of the P wave spectrum expressed as absolute values (P20, P30, etc) and as ratios of high to low frequency energy (PR20, PR30, etc) were measured. RESULTS--No difference in P wave duration was observed between the groups studied (mean (SEM) 149 (4) without medication and 152 (3) ms with sotalol). Significant decreases in high frequency P wave energy (for example P60: 4.3 (0.4) v 3.3 (0.3) microV2.s, P = 0.003) and energy ratio (PR60: 5.6 (0.5) v 4.7 (0.6), P = 0.03) were observed during sotalol treatment. These changes were independent of heart rate. CONCLUSIONS--Treatment with low dose sotalol reduces high frequency P wave energy but does not change P wave duration. These results are consistent with the class III effect of the drug and suggest that signal averaging of the surface P wave may be a useful non-invasive measure of drug induced changes in atrial electrophysiology. PMID:8541169

  5. Assessment of the effects of CT dose in averaged x-ray CT images of a dose-sensitive polymer gel

    NASA Astrophysics Data System (ADS)

    Kairn, T.; Kakakhel, M. B.; Johnston, H.; Jirasek, A.; Trapp, J. V.

    2015-01-01

    The signal-to-noise ratio achievable in x-ray computed tomography (CT) images of polymer gels can be increased by averaging over multiple scans of each sample. However, repeated scanning delivers a small additional dose to the gel which may compromise the accuracy of the dose measurement. In this study, a NIPAM-based polymer gel was irradiated and then CT scanned 25 times, with the resulting data used to derive an averaged image and a "zero-scan" image of the gel. Comparison between these two results and the first scan of the gel showed that the averaged and zero-scan images provided better contrast, higher contrast-to- noise and higher signal-to-noise than the initial scan. The pixel values (Hounsfield units, HU) in the averaged image were not noticeably elevated, compared to the zero-scan result and the gradients used in the linear extrapolation of the zero-scan images were small and symmetrically distributed around zero. These results indicate that the averaged image was not artificially lightened by the small, additional dose delivered during CT scanning. This work demonstrates the broader usefulness of the zero-scan method as a means to verify the dosimetric accuracy of gel images derived from averaged x-ray CT data.

  6. Model selection versus model averaging in dose finding studies.

    PubMed

    Schorning, Kirsten; Bornkamp, Björn; Bretz, Frank; Dette, Holger

    2016-09-30

    A key objective of Phase II dose finding studies in clinical drug development is to adequately characterize the dose response relationship of a new drug. An important decision is then on the choice of a suitable dose response function to support dose selection for the subsequent Phase III studies. In this paper, we compare different approaches for model selection and model averaging using mathematical properties as well as simulations. We review and illustrate asymptotic properties of model selection criteria and investigate their behavior when changing the sample size but keeping the effect size constant. In a simulation study, we investigate how the various approaches perform in realistically chosen settings. Finally, the different methods are illustrated with a recently conducted Phase II dose finding study in patients with chronic obstructive pulmonary disease. Copyright © 2016 John Wiley & Sons, Ltd.

  7. AVERAGE ANNUAL SOLAR UV DOSE OF THE CONTINENTAL US CITIZEN

    EPA Science Inventory

    The average annual solar UV dose of US citizens is not known, but is required for relative risk assessments of skin cancer from UV-emitting devices. We solved this problem using a novel approach. The EPA's "National Human Activity Pattern Survey" recorded the daily ou...

  8. AVERAGE ANNUAL SOLAR UV DOSE OF THE CONTINENTAL US CITIZEN

    EPA Science Inventory

    The average annual solar UV dose of US citizens is not known, but is required for relative risk assessments of skin cancer from UV-emitting devices. We solved this problem using a novel approach. The EPA's "National Human Activity Pattern Survey" recorded the daily ou...

  9. Evaluation of scatter-to-primary ratio, grid performance and normalized average glandular dose in mammography by Monte Carlo simulation including interference and energy broadening effects

    NASA Astrophysics Data System (ADS)

    Cunha, D. M.; Tomal, A.; Poletti, M. E.

    2010-08-01

    In this work, a computational code for the study of imaging systems and dosimetry in conventional and digital mammography through Monte Carlo simulations is described. The developed code includes interference and Doppler energy broadening for simulation of elastic and inelastic photon scattering, respectively. The code estimates the contribution of scattered radiation to image quality through the spatial distribution of the scatter-to-primary ratio (S/P). It allows the inclusion of different designs of anti-scatter grids (linear or cellular), for evaluation of contrast improvement factor (CIF), Bucky factor (BF) and signal difference-to-noise ratio improvement factor (SIF). It also allows the computation of the normalized average glandular dose, \\bar{D}_{g,N} . These quantities were studied for different breast thicknesses and compositions, anode/filter combinations and tube potentials. Results showed that the S/P increases linearly with breast thickness, varying slightly with breast composition or the spectrum used. Evaluation of grid performance showed that the cellular grid provides the highest CIF with smaller BF. The SIF was also greater for the cellular grid, although both grids showed SIF < 1 for thin breasts. Results for \\bar{D}_{g,N} showed that it increases with the half-value layer (HVL) of the spectrum, decreases considerably with breast thickness and has a small dependence on the anode/filter combination. Inclusion of interference effects of breast tissues affected the values of S/P obtained with the grid up to 25%, while the energy broadening effect produced smaller variations on the evaluated quantities.

  10. Dosimetry in Mammography: Average Glandular Dose Based on Homogeneous Phantom

    NASA Astrophysics Data System (ADS)

    Benevides, Luis A.; Hintenlang, David E.

    2011-05-01

    The objective of this study was to demonstrate that a clinical dosimetry protocol that utilizes a dosimetric breast phantom series based on population anthropometric measurements can reliably predict the average glandular dose (AGD) imparted to the patient during a routine screening mammogram. AGD was calculated using entrance skin exposure and dose conversion factors based on fibroglandular content, compressed breast thickness, mammography unit parameters and modifying parameters for homogeneous phantom (phantom factor), compressed breast lateral dimensions (volume factor) and anatomical features (anatomical factor). The patient fibroglandular content was evaluated using a calibrated modified breast tissue equivalent homogeneous phantom series (BRTES-MOD) designed from anthropomorphic measurements of a screening mammography population and whose elemental composition was referenced to International Commission on Radiation Units and Measurements Report 44 and 46 tissues. The patient fibroglandular content, compressed breast thickness along with unit parameters and spectrum half-value layer were used to derive the currently used dose conversion factor (DgN). The study showed that the use of a homogeneous phantom, patient compressed breast lateral dimensions and patient anatomical features can affect AGD by as much as 12%, 3% and 1%, respectively. The protocol was found to be superior to existing methodologies. The clinical dosimetry protocol developed in this study can reliably predict the AGD imparted to an individual patient during a routine screening mammogram.

  11. Dosimetry in Mammography: Average Glandular Dose Based on Homogeneous Phantom

    SciTech Connect

    Benevides, Luis A.; Hintenlang, David E.

    2011-05-05

    The objective of this study was to demonstrate that a clinical dosimetry protocol that utilizes a dosimetric breast phantom series based on population anthropometric measurements can reliably predict the average glandular dose (AGD) imparted to the patient during a routine screening mammogram. AGD was calculated using entrance skin exposure and dose conversion factors based on fibroglandular content, compressed breast thickness, mammography unit parameters and modifying parameters for homogeneous phantom (phantom factor), compressed breast lateral dimensions (volume factor) and anatomical features (anatomical factor). The patient fibroglandular content was evaluated using a calibrated modified breast tissue equivalent homogeneous phantom series (BRTES-MOD) designed from anthropomorphic measurements of a screening mammography population and whose elemental composition was referenced to International Commission on Radiation Units and Measurements Report 44 and 46 tissues. The patient fibroglandular content, compressed breast thickness along with unit parameters and spectrum half-value layer were used to derive the currently used dose conversion factor (DgN). The study showed that the use of a homogeneous phantom, patient compressed breast lateral dimensions and patient anatomical features can affect AGD by as much as 12%, 3% and 1%, respectively. The protocol was found to be superior to existing methodologies. The clinical dosimetry protocol developed in this study can reliably predict the AGD imparted to an individual patient during a routine screening mammogram.

  12. Statistical strategies for averaging EC50 from multiple dose-response experiments.

    PubMed

    Jiang, Xiaoqi; Kopp-Schneider, Annette

    2015-11-01

    In most dose-response studies, repeated experiments are conducted to determine the EC50 value for a chemical, requiring averaging EC50 estimates from a series of experiments. Two statistical strategies, the mixed-effect modeling and the meta-analysis approach, can be applied to estimate average behavior of EC50 values over all experiments by considering the variabilities within and among experiments. We investigated these two strategies in two common cases of multiple dose-response experiments in (a) complete and explicit dose-response relationships are observed in all experiments and in (b) only in a subset of experiments. In case (a), the meta-analysis strategy is a simple and robust method to average EC50 estimates. In case (b), all experimental data sets can be first screened using the dose-response screening plot, which allows visualization and comparison of multiple dose-response experimental results. As long as more than three experiments provide information about complete dose-response relationships, the experiments that cover incomplete relationships can be excluded from the meta-analysis strategy of averaging EC50 estimates. If there are only two experiments containing complete dose-response information, the mixed-effects model approach is suggested. We subsequently provided a web application for non-statisticians to implement the proposed meta-analysis strategy of averaging EC50 estimates from multiple dose-response experiments.

  13. STUDY OF NATURAL RADIOACTIVITY (226Ra, 232Th AND 40K) IN SOIL SAMPLES FOR THE ASSESSMENT OF AVERAGE EFFECTIVE DOSE AND RADIATION HAZARDS.

    PubMed

    Bangotra, Pargin; Mehra, Rohit; Kaur, Kirandeep; Jakhu, Rajan

    2016-10-01

    The activity concentration of (226)Ra (radium), (232)Th (thorium) and (40)K (potassium) has been measured in the soil samples collected from Mansa and Muktsar districts of Punjab (India) using NaI (Tikl) gamma detector. The concentration of three radionuclides ((226)Ra, (232)Th and (40)K) in the studied area has been varied from 18±4 to 46±5, 53±7 to 98±8 and 248±54 to 756±110 Bq kg(-1), respectively. Radium equivalent activities (Raeq) have been calculated in soil samples for the assessment of the radiation hazards arising due to the use of these soil samples. The absorbed dose rate of (226)Ra, (232)Th and (40)K in studied area has been varied from 8 to 21, 33 to 61 and 9 to 25 nGy h(-1), respectively. The corresponding indoor and outdoor annual effective dose in studied area was 0.38 and 0.09 mSv, respectively. The external and internal hazard has been also calculated for the assessment of radiation hazards in the studied area.

  14. Average glandular dose and phantom image quality in mammography

    NASA Astrophysics Data System (ADS)

    Oliveira, M.; Nogueira, M. S.; Guedes, E.; Andrade, M. C.; Peixoto, J. E.; Joana, G. S.; Castro, J. G.

    2007-09-01

    Doses in mammography should be maintained as low as possible without reducing the high image quality needed for early detection of the breast cancer. The breast is composed of tissues with very close composition and densities. It increases the difficulty to detect small changes in the normal anatomical structures which may be associated with breast cancer. To achieve the standards of definition and contrast for mammography, the quality and intensity of the X-ray beam, the breast positioning and compression, the film-screen system, and the film processing have to be in optimal operational conditions. This study sought to evaluate average glandular dose (AGD) and image quality on a standard phantom in 134 mammography units in the state of Minas Gerais, Brazil, between December 2004 and May 2006. AGDs were obtained by means of entrance kerma measured with TL LiF100 dosimeters on phantom surface. Phantom images were obtained with automatic exposure technique, fixed 28 kV and molybdenum anode-filter combination. The phantom used contained structures simulating tumoral masses, microcalcifications, fibers and low contrast areas. High-resolution metallic meshes to assess image definition and a stepwedge to measure image contrast index were also inserted in the phantom. The visualization of simulated structures, the mean optical density and the contrast index allowed to classify the phantom image quality in a seven-point scale. The results showed that 54.5% of the facilities did not achieve the minimum performance level for image quality. It is mainly due to insufficient film processing observed in 61.2% of the units. AGD varied from 0.41 to 2.73 mGy with a mean value of 1.32±0.44 mGy. In all optimal quality phantom images, AGDs were in this range. Additionally, in 7.3% of the mammography units, the AGD constraint of 2 mGy was exceeded. One may conclude that dose level to patient and image quality are not in conformity to regulations in most of the facilities. This

  15. Effect of Nutritionally Relevant Doses of Long-Chain N-3 Pufa on Lipid Status, Oxidative Stress and Inflammatory Markers in an Average Middle-Aged Serbian Population

    PubMed Central

    Đuričić, Ivana; Kotur-Stevuljević, Jelena; Miljković, Milica; Kerkez, Mirko; Đorđević, Vladimir; Đurašić, Ljubomir; Šobajić, Slađana

    2015-01-01

    Summary Background This study investigated the effects of a nutritionally relevant intake of eicosapentaenoic (EPA) and docosahexaenoic (DHA) fatty acids derived from oily fish or a fish oil supplement on selected cardiovascular risk factors in average middle-aged individuals. Methods Thirty-three participants were randomized to receive salmon (oily fish) providing 274 mg EPA + 671 mg DHA/day or a commercial fish oil supplement providing 396 mg EPA + 250 mg DHA/day in a cross-over trial over an 8-week period separated by a 6-month washout period. Blood samples were collected before and after each intervention and lipids, inflammatory and oxidative stress parameters were determined. Results Plasma levels of EPA, DHA and total n-3 fatty acids significantly increased after both interventions. A decreasing trend in triglycerides was more pronounced with salmon than with the fish oil supplement, but the changes noticed were not significant. Although there were no relevant changes in inflammatory marker concentrations at the end of both interventions, significant negative correlations were noticed between total plasma n-3 fatty acids and soluble intercellular adhesion molecule and C-reactive protein throughout the whole intervention period (p<0.05). Among the oxidative stress parameters, intervention with salmon showed a prooxidative effect through a superoxide anion increase (p=0.025). A relevant positive correlation was also found between its concentration and total plasma n-3 fatty acids (p<0.05). Other oxidative stress markers were not significantly influenced by the dietary interventions applied. Conclusions Following two sets of recommendations for n-3 fatty acids intake aimed at the general public had only a moderate effect on the selected cardiovascular risk factors in average healthy middle-aged subjects over a short-term period. PMID:28356841

  16. The Model Averaging for Dichotomous Response Benchmark Dose (MADr-BMD) Tool

    EPA Pesticide Factsheets

    Providing quantal response models, which are also used in the U.S. EPA benchmark dose software suite, and generates a model-averaged dose response model to generate benchmark dose and benchmark dose lower bound estimates.

  17. Calculation of effective dose.

    PubMed

    McCollough, C H; Schueler, B A

    2000-05-01

    The concept of "effective dose" was introduced in 1975 to provide a mechanism for assessing the radiation detriment from partial body irradiations in terms of data derived from whole body irradiations. The effective dose is the mean absorbed dose from a uniform whole-body irradiation that results in the same total radiation detriment as from the nonuniform, partial-body irradiation in question. The effective dose is calculated as the weighted average of the mean absorbed dose to the various body organs and tissues, where the weighting factor is the radiation detriment for a given organ (from a whole-body irradiation) as a fraction of the total radiation detriment. In this review, effective dose equivalent and effective dose, as established by the International Commission on Radiological Protection in 1977 and 1990, respectively, are defined and various methods of calculating these quantities are presented for radionuclides, radiography, fluoroscopy, computed tomography and mammography. In order to calculate either quantity, it is first necessary to estimate the radiation dose to individual organs. One common method of determining organ doses is through Monte Carlo simulations of photon interactions within a simplified mathematical model of the human body. Several groups have performed these calculations and published their results in the form of data tables of organ dose per unit activity or exposure. These data tables are specified according to particular examination parameters, such as radiopharmaceutical, x-ray projection, x-ray beam energy spectra or patient size. Sources of these organ dose conversion coefficients are presented and differences between them are examined. The estimates of effective dose equivalent or effective dose calculated using these data, although not intended to describe the dose to an individual, can be used as a relative measure of stochastic radiation detriment. The calculated values, in units of sievert (or rem), indicate the amount of

  18. Optimal Dose of Vitamin D3 400 I.U. for Average Adults has A Significant Anti-Cancer Effect, While Widely Used 2000 I.U. or Higher Promotes Cancer: Marked Reduction of Taurine & 1α, 25(OH)2D3 Was Found In Various Cancer Tissues and Oral Intake of Optimal Dose of Taurine 175mg for Average Adults, Rather Than 500mg, Was Found to Be A New Potentially Safe and More Effective Method of Cancer Treatment.

    PubMed

    Omura, Yoshiaki; Lu, Dominic; Jones, Marilyn K; Nihrane, Abdallah; Duvvi, Harsha; Yapor, Dario; Shimotsuura, Yasuhiro; Ohki, Motomu

    2016-01-01

    During the past 10 years, the author had found that the optimal dose of Vitamin D3 400 I.U. has safe & effective anticancer effects, while commonly used 2000-5000 I.U. of Vit. D3 often creates a 2-3 time increase in cancer markers. We examined the concentration of Taurine in normal internal organs and in cancer using Bi-Digital O-Ring Test. We found that Taurine levels in normal tissue are 4-6ng. But, the amount of Taurine of average normal value of 5.0-5.25ng was strikingly reduced to 0.0025-0.0028ng in this study of several examples in adenocarcinomas of the esophagus, stomach, pancreas, colon, prostate, and lung, as well as breast cancer. The lowest Taurine levels of 0.0002-0.0005ng were found in so called Zika virus infected babies from Brazil with microcephaly. While Vitamin D3 receptor stimulant 1α, 25 (OH)2D3 in normal tissues was 0.45-0.53ng, they were reduced to 0.025-0.006ng in cancers (1/100th-1/200th of normal value), particularly in various adenocarcinomas. All of these adenocarcinomas had about 1500ng HPV-16 viral infection. In 500 breast cancers, about 97% had HPV-16. The optimal dose of Taurine for average adult has been found to be about 175mg, rather than the widely used 500mg. In addition, since Taurine is markedly reduced to close to 1/1000th-1/2000th of its normal value in these cancer tissues, we examined the effect of the optimal dose of Taurine on cancer patients. Optimal dose of Taurine produced a very significant decrease in cancer-associated parameters, such as Oncogene C-fosAb2 & Integrin α5β1 being reduced to less than 1/1,000th, and 8-OH-dG (which increases in the presence of DNA mutation) reduced to less than 1/10th. The optimal dose of Taurine 175mg for average adult various cancer patient 3 times a day alone provide beneficial effects with very significant anti-cancer effects with strikingly increased urinary excretion of bacteria, viruses, & funguses, asbestos, toxic metals & other toxic substances. However, optimal doses of

  19. Dosimetric comparison of lung stereotactic body radiotherapy treatment plans using averaged computed tomography and end-exhalation computed tomography images: Evaluation of the effect of different dose-calculation algorithms and prescription methods.

    PubMed

    Mitsuyoshi, Takamasa; Nakamura, Mitsuhiro; Matsuo, Yukinori; Ueki, Nami; Nakamura, Akira; Iizuka, Yusuke; Mampuya, Wambaka Ange; Mizowaki, Takashi; Hiraoka, Masahiro

    2016-01-01

    The purpose of this article is to quantitatively evaluate differences in dose distributions calculated using various computed tomography (CT) datasets, dose-calculation algorithms, and prescription methods in stereotactic body radiotherapy (SBRT) for patients with early-stage lung cancer. Data on 29 patients with early-stage lung cancer treated with SBRT were retrospectively analyzed. Averaged CT (Ave-CT) and expiratory CT (Ex-CT) images were reconstructed for each patient using 4-dimensional CT data. Dose distributions were initially calculated using the Ave-CT images and recalculated (in the same monitor units [MUs]) by employing Ex-CT images with the same beam arrangements. The dose-volume parameters, including D95, D90, D50, and D2 of the planning target volume (PTV), were compared between the 2 image sets. To explore the influence of dose-calculation algorithms and prescription methods on the differences in dose distributions evident between Ave-CT and Ex-CT images, we calculated dose distributions using the following 3 different algorithms: x-ray Voxel Monte Carlo (XVMC), Acuros XB (AXB), and the anisotropic analytical algorithm (AAA). We also used 2 different dose-prescription methods; the isocenter prescription and the PTV periphery prescription methods. All differences in PTV dose-volume parameters calculated using Ave-CT and Ex-CT data were within 3 percentage points (%pts) employing the isocenter prescription method, and within 1.5%pts using the PTV periphery prescription method, irrespective of which of the 3 algorithms (XVMC, AXB, and AAA) was employed. The frequencies of dose-volume parameters differing by >1%pt when the XVMC and AXB were used were greater than those associated with the use of the AAA, regardless of the dose-prescription method employed. All differences in PTV dose-volume parameters calculated using Ave-CT and Ex-CT data on patients who underwent lung SBRT were within 3%pts, regardless of the dose-calculation algorithm or the dose

  20. SU-F-BRD-16: Relative Biological Effectiveness of Double-Strand Break Induction for Modeling Cell Survival in Pristine Proton Beams of Different Dose-Averaged Linear Energy Transfers

    SciTech Connect

    Peeler, C; Bronk, L; Taleei, R; Guan, F; Patel, D; Titt, U; Mirkovic, D; Grosshans, D; Mohan, R; Stewart, R

    2015-06-15

    Purpose: High throughput in vitro experiments assessing cell survival following proton radiation indicate that both the alpha and the beta parameters of the linear quadratic model increase with increasing proton linear energy transfer (LET). We investigated the relative biological effectiveness (RBE) of double-strand break (DSB) induction as a means of explaining the experimental results. Methods: Experiments were performed with two lung cancer cell lines and a range of proton LET values (0.94 – 19.4 keV/µm) using an experimental apparatus designed to irradiate cells in a 96 well plate such that each column encounters protons of different dose-averaged LET (LETd). Traditional linear quadratic survival curve fitting was performed, and alpha, beta, and RBE values obtained. Survival curves were also fit with a model incorporating RBE of DSB induction as the sole fit parameter. Fitted values of the RBE of DSB induction were then compared to values obtained using Monte Carlo Damage Simulation (MCDS) software and energy spectra calculated with Geant4. Other parameters including alpha, beta, and number of DSBs were compared to those obtained from traditional fitting. Results: Survival curve fitting with RBE of DSB induction yielded alpha and beta parameters that increase with proton LETd, which follows from the standard method of fitting; however, relying on a single fit parameter provided more consistent trends. The fitted values of RBE of DSB induction increased beyond what is predicted from MCDS data above proton LETd of approximately 10 keV/µm. Conclusion: In order to accurately model in vitro proton irradiation experiments performed with high throughput methods, the RBE of DSB induction must increase more rapidly than predicted by MCDS above LETd of 10 keV/µm. This can be explained by considering the increased complexity of DSBs or the nature of intra-track pairwise DSB interactions in this range of LETd values. NIH Grant 2U19CA021239-35.

  1. Warfarin maintenance dose in older patients: higher average dose and wider dose frequency distribution in patients of African ancestry than those of European ancestry.

    PubMed

    Garwood, Candice L; Clemente, Jennifer L; Ibe, George N; Kandula, Vijay A; Curtis, Kristy D; Whittaker, Peter

    2010-06-15

    Studies report that warfarin doses required to maintain therapeutic anticoagulation decrease with age; however, these studies almost exclusively enrolled patients of European ancestry. Consequently, universal application of dosing paradigms based on such evidence may be confounded because ethnicity also influences dose. Therefore, we determined if warfarin dose decreased with age in Americans of African ancestry, if older African and European ancestry patients required different doses, and if their daily dose frequency distributions differed. Our chart review examined 170 patients of African ancestry and 49 patients of European ancestry cared for in our anticoagulation clinic. We calculated the average weekly dose required for each stable, anticoagulated patient to maintain an international normalized ratio of 2.0 to 3.0, determined dose averages for groups <70, 70-79, and >80 years of age and plotted dose as a function of age. The maintenance dose in patients of African ancestry decreased with age (P<0.001). In addition, older patients of African ancestry required higher average weekly doses than patients of European ancestry: 33% higher in the 70- to 79-year-old group (38.2+/-1.9 vs. 28.8+/-1.7 mg; P=0.006) and 52% in the >80-year-old group (33.2+/-1.7 vs. 21.8+/-3.8 mg; P=0.011). Therefore, 43% of older patients of African ancestry required daily doses >5mg and hence would have been under-dosed using current starting-dose guidelines. The dose frequency distribution was wider for older patients of African ancestry compared to those of European ancestry (P<0.01). The higher doses required by older patients of African ancestry indicate that strategies for initiating warfarin therapy based on studies of patients of European ancestry could result in insufficient anticoagulation and thereby potentially increase their thromboembolism risk. Copyright 2010 Elsevier Inc. All rights reserved.

  2. The balanced survivor average causal effect.

    PubMed

    Greene, Tom; Joffe, Marshall; Hu, Bo; Li, Liang; Boucher, Ken

    2013-05-07

    Statistical analysis of longitudinal outcomes is often complicated by the absence of observable values in patients who die prior to their scheduled measurement. In such cases, the longitudinal data are said to be "truncated by death" to emphasize that the longitudinal measurements are not simply missing, but are undefined after death. Recently, the truncation by death problem has been investigated using the framework of principal stratification to define the target estimand as the survivor average causal effect (SACE), which in the context of a two-group randomized clinical trial is the mean difference in the longitudinal outcome between the treatment and control groups for the principal stratum of always-survivors. The SACE is not identified without untestable assumptions. These assumptions have often been formulated in terms of a monotonicity constraint requiring that the treatment does not reduce survival in any patient, in conjunction with assumed values for mean differences in the longitudinal outcome between certain principal strata. In this paper, we introduce an alternative estimand, the balanced-SACE, which is defined as the average causal effect on the longitudinal outcome in a particular subset of the always-survivors that is balanced with respect to the potential survival times under the treatment and control. We propose a simple estimator of the balanced-SACE that compares the longitudinal outcomes between equivalent fractions of the longest surviving patients between the treatment and control groups and does not require a monotonicity assumption. We provide expressions for the large sample bias of the estimator, along with sensitivity analyses and strategies to minimize this bias. We consider statistical inference under a bootstrap resampling procedure.

  3. Analysis of Mass Averaged Tissue Doses in CAM, CAF, MAX, and FAX

    NASA Technical Reports Server (NTRS)

    Slaba, Tony C.; Qualls, Garry D.; Clowdsley, Martha S.; Blattnig, Steve R.; Simonsen, Lisa C.; Walker, Steven A.; Singleterry, Robert C.

    2009-01-01

    To estimate astronaut health risk due to space radiation, one must have the ability to calculate exposure-related quantities averaged over specific organs and tissue types. In this study, we first examine the anatomical properties of the Computerized Anatomical Man (CAM), Computerized Anatomical Female (CAF), Male Adult voXel (MAX), and Female Adult voXel (FAX) models by comparing the masses of various tissues to the reference values specified by the International Commission on Radiological Protection (ICRP). Major discrepancies are found between the CAM and CAF tissue masses and the ICRP reference data for almost all of the tissues. We next examine the distribution of target points used with the deterministic transport code HZETRN to compute mass averaged exposure quantities. A numerical algorithm is used to generate multiple point distributions for many of the effective dose tissues identified in CAM, CAF, MAX, and FAX. It is concluded that the previously published CAM and CAF point distributions were under-sampled and that the set of point distributions presented here should be adequate for future studies involving CAM, CAF, MAX, or FAX. It is concluded that MAX and FAX are more accurate than CAM and CAF for space radiation analyses.

  4. Risk-Group-Specific Dose Finding Based on an Average Toxicity Score

    PubMed Central

    Bekele, B. Nebiyou; Li, Yisheng; Ji, Yuan

    2015-01-01

    Summary We propose a Bayesian dose-finding design that accounts for two important factors, the severity of toxicity and heterogeneity in patients’ susceptibility to toxicity. We consider toxicity outcomes with various levels of severity and define appropriate scores for these severity levels. We then use a multinomial likelihood function and a Dirichlet prior to model the probabilities of these toxicity scores at each dose, and characterize the overall toxicity using an average toxicity score parameter. To address the issue of heterogeneity in patients’ susceptibility to toxicity, we categorize patients into different risk groups based on their susceptibility. A Bayesian isotonic transformation is applied to induce an order-restricted posterior inference on the average toxicity scores. We demonstrate the performance of the proposed dose-finding design using simulations based on a clinical trial in multiple myeoloma. PMID:19645698

  5. [Estimation of the Average Glandular Dose Using the Mammary Gland Image Analysis in Mammography].

    PubMed

    Otsuka, Tomoko; Teramoto, Atsushi; Asada, Yasuki; Suzuki, Shoichi; Fujita, Hiroshi; Kamiya, Satoru; Anno, Hirofumi

    2016-05-01

    Currently, the glandular dose is evaluated quantitatively on the basis of the measured data using phantom, and not in a dose based on the mammary gland structure of an individual patient. However, mammary gland structures of the patients are different from each other and mammary gland dose of an individual patient cannot be obtained by the existing methods. In this study, we present an automated estimation method of mammary gland dose by means of mammary structure which is measured automatically using mammogram. In this method, mammary gland structure is extracted by Gabor filter; mammary region is segmented by the automated thresholding. For the evaluation, mammograms of 100 patients diagnosed with category 1 were collected. Using these mammograms we compared the mammary gland ratio measured by proposed method and visual evaluation. As a result, 78% of the total cases were matched. Furthermore, the mammary gland ratio and average glandular dose among the patients with same breast thickness was matched well. These results show that the proposed method may be useful for the estimation of average glandular dose for the individual patients.

  6. Absorbed Dose and Dose Equivalent Calculations for Modeling Effective Dose

    NASA Technical Reports Server (NTRS)

    Welton, Andrew; Lee, Kerry

    2010-01-01

    While in orbit, Astronauts are exposed to a much higher dose of ionizing radiation than when on the ground. It is important to model how shielding designs on spacecraft reduce radiation effective dose pre-flight, and determine whether or not a danger to humans is presented. However, in order to calculate effective dose, dose equivalent calculations are needed. Dose equivalent takes into account an absorbed dose of radiation and the biological effectiveness of ionizing radiation. This is important in preventing long-term, stochastic radiation effects in humans spending time in space. Monte carlo simulations run with the particle transport code FLUKA, give absorbed and equivalent dose data for relevant shielding. The shielding geometry used in the dose calculations is a layered slab design, consisting of aluminum, polyethylene, and water. Water is used to simulate the soft tissues that compose the human body. The results obtained will provide information on how the shielding performs with many thicknesses of each material in the slab. This allows them to be directly applicable to modern spacecraft shielding geometries.

  7. Low-dose interpolated average CT for attenuation correction in cardiac PET/CT

    NASA Astrophysics Data System (ADS)

    Wu, Tung-Hsin; Zhang, Geoffrey; Wang, Shyh-Jen; Chen, Chih-Hao; Yang, Bang-Hung; Wu, Nien-Yun; Huang, Tzung-Chi

    2010-07-01

    Because of the advantages in the use of high photon flux and thus the short scan times of CT imaging, the traditional 68Ge scans for positron emission tomography (PET) image attenuation correction have been replaced by CT scans in the modern PET/CT technology. The combination of fast CT scan and slow PET scan often causes image misalignment between the PET and CT images due to respiration motion. Use of the average CT derived from cine CT images is reported to reduce such misalignment. However, the radiation dose to patients is higher with cine CT scans. This study introduces a method that uses breath-hold CT images and their interpolations to generate the average CT for PET image attenuation correction. Breath-hold CT sets are taken at end-inspiration and end-expiration. Deformable image registration is applied to generate a voxel-to-voxel motion matrix between the two CT sets. The motion is equally divided into 5 steps from inspiration to expiration and 5 steps from expiration to inspiration, generating a total of 8 phases of interpolated CT sets. An average CT image is generated from all the 10 phase CT images, including original inhale/exhale CT and 8 interpolated CT sets. Quantitative comparison shows that the reduction of image misalignment artifacts using the average CT from the interpolation technique for PET attenuation correction is at a similar level as that using cine average CT, while the dose to the patient from the CT scans is reduced significantly. The interpolated average CT method hence provides a low dose alternative to cine CT scans for PET attenuation correction.

  8. Verification of the method of average angular response for dose measurement on different detectors

    NASA Astrophysics Data System (ADS)

    Wang, Y.; Zhou, R.; Yang, C.

    2015-07-01

    At present most radiation dose meters have serious problems on aspects of energy response and angular response. In order to improve the accuracy of dose measurements, a method of average angular response has been proposed. The method can not only correct the energy response, but also the angular response. This method has been verified on NaI(Tl)(50 mm× 50 mm) scintillation detectors, but has not been proved on other types and sizes of detectors, In this paper the method is also verified for LaBr3(Ce) scintillation detectors and HPGe detector To apply the method, first of all, five detectors are simulated by Geant4 and average angular response values are calculated. Then experiments are performed to get the count rates of full energy peak by standard point source of 137Cs, 60Co and 152Eu. After that the dose values of five detectors are calculated with the method of average angular response. Finally experimental results are got. These results are divided into two groups to analyze the impact of detectors of various types and sizes. The result of the first group shows that the method is appropriate for different types of detector to measure dose, with deviations of less than 5% compared with theoretical values. Moreover, when the detector's energy resolution is better and the count rate of the full energy peak is calculated more precisely, the measured dose can be obtained more precisely. At the same time, the result of the second group illustrates that the method is also suited for different sizes of detectors, with deviations of less than 8% compared with theoretical values.

  9. Risk-group-specific dose finding based on an average toxicity score.

    PubMed

    Bekele, B Nebiyou; Li, Yisheng; Ji, Yuan

    2010-06-01

    We propose a Bayesian dose-finding design that accounts for two important factors, the severity of toxicity and heterogeneity in patients' susceptibility to toxicity. We consider toxicity outcomes with various levels of severity and define appropriate scores for these severity levels. We then use a multinomial-likelihood function and a Dirichlet prior to model the probabilities of these toxicity scores at each dose, and characterize the overall toxicity using an average toxicity score (ATS) parameter. To address the issue of heterogeneity in patients' susceptibility to toxicity, we categorize patients into different risk groups based on their susceptibility. A Bayesian isotonic transformation is applied to induce an order-restricted posterior inference on the ATS. We demonstrate the performance of the proposed dose-finding design using simulations based on a clinical trial in multiple myeloma.

  10. Attenuation correction of PET cardiac data with low-dose average CT in PET/CT

    SciTech Connect

    Pan Tinsu; Mawlawi, Osama; Luo, Dershan; Liu, Hui H.; Chi Paichun, M.; Mar, Martha V.; Gladish, Gregory; Truong, Mylene; Erasmus, Jeremy Jr.; Liao Zhongxing; Macapinlac, H. A.

    2006-10-15

    We proposed a low-dose average computer tomography (ACT) for attenuation correction (AC) of the PET cardiac data in PET/CT. The ACT was obtained from a cine CT scan of over one breath cycle per couch position while the patient was free breathing. We applied this technique on four patients who underwent tumor imaging with {sup 18}F-FDG in PET/CT, whose PET data showed high uptake of {sup 18}F-FDG in the heart and whose CT and PET data had misregistration. All four patients did not have known myocardiac infarction or ischemia. The patients were injected with 555-740 MBq of {sup 18}F-FDG and scanned 1 h after injection. The helical CT (HCT) data were acquired in 16 s for the coverage of 100 cm. The PET acquisition was 3 min per bed of 15 cm. The duration of cine CT acquisition per 2 cm was 5.9 s. We used a fast gantry rotation cycle time of 0.5 s to minimize motion induced reconstruction artifacts in the cine CT images, which were averaged to become the ACT images for AC of the PET data. The radiation dose was about 5 mGy for 5.9 s cine duration. The selection of 5.9 s was based on our analysis of the respiratory signals of 600 patients; 87% of the patients had average breath cycles of less than 6 s and 90% had standard deviations of less than 1 s in the period of breath cycle. In all four patient studies, registrations between the CT and the PET data were improved. An increase of average uptake in the anterior and the lateral walls up to 48% and a decrease of average uptake in the septal and the inferior walls up to 16% with ACT were observed. We also compared ACT and conventional slow scan CT (SSCT) of 4 s duration in one patient study and found ACT was better than SSCT in depicting average respiratory motion and the SSCT images showed motion-induced reconstruction artifacts. In conclusion, low-dose ACT improved registration of the CT and the PET data in the heart region in our study of four patients. ACT was superior than SSCT for depicting average respiration

  11. [Investigation of quality control and average glandular dose and image quality in digital mammography in Hokkaido].

    PubMed

    Kurowarabi, Kunio; Abe, Hiroko; Horita, Hiroshi; Kaneta, Kazuyuki

    2011-01-01

    A questionnaire survey about mammography in Hokkaido was mailed to 121 facilities from August to September 2009. We surveyed the conditions of digital mammography with regard to quality control (QC) and average glandular dose at 79 facilities in Hokkaido in 2009, and the results of the survey were compared with those of 2004. We found that digital mammography techniques were widely used across Hokkaido and that computed radiography (CR) systems were quite widespread, with 70% of facilities having them. The average glandular dose ranged from 1.04 to 2.3 mGy (mean: 1.73 mGy) for digital equipment. The results revealed several problems. Although the use of 1-, 2-, and 3-megapixel (MP) liquid crystal displays (LCDs) was not uncommon, 5-MP LCDs were used in most cases when reading digital mammograms. Facilities that have mammography equipment are unlikely to have quality control instruments for mammography. Although daily QC is performed in most facilities, further quality control for digital mammography should be developed, including that for monitors. In a second study, we evaluated the 1 Shot Phantom M Plus (1 Shot Phantom), which enables objective evaluation by providing for one physical measurement rather than a subjective visual analysis. The results indicated that the 1 Shot Phantom was very useful for digital mammography systems in daily QC testing because it enabled objectivity.

  12. The use of natural language processing on narrative medication schedules to compute average weekly dose.

    PubMed

    Lu, Chao-Chin; Leng, Jianwei; Cannon, Grant W; Zhou, Xi; Egger, Marlene; South, Brett; Burningham, Zach; Zeng, Qing; Sauer, Brian C

    2016-12-01

    Medications with non-standard dosing and unstandardized units of measurement make the estimation of prescribed dose difficult from pharmacy dispensing data. A natural language processing tool named the SIG extractor was developed to identify and extract elements from narrative medication instructions to compute average weekly doses (AWDs) for disease-modifying antirheumatic drugs. The goal of this paper is to evaluate the performance of the SIG extractor. This agreement study utilized Veterans Health Affairs pharmacy data from 2008 to 2012. The SIG extractor was designed to extract key elements from narrative medication schedules (SIGs) for 17 select medications to calculate AWD, and these medications were categorized by generic name and route of administration. The SIG extractor was evaluated against an annotator-derived reference standard for accuracy, which is the fraction of AWDs accurately computed. The overall accuracy was 89% [95% confidence interval (CI) 88%, 90%]. The accuracy was ≥85% for all medications and route combinations, except for cyclophosphamide (oral) and cyclosporine (oral), which were 79% (95%CI 72%, 85%) and 66% (95%CI 58%, 73%), respectively. The SIG extractor performed well on the majority of medications, indicating that AWD calculated by the SIG extractor can be used to improve estimation of AWD when dispensed quantity or days' supply is questionable or improbable. The working model for annotating SIGs and the SIG extractor are generalized and can easily be applied to other medications. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

  13. Biosphere Dose Conversion Factors for Reasonably Maximally Exposed Individual and Average Member of Critical Group

    SciTech Connect

    K. Montague

    2000-02-23

    The purpose of this calculation is to develop additional Biosphere Dose Conversion Factors (BDCFs) for a reasonably maximally exposed individual (RMEI) for the periods 10,000 years and 1,000,000 years after the repository closure. In addition, Biosphere Dose Conversion Factors for the average member of a critical group are calculated for those additional radionuclides postulated to reach the environment during the period after 10,000 years and up to 1,000,000 years. After the permanent closure of the repository, the engineered systems within the repository will eventually lose their abilities to contain radionuclide inventory, and the radionuclides will migrate through the geosphere and eventually enter the local water table moving toward inhabited areas. The primary release scenario is a groundwater well used for drinking water supply and irrigation, and this calculation takes these postulated releases and follows them through various pathways until they result in a dose to either a member of critical group or a reasonably maximally exposed individual. The pathways considered in this calculation include inhalation, ingestion, and direct exposure.

  14. Method for the evaluation of a average glandular dose in mammography

    SciTech Connect

    Okunade, Akintunde Akangbe

    2006-04-15

    This paper concerns a method for accurate evaluation of average glandular dose (AGD) in mammography. At different energies, the interactions of photons with tissue are not uniform. Thus, optimal accuracy in the estimation of AGD is achievable when the evaluation is carried out using the normalized glandular dose values, g(x,E), that are determined for each (monoenergetic) x-ray photon energy, E, compressed breast thickness (CBT), x, breast glandular composition, and data on photon energy distribution of the exact x-ray beam used in breast imaging. A generalized model for the values of g(x,E) that is for any arbitrary CBT ranging from 2 to 9 cm (with values that are not whole numbers inclusive, say, 4.2 cm) was developed. Along with other dosimetry formulations, this was integrated into a computer software program, GDOSE.FOR, that was developed for the evaluation of AGD received from any x-ray tube/equipment (irrespective of target-filter combination) of up to 50 kVp. Results are presented which show that the implementation of GDOSE.FOR yields values of normalized glandular dose that are in good agreement with values obtained from methodologies reported earlier in the literature. With the availability of a portable device for real-time acquisition of spectra, the model and computer software reported in this work provide for the routine evaluation of AGD received by a specific woman of known age and CBT.

  15. Determination of the absorbed dose and the average LET of space radiation in dependence on shielding conditions.

    PubMed

    Vana, N; Schoner, W; Noll, M; Fugger, M; Akatov, Y; Shurshakov, V

    1999-01-01

    The HTR method, developed for determination of absorbed dose and average LET of mixed radiation fields in space, was applied during several space missions on space station MIR, space shuttles and satellites. The method utilises the changes of peak height ratios in the glow curves in dependence on the linear energy transfer LET. Due to the small size of the dosemeters the evaluation of the variation of absorbed dose and average LET in dependence on the position of the dosemeters inside the space station is possible. The dose and LET distribution was determined during the experiment ADLET where dosemeters were exposed in two positions with different shielding conditions and during two following experiments (MIR-95, MIR-96) using six positions inside the space station. The results were compared with the shielding conditions of the positions. Calculations of the absorbed dose were carried out for comparison. Results have shown that the average LET increases with increasing absorbing thickness while the absorbed dose decreases.

  16. Lagrangian averages, averaged Lagrangians, and the mean effects of fluctuations in fluid dynamics.

    PubMed

    Holm, Darryl D.

    2002-06-01

    We begin by placing the generalized Lagrangian mean (GLM) equations for a compressible adiabatic fluid into the Euler-Poincare (EP) variational framework of fluid dynamics, for an averaged Lagrangian. This is the Lagrangian averaged Euler-Poincare (LAEP) theorem. Next, we derive a set of approximate small amplitude GLM equations (glm equations) at second order in the fluctuating displacement of a Lagrangian trajectory from its mean position. These equations express the linear and nonlinear back-reaction effects on the Eulerian mean fluid quantities by the fluctuating displacements of the Lagrangian trajectories in terms of their Eulerian second moments. The derivation of the glm equations uses the linearized relations between Eulerian and Lagrangian fluctuations, in the tradition of Lagrangian stability analysis for fluids. The glm derivation also uses the method of averaged Lagrangians, in the tradition of wave, mean flow interaction. Next, the new glm EP motion equations for incompressible ideal fluids are compared with the Euler-alpha turbulence closure equations. An alpha model is a GLM (or glm) fluid theory with a Taylor hypothesis closure. Such closures are based on the linearized fluctuation relations that determine the dynamics of the Lagrangian statistical quantities in the Euler-alpha equations. Thus, by using the LAEP theorem, we bridge between the GLM equations and the Euler-alpha closure equations, through the small-amplitude glm approximation in the EP variational framework. We conclude by highlighting a new application of the GLM, glm, and alpha-model results for Lagrangian averaged ideal magnetohydrodynamics. (c) 2002 American Institute of Physics.

  17. Optimal Dose of Intrathecal Dexmedetomidine in Lower Abdominal Surgeries in Average Indian Adult

    PubMed Central

    Bandey, Jahanara; Ozair, Erum; Asghar, Adil

    2016-01-01

    Background Dexmedetomidine, a selective alpha2 adrenoceptor agonist, has been used as adjuvant to spinal anaesthesia. Aim To find out the optimum dose of dexmedetomidine to be used in lower abdomen surgery intrathecally. Materials and Methods This was a randomized, controlled, double blinded study which included adult ASA I and II patients. They were allocated into five groups (n=20). Patients allergic to drugs to be used in the study and those with co-existing neurological disorders, coagulopathies, cardiac diseases, obesity and hypertension were excluded. Groups were designed as 2.5ml hyperbaric bupivacaine with 0.5ml saline (Control) or 0.5ml dexmedetomidine: 5mcg (D1), 10mcg (D2), 15 mcg (D3) and 20mcg (D4). Data were collected for 10 point VRS for pain, Bromage motor block, Ramsay sedation score, haemodynamics, time of first rescue analgesia (TRA) and any adverse effects and groups were analysed using one way analysis of variance (ANOVA) by SPSS16.0 (p-value <0.05 significant). Results The mean duration of analgesia and need of first rescue analgesics are 201.5±29.1 mins in control group but in D1 group 259.1±15.2 mins, D2 310.7±48.1mins, D3 540.3±51.6 mins and D4 702.4±52 mins. p=0.003. The mean highest VRS score along with analgesic requirements were significantly reduced in dexemeditomidine groups, but D3 and D4 had hypotension which needed correction. Conclusion Weighing the prolongation of anesthesia and analgesia and side effects we conclude that 10 mcg of dexmedetomidine is optimum intrathecal dose. PMID:27190922

  18. Model Uncertainty and Bayesian Model Averaged Benchmark Dose Estimation for Continuous Data

    EPA Science Inventory

    The benchmark dose (BMD) approach has gained acceptance as a valuable risk assessment tool, but risk assessors still face significant challenges associated with selecting an appropriate BMD/BMDL estimate from the results of a set of acceptable dose-response models. Current approa...

  19. Estimation and Identification of the Complier Average Causal Effect Parameter in Education RCTs

    ERIC Educational Resources Information Center

    Schochet, Peter Z.; Chiang, Hanley S.

    2011-01-01

    In randomized control trials (RCTs) in the education field, the complier average causal effect (CACE) parameter is often of policy interest, because it pertains to intervention effects for students who receive a meaningful dose of treatment services. This article uses a causal inference and instrumental variables framework to examine the…

  20. Estimation and Identification of the Complier Average Causal Effect Parameter in Education RCTs

    ERIC Educational Resources Information Center

    Schochet, Peter Z.; Chiang, Hanley S.

    2011-01-01

    In randomized control trials (RCTs) in the education field, the complier average causal effect (CACE) parameter is often of policy interest, because it pertains to intervention effects for students who receive a meaningful dose of treatment services. This article uses a causal inference and instrumental variables framework to examine the…

  1. The causal meaning of Fisher’s average effect

    PubMed Central

    LEE, JAMES J.; CHOW, CARSON C.

    2013-01-01

    Summary In order to formulate the Fundamental Theorem of Natural Selection, Fisher defined the average excess and average effect of a gene substitution. Finding these notions to be somewhat opaque, some authors have recommended reformulating Fisher’s ideas in terms of covariance and regression, which are classical concepts of statistics. We argue that Fisher intended his two averages to express a distinction between correlation and causation. On this view, the average effect is a specific weighted average of the actual phenotypic changes that result from physically changing the allelic states of homologous genes. We show that the statistical and causal conceptions of the average effect, perceived as inconsistent by Falconer, can be reconciled if certain relationships between the genotype frequencies and non-additive residuals are conserved. There are certain theory-internal considerations favouring Fisher’s original formulation in terms of causality; for example, the frequency-weighted mean of the average effects equaling zero at each locus becomes a derivable consequence rather than an arbitrary constraint. More broadly, Fisher’s distinction between correlation and causation is of critical importance to gene-trait mapping studies and the foundations of evolutionary biology. PMID:23938113

  2. Radiation: Doses, Effects, Risks.

    ERIC Educational Resources Information Center

    Lean, Geoffrey, Ed.

    Few scientific issues arouse as much public controversy as the effects of radiation. This booklet is an attempt to summarize what is known about radiation and provide a basis for further discussion and debate. The first four chapters of the booklet are based on the most recent reports to the United Nations' General Assembly by the United Nations…

  3. Effects of spatial variability and scale on areal -average evapotranspiration

    NASA Technical Reports Server (NTRS)

    Famiglietti, J. S.; Wood, Eric F.

    1993-01-01

    This paper explores the effect of spatial variability and scale on areally-averaged evapotranspiration. A spatially-distributed water and energy balance model is employed to determine the effect of explicit patterns of model parameters and atmospheric forcing on modeled areally-averaged evapotranspiration over a range of increasing spatial scales. The analysis is performed from the local scale to the catchment scale. The study area is King's Creek catchment, an 11.7 sq km watershed located on the native tallgrass prairie of Kansas. The dominant controls on the scaling behavior of catchment-average evapotranspiration are investigated by simulation, as is the existence of a threshold scale for evapotranspiration modeling, with implications for explicit versus statistical representation of important process controls. It appears that some of our findings are fairly general, and will therefore provide a framework for understanding the scaling behavior of areally-averaged evapotranspiration at the catchment and larger scales.

  4. Computing effective dose in cardiac CT

    NASA Astrophysics Data System (ADS)

    Huda, Walter; Tipnis, Sameer; Sterzik, Alexander; Schoepf, U. Joseph

    2010-07-01

    We present a method of estimating effective doses in cardiac CT that accounts for selected techniques (kV mAs-1), anatomical location of the scan and patient size. A CT dosimetry spreadsheet (ImPACT CT Patient Dosimetry Calculator) was used to estimate effective doses (E) using ICRP 103 weighting factors for a 70 kg patient undergoing cardiac CT examinations. Using dose length product (DLP) for the same scans, we obtained values of E/DLP for three CT scanners used in cardiac imaging from two vendors. E/DLP ratios were obtained as a function of the anatomical location in the chest and for x-ray tube voltages ranging from 80 to 140 kV. We also computed the ratio of the average absorbed dose in a water cylinder modeling a patient weighing W kg to the corresponding average absorbed dose in a water cylinder equivalent to a 70 kg patient. The average E/DLP for a 16 cm cardiac heart CT scan was 26 µSv (mGy cm)-1, which is about 70% higher than the current E/DLP values used for chest CT scans (i.e. 14-17 µSv (mGy cm)-1). Our cardiac E/DLP ratios are higher because the cardiac region is ~30% more radiosensitive than the chest, and use of the ICRP 103 tissue weighting factors increases cardiac CT effective doses by ~30%. Increasing the x-ray tube voltage from 80 to 140 kV increases the E/DLP conversion factor for cardiac CT by 17%. For the same incident radiation at 120 kV, doses in 45 kg adults were ~22% higher than those in 70 kg adults, whereas doses in 120 kg adults were ~28% lower. Accurate estimates of the patient effective dose in cardiac CT should use ICRP 103 tissue weighting factors, and account for a choice of scan techniques (kV mAs-1), exposed scan region, as well as patient size.

  5. The Health Effects of Income Inequality: Averages and Disparities.

    PubMed

    Truesdale, Beth C; Jencks, Christopher

    2016-01-01

    Much research has investigated the association of income inequality with average life expectancy, usually finding negative correlations that are not very robust. A smaller body of work has investigated socioeconomic disparities in life expectancy, which have widened in many countries since 1980. These two lines of work should be seen as complementary because changes in average life expectancy are unlikely to affect all socioeconomic groups equally. Although most theories imply long and variable lags between changes in income inequality and changes in health, empirical evidence is confined largely to short-term effects. Rising income inequality can affect individuals in two ways. Direct effects change individuals' own income. Indirect effects change other people's income, which can then change a society's politics, customs, and ideals, altering the behavior even of those whose own income remains unchanged. Indirect effects can thus change both average health and the slope of the relationship between individual income and health.

  6. Variations in environmental tritium doses due to meteorological data averaging and uncertainties in pathway model parameters

    SciTech Connect

    Kock, A.

    1996-05-01

    The objectives of this research are: (1) to calculate and compare off site doses from atmospheric tritium releases at the Savannah River Site using monthly versus 5 year meteorological data and annual source terms, including additional seasonal and site specific parameters not included in present annual assessments; and (2) to calculate the range of the above dose estimates based on distributions in model parameters given by uncertainty estimates found in the literature. Consideration will be given to the sensitivity of parameters given in former studies.

  7. 27 CFR 19.249 - Average effective tax rate.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2011-04-01 2011-04-01 false Average effective tax rate. 19.249 Section 19.249 Alcohol, Tobacco Products and Firearms ALCOHOL AND TOBACCO TAX AND TRADE BUREAU, DEPARTMENT OF THE TREASURY LIQUORS DISTILLED SPIRITS PLANTS Distilled Spirits Taxes Effective Tax Rates § 19...

  8. Effective doses, guidelines & regulations.

    PubMed

    Burch, Michael D

    2008-01-01

    A number of countries have developed regulations or guidelines for cyanotoxins and cyanobacteria in drinking water, and in some cases in water used for recreational activity and agriculture. The main focus internationally has been upon microcystin toxins, produced predominantly by Microcystis aeruginosa. This is because microcystins are widely regarded as the most significant potential source of human injury from cyanobacteria on a world-wide scale. Many international guidelines have taken their lead from the World Health Organization's (WHO) provisional guideline of 1 microg L(-1) for microcystin-LR in drinking-water released in 1998 (WHO 2004). The WHO guideline value is stated as being 'provisional', because it covers only microcystin-LR, for reasons that the toxicology is limited and new data for toxicity of cyanobacterial toxins are being generated. The derivation of this guideline is based upon data that there is reported human injury related to consumption of drinking water containing cyanobacteria, or from limited work with experimental animals. It was also recognised that at present the human evidence for microcystin tumor promotion is inadequate and animal evidence is limited. As a result the guideline is based upon the model of deriving a Tolerable Daily intake (TDI) from an animal study No Observed Adverse Effects Level (NOAEL), with the application of appropriate safety or uncertainty factors. The resultant WHO guideline by definition is the concentration of a toxin that does not result in any significant risk to health of the consumer over a lifetime of consumption. Following the release of this WHO provisional guideline many countries have either adopted it directly (e.g., Czech Republic, France, Japan, Korea, New Zealand, Norway, Poland, Brazil and Spain), or have adopted the same animal studies, TDI and derivation convention to arrive at slight variants based upon local requirements (e.g., Australia, Canada). Brazil currently has the most

  9. Effect of brotizolam on the averaged photopalpebral reflex in man

    PubMed Central

    Tanaka, M.; Isozaki, H.; Mizuki, Y.; Inanaga, K.

    1983-01-01

    1 The photopalpebral reflex (PPR) is a useful method to assess level of arousal. Healthy males were given either brotizolam (0.0625, 0.125, 0.25 or 0.5 mg) or placebo within a double-blind, crossover design. Changes in PPR and subjective assessments were observed for 5 h after medication. 2 Prolongation of the latencies of PPR were dose dependent, and the amplitude tended to be reduced. These effects appeared within 30 min, and lasted about 4 h. 3 The dose-response curve of the maximum prolongation of the latencies was linear. 4 Sleepiness and slight ataxia were observed after drug ingestion. Sleepiness was correlated with the prolongation of the PPR latencies. 5 Brotizolam could be a potent hypnotic, with rapid onset and moderate duration of action, and it has no severe side-effects. PMID:6661378

  10. Estimation of the Dose and Dose Rate Effectiveness Factor

    NASA Technical Reports Server (NTRS)

    Chappell, L.; Cucinotta, F. A.

    2013-01-01

    Current models to estimate radiation risk use the Life Span Study (LSS) cohort that received high doses and high dose rates of radiation. Transferring risks from these high dose rates to the low doses and dose rates received by astronauts in space is a source of uncertainty in our risk calculations. The solid cancer models recommended by BEIR VII [1], UNSCEAR [2], and Preston et al [3] is fitted adequately by a linear dose response model, which implies that low doses and dose rates would be estimated the same as high doses and dose rates. However animal and cell experiments imply there should be curvature in the dose response curve for tumor induction. Furthermore animal experiments that directly compare acute to chronic exposures show lower increases in tumor induction than acute exposures. A dose and dose rate effectiveness factor (DDREF) has been estimated and applied to transfer risks from the high doses and dose rates of the LSS cohort to low doses and dose rates such as from missions in space. The BEIR VII committee [1] combined DDREF estimates using the LSS cohort and animal experiments using Bayesian methods for their recommendation for a DDREF value of 1.5 with uncertainty. We reexamined the animal data considered by BEIR VII and included more animal data and human chromosome aberration data to improve the estimate for DDREF. Several experiments chosen by BEIR VII were deemed inappropriate for application to human risk models of solid cancer risk. Animal tumor experiments performed by Ullrich et al [4], Alpen et al [5], and Grahn et al [6] were analyzed to estimate the DDREF. Human chromosome aberration experiments performed on a sample of astronauts within NASA were also available to estimate the DDREF. The LSS cohort results reported by BEIR VII were combined with the new radiobiology results using Bayesian methods.

  11. Collision and average velocity effects on the ratchet pinch

    SciTech Connect

    Vlad, M.; Benkadda, S.

    2008-03-15

    A ratchet-type average velocity V{sup R} appears for test particles moving in a stochastic potential and a magnetic field that is space dependent. This model is developed by including particle collisions and an average velocity. We show that these components of the motion can destroy the ratchet velocity but they also can produce significant increase of V{sup R}, depending on the parameters. The amplification of the ratchet pinch is a nonlinear effect that appears in the presence of trajectory eddying.

  12. Effects of velocity averaging on the shapes of absorption lines

    NASA Technical Reports Server (NTRS)

    Pickett, H. M.

    1980-01-01

    The velocity averaging of collision cross sections produces non-Lorentz line shapes, even at densities where Doppler broadening is not apparent. The magnitude of the effects will be described using a model in which the collision broadening depends on a simple velocity power law. The effect of the modified profile on experimental measures of linewidth, shift and amplitude will be examined and an improved approximate line shape will be derived.

  13. Effective dose to patients from chest examinations with tomosynthesis.

    PubMed

    Båth, Magnus; Svalkvist, Angelica; von Wrangel, Alexa; Rismyhr-Olsson, Heidi; Cederblad, Ake

    2010-01-01

    Chest tomosynthesis, which refers to the principle of collecting low-dose projections of the chest at different angles and using these projections to reconstruct section images of the chest, is an imaging technique recently introduced to health care. The main purpose of the present work was to determine the average effective dose to patients from clinical use of chest tomosynthesis. Exposure data for two chest radiography laboratories with tomosynthesis option (Definium 8000 with VolumeRAD option, GE Healthcare, Chalfont St. Giles, UK) were registered for 20 patients with a weight between 60 and 80 kg (average weight of 70.2 kg). The recorded data were used in the Monte Carlo program PCXMC 2.0 (STUK-Radiation and Nuclear Safety Authority, Helsinki, Finland) to determine the average effective dose for each projection. The effective dose for the chest tomosynthesis examination, including a scout view and the tomosynthesis acquisition, was finally obtained by adding the effective doses from all projections. Using the weighting factors given in ICRP 103, the average effective dose for the examination was found to be 0.13 mSv, whereas the average effective dose for the conventional two-view chest radiography examination was 0.05 mSv. A conversion factor of 0.26 mSv Gy(-1) cm(-2) was found suitable for determining the effective dose from a VolumeRAD chest tomosynthesis examination from the total registered kerma-area product. In conclusion, the effective dose to a standard-sized patient (170 cm/70 kg) from a VolumeRAD chest tomosynthesis examination is ~2 % of an average chest CT and only two to three times the effective dose from the conventional two-view chest radiography examination.

  14. SU-C-207-02: A Method to Estimate the Average Planar Dose From a C-Arm CBCT Acquisition

    SciTech Connect

    Supanich, MP

    2015-06-15

    Purpose: The planar average dose in a C-arm Cone Beam CT (CBCT) acquisition had been estimated in the past by averaging the four peripheral dose measurements in a CTDI phantom and then using the standard 2/3rds peripheral and 1/3 central CTDIw method (hereafter referred to as Dw). The accuracy of this assumption has not been investigated and the purpose of this work is to test the presumed relationship. Methods: Dose measurements were made in the central plane of two consecutively placed 16cm CTDI phantoms using a 0.6cc ionization chamber at each of the 4 peripheral dose bores and in the central dose bore for a C-arm CBCT protocol. The same setup was scanned with a circular cut-out of radiosensitive gafchromic film positioned between the two phantoms to capture the planar dose distribution. Calibration curves for color pixel value after scanning were generated from film strips irradiated at different known dose levels. The planar average dose for red and green pixel values was calculated by summing the dose values in the irradiated circular film cut out. Dw was calculated using the ionization chamber measurements and film dose values at the location of each of the dose bores. Results: The planar average dose using both the red and green pixel color calibration curves were within 10% agreement of the planar average dose estimated using the Dw method of film dose values at the bore locations. Additionally, an average of the planar average doses calculated using the red and green calibration curves differed from the ionization chamber Dw estimate by only 5%. Conclusion: The method of calculating the planar average dose at the central plane of a C-arm CBCT non-360 rotation by calculating Dw from peripheral and central dose bore measurements is a reasonable approach to estimating the planar average dose. Research Grant, Siemens AG.

  15. Analysis of the track- and dose-averaged LET and LET spectra in proton therapy using the geant4 Monte Carlo code

    PubMed Central

    Guan, Fada; Peeler, Christopher; Bronk, Lawrence; Geng, Changran; Taleei, Reza; Randeniya, Sharmalee; Ge, Shuaiping; Mirkovic, Dragan; Grosshans, David; Mohan, Radhe; Titt, Uwe

    2015-01-01

    Purpose: The motivation of this study was to find and eliminate the cause of errors in dose-averaged linear energy transfer (LET) calculations from therapeutic protons in small targets, such as biological cell layers, calculated using the geant 4 Monte Carlo code. Furthermore, the purpose was also to provide a recommendation to select an appropriate LET quantity from geant 4 simulations to correlate with biological effectiveness of therapeutic protons. Methods: The authors developed a particle tracking step based strategy to calculate the average LET quantities (track-averaged LET, LETt and dose-averaged LET, LETd) using geant 4 for different tracking step size limits. A step size limit refers to the maximally allowable tracking step length. The authors investigated how the tracking step size limit influenced the calculated LETt and LETd of protons with six different step limits ranging from 1 to 500 μm in a water phantom irradiated by a 79.7-MeV clinical proton beam. In addition, the authors analyzed the detailed stochastic energy deposition information including fluence spectra and dose spectra of the energy-deposition-per-step of protons. As a reference, the authors also calculated the averaged LET and analyzed the LET spectra combining the Monte Carlo method and the deterministic method. Relative biological effectiveness (RBE) calculations were performed to illustrate the impact of different LET calculation methods on the RBE-weighted dose. Results: Simulation results showed that the step limit effect was small for LETt but significant for LETd. This resulted from differences in the energy-deposition-per-step between the fluence spectra and dose spectra at different depths in the phantom. Using the Monte Carlo particle tracking method in geant 4 can result in incorrect LETd calculation results in the dose plateau region for small step limits. The erroneous LETd results can be attributed to the algorithm to determine fluctuations in energy deposition along the

  16. Patient compliance and suboptimal bowel preparation with split-dose bowel regimen in average-risk screening colonoscopy

    PubMed Central

    Menees, Stacy B.; Kim, H. Myra; Wren, Patricia; Zikmund-Fisher, Brian J.; Elta, Grace H.; Foster, Stephanie; Korsnes, Sheryl; Graustein, Brittany; Schoenfeld, Philip

    2014-01-01

    Background Although split-dose bowel regimen is recommended in colon cancer screening and surveillance guidelines, implementation in clinical practice has seemingly lagged because of concerns of patient compliance. Objectives To assess patient compliance with the split-dose bowel regimen and assess patient- and preparation process–related factors associated with compliance and bowel preparation adequacy. Design Prospective survey cohort. Setting Tertiary care setting. Patients Average-risk patients undergoing colonoscopy for colorectal cancer screening between August 2011 and January 2013. Main Outcome Measurements Split-dose bowel regimen patient-reported compliance and bowel preparation adequacy with the Boston Bowel Preparation Scale score. Results Surveys and Boston Bowel Preparation Scale score data were completed in 462 participants; 15.4% were noncompliant with the split-dose bowel regimen, and suboptimal bowel preparation (score < 5) was reported in 16% of all procedures. White (P = .009) and married (P = .01) subjects were least likely to be noncompliant, whereas Hispanic subjects and those who reported incomes of US$75,000 or less were most likely to be noncompliant (P = .004). Participants who were noncompliant with split-dosing were less likely to follow the other laxative instructions and more likely to have their colonoscopy appointment before 10:30 am. Compliance differed by bowel preparation type (P = .003, χ2 test), with those who used MiraLAX showing the highest compliance, followed by polyethylene glycol electrolyte solution and other bowel preparations. Noncompliance with split-dose bowel preparation (odds ratio 6.7; 95% confidence interval, 3.2–14.2) was the strongest predictor of suboptimal bowel preparation. Limitations Patient self-report, performed at tertiary care center. Conclusions Overall, 1 in 7 patients do not comply with a split-dose bowel regimen. Ensuring compliance with the split-dose bowel regimen will reduce the risk of a

  17. Effects of Proton Radiation Dose, Dose Rate and Dose Fractionation on Hematopoietic Cells in Mice

    PubMed Central

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

    2012-01-01

    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. PMID:20726731

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

    PubMed

    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.

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

    SciTech Connect

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

  20. Experimental validation of heterogeneity-corrected dose-volume prescription on respiratory-averaged CT images in stereotactic body radiotherapy for moving tumors

    SciTech Connect

    Nakamura, Mitsuhiro; Miyabe, Yuki; Matsuo, Yukinori; Kamomae, Takeshi; Nakata, Manabu; Yano, Shinsuke; Sawada, Akira; Mizowaki, Takashi; Hiraoka, Masahiro

    2012-04-01

    The purpose of this study was to experimentally assess the validity of heterogeneity-corrected dose-volume prescription on respiratory-averaged computed tomography (RACT) images in stereotactic body radiotherapy (SBRT) for moving tumors. Four-dimensional computed tomography (CT) data were acquired while a dynamic anthropomorphic thorax phantom with a solitary target moved. Motion pattern was based on cos (t) with a constant respiration period of 4.0 sec along the longitudinal axis of the CT couch. The extent of motion (A{sub 1}) was set in the range of 0.0-12.0 mm at 3.0-mm intervals. Treatment planning with the heterogeneity-corrected dose-volume prescription was designed on RACT images. A new commercially available Monte Carlo algorithm of well-commissioned 6-MV photon beam was used for dose calculation. Dosimetric effects of intrafractional tumor motion were then investigated experimentally under the same conditions as 4D CT simulation using the dynamic anthropomorphic thorax phantom, films, and an ionization chamber. The passing rate of {gamma} index was 98.18%, with the criteria of 3 mm/3%. The dose error between the planned and the measured isocenter dose in moving condition was within {+-} 0.7%. From the dose area histograms on the film, the mean {+-} standard deviation of the dose covering 100% of the cross section of the target was 102.32 {+-} 1.20% (range, 100.59-103.49%). By contrast, the irradiated areas receiving more than 95% dose for A{sub 1} = 12 mm were 1.46 and 1.33 times larger than those for A{sub 1} = 0 mm in the coronal and sagittal planes, respectively. This phantom study demonstrated that the cross section of the target received 100% dose under moving conditions in both the coronal and sagittal planes, suggesting that the heterogeneity-corrected dose-volume prescription on RACT images is acceptable in SBRT for moving tumors.

  1. Thermal effects in high average power optical parametric amplifiers.

    PubMed

    Rothhardt, Jan; Demmler, Stefan; Hädrich, Steffen; Peschel, Thomas; Limpert, Jens; Tünnermann, Andreas

    2013-03-01

    Optical parametric amplifiers (OPAs) have the reputation of being average power scalable due to the instantaneous nature of the parametric process (zero quantum defect). This Letter reveals serious challenges originating from thermal load in the nonlinear crystal caused by absorption. We investigate these thermal effects in high average power OPAs based on beta barium borate. Absorption of both pump and idler waves is identified to contribute significantly to heating of the nonlinear crystal. A temperature increase of up to 148 K with respect to the environment is observed and mechanical tensile stress up to 40 MPa is found, indicating a high risk of crystal fracture under such conditions. By restricting the idler to a wavelength range far from absorption bands and removing the crystal coating we reduce the peak temperature and the resulting temperature gradient significantly. Guidelines for further power scaling of OPAs and other nonlinear devices are given.

  2. Average power effects in parametric oscillators and amplifiers

    NASA Technical Reports Server (NTRS)

    Barnes, Norman P.; Williams-Byrd, Julie A.

    1995-01-01

    Average power effects relative to the operation of parametric oscillators and amplifiers have been calculated. Temperature gradients have been calculated for both radial and longitudinal heat extraction. In many instances, the thermal load on a parametric oscillator is higher than the thermal load on a parametric amplifier with the same pump power. Having one or both these wavelengths resonant increases the chances that a generated photon will be absorbed by the nonlinear crystal. Temperature profiles and thermal diffusion time constants have been calculated for Gaussian beams, given the heat-deposition rate. With radical heat extraction the temperature profile can be expressed in a power series or approximated by a Gaussian distribution function.

  3. Notes on the effect of dose uncertainty

    SciTech Connect

    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.

  4. Volume averaging for determining the effective dispersion tensor: Closure using periodic unit cells and comparison with ensemble averaging

    NASA Astrophysics Data System (ADS)

    Wood, Brian D.; Cherblanc, Fabien; Quintard, Michel; Whitaker, Stephen

    2003-08-01

    In this work, we use the method of volume averaging to determine the effective dispersion tensor for a heterogeneous porous medium; closure for the averaged equation is obtained by solution of a concentration deviation equation over a periodic unit cell. Our purpose is to show how the method of volume averaging with closure can be rectified with the results obtained by other upscaling methods under particular conditions. Although this rectification is something that is generally believed to be true, there has been very little research that explores this issue explicitly. We show that under certain limiting (but mild) assumptions, the closure problem provides a Fourier series solution for the effective dispersion tensor. When second-order spatial stationarity is imposed on the velocity field, the method yields a simple Fourier series that converges to an integral form in the limit as the period of the unit cell approaches infinity. This limiting result is identical to the quasi-Fickian forms that have been developed previously via ensemble averaging by [1993] and recently by [2000] except in the definition of the averaging operation. As a second objective we have conducted a numerical study to evaluate the influence of the size of the averaging volume on the effective dispersion tensor and its volume averaged statistics. This second objective is complimentary in many ways to recent research reported by [1999] (via ensemble averaging) and by [1999] (via volume averaging) on the block-averaged effective dispersion tensor. The variability of the effective dispersion tensor from realization to realization is assessed by computing the volume-averaged effective dispersion tensor for an ensemble of finite fields with the same (ensemble) statistics. Ensembles were generated using three different sizes of unit cells. All three unit cell sizes yield similar results for the value of the mean effective dispersion tensor. However, the coefficient of variation depends strongly

  5. Microstructural effects on the average properties in porous battery electrodes

    NASA Astrophysics Data System (ADS)

    García-García, Ramiro; García, R. Edwin

    2016-03-01

    A theoretical framework is formulated to analytically quantify the effects of the microstructure on the average properties of porous electrodes, including reactive area density and the through-thickness tortuosity as observed in experimentally-determined tomographic sections. The proposed formulation includes the microstructural non-idealities but also captures the well-known perfectly spherical limit. Results demonstrate that in the absence of any particle alignment, the through-thickness Bruggeman exponent α, reaches an asymptotic value of α ∼ 2 / 3 as the shape of the particles become increasingly prolate (needle- or fiber-like). In contrast, the Bruggeman exponent diverges as the shape of the particles become increasingly oblate, regardless of the degree of particle alignment. For aligned particles, tortuosity can be dramatically suppressed, e.g., α → 1 / 10 for ra → 1 / 10 and MRD ∼ 40 . Particle size polydispersity impacts the porosity-tortuosity relation when the average particle size is comparable to the thickness of the electrode layers. Electrode reactivity density can be arbitrarily increased as the particles become increasingly oblate, but asymptotically reach a minimum value as the particles become increasingly prolate. In the limit of a porous electrode comprised of fiber-like particles, the area density decreases by 24% , with respect to a distribution of perfectly spherical particles.

  6. Survey of computed tomography scanners in Taiwan: Dose descriptors, dose guidance levels, and effective doses

    SciTech Connect

    Tsai, H. Y.; Tung, C. J.; Yu, C. C.; Tyan, Y. S.

    2007-04-15

    The IAEA and the ICRP recommended dose guidance levels for the most frequent computed tomography (CT) examinations to promote strategies for the optimization of radiation dose to CT patients. A national survey, including on-site measurements and questionnaires, was conducted in Taiwan in order to establish dose guidance levels and evaluate effective doses for CT. The beam quality and output and the phantom doses were measured for nine representative CT scanners. Questionnaire forms were completed by respondents from facilities of 146 CT scanners out of 285 total scanners. Information on patient, procedure, scanner, and technique for the head and body examinations was provided. The weighted computed tomography dose index (CTDI{sub w}), the dose length product (DLP), organ doses and effective dose were calculated using measured data, questionnaire information and Monte Carlo simulation results. A cost-effective analysis was applied to derive the dose guidance levels on CTDI{sub w} and DLP for several CT examinations. The mean effective dose{+-}standard deviation distributes from 1.6{+-}0.9 mSv for the routine head examination to 13{+-}11 mSv for the examination of liver, spleen, and pancreas. The surveyed results and the dose guidance levels were provided to the national authorities to develop quality control standards and protocols for CT examinations.

  7. ORGAN DOSES AND EFFECTIVE DOSE FOR FIVE PET RADIOPHARMACEUTICALS.

    PubMed

    Andersson, Martin; Johansson, Lennart; Mattsson, Sören; Minarik, David; Leide-Svegborn, Sigrid

    2016-06-01

    Diagnostic investigations with positron-emitting radiopharmaceuticals are dominated by (18)F-fluorodeoxyglucose ((18)F-FDG), but other radiopharmaceuticals are also commercially available or under development. Five of them, which are all clinically important, are (18)F-fluoride, (18)F-fluoroethyltyrosine ((18)F-FET), (18)F-deoxyfluorothymidine ((18)F-FLT), (18)F-fluorocholine ((18)F-choline) and (11)C-raclopride. To estimate the potential risk of stochastic effects (mainly lethal cancer) to a population, organ doses and effective dose values were updated for all five radiopharmaceuticals. Dose calculations were performed using the computer program IDAC2.0, which bases its calculations on the ICRP/ICRU adult reference voxel phantoms and the tissue weighting factors from ICRP publication 103. The biokinetic models were taken from ICRP publication 128. For organ doses, there are substantial changes. The only significant change in effective dose compared with previous estimations was a 46 % reduction for (18)F-fluoride. The estimated effective dose in mSv MBq(-1) was 1.5E-02 for (18)F-FET, 1.5E-02 for (18)F-FLT, 2.0E-02 for (18)F-choline, 9.0E-03 for (18)F-fluoride and 4.4E-03 for (11)C-raclopride.

  8. Effective dose from direct and indirect digital panoramic units.

    PubMed

    Lee, Gun-Sun; Kim, Jin-Soo; Seo, Yo-Seob; Kim, Jae-Duk

    2013-06-01

    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 µSv and 37.8 µSv. By using the head phantom, the effective doses from the direct digital panoramic units (37.8 µSv, 27.6 µSv) were higher than those from the indirect units (8.9 µSv, 15.9 µSv). 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.

  9. Effective dose from direct and indirect digital panoramic units

    PubMed Central

    Lee, Gun-Sun; Kim, Jin-Soo; Seo, Yo-Seob

    2013-01-01

    Purpose This study aimed to provide comparative measurements of the effective dose from direct and indirect digital panoramic units according to phantoms and exposure parameters. Materials and Methods 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. Results The effective doses of the 4 digital panoramic units ranged between 8.9 µSv and 37.8 µSv. By using the head phantom, the effective doses from the direct digital panoramic units (37.8 µSv, 27.6 µSv) were higher than those from the indirect units (8.9 µSv, 15.9 µSv). The same panoramic unit showed the difference in effective doses according to the gender of the phantom, numbers and locations of TLDs, and kVp. Conclusion 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. PMID:23807930

  10. Identification and estimation of survivor average causal effects

    PubMed Central

    Tchetgen, Eric J Tchetgen

    2014-01-01

    In longitudinal studies, outcomes ascertained at follow-up are typically undefined for individuals who die prior to the follow-up visit. In such settings, outcomes are said to be truncated by death and inference about the effects of a point treatment or exposure, restricted to individuals alive at the follow-up visit, could be biased even if as in experimental studies, treatment assignment were randomized. To account for truncation by death, the survivor average causal effect (SACE) defines the effect of treatment on the outcome for the subset of individuals who would have survived regardless of exposure status. In this paper, the author nonparametrically identifies SACE by leveraging post-exposure longitudinal correlates of survival and outcome that may also mediate the exposure effects on survival and outcome. Nonparametric identification is achieved by supposing that the longitudinal data arise from a certain nonparametric structural equations model and by making the monotonicity assumption that the effect of exposure on survival agrees in its direction across individuals. A novel weighted analysis involving a consistent estimate of the survival process is shown to produce consistent estimates of SACE. A data illustration is given, and the methods are extended to the context of time-varying exposures. We discuss a sensitivity analysis framework that relaxes assumptions about independent errors in the nonparametric structural equations model and may be used to assess the extent to which inference may be altered by a violation of key identifying assumptions. © 2014 The Authors. Statistics in Medicine published by John Wiley & Sons, Ltd. PMID:24889022

  11. Propensity scores based methods for estimating average treatment effect and average treatment effect among treated: A comparative study.

    PubMed

    Abdia, Younathan; Kulasekera, K B; Datta, Somnath; Boakye, Maxwell; Kong, Maiying

    2017-09-01

    Propensity score based statistical methods, such as matching, regression, stratification, inverse probability weighting (IPW), and doubly robust (DR) estimating equations, have become popular in estimating average treatment effect (ATE) and average treatment effect among treated (ATT) in observational studies. Propensity score is the conditional probability receiving a treatment assignment with given covariates, and propensity score is usually estimated by logistic regression. However, a misspecification of the propensity score model may result in biased estimates for ATT and ATE. As an alternative, the generalized boosting method (GBM) has been proposed to estimate the propensity score. GBM uses regression trees as weak predictors and captures nonlinear and interactive effects of the covariate. For GBM-based propensity score, only IPW methods have been investigated in the literature. In this article, we provide a comparative study of the commonly used propensity score based methods for estimating ATT and ATE, and examine their performances when propensity score is estimated by logistic regression and GBM, respectively. Extensive simulation results indicate that the estimators for ATE and ATT may vary greatly due to different methods. We concluded that (i) regression may not be suitable for estimating ATE and ATT regardless of the estimation method of propensity score; (ii) IPW and stratification usually provide reliable estimates of ATT when propensity score model is correctly specified; (iii) the estimators of ATE based on stratification, IPW, and DR are close to the underlying true value of ATE when propensity score is correctly specified by logistic regression or estimated using GBM. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. On effective dose for radiotherapy based on doses to nontarget organs and tissues.

    PubMed

    Uselmann, Adam J; Thomadsen, Bruce R

    2015-02-01

    The National Council for Radiation Protection and Measurement (NCRP) published estimates for the collective population dose and the mean effective dose to the population of the United States from medical imaging procedures for 1980/1982 and for 2006. The earlier report ignored the effective dose from radiotherapy and the latter gave a cursory discussion of the topic but again did not include it in the population exposure for various reasons. This paper explains the methodology used to calculate the effective dose in due to radiotherapy procedures in the latter NCRP report and revises the values based on more detailed modeling. This study calculated the dose to nontarget organs from radiotherapy for reference populations using CT images and published peripheral dose data. Using International Commission on Radiological Protection (ICRP) 60 weighting factors, the total effective dose to nontarget organs in radiotherapy patients is estimated as 298 ± 194 mSv per patient, while the U.S. population effective dose is 0.939 ± 0.610 mSv per person, with a collective dose of 283,000 ± 184,000 person Sv per year. Using ICRP 103 weighting factors, the effective dose is 281 ± 183 mSv per patient, 0.887 ± 0.577 mSv per person in the U.S., and 268,000 ± 174,000 person Sv per year. The uncertainty in the calculations is largely governed by variations in patient size, which was accounted for by considering a range of patient sizes and taking the average treatment site to nontarget organ distance. The methods used to estimate the effective doses from radiotherapy used in NCRP Report No. 160 have been explained and the values updated.

  13. On effective dose for radiotherapy based on doses to nontarget organs and tissues

    SciTech Connect

    Uselmann, Adam J. Thomadsen, Bruce R.

    2015-02-15

    Purpose: The National Council for Radiation Protection and Measurement (NCRP) published estimates for the collective population dose and the mean effective dose to the population of the United States from medical imaging procedures for 1980/1982 and for 2006. The earlier report ignored the effective dose from radiotherapy and the latter gave a cursory discussion of the topic but again did not include it in the population exposure for various reasons. This paper explains the methodology used to calculate the effective dose in due to radiotherapy procedures in the latter NCRP report and revises the values based on more detailed modeling. Methods: This study calculated the dose to nontarget organs from radiotherapy for reference populations using CT images and published peripheral dose data. Results: Using International Commission on Radiological Protection (ICRP) 60 weighting factors, the total effective dose to nontarget organs in radiotherapy patients is estimated as 298 ± 194 mSv per patient, while the U.S. population effective dose is 0.939 ± 0.610 mSv per person, with a collective dose of 283 000 ± 184 000 person Sv per year. Using ICRP 103 weighting factors, the effective dose is 281 ± 183 mSv per patient, 0.887 ± 0.577 mSv per person in the U.S., and 268 000 ± 174 000 person Sv per year. The uncertainty in the calculations is largely governed by variations in patient size, which was accounted for by considering a range of patient sizes and taking the average treatment site to nontarget organ distance. Conclusions: The methods used to estimate the effective doses from radiotherapy used in NCRP Report No. 160 have been explained and the values updated.

  14. Monte Carlo simulation for correlation analysis of average glandular dose by breast thickness and glandular ratio in breast tissue.

    PubMed

    Kim, Sang-Tae; Cho, Jung-Keun

    2014-01-01

    A glandular breast tissue is a radio-sensitive tissue. So during the evaluation of an X-ray mammography device, Average Glandular Dose (AGD) measurement is a very important part. In reality, it is difficult to measure AGD directly, Monte Carlo simulation was used to analyze the correlation between the AGD and breast thickness. As a result, AGDs calculated through the Monte Carlo simulation were 1.64, 1.41 and 0.88 mGy. The simulated AGDs mainly depend on the glandular ratio of the breast. With the increase of glandular breast tissue, absorption of low photon-energy increased so that the AGDs increased, too. In addition, the thicker the breast was, the more the AGD became. Consequently, this study will be used as basic data for establishing the diagnostic reference levels of mammography.

  15. Effects of Polynomial Trends on Detrending Moving Average Analysis

    NASA Astrophysics Data System (ADS)

    Shao, Ying-Hui; Gu, Gao-Feng; Jiang, Zhi-Qiang; Zhou, Wei-Xing

    2015-07-01

    The detrending moving average (DMA) algorithm is one of the best performing methods to quantify the long-term correlations in nonstationary time series. As many long-term correlated time series in real systems contain various trends, we investigate the effects of polynomial trends on the scaling behaviors and the performances of three widely used DMA methods including backward algorithm (BDMA), centered algorithm (CDMA) and forward algorithm (FDMA). We derive a general framework for polynomial trends and obtain analytical results for constant shifts and linear trends. We find that the behavior of the CDMA method is not influenced by constant shifts. In contrast, linear trends cause a crossover in the CDMA fluctuation functions. We also find that constant shifts and linear trends cause crossovers in the fluctuation functions obtained from the BDMA and FDMA methods. When a crossover exists, the scaling behavior at small scales comes from the intrinsic time series while that at large scales is dominated by the constant shifts or linear trends. We also derive analytically the expressions of crossover scales and show that the crossover scale depends on the strength of the polynomial trends, the Hurst index, and in some cases (linear trends for BDMA and FDMA) the length of the time series. In all cases, the BDMA and the FDMA behave almost the same under the influence of constant shifts or linear trends. Extensive numerical experiments confirm excellently the analytical derivations. We conclude that the CDMA method outperforms the BDMA and FDMA methods in the presence of polynomial trends.

  16. Analysis of the track- and dose-averaged LET and LET spectra in proton therapy using the GEANT4 Monte Carlo code

    SciTech Connect

    Guan, Fada; Peeler, Christopher; Taleei, Reza; Randeniya, Sharmalee; Ge, Shuaiping; Mirkovic, Dragan; Mohan, Radhe; Titt, Uwe; Bronk, Lawrence; Geng, Changran; Grosshans, David

    2015-11-15

    Purpose: The motivation of this study was to find and eliminate the cause of errors in dose-averaged linear energy transfer (LET) calculations from therapeutic protons in small targets, such as biological cell layers, calculated using the GEANT 4 Monte Carlo code. Furthermore, the purpose was also to provide a recommendation to select an appropriate LET quantity from GEANT 4 simulations to correlate with biological effectiveness of therapeutic protons. Methods: The authors developed a particle tracking step based strategy to calculate the average LET quantities (track-averaged LET, LET{sub t} and dose-averaged LET, LET{sub d}) using GEANT 4 for different tracking step size limits. A step size limit refers to the maximally allowable tracking step length. The authors investigated how the tracking step size limit influenced the calculated LET{sub t} and LET{sub d} of protons with six different step limits ranging from 1 to 500 μm in a water phantom irradiated by a 79.7-MeV clinical proton beam. In addition, the authors analyzed the detailed stochastic energy deposition information including fluence spectra and dose spectra of the energy-deposition-per-step of protons. As a reference, the authors also calculated the averaged LET and analyzed the LET spectra combining the Monte Carlo method and the deterministic method. Relative biological effectiveness (RBE) calculations were performed to illustrate the impact of different LET calculation methods on the RBE-weighted dose. Results: Simulation results showed that the step limit effect was small for LET{sub t} but significant for LET{sub d}. This resulted from differences in the energy-deposition-per-step between the fluence spectra and dose spectra at different depths in the phantom. Using the Monte Carlo particle tracking method in GEANT 4 can result in incorrect LET{sub d} calculation results in the dose plateau region for small step limits. The erroneous LET{sub d} results can be attributed to the algorithm to

  17. Low Dose Effects in Psychopharmacology: Ontogenetic Considerations

    PubMed Central

    Spear, Linda Patia; Varlinskaya, Elena I.

    2005-01-01

    Low doses of psychoactive drugs often elicit a behavioral profile opposite to that observed following administration of more substantial doses. Our laboratory has observed that these effects are often age-specific in rats. For instance, whereas moderate to high doses of the dopamine agonist apomorphine increase locomotion, suppressed locomotor activity is seen following low dose exposure, with this low dose effect not emerging consistently until adolescence. A somewhat earlier emergence of a low dose “paradoxical” effect is seen with the 5HT1a receptor agonist, 8-OH-DPAT, with late preweanling, but not neonatal, rats showing increases in ingestive behavior at low doses but suppression at higher doses. In contrast to these ontogenetic increases in expression of low dose drug effects, low dose facilitation of social behavior is seen following ethanol only in adolescent rats and not their mature counterparts, although suppression of social interactions at higher doses is seen at both ages. This hormesis-like low dose stimulation appears related in part to overcompensation, with brief social suppression preceding the subsequent stimulation response, and also bears a number of ontogenetic similarities to acute tolerance, a well characterized, rapidly emerging adaptation to ethanol. Implications of these and other ontogenetic findings for studies of hormesis are discussed. PMID:19330157

  18. Technical Methods Report: Estimation and Identification of the Complier Average Causal Effect Parameter in Education RCTs. NCEE 2009-4040

    ERIC Educational Resources Information Center

    Schochet, Peter Z.; Chiang, Hanley

    2009-01-01

    In randomized control trials (RCTs) in the education field, the complier average causal effect (CACE) parameter is often of policy interest, because it pertains to intervention effects for students who receive a meaningful dose of treatment services. This report uses a causal inference and instrumental variables framework to examine the…

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

    SciTech Connect

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

    2005-08-15

    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

  20. The Effect of Honors Courses on Grade Point Averages

    ERIC Educational Resources Information Center

    Spisak, Art L.; Squires, Suzanne Carter

    2016-01-01

    High-ability entering college students give three main reasons for not choosing to become part of honors programs and colleges; they and/or their parents believe that honors classes at the university level require more work than non-honors courses, are more stressful, and will adversely affect their self-image and grade point average (GPA) (Hill;…

  1. EFFECTIVE DOSE TO PATIENTS FROM THORACIC SPINE EXAMINATIONS WITH TOMOSYNTHESIS.

    PubMed

    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.

  2. Frame average optimization of cine-mode EPID images used for routine clinical in vivo patient dose verification of VMAT deliveries

    SciTech Connect

    McCowan, P. M.; McCurdy, B. M. C.

    2016-01-15

    Purpose: The in vivo 3D dose delivered to a patient during volumetric modulated arc therapy (VMAT) delivery can be calculated using electronic portal imaging device (EPID) images. These images must be acquired in cine-mode (i.e., “movie” mode) in order to capture the time-dependent delivery information. The angle subtended by each cine-mode EPID image during an arc can be changed via the frame averaging number selected within the image acquisition software. A large frame average number will decrease the EPID’s angular resolution and will result in a decrease in the accuracy of the dose information contained within each image. Alternatively, less EPID images acquired per delivery will decrease the overall 3D patient dose calculation time, which is appealing for large-scale clinical implementation. Therefore, the purpose of this study was to determine the optimal frame average value per EPID image, defined as the highest frame averaging that can be used without an appreciable loss in 3D dose reconstruction accuracy for VMAT treatments. Methods: Six different VMAT plans and six different SBRT-VMAT plans were delivered to an anthropomorphic phantom. Delivery was carried out on a Varian 2300ix model linear accelerator (Linac) equipped with an aS1000 EPID running at a frame acquisition rate of 7.5 Hz. An additional PC was set up at the Linac console area, equipped with specialized frame-grabber hardware and software packages allowing continuous acquisition of all EPID frames during delivery. Frames were averaged into “frame-averaged” EPID images using MATLAB. Each frame-averaged data set was used to calculate the in vivo dose to the patient and then compared to the single EPID frame in vivo dose calculation (the single frame calculation represents the highest possible angular resolution per EPID image). A mean percentage dose difference of low dose (<20% prescription dose) and high dose regions (>80% prescription dose) was calculated for each frame averaged

  3. Estimates of Average Glandular Dose with Auto-modes of X-ray Exposures in Digital Breast Tomosynthesis.

    PubMed

    Kamal, Izdihar; Chelliah, Kanaga K; Mustafa, Nawal

    2015-05-01

    The aim of this research was to examine the average glandular dose (AGD) of radiation among different breast compositions of glandular and adipose tissue with auto-modes of exposure factor selection in digital breast tomosynthesis. This experimental study was carried out in the National Cancer Society, Kuala Lumpur, Malaysia, between February 2012 and February 2013 using a tomosynthesis digital mammography X-ray machine. The entrance surface air kerma and the half-value layer were determined using a 100H thermoluminescent dosimeter on 50% glandular and 50% adipose tissue (50/50) and 20% glandular and 80% adipose tissue (20/80) commercially available breast phantoms (Computerized Imaging Reference Systems, Inc., Norfolk, Virginia, USA) with auto-time, auto-filter and auto-kilovolt modes. The lowest AGD for the 20/80 phantom with auto-time was 2.28 milliGray (mGy) for two dimension (2D) and 2.48 mGy for three dimensional (3D) images. The lowest AGD for the 50/50 phantom with auto-time was 0.97 mGy for 2D and 1.0 mGy for 3D. The AGD values for both phantoms were lower against a high kilovolt peak and the use of auto-filter mode was more practical for quick acquisition while limiting the probability of operator error.

  4. Estimates of Average Glandular Dose with Auto-modes of X-ray Exposures in Digital Breast Tomosynthesis

    PubMed Central

    Kamal, Izdihar; Chelliah, Kanaga K.; Mustafa, Nawal

    2015-01-01

    Objectives: The aim of this research was to examine the average glandular dose (AGD) of radiation among different breast compositions of glandular and adipose tissue with auto-modes of exposure factor selection in digital breast tomosynthesis. Methods: This experimental study was carried out in the National Cancer Society, Kuala Lumpur, Malaysia, between February 2012 and February 2013 using a tomosynthesis digital mammography X-ray machine. The entrance surface air kerma and the half-value layer were determined using a 100H thermoluminescent dosimeter on 50% glandular and 50% adipose tissue (50/50) and 20% glandular and 80% adipose tissue (20/80) commercially available breast phantoms (Computerized Imaging Reference Systems, Inc., Norfolk, Virginia, USA) with auto-time, auto-filter and auto-kilovolt modes. Results: The lowest AGD for the 20/80 phantom with auto-time was 2.28 milliGray (mGy) for two dimension (2D) and 2.48 mGy for three dimensional (3D) images. The lowest AGD for the 50/50 phantom with auto-time was 0.97 mGy for 2D and 1.0 mGy for 3D. Conclusion: The AGD values for both phantoms were lower against a high kilovolt peak and the use of auto-filter mode was more practical for quick acquisition while limiting the probability of operator error. PMID:26052465

  5. Dose Rate Effects in Linear Bipolar Transistors

    NASA Technical Reports Server (NTRS)

    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.

  6. Dose Rate Effects in Linear Bipolar Transistors

    NASA Technical Reports Server (NTRS)

    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.

  7. Dose calculation for photon-emitting brachytherapy sources with average energy higher than 50 keV: Report of the AAPM and ESTRO

    SciTech Connect

    Perez-Calatayud, Jose; Ballester, Facundo; Das, Rupak K.; DeWerd, Larry A.; Ibbott, Geoffrey S.; Meigooni, Ali S.; Ouhib, Zoubir; Rivard, Mark J.; Sloboda, Ron S.; Williamson, Jeffrey F.

    2012-05-15

    Purpose: Recommendations of the American Association of Physicists in Medicine (AAPM) and the European Society for Radiotherapy and Oncology (ESTRO) on dose calculations for high-energy (average energy higher than 50 keV) photon-emitting brachytherapy sources are presented, including the physical characteristics of specific {sup 192}Ir, {sup 137}Cs, and {sup 60}Co source models. Methods: This report has been prepared by the High Energy Brachytherapy Source Dosimetry (HEBD) Working Group. This report includes considerations in the application of the TG-43U1 formalism to high-energy photon-emitting sources with particular attention to phantom size effects, interpolation accuracy dependence on dose calculation grid size, and dosimetry parameter dependence on source active length. Results: Consensus datasets for commercially available high-energy photon sources are provided, along with recommended methods for evaluating these datasets. Recommendations on dosimetry characterization methods, mainly using experimental procedures and Monte Carlo, are established and discussed. Also included are methodological recommendations on detector choice, detector energy response characterization and phantom materials, and measurement specification methodology. Uncertainty analyses are discussed and recommendations for high-energy sources without consensus datasets are given. Conclusions: Recommended consensus datasets for high-energy sources have been derived for sources that were commercially available as of January 2010. Data are presented according to the AAPM TG-43U1 formalism, with modified interpolation and extrapolation techniques of the AAPM TG-43U1S1 report for the 2D anisotropy function and radial dose function.

  8. Collective effective dose from diagnostic radiology in Ukraine.

    PubMed

    Stadnyk, L; Shalopa, O; Nosyk, O

    2015-07-01

    The frequencies and effective doses for the most common X-ray diagnostic examinations in Ukraine were assessed in the frame of the European Commission (EC) Study on European Population Doses from Medical Exposure (Dose Datamed 2). The average effective doses for all radiographic procedures were estimated using the ODS-60 software (Finland). The estimation of the effective doses for the chest film fluorography was carried out from the results of own representative measurements with thermoluminescent (TL) dosimetry and a standard Alderson-Rando phantom. The effective doses for fluoroscopy procedures were assessed using the Russian guidelines for estimation of effective doses. For all other X-ray examinations and procedures [computed tomography (CT), angiography and interventional procedures], typical effective dose values were taken from the EC Guidance RP154. The most frequently performed in Ukraine is chest film fluorography, with 389 examinations per 1000 population annually, reflecting in the greatest contribution to the total collective effective dose (CED) of 428 mSv per 1000 population (44 %). The total frequency and CED from all X-ray diagnostic examinations and procedures were estimated to be 1218 examinations and 1060 mSv per 1000 populations, respectively. The expected additional cancer risk from X-ray diagnostic examinations and interventional procedures is 2680 cases per year, with 1200 of them due to the contribution of chest fluorography. The main important action in radiation protection of patients in diagnostic radiology is the organisation of the monitoring of patient doses for different types of X-ray diagnostic examinations and replacement of chest film fluorography with digital X-ray systems.

  9. [Psychedelic effects of subanesthetic doses of ketamine].

    PubMed

    Zou, Liang; Tian, Shou-Yuan; Quan, Xiang; Ye, Tie-Hu

    2009-02-01

    To study the psychedelic effects in healthy volunteers when given subanesthetic dose of ketamine. Thirteen male healthy volunteers aged 24-39 years were enrolled. All subjects received subanesthetic doses of ketamine using target control infusion. A stepwise series of target plasma concentrations (0, 100, 200, and 300 ng/ml) were maintained for 20 minutes each. Visual analogue scale (VAS) of mechanical pain by von Frey hair was evaluated, and then the volunteers completed a VAS rating of 13 symptom scales. Pictures were shown to them at the same time. Heart rate, mean blood pressure, and SpO2 were monitored throughout the infusion. During the process of analgesia, ketamine produced dose-related analgesic effects. With the increase of ketamine dose, some psychedelic effects became more obvious and the memory impairment became worse stepwisely. Target control infusion of subanesthetic doses of ketamine produce obvious psychedelic effects in healthy volunteers.

  10. Behavioral support intervention for uncontrolled hypertension: a complier average causal effect (CACE) analysis.

    PubMed

    Liang, Yuanyuan; Ehler, Benjamin R; Hollenbeak, Christopher S; Turner, Barbara J

    2015-02-01

    The complier average causal effect (CACE) analysis addresses noncompliance with intervention and missing end-point measures in randomized controlled trials. To conduct a CACE analysis for the Peer Coach and Office Staff Support Trial examining the intervention's effect among "compliers," defined as subjects who would have received an effective dose of the intervention had it been offered, and to compare with an intention-to-treat analysis. A randomized controlled trial of 280 African American patients aged 40-75 with sustained uncontrolled hypertension from 2 general internal medicine practices. Change in 4-year coronary heart disease (CHD) risk (primary) and in systolic blood pressure (SBP) (secondary) from the baseline to the end of the 6-month intervention. Of 136 intervention subjects, 68% were compliers who had significantly more end points measured (86% vs. 34% for CHD risk; 99% vs. 57% for SBP) and lower baseline CHD risk (5% vs. 7.5%) and SBP (139 vs. 144 mm Hg) compared with noncompliers. In the intention-to-treat analysis, the effect of offering the intervention was nonsignificant for 4-year CHD risk (P=0.08) but significant for SBP (P=0.003). CACE analyses showed that receipt of an effective dose of the intervention resulted in a 1% greater reduction in 4-year CHD risk (P<0.05) and at least 8.1 mm Hg greater reduction in SBP compared with compliers in the control group (P<0.05). Among compliers, an effective dose of peer coach and office-based support resulted in significant reductions in 4-year CHD risk and SBP. More intensive interventions are likely to be required for noncompliers.

  11. The Lake Wobegon Effect: Are All Cancer Patients above Average?

    PubMed Central

    Wolf, Jacqueline H; Wolf, Kevin S

    2013-01-01

    Context When elderly patients face a terminal illness such as lung cancer, most are unaware that what we term in this article “the Lake Wobegon effect” taints the treatment advice imparted to them by their oncologists. In framing treatment plans, cancer specialists tend to intimate that elderly patients are like the children living in Garrison Keillor's mythical Lake Wobegon: above average and thus likely to exceed expectations. In this article, we use the story of our mother's death from lung cancer to investigate the consequences of elderly people's inability to reconcile the grave reality of their illness with the overly optimistic predictions of their physicians. Methods In this narrative analysis, we examine the routine treatment of elderly, terminally ill cancer patients through alternating lenses: the lens of a historian of medicine who also teaches ethics to medical students and the lens of an actuary who is able to assess physicians’ claims for the outcome of medical treatments. Findings We recognize that a desire to instill hope in patients shapes physicians’ messages. We argue, however, that the automatic optimism conveyed to elderly, dying patients by cancer specialists prompts those patients to choose treatment that is ineffective and debilitating. Rather than primarily prolong life, treatments most notably diminish patients’ quality of life, weaken the ability of patients and their families to prepare for their deaths, and contribute significantly to the unsustainable costs of the U.S. health care system. Conclusions The case described in this article suggests how physicians can better help elderly, terminally ill patients make medical decisions that are less damaging to them and less costly to the health care system. PMID:24320166

  12. Velocity Averaging, Kinetic Formulations and Regularizing Effects in Quasilinear PDEs

    DTIC Science & Technology

    2005-10-31

    nonlinear conservation laws. In [LPT94a], Lions, Perthame & Tadmor have shown that entropy solutions of such laws admit a regularizing effect of a fractional...one augments (1.1) with additional conditions on the behavior of Φ(ρ) for a large enough family of entropies Φ’s. These additional entropy conditions...imply that g is in fact a positive distribution, g = m ∈ M+, measuring the entropy dissipation of the nonlinear equation. We arrive at the kinetic

  13. Effects of Spatial Variability on Annual Average Water Balance

    NASA Astrophysics Data System (ADS)

    Milly, P. C. D.; Eagleson, P. S.

    1987-11-01

    Spatial variability of soil and vegetation causes spatial variability of the water balance. For an area in which the water balance is not affected by lateral water flow, the frequency distributions of storm surface runoff, evapotranspiration, and drainage to groundwater are derivable from distributions of soil hydraulic parameters by means of a point water balance model and local application of the vegetal equilibrium hypothesis. Means and variances of the components of the budget can be found by Monte Carlo simulation or by approximate local expansions. For a fixed set of mean soil parameters, soil spatial variability may induce significant changes in the areal mean water balance, particularly if storm surface runoff occurs. Variability of the pore size distribution index and permeability has a much larger effect than that of effective porosity on the means and variances of water balance variables. The importance of the pore size distribution index implies that the microscopic similarity assumption may underestimate the effects of soil spatial variability. In general, the presence of soil variability reduces the sensitivity of water balance to mean properties. For small levels of soil variability, there exists a unique equivalent homogeneous soil type that reproduces the budget components and the mean soil moisture saturation of an inhomogeneous area.

  14. Relationship between dose and health effects

    SciTech Connect

    Kimbrough, R.D.

    1984-09-01

    The health effects produced by chemicals depend on the inherent toxicity of the chemical and the dose received by the exposed individual. Health effects are modified by genetic make-up, life style, nutrition, and interaction with other chemicals. In some situations it may be difficult to impossible to determine through epidemiologic studies whether exposure to chemicals (naturally occurring or synthetic) has caused harm. For all practical purposes, the risk associated with minuscule doses of most chemicals is negligible.

  15. Abdominal pediatric cancer surveillance using serial computed tomography: evaluation of organ absorbed dose and effective dose.

    PubMed

    Lam, Diana; Wootton-Gorges, Sandra L; McGahan, John P; Stern, Robin; Boone, John M

    2011-02-01

    Computed tomography (CT) is used extensively in cancer diagnosis, staging, evaluation of response to treatment, and in active surveillance for cancer reoccurrence. A review of CT technology is provided, at a level of detail appropriate for a busy clinician to review. The basis of x-ray CT dosimetry is also discussed, and concepts of absorbed dose and effective dose (ED) are distinguished. Absorbed dose is a physical quantity (measured in milligray [mGy]) equal to the x-ray energy deposited in a mass of tissue, whereas ED uses an organ-specific weighting method that converts organ doses to ED measured in millisieverts (mSv). The organ weighting values carry with them a measure of radiation risk, and so ED (in mSv) is not a physical dose metric but rather is one that conveys radiation risk. The use of CT in a cancer surveillance protocol was used as an example of a pediatric patient who had kidney cancer, with surgery and radiation therapy. The active use of CT for cancer surveillance along with diagnostic CT scans led to a total of 50 CT scans performed on this child in a 7-year period. It was estimated that the patient received an average organ dose of 431 mGy from these CT scans. By comparison, the radiation therapy was performed and delivered 50.4 Gy to the patient's abdomen. Thus, the total dose from CT represented only 0.8% of the patient's radiation dose. Copyright © 2011 Elsevier Inc. All rights reserved.

  16. Average ambulatory measures of sound pressure level, fundamental frequency, and vocal dose do not differ between adult females with phonotraumatic lesions and matched control subjects

    PubMed Central

    Van Stan, Jarrad H.; Mehta, Daryush D.; Zeitels, Steven M.; Burns, James A.; Barbu, Anca M.; Hillman, Robert E.

    2015-01-01

    Objectives Clinical management of phonotraumatic vocal fold lesions (nodules, polyps) is based largely on assumptions that abnormalities in habitual levels of sound pressure level (SPL), fundamental frequency (f0), and/or amount of voice use play a major role in lesion development and chronic persistence. This study used ambulatory voice monitoring to evaluate if significant differences in voice use exist between patients with phonotraumatic lesions and normal matched controls. Methods Subjects were 70 adult females: 35 with vocal fold nodules or polyps and 35 age-, sex-, and occupation-matched normal individuals. Weeklong summary statistics of voice use were computed from anterior neck surface acceleration recorded using a smartphone-based ambulatory voice monitor. Results Paired t-tests and Kolmogorov-Smirnov tests resulted in no statistically significant differences between patients and matched controls regarding average measures of SPL, f0, vocal dose measures, and voicing/voice rest periods. Paired t-tests comparing f0 variability between the groups resulted in statistically significant differences with moderate effect sizes. Conclusions Individuals with phonotraumatic lesions did not exhibit differences in average ambulatory measures of vocal behavior when compared with matched controls. More refined characterizations of underlying phonatory mechanisms and other potentially contributing causes are warranted to better understand risk factors associated with phonotraumatic lesions. PMID:26024911

  17. Biologically effective uniform dose (D) for specification, report and comparison of dose response relations and treatment plans.

    PubMed

    Mavroidis, P; Lind, B K; Brahme, A

    2001-10-01

    Developments in radiation therapy planning have improved the information about the three-dimensional dose distribution in the patient. Isodose graphs, dose volume histograms and most recently radiobiological models can be used to evaluate the dose distribution delivered to the irradiated organs and volumes of interest. The concept of a biologically effective uniform dose (D) assumes that any two dose distributions are equivalent if they cause the same probability for tumour control or normal tissue complication. In the present paper the D concept both for tumours and normal tissues is presented, making use of the fact that probabilities averaged over both dose distribution and organ radiosensitivity are more relevant to the clinical outcome than the expected number of surviving clonogens or functional subunits. D can be calculated in complex target volumes or organs at risk either from the 3D dose matrix or from the corresponding dose volume histograms of the dose plan. The value of the D concept is demonstrated by applying it to two treatment plans of a cervix cancer. Comparison is made of the D concept with the effective dose (Deff ) and equivalent uniform dose (EUD) that have been suggested in the past. The value of the concept for complex targets and fractionation schedules is also pointed out.

  18. The EffectLiteR Approach for Analyzing Average and Conditional Effects.

    PubMed

    Mayer, Axel; Dietzfelbinger, Lisa; Rosseel, Yves; Steyer, Rolf

    2016-01-01

    We present a framework for estimating average and conditional effects of a discrete treatment variable on a continuous outcome variable, conditioning on categorical and continuous covariates. Using the new approach, termed the EffectLiteR approach, researchers can consider conditional treatment effects given values of all covariates in the analysis and various aggregates of these conditional treatment effects such as average effects, effects on the treated, or aggregated conditional effects given values of a subset of covariates. Building on structural equation modeling, key advantages of the new approach are (1) It allows for latent covariates and outcome variables; (2) it permits (higher order) interactions between the treatment variable and categorical and (latent) continuous covariates; and (3) covariates can be treated as stochastic or fixed. The approach is illustrated by an example, and open source software EffectLiteR is provided, which makes a detailed analysis of effects conveniently accessible for applied researchers.

  19. Position Verification for the Prostate: Effect on Rectal Wall Dose

    SciTech Connect

    Haverkort, Marie A.D.; Kamer, Jeroen B. van de; Pieters, Bradley R.; Tienhoven, Geertjan van; Assendelft, Esther; Lensing, Andrea L.; Herk, Marcel van; Reijke, Theo M. de; Stoker, Jaap; Koning, Caro C.E.

    2011-06-01

    Purpose: To evaluate the effect of gold marker (GM)-based position correction on the cumulative dose in the anorectal wall compared with traditional bony anatomy (BA)-based correction, taking into account changes in anorectal shape and position. Methods and Materials: A total of 20 consecutive prostate cancer patients, treated with curative external beam radiotherapy, were included. Four fiducial GMs were implanted in the prostate. Positioning was verified according to the shift in BA and GMs on daily electronic portal images. Position corrections were determined using on- and off-line position verification protocols according to the position of the GMs (GM-on and GM-off) and BA (BA-off). For all patients, intensity-modulated radiotherapy plans were made for the GM (8-mm planning target volume margin) and BA (10-mm planning target volume margin) protocols. The dose distribution was recomputed on 11 repeat computed tomography scans to estimate the accumulated dose to the prostate and anorectal wall while considering internal organ motion. Results: The dose that is at least received by 99% of the prostate was, on average, acceptable for all protocols. The individual patient data showed the best coverage for both GM protocols, with >95% of the prescribed dose for all patients. The anorectal wall dose was significantly lower for the GM protocols. The dose that is at least received by 30% of the rectal wall was, on average, 54.6 Gy for GM-on, 54.1 Gy for GM-off, and 58.9 Gy for BA-off (p <.001). Conclusion: Position verification with GM and reduced planning target volume margins yielded adequate treatment of the prostate and a lower rectal wall dose, even when accounting for independent movement of the prostate and anorectal wall.

  20. Adaptive fractionation therapy: II. Biological effective dose.

    PubMed

    Chen, Mingli; Lu, Weiguo; Chen, Quan; Ruchala, Kenneth; Olivera, Gustavo

    2008-10-07

    Radiation therapy is fractionized to differentiate the cell killing between the tumor and organ at risk (OAR). Conventionally, fractionation is done by dividing the total dose into equal fraction sizes. However, as the relative positions (configurations) between OAR and the tumor vary from fractions to fractions, intuitively, we want to use a larger fraction size when OAR and the tumor are far apart and a smaller fraction size when OAR and the tumor are close to each other. Adaptive fractionation accounts for variations of configurations between OAR and the tumor. In part I of this series, the adaptation minimizes the OAR (physical) dose and maintains the total tumor (physical) dose. In this work, instead, the adaptation is based on the biological effective dose (BED). Unlike the linear programming approach in part I, we build a fraction size lookup table using mathematical induction. The lookup table essentially describes the fraction size as a function of the remaining tumor BED, the OAR/tumor dose ratio and the remaining number of fractions. The lookup table is calculated by maximizing the expected survival of OAR and preserving the tumor cell kill. Immediately before the treatment of each fraction, the OAR-tumor configuration and thus the dose ratio can be obtained from the daily setup image, and then the fraction size can be determined by the lookup table. Extensive simulations demonstrate the effectiveness of our method compared with the conventional fractionation method.

  1. Aperture averaging effects on the average spectral efficiency of FSO links over turbulence channel with pointing errors

    NASA Astrophysics Data System (ADS)

    Aarthi, G.; Prabu, K.; Reddy, G. Ramachandra

    2017-02-01

    The average spectral efficiency (ASE) is investigated for the free space optical (FSO) communications employing On-Off keying (OOK), Polarization shift keying (POLSK), and Coherent optical wireless communication (Coherent OWC) systems with and without pointing errors over the Gamma-Gamma (GG) channels. Additionally, the impact of aperture averaging on the ASE is explored. The influence of different turbulence conditions along with varying receiver aperture has been studied and analyzed. For the considered system, the exact average channel capacity (ACC) expressions are derived using Meijer G function. Results reveal that when pointing errors are introduced, there is a significant reduction in the ASE performance. The enhancement in the ASE can be achieved with an increase in the receiver aperture across various turbulence regimes and reducing the beam radius in the presence of pointing errors, but the rate of increment of ASE reduces with a larger diameter and it is saturated finally. The coherent OWC system provides better ASE performance of 49 bits/s/Hz at the average transmitted optical power of 5 dBm with an aperture diameter of 10 cm and 34 bits/s/Hz without and with pointing errors under strong turbulence respectively.

  2. Transcriptional effects of gene dose reduction

    PubMed Central

    2014-01-01

    Large-scale gene dose reductions usually lead to abnormal phenotypes or death. However, male mammals, Drosophila, and Caenorhabditis elegans have only one X chromosome and thus can be considered as monosomic for a major chromosome. Despite the deleterious effects brought about by such gene dose reduction in the case of an autosome, X chromosome monosomy in males is natural and innocuous. This is because of the nearly full transcriptional compensation for X chromosome genes in males, as opposed to no or partial transcriptional compensation for autosomal one-dose genes arising due to deletions. Buffering, the passive absorption of disturbance due to enzyme kinetics, and feedback responses triggered by expression change contribute to partial compensation. Feed-forward mechanisms, which are active responses to genes being located on the X, rather than actual gene dose are important contributors to full X chromosome compensation. In the last decade, high-throughput techniques have provided us with the tools to effectively and quantitatively measure the small-fold transcriptional effects of dose reduction. This is leading to a better understanding of compensatory mechanisms. PMID:24581086

  3. A critical study of different Monte Carlo scoring methods of dose average linear-energy-transfer maps calculated in voxelized geometries irradiated with clinical proton beams.

    PubMed

    Cortés-Giraldo, M A; Carabe, A

    2015-04-07

    We compare unrestricted dose average linear energy transfer (LET) maps calculated with three different Monte Carlo scoring methods in voxelized geometries irradiated with proton therapy beams with three different Monte Carlo scoring methods. Simulations were done with the Geant4 (Geometry ANd Tracking) toolkit. The first method corresponds to a step-by-step computation of LET which has been reported previously in the literature. We found that this scoring strategy is influenced by spurious high LET components, which relative contribution in the dose average LET calculations significantly increases as the voxel size becomes smaller. Dose average LET values calculated for primary protons in water with voxel size of 0.2 mm were a factor ~1.8 higher than those obtained with a size of 2.0 mm at the plateau region for a 160 MeV beam. Such high LET components are a consequence of proton steps in which the condensed-history algorithm determines an energy transfer to an electron of the material close to the maximum value, while the step length remains limited due to voxel boundary crossing. Two alternative methods were derived to overcome this problem. The second scores LET along the entire path described by each proton within the voxel. The third followed the same approach of the first method, but the LET was evaluated at each step from stopping power tables according to the proton kinetic energy value. We carried out microdosimetry calculations with the aim of deriving reference dose average LET values from microdosimetric quantities. Significant differences between the methods were reported either with pristine or spread-out Bragg peaks (SOBPs). The first method reported values systematically higher than the other two at depths proximal to SOBP by about 15% for a 5.9 cm wide SOBP and about 30% for a 11.0 cm one. At distal SOBP, the second method gave values about 15% lower than the others. Overall, we found that the third method gave the most consistent

  4. SU-E-T-280: Reconstructed Rectal Wall Dose Map-Based Verification of Rectal Dose Sparing Effect According to Rectum Definition Methods and Dose Perturbation by Air Cavity in Endo-Rectal Balloon

    SciTech Connect

    Park, J; Park, H; Lee, J; Kang, S; Lee, M; Suh, T; Lee, B

    2014-06-01

    Purpose: Dosimetric effect and discrepancy according to the rectum definition methods and dose perturbation by air cavity in an endo-rectal balloon (ERB) were verified using rectal-wall (Rwall) dose maps considering systematic errors in dose optimization and calculation accuracy in intensity-modulated radiation treatment (IMRT) for prostate cancer patients. Methods: When the inflated ERB having average diameter of 4.5 cm and air volume of 100 cc is used for patient, Rwall doses were predicted by pencil-beam convolution (PBC), anisotropic analytic algorithm (AAA), and AcurosXB (AXB) with material assignment function. The errors of dose optimization and calculation by separating air cavity from the whole rectum (Rwhole) were verified with measured rectal doses. The Rwall doses affected by the dose perturbation of air cavity were evaluated using a featured rectal phantom allowing insert of rolled-up gafchromic films and glass rod detectors placed along the rectum perimeter. Inner and outer Rwall doses were verified with reconstructed predicted rectal wall dose maps. Dose errors and extent at dose levels were evaluated with estimated rectal toxicity. Results: While AXB showed insignificant difference of target dose coverage, Rwall doses underestimated by up to 20% in dose optimization for the Rwhole than Rwall at all dose range except for the maximum dose. As dose optimization for Rwall was applied, the Rwall doses presented dose error less than 3% between dose calculation algorithm except for overestimation of maximum rectal dose up to 5% in PBC. Dose optimization for Rwhole caused dose difference of Rwall especially at intermediate doses. Conclusion: Dose optimization for Rwall could be suggested for more accurate prediction of rectal wall dose prediction and dose perturbation effect by air cavity in IMRT for prostate cancer. This research was supported by the Leading Foreign Research Institute Recruitment Program through the National Research Foundation of Korea

  5. Digital filter suppresses effects of nonstatistical noise bursts on multichannel scaler digital averaging systems

    NASA Technical Reports Server (NTRS)

    Goodman, L. S.; Salter, F. O.

    1968-01-01

    Digital filter suppresses the effects of nonstatistical noise bursts on data averaged over multichannel scaler. Interposed between the sampled channels and the digital averaging system, it uses binary logic circuitry to compare the number of counts per channel with the average number of counts per channel.

  6. Comparison of TID Effects in Space-Like Variable Dose Rates and Constant Dose Rates

    NASA Technical Reports Server (NTRS)

    Harris, Richard D.; McClure, Steven S.; Rax, Bernard G.; Evans, Robin W.; Jun, Insoo

    2008-01-01

    The degradation of the LM193 dual voltage comparator has been studied at different TID dose rate profiles, including several different constant dose rates and a variable dose rate that simulates the behavior of a solar flare. A comparison of results following constant dose rate vs. variable dose rates is made to explore how well the constant dose rates used for typical part testing predict the performance during a simulated space-like mission. Testing at a constant dose rate equal to the lowest dose rate seen during the simulated flare provides an extremely conservative estimate of the overall amount of degradation. A constant dose rate equal to the average dose rate is also more conservative than the variable rate. It appears that, for this part, weighting the dose rates by the amount of total dose received at each rate (rather than the amount of time at each dose rate) results in an average rate that produces an amount of degradation that is a reasonable approximation to that received by the variable rate.

  7. Low dose neutron late effects: Cataractogenesis

    SciTech Connect

    Worgul, B.V.

    1991-12-01

    The work is formulated to resolve the uncertainty regarding the relative biological effectiveness (RBE) of low dose neutron radiation. The study exploits the fact that cataractogenesis is sensitive to the inverse dose-rate effect as has been observed with heavy ions and was an endpoint considered in the follow-up of the A-bomb survivors. The neutron radiations were initiated at the Radiological Research Accelerator facility (RARAF) of the Nevis Laboratory of Columbia University. Four week old ({plus minus} 1 day) rats were divided into eight dose groups each receiving single or fractionated total doses of 0.2, 1.0, 5.0 and 25.0 cGy of monoenergetic 435 KeV neutrons. Special restraining jigs insured that the eye, at the midpoint of the lens, received the appropriate energy and dose with a relative error of {plus minus}5%. The fractionation regimen consisted of four exposures, each administered at three hour ({plus minus}) intervals. The neutron irradiated groups are being compared to rats irradiated with 250kVp X-rays in doses ranging from 0.5 to 7 Gy. The animals are being examined on a biweekly basis utilizing conventional slit-lamp biomicroscopy and the Scheimpflug Slit Lamp Imaging System (Zeiss). The follows-ups, entering their second year, will continue throughout the life-span of the animals. This is essential inasmuch as given the extremely low doses which are being utilized clinically detectable opacities were not anticipated until a significant fraction of the life span has lapsed. Current data support this contention. At this juncture cataracts in the irradiated groups are beginning to exceed control levels.

  8. 21 years of Biologically Effective Dose

    PubMed Central

    Fowler, J F

    2010-01-01

    In 1989 the British Journal of Radiology published a review proposing the term biologically effective dose (BED), based on linear quadratic cell survival in radiobiology. It aimed to indicate quantitatively the biological effect of any radiotherapy treatment, taking account of changes in dose-per-fraction or dose rate, total dose and (the new factor) overall time. How has it done so far? Acceptable clinical results have been generally reported using BED, and it is in increasing use, although sometimes mistaken for “biologically equivalent dose”, from which it differs by large factors, as explained here. The continuously bending nature of the linear quadratic curve has been questioned but BED has worked well for comparing treatments in many modalities, including some with large fractions. Two important improvements occurred in the BED formula. First, in 1999, high linear energy transfer (LET) radiation was included; second, in 2003, when time parameters for acute mucosal tolerance were proposed, optimum overall times could then be “triangulated” to optimise tumour BED and cell kill. This occurs only when both early and late BEDs meet their full constraints simultaneously. New methods of dose delivery (intensity modulated radiation therapy, stereotactic body radiation therapy, protons, tomotherapy, rapid arc and cyberknife) use a few large fractions and obviously oppose well-known fractionation schedules. Careful biological modelling is required to balance the differing trends of fraction size and local dose gradient, as explained in the discussion “How Fractionation Really Works”. BED is now used for dose escalation studies, radiochemotherapy, brachytherapy, high-LET particle beams, radionuclide-targeted therapy, and for quantifying any treatments using ionising radiation. PMID:20603408

  9. Low dose neutron late effects: Cataractogenesis

    SciTech Connect

    Worgul, B.V.

    1991-04-01

    The work is formulated to resolve the uncertainty regarding the relative biological effectiveness. The endpoint which is being utilized is cataractogenesis. The advantages conferred by this system stems primarily from the non-invasive longitudinal analysis which it allows. It also exploits a well defined system and one which has demonstrated sensitivity to the inverse dose rate effect observed with heavy ions. Four week old rats were divided into 8 dose groups which received single or fractionated total doses of .2, 1.0, 5.0 and 25 cGy of monoenergetic 435 keV neutrons. Special restraining jigs were devised to insure that the eye at the midpoint of the lens received the appropriate energy and dose with a relative error of {plus minus} 5%. The fractionated regimen consisted of four exposures, each administered at 3 hour intervals. The reference radiations, 250 kVp X-rays, were administered in the same fashion but in doses ranging from .5 to 6.0 Gy. The animals are examined on a bi-weekly basis utilizing conventional slit-lamp biomicroscopy and the Scheimpflug Slit-lamp Imaging System. The follow-ups will continue throughout the lifespan of the animals. When opacification begins full documentation will involve the Zeiss imaging system and Oxford retroillumination photography. The processing routinely employs the Merriam/Focht scoring system for cross-referencing with previous cataract studies and establish cataractogenecity using a proven scoring method.

  10. Effective dose equivalent and effective dose: comparison for common projections in oral and maxillofacial radiology.

    PubMed

    Gibbs, S J

    2000-10-01

    Effective dose equivalents (H(E)) and effective doses (E) for radiographic projections common in dentistry, calculated from the same organ dose distributions, are presented to determine whether the 2 quantities can be directly compared. Doses to all organs and tissues in the head, neck, trunk, and proximal extremities were determined for each projection (intraoral full-mouth radiographic survey, panoramic, cephalometric, temporomandibular tomograms, and submentovertex view) by computer simulation with Monte Carlo methods. H(E) and E were calculated from these complete distributions and by methods prescribed by the International Commission on Radiological Protection (ICRP). H(E) and E computed from complete dose distributions were found comparable within a few percentage points. However, those computed by strict application of ICRP methods were not. For radiographic projections with highly localized dose distributions, such as those common in dentistry, direct comparison of H(E) and E may not be meaningful, unless both computation algorithms are known.

  11. GI Joe or Average Joe? The impact of average-size and muscular male fashion models on men's and women's body image and advertisement effectiveness.

    PubMed

    Diedrichs, Phillippa C; Lee, Christina

    2010-06-01

    Increasing body size and shape diversity in media imagery may promote positive body image. While research has largely focused on female models and women's body image, men may also be affected by unrealistic images. We examined the impact of average-size and muscular male fashion models on men's and women's body image and perceived advertisement effectiveness. A sample of 330 men and 289 women viewed one of four advertisement conditions: no models, muscular, average-slim or average-large models. Men and women rated average-size models as equally effective in advertisements as muscular models. For men, exposure to average-size models was associated with more positive body image in comparison to viewing no models, but no difference was found in comparison to muscular models. Similar results were found for women. Internalisation of beauty ideals did not moderate these effects. These findings suggest that average-size male models can promote positive body image and appeal to consumers.

  12. Normalized organ doses and effective doses to a reference Indian adult male in conventional medical diagnostic x-ray examinations.

    PubMed

    Biju, K; Nagarajan, P S

    2006-03-01

    This work discusses the dose computations of 80 kV diagnostic x-rays made on a mathematical phantom representing an average Indian adult, since it is felt that results based on MIRD adult phantom calculations are not strictly appropriate for the population in India. Normalized organ equivalent doses and effective doses for an Indian adult male have been estimated. Normalization is done with respect to the entrance skin dose of the patient. Twenty common diagnostic x-ray examinations have been considered in this study and the doses are presented. This study would enable estimation of radiation induced detriment to the patient subpopulation in India. Since the external dimensions of the phantom are nearly the same as that of 15-y-old NRPB pediatric phantom, our results are also compared with those of latter and the agreement was found to be satisfactory.

  13. Determining Effective Methadone Doses for Individual Opioid-Dependent Patients

    PubMed Central

    Trafton, Jodie A; Minkel, Jared; Humphreys, Keith

    2006-01-01

    Background Randomized clinical trials of methadone maintenance have found that on average high daily doses are more effective for reducing heroin use, and clinical practice guidelines recommend 60 mg/d as a minimum dosage. Nevertheless, many clinicians report that some patients can be stably maintained on lower methadone dosages to optimal effect, and clinic dosing practices vary substantially. Studies of individual responses to methadone treatment may be more easily translated into clinical practice. Methods and Findings A volunteer sample of 222 opioid-dependent US veterans initiating methadone treatment was prospectively observed over the year after treatment entry. In the 168 who achieved at least 1 mo of heroin abstinence, methadone dosages on which patients maintained heroin-free urine samples ranged from 1.5 mg to 191.2 mg (median = 69 mg). Among patients who achieved heroin abstinence, higher methadone dosages were predicted by having a diagnosis of posttraumatic stress disorder or depression, having a greater number of previous opioid detoxifications, living in a region with lower average heroin purity, attending a clinic where counselors discourage dosage reductions, and staying in treatment longer. These factors predicted 42% of the variance in dosage associated with heroin abstinence. Conclusions Effective and ineffective methadone dosages overlap substantially. Dosing guidelines should focus more heavily on appropriate processes of dosage determination rather than solely specifying recommended dosages. To optimize therapy, methadone dosages must be titrated until heroin abstinence is achieved. PMID:16448216

  14. SU-D-213-04: Accounting for Volume Averaging and Material Composition Effects in An Ionization Chamber Array for Patient Specific QA

    SciTech Connect

    Fugal, M; McDonald, D; Jacqmin, D; Koch, N; Ellis, A; Peng, J; Ashenafi, M; Vanek, K

    2015-06-15

    Purpose: This study explores novel methods to address two significant challenges affecting measurement of patient-specific quality assurance (QA) with IBA’s Matrixx Evolution™ ionization chamber array. First, dose calculation algorithms often struggle to accurately determine dose to the chamber array due to CT artifact and algorithm limitations. Second, finite chamber size and volume averaging effects cause additional deviation from the calculated dose. Methods: QA measurements were taken with the Matrixx positioned on the treatment table in a solid-water Multi-Cube™ phantom. To reduce the effect of CT artifact, the Matrixx CT image set was masked with appropriate materials and densities. Individual ionization chambers were masked as air, while the high-z electronic backplane and remaining solid-water material were masked as aluminum and water, respectively. Dose calculation was done using Varian’s Acuros XB™ (V11) algorithm, which is capable of predicting dose more accurately in non-biologic materials due to its consideration of each material’s atomic properties. Finally, the exported TPS dose was processed using an in-house algorithm (MATLAB) to assign the volume averaged TPS dose to each element of a corresponding 2-D matrix. This matrix was used for comparison with the measured dose. Square fields at regularly-spaced gantry angles, as well as selected patient plans were analyzed. Results: Analyzed plans showed improved agreement, with the average gamma passing rate increasing from 94 to 98%. Correction factors necessary for chamber angular dependence were reduced by 67% compared to factors measured previously, indicating that previously measured factors corrected for dose calculation errors in addition to true chamber angular dependence. Conclusion: By comparing volume averaged dose, calculated with a capable dose engine, on a phantom masked with correct materials and densities, QA results obtained with the Matrixx Evolution™ can be significantly

  15. Effective dose and organ doses estimation taking tube current modulation into account with a commercial software package.

    PubMed

    Lopez-Rendon, X; Bosmans, H; Oyen, R; Zanca, F

    2015-07-01

    To evaluate the effect of including tube current modulation (TCM) versus using the average mAs in estimating organ and effective dose (E) using commercial software. Forty adult patients (24 females, 16 males) with normal BMI underwent chest/abdomen computed tomography (CT) performed with TCM at 120 kVp, reference mAs of 110 (chest) and 200 (abdomen). Doses to fully irradiated organs (breasts, lungs, stomach, liver and ovaries) and E were calculated using two versions of a dosimetry software: v.2.0, which uses the average mAs, and v.2.2, which accounts for TCM by implementing a gender-specific mAs profile. Student's t-test was used to assess statistically significant differences between organ doses calculated with the two versions. A statistically significant difference (p < 0.001) was found for E on chest and abdomen CT, with E being lower by 4.2% when TCM is considered. Similarly, organ doses were also significantly lower (p < 0.001): 13.7% for breasts, 7.3% for lungs, 9.1% for the liver and 8.5% for the stomach. Only the dose to the ovaries was higher with TCM (11.5%). When TCM is used, for the stylized phantom, the doses to lungs, breasts, stomach and liver decreased while the dose to the ovaries increased. • Estimated dose to the ovaries increased with TCM. • Estimated dose to lungs, breasts, stomach and liver decreased with TCM. • A unique but gender-specific mAs profile resulted in a radiation dose shift. • Even for normal size patients there is a variety in mAs profiles.

  16. Culmination of Low-Dose Pesticide Effects

    PubMed Central

    2013-01-01

    Pesticides applied in agriculture can affect the structure and function of nontarget populations at lower doses and for longer timespans than predicted by the current risk assessment frameworks. We identified a mechanism for this observation. The populations of an aquatic invertebrate (Culex pipiens) exposed over several generations to repeated pulses of low concentrations of the neonicotinoid insecticide (thiacloprid) continuously declined and did not recover in the presence of a less sensitive competing species (Daphnia magna). By contrast, in the absence of a competitor, insecticide effects on the more sensitive species were only observed at concentrations 1 order of magnitude higher, and the species recovered more rapidly after a contamination event. The underlying processes are experimentally identified and reconstructed using a simulation model. We conclude that repeated toxicant pulse of populations that are challenged with interspecific competition may result in a multigenerational culmination of low-dose effects. PMID:23859631

  17. Estimation of effective imaging dose for kilovoltage intratreatment monitoring of the prostate position during cancer radiotherapy

    PubMed Central

    Ng, J A; Booth, J; Poulsen, P; Kuncic, Z; Keall, P J

    2013-01-01

    Kilovoltage Intratreatment Monitoring (KIM) is a novel real-time localization modality where the tumor position is continuously measured during Intensity Modulated Radiation Therapy (IMRT) or Intensity Modulated Arc Therapy (IMAT) by a kilovoltage (kV) x-ray imager. Adding kV imaging during therapy adds radiation dose. The additional effective dose is quantified for prostate radiotherapy and compared to dose from other localization modalities. The software PCXMC 2.0 was used to calculate the effective dose delivered to a phantom as a function of imager angle and field size for a Varian On-Board Imager. The average angular effective dose was calculated for a field size of 6 cm × 6 cm. The average angular effective dose was used in calculations for different treatment scenarios. Treatment scenarios considered were treatment type and fractionation. For all treatment scenarios, (i.e. conventionally fractionated and SBRT; IMRT and IMAT), the total KIM dose at 1 Hz ranged from 2–10 mSv. This imaging dose is less than the Navotek radioactive implant dose (64 mSv) and a standard SBRT CBCT pretreatment scan dose (22 mSv) over an entire treatment regime. KIM delivers an acceptably low effective dose for daily use as a real-time image-guidance method for prostate radiotherapy. PMID:23938470

  18. Estimation of effective imaging dose for kilovoltage intratreatment monitoring of the prostate position during cancer radiotherapy

    NASA Astrophysics Data System (ADS)

    Ng, J. A.; Booth, J.; Poulsen, P.; Kuncic, Z.; Keall, P. J.

    2013-09-01

    Kilovoltage intratreatment monitoring (KIM) is a novel real-time localization modality where the tumor position is continuously measured during intensity modulated radiation therapy (IMRT) or intensity modulated arc therapy (IMAT) by a kilovoltage (kV) x-ray imager. Adding kV imaging during therapy adds radiation dose. The additional effective dose is quantified for prostate radiotherapy and compared to dose from other localization modalities. The software PCXMC 2.0 was used to calculate the effective dose delivered to a phantom as a function of imager angle and field size for a Varian On-Board Imager. The average angular effective dose was calculated for a field size of 6 cm × 6 cm. The average angular effective dose was used in calculations for different treatment scenarios. Treatment scenarios considered were treatment type and fractionation. For all treatment scenarios, (i.e. conventionally fractionated and stereotactic body radiotherapy (SBRT), IMRT and IMAT), the total KIM dose at 1 Hz ranged from 2-10 mSv. This imaging dose is less than the Navotek radioactive implant dose (64 mSv) and a standard SBRT cone beam computed tomography pretreatment scan dose (22 mSv) over an entire treatment regime. KIM delivers an acceptably low effective dose for daily use as a real-time image-guidance method for prostate radiotherapy.

  19. A randomised clinical trial on the efficacy of oxytetracycline dose through water medication of nursery pigs on diarrhoea, faecal shedding of Lawsonia intracellularis and average daily weight gain.

    PubMed

    Larsen, Inge; Hjulsager, Charlotte Kristiane; Holm, Anders; Olsen, John Elmerdahl; Nielsen, Søren Saxmose; Nielsen, Jens Peter

    2016-01-01

    Oral treatment with antimicrobials is widely used in pig production for the control of gastrointestinal infections. Lawsonia intracellularis (LI) causes enteritis in pigs older than six weeks of age and is commonly treated with antimicrobials. The objective of this study was to evaluate the efficacy of three oral dosage regimens (5, 10 and 20mg/kg body weight) of oxytetracycline (OTC) in drinking water over a five-day period on diarrhoea, faecal shedding of LI and average daily weight gain (ADG). A randomised clinical trial was carried out in four Danish pig herds. In total, 539 animals from 37 batches of nursery pigs were included in the study. The dosage regimens were randomly allocated to each batch and initiated at presence of assumed LI-related diarrhoea. In general, all OTC doses used for the treatment of LI infection resulted in reduced diarrhoea and LI shedding after treatment. Treatment with a low dose of 5mg/kg OTC per kg body weight, however, tended to cause more watery faeces and resulted in higher odds of pigs shedding LI above detection level when compared to medium and high doses (with odds ratios of 5.5 and 8.4, respectively). No association was found between the dose of OTC and the ADG. In conclusion, a dose of 5mg OTC per kg body weight was adequate for reducing the high-level LI shedding associated with enteropathy, but a dose of 10mg OTC per kg body weight was necessary to obtain a maximum reduction in LI shedding.

  20. The biologically effective dose in inhalation nanotoxicology.

    PubMed

    Donaldson, Ken; Schinwald, Anja; Murphy, Fiona; Cho, Wan-Seob; Duffin, Rodger; Tran, Lang; Poland, Craig

    2013-03-19

    In all branches of toxicology, the biologically effective dose (BED) is the fraction of the total dose of a toxin that actually drives any toxic effect. Knowledge of the BED has a number of applications including in building structure-activity relationships, the selection of metrics, the design of safe particles, and the determination of when a nanoparticle (NP) can be considered to be "new" for regulatory purposes. In particle toxicology, we define the BED as "the entity within any dose of particles in tissue that drives a critical pathophysiogically relevant form of toxicity (e.g., oxidative stress, inflammation, genotoxicity, or proliferation) or a process that leads to it." In conventional chemical toxicology, researchers generally use the mass as the metric to describe dose (such as mass per unit tissue or cells in culture) because of its convenience. Concentration, calculated from mass, may also figure in any description of dose. In the case of a nanoparticle dose, researchers use either the mass or the surface area. The mass of nanoparticles is not the only driver of their activity: the surfaces of insoluble particles interact with biological systems, and soluble nanoparticles can release factors that interact with these systems. Nanoparticle shape can modify activity. In this Account, we describe the current knowledge of the BED as it pertains to different NP types. Soluble toxins released by NPs represent one potential indicator of BED for wholly or partially soluble NPs composed of copper or zinc. Rapid dissolution of these NPs into their toxic ions in the acidic environment of the macrophage phagolysosome causes those ions to accumulate, which leads to lysosome destabilization and inflammation. In contrast, soluble NPs that release low toxicity ions, such as magnesium oxide NPs, are not inflammogenic. For insoluble NPs, ζ potential can serve as a BED measurement because the exposure of the particle surface to the acidic milieu of the phagolysosome and

  1. GENERAL CONSIDERATIONS OF DOSE-EFFECT AND DOSE-RESPONSE RELATIONSHIPS

    EPA Science Inventory

    ABSTRACT In 2003, the International Union of Pure and Applied chemistry (IUPAC) issued a glossary of terms that included the defi nition of dose-effect and doseresponse relationships (Nordberg et al., 2004). Dose effect relationship is defined as an association between dose and...

  2. GENERAL CONSIDERATIONS OF DOSE-EFFECT AND DOSE-RESPONSE RELATIONSHIPS

    EPA Science Inventory

    ABSTRACT In 2003, the International Union of Pure and Applied chemistry (IUPAC) issued a glossary of terms that included the defi nition of dose-effect and doseresponse relationships (Nordberg et al., 2004). Dose effect relationship is defined as an association between dose and...

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

    PubMed Central

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

    2014-01-01

    Objective: 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. Methods: 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. Results: 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. Conclusion: 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. Advances in knowledge: 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. PMID:25189417

  4. Prospective memory deficits in illicit polydrug users are associated with the average long-term typical dose of ecstasy typically consumed in a single session.

    PubMed

    Gallagher, Denis T; Hadjiefthyvoulou, Florentia; Fisk, John E; Montgomery, Catharine; Robinson, Sarita J; Judge, Jeannie

    2014-01-01

    Neuroimaging evidence suggests that ecstasy-related reductions in SERT densities relate more closely to the number of tablets typically consumed per session rather than estimated total lifetime use. To better understand the basis of drug related deficits in prospective memory (p.m.) we explored the association between p.m. and average long-term typical dose and long-term frequency of use. Study 1: Sixty-five ecstasy/polydrug users and 85 nonecstasy users completed an event-based, a short-term and a long-term time-based p.m. task. Study 2: Study 1 data were merged with outcomes on the same p.m. measures from a previous study creating a combined sample of 103 ecstasy/polydrug users, 38 cannabis-only users, and 65 nonusers of illicit drugs. Study 1: Ecstasy/polydrug users had significant impairments on all p.m. outcomes compared with nonecstasy users. Study 2: Ecstasy/polydrug users were impaired in event-based p.m. compared with both other groups and in long-term time-based p.m. compared with nonillicit drug users. Both drug using groups did worse on the short-term time-based p.m. task compared with nonusers. Higher long-term average typical dose of ecstasy was associated with poorer performance on the event and short-term time-based p.m. tasks and accounted for unique variance in the two p.m. measures over and above the variance associated with cannabis and cocaine use. The typical ecstasy dose consumed in a single session is an important predictor of p.m. impairments with higher doses reflecting increasing tolerance giving rise to greater p.m. impairment.

  5. Effects of low doses of radiation.

    PubMed

    Fry, R J

    1996-06-01

    This is a brief review of what is known from experimental studies about the effects of low doses of radiation, and approaches that might improve risk estimates are discussed. The dose-response relationships for cancer induction by radiation vary markedly between tissues. The evidence suggests that 1) the induction of the initial events is dependent on the cell type because the size and/or the number of targets and how the cells handle the initial lesions differs between cell types; and 2) there are marked differences among tissues how initial lesions are expressed and proceed to overt cancer. The recent findings about adaptive responses are discussed in the context of what they contribute to our understanding about the response to irradiation. Lastly, the possibility of extending the approach of determining "The probability of causation," which Vic Bond played such an important role in establishing, is raised.

  6. Space Radiation Quality Factors and the Delta Ray Dose and Dose-Rate Reduction Effectiveness Factor.

    PubMed

    Cucinotta, Francis A; Cacao, Eliedonna; Alp, Murat

    2016-03-01

    In this paper, the authors recommend that the dose and dose-rate effectiveness factor used for space radiation risk assessments should be based on a comparison of the biological effects of energetic electrons produced along a cosmic ray particles path in low fluence exposures to high dose-rate gamma-ray exposures of doses of about 1 Gy. Methods to implement this approach are described.

  7. Hormones and Endocrine-Disrupting Chemicals: Low-Dose Effects and Nonmonotonic Dose Responses

    PubMed Central

    Colborn, Theo; Hayes, Tyrone B.; Heindel, Jerrold J.; Jacobs, David R.; Lee, Duk-Hee; Shioda, Toshi; Soto, Ana M.; vom Saal, Frederick S.; Welshons, Wade V.; Zoeller, R. Thomas

    2012-01-01

    For decades, studies of endocrine-disrupting chemicals (EDCs) have challenged traditional concepts in toxicology, in particular the dogma of “the dose makes the poison,” because EDCs can have effects at low doses that are not predicted by effects at higher doses. Here, we review two major concepts in EDC studies: low dose and nonmonotonicity. Low-dose effects were defined by the National Toxicology Program as those that occur in the range of human exposures or effects observed at doses below those used for traditional toxicological studies. We review the mechanistic data for low-dose effects and use a weight-of-evidence approach to analyze five examples from the EDC literature. Additionally, we explore nonmonotonic dose-response curves, defined as a nonlinear relationship between dose and effect where the slope of the curve changes sign somewhere within the range of doses examined. We provide a detailed discussion of the mechanisms responsible for generating these phenomena, plus hundreds of examples from the cell culture, animal, and epidemiology literature. We illustrate that nonmonotonic responses and low-dose effects are remarkably common in studies of natural hormones and EDCs. Whether low doses of EDCs influence certain human disorders is no longer conjecture, because epidemiological studies show that environmental exposures to EDCs are associated with human diseases and disabilities. We conclude that when nonmonotonic dose-response curves occur, the effects of low doses cannot be predicted by the effects observed at high doses. Thus, fundamental changes in chemical testing and safety determination are needed to protect human health. PMID:22419778

  8. Analysis of average density difference effect in a new two-lane lattice model

    NASA Astrophysics Data System (ADS)

    Zhang, Geng; Sun, Di-Hua; Zhao, Min; Liu, Wei-Ning; Cheng, Sen-Lin

    2015-11-01

    A new lattice model is proposed by taking the average density difference effect into account for two-lane traffic system according to Transportation Cyber-physical Systems. The influence of average density difference effect on the stability of traffic flow is investigated through linear stability theory and nonlinear reductive perturbation method. The linear analysis results reveal that the unstable region would be reduced by considering the average density difference effect. The nonlinear kink-antikink soliton solution derived from the mKdV equation is analyzed to describe the properties of traffic jamming transition near the critical point. Numerical simulations confirm the analytical results showing that traffic jam can be suppressed efficiently by considering the average density difference effect for two-lane traffic system.

  9. Measurement of the depth distribution of average LET and absorbed dose inside a water-filled phantom on board space station MIR.

    PubMed

    Berger, T; Hajek, M; Schoner, W; Fugger, M; Vana, N; Noll, M; Ebner, R; Akatov, Y; Shurshakov, V; Arkhangelsky, V

    2001-01-01

    The Atominstitute of the Austrian Universities developed the HTR-method for determination of absorbed dose and "averaged" linear energy transfer (LET) in mixed radiation fields. The method was applied with great success during several space missions (e.g. STS-60, STS-63, BION-10 and BION-11) and on space station MIR in the past 10 years. It utilises the changes of peak height ratios in LiF thermoluminescent glowcurves in dependence on the LET. Due to the small size of these dosemeters the HTR-method can be used also for measurements inside tissue equivalent phantoms. A water filled phantom with a diameter of 35 cm containing four channels where dosemeters can be exposed in different depths was developed by the Institute for Biomedical Problems. This opens the possibility to measure the depth distribution of the average LET and the dose equivalent simultaneously. During phase 1 dosemeters were exposed for 271 days (05.1997-02.1998) in 6 different depths inside the phantom, which was positioned in the commander cabin. In phase 2 dosemeters were exposed in 2 channels in 6 different depths for 102 days (05.1998-08.1998) in the board engineer cabin, following an exposure in different channels in 3 different depths for 199 days (08.1998- 02.1999) in the Modul KWANT 2.

  10. Dose rate and annealing effects on total dose response of MOS and bipolar circuits

    SciTech Connect

    Carriere, T.; Beaucour, J.; Gach, A.; Johlander, B.; Adams, L.

    1995-12-01

    Different part types of major technology families were irradiated in order to study dose rate and post irradiation annealing effects. Results confirm that degradation of MOS technologies at low dose rates can be predicted from high dose rate and annealing measurements, while this is not possible for bipolar linear IC`s. The ESA/SCC22900 test method is discussed.

  11. MO-F-CAMPUS-I-02: Accuracy in Converting the Average Breast Dose Into the Mean Glandular Dose (MGD) Using the F-Factor in Cone Beam Breast CT- a Monte Carlo Study Using Homogeneous and Quasi-Homogeneous Phantoms

    SciTech Connect

    Lai, C; Zhong, Y; Wang, T; Shaw, C

    2015-06-15

    Purpose: To investigate the accuracy in estimating the mean glandular dose (MGD) for homogeneous breast phantoms by converting from the average breast dose using the F-factor in cone beam breast CT. Methods: EGSnrc-based Monte Carlo codes were used to estimate the MGDs. 13-cm in diameter, 10-cm high hemi-ellipsoids were used to simulate pendant-geometry breasts. Two different types of hemi-ellipsoidal models were employed: voxels in quasi-homogeneous phantoms were designed as either adipose or glandular tissue while voxels in homogeneous phantoms were designed as the mixture of adipose and glandular tissues. Breast compositions of 25% and 50% volume glandular fractions (VGFs), defined as the ratio of glandular tissue voxels to entire breast voxels in the quasi-homogeneous phantoms, were studied. These VGFs were converted into glandular fractions by weight and used to construct the corresponding homogeneous phantoms. 80 kVp x-rays with a mean energy of 47 keV was used in the simulation. A total of 109 photons were used to image the phantoms and the energies deposited in the phantom voxels were tallied. Breast doses in homogeneous phantoms were averaged over all voxels and then used to calculate the MGDs using the F-factors evaluated at the mean energy of the x-rays. The MGDs for quasi-homogeneous phantoms were computed directly by averaging the doses over all glandular tissue voxels. The MGDs estimated for the two types of phantoms were normalized to the free-in-air dose at the iso-center and compared. Results: The normalized MGDs were 0.756 and 0.732 mGy/mGy for the 25% and 50% VGF homogeneous breasts and 0.761 and 0.733 mGy/mGy for the corresponding quasi-homogeneous breasts, respectively. The MGDs estimated for the two types of phantoms were similar within 1% in this study. Conclusion: MGDs for homogeneous breast models may be adequately estimated by converting from the average breast dose using the F-factor.

  12. Dose-dependent model of caffeine effects on human vigilance during total sleep deprivation.

    PubMed

    Ramakrishnan, Sridhar; Laxminarayan, Srinivas; Wesensten, Nancy J; Kamimori, Gary H; Balkin, Thomas J; Reifman, Jaques

    2014-10-07

    Caffeine is the most widely consumed stimulant to counter sleep-loss effects. While the pharmacokinetics of caffeine in the body is well-understood, its alertness-restoring effects are still not well characterized. In fact, mathematical models capable of predicting the effects of varying doses of caffeine on objective measures of vigilance are not available. In this paper, we describe a phenomenological model of the dose-dependent effects of caffeine on psychomotor vigilance task (PVT) performance of sleep-deprived subjects. We used the two-process model of sleep regulation to quantify performance during sleep loss in the absence of caffeine and a dose-dependent multiplier factor derived from the Hill equation to model the effects of single and repeated caffeine doses. We developed and validated the model fits and predictions on PVT lapse (number of reaction times exceeding 500 ms) data from two separate laboratory studies. At the population-average level, the model captured the effects of a range of caffeine doses (50-300 mg), yielding up to a 90% improvement over the two-process model. Individual-specific caffeine models, on average, predicted the effects up to 23% better than population-average caffeine models. The proposed model serves as a useful tool for predicting the dose-dependent effects of caffeine on the PVT performance of sleep-deprived subjects and, therefore, can be used for determining caffeine doses that optimize the timing and duration of peak performance.

  13. Thermal motion in proteins: Large effects on the time-averaged interaction energies

    SciTech Connect

    Goethe, Martin Rubi, J. Miguel; Fita, Ignacio

    2016-03-15

    As a consequence of thermal motion, inter-atomic distances in proteins fluctuate strongly around their average values, and hence, also interaction energies (i.e. the pair-potentials evaluated at the fluctuating distances) are not constant in time but exhibit pronounced fluctuations. These fluctuations cause that time-averaged interaction energies do generally not coincide with the energy values obtained by evaluating the pair-potentials at the average distances. More precisely, time-averaged interaction energies behave typically smoother in terms of the average distance than the corresponding pair-potentials. This averaging effect is referred to as the thermal smoothing effect. Here, we estimate the strength of the thermal smoothing effect on the Lennard-Jones pair-potential for globular proteins at ambient conditions using x-ray diffraction and simulation data of a representative set of proteins. For specific atom species, we find a significant smoothing effect where the time-averaged interaction energy of a single atom pair can differ by various tens of cal/mol from the Lennard-Jones potential at the average distance. Importantly, we observe a dependency of the effect on the local environment of the involved atoms. The effect is typically weaker for bulky backbone atoms in beta sheets than for side-chain atoms belonging to other secondary structure on the surface of the protein. The results of this work have important practical implications for protein software relying on free energy expressions. We show that the accuracy of free energy expressions can largely be increased by introducing environment specific Lennard-Jones parameters accounting for the fact that the typical thermal motion of protein atoms depends strongly on their local environment.

  14. The Better-than-Average Effect and 1 Corinthians 13: A Classroom Exercise

    ERIC Educational Resources Information Center

    Swenson, John Eric, III; Schneller, Gregory R.; Henderson, Joy Ann

    2014-01-01

    People tend to evaluate themselves more favorably than they evaluate others, a tendency that is known as the better-than-average effect (BTA effect; Alicke, 1985; Brown, 1986). In an attempt to demonstrate the concept of the BTA effect, a classroom exercise was conducted with 78 undergraduate students in an "Introduction to Psychology"…

  15. The Dopaminergic Midbrain Mediates an Effect of Average Reward on Pavlovian Vigor.

    PubMed

    Rigoli, Francesco; Chew, Benjamin; Dayan, Peter; Dolan, Raymond J

    2016-09-01

    Dopamine plays a key role in motivation. Phasic dopamine response reflects a reinforcement prediction error (RPE), whereas tonic dopamine activity is postulated to represent an average reward that mediates motivational vigor. However, it has been hard to find evidence concerning the neural encoding of average reward that is uncorrupted by influences of RPEs. We circumvented this difficulty in a novel visual search task where we measured participants' button pressing vigor in a context where information (underlying an RPE) about future average reward was provided well before the average reward itself. Despite no instrumental consequence, participants' pressing force increased for greater current average reward, consistent with a form of Pavlovian effect on motivational vigor. We recorded participants' brain activity during task performance with fMRI. Greater average reward was associated with enhanced activity in dopaminergic midbrain to a degree that correlated with the relationship between average reward and pressing vigor. Interestingly, an opposite pattern was observed in subgenual cingulate cortex, a region implicated in negative mood and motivational inhibition. These findings highlight a crucial role for dopaminergic midbrain in representing aspects of average reward and motivational vigor.

  16. Platelet inhibitory effects of OTC doses of naproxen sodium compared with prescription dose naproxen sodium and low-dose aspirin.

    PubMed

    Schiff, Michael; Hochberg, Marc C; Oldenhof, John; Brune, Kay

    2009-10-01

    Prescription dose naproxen has been reported to have an antiplatelet effect similar to low-dose aspirin (ASA). This study evaluated the platelet inhibitory effects of over-the-counter (OTC) doses of naproxen sodium (NAPSO) compared to that of a prescription dose of NAPSO and to low-dose enteric-coated aspirin (EC-ASA). This was a phase I, open-label, randomized, placebo-controlled, two-way crossover, multi-dose, pharmacodynamic trial conducted in healthy male and female volunteers (n = 48, mean age = 41.7 years). All subjects received 7 days of either prescription dose NAPSO (550 mg twice daily), OTC doses of NAPSO (220 mg two or three times daily), or placebo twice daily (period 1). After a minimum 6-day washout period, all subjects then received 7 days of EC-ASA 81 mg once daily (period 2). All study medications were taken by mouth. Inhibition of serum thromboxane B(2) (TXB(2)), as a marker of platelet cyclooxygenase-1 (COX-1) inhibition, measured 24 h after the day 7 morning dose. This was measured after both period 1 and period 2. After 7 days of treatment in period 1, mean inhibition of TXB(2) was 47% for placebo and > or =98% for all doses of NAPSO. After 7 days of EC-ASA 81 mg, mean inhibition of TXB(2) was > or = 97% (period 2). Out-patient study setting. These data suggest that OTC doses of NAPSO (220 mg two or three times daily) have an antiplatelet effect similar to EC-ASA 81 mg and to prescription dose NAPSO (550 mg twice daily).

  17. Bayesian designs of phase II oncology trials to select maximum effective dose assuming monotonic dose-response relationship

    PubMed Central

    2014-01-01

    Background For many molecularly targeted agents, the probability of response may be assumed to either increase or increase and then plateau in the tested dose range. Therefore, identifying the maximum effective dose, defined as the lowest dose that achieves a pre-specified target response and beyond which improvement in the response is unlikely, becomes increasingly important. Recently, a class of Bayesian designs for single-arm phase II clinical trials based on hypothesis tests and nonlocal alternative prior densities has been proposed and shown to outperform common Bayesian designs based on posterior credible intervals and common frequentist designs. We extend this and related approaches to the design of phase II oncology trials, with the goal of identifying the maximum effective dose among a small number of pre-specified doses. Methods We propose two new Bayesian designs with continuous monitoring of response rates across doses to identify the maximum effective dose, assuming monotonicity of the response rate across doses. The first design is based on Bayesian hypothesis tests. To determine whether each dose level achieves a pre-specified target response rate and whether the response rates between doses are equal, multiple statistical hypotheses are defined using nonlocal alternative prior densities. The second design is based on Bayesian model averaging and also uses nonlocal alternative priors. We conduct simulation studies to evaluate the operating characteristics of the proposed designs, and compare them with three alternative designs. Results In terms of the likelihood of drawing a correct conclusion using similar between-design average sample sizes, the performance of our proposed design based on Bayesian hypothesis tests and nonlocal alternative priors is more robust than that of the other designs. Specifically, the proposed Bayesian hypothesis test-based design has the largest probability of being the best design among all designs under comparison and

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

    NASA Technical Reports Server (NTRS)

    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.

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

    PubMed

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

    2016-12-01

    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. 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. 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. 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. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

  20. Investigation of natural effective gamma dose rates case study: Ardebil Province in Iran

    PubMed Central

    2012-01-01

    Gamma rays pose enough energy to induce chemical changes that may be biologically important for the normal functioning of body cells. The external exposure of human beings to natural environmental gamma radiation normally exceeds that from all man-made sources combined. In this research natural background gamma dose rates and corresponding annual effective doses were determined for selected cities of Ardebil province. Outdoor gamma dose rates were measured using an Ion Chamber Survey Meter in 105 locations in selected districts. Average absorbed doses for Ardebil, Sar-Ein, Germy, Neer, Shourabil Recreational Lake, and Kosar were determined as 265, 219, 344, 233, 352, and 358 nSv/h, respectively. Although dose rates recorded for Germi and Kosar are comparable with some areas with high natural radiation background, however, the dose rates in other districts are well below the levels reported for such locations. Average annual effective dose due to indoor and outdoor gamma radiation for Ardebil province was estimated as 1.73 (1.35–2.39) mSv, which is on average 2 times higher than the world population weighted average. PMID:23369115

  1. The effect of sensor sheltering and averaging techniques on wind measurements at the Shuttle Landing Facility

    NASA Technical Reports Server (NTRS)

    Merceret, Francis J.

    1995-01-01

    This document presents results of a field study of the effect of sheltering of wind sensors by nearby foliage on the validity of wind measurements at the Space Shuttle Landing Facility (SLF). Standard measurements are made at one second intervals from 30-feet (9.1-m) towers located 500 feet (152 m) from the SLF centerline. The centerline winds are not exactly the same as those measured by the towers. A companion study, Merceret (1995), quantifies the differences as a function of statistics of the observed winds and distance between the measurements and points of interest. This work examines the effect of nearby foliage on the accuracy of the measurements made by any one sensor, and the effects of averaging on interpretation of the measurements. The field program used logarithmically spaced portable wind towers to measure wind speed and direction over a range of conditions as a function of distance from the obstructing foliage. Appropriate statistics were computed. The results suggest that accurate measurements require foliage be cut back to OFCM standards. Analysis of averaging techniques showed that there is no significant difference between vector and scalar averages. Longer averaging periods reduce measurement error but do not otherwise change the measurement in reasonably steady flow regimes. In rapidly changing conditions, shorter averaging periods may be required to capture trends.

  2. Ergogenic effects of low doses of caffeine on cycling performance.

    PubMed

    Jenkins, Nathan T; Trilk, Jennifer L; Singhal, Arpit; O'Connor, Patrick J; Cureton, Kirk J

    2008-06-01

    The purpose of this experiment was to learn whether low doses of caffeine have ergogenic, perceptual, and metabolic effects during cycling. To determine the effects of 1, 2, and 3 mg/kg caffeine on cycling performance, differentiated ratings of perceived exertion (D-RPE), quadriceps pain intensity, and metabolic responses to cycling exercise, 13 cyclists exercised on a stationary ergometer for 15 min at 80% VO, then, after 4 min of active recovery, completed a 15-min VO2peak performance ride 60 min after ingesting caffeine or placebo. Work done (kJ/kg) during the performance ride was used as a measure of performance. D-RPE, pain ratings, and expired-gas data were obtained every 3 min, and blood lactate concentrations were obtained at 15 and 30 min. Compared with placebo, caffeine doses of 2 and 3 mg/kg increased performance by 4% (95% CI: 1.0-6.8%, p = .02) and 3% (95% CI: -0.4% to 6.8%, p = .077), respectively. These effects were ergogenic, on average, but varied considerably in magnitude among individual cyclists. There were no effects of caffeine on D-RPE or pain throughout the cycling task. Selected metabolic variables were affected by caffeine, consistent with its known actions. The authors conclude that caffeine preparations of 2 and 3 mg/kg enhanced performance, but future work should aim to explain the considerable interindividual variability of the drug's ergogenic properties.

  3. TOLUENE DOSE-EFFECT META ANALYSIS AND IMPORTANCE OF EFFECTS

    EPA Science Inventory

    TOLUENE DOSE-EFFECT META ANALYSES AND IMPORTANCE OF EFFECTS
    Benignus, V.A., Research Psychologist, ORD, NHEERL, Human Studies Division,
    919-966-6242, benignus.vernon@epa.gov
    Boyes, W.K., Supervisory Health Scientist, ORD, NHEERL, Neurotoxicology Division
    919-541-...

  4. TOLUENE DOSE-EFFECT META ANALYSIS AND IMPORTANCE OF EFFECTS

    EPA Science Inventory

    TOLUENE DOSE-EFFECT META ANALYSES AND IMPORTANCE OF EFFECTS
    Benignus, V.A., Research Psychologist, ORD, NHEERL, Human Studies Division,
    919-966-6242, benignus.vernon@epa.gov
    Boyes, W.K., Supervisory Health Scientist, ORD, NHEERL, Neurotoxicology Division
    919-541-...

  5. Red bone marrow doses, integral absorbed doses, and somatically effective dose equivalent from four maxillary occlusal projections

    SciTech Connect

    Berge, T.I.; Wohni, T.

    1984-02-01

    Phantom measurements of red bone marrow (RBM) doses, integral absorbed doses, and somatically effective dose equivalent (SEDE) from four different maxillary occlusal projections are presented. For each projection, different combinations of focus-skin distances and tube potentials were compared with regard to the patient's radiation load. The axial incisal view produced the highest patient exposures, with a maximum red bone marrow dose of 122.5 microGy/exposure, integral absorbed dose of 8.6 mJ/exposure, and SEDE values of 39.6 microSv/exposure. The corresponding values from the frontal, lateral occlusal, and tuber views ranged between 4% and 44% of the axial incisal view values for the integral absorbed dose and SEDE values, and between 0.3% and 3% for the red bone marrow doses. Increasing the focus-skin distance from 17.5 cm to 27 cm is accompanied by a 24% to 30% reduction in integral absorbed dose. Increasing the tube potential from 50 kV to 65 kV likewise results in a 23% reduction in absorbed energy.

  6. Appropriate Use of Effective Dose in Radiation Protection and Risk Assessment.

    PubMed

    Fisher, Darrell R; Fahey, Frederic H

    2017-08-01

    Effective dose was introduced by the ICRP for the single, over-arching purpose of setting limits for radiation protection. Effective dose is a derived quantity or mathematical construct and not a physical, measurable quantity. The formula for calculating effective dose to a reference model incorporates terms to account for all radiation types, organ and tissue radiosensitivities, population groups, and multiple biological endpoints. The properties and appropriate applications of effective dose are not well understood by many within and outside the health physics profession; no other quantity in radiation protection has been more confusing or misunderstood. According to ICRP Publication 103, effective dose is to be used for "prospective dose assessment for planning and optimization in radiological protection, and retrospective demonstration of compliance for regulatory purposes." In practice, effective dose has been applied incorrectly to predict cancer risk among exposed persons. The concept of effective dose applies generally to reference models only and not to individual subjects. While conceived to represent a measure of cancer risk or heritable detrimental effects, effective dose is not predictive of future cancer risk. The formula for calculating effective dose incorporates committee-selected weighting factors for radiation quality and organ sensitivity; however, the organ weighting factors are averaged across all ages and both genders and thus do not apply to any specific individual or radiosensitive subpopulations such as children and young women. Further, it is not appropriate to apply effective dose to individual medical patients because patient-specific parameters may vary substantially from the assumptions used in generalized models. Also, effective dose is not applicable to therapeutic uses of radiation, as its mathematical underpinnings pertain only to observed late (stochastic) effects of radiation exposure and do not account for short-term adverse

  7. Effects of average speed enforcement on speed compliance and crashes: a review of the literature.

    PubMed

    Soole, David W; Watson, Barry C; Fleiter, Judy J

    2013-05-01

    Average speed enforcement is a relatively new approach gaining popularity throughout Europe and Australia. This paper reviews the evidence regarding the impact of this approach on vehicle speeds, crash rates and a number of additional road safety and public health outcomes. The economic and practical viability of the approach as a road safety countermeasure is also explored. A literature review, with an international scope, of both published and grey literature was conducted. There is a growing body of evidence to suggest a number of road safety benefits associated with average speed enforcement, including high rates of compliance with speed limits, reductions in average and 85th percentile speeds and reduced speed variability between vehicles. Moreover, the approach has been demonstrated to be particularly effective in reducing excessive speeding behaviour. Reductions in crash rates have also been reported in association with average speed enforcement, particularly in relation to fatal and serious injury crashes. In addition, the approach has been shown to improve traffic flow, reduce vehicle emissions and has also been associated with high levels of public acceptance. Average speed enforcement offers a greater network-wide approach to managing speeds that reduces the impact of time and distance halo effects associated with other automated speed enforcement approaches. Although comparatively expensive it represents a highly reliable approach to speed enforcement that produces considerable returns on investment through reduced social and economic costs associated with crashes.

  8. [Absorbed dose and the effective dose of panoramic temporo mandibular joint radiography].

    PubMed

    Matsuo, Ayae; Okano, Tsuneichi; Gotoh, Kenichi; Yokoi, Midori; Hirukawa, Akiko; Okumura, Shinji; Koyama, Syuji

    2011-01-01

    This study measured the radiation doses absorbed by the patient during Panoramic temporo mandibular joint radiography (Panoramic TMJ), Schüllers method and Orbitoramus projection. The dose of the frontal view in Panoramic TMJ was compared to that with Orbitoramus projection and the lateral view in Panoramic TMJ was compared to that with Schüllers method. We measured the doses received by various organs and calculated the effective doses using the guidelines of the International Commission on Radiological Protection in Publication 103. Organ absorbed doses were measured using an anthropomorphic phantom, loaded with thermoluminescent dosimeters (TLD), located at 160 sensitive sites. The dose shows the sum value of irradiation on both the right and left sides. In addition, we set a few different exposure field sizes. The effective dose for a frontal view in Panoramic TMJ was 11 µSv, and that for the lateral view was 14 µSv. The lens of the Orbitoramus projection was 40 times higher than the frontal view in Panoramic TMJ. Although the effective dose of the lateral view in Panoramic TMJ was 3 times higher than that of the small exposure field (10×10 cm on film) in Schüller's method, it was the same as that of a mid-sized exposure field. When the exposure field in the inferior 1/3 was reduced during panoramic TMJ, the effective doses could be decreased. Therefore we recommend that the size of the exposure field in Panoramic TMJ be decreased.

  9. Total ionizing dose effects of domestic SiGe HBTs under different dose rates

    NASA Astrophysics Data System (ADS)

    Liu, Mo-Han; Lu, Wu; Ma, Wu-Ying; Wang, Xin; Guo, Qi; He, Cheng-Fa; Jiang, Ke; Li, Xiao-Long; Xun, Ming-Zhu

    2016-03-01

    The total ionizing radiation (TID) response of commercial NPN silicon germanium hetero-junction bipolar transistors (SiGe HBTs) produced domestically are investigated under dose rates of 800 mGy(Si)/s and 1.3 mGy(Si)/s with a Co-60 gamma irradiation source. The changes of transistor parameters such as Gummel characteristics, and excess base current before and after irradiation, are examined. The results of the experiments show that for the KT1151, the radiation damage is slightly different under the different dose rates after prolonged annealing, and shows a time dependent effect (TDE). For the KT9041, however, the degradations of low dose rate irradiation is higher than for the high dose rate, demonstrating that there is a potential enhanced low dose rate sensitivity (ELDRS) effect for the KT9041. The possible underlying physical mechanisms of the different dose rates responses induced by the gamma rays are discussed.

  10. Estimation of genetic parameters for average daily gain using models with competition effects

    USDA-ARS?s Scientific Manuscript database

    Components of variance for ADG with models including competition effects were estimated from data provided by Pig Improvement Company on 11,235 pigs from 4 selected lines of swine. Fifteen pigs with average age of 71 d were randomly assigned to a pen by line and sex and taken off test after approxi...

  11. The Nexus between the Above-Average Effect and Cooperative Learning in the Classroom

    ERIC Educational Resources Information Center

    Breneiser, Jennifer E.; Monetti, David M.; Adams, Katharine S.

    2012-01-01

    The present study examines the above-average effect (Chambers & Windschitl, 2004; Moore & Small, 2007) in assessments of task performance. Participants completed self-estimates of performance and group estimates of performance, before and after completing a task. Participants completed a task individually and in groups. Groups were…

  12. Optimal transformation for correcting partial volume averaging effects in magnetic resonance imaging

    SciTech Connect

    Soltanian-Zadeh, H. Henry Ford Hospital, Detroit, MI ); Windham, J.P. ); Yagle, A.E. )

    1993-08-01

    Segmentation of a feature of interest while correcting for partial volume averaging effects is a major tool for identification of hidden abnormalities, fast and accurate volume calculation, and three-dimensional visualization in the field of magnetic resonance imaging (MRI). The authors present the optimal transformation for simultaneous segmentation of a desired feature and correction of partial volume averaging effects, while maximizing the signal-to-noise ratio (SNR) of the desired feature. It is proved that correction of partial volume averaging effects requires the removal of the interfering features from the scene. It is also proved that correction of partial volume averaging effects can be achieved merely by a linear transformation. It is finally shown that the optimal transformation matrix is easily obtained using the Gram-Schmidt orthogonalization procedure, which is numerically stable. Applications of the technique to MRI simulation, phantom, and brain images are shown. They show that in all cases the desired feature is segmented from the interfering features and partial volume information is visualized in the resulting transformed images.

  13. Raven's Test Performance of Sub-Saharan Africans: Average Performance, Psychometric Properties, and the Flynn Effect

    ERIC Educational Resources Information Center

    Wicherts, Jelte M.; Dolan, Conor V.; Carlson, Jerry S.; van der Maas, Han L. J.

    2010-01-01

    This paper presents a systematic review of published data on the performance of sub-Saharan Africans on Raven's Progressive Matrices. The specific goals were to estimate the average level of performance, to study the Flynn Effect in African samples, and to examine the psychometric meaning of Raven's test scores as measures of general intelligence.…

  14. Evaluating Marginal Policy Changes and the Average Effect of Treatment for Individuals at the Margin.

    PubMed

    Carneiro, Pedro; Heckman, James J; Vytlacil, Edward

    2010-01-01

    This paper develops methods for evaluating marginal policy changes. We characterize how the effects of marginal policy changes depend on the direction of the policy change, and show that marginal policy effects are fundamentally easier to identify and to estimate than conventional treatment parameters. We develop the connection between marginal policy effects and the average effect of treatment for persons on the margin of indifference between participation in treatment and nonparticipation, and use this connection to analyze both parameters. We apply our analysis to estimate the effect of marginal changes in tuition on the return to going to college.

  15. The effect of surface roughness on the average film thickness between lubricated rollers

    NASA Technical Reports Server (NTRS)

    Chow, L. S. H.; Cheng, H. S.

    1976-01-01

    The Christensen theory of stochastic models for hydrodynamic lubrication of rough surfaces is extended to elastohydrodynamic lubrication between two rollers. The Grubin-type equation including asperity effects in the inlet region is derived. Solutions for the reduced pressure at the entrance as a function of the ratio of the average nominal film thickness to the rms surface roughness (in terms of standard deviation), have been obtained numerically. Results were obtained for purely transverse and purely longitudinal surface roughness for cases with or without slip. The reduced pressure is shown to decrease slightly by considering longitudinal surface roughness. Transverse surface roughness has a slight beneficial effect on the average film thickness at the inlet. The same approach was used to study the effect of surface roughness on lubrication between rigid rollers and lubrication of an infinitely-wide slider bearing. The effects of surface roughness are shown to be similar to those found in elastohydrodynamic contacts.

  16. Visualization of Radial Peripapillary Capillaries Using Optical Coherence Tomography Angiography: The Effect of Image Averaging

    PubMed Central

    Phillips, Erika; Krawitz, Brian D.; Garg, Reena; Salim, Sarwat; Geyman, Lawrence S.; Efstathiadis, Eleni; Carroll, Joseph; Rosen, Richard B.; Chui, Toco Y. P.

    2017-01-01

    Objectives To assess the effect of image registration and averaging on the visualization and quantification of the radial peripapillary capillary (RPC) network on optical coherence tomography angiography (OCTA). Methods Twenty-two healthy controls were imaged with a commercial OCTA system (AngioVue, Optovue, Inc.). Ten 10x10° scans of the optic disc were obtained, and the most superficial layer (50-μm slab extending from the inner limiting membrane) was extracted for analysis. Rigid registration was achieved using ImageJ, and averaging of each 2 to 10 frames was performed in five ~2x2° regions of interest (ROI) located 1° from the optic disc margin. The ROI were automatically skeletonized. Signal-to-noise ratio (SNR), number of endpoints and mean capillary length from the skeleton, capillary density, and mean intercapillary distance (ICD) were measured for the reference and each averaged ROI. Repeated measures analysis of variance was used to assess statistical significance. Three patients with primary open angle glaucoma were also imaged to compare RPC density to controls. Results Qualitatively, vessels appeared smoother and closer to histologic descriptions with increasing number of averaged frames. Quantitatively, number of endpoints decreased by 51%, and SNR, mean capillary length, capillary density, and ICD increased by 44%, 91%, 11%, and 4.5% from single frame to 10-frame averaged, respectively. The 10-frame averaged images from the glaucomatous eyes revealed decreased density correlating to visual field defects and retinal nerve fiber layer thinning. Conclusions OCTA image registration and averaging is a viable and accessible method to enhance the visualization of RPCs, with significant improvements in image quality and RPC quantitative parameters. With this technique, we will be able to non-invasively and reliably study RPC involvement in diseases such as glaucoma. PMID:28068370

  17. A second-order closure model for the effect of averaging time on turbulent plume dispersion

    SciTech Connect

    Sykes, R.I.; Gabruk, R.S.

    1996-12-31

    Turbulent dispersion in the atmosphere is a result of chaotic advection by a wide spectrum of eddy motions. In genera, the larger scale motions behave like a time-dependent, spatially inhomogeneous mean wind and produce coherent meandering of a pollutant cloud or plume, while the smaller scale motions act to diffuse the pollutant and mix it with the ambient air. The distinction between the two types of motion is dependent on both the sampling procedure and the scale of the pollutant cloud. For the case of a continuous plume of material, the duration of the sampling time (the time average period) determines the effective size of the plume. The objective is the development of a practical scheme for representing the effect of time-averaging on plume width. The model must describe relative dispersion in the limit of short-term averages, and give the absolute, or ensemble, dispersion rate for long-term sampling. The authors shall generalize the second-order closure ensemble dispersion model of Sykes et al. to include the effect of time-averaging, so they first briefly review the basic model.

  18. An extended car-following model accounting for the average headway effect in intelligent transportation system

    NASA Astrophysics Data System (ADS)

    Kuang, Hua; Xu, Zhi-Peng; Li, Xing-Li; Lo, Siu-Ming

    2017-04-01

    In this paper, an extended car-following model is proposed to simulate traffic flow by considering average headway of preceding vehicles group in intelligent transportation systems environment. The stability condition of this model is obtained by using the linear stability analysis. The phase diagram can be divided into three regions classified as the stable, the metastable and the unstable ones. The theoretical result shows that the average headway plays an important role in improving the stabilization of traffic system. The mKdV equation near the critical point is derived to describe the evolution properties of traffic density waves by applying the reductive perturbation method. Furthermore, through the simulation of space-time evolution of the vehicle headway, it is shown that the traffic jam can be suppressed efficiently with taking into account the average headway effect, and the analytical result is consistent with the simulation one.

  19. On the Correlation of Effective Terahertz Refractive Index and Average Surface Roughness of Pharmaceutical Tablets

    NASA Astrophysics Data System (ADS)

    Chakraborty, Mousumi; Bawuah, Prince; Tan, Nicholas; Ervasti, Tuomas; Pääkkönen, Pertti; Zeitler, J. Axel; Ketolainen, Jarkko; Peiponen, Kai-Erik

    2016-08-01

    In this paper, we have studied terahertz (THz) pulse time delay of porous pharmaceutical microcrystalline compacts and also pharmaceutical tablets that contain indomethacin (painkiller) as an active pharmaceutical ingredient (API) and microcrystalline cellulose as the matrix of the tablet. The porosity of a pharmaceutical tablet is important because it affects the release of drug substance. In addition, surface roughness of the tablet has much importance regarding dissolution of the tablet and hence the rate of drug release. Here, we show, using a training set of tablets containing API and with a priori known tablet's quality parameters, that the effective refractive index (obtained from THz time delay data) of such porous tablets correlates with the average surface roughness of a tablet. Hence, THz pulse time delay measurement in the transmission mode provides information on both porosity and the average surface roughness of a compact. This is demonstrated for two different sets of pharmaceutical tablets having different porosity and average surface roughness values.

  20. Why aren't lower, effective, OTC doses available earlier by prescription?

    PubMed

    Cohen, Jay S

    2003-01-01

    Many popular oral over-the-counter (OTC) drugs were originally available only by prescription, but not at the low doses contained in their OTC counterparts. Yet, if OTC doses are effective for treating mild symptoms, why weren't these low, often safer doses made available at least by prescription when the drugs were first approved? To examine issues surrounding the delayed approval of OTC doses by the Food and Drug Administration (FDA). Information reviewed included package inserts, data obtained from manufacturers, and articles published in MEDLINE (1966 to December 2001). Medications examined included presently available and potentially approved OTC antiinflammatory, gastrointestinal, and antihistamine drugs. Considerable data demonstrate the effectiveness of ibuprofen, naproxen, ranitidine, famotidine, nizatidine, diphenhydramine, and clemastine at OTC doses. Published studies also show the effectiveness of celecoxib, omeprazole, and fexofenadine at doses 33-50% lower than currently recommended for prescription use. OTC doses are effective for many patients with mild symptoms and for some with serious symptoms. However, OTC-like doses are usually not offered when drugs are approved for prescription use because new drugs are usually studied in patients with serious conditions requiring higher doses; manufacturers and the FDA seem to prefer a middle-dose approach; >75% of subjects in premarketing dose studies are male; and averaging the responses of study subjects may obscure a wide range of interindividual variation in drug response. Simplistic dosage guidelines make therapeutic decisions easier. Because dose-related adverse effects frequently diminish quality-of-life and reduce adherence, the early availability of OTC-like doses, at least by prescription, would allow healthcare professionals greater flexibility in matching medication doses to patients' widely differing needs.

  1. Low-dose effects of hormones and endocrine disruptors.

    PubMed

    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.

  2. Effect of deformable registration uncertainty on lung SBRT dose accumulation

    PubMed Central

    Samavati, Navid; Velec, Michael; Brock, Kristy K.

    2016-01-01

    Purpose: Deformable image registration (DIR) plays an important role in dose accumulation, such as incorporating breathing motion into the accumulation of the delivered dose based on daily 4DCBCT images. However, it is not yet well understood how the uncertainties associated with DIR methods affect the dose calculations and resulting clinical metrics. The purpose of this study is to evaluate the impact of DIR uncertainty on the clinical metrics derived from its use in dose accumulation. Methods: A biomechanical model based DIR method and a biomechanical-intensity-based hybrid method, which reduced the average registration error by 1.6 mm, were applied to ten lung cancer patients. A clinically relevant dose parameter [minimum dose to 0.5 cm3 (Dmin)] was calculated for three dose scenarios using both algorithms. Dose scenarios included static (no breathing motion), predicted (breathing motion at the time of planning), and total accumulated (interfraction breathing motion). The relationship between the dose parameter and a combination of DIR uncertainty metrics, tumor volume, and dose heterogeneity of the plan was investigated. Results: Depending on the dose heterogeneity, tumor volume, and DIR uncertainty, in over 50% of the patients, differences greater than 1.0 Gy were observed in the Dmin of the tumor in the static dose calculation on exhale phase of the 4DCT. Such differences were due to the errors in propagating the tumor contours from the reference planning 4DCT phase onto a subsequent 4DCT phase using each DIR algorithm and calculating the dose on that phase. The differences in predicted dose were more subtle when breathing motion was modeled explicitly at the time of planning with only one patient exhibiting a greater than 1.0 Gy difference in Dmin. Dmin differences of up to 2.5 Gy were found in the total accumulated delivered dose due to difference in quantifying the interfraction variations. Such dose uncertainties could potentially be clinically

  3. The relative biological effectiveness of out-of-field dose

    NASA Astrophysics Data System (ADS)

    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.

  4. Effects of oral doses of fluoride on nestling European starlings

    USGS Publications Warehouse

    Fleming, W.J.; Grue, C.E.; Schuler, C.A.; Bunck, C.M.

    1987-01-01

    Nestling European starlings (Sturnus vulgaris), raised and fed by free-living adults, were given daily oral doses of either distilled water, 193 mg sodium as Na2CO3 per kg of body weight (sodium control group), or 6, 10, 13, 17,23, 30, 40, 80, 160 mg of the fluoride ion as NaF in distilled water per kg of body weight (mg/kg). Dosing began when nestlings were 24-48 hr old and continued for 16 days. The 24-hr LD50 of fluoride for day-old starlings was 50 mg/kg. The 16-day LD50 was 17 mg/kg. The sodium control group did not differ from the water control group with respect to any of the measured variables. Growth rates were significantly reduced in the 13 and 17 mg of fluoride/kg groups; weights of birds given higher dose levels were omitted from growth comparisons because of high, fluoride-induced mortality. Although pre-fledging weights for the 10, 13, and 17 mg of fluoride/kg groups averaged 3.6 to 8.6% less than controls at 17 days, this difference was not significant. Feather and bone growth of the fluoride and control groups were not different, except for keel length measured at 17 days of age which averaged less in the fluoride groups. Liver and spleen weights were not affected by fluoride treatments. No histological damage related to fluoride treatments was found in liver, spleen, or kidney. The logarithm of bone fluoride and magnesium concentration increased with the logarithm of increasing fluoride treatment levels and were significantly correlated with each other. Fluoride treatments had no effect on percent calcium or phosphorus in bone or plasma alkaline phosphatase activity. Oral doses of fluoride appear to be more toxic than equivalent dietary levels. Most birds probably acquire fluoride through their diet. Therefore, the results of the study may overestimate the potential effects of fluorides on songbirds living in fluoride-contaminated environments.

  5. Equivalent dose and effective dose from stray radiation during passively scattered proton radiotherapy for prostate cancer

    NASA Astrophysics Data System (ADS)

    Fontenot, Jonas; Taddei, Phillip; Zheng, Yuanshui; Mirkovic, Dragan; Jordan, Thomas; Newhauser, Wayne

    2008-03-01

    Proton therapy reduces the integral therapeutic dose required for local control in prostate patients compared to intensity-modulated radiotherapy. One proposed benefit of this reduction is an associated decrease in the incidence of radiogenic secondary cancers. However, patients are also exposed to stray radiation during the course of treatment. The purpose of this study was to quantify the stray radiation dose received by patients during proton therapy for prostate cancer. Using a Monte Carlo model of a proton therapy nozzle and a computerized anthropomorphic phantom, we determined that the effective dose from stray radiation per therapeutic dose (E/D) for a typical prostate patient was approximately 5.5 mSv Gy-1. Sensitivity analysis revealed that E/D varied by ±30% over the interval of treatment parameter values used for proton therapy of the prostate. Equivalent doses per therapeutic dose (HT/D) in specific organs at risk were found to decrease with distance from the isocenter, with a maximum of 12 mSv Gy-1 in the organ closest to the treatment volume (bladder) and 1.9 mSv Gy-1 in the furthest (esophagus). Neutrons created in the nozzle predominated effective dose, though neutrons created in the patient contributed substantially to the equivalent dose in organs near the proton field. Photons contributed less than 15% to equivalent doses.

  6. Cognitive Capitalism: Economic Freedom Moderates the Effects of Intellectual and Average Classes on Economic Productivity.

    PubMed

    Coyle, Thomas R; Rindermann, Heiner; Hancock, Dale

    2016-10-01

    Cognitive ability stimulates economic productivity. However, the effects of cognitive ability may be stronger in free and open economies, where competition rewards merit and achievement. To test this hypothesis, ability levels of intellectual classes (top 5%) and average classes (country averages) were estimated using international student assessments (Programme for International Student Assessment; Trends in International Mathematics and Science Study; and Progress in International Reading Literacy Study) (N = 99 countries). The ability levels were correlated with indicators of economic freedom (Fraser Institute), scientific achievement (patent rates), innovation (Global Innovation Index), competitiveness (Global Competitiveness Index), and wealth (gross domestic product). Ability levels of intellectual and average classes strongly predicted all economic criteria. In addition, economic freedom moderated the effects of cognitive ability (for both classes), with stronger effects at higher levels of freedom. Effects were particularly robust for scientific achievements when the full range of freedom was analyzed. The results support cognitive capitalism theory: cognitive ability stimulates economic productivity, and its effects are enhanced by economic freedom. © The Author(s) 2016.

  7. Spatial averaging effects of hydrophone on field characterization of planar transducer using Fresnel approximation.

    PubMed

    Xing, Guangzhen; Yang, Ping; He, Longbiao; Feng, Xiujuan

    2016-09-01

    The purpose of this work was to improve the existing models that allow spatial averaging effects of piezoelectric hydrophones to be accounted for. The model derived in the present study is valid for a planar source and was verified using transducers operating at 5 and 20MHz. It is based on Fresnel approximation and enables corrections for both on-axis and off-axis measurements. A single-integral approximate formula for the axial acoustic pressure was derived, and the validity of the Fresnel approximation in the near field of the planar transducer was examined. The numerical results obtained using 5 and 20MHz planar transmitters with an effective diameter of 12.7mm showed that the derived model could account for spatial averaging effects to within 0.2% with Beissner's exact integral (Beissner, 1981), for k(a+b)2≫π (where k is the circular wavenumber, and a and b are the effective radii of the transmitter and hydrophone, respectively). The field distributions along the acoustic axis and the beam directivity patterns are also included in the model. The spatial averaging effects of the hydrophone were generally observed to cause underestimation of the absolute pressure amplitudes of the acoustic beam, and overestimation of the cross-sectional size of the beam directivity pattern. However, the cross-sectional size of the directivity pattern was also found to be underestimated in the "far zone" (beyond Y0=a(2)/λ) of the transmitter. The results of this study indicate that the spatial averaging effect on the beam directivity pattern is negligible for π(γ(2)+4γ)s≪1 (where γ=b/a, and s is the normalized distance to the planar transducer).

  8. Effective dose estimation during conventional and CT urography

    NASA Astrophysics Data System (ADS)

    Alzimami, K.; Sulieman, A.; Omer, E.; Suliman, I. I.; Alsafi, K.

    2014-11-01

    Intravenous urography (IVU) and CT urography (CTU) are efficient radiological examinations for the evaluation of the urinary system disorders. However patients are exposed to a significant radiation dose. The objectives of this study are to: (i) measure and compare patient radiation dose by computed tomography urography (CTU) and conventional intravenous urography (IVU) and (ii) evaluate organ equivalent dose and cancer risks from CTU and IVU imaging procedures. A total of 141 patients were investigated. A calibrated CT machine (Siemens-Somatom Emotion duo) was used for CTU, while a Shimadzu X ray machine was used for IVU. Thermoluminescence dosimeters (TLD-GR200A) were used to measure patients' entrance surface doses (ESD). TLDs were calibrated under reproducible reference conditions. Patients radiation dose values (DLP) for CTU were 172±61 mGy cm, CTDIvol 4.75±2 mGy and effective dose 2.58±1 mSv. Patient cancer probabilities were estimated to be 1.4 per million per CTU examination. Patients ESDs values for IVU were 21.62±5 mGy, effective dose 1.79±1 mSv. CT involves a higher effective dose than IVU. In this study the radiation dose is considered low compared to previous studies. The effective dose from CTU procedures was 30% higher compared to IVU procedures. Wide dose variation between patient doses suggests that optimization is not fulfilled yet.

  9. Effects of Respiration-Induced Density Variations on Dose Distributions in Radiotherapy of Lung Cancer

    SciTech Connect

    Mexner, Vanessa; Wolthaus, Jochem W.H.; Herk, Marcel van; Damen, Eugene M.F.; Sonke, Jan-Jakob

    2009-07-15

    Purpose: To determine the effect of respiration-induced density variations on the estimated dose delivered to moving structures and, consequently, to evaluate the necessity of using full four-dimensional (4D) treatment plan optimization. Methods and Materials: In 10 patients with large tumor motion (median, 1.9 cm; range, 1.1-3.6 cm), the clinical treatment plan, designed using the mid-ventilation ([MidV]; i.e., the 4D-CT frame closest to the time-averaged mean position) CT scan, was recalculated on all 4D-CT frames. The cumulative dose was determined by transforming the doses in all breathing phases to the MidV geometry using deformable registration and then averaging the results. To determine the effect of density variations, this cumulative dose was compared with the accumulated dose after similarly deforming the planned (3D) MidV-dose in each respiratory phase using the same transformation (i.e., 'blurring the dose'). Results: The accumulated tumor doses, including and excluding density variations, were almost identical. Relative differences in the minimum gross tumor volume (GTV) dose were less than 2% for all patients. The relative differences were even smaller in the mean lung dose and the V20 (<0.5% and 1%, respectively). Conclusions: The effect of respiration-induced density variations on the dose accumulated over the respiratory cycle was very small, even in the presence of considerable respiratory motion. A full 4D-dose calculation for treatment planning that takes into account such density variations is therefore not required. Planning using the MidV-CT derived from 4D-CT with an appropriate margin for geometric uncertainties is an accurate and safe method to account for respiration-induced anatomy variations.

  10. Comparing effects in spike-triggered averages of rectified EMG across different behaviors

    PubMed Central

    Davidson, Adam G.; O’Dell, Ryan; Chan, Vanessa; Schieber, Marc H.

    2007-01-01

    Effects in spike-triggered averages (SpikeTAs) of rectified electromyographic activity (EMG) compiled for the same neuron-muscle pair during various behaviors often appear different. Do these differences represent significant changes in the effect of the neuron on the muscle activity? Quantitative comparison of such differences has been limited by two methodological problems, which we address here. First, although the linear baseline trend of many SpikeTAs can be adjusted with ramp subtraction, the curvilinear baseline trend of other SpikeTAs can not. To address this problem, we estimated baseline trends using a form of moving average. Artificial triggers were created in 1 ms increments from 40 ms before to 40 ms after each spike used to compile the SpikeTA. These 81 triggers were used to compile another average of rectified EMG, which we call a single-spike increment shifted average (single-spike ISA). Single-spike ISAs were averaged to produce an overall ISA, which captured slow trends in the baseline EMG while distributing any spike-locked features evenly throughout the 80 ms analysis window. The overall ISA then was subtracted from the initial SpikeTA, removing any slow baseline trends for more accurate measurement of SpikeTA effects. Second, the measured amplitude and temporal characteristics of SpikeTA effects produced by the same neuron-muscle pair may vary during different behaviors. But whether or not such variation is significant has been difficult to ascertain. We therefore applied a multiple fragment approach to permit statistical comparison of the measured features of SpikeTA effects for the same neuron-muscle pair during different behavioral epochs. Spike trains recorded in each task were divided into non-overlapping fragments of 100 spikes each, and a separate, ISA-corrected, SpikeTA was compiled for each fragment. Measurements made on these fragment SpikeTAs then were used as test statistics for comparison of peak percent increase, mean percent

  11. Determination of minimum effective dose and optimal dosing schedule for liposomal curcumin in a xenograft human pancreatic cancer model.

    PubMed

    Mach, Claire M; Mathew, Lata; Mosley, Scott A; Kurzrock, Razelle; Smith, Judith A

    2009-06-01

    Curcumin is a food chemical present in tumeric (Curcuma longa) that has pharmacological activity to suppress carcinogenesis and inhibits multiple signaling pathways such as nuclear factor kappaB (NF-kappaB), cyclooxygenase-2 (Cox-2) and interleukin-8 (IL-8). Oral curcumin has poor oral bioavailability limiting its clinical activity; however, a patent pending liposomal formulation of curcumin was developed to improve drug delivery and has demonstrated activity in multiple cancers. This study was designed to determine the minimum effective dose (MED) as well as the optimal dosing schedule of liposomal curcumin in a xenograft mouse model of human pancreatic cancer. The MED determination and optimal schedule was evaluated in female athymic nude mice injected subcutaneously with MiaPaCa-2 cells. Dosing was initiated at an average tumor size of 5mm. For the MED, mice were treated with the following dose levels of liposomal curcumin: no treatment, liposome only, 1 mg/kg, 2 mg/kg, 5 mg/kg, 10 mg/kg, 20 mg/kg and 40 mg/kg given by tail vein injection three times weekly for 28 days. For the optimum dosing schedule, three additional schedules were evaluated and compared to the control of three times weekly; daily (five days per week), every four days, and weekly for 28 days. All mice were weighed and tumor measurements taken three times weekly to evaluate toxicity and efficacy. The 20 mg/kg dose had the greatest decrease in tumor growth at 52% decrease in tumor growth when compared to no treatment control mice. MED was determined to be 20 mg/kg and was used for the optimal dosing schedule determination. Daily dosing and three times per week dosing had greater inhibition of tumor growth with no discernable difference than once weekly or every 4 day dosing. No toxicity was observed at any dose or schedule. The MED for liposomal curcumin is 20 mg/kg given once daily three times per week to achieve optimal tumor growth inhibition. This was dose recommended for additional

  12. [Radon risk in healthcare facilities: environmental monitoring and effective dose].

    PubMed

    Cammarota, B; Cascone, Maria Teresa; De Paola, L; Schillirò, F; Del Prete, U

    2009-01-01

    Radon, the second cause of lung cancer after smoking (WHO- IARC), is a natural, radioactive gas, which originates from the soil and pollutes indoor air, especially in closed or underground spaces. The purpose of this study was to determine the concentration of radon gas, its effective dose, and the measurement of microclimatic degrees C; U.R. % and air velocity in non-academic intensive care units of public hospitals in the Naples area. The annual average concentrations of radon gas were detected with EIC type ionization electret chambers, type LLT with exposure over four 3-month periods. The concentrations varied for all health facilities between 186 and 1191 Bq/m3. Overall, the effective dose of exposure to radon gas of 3mSv/a recommended by Italian legislation was never exceeded. The concentration of radon gas showed a decreasing trend starting from the areas below ground level to those on higher floors; such concentrations were also influenced by natural and artificial ventilation of the rooms, building materials used for walls, and by the state of maintenance and improvements of the building (insulation of floors and walls). The data obtained confirmed the increased concentration of radionuclides in the yellow tuff of volcanic origin in the Campania Region and the resulting rate of release of radon gas, whereas the reinforced concrete structure (a hospital located on the hillside), which had the lowest values, proved to provide good insulation against penetration and accumulation of radon gas.

  13. Single-dose pharmacokinetics of lenalidomide in healthy volunteers: dose proportionality, food effect, and racial sensitivity.

    PubMed

    Chen, N; Kasserra, C; Reyes, J; Liu, L; Lau, H

    2012-11-01

    Lenalidomide is an immunomodulatory drug with efficacy in various hematological malignancies. The purpose of these studies was to evaluate the single-dose pharmacokinetics of lenalidomide, including dose proportionality, food effect, and racial sensitivity. Three studies were conducted including a total of 58 healthy subjects: a randomized, single-blind, alternating group, single-ascending dose study; a randomized, two-way crossover food effect study; and a randomized, double-blind, two-group, within-subject, single-ascending dose study. Oral absorption of lenalidomide was rapid and the maximum plasma concentration (C (max)) was observed approximately 1 h post-dose. Co-administration with a high-fat meal reduced the area under the concentration-time curve (AUC) and C (max) by approximately 20 and 50 %, respectively, and delayed time to C (max) (t (max)) by 1.63 h. However, phase III trials were dosed without regard to food; therefore, clinical relevance of the food effect was minimal. The terminal elimination half-life (t (½)) was 3-4 h at doses up to 50 mg and was not affected by food. The AUC and C (max) were proportional to lenalidomide single doses (5-400 mg), and total and renal clearance were dose-independent. The R- to S-lenalidomide ratio in plasma was stable over time, approximately 45-55 % of total drug. There were no differences in pharmacokinetic parameters, dose-exposure relationship, or enantiomeric ratio, between Japanese and Caucasian subjects. Lenalidomide displayed linear pharmacokinetics from doses 5-400 mg in healthy subjects. Although food reduced bioavailability, this was not considered clinically relevant. Lenalidomide was generally well tolerated in both ethnic groups.

  14. Effects of stream-associated fluctuations upon the radial variation of average solar-wind parameters

    NASA Technical Reports Server (NTRS)

    Goldstein, B. E.; Jokipii, J. R.

    1976-01-01

    The effects of nonlinear fluctuations due to solar wind streams upon radial gradients of average solar wind parameters are computed, using a numerical MHD model for both spherically symmetric time dependent and corotating equatorial flow approximations. Significant effects of correlations are found between fluctuations upon the gradients of azimuthal magnetic fields, radial velocity, density and azimuthal velocity. Between 400 to 900 solar radii stream interactions have transferred the major portion of the angular momentum flux to the magnetic field; at even greater distances the plasma again carries the bulk of the angular momentum flux. The average azimuthal component of the magnetic field may decrease as much as 10% faster than the Archimedean spiral out to 6 AU due to stream interactions, but this result is dependent upon inner boundary conditions.

  15. Evidence-Based Medicine, Heterogeneity of Treatment Effects, and the Trouble with Averages

    PubMed Central

    Kravitz, Richard L; Duan, Naihua; Braslow, Joel

    2004-01-01

    Evidence-based medicine is the application of scientific evidence to clinical practice. This article discusses the difficulties of applying global evidence (“average effects” measured as population means) to local problems (individual patients or groups who might depart from the population average). It argues that the benefit or harm of most treatments in clinical trials can be misleading and fail to reveal the potentially complex mixture of substantial benefits for some, little benefit for many, and harm for a few. Heterogeneity of treatment effects reflects patient diversity in risk of disease, responsiveness to treatment, vulnerability to adverse effects, and utility for different outcomes. Recognizing these factors, researchers can design studies that better characterize who will benefit from medical treatments, and clinicians and policymakers can make better use of the results. PMID:15595946

  16. Ultra-low dose naltrexone potentiates the anticonvulsant effect of low dose morphine on clonic seizures.

    PubMed

    Honar, H; Riazi, K; Homayoun, H; Sadeghipour, H; Rashidi, N; Ebrahimkhani, M R; Mirazi, N; Dehpour, A R

    2004-01-01

    Significant potentiation of analgesic effects of opioids can be achieved through selective blockade of their stimulatory effects on intracellular signaling pathways by ultra-low doses of opioid receptor antagonists. However, the generality and specificity of this interaction is not well understood. The bimodal modulation of pentylenetetrazole-induced seizure threshold by opioids provide a model to assess the potential usefulness of this approach in seizure disorders and to examine the differential mechanisms involved in opioid anti- (morphine at 0.5-3 mg/kg) versus pro-convulsant (20-100 mg/kg) effects. Systemic administration of ultra-low doses of naltrexone (100 fg/kg-10 ng/kg) significantly potentiated the anticonvulsant effect of morphine at 0.5 mg/kg while higher degrees of opioid receptor antagonism blocked this effect. Moreover, inhibition of opioid-induced excitatory signaling by naltrexone (1 ng/kg) unmasked a strong anticonvulsant effect for very low doses of morphine (1 ng/kg-100 microg/kg), suggesting that a presumed inhibitory component of opioid receptor signaling can exert strong seizure-protective effects even at very low levels of opioid receptor activation. However, ultra-low dose naltrexone could not increase the maximal anticonvulsant effect of morphine (1-3 mg/kg), possibly due to a ceiling effect. The proconvulsant effects of morphine on seizure threshold were minimally altered by ultra-low doses of naltrexone while being completely blocked by a higher dose (1 mg/kg) of the antagonist. The present data suggest that ultra-low doses of opioid receptor antagonists may provide a potent strategy to modulate seizure susceptibility, especially in conjunction with very low doses of opioids.

  17. Cognitive performance in methadone maintenance patients: Effects of time relative to dosing and maintenance dose level

    PubMed Central

    Rass, Olga; Kleykamp, Bethea A.; Vandrey, Ryan G.; Bigelow, George E.; Leoutsakos, Jeannie-Marie; Stitzer, Maxine L.; Strain, Eric; Copersino, Marc L.; Mintzer, Miriam Z.

    2014-01-01

    Given the long-term nature of methadone maintenance treatment, it is important to assess the extent of cognitive side effects. This study investigated cognitive and psychomotor performance in fifty-one methadone maintenance patients (MMP) as a function of time since last methadone dose and maintenance dose level. MMP maintained on doses ranging from 40 to 200 mg (Mean = 97 mg) completed a battery of psychomotor and cognitive measures across two sessions, during peak and trough states, in a double-blind crossover design. Peak sessions were associated with worse performance on measures of sensory processing, psychomotor speed, divided attention, and working memory, compared to trough sessions. The effects of maintenance dose were mixed, with higher dose resulting in worse performance on aspects of attention and working memory, improved performance on executive function, and no effects on several measures. Longer treatment duration was associated with better performance on some measures, but was also associated with increased sensitivity to time since last dose (i.e., worse performance at peak vs. trough) on some measures. The results suggest that cognitive functioning can fluctuate as a function of time since last dose even in MMP who have been maintained on stable doses for an extended time (mean duration in treatment = 4 years), but worsened performance at peak is limited to a subset of functions and may not be clinically significant at these modest levels of behavioral effect. For patients on stable methadone maintenance doses, maintenance at higher doses may not significantly increase the risk of performance impairment. PMID:24548244

  18. Leading multiple teams: average and relative external leadership influences on team empowerment and effectiveness.

    PubMed

    Luciano, Margaret M; Mathieu, John E; Ruddy, Thomas M

    2014-03-01

    External leaders continue to be an important source of influence even when teams are empowered, but it is not always clear how they do so. Extending research on structurally empowered teams, we recognize that teams' external leaders are often responsible for multiple teams. We adopt a multilevel approach to model external leader influences at both the team level and the external leader level of analysis. In doing so, we distinguish the influence of general external leader behaviors (i.e., average external leadership) from those that are directed differently toward the teams that they lead (i.e., relative external leadership). Analysis of data collected from 451 individuals, in 101 teams, reporting to 25 external leaders, revealed that both relative and average external leadership related positively to team empowerment. In turn, team empowerment related positively to team performance and member job satisfaction. However, while the indirect effects were all positive, we found that relative external leadership was not directly related to team performance, and average external leadership evidenced a significant negative direct influence. Additionally, relative external leadership exhibited a significant direct positive influence on member job satisfaction as anticipated, whereas average external leadership did not. These findings attest to the value in distinguishing external leaders' behaviors that are exhibited consistently versus differentially across empowered teams. Implications and future directions for the study and management of external leaders overseeing multiple teams are discussed.

  19. Uncertainty in Propensity Score Estimation: Bayesian Methods for Variable Selection and Model Averaged Causal Effects

    PubMed Central

    Zigler, Corwin Matthew; Dominici, Francesca

    2014-01-01

    Causal inference with observational data frequently relies on the notion of the propensity score (PS) to adjust treatment comparisons for observed confounding factors. As decisions in the era of “big data” are increasingly reliant on large and complex collections of digital data, researchers are frequently confronted with decisions regarding which of a high-dimensional covariate set to include in the PS model in order to satisfy the assumptions necessary for estimating average causal effects. Typically, simple or ad-hoc methods are employed to arrive at a single PS model, without acknowledging the uncertainty associated with the model selection. We propose three Bayesian methods for PS variable selection and model averaging that 1) select relevant variables from a set of candidate variables to include in the PS model and 2) estimate causal treatment effects as weighted averages of estimates under different PS models. The associated weight for each PS model reflects the data-driven support for that model’s ability to adjust for the necessary variables. We illustrate features of our proposed approaches with a simulation study, and ultimately use our methods to compare the effectiveness of surgical vs. nonsurgical treatment for brain tumors among 2,606 Medicare beneficiaries. Supplementary materials are available online. PMID:24696528

  20. Uncertainty in Propensity Score Estimation: Bayesian Methods for Variable Selection and Model Averaged Causal Effects.

    PubMed

    Zigler, Corwin Matthew; Dominici, Francesca

    2014-01-01

    Causal inference with observational data frequently relies on the notion of the propensity score (PS) to adjust treatment comparisons for observed confounding factors. As decisions in the era of "big data" are increasingly reliant on large and complex collections of digital data, researchers are frequently confronted with decisions regarding which of a high-dimensional covariate set to include in the PS model in order to satisfy the assumptions necessary for estimating average causal effects. Typically, simple or ad-hoc methods are employed to arrive at a single PS model, without acknowledging the uncertainty associated with the model selection. We propose three Bayesian methods for PS variable selection and model averaging that 1) select relevant variables from a set of candidate variables to include in the PS model and 2) estimate causal treatment effects as weighted averages of estimates under different PS models. The associated weight for each PS model reflects the data-driven support for that model's ability to adjust for the necessary variables. We illustrate features of our proposed approaches with a simulation study, and ultimately use our methods to compare the effectiveness of surgical vs. nonsurgical treatment for brain tumors among 2,606 Medicare beneficiaries. Supplementary materials are available online.

  1. Still equivalent for dose calculation in the Monte Carlo era? A comparison of free breathing and average intensity projection CT datasets for lung SBRT using three generations of dose calculation algorithms.

    PubMed

    Zvolanek, Kristina; Ma, Rongtao; Zhou, Christina; Liang, Xiaoying; Wang, Shuo; Verma, Vivek; Zhu, Xiaofeng; Zhang, Qinghui; Driewer, Joseph; Lin, Chi; Zhen, Weining; Wahl, Andrew; Zhou, Su-Min; Zheng, Dandan

    2017-05-01

    Inhomogeneity dose modeling and respiratory motion description are two critical technical challenges for lung stereotactic body radiotherapy, an important treatment modality for small size primary and secondary lung tumors. Recent studies revealed lung density-dependent target dose differences between Monte Carlo (Type-C) algorithm and earlier algorithms. Therefore, this study aimed to investigate the equivalence of the two most popular CT datasets for treatment planning, free breathing (FB) and average intensity projection (AIP) CTs, using Type-C algorithms, and comparing with two older generation algorithms (Type-A and Type-B). Twenty patients (twenty-one lesions) were planned using a Type-A algorithm on the FB CT. Lung was contoured separately on FB and AIP CTs and compared. Dose comparison was obtained between the two CTs using four commercial dose algorithms including one Type-A (Pencil Beam Convolution - PBC), one Type-B (Analytical Anisotropic Algorithm - AAA), and two Type-C algorithms (Voxel Monte Carlo - VMC and Acuros External Beam - AXB). For each algorithm, the dosimetric parameters of the target (PTV, Dmin , Dmax , Dmean , D95, and D90) and lung (V5, V10, V20, V30, V35, and V40) were compared between the two CTs using the Wilcoxon signed rank test. Correlation between dosimetric differences and density differences for each algorithm were studied using linear regression and Spearman correlation, in which both global and local density differences were evaluated. Although the lung density differences on FB and AIP CTs were statistically significant (P = 0.003), the magnitude was small at 1.21 ± 1.45%. Correspondingly, for the two Type-C algorithms, target and lung dosimetric differences were small in magnitude and statistically insignificant (P > 0.05) for all but one instance, similar to the findings for the older generation algorithms. Nevertheless, a significant correlation was shown between the dosimetric and density differences for Type-C and Type

  2. Effects of time-averaging climate parameters on predicted multicompartmental fate of pesticides and POPs.

    PubMed

    Lammel, Gerhard

    2004-01-01

    With the aim to investigate the justification of time-averaging of climate parameters in multicompartment modelling the effects of various climate parameters and different modes of entry on the predicted substances' total environmental burdens and the compartmental fractions were studied. A simple, non-steady state zero-dimensional (box) mass-balance model of intercompartmental mass exchange which comprises four compartments was used for this purpose. Each two runs were performed, one temporally unresolved (time-averaged conditions) and a time-resolved (hourly or higher) control run. In many cases significant discrepancies are predicted, depending on the substance and on the parameter. We find discrepancies exceeding 10% relative to the control run and up to an order of magnitude for prediction of the total environmental burden from neglecting seasonalities of the soil and ocean temperatures and the hydroxyl radical concentration in the atmosphere and diurnalities of atmospheric mixing depth and the hydroxyl radical concentration in the atmosphere. Under some conditions it was indicated that substance sensitivity could be explained by the magnitude of the sink terms in the compartment(s) with parameters varying. In general, however, any key for understanding substance sensitivity seems not be linked in an easy manner to the properties of the substance, to the fractions of its burden or to the sink terms in either of the compartments with parameters varying. Averaging of diurnal variability was found to cause errors of total environmental residence time of different sign for different substances. The effects of time-averaging of several parameters are in general not additive but synergistic as well as compensatory effects occur. An implication of these findings is that the ranking of substances according to persistence is sensitive to time resolution on the scale of hours to months. As a conclusion it is recommended to use high temporal resolution in multi

  3. Averaging period effects on the turbulent flux and transport efficiency during haze pollution in Beijing, China

    NASA Astrophysics Data System (ADS)

    Guo, Xiaofeng; Yang, Ting; Sun, Yele

    2015-08-01

    Based on observations at the heights of 140 and 280 m on the Beijing 325-m meteorological tower, this study presents an assessment of the averaging period effects on eddy-covariance measurements of the momentum/scalar flux and transport efficiency during wintertime haze pollution. The study period, namely from January 6 to February 28 2013, is divided into different episodes of particulate pollution, as featured by varied amounts of the turbulent exchange and conditions of the atmospheric stability. Overall, turbulent fluxes of the momentum and scalars (heat, water vapor, and CO2) increase with the averaging period, namely from 5, 15, and 30 up to 60 min, an outcome most evident during the `transient' episodes (each lasting for 2-3 days, i.e., preceded and followed by clean-air days with mean concentrations of PM1 less than 40 μg m-3). The conventional choice of 30 min is deemed to be appropriate for calculating the momentum flux and its transport efficiency. By comparison, scalar fluxes and their transport efficiencies appear more sensitive to the choice of an averaging period, particularly at the upper level (i.e., 280 m). It is presupposed that, for urban environments, calculating the momentum and scalar fluxes could invoke separate averaging periods, rather than relying on a single prescription (e.g., 30 min). Furthermore, certain characteristics of urban turbulence are found less sensitive to the choice of an averaging period, such as the relationship between the heat-to-momentum transport efficiency and the local stability parameter.

  4. Cardiac-Specific Conversion Factors to Estimate Radiation Effective Dose From Dose-Length Product in Computed Tomography.

    PubMed

    Trattner, Sigal; Halliburton, Sandra; Thompson, Carla M; Xu, Yanping; Chelliah, Anjali; Jambawalikar, Sachin R; Peng, Boyu; Peters, M Robert; Jacobs, Jill E; Ghesani, Munir; Jang, James J; Al-Khalidi, Hussein; Einstein, Andrew J

    2017-08-16

    This study sought to determine updated conversion factors (k-factors) that would enable accurate estimation of radiation effective dose (ED) for coronary computed tomography angiography (CTA) and calcium scoring performed on 12 contemporary scanner models and current clinical cardiac protocols and to compare these methods to the standard chest k-factor of 0.014 mSv·mGy(-1)cm(-1). Accurate estimation of ED from cardiac CT scans is essential to meaningfully compare the benefits and risks of different cardiac imaging strategies and optimize test and protocol selection. Presently, ED from cardiac CT is generally estimated by multiplying a scanner-reported parameter, the dose-length product, by a k-factor which was determined for noncardiac chest CT, using single-slice scanners and a superseded definition of ED. Metal-oxide-semiconductor field-effect transistor radiation detectors were positioned in organs of anthropomorphic phantoms, which were scanned using all cardiac protocols, 120 clinical protocols in total, on 12 CT scanners representing the spectrum of scanners from 5 manufacturers (GE, Hitachi, Philips, Siemens, Toshiba). Organ doses were determined for each protocol, and ED was calculated as defined in International Commission on Radiological Protection Publication 103. Effective doses and scanner-reported dose-length products were used to determine k-factors for each scanner model and protocol. k-Factors averaged 0.026 mSv·mGy(-1)cm(-1) (95% confidence interval: 0.0258 to 0.0266) and ranged between 0.020 and 0.035 mSv·mGy(-1)cm(-1). The standard chest k-factor underestimates ED by an average of 46%, ranging from 30% to 60%, depending on scanner, mode, and tube potential. Factors were higher for prospective axial versus retrospective helical scan modes, calcium scoring versus coronary CTA, and higher (100 to 120 kV) versus lower (80 kV) tube potential and varied among scanner models (range of average k-factors: 0.0229 to 0.0277 mSv·mGy(-1)cm(-1)). Cardiac

  5. Fractional averaging of repetitive waveforms induced by self-imaging effects

    NASA Astrophysics Data System (ADS)

    Romero Cortés, Luis; Maram, Reza; Azaña, José

    2015-10-01

    We report the theoretical prediction and experimental observation of averaging of stochastic events with an equivalent result of calculating the arithmetic mean (or sum) of a rational number of realizations of the process under test, not necessarily limited to an integer record of realizations, as discrete statistical theory dictates. This concept is enabled by a passive amplification process, induced by self-imaging (Talbot) effects. In the specific implementation reported here, a combined spectral-temporal Talbot operation is shown to achieve undistorted, lossless repetition-rate division of a periodic train of noisy waveforms by a rational factor, leading to local amplification, and the associated averaging process, by the fractional rate-division factor.

  6. Cumulative effects of repeated subthreshold doses of ultraviolet radiation

    SciTech Connect

    Parrish, J.A.; Zaynoun, S.; Anderson, R.R.

    1981-05-01

    For fair Caucasian skin, the minimal delayed erythema dose (MED) 24 hr after exposure to broadband UVA is about 1200 times greater than the MED of broadband UVB, for both single and multiple daily exposures. Repeated daily exposure to doses less than MED results in cumulative effects manifest by gradual lowering of the daily dose threshold for delayed erythema and pigmentation induced by UVA or UVB. At threshold doses, UVB is more erythemogenic than melanogenic; the opposite is true for UVA. Repeated daily UVA exposure greatly enhances melanogenesis such that markedly suberythemogenic exposure doses of UVA result in true melanogenesis.

  7. Dose, effect severity, and imparted energy in assessing biological effects.

    PubMed

    Bond, V P

    1995-05-01

    Because of the widespread efforts in cancer radioepidemiological studies to attach a value of absorbed dose to each exposed individual, the notion seems to have become prevalent that dose plays an essential role in the medical determination of the diagnosis and prognosis of the individual. This view is enhanced by the fact that, while the present quantities and units for radiological physics were developed in the context of the acute effects of large exposures to radiation, e.g., in radiotherapy where they still apply well, these same quantities and units have been used, without modification, to apply to cancer radioepidemiology in the context of low level irradiation. A principle purpose of the present communication is to show that, in medicine, dose plays a limited role even in the deterministic application of therapeutic agents, and that diagnosis and estimates of prognosis in medicine are based, not on dose, but on the severity of effect on, or damage to the organ or organs involved in a particular medical condition. Thus it is "going backward" to view estimates of the severity of effect, e.g., the fraction of cells with abnormalities, or killed, as a "biological dosimeter," rather than as a quantitative estimate of the severity of effect. The use of biological indicators is of maximum value in noncancerous disease or injury in which the severity of an effect causative for organ failure and a consequent quantal, e.g., a lethal response in the individual, can be measured with increasing accuracy by modern medical techniques.(ABSTRACT TRUNCATED AT 250 WORDS)

  8. Assessment of the effective dose equivalent for external photon radiation

    SciTech Connect

    Reece, W.D.; Poston, J.W.; Xu, X.G. )

    1993-02-01

    Beginning in January 1994, US nuclear power plants must change the way that they determine the radiation exposure to their workforce. At that time, revisions to Title 10 Part 20 of the Code of Federal Regulations will be in force requiring licensees to evaluate worker radiation exposure using a risk-based methodology termed the effective dose equivalent.'' A research project was undertaken to improve upon the conservative method presently used for assessing effective dose equivalent. In this project effective dose equivalent was calculated using a mathematical model of the human body, and tracking photon interactions for a wide variety of radiation source geometries using Monte Carlo computer code simulations. Algorithms were then developed to relate measurements of the photon flux on the surface of the body (as measured by dosimeters) to effective dose equivalent. This report (Volume I of a two-part study) describes: the concept of effective dose equivalent, the evolution of the concept and its incorporation into regulations, the variations in human organ susceptibility to radiation, the mathematical modeling and calculational techniques used, the results of effective dose equivalent calculations for a broad range of photon energiesand radiation source geometries. The study determined that for beam radiation sources the highest effective dose equivalent occurs for beams striking the front of the torso. Beams striking the rear of the torsoproduce the next highest effective dose equivalent, with effective dose equivalent falling significantly as one departs from these two orientations. For point sources, the highest effective dose equivalent occurs when the sources are in contact with the body on the front of the torso. For females the highest effective dose equivalent occurs when the source is on the sternum, for males when it is on the gonads.

  9. Evaluation of Potential Average Daily Doses (ADDs) of PM2.5 for Homemakers Conducting Pan-Frying Inside Ordinary Homes under Four Ventilation Conditions.

    PubMed

    Lee, Seonyeop; Yu, Sol; Kim, Sungroul

    2017-01-13

    Several studies reported that commercial barbecue restaurants likely contribute to the indoor emission of particulate matters with a diameter of 2.5 micrometers or less (PM2.5) while pan-frying meat. However, there is inadequate knowledge of exposure level to indoor PM2.5 in homes and the contribution of a typical indoor pan-frying event. We measured the indoor PM2.5 concentration and, using Monte-Carlo simulation, estimated potential average daily dose (ADD) of PM2.5 for homemakers pan-frying a piece of pork inside ordinary homes. Convenience-based sampling at 13 homes was conducted over four consecutive days in June 2013 (n = 52). Although we pan-fried 100 g pork for only 9 min, the median (interquartile range, IQR) value was 4.5 (2.2-5.6) mg/m³ for no ventilation and 0.5 (0.1-1.3) mg/m³ with an active stove hood ventilation system over a 2 h sampling interval. The probabilities that the ADDs from inhalation of indoor PM2.5 would be higher than the ADD from inhalation of PM2.5 on an outdoor roadside (4.6 μg/kg·day) were 99.44%, 97.51%, 93.64%, and 67.23%, depending on the ventilation conditions: (1) no window open; (2) one window open in the kitchen; (3) two windows open, one each in the kitchen and living room; and (4) operating a forced-air stove hood, respectively.

  10. Evaluation of Potential Average Daily Doses (ADDs) of PM2.5 for Homemakers Conducting Pan-Frying Inside Ordinary Homes under Four Ventilation Conditions

    PubMed Central

    Lee, Seonyeop; Yu, Sol; Kim, Sungroul

    2017-01-01

    Several studies reported that commercial barbecue restaurants likely contribute to the indoor emission of particulate matters with a diameter of 2.5 micrometers or less (PM2.5) while pan-frying meat. However, there is inadequate knowledge of exposure level to indoor PM2.5 in homes and the contribution of a typical indoor pan-frying event. We measured the indoor PM2.5 concentration and, using Monte-Carlo simulation, estimated potential average daily dose (ADD) of PM2.5 for homemakers pan-frying a piece of pork inside ordinary homes. Convenience-based sampling at 13 homes was conducted over four consecutive days in June 2013 (n = 52). Although we pan-fried 100 g pork for only 9 min, the median (interquartile range, IQR) value was 4.5 (2.2–5.6) mg/m3 for no ventilation and 0.5 (0.1–1.3) mg/m3 with an active stove hood ventilation system over a 2 h sampling interval. The probabilities that the ADDs from inhalation of indoor PM2.5 would be higher than the ADD from inhalation of PM2.5 on an outdoor roadside (4.6 μg/kg·day) were 99.44%, 97.51%, 93.64%, and 67.23%, depending on the ventilation conditions: (1) no window open; (2) one window open in the kitchen; (3) two windows open, one each in the kitchen and living room; and (4) operating a forced-air stove hood, respectively. PMID:28098788

  11. Mental health care and average happiness: strong effect in developed nations.

    PubMed

    Touburg, Giorgio; Veenhoven, Ruut

    2015-07-01

    Mental disorder is a main cause of unhappiness in modern society and investment in mental health care is therefore likely to add to average happiness. This prediction was checked in a comparison of 143 nations around 2005. Absolute investment in mental health care was measured using the per capita number of psychiatrists and psychologists working in mental health care. Relative investment was measured using the share of mental health care in the total health budget. Average happiness in nations was measured with responses to survey questions about life-satisfaction. Average happiness appeared to be higher in countries that invest more in mental health care, both absolutely and relative to investment in somatic medicine. A data split by level of development shows that this difference exists only among developed nations. Among these nations the link between mental health care and happiness is quite strong, both in an absolute sense and compared to other known societal determinants of happiness. The correlation between happiness and share of mental health care in the total health budget is twice as strong as the correlation between happiness and size of the health budget. A causal effect is likely, but cannot be proved in this cross-sectional analysis.

  12. Effects of an absorbing boundary on the average volume visited by N spherical Brownian particles

    NASA Astrophysics Data System (ADS)

    Larralde, Hernan; M. Berezhkovskii, Alexander; Weiss, George H.

    2003-12-01

    The number of distinct sites visited by a lattice random walk and its continuum analog, the volume swept out by a diffusing spherical particle are used to model different phenomena in physics, chemistry and biology. Therefore the problem of finding statistical properties of these random variables is of importance. There have been several studies of the more general problem of the volume of the region explored by N random walks or Brownian particles in an unbounded space. We here study the effects of a planar absorbing boundary on the average of this volume. The boundary breaks the translational invariance of the space, and introduces an additional spatial parameter, the initial distance of the Brownian particles from the surface. We derive expressions for the average volume visited in three dimensions and the average span in one dimension as functions of the time for given values of the initial distance to the absorbing boundary and N. The results can be transformed to those for N lattice random walks by appropriately choosing the radius and diffusion constant of the spheres.

  13. Effects of surface roughness on the average heat transfer of an impinging air jet

    SciTech Connect

    Beitelmal, A.H.; Saad, M.A.; Patel, C.D.

    2000-01-01

    Localized cooling by impinging flow has been used in many industrial applications such as in cooling of gas turbine blades and drying processes. Here, effect of surface roughness of a uniformly heated plate on the average heat transfer characteristics of an impinging air jet was experimentally investigated. Two aluminum plates, one with a flat surface and the second with some roughness added to the surface were fabricated. The roughness took the shape of a circular array of protrusions of 0.5mm base and 0.5mm height. A circular Kapton heater of the same diameter as the plates (70mm) supplied the necessary power. The surfaces of the plates were polished to reduce radiation heat losses and the back and sides insulated to reduce conduction heat losses. temperatures were measured over a Reynolds number ranging from 9,600 to 38,500 based on flow rate through a 6.85mm diameter nozzle. The temperature measurements were repeated for nozzle exit-to-plate spacing, z/d, ranging from 1 to 10. The average Nusselt number for both cases was plotted versus the Reynolds number and their functional correlation was determined. The results indicate an increase of up to 6.0% of the average Nusselt number due to surface roughness. This modest increase provides evidence to encourage further investigation and characterization of the surface roughness as a parameter for enhancing heat transfer.

  14. Radiation damage in single-particle cryo-electron microscopy: effects of dose and dose rate

    PubMed Central

    Karuppasamy, Manikandan; Karimi Nejadasl, Fatemeh; Vulovic, Milos; Koster, Abraham J.; Ravelli, Raimond B. G.

    2011-01-01

    Radiation damage is an important resolution limiting factor both in macromolecular X-ray crystallography and cryo-electron microscopy. Systematic studies in macromolecular X-ray crystallography greatly benefited from the use of dose, expressed as energy deposited per mass unit, which is derived from parameters including incident flux, beam energy, beam size, sample composition and sample size. In here, the use of dose is reintroduced for electron microscopy, accounting for the electron energy, incident flux and measured sample thickness and composition. Knowledge of the amount of energy deposited allowed us to compare doses with experimental limits in macromolecular X-ray crystallography, to obtain an upper estimate of radical concentrations that build up in the vitreous sample, and to translate heat-transfer simulations carried out for macromolecular X-ray crystallography to cryo-electron microscopy. Stroboscopic exposure series of 50–250 images were collected for different incident flux densities and integration times from Lumbricus terrestris extracellular hemoglobin. The images within each series were computationally aligned and analyzed with similarity metrics such as Fourier ring correlation, Fourier ring phase residual and figure of merit. Prior to gas bubble formation, the images become linearly brighter with dose, at a rate of approximately 0.1% per 10 MGy. The gradual decomposition of a vitrified hemoglobin sample could be visualized at a series of doses up to 5500 MGy, by which dose the sample was sublimed. Comparison of equal-dose series collected with different incident flux densities showed a dose-rate effect favoring lower flux densities. Heat simulations predict that sample heating will only become an issue for very large dose rates (50 e−Å−2 s−1 or higher) combined with poor thermal contact between the grid and cryo-holder. Secondary radiolytic effects are likely to play a role in dose-rate effects. Stroboscopic data collection

  15. Calculation of the biological effective dose for piecewise defined dose-rate fits

    SciTech Connect

    Hobbs, Robert F.; Sgouros, George

    2009-03-15

    An algorithmic solution to the biological effective dose (BED) calculation from the Lea-Catcheside formula for a piecewise defined function is presented. Data from patients treated for metastatic thyroid cancer were used to illustrate the solution. The Lea-Catcheside formula for the G-factor of the BED is integrated numerically using a large number of small trapezoidal fits to each integral. The algorithmically calculated BED is compatible with an analytic calculation for a similarly valued exponentially fitted dose-rate plot and is the only resolution for piecewise defined dose-rate functions.

  16. Temporal compartmental dosing effects for robotic prostate stereotactic body radiotherapy

    NASA Astrophysics Data System (ADS)

    Shiao, Stephen L.; Sahgal, Arjun; Hu, Weigang; Jabbari, Siavash; Chuang, Cynthia; Descovich, Martina; Hsu, I.-Chow; Gottschalk, Alexander R.; Roach, Mack, III; Ma, Lijun

    2011-12-01

    The rate of dose accumulation within a given area of a target volume tends to vary significantly for non-isocentric delivery systems such as Cyberknife stereotactic body radiotherapy. In this study, we investigated whether intra-target temporal dose distributions produce significant variations in the biological equivalent dose. For the study, time courses of ten patients were reconstructed and calculation of a biologically equivalent uniform dose (EUD) was performed using a formula derived from the linear quadratic model (α/β = 3 for prostate cancer cells). The calculated EUD values obtained for the actual patient treatments were then compared with theoretical EUD values for delivering the same physical dose distribution except that the whole target being irradiated continuously (e.g. large-field ‘dose-bathing’ type of delivery). For all the case, the EUDs for the actual treatment delivery were found to correlate strongly with the EUDs for the large-field delivery: a linear correlation coefficient of R2 = 0.98 was obtained and the average EUD for the actual Cyberknife delivery was somewhat higher (5.0 ± 4.7%) than that for the large-field delivery. However, no statistical significance was detected between the two types of delivery (p = 0.21). We concluded that non-isocentric small-field Cyberknife delivery produced consistent biological dosing that tracked well with the constant-dose-rate, large-field-type delivery for prostate stereotactic body radiotherapy.

  17. Simulating total-dose and dose-rate effects on digital microelectronics timing delays using VHDL

    SciTech Connect

    Brothers, C.P. Jr.; Pugh, R.D.

    1995-12-01

    This paper describes a fast timing simulator based on Very High Speed Integrated Circuit (VHSIC) Hardware Description Language (VHDL) for simulating the timing of digital microelectronics in pre-irradiation, total dose, and dose-rate radiation environments. The goal of this research is the rapid and accurate timing simulation of radiation-hardened microelectronic circuits before, during, and after exposure to ionizing radiation. The results of this research effort were the development of VHDL compatible models capable of rapid and accurate simulation of the effect of radiation on the timing performance of microelectronic circuits. The effects of radiation for total dose at 1 Mrad(Si) and dose rates up to 2 {times} 10{sup 12} rads(Si) per second were modeled for a variety of Separation by IMplantion of OXygen (SIMOX) circuits. In all cases tested, the VHDL simulations ran at least 600 times faster than SPICE while maintaining a timing accuracy to within 15% of SPICE values.

  18. Assessment of the effective doses from two dental cone beam CT devices

    PubMed Central

    Schilling, R; Geibel, M-A

    2013-01-01

    Objectives: This study compares the effective dose for different fields of view (FOVs), resolutions and X-ray parameters from two cone beam CT units: the KaVo 3D (three-dimensional) eXam and the KaVo Pan eXam Plus 3D (KaVo Dental, Biberach, Germany). Methods: Measurements were made using thermoluminescent dosemeter chips in a radiation analog dosimetry head and neck phantom. The calculations of effective doses are based on the ICRP 60 and ICRP 103 recommendations of the International Commission on Radiological Protection. Results: Effective doses from the 3D eXam ranged between 32.8 µSv and 169.8 µSv, and for the Pan eXam Plus effective doses ranged between 40.2 µSv and 183.7 µSv; these were measured using ICRP 103 weighting factors in each case. The increase in effective dose between ICRP 60 and ICRP 103 recommendations averaged 157% for all measurements. Conclusions: Effective doses can be reduced significantly with the choice of lower resolutions and mAs settings as well as smaller FOVs to avoid tissues sensitive to radiation being inside the direct beam. Larger FOVs do not necessarily lead to higher effective doses. PMID:23420855

  19. Assessment of the effective doses from two dental cone beam CT devices.

    PubMed

    Schilling, R; Geibel, M-A

    2013-01-01

    This study compares the effective dose for different fields of view (FOVs), resolutions and X-ray parameters from two cone beam CT units: the KaVo 3D (three-dimensional) eXam and the KaVo Pan eXam Plus 3D (KaVo Dental, Biberach, Germany). Measurements were made using thermoluminescent dosemeter chips in a radiation analog dosimetry head and neck phantom. The calculations of effective doses are based on the ICRP 60 and ICRP 103 recommendations of the International Commission on Radiological Protection. Effective doses from the 3D eXam ranged between 32.8 µSv and 169.8 µSv, and for the Pan eXam Plus effective doses ranged between 40.2 µSv and 183.7 µSv; these were measured using ICRP 103 weighting factors in each case. The increase in effective dose between ICRP 60 and ICRP 103 recommendations averaged 157% for all measurements. Effective doses can be reduced significantly with the choice of lower resolutions and mAs settings as well as smaller FOVs to avoid tissues sensitive to radiation being inside the direct beam. Larger FOVs do not necessarily lead to higher effective doses.

  20. Time-averages for Plane Travelling Waves—The Effect of Attenuation: I, Adiabatic Approach

    NASA Astrophysics Data System (ADS)

    Makarov, S. N.

    1993-05-01

    The analysis of the effect of attenuation on the time-averages for a plane travelling wave is presented. The barotropic equation of state is considered: i.e., acoustic heating is assumed to be negligible. The problem statement consists of calculating means in a finite region bounded by a transducer surface as well as by a perfectly absorbing surface, respectively. Although the simple wave approximation cannot be used throughout the field it is still valid near the perfect absorber. The result for radiation pressure is different from the conclusions given previously by Beyer and Livett, Emery and Leeman.

  1. Effects analysis of array geometry for resolving performance based on spatial average ambiguity function

    NASA Astrophysics Data System (ADS)

    Zha, Guofeng; Wang, Hongqiang; Cheng, Yongqiang; Qin, Yuliang

    2016-03-01

    For analyzing the three dimension (3D) spatial resolving performance of Multi-Transmitter Single-Receiver (MTSR) array radar with stochastic signals, the spatial average ambiguity function (SAAF) was introduced. The analytic expression of SAAF of array radar with stochastic is derived. To analyze the effects of array geometry, comparisons are implemented for three typical array geometries including circular, decussate and planar configuration. Simulated results illustrate that the spatial resolving performance is better for the circular array than that of others. Furthermore, it is shown that the array aperture size and the target's radial range are the main factors impacting the resolving performance.

  2. The effect of three-dimensional fields on bounce averaged particle drifts in a tokamak

    SciTech Connect

    Hegna, C. C.

    2015-07-15

    The impact of applied 3D magnetic fields on the bounce-averaged precessional drifts in a tokamak plasma are calculated. Local 3D MHD equilibrium theory is used to construct solutions to the equilibrium equations in the vicinity of a magnetic surface for a large aspect ratio circular tokamak perturbed by applied 3D fields. Due to modulations of the local shear caused by near-resonant Pfirsch-Schlüter currents, relatively weak applied 3D fields can have a large effect on trapped particle precessional drifts.

  3. Effective Block-Scale Dispersion and Its Self-Averaging Behavior in Heterogeneous Porous Media

    NASA Astrophysics Data System (ADS)

    de Barros, Felipe; Dentz, Marco

    2015-04-01

    Upscaled (effective) dispersion coefficients in spatially heterogeneous flow fields must (1) account for the sub-scale variability that is filtered out by homogenization and (2) be modeled as a random function to incorporate the uncertainty associated with non-ergodic solute bodies. In this study, we use the framework developed in de Barros and Rubin (2011) [de Barros F.P.J. and Rubin Y., Modelling of block-scale macrodispersion as a random function. Journal of Fluid Mechanics 676 (2011): 514-545] to develop novel semi-analytical expressions for the first two statistical moments of the block-effective dispersion coefficients in three-dimensional spatially random flow fields as a function of the key characteristic length scales defining the transport problem. The derived expressions are based on perturbation theory and limited to weak-to-mild heterogeneity and uniform-in-the-mean steady state flow fields. The semi-analytical solutions provide physical insights of the main controlling factors influencing the temporal scaling of the dispersion coefficient of the solute body and its self-averaging dispersion behavior. Our results illustrate the relevance of the joint influence of the block-scale and local-scale dispersion in diminishing the macrodispersion variance under non-ergodic conditions. The impact of the statistical anisotropy ratio in the block-effective macrodispersion self-averaging behavior is also investigated. The analysis performed in this work has implications in numerical modeling and grid design.

  4. Bounds on the average causal effects in randomized trials with noncompliance by covariate adjustment.

    PubMed

    Shan, Na; Xu, Ping-Feng

    2016-11-01

    In randomized trials with noncompliance, causal effects cannot be identified without strong assumptions. Therefore, several authors have considered bounds on the causal effects. Applying an idea of VanderWeele (), Chiba () gave bounds on the average causal effects in randomized trials with noncompliance using the information on the randomized assignment, the treatment received and the outcome under monotonicity assumptions about covariates. But he did not consider any observed covariates. If there are some observed covariates such as age, gender, and race in a trial, we propose new bounds using the observed covariate information under some monotonicity assumptions similar to those of VanderWeele and Chiba. And we compare the three bounds in a real example. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Aspects of the relationship between drug dose and drug effect.

    PubMed

    Peper, Abraham

    2009-02-09

    It is generally assumed that there exists a well-defined relationship between drug dose and drug effect and that this can be expressed by a dose-response curve. This paper argues that there is no such clear relation and that the dose-response curve provides only limited information about the drug effect. It is demonstrated that tolerance development during the measurement of the dose-response curve may cause major distortion of the curve and it is argued that the curve may only be used to indicate the response to the first administration of a drug, before tolerance has developed. The precise effect of a drug on an individual depends on the dynamic relation between several variables, particularly the level of tolerance, the dose anticipated by the organism and the actual drug dose. Simulations with a previously published mathematical model of drug tolerance demonstrate that the effect of a dose smaller than the dose the organism has developed tolerance to is difficult to predict and may be opposite to the action of the usual dose.

  6. Quaternion Averaging

    NASA Technical Reports Server (NTRS)

    Markley, F. Landis; Cheng, Yang; Crassidis, John L.; Oshman, Yaakov

    2007-01-01

    Many applications require an algorithm that averages quaternions in an optimal manner. For example, when combining the quaternion outputs of multiple star trackers having this output capability, it is desirable to properly average the quaternions without recomputing the attitude from the the raw star tracker data. Other applications requiring some sort of optimal quaternion averaging include particle filtering and multiple-model adaptive estimation, where weighted quaternions are used to determine the quaternion estimate. For spacecraft attitude estimation applications, derives an optimal averaging scheme to compute the average of a set of weighted attitude matrices using the singular value decomposition method. Focusing on a 4-dimensional quaternion Gaussian distribution on the unit hypersphere, provides an approach to computing the average quaternion by minimizing a quaternion cost function that is equivalent to the attitude matrix cost function Motivated by and extending its results, this Note derives an algorithm that deterniines an optimal average quaternion from a set of scalar- or matrix-weighted quaternions. Rirthermore, a sufficient condition for the uniqueness of the average quaternion, and the equivalence of the mininiization problem, stated herein, to maximum likelihood estimation, are shown.

  7. Committed effective dose from naturally occuring radionuclides in shellfish

    NASA Astrophysics Data System (ADS)

    Khandaker, Mayeen Uddin; Wahib, Norfadira Binti; Amin, Yusoff Mohd.; Bradley, D. A.

    2013-07-01

    Recognizing their importance in the average Malaysian daily diet, the radioactivity concentrations in mollusc- and crustacean-based food have been determined for key naturally occuring radionuclides. Fresh samples collected from various maritime locations around peninsular Malaysia have been processed using standard procedures; the radionuclide concentrations being determined using an HPGe γ-ray spectrometer. For molluscs, assuming secular equilibrium, the range of activities of 238U (226Ra), 232Th (228Ra) and 40K were found to be 3.28±0.35 to 5.34±0.52, 1.20±0.21 to 2.44±0.21 and 118±6 to 281±14 Bq kg-1 dry weight, respectively. The respective values for crustaceans were 3.02±0.57 to 4.70±0.52, 1.38±0.21 to 2.40±0.35 and 216±11 to 316±15 Bq kg-1. The estimated average daily intake of radioactivity from consumption of molluscs are 0.37 Bq kg-1 for 238U (226Ra), 0.16 Bq kg-1 for 232Th (228Ra) and 18 Bq kg-1 for 40K; the respective daily intake values from crustaceans are 0.36 Bq kg-1, 0.16 Bq kg-1 and 23 Bq kg-1. Associated annual committed effective doses from molluscs are estimated to be in the range 21.3 to 34.7 μSv for 226Ra, 19.3 to 39.1 μSv for 228Ra and 17.0 to 40.4 μSv for 40K. For crustaceans, the respective dose ranges are 19.6 to 30.5 μSv, 22.0 to 38.4 μSv and 31.1 to 45.5 μSv, being some several times world average values.

  8. Errors and Uncertainties in Dose Reconstruction for Radiation Effects Research

    SciTech Connect

    Strom, Daniel J.

    2008-04-14

    Dose reconstruction for studies of the health effects of ionizing radiation have been carried out for many decades. Major studies have included Japanese bomb survivors, atomic veterans, downwinders of the Nevada Test Site and Hanford, underground uranium miners, and populations of nuclear workers. For such studies to be credible, significant effort must be put into applying the best science to reconstructing unbiased absorbed doses to tissues and organs as a function of time. In many cases, more and more sophisticated dose reconstruction methods have been developed as studies progressed. For the example of the Japanese bomb survivors, the dose surrogate “distance from the hypocenter” was replaced by slant range, and then by TD65 doses, DS86 doses, and more recently DS02 doses. Over the years, it has become increasingly clear that an equal level of effort must be expended on the quantitative assessment of uncertainty in such doses, and to reducing and managing uncertainty. In this context, this paper reviews difficulties in terminology, explores the nature of Berkson and classical uncertainties in dose reconstruction through examples, and proposes a path forward for Joint Coordinating Committee for Radiation Effects Research (JCCRER) Project 2.4 that requires a reasonably small level of effort for DOSES-2008.

  9. The Effects of ELDRS at Ultra-Low Dose Rates

    NASA Technical Reports Server (NTRS)

    Chen, Dakai; Forney, James; Carts, Martin; Phan, Anthony; Pease, Ronald; Kruckmeyer, Kirby; Cox, Stephen; LaBel, Kenneth; Burns, Samuel; Albarian, Rafi; Holcombe, Bruce; Little, Bradley; Salzman, James; Chaumont, Geraldine; Duperray, Herve; Ouellet, Al

    2011-01-01

    We present results on the effects on ELDRS at dose rates of 10, 5, 1, and 0.5 mrad(Si)/s for a variety of radiation hardened and commercial devices. We observed low dose rate enhancement below 10 mrad(Si)/s in several different parts. The magnitudes of the dose rate effects vary. The TL750L, a commercial voltage regulator, showed dose rate dependence in the functional failures, with initial failures occurring after 10 krad(Si) for the parts irradiated at 0.5 mrad(Si)/s. The RH1021 showed an increase in low dose rate enhancement by 2x at 5 mrad(Si)/s relative to 8 mrad(Si)/s and high dose rate, and parametric failure after 100 krad(Si). Additionally the ELDRS-free devices, such as the LM158 and LM117, showed evidence of dose rate sensitivity in parametric degradations. Several other parts also displayed dose rate enhancement, with relatively lower degradations up to approx.15 to 20 krad(Si). The magnitudes of the dose rate enhancement will likely increase in significance at higher total dose levels.

  10. Dose- and Rate-Dependent Effects of Cocaine on Striatal Firing Related to Licking

    PubMed Central

    Tang, Chengke; Mittler, Taliah; Duke, Dawn C.; Zhu, Yun; Pawlak, Anthony P.; West, Mark O.

    2011-01-01

    To examine the role of striatal mechanisms in cocaine-induced stereotyped licking, we investigated the acute effects of cocaine on striatal neurons in awake, freely moving rats before and after cocaine administration (0, 5, 10, or 20 mg/kg). Stereotyped licking was induced only by the high dose. Relative to control (saline), cocaine reduced lick duration and concurrently increased interlick interval, particularly at the high dose, but it did not affect licking rhythm. Firing rates of striatal neurons phasically related to licking movements were compared between matched licks before and after injection, minimizing any influence of sensorimotor variables on changes in firing. Both increases and decreases in average firing rate of striatal neurons were observed after cocaine injection, and these changes exhibited a dose-dependent pattern that strongly depended on predrug firing rate. At the middle and high doses relative to the saline group, the average firing rates of slow firing neurons were increased by cocaine, resulting from a general elevation of movement-related firing rates. In contrast, fast firing neurons showed decreased average firing rates only in the high-dose group, with reduced firing rates across the entire range for these neurons. Our findings suggest that at the high dose, increased phasic activity of slow firing striatal neurons and simultaneously reduced phasic activity of fast firing striatal neurons may contribute, respectively, to the continual initiation of stereotypic movements and the absence of longer movements. PMID:17991811

  11. Catalogue of averaged stellar effective magnetic fields. I. Chemically peculiar A and B type stars

    NASA Astrophysics Data System (ADS)

    Bychkov, V. D.; Bychkova, L. V.; Madej, J.

    2003-08-01

    This paper presents the catalogue and the method of determination of averaged quadratic effective magnetic fields < B_e > for 596 main sequence and giant stars. The catalogue is based on measurements of the stellar effective (or mean longitudinal) magnetic field strengths B_e, which were compiled from the existing literature. We analysed the properties of 352 chemically peculiar A and B stars in the catalogue, including Am, ApSi, He-weak, He-rich, HgMn, ApSrCrEu, and all ApSr type stars. We have found that the number distribution of all chemically peculiar (CP) stars vs. averaged magnetic field strength is described by a decreasing exponential function. Relations of this type hold also for stars of all the analysed subclasses of chemical peculiarity. The exponential form of the above distribution function can break down below about 100 G, the latter value representing approximately the resolution of our analysis for A type stars. Table A.1 and its references are only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/407/631 and Tables 3 to 9 are only available in electronic form at http://www.edpsciences.org

  12. Multi-Repeated Projection Lithography for High-Precision Linear Scale Based on Average Homogenization Effect

    PubMed Central

    Ren, Dongxu; Zhao, Huiying; Zhang, Chupeng; Yuan, Daocheng; Xi, Jianpu; Zhu, Xueliang; Ban, Xinxing; Dong, Longchao; Gu, Yawen; Jiang, Chunye

    2016-01-01

    A multi-repeated photolithography method for manufacturing an incremental linear scale using projection lithography is presented. The method is based on the average homogenization effect that periodically superposes the light intensity of different locations of pitches in the mask to make a consistent energy distribution at a specific wavelength, from which the accuracy of a linear scale can be improved precisely using the average pitch with different step distances. The method’s theoretical error is within 0.01 µm for a periodic mask with a 2-µm sine-wave error. The intensity error models in the focal plane include the rectangular grating error on the mask, static positioning error, and lithography lens focal plane alignment error, which affect pitch uniformity less than in the common linear scale projection lithography splicing process. It was analyzed and confirmed that increasing the repeat exposure number of a single stripe could improve accuracy, as could adjusting the exposure spacing to achieve a set proportion of black and white stripes. According to the experimental results, the effectiveness of the multi-repeated photolithography method is confirmed to easily realize a pitch accuracy of 43 nm in any 10 locations of 1 m, and the whole length accuracy of the linear scale is less than 1 µm/m. PMID:27089348

  13. Multi-Repeated Projection Lithography for High-Precision Linear Scale Based on Average Homogenization Effect.

    PubMed

    Ren, Dongxu; Zhao, Huiying; Zhang, Chupeng; Yuan, Daocheng; Xi, Jianpu; Zhu, Xueliang; Ban, Xinxing; Dong, Longchao; Gu, Yawen; Jiang, Chunye

    2016-04-14

    A multi-repeated photolithography method for manufacturing an incremental linear scale using projection lithography is presented. The method is based on the average homogenization effect that periodically superposes the light intensity of different locations of pitches in the mask to make a consistent energy distribution at a specific wavelength, from which the accuracy of a linear scale can be improved precisely using the average pitch with different step distances. The method's theoretical error is within 0.01 µm for a periodic mask with a 2-µm sine-wave error. The intensity error models in the focal plane include the rectangular grating error on the mask, static positioning error, and lithography lens focal plane alignment error, which affect pitch uniformity less than in the common linear scale projection lithography splicing process. It was analyzed and confirmed that increasing the repeat exposure number of a single stripe could improve accuracy, as could adjusting the exposure spacing to achieve a set proportion of black and white stripes. According to the experimental results, the effectiveness of the multi-repeated photolithography method is confirmed to easily realize a pitch accuracy of 43 nm in any 10 locations of 1 m, and the whole length accuracy of the linear scale is less than 1 µm/m.

  14. Globally efficient non-parametric inference of average treatment effects by empirical balancing calibration weighting

    PubMed Central

    Chan, Kwun Chuen Gary; Yam, Sheung Chi Phillip; Zhang, Zheng

    2015-01-01

    Summary The estimation of average treatment effects based on observational data is extremely important in practice and has been studied by generations of statisticians under different frameworks. Existing globally efficient estimators require non-parametric estimation of a propensity score function, an outcome regression function or both, but their performance can be poor in practical sample sizes. Without explicitly estimating either functions, we consider a wide class calibration weights constructed to attain an exact three-way balance of the moments of observed covariates among the treated, the control, and the combined group. The wide class includes exponential tilting, empirical likelihood and generalized regression as important special cases, and extends survey calibration estimators to different statistical problems and with important distinctions. Global semiparametric efficiency for the estimation of average treatment effects is established for this general class of calibration estimators. The results show that efficiency can be achieved by solely balancing the covariate distributions without resorting to direct estimation of propensity score or outcome regression function. We also propose a consistent estimator for the efficient asymptotic variance, which does not involve additional functional estimation of either the propensity score or the outcome regression functions. The proposed variance estimator outperforms existing estimators that require a direct approximation of the efficient influence function. PMID:27346982

  15. Globally efficient non-parametric inference of average treatment effects by empirical balancing calibration weighting.

    PubMed

    Chan, Kwun Chuen Gary; Yam, Sheung Chi Phillip; Zhang, Zheng

    2016-06-01

    The estimation of average treatment effects based on observational data is extremely important in practice and has been studied by generations of statisticians under different frameworks. Existing globally efficient estimators require non-parametric estimation of a propensity score function, an outcome regression function or both, but their performance can be poor in practical sample sizes. Without explicitly estimating either functions, we consider a wide class calibration weights constructed to attain an exact three-way balance of the moments of observed covariates among the treated, the control, and the combined group. The wide class includes exponential tilting, empirical likelihood and generalized regression as important special cases, and extends survey calibration estimators to different statistical problems and with important distinctions. Global semiparametric efficiency for the estimation of average treatment effects is established for this general class of calibration estimators. The results show that efficiency can be achieved by solely balancing the covariate distributions without resorting to direct estimation of propensity score or outcome regression function. We also propose a consistent estimator for the efficient asymptotic variance, which does not involve additional functional estimation of either the propensity score or the outcome regression functions. The proposed variance estimator outperforms existing estimators that require a direct approximation of the efficient influence function.

  16. The effect of aperture averaging upon tropospheric delay fluctuations seen with a DSN antenna

    NASA Technical Reports Server (NTRS)

    Linfield, R.

    1996-01-01

    The spectrum of tropospheric delay fluctuations expected for a DSN antenna at time scales less than 100 s has been calculated. A new feature included in these calculations is the effect of aperture averaging, which causes a reduction in delay fluctuations on time scales less than the antenna wind speed crossing time, approximately equal to 5-10 s. On time scales less than a few seconds, the Allan deviation sigma(sub y)(Delta(t)) varies as (Delta(t))(sup +1), rather than sigma(sub y)(Delta(t)) varies as (Delta(t))(exp -1/6) without aperture averaging. Due to thermal radiometer noise, calibration of tropospheric delay fluctuations with water vapor radiometers will not be possible on time scales less than approximately 10 s. However, the tropospheric fluctuation level will be small enough that radio science measurements with a spacecraft on time scales less than a few seconds will be limited by the stability of frequency standards and/or other nontropospheric effects.

  17. Effects of multiple doses of isoprinosine on Echinococcus multilocularis metacestodes.

    PubMed Central

    Sarciron, M E; Delabre, I; Walbaum, S; Raynaud, G; Petavy, A F

    1992-01-01

    Isoprinosine was given at daily doses of 0.5, 1, 2, and 4 g kg-1 of body weight to jirds that were infected for 3 months with Echinococcus multilocularis metacestodes. The effects of the different drug doses on metacestodes were studied by transmission electron microscopy and biochemical methods. At lower doses, increases in uric acid and adenosine deaminase activity were noted. At 4 g kg-1 of body weight, marked ultrastructural damage with metabolic perturbations was observed. Images PMID:1375448

  18. [About Dose-Effect Relationship in the Environment Radiation Protection].

    PubMed

    Udalova, A A

    2015-01-01

    One of the most important stages in the development of a methodology for the environment radiation protection is the assessment and justification of critical radiation exposure levels for ecosystem components. In this study application of the approach for critical dose level estimation is demonstrated on the example of the data about ionizing radiation effect on reproduction and survival of agricultural plants after acute and chronic exposures. Influence of the type of dose-effect relationship on the estimated values of the critical doses and dose rates is studied using three models (linear, logarithmic and logistic). The findings obtained do not provide any robust recommendations in favor of one of the three tested functions. The models of dose-effect relationship (threshold or non-threshold) and types of radiation-induced effects (stochastic and deterministic) are discussed from the viewpoint of developing a system for radiation protection of human and non-human biota.

  19. Effects of turbulence on average refraction angles in occultations by planetary atmospheres

    NASA Technical Reports Server (NTRS)

    Eshleman, V. R.; Haugstad, B. S.

    1978-01-01

    Four separable effects of atmospheric turbulence on average refraction angles in occultation experiments are derived from a simplified analysis, and related to more general formulations by B. S. Haugstad. The major contributors are shown to be due to gradients in height of the strength of the turbulence, and the sense of the resulting changes in refraction angles is explained in terms of Fermat's principle. Because the results of analyses of such gradient effects by W. B. Hubbard and J. R. Jokipii are expressed in other ways, a special effort is made to compare all of the predictions on a common basis. We conclude that there are fundamental differences, and use arguments based on energy conservation and Fermat's principle to help characterize the discrepancies.

  20. Effects of turbulence on average refraction angles in occultations by planetary atmospheres

    NASA Technical Reports Server (NTRS)

    Eshleman, V. R.; Haugstad, B. S.

    1978-01-01

    Four separable effects of atmospheric turbulence on average refraction angles in occultation experiments are derived from a simplified analysis, and related to more general formulations by B. S. Haugstad. The major contributors are shown to be due to gradients in height of the strength of the turbulence, and the sense of the resulting changes in refraction angles is explained in terms of Fermat's principle. Because the results of analyses of such gradient effects by W. B. Hubbard and J. R. Jokipii are expressed in other ways, a special effort is made to compare all of the predictions on a common basis. We conclude that there are fundamental differences, and use arguments based on energy conservation and Fermat's principle to help characterize the discrepancies.

  1. Spin interference controlled by electric field: Ensemble average effect on AAS and AB oscillation amplitudes

    NASA Astrophysics Data System (ADS)

    Nitta, Junsaku; Bergsten, Tobias

    2008-03-01

    Time reversal symmetric Al’tshuler-Aronov-Spivak (AAS) oscillations are measured in an array of InGaAs mesoscopic loops. We confirm that gate voltage dependence of h/2 e period oscillations is due to spin interference from the effect of ensemble average on the AAS and Aharonov-Bohm (AB) amplitudes. This spin interference is based on the time reversal Aharonov-Casher (AC) effect. The AC interference oscillations are controlled over several periods. This result shows evidence for electrical manipulation of the spin precession angle in an InGaAs two-dimensional electron gas channel. We control the precession rate in a precise and predictable way with an electrostatic gate.

  2. CT effective dose per dose length product using ICRP 103 weighting factors

    SciTech Connect

    Huda, Walter; Magill, Dennise; He Wenjun

    2011-03-15

    Purpose: To generate effective dose per unit dose length product (E/DLP) conversion factors incorporating ICRP Publication 103 tissue weighting factors. Methods: Effective doses for CT examinations were obtained using the IMPACT Dosimetry Calculator using all 23 dose data sets that are offered by this spreadsheet. CT examinations were simulated for scans performed along the patient long axis for each dosimetry data set using a 4 cm beam width ranging from the upper thighs to top of the head. Five basic body regions (head, neck, chest, abdomen, and pelvis), as well as combinations of the regions (head/neck, chest/abdomen, abdomen/pelvis, and chest/abdomen/pelvis) and whole body CT scans were investigated. Correction factors were generated that can be applied to convert E/DLP conversion factors based on ICRP 60 data to conversion factors that are valid for ICRP 103 data (i.e., E{sub 103}/E{sub 60}). Results: Use of ICRP 103 weighting factors increase effective doses for head scans by {approx}11%, for chest scans by {approx}20%, and decrease effective doses for pelvis scans by {approx}25%. Current E/DLP conversion factors are estimated to be 2.4 {mu}Sv/mGy cm for head CT examinations and range between 14 and 20 {mu}Sv/mGy cm for body CT examinations. Conclusions: Factors that enable patient CT doses to be adjusted to account for ICRP 103 tissue weighting factors are provided, which result in E/DLP factors that were increased in head and chest CT, reduced in pelvis CT, and showed no marked change in neck and abdomen CT.

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

    PubMed

    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 < 0.001). The mean effective radiation dose for the lateral 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.

  4. Estimation of the effects of normal tissue sparing using equivalent uniform dose-based optimization

    PubMed Central

    Senthilkumar, K.; Maria Das, K. J.; Balasubramanian, K.; Deka, A. C.; Patil, B. R.

    2016-01-01

    In this study, we intend to estimate the effects of normal tissue sparing between intensity modulated radiotherapy (IMRT) treatment plans generated with and without a dose volume (DV)-based physical cost function using equivalent uniform dose (EUD). Twenty prostate cancer patients were retrospectively selected for this study. For each patient, two IMRT plans were generated (i) EUD-based optimization with a DV-based physical cost function to control inhomogeneity (EUDWith DV) and (ii) EUD-based optimization without a DV-based physical cost function to allow inhomogeneity (EUDWithout DV). The generated plans were prescribed a dose of 72 Gy in 36 fractions to planning target volume (PTV). Mean dose, D30%, and D5% were evaluated for all organ at risk (OAR). Normal tissue complication probability was also calculated for all OARs using BioSuite software. The average volume of PTV for all patients was 103.02 ± 27 cm3. The PTV mean dose for EUDWith DV plans was 73.67 ± 1.7 Gy, whereas for EUDWithout DV plans was 80.42 ± 2.7 Gy. It was found that PTV volume receiving dose more than 115% of prescription dose was negligible in EUDWith DV plans, whereas it was 28% in EUDWithout DV plans. In almost all dosimetric parameters evaluated, dose to OARs in EUDWith DV plans was higher than in EUDWithout DV plans. Allowing inhomogeneous dose (EUDWithout DV) inside the target would achieve better normal tissue sparing compared to homogenous dose distribution (EUDWith DV). Hence, this inhomogeneous dose could be intentionally dumped on the high-risk volume to achieve high local control. Therefore, it was concluded that EUD optimized plans offer added advantage of less OAR dose as well as selectively boosting dose to gross tumor volume. PMID:27217624

  5. The annual effective dose from natural sources of ionising radiation in Canada.

    PubMed

    Grasty, R L; LaMarre, J R

    2004-01-01

    A review and analysis of published information combined with the results of recent gamma ray surveys were used to determine the annual effective dose to Canadians from natural sources of radiation. The dose due to external radiation was determined from ground gamma ray surveys carried out in the cities of Toronto, Ottawa, Montreal and Winnipeg and was calculated to be 219 microSv. A compilation of airborne gamma ray data from Canada and the United States shows that there are large variations in external radiation with the highest annual outdoor level of 1424 microSv being found in northern Canada. The annual effective inhalation dose of 926 microSv from 222Rn and 220Rn was calculated from approximately 14,000 measurements across Canada. This value includes a contribution of 128 microSv from 222Rn in the outdoor air together with 6 microSv from long-lived uranium and thorium series radionuclides in dust particles. Based on published information, the annual effective dose due to internal radioactivity is 306 microSv. A program developed by the Federal Aviation Administration was used to calculate a population-weighted annual effective dose from cosmic radiation of 318 microSv. The total population-weighted average annual effective dose to Canadians from all sources of natural background radiation was calculated to be 1769 microSv but varies significantly from city to city, largely due to differences in the inhalation dose from 222Rn.

  6. Facial averageness and genetic quality: Testing heritability, genetic correlation with attractiveness, and the paternal age effect.

    PubMed

    Lee, Anthony J; Mitchem, Dorian G; Wright, Margaret J; Martin, Nicholas G; Keller, Matthew C; Zietsch, Brendan P

    2016-01-01

    Popular theory suggests that facial averageness is preferred in a partner for genetic benefits to offspring. However, whether facial averageness is associated with genetic quality is yet to be established. Here, we computed an objective measure of facial averageness for a large sample (N = 1,823) of identical and nonidentical twins and their siblings to test two predictions from the theory that facial averageness reflects genetic quality. First, we use biometrical modelling to estimate the heritability of facial averageness, which is necessary if it reflects genetic quality. We also test for a genetic association between facial averageness and facial attractiveness. Second, we assess whether paternal age at conception (a proxy of mutation load) is associated with facial averageness and facial attractiveness. Our findings are mixed with respect to our hypotheses. While we found that facial averageness does have a genetic component, and a significant phenotypic correlation exists between facial averageness and attractiveness, we did not find a genetic correlation between facial averageness and attractiveness (therefore, we cannot say that the genes that affect facial averageness also affect facial attractiveness) and paternal age at conception was not negatively associated with facial averageness. These findings support some of the previously untested assumptions of the 'genetic benefits' account of facial averageness, but cast doubt on others.

  7. The effect of averaging cardiac Doppler spectrograms on the reduction of their amplitude variability.

    PubMed

    Cloutier, G; Allard, L; Guo, Z; Durand, L G

    1992-03-01

    The effect of averaging cardiac Doppler spectrograms on the reduction of their amplitude variability was investigated in 30 patients. Beat-to-beat variations in the amplitude of Doppler spectrograms were also analysed. The quantification of amplitude variability was based on the computation of the area under the absolute value of the derivative function of each spectrum composing mean spectrograms. Fast Fourier transform using a Hanning window was used to compute Doppler spectra. Results obtained over systolic and diastolic periods showed that the reduction of amplitude variability followed an exponentially decreasing curve characterised by the equation f (r) = 100 e-beta(r-1), where r is the number of cardiac cycles, beta the exponentially decreasing rate, and 100 the normalised variability for r = 1. In systole, the decreasing rate beta was 0.165, whereas in diastole it was 0.225. Reductions of the variability in systole for a number of cardiac cycles of 5, 10, 15, and 20 were 48, 77, 90 and 96 per cent, respectively. In diastole, reductions of the variability for the same numbers of cardiac cycles were 59, 87, 96 and 99 per cent, respectively. Based on these results, it can be concluded that no significant improvement in the reduction of amplitude variability may be obtained by averaging more than 20 cardiac cycles.

  8. The peripheral vascular effects of diltiazem--dose-response characteristics.

    PubMed Central

    Finch, M B; Johnston, G D

    1985-01-01

    The acute effects of increasing doses of diltiazem on peripheral blood flow were observed in six subjects. Each subject received, in random order, a single oral dose of placebo or diltiazem 60, 120 or 180 mg. Supine heart rate, blood pressure, skin temperature, digital systolic pressure, forearm and digital blood flow were recorded before and at 1, 2, 3, 4 and 6 h post-dosing. Plasma diltiazem concentrations were measured at each time interval and at 12 and 24 h after the 120 mg dose. At doses of 120 and 180 mg, diltiazem significantly increased digital blood flow at 1, 2, 3, 4 and 6 h post-dosing and forearm blood flow at 2 and 3 h following 180 mg and 3 h following 120 mg. No correlation was observed between plasma diltiazem concentration and changes in peripheral blood flow. PMID:4074614

  9. Radiation Dose-Volume Effects in the Lung

    SciTech Connect

    Marks, Lawrence B.; Bentzen, Soren M. D.Sc.; Deasy, Joseph O.; Kong, F.-M.; Bradley, Jeffrey D.; Vogelius, Ivan S.; El Naqa, Issam; Hubbs, Jessica L. M.S.; Lebesque, Joos V.; Timmerman, Robert D.; Martel, Mary K.; Jackson, Andrew

    2010-03-01

    The three-dimensional dose, volume, and outcome data for lung are reviewed in detail. The rate of symptomatic pneumonitis is related to many dosimetric parameters, and there are no evident threshold 'tolerance dose-volume' levels. There are strong volume and fractionation effects.

  10. Effects Of Dose Rates On Radiation Damage In CMOS Parts

    NASA Technical Reports Server (NTRS)

    Goben, Charles A.; Coss, James R.; Price, William E.

    1990-01-01

    Report describes measurements of effects of ionizing-radiation dose rate on consequent damage to complementary metal oxide/semiconductor (CMOS) electronic devices. Depending on irradiation time and degree of annealing, survivability of devices in outer space, or after explosion of nuclear weapons, enhanced. Annealing involving recovery beyond pre-irradiation conditions (rebound) detrimental. Damage more severe at lower dose rates.

  11. CARCINOGENIC EFFECTS OF LOW DOSES OF IONIZING RADIATION

    EPA Science Inventory

    Carcinogenic Effects of Low Doses of Ionizing Radiation

    R Julian Preston, Environmental Carcinogenesis Division, NHEERL, U.S. Environmental Protection Agency, Research Triangle Park, NC 27711

    The form of the dose-response curve for radiation-induced cancers, particu...

  12. Total dose dependency and ELDRS effects on bipolar linear devices

    NASA Technical Reports Server (NTRS)

    Yui, C. C.; McClure, S. S.; Rax, B. G.; Lehman, J. M.; Minto, T. D.; Wiedeman, M.

    2002-01-01

    The use of bipolar linear devices is prevalent in most satellite and some space applications. However, degradation as a result of low dose irradiations known as ELDERS (effects of enhanced low dose rate sensitivity) is a major concern when selecting flight hardware. Many studies and reports have been conducted on this possible phenomenon as well as their responsible physical mechanisms.

  13. Total dose dependency and ELDRS effects on bipolar linear devices

    NASA Technical Reports Server (NTRS)

    Yui, C. C.; McClure, S. S.; Rax, B. G.; Lehman, J. M.; Minto, T. D.; Wiedeman, M.

    2002-01-01

    The use of bipolar linear devices is prevalent in most satellite and some space applications. However, degradation as a result of low dose irradiations known as ELDERS (effects of enhanced low dose rate sensitivity) is a major concern when selecting flight hardware. Many studies and reports have been conducted on this possible phenomenon as well as their responsible physical mechanisms.

  14. CARCINOGENIC EFFECTS OF LOW DOSES OF IONIZING RADIATION

    EPA Science Inventory

    Carcinogenic Effects of Low Doses of Ionizing Radiation

    R Julian Preston, Environmental Carcinogenesis Division, NHEERL, U.S. Environmental Protection Agency, Research Triangle Park, NC 27711

    The form of the dose-response curve for radiation-induced cancers, particu...

  15. Effects of pH and dose on nasal absorption of scopolamine hydrobromide in human subjects

    NASA Technical Reports Server (NTRS)

    Ahmed, S.; Sileno, A. P.; deMeireles, J. C.; Dua, R.; Pimplaskar, H. K.; Xia, W. J.; Marinaro, J.; Langenback, E.; Matos, F. J.; Putcha, L.; hide

    2000-01-01

    PURPOSE: The present study was conducted to evaluate the effects of formulation pH and dose on nasal absorption of scopolamine hydrobromide, the single most effective drug available for the prevention of nausea and vomiting induced by motion sickness. METHODS: Human subjects received scopolamine nasally at a dose of 0.2 mg/0.05 mL or 0.4 mg/0.10 mL, blood samples were collected at different time points, and plasma scopolamine concentrations were determined by LC-MS/MS. RESULTS: Following administration of a 0.2 mg dose, the average Cmax values were found to be 262+/-118, 419+/-161, and 488+/-331 pg/ mL for pH 4.0, 7.0, and 9.0 formulations, respectively. At the 0.4 mg dose the average Cmax values were found to be 503+/-199, 933+/-449, and 1,308+/-473 pg/mL for pH 4.0, 7.0, and 9.0 formulations, respectively. At a 0.2 mg dose, the AUC values were found to be 23,208+/-6,824, 29,145+/-9,225, and 25,721+/-5,294 pg x min/mL for formulation pH 4.0, 7.0, and 9.0, respectively. At a 0.4 mg dose, the average AUC value was found to be high for pH 9.0 formulation (70,740+/-29,381 pg x min/mL) as compared to those of pH 4.0 (59,573+/-13,700 pg x min/mL) and pH 7.0 (55,298+/-17,305 pg x min/mL) formulations. Both the Cmax and AUC values were almost doubled with doubling the dose. On the other hand, the average Tmax, values decreased linearly with a decrease in formulation pH at both doses. For example, at a 0.4 mg dose, the average Tmax values were 26.7+/-5.8, 15.0+/-10.0, and 8.8+/-2.5 minutes at formulation pH 4.0, 7.0, and 9.0, respectively. CONCLUSIONS: Nasal absorption of scopolamine hydrobromide in human subjects increased substantially with increases in formulation pH and dose.

  16. Effects of pH and dose on nasal absorption of scopolamine hydrobromide in human subjects

    NASA Technical Reports Server (NTRS)

    Ahmed, S.; Sileno, A. P.; deMeireles, J. C.; Dua, R.; Pimplaskar, H. K.; Xia, W. J.; Marinaro, J.; Langenback, E.; Matos, F. J.; Putcha, L.; Romeo, V. D.; Behl, C. R.

    2000-01-01

    PURPOSE: The present study was conducted to evaluate the effects of formulation pH and dose on nasal absorption of scopolamine hydrobromide, the single most effective drug available for the prevention of nausea and vomiting induced by motion sickness. METHODS: Human subjects received scopolamine nasally at a dose of 0.2 mg/0.05 mL or 0.4 mg/0.10 mL, blood samples were collected at different time points, and plasma scopolamine concentrations were determined by LC-MS/MS. RESULTS: Following administration of a 0.2 mg dose, the average Cmax values were found to be 262+/-118, 419+/-161, and 488+/-331 pg/ mL for pH 4.0, 7.0, and 9.0 formulations, respectively. At the 0.4 mg dose the average Cmax values were found to be 503+/-199, 933+/-449, and 1,308+/-473 pg/mL for pH 4.0, 7.0, and 9.0 formulations, respectively. At a 0.2 mg dose, the AUC values were found to be 23,208+/-6,824, 29,145+/-9,225, and 25,721+/-5,294 pg x min/mL for formulation pH 4.0, 7.0, and 9.0, respectively. At a 0.4 mg dose, the average AUC value was found to be high for pH 9.0 formulation (70,740+/-29,381 pg x min/mL) as compared to those of pH 4.0 (59,573+/-13,700 pg x min/mL) and pH 7.0 (55,298+/-17,305 pg x min/mL) formulations. Both the Cmax and AUC values were almost doubled with doubling the dose. On the other hand, the average Tmax, values decreased linearly with a decrease in formulation pH at both doses. For example, at a 0.4 mg dose, the average Tmax values were 26.7+/-5.8, 15.0+/-10.0, and 8.8+/-2.5 minutes at formulation pH 4.0, 7.0, and 9.0, respectively. CONCLUSIONS: Nasal absorption of scopolamine hydrobromide in human subjects increased substantially with increases in formulation pH and dose.

  17. Estimation of effective dose and lifetime attributable risk from multiple head CT scans in ventriculoperitoneal shunted children

    PubMed Central

    Aw-Zoretic, J.; Seth, D.; Katzman, G.; Sammet, S.

    2015-01-01

    Purpose The purpose of this review is to determine the averaged effective dose and lifetime attributable risk factor from multiple head computed tomography (CT) dose data on children with ventriculoperitoneal shunts (VPS). Method and materials A total of 422 paediatric head CT exams were found between October 2008 and January 2011 and retrospectively reviewed. The CT dose data was weighted with the latest IRCP 103 conversion factor to obtain the effective dose per study and the averaged effective dose was calculated. Estimates of the lifetime attributable risk were also calculated from the averaged effective dose using a conversion factor from the latest BEIR VII report. Results Our study found the highest effective doses in neonates and the lowest effective doses were observed in the 10–18 years age group. We estimated a 0.007% potential increase risk in neonates and 0.001% potential increased risk in teenagers over the base risk. Conclusion Multiple head CTs in children equates to a slight potential increase risk in lifetime attributable risk over the baseline risk for cancer, slightly higher in neonates relative to teenagers. The potential risks versus clinical benefit must be assessed. PMID:25130177

  18. Dose rate effects in radiation degradation of polymer-based cable materials

    NASA Astrophysics Data System (ADS)

    Plaček, V.; Bartoníček, B.; Hnát, V.; Otáhal, B.

    2003-08-01

    Cable ageing under the nuclear power plant (NPP) conditions must be effectively managed to ensure that the required plant safety and reliability are maintained throughout the plant service life. Ionizing radiation is one of the main stressors causing age-related degradation of polymer-based cable materials in air. For a given absorbed dose, radiation-induced damage to a polymer in air environment usually depends on the dose rate of the exposure. In this work, the effect of dose rate on the degradation rate has been studied. Three types of NPP cables (with jacket/insulation combinations PVC/PVC, PVC/PE, XPE/XPE) were irradiated at room temperature using 60Co gamma ray source at average dose rates of 7, 30 and 100 Gy/h with the doses up to 590 kGy. The irradiated samples have been tested for their mechanical properties, thermo-oxidative stability (using differential scanning calorimetry, DSC), and density. In the case of PVC and PE samples, the tested properties have shown evident dose rate effects, while the XPE material has shown no noticeable ones. The values of elongation at break and the thermo-oxidative stability decrease with the advanced degradation, density tends to increase with the absorbed dose. For XPE samples this effect can be partially explained by the increase of crystallinity. It was tested by the DSC determination of the crystalline phase amount.

  19. The effective dose result of 18F-FDG PET-CT paediatric patients

    NASA Astrophysics Data System (ADS)

    Hussin, D.; Said, M. A.; Ali, N. S.; Tajuddin, A. A.; Zainon, R.

    2017-05-01

    Paediatric patient received high exposure from both CT and PET examination. Automatic Exposure Control (AEC) is important in CT dose reduction. This study aimed to compare the effective dose obtained from PET-CT scanner with and without the use of AEC function. In this study, 68 patients underwent PET-CT examination without the use of AEC function, while 25 patients used the AEC function during the examination. Patients involved in this study were between 2 to 15 years old with varies of malignancies and epilepsy diseases. The effective dose obtained from PET and CT examinations was calculated based on recommendation from International Commission on Radiological Protection (ICRP) Publication 106 and ICRP publication 102. The outcome of this study shows that the radiation dose was reduced up to 20% with the use of AEC function. The mean average of effective dose result obtained from PET and CT examinations without the use of AEC and AEC function were found to be as 6.67 mSv, 6.77 mSv, 6.03mSv and 4.96 mSv respectively. Where total effective dose result of PET-CT with non-AEC and AEC were found to be 13.44 mSv and 10.99 mSv respectively. Conclusion of this study is, the installation of AEC function in PET-CT machine does play important role in CT dose reduction especially for paediatric patient.

  20. The effect of temperature on the average volume of Barkhausen jump on Q235 carbon steel

    NASA Astrophysics Data System (ADS)

    Guo, Lei; Shu, Di; Yin, Liang; Chen, Juan; Qi, Xin

    2016-06-01

    On the basis of the average volume of Barkhausen jump (AVBJ) vbar generated by irreversible displacement of magnetic domain wall under the effect of the incentive magnetic field on ferromagnetic materials, the functional relationship between saturation magnetization Ms and temperature T is employed in this paper to deduce the explicit mathematical expression among AVBJ vbar, stress σ, incentive magnetic field H and temperature T. Then the change law between AVBJ vbar and temperature T is researched according to the mathematical expression. Moreover, the tensile and compressive stress experiments are carried out on Q235 carbon steel specimens at different temperature to verify our theories. This paper offers a series of theoretical bases to solve the temperature compensation problem of Barkhausen testing method.

  1. Effects of stratospheric aerosol surface processes on the LLNL two-dimensional zonally averaged model

    NASA Technical Reports Server (NTRS)

    Connell, Peter S.; Kinnison, Douglas E.; Wuebbles, Donald J.; Burley, Joel D.; Johnston, Harold S.

    1994-01-01

    We have investigated the effects of incorporating representations of heterogeneous chemical processes associated with stratospheric sulfuric acid aerosol into the LLNL two-dimensional, zonally averaged, model of the troposphere and stratosphere. Using distributions of aerosol surface area and volume density derived from SAGE II satellite observations, we were primarily interested in changes in partitioning within the Cl- and N- families in the lower stratosphere, compared to a model including only gas phase photochemical reactions. We have considered the heterogeneous hydrolysis reactions N2O5 + H2O(aerosol) yields 2 HNO3 and ClONO2 + H2O(aerosol) yields HOCl + HNO3 alone and in combination with the proposed formation of nitrosyl sulfuric acid (NSA) in the aerosol and its reaction with HCl. Inclusion of these processes produces significant changes in partitioning in the NO(y) and ClO(y) families in the middle stratosphere.

  2. Finite size effects in the averaged eigenvalue density of Wigner random-sign real symmetric matrices

    NASA Astrophysics Data System (ADS)

    Dhesi, G. S.; Ausloos, M.

    2016-06-01

    Nowadays, strict finite size effects must be taken into account in condensed matter problems when treated through models based on lattices or graphs. On the other hand, the cases of directed bonds or links are known to be highly relevant in topics ranging from ferroelectrics to quotation networks. Combining these two points leads us to examine finite size random matrices. To obtain basic materials properties, the Green's function associated with the matrix has to be calculated. To obtain the first finite size correction, a perturbative scheme is hereby developed within the framework of the replica method. The averaged eigenvalue spectrum and the corresponding Green's function of Wigner random sign real symmetric N ×N matrices to order 1 /N are finally obtained analytically. Related simulation results are also presented. The agreement is excellent between the analytical formulas and finite size matrix numerical diagonalization results, confirming the correctness of the first-order finite size expression.

  3. On the average temperature of airless spherical bodies and the magnitude of Earth's atmospheric thermal effect.

    PubMed

    Volokin, Den; ReLlez, Lark

    2014-01-01

    The presence of atmosphere can appreciably warm a planet's surface above the temperature of an airless environment. Known as a natural Greenhouse Effect (GE), this near-surface Atmospheric Thermal Enhancement (ATE) as named herein is presently entirely attributed to the absorption of up-welling long-wave radiation by greenhouse gases. Often quoted as 33 K for Earth, GE is estimated as a difference between planet's observed mean surface temperature and an effective radiating temperature calculated from the globally averaged absorbed solar flux using the Stefan-Boltzmann (SB) radiation law. This approach equates a planet's average temperature in the absence of greenhouse gases or atmosphere to an effective emission temperature assuming ATE ≡ GE. The SB law is also routinely employed to estimating the mean temperatures of airless bodies. We demonstrate that this formula as applied to spherical objects is mathematically incorrect owing to Hölder's inequality between integrals and leads to biased results such as a significant underestimation of Earth's ATE. We derive a new expression for the mean physical temperature of airless bodies based on an analytic integration of the SB law over a sphere that accounts for effects of regolith heat storage and cosmic background radiation on nighttime temperatures. Upon verifying our model against Moon surface temperature data provided by the NASA Diviner Lunar Radiometer Experiment, we propose it as a new analytic standard for evaluating the thermal environment of airless bodies. Physical evidence is presented that Earth's ATE should be assessed against the temperature of an equivalent airless body such as the Moon rather than a hypothetical atmosphere devoid of greenhouse gases. Employing the new temperature formula we show that Earth's total ATE is ~90 K, not 33 K, and that ATE = GE + TE, where GE is the thermal effect of greenhouse gases, while TE > 15 K is a thermodynamic enhancement independent of the

  4. The effect of a slower than standard dose escalation scheme for dipyridamole on headaches in secondary prevention therapy of strokes: a randomized, open-label trial (DOSE).

    PubMed

    de Vos-Koppelaar, N C Martine; Kerkhoff, Henk; de Vogel, Ed M; Zock, Elles; Dieleman, Hetty G

    2014-01-01

    Combination therapy with acetylsalicylic acid and dipyridamole is first-line treatment in secondary prevention of strokes. Approximately 40% of patients report headache as a side effect of dipyridamole. Dose escalation of dipyridamole reduces this side effect. In practice, different dose escalation schemes are used. In theory, slower dose escalation than a standard scheme reduces headaches even more. This study aimed to find the best dose escalation scheme for prevention of headaches as a side effect of dipyridamole in the secondary prevention of strokes. In this randomized, open-label, 4-week trial, 114 patients who had an ischemic stroke or transient ischemic attack were randomized to receive either a standard or slow dose escalation scheme of dipyridamole. Participants were asked to report the four most common side effects of dipyridamole in a study diary on study days 1, 3, 5, 7, 14, 21 and 28. They were asked to score headache intensity on a visual analog scale (VAS). Participants were unaware that the trial was focused on headaches. Primary end point was to determine if a slow dose escalation scheme reduces the percentage of patients with headaches. Secondary objective was to determine the number of patients who discontinued treatment with dipyridamole because of headaches. Overall 37 patients (38%) of the final population reported headache, 19 (39%) in the standard dose escalation group and 18 (37%) in the slow dose escalation group (p = 1.0). In the standard dose escalation group patients scored headaches (VAS >4) on an average of 3.3 days and patients in the slow dose escalation group on 3.6 days (p = 0.82). Mean VAS scores on study days 1, 3, 5, 7, 14 and 21 ranged from 1.4 to 3.7 in both groups. These scores did not differ significantly. However, on day 28 patients scored a significantly lower mean VAS score in the standard dose escalation group than in the slow dose escalation group (2.5 vs. 4.8; p = 0.05). In the standard dose escalation group 6

  5. [The Dose Effect of Isocenter Selection during IMRT Dose Verification with the 2D Chamber Array].

    PubMed

    Xie, Chuanbin; Cong, Xiaohu; Xu, Shouping; Dai, Xiangkun; Wang, Yunlai; Han, Lu; Gong, Hanshun; Ju, Zhongjian; Ge, Ruigang; Ma, Lin

    2015-03-01

    To investigate the dose effect of isocenter difference during IMRT dose verification with the 2D chamber array. The samples collected from 10 patients were respectively designed for IMRT plans, the isocenter of which was independently defined as P(o), P(x) and P(y). P(o) was fixed on the target center and the other points shifted 8cm from the target center in the orientation of x/y. The PTW729 was used for 2D dose verification in the 3 groups which beams of plans were set to 0 degrees. The γ-analysis passing rates for the whole plan and each beam were gotten using the different standards in the 3 groups, The results showed the mean passing rate of γ-analysis was highest in the P(o) group, and the mean passing rate of the whole plan was better than that of each beam. In addition, it became worse with the increase of dose leakage between the leaves in P(y) group. Therefore, the determination of isocenter has a visible effect for IMRT dose verification of the 2D chamber array, The isocenter of the planning design should be close to the geometric center of target.

  6. Elucidating the role of dose in the biopharmaceutics classification of drugs: the concepts of critical dose, effective in vivo solubility, and dose-dependent BCS.

    PubMed

    Charkoftaki, Georgia; Dokoumetzidis, Aristides; Valsami, Georgia; Macheras, Panos

    2012-11-01

    To develop a dose dependent version of BCS and identify a critical dose after which the amount absorbed is independent from the dose. We utilized a mathematical model of drug absorption in order to produce simulations of the fraction of dose absorbed (F) and the amount absorbed as function of the dose for the various classes of BCS and the marginal cases in between classes. Simulations based on the mathematical model of F versus dose produced patterns of a constant F throughout a wide range of doses for drugs of Classes I, II and III, justifying biowaiver claim. For Classes I and III the pattern of a constant F stops at a critical dose Dose(cr) after which the amount of drug absorbed, is independent from the dose. For doses higher than Dose(cr), Class I drugs become Class II and Class III drugs become Class IV. Dose(cr) was used to define an in vivo effective solubility as S(eff) = Dose(cr)/250 ml. Literature data were used to support our simulation results. A new biopharmaceutic classification of drugs is proposed, based on F, separating drugs into three regions, taking into account the dose, and Dose(cr), while the regions for claiming biowaiver are clearly defined.

  7. Parent training plus contingency management for substance abusing families: A Complier Average Causal Effects (CACE) analysis*

    PubMed Central

    Stanger, Catherine; Ryan, Stacy R.; Fu, Hongyun; Budney, Alan J.

    2011-01-01

    Background Children of substance abusers are at risk for behavioral/emotional problems. To improve outcomes for these children, we developed and tested an intervention that integrated a novel contingency management (CM) program designed to enhance compliance with an empirically-validated parent training curriculum. CM provided incentives for daily monitoring of parenting and child behavior, completion of home practice assignments, and session attendance. Methods Forty-seven mothers with substance abuse or dependence were randomly assigned to parent training + incentives (PTI) or parent training without incentives (PT). Children were 55% male, ages 2-7 years. Results Homework completion and session attendance did not differ between PTI and PT mothers, but PTI mothers had higher rates of daily monitoring. PTI children had larger reductions in child externalizing problems in all models. Complier Average Causal Effects (CACE) analyses showed additional significant effects of PTI on child internalizing problems, parent problems and parenting. These effects were not significant in standard Intent-to-Treat analyses. Conclusion Results suggest our incentive program may offer a method for boosting outcomes. PMID:21466925

  8. The effect of methadone dose regimen on neonatal abstinence syndrome.

    PubMed

    McCarthy, John J; Leamon, Martin H; Willits, Neil H; Salo, Ruth

    2015-01-01

    To evaluate the effects of a multiple daily dose methadone regimen in pregnancy on neonatal outcomes. Although methadone maintenance has been the standard for the treatment of opioid dependence in pregnancy, there is no consensus on proper dosing. Single daily dosing is the most common strategy. Because of accelerated metabolism of methadone in pregnancy, this regimen may expose mother and fetus to daily episodes of withdrawal and possibly contribute to more severe Neonatal Abstinence Syndrome (NAS). This study reports on a protocol that increased both methadone dose and dose frequency in response to maternal reports of withdrawal. Treatment of NAS was needed in 29% of neonates, compared to a published rate of 60% to 80%. The mean methadone dose was 152 mg at delivery, divided into 2 to 6 doses per day. Ninety-two percent of mothers were free of illicit drug use at delivery. There was no relationship between methadone dose and treatment of NAS. Female babies had a treatment rate of 16% versus 38% for male babies. Beyond abstinence symptoms, cohort outcomes in terms of gestational age, birth weight, prematurity, Caesarian sections, and breastfeeding equaled or approximated US population norms. The protocol was associated with low rates of treatment of NAS and high rates of maternal recovery. High rates of treatment for NAS reported in methadone-exposed neonates might relate in part to iatrogenic factors and be reduced through the use of divided daily doses and protocols that minimize maternal withdrawal.

  9. Lifetime Effective Dose Assessment Based on Background Outdoor Gamma Exposure in Chihuahua City, Mexico

    PubMed Central

    Luevano-Gurrola, Sergio; Perez-Tapia, Angelica; Pinedo-Alvarez, Carmelo; Carrillo-Flores, Jorge; Montero-Cabrera, Maria Elena; Renteria-Villalobos, Marusia

    2015-01-01

    Determining ionizing radiation in a geographic area serves to assess its effects on a population’s health. The aim of this study was to evaluate the spatial distribution of the background environmental outdoor gamma dose rates in Chihuahua City. This study also estimated the annual effective dose and the lifetime cancer risks of the population of this city. To determine the outdoor gamma dose rate in air, the annual effective dose and the lifetime cancer risk, 48 sampling points were randomly selected in Chihuahua City. Outdoor gamma dose rate measurements were carried out by using a Geiger-Müller counter. Outdoor gamma dose rates ranged from 113 to 310 nGy·h−1. At the same sites, 48 soil samples were taken to obtain the activity concentrations of 226Ra, 232Th and 40K and to calculate their terrestrial gamma dose rates. Radioisotope activity concentrations were determined by gamma spectrometry. Calculated gamma dose rates ranged from 56 to 193 nGy·h−1. Results indicated that the lifetime effective dose of the inhabitants of Chihuahua City is on average 19.8 mSv, resulting in a lifetime cancer risk of 0.001. In addition, the mean of the activity concentrations in soil were 52, 73 and 1097 Bq·kg−1, for 226Ra, 232Th and 40K, respectively. From the analysis, the spatial distribution of 232Th, 226Ra and 40K is to the north, to the north-center and to the south of city, respectively. In conclusion, the natural background gamma dose received by the inhabitants of Chihuahua City is high and mainly due to the geological characteristics of the zone. From the radiological point of view, this kind of study allows us to identify the importance of manmade environments, which are often highly variable and difficult to characterize. PMID:26437425

  10. Lifetime Effective Dose Assessment Based on Background Outdoor Gamma Exposure in Chihuahua City, Mexico.

    PubMed

    Luevano-Gurrola, Sergio; Perez-Tapia, Angelica; Pinedo-Alvarez, Carmelo; Carrillo-Flores, Jorge; Montero-Cabrera, Maria Elena; Renteria-Villalobos, Marusia

    2015-09-30

    Determining ionizing radiation in a geographic area serves to assess its effects on a population's health. The aim of this study was to evaluate the spatial distribution of the background environmental outdoor gamma dose rates in Chihuahua City. This study also estimated the annual effective dose and the lifetime cancer risks of the population of this city. To determine the outdoor gamma dose rate in air, the annual effective dose and the lifetime cancer risk, 48 sampling points were randomly selected in Chihuahua City. Outdoor gamma dose rate measurements were carried out by using a Geiger-Müller counter. Outdoor gamma dose rates ranged from 113 to 310 nGy·h(-1). At the same sites, 48 soil samples were taken to obtain the activity concentrations of (226)Ra, (232)Th and (40)K and to calculate their terrestrial gamma dose rates. Radioisotope activity concentrations were determined by gamma spectrometry. Calculated gamma dose rates ranged from 56 to 193 nGy·h(-1). Results indicated that the lifetime effective dose of the inhabitants of Chihuahua City is on average 19.8 mSv, resulting in a lifetime cancer risk of 0.001. In addition, the mean of the activity concentrations in soil were 52, 73 and 1097 Bq·kg(-1), for (226)Ra, (232)Th and (40)K, respectively. From the analysis, the spatial distribution of (232)Th, (226)Ra and (40)K is to the north, to the north-center and to the south of city, respectively. In conclusion, the natural background gamma dose received by the inhabitants of Chihuahua City is high and mainly due to the geological characteristics of the zone. From the radiological point of view, this kind of study allows us to identify the importance of manmade environments, which are often highly variable and difficult to characterize.

  11. Effective dose of dental CBCT-a meta analysis of published data and additional data for nine CBCT units.

    PubMed

    Ludlow, J B; Timothy, R; Walker, C; Hunter, R; Benavides, E; Samuelson, D B; Scheske, M J

    2015-01-01

    This article analyses dose measurement and effective dose estimation of dental CBCT examinations. Challenges to accurate calculation of dose are discussed and the use of dose-height product (DHP) as an alternative to dose-area product (DAP) is explored. The English literature on effective dose was reviewed. Data from these studies together with additional data for nine CBCT units were analysed. Descriptive statistics, ANOVA and paired analysis are used to characterize the data. PubMed and EMBASE searches yielded 519 and 743 publications, respectively, which were reduced to 20 following review. Reported adult effective doses for any protocol ranged from 46 to 1073 µSv for large fields of view (FOVs), 9-560 µSv for medium FOVs and 5-652 µSv for small FOVs. Child effective doses from any protocol ranged from 13 to 769 µSv for large or medium FOVs and 7-521 µSv for small FOVs. Effective doses from standard or default exposure protocols were available for 167 adult and 52 child exposures. Mean adult effective doses grouped by FOV size were 212 µSv (large), 177 µSv (medium) and 84 µSv (small). Mean child doses were 175 µSv (combined large and medium) and 103 µSv (small). Large differences were seen between different CBCT units. Additional low-dose and high-definition protocols available for many units extend the range of doses. DHP was found to reduce average absolute error for calculation of dose by 45% in comparison with DAP. Large exposure ranges make CBCT doses difficult to generalize. Use of DHP as a metric for estimating effective dose warrants further investigation.

  12. SU-E-J-89: Motion Effects On Organ Dose in Respiratory Gated Stereotactic Body Radiation Therapy

    SciTech Connect

    Wang, T; Zhu, L; Khan, M; Landry, J; Rajpara, R; Hawk, N

    2014-06-01

    Purpose: Existing reports on gated radiation therapy focus mainly on optimizing dose delivery to the target structure. This work investigates the motion effects on radiation dose delivered to organs at risk (OAR) in respiratory gated stereotactic body radiation therapy (SBRT). A new algorithmic tool of dose analysis is developed to evaluate the optimality of gating phase for dose sparing on OARs while ensuring adequate target coverage. Methods: Eight patients with pancreatic cancer were treated on a phase I prospective study employing 4DCT-based SBRT. For each patient, 4DCT scans are acquired and sorted into 10 respiratory phases (inhale-exhale- inhale). Treatment planning is performed on the average CT image. The average CT is spatially registered to other phases. The resultant displacement field is then applied on the plan dose map to estimate the actual dose map for each phase. Dose values of each voxel are fitted to a sinusoidal function. Fitting parameters of dose variation, mean delivered dose and optimal gating phase for each voxel over respiration cycle are mapped on the dose volume. Results: The sinusoidal function accurately models the dose change during respiratory motion (mean fitting error 4.6%). In the eight patients, mean dose variation is 3.3 Gy on OARs with maximum of 13.7 Gy. Two patients have about 100cm{sup 3} volumes covered by more than 5 Gy deviation. The mean delivered dose maps are similar to plan dose with slight deformation. The optimal gating phase highly varies across the patient, with phase 5 or 6 on about 60% of the volume, and phase 0 on most of the rest. Conclusion: A new algorithmic tool is developed to conveniently quantify dose deviation on OARs from plan dose during the respiratory cycle. The proposed software facilitates the treatment planning process by providing the optimal respiratory gating phase for dose sparing on each OAR.

  13. The Population Effective Dose of Medical Computed Tomography Examinations in Taiwan for 2013

    PubMed Central

    Yeh, Da-Ming; Tsai, Hui-Yu; Tyan, Yen-Sheng; Chang, Yu-Cheng; Pan, Lung-Kwang

    2016-01-01

    Purpose To evaluate the annual effective dose per capita attributed to computed tomography (CT) examinations in 2013 and to predict the population effective dose from 2000 to 2013 in Taiwan. Methods A CT examination database collected from 30 hospitals was divided into 22 procedures and classified into six regions: head, neck, chest, abdomen, pelvis, and other, respectively. The effective doses in different regions were evaluated by dose-length product (DLP) multiplied by conversion factors. Results The CT scan dose parameters were collected from 4,407 patients. For the six scanned regions, the percentages of patients scanned were: head (39.8%), neck (3.9%), chest (23.3%), abdomen (26.7%), pelvis (4.8%), and other (1.6%), respectively. The DLPs per patient (mGy·cm/patient) were head (1,071±225), neck (1,103±615), chest (724±509), abdomen (1,315±550), pelvis (1,231±620) and other (1,407±937), respectively. The number of CT examinations increased rapidly, with an average annual growth rate of 7.6%. The number of CT examinations in 2013 was 2.6 times that in 2000. The population effective dose was 0.30 mSv per capita in 2000 and increased to 0.74 mSv per capita in 2013, with an annual growth rate of 7.2%. The growth trend indicates that the effective dose will continue to rise in Taiwan. Conclusion Some strategies should be applied to cope with this growth. Defining the CT dose reference level stipulated in official recommendations and encouraging the use of iterative reconstruction imaging instead of filtered back-projection imaging could be a useful method for optimizing the effective dose and image quality. PMID:27788231

  14. Correlation between effective dose and radiological risk: general concepts.

    PubMed

    Costa, Paulo Roberto; Yoshimura, Elisabeth Mateus; Nersissian, Denise Yanikian; Melo, Camila Souza

    2016-01-01

    The present review aims to offer an educational approach related to the limitations in the use of the effective dose mgnitude as a tool for the quantification of doses resulting from diagnostic applications of ionizing radiation. We present a critical analysis of the quantities accepted and currently used for dosimetric evaluation in diagnostic imaging procedures, based on studies published in the literature. It is highlighted the use of these quantities to evaluate the risk attributed to the procedure and to calculate the effective dose, as well as to determine its correct use and interpretation.

  15. Correlation between effective dose and radiological risk: general concepts*

    PubMed Central

    Costa, Paulo Roberto; Yoshimura, Elisabeth Mateus; Nersissian, Denise Yanikian; Melo, Camila Souza

    2016-01-01

    The present review aims to offer an educational approach related to the limitations in the use of the effective dose mgnitude as a tool for the quantification of doses resulting from diagnostic applications of ionizing radiation. We present a critical analysis of the quantities accepted and currently used for dosimetric evaluation in diagnostic imaging procedures, based on studies published in the literature. It is highlighted the use of these quantities to evaluate the risk attributed to the procedure and to calculate the effective dose, as well as to determine its correct use and interpretation. PMID:27403018

  16. Beyond intent to treat (ITT): A complier average causal effect (CACE) estimation primer.

    PubMed

    Peugh, James L; Strotman, Daniel; McGrady, Meghan; Rausch, Joseph; Kashikar-Zuck, Susmita

    2017-02-01

    Randomized control trials (RCTs) have long been the gold standard for allowing causal inferences to be made regarding the efficacy of a treatment under investigation, but traditional RCT data analysis perspectives do not take into account a common reality: imperfect participant compliance to treatment. Recent advances in both maximum likelihood parameter estimation and mixture modeling methodology have enabled treatment effects to be estimated, in the presence of less than ideal levels of participant compliance, via a Complier Average Causal Effect (CACE) structural equation mixture model. CACE is described in contrast to "intent to treat" (ITT), "per protocol", and "as treated" RCT data analysis perspectives. CACE model assumptions, specification, estimation, and interpretation will all be demonstrated with simulated data generated from a randomized controlled trial of cognitive-behavioral therapy for Juvenile Fibromyalgia. CACE analysis model figures, linear model equations, and Mplus estimation syntax examples are all provided. Data needed to reproduce analyses in this article are available as supplemental materials (online only) in the Appendix of this article.

  17. Effective radiation dose of ProMax 3D cone-beam computerized tomography scanner with different dental protocols.

    PubMed

    Qu, Xing-min; Li, Gang; Ludlow, John B; Zhang, Zu-yan; Ma, Xu-chen

    2010-12-01

    The aim of this study was to compare effective doses resulting from different scan protocols for cone-beam computerized tomography (CBCT) using International Commission on Radiological Protection (ICRP) 1990 and 2007 calculations of dose. Average tissue-absorbed dose, equivalent dose, and effective dose for a ProMax 3D CBCT with different dental protocols were calculated using thermoluminescent dosimeter chips in a human equivalent phantom. Effective doses were derived using ICRP 1990 and the superseding 2007 recommendations. Effective doses (ICRP 2007) for default patient sizes from small to large ranged from 102 to 298 μSv. The coefficient of determination (R(2)) between tube current and effective dose (ICRP 2007) was 0.90. When scanning with lower resolution settings, the effective doses were reduced significantly (P < .05). ProMax 3D can provide a wide range of radiation dose levels. Reduction in radiation dose can be achieved when using lower settings of exposure parameters. Copyright © 2010 Mosby, Inc. All rights reserved.

  18. Effective dose range for dental cone beam computed tomography scanners.

    PubMed

    Pauwels, Ruben; Beinsberger, Jilke; Collaert, Bruno; Theodorakou, Chrysoula; Rogers, Jessica; Walker, Anne; Cockmartin, Lesley; Bosmans, Hilde; Jacobs, Reinhilde; Bogaerts, Ria; Horner, Keith

    2012-02-01

    To estimate the absorbed organ dose and effective dose for a wide range of cone beam computed tomography scanners, using different exposure protocols and geometries. Two Alderson Radiation Therapy anthropomorphic phantoms were loaded with LiF detectors (TLD-100 and TLD-100 H) which were evenly distributed throughout the head and neck, covering all radiosensitive organs. Measurements were performed on 14 CBCT devices: 3D Accuitomo 170, Galileos Comfort, i-CAT Next Generation, Iluma Elite, Kodak 9000 3D, Kodak 9500, NewTom VG, NewTom VGi, Pax-Uni3D, Picasso Trio, ProMax 3D, Scanora 3D, SkyView, Veraviewepocs 3D. Effective dose was calculated using the ICRP 103 (2007) tissue weighting factors. Effective dose ranged between 19 and 368 μSv. The largest contributions to the effective dose were from the remainder tissues (37%), salivary glands (24%), and thyroid gland (21%). For all organs, there was a wide range of measured values apparent, due to differences in exposure factors, diameter and height of the primary beam, and positioning of the beam relative to the radiosensitive organs. The effective dose for different CBCT devices showed a 20-fold range. The results show that a distinction is needed between small-, medium-, and large-field CBCT scanners and protocols, as they are applied to different indication groups, the dose received being strongly related to field size. Furthermore, the dose should always be considered relative to technical and diagnostic image quality, seeing that image quality requirements also differ for patient groups. The results from the current study indicate that the optimisation of dose should be performed by an appropriate selection of exposure parameters and field size, depending on the diagnostic requirements. Copyright © 2010 Elsevier Ireland Ltd. All rights reserved.

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

    SciTech Connect

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

    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

  20. Effect of diameter of nanoparticles and capture cross-section library on macroscopic dose enhancement in boron neutron capture therapy

    PubMed Central

    Farhood, Bagher

    2014-01-01

    Purpose The aim of this study is evaluation of the effect of diameter of 10B nanoparticles and various neutron capture cross-section libraries on macroscopic dose enhancement in boron neutron capture therapy (BNCT). Material and methods MCNPX Monte Carlo code was used for simulation of a 252Cf source, a soft tissue phantom and a tumor containing 10B nanoparticles. Using 252Cf as a neutron source, macroscopic dose enhancement factor (MDEF) and total dose rate in tumor in the presence of 100, 200, and 500 ppm of 10B nanoparticles with 25 nm, 50 nm, and 100 nm diameters were calculated. Additionally, the effect of ENDF, JEFF, JENDL, and CENDL neutron capture cross-section libraries on MDEF was evaluated. Results There is not a linear relationship between the average MDEF value and nanoparticles’ diameter but the average MDEF grows with increased concentration of 10B nanoparticles. There is an increasing trend for average MDEF with the tumor distance. The average MDEF values were obtained the same for various neutron capture cross-section libraries. The maximum and minimum doses that effect on the total dose in tumor were neutron and secondary photon doses, respectively. Furthermore, the boron capture related dose component reduced in some extent with increase of diameter of 10B nanoparticles. Conclusions Based on the results of this study, it can be concluded that from physical point of view, various nanoparticle diameters have no dominant effect on average MDEF value in tumor. Furthermore, it is concluded that various neutron capture cross-section libraries are resulted to the same macroscopic dose enhancements. However, it is predicted that taking into account the biological effects for various nanoparticle diameters will result in different dose enhancements. PMID:25834582

  1. Biological effects and equivalent doses in radiotherapy: A software solution

    PubMed Central

    Voyant, Cyril; Julian, Daniel; Roustit, Rudy; Biffi, Katia; Lantieri, Céline

    2013-01-01

    Background The limits of TDF (time, dose, and fractionation) and linear quadratic models have been known for a long time. Medical physicists and physicians are required to provide fast and reliable interpretations regarding delivered doses or any future prescriptions relating to treatment changes. Aim We, therefore, propose a calculation interface under the GNU license to be used for equivalent doses, biological doses, and normal tumor complication probability (Lyman model). Materials and methods The methodology used draws from several sources: the linear-quadratic-linear model of Astrahan, the repopulation effects of Dale, and the prediction of multi-fractionated treatments of Thames. Results and conclusions The results are obtained from an algorithm that minimizes an ad-hoc cost function, and then compared to an equivalent dose computed using standard calculators in seven French radiotherapy centers. PMID:24936319

  2. Influence of CT automatic tube current modulation on uncertainty in effective dose.

    PubMed

    Sookpeng, S; Martin, C J; Gentle, D J

    2016-01-01

    Computed tomography (CT) scanners are equipped with automatic tube current modulation (ATCM) systems that adjust the current to compensate for variations in patient attenuation. CT dosimetry variables are not defined for ATCM situations and, thus, only the averaged values are displayed and analysed. The patient effective dose (E), which is derived from a weighted sum of organ equivalent doses, will be modified by the ATCM. Values for E for chest-abdomen-pelvis CT scans have been calculated using the ImPACT spreadsheet for patients on five CT scanners. Values for E resulting from the z-axis modulation under ATCM have been compared with results assessed using the same effective mAs values with constant tube currents. Mean values for E under ATCM were within ±10 % of those for fixed tube currents for all scanners. Cumulative dose distributions under ATCM have been simulated for two patient scans using single-slice dose profiles measured in elliptical and cylindrical phantoms on one scanner. Contributions to the effective dose from organs in the upper thorax under ATCM are 30-35 % lower for superficial tissues (e.g. breast) and 15-20 % lower for deeper organs (e.g. lungs). The effect on doses to organs in the abdomen depends on body shape, and they can be 10-22 % higher for larger patients. Results indicate that scan dosimetry parameters, dose-length product and effective mAs averaged over the whole scan can provide an assessment in terms of E that is sufficiently accurate to quantify relative risk for routine patient exposures under ATCM.

  3. Marijuana's dose-dependent effects in daily marijuana smokers.

    PubMed

    Ramesh, Divya; Haney, Margaret; Cooper, Ziva D

    2013-08-01

    Active marijuana produces significant subjective, psychomotor, and physiological effects relative to inactive marijuana, yet demonstrating that these effects are dose-dependent has proven difficult. This within-subject, double-blind study was designed to develop a smoking procedure to obtain a marijuana dose-response function. In four outpatient laboratory sessions, daily marijuana smokers (N = 17 males, 1 female) smoked six 5-s puffs from 3 marijuana cigarettes (2 puffs/cigarette). The number of puffs from active (≥5.5% Δ⁹-tetrahydrocannabinol/THC) and inactive (0.0% THC) marijuana varied according to condition (0, 2, 4, or 6 active puffs); active puffs were always smoked before inactive puffs. Subjective, physiological, and performance effects were assessed prior to and at set time points after marijuana administration. Active marijuana dose-dependently increased heart rate and decreased marijuana craving, despite evidence (carbon monoxide expiration, weight of marijuana cigarettes post-smoking) that participants inhaled less of each active marijuana cigarette than inactive cigarettes. Subjective ratings of marijuana "strength," "high," "liking," "good effect," and "take again" were increased by active marijuana compared with inactive marijuana, but these effects were not dose-dependent. Active marijuana also produced modest, non-dose-dependent deficits in attention, psychomotor function, and recall relative to the inactive condition. In summary, although changes in inhalation patterns as a function of marijuana strength likely minimized the difference between dose conditions, dose-dependent differences in marijuana's cardiovascular effects and ratings of craving were observed, whereas subjective ratings of marijuana effects did not significantly vary as a function of dose. PsycINFO Database Record (c) 2013 APA, all rights reserved

  4. External beam irradiation in angioplasted arteries of hypercholesterolemic rabbits The dose and time effect

    SciTech Connect

    Kalef-Ezra, J.; Michalis, L.K.; Malamou-Mitsi, V.; Tsekeris, P.; Katsouras, C.; Boziari, A.; Toumpoulis, I.; Bozios, G.; Charchanti, A.; Sideris, D.A

    2002-03-01

    Purpose: To study the dose and time effect of external beam irradiation on the morphometry of both angioplasted and nonangioplasted arteries in a hypercholesterolemic rabbit model. Methods and materials: Eight groups of rabbit femoral arteries were studied: arteries (a) with no intervention, (b) irradiated with a 12-Gy 6 MV X-ray dose, (c) with a 18-Gy, (d) treated with balloon angioplasty, (e) dosed with 12-Gy half an hour post-angioplasty, (f) dosed with 18-Gy half an hour post-angioplasty, (g) dosed with 12-Gy 48 h post angioplasty, (g) dosed with 18-Gy 48 h post angioplasty. Results: External irradiation at either 12 or 18 Gy was not found to change vessel morphometry in noninjured arteries. The 12-Gy dose given soon after angioplasty further increased percentage stenosis (63% on the average), despite the preservation of the lumen cross-sectional area. Positive remodeling was not observed in arteries given 18-Gy half an hour post angioplasty to counterbalance the increased neointimal formation. Therefore, this treatment resulted in a drastic reduction in lumen area and in enhancement of percentage stenosis (84% on the average). On the contrary, the delayed irradiation of the angioplasted arteries at either 12 or 18 Gy was not found to influence any of the studied morphometric parameters 5 weeks after angioplasty. Conclusions: Uniform external beam irradiation up to 18 Gy was well tolerated by intact femoral arteries. Prompt 12- or 18-Gy irradiations accentuated percentage stenosis. However the lumen cross-sectional area was preserved only at the lower dose point. Delayed irradiation at any dose did not influence the restenosis process.

  5. MO-G-BRF-09: Investigating Magnetic Field Dose Effects in Mice: A Monte Carlo Study

    SciTech Connect

    Rubinstein, A; Guindani, M; Followill, D; Melancon, A; Hazle, J; Court, L

    2014-06-15

    Purpose: In MRI-linac treatments, radiation dose distributions are affected by magnetic fields, especially at high-density/low-density interfaces. Radiobiological consequences of magnetic field dose effects are presently unknown; therefore, preclinical studies are needed to ensure the safe clinical use of MRI-linacs. This study investigates the optimal combination of beam energy and magnetic field strength needed for preclinical murine studies. Methods: The Monte Carlo code MCNP6 was used to simulate the effects of a magnetic field when irradiating a mouse-sized lung phantom with a 1.0cmx1.0cm photon beam. Magnetic field effects were examined using various beam energies (225kVp, 662keV[Cs-137], and 1.25MeV[Co-60]) and magnetic field strengths (0.75T, 1.5T, and 3T). The resulting dose distributions were compared to Monte Carlo results for humans with various field sizes and patient geometries using a 6MV/1.5T MRI-linac. Results: In human simulations, the addition of a 1.5T magnetic field caused an average dose increase of 49% (range:36%–60%) to lung at the soft tissue-to-lung interface and an average dose decrease of 30% (range:25%–36%) at the lung-to-soft tissue interface. In mouse simulations, the magnetic fields had no effect on the 225kVp dose distribution. The dose increases for the Cs-137 beam were 12%, 33%, and 49% for 0.75T, 1.5T, and 3.0T magnetic fields, respectively while the dose decreases were 7%, 23%, and 33%. For the Co-60 beam, the dose increases were 14%, 45%, and 41%, and the dose decreases were 18%, 35%, and 35%. Conclusion: The magnetic field dose effects observed in mouse phantoms using a Co-60 beam with 1.5T or 3T fields and a Cs-137 beam with a 3T field compare well with those seen in simulated human treatments with an MRI-linac. These irradiator/magnet combinations are suitable for preclinical studies investigating potential biological effects of delivering radiation therapy in the presence of a magnetic field. Partially funded by Elekta.

  6. Extracurricular Activities and Their Effect on the Student's Grade Point Average: Statistical Study

    ERIC Educational Resources Information Center

    Bakoban, R. A.; Aljarallah, S. A.

    2015-01-01

    Extracurricular activities (ECA) are part of students' everyday life; they play important roles in students' lives. Few studies have addressed the question of how student engagements to ECA affect student's grade point average (GPA). This research was conducted to know whether the students' grade point average in King Abdulaziz University,…

  7. Dose-effect and dose-response relationships of blood lead to erythrocytic protoporphyrin in young children

    SciTech Connect

    Hammond, P.B.; Bornschein, R.L.; Succop, P.

    1985-10-01

    Dose-effect and dose-response relationships were analyzed for blood lead concentration (PbB) vs blood protoporphyrin concentration using multiple data points from 165 children, ages 3-36 months. Protoporphyrin concentrations were measured using a front-face flurometer designed to measure zinc protoporphyrin (ZPP) and an extraction method designed to measure total protoporphyrin as the free base (FEP). Estimations were made of the thresholds for PbB effects on FEP and ZPP, as well as the slopes of the PbB-FEP and PbB-ZPP interactions. There was essentially no difference in thresholds estimated using ZPP vs FEP as the effect parameter. There was no apparent effect of age on threshold. However, the slope for PbB vs ZPP was less steep than the slope for PbB vs FEP. Moreover, the average ratio FEP:ZPP was markedly elevated at 3 months (1.84:1) and decreased slowly, attaining unity at 33 months. The possible reasons for this discrepancy are discussed, as well as the implications for interpretation of lead screening program data.

  8. Calculation of patient effective dose and scattered dose for dental mobile fluoroscopic equipment: application of the Monte Carlo simulation.

    PubMed

    Lee, Boram; Lee, Jungseok; Kang, Sangwon; Cho, Hyelim; Shin, Gwisoon; Lee, Jeong-Woo; Choi, Jonghak

    2013-01-01

    The objective of this study was to evaluate the patient effective dose and scattered dose from recently developed dental mobile equipment in Korea. The MCNPX 2.6 (Los Alamos National Laboratory, USA) was used in a Monte Carlo simulation to calculate both the effective and scattered doses. The MCNPX code was constructed identically as in the general use of equipment and the effective dose and scattered dose were calculated using the KTMAN-2 digital phantom. The effective dose was calculated as 906 μSv. The equivalent doses per organ were calculated via the MCNPX code, and were 32 174 and 19 μSv in the salivary gland and oesophagus, respectively. The scattered dose of 22.5-32.6 μSv of the tube side at 25 cm from the centre in anterior and posterior planes was measured as 1.4-3 times higher than the detector side of 10.5-16.0 μSv.

  9. Effects of quantum noise and binocular summation on dose requirements in stereoradiography.

    PubMed

    Maidment, Andrew D A; Bakic, Predrag R; Albert, Michael

    2003-12-01

    In the case of a quantum-noise limited detector, signal detection theory suggests that stereoradiographic images can be acquired with one half of the per-image dose needed for a standard radiographic projection, as information from the two stereo images can be combined. Previously, film-screen stereoradiography has been performed using the same per-image dose as in projection radiography, i.e., doubling the total dose. In this paper, the assumption of a possible decrease in dose for stereoradiography was tested by a series of contrast-detail experiments, using phantom images acquired over a range of exposures. The number of visible details, the effective reduction of the dose, and the effective decrease in the threshold signal-to-noise ratio were determined using human observers under several display and viewing conditions. These results were averaged over five observers and compared with multiple readings by a single observer and with the results of an additional observer with limited stereoscopic acuity. Experimental results show that the total dose needed to produce a stereoradiographic image pair is approximately 1.1 times the dose needed for a single projection in standard radiography, indicating that under these conditions the human visual system demonstrates almost ideal binocular summation.

  10. Effect of Body Habitus on Radiation Dose During CT Fluoroscopy-Guided Spine Injections.

    PubMed

    Viola, Ronald J; Nguyen, Giao B; Yoshizumi, Terry T; Stinnett, Sandra S; Hoang, Jenny K; Kranz, Peter G

    2014-10-31

    This study investigated the degree to which body habitus influences radiation dose during CT fluoroscopy (CTF)-guided lumbar epidural steroid injections (ESI). An anthropomorphic phantom containing metal oxide semiconductor field effect transistor (MOSFET) detectors was scanned at two transverse levels to simulate upper and lower lumbar CTF-guided ESI. Circumferential layers of adipose-equivalent material were sequentially added to model patients of three sizes: small (cross-sectional dimensions 25×30 cm), average (34×39 cm), and oversize (43×48 cm). Point dose rates to skin and internal organs within the CTF beam were measured. Scattered point dose rates 5 cm from the radiation beam were also measured. Direct point dose rates to the internal organs ranged from 0.05-0.11 mGy/10mAs in the oversized phantom, and from 0.18-0.43 mGy/10mAs in the small phantom. Skin direct point dose rates ranged from 0.69-0.71 mGy/10mAs in the oversized phantom and 0.88-0.94 mGy/10mAs in the small phantom. This represents a 180-310% increase in organ point dose rates and 24-36% increase in skin point dose rates in the small habitus compared with the oversize habitus. Scatter point dose rates increased by 83-117% for the small compared to the oversize phantom. Decreasing body habitus results in substantial increases in direct organ and skin point doses as well as scattered dose during simulated CTF-guided procedures. Failure to account for individual variations in body habitus will result in inaccurate dose estimation and inappropriate choice of tube current in CTF-guided procedures.

  11. Reduction in average fluoroscopic exposure times for interventional spinal procedures through the use of pulsed and low-dose image settings.

    PubMed

    Goodman, Bradly S; Carnel, Charles T; Mallempati, Srinivas; Agarwal, Pooja

    2011-11-01

    A practice improvement project was completed with the goal of reducing radiation exposure times in a busy spinal intervention practice through the use of "pulsed" and "low-dose fluoroscopy." The goal was to quantify the reduction in fluoroscopy exposure times with these modes. Exposure times were recorded for 316 patients undergoing spinal interventional procedures before and after the implementation of this project. Before implementation, 158 consecutive patients received spinal interventions with nonpulsed fluoroscopy on an Orthopedic Equipment Company 9800 and exposure times were recorded. After implementation of the practice improvement project, 158 consecutive patients received spinal interventions with pulsed and low-dose modes. Exposure times were then compared between these groups. Pulsed and low-dose fluoroscopy modes reduced overall exposure times by 56.7% after implementation of the practice improvement project. The use of pulsed and low-dose fluoroscopy in addition to lead shielding; increasing distance from the radiation source; collimation; limited use of magnification, boost, or digital subtraction; and proficiency with interventional techniques should be used to reduce radiation exposure in concordance with the principle of "as low as reasonably achievable."

  12. Estimation of treatment efficacy with complier average causal effects (CACE) in a randomized stepped wedge trial.

    PubMed

    Gruber, Joshua S; Arnold, Benjamin F; Reygadas, Fermin; Hubbard, Alan E; Colford, John M

    2014-05-01

    Complier average causal effects (CACE) estimate the impact of an intervention among treatment compliers in randomized trials. Methods used to estimate CACE have been outlined for parallel-arm trials (e.g., using an instrumental variables (IV) estimator) but not for other randomized study designs. Here, we propose a method for estimating CACE in randomized stepped wedge trials, where experimental units cross over from control conditions to intervention conditions in a randomized sequence. We illustrate the approach with a cluster-randomized drinking water trial conducted in rural Mexico from 2009 to 2011. Additionally, we evaluated the plausibility of assumptions required to estimate CACE using the IV approach, which are testable in stepped wedge trials but not in parallel-arm trials. We observed small increases in the magnitude of CACE risk differences compared with intention-to-treat estimates for drinking water contamination (risk difference (RD) = -22% (95% confidence interval (CI): -33, -11) vs. RD = -19% (95% CI: -26, -12)) and diarrhea (RD = -0.8% (95% CI: -2.1, 0.4) vs. RD = -0.1% (95% CI: -1.1, 0.9)). Assumptions required for IV analysis were probably violated. Stepped wedge trials allow investigators to estimate CACE with an approach that avoids the stronger assumptions required for CACE estimation in parallel-arm trials. Inclusion of CACE estimates in stepped wedge trials with imperfect compliance could enhance reporting and interpretation of the results of such trials.

  13. Estimation of paediatric organ and effective doses from dental cone beam CT using anthropomorphic phantoms

    PubMed Central

    Theodorakou, C; Walker, A; Horner, K; Pauwels, R; Bogaerts, R; Jacobs Dds, R

    2012-01-01

    Objectives Cone beam CT (CBCT) is an emerging X-ray technology applied in dentomaxillofacial imaging. Previous published studies have estimated the effective dose and radiation risks using adult anthropomorphic phantoms for a wide range of CBCT units and imaging protocols. Methods Measurements were made five dental CBCT units for a range of imaging protocols, using 10-year-old and adolescent phantoms and thermoluminescent dosimeters. The purpose of the study was to estimate paediatric organ and effective doses from dental CBCT. Results The average effective doses to the 10-year-old and adolescent phantoms were 116 μSv and 79 μSv, respectively, which are similar to adult doses. The salivary glands received the highest organ dose and there was a fourfold increase in the thyroid dose of the 10-year-old relative to that of the adolescent because of its smaller size. The remainder tissues and salivary and thyroid glands contributed most significantly to the effective dose for a 10-year-old, whereas for an adolescent the remainder tissues and the salivary glands contributed the most significantly. It was found that the percentage attributable lifetime mortality risks were 0.002% and 0.001% for a 10-year-old and an adolescent patient, respectively, which are considerably higher than the risk to an adult having received the same doses. Conclusion It is therefore imperative that dental CBCT examinations on children should be fully justified over conventional X-ray imaging and that dose optimisation by field of view collimation is particularly important in young children. PMID:22308220

  14. [High-dose progestational contraception: side effects].

    PubMed

    Gorins, A

    1993-02-01

    Women rarely depend on progestational contraception. In France, physicians are unsure of its indications. Progestational contraception presents advantages for certain indications where a particular condition exists and, more particularly, for women aged 40 and over. Women who can use it are those who have contraindications to estrogen use. These contraindications include uterine fibroids, endometrial hyperplasia, endometriosis, and fibro-cystic disease of the breast. It does produces side effects but those affecting metabolism seem to be almost negligible, like those of the third generation progestins. These side effects are metrorrhagias, amenorrhea, weight gain, and atherogenic metabolic changes. Yet, the nor-pregnane derivatives (which do effectively suppress ovulation) do not adversely affect glucose and lipid parameters. Progestational contraception probably cannot assure absolute safety as can combined oral contraceptives. It is not yet clear whether women who have been treated for breast cancer should use progestational contraception.

  15. Isolated and synergistic effects of PM10 and average temperature on cardiovascular and respiratory mortality

    PubMed Central

    Pinheiro, Samya de Lara Lins de Araujo; Saldiva, Paulo Hilário Nascimento; Schwartz, Joel; Zanobetti, Antonella

    2014-01-01

    OBJECTIVE To analyze the effect of air pollution and temperature on mortality due to cardiovascular and respiratory diseases. METHODS We evaluated the isolated and synergistic effects of temperature and particulate matter with aerodynamic diameter < 10 µm (PM10) on the mortality of individuals > 40 years old due to cardiovascular disease and that of individuals > 60 years old due to respiratory diseases in Sao Paulo, SP, Southeastern Brazil, between 1998 and 2008. Three methodologies were used to evaluate the isolated association: time-series analysis using Poisson regression model, bidirectional case-crossover analysis matched by period, and case-crossover analysis matched by the confounding factor, i.e., average temperature or pollutant concentration. The graphical representation of the response surface, generated by the interaction term between these factors added to the Poisson regression model, was interpreted to evaluate the synergistic effect of the risk factors. RESULTS No differences were observed between the results of the case-crossover and time-series analyses. The percentage change in the relative risk of cardiovascular and respiratory mortality was 0.85% (0.45;1.25) and 1.60% (0.74;2.46), respectively, due to an increase of 10 μg/m3 in the PM10 concentration. The pattern of correlation of the temperature with cardiovascular mortality was U-shaped and that with respiratory mortality was J-shaped, indicating an increased relative risk at high temperatures. The values for the interaction term indicated a higher relative risk for cardiovascular and respiratory mortalities at low temperatures and high temperatures, respectively, when the pollution levels reached approximately 60 μg/m3. CONCLUSIONS The positive association standardized in the Poisson regression model for pollutant concentration is not confounded by temperature, and the effect of temperature is not confounded by the pollutant levels in the time-series analysis. The simultaneous exposure

  16. Isolated and synergistic effects of PM10 and average temperature on cardiovascular and respiratory mortality.

    PubMed

    Pinheiro, Samya de Lara Lins de Araujo; Saldiva, Paulo Hilário Nascimento; Schwartz, Joel; Zanobetti, Antonella

    2014-12-01

    OBJECTIVE To analyze the effect of air pollution and temperature on mortality due to cardiovascular and respiratory diseases. METHODS We evaluated the isolated and synergistic effects of temperature and particulate matter with aerodynamic diameter < 10 µm (PM10) on the mortality of individuals > 40 years old due to cardiovascular disease and that of individuals > 60 years old due to respiratory diseases in Sao Paulo, SP, Southeastern Brazil, between 1998 and 2008. Three methodologies were used to evaluate the isolated association: time-series analysis using Poisson regression model, bidirectional case-crossover analysis matched by period, and case-crossover analysis matched by the confounding factor, i.e., average temperature or pollutant concentration. The graphical representation of the response surface, generated by the interaction term between these factors added to the Poisson regression model, was interpreted to evaluate the synergistic effect of the risk factors. RESULTS No differences were observed between the results of the case-crossover and time-series analyses. The percentage change in the relative risk of cardiovascular and respiratory mortality was 0.85% (0.45;1.25) and 1.60% (0.74;2.46), respectively, due to an increase of 10 μg/m3 in the PM10 concentration. The pattern of correlation of the temperature with cardiovascular mortality was U-shaped and that with respiratory mortality was J-shaped, indicating an increased relative risk at high temperatures. The values for the interaction term indicated a higher relative risk for cardiovascular and respiratory mortalities at low temperatures and high temperatures, respectively, when the pollution levels reached approximately 60 μg/m3. CONCLUSIONS The positive association standardized in the Poisson regression model for pollutant concentration is not confounded by temperature, and the effect of temperature is not confounded by the pollutant levels in the time-series analysis. The simultaneous exposure

  17. Radiation dose reduction in paediatric coronary computed tomography: assessment of effective dose and image quality.

    PubMed

    Habib Geryes, Bouchra; Calmon, Raphael; Khraiche, Diala; Boddaert, Nathalie; Bonnet, Damien; Raimondi, Francesca

    2016-07-01

    To assess the impact of different protocols on radiation dose and image quality for paediatric coronary computed tomography (cCT). From January-2012 to June-2014, 140 children who underwent cCT on a 64-slice scanner were included. Two consecutive changes in imaging protocols were performed: 1) the use of adaptive statistical iterative reconstruction (ASIR); 2) the optimization of acquisition parameters. Effective dose (ED) was calculated by conversion of the dose-length product. Image quality was assessed as excellent, good or with significant artefacts. Patients were divided in three age groups: 0-4, 5-7 and 8-18 years. The use of ASIR combined to the adjustment of scan settings allowed a reduction in the median ED of 58 %, 82 % and 85 % in 0-4, 5-7 and 8-18 years group, respectively (7.3 ± 1.4 vs 3.1 ± 0.7 mSv, 5.5 ± 1.6 vs 1 ± 1.9 mSv and 5.3 ± 5.0 vs 0.8 ± 2.0 mSv, all p < 0,05). Prospective protocol was used in 51 % of children. The reduction in radiation dose was not associated with reduction in diagnostic image quality as assessed by the frequency of coronary segments with excellent or good image quality (88 %). cCT can be obtained at very low radiation doses in children using ASIR, and prospective acquisition with optimized imaging parameters. • Using ASIR allows 25 % to 41 % reduction in the ED. • Prospective protocol is used up to 51 % of children after premedication. • Low dose is possible using ASIR and optimized prospective paediatric cCT.

  18. Neuroimmune Effects of Inhaling Low Dose Sarin

    DTIC Science & Technology

    2005-02-01

    ORGANIZA TION Lovelace Respiratory Research Institute REPORT NUMBER Albuquerque, New Mexico 87108-5127 E-Mail: msopori@lrri . org 9. SPONSORING...J.C., 1958. Effects in man of the anticholinesterase tation. andconducting rearchG using anima the iara nd ses- ocompound sarin (isopropyl

  19. Effects of Averaging Mass on Predicted Specific Absorption Rate (SAR) Values

    DTIC Science & Technology

    2002-09-01

    lung, liver , muscle, cerebral spinal fluid, nerve spinal, heart) in relation to various frequencies and orientations. This parametric study...relatively low ratios between spatial peak SAR and whole body SAR average were found in heart, liver , lung outer and lung inner (between 3 and 7) (see...MASS ON PREDICTED SAR 38 Figure 19. Ratios between peak localized SAR and whole body SAR average for liver for various mass intervals (1g and 10 g

  20. Effects of Average and Point Capillary Pressure-Saturation Function Parameters on Multiphase Flow Simulations

    NASA Astrophysics Data System (ADS)

    Cheng, C.; Perfect, E.; Cropper, C.

    2011-12-01

    Numerical models are an important tool in petroleum engineering, geoscience, and environmental applications, e.g. feasibility evaluation and prediction for enhanced oil recovery, enhanced geothermal systems, geological carbon storage, and remediation of contaminated sites. Knowledge of capillary pressure-saturation functions is essential in such applications for simulating multiphase fluid flow and chemical transport in variably-saturated rocks and soils in the subsurface. Parameters from average capillary pressure-saturation functions are sometimes employed due to their relative ease of measurement in the laboratory. However, the use of average capillary pressure-saturation function parameters instead of point capillary pressure-saturation function parameters for numerical simulations of flow and transport can result in significant errors, especially in the case of coarse-grained sediments and fractured rocks. Such erroneous predications can impose great risks and challenges to decision-making. In this paper we present a comparison of simulation results based on average and point estimates of van Genuchten model parameters (Sr, α, and n) for Berea sandstone, packed glass beads, and Hanford sediments. The capillary pressure-saturation functions were measured using steady-state centrifugation. Average and point parameters were estimated for each sample using the averaging and integral methods, respectively. Results indicated that the Sr and α parameters estimated using averaging and integral methods were close to a 1-to-1 correspondence, with R-squared values of 0.958 and 0.994, respectively. The n parameter, however, showed a major curvilinear deviation from the 1-to-1 line for the two estimation methods. This trend indicates that the averaging method systematically underestimates the n parameter relative to the point-based estimates of the integral method leading to an over predication of the breadth of the pore size distribution. Forward numerical simulations

  1. Effectiveness of the Medical Emergency Team: the importance of dose.

    PubMed

    Jones, Daryl; Bellomo, Rinaldo; DeVita, Michael A

    2009-01-01

    Up to 17% of hospital admissions are complicated by serious adverse events unrelated to the patients presenting medical condition. Rapid Response Teams (RRTs) review patients during early phase of deterioration to reduce patient morbidity and mortality. However, reports of the efficacy of these teams are varied. The aims of this article were to explore the concept of RRT dose, to assess whether RRT dose improves patient outcomes, and to assess whether there is evidence that inclusion of a physician in the team impacts on the effectiveness of the team. A review of available literature suggested that the method of reporting RRT utilization rate, (RRT dose) is calls per 1,000 admissions. Hospitals with mature RRTs that report improved patient outcome following RRT introduction have a RRT dose between 25.8 and 56.4 calls per 1,000 admissions. Four studies report an association between increasing RRT dose and reduced in-hospital cardiac arrest rates. Another reported that increasing RRT dose reduced in-hospital mortality for surgical but not medical patients. The MERIT study investigators reported a negative relationship between MET-like activity and the incidence of serious adverse events. Fourteen studies reported improved patient outcome in association with the introduction of a RRT, and 13/14 involved a Physician-led MET. These findings suggest that if the RRT is the major method for reviewing serious adverse events, the dose of RRT activation must be sufficient for the frequency and severity of the problem it is intended to treat. If the RRT dose is too low then it is unlikely to improve patient outcomes. Increasing RRT dose appears to be associated with reduction in cardiac arrests. The majority of studies reporting improved patient outcome in association with the introduction of an RRT involve a MET, suggesting that inclusion of a physician in the team is an important determinant of its effectiveness.

  2. The effect of dosing regimen on the pharmacokinetics of risedronate

    PubMed Central

    Mitchell, David Y; Heise, Mark A; Pallone, Karen A; Clay, Marian E; Nesbitt, John D; Russell, Darrell A; Melson, Chad W

    1999-01-01

    Aims To examine the effect of timing of a risedronate dose relative to food intake on the rate and extent of risedronate absorption following single-dose, oral administration to healthy male and female volunteers. Methods A single-dose, randomized, parallel study design was conducted with volunteers assigned to four treatment groups (31 or 32 subjects per group, 127 subjects total). Each subject was orally administered 30 mg risedronate. Group 1 was fasted for 10 h prior to and 4 h after dosing (fasted group); Groups 2 and 3 were fasted for 10 h and were dosed 1 and 0.5 h, respectively, before a high-fat breakfast; and Group 4 was dosed 2 h after a standard dinner. Blood and urine samples were collected for 168 h after dosing. Pharmacokinetic parameters were estimated by simultaneous analysis of risedronate serum concentration and urinary excretion rate-time data. Results Extent of risedronate absorption (AUC and Ae) was comparable (P = 0.4) in subjects dosed 2 h after dinner and 0.5 h before breakfast; however, a significantly greater extent of absorption occurred when risedronate was given 1 or 4 h prior to a meal (1.4- to 2.3-fold greater). Administration 0.5, 1, or 4 h prior to a meal resulted in a significantly greater rate of absorption (Cmax 2.8-, 3.5-, and 4.1-fold greater, respectively) when compared with 2 h after dinner. Conclusions The comparable extent of risedronate absorption when administered either 0.5–1 h before breakfast or 2 h after an evening meal support previous clinical studies where risedronate was found to have similar effectiveness using these dosing regimens. This flexibility in the timing of risedronate administration may provide patients an alternative means to achieve the desired efficacy while maintaining their normal daily routine. PMID:10583024

  3. Estimation of annual effective dose due to radon and thoron concentrations in mud dwellings of Mrima Hill, Kenya.

    PubMed

    Chege, M W; Hashim, N O; Merenga, A S; Meisenberg, O; Tschiersch, J

    2015-11-01

    This study presents radon and thoron concentration measurements and the corresponding effective dose rates in mud dwellings located in the high background radiation area of Mrima Hill, Kenya. Discriminative technique was used for simultaneous measurement of radon and thoron. The effective dose was evaluated based on the concentration of the isotopes and the time spent indoors. Radon concentration ranged from 16 to 56 Bq m(-3) with an average of 35±14 Bq m(-3) and a corresponding annual effective dose of 0.67 mSv y(-1), while that of thoron ranged from 132 to 1295 Bq m(-3) with an average of 652±397 Bq m(-3) and an effective dose of 13.7 mSv y(-1).

  4. Accounting for uncertainty in confounder and effect modifier selection when estimating average causal effects in generalized linear models.

    PubMed

    Wang, Chi; Dominici, Francesca; Parmigiani, Giovanni; Zigler, Corwin Matthew

    2015-09-01

    Confounder selection and adjustment are essential elements of assessing the causal effect of an exposure or treatment in observational studies. Building upon work by Wang et al. (2012, Biometrics 68, 661-671) and Lefebvre et al. (2014, Statistics in Medicine 33, 2797-2813), we propose and evaluate a Bayesian method to estimate average causal effects in studies with a large number of potential confounders, relatively few observations, likely interactions between confounders and the exposure of interest, and uncertainty on which confounders and interaction terms should be included. Our method is applicable across all exposures and outcomes that can be handled through generalized linear models. In this general setting, estimation of the average causal effect is different from estimation of the exposure coefficient in the outcome model due to noncollapsibility. We implement a Bayesian bootstrap procedure to integrate over the distribution of potential confounders and to estimate the causal effect. Our method permits estimation of both the overall population causal effect and effects in specified subpopulations, providing clear characterization of heterogeneous exposure effects that may vary considerably across different covariate profiles. Simulation studies demonstrate that the proposed method performs well in small sample size situations with 100-150 observations and 50 covariates. The method is applied to data on 15,060 US Medicare beneficiaries diagnosed with a malignant brain tumor between 2000 and 2009 to evaluate whether surgery reduces hospital readmissions within 30 days of diagnosis.

  5. On the use of age-specific effective dose coefficients in radiation protection of the public

    SciTech Connect

    Kocher, D.C.; Eckerman, K.F.

    1998-11-01

    Current radiation protection standards for the public include a limit on effective dose in any year for individuals in critical groups. This paper considers the question of how the annual dose limit should be applied in controlling routine exposures of populations consisting of individuals of all ages. The authors assume that the fundamental objective of radiation protection is limitation of lifetime risk and, therefore, that standards for controlling routine exposures of the public should provide a reasonable correspondence with lifetime risk, taking into account the age dependence of intakes and doses and the variety of radionuclides and exposure pathways of concern. Using new calculations of the per capita (population-averaged) risk of cancer mortality per unit activity inhaled or ingested in the US Environmental Protection Agency`s Federal Guidance Report No. 13, the authors show that applying a limit on annual effective dose only to adults, which was the usual practice in radiation protection of the public before the development of age-specific effective dose coefficients, provides a considerably better correspondence with lifetime risk than applying the annual dose limit to the critical group of any age.

  6. The effect of different doses of isotretinoin on pituitary hormones.

    PubMed

    Karadag, Ayse Serap; Takci, Zennure; Ertugrul, Derun Taner; Bilgili, Serap Gunes; Balahoroglu, Ragip; Takir, Mumtaz

    2015-01-01

    There are a limited number of studies investigating the side effects and effectiveness of various doses of isotretinoin (ISO). We have previously shown that high-dose ISO affects pituitary hormones. To our knowledge, there is no study in the literature looking into the effects of various doses of ISO on pituitary hormones. We searched pituitary hormones in three groups of different doses in acne patients. We included 105 acne vulgaris patients from two different centers. We divided the patients into three groups; the first group received 0.5-1 mg/kg/day, the second 0.2-0.5 mg/kg/day and the third intermittent 0.5-1 mg/kg/day (only 1 week in 1 month) ISO treatment. Blood samples were collected for biochemistry and hormone analysis, before the treatment and after 3 months. After 3 months of treatment with ISO, luteinizing hormone (LH) (p < 0.001), prolactin (p < 0.001), total testosterone (p < 0.001), adrenocorticotropic hormone (ACTH) (p < 0.001), cortisol (p < 0.001), insulin-like growth factor-binding protein 3 (p < 0.001), insulin-like growth factor 1 (IGF-1) (p = 0.002), growth hormone (GH) (p = 0.002) and free T3 (fT3) (p < 0.001) levels had decreased significantly. Furthermore, we split data into three different groups. Among the patients receiving intermittent-dose ISO, LH, ACTH, IGF-1, GH and fT3 measurements lost significance. Most of the significant measurements observed in the whole group were also significant among the patients receiving high-dose ISO. Additionally, dehydroepiandrosterone sulfate (p = 0.003) levels increased, and free T4 levels decreased significantly. ISO affects pituitary hormones at all of these three doses. The differences in pituitary hormones are more pronounced in high-dose treatment. The weakest effect was observed in the intermittent-dose group. Choosing lower doses of ISO may decrease side effects, however the effectiveness of the treatment may also be diminished. ISO, by affecting the PPARγ/RXR system, may affecting hormone

  7. Radiation effects on livestock: physiological effects, dose response

    SciTech Connect

    Bell, M.C.

    1985-06-01

    Farm livestock show no measurable effects from being exposed to ionizing radiation unless the level is greatly in excess of the natural background radiation. Possible sources of ionizing radiation which might affect livestock or contribute to radioactivity in the food chain to humans are reactor accidents, fuel reprocessing plant accidents and thermonuclear explosions. Most data on ionizing radiation effects on livestock are from whole body gamma doses near the LD 50/60 level. However, grazing livestock would be subjected to added beta exposure from ingested and skin retained radioactive particles. Results of attempts to simulate exposure of the Hereford cattle at Alamogardo, NM show that cattle are more sensitive to ingested fallout radiation than other species. Poultry LD 50/60 for gamma exposure is about twice the level for mammals, and swine appear to have the most efficient repair system being able to withstand the most chronic gamma exposure. Productivity of most livestock surviving an LD 50/60 exposure is temporarily reduced and longterm effects are small. Livestock are good screeners against undesirables in our diet and with the exception of radiosotopes of iodine in milk, very little fission product radioactivity would be expected to be transferred through the food chain in livestock products for humans. Feeding of stored feed or moving livestock to uncontaminated pastures would be the best protective action to follow. 29 references.

  8. Effects of error covariance structure on estimation of model averaging weights and predictive performance

    USGS Publications Warehouse

    Lu, Dan; Ye, Ming; Meyer, Philip D.; Curtis, Gary P.; Shi, Xiaoqing; Niu, Xu-Feng; Yabusaki, Steve B.

    2013-01-01

    When conducting model averaging for assessing groundwater conceptual model uncertainty, the averaging weights are often evaluated using model selection criteria such as AIC, AICc, BIC, and KIC (Akaike Information Criterion, Corrected Akaike Information Criterion, Bayesian Information Criterion, and Kashyap Information Criterion, respectively). However, this method often leads to an unrealistic situation in which the best model receives overwhelmingly large averaging weight (close to 100%), which cannot be justified by available data and knowledge. It was found in this study that this problem was caused by using the covariance matrix, CE, of measurement errors for estimating the negative log likelihood function common to all the model selection criteria. This problem can be resolved by using the covariance matrix, Cek, of total errors (including model errors and measurement errors) to account for the correlation between the total errors. An iterative two-stage method was developed in the context of maximum likelihood inverse modeling to iteratively infer the unknown Cek from the residuals during model calibration. The inferred Cek was then used in the evaluation of model selection criteria and model averaging weights. While this method was limited to serial data using time series techniques in this study, it can be extended to spatial data using geostatistical techniques. The method was first evaluated in a synthetic study and then applied to an experimental study, in which alternative surface complexation models were developed to simulate column experiments of uranium reactive transport. It was found that the total errors of the alternative models were temporally correlated due to the model errors. The iterative two-stage method using Cekresolved the problem that the best model receives 100% model averaging weight, and the resulting model averaging weights were supported by the calibration results and physical understanding of the alternative models. Using Cek

  9. Effects of artefact rejection and Bayesian weighted averaging on the efficiency of recording the newborn ABR.

    PubMed

    Lightfoot, Guy; Stevens, John

    2014-01-01

    This study seeks to identify whether the most efficient artefact rejection (AR) level to use for recording the newborn auditory brainstem response (ABR) changes with recording conditions and if so, to suggest a simple strategy for testers to adopt when faced with nonideal test conditions. Twenty-six babies referred from the English Newborn Hearing Screening Programme were tested with ABR as a routine component of their postscreening assessment but their raw EEG responses were recorded for off-line analysis. One hundred 61 second data samples (equivalent to 3000 stimuli) were reaveraged off-line at five AR levels and two AR levels with Bayesian averaging; a total of 700 waveforms. An objective measurement of residual noise was used to determine the most efficient AR level (i.e., associated with the highest signal to noise ratio) to use in low, moderate, and severe noise conditions. The best performing AR levels were as follows: (1) low noise conditions: conventional averaging with AR = ±5 μV, (2) moderate noise conditions: conventional averaging with AR = ±5 μV or ± 6.5μV; Bayesian averaging with AR ±10 μV, and (3) severe noise conditions: Bayesian averaging with AR = ±10 μV. In severe noise conditions a more lenient AR level was most efficient for conventional averaging but a greater number of sweeps would be needed to reduce the noise allowed to enter the average. An interactive AR strategy has been proposed, including the trade-off between AR level and the number of sweeps required to control residual noise. AR level does influence test efficiency and the optimum level depends on the prevailing noise levels, which can change during the test session. It is important that testers are aware of this and develop evidence-based skills to optimize test quality, particularly in challenging test conditions.

  10. Effective dose of dental CBCT—a meta analysis of published data and additional data for nine CBCT units

    PubMed Central

    Timothy, R; Walker, C; Hunter, R; Benavides, E; Samuelson, D B; Scheske, M J

    2015-01-01

    Objectives: This article analyses dose measurement and effective dose estimation of dental CBCT examinations. Challenges to accurate calculation of dose are discussed and the use of dose–height product (DHP) as an alternative to dose–area product (DAP) is explored. Methods: The English literature on effective dose was reviewed. Data from these studies together with additional data for nine CBCT units were analysed. Descriptive statistics, ANOVA and paired analysis are used to characterize the data. Results: PubMed and EMBASE searches yielded 519 and 743 publications, respectively, which were reduced to 20 following review. Reported adult effective doses for any protocol ranged from 46 to 1073 µSv for large fields of view (FOVs), 9–560 µSv for medium FOVs and 5–652 µSv for small FOVs. Child effective doses from any protocol ranged from 13 to 769 µSv for large or medium FOVs and 7–521 µSv for small FOVs. Effective doses from standard or default exposure protocols were available for 167 adult and 52 child exposures. Mean adult effective doses grouped by FOV size were 212 µSv (large), 177 µSv (medium) and 84 µSv (small). Mean child doses were 175 µSv (combined large and medium) and 103 µSv (small). Large differences were seen between different CBCT units. Additional low-dose and high-definition protocols available for many units extend the range of doses. DHP was found to reduce average absolute error for calculation of dose by 45% in comparison with DAP. Conclusions: Large exposure ranges make CBCT doses difficult to generalize. Use of DHP as a metric for estimating effective dose warrants further investigation. PMID:25224586

  11. The MapCHECK Measurement Uncertainty function and its effect on planar dose pass rates.

    PubMed

    Bailey, Daniel W; Spaans, Jason D; Kumaraswamy, Lalith K; Podgorsak, Matthew B

    2016-03-01

    Our study aimed to quantify the effect of the Measurement Uncertainty function on planar dosimetry pass rates, as measured and analyzed with the Sun Nuclear Corporation MapCHECK 2 array and its associated software. This optional function is toggled in the program preferences of the software (though turned on by default upon installation), and automatically increases the dose difference tolerance defined by the user for each planar dose comparison. Dose planes from 109 static-gantry IMRT fields and 40 VMAT arcs, of varying modulation complexity, were measured at 5 cm water-equivalent depth in the MapCHECK 2 diode array, and respective calculated dose planes were exported from a commercial treatment planning system. Planar dose comparison pass rates were calculated within the Sun Nuclear Corporation analytic software using a number of calculation parameters, including Measurement Uncertainty on and off. By varying the percent difference (%Diff) criterion for similar analyses performed with Measurement Uncertainty turned off, an effective %Diff criterion was defined for each field/arc corresponding to the pass rate achieved with Measurement Uncertainty turned on. On average, the Measurement Uncertainty function increases the user-defined %Diff criterion by 0.8%-1.1% for 3%/3 mm analysis, depending on plan type and calculation technique (corresponding to an average change in pass rate of 1.0%-3.5%, and a maximum change of 8.7%). At the 2%/2 mm level, the Measurement Uncertainty function increases the user-defined %Diff criterion by 0.7%-1.2% on average, again depending on plan type and calculation technique (corresponding to an average change in pass rate of 3.5%-8.1%, and a maximum change of 14.2%). The largest increases in pass rate due to the Measurement Uncertainty function are generally seen with poorly matched planar dose comparisons, while the function has a notably smaller effect as pass rates approach 100%. The Measurement Uncertainty function, then, may

  12. The MapCHECK Measurement Uncertainty function and its effect on planar dose pass rates.

    PubMed

    Bailey, Daniel W; Spaans, Jason D; Kumaraswamy, Lalith K; Podgorsak, Matthew B

    2016-03-08

    Our study aimed to quantify the effect of the Measurement Uncertainty function on planar dosimetry pass rates, as measured and analyzed with the Sun Nuclear Corporation MapCHECK 2 array and its associated software. This optional function is toggled in the program preferences of the software (though turned on by default upon installation), and automatically increases the dose difference tolerance defined by the user for each planar dose comparison. Dose planes from 109 static-gantry IMRT fields and 40 VMAT arcs, of varying modulation complexity, were measured at 5 cm water-equivalent depth in the MapCHECK 2 diode array, and respective calculated dose planes were exported from a commercial treatment planning system. Planar dose comparison pass rates were calculated within the Sun Nuclear Corporation analytic software using a number of calculation parameters, including Measurement Uncertainty on and off. By varying the percent difference (%Diff) criterion for similar analyses performed with Measurement Uncertainty turned off, an effective %Diff criterion was defined for each field/arc corresponding to the pass rate achieved with Measurement Uncertainty turned on. On average, the Measurement Uncertainty function increases the user-defined %Diff criterion by 0.8%-1.1% for 3%/3 mm analysis, depending on plan type and calculation technique (corresponding to an average change in pass rate of 1.0%-3.5%, and a maximum change of 8.7%). At the 2%/2 mm level, the Measurement Uncertainty function increases the user-defined %Diff criterion by 0.7%-1.2% on average, again depending on plan type and calculation technique (corresponding to an average change in pass rate of 3.5%-8.1%, and a maximum change of 14.2%). The largest increases in pass rate due to the Measurement Uncertainty function are generally seen with poorly matched planar dose comparisons, while the function has a notably smaller effect as pass rates approach 100%. The Measurement Uncertainty function, then, may

  13. Effect of pill burden on dosing preferences, willingness to pay, and likely adherence among patients with type 2 diabetes

    PubMed Central

    Hauber, A Brett; Han, Steven; Yang, Jui-Chen; Gantz, Ira; Tunceli, Kaan; Gonzalez, Juan Marcos; Brodovicz, Kimberly; Alexander, Charles M; Davies, Michael; Iglay, Kristy; Zhang, Qiaoyi; Radican, Larry

    2013-01-01

    Purpose To quantify willingness-to-pay (WTP) for reducing pill burden and dosing frequency among patients with type 2 diabetes mellitus (T2DM), and to examine the effect of dosing frequency and pill burden on likely medication adherence. Patients and methods Participants were US adults with T2DM on oral antihyperglycemic therapy. Each patient completed an online discrete-choice experiment (DCE) with eight choice questions, each including a pair of hypothetical medication profiles. Each profile was defined by reduction in average glucose (AG), daily dosing, chance of mild-to-moderate stomach problems, frequency of hypoglycemia, weight change, incremental risk of congestive heart failure (CHF), and cost. Patients were asked to rate their likely adherence to the profiles presented in each question. Choice questions were based on a predetermined experimental design. Choice data were analyzed using random-parameters logit. Likely treatment adherence was analyzed using a Heckman two-stage model. Results Of the 1,114 patients who completed the survey, 90 had lower dosing burden (<5 pills/day taken once/day or as needed) for all medications, and 1,024 had higher dosing burden (≥5 pills/day or more than once/day). Reduction in AG was valued most highly by patients. Hypoglycemia, chance of mild-to-moderate stomach problems, weight change, incremental risk of CHF, and daily dosing were less valued. Patients with higher current dosing burden had lower WTP for more convenient dosing schedules than patients with lower current dosing burden. Changes in dosing and cost impacted likely adherence. The magnitude of the impact of dosing on likely adherence was higher for patients with lower current dosing burden than for patients with higher current dosing burden. Conclusion Patients with T2DM were willing to pay for improvements in efficacy, side effects, and dosing. Patients’ WTP for more convenient dosing depended on current dosing burden, as did the effect of these attributes

  14. Effect of deformable registration on the dose calculated in radiation therapy planning CT scans of lung cancer patients

    SciTech Connect

    Cunliffe, Alexandra R.; Armato, Samuel G.; White, Bradley; Justusson, Julia; Contee, Clay; Malik, Renuka; Al-Hallaq, Hania A.

    2015-01-15

    Purpose: To characterize the effects of deformable image registration of serial computed tomography (CT) scans on the radiation dose calculated from a treatment planning scan. Methods: Eighteen patients who received curative doses (≥60 Gy, 2 Gy/fraction) of photon radiation therapy for lung cancer treatment were retrospectively identified. For each patient, a diagnostic-quality pretherapy (4–75 days) CT scan and a treatment planning scan with an associated dose map were collected. To establish correspondence between scan pairs, a researcher manually identified anatomically corresponding landmark point pairs between the two scans. Pretherapy scans then were coregistered with planning scans (and associated dose maps) using the demons deformable registration algorithm and two variants of the Fraunhofer MEVIS algorithm (“Fast” and “EMPIRE10”). Landmark points in each pretherapy scan were automatically mapped to the planning scan using the displacement vector field output from each of the three algorithms. The Euclidean distance between manually and automatically mapped landmark points (d{sub E}) and the absolute difference in planned dose (|ΔD|) were calculated. Using regression modeling, |ΔD| was modeled as a function of d{sub E}, dose (D), dose standard deviation (SD{sub dose}) in an eight-pixel neighborhood, and the registration algorithm used. Results: Over 1400 landmark point pairs were identified, with 58–93 (median: 84) points identified per patient. Average |ΔD| across patients was 3.5 Gy (range: 0.9–10.6 Gy). Registration accuracy was highest using the Fraunhofer MEVIS EMPIRE10 algorithm, with an average d{sub E} across patients of 5.2 mm (compared with >7 mm for the other two algorithms). Consequently, average |ΔD| was also lowest using the Fraunhofer MEVIS EMPIRE10 algorithm. |ΔD| increased significantly as a function of d{sub E} (0.42 Gy/mm), D (0.05 Gy/Gy), SD{sub dose} (1.4 Gy/Gy), and the algorithm used (≤1 Gy). Conclusions: An

  15. Dose rate effects during damage accumulation in silicon

    SciTech Connect

    Caturla, M.J.; Diaz de la Rubia, T.

    1997-01-01

    We combine molecular dynamics and Monte Carlo simulations to study damage accumulation and dose rate effects during irradiation of Silicon. We obtain the initial stage of the damage produced by heavy and light ions using classical molecular dynamics simulations. While heavy ions like As or Pt induce amorphization by single ion impact, light ions like B only produce point defects or small clusters of defects. The amorphous pockets generated by heavy ions are stable below room temperature and recrystallize at temperatures below the threshold for recrystallization of a planar amorphous-crystalline interface. The damage accumulation during light ion irradiation is simulated using a Monte Carlo model for defect diffusion. In this approach, we study the damage in the lattice as a function of dose and dose rate. A strong reduction in the total number of defects left in the lattice is observed for lower dose rates.

  16. Endothelial Effect of Statin Therapy at a High Dose Versus Low Dose Associated with Ezetimibe

    PubMed Central

    Garcia, Maristela Magnavita Oliveira; Varela, Carolina Garcez; Silva, Patricia Fontes; Lima, Paulo Roberto Passos; Góes, Paulo Meira; Rodrigues, Marilia Galeffi; Silva, Maria de Lourdes Lima Souza e; Ladeia, Ana Marice Teixeira; Guimarães, Armênio Costa; Correia, Luis Claudio Lemos

    2016-01-01

    Background The effect of statins on the endothelial function in humans remains under discussion. Particularly, it is still unclear if the improvement in endothelial function is due to a reduction in LDL-cholesterol or to an arterial pleiotropic effect. Objective To test the hypothesis that modulation of the endothelial function promoted by statins is primarily mediated by the degree of reduction in LDL-cholesterol, independent of the dose of statin administered. Methods Randomized clinical trial with two groups of lipid-lowering treatment (16 patients/each) and one placebo group (14 patients). The two active groups were designed to promote a similar degree of reduction in LDL-cholesterol: the first used statin at a high dose (80 mg, simvastatin 80 group) and the second used statin at a low dose (10 mg) associated with ezetimibe (10 mg, simvastatin 10/ezetimibe group) to optimize the hypolipidemic effect. The endothelial function was assessed by flow-mediated vasodilation (FMV) before and 8 weeks after treatment. Results The decrease in LDL-cholesterol was similar between the groups simvastatin 80 and simvastatin 10/ezetimibe (27% ± 31% and 30% ± 29%, respectively, p = 0.75). The simvastatin 80 group presented an increase in FMV from 8.4% ± 4.3% at baseline to 11% ± 4.2% after 8 weeks (p = 0.02). Similarly, the group simvastatin 10/ezetimibe showed improvement in FMV from 7.3% ± 3.9% to 12% ± 4.4% (p = 0.001). The placebo group showed no variation in LDL-cholesterol level or endothelial function. Conclusion The improvement in endothelial function with statin seems to depend more on a reduction in LDL-cholesterol levels, independent of the dose of statin administered, than on pleiotropic mechanisms. PMID:27142792

  17. Radon induced hyperplasia: effective adaptation reducing the local doses in the bronchial epithelium.

    PubMed

    Madas, Balázs G

    2016-09-01

    There is experimental and histological evidence that chronic irritation and cell death may cause hyperplasia in the exposed tissue. As the heterogeneous deposition of inhaled radon progeny results in high local doses at the peak of the bronchial bifurcations, it was proposed earlier that hyperplasia occurs in these deposition hot spots upon chronic radon exposure. The objective of the present study is to quantify how the induction of basal cell hyperplasia modulates the microdosimetric consequences of a given radon exposure. For this purpose, computational epithelium models were constructed with spherical cell nuclei of six different cell types based on histological data. Basal cell hyperplasia was modelled by epithelium models with additional basal cells and increased epithelium thickness. Microdosimetry for alpha-particles was performed by an own-developed Monte-Carlo code. Results show that the average tissue dose, and the average hit number and dose of basal cells decrease by the increase of the measure of hyperplasia. Hit and dose distribution reveal that the induction of hyperplasia may result in a basal cell pool which is shielded from alpha-radiation. It highlights that the exposure history affects the microdosimetric consequences of a present exposure, while the biological and health effects may also depend on previous exposures. The induction of hyperplasia can be considered as a radioadaptive response at the tissue level. Such an adaptation of the tissue challenges the validity of the application of the dose and dose rate effectiveness factor from a mechanistic point of view. As the location of radiosensitive target cells may change due to previous exposures, dosimetry models considering the tissue geometry characteristic of normal conditions may be inappropriate for dose estimation in case of protracted exposures. As internal exposures are frequently chronic, such changes in tissue geometry may be highly relevant for other incorporated radionuclides.

  18. Soil biochar amendments: type and dose effects

    NASA Astrophysics Data System (ADS)

    Ojeda, G.; Domene, X.; Mattana, S.; Sousa, J. P.; Ortiz, O.; Andres, P.; Alcañiz, J. M.

    2012-04-01

    Biochar is an organic material produced via the pyrolysis of C-based biomass, which is increasingly being recognized by scientists and policy makers for its potential role in carbon sequestration, reducing greenhouse gas emissions, waste mitigation, and as a soil amendment. Recent studies indicated that biochar improves soil fertility through its positive influence on physical-chemical properties, since not only improves water retention, aggregation and permeability, but its high charge density can also hold large amounts of nutrients, increasing crop production. However, it was observed that combustion temperature could affects the degree of aromaticity and the size of aromatic sheets, which in turns determine short-term mineralization rates. To reconcile the different decompasibility observations of biochar, it has sugested that physical protection and interactions with soil minerals play a significant part in biochar stability. In this context, it has initiated one pilot studies which aims to assess the effects of biochar application on physical and chemical properties of agricultural soil under Mediterranean conditions, such as changes in aggregate formation, intra-aggregate carbon sequestration and chemistry of soil water. In the present study, different clases of biochar produced from fast, slow and gasification pyrolisis of vegetal (pine, poplar) and dried sludge biomass, were applied at 1% of biochar-C to mesocosmos of an agricultural soil. Preliminary, it must be pointed out that slow and gasification pyrolisis changes the proportion of particles < 2 mm in diameter, from 10% (original materials) to almost 100%. In contrast, slow pyrolisis not modifies significantly biochar granulometry. As a consequence, bulk density of poplar and pine splinters decreases after fast pyrolisis. Regarding to organic carbon contents of biochar, all biochars obtained from plant biomass presented percentagens of total organic carbon (TOC) between 70 - 90%, while biochar

  19. The effect of the behavior of an average consumer on the public debt dynamics

    NASA Astrophysics Data System (ADS)

    De Luca, Roberto; Di Mauro, Marco; Falzarano, Angelo; Naddeo, Adele

    2017-09-01

    An important issue within the present economic crisis is understanding the dynamics of the public debt of a given country, and how the behavior of average consumers and tax payers in that country affects it. Starting from a model of the average consumer behavior introduced earlier by the authors, we propose a simple model to quantitatively address this issue. The model is then studied and analytically solved under some reasonable simplifying assumptions. In this way we obtain a condition under which the public debt steadily decreases.

  20. More efficient formulas for efficiency correction of cumulants and effect of using averaged efficiency

    NASA Astrophysics Data System (ADS)

    Nonaka, Toshihiro; Kitazawa, Masakiyo; Esumi, ShinIchi

    2017-06-01

    We derive formulas for the efficiency correction of cumulants with many efficiency bins. The derivation of the formulas is simpler than the previously suggested method, but the numerical cost is drastically reduced from the naïve method. From analytical and numerical analyses in simple toy models, we show that use of the averaged efficiency in the efficiency correction might cause large deviations in some cases and should not be used, especially for high order cumulants. These analyses show the importance of carrying out the efficiency correction without taking the average.

  1. The Assessment of Effective Dose Equivalent Using Personnel Dosimeters

    NASA Astrophysics Data System (ADS)

    Xu, Xie

    From January 1994, U.S. nuclear plants must develop a technically rigorous approach for determining the effective dose equivalent for their work forces. This dissertation explains concepts associated with effective dose equivalent and describes how to assess effective dose equivalent by using conventional personnel dosimetry measurements. A Monte Carlo computer code, MCNP, was used to calculate photon transport through a model of the human body. Published mathematical phantoms of the human adult male and female were used to simulate irradiation from a variety of external radiation sources in order to calculate organ and tissue doses, as well as effective dose equivalent using weighting factors from ICRP Publication 26. The radiation sources considered were broad parallel photon beams incident on the body from 91 different angles and isotropic point sources located at 234 different locations in contact with or near the body. Monoenergetic photons of 0.08, 0.3, and 1.0 MeV were considered for both sources. Personnel dosimeters were simulated on the surface of the body and exposed to with the same sources. From these data, the influence of dosimeter position on dosimeter response was investigated. Different algorithms for assessing effective dose equivalent from personnel dosimeter responses were proposed and evaluated. The results indicate that the current single-badge approach is satisfactory for most common exposure situations encountered in nuclear plants, but additional conversion factors may be used when more accurate results become desirable. For uncommon exposures involving source situated at the back of the body or source located overhead, the current approach of using multi-badges and assigning the highest dose is overly conservative and unnecessarily expensive. For these uncommon exposures, a new algorithm, based on two dosimeters, one on the front of the body and another one on the back of the body, has been shown to yield conservative assessment of

  2. The effects of x-ray beam hardening on detective quantum efficiency and radiation dose.

    PubMed

    Wong, Molly Donovan; Wu, Xizeng; Liu, Hong

    2011-01-01

    The goal of this preliminary study was to investigate the effects of x-ray beam hardening on the detective quantum efficiency (DQE) and the radiation dose of an inline x-ray imaging system. The ability to decrease the risk of harmful radiation to the patient without compromising the detection capability would more effectively balance the tradeoff between image quality and radiation dose, and therefore benefit the fields of diagnostic x-ray imaging, especially mammography. The DQE and the average glandular dose were both calculated under the same experimental conditions for a range of beam hardening levels, corresponding to no added beam hardening and two thicknesses each of Rhodium (Rh) and Molybdenum (Mo) filters. The dose calculation results demonstrate a reduction of 15% to 24% for the range of beam hardening levels. The comparison of all quantities comprising the DQE exhibit very close correlation between the results obtained without added beam hardening to the results corresponding to the range of beam hardening levels. For the specific experimental conditions utilized in this preliminary study, the results are an indication that the use of beam hardening holds the potential to reduce the radiation dose without decreasing the performance of the system. Future studies will seek to apply this method in a clinical environment and perform a comprehensive image quality evaluation, in an effort to further evaluate the potential of beam hardening to balance the tradeoff between dose and image quality.

  3. Assessment of Annual Effective Dose for Natural Radioactivity of Gamma Emitters in Biscuit Samples in Iraq.

    PubMed

    Abojassim, Ali Abid; Al-Alasadi, Lubna A; Shitake, Ahmed R; Al-Tememie, Faeq A; Husain, Afnan A

    2015-09-01

    Biscuits are an important type of food, widely consumed by babies in Iraq and other countries. This work uses gamma spectroscopy to measure the natural radioactivity due to long-lived gamma emitters in children's biscuits; it also estimates radiation hazard indices, that is, the radium equivalent activity, the representative of gamma level index, the internal hazard index, and the annual effective dose in children. Ten samples were collected from the Iraqi market from different countries of origin. The average specific activities for (226)Ra, (232)Th, and (40)K were 9.390, 3.1213, and 214.969 Bq/kg, respectively, but the average of the radium equivalent activity and the internal hazard index were 33.101 Bq/kg and 0.107, respectively. The total average annual effective dose from consumption by adults, children, and infants is estimated to be 0.655, 1.009, and 0.875 mSv, respectively. The values found for specific activity, radiation hazard indices, and annual effective dose in all samples in this study were lower than worldwide median values for all groups; therefore, these values are found to be safe.

  4. Monthly averages of the daily effective optical air mass and solar related angles for horizontal or inclined surfaces

    SciTech Connect

    Gueymard, C.

    1986-11-01

    An analytical method is described for calculating the daily averages or effective values of the sun's elevation, azimuth, hour angle, angle of incidence and air mass. A particular case is considered first and corresponds to the extraterrestrial radiation. The general derivation takes into account atmospheric effects in a simple way, provided that long-term averages of solar radiation are available. Examples of application are given for the climate of Montreal, Canada. In particular, it is shown that monthly averages of beam radiation on the horizontal may be directly converted to normal incidence values (and vice versa) by use of the mean solar elevation.

  5. Radon contribution to the total effective dose of uranium miners.

    PubMed

    Otahal, P; Burian, I; Nasir, M M; Gregor, Z

    2014-07-01

    Exposure to radon and its decay products is one of the three parts that create the total effective dose of uranium miners. Photons from gamma radiation and exposition to long-lived alpha emitters which are members of uranium family are the other two parts. The monthly total effective dose of uranium miners in mine Rozna I (Czech republic) is determined by the personal dosemeter ALGADE, which ensures the continual individual monitoring of all three parts. The exposed dosemeters are evaluated in the National Institute for Nuclear, Chemical and Biological Protection in Kamenna near Pribram. This paper describes the individual parts of miners' total effective dose considering the different types of work activities and workplaces. The main input data are the evaluation results of the uranium miners' personal dosemeters ALGADE in mine Rozna I in the time period from 2000 till 2012.

  6. Effect of ensemble averaging on amplitude and feature variabilities of Doppler spectrograms recorded in the lower limb arteries.

    PubMed

    Allard, L; Langlois, Y E; Durand, L G; Roederer, G O; Cloutier, G

    1992-05-01

    The objective of the present study was to analyse the effect of averaging Doppler blood flow signals in lower limb arteries on amplitude and feature variabilities. Doppler signals recorded in 41 iliac and 35 superficial femoral arteries having different categories of stenosis were averaged over 1-15 cardiac cycles. Based on the relative decreasing rate of an index of variability, results indicated that amplitude variability of the spectrograms was exponentially reduced to 30, 6 and 1 per cent when averaging five, ten and 15 cardiac cycles, respectively. Nine diagnostic features were extracted from Doppler spectrograms and their variations from one cardiac cycle to the next quantified. Based on the relative decreasing rate of these variations, results indicated that feature variability was exponentially reduced to 30, 4 and 1 per cent when averaging five, ten and 15 cardiac cycles, respectively. The effect of averaging on the discriminant power of the features to separate the different categories of stenosis was also investigated by performing t-test analyses. Results showed that averaging between five and ten cardiac cycles provided the better discriminant power for most cases, whereas averaging over more than ten cardiac cycles was of little benefit. Based on the spectral analysis technique used in the present study, we conclude that averaging over ten cardiac cycles is sufficient for the analysis of Doppler spectrograms recorded in the lower limbs.

  7. Average Tenure of Academic Department Heads: The Effects of Paradigm, Size, and Departmental Demography.

    ERIC Educational Resources Information Center

    Pfeffer, Jeffrey; Moore, William L.

    1980-01-01

    The average tenure of academic department heads was found to be positively related to the level of paradigm development characterizing the department, negatively related to departmental size, and related to interactions of the level of paradigm development with the seniority mix of the faculty and with the departmental size. (Author/IRT)

  8. Using National Data to Estimate Average Cost Effectiveness of EFNEP Outcomes by State/Territory

    ERIC Educational Resources Information Center

    Baral, Ranju; Davis, George C.; Blake, Stephanie; You, Wen; Serrano, Elena

    2013-01-01

    This report demonstrates how existing national data can be used to first calculate upper limits on the average cost per participant and per outcome per state/territory for the Expanded Food and Nutrition Education Program (EFNEP). These upper limits can then be used by state EFNEP administrators to obtain more precise estimates for their states,…

  9. Effect of parameters in moving average method for event detection enhancement using phase sensitive OTDR

    NASA Astrophysics Data System (ADS)

    Kwon, Yong-Seok; Naeem, Khurram; Jeon, Min Yong; Kwon, Il-bum

    2017-04-01

    We analyze the relations of parameters in moving average method to enhance the event detectability of phase sensitive optical time domain reflectometer (OTDR). If the external events have unique frequency of vibration, then the control parameters of moving average method should be optimized in order to detect these events efficiently. A phase sensitive OTDR was implemented by a pulsed light source, which is composed of a laser diode, a semiconductor optical amplifier, an erbium-doped fiber amplifier, a fiber Bragg grating filter, and a light receiving part, which has a photo-detector and high speed data acquisition system. The moving average method is operated with the control parameters: total number of raw traces, M, number of averaged traces, N, and step size of moving, n. The raw traces are obtained by the phase sensitive OTDR with sound signals generated by a speaker. Using these trace data, the relation of the control parameters is analyzed. In the result, if the event signal has one frequency, then the optimal values of N, n are existed to detect the event efficiently.

  10. Using National Data to Estimate Average Cost Effectiveness of EFNEP Outcomes by State/Territory

    ERIC Educational Resources Information Center

    Baral, Ranju; Davis, George C.; Blake, Stephanie; You, Wen; Serrano, Elena

    2013-01-01

    This report demonstrates how existing national data can be used to first calculate upper limits on the average cost per participant and per outcome per state/territory for the Expanded Food and Nutrition Education Program (EFNEP). These upper limits can then be used by state EFNEP administrators to obtain more precise estimates for their states,…

  11. The dose delivery effect of the different Beam ON interval in FFF SBRT: TrueBEAM

    NASA Astrophysics Data System (ADS)

    Tawonwong, T.; Suriyapee, S.; Oonsiri, S.; Sanghangthum, T.; Oonsiri, P.

    2016-03-01

    The purpose of this study is to determine the dose delivery effect of the different Beam ON interval in Flattening Filter Free Stereotactic Body Radiation Therapy (FFF-SBRT). The three 10MV-FFF SBRT plans (2 half rotating Rapid Arc, 9 to10 Gray/Fraction) were selected and irradiated in three different intervals (100%, 50% and 25%) using the RPM gating system. The plan verification was performed by the ArcCHECK for gamma analysis and the ionization chamber for point dose measurement. The dose delivery time of each interval were observed. For gamma analysis (2%&2mm criteria), the average percent pass of all plans for 100%, 50% and 25% intervals were 86.1±3.3%, 86.0±3.0% and 86.1±3.3%, respectively. For point dose measurement, the average ratios of each interval to the treatment planning were 1.012±0.015, 1.011±0.014 and 1.011±0.013 for 100%, 50% and 25% interval, respectively. The average dose delivery time was increasing from 74.3±5.0 second for 100% interval to 154.3±12.6 and 347.9±20.3 second for 50% and 25% interval, respectively. The same quality of the dose delivery from different Beam ON intervals in FFF-SBRT by TrueBEAM was illustrated. While the 100% interval represents the breath-hold treatment technique, the differences for the free-breathing using RPM gating system can be treated confidently.

  12. Effects of error covariance structure on estimation of model averaging weights and predictive performance

    NASA Astrophysics Data System (ADS)

    Lu, Dan; Ye, Ming; Meyer, Philip D.; Curtis, Gary P.; Shi, Xiaoqing; Niu, Xu-Feng; Yabusaki, Steve B.

    2013-09-01

    When conducting model averaging for assessing groundwater conceptual model uncertainty, the averaging weights are often evaluated using model selection criteria such as AIC, AICc, BIC, and KIC (Akaike Information Criterion, Corrected Akaike Information Criterion, Bayesian Information Criterion, and Kashyap Information Criterion, respectively). However, this method often leads to an unrealistic situation in which the best model receives overwhelmingly large averaging weight (close to 100%), which cannot be justified by available data and knowledge. It was found in this study that this problem was caused by using the covariance matrix, Cɛ, of measurement errors for estimating the negative log likelihood function common to all the model selection criteria. This problem can be resolved by using the covariance matrix, Cek, of total errors (including model errors and measurement errors) to account for the correlation between the total errors. An iterative two-stage method was developed in the context of maximum likelihood inverse modeling to iteratively infer the unknown Cek from the residuals during model calibration. The inferred Cek was then used in the evaluation of model selection criteria and model averaging weights. While this method was limited to serial data using time series techniques in this study, it can be extended to spatial data using geostatistical techniques. The method was first evaluated in a synthetic study and then applied to an experimental study, in which alternative surface complexation models were developed to simulate column experiments of uranium reactive transport. It was found that the total errors of the alternative models were temporally correlated due to the model errors. The iterative two-stage method using Cek resolved the problem that the best model receives 100% model averaging weight, and the resulting model averaging weights were supported by the calibration results

  13. Determination of behaviorally effective tobacco constituent doses in rats.

    PubMed

    Wiley, Jenny L; Marusich, Julie A; Thomas, Brian F; Jackson, Kia J

    2015-03-01

    While nicotine has been established as the primary addictive drug that promotes tobacco use, recent peer-reviewed studies suggest that tobacco smoke contains additional chemical constituents that may have addictive potential. Additional research is necessary to determine the addictive potential of these tobacco constituents individually and in combination with tobacco smoke condensate; however, the behaviorally effective constituent doses necessary to conduct such studies are unclear. The primary objective of this study was to conduct behavioral studies in adult rats to determine the relevant behaviorally effective doses of the tobacco constituents, cotinine, myosmine, and anatabine to be used in future studies assessing the addictive potential of these compounds. Separate groups of adult male Sprague Dawley rats were treated with vehicle, nicotine, or various doses of cotinine, mysomine, or anatabine. Effects on locomotor activity were measured in 10-min bins for 60min. Nicotine (0.8mg/kg) produced a biphasic effect on locomotor activity, with hypoactivity during the first 10min and hyperactivity at 40-50min. In contrast, cotinine (0.1mg/kg) and myosmine (10-50mg/kg) decreased activity without a later increase. Anatabine significantly increased locomotor activity at 1mg/kg, but decreased it at 10mg/kg. Prominent effects on overt behavior were observed at anatabine doses of 10mg/kg and above. Nicotine, cotinine, myosmine, and anatabine produced distinct time- and dose-dependent patterns of effects on locomotor activity. Results from the study will aid in the selection of relevant doses for future studies assessing the addictive potential of these non-nicotine tobacco constituents. © The Author 2014. Published by Oxford University Press on behalf of the Society for Research on Nicotine and Tobacco. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

  14. Effect of deformable registration on the dose calculated in radiation therapy planning CT scans of lung cancer patients.

    PubMed

    Cunliffe, Alexandra R; Contee, Clay; Armato, Samuel G; White, Bradley; Justusson, Julia; Malik, Renuka; Al-Hallaq, Hania A

    2015-01-01

    To characterize the effects of deformable image registration of serial computed tomography (CT) scans on the radiation dose calculated from a treatment planning scan. Eighteen patients who received curative doses (≥ 60 Gy, 2 Gy/fraction) of photon radiation therapy for lung cancer treatment were retrospectively identified. For each patient, a diagnostic-quality pretherapy (4-75 days) CT scan and a treatment planning scan with an associated dose map were collected. To establish correspondence between scan pairs, a researcher manually identified anatomically corresponding landmark point pairs between the two scans. Pretherapy scans then were coregistered with planning scans (and associated dose maps) using the demons deformable registration algorithm and two variants of the Fraunhofer MEVIS algorithm ("Fast" and "EMPIRE10"). Landmark points in each pretherapy scan were automatically mapped to the planning scan using the displacement vector field output from each of the three algorithms. The Euclidean distance between manually and automatically mapped landmark points (dE) and the absolute difference in planned dose (|ΔD|) were calculated. Using regression modeling, |ΔD| was modeled as a function of dE, dose (D), dose standard deviation (SD(dose)) in an eight-pixel neighborhood, and the registration algorithm used. Over 1400 landmark point pairs were identified, with 58-93 (median: 84) points identified per patient. Average |ΔD| across patients was 3.5 Gy (range: 0.9-10.6 Gy). Registration accuracy was highest using the Fraunhofer MEVIS EMPIRE10 algorithm, with an average dE across patients of 5.2 mm (compared with >7 mm for the other two algorithms). Consequently, average |ΔD| was also lowest using the Fraunhofer MEVIS EMPIRE10 algorithm. |ΔD| increased significantly as a function of dE (0.42 Gy/mm), D (0.05 Gy/Gy), SD(dose) (1.4 Gy/Gy), and the algorithm used (≤ 1 Gy). An average error of <4 Gy in radiation dose was introduced when points were mapped between

  15. COCAINE AND PAVLOVIAN FEAR CONDITIONING: DOSE-EFFECT ANALYSIS

    PubMed Central

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

    2007-01-01

    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 – 15 mg/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 (15 mg/kg) displayed significantly less contextual and cued memory, compared to saline control animals. Conversely, mice pre-treated with a very low dose of cocaine (0.1 mg/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. PMID:17098299

  16. Epidemiologic detection of low dose effects on the developing fetus.

    PubMed Central

    Kline, J; Levin, B; Stein, Z; Susser, M; Warburton, D

    1981-01-01

    Evaluations of the health effects of exposures in the workplace and environment have broadened to include effects on reproduction, as well as on the development of cancer. Models to assess risks associated with varying doses of exposure rest almost entirely on data about cancer. In this paper we discuss some distinctive features of reproduction which bear on the interpretation of such models, when applied to reproduction, rather than carcinogenesis. Dose-response curves describe the relationship between two exposures (smoking and alcohol drinking) and two outcomes (spontaneous abortion and birthweight) are used to illustrate some of the questions which arise in attempting to determine a "safe" level of exposure. PMID:7333249

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

    SciTech Connect

    Kok, H. Petra; Crezee, Johannes; Franken, Nicolaas A.P.; Barendsen, Gerrit W.

    2014-03-01

    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{sup −1}) and β (Gy{sup −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

  18. Verification of an effective dose equivalent model for neutrons

    SciTech Connect

    Tanner, J.E.; Piper, R.K.; Leonowich, J.A.; Faust, L.G.

    1991-10-01

    Since the effective dose equivalent, based on the weighted sum of organ dose equivalents, is not a directly measurable quantity, it must be estimated with the assistance of computer modeling techniques and a knowledge of the radiation field. Although extreme accuracy is not necessary for radiation protection purposes, a few well-chosen measurements are required to confirm the theoretical models. Neutron measurements were performed in a RANDO phantom using thermoluminescent dosemeters, track etch dosemeters, and a 1/2-in. (1.27-cm) tissue equivalent proportional counter in order to estimate neutron doses and dose equivalents within the phantom at specific locations. The phantom was exposed to bare and D{sub 2}O-moderated {sup 252}Cf neutrons at the Pacific Northwest Laboratory's Low Scatter Facility. The Monte Carlo code MCNP with the MIRD-V mathematical phantom was used to model the human body and calculate organ doses and dose equivalents. The experimental methods are described and the results of the measurements are compared to the calculations. 8 refs., 3 figs., 3 tabs.

  19. Low dose naltrexone: side effects and efficacy in gastrointestinal disorders.

    PubMed

    Ploesser, Jennifer; Weinstock, Leonard B; Thomas, Erin

    2010-01-01

    Use of low dose naltrexone has been advocated for a variety of medical problems. Only a few articles published in peer review journals have documented side effects of low dose naltrexone. The purpose of this study was to determine the frequency of adverse effects of low dose naltrexone in patients who have been treated for a variety of gastrointestinal disorders. The secondary purpose was to determine global efficacy in a retrospective survey. Patients (206) form a single gastroenterologist's clinical practice who had been prescribed naltrexone were mailed a survey to evaluate the side effects and efficacy of naltrexone. Patients had either irritable bowel syndrome without evidence for small intestinal bacterial overgrowth, chronic idiopathic constipation, or inflammatory bowel disease. Patients with diarrhea were given 2.5 mg daily, constipation 2.5 mg twice daily, and inflammatory bowel disease 4.5 mg daily. In the patients who returned the survey, 47/121 (38.8%) had no side effects. Of the 74/121 (61.2%) patients who had side effects, 58 had one or more neurological complaints, and 32 had one or more gastrointestinal side effects. In the patients with side effects, 24/74 (32.4%) had short lived symptoms. Low dose naltrexone was terminated owing to side effects in 20/74 patients (27.0%). In 13 patients with idiopathic irritable bowel syndrome, 2 were markedly worse. In 85 patients with irritable bowel syndrome-small intestinal bacterial overgrowth, 15 were markedly improved, 32 were moderately worse, and 1 was markedly worse. In 12 patients with chronic constipation, 7 were markedly improved, 1 was moderately improved, 1 was mildly improved, and 4 were unchanged. Low dose naltrexone frequently has side effects but in most is tolerable. It appears to be helpful for a member of patients with gastrointestinal disorders.

  20. Work to save dose: contrasting effective dose rates from radon exposure in workplaces and residences against the backdrop of public and occupational limits

    SciTech Connect

    Whicker, Jeffrey J; Mcnaughton, Michael W

    2009-01-01

    Office workers are exposed to radon while at work and at home. Though there has been a multitude of studies reporting the measurements of radon concentrations and potential lung and effective doses associated with radon and progeny exposure in homes, similar studies on the concentrations and subsequent effective dose rates in the non-mine workplaces are lacking. Additionally, there are few, if any, comparative analyses of radon exposures at more 'typical' workplace with residential exposures within the same county. The purposes of this study were to measure radon concentrations in office and residential spaces in the same county and explore the radiation dose implications. Sixty-five track-etch detectors were deployed in office spaces and 47 were deployed in residences, all within Los Alamos County, New Mexico, USA. The sampling periods for these measurements were generally about three months. The measured concentrations were used to calculate and compare effective dose rates resulting from exposure while at work and at home. Results showed that full-time office workers receive on average about 8 times greater exposure at home than while in the office (2.3 mSv yr-! versus 0.3 mSv yr-!). The estimated effective dose rate for a more homebound person was about 3 mSv yr-!. Estimating effective doses from background radon exposure in the same county as Los Alamos National Laboratory, with thousands of'radiological workers,' highlights interesting contrasts in radiation protection standards that span public and occupational settings. For example, the effective dose rate from background radon exposure in unregulated office spaces ranged up to 1.1 mSv yr-!, which is similar to the 1 mSv yr-! threshold for regulation ofa 'radiological worker,' as defined in the Department of Energy regulations for occupational exposure. Additionally, the estimated average effective dose total of> 3 mSv yf! from radon background exposure in homes stands in contrast to the 0.1 mSv yr-! air

  1. Work to save dose: contrasting effective dose rates from radon exposure in workplaces and residences against the backdrop of public and occupational regulatory limits.

    PubMed

    Whicker, Jeffrey J; McNaughton, Michael W

    2009-09-01

    Office workers are exposed to radon while at work and at home. Though there are a multitude of studies reporting radon concentrations and potential lung and effective doses associated with radon progeny exposure in homes, similar studies in non-mine workplaces are lacking. Additionally, there are few, if any, comparative analyses of radon exposures at more "typical" workplace with residential exposures within the same county. The purposes of this study were to measure radon concentrations in office and residential spaces in the same county and explore the radiation dose implications. Sixty-five track-etch detectors were deployed for 3-mo sampling periods in office spaces and 47 were deployed in residences, all within Los Alamos County, New Mexico. The measured concentrations were used to calculate and compare effective dose rates resulting from exposure while at work and at home. Results showed that full-time office workers receive on average about 8 times greater exposure at home than while in the office (2.3 mSv y-1 vs. 0.3 mSv y-1). The estimated effective dose rate for a more homebound person was about 3 mSv y-1. Estimating effective doses from background radon exposure in the same county as Los Alamos National Laboratory, with thousands of "radiological workers," highlights interesting contrasts in radiation protection standards that span public and occupational settings. For example, the effective dose rate from background radon exposure in unregulated office spaces ranged up to 1.1 mSv y-1, which is similar to the 1 mSv y-1 threshold for regulation of a "radiological worker," as defined in the Department of Energy regulations for occupational exposure. Additionally, the estimated average effective dose total of >3 mSv y-1 from radon background exposure in homes stands in contrast to the 0.1 mSv y-1 air pathway effective public dose limit regulated by the Environmental Protection Agency for radioactive air emissions, and both these are substantially lower

  2. Natural radioactivity and evaluation of effective dose equivalent of granites in Turkey.

    PubMed

    Osmanlioglu, Ahmet Erdal

    2006-01-01

    Annual effective dose equivalent due to natural gamma radiation from (238)U, (232)Th and (40)K have been evaluated from granites in Turkey. Forty samples were taken for spectrometric analysis. Specific concentrations of (238)U, (232)Th and (40)K in granite samples were determined. Spectroscopy system was used with 1.8 keV (FWHM) coaxial high purity germanium (HPGe) detector. Average values of concentrations of (238)U, (232)Th and (40)K were detected at 15.85, 33.76 and 359 Bq kg(-1), respectively. The average value of radon varies from 0.073 to 0.185 Bq m(-2) h(-1) exhalation depends on the specific concentration of uranium. The dose rate due to this highest activity which have been evaluated by a Monte Carlo transport calculations does not exceed 0.4 mSv a(-1).

  3. Underestimating calorie content when healthy foods are present: an averaging effect or a reference-dependent anchoring effect?

    PubMed

    Forwood, Suzanna E; Ahern, Amy; Hollands, Gareth J; Fletcher, Paul C; Marteau, Theresa M

    2013-01-01

    Previous studies have shown that estimations of the calorie content of an unhealthy main meal food tend to be lower when the food is shown alongside a healthy item (e.g. fruit or vegetables) than when shown alone. This effect has been called the negative calorie illusion and has been attributed to averaging the unhealthy (vice) and healthy (virtue) foods leading to increased perceived healthiness and reduced calorie estimates. The current study aimed to replicate and extend these findings to test the hypothesized mediating effect of ratings of healthiness of foods on calorie estimates. In three online studies, participants were invited to make calorie estimates of combinations of foods. Healthiness ratings of the food were also assessed. The first two studies failed to replicate the negative calorie illusion. In a final study, the use of a reference food, closely following a procedure from a previously published study, did elicit a negative calorie illusion. No evidence was found for a mediating role of healthiness estimates. The negative calorie illusion appears to be a function of the contrast between a food being judged and a reference, supporting the hypothesis that the negative calorie illusion arises from the use of a reference-dependent anchoring and adjustment heuristic and not from an 'averaging' effect, as initially proposed. This finding is consistent with existing data on sequential calorie estimates, and highlights a significant impact of the order in which foods are viewed on how foods are evaluated.

  4. Ionization chamber volume averaging effects in dynamic intensity modulated radiation therapy beams.

    PubMed

    Low, Daniel A; Parikh, Parag; Dempsey, James F; Wahab, Sasha; Huq, Saiful

    2003-07-01

    The commercial cylindrical ionization chamber ionization integration accuracy of dynamically moving fields was evaluated. The ionization chambers were exposed to long (14 cm), narrow (0.6, 1.0, 2.0, and 4.0 cm) 6 MV and 18 MV fields. Rather than rely on the linear accelerator to reproducibly scan across the chamber, the chambers were scanned beneath fixed portals. A water-equivalent phantom was constructed with cavities that matched the chambers and placed on a computer-controlled one-dimensional table. Computer-controlled electrometers were utilized in continuous charge integrate mode, with 10 samples of the charge, along with time stamps, acquired for each chamber location. A reference chamber was placed just beneath the linear accelerator jaws to adjust for variations in linear accelerator dose rate. The scan spatial resolution was selected to adequately sample regions of steep dose gradient and second spatial derivative (curvature). A fixed measurement in a 10 x 10 cm2 field was used to normalize the profiles to absolute chamber response. Three ionization chambers were tested, a microchamber (0.009 cm3), a Farmer chamber (0.6 cm3) and a waterproof scanning chamber (0.125 cm3). The larger chambers exhibited severe under-response at the small field's centers, but all of the chambers, independent of orientation, accurately integrated the ionization across the scanned portal. This indicates that the tested ionization chambers provide accurate integrated charges in regions of homogeneous dose regions. Partial integration (less than the field width plus the chamber length plus 2 cm), yielded integration errors of greater than 1% and 2% for 6 MV and 18 MV, respectively, with errors for the Farmer chamber of greater than 10% even for the 4 cm wide field.

  5. Dataset demonstrating the temperature effect on average output polarization for QCA based reversible logic gates.

    PubMed

    Hassan, Md Kamrul; Nahid, Nur Mohammad; Bahar, Ali Newaz; Bhuiyan, Mohammad Maksudur Rahman; Abdullah-Al-Shafi, Md; Ahmed, Kawsar

    2017-08-01

    Quantum-dot cellular automata (QCA) is a developing nanotechnology, which seems to be a good candidate to replace the conventional complementary metal-oxide-semiconductor (CMOS) technology. In this article, we present the dataset of average output polarization (AOP) for basic reversible logic gates presented in Ali Newaz et al. (2016) [1]. QCADesigner 2.0.3 has been employed to analysis the AOP of reversible gates at different temperature levels in Kelvin (K) unit.

  6. Inhomogeneity Effects on Dose Deposition for Photon and Electron Beams

    NASA Astrophysics Data System (ADS)

    Yu, Xinsheng

    1989-03-01

    A long-standing problem in radiation therapy has been to correct the dose distributions for the presence of inhomogeneities. The availability of CT and MRI imaging for treatment planning has led to many new algorithms for making such corrections. Unfortunately, each of these methods shows a limited range of validity outside of which errors exceeding 10% may occur due to the assumptions made in the algorithm. In order for valid assumptions to be made, the physical processes involved in the perturbation effects of inhomogeneities on radiation dose deposition must be identified and understood. The work presented in this thesis is to achieve this goal. Inhomogeneity effects on photon dose deposition have been studied by means of experimental measurements and theoretical simulations. The results indicated that changes in atomic number could result in large changes in dose by perturbing the transport of the secondary electrons. Electron transport theory was then studied with the emphasis on the electron multiple scattering. The small angle approximation in the Fermi-Eyges theory and the assumption of semi-infinite slab geometry in current electron dose calculation algorithms were found to cause inaccurate prediction of dose in the vicinity of local inhomogeneities. Using the concept of mean path, a new multiray model has been derived, which is sensitive to local inhomogeneities and gives good agreement with Monte -Carlo simulations. Based on the understanding of both photon and electron transport, a new photon-electron cascade model is proposed for calculating photon dose deposition. The model explicitly includes the transport of the secondary charged particles and is applicable for the presence of inhomogeneities with different electron densities and atomic numbers.

  7. 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.

    PubMed

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

    2010-09-21

    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 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

  8. Effects of Prostate-Rectum Separation on Rectal Dose From External Beam Radiotherapy

    SciTech Connect

    Susil, Robert C.; McNutt, Todd R.; DeWeese, Theodore L.; Song, Danny

    2010-03-15

    Purpose: In radiotherapy for prostate cancer, the rectum is the major dose-limiting structure. Physically separating the rectum from the prostate (e.g., by injecting a spacer) can reduce the rectal radiation dose. Despite pilot clinical studies, no careful analysis has been done of the risks, benefits, and dosimetric effects of this practice. Methods and Materials: Using cadaveric specimens, 20 mL of a hydrogel was injected between the prostate and rectum using a transperineal approach. Imaging was performed before and after spacer placement, and the cadavers were subsequently dissected. Ten intensity-modulated radiotherapy plans were generated (five before and five after separation), allowing for characterization of the rectal dose reduction. To quantify the amount of prostate-rectum separation needed for effective rectal dose reduction, simulations were performed using nine clinically generated intensity-modulated radiotherapy plans. Results: In the cadaveric studies, an average of 12.5 mm of prostate-rectum separation was generated with the 20-mL hydrogel injections (the seminal vesicles were also separated from the rectum). The average rectal volume receiving 70 Gy decreased from 19.9% to 4.5% (p < .05). In the simulation studies, a prostate-rectum separation of 10 mm was sufficient to reduce the mean rectal volume receiving 70 Gy by 83.1% (p <.05). No additional reduction in the average rectal volume receiving 70 Gy was noted after 15 mm of separation. In addition, spacer placement allowed for increased planning target volume margins without exceeding the rectal dose tolerance. Conclusion: Prostate-rectum spacers can allow for reduced rectal toxicity rates, treatment intensification, and/or reduced dependence on complex planning and treatment delivery techniques.

  9. Effective biological dose from occupational exposure during nanoparticle synthesis

    NASA Astrophysics Data System (ADS)

    Demou, Evangelia; Tran, Lang; Housiadas, Christos

    2009-02-01

    Nanomaterial and nanotechnology safety require the characterization of occupational exposure levels for completing a risk assessment. However, equally important is the estimation of the effective internal dose via lung deposition, transport and clearance mechanisms. An integrated source-to-biological dose assessment study is presented using real monitoring data collected during nanoparticle synthesis. Experimental monitoring data of airborne exposure levels during nanoparticle synthesis of CaSO4 and BiPO4 nanoparticles in a research laboratory is coupled with a human lung transport and deposition model, which solves in an Eulerian framework the general dynamic equation for polydisperse aerosols using particle specific physical-chemical properties. Subsequently, the lung deposition model is coupled with a mathematical particle clearance model providing the effective biological dose as well as the time course of the biological dose build-up after exposure. The results for the example of BiPO4 demonstrate that even short exposures throughout the day can lead to particle doses of 1.10·E+08#/(kg-bw·8h-shift), with the majority accumulating in the pulmonary region. Clearance of particles is slow and is not completed within a working shift following a 1 hour exposure. It mostly occurs via macrophage activity in the alveolar region, with small amounts transported to the interstitium and less to the lymph nodes.

  10. Effective dose from cone beam CT examinations in dentistry.

    PubMed

    Roberts, J A; Drage, N A; Davies, J; Thomas, D W

    2009-01-01

    Cone beam CT (CBCT) is becoming an increasingly utilized imaging modality for dental examinations in the UK. Previous studies have presented little information on patient dose for the range of fields of view (FOVs) that can be utilized. The purpose of the study was therefore to calculate the effective dose delivered to the patient during a selection of CBCT examinations performed in dentistry. In particular, the i-CAT CBCT scanner was investigated for several imaging protocols commonly used in clinical practice. A Rando phantom containing thermoluminescent dosemeters was scanned. Using both the 1990 and recently approved 2007 International Commission on Radiological Protection recommended tissue weighting factors, effective doses were calculated. The doses (E(1990), E(2007)) were: full FOV head (92.8 microSv, 206.2 microSv); 13 cm scan of the jaws (39.5 microSv, 133.9 microSv); 6 cm high-resolution mandible (47.2 microSv, 188.5 microSv); 6 cm high-resolution maxilla (18.5 microSv, 93.3 microSv); 6 cm standard mandible (23.9 microSv, 96.2 microSv); and 6 cm standard maxilla (9.7 microSv, 58.9 microSv). The doses from CBCT are low compared with conventional CT but significantly higher than conventional dental radiography techniques.

  11. Estimation of annual occupational effective doses from external ionizing radiation at medical institutions in Kenya

    NASA Astrophysics Data System (ADS)

    Korir, Geoffrey; Wambani, Jeska; Korir, Ian

    2011-04-01

    This study details the distribution and trends of doses due to occupational radiation exposure among radiation workers from participating medical institutions in Kenya, where monthly dose measurements were collected for a period of one year ranging from January to December in 2007. A total of 367 medical radiation workers were monitored using thermoluminescent dosemeters. They included radiologists (27%), oncologists (2%), dentists (4%), Physicists (5%), technologists (45%), nurses (4%), film processor technicians (3%), auxiliary staff (4%), and radiology office staff (5%). The average annual effective dose of all categories of staff was found to range from 1.19 to 2.52 mSv. This study formed the initiation stage of wider, comprehensive and more frequent monitoring of occupational radiation exposures and long-term investigations into its accumulation patterns in our country.

  12. Comparison of different approaches of estimating effective dose from reported exposure data in 3D imaging with interventional fluoroscopy systems

    NASA Astrophysics Data System (ADS)

    Svalkvist, Angelica; Hansson, Jonny; Bâth, Magnus

    2014-03-01

    Three-dimensional (3D) imaging with interventional fluoroscopy systems is today a common examination. The examination includes acquisition of two-dimensional projection images, used to reconstruct section images of the patient. The aim of the present study was to investigate the difference in resulting effective dose obtained using different levels of complexity in calculations of effective doses from these examinations. In the study the Siemens Artis Zeego interventional fluoroscopy system (Siemens Medical Solutions, Erlangen, Germany) was used. Images of anthropomorphic chest and pelvis phantoms were acquired. The exposure values obtained were used to calculate the resulting effective doses from the examinations, using the computer software PCXMC (STUK, Helsinki, Finland). The dose calculations were performed using three different methods: 1. using individual exposure values for each projection image, 2. using the mean tube voltage and the total DAP value, evenly distributed over the projection images, and 3. using the mean kV and the total DAP value, evenly distributed over smaller selection of projection images. The results revealed that the difference in resulting effective dose between the first two methods was smaller than 5%. When only a selection of projection images were used in the dose calculations the difference increased to over 10%. Given the uncertainties associated with the effective dose concept, the results indicate that dose calculations based on average exposure values distributed over a smaller selection of projection angles can provide reasonably accurate estimations of the radiation doses from 3D imaging using interventional fluoroscopy systems.

  13. Patient effective dose from endovascular brachytherapy with 192Ir sources.

    PubMed

    Perma, L; Bianchi, C; Nicolini, G; Novario, R; Tanzi, F; Conte, L

    2002-01-01

    The growing use of endovascular brachytherapy has been accompanied by the publication of a large number of studies in several fields, but few studies on patient dose have been found in the literature. Moreover, these studies were carried out on the basis of Monte Carlo simulation. The aim of the present study was to estimate the effective dose to the patient undergoing endovascular brachytherapy treatment with 112Ir sources, by means of experimental measurements. Two standard treatments were taken into account: an endovascular brachytherapy of the coronary artery corresponding to the activity x time product of 184 GBq.min and an endovascular brachytherapy of the renal artery (898 GBq.min). Experimental assessment was accomplished by thermoluminescence dosemeters positioned in more than 300 measurement points in a properly adapted Rqndo phantom. A method has been developed to estimate the mean organ doses for all tissues and organs concerned in order to calculate the effective dose associated with intravascular brachytherapy. The normalised organ doses resulting from cronary treatment were 2.4 x 10(-2) mSv.GBq(-1).min(-1) for lung, 0.9 x 10(-2) mSv.GBSq(-1).min(-1) for oesophagus and 0.48 x 10(-2) mS.GBq(-1).min(-1) for bone marrow. During brachytherapy of the renal artery, the corresponding normalised doses were 4.2 x 10(-2) mS.GBq(-1).min(-1) for colon, 7.8 x 10(-2) mSv.GBq(-1).min(-1) for stomach and 1.7 x 10(-2) mSv.GBq(-1).min(-1) for liver. Coronary treatment iJnvlled an efl'fective dose of (0.046 mSv.GBq(-1).min(-1), whereas the treatment of the renal artery resulted in an effective dose of 0.15 mSv.GBq(-1).min(-1); there were many similarities with data from former studies. Based on these results it can be concluded that the dose level of patients exposed during brachytherapy treatment is low.

  14. Organ and effective dose coefficients for cranial and caudal irradiation geometries: photons

    SciTech Connect

    Veinot, K. G.; Eckerman, K. F.; Hertel, N. E.

    2015-05-02

    With the introduction of new recommendations of the International Commission on Radiological Protection (ICRP) in Publication 103, the methodology for determining the protection quantity, effective dose, has been modified. The modifications include changes to the defined organs and tissues, the associated tissue weighting factors, radiation weighting factors and the introduction of reference sex-specific computational phantoms. Computations of equivalent doses in organs and tissues are now performed in both the male and female phantoms and the sex-averaged values used to determine the effective dose. Dose coefficients based on the ICRP 103 recommendations were reported in ICRP Publication 116, the revision of ICRP Publication 74 and ICRU Publication 57. The coefficients were determined for the following irradiation geometries: anterior-posterior (AP), posterior-anterior (PA), right and left lateral (RLAT and LLAT), rotational (ROT) and isotropic (ISO). In this work, the methodology of ICRP Publication 116 was used to compute dose coefficients for photon irradiation of the body with parallel beams directed upward from below the feet (caudal) and directed downward from above the head (cranial). These geometries may be encountered in the workplace from personnel standing on contaminated surfaces or volumes and from overhead sources. Calculations of organ and tissue kerma and absorbed doses for caudal and cranial exposures to photons ranging in energy from 10 keV to 10 GeV have been performed using the MCNP6.1 radiation transport code and the adult reference phantoms of ICRP Publication 110. As with calculations reported in ICRP 116, the effects of charged-particle transport are evident when compared with values obtained by using the kerma approximation. At lower energies the effective dose per particle fluence for cranial and caudal exposures is less than AP orientations while above similar to 30 MeV the cranial and caudal values are greater.

  15. Organ and effective dose coefficients for cranial and caudal irradiation geometries: photons.

    PubMed

    Veinot, K G; Eckerman, K F; Hertel, N E

    2016-02-01

    With the introduction of new recommendations of the International Commission on Radiological Protection (ICRP) in Publication 103, the methodology for determining the protection quantity, effective dose, has been modified. The modifications include changes to the defined organs and tissues, the associated tissue weighting factors, radiation weighting factors and the introduction of reference sex-specific computational phantoms. Computations of equivalent doses in organs and tissues are now performed in both the male and female phantoms and the sex-averaged values used to determine the effective dose. Dose coefficients based on the ICRP 103 recommendations were reported in ICRP Publication 116, the revision of ICRP Publication 74 and ICRU Publication 57. The coefficients were determined for the following irradiation geometries: anterior-posterior (AP), posterior-anterior (PA), right and left lateral (RLAT and LLAT), rotational (ROT) and isotropic (ISO). In this work, the methodology of ICRP Publication 116 was used to compute dose coefficients for photon irradiation of the body with parallel beams directed upward from below the feet (caudal) and directed downward from above the head (cranial). These geometries may be encountered in the workplace from personnel standing on contaminated surfaces or volumes and from overhead sources. Calculations of organ and tissue kerma and absorbed doses for caudal and cranial exposures to photons ranging in energy from 10 keV to 10 GeV have been performed using the MCNP6.1 radiation transport code and the adult reference phantoms of ICRP Publication 110. As with calculations reported in ICRP 116, the effects of charged-particle transport are evident when compared with values obtained by using the kerma approximation. At lower energies the effective dose per particle fluence for cranial and caudal exposures is less than AP orientations while above ∼30 MeV the cranial and caudal values are greater. Published by Oxford University

  16. Organ and effective dose coefficients for cranial and caudal irradiation geometries: photons

    DOE PAGES

    Veinot, K. G.; Eckerman, K. F.; Hertel, N. E.

    2015-05-02

    With the introduction of new recommendations of the International Commission on Radiological Protection (ICRP) in Publication 103, the methodology for determining the protection quantity, effective dose, has been modified. The modifications include changes to the defined organs and tissues, the associated tissue weighting factors, radiation weighting factors and the introduction of reference sex-specific computational phantoms. Computations of equivalent doses in organs and tissues are now performed in both the male and female phantoms and the sex-averaged values used to determine the effective dose. Dose coefficients based on the ICRP 103 recommendations were reported in ICRP Publication 116, the revision ofmore » ICRP Publication 74 and ICRU Publication 57. The coefficients were determined for the following irradiation geometries: anterior-posterior (AP), posterior-anterior (PA), right and left lateral (RLAT and LLAT), rotational (ROT) and isotropic (ISO). In this work, the methodology of ICRP Publication 116 was used to compute dose coefficients for photon irradiation of the body with parallel beams directed upward from below the feet (caudal) and directed downward from above the head (cranial). These geometries may be encountered in the workplace from personnel standing on contaminated surfaces or volumes and from overhead sources. Calculations of organ and tissue kerma and absorbed doses for caudal and cranial exposures to photons ranging in energy from 10 keV to 10 GeV have been performed using the MCNP6.1 radiation transport code and the adult reference phantoms of ICRP Publication 110. As with calculations reported in ICRP 116, the effects of charged-particle transport are evident when compared with values obtained by using the kerma approximation. At lower energies the effective dose per particle fluence for cranial and caudal exposures is less than AP orientations while above similar to 30 MeV the cranial and caudal values are greater.« less

  17. Analysis of uncertainties in Monte Carlo simulated organ and effective dose in chest CT: scanner- and scan-related factors

    NASA Astrophysics Data System (ADS)

    Muryn, John S.; Morgan, Ashraf G.; Liptak, Chris L.; Dong, Frank F.; Segars, W. Paul; Primak, Andrew N.; Li, Xiang

    2017-04-01

    In Monte Carlo simulation of CT dose, many input parameters are required (e.g. bowtie filter properties and scan start/end location). Our goal was to examine the uncertainties in patient dose when input parameters were inaccurate. Using a validated Monte Carlo program, organ dose from a chest CT scan was simulated for an average-size female phantom using a reference set of input parameter values (treated as the truth). Additional simulations were performed in which errors were purposely introduced into the input parameter values. The effects on four dose quantities were analyzed: organ dose (mGy/mAs), effective dose (mSv/mAs), CTDIvol-normalized organ dose (unitless), and DLP-normalized effective dose (mSv/mGy · cm). At 120 kVp, when spectral half value layer deviated from its true value by  ±1.0 mm Al, the four dose quantities had errors of 18%, 7%, 14% and 2%, respectively. None of the dose quantities were affected significantly by errors in photon path length through the graphite section of the bowtie filter; path length error as large as 5 mm produced dose errors of  ⩽2%. In contrast, error of this magnitude in the aluminum section produced dose errors of  ⩽14%. At a total collimation of 38.4 mm, when radiation beam width deviated from its true value by  ±  3 mm, dose errors were  ⩽7%. Errors in tube starting angle had little impact on effective dose (errors  ⩽  1%) however, they produced organ dose errors as high as 66%. When the assumed scan length was longer by 4 cm than the truth, organ dose errors were up to 137%. The corresponding error was 24% for effective dose, but only 3% for DLP-normalized effective dose. Lastly, when the scan isocenter deviated from the patient’s anatomical center by 5 cm, organ and effective dose errors were up 18% and 8%, respectively.

  18. [Effectiveness of ultrasmall doses of endogenous bioregulators and immunoactive compounds].

    PubMed

    Ashmarin, I P; Karazeeva, E P; Lelekova, T V

    2005-01-01

    The data and hypotheses on the mechanisms of action of ultrasmall doses (USD) and ultralow concentrations (ULC) of endogenous bioregulators and immunoactive compounds (regulatory peptides, cytokines, etc.) are presented. The reliability of the published data on the effectiveness of USD and ULC within the concentration limits 10(-13) - 10(-24) M and lower is considered.

  19. Effective doses from cone beam CT investigation of the jaws

    PubMed Central

    Davies, J; Johnson, B; Drage, NA

    2012-01-01

    Objectives The purpose of the study was to calculate the effective dose delivered to the patient undergoing cone beam (CB) CT of the jaws and maxillofacial complex using the i-CAT Next Generation CBCT scanner (Imaging Sciences International, Hatfield, PA). Methods A RANDO® phantom (The Phantom Laboratory, Salem, NY) containing thermoluminence dosemeters were scanned 10 times for each of the 6 imaging protocols. Effective doses for each protocol were calculated using the 1990 and approved 2007 International Commission on Radiological Protection (ICRP) recommended tissue weighting factors (E1990, E2007). Results The effective dose for E1990 and E2007, respectively, were: full field of view (FOV) of the head, 47 μSv and 78 μSv; 13 cm scan of the jaws, 44 μSv and 77 μSv; 6 cm standard mandible, 35 μSv and 58 μSv; 6 cm high resolution mandible, 69 μSv and 113 μSv; 6 cm standard maxilla, 18 μSv and 32 μSv; and 6 cm high resolution maxilla, 35 μSv and 60 μSv. Conclusions Using the new generation of CBCT scanner, the effective dose is lower than the original generation machine for a similar FOV using the ICRP 2007 tissue weighting factors. PMID:22184626

  20. Effect of the initial excitation energy on the average fission lifetime of nuclei

    SciTech Connect

    Gontchar, I. I. Ponomarenko, N. A. Litnevsky, A. L.

    2008-07-15

    The dependence of the fission time on the initial nuclear excitation energy E{sub tot0}* is studied on the basis of a refined combined dynamical and statistical model. It is shown that this dependence may be nonmonotonic, in which case it features a broad maximum. It turns out that the form of the average fission time as a function of E{sub tot0}* depends greatly on the orbital angular momentum L{sub n} carried away by prescission neutrons.

  1. Surface enhanced Raman optical activity of molecules on orientationally averaged substrates: theory of electromagnetic effects.

    PubMed

    Janesko, Benjamin G; Scuseria, Gustavo E

    2006-09-28

    We present a model for electromagnetic enhancements in surface enhanced Raman optical activity (SEROA) spectroscopy. The model extends previous treatments of SEROA to substrates, such as metal nanoparticles in solution, that are orientationally averaged with respect to the laboratory frame. Our theoretical treatment combines analytical expressions for unenhanced Raman optical activity with molecular polarizability tensors that are dressed by the substrate's electromagnetic enhancements. We evaluate enhancements from model substrates to determine preliminary scaling laws and selection rules for SEROA. We find that dipolar substrates enhance Raman optical activity (ROA) scattering less than Raman scattering. Evanescent gradient contributions to orientationally averaged ROA scale to first or higher orders in the gradient of the incident plane-wave field. These evanescent gradient contributions may be large for substrates with quadrupolar responses to the plane-wave field gradient. Some substrates may also show a ROA contribution that depends only on the molecular electric dipole-electric dipole polarizability. These conclusions are illustrated via numerical calculations of surface enhanced Raman and ROA spectra from (R)-(-)-bromochlorofluoromethane on various model substrates.

  2. Effect of spatial averaging on temporal statistical and scaling properties of rainfall

    NASA Astrophysics Data System (ADS)

    Olsson, Jonas; Singh, Vijay P.; Jinno, Kenji

    1999-08-01

    The variation of temporal continuous rainfall properties with spatial scale was investigated by analyses of daily 11.2-year rainfall time series of point values and spatial averages obtained from a network of 161 rain gauges in southern Sweden. The number of series studied ranged from 16 for point values to 1 for 8000 km2, the latter corresponding to the total network area. The analyses included investigations of general descriptive statistics, power spectra, empirical probability distribution functions, and scaling of statistical moments. Two important characteristics of the rainfall process in the region were indicated. The first was that temporal statistical properties related to extreme values qualitatively changed at a spatial scale of ˜2800 km2, whereas properties of the mean process did not. Although this change may partly be related to changes in the sample size, its presence does raise some important questions concerning the transformation between point values and regional scales in hydroclimatological rainfall modeling. The second important characteristic was a temporal scaling behavior between 1 day and 1 month with properties depending on the spatial averaging area. This finding is in agreement with previous investigations where a spatial variation of temporal scaling properties has been found and suggests the possibility of scaling-based time series modeling where the regional parameters are adjusted to take local climatological factors affecting the rainfall process into account.

  3. Distributions and averages of electron density parameters: Explaining the effects of gradient corrections

    NASA Astrophysics Data System (ADS)

    Zupan, Ales; Burke, Kieron; Ernzerhof, Matthias; Perdew, John P.

    1997-06-01

    We analyze the electron densities n(r) of atoms, molecules, solids, and surfaces. The distributions of values of the Seitz radius rs=(3/4πn)1/3 and the reduced density gradient s=|∇n|/(2(3π2)1/3n4/3) in an electron density indicate which ranges of these variables are significant for physical processes. We also define energy-weighted averages of these variables, and , from which local spin density (LSD) and generalized gradient approximation (GGA) exchange-correlation energies may be estimated. The changes in these averages upon rearrangement of the nuclei (atomization of molecules or solids, stretching of bond lengths or lattice parameters, change of crystal structure, etc.) are used to explain why GGA corrects LSD in the way it does. A thermodynamic-like inequality (essentially d/>d/2) determines whether the gradient corrections drive a process forward. We use this analysis to explain why gradient corrections usually stretch bonds (but not for example H-H bonds), reduce atomization and surface energies, and raise energy barriers to formation at transition states.

  4. Effective doses from panoramic radiography and CBCT (cone beam CT) using dose area product (DAP) in dentistry

    PubMed Central

    Shin, H S; Nam, K C; Park, H; Choi, H U; Kim, H Y

    2014-01-01

    Objectives: We compared the effective dose from panoramic radiography with that from cone beam CT (CBCT) using dose area product under adult and child exposure conditions. Methods: The effective doses of the cephalo, panorama, implant and dental modes of Alphard 3030 (Asahi Roentgen Ind., Co. Ltd, Kyoto, Japan) CBCT and the Jaw, Wide, Facial and temporomandibular joint modes of Rayscan Symphony (RAY Co., Ltd, Hwaseong, Republic of Korea) CBCT were compared with those of CRANEX® 3+ CEPH (Soredex Orion Corporation, Helsinki, Finland) panoramic radiography equipment under adult and child exposure conditions. Each effective dose was calculated using a conversion formula from dose area product meter measured values (VacuTec Messtechnik GmbH, Dresden, Germany). The conversion formulae used were suggested by Helmrot and Alm Carlsson and Batista et al, and they were applied with the tube voltage taken into consideration. Results: The maximum effective doses from the Alphard 3030 and Rayscan Symphony were 67 and 21 times greater than that from panoramic radiography, respectively. The ratios of the effective dose under the child setting to that under the adult condition were 0.60–0.62 and 0.84–0.95, and the maximum differences in effective doses between the adult and child exposure settings were equivalent to 27 and 4 times greater than a panoramic examination in the Alphard 3030 and Rayscan Symphony, respectively. Conclusions: The effective CBCT doses were higher than those of panoramic radiography. The differences in effective doses between the adult and child CBCT settings were dependent on equipment type and exposure parameters. Therefore, adequate mode selection and control of exposure as well as further research are necessary to minimize the effective dose to patients, especially for radiosensitive children. PMID:24845340

  5. Effects of dose and dose protraction on embryotoxicity of 14.1 MeV neutron irradiation in rats

    SciTech Connect

    Beckman, D.A.; Buck, S.J. |; Solomon, H.M.; Gorson, R.O.; Mills, R.E.; Brent, R.L. |

    1994-06-01

    The embryotoxic effects of neutron radiation on rodent embryos are documented, but there is disagreement about the dose-response relationship and the impact of protracting the dose. Pregnant rats were exposed to total absorbed doses of 0.15 to 1.50 Gy 14.1 MeV neutrons on day 9.5 after conception, coincident with the most sensitive stage of embryonic development for the induction of major congenital malformations. In general terms, the incidence of embryotoxic effects increased with increasing total absorbed dose. However, the dose-response relationship differed depending on the parameter of embryotoxicity chosen, namely, intrauterine death, malformations or very low body weight. In a second study, embryos were exposed to a single embryotoxic absorbed dose (0.75 Gy) administered at a range of dose rates, from 0.10 to 0.50 Gy/h. The results offer no evidence that protraction of this selected dose significantly increased or decreased the incidence or pattern of embryotoxicity of the neutron exposure used in this study. The results do not support the hypothesis of a linear dose-response relationship for the effects of prenatal neutron irradiation that contribute to embryotoxicity for total absorbed doses of 0.15 to 1.50 Gy. 23 refs., 8 tabs.

  6. Committed effective dose determination in southern Brazilian cereal flours.

    PubMed

    Scheibel, V; Appoloni, C R

    2013-01-01

    The health impact of radionuclide ingestion from foodstuffs was evaluated by the committed effective doses determined in eight commercial samples of South-Brazilian cereal flours (soy, wheat, cornmeal, cassava, rye, oat, barley and rice flours). The radioactivity traces of (228)Th, (228)Ra, (226)Ra, (40)K, (7)Be and (137)Cs were measured by gamma-ray spectrometry employing an HPGe detector of 66 % relative efficiency. The efficiency curve has taken into account the differences in densities and chemical composition between the matrix and the certified sample. The highest concentration levels of (228)Th and (40)K were 3.5±0.4 and 1469±17 Bq kg(-1) for soy flour, respectively, within the 95 % confidence level. The lower limit of detection for (137)Cs ranged from 0.04 to 0.4 Bq kg(-1). The highest committed effective dose was 0.36 μSv.y(-1) for (228)Ra in cassava flour (adults). All committed effective doses determined at the present work were lower than the International Atomic Energy Agency dose limit of 1 mSv.y(-1), to the public exposure.

  7. Methods of determining the effective dose in dental radiology.

    PubMed

    Thilander-Klang, Anne; Helmrot, Ebba

    2010-01-01

    A wide variety of X-ray equipment is used today in dental radiology, including intra-oral, orthopantomographic, cephalometric, cone-beam computed tomography (CBCT) and computed tomography (CT). This raises the question of how the radiation risks resulting from different kinds of examinations should be compared. The risk to the patient is usually expressed in terms of effective dose. However, it is difficult to determine its reliability, and it is difficult to make comparisons, especially when different modalities are used. The classification of the new CBCT units is also problematic as they are sometimes classified as CT units. This will lead to problems in choosing the best dosimetric method, especially when the examination geometry resembles more on an ordinary orthopantomographic examination, as the axis of rotation is not at the centre of the patient, and small radiation field sizes are used. The purpose of this study was to present different methods for the estimation of the effective dose from the equipment currently used in dental radiology, and to discuss their limitations. The methods are compared based on commonly used measurable and computable dose quantities, and their reliability in the estimation of the effective dose.

  8. Biases in Social Comparative Judgments: The Role of Nonmotivated Factors in Above-Average and Comparative-Optimism Effects

    ERIC Educational Resources Information Center

    Chambers, John R.; Windschitl, Paul D.

    2004-01-01

    Biases in social comparative judgments, such as those illustrated by above-average and comparative-optimism effects, are often regarded as products of motivated reasoning (e.g., self-enhancement). These effects, however, can also be produced by information-processing limitations or aspects of judgment processes that are not necessarily biased by…

  9. Organ and Effective Dose Coefficients for Cranial and Caudal Irradiation Geometries: Neutrons

    NASA Astrophysics Data System (ADS)

    Veinot, K. G.; Eckerman, K. F.; Hertel, N. E.; Hiller, M. M.

    2017-09-01

    With the introduction of new recommendations by ICRP Publication 103, the methodology for determining the protection quantity, effective dose, has been modified. The modifications include changes to the defined organs and tissues, the associated tissue weighting factors, radiation weighting factors, and the introduction of reference sex-specific computational phantoms (ICRP Publication 110). Computations of equivalent doses in organs and tissues are now performed in both the male and female phantoms and the sex-averaged values used to determine the effective dose. Dose coefficients based on the ICRP 103 recommendations were reported in ICRP Publication 116, the revision of ICRP Publication 74 and ICRU Publication 57. The coefficients were determined for the following irradiation geometries: anterior-posterior (AP), posterior-anterior (PA), right and left lateral (RLAT and LLAT), rotational (ROT), and isotropic (ISO). In this work, the methodology of ICRP Publication 116 was used to compute dose coefficients for neutron irradiation of the body with parallel beams directed upward from below the feet (caudal) and directed downward from above the head (cranial). These geometries may be encountered in the workplace from personnel standing on contaminated surfaces or volumes and from overhead sources. Calculations of organ and tissue absorbed doses for caudal and cranial exposures to neutrons ranging in energy from 10-9 MeV to 10 GeV have been performed using the MCNP6 radiation transport code and the adult reference voxel phantoms of ICRP Publication 110. At lower energies the effective dose per particle fluence for cranial and caudal exposures is less than AP orientations while above about 30 MeV the cranial and caudal values are greater.

  10. Potential Microbiological Effects of Higher Dosing of Echinocandins.

    PubMed

    Steinbach, William J; Lamoth, Frédéric; Juvvadi, Praveen R

    2015-12-01

    The antifungal "paradoxical effect" has been described as the reversal of growth inhibition at high doses of echinocandins, most usually caspofungin. This microbiological effect appears to be a cellular compensatory response to cell wall damage, resulting in alteration of cell wall content and structure as well as fungal morphology and growth. In vitro studies demonstrate this reproducible effect in a certain percentage of fungal isolates, but animal model and clinical studies are less consistent. The calcineurin and Hsp90 cell signaling pathways appear to play a major role in regulating these cellular and structural changes. Regardless of the clinical relevance of this paradoxical growth effect, understanding the specific actions of echinocandins is paramount to optimizing their use at either standard or higher dosing schemes, as well as developing future improvements in our antifungal arsenal.

  11. Dosimetry for quantitative analysis of low dose ionizing radiation effects on humans in radiation therapy patients

    SciTech Connect

    Lehmann, J; Stern, R L; Daly, T P; Schwieter, C W; Jones, G E; Arnold, M L; Hartmann-Siantar, C L; Goldberg, Z

    2004-04-20

    We have successfully developed a practical approach to predicting the location of skin surface dose at potential biopsy sites that receive 1 cGy and 10 cGy, respectively, in support of in vivo biologic dosimetry in humans. This represents a significant technical challenge as the sites lie on the patient surface out side the radiation fields. The PEREGRINE Monte Carlo simulation system was used to model radiation dose delivery and TLDs were used for validation on a phantom and confirmation during patient treatment. In the developmental studies the Monte Carlo simulations consistently underestimated the dose at the biopsy site by approximately 15% for a realistic treatment configuration, most likely due to lack of detail in the simulation of the linear accelerator outside the main beam line. Using a single, thickness-independent correction factor for the clinical calculations, the average of 36 measurements for the predicted 1 cGy point was 0.985 cGy (standard deviation: 0.110 cGy) despite patient breathing motion and other real world challenges. Since the 10 cGy point is situated in the region of high dose gradient at the edge of the field, patient motion had a greater effect and the six measured points averaged 5.90 cGy (standard deviation: 1.01 cGy), a difference that is equivalent to approximately a 6 mm shift on the patient's surface.

  12. Effective doses due to external irradiation from the Chernobyl accident for different population groups of Ukraine.

    PubMed

    Likhtariov, I; Kovgan, L; Novak, D; Vavilov, S; Jacob, P; Paretzke, H G

    1996-01-01

    A model for the external exposure of the Ukrainian population after the Chernobyl accident was developed. It is based on extensive measurements of external gamma-exposure rates (EGER) in air and of external effective doses of members of five population groups. Questionnaires were used to determine the occupancy times of members of the population groups at three types of locations; inside houses, outdoors, and outside of the home settlement. Behavior factors are defined as the ratio of individual external doses to a reference dose for a phantom standing permanently over an open field with the same average 137Cs activity per unit area as in the settlement. The behavior factors were derived for five population groups (children younger than seven years, the age group from eight to seventeen years, employees, agricultural workers, and pensioners) by two methods: first from direct measurements of individual doses by thermoluminescent dosimetry and an experimental determination of the average 137Cs activity per unit area in the settlement of interest; and second from external gamma-exposure rates in air at various types of locations and from the questionnaire data. The methods were found to be consistent and the results were used to calculate external exposures of the five population groups in the years 1987 through 1991.

  13. Organ doses, effective doses, and risk indices in adult CT: Comparison of four types of reference phantoms across different examination protocols

    SciTech Connect

    Zhang Yakun; Li Xiang; Paul Segars, W.; Samei, Ehsan

    2012-06-15

    male and female stylized phantoms. Results: For fully irradiated organs, average coefficients of variation (COV) ranged from 0.07 to 0.22 across the four male phantoms and from 0.06 to 0.18 across the four female phantoms; for partially irradiated organs, average COV ranged from 0.13 to 0.30 across the four male phantoms and from 0.15 to 0.30 across the four female phantoms. Doses to the testes, breasts, and esophagus showed large variations between phantoms. COV for gender-averaged effective dose and k factor ranged from 0.03 to 0.23 and from 0.06 to 0.30, respectively. COV for male risk index and q factor ranged from 0.06 to 0.30 and from 0.05 to 0.36, respectively; COV for female risk index and q factor ranged from 0.06 to 0.49 and from 0.07 to 0.54, respectively. Conclusions: Despite closely matched organ mass, total body weight, and height, large differences in organ dose exist due to variation in organ location, spatial distribution, and dose approximation method. Dose differences for fully irradiated radiosensitive organs were much smaller than those for partially irradiated organs. Weighted dosimetry quantities including effective dose, male risk indices, k factors, and male q factors agreed well across phantoms. The female risk indices and q factors varied considerably across phantoms.

  14. Organ doses, effective doses, and risk indices in adult CT: Comparison of four types of reference phantoms across different examination protocols

    PubMed Central

    Zhang, Yakun; Li, Xiang; Paul Segars, W.; Samei, Ehsan

    2012-01-01

    male and female stylized phantoms. Results: For fully irradiated organs, average coefficients of variation (COV) ranged from 0.07 to 0.22 across the four male phantoms and from 0.06 to 0.18 across the four female phantoms; for partially irradiated organs, average COV ranged from 0.13 to 0.30 across the four male phantoms and from 0.15 to 0.30 across the four female phantoms. Doses to the testes, breasts, and esophagus showed large variations between phantoms. COV for gender-averaged effective dose and k factor ranged from 0.03 to 0.23 and from 0.06 to 0.30, respectively. COV for male risk index and q factor ranged from 0.06 to 0.30 and from 0.05 to 0.36, respectively; COV for female risk index and q factor ranged from 0.06 to 0.49 and from 0.07 to 0.54, respectively. Conclusions: Despite closely matched organ mass, total body weight, and height, large differences in organ dose exist due to variation in organ location, spatial distribution, and dose approximation method. Dose differences for fully irradiated radiosensitive organs were much smaller than those for partially irradiated organs. Weighted dosimetry quantities including effective dose, male risk indices, k factors, and male q factors agreed well across phantoms. The female risk indices and q factors varied considerably across phantoms. PMID:22755721

  15. The latitude dependence of the variance of zonally averaged quantities. [in polar meteorology with attention to geometrical effects of earth

    NASA Technical Reports Server (NTRS)

    North, G. R.; Bell, T. L.; Cahalan, R. F.; Moeng, F. J.

    1982-01-01

    Geometric characteristics of the spherical earth are shown to be responsible for the increase of variance with latitude of zonally averaged meteorological statistics. An analytic model is constructed to display the effect of a spherical geometry on zonal averages, employing a sphere labeled with radial unit vectors in a real, stochastic field expanded in complex spherical harmonics. The variance of a zonally averaged field is found to be expressible in terms of the spectrum of the vector field of the spherical harmonics. A maximum variance is then located at the poles, and the ratio of the variance to the zonally averaged grid-point variance, weighted by the cosine of the latitude, yields the zonal correlation typical of the latitude. An example is provided for the 500 mb level in the Northern Hemisphere compared to 15 years of data. Variance is determined to increase north of 60 deg latitude.

  16. The latitude dependence of the variance of zonally averaged quantities. [in polar meteorology with attention to geometrical effects of earth

    NASA Technical Reports Server (NTRS)

    North, G. R.; Bell, T. L.; Cahalan, R. F.; Moeng, F. J.

    1982-01-01

    Geometric characteristics of the spherical earth are shown to be responsible for the increase of variance with latitude of zonally averaged meteorological statistics. An analytic model is constructed to display the effect of a spherical geometry on zonal averages, employing a sphere labeled with radial unit vectors in a real, stochastic field expanded in complex spherical harmonics. The variance of a zonally averaged field is found to be expressible in terms of the spectrum of the vector field of the spherical harmonics. A maximum variance is then located at the poles, and the ratio of the variance to the zonally averaged grid-point variance, weighted by the cosine of the latitude, yields the zonal correlation typical of the latitude. An example is provided for the 500 mb level in the Northern Hemisphere compared to 15 years of data. Variance is determined to increase north of 60 deg latitude.

  17. On the averaging of cardiac diffusion tensor MRI data: the effect of distance function selection

    NASA Astrophysics Data System (ADS)

    Giannakidis, Archontis; Melkus, Gerd; Yang, Guang; Gullberg, Grant T.

    2016-11-01

    Diffusion tensor magnetic resonance imaging (DT-MRI) allows a unique insight into the microstructure of highly-directional tissues. The selection of the most proper distance function for the space of diffusion tensors is crucial in enhancing the clinical application of this imaging modality. Both linear and nonlinear metrics have been proposed in the literature over the years. The debate on the most appropriate DT-MRI distance function is still ongoing. In this paper, we presented a framework to compare the Euclidean, affine-invariant Riemannian and log-Euclidean metrics using actual high-resolution DT-MRI rat heart data. We employed temporal averaging at the diffusion tensor level of three consecutive and identically-acquired DT-MRI datasets from each of five rat hearts as a means to rectify the background noise-induced loss of myocyte directional regularity. This procedure is applied here for the first time in the context of tensor distance function selection. When compared with previous studies that used a different concrete application to juxtapose the various DT-MRI distance functions, this work is unique in that it combined the following: (i) metrics were judged by quantitative—rather than qualitative—criteria, (ii) the comparison tools were non-biased, (iii) a longitudinal comparison operation was used on a same-voxel basis. The statistical analyses of the comparison showed that the three DT-MRI distance functions tend to provide equivalent results. Hence, we came to the conclusion that the tensor manifold for cardiac DT-MRI studies is a curved space of almost zero curvature. The signal to noise ratio dependence of the operations was investigated through simulations. Finally, the ‘swelling effect’ occurrence following Euclidean averaging was found to be too unimportant to be worth consideration.

  18. The effective dose assessment of C-arm CT in hepatic arterial embolisation therapy.

    PubMed

    Tyan, Y-S; Li, Y-Y; Ku, M-C; Huang, H-H; Chen, T-R

    2013-04-01

    To assess the effective dose of the liver C-arm computed tomography (CT) scan during hepatic arterial embolisation surgery with clinical dose-area product (DAP) data from Taiwan. The experiment used two kinds of phantoms: RANDO® Man and RANDO Woman (The Phantom Laboratory, Salem, NY), embedded with thermoluminescent dosemeters at locations according to the International Commission on Radiological Protection 103 report. The conversion factors of DAP to effective doses for males and females, respectively, were obtained. The clinical DAP data of liver C-arm CT scan during hepatic arterial embolisation surgery were collected in a hospital in Taiwan. There were 125 liver transarterial embolisation therapy cases, including 94 males and 31 females, from February 2009 to June 2010. C-arm CT was used 38 times for males and 17 times for females. The corresponding average and standard deviation of clinical DAP were 61.0±6.6 Gy cm(2) and 52.2±8.3 Gy cm(2), respectively. The DAP of RANDO Man and RANDO Woman phantoms simply scanned by C-arm CT are much lower than that of patients. After consideration of the clinical DAP of patients, the effective doses of a liver C-arm CT scan recommended for males and females in Taiwan are 11.5±2.3 mSv and 11.3±3.0 mSv, respectively. The conversion factors of DAP to effective doses for males and females are 0.19±0.03 mSv Gy(-1) cm(-2) and 0.22±0.05 mSv Gy(-1) cm(-2). Only if the actual DAP value of a patient scan is multiplied by the conversion factor can the correct effective dose be determined.

  19. Organ dose and effective dose estimation in paediatric chest radiographic examinations by using pin silicon photodiode dosemeters.

    PubMed

    Kawasaki, Toshio; Aoyama, Takahiko; Yamauchi-Kawaura, Chiyo; Fujii, Keisuke; Koyama, Shuji

    2013-01-01

    Organ and effective doses during paediatric chest radiographic examination were investigated for various tube voltages between 60 and 110 kV at a constant milliampere-second value and focus-to-film distance by using an in-phantom dose measuring system and a Monte Carlo (MC) simulation software (PCXMC), where the former was composed of 32 photodiode dosemeters embedded in various tissue and organ sites within a 6-y-old child anthropomorphic phantom. Lung doses obtained ranged from 0.010 to 0.066 mGy and effective doses from 0.004 to 0.025 mSv, where these doses varied by a factor of 6 with the change in the tube voltage. Effective doses obtained using the MC simulation software agreed with those obtained using the dose measuring system within 23 %, revealing the usefulness of PCXMC software for evaluating effective doses. The present study would provide helpful dose data for the selection of technical parameters in paediatric chest radiography in Japan.

  20. Introducing the at-risk average causal effect with application to HealthWise South Africa.

    PubMed

    Coffman, Donna L; Caldwell, Linda L; Smith, Edward A

    2012-08-01

    Researchers often hypothesize that a causal variable, whether randomly assigned or not, has an effect on an outcome behavior and that this effect may vary across levels of initial risk of engaging in the outcome behavior. In this paper, we propose a method for quantifying initial risk status. We then illustrate the use of this risk-status variable as a moderator of the causal effect of leisure boredom, a non-randomized continuous variable, on cigarette smoking initiation. The data come from the HealthWise South Africa study. We define the causal effects using marginal structural models and estimate the causal effects using inverse propensity weights. Indeed, we found leisure boredom had a differential causal effect on smoking initiation across different risk statuses. The proposed method may be useful for prevention scientists evaluating causal effects that may vary across levels of initial risk.

  1. Introducing the At-Risk Average Causal Effect with Application to HealthWise South Africa

    PubMed Central

    Caldwell, Linda L.; Smith, Edward A.

    2012-01-01

    Researchers often hypothesize that a causal variable, whether randomly assigned or not, has an effect on an outcome behavior and that this effect may vary across levels of initial risk of engaging in the outcome behavior. In this paper, we propose a method for quantifying initial risk status. We then illustrate the use of this risk-status variable as a moderator of the causal effect of leisure boredom, a non-randomized continuous variable, on cigarette smoking initiation. The data come from the HealthWise South Africa study. We define the causal effects using marginal structural models and estimate the causal effects using inverse propensity weights. Indeed, we found leisure boredom had a differential causal effect on smoking initiation across different risk statuses. The proposed method may be useful for prevention scientists evaluating causal effects that may vary across levels of initial risk. PMID:22477557

  2. Radiation Dose-Volume Effects in the Brain

    SciTech Connect

    Lawrence, Yaacov Richard; Li, X. Allen; El Naqa, Issam; Hahn, Carol A.; Marks, Lawrence B.; Merchant, Thomas E.; Dicker, Adam P.

    2010-03-01

    We have reviewed the published data regarding radiotherapy (RT)-induced brain injury. Radiation necrosis appears a median of 1-2 years after RT; however, cognitive decline develops over many years. The incidence and severity is dose and volume dependent and can also be increased by chemotherapy, age, diabetes, and spatial factors. For fractionated RT with a fraction size of <2.5 Gy, an incidence of radiation necrosis of 5% and 10% is predicted to occur at a biologically effective dose of 120 Gy (range, 100-140) and 150 Gy (range, 140-170), respectively. For twice-daily fractionation, a steep increase in toxicity appears to occur when the biologically effective dose is >80 Gy. For large fraction sizes (>=2.5 Gy), the incidence and severity of toxicity is unpredictable. For single fraction radiosurgery, a clear correlation has been demonstrated between the target size and the risk of adverse events. Substantial variation among different centers' reported outcomes have prevented us from making toxicity-risk predictions. Cognitive dysfunction in children is largely seen for whole brain doses of >=18 Gy. No substantial evidence has shown that RT induces irreversible cognitive decline in adults within 4 years of RT.

  3. Renal dysfunction after total body irradiation: Dose-effect relationship

    SciTech Connect

    Kal, Henk B. . E-mail: H.B.Kal@UMCUtrecht.nl; Kempen-Harteveld, M. Loes van

    2006-07-15

    Purpose: Late complications related to total body irradiation (TBI) as part of the conditioning regimen for hematopoietic stem cell transplantation have been increasingly noted. We reviewed and compared the results of treatments with various TBI regimens and tried to derive a dose-effect relationship for the endpoint of late renal dysfunction. The aim was to find the tolerance dose for the kidney when TBI is performed. Methods and Materials: A literature search was performed using PubMed for articles reporting late renal dysfunction. For intercomparison, the various TBI regimens were normalized using the linear-quadratic model, and biologically effective doses (BEDs) were calculated. Results: Eleven reports were found describing the frequency of renal dysfunction after TBI. The frequency of renal dysfunction as a function of the BED was obtained. For BED >16 Gy an increase in the frequency of dysfunction was observed. Conclusions: The tolerance BED for kidney tissue undergoing TBI is about 16 Gy. This BED can be realized with highly fractionated TBI (e.g., 6 x 1.7 Gy or 9 x 1.2 Gy at dose rates >5 cGy/min). To prevent late renal dysfunction, the TBI regimens with BED values >16 Gy (almost all found in published reports) should be applied with appropriate shielding of the kidneys.

  4. Evaluation of effective dose in region-of-interest neuroimaging

    NASA Astrophysics Data System (ADS)

    Gill, Kamaljit K.

    We used small field-of-view (FOV) region-of-interest (ROI) imaging for integral dose reduction and to improve image quality by reducing scatter and providing increased resolution. We quantify the reduction of effective dose (ED) realized when using ROI techniques in neuroimaging. Microangiographic fluoroscopic (MAF) detector being used to provide improved visualization of fine detail in the treatment volume during neurointerventional procedures and in ROI cone-beam CT. Using PCXMC (STUK, Helsinki, Finland), the ED was calculated for the 3.6x3.6-cm FOV of the MAF, for the 20x20-cm FOV of the Varian PaxScan 2020 FPD and for a 20x3.6-cm FOV as used in dual detector ROI CBCT for circle of Willis. Substantial reduction in effective dose per detector exposure is realized using ROI techniques in neuroimaging. This reduction would allow the dose in the ROI to be increased over an order of magnitude to provide increased contrast resolution without increasing the stochastic risk to the patient compared to full-FOV imaging.

  5. Estimation of the indoor radon and the annual effective dose from granite samples

    NASA Astrophysics Data System (ADS)

    Sola, P.; Srinuttrakul, W.; Kewsuwan, P.

    2015-05-01

    Inhalation of radon and thoron daughters increases the risk of lung cancer. The main sources of indoor radon are building materials. The aim of this research is to estimate the indoor radon and the annual effective dose from the building materials. Eighteen granite samples bought from the markets in Thailand were measured using an ionization chamber (ATMOS 12 DPX) for the radon concentration in air. Radon exhalation rates were calculated from the radon concentration in chamber. The indoor radon from the granite samples ranged from 10.04 to 55.32 Bq·m-2·h-1 with an average value of 20.30 Bq·m-2·h-1 and the annual effective dose ranged from 0.25 to 1.39 mSv·y-1 with an average value of 0.48 mSv·y-1. The results showed that the annual effective doses of three granite samples were higher than the annual exposure limit for the general public (1 mSv·y-1) recommended by the International Commission on Radiological Protection (ICRP). In addition, the relationship between the colours and radon exhalation rates of granite samples was also explained.

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

    SciTech Connect

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

    2006-04-15

    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 ({alpha}=0.15 Gy{sup -1} and {alpha}/{beta}=3.1 Gy) determined in earlier studies were used to calculate the equivalent uniform dose in 2 Gy fractions (EUD{sub 2}) with respect to three effects: edema, RBE, and dose heterogeneity for {sup 125}I and {sup 103}Pd implants. The EUD{sub 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{sub 100} (volume covered by 100% of prescription dose) decreases from 93% to 91% and 86%, and the D{sub 90} (dose covering 90% of target volume) decrease from 107% to 102% and 94% of prescription dose for {sup 125}I and {sup 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 {sup 125}I and 1.3-1.6 for {sup 103}Pd implants. These RBE values are consistent with the RBE data published in the

  7. Effects of anisotropic turbulence on average polarizability of Gaussian Schell-model quantized beams through ocean link.

    PubMed

    Li, Ye; Zhang, Yixin; Zhu, Yun; Chen, Minyu

    2016-07-01

    Based on the spatial power spectrum of the refractive index of anisotropic turbulence, the average polarizability of the Gaussian Schell-model quantized beams and lateral coherence length of the spherical wave propagating through the ocean water channel are derived. Numerical results show that, in strong temperature fluctuation, the depolarization effects of anisotropic turbulence are inferior to isotropic turbulence, as the other parameters of two links are the same. The depolarization effects of salinity fluctuation are less than the effects of the temperature fluctuation; the average polarizability of beams increases when increasing the inner scale of turbulence and the source's transverse size; and the larger rate of dissipation of kinetic energy per unit mass of fluid enhances the average polarizability of beams. The region of the receiving radius is smaller than the characteristic radius and the average polarizability of beams in isotropy turbulence is smaller than that of beams in anisotropy turbulence. However, the receiving radius region is larger than a characteristic radius and the average polarizability of beams in isotropy turbulence is larger than that of beams in anisotropy turbulence.

  8. The Averaged Face Growth Rates of lysozyme Crystals: The Effect of Temperature

    NASA Technical Reports Server (NTRS)

    Nadarajah, Arunan; Forsythe, Elizabeth L.; Pusey, Marc L.

    1995-01-01

    Measurements of the averaged or macroscopic face growth rates of lysozyme crystals are reported here for the (110) face of tetragonal lysozyme, at three sets of pH and salt concentrations, with temperatures over a 4-22 C range for several protein concentrations. The growth rate trends with supersaturation were similar to previous microscopic growth rate measurements. However, it was found that at high super-saturations the growth rates attain a maximum and then start decreasing. No 'dead zone' was observed but the growth rates were found to approach zero asymptotically at very low super-saturations. The growth rate data also displayed a dependence on pH and salt concentration which could not be characterized solely by the super-saturation. A complete mechanism for lysozyme crystal growth, involving the formation of an aggregate growth unit, mass transport of the growth unit to the crystal interface and faceted crystal growth by growth unit addition, is suggested. Such a mechanism may provide a more consistent explanation for the observed growth rate trends than those suggested by other investigators. The nutrient solution interactions leading to the formation of the aggregate growth unit may, thus, be as important as those occurring at the crystal interface and may account for the differences between small molecule and protein crystal growth.

  9. Loop expansion of the average effective action in the functional renormalization group approach

    NASA Astrophysics Data System (ADS)

    Lavrov, Peter M.; Merzlikin, Boris S.

    2015-10-01

    We formulate a perturbation expansion for the effective action in a new approach to the functional renormalization group method based on the concept of composite fields for regulator functions being their most essential ingredients. We demonstrate explicitly the principal difference between the properties of effective actions in these two approaches existing already on the one-loop level in a simple gauge model.

  10. Underestimating Calorie Content When Healthy Foods Are Present: An Averaging Effect or a Reference-Dependent Anchoring Effect?

    PubMed Central

    Forwood, Suzanna E.; Ahern, Amy; Hollands, Gareth J.; Fletcher, Paul C.; Marteau, Theresa M.

    2013-01-01

    Objective Previous studies have shown that estimations of the calorie content of an unhealthy main meal food tend to be lower when the food is shown alongside a healthy item (e.g. fruit or vegetables) than when shown alone. This effect has been called the negative calorie illusion and has been attributed to averaging the unhealthy (vice) and healthy (virtue) foods leading to increased perceived healthiness and reduced calorie estimates. The current study aimed to replicate and extend these findings to test the hypothesized mediating effect of ratings of healthiness of foods on calorie estimates. Methods In three online studies, participants were invited to make calorie estimates of combinations of foods. Healthiness ratings of the food were also assessed. Results The first two studies failed to replicate the negative calorie illusion. In a final study, the use of a reference food, closely following a procedure from a previously published study, did elicit a negative calorie illusion. No evidence was found for a mediating role of healthiness estimates. Conclusion The negative calorie illusion appears to be a function of the contrast between a food being judged and a reference, supporting the hypothesis that the negative calorie illusion arises from the use of a reference-dependent anchoring and adjustment heuristic and not from an ‘averaging’ effect, as initially proposed. This finding is consistent with existing data on sequential calorie estimates, and highlights a significant impact of the order in which foods are viewed on how foods are evaluated. PMID:23967216

  11. Effective dose efficiency: an application-specific metric of quality and dose for digital radiography.

    PubMed

    Samei, Ehsan; Ranger, Nicole T; Dobbins, James T; Ravin, Carl E

    2011-08-21

    The detective quantum efficiency (DQE) and the effective DQE (eDQE) are relevant metrics of image quality for digital radiography detectors and systems, respectively. The current study further extends the eDQE methodology to technique optimization using a new metric of the effective dose efficiency (eDE), reflecting both the image quality as well as the effective dose (ED) attributes of the imaging system. Using phantoms representing pediatric, adult and large adult body habitus, image quality measurements were made at 80, 100, 120 and 140 kVp using the standard eDQE protocol and exposures. ED was computed using Monte Carlo methods. The eDE was then computed as a ratio of image quality to ED for each of the phantom/spectral conditions. The eDQE and eDE results showed the same trends across tube potential with 80 kVp yielding the highest values and 120 kVp yielding the lowest. The eDE results for the pediatric phantom were markedly lower than the results for the adult phantom at spatial frequencies lower than 1.2-1.7 mm(-1), primarily due to a correspondingly higher value of ED per entrance exposure. The relative performance for the adult and large adult phantoms was generally comparable but affected by kVps. The eDE results for the large adult configuration were lower than the eDE results for the adult phantom, across all spatial frequencies (120 and 140 kVp) and at spatial frequencies greater than 1.0 mm(-1) (80 and 100 kVp). Demonstrated for chest radiography, the eDE shows promise as an application-specific metric of imaging performance, reflective of body habitus and radiographic technique, with utility for radiography protocol assessment and optimization.

  12. LDL-cholesterol-lowering effect of plant sterols and stanols across different dose ranges: a meta-analysis of randomised controlled studies.

    PubMed

    Ras, Rouyanne T; Geleijnse, Johanna M; Trautwein, Elke A

    2014-07-28

    Phytosterols (PS, comprising plant sterols and plant stanols) have been proven to lower LDL-cholesterol concentrations. The dose-response relationship for this effect has been evaluated in several meta-analyses by calculating averages for different dose ranges or by applying continuous dose-response functions. Both approaches have advantages and disadvantages. So far, the calculation of averages for different dose ranges has not been done for plant sterols and stanols separately. The objective of the present meta-analysis was to investigate the combined and separate effects of plant sterols and stanols when classified into different dose ranges. Studies were searched and selected based on predefined criteria. Relevant data were extracted. Average LDL-cholesterol effects were calculated when studies were categorised by dose, according to random-effects models while using the variance as weighing factor. This was done for plant sterols and stanols combined and separately. In total, 124 studies (201 strata) were included. Plant sterols and stanols were administered in 129 and fifty-nine strata, respectively; the remaining used a mix of both. The average PS dose was 2.1 (range 0.2-9.0) g/d. PS intakes of 0.6-3.3 g/d were found to gradually reduce LDL-cholesterol concentrations by, on average, 6-12%. When plant sterols and stanols were analysed separately, clear and comparable dose-response relationships were observed. Studies carried out with PS doses exceeding 4 g/d were not pooled, as these were scarce and scattered across a wide range of doses. In conclusion, the LDL-cholesterol-lowering effect of both plant sterols and stanols continues to increase up to intakes of approximately 3 g/d to an average effect of 12%.

  13. The effects of x-ray beam hardening on detective quantum efficiency and radiation dose

    PubMed Central

    Wong, Molly Donovan; Wu, Xizeng; Liu, Hong

    2011-01-01

    The goal of this preliminary study was to investigate the effects of x-ray beam hardening on the detective quantum efficiency (DQE) and the radiation dose of an inline x-ray imaging system. The DQE and the average glandular dose were both calculated under the same experimental conditions for a range of beam hardening levels, corresponding to no added beam hardening and two thicknesses each of Rhodium (Rh) and Molybdenum (Mo) filters. The dose calculation results demonstrate a reduction of 15% to 24% for the range of beam hardening levels. The comparison of all quantities comprising the DQE exhibit very close correlation between the results obtained without added beam hardening to the results corresponding to the range of beam hardening levels. For the specific experimental conditions utilized in this preliminary study, the results are an indication that the use of beam hardening holds the potential to reduce the radiation dose without decreasing the performance of the system. Future studies will seek to apply this method in a clinical environment and perform a comprehensive image quality evaluation, in an effort to further evaluate the potential of beam hardening to balance the tradeoff between dose and image quality. PMID:25214383

  14. The effect of averaging adjacent planes for artifact reduction in matrix inversion tomosynthesis.

    PubMed

    Godfrey, Devon J; McAdams, H Page; Dobbins, James T

    2013-02-01

    Matrix inversion tomosynthesis (MITS) uses linear systems theory and knowledge of the imaging geometry to remove tomographic blur that is present in conventional backprojection tomosynthesis reconstructions, leaving in-plane detail rendered clearly. The use of partial-pixel interpolation during the backprojection process introduces imprecision in the MITS modeling of tomographic blur, and creates low-contrast artifacts in some MITS planes. This paper examines the use of MITS slabs, created by averaging several adjacent MITS planes, as a method for suppressing partial-pixel artifacts. Human chest tomosynthesis projection data, acquired as part of an IRB-approved pilot study, were used to generate MITS planes, three-plane MITS slabs (MITSa3), five-plane MITS slabs (MITSa5), and seven-plane MITS slabs (MITSa7). These were qualitatively examined for partial-pixel artifacts and the visibility of normal and abnormal anatomy. Additionally, small (5 mm) subtle pulmonary nodules were simulated and digitally superimposed upon human chest tomosynthesis projection images, and their visibility was qualitatively assessed in the different reconstruction techniques. Simulated images of a thin wire were used to generate modulation transfer function (MTF) and slice-sensitivity profile curves for the different MITS and MITS slab techniques, and these were examined for indications of partial-pixel artifacts and frequency response uniformity. Finally, mean-subtracted, exposure-normalized noise power spectra (ENNPS) estimates were computed and compared for MITS and MITS slab reconstructions, generated from 10 sets of tomosynthesis projection data of an acrylic slab. The simulated in-plane MTF response of each technique was also combined with the square root of the ENNPS estimate to yield stochastic signal-to-noise ratio (SNR) information about the different reconstruction techniques. For scan angles of 20° and 5 mm plane separation, seven MITS planes must be averaged to sufficiently

  15. The effect of averaging adjacent planes for artifact reduction in matrix inversion tomosynthesis

    PubMed Central

    Godfrey, Devon J.; Page McAdams, H.; Dobbins, James T.

    2013-01-01

    Purpose: Matrix inversion tomosynthesis (MITS) uses linear systems theory and knowledge of the imaging geometry to remove tomographic blur that is present in conventional backprojection tomosynthesis reconstructions, leaving in-plane detail rendered clearly. The use of partial-pixel interpolation during the backprojection process introduces imprecision in the MITS modeling of tomographic blur, and creates low-contrast artifacts in some MITS planes. This paper examines the use of MITS slabs, created by averaging several adjacent MITS planes, as a method for suppressing partial-pixel artifacts. Methods: Human chest tomosynthesis projection data, acquired as part of an IRB-approved pilot study, were used to generate MITS planes, three-plane MITS slabs (MITSa3), five-plane MITS slabs (MITSa5), and seven-plane MITS slabs (MITSa7). These were qualitatively examined for partial-pixel artifacts and the visibility of normal and abnormal anatomy. Additionally, small (5 mm) subtle pulmonary nodules were simulated and digitally superimposed upon human chest tomosynthesis projection images, and their visibility was qualitatively assessed in the different reconstruction techniques. Simulated images of a thin wire were used to generate modulation transfer function (MTF) and slice-sensitivity profile curves for the different MITS and MITS slab techniques, and these were examined for indications of partial-pixel artifacts and frequency response uniformity. Finally, mean-subtracted, exposure-normalized noise power spectra (ENNPS) estimates were computed and compared for MITS and MITS slab reconstructions, generated from 10 sets of tomosynthesis projection data of an acrylic slab. The simulated in-plane MTF response of each technique was also combined with the square root of the ENNPS estimate to yield stochastic signal-to-noise ratio (SNR) information about the different reconstruction techniques. Results: For scan angles of 20° and 5 mm plane separation, seven MITS planes must be

  16. The effect of averaging adjacent planes for artifact reduction in matrix inversion tomosynthesis

    SciTech Connect

    Godfrey, Devon J.; Page McAdams, H.; Dobbins, James T. III

    2013-02-15

    Purpose: Matrix inversion tomosynthesis (MITS) uses linear systems theory and knowledge of the imaging geometry to remove tomographic blur that is present in conventional backprojection tomosynthesis reconstructions, leaving in-plane detail rendered clearly. The use of partial-pixel interpolation during the backprojection process introduces imprecision in the MITS modeling of tomographic blur, and creates low-contrast artifacts in some MITS planes. This paper examines the use of MITS slabs, created by averaging several adjacent MITS planes, as a method for suppressing partial-pixel artifacts. Methods: Human chest tomosynthesis projection data, acquired as part of an IRB-approved pilot study, were used to generate MITS planes, three-plane MITS slabs (MITSa3), five-plane MITS slabs (MITSa5), and seven-plane MITS slabs (MITSa7). These were qualitatively examined for partial-pixel artifacts and the visibility of normal and abnormal anatomy. Additionally, small (5 mm) subtle pulmonary nodules were simulated and digitally superimposed upon human chest tomosynthesis projection images, and their visibility was qualitatively assessed in the different reconstruction techniques. Simulated images of a thin wire were used to generate modulation transfer function (MTF) and slice-sensitivity profile curves for the different MITS and MITS slab techniques, and these were examined for indications of partial-pixel artifacts and frequency response uniformity. Finally, mean-subtracted, exposure-normalized noise power spectra (ENNPS) estimates were computed and compared for MITS and MITS slab reconstructions, generated from 10 sets of tomosynthesis projection data of an acrylic slab. The simulated in-plane MTF response of each technique was also combined with the square root of the ENNPS estimate to yield stochastic signal-to-noise ratio (SNR) information about the different reconstruction techniques. Results: For scan angles of 20 Degree-Sign and 5 mm plane separation, seven MITS

  17. Doppler broadening effect on collision cross section functions - Deconvolution of the thermal averaging

    NASA Technical Reports Server (NTRS)

    Bernstein, R. B.

    1973-01-01

    The surprising feature of the Doppler problem in threshold determination is the 'amplification effect' of the target's thermal energy spread. The small thermal energy spread of the target molecules results in a large dispersion in relative kinetic energy. The Doppler broadening effect in connection with thermal energy beam experiments is discussed, and a procedure is recommended for the deconvolution of molecular scattering cross-section functions whose dominant dependence upon relative velocity is approximately that of the standard low-energy form.

  18. Doppler broadening effect on collision cross section functions - Deconvolution of the thermal averaging

    NASA Technical Reports Server (NTRS)

    Bernstein, R. B.

    1973-01-01

    The surprising feature of the Doppler problem in threshold determination is the 'amplification effect' of the target's thermal energy spread. The small thermal energy spread of the target molecules results in a large dispersion in relative kinetic energy. The Doppler broadening effect in connection with thermal energy beam experiments is discussed, and a procedure is recommended for the deconvolution of molecular scattering cross-section functions whose dominant dependence upon relative velocity is approximately that of the standard low-energy form.

  19. Organ and effective doses in pediatric patients undergoing helical multislice computed tomography examination

    SciTech Connect

    Lee, Choonik; Lee, Choonsik; Staton, Robert J.; Hintenlang, David E.; Arreola, Manuel M.; Williams, Jonathon L.; Bolch, Wesley E.

    2007-05-15

    As multidetector computed tomography (CT) serves as an increasingly frequent diagnostic modality, radiation risks to patients became a greater concern, especially for children due to their inherently higher radiosensitivity to stochastic radiation damage. Current dose evaluation protocols include the computed tomography dose index (CTDI) or point detector measurements using anthropomorphic phantoms that do not sufficiently provide accurate information of the organ-averaged absorbed dose and corresponding effective dose to pediatric patients. In this study, organ and effective doses to pediatric patients under helical multislice computed tomography (MSCT) examinations were evaluated using an extensive series of anthropomorphic computational phantoms and Monte Carlo radiation transport simulations. Ten pediatric phantoms, five stylized (equation-based) ORNL phantoms (newborn, 1-year, 5-year, 10-year, and 15-year) and five tomographic (voxel-based) UF phantoms (9-month male, 4-year female, 8-year female, 11-year male, and 14-year male) were implemented into MCNPX for simulation, where a source subroutine was written to explicitly simulate the helical motion of the CT x-ray source and the fan beam angle and collimator width. Ionization chamber measurements were performed and used to normalize the Monte Carlo simulation results. On average, for the same tube current setting, a tube potential of 100 kVp resulted in effective doses that were 105% higher than seen at 80 kVp, and 210% higher at 120 kVp regardless of phantom type. Overall, the ORNL phantom series was shown to yield values of effective dose that were reasonably consistent with those of the gender-specific UF phantom series for CT examinations of the head, pelvis, and torso. However, the ORNL phantoms consistently overestimated values of the effective dose as seen in the UF phantom for MSCT scans of the chest, and underestimated values of the effective dose for abdominal CT scans. These discrepancies increased

  20. Effective dose span of ten different cone beam CT devices.

    PubMed

    Rottke, D; Patzelt, S; Poxleitner, P; Schulze, D

    2013-01-01

    Evaluation and reduction of dose are important issues. Since cone beam CT (CBCT) has been established now not just in dentistry, the number of acquired examinations continues to rise. Unfortunately, it is very difficult to compare the doses of available devices on the market owing to different exposition parameters, volumes and geometries. The aim of this study was to evaluate the spans of effective doses (EDs) of ten different CBCT devices. 48 thermoluminescent dosemeters were placed in 24 sites in a RANDO(®) head phantom. Protocols with lowest exposition parameters and protocols with highest exposition parameters were performed for each of the ten devices. The ED was calculated from the measured energy doses according to the International Commission on Radiological Protection 2007 recommendations for each protocol and device, and the statistical values were evaluated afterwards. The calculation of the ED resulted in values between 17.2 µSv and 396 µSv for the ten devices. The mean values for protocols with lowest and highest exposition parameters were 31.6 µSv and 209 µSv, respectively. It was not the aim of this study to evaluate the image quality depending on different exposition parameters but to define the spans of EDs in which different CBCT devices work. There is a wide span of ED for different CBCT devices depending on the selected exposition parameters, required spatial resolution and many other factors.

  1. Effective dose span of ten different cone beam CT devices

    PubMed Central

    Rottke, D; Patzelt, S; Poxleitner, P; Schulze, D

    2013-01-01

    Objectives: Evaluation and reduction of dose are important issues. Since cone beam CT (CBCT) has been established now not just in dentistry, the number of acquired examinations continues to rise. Unfortunately, it is very difficult to compare the doses of available devices on the market owing to different exposition parameters, volumes and geometries. The aim of this study was to evaluate the spans of effective doses (EDs) of ten different CBCT devices. Methods: 48 thermoluminescent dosemeters were placed in 24 sites in a RANDO® head phantom. Protocols with lowest exposition parameters and protocols with highest exposition parameters were performed for each of the ten devices. The ED was calculated from the measured energy doses according to the International Commission on Radiological Protection 2007 recommendations for each protocol and device, and the statistical values were evaluated afterwards. Results: The calculation of the ED resulted in values between 17.2 µSv and 396 µSv for the ten devices. The mean values for protocols with lowest and highest exposition parameters were 31.6 µSv and 209 µSv, respectively. Conclusions: It was not the aim of this study to evaluate the image quality depending on different exposition parameters but to define the spans of EDs in which different CBCT devices work. There is a wide span of ED for different CBCT devices depending on the selected exposition parameters, required spatial resolution and many other factors. PMID:23584925

  2. Effects of erythropoietin in skin wound healing are dose related.

    PubMed

    Sorg, Heiko; Krueger, Christian; Schulz, Torsten; Menger, Michael D; Schmitz, Frank; Vollmar, Brigitte

    2009-09-01

    The hematopoietic growth factor erythropoietin (EPO) attracts attention due to its all-tissue-protective pleiotropic properties. We studied the effect of EPO on dermal regeneration using intravital microscopy in a model of full dermal thickness wounds in the skin-fold chamber of hairless mice. Animals received repetitive low doses or high doses of EPO (RLD-EPO or RHD-EPO) or a single high dose of EPO (SHD-EPO). SHD-EPO accelerated wound epithelialization, reduced wound cellularity, and induced maturation of newly formed microvascular networks. In contrast, RHD-EPO impaired the healing process, as indicated by delayed epithelialization, high wound cellularity, and lack of maturation of microvascular networks. Also, RHD-EPO caused an excessive erythrocyte mass and rheological malfunction, further deteriorating vessel and tissue maturation. Moreover, RHD-EPO altered fibroblast and keratinocyte migration in vitro, while both cell types exposed to RLD-EPO, and, in particular, to SHD-EPO showed accelerated wound scratch closure. In summary, our data show that a single application of a high dose of EPO accelerates and improves skin wound healing.

  3. Radiation-thermal degradation of PE and PVC: Mechanism of synergism and dose rate effects

    NASA Astrophysics Data System (ADS)

    Clough, Roger L.; Gillen, Kenneth T.

    Polyethylene insulation and polyvinyl chloride jacketing materials that had been in use in a nuclear application were recently found to be substantially deteriorated. The damage had occurred under conditions where both the total estimated dose (about 2.5 Mrad) and the operating temperatures (about 43°C average) seemed relatively moderate. These results prompted us to initiate a program to study polyvinyl chloride and polyethylene degradation under conditions of combined γ-radiation and elevated temperature environments. A number of interesting aging effects were observed, including 1) a striking synergism between radiation and temperature and 2) strong dose-rate dependent effects which occur over a wide range of dose rates. The aging effects are explained in terms of a chain branching degradation mechanism involving thermally induced breakdown of peroxides which are formed in reactions initiated by the radiation. Evidence for this mechanism is derived from infrared spectra, from sequential radiation-elevated temperature experiments including experiments under inert atmosphere, from activation energy estimates and from a new technique involving treatment of intact samples with PH 3 for chemical reduction of peroxides. The results of our studies raise significant doubts about the utility of earlier compilations which purportedly serve as radiation life expectancy guides by indicating "tolerable radiation doses" for a variety of polymers.

  4. Estimating Effective Dose of Radiation From Pediatric Cardiac CT Angiography Using a 64-MDCT Scanner: New Conversion Factors Relating Dose-Length Product to Effective Dose.

    PubMed

    Trattner, Sigal; Chelliah, Anjali; Prinsen, Peter; Ruzal-Shapiro, Carrie B; Xu, Yanping; Jambawalikar, Sachin; Amurao, Maxwell; Einstein, Andrew J

    2017-03-01

    The purpose of this study is to determine the conversion factors that enable accurate estimation of the effective dose (ED) used for cardiac 64-MDCT angiography performed for children. Anthropomorphic phantoms representative of 1- and 10-year-old children, with 50 metal oxide semiconductor field-effect transistor dosimeters placed in organs, underwent scanning performed using a 64-MDCT scanner with different routine clinical cardiac scan modes and x-ray tube potentials. Organ doses were used to calculate the ED on the basis of weighting factors published in 1991 in International Commission on Radiological Protection (ICRP) publication 60 and in 2007 in ICRP publication 103. The EDs and the scanner-reported dose-length products were used to determine conversion factors for each scan mode. The effect of infant heart rate on the ED and the conversion factors was also assessed. The mean conversion factors calculated using the current definition of ED that appeared in ICRP publication 103 were as follows: 0.099 mSv · mGy(-1) · cm(-1), for the 1-year-old phantom, and 0.049 mSv · mGy(-1) · cm(-1), for the 10-year-old phantom. These conversion factors were a mean of 37% higher than the corresponding conversion factors calculated using the older definition of ED that appeared in ICRP publication 60. Varying the heart rate did not influence the ED or the conversion factors. Conversion factors determined using the definition of ED in ICRP publication 103 and cardiac, rather than chest, scan coverage suggest that the radiation doses that children receive from cardiac CT performed using a contemporary 64-MDCT scanner are higher than the radiation doses previously reported when older chest conversion factors were used. Additional up-to-date pediatric cardiac CT conversion factors are required for use with other contemporary CT scanners and patients of different age ranges.

  5. Effects of metabolizable energy intake on tympanic temperature and average daily gain of steers finished in southern Chile during wintertime

    USDA-ARS?s Scientific Manuscript database

    A total of 24 Angus x Hereford steers (BW = 479.8 ± 4.48) were used to assess the effect of Metabolizable Energy Intake (MEI) on Average Daily Gain (ADG) and Tympanic Temperature (TT) during the wintertime in southern Chile. The study was conducted at the experimental field of the Catholic Universit...

  6. The Effect of Computer Based Instructional Technique for the Learning of Elementary Level Mathematics among High, Average and Low Achievers

    ERIC Educational Resources Information Center

    Afzal, Muhammad Tanveer; Gondal, Bashir; Fatima, Nuzhat

    2014-01-01

    The major objective of the study was to elicit the effect of three instructional methods for teaching of mathematics on low, average and high achiever elementary school students. Three methods: traditional instructional method, computer assisted instruction (CAI) and teacher facilitated mathematics learning software were employed for the teaching…

  7. The Effect on Non-Normal Distributions on the Integrated Moving Average Model of Time-Series Analysis.

    ERIC Educational Resources Information Center

    Doerann-George, Judith

    The Integrated Moving Average (IMA) model of time series, and the analysis of intervention effects based on it, assume random shocks which are normally distributed. To determine the robustness of the analysis to violations of this assumption, empirical sampling methods were employed. Samples were generated from three populations; normal,…

  8. The Effects of Part-Time Employment on High School Students' Grade Point Averages and Rate of School Attendance.

    ERIC Educational Resources Information Center

    Heffez, Jack

    To determine what effects employment will have on high school students' grade point averages and rate of school attendance, the author involved fifty-six students in an experiment. Twenty-eight students were employed part-time under the Youth Incentive Entitlement Project (YIEP). The twenty-eight students in the control group were eligible for…

  9. Low dose radiation damage effects in silicon strip detectors

    NASA Astrophysics Data System (ADS)

    Wiącek, P.; Dąbrowski, W.

    2016-11-01

    The radiation damage effects in silicon segmented detectors caused by X-rays have become recently an important research topic driven mainly by development of new detectors for applications at the European X-ray Free Electron Laser (E-XFEL). However, radiation damage in silicon strip is observed not only after extreme doses up to 1 GGy expected at E-XFEL, but also at doses in the range of tens of Gy, to which the detectors in laboratory instruments like X-ray diffractometers or X-ray spectrometers can be exposed. In this paper we report on investigation of radiation damage effects in a custom developed silicon strip detector used in laboratory diffractometers equipped with X-ray tubes. Our results show that significant degradation of detector performance occurs at low doses, well below 200 Gy, which can be reached during normal operation of laboratory instruments. Degradation of the detector energy resolution can be explained by increasing leakage current and increasing interstrip capacitance of the sensor. Another observed effect caused by accumulation of charge trapped in the surface oxide layer is change of charge division between adjacent strips. In addition, we have observed unexpected anomalies in the annealing process.

  10. Strategy Precedes Operational Effectiveness: Aligning High Graduation Rankings with Competitive Graduation Grade Point Averages

    ERIC Educational Resources Information Center

    Apprey, Maurice; Bassett, Kimberley C.; Preston-Grimes, Patrice; Lewis, Dion W.; Wood, Beverly

    2014-01-01

    Two pivotal and interconnected claims are addressed in this article. First, strategy precedes program effectiveness. Second, graduation rates and rankings are insufficient in any account of academic progress for African American students. In this article, graduation is regarded as the floor and not the ceiling, as it were. The ideal situation in…

  11. Is Scientifically Based Reading Instruction Effective for Students with Below-Average IQs?

    ERIC Educational Resources Information Center

    Allor, Jill H.; Mathes, Patricia G.; Roberts, J. Kyle; Cheatham, Jennifer P.; Al Otaiba, Stephanie

    2014-01-01

    This longitudinal randomized-control trial investigated the effectiveness of scientifically based reading instruction for students with IQs ranging from 40 to 80, including students with intellectual disability (ID). Students were randomly assigned into treatment (n = 76) and contrast (n = 65) groups. Students in the treatment group received…

  12. Effects of Social Interactions on Empirical Responses to Selection for Average Daily Gain of Boars

    USDA-ARS?s Scientific Manuscript database

    Effects of competition on responses to selection for ADG were examined with records of 9,720 boars from dam lines (1 and 2) and sire lines (3 and 4) provided by Pig Improvement Company. Each line was analyzed separately. Pens contained 15 boars. Gains (ADG) were measured from about 71 to 161 d of...

  13. What Is the Minimum Information Needed to Estimate Average Treatment Effects in Education RCTs?

    ERIC Educational Resources Information Center

    Schochet, Peter Z.

    2014-01-01

    Randomized controlled trials (RCTs) are considered the "gold standard" for evaluating an intervention's effectiveness. Recently, the federal government has placed increased emphasis on the use of opportunistic experiments. A key criterion for conducting opportunistic experiments, however, is that there is relatively easy access to data…

  14. A Statistical Analysis of the Effects of Housing Environment on Grade Point Average.

    ERIC Educational Resources Information Center

    Maurais, Roger L.

    This study examined the effect on GPA of increased occupancy of double dormitory rooms. Seven groups of 50 students each were randomly selected: Group (1) freshmen, two per room; (2) freshmen, three per room; (3) freshmen living off campus, (4) seniors, two per room; (5) seniors, three per room; (6) seniors living off campus; (7) seniors in…

  15. Strategy Precedes Operational Effectiveness: Aligning High Graduation Rankings with Competitive Graduation Grade Point Averages

    ERIC Educational Resources Information Center

    Apprey, Maurice; Bassett, Kimberley C.; Preston-Grimes, Patrice; Lewis, Dion W.; Wood, Beverly

    2014-01-01

    Two pivotal and interconnected claims are addressed in this article. First, strategy precedes program effectiveness. Second, graduation rates and rankings are insufficient in any account of academic progress for African American students. In this article, graduation is regarded as the floor and not the ceiling, as it were. The ideal situation in…

  16. Examining the Average and Local Effects of a Standardized Treatment for Fourth Graders with Reading Difficulties

    ERIC Educational Resources Information Center

    Wanzek, Jeanne; Petscher, Yaacov; Al Otaiba, Stephanie; Kent, Shawn C.; Schatschneider, Christopher; Haynes, Martha; Rivas, Brenna K.; Jones, Francesca G.

    2016-01-01

    The present study used a randomized control trial to examine the effects of a widely used multicomponent Tier 2-type intervention, Passport to Literacy, on the reading ability of 221 fourth graders who initially scored at or below the 30th percentile in reading comprehension. Intervention was provided by research staff to groups of 4-7 students…

  17. Examining the Average and Local Effects of a Standardized Treatment for Fourth Graders with Reading Difficulties

    ERIC Educational Resources Information Center

    Wanzek, Jeanne; Petscher, Yaacov; Al Otaiba, Stephanie; Kent, Shawn C.; Schatschneider, Christopher; Haynes, Martha; Rivas, Brenna K.; Jones, Francesca G.

    2016-01-01

    The present study used a randomized control trial to examine the effects of a widely used multicomponent Tier 2-type intervention, Passport to Literacy, on the reading ability of 221 fourth graders who initially scored at or below the 30th percentile in reading comprehension. Intervention was provided by research staff to groups of 4-7 students…

  18. Neuromuscular responses to incremental caffeine doses: performance and side effects.

    PubMed

    Pallarés, Jesús G; Fernández-Elías, Valentín E; Ortega, Juan F; Muñoz, Gloria; Muñoz-Guerra, Jesús; Mora-Rodríguez, Ricardo

    2013-11-01

    The purpose of this study was to determine the oral dose of caffeine needed to increase muscle force and power output during all-out single multijoint movements. Thirteen resistance-trained men underwent a battery of muscle strength and power tests in a randomized, double-blind, crossover design, under four different conditions: (a) placebo ingestion (PLAC) or with caffeine ingestion at doses of (b) 3 mg · kg(-1) body weight (CAFF 3mg), (c) 6 mg · kg(-1) (CAFF 6mg), and (d) 9 mg · kg(-1) (CAFF 9mg). The muscle strength and power tests consisted in the measurement of bar displacement velocity and muscle power output during free-weight full-squat (SQ) and bench press (BP) exercises against four incremental loads (25%, 50%, 75%, and 90% one-repetition maximum [1RM]). Cycling peak power output was measured using a 4-s inertial load test. Caffeine side effects were evaluated at the end of each trial and 24 h later. Mean propulsive velocity at light loads (25%-50% 1RM) increased significantly above PLAC for all caffeine doses (5.4%-8.5%, P = 0.039-0.003). At the medium load (75% 1RM), CAFF 3mg did not improve SQ or BP muscle power or BP velocity. CAFF 9mg was needed to enhance BP velocity and SQ power at the heaviest load (90% 1RM) and cycling peak power output (6.8%-11.7%, P = 0.03-0.05). The CAFF 9mg trial drastically increased the frequency of the adverse side effects (15%-62%). The ergogenic dose of caffeine required to enhance neuromuscular performance during a single all-out contraction depends on the magnitude of load used. A dose of 3 mg · kg(-1) is enough to improve high-velocity muscle actions against low loads, whereas a higher caffeine dose (9 mg · kg(-1)) is necessary against high loads, despite the appearance of adverse side effects.

  19. Effect of low-dose gaseous ozone on pathogenic bacteria

    PubMed Central

    2012-01-01

    Background Treatment of chronically infected wounds is a challenge, and bacterial environmental contamination is a growing issue in infection control. Ozone may have a role in these situations. The objective of this study was to determine whether a low dose of gaseous ozone/oxygen mixture eliminates pathogenic bacteria cultivated in Petri dishes. Methods A pilot study with 6 bacterial strains was made using different concentrations of ozone in an ozone-oxygen mixture to determine a minimally effective dose that completely eliminated bacterial growth. The small and apparently bactericidal gaseous dose of 20 μg/mL ozone/oxygen (1:99) mixture, applied for 5min under atmospheric pressure was selected. In the 2nd phase, eight bacterial strains with well characterized resistance patterns were evaluated in vitro using agar-blood in adapted Petri dishes (105 bacteria/dish). The cultures were divided into 3 groups: 1- ozone-oxygen gaseous mixture containing 20 μg of O3/mL for 5 min; 2- 100% oxygen for 5 min; 3- baseline: no gas was used. Results The selected ozone dose was applied to the following eight strains: Escherichia coli, oxacillin-resistant Staphylococcus aureus, oxacillin-susceptible Staphylococcus aureus, vancomycin-resistant Enterococcus faecalis, extended-spectrum beta-lactamase-producing Klebsiella pneumoniae, carbapenem-resistant Acinetobacter baumannii, Acinetobacter baumannii susceptible only to carbapenems, and Pseudomonas aeruginosa susceptible to imipenem and meropenem. All isolates were completely inhibited by the ozone-oxygen mixture while growth occurred in the other 2 groups. Conclusion A single topical application by nebulization of a low ozone dose completely inhibited the growth of all potentially pathogenic bacterial strains with known resistance to antimicrobial agents. PMID:23249441

  20. A group's physical attractiveness is greater than the average attractiveness of its members: the group attractiveness effect.

    PubMed

    van Osch, Yvette; Blanken, Irene; Meijs, Maartje H J; van Wolferen, Job

    2015-04-01

    We tested whether the perceived physical attractiveness of a group is greater than the average attractiveness of its members. In nine studies, we find evidence for the so-called group attractiveness effect (GA-effect), using female, male, and mixed-gender groups, indicating that group impressions of physical attractiveness are more positive than the average ratings of the group members. A meta-analysis on 33 comparisons reveals that the effect is medium to large (Cohen's d = 0.60) and moderated by group size. We explored two explanations for the GA-effect: (a) selective attention to attractive group members, and (b) the Gestalt principle of similarity. The results of our studies are in favor of the selective attention account: People selectively attend to the most attractive members of a group and their attractiveness has a greater influence on the evaluation of the group.

  1. Covariant and background independent functional RG flow for the effective average action

    NASA Astrophysics Data System (ADS)

    Safari, Mahmoud; Vacca, Gian Paolo

    2016-11-01

    We extend our prescription for the construction of a covariant and background-independent effective action for scalar quantum field theories to the case where momentum modes below a certain scale are suppressed by the presence of an infrared regulator. The key step is an appropriate choice of the infrared cutoff for which the Ward identity, capturing the information from single-field dependence of the ultraviolet action, continues to be exactly solvable, and therefore, in addition to covariance, manifest background independence of the effective action is guaranteed at any scale. A practical consequence is that in this framework one can adopt truncations dependent on the single total field. Furthermore we discuss the necessary and sufficient conditions for the preservation of symmetries along the renormalization group flow.

  2. Estimated effective dose rates from radon exposure in workplaces and residences within Los Alamos county in New Mexico

    SciTech Connect

    Whicker, Jeffrey J; Mcnaughton, Michael

    2009-01-01

    Many millions of office workers are exposed to radon while at work and at home. Though there has been a multitude of studies reporting the measurements of radon concentrations and potential lung and effective doses associated with radon and progeny exposure in homes, similar studies on the concentrations and subsequent effective dose rates in the workplace are lacking. The purposes of this study were to measure radon concentrations in office and residential spaces in the same county and explore the radiation dose implications. Sixty-five track-etch detectors were deployed in office spaces and 47 were deployed in residences, all within Los Alamos County, New Mexico, USA. The sampling periods for these measurements were generally about three months. The measured concentrations were then used to calculate and compare effective dose rates resulting from exposure while at work and at home. Results showed that full-time office workers receive on average about nine times greater exposure at home than while in the office (691 mrem yr{sup -1} versus 78 mrem yr{sup -1}). The estimated effective dose rate for a more homebound person was 896 mrem yr{sup -1}. These effective dose rates are contrasted against the 100 mrem yr{sup -1} threshold for regulation of a 'radiological worker' defined in the Department of Energy regulations occupational exposure and the 10 mrem yr{sup -1} air pathway effective public dose limit regulated by the Environmental Protection Agency.

  3. Pathology effects at radiation doses below those causing increased mortality

    NASA Technical Reports Server (NTRS)

    Carnes, Bruce A.; Gavrilova, Natalia; Grahn, Douglas

    2002-01-01

    Mortality data from experiments conducted at the Argonne National Laboratory (ANL) on the long-term effects of external whole-body irradiation on B6CF(1) mice were used to investigate radiation-induced effects at intermediate doses of (60)Co gamma rays or fission-spectrum neutrons either delivered as a single exposure or protracted over 60 once-weekly exposures. Kaplan-Meier analyses were used to identify the lowest dose in the ANL data (within radiation quality, pattern of exposure, and sex) at which radiation-induced mortality caused by primary tumors could be detected (approximately 1-2 Gy for gamma rays and 10-15 cGy for neutrons). Doses at and below these levels were then examined for radiation-induced shifts in the spectrum of pathology detected at death. To do this, specific pathology events were pooled into larger assemblages based on whether they were cancer, cardiovascular disease or non-neoplastic diseases detected within the lungs and pleura, liver and biliary tract, reproductive organs, or urinary tract. Cancer and cardiovascular disease were further subdivided into categories based on whether they caused death, contributed to death, or were simply observed at death. Counts of how often events falling within each of these combined pathology categories occurred within a mouse were then used as predictor variables in logistic regression to determine whether irradiated mice could be distinguished from control mice. Increased pathology burdens were detected in irradiated mice at doses lower than those causing detectable shifts in mortality-22 cGy for gamma rays and 2 cGy for neutrons. These findings suggest that (1) models based on mortality data alone may underestimate radiation effects, (2) radiation may have adverse health consequences (i.e. elevated health risks) even when mortality risks are not detected, and (3) radiation-induced pathologies other than cancer do occur, and they involve multiple organ systems.

  4. Compelling Issues Compounding the Understanding of Low Dose Radiation Effects: But Do They Matter?

    PubMed

    Morgan, William F

    2016-03-01

    Recent advances in low dose radiation research have raised a number of compelling issues that have compounded the understanding of low dose radiation effects. Here some of them are outlined: the linear no-threshold model for predicting effects at low radiation doses, dose rate effectiveness factor, attributability, and public perception of low dose radiation effects. The impact of changes in any of these hotly debated issues on radiation protection is considered.

  5. Gamma irradiation: Effect of dose and dose rate on development of mature codling moth larvae and adult eclosion

    NASA Astrophysics Data System (ADS)

    Burditt, Arthur K.; Hungate, Frank P.; Toba, H. Harold

    Codling moth, Cydia pomonella (L.), larvae infest apples, pears and many other fruits and nuts. Mature, nondiapausing, cocooned larvae in fiberboard strips were exposed to γ-irradiation at applied doses ranging from 0 to 98 Gy and dose rates from 0.77 to 204.4 Gy/min and subsequently held to permit further development, pupation and adult emergence. At or above an applied dose of 58 Gy, many of the adults that emerged were physically deformed and most were males. As the applied dose increased from 44 to 98 Gy, the percentage of normal adults decreased, the primary effect shifting from a higher percentage of abnormal adults, pupal mortality, to larval mortility. The effects were more pronounced at higher than at lower dose rates. Insect development apparently was not affected when larvae were irradiated at applied doses up to 31.7 Gy. Significantly more adults emerged when larvae were treated at low dose rates (1.0 Gy/min) than at higher dose rates (204 Gy/min). A rate of 52.2 Gy/min was more effective at preventing adult emergence than rates of 1, 4.4 or 201.5 Gy/min.

  6. Peripheral Dose Heterogeneity Due to the Thread Effect in Total Marrow Irradiation With Helical Tomotherapy

    SciTech Connect

    Takahashi, Yutaka; Verneris, Michael R.; Dusenbery, Kathryn E.; Wilke, Christopher T.; Storme, Guy; Weisdorf, Daniel J.; Hui, Susanta K.

    2013-11-15

    Purpose: To report potential dose heterogeneity leading to underdosing at different skeletal sites in total marrow irradiation (TMI) with helical tomotherapy due to the thread effect and provide possible solutions to reduce this effect. Methods and Materials: Nine cases were divided into 2 groups based on patient size, defined as maximum left-to-right arm distance (mLRD): small mLRD (≤47 cm) and large mLRD (>47 cm). TMI treatment planning was conducted by varying the pitch and modulation factor while a jaw size (5 cm) was kept fixed. Ripple amplitude, defined as the peak-to-trough dose relative to the average dose due to the thread effect, and the dose–volume histogram (DVH) parameters for 9 cases with various mLRD was analyzed in different skeletal regions at off-axis (eg, bones of the arm or femur), at the central axis (eg, vertebrae), and planning target volume (PTV), defined as the entire skeleton plus 1-cm margin. Results: Average ripple amplitude for a pitch of 0.430, known as one of the magic pitches that reduce thread effect, was 9.2% at 20 cm off-axis. No significant differences in DVH parameters of PTV, vertebrae, or femur were observed between small and large mLRD groups for a pitch of ≤0.287. Conversely, in the bones of the arm, average differences in the volume receiving 95% and 107% dose (V95 and V107, respectively) between large and small mLRD groups were 4.2% (P=.016) and 16% (P=.016), respectively. Strong correlations were found between mLRD and ripple amplitude (rs=.965), mLRD and V95 (rs=−.742), and mLRD and V107 (rs=.870) of bones of the arm. Conclusions: Thread effect significantly influences DVH parameters in the bones of the arm for large mLRD patients. By implementing a favorable pitch value and adjusting arm position, peripheral dose heterogeneity could be reduced.

  7. 241Am Ingrowth and Its Effect on Internal Dose

    DOE PAGES

    Konzen, Kevin

    2016-07-01

    Generally, plutonium has been manufactured to support commercial and military applications involving heat sources, weapons and reactor fuel. This work focuses on three typical plutonium mixtures, while observing the potential of 241Am ingrowth and its effect on internal dose. The term “ingrowth” is used to describe 241Am production due solely from the decay of 241Pu as part of a plutonium mixture, where it is initially absent or present in a smaller quantity. Dose calculation models do not account for 241Am ingrowth unless the 241Pu quantity is specified. This work suggested that 241Am ingrowth be considered in bioassay analysis when theremore » is a potential of a 10% increase to the individual’s committed effective dose. It was determined that plutonium fuel mixtures, initially absent of 241Am, would likely exceed 10% for typical reactor grade fuel aged less than 30 years; however, heat source grade and aged weapons grade fuel would normally fall below this threshold. In conclusion, although this work addresses typical plutonium mixtures following separation, it may be extended to irradiated commercial uranium fuel and is expected to be a concern in the recycling of spent fuel.« less

  8. Dose rate effects on damage formation in ion-implanted gallium arsenide

    SciTech Connect

    Haynes, T.E.; Holland, O.W.

    1990-09-01

    The residual damage in GaAs was measured by ion channeling following implantation of either 100 keV {sup 30}Si{sup +} at temperatures of 300K or 77K, or 360 keV {sup 120}Sn{sup +} at 300K. For room-temperature Si implants and fluences between 1 and 10 {times} 10{sup 14} Si/cm{sup 2}, the amount of damage created was strongly dependent upon the ion current density, which was varied between 0.05 and 12 {mu}A/cm{sup 2}. Two different stages of damage growth were identified by an abrupt increase in the damage growth rate as a function of fluence, and the threshold fluence for the onset of the second stage was found to be dependent on the dose rate. The dose rate effect on damage was substantially weaker for {sup 120}Sn{sup +} implants and was negligible for Si implants at 77K. The damage was found to be most sensitive to the average current density, demonstrating that the defects which are the precursors to the residual dose-rate dependent damage have active lifetimes of at least 3 {times} 10{sup {minus}4} s. The dose rate effect and its variation with ion mass and temperature are discussed in the context of homogeneous nucleation and growth of damage during ion irradiation.

  9. Dose and dose rate effects of whole-body proton-irradiation on lymphocyte blastogenesis and hematological variables: part II

    NASA Technical Reports Server (NTRS)

    Pecaut, Michael J.; Gridley, Daila S.; Smith, Anna L.; Nelson, Gregory A.

    2002-01-01

    The goal of part II of this study was to evaluate functional characteristics of leukocytes and circulating blood cell parameters after whole-body proton irradiation at varying doses and at low- and high-dose-rates (LDR and HDR, respectively). C57BL/6 mice (n=51) were irradiated and euthanized at 4 days post-exposure for assay. Significant radiation dose- (but not dose-rate-) dependent decreases were observed in splenocyte responses to T and B cell mitogens when compared to sham-irradiated controls (P<0.001). Spontaneous blastogenesis, also significantly dose-dependent, was increased in both blood and spleen (P<0.001). Red blood cell counts, hemoglobin concentration, and hematocrit were decreased in a dose-dependent manner (P<0.05), whereas thrombocyte numbers were only slightly affected. Comparison of proton- and gamma-irradiated groups (both receiving 3 Gy at HDR) showed a higher level of spontaneous blastogenesis in blood leukocytes and a lower splenocyte response to concanavalin A following proton irradiation (P<0.05). There were no dose rate effects. Collectively, the data demonstrate that the measurements in blood and spleen were largely dependent upon the total dose of proton radiation and that an 80-fold difference in the dose rate was not a significant factor. A difference, however, was found between protons and gamma-rays in the degree of change induced in some of the measurements.

  10. Dose and dose rate effects of whole-body proton-irradiation on lymphocyte blastogenesis and hematological variables: part II

    NASA Technical Reports Server (NTRS)

    Pecaut, Michael J.; Gridley, Daila S.; Smith, Anna L.; Nelson, Gregory A.

    2002-01-01

    The goal of part II of this study was to evaluate functional characteristics of leukocytes and circulating blood cell parameters after whole-body proton irradiation at varying doses and at low- and high-dose-rates (LDR and HDR, respectively). C57BL/6 mice (n=51) were irradiated and euthanized at 4 days post-exposure for assay. Significant radiation dose- (but not dose-rate-) dependent decreases were observed in splenocyte responses to T and B cell mitogens when compared to sham-irradiated controls (P<0.001). Spontaneous blastogenesis, also significantly dose-dependent, was increased in both blood and spleen (P<0.001). Red blood cell counts, hemoglobin concentration, and hematocrit were decreased in a dose-dependent manner (P<0.05), whereas thrombocyte numbers were only slightly affected. Comparison of proton- and gamma-irradiated groups (both receiving 3 Gy at HDR) showed a higher level of spontaneous blastogenesis in blood leukocytes and a lower splenocyte response to concanavalin A following proton irradiation (P<0.05). There were no dose rate effects. Collectively, the data demonstrate that the measurements in blood and spleen were largely dependent upon the total dose of proton radiation and that an 80-fold difference in the dose rate was not a significant factor. A difference, however, was found between protons and gamma-rays in the degree of change induced in some of the measurements.

  11. High dose bystander effects in spatially fractionated radiation therapy

    PubMed Central

    Asur, Rajalakshmi; Butterworth, Karl T.; Penagaricano, Jose A.; Prise, Kevin M.; Griffin, Robert J.

    2014-01-01

    Traditional radiotherapy of bulky tumors has certain limitations. Spatially fractionated radiation therapy (GRID) and intensity modulated radiotherapy (IMRT) are examples of advanced modulated beam therapies that help in significant reductions in normal tissue damage. GRID refers to the delivery of a single high dose of radiation to a large treatment area that is divided into several smaller fields, while IMRT allows improved dose conformity to the tumor target compared to conventional three-dimensional conformal radiotherapy. In this review, we consider spatially fractionated radiotherapy approaches focusing on GRID and IMRT, and present complementary evidence from different studies which support the role of radiation induced signaling effects in the overall radiobiological rationale for these treatments. PMID:24246848

  12. UV dose-effect relationships and current protection exposure standards

    SciTech Connect

    Singh, M.S.; Campbell, G.W.

    1982-04-01

    In this paper we have attempted to quantify the health effects in man of uv-radiation exposure of wavelengths from 240 nm to 320 nm. Exposure to uv in this region could result in the formation of skin cancer or premature aging in man. The induction of cancer by uv radiation results from changes in genetic material. We have used the DNA action spectrum coupled with the uv skin cancer data available in the literature to derive the dose-effect relationships. The results are compared against the current uv protection standards.

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

    NASA Technical Reports Server (NTRS)

    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.

  14. Dose-effect relation of interstitial low-dose-rate radiation (Ir192) in an animal tumor model

    SciTech Connect

    Ruifrok, A.C.; Levendag, P.C.; Lakeman, R.F.; Deurloo, I.K.; Visser, A.G. )

    1990-01-01

    One way to deliver high doses of radiation to deep seated tumors without damaging the surrounding tissue is by interstitial techniques. This is commonly applied clinically; however, biological data of tumor response to interstitial low-dose-rate gamma irradiation are scarce. Therefore, we have studied the response of rhabdomyosarcoma R1 tumors implanted in the flanks of female Wag/Rij rats using an interstitial Ir192 afterloading system. A template was developed by which four catheters can be implanted in a square geometry with a fixed spacing. Subsequently four Ir192 wires of 2 cm length each are inserted. For dose prescription the highest isodose enveloping the tumor volume was chosen. Interstitial irradiation was performed using tumor volumes of 1500-2000 mm3. A range of minimum tumor doses of 20 up to 115 Gy were given at a mean dose-rate of 48 cGy/hr. Dose-effect relations were obtained from tumor growth curves and tumor cure data, and compared to data from external irradiation. The dose required for 50% cures with interstitial irradiation (TCD50) appears to be 95 +/- 9 Gy. The TCD50 for low-dose-rate interstitial gamma irradiation is 1.5 times the TCD50 for single dose external X ray irradiation at high dose rates, but is comparable to the TCD50 found after fractionated X ray irradiation at high dose rate. Sham treatment of the tumors had no effect on the time needed to reach twice the treatment volume. The growth rate of tumors regrowing after interstitial radiotherapy is not markedly different from the growth rate of untreated (control) tumors (volume doubting time 5.6 +/- 1 day), in contrast to the decreased growth rate after external X ray irradiation.

  15. Proton dose distribution measurements using a MOSFET detector with a simple dose-weighted correction method for LET effects.

    PubMed

    Kohno, Ryosuke; Hotta, Kenji; Matsuura, Taeko; Matsubara, Kana; Nishioka, Shie; Nishio, Teiji; Kawashima, Mitsuhiko; Ogino, Takashi

    2011-04-04

    We experimentally evaluated the proton beam dose reproducibility, sensitivity, angular dependence and depth-dose relationships for a new Metal Oxide Semiconductor Field Effect Transistor (MOSFET) detector. The detector was fabricated with a thinner oxide layer and was operated at high-bias voltages. In order to accurately measure dose distributions, we developed a practical method for correcting the MOSFET response to proton beams. The detector was tested by examining lateral dose profiles formed by protons passing through an L-shaped bolus. The dose reproducibility, angular dependence and depth-dose response were evaluated using a 190 MeV proton beam. Depth-output curves produced using the MOSFET detectors were compared with results obtained using an ionization chamber (IC). Since accurate measurements of proton dose distribution require correction for LET effects, we developed a simple dose-weighted correction method. The correction factors were determined as a function of proton penetration depth, or residual range. The residual proton range at each measurement point was calculated using the pencil beam algorithm. Lateral measurements in a phantom were obtained for pristine and SOBP beams. The reproducibility of the MOSFET detector was within 2%, and the angular dependence was less than 9%. The detector exhibited a good response at the Bragg peak (0.74 relative to the IC detector). For dose distributions resulting from protons passing through an L-shaped bolus, the corrected MOSFET dose agreed well with the IC results. Absolute proton dosimetry can be performed using MOSFET detectors to a precision of about 3% (1 sigma). A thinner oxide layer thickness improved the LET in proton dosimetry. By employing correction methods for LET dependence, it is possible to measure absolute proton dose using MOSFET detectors.

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

    NASA Technical Reports Server (NTRS)

    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.

  17. Measurement of Entrance Skin Dose and Calculation of Effective Dose for Common Diagnostic X-Ray Examinations in Kashan, Iran.

    PubMed

    Aliasgharzadeh, Akbar; Mihandoost, Ehsan; Masoumbeigi, Mahboubeh; Salimian, Morteza; Mohseni, Mehran

    2015-02-24

    The knowledge of the radiation dose received by the patient during the radiological examination is essential to prevent risks of exposures. The aim of this work is to study patient doses for common diagnostic radiographic examinations in hospitals affiliated to Kashan University of Medical sciences, Iran. The results of this survey are compared with those published by some national and international values. Entrance surface dose (ESD) was measured based on the exposure parameters used for the actual examination and effective dose (ED) was calculated by use of conversion coefficients calculated by Monte Carlo methods. The mean entrance surface dose and effective dose for examinations of the chest (PA, Lat), abdomen (AP), pelvis (AP), lumbar spine (AP, Lat) and skull (AP, Lat) are 0.37, 0.99, 2.01, 1.76, 2.18, 5.36, 1.39 and 1.01 mGy, and 0.04, 0.1, 0.28, 0,28, 0.23, 0.13, 0.01 and 0.01 mSv, respectively. The ESDs and EDs reported in this study, except for examinations of the chest, are generally lower than comparable reference dose values published in the literature. On the basis of the results obtained in this study can conclude that use of newer equipment and use of the proper radiological parameter can significantly reduce the absorbed dose. It is recommended that radiological parameter in chest examinations be revised.

  18. Measurement of Entrance Skin Dose and Calculation of Effective Dose for Common Diagnostic X-Ray Examinations in Kashan, Iran

    PubMed Central

    Aliasgharzadeh, Akbar; Mihandoost, Ehsan; Masoumbeigi, Mahboubeh; Salimian, Morteza; Mohseni, Mehran

    2015-01-01

    The knowledge of the radiation dose received by the patient during the radiological examination is essential to prevent risks of exposures. The aim of this work is to study patient doses for common diagnostic radiographic examinations in hospitals affiliated to Kashan University of Medical sciences, Iran. The results of this survey are compared with those published by some national and international values. Entrance surface dose (ESD) was measured based on the exposure parameters used for the actual examination and effective dose (ED) was calculated by use of conversion coefficients calculated by Monte Carlo methods. The mean entrance surface dose and effective dose for examinations of the chest (PA, Lat), abdomen (AP), pelvis (AP), lumbar spine (AP, Lat) and skull (AP, Lat) are 0.37, 0.99, 2.01, 1.76, 2.18, 5.36, 1.39 and 1.01 mGy, and 0.04, 0.1, 0.28, 0,28, 0.23, 0.13, 0.01 and 0.01 mSv, respectively. The ESDs and EDs reported in this study, except for examinations of the chest, are generally lower than comparable reference dose values published in the literature. On the basis of the results obtained in this study can conclude that use of newer equipment and use of the proper radiological parameter can significantly reduce the absorbed dose. It is recommended that radiological parameter in chest examinations be revised. PMID:26156930

  19. Effects of Coordinate Rotation and Averaging Period on Energy Closure Characteristics of Eddy Covariance Measurements over Mountainous Terrain

    NASA Astrophysics Data System (ADS)

    Li, M.; Chen, Y.

    2009-12-01

    Coordinate rotation is typically applied to align measured turbulence data along the stream wise direction before calculating turbulent fluxes. A standard averaging period (30 min) is commonly used when estimating these fluxes. Different rotation approaches with various averaging periods can cause systemic bias and significant variations in flux estimations. Thus, measuring surface fluxes over a non-flat terrain requires that an appropriate rotation technique and optimal averaging period are applied. In this study, two coordinate rotation approaches (double and planar-fit rotations) and no-rotation, in associated with averaging periods of 15-240 min, were applied to compute heat and water vapor fluxes over a mountainous terrain using the eddy covariance method. Measurements were conducted in an experimental watershed, the Lien-Hua-Chih (LHC) watershed, located in the central Taiwan. This watershed has considerable meso-scale circulation and mountainous terrain. Vegetation type is a mixture of natural deciduous forest and shrubs; canopy height is about 17 m. A 22 m tall observation tower was built inside the canopy. The prevailing wind direction is NW during daytime and ES during the night time at the LHC site in both the dry and wet seasons. Turbulence data above the canopy were measured with an eddy covariance system comprising a 3-D sonic anemometer (Young 81000) and a krypton hygrometer (Campbell KH20). Raw data of 10 Hz were recorded simultaneously with a data logger (CR1000) and a CF card. Air temperature/humidity profiles were measured to calculate the heat/moisture storage inside the canopy layer. Air pressure data were used to correct the effect of air density fluctuations on surface fluxes. The effects of coordinate rotation approaches with various averaging periods on the average daily energy closure fraction are presented. The criteria of the best energy closure fraction and minimum uncertainty indicate that planar-fit rotation with an averaging period

  20. Distribution, elimination, and renal effects of single oral doses of europium in rats.

    PubMed

    Ohnishi, Keiko; Usuda, Kan; Nakayama, Shin; Sugiura, Yumiko; Kitamura, Yasuhiro; Kurita, Akihiro; Tsuda, Yuko; Kimura, Motoshi; Kono, Koichi

    2011-11-01

    Single doses of europium (III) chloride hexahydrate were orally administered to several groups of rats. Cumulative urine samples were taken at 0-24 h, and blood samples were drawn after 24-h administration. The europium concentration was determined in these samples by inductively coupled plasma atomic emission spectroscopy. The volume, creatinine, ß-2-microglobulin, and N-acetyl-ß-D-glucosaminidase were measured in the urine samples to evaluate possible europium-induced renal effects. The blood samples showed low europium distribution, with an average of 77.5 μg/L for all groups. Although the urinary concentration and excretion showed dose-dependent increases, the percentage of europium excreted showed a dose-dependent decrease, with an average of 0.31% in all groups. The administration of europium resulted in a significant decrease of creatinine and a significant increase of urinary volume, N-acetyl-ß-D-glucosaminidase, and ß-2-microglobulin. Rare earth elements, including europium, are believed to form colloidal conjugates that deposit in the reticuloendothelial system and glomeruli. This specific reaction may contribute to low europium bioavailability and renal function disturbances. Despite low bioavailability, the high performance of the analytical method for determination of europium makes the blood and urine sampling suitable tools for monitoring of exposure to this element. The results presented in this study will be of great importance in future studies on the health impacts of rare earth elements.

  1. Modeling Effective Dosages in Hormetic Dose-Response Studies

    PubMed Central

    Belz, Regina G.; Piepho, Hans-Peter

    2012-01-01

    Background Two hormetic modifications of a monotonically decreasing log-logistic dose-response function are most often used to model stimulatory effects of low dosages of a toxicant in plant biology. As just one of these empirical models is yet properly parameterized to allow inference about quantities of interest, this study contributes the parameterized functions for the second hormetic model and compares the estimates of effective dosages between both models based on 23 hormetic data sets. Based on this, the impact on effective dosage estimations was evaluated, especially in case of a substantially inferior fit by one of the two models. Methodology/Principal Findings The data sets evaluated described the hormetic responses of four different test plant species exposed to 15 different chemical stressors in two different experimental dose-response test designs. Out of the 23 data sets, one could not be described by any of the two models, 14 could be better described by one of the two models, and eight could be equally described by both models. In cases of misspecification by any of the two models, the differences between effective dosages estimates (0–1768%) greatly exceeded the differences observed when both models provided a satisfactory fit (0–26%). This suggests that the conclusions drawn depending on the model used may diverge considerably when using an improper hormetic model especially regarding effective dosages quantifying hormesis. Conclusions/Significance The study showed that hormetic dose responses can take on many shapes and that this diversity can not be captured by a single model without risking considerable misinterpretation. However, the two empirical models considered in this paper together provide a powerful means to model, prove, and now also to quantify a wide range of hormetic responses by reparameterization. Despite this, they should not be applied uncritically, but after statistical and graphical assessment of their adequacy. PMID

  2. Measurements of time average series resonance effect in capacitively coupled radio frequency discharge plasma

    SciTech Connect

    Bora, B.; Bhuyan, H.; Favre, M.; Wyndham, E.; Chuaqui, H.; Kakati, M.

    2011-10-15

    Self-excited plasma series resonance is observed in low pressure capacitvely coupled radio frequency discharges as high-frequency oscillations superimposed on the normal radio frequency current. This high-frequency contribution to the radio frequency current is generated by a series resonance between the capacitive sheath and the inductive and resistive bulk plasma. In this report, we present an experimental method to measure the plasma series resonance in a capacitively coupled radio frequency argon plasma by modifying the homogeneous discharge model. The homogeneous discharge model is modified by introducing a correction factor to the plasma resistance. Plasma parameters are also calculated by considering the plasma series resonances effect. Experimental measurements show that the self-excitation of the plasma series resonance, which arises in capacitive discharge due to the nonlinear interaction of plasma bulk and sheath, significantly enhances both the Ohmic and stochastic heating. The experimentally measured total dissipation, which is the sum of the Ohmic and stochastic heating, is found to increase significantly with decreasing pressure.

  3. Radiological dose reconstruction for birds reconciles outcomes of Fukushima with knowledge of dose-effect relationships

    PubMed Central

    Garnier-Laplace, Jacqueline; Beaugelin-Seiller, Karine; Della-Vedova, Claire; Métivier, Jean-Michel; Ritz, Christian; Mousseau, Timothy A.; Pape Møller, Anders

    2015-01-01

    We reconstructed the radiological dose for birds observed at 300 census sites in the 50-km northwest area affected by the accident at the Fukushima Daiichi nuclear power plant over 2011–2014. Substituting the ambient dose rate measured at the census points (from 0.16 to 31 μGy h−1) with the dose rate reconstructed for adult birds of each species (from 0.3 to 97 μGy h−1), we confirmed that the overall bird abundance at Fukushima decreased with increasing total doses. This relationship was directly consistent with exposure levels found in the literature to induce physiological disturbances in birds. Among the 57 species constituting the observed bird community, we found that 90% were likely chronically exposed at a dose rate that could potentially affect their reproductive success. We quantified a loss of 22.6% of the total number of individuals per increment of one unit log10-tansformed total dose (in Gy), over the four-year post-accident period in the explored area. We estimated that a total dose of 0.55 Gy reduced by 50% the total number of birds in the study area over 2011–2014. The data also suggest a significant positive relationship between total dose and species diversity. PMID:26567770

  4. Radiological dose reconstruction for birds reconciles outcomes of Fukushima with knowledge of dose-effect relationships

    NASA Astrophysics Data System (ADS)

    Garnier-Laplace, Jacqueline; Beaugelin-Seiller, Karine; Della-Vedova, Claire; Métivier, Jean-Michel; Ritz, Christian; Mousseau, Timothy A.; Pape Møller, Anders

    2015-11-01

    We reconstructed the radiological dose for birds observed at 300 census sites in the 50-km northwest area affected by the accident at the Fukushima Daiichi nuclear power plant over 2011-2014. Substituting the ambient dose rate measured at the census points (from 0.16 to 31 μGy h-1) with the dose rate reconstructed for adult birds of each species (from 0.3 to 97 μGy h-1), we confirmed that the overall bird abundance at Fukushima decreased with increasing total doses. This relationship was directly consistent with exposure levels found in the literature to induce physiological disturbances in birds. Among the 57 species constituting the observed bird community, we found that 90% were likely chronically exposed at a dose rate that could potentially affect their reproductive success. We quantified a loss of 22.6% of the total number of individuals per increment of one unit log10-tansformed total dose (in Gy), over the four-year post-accident period in the explored area. We estimated that a total dose of 0.55 Gy reduced by 50% the total number of birds in the study area over 2011-2014. The data also suggest a significant positive relationship between total dose and species diversity.

  5. Effect of an acute dose of omega-3 fish oil following exercise-induced muscle damage.

    PubMed

    Jakeman, J R; Lambrick, D M; Wooley, B; Babraj, J A; Faulkner, J A

    2017-03-01

    The purpose of this double-blind, placebo-controlled study was to examine the effect of two fish oil supplements, one high in EPA (750 mg EPA, 50 mg DHA) and one low in EPA (150 mg EPA, 100 mg DHA), taken acutely as a recovery strategy following EIMD. Twenty-seven physically active males (26 ± 4 year, 1.77 ± 0.07 m, 80 ± 10 kg) completed 100 plyometric drop jumps to induce muscle damage. Perceptual (perceived soreness) and functional (isokinetic muscle strength at 60° and 180° s(-1), squat jump performance and countermovement jump performance) indices of EIMD were recorded before, and 1, 24, 48, 72, and 96h after the damaging protocol. Immediately after the damaging protocol, volunteers ingested either a placebo (Con), a low-EPA fish oil (Low EPA) or a high-EPA fish oil (High EPA) at a dose of 1 g per 10 kg body mass. A significant group main effect was observed for squat jump, with the High EPA group performing better than Con and Low EPA groups (average performance decrement, 2.1, 8.3 and 9.8%, respectively), and similar findings were observed for countermovement jump performance, (average performance decrement, 1.7, 6.8 and 6.8%, respectively, p = 0.07). Significant time, but no interaction main effects were observed for all functional and perceptual indices measured, although large effect sizes demonstrate a possible ameliorating effect of high dose of EPA fish supplementation (effect sizes ≥0.14). This study indicates that an acute dose of high-EPA fish oil may ameliorate the functional changes following EIMD.

  6. Dose-effect relation of interstitial low-dose-rate radiation (Ir192) in an animal tumor model.

    PubMed

    Ruifrok, A C; Levendag, P C; Lakeman, R F; Deurloo, I K; Visser, A G

    1990-01-01

    One way to deliver high doses of radiation to deep seated tumors without damaging the surrounding tissue is by interstitial techniques. This is commonly applied clinically; however, biological data of tumor response to interstitial low-dose-rate gamma irradiation are scarce. Therefore, we have studied the response of rhabdomyosarcoma R1 tumors implanted in the flanks of female Wag/Rij rats using an interstitial Ir192 afterloading system. A template was developed by which four catheters can be implanted in a square geometry with a fixed spacing. Subsequently four Ir192 wires of 2 cm length each are inserted. For dose prescription the highest isodose enveloping the tumor volume was chosen. Interstitial irradiation was performed using tumor volumes of 1500-2000 mm3. A range of minimum tumor doses of 20 up to 115 Gy were given at a mean dose-rate of 48 cGy/hr. Dose-effect relations were obtained from tumor growth curves and tumor cure data, and compared to data from external irradiation. The dose required for 50% cures with interstitial irradiation (TCD50) appears to be 95 +/- 9 Gy. The TCD50 for low-dose-rate interstitial gamma irradiation is 1.5 times the TCD50 for single dose external X ray irradiation at high dose rates, but is comparable to the TCD50 found after fractionated X ray irradiation at high dose rate. Sham treatment of the tumors had no effect on the time needed to reach twice the treatment volume. The growth rate of tumors regrowing after interstitial radiotherapy is not markedly different from the growth rate of untreated (control) tumors (volume doubting time 5.6 +/- 1 day), in contrast to the decreased growth rate after external X ray irradiation. It is argued that the absence of a clear tumor bed effect may be explained by some sparing of the stroma by the low-dose-rate of the interstitial irradiation per se as well as by the physical dose distribution of the interstitial Ir192 sources, giving a relative low dose of radiation to the surrounding

  7. Cardiac effects of standard-dose halofantrine therapy.

    PubMed

    Matson, P A; Luby, S P; Redd, S C; Rolka, H R; Meriwether, R A

    1996-03-01

    The antimalarial drug halofantrine hydrochloride has been associated with cardiac arrhythmias. This is a report of a study on the cardiac effects of standard-dose halofantrine (24 mg/kg) on a sample of 48 patients selected from a group of 402 Dega (Montagnard) refugees treated for Plasmodium falciparum infection. Prolongation of the rate-corrected QT interval (QTc) on the electrocardiogram (ECG) was used as an indicator of risk for halofantrine-associated cardiac arrhythmias. We found that standard-dose halofantrine was associated with a lengthening of the mean QTc from 0.04 sec(1/2) to 0.44 sec(1/2). Two patients had a QTc increase of greater than 25%, but none had a follow-up QTc of more than 0.55 sec(1/2), an interval length generally considered to be a risk factor for ventricular arrhythmias. Regression analysis indicated that pretreatment ECGs were poorly predictive of QTc lengthening during therapy, although pretreatment ECGs may be useful to evaluate patients with pre-existing cardiac conditions. The manufacturer has recommended that the halofantrine dose not exceed 24 mg/kg and revised the list of medication contraindications to include some cardiac conditions. Clinicians should weigh a patient's risk, including history of cardiac disease and availability of alternative therapy before use of halofantrine.

  8. Effects of high-dose isoflavones on rat uterus.

    PubMed

    Carbonel, Adriana Aparecida Ferraz; Simões, Ricardo Santos; Santos, Regiane Helena Barros Rabelo; Baracat, Maria Cândida Pinheiro; Simões, Manuel de Jesus; Baracat, Edmund Chada; Soares Júnior, José Maria

    2011-01-01

    To evaluate the effects of high-dose isoflavones on the uterus of castrated adult rats. Adult, ovariectomized virgin rats (n = 40) were treated by gavage during 30 consecutive days with vehicle (propylene glycol, group GCtrl) or different doses of genistein: 42 (group GES42), 125 (GES125), or 250 (GES250) µg/g body weight per day. Animals were killed, weighed, vaginal and uterine samples were taken for cytologic evaluation, and serum levels of 17 β-estradiol and progesterone were determined. The middle third of the uterine horns was dissected, fixed in 10% formaldehyde and processed for paraffin inclusion; 5-µm thick sections were obtained and stained with HE for further histological study under light microscopy. The endometrial morphology and area, number and area of glands, and number of eosinophils in the lamina propria were analyzed. ANOVA and the Tukey-Kramer test were used for statistical analyses. Uterine weight, endometrial glandular area, and number of glands and eosinophils were all higher in GES250 > G125 than in the other groups (GES250 > GES125 > GES42 = GCtrl; p < 0.05). Morphological data showed signs of endometrial proliferation upon treatment with genistein, especially in animals in GES125 and GES250 compared to other groups. In all animals in GES250, signs of uterine squamous metaplasia were observed. A short treatment period with high daily doses of isoflavones can promote endometrial squamous metaplasia in ovariectomized rats.

  9. Ovarian epithelial dysplasia after ovulation induction: time and dose effects.

    PubMed

    Chene, G; Penault-Llorca, F; Le Bouëdec, G; Mishellany, F; Dauplat, M M; Jaffeux, P; Aublet-Cuvelier, B; Pouly, J L; Dechelotte, P; Dauplat, J

    2009-01-01

    Ovarian epithelial dysplasia was first described after prophylactic oophorectomies for genetic risk. Ovarian stimulation has been considered as a risk factor of ovarian cancer by Fathalla's incessant ovulation theory. In this study, we have investigated the risk of ovarian dysplasia after ovulation induction. We reviewed 99 oophorectomies or cystectomies between 1990 and 2005 divided them into two groups: previous in vitro fertilization (n = 37) and a panel of fertile controls (n = 62). Eleven epithelial cytological and architectural features were defined and an ovarian epithelial dysplasia score was calculated to quantify the degree of ovarian epithelial abnormalities. All the ovaries were macroscopically non-cancerous except in two patients (one endometrioid cancer and one borderline tumour). The mean ovarian dysplasia score was significantly higher in the ovulation induction group than in the control group (7.64 versus 3.62, P = 0.0002). We also found a relationship between the number of ovulation-inducted cycles and the severity of ovarian dysplasia ('dose-effect') and a relationship between time after the end of ovulation induction (over 7 years) and the severity of ovarian dysplasia ('time-effect'). There is probably a relationship between ovarian epithelial dysplasia and either ovulation inducing drugs or infertility. By Fathalla's incessant ovulation theory, 'the dose effect and the time effect' of ovarian stimulation may explain ovarian dysplasia formation.

  10. Dose and dose rate effects of whole-body proton irradiation on leukocyte populations and lymphoid organs: part I

    NASA Technical Reports Server (NTRS)

    Gridley, Daila S.; Pecaut, Michael J.; Dutta-Roy, Radha; Nelson, Gregory A.

    2002-01-01

    The goal of part I of this study was to evaluate the effects of whole-body proton irradiation on lymphoid organs and specific leukocyte populations. C57BL/6 mice were exposed to the entry region of the proton Bragg curve to total doses of 0.5 gray (Gy), 1.5 Gy, and 3.0 Gy, each delivered at a low dose rate (LDR) of 1 cGy/min and high dose rate (HDR) of 80 cGy/min. Non-irradiated and 3 Gy HDR gamma-irradiated groups were included as controls. At 4 days post-irradiation, highly significant radiation dose-dependent reductions were observed in the mass of both lymphoid organs and the numbers of leukocytes and T (CD3(+)), T helper (CD3(+)/CD4(+)), T cytotoxic (CD3(+)/CD8(+)), and B (CD19(+)) cells in both blood and spleen. A less pronounced dose effect was noted for natural killer (NK1.1(+) NK) cells in spleen. Monocyte, but not granulocyte, counts in blood were highly dose-dependent. The numbers for each population generally tended to be lower with HDR than with LDR radiation; a significant dose rate effect was found in the percentages of T and B cells, monocytes, and granulocytes and in CD4(+):CD8(+) ratios. These data indicate that mononuclear cell response to the entry region of the proton Bragg curve is highly dependent upon the total dose and that dose rate effects are evident with some cell types. Results from gamma- and proton-irradiated groups (both at 3 Gy HDR) were similar, although proton-irradiation gave consistently lower values in some measurements.

  11. Dose and dose rate effects of whole-body proton irradiation on leukocyte populations and lymphoid organs: part I

    NASA Technical Reports Server (NTRS)

    Gridley, Daila S.; Pecaut, Michael J.; Dutta-Roy, Radha; Nelson, Gregory A.

    2002-01-01

    The goal of part I of this study was to evaluate the effects of whole-body proton irradiation on lymphoid organs and specific leukocyte populations. C57BL/6 mice were exposed to the entry region of the proton Bragg curve to total doses of 0.5 gray (Gy), 1.5 Gy, and 3.0 Gy, each delivered at a low dose rate (LDR) of 1 cGy/min and high dose rate (HDR) of 80 cGy/min. Non-irradiated and 3 Gy HDR gamma-irradiated groups were included as controls. At 4 days post-irradiation, highly significant radiation dose-dependent reductions were observed in the mass of both lymphoid organs and the numbers of leukocytes and T (CD3(+)), T helper (CD3(+)/CD4(+)), T cytotoxic (CD3(+)/CD8(+)), and B (CD19(+)) cells in both blood and spleen. A less pronounced dose effect was noted for natural killer (NK1.1(+) NK) cells in spleen. Monocyte, but not granulocyte, counts in blood were highly dose-dependent. The numbers for each population generally tended to be lower with HDR than with LDR radiation; a significant dose rate effect was found in the percentages of T and B cells, monocytes, and granulocytes and in CD4(+):CD8(+) ratios. These data indicate that mononuclear cell response to the entry region of the proton Bragg curve is highly dependent upon the total dose and that dose rate effects are evident with some cell types. Results from gamma- and proton-irradiated groups (both at 3 Gy HDR) were similar, although proton-irradiation gave consistently lower values in some measurements.

  12. Reinforcing, subject-rated, and physiological effects of intranasal methylphenidate in humans: a dose-response analysis.

    PubMed

    Stoops, William W; Glaser, Paul E A; Rush, Craig R

    2003-08-20

    The results of previously published reports suggest that oral methylphenidate has potential for abuse. An increase in insufflation of methylphenidate has been reported recently. To our knowledge, however, there are no published reports that examined the effects of intranasal methylphenidate. The purpose of this experiment was to characterize the reinforcing, subject-rated, and physiological effects of intranasal methylphenidate (0, 10, 20, and 30 mg). Eight volunteers (five males and three females) with recent histories of recreational stimulant use were recruited to participate in this experiment. Drug doses were administered in a double-blind fashion under medical supervision, but for safety purposes they were administered in ascending order. Intranasal methylphenidate increased the crossover point on the Multiple-Choice Questionnaire in a linear fashion, which suggests that intranasal methylphenidate functioned as a reinforcer. Intranasal methylphenidate also produced linear dose-dependent prototypical stimulant-like subjective effects (e.g. increases in ratings of Good Effects and High). Intranasal methylphenidate increased heart rate as a function of dose, but the magnitude of this effect was not clinically significant (i.e. average peak heart rate following administration of the highest dose was less than 82 beats per min). The results of this study suggest that across a range of doses, intranasal methylphenidate produces behavioral effects that are characteristic of abused stimulants. Future studies should test higher doses and directly compare the behavioral effects of intranasal methylphenidate to those of a prototypical abused stimulant (e.g. cocaine).

  13. Evaluation of organ doses and specific k effective dose of 64-slice CT thorax examination using an adult anthropomorphic phantom

    NASA Astrophysics Data System (ADS)

    Hashim, S.; Karim, M. K. A.; Bakar, K. A.; Sabarudin, A.; Chin, A. W.; Saripan, M. I.; Bradley, D. A.

    2016-09-01

    The magnitude of radiation dose in computed tomography (CT) depends on the scan acquisition parameters, investigated herein using an anthropomorphic phantom (RANDO®) and thermoluminescence dosimeters (TLD). Specific interest was in the organ doses resulting from CT thorax examination, the specific k coefficient for effective dose estimation for particular protocols also being determined. For measurement of doses representing five main organs (thyroid, lung, liver, esophagus and skin), TLD-100 (LiF:Mg, Ti) were inserted into selected holes in a phantom slab. Five CT thorax protocols were investigated, one routine (R1) and four that were modified protocols (R2 to R5). Organ doses were ranked from greatest to least, found to lie in the order: thyroid>skin>lung>liver>breast. The greatest dose, for thyroid at 25 mGy, was that in use of R1 while the lowest, at 8.8 mGy, was in breast tissue using R3. Effective dose (E) was estimated using three standard methods: the International Commission on Radiological Protection (ICRP)-103 recommendation (E103), the computational phantom CT-EXPO (E(CTEXPO)) method, and the dose-length product (DLP) based approach. E103 k factors were constant for all protocols, ~8% less than that of the universal k factor. Due to inconsistency in tube potential and pitch factor the k factors from CTEXPO were found to vary between 0.015 and 0.010 for protocols R3 and R5. With considerable variation between scan acquisition parameters and organ doses, optimization of practice is necessary in order to reduce patient organ dose.

  14. Radiation dose during CT-guided percutaneous cryoablation of renal tumors: Effect of a dose reduction protocol.

    PubMed

    Levesque, Vincent M; Shyn, Paul B; Tuncali, Kemal; Tatli, Servet; Nawfel, Richard D; Olubiyi, Olutayo; Silverman, Stuart G

    2015-11-01

    To estimate and compare the radiation dose using a standard protocol and that of a dose reduction protocol in patients undergoing CT-guided percutaneous cryoablation of renal tumors. An IRB-approved, HIPAA-compliant retrospective study of 97 CT-guided cryoablation procedures to treat a solitary renal tumor in each of 97 patients (64 M, 33 F; range 31-84 yrs) was performed. Fifty patients were treated using a standard dose protocol (kVp=120, mean mAs=180, monitoring scans every 3 min during freezes), and an additional 47 patients were treated using a dose reduction protocol (kVp=100, mean mAs=100, monitoring scans less frequently than every 3 min during freezes). Multiple Wilcoxon Mann-Whitney (rank-sum) tests were used to compare dose-length product (DLP) between the two groups. Fisher's exact test was used to compare technique effectiveness at 12 months post ablation between the two groups. Median DLP for the standard protocol group was 4833.5 mGy*cm (range, 1667-8267 mGy*cm); median DLP for the dose reduction group was 2648 mGy*cm (range, 850-7169 mGy*cm), significantly less than that of the standard protocol group (p<0.01). The technique effectiveness for the dose reduction group was not significantly different from that of the standard protocol group at 12 month follow up (p=0.434). The radiation dose during percutaneous CT-guided cryoablation of renal tumors was substantial in both the standard and the dose reduction groups; however, it was significantly lower with the protocol change that reduced dose parameters and decreased the number of CT scans. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

  15. Effects of single-dose and fractionated cranial irradiation on rat brain accumulation of methotrexate

    SciTech Connect

    Kamen, B.A.; Moulder, J.E.; Kun, L.E.; Ring, B.J.; Adams, S.M.; Fish, B.L.; Holcenberg, J.S.

    1984-11-01

    The effects of single-dose and fractionated whole-brain irradiation on brain methotrexate (MTX) has been studied in a rat model. The amount of MTX present in the brain 24 hr after a single i.p. dose (100 mg/kg) was the same whether animals were sham irradiated or given a single dose of 2000 rads 6 or 48 hr prior to the drug (6.9, 8.3, and 6.8 pmol MTX/g, wet weight, respectively). Animals sham irradiated or given 2000 rads in 10 fractions over 11 days and treated with an average dose of 1.2 mg MTX/kg i.p. twice a week for 24 weeks did not differ significantly in their brain MTX concentration (7.9 and 8.3 pmol MTX/g, wet weight, respectively). Chronically MTX-treated animals became folate deficient whether they were irradiated or not (450 and 670 pmol folate/g, wet weight, brain in MTX-treated and control animals). Thus, MTX accumulates in the brain with acute or chronic administration, and this accumulation is not altered by this amount of brain irradiation.

  16. Effective doses of cisatracurium in the adult and the elderly

    PubMed Central

    Lee, Yoon Chan; Lee, Soo Il; Park, Sang Yoong; Choi, So Ron; Lee, Jong Hwan; Chung, Chan Jong

    2016-01-01

    Background There are few information about the differences of the effective dose (ED) of cisatracurium between the adult and the elderly. We investigated the ED and the onset time of cisatracurium in the adults and the elderly. Methods We studied two hundred patients of the adults aged 20 through 64 years and the elderly aged ≥ 65 years, with American Society of Anesthesiologists physical status I or II. Each 100 patients with 20 patients of each dose group, randomly selected from 30, 40, 50, 60 or 70 µg/kg of cisatracurium, were randomly allocated to the adults and the elderly groups. We recorded the 0.1 Hz single twitch responses of the adductor pollicis and the onset times to maximal blockade. The magnitude of muscle relaxation was recorded by using an acceleromyography. The effect of cisatracurium on single twitch was calculated as percent reduction. After converting each drug dose into logarithm and percent reduction of the muscle reduction into probit, the EDs representing the muscle relaxation effects of 5%, 25%, 50%, 75% and 95% were estimated using the linear regression analysis. Results No significant differences were found in age, weight, height, or body mass index within or between the groups. The ED50 and ED95 of the adult group were 35.39 and 59.58 µg/kg. The ED50 and ED95 of the elderly group were 34.89 and 55.50 µg/kg, respectively. The onset times were 375.4 ± 76.9 seconds in the adult group and 369.1 ± 70.0 seconds in the elderly group. Conclusions The ED and the onset time were not significantly different between the adult and the elderly. PMID:27703625

  17. Radiation Dose-Volume Effects of Optic Nerves and Chiasm

    SciTech Connect

    Mayo, Charles; Martel, Mary K.; Marks, Lawrence B.; Flickinger, John; Nam, Jiho; Kirkpatrick, John

    2010-03-01

    Publications relating radiation toxicity of the optic nerves and chiasm to quantitative dose and dose-volume measures were reviewed. Few studies have adequate data for dose-volume outcome modeling. The risk of toxicity increased markedly at doses >60 Gy at {approx}1.8 Gy/fraction and at >12 Gy for single-fraction radiosurgery. The evidence is strong that radiation tolerance is increased with a reduction in the dose per fraction. Models of threshold tolerance were examined.

  18. Effectiveness and safety of adjustable maintenance dosing with budesonide/formoterol turbuhaler compared with traditional fixed doses in bronchial asthma: a multi-centre Nigerian study.

    PubMed

    Ige, O M; Ohaju-Obodo, J O; Chukwu, C; Peters, E J; Okpapi, J; Chukwuka, C

    2010-09-01

    patients in the adjustable groups used less number of inhalations of budesonide/formoterol for treatment on average of 2.5 inhalations per day compared to those on fixed dosing who used 4 inhalations per day (p = 0.0001). The number of times patients stayed awake because of asthma was noticed to be more reduced at the adjustable arm of treatment but this was of no statistical significance. It is therefore concluded, that budesonide/formoterol combination in a single inhaler is a simple, well tolerated, convenient treatment which provides effective control of bronchial asthma using a practical self-management plan consistent with current guidelines.

  19. Ventilatory effects of low-dose paraoxon result from central muscarinic effects

    SciTech Connect

    Houze, Pascal; Pronzola, Laetita; Kayouka, Maya; Villa, Antoine; Debray, Marcel; Baud, Frederic J.

    2008-12-01

    Paraoxon induces respiratory toxicity. Atropine completely reversed parathion- and paraoxon-induced respiratory toxicity. The aim of this study was to assess the peripheral or central origin of ventilatory effects of low-dose paraoxon. Male Sprague-Dawley rats were given paraoxon 0.215 mg/kg subcutaneously and treated with either atropine (10 mg/kg sc) or ascending doses of methylatropine of 5.42 (equimolar to that of atropine), 54.2, and 542 mg/kg administered subcutaneously 30 min after paraoxon. Ventilation at rest was assessed using whole-body plethysmography and rat temperature using infra-red telemetry. Results are expressed as mean {+-} SE. Statistical analysis used two-way ANOVA for repeated measurements. Paraoxon induced a significant decrease in temperature 30 min after injection lasting the 90 min of the study period. This effect was partially corrected by atropine, but not by methylatropine whatever the dose. Paraoxon induced a decrease in respiratory rate resulting from an increase in expiratory time associated with an increase in tidal volume. Atropine completely reversed the ventilatory effects of low-dose paraoxon while the equimolar dose of methylatropine had no significant effects. The 54.2 and 542 mg/kg doses of methylatropine had no significant effects. Atropine crosses the blood-brain barrier and reverses peripheral and central muscarinic effects. In contrast, methylatropine does not cross the blood-brain barrier. Atropine completely reversed the ventilatory effects of low-dose paraoxon, while methylatropine had no significant effects at doses up to 100-fold the equimolar dose of atropine. We conclude that the ventilatory effects of low-dose paraoxon are mediated by disrupted muscarinic signaling in the central nervous system.

  20. Influence of organs in the ICRP's remainder on effective dose equivalent computed for diagnostic radiation exposures

    SciTech Connect

    Gibbs, S.J.

    1989-04-01

    The ICRP effective dose equivalent has been compared with a weighted dose equivalent, computed by treating the entire remainder instead of the sample of five remainder organs in the ICRP method as uniformly radiosensitive, for dose distributions from three common diagnostic exposures: chest, dental full-mouth and dental panoramic. Complete dose distributions were computed by a Monte Carlo model. In all three cases the effective dose equivalent was greater than the weighted dose equivalent. The difference was only 20% for the chest exam but was more than fivefold for both dental exposures. Dose distributions for the dental exposures were less homogeneous than for the chest examination. Selection of organs to be included in the remainder markedly affects the effective dose equivalent. In the case of highly inhomogeneous dose distributions, the effective dose equivalent probably significantly over-estimates radiation detriment.

  1. Development of an effective dose coefficient database using a computational human phantom and Monte Carlo simulations to evaluate exposure dose for the usage of NORM-added consumer products.

    PubMed

    Yoo, Do Hyeon; Shin, Wook-Geun; Lee, Jaekook; Yeom, Yeon Soo; Kim, Chan Hyeong; Chang, Byung-Uck; Min, Chul Hee

    2017-11-01

    After the Fukushima accident in Japan, the Korean Government implemented the "Act on Protective Action Guidelines Against Radiation in the Natural Environment" to regulate unnecessary radiation exposure to the public. However, despite the law which came into effect in July 2012, an appropriate method to evaluate the equivalent and effective doses from naturally occurring radioactive material (NORM) in consumer products is not available. The aim of the present study is to develop and validate an effective dose coefficient database enabling the simple and correct evaluation of the effective dose due to the usage of NORM-added consumer products. To construct the database, we used a skin source method with a computational human phantom and Monte Carlo (MC) simulation. For the validation, the effective dose was compared between the database using interpolation method and the original MC method. Our result showed a similar equivalent dose across the 26 organs and a corresponding average dose between the database and the MC calculations of < 5% difference. The differences in the effective doses were even less, and the result generally show that equivalent and effective doses can be quickly calculated with the database with sufficient accuracy. Copyright © 2017 Elsevier Ltd. All rights reserved.

  2. Effect of particulate adjuvant on the anthrax protective antigen dose required for effective nasal vaccination.

    PubMed

    Bento, Dulce; Staats, Herman F; Borges, Olga

    2015-07-17

    Successful vaccine development is dependent on the development of effective adjuvants since the poor immunogenicity of modern subunit vaccines typically requires the use of potent adjuvants and high antigen doses. In recent years, adjuvant formulations combining both immunopotentiators and delivery systems have emerged as a promising strategy to develop effective and improved vaccines. In this study we investigate if the association of the mast cell activating adjuvant compound 48/80 (C48/80) with chitosan nanoparticles would promote an antigen dose sparing effect when administered intranasally. Even though the induction of strong mucosal immunity required higher antigen doses, incorporation of C48/80 into nanoparticles provided significant dose sparing when compared to antigen and C48/80 in solution with no significant effect on serum neutralizing antibodies titers. These results suggest the potential of this novel adjuvant combination to improve the immunogenicity of a vaccine and decrease the antigen dose required for vaccination.

  3. Mechanistic Basis for Nonlinear Dose-Response Relationships for Low-Dose Radiation-Induced Stochastic Effects

    PubMed Central

    Scott, Bobby R.; Walker, Dale M.; Tesfaigzi, Yohannes; Schöllnberger, Helmut; Walker, Vernon

    2003-01-01

    The linear nonthreshold (LNT) model plays a central role in low-dose radiation risk assessment for humans. With the LNT model, any radiation exposure is assumed to increase one’s risk of cancer. Based on the LNT model, others have predicted tens of thousands of deaths related to environmental exposure to radioactive material from nuclear accidents (e.g., Chernobyl) and fallout from nuclear weapons testing. Here, we introduce a mechanism-based model for low-dose, radiation-induced, stochastic effects (genomic instability, apoptosis, mutations, neoplastic transformation) that leads to a LNT relationship between the risk for neoplastic transformation and dose only in special cases. It is shown that nonlinear dose-response relationships for risk of stochastic effects (problematic nonlethal mutations, neoplastic transformation) should be expected based on known biological mechanisms. Further, for low-dose, low-dose rate, low-LET radiation, large thresholds may exist for cancer induction. We summarize previously published data demonstrating large thresholds for cancer induction. We also provide evidence for low-dose-radiation-induced, protection (assumed via apoptosis) from neoplastic transformation. We speculate based on work of others (Chung 2002) that such protection may also be induced to operate on existing cancer cells and may be amplified by apoptosis-inducing agents such as dietary isothiocyanates. PMID:19330114

  4. A novel convolution-based approach to address ionization chamber volume averaging effect in model-based tre