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1

Polymer gel dosimetry.  

PubMed

Polymer gel dosimeters are fabricated from radiation sensitive chemicals which, upon irradiation, polymerize as a function of the absorbed radiation dose. These gel dosimeters, with the capacity to uniquely record the radiation dose distribution in three-dimensions (3D), have specific advantages when compared to one-dimensional dosimeters, such as ion chambers, and two-dimensional dosimeters, such as film. These advantages are particularly significant in dosimetry situations where steep dose gradients exist such as in intensity-modulated radiation therapy (IMRT) and stereotactic radiosurgery. Polymer gel dosimeters also have specific advantages for brachytherapy dosimetry. Potential dosimetry applications include those for low-energy x-rays, high-linear energy transfer (LET) and proton therapy, radionuclide and boron capture neutron therapy dosimetries. These 3D dosimeters are radiologically soft-tissue equivalent with properties that may be modified depending on the application. The 3D radiation dose distribution in polymer gel dosimeters may be imaged using magnetic resonance imaging (MRI), optical-computerized tomography (optical-CT), x-ray CT or ultrasound. The fundamental science underpinning polymer gel dosimetry is reviewed along with the various evaluation techniques. Clinical dosimetry applications of polymer gel dosimetry are also presented. PMID:20150687

Baldock, C; De Deene, Y; Doran, S; Ibbott, G; Jirasek, A; Lepage, M; McAuley, K B; Oldham, M; Schreiner, L J

2010-03-01

2

TOPICAL REVIEW: Polymer gel dosimetry  

NASA Astrophysics Data System (ADS)

Polymer gel dosimeters are fabricated from radiation sensitive chemicals which, upon irradiation, polymerize as a function of the absorbed radiation dose. These gel dosimeters, with the capacity to uniquely record the radiation dose distribution in three-dimensions (3D), have specific advantages when compared to one-dimensional dosimeters, such as ion chambers, and two-dimensional dosimeters, such as film. These advantages are particularly significant in dosimetry situations where steep dose gradients exist such as in intensity-modulated radiation therapy (IMRT) and stereotactic radiosurgery. Polymer gel dosimeters also have specific advantages for brachytherapy dosimetry. Potential dosimetry applications include those for low-energy x-rays, high-linear energy transfer (LET) and proton therapy, radionuclide and boron capture neutron therapy dosimetries. These 3D dosimeters are radiologically soft-tissue equivalent with properties that may be modified depending on the application. The 3D radiation dose distribution in polymer gel dosimeters may be imaged using magnetic resonance imaging (MRI), optical-computerized tomography (optical-CT), x-ray CT or ultrasound. The fundamental science underpinning polymer gel dosimetry is reviewed along with the various evaluation techniques. Clinical dosimetry applications of polymer gel dosimetry are also presented.

Baldock, C.; De Deene, Y.; Doran, S.; Ibbott, G.; Jirasek, A.; Lepage, M.; McAuley, K. B.; Oldham, M.; Schreiner, L. J.

2010-03-01

3

Topical Review: Polymer gel dosimetry  

PubMed Central

Polymer gel dosimeters are fabricated from radiation sensitive chemicals which, upon irradiation, polymerize as a function of the absorbed radiation dose. These gel dosimeters, with the capacity to uniquely record the radiation dose distribution in three-dimensions (3D), have specific advantages when compared to one-dimensional dosimeters, such as ion chambers, and two-dimensional dosimeters, such as film. These advantages are particularly significant in dosimetry situations where steep dose gradients exist such as in intensity-modulated radiation therapy (IMRT) and stereotactic radiosurgery. Polymer gel dosimeters also have specific advantages for brachytherapy dosimetry. Potential dosimetry applications include those for low-energy x-rays, high-linear energy transfer (LET) and proton therapy, radionuclide and boron capture neutron therapy dosimetries. These 3D dosimeters are radiologically soft-tissue equivalent with properties that may be modified depending on the application. The 3D radiation dose distribution in polymer gel dosimeters may be imaged using magnetic resonance imaging (MRI), optical-computerized tomography (optical-CT), x-ray CT or ultrasound. The fundamental science underpinning polymer gel dosimetry is reviewed along with the various evaluation techniques. Clinical dosimetry applications of polymer gel dosimetry are also presented. PMID:20150687

Baldock, C; De Deene, Y; Doran, S; Ibbott, G; Jirasek, A; Lepage, M; McAuley, K B; Oldham, M; Schreiner, L J

2010-01-01

4

Research software for radiotherapy gel dosimetry.  

PubMed

Gel dosimetry using magnetic resonance imaging is a technique which allows measurement of three-dimensional absorbed dose distributions in radiation therapy. This paper presents details of a software tool written specifically to provide facilities to perform image processing required in research and development of gel dosimetry. Collections of magnetic resonance images can be converted into either longitudinal or transverse nuclear magnetic resonance relaxation images. The conversions are accomplished by means of a pixel-by-pixel non-linear least squares fitting algorithm. Adjustments can be made to the number of parameters used in the fitting algorithm. Fundamental image manipulation tools such as window width/level display adjustment, zooming, profile and region of interest tools are provided. The software has been developed using MATLAB (The MathWorks Inc., Natick, MA) running on Windows 95. User interaction is via a windows graphical user interface (GUI). Data such as statistics from regions of interest can be exported to other windows applications for further processing. Flexibility is incorporated in the GUI design by taking advantage of the developmental aspects of the MATLAB environment. Although originally designed for gel dosimetry, the software can be used in any application of MRI which requires production and manipulation of relaxation time images. PMID:10979593

Murry, P; Baldock, C

2000-06-01

5

Uncertainty in 3D gel dosimetry  

NASA Astrophysics Data System (ADS)

Three-dimensional (3D) gel dosimetry has a unique role to play in safeguarding conformal radiotherapy treatments as the technique can cover the full treatment chain and provides the radiation oncologist with the integrated dose distribution in 3D. It can also be applied to benchmark new treatment strategies such as image guided and tracking radiotherapy techniques. A major obstacle that has hindered the wider dissemination of gel dosimetry in radiotherapy centres is a lack of confidence in the reliability of the measured dose distribution. Uncertainties in 3D dosimeters are attributed to both dosimeter properties and scanning performance. In polymer gel dosimetry with MRI readout, discrepancies in dose response of large polymer gel dosimeters versus small calibration phantoms have been reported which can lead to significant inaccuracies in the dose maps. The sources of error in polymer gel dosimetry with MRI readout are well understood and it has been demonstrated that with a carefully designed scanning protocol, the overall uncertainty in absolute dose that can currently be obtained falls within 5% on an individual voxel basis, for a minimum voxel size of 5 mm3. However, several research groups have chosen to use polymer gel dosimetry in a relative manner by normalizing the dose distribution towards an internal reference dose within the gel dosimeter phantom. 3D dosimetry with optical scanning has also been mostly applied in a relative way, although in principle absolute calibration is possible. As the optical absorption in 3D dosimeters is less dependent on temperature it can be expected that the achievable accuracy is higher with optical CT. The precision in optical scanning of 3D dosimeters depends to a large extend on the performance of the detector. 3D dosimetry with X-ray CT readout is a low contrast imaging modality for polymer gel dosimetry. Sources of error in x-ray CT polymer gel dosimetry (XCT) are currently under investigation and include inherent limitations in dosimeter homogeneity, imaging performance, and errors induced through post-acquisition processing. This overview highlights a number of aspects relating to uncertainties in polymer gel dosimetry.

De Deene, Yves; Jirasek, Andrew

2015-01-01

6

Evaluation of radiochromic gel dosimetry and polymer gel dosimetry in a clinical dose verification.  

PubMed

A quantitative comparison of two full three-dimensional (3D) gel dosimetry techniques was assessed in a clinical setting: radiochromic gel dosimetry with an in-house developed optical laser CT scanner and polymer gel dosimetry with magnetic resonance imaging (MRI). To benchmark both gel dosimeters, they were exposed to a 6 MV photon beam and the depth dose was compared against a diamond detector measurement that served as golden standard. Both gel dosimeters were found accurate within 4% accuracy. In the 3D dose matrix of the radiochromic gel, hotspot dose deviations up to 8% were observed which are attributed to the fabrication procedure. The polymer gel readout was shown to be sensitive to B0 field and B1 field non-uniformities as well as temperature variations during scanning. The performance of the two gel dosimeters was also evaluated for a brain tumour IMRT treatment. Both gel measured dose distributions were compared against treatment planning system predicted dose maps which were validated independently with ion chamber measurements and portal dosimetry. In the radiochromic gel measurement, two sources of deviations could be identified. Firstly, the dose in a cluster of voxels near the edge of the phantom deviated from the planned dose. Secondly, the presence of dose hotspots in the order of 10% related to inhomogeneities in the gel limit the clinical acceptance of this dosimetry technique. Based on the results of the micelle gel dosimeter prototype presented here, chemical optimization will be subject of future work. Polymer gel dosimetry is capable of measuring the absolute dose in the whole 3D volume within 5% accuracy. A temperature stabilization technique is incorporated to increase the accuracy during short measurements, however keeping the temperature stable during long measurement times in both calibration phantoms and the volumetric phantom is more challenging. The sensitivity of MRI readout to minimal temperature fluctuations is demonstrated which proves the need for adequate compensation strategies. PMID:23965800

Vandecasteele, Jan; De Deene, Yves

2013-09-21

7

Evaluation of radiochromic gel dosimetry and polymer gel dosimetry in a clinical dose verification  

NASA Astrophysics Data System (ADS)

A quantitative comparison of two full three-dimensional (3D) gel dosimetry techniques was assessed in a clinical setting: radiochromic gel dosimetry with an in-house developed optical laser CT scanner and polymer gel dosimetry with magnetic resonance imaging (MRI). To benchmark both gel dosimeters, they were exposed to a 6 MV photon beam and the depth dose was compared against a diamond detector measurement that served as golden standard. Both gel dosimeters were found accurate within 4% accuracy. In the 3D dose matrix of the radiochromic gel, hotspot dose deviations up to 8% were observed which are attributed to the fabrication procedure. The polymer gel readout was shown to be sensitive to B0 field and B1 field non-uniformities as well as temperature variations during scanning. The performance of the two gel dosimeters was also evaluated for a brain tumour IMRT treatment. Both gel measured dose distributions were compared against treatment planning system predicted dose maps which were validated independently with ion chamber measurements and portal dosimetry. In the radiochromic gel measurement, two sources of deviations could be identified. Firstly, the dose in a cluster of voxels near the edge of the phantom deviated from the planned dose. Secondly, the presence of dose hotspots in the order of 10% related to inhomogeneities in the gel limit the clinical acceptance of this dosimetry technique. Based on the results of the micelle gel dosimeter prototype presented here, chemical optimization will be subject of future work. Polymer gel dosimetry is capable of measuring the absolute dose in the whole 3D volume within 5% accuracy. A temperature stabilization technique is incorporated to increase the accuracy during short measurements, however keeping the temperature stable during long measurement times in both calibration phantoms and the volumetric phantom is more challenging. The sensitivity of MRI readout to minimal temperature fluctuations is demonstrated which proves the need for adequate compensation strategies.

Vandecasteele, Jan; De Deene, Yves

2013-09-01

8

Magnetization transfer imaging for polymer gel dosimetry  

NASA Astrophysics Data System (ADS)

Off-resonance RF pre-saturation was used to obtain contrast in MRI images of polymer gel dosimeters irradiated to doses up to 50 Gy. Two different polymer gel dosimeters composed of 2-hydroxyethyl-acrylate or methacrylic acid monomers mixed with N, N'-methylene-bisacrylamide (BIS), dispersed in an aqueous gelatin matrix were evaluated. Radiation-induced polymerization of the co-monomers generates a fast-relaxing insoluble polymer. Saturation of the polymer using off-resonance Gaussian RF pulses prior to a spin-echo read-out with a short echo time leads to contrast that is dependent on the absorbed dose. This contrast is attributed to magnetization transfer (MT) between free water and the polymer, and direct saturation of water was found to be negligible under the prevailing experimental conditions. The usefulness of MT imaging was assessed by computing the dose resolution obtained with this technique. We found a low value of dose resolution over a wide range of doses could be obtained with a single experiment. This is an advantage over multiple spin echo (MSE) experiments using a single echo spacing where an optimal dose resolution is achieved over only very limited ranges of doses. The results suggest MT imaging protocols may be developed into a useful tool for polymer gel dosimetry.

Lepage, M.; McMahon, K.; Galloway, G. J.; DeDeene, Y.; Bäck, S. Å. J.; Baldock, C.

2002-06-01

9

Laser microbeam CT scanning of dosimetry gels  

NASA Astrophysics Data System (ADS)

A novel design of an optical tomographic scanner is described that can be used for 3D mapping of optical attenuation coefficient within translucent cylindrical objects with spatial resolution on the order of 100 microns. Our scanner design utilizes the cylindrical geometry of the imaged object to obtain the desired paths of the scanning light rays. A rotating mirror and a photodetector are placed at two opposite foci of the translucent cylinder that acts as a cylindrical lens. A He-Ne laser beam passes first through a focusing lens and then is reflected by the rotating mirror, so as to scan the interior of the cylinder with focused and parallel paraxial rays that are subsequently collected by the photodetector to produce the projection data, as the cylinder rotates in small angle increments between projections. Filtered backprojection is then used to reconstruct planar distributions of optical attenuation coefficient in the cylinder. Multiplanar scans are used to obtain a complete 3D tomographic reconstruction. Among other applications, the scanner can be used in radiation therapy dosimetry and quality assurance for mapping 3D radiation dose distributions in various types of tissue-equivalent gel phantoms that change their optical attenuation coefficients in proportion to the absorbed radiation dose.

Maryanski, Marek J.; Ranade, Manisha K.

2001-06-01

10

Further developments and applications of layer gel dosimetry  

Microsoft Academic Search

The method used to perform dosimetry with Fricke-xylenol orange-infused gels in form of layers remains the most reliable method for in-phantom dose profiling and imaging in high fluxes of thermal and epithermal neutrons. Gel-dosimeters in form of layers really give the possibility not only of obtaining spatial dose distributions but also of achieving measurements of each dose contribution in neutron

G. Gambarini; M. Carrara; V. Colli; S. Gay; S. Tomatis

2004-01-01

11

Investigations in x-ray computed tomography polyacrylamide gel dosimetry  

SciTech Connect

Polyacrylamide gels (PAGs) are radiosensitive materials currently under development for use as three-dimensional (3D) dosimeters in radiation therapy. Dose information is recorded in the gels and extracted through imaging. X-ray computed tomography (CT) has emerged as a promising gel imaging method due to a change in gel density that occurs upon irradiation. The accessibility of CT technology to cancer hospitals makes CT read out clinically attractive; however, the technique remains of limited clinical use due in part to poor dose resolution. This thesis investigates the use of CT for extracting dose information from PAGs with an overall goal of improving achievable dose resolution. Thesis results are divided into three studies: a gel-compositional study, a study of noise and dose resolution, and a digital filtering study. The first study investigates the effects of gel composition on PAG CT dose response and the underlying density change. Results indicate dramatic variation in CT dose response sensitivity and range with gel composition. A model is developed to describe gel density change with dose, revealing two fundamental properties of the density to dose response: the density change per unit polymer yield is highest for gels with low and high concentrations of crosslinking molecules, and dose response sensitivity is linearly dependent on the total concentration of monomers in the gel. The second study investigates strategies for minimizing noise in CT polymer gel dosimetry and assesses system performance. Specifically, the effects of phantom design, scanning technique, and voxel size on image noise are investigated and the effect of scanning protocol on imaging time is established. The dose resolution achievable with an optimized system is then calculated, given voxel size and imaging time constraints, and compared with published values for magnetic resonance imaging (MRI) and optical CT gel dosimetry. The third study investigates the potential of image filtering for improved dose resolution in CT gel dosimetry. CT image noise is characterized and appropriate filters are tested on a CT image of a PAG irradiated with a clinically relevant dose distribution. Filter performance is found to vary dramatically, with the best filters more than halving the dose resolution without significantly distorting the spatial distribution of dose. In summary, this thesis provides insight into the fundamental nature of PAG density to dose response, develops strategies for minimizing image noise, quantifies system performance, and demonstrates that digital image filtering is an effective tool to provide additional improvements to dose resolution.

Hilts, Michelle [Physics and Astronomy, University of British Columbia, British Columbia, Canada and Medical Physics, BC Cancer Agency, Vancouver Centre, British Columbia (Canada)]. E-mail: mhilts@bccancer.bc.ca

2005-09-15

12

Particle size analysis of PAGAT gel dosimetry  

NASA Astrophysics Data System (ADS)

This work represents the response of PAGAT gel dosimeter using UV-Visible Spectrophotometry. The particle size and optimal wavelength of the gel sample were analyzed from the obtained spectrum. In addition, the compressibility was estimated using Ultrasonic Interferometer. The results showed that the particle size of the PAGAT varied appreciably with respect to the dose applied but did not vary significantly with the post irradiation time.

Samuel, E. J. J.; Sathiyaraj, P.; Titus, D.; Kumar, D. S.

2015-01-01

13

Implementation of an efficient workflow process for gel dosimetry using 3D Slicer  

NASA Astrophysics Data System (ADS)

One challenge in gel dosimetry is the manipulation and analysis of complex data sets from different systems. In this paper, we describe a simple and fast gel dosimetry analysis tool for radiation therapy dose deliveries. Using the open source medical imaging software 3D Slicer, an extension was designed and implemented for the purpose of importing treatment planning system dose, CT imaging from simulation and at treatment, and optical CT gel dosimeter data. The extension also allows for calibration of gel dosimeter data, registration, and comparison of 3D dose distributions. The development of an open source gel dosimetry processing environment may help adoption of gels in the clinic.

Alexander, K. M.; Pinter, C.; Andrea, J.; Fichtinger, G.; Schreiner, L. J.

2015-01-01

14

An x-ray CT polymer gel dosimetry prototype: II. Gel characterization and clinical application  

NASA Astrophysics Data System (ADS)

This article reports on the dosimetric properties of a new N-isopropylacrylamide, high %T, polymer gel formulation (19.5%T, 23%C), optimized for x-ray computed tomography (CT) polymer gel dosimetry (PGD). In addition, a new gel calibration technique is introduced together with an intensity-modulated radiation therapy (IMRT) treatment validation as an example of a clinical application of the new gel dosimeter. The dosimetric properties investigated include the temporal stability, spatial stability, batch reproducibility and dose rate dependence. The polymerization reaction is found to stabilize after 15 h post-irradiation. Spatial stability investigations reveal a small overshoot in response for gels imaged later than 36 h post-irradiation. Based on these findings, it is recommended that the new gel formulation be imaged between 15-36 h after irradiation. Intra- and inter-batch reproducibility are found to be excellent over the entire range of doses studied (0-28 Gy). A significant dose rate dependence is found for gels irradiated between 100-600 MU?min-1. Overall, the new gel is shown to have promising characteristics for CT PGD, however the implication of the observed dose rate dependence for some clinical applications remains to be determined. The new gel calibration method, based on pixel-by-pixel matching of dose and measured CT numbers, is found to be robust and to agree with the previously used region of interest technique. Pixel-by-pixel calibration is the new recommended standard for CT PGD. The dose resolution for the system was excellent, ranging from 0.2-0.5 Gy for doses between 0-20 Gy and 0.3-0.6 Gy for doses beyond 20 Gy. Comparison of the IMRT irradiation with planned doses yields excellent results: gamma pass rate (3%, 3 mm) of 99.3% at the isocentre slice and 93.4% over the entire treated volume.

Johnston, H.; Hilts, M.; Carrick, J.; Jirasek, A.

2012-05-01

15

Ferrous sulphate gel dosimetry and MRI for proton beam dose measurements  

Microsoft Academic Search

Ferrous sulphate gel dosimetry has the potential for measurement of absorbed dose distributions in proton therapy. The chemical properties of the gel are altered according to the radiation dose and these changes can be evaluated in three dimensions using MRI. The purpose of this work was to investigate the properties of a ferrous gel used with clinical proton beams. The

Sven Å. J. Bäck; Joakim Medin; Peter Magnusson; Peter Olsson; Erik Grusell; Lars E. Olsson

1999-01-01

16

Isotropic three-dimensional MRI-Fricke-infused gel dosimetry  

SciTech Connect

Purpose: Fricke-infused gel has been shown to be a simple and attainable method for the conformal measurement of absorbed radiation dose. Nevertheless, its accuracy is seriously hindered by the irreversible ferric ion diffusion during magnetic resonance imaging, particularly when three-dimensional (3D) dose measurement in radiosurgery is considered. In this study, the authors developed a fast three-dimensional spin-echo based Fricke gel dosimetry technique to reduce the adverse effects of ferric ion diffusion and to obtain an accurate isotropic 3D dose measurement. Methods: A skull shaped phantom containing Fricke-infused gel was irradiated using Leksell Gamma Knife. The rapid image-based dosimetry technique was applied with the use of a 3D fast spin-echo magnetic resonance imaging sequence. The authors mathematically derived and experimentally validated the correlations between dose-response characteristics and parameters of the 3D fast spin-echo MR imaging sequence. Absorbed dose profiles were assessed and compared to the calculated profiles given by the Gamma Knife treatment planning system. Coefficient of variance (CV%) and coefficient of determination (R{sup 2}) were used to evaluate the precision of dose-response curve estimation. The agreement between the measured and the planned 3D dose distributions was quantified by gamma-index analysis of two acceptance criteria. Results: Proper magnetic resonance imaging parameters were explored to render an accurate three-dimensional absorbed dose mapping with a 1 mm{sup 3} isotropic image resolution. The efficacy of the dose-response estimation was approved by an R{sup 2} > 0.99 and an average CV% of 1.6%. Average gamma pass-rate between the experimentally measured and GammaPlan calculated dose distributions were 83.8% and 99.7% for 2%/2 and 3%/3 mm criteria, respectively. Conclusions: With the designed MR imaging sequence and parameters, total 3D MR acquisition time was confined to within 20 min postirradiation, during which time ferric ion diffusion effects were negligible, thus enabling an accurate 3D radiation dose measurement.

Cho, Nai-Yu; Chu, Woei-Chyn [Institute of Biomedical Engineering, National Yang-Ming University, Taipei 11221, Taiwan (China); Huang, Sung-Cheng [Department of Molecular and Medical Pharmacology, UCLA David Geffen School of Medicine, Los Angeles, California 90095 (United States); Chung, Wen-Yuh [Neurological Institute, Taipei Veterans General Hospital, Taipei 11217, Taiwan (China); Guo, Wan-Yuo [Department of Radiology, Taipei Veterans General Hospital, Taipei 11217, Taiwan (China)

2013-05-15

17

Dosimetry of gamma chamber blood irradiator using PAGAT gel dosimeter and Monte Carlo simulations.  

PubMed

Currently, the use of blood irradiation for inactivating pathogenic microbes in infected blood products and preventing graft-versus-host disease (GVHD) in immune suppressed patients is greater than ever before. In these systems, dose distribution and uniformity are two important concepts that should be checked. In this study, dosimetry of the gamma chamber blood irradiator model Gammacell 3000 Elan was performed by several dosimeter methods including thermoluminescence dosimeters (TLD), PAGAT gel dosimetry, and Monte Carlo simulations using MCNP4C code. The gel dosimeter was put inside a glass phantom and the TL dosimeters were placed on its surface, and the phantom was then irradiated for 5 min and 27 sec. The dose values at each point inside the vials were obtained from the magnetic resonance imaging of the phantom. For Monte Carlo simulations, all components of the irradiator were simulated and the dose values in a fine cubical lattice were calculated using tally F6. This study shows that PAGAT gel dosimetry results are in close agreement with the results of TL dosimetry, Monte Carlo simulations, and the results given by the vendor, and the percentage difference between the different methods is less than 4% at different points inside the phantom. According to the results obtained in this study, PAGAT gel dosimetry is a reliable method for dosimetry of the blood irradiator. The major advantage of this kind of dosimetry is that it is capable of 3D dose calculation. PMID:24423829

Mohammadyari, Parvin; Zehtabian, Mehdi; Sina, Sedigheh; Tavasoli, Ali Reza; Faghihi, Reza

2014-01-01

18

Femtosecond laser pulse filamentation characterized by polymer gel dosimetry and Fricke dosimetry  

NASA Astrophysics Data System (ADS)

A femtosecond laser pulse that can generate water radiolysis species was studied in view of its potential medical and biological applications. Intense ultra-short laser pulses can propagate in liquid water, leading to self-focusing and filamentation. Briefly, electrons produced by either multiphoton or tunnel ionization are further accelerated by the electric field of the pulse in an inverse Bremsstrahlung effect. If the electrons acquire enough kinetic energy, they will give rise to a second generation of electrons by impact ionization of other molecules in an avalanche-like process. The geometry and trajectory of femtosecond filaments were captured within a polymer gel dosimeter and imaged by magnetic resonance imaging (MRI) at high resolution. The results revealed that changing pulse duration modifies the penetration of the filament track in the medium. In addition, we used Fricke dosimetry to measure the absorbed dose and dose rate of the femtosecond laser pulse filamentation. A very high dose rate of 5.3 × 1012 Gy/s was calculated in filaments having a diameter of ~600 ?m.

Meesat, Ridthee; Allard, Jean-François; Houde, Daniel; Tremblay, Luc; Khalil, Abdelouahed; Jay-Gerin, Jean-Paul; Lepage, Martin

2010-11-01

19

True 3D chemical dosimetry (gels, plastics): Development and clinical role  

NASA Astrophysics Data System (ADS)

Since the introduction of volumetric chemical dosimetry with Fricke gel dosimeters in the 1980s, three-dimensional (3D) dosimetry has been a promising technique for the clinic, since it provides a unique methodology for 3D dose measurement of the complex conformal dose distributions achieved by modern techniques such as Intensity Modulated and Volumetric Arc Radiation Therapy. In the last decade, the potential for improved clinical applicability has been advanced by the development of improved 3D dosimeters such as normoxic polymer gel systems, radiochromic plastics (such as PRESAGE) and, recently, newer radiochromic gel dosimeters. Some of these new 3D dosimetry systems were enabled by the availability of optical computed tomography imaging systems for fast dose readout. However, despite its promise, true 3D dosimetry is still not widely practiced in the community. Its use has been confined primarily to select centres of expertise and to specialised quality assurance or commissioning roles where other dosimetry techniques are difficult to implement. In this paper I review some of the current 3D chemical dosimeters available, discuss the requirements for their use and briefly review the roles that these systems can provide to complement the other dose delivery validation approaches available in the clinic. I conclude by describing two roles that may be uniquely served by 3D chemical dosimetry in end-to-end process testing and validation in the complex environment coming into play with the development of Image Guided Adaptive Radiation Therapy.

Schreiner, L. J.

2015-01-01

20

Fricke gel diffusion coefficient measurements for applications in radiotherapy level dosimetry  

NASA Astrophysics Data System (ADS)

In gel dosimetry applied to radiotherapy, the space-time corrections are necessary due to the diffusion of ions in the oxidized solution dosimetry. Consequently, methodologies are applied in order to determine diffusion coefficients corrected in space and time. Therefore, in this study the dosimetric solution Fricke Xylenol Gel (FXG) was modified and applied to two Gaussian and ISQR methodologies for comparison of the diffusion coefficients obtained. The results show that the FXG system can be modified for new applications in radiotherapy, and it may be corrected in space-time to the appropriate methodologies in the determination of diffusion coefficients.

de Oliveira, Lucas Nonato; de Almeida, Adelaide; Caldas, Linda V. E.

2014-05-01

21

Optical computed tomography of radiochromic gels for accurate three-dimensional dosimetry  

NASA Astrophysics Data System (ADS)

In this thesis, three-dimensional (3-D) radiochromic Ferrous Xylenol-orange (FX) and Leuco Crystal Violet (LCV) micelles gels were imaged by laser and cone-beam (Vista(TM)) optical computed tomography (CT) scanners. The objective was to develop optical CT of radiochromic gels for accurate 3-D dosimetry of intensity-modulated radiation therapy (IMRT) and small field techniques used in modern radiotherapy. First, the cause of a threshold dose response in FX gel dosimeters when scanned with a yellow light source was determined. This effect stems from a spectral sensitivity to multiple chemical complexes that are at different dose levels between ferric ions and xylenol-orange. To negate the threshold dose, an initial concentration of ferric ions is needed in order to shift the chemical equilibrium so that additional dose results in a linear production of a coloured complex that preferentially absorbs at longer wavelengths. Second, a low diffusion leuco-based radiochromic gel consisting of Triton X-100 micelles was developed. The diffusion coefficient of the LCV micelle gel was found to be minimal (0.036 + 0.001 mm2 hr-1 ). Although a dosimetric characterization revealed a reduced sensitivity to radiation, this was offset by a lower auto-oxidation rate and base optical density, higher melting point and no spectral sensitivity. Third, the Radiological Physics Centre (RPC) head-and-neck IMRT protocol was extended to 3-D dose verification using laser and cone-beam (Vista(TM)) optical CT scans of FX gels. Both optical systems yielded comparable measured dose distributions in high-dose regions and low gradients. The FX gel dosimetry results were crossed checked against independent thermoluminescent dosimeter and GAFChromicRTM EBT film measurements made by the RPC. It was shown that optical CT scanned FX gels can be used for accurate IMRT dose verification in 3-D. Finally, corrections for FX gel diffusion and scattered stray light in the Vista(TM) scanner were developed to enable accurate acquisition of small beam dosimetric parameters for treatment planning commissioning. By applying these corrections, optically CT scanned FX and LCV gel dose measurements were found to be in agreement with reference GAFChromicRTM EBT film measurements. In conclusion, once specific problems affecting radiochromic gel materials and optical CT scanners are well understood and resolved, accurate 3-D dosimetry can be achieved. Ultimately, this will facilitate the safe clinical implementation of novel radiation treatments of cancer. Keywords. three-dimensional dosimetry, ferrous xylenol-orange gels, leuco crystal violet micelle gels, optical computed tomography, laser scanner, Vista(TM) cone-beam scanner, intensity-modulated radiation therapy, small field dosimetry.

Babic, Steven

22

High field magnetic resonance imaging-based gel dosimetry for small radiation fields  

NASA Astrophysics Data System (ADS)

Small megavoltage photon radiation fields (< 3cm diameter) are used in advanced radiation therapy techniques, such as intensity modulated radiotherapy, and stereotactic radiosurgery, as well as for cellular and preclinical radiobiology studies (very small fields, <1 mm diameter). Radiation dose characteristics for these small fields are difficult to determine in multiple dimensions because of steep dose gradients (30--40% per mm) and conditions of electronic disequilibrium. Conventional radiation dosimetry techniques have limitations for small fields because detector size may be large compared to radiation field size and/or dose acquisition may be restricted to one or two dimensions. Polymer gel dosimetry, is a three-dimensional (3D) dosimeter based on radiation-induced polymerization of tissue equivalent gelatin. Polymer gel dosimeters can be read using magnetic resonance imaging (MRI), which detects changes in relaxivity due to gel polymerization. Spatial resolution for dose readout is limited to 0.25--0.5mm pixel size because of available the magnetic field strengths (1.5T and 3T) and the stability of polymer gelatin at room temperature. A reliable glucose-based MAGIC (methacrylic and ascorbic acid in gelatine initiated by copper) gel dosimeter was formulated and evaluated for small field 3D dosimetry using 3T and 7T high field MRI for dose readout. The melting point of the original recipe MAGIC gel was increased by 4°C by adding 10% glucose to improve gel stability. Excellent spatial resolution of 79um (1.5 hr scan) and 39um (12 hr scan) was achieved using 7T MRI, proving gel stability for long scan times and high resolution 3D dosimetry.

Ding, Xuanfeng

23

Comparison between polymer gel dosimetry and calculated dose with small field in stereotactic irradiation  

NASA Astrophysics Data System (ADS)

The purpose of this study is to investigate gel dosimetry for a small irradiation field in stereotactic radiotherapy. Treatment plans were generated by the Pinnacle3 treatment plan system (TPS) for three different circular irradiated fields: 10 mm, 15 mm, and 20 mm. The polymer gels were irradiated to 6 Gy with 10-, 15-, and 20-mm-diameter collimators in 4 MV photon beams for stereotactic irradiation following TPS. Irradiated gels were evaluated with MRI at 1.5 T with R2 images. Firstly, the line profile of the irradiated center between TPS plan and the R2 image was compared. In the center profile at a dose calculated from the treatment plan, the full width at half maximum (FWHM) of 10-mm, 15-mm, and 20-mm collimators, were 13 mm, 19 mm, and 25 mm, respectively. In the center profile at R2 from the gel dosimetry, the FWHM were 13 mm, 20 mm, and 23 mm, respectively. Secondly, R2 images were converted to dosimetric maps to apply the gamma evaluation method. Comparison using gamma evaluation in the center of the irradiated plane between TPS plan and the dose map from the R2 image was performed. In gamma evaluation, when 3% and 3 mm criteria were used for comparison of the center plane of dose image from TPS and gel dosimetry, the pass ratio of the gamma criterion between calculated dose from the TPS and the dose map of irradiated gels in stereotactic irradiation was 98.6%. In comparison of the center profile and center plane, results of gel dosimetry were shown to have good agreement with the generated treatment plan dosimetric map for stereotactic irradiation.

Kawamura, H.; Shinoda, K.; Fuse, H.; Terunuma, T.; Miyamoto, K.; Sakae, T.; Matsumura, A.

2013-06-01

24

Feasibility of polymer gel dosimetry measurements in a dynamic porcine lung phantom  

NASA Astrophysics Data System (ADS)

A dynamic ex-vivo porcine lung phantom combined with polymer gel dosimetry is tested as a new tool to validate modern adaptive radiotherapy techniques (e.g. gating or tracking). The gel was inserted into the lung via a latex balloon to simulate a tumor. After irradiation, the location of the dose maximum was verified, however, the dose was higher than planned and a high background signal was seen. Potential reasons for this finding are the nonstandard conditions of gel handling. These conditions were systematically studied. Besides temperature, the material of the balloon seems to be of special importance. The results identify open issues that have to be addressed in future studies.

Mann, P.; Witte, M.; Armbruster, S.; Runz, A.; Lang, C.; Breithaupt, M.; Berger, M.; Biederer, J.; Karger, C. P.; Moser, T.

2015-01-01

25

Polymer gel dosimetry of an electron beam in the presence of a magnetic field  

NASA Astrophysics Data System (ADS)

The effect of a strong external magnetic field on 4 MeV electron beam was measured with polymer gel dosimetry. The measured entrance dose distribution was compared with a calculated fluence map. The magnetic field was created by use of two permanent Neodymium (NdFeB) magnets that were positioned perpendicular to the electron beam. The magnetic field between the magnets was measured with Hall sensors. Based on the magnetic field measurement and the law of Biot-Savart, the magnetic field distribution was extrapolated. Electron trajectories were calculated using a relativistic Lorentz force operator. Although the simplified computational model that was applied, the shape and position of the calculated entrance fluence map are found to be in good agreement with the measured dose distribution in the first layer of the phantom. In combination with the development of low density polymer gel dosimeters, these preliminary results show the potential of 3D gel dosimetry in MRI-linac applications.

Vandecasteele, J.; De Deene, Y.

2013-06-01

26

Application of MAGAT polymer gel dosimetry in breast balloon  

NASA Astrophysics Data System (ADS)

The purpose of this study is to characterize the response of MAGAT normoxic polymer gel for breast brachytherapy applications using two balloon applicators (MammoSite® and Contoura®) and verify the dose distribution with a commercial treatment planning system (BrachyVision® version 8.9.15). We present the fabrication, irradiation and readout of the gel used for the work described herein.

Govi, N.; Gueye, P.; Avery, S.

2013-06-01

27

Preliminary study of MAGAT polymer gel dosimetry for boron-neutron capture therapy  

NASA Astrophysics Data System (ADS)

MAGAT gel dosimeter with boron is irradiated in Heavy Water Neutron Irradiation Facility (HWNIF) of Kyoto University Research Reactor (KUR). The cylindrical gel phantoms are exposed to neutron beams of three different energy spectra (thermal neutron rich, epithermal and fast neutron rich and the mixed modes) in air. Preliminary results corresponding to depth-dose responses are obtained as the transverse relaxation rate (R2=1/T2) from magnetic resonance imaging data. As the results MAGAT gel dosimeter has the higher sensitivity on thermal neutron than on epi-thermal and fast neutron, and the gel with boron showed an enhancement and a change in the depth-R2 response explicitly. From these results, it is suggested that MAGAT gel dosimeter can be an effective tool in BNCT dosimetry.

Hayashi, Shin-ichiro; Sakurai, Yoshinori; Uchida, Ryohei; Suzuki, Minoru; Usui, Shuji; Tominaga, Takahiro

2015-01-01

28

Design and construction of an optical computed tomography scanner for polymer gel dosimetry application.  

PubMed

Polymer gel dosimeter is the only accurate three dimensional (3D) dosimeter that can measure the absorbed dose distribution in a perfect 3D setting. Gel dosimetry by using optical computed tomography (OCT) has been promoted by several researches. In the current study, we designed and constructed a prototype OCT system for gel dosimetry. First, the electrical system for optical scanning of the gel container using a Helium-Neon laser and a photocell was designed and constructed. Then, the mechanical part for two rotational and translational motions was designed and step motors were assembled to it. The data coming from photocell was grabbed by the home-built interface and sent to a personal computer. Data processing was carried out using MATLAB software. To calibrate the system and tune up the functionality of it, different objects was designed and scanned. Furthermore, the spatial and contrast resolution of the system was determined. The system was able to scan the gel dosimeter container with a diameter up to 11 cm inside the water phantom. The standard deviation of the pixels within water flask image was considered as the criteria for image uniformity. The uniformity of the system was about ±0.05%. The spatial resolution of the system was approximately 1 mm and contrast resolution was about 0.2%. Our primary results showed that this system is able to obtain two-dimensional, cross-sectional images from polymer gel samples. PMID:24761377

Zakariaee, Seyed Salman; Mesbahi, Asghar; Keshtkar, Ahmad; Azimirad, Vahid

2014-04-01

29

Design and Construction of an Optical Computed Tomography Scanner for Polymer Gel Dosimetry Application  

PubMed Central

Polymer gel dosimeter is the only accurate three dimensional (3D) dosimeter that can measure the absorbed dose distribution in a perfect 3D setting. Gel dosimetry by using optical computed tomography (OCT) has been promoted by several researches. In the current study, we designed and constructed a prototype OCT system for gel dosimetry. First, the electrical system for optical scanning of the gel container using a Helium-Neon laser and a photocell was designed and constructed. Then, the mechanical part for two rotational and translational motions was designed and step motors were assembled to it. The data coming from photocell was grabbed by the home-built interface and sent to a personal computer. Data processing was carried out using MATLAB software. To calibrate the system and tune up the functionality of it, different objects was designed and scanned. Furthermore, the spatial and contrast resolution of the system was determined. The system was able to scan the gel dosimeter container with a diameter up to 11 cm inside the water phantom. The standard deviation of the pixels within water flask image was considered as the criteria for image uniformity. The uniformity of the system was about ±0.05%. The spatial resolution of the system was approximately 1 mm and contrast resolution was about 0.2%. Our primary results showed that this system is able to obtain two-dimensional, cross-sectional images from polymer gel samples. PMID:24761377

Zakariaee, Seyed Salman; Mesbahi, Asghar; Keshtkar, Ahmad; Azimirad, Vahid

2014-01-01

30

Gamma Knife output factor measurements using VIP polymer gel dosimetry  

SciTech Connect

Purpose: Water equivalent polymer gel dosimeters and magnetic resonance imaging were employed to measure the output factors of the two smallest treatment fields available in a Gamma Knife model C radiosurgery unit, those formed employing the 4 and 8 mm final collimator helmets. Methods: Three samples of the VIP normoxic gel formulation were prepared and irradiated so that a single shot of the field whose output factor is to be measured and a single shot of the reference 18 mm field were delivered in each one. Emphasis is given to the development and benchmarking of a refined data processing methodology of reduced uncertainty that fully exploits the 3D dose distributions registered in the dosimeters. Results: Polymer gel results for the output factor of the 8 mm collimator helmet are found to be in close agreement with the corresponding value recommended by the vendor (0.955{+-}0.007 versus 0.956, respectively). For the 4 mm collimator helmet, however, polymer gel results suggest an output factor 3% lower than the value recommended by the vendor (0.841{+-}0.009 versus 0.870, respectively). Conclusions: A comparison with corresponding measurements published in the literature indicates that output factor results of this work are in agreement with those obtained using dosimetric systems which, besides fine spatial resolution and lack of angular and dose rate dependence of the dosimeter's response, share with polymer gels the favorable characteristic of minimal radiation field perturbation.

Moutsatsos, A.; Petrokokkinos, L.; Karaiskos, P.; Papagiannis, P.; Georgiou, E.; Dardoufas, K.; Sandilos, P.; Torrens, M.; Pantelis, E.; Kantemiris, I.; Sakelliou, L.; Seimenis, I. [Medical Physics Laboratory, Medical School, University of Athens, 75 Mikras Asias, 115 27 Athens (Greece); Department of Radiology, Medical School, University of Athens, Areteion Hospital, 76 Vas. Sofias Avenue, 115 28 Athens (Greece); Department of Radiosurgery, Hygeia Hospital, Kiffisias Avenue and 4 Erythrou Stavrou, Marousi, 151 23 Athens (Greece); Department of Physics, Nuclear and Particle Physics Section, University of Athens, Panepistimioupolis, Ilisia, 157 71 Athens (Greece)

2009-09-15

31

Feasibility of CBCT dosimetry for IMRT using a normoxic polymethacrylic-acid gel dosimeter  

NASA Astrophysics Data System (ADS)

The purpose of this study is to evaluate the availability of cone-beam computed tomography(CBCT) for gel dosimetry. The absorbed dose was analyzed by using intensity-modulated radiation therapy(IMRT) to irradiate several tumor shapes with a calculated dose and several tumor acquiring images with CBCT in order to verify the possibility of reading a dose on the polymer gel dosimeter by means of the CBCT image. The results were compared with those obtained using magnetic resonance imaging(MRI) and CT. The linear correlation coefficients at doses less than 10 Gy for the polymer gel dosimeter were 0.967, 0.933 and 0.985 for MRI, CT and CBCT, respectively. The dose profile was symmetric on the basis of the vertical axis in a circular shape, and the uniformity was 2.50% for the MRI and 8.73% for both the CT and the CBCT. In addition, the gradient in the MR image of the gel dosimeter irradiated in an H shape was 109.88 while the gradients of the CT and the CBCT were 71.95 and 14.62, respectively. Based on better image quality, the present study showed that CBCT dosimetry for IMRT could be restrictively performed using a normoxic polymethacrylic-acid gel dosimeter.

Bong, Ji Hye; Kwon, Soo-Il; Kim, Kum Bae; Kim, Mi Suk; Jung, Hai Jo; Ji, Young Hoon; Ko, In Ok; Park, Ji Ae; Kim, Kyeong Min

2013-09-01

32

Radiological characterization and water equivalency of genipin gel for x-ray and electron beam dosimetry.  

PubMed

The genipin radiochromic gel offers enormous potential as a three-dimensional dosimeter in advanced radiotherapy techniques. We have used several methods (including Monte Carlo simulation), to investigate the water equivalency of genipin gel by characterizing its radiological properties, including mass and electron densities, photon interaction cross sections, mass energy absorption coefficient, effective atomic number, collisional, radiative and total mass stopping powers and electron mass scattering power. Depth doses were also calculated for clinical kilovoltage and megavoltage x-ray beams as well as megavoltage electron beams. The mass density, electron density and effective atomic number of genipin were found to differ from water by less than 2%. For energies below 150 keV, photoelectric absorption cross sections are more than 3% higher than water due to the strong dependence on atomic number. Compton scattering and pair production interaction cross sections for genipin gel differ from water by less than 1%. The mass energy absorption coefficient is approximately 3% higher than water for energies <60 keV due to the dominance of photoelectric absorption in this energy range. The electron mass stopping power and mass scattering power differ from water by approximately 0.3%. X-ray depth dose curves for genipin gel agree to within 1% with those for water. Our results demonstrate that genipin gel can be considered water equivalent for kilovoltage and megavoltage x-ray beam dosimetry. For megavoltage electron beam dosimetry, however, our results suggest that a correction factor may be needed to convert measured dose in genipin gel to that of water, since differences in some radiological properties of up to 3% compared to water are observed. Our results indicate that genipin gel exhibits greater water equivalency than polymer gels and PRESAGE formulations. PMID:21734335

Gorjiara, Tina; Hill, Robin; Kuncic, Zdenka; Bosi, Stephen; Davies, Justin B; Baldock, Clive

2011-08-01

33

Gamma Knife 3-D dose distribution near the area of tissue inhomogeneities by normoxic gel dosimetry.  

PubMed

The accuracy of the Leksell GammaPlan, the dose planning system of the Gamma Knife Model-B, was evaluated near tissue inhomogeneities, using the gel dosimetry method. The lack of electronic equilibrium around the small-diameter gamma beams can cause dose calculation errors in the neighborhood of an air-tissue interface. An experiment was designed to investigate the effects of inhomogeneity near the paranosal sinuses cavities. The homogeneous phantom was a spherical glass balloon of 16 cm diameter, filled with MAGIC gel; i.e., the normoxic polymer gel. Two hollow PVC balls of 2 cm radius, filled with N2 gas, represented the air cavities inside the inhomogeneous phantom. For dose calibration purposes, 100 ml gel-containing vials were irradiated at predefined doses, and then scanned in a MR unit. Linearity was observed between the delivered dose and the reciprocal of the T2 relaxation time constant of the gel. Dose distributions are the results of a single shot of irradiation, obtained by collimating all 201 cobalt sources to a known target in the phantom. Both phantoms were irradiated at the same dose level at the same coordinates. Stereotactic frames and fiducial markers were attached to the phantoms prior to MR scanning. The dose distribution predicted by the Gamma Knife planning system was compared with that of the gel dosimetry. As expected, for the homogeneous phantom the isodose diameters measured by the gel dosimetry and the GammaPlan differed by 5% at most. However, with the inhomogeneous phantom, the dose maps in the axial, coronal and sagittal planes were spatially different. The diameters of the 50% isodose curves differed 43% in the X axis and 32% in the Y axis for the Z =90 mm axial plane; by 44% in the X axis and 24% in the Z axis for the Y=90 mm coronal plane; and by 32% in the Z axis and 42% in the Y axis for the X=92 mm sagittal plane. The lack of ability of the GammaPlan to predict the rapid dose fall off, due to the air cavities behind or near the lesion led to an overestimation of the dose that was actually delivered. Clinically, this can result in underdosing of lesions near tissue inhomogeneities in patients under treatment. PMID:17555244

Isbakan, Fatih; Ulgen, Yekta; Bilge, Hatice; Ozen, Zeynep; Agus, Onur; Buyuksarac, Bora

2007-05-01

34

A modified Fricke gel dosimeter for fast electron blood dosimetry  

NASA Astrophysics Data System (ADS)

It has been suggested for more than forty years that blood and blood components be irradiated before allogeneic transfusions for immunosuppressed patients in order to avoid the Transfusion-Associated Graft-versus-Host Disease (TA-GVHD). Whole blood, red blood cells, platelets and granulocytes may have viable T cells and should be irradiated before transfusion for different patient clinical conditions. According to international guides, absorbed doses from 25 up to 50 Gy should be delivered to the central middle plane of each blood bag. Although gamma and X-rays from radiotherapy equipments and dedicated cell irradiators are commonly used for this purpose, electron beams from Linear Accelerators (LINACs) could be used as well. In this work, we developed a methodology able to acquire dosimetric data from blood irradiations, especially after fast electrons exposures. This was achieved using a proposed Fricke Xylenol Gel (FXGp) dosimeter, which presents closer radiological characteristics (attenuation coefficients and stopping-powers) to the whole blood, as well as complete absorbed dose range linearity. The developed methodology and the FXGp dosimeter were also able to provide isodose curves and field profiles for the irradiated samples.

Del Lama, L. S.; de Góes, E. G.; Sampaio, F. G. A.; Petchevist, P. C. D.; de Almeida, A.

2014-12-01

35

Deformable gel dosimetry I: application to external beam radiotherapy and brachytherapy  

NASA Astrophysics Data System (ADS)

Inter- and intra-fractional variation in anatomic structures is a significant challenge in contemporary radiotherapy (RT). In this study, we describe the implementation of a novel deformable gel dosimetry system (dubbed 'DEFGEL') for application to external beam RT and brachytherapy experimental measurements. Complex / redistributed dose distributions due to applied deformations were readily observed and the discrepancies relative to a control case with an absence of deformation could be quantified. This work has obvious extensions to validation of deformable image registration algorithms, deformable dose calculation algorithms, and quality assurance of motion compensation strategies in RT.

Yeo, U. J.; Taylor, M. L.; Supple, J. R.; Smith, R. L.; Kron, T.; Franich, R. D.

2013-06-01

36

The spatial resolution in dosimetry with normoxic polymer-gels investigated with the dose modulation transfer approach  

SciTech Connect

The verification of dose distributions with high dose gradients as appearing in brachytherapy or stereotactic radiotherapy for example, calls for dosimetric methods with sufficiently high spatial resolution. Polymer gels in combination with a MR or optical scanner as a readout device have the potential of performing the verification of a three-dimensional dose distribution within a single measurement. The purpose of this work is to investigate the spatial resolution achievable in MR-based polymer gel dosimetry. The authors show that dosimetry on a very small spatial scale (voxel size: 94x94x1000 {mu}m{sup 3}) can be performed with normoxic polymer gels using parameter selective T2 imaging. In order to prove the spatial resolution obtained we are relying on the dose-modulation transfer function (DMTF) concept based on very fine dose modulations at half periods of 200 {mu}m. Very fine periodic dose modulations of a {sup 60}Co photon field were achieved by means of an absorption grid made of tungsten-carbide, specifically designed for quality control. The dose modulation in the polymer gel is compared with that of film dosimetry in one plane via the DMTF concept for general access to the spatial resolution of a dose imaging system. Additionally Monte Carlo simulations were performed and used for the calculation of the DMTF of both, the polymer gel and film dosimetry. The results obtained by film dosimetry agree well with those of Monte Carlo simulations, whereas polymer gel dosimetry overestimates the amplitude value of the fine dose modulations. The authors discuss possible reasons. The in-plane resolution achieved in this work competes with the spatial resolution of standard clinical film-scanner systems.

Bayreder, Christian; Schoen, Robert; Wieland, M.; Georg, Dietmar; Moser, Ewald; Berg, Andreas [MR Centre of Excellence, Center for Biomedical Engineering and Physics, Medical University of Vienna, Vienna (Austria); Department of Nuclear Medicine, Medical University of Vienna, Vienna (Austria); MR Centre of Excellence, Center for Biomedical Engineering and Physics, Medical University of Vienna, Vienna (Austria); Division of Medical Radiation Physics, Medical University of Vienna/AKH, Vienna (Austria); MR Centre of Excellence, Center for Biomedical Engineering and Physics, Medical University of Vienna, Vienna (Austria)

2008-05-15

37

Pushing the boundaries of spatial resolution in dosimetry using polymer gels and radiochromic films  

NASA Astrophysics Data System (ADS)

Advanced radiotherapy and brachytherapy techniques are raising the bar for detectors with respect to high spatial resolution. Dosimetry based on most point-like dosimeters, e.g. diamond detectors or small volume ionization chambers cannot be used efficiently and accurately for detecting 2 or 3D-dose variations at millimeter scale. Hence radiochromic films and polymer gels with high two/three-dimensional resolution provide a good verification tool for measuring dose distributions of very small collimated beams. In this study the performance of film and gel detectors in detecting the very fine dose distributions generated from collimation holes of four different sizes is investigated. Pencil beams with diameters down to 0.455 mm could be resolved by both detector types comparably.

Heilemann, G.; Georg, D.; Berg, A.

2015-01-01

38

Polymer gel dosimetry utilizing a 2D (SE) and a 2D (HASTE) multiple echo sequences  

NASA Astrophysics Data System (ADS)

Two pulse sequences were used for the estimation of dosimetric characteristics of VIPET polymer gels. The first one, multi- echo spin echo (MESE) is the well-established method for T2 measurements. The other method is a new multi-echo single shot turbo spin echo pulse sequence, MEHASTE that reduces the acquisition time significantly. Both techniques showed a linear R2-dose response. With MESE sequence, the dose sensitivity was slightly enhanced as compared to MEHASTE. The linear portion of the R2-dose curve was restricted using the MEHASTE sequence. For doses above 7 Gy both methods fulfill the 2% ICRU criterion limit for dose resolution estimations (95% confidence level). Finally, for a time period of one month the temporal stability of R2-dose response was maintained stable utilizing both MESE and MEHASTE pulse sequences. MEHASTE serves as an excellent means for fast 3D polymer gel dosimetry.

Papoutsaki, M.-V.; Pappas, E.; Papadakis, A. E.; Varveris, C.; Damilakis, J.; Maris, T. G.

2013-06-01

39

Verification of motion induced thread effect during tomotherapy using gel dosimetry  

NASA Astrophysics Data System (ADS)

The purpose of the study was to evaluate how breathing motion during tomotherapy (Accuray, CA, USA) treatment affects the absorbed dose distribution. The experiments were carried out using gel dosimetry and a motion device simulating respiratory-like motion (HexaMotion, ScandiDos, Uppsala, Sweden). Normoxic polyacrylamide gels (nPAG) were irradiated, both during respiratory-like motion and in a static mode. To be able to investigate interplay effects the static absorbed dose distribution was convolved with the motion function and differences between the dynamic and convolved static absorbed dose distributions were interpreted as interplay effects. The expected dose blurring was present and the interplay effects formed a spiral pattern in the lower dose volume. This was expected since the motion induced affects the preset pitch and the theoretically predicted thread effect may emerge. In this study, the motion induced thread effect was experimentally verified for the first time.

Edvardsson, Anneli; Ljusberg, Anna; Ceberg, Crister; Medin, Joakim; Ambolt, Lee; Nordström, Fredrik; Ceberg, Sofie

2015-01-01

40

Improved MAGIC gel for higher sensitivity and elemental tissue equivalent 3D dosimetry  

PubMed Central

Purpose: Polymer-based gel dosimeter (MAGIC type) is a preferable phantom material for PET range verification of proton beam therapy. However, improvement in elemental tissue equivalency (specifically O?C ratio) is very desirable to ensure realistic time-activity measurements. Methods: Glucose and urea was added to the original MAGIC formulation to adjust the O?C ratio. The dose responses of the new formulations were tested with MRI transverse relaxation rate (R2) measurements. Results: The new ingredients improved not only the elemental composition but also the sensitivity of the MAGIC gel. The O?C ratios of our new gels agree with that of soft tissue within 1%. The slopes of dose response curves were 1.6–2.7 times larger with glucose. The melting point also increased by 5 °C. Further addition of urea resulted in a similar slope but with an increased intercept and a decreased melting point. Conclusions: Our improved MAGIC gel formulations have higher sensitivity and better elemental tissue equivalency for 3D dosimetry applications involving nuclear reactions. PMID:20175480

Zhu, Xuping; Reese, Timothy G.; Crowley, Elizabeth M.; El Fakhri, Georges

2010-01-01

41

Improved MAGIC gel for higher sensitivity and elemental tissue equivalent 3D dosimetry  

SciTech Connect

Purpose: Polymer-based gel dosimeter (MAGIC type) is a preferable phantom material for PET range verification of proton beam therapy. However, improvement in elemental tissue equivalency (specifically O/C ratio) is very desirable to ensure realistic time-activity measurements. Methods: Glucose and urea was added to the original MAGIC formulation to adjust the O/C ratio. The dose responses of the new formulations were tested with MRI transverse relaxation rate (R2) measurements. Results: The new ingredients improved not only the elemental composition but also the sensitivity of the MAGIC gel. The O/C ratios of our new gels agree with that of soft tissue within 1%. The slopes of dose response curves were 1.6-2.7 times larger with glucose. The melting point also increased by 5 deg. C. Further addition of urea resulted in a similar slope but with an increased intercept and a decreased melting point. Conclusions: Our improved MAGIC gel formulations have higher sensitivity and better elemental tissue equivalency for 3D dosimetry applications involving nuclear reactions.

Zhu Xuping; Reese, Timothy G.; Crowley, Elizabeth M.; El Fakhri, Georges [Department of Radiology, Massachusetts General Hospital, 55 Fruit Street, Boston, Massachusetts 02114 (United States); Department of Radiology, Massachusetts General Hospital, Athinoula A. Martinos Center for Biomedical Imaging, 149 Thirteenth Street, Charlestown, Massachusetts 02129 (United States); Department of Radiation Oncology, Massachusetts General Hospital, 100 Blossom Street, Boston, Massachusetts 02114 (United States); Department of Radiology, Massachusetts General Hospital, 55 Fruit Street, Boston, Massachusetts 02114 (United States)

2010-01-15

42

Polymer gel dosimetry for neutron beam in the Neutron Exposure Accelerator System for Biological Effect Experiments (NASBEE)  

NASA Astrophysics Data System (ADS)

This study aimed to investigate whether gel dosimetry could be used to measure neutron beams. We irradiated a BANG3-type polymer gel dosimeter using neutron beams in the Neutron exposure Accelerator System for Biological Effect Experiments (NASBEE) at the National Institute of Radiological Sciences (NIRS) in Japan. First, the polymer gels were irradiated from 0 to 7.0 Gy to investigate the dose-R2 responses. Irradiated gels were evaluated using 1.5-T magnetic resonance R2 images. Second, the polymer gels were irradiated to 1.0, 3.0, and 5.0 Gy to acquire a depth-R2 response curve. The dose-R2 response curve was linear up to approximately 7 Gy, with a slope of 1.25 Gy?1·s?1. Additionally, compared with the photon- irradiated gels, the neutron-irradiated gels had lower R2 values. The acquired depth-R2 curves of the central axis from the 3.0- and 5.0-Gy neutron dose-irradiated gels exhibited an initial build-up. Although, a detailed investigation is needed, polymer gel dosimetry is effective for measuring the dose-related R2 linearity and depth-R2 relationships of neutron beams.

Kawamura, H.; Sato, H.; Hamano, T.; Suda, M.; Yoshii, H.

2015-01-01

43

Fourier transform Raman spectroscopy of polyacrylamide gels (PAGs) for radiation dosimetry  

NASA Astrophysics Data System (ADS)

Polyacrylamide gels (PAGs) are used for magnetic resonance imaging radiation dosimetry. Fourier transform (FT) Raman spectroscopy studies were undertaken to investigate cross-linking changes during the copolymerization of polyacrylamide gels in the spectral range of 200-3500 . Vibrational bands of 1285 and 1256 were assigned to acrylamide and bis-acrylamide single binding modes. Bands were found to decrease in amplitude with increasing absorbed radiation dose as a result of copolymerization. Principal component regression was performed on FT-Raman spectra of PAG samples irradiated to 50 Gy. Two components were found to be sufficient to account for 98.7% of the variance in the data. Cross validation was used to establish the absorbed radiation dose of an unknown PAG sample from the FT-Raman spectra. The calculated correlation coefficient between measured and predictive samples was 0.997 with a standard error of estimate of 0.976 and a standard error of prediction of 1.140. Results demonstrate the potential of FT-Raman spectroscopy for ionizing radiation dosimetry using polyacrylamide gels.

Baldock, C.; Rintoul, L.; Keevil, S. F.; Pope, J. M.; George, G. A.

1998-12-01

44

High resolution polymer gel dosimetry for small beam irradiation using a 7T micro-MRI scanner  

NASA Astrophysics Data System (ADS)

The use of small field radiation beams has greatly increased with advanced radiation therapy techniques such as IMRT, rotational IMRT, and stereotactic body radiotherapy. In this work small field 3D dose distributions have been measured with high spatial resolution using polymer gels and 7T micro-MR imaging. A MAGIC (Methacrylic and Ascorbic acid in Gelatin Initiated by Copper) polymer gel [1] phantom was used to capture the 3D dose distributions for two small field (5 × 5 mm2 and 10 × 10 mm2) for a 6MV x-ray beam. High resolution 3D T2 maps were obtained with 7T micro-MRI (0.156mm × 0.156mm × 1mm, MSME pulse sequence). For comparison T2 maps, the gel phantom was scanned in a 3T MRI clinical scanner (0.254mm × 0.254mm × 2mm, FSE pulse sequence). Normalized 3D dose maps were calculated in Matlab. Results show that 7T micro-MRI 3D gel dosimetry measurements are much more stable, less noisy, and have higher spatial resolution than those obtained using a 3T clinical scanner for the same amount of scan time. In general, 3D gel dosimetry results also agree with simultaneously-obtained radiochromic film dosimetry. This study indicates that the MAGIC polymer gel with 7T micro-MRI for 3D dose readout could potentially be used for small radiation beams, including measurements for micro-beams (field size ~ 100um).

Ding, Xuanfeng; Olsen, John; Best, Ryan; Bennett, Marcus; McGowin, Inna; Dorand, Jennifer; Link, Kerry; Bourland, J. Daniel

2010-11-01

45

High-resolution gel dosimetry using flat-panel detector cone-beam computed tomography: preliminary study.  

PubMed

This study compares the dose response of irradiated polymer gel with acrylic and styrofoam housing while applying multi-detector CT (MDCT) and cone-beam CT (CBCT). The dose response for MDCT and CBCT, while using an acrylic phantom is 1.34 and 0.67 DeltaHU Gy(-1), respectively, and becomes 1.54 and 0.84 DeltaHU Gy(-1) while using styrofoam, suggesting styrofoam is the better housing material. While the dose response of MDCT is better than that of CBCT, CBCT is yet a promising 3D dosimetry technique, given its potentially better spatial resolution and sensitive dose interpretation capability. PMID:19914082

Huang, Kuo-Ming; Huang, Tzung-Chi; Tsai, Chia-Jung; Lu, Kun-Mu; Chen, Liang-Kuang; Wu, Tung-Hsin

2010-01-01

46

The use of high field strength and parallel imaging techniques for MRI-based gel dosimetry in stereotactic radiosurgery  

NASA Astrophysics Data System (ADS)

The poor clinical acceptance of polymer gel dosimetry for dose verification in stereotactic radio-surgery applications stems, inter alia, from the increased MRI acquisition times needed to meet the associated spatial resolution demands. To examine whether this could be partly alleviated by the employment of 3 Tesla imagers and parallel imaging techniques, a PolyAcrylamide Gel filled tube was irradiated in a Leksell Gamma Knife unit with two single irradiation shots (4 mm and 8 mm) and underwent four different scanning sessions using an optimised, volume selective, 32 echo CPMG pulse sequence: One performed on a 1.5 T imager with 0.5 × 0.5 mm2 in-plane spatial resolution and 0.75 mm slice thickness (scan A), while the rest three on a 3.0 T imager; one with the same spatial resolution as in scan A (scan B) and two with finer in-plane resolution (scans C and D). In scans B and C the sensitivity encoding (SENSE) parallel imaging technique was employed. Relative dose distributions derived by scan A were benchmarked against Monte Carlo and treatment planning system calculations, and then used as the reference for the comparison of 2D relative dose distributions derived by each scan in terms of dose difference and distance-to-agreement criteria (? index tool). Findings suggest that careful MRI planning based on a figure of merit accounting for scanning time and precision for a given increase in spatial resolution, could facilitate the introduction of polymer gel dosimetry into the clinical setting as a practical quality assurance tool for complex radio-surgery techniques.

Seimenis, I.; Moutsatsos, A.; Petrokokkinos, L.; Kantemiris, I.; Benekos, O.; Efstathopoulos, E.; Papagiannis, P.; Spevacek, V.; Semnicka, J.; Dvorak, P.

2009-07-01

47

3-D dose verification for IMRT using optical CT based polymer gel dosimetry  

NASA Astrophysics Data System (ADS)

In this study BANG® polymer gels in conjunction with OCTOPUSTM optical CT scanner (MGS Research Inc., Madison, CT) was employed to measure the relative 3D dose distribution of an IMRT treatment. Measured relative dose distributions from the gel measurement were compared with those from treatment planning system calculations and EDR2 film measurements with regard to planar dose distributions in axial, coronal, and sagittal orientations.

Wuu, C.; Xu, Y.; Maryanski, M. J.

2004-01-01

48

Tomotherapy dose distribution verification using MAGIC-f polymer gel dosimetry  

SciTech Connect

Purpose: This paper presents the application of MAGIC-f gel in a three-dimensional dose distribution measurement and its ability to accurately measure the dose distribution from a tomotherapy unit. Methods: A prostate intensity-modulated radiation therapy (IMRT) irradiation was simulated in the gel phantom and the treatment was delivered by a TomoTherapy equipment. Dose distribution was evaluated by the R2 distribution measured in magnetic resonance imaging. Results: A high similarity was found by overlapping of isodoses of the dose distribution measured with the gel and expected by the treatment planning system (TPS). Another analysis was done by comparing the relative absorbed dose profiles in the measured and in the expected dose distributions extracted along indicated lines of the volume and the results were also in agreement. The gamma index analysis was also applied to the data and a high pass rate was achieved (88.4% for analysis using 3%/3 mm and of 96.5% using 4%/4 mm). The real three-dimensional analysis compared the dose-volume histograms measured for the planning volumes and expected by the treatment planning, being the results also in good agreement by the overlapping of the curves. Conclusions: These results show that MAGIC-f gel is a promise for tridimensional dose distribution measurements.

Pavoni, J. F.; Pike, T. L.; Snow, J.; DeWerd, L.; Baffa, O. [Departamento de Fisica, Faculdade de Filosofia Ciencias e Letras de Ribeirao Preto-Universidade de Sao Paulo, Av. Bandeirantes, 3900 - CEP 14040-901 - Bairro Monte Alegre - Ribeirao Preto, SP (Brazil); Medical Radiation Research Center, Department of Medical Physics, University of Wisconsin, 1111 Highland Avenue, B1002 WIMR, Madison, Wisconsin 53705-2275 (United States); Departamento de Fisica, Faculdade de Filosofia Ciencias e Letras de Ribeirao Preto-Universidade de Sao Paulo, Av. Bandeirantes, 3900 - CEP 14040-901 - Bairro Monte Alegre - Ribeirao Preto, SP (Brazil)

2012-05-15

49

3D polymer gel dosimetry and Geant4 Monte Carlo characterization of novel needle based X-ray source  

NASA Astrophysics Data System (ADS)

In the recent years, there have been a few attempts to develop a low energy x-ray radiation sources alternative to conventional radioisotopes used in brachytherapy. So far, all efforts have been centered around the intent to design an interstitial miniaturized x-ray tube. Though direct irradiation of tumors looks very promising, the known insertable miniature x-ray tubes have many limitations: (a) difficulties with focusing and steering the electron beam to the target; (b)necessity to cool the target to increase x-ray production efficiency; (c)impracticability to reduce the diameter of the miniaturized x-ray tube below 4mm (the requirement to decrease the diameter of the x-ray tube and the need to have a cooling system for the target have are mutually exclusive); (c) significant limitations in changing shape and energy of the emitted radiation. The specific aim of this study is to demonstrate the feasibility of a new concept for an insertable low-energy needle x-ray device based on simulation with Geant4 Monte Carlo code and to measure the dose rate distribution for low energy (17.5 keV) x-ray radiation with the 3D polymer gel dosimetry.

Liu, Y.; Sozontov, E.; Safronov, V.; Gutman, G.; Strumban, E.; Jiang, Q.; Li, S.

2010-11-01

50

Deformable gel dosimetry II: experimental validation of DIR-based dose-warping  

NASA Astrophysics Data System (ADS)

Algorithms exist for the deformation of radiotherapy doses based on patient image sets, though these are sometimes contentious because not all such image calculations are constrained by appropriate physical laws. By use of a deformable dosimetric gel phantom, 'DEFGEL', we demonstrate a full 3D experimental validation of a range of dose deformation algorithms publicly available. Spatial accuracy in low contrast areas was assessed using "ghost" fiducial markers (digitally removed from CT images prior to registration) implanted in the phantom. The accuracy with which the different algorithms deform dose was evaluated by comparing doses measured with the deformable phantom to warped planned doses, via 3D g-analysis. Mean spatial errors ranged from 1.9 mm with a g3D passing ratio of 95.8 % for the original Horn and Schunck algorithm to 3.9 mm with a g3D passing ratio of 39.9 % for the modified demons algorithm.

Yeo, U. J.; Taylor, M. L.; Supple, J. R.; Smith, R. L.; Kron, T.; Franich, R. D.

2013-06-01

51

Cone-beam optical computed tomography for gel dosimetry II: imaging protocols  

NASA Astrophysics Data System (ADS)

This work develops imaging protocols for improved dose readout of a Fricke-xylenol orange-gelatin (FXG) gel-filled 1 L polyethylene terephthalate (PETE) jar dosimeter using a commercial VistaTM cone-beam optical computed tomography (CT) scanner from Modus Medical Devices Inc. (London, ON, Canada). To ensure good management of light source-detector stability, it was determined that (a) a minimum of 2 h warm-up time is necessary prior to dosimeter scanning, (b) the light source should be kept on until the completion of the last data scan except for the minimum amount of time required to acquire dark field images, and (c) the optional Vista software projection image normalization routine should be used in image reconstruction. The institution of dosimeter scan time and temperature control was strongly indicated from the experiments. A standard post-irradiation wait time of 30 min measured to within ±30 s was established to minimize the measurement uncertainties due to dosimeter development and diffusion. To alleviate thermochromic behavior leading to inaccurate dose readout, holding bath warm up and pre-scan temperature adjustment procedures were developed to control dosimeter temperature to within ±0.2 °C. The possibility of stray light minimizing protocols was also investigated and deemed to be unnecessary. The largest significant sources of stray light in the system were identified as being due to angled scatter from the dosimeter gelatin matrix and refraction from the jar wall interfaces. It was concluded that these phenomena would be better addressed through dosimeter modification and an inter-jar dose-to-attenuation calibration methodology, rather than by setting additional imaging protocols.

Olding, Tim; Schreiner, L. John

2011-03-01

52

Three dimensional radiation dosimetry in lung-equivalent regions by use of a radiation sensitive gel foam: Proof of principle  

SciTech Connect

A polymer hydrogel foam is proposed as a potential three dimensional experimental dosimeter for radiation treatment verification in low-density tissue such as the lung. A gel foam is created by beating a radiation sensitive polymer gel mixture in an anoxic atmosphere. The mass density of the gel foam is in the order of 0.25-0.35 kg/dm{sup 3}. Both nuclear magnetic resonance (NMR) spin-spin relaxation rate (R2) and magnetization transfer ratio (MTR) have been used to map the dose distribution from the gel dosimeter. It is found that MTR has significant advantages compared to R2 for mapping the dose distribution in the polymer gel foam dosimeters. The magnetization transfer ratio is found to be less dependent on the density and microstructure of the gel foam dosimeter while spin-spin relaxation dispersion has been observed making the spin-spin relaxation rate dependent on the interecho time interval. Optical microscopy reveals a microstructure that shows great similarity with human lung tissue. It is also shown how NMR hydrogen proton density measurements can be used to map the density distributions in gel dosimeters.

Deene, Yves de; Vergote, Koen; Claeys, Carolien; De Wagter, Carlos [Radiotherapy and Nuclear Medicine, Ghent University Hospital, De Pintelaan 185, 9000 Gent, Belgium and MR Department, Ghent University Hospital, De Pintelaan 185, 9000 Gent (Belgium); Radiotherapy and Nuclear Medicine, Ghent University Hospital, De Pintelaan 185, 9000 Gent (Belgium)

2006-07-15

53

Feasibility on using composite gel-alanine dosimetry on the validation of a multiple brain metastasis radiosurgery VMAT technique  

NASA Astrophysics Data System (ADS)

This work presents an end-to-end test using a composite Gel-Alanine phantom, in order to validate 3-dimensionally the dose distribution delivered by a single isocenter VMAT technique on the simultaneous treatment of multiple brain metastases. The results obtained with the gel and alanine dosimeters are consistent with the expected by the treatment planning system, showing the potential of this multidosimetric approach and validating dosimetrically the multiple brain metastases treatment using VMAT.

Pavoni, J. F.; Neves-Junior, W. F. P.; Silveira, M. A.; Ramos, P. A. M. M.; Haddad, C. M. K.; Baffa, O.

2015-01-01

54

Fundamentals of gel dosimeters  

NASA Astrophysics Data System (ADS)

Fundamental chemical and physical phenomena that occur in Fricke gel dosimeters, polymer gel dosimeters, micelle gel dosimeters and genipin gel dosimeters are discussed. Fricke gel dosimeters are effective even though their radiation sensitivity depends on oxygen concentration. Oxygen contamination can cause severe problems in polymer gel dosimeters, even when THPC is used. Oxygen leakage must be prevented between manufacturing and irradiation of polymer gels, and internal calibration methods should be used so that contamination problems can be detected. Micelle gel dosimeters are promising due to their favourable diffusion properties. The introduction of micelles to gel dosimetry may open up new areas of dosimetry research wherein a range of water-insoluble radiochromic materials can be explored as reporter molecules.

McAuley, K. B.; Nasr, A. T.

2013-06-01

55

Spot quantification in two dimensional gel electrophoresis image analysis: comparison of different approaches and presentation of a novel compound fitting algorithm  

PubMed Central

Background Various computer-based methods exist for the detection and quantification of protein spots in two dimensional gel electrophoresis images. Area-based methods are commonly used for spot quantification: an area is assigned to each spot and the sum of the pixel intensities in that area, the so-called volume, is used a measure for spot signal. Other methods use the optical density, i.e. the intensity of the most intense pixel of a spot, or calculate the volume from the parameters of a fitted function. Results In this study we compare the performance of different spot quantification methods using synthetic and real data. We propose a ready-to-use algorithm for spot detection and quantification that uses fitting of two dimensional Gaussian function curves for the extraction of data from two dimensional gel electrophoresis (2-DE) images. The algorithm implements fitting using logical compounds and is computationally efficient. The applicability of the compound fitting algorithm was evaluated for various simulated data and compared with other quantification approaches. We provide evidence that even if an incorrect bell-shaped function is used, the fitting method is superior to other approaches, especially when spots overlap. Finally, we validated the method with experimental data of urea-based 2-DE of A? peptides andre-analyzed published data sets. Our methods showed higher precision and accuracy than other approaches when applied to exposure time series and standard gels. Conclusion Compound fitting as a quantification method for 2-DE spots shows several advantages over other approaches and could be combined with various spot detection methods. The algorithm was scripted in MATLAB (Mathworks) and is available as a supplemental file. PMID:24915860

2014-01-01

56

Microbeam Radiation Therapy: Tissue Dose Penetration and BANG-Gel Dosimetry of Thick-Beams' Array Intelacing  

SciTech Connect

The tissue-sparing effect of parallel, thin (narrower than 100em) synchrotron-generated X-ray planar beams (microbeams) in healthy tissues including the central nervous system (CNS) is known since early 1990s. This, together with a remarkable preferential tumoricidal effect of such beam arrays observed at high doses, has been the basis for labeling the method microbeam radiation therapy (MRT). Recent studies showed that beams as thick as 0.68mm ('thick microbeams') retain part of their sparing effect in the rat's CNS, and that two such orthogonal microbeams arrays can be interlaced to produce an unsegmented field at the target, thus producing focal targeting. We measured the half-value layer (HVL) of our 120-keV median-energy beam in water phantoms, and we irradiated stereotactically bis acrylamide nitrogen gelatin (BANG)-gel-filled phantoms, including one containing a human skull, with interlaced microbeams and imaged them with MRI. A 43-mm water HVL resulted, together with an adequately large peak-to-valley ratio of the microbeams' three-dimensional dose distribution in the vicinity of the 20mmx20mmx20mm target deep into the skull. Furthermore, the 80-20% dose falloff was a fraction of a millimeter as predicted by Monte Carlo simulations. We conclude that clinical MRT will benefit from the use of higher beam energies than those used here, although the current energy could serve certain neurosurgical applications. Furthermore, thick microbeams particularly when interlaced present some advantages over thin microbeams in that they allow the use of higher beam energies and they could conceivably be implemented with high power orthovoltage X-ray tubes.

Dilmanian, F.; Romanelli, P; Zhong, Z; Wang, R; Wagshul, M; Kalef-Ezra, J; Maryanski, M; Rosen, E; Anschel, D

2008-01-01

57

A study on the reproducibility and spatial uniformity of N-isopropylacrylamide polymer gel dosimetry using a commercial 10X fast optical-computed tomography scanner  

NASA Astrophysics Data System (ADS)

This study investigated the reproducibility and spatial uniformity of N-isopropylacrylamide (NIPAM) polymer gel as well as the reproducibility of a NIPAM polymer gel dosimeter. A commercial 10X fast optical computed tomography scanner (OCTOPUS-10X, MGS Research, Inc., Madison, CT, USA) was used as the readout tool of the NIPAM polymer gel dosimeter. A cylindrical NIPAM gel phantom measuring 10 cm (diameter) by 10 cm (height) by 3 mm (thickness) was irradiated by the four-field box treatment with a field size of 3 cm × 3 cm. The dose profiles were found to be consistent at the depths of 2.0 cm to 5.0 cm for two independent gel phantom batches, and the average uncertainty was less than 2%. The gamma pass rates were calculated to be between 94% and 95% at depths of 40 mm for two independent gel phantom batches using 4% dose difference and 4 mm distance-to-agreement criterion. The NIPAM polymer gel dosimeter was highly reproducible and spatially uniform. The results highlighted the potential of the NIPAM polymer gel dosimeter in radiotherapy.

Chang, Y. J.; Lin, J. Q.; Hsieh, B. T.; Chen, C. H.

2013-06-01

58

NOTE: Preliminary study on the use of an inhomogeneous anthropomorphic Fricke gel phantom and 3D magnetic resonance dosimetry for verification of IMRT treatment plans  

Microsoft Academic Search

An inhomogeneous anthropomorphic phantom of the human thorax including lungs and spine was developed for verification of three-dimensional (3D) intensity-modulated radiotherapy (IMRT). The phantom and spinal cord were filled with undiluted Fricke gel, whereas the lungs were filled with a special low-density Fricke gel. Based on a computed tomography scan of the phantom, an intensity-modulated stereotactic radiotherapy plan for a

F. Gum; J. Scherer; L. Bogner; M. Solleder; B. Rhein; M. Bock

2002-01-01

59

Improved image quality for x-ray CT imaging of gel dosimeters  

SciTech Connect

Purpose: This study provides a simple method for improving precision of x-ray computed tomography (CT) scans of irradiated polymer gel dosimetry. The noise affecting CT scans of irradiated gels has been an impediment to the use of clinical CT scanners for gel dosimetry studies. Methods: In this study, it is shown that multiple scans of a single PAGAT gel dosimeter can be used to extrapolate a ''zero-scan'' image which displays a similar level of precision to an image obtained by averaging multiple CT images, without the compromised dose measurement resulting from the exposure of the gel to radiation from the CT scanner. Results: When extrapolating the zero-scan image, it is shown that exponential and simple linear fits to the relationship between Hounsfield unit and scan number, for each pixel in the image, provide an accurate indication of gel density. Conclusions: It is expected that this work will be utilized in the analysis of three-dimensional gel volumes irradiated using complex radiotherapy treatments.

Kakakhel, M. B.; Kairn, T.; Kenny, J.; Trapp, J. V. [Faculty of Science and Technology, Queensland University of Technology, GPO Box 2434, Brisbane, Queesland 4001, Australia and Department of Physics and Applied Mathematics, DPAM, Pakistan Institute of Engineering and Applied Sciences, PO Nilore, Islamabad 45450 (Pakistan); Premion, The Wesley Medical Centre, Suite 1, 40 Chasely St, Auchenflower, Queensland 4066 (Australia); Premion, The Wesley Medical Centre, Suite 1, 40 Chasely St, Auchenflower, Queensland 4066, Australia and Australian Clinical Dosimetry Service, ARPANSA, Yallambie, Vic 3085 (Australia); Faculty of Science and Technology, Queensland University of Technology, GPO Box 2434, Brisbane, Ql d 4001 (Australia)

2011-09-15

60

Computational dosimetry  

SciTech Connect

The paper presents a definition of the term ``Computational Dosimetry`` that is interpreted as the sub-discipline of computational physics which is devoted to radiation metrology. It is shown that computational dosimetry is more than a mere collection of computational methods. Computational simulations directed at basic understanding and modelling are important tools provided by computational dosimetry, while another very important application is the support that it can give to the design, optimization and analysis of experiments. However, the primary task of computational dosimetry is to reduce the variance in the determination of absorbed dose (and its related quantities), for example in the disciplines of radiological protection and radiation therapy. In this paper emphasis is given to the discussion of potential pitfalls in the applications of computational dosimetry and recommendations are given for their avoidance. The need for comparison of calculated and experimental data whenever possible is strongly stressed.

Siebert, B.R.L.; Thomas, R.H.

1996-01-01

61

Differential dose volume histograms of Gamma Knife in the presence of inhomogeneities using MRI-polymer gel dosimetry and MC simulation  

SciTech Connect

Polymer gel dosimeters offer a practical solution to 3D dose verification for conventional radiotherapy as well as intensity-modulated and stereotactic radiotherapy. In this study, EGSnrc calculated and PAGAT polymer gel dosimeter measured dose volume histograms (DVHs) for single-shot irradiations of the Gamma Knife (GK) unit were used to investigate the effects of the presence of inhomogeneities on 3D dose distribution. The head phantom was a custom-built 16 cm diameter Plexiglas sphere. Inside the phantom, there is a cubic cutout for inserting the gel vials and another cutout for inserting the inhomogeneities. Following irradiation with the GK unit, the polymer gel phantoms were scanned with a 1.5 T MRI scanner. Comparing the results of measurement in homogeneous and heterogeneous phantoms revealed that inserting inhomogeneities inside the homogeneous phantom did not cause considerable disturbances on dose distribution in irradiation with 8 mm collimator within low isodose levels (<50%), which is essential for the dose sparing of sensitive structures. The results of simulation for homogeneous and inhomogeneous phantoms in irradiation with 18 mm collimator of the GK unit showed 23.24% difference in DVH within 90%-100% relative isodose level and also revealed that a significant part of the target (28.56%) received relative doses higher than the maximum dose, which exceeds the acceptance criterion (5%). Based on these results it is concluded that the presence of inhomogeneities inside the phantom can cause considerable errors in dose calculation within high isodose levels with respect to LGP prediction which assumes that the target is a homogeneous material. Moreover, it is demonstrated that the applied MC code is an accurate and stand-alone tool for 3D evaluation of dose distribution in irradiation with the GK unit, which can provide important, 3D plan evaluation criteria used in clinical practice.

Allahverdi Pourfallah, Tayyeb; Allahverdi, Mahmoud; Riahi Alam, Nader; Ay, Mohammad-Reza; Zahmatkesh, Mohammad-Hasan [Department of Biochemistry and Biophysics, Faculty of Medicine, Mazandaran University of Medical Sciences, 48175-1665 Sari (Iran, Islamic Republic of) and Department of Medical Physics and Biomedical Engineering, Tehran University of Medical Sciences, 14155-7661 Tehran (Iran, Islamic Republic of); Department of Medical Physics and Biomedical Engineering, Tehran University of Medical Sciences, 14155-7661 Tehran (Iran, Islamic Republic of); Novin Medical Radiation Center, 14665-599 Tehran (Iran, Islamic Republic of)

2009-07-15

62

Epid Dosimetry  

NASA Astrophysics Data System (ADS)

Electronic portal imaging devices (EPIDs) were introduced originally for patient position verification. The idea of using EPIDs for dosimetry was realised in the 1980s. Little was published on the topic until the mid 1990's, when the interest in EPIDs for dosimetry increased rapidly and continues to grow. The increasing research on EPID dosimetry coincided with the introduction of intensity modulated radiation therapy (IMRT). EPIDs are well suited to IMRT dosimetry because they are high resolution, two-dimensional (2D) digital detectors. They are also pre-existing on almost all modern linear accelerators. They generally show a linear response to increasing dose. Different types of EPIDs have been clinically implemented, and these have been described in several review papers. The current generation of commercially available EPIDs are indirect detection active matrix flat panel imagers, also known as amorphous silicon (a-Si) EPIDs. Disadvantages of a-Si EPIDs for dosimetry include non-water equivalent construction materials, and the energy sensitivity and optical scatter of the phosphor scintillators used to create optical signal from the megavoltage beam. This report discusses current knowledge regarding a-Si EPIDs for dosimetry.

Greer, Peter B.; Vial, Philip

2011-05-01

63

Does prewarming the i-gel supraglottic airway device fit the larynx better compared to keeping it at room temperature for non-paralysed, sedated patients: a randomised controlled trial  

PubMed Central

Objective This study aimed to test the hypothesis that the i-gel supraglottic airway device would fit the larynx and provide better sealing pressure if prewarmed to 42°C relative to the device kept at room temperature in non-paralysed, sedated patients. Methods A total of 74 adult patients were assigned to the warm (i-gel prewarmed to 42°C; W group; 37 patients) or the control (i-gel kept at room temperature; C group; 37 patients) groups. Anaesthesia was induced with propofol and fentanyl. The i-gel was prewarmed to 42°C for 30?min before insertion in the W group, but kept at room temperature (approximately 23°C) for the C group. The number of attempts made until successful insertion and sealing pressure were compared between the two groups. Results Insertion was successful with one attempt in 35 cases each for the W and C groups. Two attempts were needed in two cases for the W group and one case for the C group. There was one failed attempt in the C group, but none in the W group. None of the differences between the two groups were significant (p=0.51). Sealing pressure was slightly, but not significantly, higher in the W group than in the C group (W group 22.6±6.1?cm?H2O; C group 20.7±6.1?cm?H2O; p=0.15). Conclusions Prewarming of the i-gel to 42°C did not increase the success rate of insertion, nor did it significantly increase sealing pressure in anaesthetised, non-paralysed patients. Our data suggest that we can keep the i-gel at room temperature for emergency airway management for non-paralysed, sedated patients. Trial registration number University Medical Information Network, Japan 000012287. PMID:25586372

Komasawa, Nobuyasu; Nishihara, Isao; Tatsumi, Shinichi; Minami, Toshiaki

2015-01-01

64

TVA's dosimetry technician training program  

SciTech Connect

In 1984, the Tennessee Valley Authority decentralized its personnel TLD program and established TLD processing facilities at each of its nuclear plant sites. This article describes the training program that was developed to aid in staffing dosimetry technician positions at each of the plants. The scope of the dosimetry technician's duties include TLD processing, operation of a computerized records system, whole-body counting system operation, and respirator mask fit-testing. The training program includes thirteen weeks of classroom and laboratory training plus a 15-month apprenticeship at a nuclear plant. Retraining and requalification are performed on an annual basis.

Hudson, C.G.; Faust, V.L.; Cornelius, T.W.; Regan, J.M.; Farrell, W.E. (Tennessee Valley Authority, Power Operations Training Center, Daisy, TN (US))

1984-04-01

65

(Biological dosimetry)  

SciTech Connect

The traveler attended the 1st International Conference on Biological Dosimetry in Madrid, Spain. This conference was organized to provide information to a general audience of biologists, physicists, radiotherapists, industrial hygiene personnel and individuals from related fields on the current ability of cytogenetic analysis to provide estimates of radiation dose in cases of occupational or environmental exposure. There is a growing interest in Spain in biological dosimetry because of the increased use of radiation sources for medical and occupational uses, and with this the anticipated and actual increase in numbers of overexposure. The traveler delivered the introductory lecture on Biological Dosimetry: Mechanistic Concepts'' that was intended to provide a framework by which the more applied lectures could be interpreted in a mechanistic way. A second component of the trip was to provide advice with regard to several recent cases of overexposure that had been or were being assessed by the Radiopathology and Radiotherapy Department of the Hospital General Gregorio Maranon'' in Madrid. The traveler had provided information on several of these, and had analyzed cells from some exposed or purportedly exposed individuals. The members of the biological dosimetry group were referred to individuals at REACTS at Oak Ridge Associated Universities for advice on follow-up treatment.

Preston, R.J.

1990-12-17

66

Reconstructing 3D x-ray CT images of polymer gel dosimeters using the zero-scan method  

NASA Astrophysics Data System (ADS)

In this study x-ray CT has been used to produce a 3D image of an irradiated PAGAT gel sample, with noise-reduction achieved using the 'zero-scan' method. The gel was repeatedly CT scanned and a linear fit to the varying Hounsfield unit of each pixel in the 3D volume was evaluated across the repeated scans, allowing a zero-scan extrapolation of the image to be obtained. To minimise heating of the CT scanner's x-ray tube, this study used a large slice thickness (1 cm), to provide image slices across the irradiated region of the gel, and a relatively small number of CT scans (63), to extrapolate the zero-scan image. The resulting set of transverse images shows reduced noise compared to images from the initial CT scan of the gel, without being degraded by the additional radiation dose delivered to the gel during the repeated scanning. The full, 3D image of the gel has a low spatial resolution in the longitudinal direction, due to the selected scan parameters. Nonetheless, important features of the dose distribution are apparent in the 3D x-ray CT scan of the gel. The results of this study demonstrate that the zero-scan extrapolation method can be applied to the reconstruction of multiple x-ray CT slices, to provide useful 2D and 3D images of irradiated dosimetry gels.

Kakakhel, M. B.; Kairn, T.; Kenny, J.; Trapp, J. V.

2013-06-01

67

Methylthymol blue in Fricke gels  

NASA Astrophysics Data System (ADS)

The initial trial of methylthymol blue (MTB) as a chelator for ferric iron in Fricke gel dosimeters, used for three-dimensional (3D) dosimetry in cancer radiotherapy, is reported. MTB is a structural analogue of the conventionally used xylenol orange (XO); however, the absorbance spectrum of the ferric-MTB complex is shifted to higher wavelengths, which should allow for lower amount of light scattering during gel scanning. In this study, two gelatin substrates, two sources of XO and one source of MTB have been compared. The MTB- containing gels exhibited similar dose response and diffusion coefficient to the XO-containing gels at their wavelengths of maximum absorption (620 and 585 nm, respectively). In addition, the MTB gels gave an excellent dose response at 633 nm, which is an important wavelength that is already used with other 3D dosimeters.

Penev, K. I.; Mequanint, K.

2015-01-01

68

Personnel neutron dosimetry  

SciTech Connect

This edited transcript of a presentation on personnel neutron discusses the accuracy of present dosimetry practices, requirements, calibration, dosemeter types, quality factors, operational problems, and dosimetry for a criticality accident. 32 figs. (ACR)

Hankins, D.

1982-04-01

69

Software for 3D radiotherapy dosimetry. Validation  

NASA Astrophysics Data System (ADS)

The subject of this work is polyGeVero® software (GeVero Co., Poland), which has been developed to fill the requirements of fast calculations of 3D dosimetry data with the emphasis on polymer gel dosimetry for radiotherapy. This software comprises four workspaces that have been prepared for: (i) calculating calibration curves and calibration equations, (ii) storing the calibration characteristics of the 3D dosimeters, (iii) calculating 3D dose distributions in irradiated 3D dosimeters, and (iv) comparing 3D dose distributions obtained from measurements with the aid of 3D dosimeters and calculated with the aid of treatment planning systems (TPSs). The main features and functions of the software are described in this work. Moreover, the core algorithms were validated and the results are presented. The validation was performed using the data of the new PABIGnx polymer gel dosimeter. The polyGeVero® software simplifies and greatly accelerates the calculations of raw 3D dosimetry data. It is an effective tool for fast verification of TPS-generated plans for tumor irradiation when combined with a 3D dosimeter. Consequently, the software may facilitate calculations by the 3D dosimetry community. In this work, the calibration characteristics of the PABIGnx obtained through four calibration methods: multi vial, cross beam, depth dose, and brachytherapy, are discussed as well.

Kozicki, Marek; Maras, Piotr; Karwowski, Andrzej C.

2014-08-01

70

Software for 3D radiotherapy dosimetry. Validation.  

PubMed

The subject of this work is polyGeVero(®) software (GeVero Co., Poland), which has been developed to fill the requirements of fast calculations of 3D dosimetry data with the emphasis on polymer gel dosimetry for radiotherapy. This software comprises four workspaces that have been prepared for: (i) calculating calibration curves and calibration equations, (ii) storing the calibration characteristics of the 3D dosimeters, (iii) calculating 3D dose distributions in irradiated 3D dosimeters, and (iv) comparing 3D dose distributions obtained from measurements with the aid of 3D dosimeters and calculated with the aid of treatment planning systems (TPSs). The main features and functions of the software are described in this work. Moreover, the core algorithms were validated and the results are presented. The validation was performed using the data of the new PABIG(nx) polymer gel dosimeter. The polyGeVero(®) software simplifies and greatly accelerates the calculations of raw 3D dosimetry data. It is an effective tool for fast verification of TPS-generated plans for tumor irradiation when combined with a 3D dosimeter. Consequently, the software may facilitate calculations by the 3D dosimetry community. In this work, the calibration characteristics of the PABIG(nx) obtained through four calibration methods: multi vial, cross beam, depth dose, and brachytherapy, are discussed as well. PMID:25003788

Kozicki, Marek; Maras, Piotr; Karwowski, Andrzej C

2014-08-01

71

Gel Electrophoresis  

NSDL National Science Digital Library

This interactive activity from the Dolan DNA Learning Center illustrates the process of gel electrophoresis, in which DNA fragments are separated by size as they migrate at different rates through a gel matrix.

Foundation, Wgbh E.

2007-04-19

72

Study of density and stability of a lung-equivalent gel  

NASA Astrophysics Data System (ADS)

Gel dosimetry is a useful tool for the verification of radiation treatments in water-equivalent tissues. In order to extend the application of gel dosimetry to the lung, the density of the dosimeter should be reduced. Some methods have been proposed for the fabrication of low-density gels. Major challenges in the fabrication of these gel dosimeters are to achieve a density that equals the electron-density of lung tissue and to obtain an acceptable homogeneity. Both polymer and Fricke gel formulations have been used as basic chemical compositions for low-density gel dosimeters. To reduce the density, two approaches have been suggested: (1) Styrofoam beads can be added to the gel or (2) the gel can be beaten until a foam is obtained. In this study we followed the latter method and added sodium-dodecyl-sulphate (SDS) as a surfactant to increase the surface tension of the gel.

Claeys, Carolien; de Deene, Yves; Truyens, Bart; de Wagter, Carlos

2006-12-01

73

Dosimetry of the Leksell gamma knife  

NASA Astrophysics Data System (ADS)

No accepted official protocol exists for the dosimetry of the Leksell Gamma KnifeRTM (GK) stereotactic radiosurgery device. Establishment of a dosimetry protocol has been complicated by the unique partial-hemisphere arrangement of 201 separate 60Co beams simultaneously focused on the treatment volume and by the rigid geometry of the GK unit itself. This paper proposes an air kerma based dosimetry protocol using an in-air or in-acrylic phantom measurement to determine the dose rate of fields collimated by the 18 mm helmet of a GK unit. A small-volume ionization chamber was used to make measurements at the physical isocenter of three GK units. The dose rate to water was determined using a modified version of the AAPM Task Group 21 protocol designed for use with 60Co-based teletherapy machines. This experimentally determined dose rate was compared to the treatment planning system (TPS) dose rate that is determined by the clinical medical physicist at the time of machine commissioning. The TPS dose rate is defined as dose rate to water at a depth of 8 cm. The dose rate to water for the 18 mm helmet determined using the air kerma based calculations presented here is consistently between 1.5% and 2.9% higher than the TPS dose rate. These air kerma based measurements allow GK dosimetry to be performed with an established dosimetry protocol and without complications arising from the use of and possible variations in solid phantom material. Measurements were made with the same chamber in a spherical acrylic phantom for comparison. This methodology will allow future development of calibration methods appropriate for the smaller fields of GK units to be compared to a well established standard. Multiple three-dimensional dosimetry methods were also used to capture the dose distribution of the entire field of the GK. These methods included radiosensitive gel, a novel three-dimensional radiochromic film phantom, and Monte Carlo modeling. These methods were also compared to the dose distribution calculated by the TPS used with the GK unit. Volume analysis was performed that compared the volume irradiated to relative dose levels for the GK fields using data from dose volume histograms computed for these methods.

Meltsner, Sheridan Griffin

74

A genipin-gelatin gel dosimeter for radiation processing  

Microsoft Academic Search

Genipin, a fruit extract from Gardenia jasminoides Ellis, forms cross-links in solutions of gelatin, to form a blue hydrogel that bleaches quantitatively upon irradiation and the colour change can be measured with a spectrophotometer. With the addition of sulphuric acid this dosimeter is sufficiently sensitive for quality assurance of radiotherapy level dosimetry. Without sulphuric acid the gel has a reduced

J. B. Davies; S. G. Bosi; C. Baldock

75

Fitness Factor  

NSDL National Science Digital Library

In this online activity, learners partner up to complete several physical exercises and assess their starting fitness level. Over the course of 6 weeks, learners practice the activities and record their improvement. This is a simple way to get young learners interested in practicing fitness. When learners set up a free account at Kinetic City, they can answer bonus questions at the end of the activity as a quick assessment. They can also keep track of their progress in all of the Kinetic City activities, and compare their progress to other participants worldwide.

American Association for the Advancement of Science

2009-01-01

76

Monte Carlo simulations to optimize experimental dosimetry of narrow beams used in Gamma Knife radio-surgery  

NASA Astrophysics Data System (ADS)

The Leksell Gamma Knife is a stereotactic radio-surgery unit for the treatment of small volumes (on the order of 25 mm 3) that employs a hemispherical configuration of 201 60Co sources and appropriate configurations of collimation to form beams of 4, 8, 14 and 18 mm nominal diameter at the Unit Center Point (UCP). Although Monte Carlo (MC) simulation is well suited for narrow-beam dosimetry, experimental dosimetry is required at least for acceptance testing and quality assurance purposes. Besides other drawbacks of conventional point dosimeters, the main problems associated with narrow-beam dosimetry in stereotactic applications are accurate positioning and volume averaging. In this work, MCNPX and EGSnrc MC simulation dosimetry results for a Gamma Knife unit are benchmarked through their comparison to treatment planning software calculations based on radio-chromic film measurements. Then, MC dosimetry results are utilized to optimize the only three-dimensional experimental dosimetry method available; the polymer gel-Magnetic Resonance Imaging (MRI) method. MC results are used to select the spatial resolution in the imaging session of the irradiated gels and validate a mathematical tool for the localization of the UCP in the three-dimensional experimental dosimetry data acquired. Experimental results are compared with corresponding MC calculations and shown capable to provide accurate dosimetry, free of volume averaging and positioning uncertainties.

Lymperopoulou, G.; Petrokokkinos, L.; Papagiannis, P.; Steiner, M.; Spevacek, V.; Semnicka, J.; Dvorak, P.; Seimenis, I.

2007-09-01

77

Gel Electrophoresis  

NSDL National Science Digital Library

In this activity, learners simulate the process of DNA fingerprinting by using electricity to separate colored dyes. Learners use simple materials to assemble a comb (electrophoresis chamber) to hold the samples, make a 0.2% sodium bicarbonate buffer and 1% gel solution, connect a high voltage power supply, and prepare 5 different samples. Then learners test their model and observe each sample.

Yu, Julie

2007-01-01

78

Ion-kill dosimetry  

NASA Technical Reports Server (NTRS)

Unanticipated late effects in neutron and heavy ion therapy, not attributable to overdose, imply a qualitative difference between low and high LET therapy. We identify that difference as 'ion kill', associated with the spectrum of z/beta in the radiation field, whose measurement we label 'ion-kill dosimetry'.

Katz, R.; Cucinotta, F. A.; Fromm, M.; Chambaudet, A.

2001-01-01

79

Gamma/neutron dose evaluation using Fricke gel and alanine gel dosimeters to be applied in boron neutron capture therapy.  

PubMed

Gel dosimetry has been studied mainly for medical applications. The radiation induced ferric ions concentration can be measured by different techniques to be related with the absorbed dose. Aiming to assess gamma/thermal neutrons dose from research reactors, Fricke gel and alanine gel solutions produced at IPEN using 300 bloom gelatin were mixed with Na(2)B(4)O(7) salt, and the mixtures were irradiated at the beam hole #3 of the IEA-R1 research reactor, (BH#3) adapted to BNCT studies, and the dose-response was evaluated using spectrophotometry technique. PMID:20122843

Mangueira, T F; Silva, C F; Coelho, P R P; Campos, L L

2010-01-01

80

Electron Paramagnetic Resonance Retrospective Dosimetry  

SciTech Connect

Necessity for, principles of, and general concepts of the electron paramagnetic resonance (EPR) retrospective dosimetry are presented. Also presented and given in details are examples of EPR retrospective dosimetry applications in tooth enamel, bone, and fingernails with focus on general approaches for solving technical and methodological problems. Advantages, drawbacks, and possible future developments are discussed and an extensive bibliography on EPR retrospective dosimetry is provided.

Romanyukha, Alex [Naval Dosimetry Center, 8901 Wisconsin Ave., Bethesda, MD, 20889 (United States); Trompier, Francois [Institute for Radiological Protection and Nuclear Safety, Fontenay-aux-Roses, France 92262 (France)

2011-05-05

81

Evaluation du potentiel radiosensibilisateur ou radioprotecteur/antioxydant de quelques composes selectionnes par dosimetrie par gel de polyacrylamide et dosimetre de Fricke, et utilisation de la filamentation par impulsion laser infrarouge fenitoseconde comme un nouveau et puissant faisceau pour la radiotherapie du cancer  

NASA Astrophysics Data System (ADS)

In radiation treatment, a sufficiently high radiation dose must be delivered to the tissue volumes containing the tumor cells while the lowest possible dose should be deposited in surrounding healthy tissue. We developed an original approach that is fast and easy to implement for the early assessment of the efficiency of radiation sensitizers and protectors. In addition, we characterized a new femtosecond laser pulse irradiation technique. We are able to deposit a considerable dose with a very high dose rate inside a well-controlled macroscopic volume without deposition of energy in front or behind the target volume. The radioprotective efficiency was measured by irradiation of the Fricke solution incorporating a compound under study and measuring the corresponding production of ferric ions G(Fe3+). The production of ferric ions is most sensitive to the radical species produced in the radiolysis of water. We studied experimentally and simulated with a full Monte-Carlo computer code the radiation-induced chemistry of Fricke/cystamine solutions. Results clearly indicate that the protective effect of cystamine originates from its radical-capturing ability, which allows this compound to compete with the ferrous ions for the various free radicals - especially ·OH radicals and H· atoms - formed during irradiation of the surrounding water. The sensitizing capacity of radiation sensitizers was measured by irradiation of a polyacrylamide gel (PAG) dosimeter incorporating a compound under study and measuring the corresponding increase in the gradient between spin-spin relaxation rate (R2) and absorbed dose. We measured an irradiation energy-dependent increase in R 2-dose sensitivity for halogenated compounds or a decrease for radioprotectors. Finally, we studied a novel laser irradiation method called "filamentation". We showed that this phenomenon results in an unprecedented deposition of energy and the dose rate thus achieved exceeds by orders of magnitude values previously reported for the most intense clinical radiotherapy systems. Moreover, the length of the dose-free entrance region was adjusted by selecting the duration of femtosecond laser pulses. In addition, we provided evidence that the biological damage caused by this irradiation was similar to other ionizing radiation sources. Keywords: Radiotherapy, radiosensitization, radioprotection, laser, filamentation, dosimetry.

Meesat, Ridthee

82

Hanford External Dosimetry Program  

SciTech Connect

This document describes the Hanford External Dosimetry Program as it is administered by Pacific Northwest Laboratory (PNL) in support of the US Department of Energy (DOE) and its Hanford contractors. Program services include administrating the Hanford personnel dosimeter processing program and ensuring that the related dosimeter data accurately reflect occupational dose received by Hanford personnel or visitors. Specific chapters of this report deal with the following subjects: personnel dosimetry organizations at Hanford and the associated DOE and contractor exposure guidelines; types, characteristics, and procurement of personnel dosimeters used at Hanford; personnel dosimeter identification, acceptance testing, accountability, and exchange; dosimeter processing and data recording practices; standard sources, calibration factors, and calibration processes (including algorithms) used for calibrating Hanford personnel dosimeters; system operating parameters required for assurance of dosimeter processing quality control; special dose evaluation methods applied for individuals under abnormal circumstances (i.e., lost results, etc.); and methods for evaluating personnel doses from nuclear accidents. 1 ref., 14 figs., 5 tabs.

Fix, J.J.

1990-10-01

83

Thorium metabolism and dosimetry  

SciTech Connect

Thorium occurs widely in nature, and has been used in medicine, industry, and advanced nuclear fuel cycles. Despite many studies, there still remains uncertainty in the dosimetry of Th, particularly that associated with the Th-232 decay chain. This presentation reviews past and current uses of thorium, and describes the residual difficulties involved with monitoring methods and calculations used in both environmental and occupational exposure evaluations.

Johnson, J.R.; Hill, R.L. [Pacific Northwest Lab., Richland, WA (United States); Birchall, A.; Jarvis, N.S. [National Radiological Protection Board, Chilton (United Kingdom)

1994-07-01

84

Fricke Gel Dosimeter Tissue-Equivalence a Monte Carlo Study  

NASA Astrophysics Data System (ADS)

Gel dosimetry has proved to be a valuable technique for absorbed dose distribution measurements in radiotherapy. FriXy-gel dosimeters consist of Fricke (ferrous sulphate) solution infused with xylenol orange. The solution is incorporated to a gel matrix in order to fix it to a solid structure allowing good spatial resolution and is imaged with a transportable optical system, measuring visible light transmittance before and after irradiation. This paper presents an evaluation of total photon mass attenuation coefficients at energies in the range of 50 keV-10MeV for the radiochromic FriXy gel dosimeter sensitive material. Mass attenuation coefficient estimations have been performed by means of Monte Carlo (PENELOPE) simulations. These calculations have been carried out for the FriXy gel sensitive material as well as for soft tissue (ICRU) and pure liquid water; a comparison of the obtained data shows good agreement between the different materials.

Valente, M.; Bartesaghi, G.; Gambarini, G.; Brusa, D.; Castellano, G.; Carrara, M.

2008-06-01

85

Laser CT evaluation on normoxic PAGAT gel dosimeter  

NASA Astrophysics Data System (ADS)

Optical computed tomography has been shown to be a potentially useful imaging tool for the radiation therapy physicists. In radiation therapy, researchers have used optical CT for the readout of 3D dosimeters. The purpose of this paper is to describe the initial evaluation of a newly fabricated laser CT scanner for 3D gel dosimetry which works using the first generation principle. A normoxic PAGAT (Polyacrylamide Gelatin and Tetrakis) gel is used as a dosimeter for this analysis. When a laser passes through the gel phantom, absorption and scattering of photon take place. The optical attenuation coefficient of the laser can be obtained by measuring its intensity after passing through the gel by a sensor. The scanner motion is controlled by a computer program written in Microsoft Visual C++. Reconstruction and data analysis on the irradiated gel phantom is performed by suitable algorithm using Matlab software.

Kumar, D. S.; Samuel, E. J. J.; Watanabe, Y.

2013-06-01

86

Men's Fitness  

NSDL National Science Digital Library

It seems that people in the United States are going through a new and renewed commitment to getting back in shape, and there are a variety of helpful online resources to make this a viable possibility for millions of Americans. This particular site (sponsored by a number of fitness-related publications) brings together information on a host of timely topics, including weight loss, healthy eating, building muscle mass, and seasonal training suggestions. The homepage contains links on such topics as diminishing cellulite and eating organic, and also contains a number of online calculators. These calculators can help individuals determine their body mass index, their weight loss potential, and their ideal weight. The site also has an area where visitors can sign up to receive any number of free electronic newsletters from some of the magazines that sponsor the site.

87

Effect of bloom strength on radiochromic gel dosimeters  

NASA Astrophysics Data System (ADS)

The Fricke gel dosimeter has been the widely used dosimeter among the gel dosimeters because of its dose response characteristics and easy preparation. The ferrous to ferric conversion that happens in this gel dosimeter on irradiation, corresponds to the absorbed dose of radiation. Gel dosimetry in India is not moving forward because of the import restrictions on the commercially available high bloom strength gelatin (imported 300 bloom). The feasibility of using Fricke gel dosimeter prepared with the locally available gelatin of 240 bloom and 200 bloom were compared with the 300 bloom gelatin taken as standard. The gel samples were prepared with 5% gelatin by weight and irradiated with 60Co gamma radiation for a dose range from 0-3 Gy used clinically. The optical absorption of gel samples were analyzed using spectrophotometer at 585 nm and dose response curves were generated. The results indicate that Fricke gels prepared with 240 bloom have linear dose response and comparable with those prepared with 300 bloom but the use of gels prepared with 200 bloom was found to be limited because of its poor optical transmittance.

Ebenezer Suman Babu, S.; Ravindran, B. Paul

2015-01-01

88

Fast neutron dosimetry  

SciTech Connect

This progress report concentrates on two major areas of dosimetry research: measurement of fast neutron kerma factors for several elements for monochromatic and white spectrum neutron fields and determination of the response of thermoluminescent phosphors to various ultra-soft X-ray energies and beta-rays. Dr. Zhixin Zhou from the Shanghai Institute of Radiation Medicine, People's Republic of China brought with him special expertise in the fabrication and use of ultra-thin TLD materials. Such materials are not available in the USA. The rather unique properties of these materials were investigated during this grant period.

DeLuca, P.M. Jr.; Pearson, D.W.

1992-01-01

89

Heavy-ion dosimetry  

SciTech Connect

This lecture deals with some of the more important physical characteristics of relativistic heavy ions and their measurement, with beam delivery and beam monitoring, and with conventional radiation dosimetry as used in the operation of the BEVALAC biomedical facility for high energy heavy ions (Lyman and Howard, 1977; BEVALAC, 1977). Even so, many fundamental aspects of the interaction of relativistic heavy ions with matter, including important atomic physics and radiation chemical considerations, are not discussed beyond the reminder that such additional understanding is required before an adequte perspective of the problem can be attained.

Schimmerling, W.

1980-03-01

90

PREFACE: 7th International Conference on 3D Radiation Dosimetry (IC3DDose)  

NASA Astrophysics Data System (ADS)

IC3DDose 2013, the 7th International Conference on 3D Radiation Dosimetry held in Sydney, Australia from 4-8 November 2012, grew out of the DosGel series, which began as DosGel99, the 1st International Workshop on Radiation Therapy Gel Dosimetry in Lexington, Kentucky. Since 1999 subsequent DoSGel conferences were held in Brisbane, Australia (2001), Ghent, Belgium (2004), Sherbrooke, Canada (2006) and Crete, Greece (2008). In 2010 the conference was held on Hilton Head Island, South Carolina and underwent a name-change to IC3DDose. The aim of the first workshop was to bring together individuals, both researchers and users, with an interest in 3D radiation dosimetry techniques, with a mix of presentations from basic science to clinical applications, which has remained an objective for all of the meetings. One rationale of DosGel99 was stated as supporting the increasing clinical implementation of gel dosimetry, as the technique appeared, at that time, to be leaving the laboratories of gel dosimetry enthusiasts and entering clinical practice. Clearly by labelling the first workshop as the 1st, there was a vision of a continuing series, which has been fulfilled. On the other hand, the expectation of widespread clinical use of gel dosimetry has perhaps not been what was hoped for and anticipated. Nevertheless the rapidly increasing demand for advanced high-precision 3D radiotherapy technology and techniques has continued apace. The need for practical and accurate 3D dosimetry methods for development and quality assurance has only increased. By the 6th meeting, held in South Carolina in 2010, the Conference Scientific Committee recognised the wider developments in 3D systems and methods and decided to widen the scope, whilst keeping the same span from basic science to applications. This was signalled by a change of name from 'Dosgel' to 'IC3DDose', a name that has continued to this latest conference. The conference objectives were: to enhance the quality and accuracy of radiation therapy treatment through improved clinical dosimetry to investigate and understand the dosimetric challenges of modern radiation treatments to provide a forum to discuss the latest research and developments in 3D and advanced radiation dosimetry to energise and diversify dosimetry research and clinical practice by encouraging interaction and synergy between advanced, 3D and semi-3D dosimetry techniques We believe the conference program, with its excellent range of expert and specialist speakers, met these objectives. Thanks are due to all invited speakers for their participation, to the Local Organising Committee members for all their hard work in making the conference happen, particularly the small core administrative support group, and to the range of academic, organisation and commercial sponsors who generously supported the meeting. The Scientific Committee members are also thanked for reviewing the submitted manuscripts and for assisting in the editorial process. Finally, all who travelled to Sydney, Australia for the meeting are acknowledged for choosing to attend and contribute to making this a successful conference. Local Conference Organising Committee David Thwaites (Conference Convener) Clive Baldock Leanne Price Elizabeth Starkey May Whitaker Peter Greer Lois Holloway Phil Vial Robin Hill Conference Scientific Committee Sven Back (Sweden) Clive Baldock (Australia) Cheng-Shie Wuu (USA) Yves de Deene (Belgium) Simon Doran (UK) Geoffrey Ibbott (USA) Andrew Jirasek (Canada) Kevin Jordan (Canada) Martin Lepage (Canada) Mark Oldham (USA) Evangelos Pappas (Greece) John Schreiner (Canada) David Thwaites (Australia) David ThwaitesClive Baldock DirectorExecutive Dean Institute of Medical PhysicsFaculty of Science School of PhysicsMacquarie University University of SydneyNorth Ryde NSW 2006NSW 2109 AustraliaAustralia The PDF also contains the conference program.

Thwaites, David; Baldock, Clive

2013-06-01

91

Availability of a containerless polymer gel detector and a gelatin container  

NASA Astrophysics Data System (ADS)

We considered an availability of the polymer gel detector without container but with a plastic wrap under assumption of the low oxygen transmissivity of a sheet of plastic wrap. And a gelatin container was also examined for a gel detector. These samples can be made easily and this containerless polymer gel detector well works without any artifacts by means of wrapping with a thin plastic sheet. Nevertheless, there is still room for improvement on preventing oxygen contamination. Combination with a gelatin container and a polymer gel detector and/or Gafchromic films has a various potential for extension of 3D dosimetry.

Tominaga, Takahiro; Yoshioka, Munenori; Hayashi, Shin-ichiro; Usui, Shuji; Tada, Mitsutoshi

2015-01-01

92

Internal dosimetry technical basis manual  

SciTech Connect

The internal dosimetry program at the Savannah River Site (SRS) consists of radiation protection programs and activities used to detect and evaluate intakes of radioactive material by radiation workers. Examples of such programs are: air monitoring; surface contamination monitoring; personal contamination surveys; radiobioassay; and dose assessment. The objectives of the internal dosimetry program are to demonstrate that the workplace is under control and that workers are not being exposed to radioactive material, and to detect and assess inadvertent intakes in the workplace. The Savannah River Site Internal Dosimetry Technical Basis Manual (TBM) is intended to provide a technical and philosophical discussion of the radiobioassay and dose assessment aspects of the internal dosimetry program. Detailed information on air, surface, and personal contamination surveillance programs is not given in this manual except for how these programs interface with routine and special bioassay programs.

Not Available

1990-12-20

93

Fundamentals of Radiation Dosimetry  

NASA Astrophysics Data System (ADS)

The basic concepts of radiation dosimetry are reviewed on basis of ICRU reports and text books. The radiation field is described with, among others, the particle fluence. Cross sections for indirectly ionizing radiation are defined and indicated is how they are related to the mass energy transfer and mass energy absorption coefficients. Definitions of total and restricted mass stopping powers of directly ionizing radiation are given. The dosimetric quantities, kerma, absorbed dose and exposure together with the relations between them are discussed in depth. Finally it is indicated how the absorbed dose can be measured with a calorimeter by measuring the temperature increase and with an ionisation chamber measuring the charge produced by the ionizing radiation and making use of the Bragg-Gray relation.

Bos, Adrie J. J.

2011-05-01

94

Fundamentals of Radiation Dosimetry  

SciTech Connect

The basic concepts of radiation dosimetry are reviewed on basis of ICRU reports and text books. The radiation field is described with, among others, the particle fluence. Cross sections for indirectly ionizing radiation are defined and indicated is how they are related to the mass energy transfer and mass energy absorption coefficients. Definitions of total and restricted mass stopping powers of directly ionizing radiation are given. The dosimetric quantities, kerma, absorbed dose and exposure together with the relations between them are discussed in depth. Finally it is indicated how the absorbed dose can be measured with a calorimeter by measuring the temperature increase and with an ionisation chamber measuring the charge produced by the ionizing radiation and making use of the Bragg-Gray relation.

Bos, Adrie J. J. [Delft University of Technology, Faculty of Applied Sciences, Mekelweg 15, 2629JB Delft (Netherlands)

2011-05-05

95

Temperature responsive gel displays  

NASA Astrophysics Data System (ADS)

Synthesis and application of engineered surface patterns on environmentally responsive polymer gels are reported here. N-isopropylacrylamide (NIPA) gel was deposited on the masked-surface of an acrylamide gel using photo-initiated polymerization method. The pattern of the NIPA deposited area can be either visible or invisible by simply switching temperature above or below the low critical solution temperature (LCST) of the NIPA gel. Such gels can be used as displays.

Zheng, Yindong; Wang, Changjie; Hu, Zhibing; Li, Yong

1999-10-01

96

Hamiltonian inclusive fitness: a fitter fitness concept  

PubMed Central

In 1963–1964 W. D. Hamilton introduced the concept of inclusive fitness, the only significant elaboration of Darwinian fitness since the nineteenth century. I discuss the origin of the modern fitness concept, providing context for Hamilton's discovery of inclusive fitness in relation to the puzzle of altruism. While fitness conceptually originates with Darwin, the term itself stems from Spencer and crystallized quantitatively in the early twentieth century. Hamiltonian inclusive fitness, with Price's reformulation, provided the solution to Darwin's ‘special difficulty’—the evolution of caste polymorphism and sterility in social insects. Hamilton further explored the roles of inclusive fitness and reciprocation to tackle Darwin's other difficulty, the evolution of human altruism. The heuristically powerful inclusive fitness concept ramified over the past 50 years: the number and diversity of ‘offspring ideas’ that it has engendered render it a fitter fitness concept, one that Darwin would have appreciated. PMID:24132089

Costa, James T.

2013-01-01

97

Chemical dosimetry in the near zone of brachytherapy sources  

NASA Astrophysics Data System (ADS)

New treatment methods and technical advances in the field of radiation oncology have challenged Medical Physicists to design sophisticated dosimeters to measure the dose in the near-zone of brachytherapy sources. To accurately map steep dose-gradients in the near-zone the detector should not perturb the radiation field and should be tissue equivalent, energy independent, and dose rate independent. The treatment of neointimal hyperplasia, prostate cancer with permanent brachytherapy seed implants, and transition zone effects in 3-D conformal therapy has spurred the development of new dosimeters and apparatuses for evaluating steep dose-gradient regions. This project has developed two dosimetry systems to accurately measure the radial dose in the near-zone of clinically used 137Cs and 192Ir sources. A polymer gel dosimeter was designed and implemented for this project. This study represents the first attempt to use a custom-made polymer gel dosimeter to exclusively investigate the radial dose in the near-zone of brachytherapy sources. The custom-made polymer gel dosimeter in conjunction with a high-field strength small-bore MR scanner was determined to provide accurate and reproducible data of the dose in the near-zone. A second dosimetry system consisted of gaf-chromic film- 'the gold standard'-and a custom-built precision scanner. The scanner was designed with a 670nm wave length diode-laser and precision-built micrometers for scanning. The scanner provided optimal scanning conditions for the gaf-chromic film. The gaf-chromic film data for the radial dose in the near-zone of the clinically used 137Cs and 192Ir sources agreed well with the data from the polymer gel dosimeter. This project has confirmed the radial dose results in the near-zone of the often-cited Monte-Carlo data of Williamson. The polymer gel and the gaf-chromic film radial dose data agree well with the Monte-Carlo data in the near-zone of a single 137Cs source and a single 192Ir seed. This project has extended the reliable data in the near-zone from 3mm down to 1mm. Both detectors were shown to be excellent candidates for near- zone dosimetry, and have created an empirical benchmark for the Monte-Carlo theorist.

Hasson, Brian Fitzgerald

98

Alternative statistical methods for cytogenetic radiation biological dosimetry  

E-print Network

The paper presents alternative statistical methods for biological dosimetry, such as the Bayesian and Monte Carlo method. The classical Gaussian and robust Bayesian fit algorithms for the linear, linear-quadratic as well as saturated and critical calibration curves are described. The Bayesian model selection algorithm for those curves is also presented. In addition, five methods of dose estimation for a mixed neutron and gamma irradiation field were described: two classical methods, two Bayesian methods and one Monte Carlo method. Bayesian methods were also enhanced and generalized for situations with many types of mixed radiation. All algorithms were presented in easy-to-use form, which can be applied to any computational programming language. The presented algorithm is universal, although it was originally dedicated to cytogenetic biological dosimetry of victims of a nuclear reactor accident.

Fornalski, Krzysztof Wojciech

2014-01-01

99

4.2 Methods for Internal Dosimetry  

NASA Astrophysics Data System (ADS)

This document is part of Subvolume A 'Fundamentals and Data in Radiobiology, Radiation Biophysics, Dosimetry and Medical Radiological Protection' of Volume 7 'Medical Radiological Physics' of Landolt-Börnstein - Group VIII 'Advanced Materials and Technologies'. It contains the Section '4.2 Methods for Internal Dosimetry' of the Chapter '4 Dosimetry in Nuclear Medicine Diagnosis and Therapy' with the contents:

Noßke, D.; Mattsson, S.; Johansson, L.

100

Individual dosimetry for neutron radiation fields  

NASA Astrophysics Data System (ADS)

Neutron dosimetry techniques used in a dosimetric center are discussed, including film individual dosimetry for slow and fast neutrons, albedo individual dosimetry with either thermoluminescent detectors or alpha particle tracer detectors, and alpha tracer detectors using the CR-39 commercial reticulated polymer. The technique using the CR-39 is found to be easy to use, low cost and has a low neutron energy threshold.

Lembo, L.

1982-10-01

101

Initial radiation dosimetry at Hiroshima and Nagasaki  

SciTech Connect

The dosimetry of A-bomb survivors at Hiroshima and Nagasaki is discussed in light of the new dosimetry developed in 1980 by the author. The important changes resulting from the new dosimetry are the ratios of neutron to gamma doses, particularly at Hiroshima. The implications of these changes in terms of epidemiology and radiation protection standards are discussed. (ACR)

Loewe, W.E.

1983-09-01

102

EUVL dosimetry at NIST  

NASA Astrophysics Data System (ADS)

As part of its role in providing radiometric standards in support of industry, NIST has been active in advancing extreme ultraviolet dosimetry on various fronts. Recently, we undertook a major effort in accurately measuring the sensitivity of three extreme ultraviolet photoresists. It has been common practice to use photoresists as a transfer "standards" to determine the intensity and uniformity of the radiation transmitted by extreme ultraviolet steppers. In response to preliminary results from Lawrence Berkeley National Laboratory that showed that two "standard" photoresists were almost twice as sensitive as had been previously believed, NIST carried out similar measurements and confirmed the Berkeley results. However, we have found that the assumed sensitivities are more a question of system calibration than of absolute resist dose sensitivity. We will describe the facility we used to make these measurements. Photoresists make less than perfect radiometers. They are very non-linear, sensitive to atmosphere, and difficult to calibrate. All of these characteristics led to the disparate results in assumed sensitivity values. We have developed an alternate wafer-plane dosimeter based on image plates. The dosimeter is linear over several orders of magnitude, comparatively insensitive to atmosphere, and can be re-calibrated as necessary. Moreover it can pass through a stepper as any other wafer. We will describe this dosimeter in detail

Tarrio, C.; Grantham, S.; Cangemi, M.; Vest, R. E.; Lucatorto, T. B.; Harned, Noreen

2009-03-01

103

Unified Theory for Gel Electrophoresis and Gel Filtration  

Microsoft Academic Search

Unified theory for gel electrophoresis and gel filtration: The behavior of macromolecules in gel filtration and gel electrophoresis may be predicted from Ogston's model for a random meshwork of fibers. This model has been generalized to apply to nonspherical molecules and to several gel types. The model provides equations for inter-relationships between mobility, partition coefficient, gel concentration, and molecular radius;

David Rodbard; Andreas Chrambach

1970-01-01

104

Light dosimetry in vivo  

NASA Astrophysics Data System (ADS)

This paper starts with definitions of radiance, fluence (rate) and other quantities that are important with regard to in vivo light dosimetry. The light distribution in mammalian tissues can be estimated from model calculations using measured optical properties or from direct measurements of fluence rate using a suitable detector. A historical introduction is therefore followed by a brief discussion of tissue optical properties and of calculations using diffusion theory, the -approximation or Monte Carlo simulations. In particular the form of the scattering function is considered in relation to the fluence rate close to the tissue boundary, where light is incident. Non-invasive measurements of optical properties yield the absorption coefficient and , where is the scattering coefficient and g is the mean cosine of the scattering angle. An important question is whether this combination is sufficient, or whether g itself must be known. It appears that for strongly forward scattering, as in mammalian tissues, rather detailed knowledge of the scattering function is needed to reliably calculate the fluence rate close to the surface. Deeper in the tissue is sufficient. The construction, calibration and use of fibre-optic probes for measurements of fluence rate in tissues or optical phantoms is discussed. At present, minimally invasive absolute fluence (rate) measurements seem to be possible with an accuracy of 10 - 20%. Examples are given of in vivo measurements in animal experiments and in humans during clinical treatments. Measurements in mammalian tissues, plant leaves and marine sediments are compared and similarities and differences pointed out. Most in vivo light fluence rate measurements have been concerned with photodynamic therapy (PDT). Optical properties of the same normal tissue may differ between patients. Tumours of the same histological type may even show different optical properties in a single patient. Treatment-induced changes of optical properties may also occur. Scattered light appears to contribute substantially to the light dose. All these phenomena emphasize the importance of in situ light measurements. Another important dosimetric parameter in PDT is the concentration and distribution of the photosensitizer. Apart from in vivo fluorescence monitoring, the photosensitizer part of in vivo PDT dosimetry is still in its infancy.

Star, Willem M.

1997-05-01

105

Fitness Landscapes and Evolvability  

Microsoft Academic Search

In this paper, we develop techniques based on evolvability statistics of the fitness land- scape surrounding sampled solutions. Averaging the measures over a sample of equal fitness solutions allows us to build up fitness evolvability portraits of the fitness land- scape, which we show can be used to compare both the ruggedness and neutrality in a set of tunably rugged

Tom Smith; Phil Husbands; Paul J. Layzell; Michael O'shea

2002-01-01

106

Webster Pool Fitness Center  

E-print Network

Archbold/ Flanagan Webster Pool (Archbold) Women's Building Goldstein Fitness Center Marion Fitness Center Brockway Fitness Center Marshall Square Mall Fitness Center Tennity Ice Skating Pavilion Ernie Davis Hall Fitness Center 6:30am- 11:30pm 7:00- 9:30am, 11:30am- 2:30pm 5:00pm- 11:30pm 7:00am- 2:00am

Mather, Patrick T.

107

Sol-Gel Glasses  

NASA Technical Reports Server (NTRS)

Multicomponent homogeneous, ultrapure noncrystalline gels/gel derived glasses are promising batch materials for the containerless glass melting experiments in microgravity. Hence, ultrapure, homogeneous gel precursors could be used to: (1) investigate the effect of the container induced nucleation on the glass forming ability of marginally glass forming compositions; and (2) investigate the influence of gravity on the phase separation and coarsening behavior of gel derived glasses in the liquid-liquid immiscibility zone of the nonsilicate systems having a high density phase. The structure and crystallization behavior of gels in the SiO2-GeO2 as a function of gel chemistry and thermal treatment were investigated. As are the chemical principles involved in the distribution of a second network former in silica gel matrix being investigated. The procedures for synthesizing noncrystalline gels/gel-monoliths in the SiO2-GeO2, GeO2-PbO systems were developed. Preliminary investigations on the levitation and thermal treatment of germania silicate gel-monoliths in the Pressure Facility Acoustic Levitator were done.

Mukherjee, S. P.

1985-01-01

108

An alternative method using microwave power saturate in fingernail/electron paramagnetic resonance dosimetry.  

PubMed

An alternative method for fingernail/electron paramagnetic resonance (EPR) dosimetry valid at low doses (0-3 Gy) is suggested in this paper. The method consisted of two steps. The first step involved dehydrating fingernail clippings to remove their water content by heating them at 70 °C for 72 h. As the water content in the fingernails decreased, the variability of the EPR signals improved. The second step involved measuring and fitting the EPR signals at successive microwave power levels. A newly derived value known as 'curvature', which was based on the conventional peak-to-peak amplitudes of the EPR signals, was applied for the dosimetry. This method could be used as an alternative method in cases of low-radiation exposure doses (<3 Gy) or where use of the conventional dosimetry method is not proper for a fingernail sample. PMID:24876339

Choi, Hoon; Park, Byeongryong; Choi, Muhyun; Lee, Byungil; Lee, Cheol Eui

2014-06-01

109

CONFORMANCE IMPROVEMENT USING GELS  

SciTech Connect

This report describes work performed during the second year of the project, ''Conformance Improvement Using Gels.'' The project has two objectives. The first objective is to identify gel compositions and conditions that substantially reduce flow through fractures that allow direct channeling between wells, while leaving secondary fractures open so that high fluid injection and production rates can be maintained. The second objective is to optimize treatments in fractured production wells, where the gel must reduce permeability to water much more than that to oil. Pore-level images from X-ray computed microtomography were re-examined for Berea sandstone and porous polyethylene. This analysis suggests that oil penetration through gel-filled pores occurs by a gel-dehydration mechanism, rather than a gel-ripping mechanism. This finding helps to explain why aqueous gels can reduce permeability to water more than to oil. We analyzed a Cr(III)-acetate-HPAM gel treatment in a production well in the Arbuckle formation. The availability of accurate pressure data before, during, and after the treatment was critical for the analysis. After the gel treatment, water productivity was fairly constant at about 20% of the pre-treatment value. However, oil productivity was stimulated by a factor of 18 immediately after the treatment. During the six months after the treatment, oil productivity gradually decreased to approach the pre-treatment value. To explain this behavior, we proposed that the fracture area open to oil flow was increased substantially by the gel treatment, followed by a gradual closing of the fractures during subsequent production. For a conventional Cr(III)-acetate-HPAM gel, the delay between gelant preparation and injection into a fracture impacts the placement, leakoff, and permeability reduction behavior. Formulations placed as partially formed gels showed relatively low pressure gradients during placement, and yet substantially reduced the flow capacity of fractures (with widths from 1 to 4 mm) during brine and oil flow after placement. Regardless of gel age before placement, very little gel washed out from the fractures during brine or oil flow. However, increased brine or oil flow rate and cyclic injection of oil and water significantly decreased the level of permeability reduction. A particular need exists for gels that can plug large apertures (e.g., wide fractures and vugs). Improved mechanical strength and stability were demonstrated (in 1- to 4-mm-wide fractures) for a gel that contained a combination of high- and low-molecular weight polymers. This gel reduced the flow capacity of 2- and 4-mm-wide fractures by 260,000. In a 1-mm-wide fracture, it withstood 26 psi/ft without allowing any brine flow through the fracture. Cr(III)-acetate-HPAM gels exhibited disproportionate permeability reduction in fractures. The effect was most pronounced when the gel was placed as gelant or partially formed gels. The effect occurred to a modest extent with concentrated gels and with gels that were ''fully formed'' when placed. The effect was not evident in tubes. We explored swelling polymers for plugging fractures. Polymer suspensions were quickly prepared and injected. In concept, the partially dissolved polymer would lodge and swell to plug the fracture. For three types of swelling polymers, behavior was promising. However, additional development is needed before their performance will be superior to that of conventional gels.

Randall S. Seright

2003-09-01

110

Dosimetry User's Perspective on Covariance Needs  

NASA Astrophysics Data System (ADS)

The dosimetry community has a critical need for covariance matrices to characterize the uncertainty in the input nuclear data used in a range of applications. This need is growing more acute as the nuclear regulatory community increases the rigor with which dosimetry statements must be made and supported. This paper presents and prioritizes a set of needs that reflect the application of neutron dosimetry to the research reactor and commercial nuclear power industry.

Griffin, P. J.

2008-12-01

111

Results from 2010 Caliban Criticality Dosimetry Intercomparison  

SciTech Connect

The external dosimetry program participated in a criticality dosimetry intercomparison conducted at the Caliban facility in Valduc, France in 2010. Representatives from the dosimetry and instrumentation groups were present during testing which included irradiations of whole-body beta/gamma (HBGT) and neutron thermoluminescent dosimeters (TLDs), a fixed nuclear accident dosimeter (FNAD), electronic alarming dosimeters, and a humanoid phantom filled with reference man concentrations of sodium. This report reviews the testing procedures, preparations, irradiations, and presents results of the tests.

Veinot, K. G.

2011-10-12

112

SEGMENTATION AND FITTING USING  

E-print Network

examples. Example: Owls and Rats In a study area, there are g different species of rat. A rat of the l how to generalize our line fitting techniques to handle curve fitting problems in section 17.3. Finally, we discuss methods for determining how many elements (lines, curves, segments, etc.) to fit

Keren, Daniel

113

Explicit dosimetry for photodynamic therapy: macroscopic singlet oxygen modeling  

PubMed Central

Singlet oxygen (1O2) is the major cytotoxic agent responsible for cell killing for type-II photodynamic therapy (PDT). An empirical four-parameter macroscopic model is proposed to calculate the “apparent reacted 1O2 concentration”, [1O2]rx, as a clinical PDT dosimetry quantity. This model incorporates light diffusion equation and a set of PDT kinetics equations, which can be applied in any clinical treatment geometry. We demonstrate that by introducing a fitting quantity “apparent singlet oxygen threshold concentration” [1O2]rx,sd, it is feasible to determine the model parameters by fitting the computed [1O2]rx to the Photofrin-mediated PDT-induced necrotic distance using interstitially-measured Photofrin concentration and optical properties within each mouse. After determining the model parameters and the [1O2]rx,sd, we expect to use this model as an explicit dosimetry to assess PDT treatment outcome for a specific photosensitizer in an in vivo environment. The results also provide evidence that the [1O2]rx, because it takes into account the oxygen consumption (or light fluence rate) effect, can be a better predictor of PDT outcome than the PDT dose defined as the energy absorbed by the photosensitizer, which is proportional to the product of photosensitizer concentration and light fluence. PMID:20222102

Wang, Ken Kang-Hsin; Finlay, Jarod C.; Busch, Theresa M.; Hahn, Stephen M.; Zhu, Timothy C.

2011-01-01

114

Dosimetry of intensive synchrotron microbeams  

Microsoft Academic Search

Intensive synchrotron X-ray microbeams form an integral part of microbeam radiation therapy (MRT). MRT is a novel radiation medicine modality being developed for inoperable and otherwise untreatable brain tumours. The extremely high dose rate (?20 kGy\\/s), laterally fractionated radiation field and steep dose gradients utilized in this therapy make real-time dosimetry a significant challenge. In order for this treatment to advance

M. L. F. Lerch; M. Petasecca; A. Cullen; A. Hamad; H. Requardt; E. Bräuer-Krisch; A. Bravin; V. L. Pervertaylo; A. B. Rosenfeld

115

Surfactant Templated Polyacrylamide Gels  

NASA Astrophysics Data System (ADS)

The controlled modification of gel structure by using surfactant self-assemblies as templates provides new opportunities in the development of novel materials. Polyacrylamide gels were synthesized in the presence of tetradecyltrimethylammonium bromide (TTAB) surfactant. Small-angle X-ray scattering (SAXS) results indicate that acrylamide monomer does not prevent the self-assembly of TTAB surfactants. Dynamic rheology measurements indicated a transition from an isotropic micellar phase to a hexagonal columnar phase occurred about 10% higher TTAB concentration in the presence of acrylamide (the transition occurs at 35% (by weight) for TTAB in buffer solution). The presence of surfactant during the gelation profoundly affected the final gel structure. Real time rheology measurements showed evidence of a demixing of the polymer and the surfactant phase in gels formed in the presence of high TTAB concentration (> 30% by weight) leading to the formation of highly macroporous gels. Bulk structure characterization using SAXS showed that TTAB micelles were separated by about 10 nm in gels synthesized in the presence of low and moderate TTAB concentration (< 30%). Protein separation on gels templated by TTAB surfactants showed significant improvements over conventional gels.

Chakrapani, Mukundan; van Winkle, D. H.; Rill, R. L.

2003-03-01

116

Small fields: Nonequilibrium radiation dosimetry  

SciTech Connect

Advances in radiation treatment with beamlet-based intensity modulation, image-guided radiation therapy, and stereotactic radiosurgery (including specialized equipments like CyberKnife, Gamma Knife, tomotherapy, and high-resolution multileaf collimating systems) have resulted in the use of reduced treatment fields to a subcentimeter scale. Compared to the traditional radiotherapy with fields {>=}4x4 cm{sup 2}, this can result in significant uncertainty in the accuracy of clinical dosimetry. The dosimetry of small fields is challenging due to nonequilibrium conditions created as a consequence of the secondary electron track lengths and the source size projected through the collimating system that are comparable to the treatment field size. It is further complicated by the prolonged electron tracks in the presence of low-density inhomogeneities. Also, radiation detectors introduced into such fields usually perturb the level of disequilibrium. Hence, the dosimetric accuracy previously achieved for standard radiotherapy applications is at risk for both absolute and relative dose determination. This article summarizes the present knowledge and gives an insight into the future procedures to handle the nonequilibrium radiation dosimetry problems. It is anticipated that new miniature detectors with controlled perturbations and corrections will be available to meet the demand for accurate measurements. It is also expected that the Monte Carlo techniques will increasingly be used in assessing the accuracy, verification, and calculation of dose, and will aid perturbation calculations of detectors used in small and highly conformal radiation beams.

Das, Indra J.; Ding, George X.; Ahnesjoe, Anders [Department of Radiation Oncology, University of Pennsylvania, Philadelphia, Pennsylvania 19104 (United States); Department of Radiation Oncology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232 (United States); Department of Oncology, Radiology and Clinical Immunology, Section of Oncology, Uppsala University, S-751 85 Uppsala and Nucletron AB, S-751 47 Uppsala (Sweden)

2008-01-15

117

Modeling chemoresponsive polymer gels.  

PubMed

Stimuli-responsive gels are vital components in the next generation of smart devices, which can sense and dynamically respond to changes in the local environment and thereby exhibit more autonomous functionality. We describe recently developed computational methods for simulating the properties of such stimuli-responsive gels in the presence of optical, chemical, and thermal gradients. Using these models, we determine how to harness light to drive shape changes and directed motion in spirobenzopyran-containing gels. Focusing on oscillating gels undergoing the Belousov-Zhabotinksy reaction, we demonstrate that these materials can spontaneously form self-rotating assemblies, or pinwheels. Finally, we model temperature-sensitive gels that encompass chemically reactive filaments to optimize the performance of this system as a homeostatic device for regulating temperature. These studies could facilitate the development of soft robots that autonomously interconvert chemical and mechanical energy and thus perform vital functions without the continuous need of external power sources. PMID:24498954

Kuksenok, Olga; Deb, Debabrata; Dayal, Pratyush; Balazs, Anna C

2014-01-01

118

Dosimetric evaluation of a novel polymer gel dosimeter for proton therapy  

SciTech Connect

Purpose: The aim of this study is to evaluate the dosimetric performance of a newly developed proton-sensitive polymer gel formulation for proton therapy dosimetry. Methods: Using passive scattered modulated and nonmodulated proton beams, the dose response of the gel was assessed. A next-generation optical CT scanner is used as the readout mechanism of the radiation-induced absorbance in the gel medium. Comparison of relative dose profiles in the gel to ion chamber profiles in water is performed. A simple and easily reproducible calibration protocol is established for routine gel batch calibrations. Relative stopping power ratio measurement of the gel medium was performed to ensure accurate water-equivalent depth dose scaling. Measured dose distributions in the gel were compared to treatment planning system for benchmark irradiations and quality of agreement is assessed using clinically relevant gamma index criteria. Results: The dosimetric response of the gel was mapped up to 600 cGy using an electron-based calibration technique. Excellent dosimetric agreement is observed between ion chamber data and gel. The most notable result of this work is the fact that this gel has no observed dose quenching in the Bragg peak region. Quantitative dose distribution comparisons to treatment planning system calculations show that most (>97%) of the gel dose maps pass the 3%/3 mm gamma criterion. Conclusions: This study shows that the new proton-sensitive gel dosimeter is capable of reproducing ion chamber dose data for modulated and nonmodulated Bragg peak beams with different clinical beam energies. The findings suggest that the gel dosimeter can be used as QA tool for millimeter range verification of proton beam deliveries in the dosimeter medium.

Zeidan, O. A.; Sriprisan, S. I.; Lopatiuk-Tirpak, O.; Kupelian, P. A.; Meeks, S. L.; Hsi, W. C.; Li, Z.; Palta, J. R.; Maryanski, M. J. [M. D. Anderson Cancer Center Orlando, Orlando, Florida 32806 (United States); University of Florida Proton Therapy Institute, Jacksonville, Florida 32206 (United States); MGS Research, Inc., Madison, Connecticut 06443 (United States)

2010-05-15

119

Dosimetry in Nuclear Medicine Diagnosis and Therapy  

NASA Astrophysics Data System (ADS)

This document is part of Subvolume A 'Fundamentals and Data in Radiobiology, Radiation Biophysics, Dosimetry and Medical Radiological Protection' of Volume 7 'Medical Radiological Physics' of Landolt-Börnstein - Group VIII 'Advanced Materials and Technologies'. It contains the Section '4.7 Necessity of Patient-Specific Dose Planning in Radionuclide Therapy' of the Chapter '4 Dosimetry in Nuclear Medicine Diagnosis and Therapy'.

Noßke, D.; Mattsson, S.; Johansson, L.

120

Uranium Dispersion and Dosimetry (UDAD) Code  

Microsoft Academic Search

The Uranium Dispersion and Dosimetry (UDAD) Code provides estimates of potential radiation exposure to individuals and to the general population in the vicinity of a uranium processing facility. The UDAD Code incorporates the radiation dose from the airborne release of radioactive materials, and includes dosimetry of inhalation, ingestion, and external exposures. The removal of raioactive particles from a contaminated area

M. H. Momeni; Y. Yuan; A. J. Zielen

1979-01-01

121

Thermoluminescence and Thermoluminescent Dosimetry, v. 3  

SciTech Connect

This work is a comprehensive review and guide to the fields of thermoluminescence and thermoluminescent dosimetry. Three up-to-date volumes contain useful tables, illustrations, formulas and references to aid researchers in radiation and nuclear science, dosimetry and solid state physics. Volume III focuses on clinical and archeological-geological applications of TLD. Detailed technical information on TL instrumentation is also included.

Horowitz, Y.S.

1984-01-01

122

Fitness and evolutionary explanation  

Microsoft Academic Search

Recent philosophical discussions have failed to clarify the roles of the concept fitness in evolutionary theory. Neither the\\u000a propensity interpretation of fitness nor the construal of fitness as a primitive theoretical term succeed in explicating the\\u000a empirical content and explanatory power of the theory of natural selection. By appealing to the structure of simple mathematical\\u000a models of natural selection, we

Henry C. Byerly; Richard E. Michod

1991-01-01

123

A genipin-gelatin gel dosimeter for radiation processing  

NASA Astrophysics Data System (ADS)

Genipin, a fruit extract from Gardenia jasminoides Ellis, forms cross-links in solutions of gelatin, to form a blue hydrogel that bleaches quantitatively upon irradiation and the colour change can be measured with a spectrophotometer. With the addition of sulphuric acid this dosimeter is sufficiently sensitive for quality assurance of radiotherapy level dosimetry. Without sulphuric acid the gel has a reduced sensitivity and responds linearly with dose between 100 and 1000 Gy, making it potentially useful as a dosimeter for radiation processing applications such as the phytosanitary irradiation treatment of food. We investigated the dose response characteristics of this new formulation and found that the darker gels are more sensitive to dose and have a reduced uncertainty.

Davies, J. B.; Bosi, S. G.; Baldock, C.

2012-08-01

124

Leak test fitting  

DOEpatents

A hollow fitting for use in gas spectrometry leak testing of conduit joints is divided into two generally symmetrical halves along the axis of the conduit. A clip may quickly and easily fasten and unfasten the halves around the conduit joint under test. Each end of the fitting is sealable with a yieldable material, such as a piece of foam rubber. An orifice is provided in a wall of the fitting for the insertion or detection of helium during testing. One half of the fitting also may be employed to test joints mounted against a surface.

Pickett, Patrick T. (Kettering, OH)

1981-01-01

125

PREFACE: 8th International Conference on 3D Radiation Dosimetry (IC3DDose)  

NASA Astrophysics Data System (ADS)

IC3DDose 2014, the 8th International Conference on 3D Radiation Dosimetry was held in Ystad, Sweden, from 4-7 September 2014. This grew out of the DosGel series, which began as DosGel99, the 1st International Workshop on Radiation Therapy Gel Dosimetry in Lexington, Kentucky. Since 1999 subsequent DoSGel conferences were held in Brisbane, Australia (2001), Ghent, Belgium (2004), Sherbrooke, Canada (2006) and Crete, Greece (2008). In 2010 the conference was held on Hilton Head Island, South Carolina and underwent a name-change to IC3DDose. The 7th and last meeting was held in Sydney, Australia from 4–8 November 2012. It is worth remembering that the conference series started at the very beginning of the intensity modulated radiotherapy era and that the dosimeters being developed then were, to some extent, ahead of the clinical need of radiotherapy. However, since then the technical developments in radiation therapy have been dramatic, with dynamic treatments, including tracking, gating and volumetric modulated arc therapy, widely introduced in the clinic with the need for 3D dosimetry thus endless. This was also reflected by the contributions at the meeting in Ystad. Accordingly the scope of the meeting has also broadened to IC3DDOSE - I See Three-Dimensional Dose. A multitude of dosimetry techniques and radiation detectors are now represented, all with the common denominator: three-dimensional or 3D. Additionally, quality assurance (QA) procedures and other aspects of clinical dosimetry are represented. The implementation of new dosimetric techniques in radiotherapy is a process that needs every kind of caution, carefulness and thorough validation. Therefore, the clinical needs, reformulated as the aims for IC3DDOSE - I See Three-Dimensional Dose, are: • Enhance the quality and accuracy of radiation therapy treatments through improved clinical dosimetry. • Investigate and understand the dosimetric challenges of modern radiation treatment techniques. • Provide a forum to discuss the latest research and developments in 3D and advanced radiation dosimetry. • Energize and diversify dosimetry research and clinical practice by encouraging interaction and synergy between advanced, 3D, and semi-3D dosimetry techniques. We commend these IC3Dose 2014 conference proceedings to you and strongly believe they include significant contributions to scientific progress in this field. We would like to express our sincere gratitude to everybody involved in making the conference possible, the Scientific committee for their work on the general planning, paper review and program formulation, the distinguished invited speakers for their contributions and the local organizing committee members for all their hard work on the practical preparation for the meeting. Lars E. Olsson, Sven Bäck and Sofie Ceberg Lund University and Skåne University Hospital, Sweden International Scientific Committee Sven Bäck, Sweden (chair) Clive Baldock, Australia Sam Beddar, USA Crister Ceberg, Sweden Yves de Deene, Belgium/Australia Simon Doran, UK Geoffrey Ibbott, USA Andrew Jirasek, Canada Kevin Jordan, Canada Martin Lepage, Canada Daniel Low, USA Mark Oldham, USA Tony Popescu, Canada John Schreiner, Canada Cheng-Shie Wuu, USA David Thwaites, Australia Local Organizing Committee Sofie Ceberg (chair) Lars E. Olsson (conference chair) Fredrik Nordstrom Anneli Edvardsson Anna Karlsson Hauer Anna Bäck

Olsson, Lars E.; Bäck, S.; Ceberg, Sofie

2015-01-01

126

Periodic mesoporous silica gels  

SciTech Connect

We have synthesized monolithic particulate gels of periodic mesoporous silica by adding tetramethoxysilane to a homogeneous alkaline micellar precursor solution. The gels exhibit 5 characteristic length scales over 4 orders of magnitude: fractal domains larger than the particle size (>500 nm), particles that are {approximately}150 to 500 nm in diameter, interparticle pores that are on the order of the particle size, a feature in the gas adsorption measurements that indicates pores {approximately}10-50 nm, and periodic hexagonal arrays of {approximately}3 nm channels within each particle. The wet gel monoliths exhibit calculated densities as low as {approximately}0.02 g/cc; the dried and calcined gels have bulk densities that range from {approximately}0.3-0.5 g/cc. The materials possess large interparticle ({approximately}1.0-2.3 cc/g) and intraparticle ({approximately}0.6 cc/g) porosities.

Anderson, M.T.; Martin, J.E.; Odinek, J.G. [and others

1996-06-01

127

Electrophoresis and Gel Analysis  

NSDL National Science Digital Library

In this animation produced by WGBH and Digizyme, Inc., see how molecules of DNA are separated using gel electrophoresis, and how this process enables scientists to compare the molecular variations of two or more DNA samples.

2011-08-05

128

Measuring output factors and beam profiles formed by multileaf collimators using Fricke gel dosimeter.  

PubMed

The accuracy and precision are necessary factors in radiotherapy, especially for measurements involving output factors and beam profiles; in this case multileaf collimators (MLCs) and dosimeter systems are not employed to obtain an adequate absorbed dose. In this work, output factors and beam profiles using multileaf collimators were obtained through the Fricke Xylenol Gel (FXG) dosimeter irradiated with 6 MV photon beams. From the results, FXG dosimetry demonstrated to be an adequate dosimetric tool for radiotherapy applications using MLC. PMID:24767977

Nonato de Oliveira, Lucas; de Almeida, Adelaide; Caldas, Linda V E

2014-11-01

129

Feasibility of a dual wavelength laser optical CT scanner with in-air gel readout  

NASA Astrophysics Data System (ADS)

Net optical attenuation in optical CT scanning is usually determined by pre and postirradiation scans. Replacement of the pre-irradiation scan by a scan of different wavelength, acquired concurrently with the post irradiation scan is proposed. This would result in greater practicality of gel dosimetry and potentially improved image quality. This study indicates that the approach may be viable, however experimental investigation is required for analysis of the prospective benefits of removing inter-scan variations.

Ramm, D.; Rutten, T. P.

2015-01-01

130

Study of the relative dose-response of BANG-3 polymer gel dosimeters in epithermal neutron irradiation.  

PubMed

Polymer gels have been reported as a new, potential tool for dosimetry in mixed neutron-gamma radiation fields. In this work, BANG-3 (MGS Research Inc.) gel vials from three production batches were irradiated with 6 MV photons of a Varian Clinac 2100 C linear accelerator and with the epithermal neutron beam of the Finnish boron neutron capture therapy (BNCT) facility at the FiR 1 nuclear reactor. The gel is tissue equivalent in main elemental composition and density and its T2 relaxation time is dependent on the absorbed dose. The T2 relaxation time map of the irradiated gel vials was measured with a 1.5 T magnetic resonance (MR) scanner using spin echo sequence. The absorbed doses of neutron irradiation were calculated using DORT computer code, and the accuracy of the calculational model was verified by measuring gamma ray dose rate with thermoluminescent dosimeters and 55Mn(n,gamma) activation reaction rate with activation detectors. The response of the BANG-3 gel dosimeter for total absorbed dose in the neutron irradiation was linear, and the magnitude of the response relative to the response in the photon irradiation was observed to vary between different gel batches. The results support the potential of polymer gels in BNCT dosimetry, especially for the verification of two- or three-dimensional dose distributions. PMID:14516107

Uusi-Simola, J; Savolainen, S; Kangasmäki, A; Heikkinen, S; Perkiö, J; Abo Ramadan, U; Seppälä, T; Karila, J; Serén, T; Kotiluoto, P; Sorvari, P; Auterinen, I

2003-09-01

131

The effect of mixed dopants on the stability of Fricke gel dosimeters  

NASA Astrophysics Data System (ADS)

Auto-oxidation and fast diffusion in Fricke gels are major drawbacks to wide-spread application of these gels in 3D dosimetry. Aiming to limit both processes, we used mixed dopants: the ferric-specific ligand xylenol orange with a ferrous-specific ligand (1,10-phenanthroline) and/or a bi-functional cross-linking agent (glyoxal). Markedly improved auto-oxidation stability was observed in the xylenol orange and phenanthroline doped gel at the expense of increased background absorbance and faster diffusion. Addition of glyoxal limited the diffusion rate and led to a partial bleaching of the gel. It is conceivable that these two new compositions may find useful practical application.

Penev, K.; Mequanint, K.

2013-06-01

132

Solid-State Personal Dosimetry  

NASA Technical Reports Server (NTRS)

This document is a web site page, and a data sheet about Personal protection (i.e., space suits) presented to the Radiation and Micrometeoroid Mitigation Technology Focus Group meeting. The website describes the work of the PI to improve solid state personal radiation dosimetry. The data sheet presents work on the active personal radiation detection system that is to provide real-time local radiation exposure information during EVA. Should undue exposure occur, knowledge of the dynamic intensity conditions during the exposure will allow more precise diagnostic assessment of the potential health risk to the exposed individual.

Wrbanek, John D.; Fralick, Gustave C.; Wrbanek, Susan Y.

2005-01-01

133

Crystallization from Gels  

NASA Astrophysics Data System (ADS)

Among the various crystallization techniques, crystallization in gels has found wide applications in the fields of biomineralization and macromolecular crystallization in addition to crystallizing materials having nonlinear optical, ferroelectric, ferromagnetic, and other properties. Furthermore, by using this method it is possible to grow single crystals with very high perfection that are difficult to grow by other techniques. The gel method of crystallization provides an ideal technique to study crystal deposition diseases, which could lead to better understanding of their etiology. This chapter focuses on crystallization in gels of compounds that are responsible for crystal deposition diseases. The introduction is followed by a description of the various gels used, the mechanism of gelling, and the fascinating phenomenon of Liesegang ring formation, along with various gel growth techniques. The importance and scope of study on crystal deposition diseases and the need for crystal growth experiments using gel media are stressed. The various crystal deposition diseases, viz. (1) urolithiasis, (2) gout or arthritis, (3) cholelithiasis and atherosclerosis, and (4) pancreatitis and details regarding the constituents of the crystal deposits responsible for the pathological mineralization are discussed. Brief accounts of the theories of the formation of urinary stones and gallstones and the role of trace elements in urinary stone formation are also given. The crystallization in gels of (1) the urinary stone constituents, viz. calcium oxalate, calcium phosphates, uric acid, cystine, etc., (2) the constituents of the gallstones, viz. cholesterol, calcium carbonate, etc., (3) the major constituent of the pancreatic calculi, viz., calcium carbonate, and (4) cholic acid, a steroidal hormone are presented. The effect of various organic and inorganic ions, trace elements, and extracts from cereals, herbs, and fruits on the crystallization of major urinary stone and gallstone constituents are described. In addition, tables of gel-grown organic and inorganic crystals are provided.

Narayana Kalkura, S.; Natarajan, Subramanian

134

Conformance Improvement Using Gels  

SciTech Connect

This research project had two objectives. The first objective was to identify gel compositions and conditions that substantially reduce flow through fractures that allow direct channeling between wells, while leaving secondary fractures open so that high fluid injection and production rates can be maintained. The second objective was to optimize treatments in fractured production wells, where the gel must reduce permeability to water much more than that to oil.

Seright, Randall S.; Schrader, Richard; II Hagstrom, John; Wang, Ying; Al-Dahfeeri, Abdullah; Gary, Raven; Marin; Amaury; Lindquist, Brent

2002-09-26

135

Programming for Physical Fitness.  

ERIC Educational Resources Information Center

Physical fitness is an ongoing process and should be included in planned instruction throughout the year. Options are presented for scheduling fitness activities during the school year, within a motor skill unit, and within an individual lesson plan. A sample yearly plan and lesson plan are included. (IAH)

Petray, Clayre; And Others

1989-01-01

136

Outfitting Campus Fitness Centers.  

ERIC Educational Resources Information Center

Explains how universities and colleges, both private and public, are including fitness centers as ways of increasing their student enrollment levels. Comments are provided on school experiences in fitness-center design, equipment purchasing, and maintenance and operating-costs issues. (GR)

Fickes, Michael

1999-01-01

137

Uncertainty propagation: Curve fitting  

NSDL National Science Digital Library

Students will learn a sample-variance curve fitting method that can be used to determine whether a set of experimental data appears to have been generated by a model. This method is based on minimizing the reduced chi-squared value. This video includes a reminder to inspect normalized residuals before reporting fitted parameters.

2013-06-21

138

Women and Physical Fitness  

Microsoft Academic Search

Although the promotion of health, sports, and physical fitness are pervasive themes as well as part of federal U.S. policy, women lag behind their male counterparts in the areas of health and physical fitness. And, although there is a general trend toward increased participation of women in sports and physical activity across a life span, a large number of women

Diana J. Cunningham; Janet A. Ohles

2000-01-01

139

Fun & Fitness with Balloons  

ERIC Educational Resources Information Center

The urgency to improve fitness levels and decrease the rate of childhood obesity has been at the forefront of physical education philosophy and praxis. Few would dispute that school-age youth need to participate regularly in physical activities that enhance and maintain both skill- and health-related physical fitness. Regular physical activity…

Farrell, Anne; Faigenbaum, Avery; Radler, Tracy

2010-01-01

140

Quenching correction for volumetric scintillation dosimetry of proton beams  

PubMed Central

Purpose Volumetric scintillation dosimetry has the potential to provide fast, high-resolution, three-dimensional radiation dosimetry. However, scintillators exhibit a nonlinear response at the high linear energy transfer (LET) values characteristic of proton Bragg peaks. The purpose of this study was to develop a quenching correction method for volumetric scintillation dosimetry of proton beams. Methods Scintillation light from a miniature liquid scintillator detector was measured along the central axis of a 161.6-MeV proton pencil beam. Three-dimensional dose and LET distributions were calculated for 85.6-, 100.9-, 144.9-, and 161.6-MeV beams using a validated Monte Carlo model. LET values were also calculated using an analytical formula. A least-squares fit to the data established the empirical parameters of a quenching correction model. The light distribution in a tank of liquid scintillator was measured with a CCD camera at all four beam energies. The quenching model and LET data were used to correct the measured light distribution. Results The calculated and measured Bragg peak heights agreed within ±3% for all energies except 85.6 MeV, where the agreement was within ±10%. The quality of the quenching correction was poorer for sharp low-energy Bragg peaks because of blurring and detector size effects. The corrections performed using analytical LET values resulted in doses within 1% of those obtained using Monte Carlo LET values. Conclusion The proposed method can correct for quenching with sufficient accuracy for dosimetric purposes. The required LET values may be computed effectively using Monte Carlo or analytical methods. Future detectors should improve blurring correction methods and optimize the pixel size to improve accuracy for low-energy Bragg peaks. PMID:23257200

Robertson, Daniel; Mirkovic, Dragan; Sahoo, Narayan; Beddar, Sam

2013-01-01

141

Development of dosimetry using detectors of diagnostic digital radiography systems  

SciTech Connect

Dosimetry using an imaging plate (IP) of computed radiography (CR) systems was developed for quality control of output of the x-ray equipment. Sensitivity index, or the S number, of the CR systems was used for estimating exposure dose under the routine condition: exposure dose from 1.0 to 1.0x10{sup 2} {mu}C kg{sup -1}, tube voltages from 50 to 120 kV, and added filtration from 0 to 4.0 mm Al. The IP was calibrated by using a 6 cc ionization chamber having traceability to the National Standard Ionization Chamber. The uncertainty concerning the fading effect was suppressed less than 1.9% by reading the latent image 4 min{+-}5 s after irradiation at the room temperature 25.9{+-}1.0 degree sign C. The S number decreased linearly on the logarithmic graph regardless of the beam quality as exposure dose increased. The relationship between the exposure dose (E) and the S number was fitted by the equation E=a{sup '}xS{sup -b}. The coefficient a{sup '} decreased when the added filtration and the tube voltage were increased. The coefficient b was 0.977{+-}0.007 in all beam qualities. The dosimetry using the IP and the equation can estimate the exposure dose in a range from 9.0x10{sup -2} to 5.0 {mu}C kg{sup -1} within an uncertainty of {+-}5% required by the Japanese Industry Standard. This dose range partially included the doses under routine condition. The doses between 1.0 and 1.0x10{sup 2} {mu}C kg{sup -1} under the routine condition can be shifted to the 5% region by using an absorber. The IP dosimetry is applicable to the quality control of the CR systems.

Ariga, Eiji; Ito, Shigeki; Deji, Shizuhiko; Saze, Takuya; Nishizawa, Kunihide [Graduate School of Environmental Studies, Nagoya University and Nagoya Daini Red Cross Hospital, 466-8650, Nagoya (Japan); Radioisotope Research Center, Nagoya University, 464-8602, Nagoya (Japan); Radioisotope Research Center, Tokushima University, 770-8503, Tokushima (Japan); Radioisotope Research Center, Nagoya University, 464-8602, Nagoya (Japan)

2007-01-15

142

In vitro dosimetry of agglomerates  

NASA Astrophysics Data System (ADS)

Agglomeration of nanoparticles in biological fluids is a pervasive phenomenon that leads to difficulty in the interpretation of results from in vitro exposure, primarily due to differing particokinetics of agglomerates to nanoparticles. Therefore, well-defined small agglomerates were designed that possessed different particokinetic profiles, and their cellular uptake was compared to a computational model of dosimetry. The approach used here paves the way for a better understanding of the impact of agglomeration on the nanoparticle-cell interaction.Agglomeration of nanoparticles in biological fluids is a pervasive phenomenon that leads to difficulty in the interpretation of results from in vitro exposure, primarily due to differing particokinetics of agglomerates to nanoparticles. Therefore, well-defined small agglomerates were designed that possessed different particokinetic profiles, and their cellular uptake was compared to a computational model of dosimetry. The approach used here paves the way for a better understanding of the impact of agglomeration on the nanoparticle-cell interaction. Electronic supplementary information (ESI) available: ITC data for tiopronin/Au-NP interactions, agglomeration kinetics at different pHs for tiopronin-coated Au-NPs, UV-Vis spectra in water, PBS and DMEM and temporal correlation functions for single Au-NPs and corresponding agglomerates, calculation of diffusion and sedimentation parameters, modelling of relative cell uptake based on the ISDD model and cytotoxicity of single Au-NPs and their agglomerates, and synthesis and cell uptake of large spherical Au-NPs. See DOI: 10.1039/c4nr00460d

Hirsch, V.; Kinnear, C.; Rodriguez-Lorenzo, L.; Monnier, C. A.; Rothen-Rutishauser, B.; Balog, S.; Petri-Fink, A.

2014-06-01

143

Advances in radiation therapy dosimetry  

PubMed Central

During the last decade, there has been an explosion of new radiation therapy planning and delivery tools. We went through a rapid transition from conventional three-dimensional (3D) conformal radiation therapy to intensity-modulated radiation therapy (IMRT) treatments, and additional new techniques for motion-adaptive radiation therapy are being introduced. These advances push the frontiers in our effort to provide better patient care; and with the addition of IMRT, temporal dimensions are major challenges for the radiotherapy patient dosimetry and delivery verification. Advanced techniques are less tolerant to poor implementation than are standard techniques. Mis-administrations are more difficult to detect and can possibly lead to poor outcomes for some patients. Instead of presenting a manual on quality assurance for radiation therapy, this manuscript provides an overview of dosimetry verification tools and a focused discussion on breath holding, respiratory gating and the applications of four-dimensional computed tomography in motion management. Some of the major challenges in the above areas are discussed. PMID:20098555

Paliwal, Bhudatt; Tewatia, Dinesh

2009-01-01

144

Limitations of inclusive fitness  

PubMed Central

Until recently, inclusive fitness has been widely accepted as a general method to explain the evolution of social behavior. Affirming and expanding earlier criticism, we demonstrate that inclusive fitness is instead a limited concept, which exists only for a small subset of evolutionary processes. Inclusive fitness assumes that personal fitness is the sum of additive components caused by individual actions. This assumption does not hold for the majority of evolutionary processes or scenarios. To sidestep this limitation, inclusive fitness theorists have proposed a method using linear regression. On the basis of this method, it is claimed that inclusive fitness theory (i) predicts the direction of allele frequency changes, (ii) reveals the reasons for these changes, (iii) is as general as natural selection, and (iv) provides a universal design principle for evolution. In this paper we evaluate these claims, and show that all of them are unfounded. If the objective is to analyze whether mutations that modify social behavior are favored or opposed by natural selection, then no aspect of inclusive fitness theory is needed. PMID:24277847

Allen, Benjamin; Nowak, Martin A.; Wilson, Edward O.

2013-01-01

145

Mayo Clinic: Fitness Center  

NSDL National Science Digital Library

The Mayo Clinic offers a wide range of outreach services for the general public, including websites providing basic information about cancer, smoking cessation techniques, and others. Their online Fitness Center website will be a real boon to anyone who is looking to pick up some basic fitness awareness, learn about strength training, or read up on sports nutrition. First-time visitors can start by reading through the "Fitness Basics" area, which answers common questions like "Why exercise?" and also provides information on getting warmed up before exercising. Visitors can also sign up for the Mayo Clinic's free e-newsletter, "Housecall".

146

Small Angle Neutron Scattering study of steroidal gels P. Terech (*), F. Volino (*) and R. Ramasseul (**)  

E-print Network

895 Small Angle Neutron Scattering study of steroidal gels P. Terech (*), F. Volino (*) and R diffusion est discutée. Abstract. 2014 Gels formed by a dilute solution of modified steroids in cyclohexane are essentially composed of steroid molecules. Absolute intensity measurements, and fits of the full scattering

Paris-Sud XI, Université de

147

Integrating the Levels of Person-Environment Fit: The Roles of Vocational Fit and Group Fit  

ERIC Educational Resources Information Center

Previous research on fit has largely focused on person-organization (P-O) fit and person-job (P-J) fit. However, little research has examined the interplay of person-vocation (P-V) fit and person-group (P-G) fit with P-O fit and P-J fit in the same study. This article advances the fit literature by examining these relationships with data collected…

Vogel, Ryan M.; Feldman, Daniel C.

2009-01-01

148

VIDA: A Voxel-Based Dosimetry Method for Targeted Radionuclide Therapy Using Geant4.  

PubMed

We have developed the Voxel-Based Internal Dosimetry Application (VIDA) to provide patient-specific dosimetry in targeted radionuclide therapy performing Monte Carlo simulations of radiation transport with the Geant4 toolkit. The code generates voxel-level dose rate maps using anatomical and physiological data taken from individual patients. Voxel level dose rate curves are then fit and integrated to yield a spatial map of radiation absorbed dose. In this article, we present validation studies using established dosimetry results, including self-dose factors (DFs) from the OLINDA/EXM program for uniform activity in unit density spheres and organ self- and cross-organ DFs in the Radiation Dose Assessment Resource (RADAR) reference adult phantom. The comparison with reference data demonstrated agreement within 5% for self-DFs to spheres and reference phantom source organs for four common radionuclides used in targeted therapy ((131)I, (90)Y, (111)In, (177)Lu). Agreement within 9% was achieved for cross-organ DFs. We also present dose estimates to normal tissues and tumors from studies of two non-Hodgkin Lymphoma patients treated by (131)I radioimmunotherapy, with comparison to results generated independently with another dosimetry code. A relative difference of 12% or less was found between methods for mean absorbed tumor doses accounting for tumor regression. PMID:25594357

Kost, Susan D; Dewaraja, Yuni K; Abramson, Richard G; Stabin, Michael G

2015-02-01

149

Computational methods in radionuclide dosimetry  

NASA Astrophysics Data System (ADS)

The various approaches in radionuclide dosimetry depend on the size and spatial relation of the sources and targets considered in conjunction with the emission range of the radionuclide used. We present some of the frequently reported computational techniques on the basis of the source/target size. For whole organs, or for sources or targets bigger than some centimetres, the acknowledged standard was introduced 30 years ago by the MIRD committee and is still being updated. That approach, based on the absorbed fraction concept, is mainly used for radioprotection purposes but has been updated to take into account the dosimetric challenge raised by therapeutic use of vectored radiopharmaceuticals. At this level, the most important computational effort is in the field of photon dosimetry. On the millimetre scale, photons can often be disregarded, and or electron dosimetry is generally reported. Heterogeneities at this level are mainly above the cell level, involving groups of cell or a part of an organ. The dose distribution pattern is often calculated by generalizing a point source dose distribution, but direct calculation by Monte Carlo techniques is also frequently reported because it allows media of inhomogeneous density to be considered. At the cell level, and electron (low-range or Auger) are the predominant emissions examined. Heterogeneities in the dose distribution are taken into account, mainly to determine the mean dose at the nucleus. At the DNA level, Auger electrons or -particles are considered from a microdosimetric point of view. These studies are often connected with radiobiological experiments on radionuclide toxicity.

Bardiès, M.; Myers, M. J.

1996-10-01

150

Dosimetry of [??Ga]-labeled compounds.  

PubMed

This review compiles and analyzes the available dosimetry data of [(68)Ga] labeled compounds. Dosimetry data are given for [(68)Ga]DOTA-NOC, TOC, TATE, and NODAGA-RGDyK. The number of PET-scans with [(68)Ga]DOTA-compounds for imaging neuroendocrine tumors is increasing because [(68)Ga] has a higher affinity to somatostatin receptors (SSTR) in comparison to comparable [(111)In]-compounds. In addition, the better image resolution of the PET images provides improved diagnostics. Despite its widespread use literature on dosimetry of [(68)Ga]-labeled radiopharmaceuticals is sparse. In some cases the description of the underlying methodology is missing or human data are gained from the extrapolation of animal experiments. More and better documented dosimetry data will further promote the use of these promising new agents. PMID:22884623

Eberlein, U; Lassmann, M

2013-06-01

151

Gel Electrophoresis of Dyes  

NSDL National Science Digital Library

In this experiment related to plant biotechnology, learners discover how to prepare and load an electrophoresis gel. They will then run the gels in an electrophoresis system to separate several dyes that are of different molecular sizes and carry different charges. This technique is fundamental to many of the procedures used in biotechnology. This lesson guide includes background information for the educator, safety precautions, and questions with answers for learners. For safety reasons, adult supervision is recommended. Modifications for use with younger learners are described in a related PDF (see related resource).

Stephens, Janice; Leach, Jan

2011-01-01

152

Swelling of Olympic Gels  

NASA Astrophysics Data System (ADS)

The swelling equilibrium of Olympic gels, which are composed of entangled cyclic polymers, is studied by Monte Carlo simulations. In contrast to chemically cross-linked polymer networks, we observe that Olympic gels made of chains with a larger degree of polymerization, N, exhibit a smaller equilibrium swelling degree, Q?N-0.28?0-0.72, at the same polymer volume fraction ?0 at network preparation. This observation is explained by a desinterspersion (reorganization with release of nontrapped entanglements) process of overlapping nonconcatenated rings upon swelling.

Lang, M.; Fischer, J.; Werner, M.; Sommer, J.-U.

2014-06-01

153

In vivo dosimetry in brachytherapy  

SciTech Connect

In vivo dosimetry (IVD) has been used in brachytherapy (BT) for decades with a number of different detectors and measurement technologies. However, IVD in BT has been subject to certain difficulties and complexities, in particular due to challenges of the high-gradient BT dose distribution and the large range of dose and dose rate. Due to these challenges, the sensitivity and specificity toward error detection has been limited, and IVD has mainly been restricted to detection of gross errors. Given these factors, routine use of IVD is currently limited in many departments. Although the impact of potential errors may be detrimental since treatments are typically administered in large fractions and with high-gradient-dose-distributions, BT is usually delivered without independent verification of the treatment delivery. This Vision 20/20 paper encourages improvements within BT safety by developments of IVD into an effective method of independent treatment verification.

Tanderup, Kari [Department of Oncology, Aarhus University Hospital, Aarhus 8000 (Denmark); Department of Clinical Medicine, Aarhus University, Aarhus 8000 (Denmark); Beddar, Sam [Department of Radiation Oncology, University of Texas MD Anderson Cancer Center, Houston, Texas 77030 (United States); Andersen, Claus E.; Kertzscher, Gustavo [Center of Nuclear Technologies, Technical University of Denmark, Roskilde 4000 (Denmark); Cygler, Joanna E. [Department of Physics, Ottawa Hospital Cancer Centre, Ottawa, Ontario K1H 8L6 (Canada)

2013-07-15

154

Audits for advanced treatment dosimetry  

NASA Astrophysics Data System (ADS)

Radiation therapy has advanced rapidly over the last few decades, progressing from 3D conformal treatment to image-guided intensity modulated therapy of several different flavors, both 3D and 4D and to adaptive radiotherapy. The use of intensity modulation has increased the complexity of quality assurance and essentially eliminated the physicist's ability to judge the validity of a treatment plan, even approximately, on the basis of appearance and experience. Instead, complex QA devices and procedures are required at the institutional level. Similarly, the assessment of treatment quality through remote and on-site audits also requires greater sophistication. The introduction of 3D and 4D dosimetry into external audit systems must follow, to enable quality assurance systems to perform meaningful and thorough audits.

Ibbott, G. S.; Thwaites, D. I.

2015-01-01

155

Rules, culture, and fitness  

PubMed Central

Behavior analysis risks intellectual isolation unless it integrates its explanations with evolutionary theory. Rule-governed behavior is an example of a topic that requires an evolutionary perspective for a full understanding. A rule may be defined as a verbal discriminative stimulus produced by the behavior of a speaker under the stimulus control of a long-term contingency between the behavior and fitness. As a discriminative stimulus, the rule strengthens listener behavior that is reinforced in the short run by socially mediated contingencies, but which also enters into the long-term contingency that enhances the listener's fitness. The long-term contingency constitutes the global context for the speaker's giving the rule. When a rule is said to be “internalized,” the listener's behavior has switched from short- to long-term control. The fitness-enhancing consequences of long-term contingencies are health, resources, relationships, or reproduction. This view ties rules both to evolutionary theory and to culture. Stating a rule is a cultural practice. The practice strengthens, with short-term reinforcement, behavior that usually enhances fitness in the long run. The practice evolves because of its effect on fitness. The standard definition of a rule as a verbal statement that points to a contingency fails to distinguish between a rule and a bargain (“If you'll do X, then I'll do Y”), which signifies only a single short-term contingency that provides mutual reinforcement for speaker and listener. In contrast, the giving and following of a rule (“Dress warmly; it's cold outside”) can be understood only by reference also to a contingency providing long-term enhancement of the listener's fitness or the fitness of the listener's genes. Such a perspective may change the way both behavior analysts and evolutionary biologists think about rule-governed behavior. ImagesFigure 1 PMID:22478201

Baum, William M.

1995-01-01

156

Adaptation and inclusive fitness.  

PubMed

Inclusive fitness theory captures how individuals can influence the transmission of their genes to future generations by influencing either their own reproductive success or that of related individuals. This framework is frequently used for studying the way in which natural selection leads to organisms being adapted to their environments. A number of recent papers have criticised this approach, suggesting that inclusive fitness is just one of many possible mathematical methods for modelling when traits will be favoured by natural selection, and that it leads to errors, such as overemphasising the role of common ancestry relative to other mechanisms that could lead to individuals being genetically related. Here, we argue that these suggested problems arise from a misunderstanding of two fundamental points: first, inclusive fitness is more than just a mathematical 'accounting method' - it is the answer to the question of what organisms should appear designed to maximise; second, there is something special about relatedness caused by common ancestry, in contrast with the other mechanisms that may lead to individuals being genetically related, because it unites the interests of genes across the genome, allowing complex, multigenic adaptations to evolve. The critiques of inclusive fitness theory have provided neither an equally valid answer to the question of what organisms should appear designed to maximise, nor an alternative process to unite the interest of genes. Consequently, inclusive fitness remains the most general theory for explaining adaptation. PMID:23845249

West, Stuart A; Gardner, Andy

2013-07-01

157

Ames Fitness Program  

NASA Technical Reports Server (NTRS)

The Ames Fitness Program services 5,000 civil servants and contractors working at Ames Research Center. A 3,000 square foot fitness center, equipped with cardiovascular machines, weight training machines, and free weight equipment is on site. Thirty exercise classes are held each week at the Center. A weight loss program is offered, including individual exercise prescriptions, fitness testing, and organized monthly runs. The Fitness Center is staffed by one full-time program coordinator and 15 hours per week of part-time help. Membership is available to all employees at Ames at no charge, and there are no fees for participation in any of the program activities. Prior to using the Center, employees must obtain a physical examination and complete a membership package. Funding for the Ames Fitness Program was in jeopardy in December 1992; however, the employees circulated a petition in support of the program and collected more than 1500 signatures in only three days. Funding has been approved through October 1993.

Pratt, Randy

1993-01-01

158

Transdermal delivery of paeonol using cubic gel and microemulsion gel  

PubMed Central

Background The aim of this study was to develop new systems for transdermal delivery of paeonol, in particular microemulsion gel and cubic gel formulations. Methods Various microemulsion vehicles were prepared using isopropyl myristate as an oil phase, polyoxyethylated castor oil (Cremophor® EL) as a surfactant, and polyethylene glycol 400 as a cosurfactant. In the optimum microemulsion gel formulation, carbomer 940 was selected as the gel matrix, and consisted of 1% paeonol, 4% isopropyl myristate, 28% Cremophor EL/polyethylene glycol 400 (1:1), and 67% water. The cubic gel was prepared containing 3% paeonol, 30% water, and 67% glyceryl monooleate. Results A skin permeability test using excised rat skins indicated that both the cubic gel and microemulsion gel formulations had higher permeability than did the paeonol solution. An in vivo pharmacokinetic study done in rats showed that the relative bioavailability of the cubic gel and microemulsion gel was enhanced by about 1.51-fold and 1.28-fold, respectively, compared with orally administered paeonol suspension. Conclusion Both the cubic gel and microemulsion gel formulations are promising delivery systems to enhance the skin permeability of paeonol, in particular the cubic gel. PMID:21904450

Luo, Maofu; Shen, Qi; Chen, Jinjin

2011-01-01

159

Calcium tartrate gel.  

PubMed

A method for preparation of a gel for chromatography has been developed. The adsorbent is calcium tartrate treated with potassium phosphate. By changing the temperature of synthesis (10-65 degrees C) and concentration of the salts (calcium chloride and sodium potassium tartrate) from 0.3 to 3.0 M, we have been able to prepare adsorbent crystals of definite sizes in the range 35-200 microns. In all cases, for synthesis of adsorbent, the Ca2+/K+Na+ ratio was greater than 1. After treatment of calcium tartrate crystals with 0.075-1.5 M potassium phosphate at 80-100 degrees C and pH 8.5-9.0, an appropriate chromatographic adsorbent was prepared. The chromatographic properties of calcium tartrate gel have been studied. The adsorbent permits flow rates of 25-150 ml/h, depending on the particle size. The capacity of calcium tartrate gel for binding BSA, RNA, and DNA was similar to that of Tiselius' hydroxyapatite (A. Tiselius, S. Hjerten, O. Levin (1956) Arch. Biochem. Biophys. 65, 132-155). The spheric shape of gel particles permits uniform and compact packing of adsorbent under the conditions of column chromatography. PMID:2757203

Akhrem, A A; Drozhdenyuk, A P

1989-05-15

160

Personal Fitness Plan  

NSDL National Science Digital Library

This activity will help you create a personal fitness plan that is right for you. Maintaining a physically active lifestyle can help you feel your best and prevent the onset of certain diseases. At the conclusion of this activity, you will: Understand the health benefits of physical activity. Be able to describe three types of exercise. Create a custom plan based on your own preferences. The first step in creating your personal fitness plan is to understand why one is important to have and to maintain. Read ...

Cross, Mrs.

2005-11-26

161

Line of Best Fit  

NSDL National Science Digital Library

When data is displayed with a scatter plot, it is often useful to attempt to represent that data with the equation of a straight line for purposes of predicting values that may not be displayed on the plot. Such a straight line is called the "line of best fit." In this activity, students discover the relationship between the fat grams and the total calories in fast food by graphing the given data, estimate the line of best fit using a strand of spaghetti, calculate the slope of that line, and translate it into an equation. Then, they use that equation to predict information not originally included in the scatter plot.

2012-08-13

162

10 CFR 835.1304 - Nuclear accident dosimetry.  

Code of Federal Regulations, 2013 CFR

...2013-01-01 2013-01-01 false Nuclear accident dosimetry. 835.1304 Section 835...Exposure Situations § 835.1304 Nuclear accident dosimetry. (a) Installations...individuals to radiation from a nuclear accident is possible, shall provide...

2013-01-01

163

10 CFR 835.1304 - Nuclear accident dosimetry.  

Code of Federal Regulations, 2012 CFR

...2012-01-01 2012-01-01 false Nuclear accident dosimetry. 835.1304 Section 835...Exposure Situations § 835.1304 Nuclear accident dosimetry. (a) Installations...individuals to radiation from a nuclear accident is possible, shall provide...

2012-01-01

164

10 CFR 835.1304 - Nuclear accident dosimetry.  

Code of Federal Regulations, 2014 CFR

...2014-01-01 2014-01-01 false Nuclear accident dosimetry. 835.1304 Section 835...Exposure Situations § 835.1304 Nuclear accident dosimetry. (a) Installations...individuals to radiation from a nuclear accident is possible, shall provide...

2014-01-01

165

10 CFR 835.1304 - Nuclear accident dosimetry.  

Code of Federal Regulations, 2011 CFR

...2011-01-01 2011-01-01 false Nuclear accident dosimetry. 835.1304 Section 835...Exposure Situations § 835.1304 Nuclear accident dosimetry. (a) Installations...individuals to radiation from a nuclear accident is possible, shall provide...

2011-01-01

166

10 CFR 835.1304 - Nuclear accident dosimetry.  

Code of Federal Regulations, 2010 CFR

...2010-01-01 2010-01-01 false Nuclear accident dosimetry. 835.1304 Section 835...Exposure Situations § 835.1304 Nuclear accident dosimetry. (a) Installations...individuals to radiation from a nuclear accident is possible, shall provide...

2010-01-01

167

Micro-Fabricated Solid-State Radiation Detectors for Active Personal Dosimetry  

NASA Technical Reports Server (NTRS)

Active radiation dosimetry is important to human health and equipment functionality for space applications outside the protective environment of a space station or vehicle. This is especially true for long duration missions to the moon, where the lack of a magnetic field offers no protection from space radiation to those on extravehicular activities. In order to improve functionality, durability and reliability of radiation dosimeters for future NASA lunar missions, single crystal silicon carbide devices and scintillating fiber detectors are currently being investigated for applications in advanced extravehicular systems. For many years, NASA Glenn Research Center has led significant efforts in silicon carbide semiconductor technology research and instrumentation research for sensor applications under extreme conditions. This report summarizes the technical progress and accomplishments toward characterization of radiation-sensing components for the recommendation of their fitness for advanced dosimetry development.

Wrbanek, John D.; Wrbanek, Susan Y.; Fralick, Gustave C.; Chen, Liang-Yu

2007-01-01

168

Manual for physical fitness  

NASA Technical Reports Server (NTRS)

Training manual used for preflight conditioning of NASA astronauts is written for audience with diverse backgrounds and interests. It suggests programs for various levels of fitness, including sample starter programs, safe progression schedules, and stretching exercises. Related information on equipment needs, environmental coonsiderations, and precautions can help readers design safe and effective running programs.

Coleman, A. E.

1981-01-01

169

Senior Women's Fitness Project  

Microsoft Academic Search

To determine the special exercise needs of older, overweight women and the effects of gentle progressive exercise on physical fitness and psychological parameters, we recruited 30 sedentary women aged 60 to 72 years old to participate in an 11-week-long exercise study. The women were assigned to either a low-impact aerobic dance exercise class (N = 20) who exercised for 1

Patricia A. Gillett

1993-01-01

170

Talking Sport and Fitness  

ERIC Educational Resources Information Center

For some time the Association for Science Education (ASE) has been aware that it would be useful to have some resources available to get children talking and thinking about issues related to health, sport and fitness. Some of the questions about pulse, breathing rate and so on are pretty obvious to everyone, and there is a risk of these being…

Dixon-Watmough, Rebecca; Keogh, Brenda; Naylor, Stuart

2012-01-01

171

Physical Fitness Training  

Microsoft Academic Search

An evaluation of a program designed to enhance self concept, reduce muscular tension and alleviate feelings of helplessness and depression was presented. Results indicated that physical fitness training alone may be as effective as relaxation on the aforementioned variables. Additionally, a combination of both treatments may not be as effective as either single treatment programs. Suggestions are given as to

Frank A. De Piano; Linda C. De Piano; Wayne Carter; Richard L. Wanlass

1984-01-01

172

Teaching Aerobic Fitness Concepts.  

ERIC Educational Resources Information Center

Discusses how to teach aerobic fitness concepts to elementary students. Some of the K-2 activities include location, size, and purpose of the heart and lungs; the exercise pulse; respiration rate; and activities to measure aerobic endurance. Some of the 3-6 activities include: definition of aerobic endurance; heart disease risk factors;…

Sander, Allan N.; Ratliffe, Tom

2002-01-01

173

Fit for Life.  

ERIC Educational Resources Information Center

Children who hate gym grow into adults who associate physical activity with ridicule and humiliation. Physical education is reinventing itself, stressing enjoyable activities that continue into adulthood: aerobic dance, weight training, fitness walking, mountain biking, hiking, inline skating, karate, rock-climbing, and canoeing. Cooperative,…

Vail, Kathleen

1999-01-01

174

Measuring Your Fitness Progress  

MedlinePLUS

... you’re becoming more fit, such as increased energy, greater ability to perform daily tasks, or even an improved outlook on life. VISIT www.nia.nih.gov/Go4Life l Read more about increasing your activity level. l Print useful tools. l Order a free exercise guide or DVD. l Share your exercise ...

175

In aqua vivo EPID dosimetry  

SciTech Connect

Purpose: At the Netherlands Cancer Institute-Antoni van Leeuwenhoek Hospital in vivo dosimetry using an electronic portal imaging device (EPID) has been implemented for almost all high-energy photon treatments of cancer with curative intent. Lung cancer treatments were initially excluded, because the original back-projection dose-reconstruction algorithm uses water-based scatter-correction kernels and therefore does not account for tissue inhomogeneities accurately. The aim of this study was to test a new method, in aqua vivo EPID dosimetry, for fast dose verification of lung cancer irradiations during actual patient treatment. Methods: The key feature of our method is the dose reconstruction in the patient from EPID images, obtained during the actual treatment, whereby the images have been converted to a situation as if the patient consisted entirely of water; hence, the method is termed in aqua vivo. This is done by multiplying the measured in vivo EPID image with the ratio of two digitally reconstructed transmission images for the unit-density and inhomogeneous tissue situation. For dose verification, a comparison is made with the calculated dose distribution with the inhomogeneity correction switched off. IMRT treatment verification is performed for each beam in 2D using a 2D {gamma} evaluation, while for the verification of volumetric-modulated arc therapy (VMAT) treatments in 3D a 3D {gamma} evaluation is applied using the same parameters (3%, 3 mm). The method was tested using two inhomogeneous phantoms simulating a tumor in lung and measuring its sensitivity for patient positioning errors. Subsequently five IMRT and five VMAT clinical lung cancer treatments were investigated, using both the conventional back-projection algorithm and the in aqua vivo method. The verification results of the in aqua vivo method were statistically analyzed for 751 lung cancer patients treated with IMRT and 50 lung cancer patients treated with VMAT. Results: The improvements by applying the in aqua vivo approach are considerable. The percentage of {gamma} values {<=}1 increased on average from 66.2% to 93.1% and from 43.6% to 97.5% for the IMRT and VMAT cases, respectively. The corresponding mean {gamma} value decreased from 0.99 to 0.43 for the IMRT cases and from 1.71 to 0.40 for the VMAT cases, which is similar to the accepted clinical values for the verification of IMRT treatments of prostate, rectum, and head-and-neck cancers. The deviation between the reconstructed and planned dose at the isocenter diminished on average from 5.3% to 0.5% for the VMAT patients and was almost the same, within 1%, for the IMRT cases. The in aqua vivo verification results for IMRT and VMAT treatments of a large group of patients had a mean {gamma} of approximately 0.5, a percentage of {gamma} values {<=}1 larger than 89%, and a difference of the isocenter dose value less than 1%. Conclusions: With the in aqua vivo approach for the verification of lung cancer treatments (IMRT and VMAT), we can achieve results with the same accuracy as obtained during in vivo EPID dosimetry of sites without large inhomogeneities.

Wendling, Markus; McDermott, Leah N.; Mans, Anton; Olaciregui-Ruiz, Igor; Pecharroman-Gallego, Raul; Sonke, Jan-Jakob; Stroom, Joep; Herk, Marcel J.; Mijnheer, Ben van [Department of Radiation Oncology, Netherlands Cancer Institute-Antoni van Leeuwenhoek Hospital, Plesmanlaan 121, 1066 CX Amsterdam (Netherlands)

2012-01-15

176

Personnel neutron dosimetry at Department of Energy facilities  

SciTech Connect

This study assesses the state of personnel neutron dosimetry at DOE facilities. A survey of the personnel dosimetry systems in use at major DOE facilities was conducted, a literature search was made to determine recent advances in neutron dosimetry, and several dosimetry experts were interviewed. It was concluded that personnel neutron dosimeters do not meet current needs and that serious problems exist now and will increase in the future if neutron quality factors are increased and/or dose limits are lowered.

Brackenbush, L.W.; Endres, G.W.R.; Selby, J.M.; Vallario, E.J.

1980-08-01

177

Review of recent advances in radiochromic materials for 3D dosimetry  

NASA Astrophysics Data System (ADS)

Recent papers concerning radiochromic films, plastics and hydrogels for 3D dosimetry are summarized. The utility of Presage", a radiochromic plastic, with optical CT readout was demonstrated for the following applications: motion and gated treatment delivery, commissioning of small fields for radiosurgery, 192Ir high dose rate brachytherapy source commissioning and as a 3D insert for IMRT credentialing tests with Radiological Physics Centre (RPC) phantoms. Preliminary performance for characterizing microbeams from a synchrotron with optic projection tomography readout demonstrated resolution of an 83 micron diameter beam. Hydrogel chemistries based on nonionic micelles for leuco malachite green and leuco crystal violet demonstrated that low diffusion gels can be designed by choosing product dyes that are poorly soluble and water and tend to remain in the micelles. Turnbull blue chemistry has been successfully adapted to form a non-difffusing gel as well. The performance of ferrous xylenol orange hydrogel layers doped with boron to form neutron dosimeters demonstrated another practical application. Polymerization hydrogels are alternate materials that can be read with optical CT scanners. High dose gradient applications in brachytherapy with 90Sr/90Y sources and proton dosimetry are presented for comparison.

Jordan, Kevin

2010-11-01

178

Stability and Influence of Dose Rate in the Signal Response of the Alanine Gel Dosimeter  

NASA Astrophysics Data System (ADS)

Nowadays, the three dimensional (3D) dosimetry has been studied by many researchers for application in radiotherapy and radiosurgery treatments, because this kind of dosimeter enable to evaluate the 3D dose distribution. The alanine gel dosimeter was developed at IPEN to be applied to 3D dose evaluations using magnetic resonance imaging. This dosimeter is a gel material based on the transformation of the ferrous ions in ferric ions, which presents significant improvement on previous alanine systems developed by Costa (1994). The DL-Alanine (C3H7NO2) is an amino acid tissue equivalent that improves the production of ferric ions in the solution. The ferric ions concentration can be measured by spectrophometry technique. This work aims to analyse the stability and influence of the dose rate in the optical signal response of alanine gel dosimeter, since these two properties are very important for characterization and standardization of any dosimeter.

Feijó Silva, Cléber; Lucente Campos, Letícia

2010-11-01

179

Breast dosimetry in clinical mammography  

NASA Astrophysics Data System (ADS)

The objective of this study was show 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. In the study, 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 protocol proposes the use of a fiber-optic coupled (FOCD) or Metal Oxide Semiconductor Field Effect Transistor (MOSFET) dosimeter to measure the entrance skin exposure at the time of the mammogram without interfering with diagnostic information of the mammogram. The study showed that FOCD had sensitivity with less than 7% energy dependence, linear in all tube current-time product stations, and was reproducible within 2%. FOCD was superior to MOSFET dosimeter in sensitivity, reusability, and reproducibility. 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 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. In addition, the study population anthropometric measurements enabled the development of analytical equations to calculate the whole breast area, estimate for the skin layer thickness and optimal location for automatic exposure control ionization chamber. The clinical dosimetry protocol developed in this study can reliably predict the AGD imparted to an individual patient during a routine screening mammogram.

Benevides, Luis Alberto Do Rego

180

Characterizing matrix remodeling in collagen gels using optical coherence tomography  

NASA Astrophysics Data System (ADS)

Optical coherence tomography (OCT) has shown promise at non-destructively characterizing engineered tissues such as collagen gels. However, as the collagen gels develop, the OCT images lose contrast of structures as the gels develop, making visual assessment difficult. Our group proposed quantitatively characterizing these gels by fitting the optical properties from the OCT signals. In this paper, we imaged collagen gels seeded with smooth muscle cells (SMCs) over a 5-day period and used the data to measure their optical properties. Our results showed that over time, the reflectivity of the samples increased 10-fold, corresponding to a decrease in anisotropy factor g, without much change in the scattering coefficient ?s. Overall, the optical properties appeared to be dominated by scattering from the collagen matrix, not the cells. However, SMCs remodeled the collagen matrix, and this collagen remodeling by the cells is what causes the observed changes in optical properties. Moreover, the data showed that the optical properties were sensitive to the activity of matrix metalloproteinases (MMPs), enzymes that break down local collagen fibrils into smaller fragments. Blocking MMPs in the SMC gels greatly impeded both the remodeling process and change in optical properties at day 5. Treating day 1 acellular gels with MMP-8 for 3 hr managed to partially reproduce the remodeling observed in SMC gels at day 5. Altogether, we conclude that matrix remodeling in general, and MMPs specifically, greatly affect the local optical properties of the sample, and OCT is a unique tool that can assess MMP activity in collagen gels both non-destructively and label free.

Levitz, David; Hinds, Monica T.; Hanson, Stephen R.; Jacques, Steven L.

2010-02-01

181

Fitting fragility functions 1 Fitting Fragility Functions to  

E-print Network

Fitting fragility functions 1 Fitting Fragility Functions to Structural Analysis Data Using Maximum Likelihood Estimation 1. Introduction This appendix describes a statistical procedure for fitting fragility Incremental Dynamic Analysis). In such a case, the most popular current method for fragility function fitting

Baker, Jack W.

182

Vver Pressure Vessel Neutron Dosimetry and Lifetime Prediction  

NASA Astrophysics Data System (ADS)

The role and problems of neutron dosimetry have been analysed with regard to RPV embrittlement and lifetime prolongation. The status of Russian regulatory documents concerning neutron dosimetry has been considered. The ways of neutron dosimetry improvement have been discussed and recommended.

Adamchik, S. A.; Grivizirsky, V. A.; Gordon, B. G.; Kaliberda, I. V.; Khrennikov, N. N.; Borodkin, G. I.

2003-06-01

183

Application of radiochromic gel detector (FXG) for UVA dose measurements  

NASA Astrophysics Data System (ADS)

Tissue equivalent radiochromic gel material containing ferrous ions, xylenol-orange ion indicator and gelatin as gelling agent (FXG) is known to be sensitive to ?- and X-rays; hence it has been used for ionizing radiation dosimetry. Changes in optical absorbance properties of FXG material over a wide region in the visible spectrum were found to be proportional to the radiation absorbed dose. An earlier study demonstrated the sensitivity of FXG gel detector to ultraviolet radiation and therefore that could give quantitative measure for UV exposure. This study focuses on the detection of UVA radiation (315-400 nm), which forms an important part (˜97%) of the natural solar UV radiation reaching the earth surface. A solar UV simulator device was used to deliver UVA radiation to FXG samples. The beam was optically modified to irradiate gel samples at an exposure level about 58 W/m 2, which is comparable to the summer natural UVA radiation measured outside the laboratory building at midday (˜60 W/m 2). Experimental results were used to generate mathematical second order formulas that give the relationship between UVA dose and optical absorbance changes observed at two wavelengths in the visible region of the spectrum—430 and 560 nm.

Abukassem, Issam; Bero, Mamdouh A.

2010-12-01

184

Linear electrochemical gel actuators  

NASA Astrophysics Data System (ADS)

By using electroactive monomers it is possible to produce gels that respond to oxidation or reduction by swelling and deswelling in the presence of solvent. By the inclusion of an appropriate biasing element such as a spring, it is possible to produce linear, reversible actuation. The process can be driven electrochemically in a standard cell, with driving voltages under +/- 1 V. For many systems, the intrinsic conductivity of the gel, leading to poor or no performance. This can be overcome by blending conductive carbon nanotubes at 1% concentration, which give reasonable conductivity without affecting mechanical performance. Extensions of up to 40% are possible, against an external pressure of 30 kPa. The process is slow, taking up to 160 minutes per cycle due to slow ionic diffusion. The electrochemical cell can be cycled many times without degradation.

Goswami, Shailesh; McAdam, C. John; Hanton, Lyall R.; Moratti, Stephen C.

2011-11-01

185

Linear electrochemical gel actuators  

NASA Astrophysics Data System (ADS)

By using electroactive monomers it is possible to produce gels that respond to oxidation or reduction by swelling and deswelling in the presence of solvent. By the inclusion of an appropriate biasing element such as a spring, it is possible to produce linear, reversible actuation. The process can be driven electrochemically in a standard cell, with driving voltages under +/- 1 V. For many systems, the intrinsic conductivity of the gel, leading to poor or no performance. This can be overcome by blending conductive carbon nanotubes at 1% concentration, which give reasonable conductivity without affecting mechanical performance. Extensions of up to 40% are possible, against an external pressure of 30 kPa. The process is slow, taking up to 160 minutes per cycle due to slow ionic diffusion. The electrochemical cell can be cycled many times without degradation.

Goswami, Shailesh; McAdam, C. John; Hanton, Lyall R.; Moratti, Stephen C.

2012-04-01

186

Chemical dosimetry system for criticality accidents.  

PubMed

Ruder Boskovi? Institute (RBI) criticality dosimetry system consists of a chemical dosimetry system for measuring the total (neutron + gamma) dose, and a thermoluminescent (TL) dosimetry system for a separate determination of the gamma ray component. The use of the chemical dosemeter solution chlorobenzene-ethanol-trimethylpentane (CET) is based on the radiolytic formation of hydrochloric acid, which protonates a pH indicator, thymolsulphonphthalein. The high molar absorptivity of its red form at 552 nm is responsible for a high sensitivity of the system: doses in the range 0.2-15 Gy can be measured. The dosemeter has been designed as a glass ampoule filled with the CET solution and inserted into a pen-shaped plastic holder. For dose determinations, a newly constructed optoelectronic reader has been used. The RBI team took part in the International Intercomparison of Criticality Accident Dosimetry Systems at the SILENE Reactor, Valduc, June 2002, with the CET dosimetry system. For gamma ray dose determination TLD-700 TL detectors were used. The results obtained with CET dosemeter show very good agreement with the reference values. PMID:15353694

Miljani?, Saveta; Ilijas, Boris

2004-01-01

187

Dosimetry And Its Enhancement Using Gold Nanoparticles In Synchrotron Based Microbeam And Stereotactic Radiosurgery  

NASA Astrophysics Data System (ADS)

Research into the areas of synchrotron generated microbeam radiotherapy (MRT) and stereotactic radiosurgery is increasing. Such MRT techniques are showing potential of tackling some of the more difficult radiotherapy cases such as certain type of brain tumours. Two challenging aspects of these techniques are addressed in this investigation; the difficulty of dose determination and the delivery of the treatments at lower dose levels. In this research polymer gels were used as phantoms and dosimeters and cells were used to confirm outcomes. Normoxic polyacrylamide gels (nPAG) were tested as potential dosimeters for microbeam dosimetry. Following irradiation using microbeam and minibeam radiation from the BL28BU beam-line at Spring-8, Japan, the nPAG were scanned using a Raman spectroscopy technique. Dose enhancement caused by the inclusion of the gold nanoparticles (AuNPs) in the target was investigated using both cells and polymer gels. The use of AuNP could potentially reduce the dose required for the delivery of MRT. In this study it was shown that using endothelial cells with AuNPs, the minimal dose for clear cell killing along the beam line was reduced to 10 Gy. Both studies cell and gel studies indicates significant dose enhancement caused by the gold atoms in the target.

Rahman, Wan Nordiana; Wong, Christopher James; Yagi, Naoto; Davidson, Robert; Geso, Moshi

2010-07-01

188

Dosimetry And Its Enhancement Using Gold Nanoparticles In Synchrotron Based Microbeam And Stereotactic Radiosurgery  

SciTech Connect

Research into the areas of synchrotron generated microbeam radiotherapy (MRT) and stereotactic radiosurgery is increasing. Such MRT techniques are showing potential of tackling some of the more difficult radiotherapy cases such as certain type of brain tumours. Two challenging aspects of these techniques are addressed in this investigation; the difficulty of dose determination and the delivery of the treatments at lower dose levels. In this research polymer gels were used as phantoms and dosimeters and cells were used to confirm outcomes. Normoxic polyacrylamide gels (nPAG) were tested as potential dosimeters for microbeam dosimetry. Following irradiation using microbeam and minibeam radiation from the BL28BU beam-line at Spring-8, Japan, the nPAG were scanned using a Raman spectroscopy technique. Dose enhancement caused by the inclusion of the gold nanoparticles (AuNPs) in the target was investigated using both cells and polymer gels. The use of AuNP could potentially reduce the dose required for the delivery of MRT. In this study it was shown that using endothelial cells with AuNPs, the minimal dose for clear cell killing along the beam line was reduced to 10 Gy. Both studies cell and gel studies indicates significant dose enhancement caused by the gold atoms in the target.

Rahman, Wan Nordiana; Davidson, Robert; Geso, Moshi [Division of Medical Radiation, School of Medical Sciences, RMIT University, Bundoora, Victoria (Australia); Wong, Christopher James [Division of Medical Radiation, School of Medical Sciences, RMIT University, Bundoora, Victoria (Australia); William Buckland Radiotherapy Centre, Alfred Hospital (Australia); Yagi, Naoto [Japanese Synchrotron Radiation Research Institute, Sayo-gun, Hyogo (Japan)

2010-07-23

189

Fitness and employee productivity.  

PubMed

What should management consider when deciding whether to sponsor a company fitness program? This article gives pragmatic answers to the business community as well as outlining critical avenues for future research for both academics and corporations. Understanding the nature of the commitment is a prerequisite for success. Whether the program should be short term and serve as a catalyst for future individual efforts, or a long-term commitment, is a question which must be considered. Decisions of this type are partially dependent on what criteria are used to evaluate success. As measurements of employee productivity are very subjective or non-existent, absenteeism and turnover are potential yardsticks. Details of employee programs must also address the issue of participation as well as the frequency, intensity and duration. Future research must separate the effect of the fitness improvement from the benfits derived from just being in a program. The measurement of productivity and the long-term effect of fitness programs, especially short-term programs, are also areas for future work. PMID:540412

Howard, J; Mikalachki, A

1979-09-01

190

A dynamic dosimetry system for prostate brachytherapy  

NASA Astrophysics Data System (ADS)

The lack of dynamic dosimetry tools for permanent prostate brachytherapy causes otherwise avoidable problems in prostate cancer patient care. The goal of this work is to satisfy this need in a readily adoptable manner. Using the ubiquitous ultrasound scanner and mobile non-isocentric C-arm, we show that dynamic dosimetry is now possible with only the addition of an arbitrarily configured marker-based fiducial. Not only is the system easily configured from accessible hardware, but it is also simple and convenient, requiring little training from technicians. Furthermore, the proposed system is built upon robust algorithms of seed segmentation, fiducial detection, seed reconstruction, and image registration. All individual steps of the pipeline have been thoroughly tested, and the system as a whole has been validated on a study of 25 patients. The system has shown excellent results of accurately computing dose, and does so with minimal manual intervention, therefore showing promise for widespread adoption of dynamic dosimetry.

Kuo, Nathanael; Dehghan, Ehsan; Deguet, Anton; Song, Danny Y.; Prince, Jerry L.; Lee, Junghoon

2013-03-01

191

Characterisation of a Ferrous Agarose Xylenol (FAX) gel for radiotherapy dose measurement.  

PubMed

The oxidation of ferrous to ferric ions due to ionizing radiation has been used for chemical dosimetry since 1927. The introduction of metal indicator dye xylenol orange (XO) sensitises the measurement of ferric ion yield. A ferrous sulphate- agarose- xylenol orange (FAX) gel was prepared and the gel then exposed to dose ranging from 0.2 to 10 Gy using various high energy photon and electron beams from a linear accelerator. Some general characteristics of FAX such as energy dependence, optical density (OD)-dose relationship, reproducibility and auto-oxidation of ferrous ions were analysed. The radiation yield G of the gel was calculated for gels prepared in oxygen and in air and the values were 46.3 +/- 2.1 and 40.9 +/- 1.4 Fe3+ per 100 eV for photons respectively. However for stock gel which was kept for 5 days pre-irradiation the G value decreased to 36.6 +/- 1.1. The gel shows linearity in OD-dose relationship, energy independence and reproducibility over the dose range investigated. Auto-oxidation of ferrous ions resulted in optical density changes of less than 1.5% per day. PMID:17682403

Leong, Lee Hon; Kandaiya, S; Seng, Ng Bong

2007-06-01

192

Nonlinear Curve-Fitting Program  

NASA Technical Reports Server (NTRS)

Nonlinear optimization algorithm helps in finding best-fit curve. Nonlinear Curve Fitting Program, NLINEAR, interactive curve-fitting routine based on description of quadratic expansion of X(sup 2) statistic. Utilizes nonlinear optimization algorithm calculating best statistically weighted values of parameters of fitting function and X(sup 2) minimized. Provides user with such statistical information as goodness of fit and estimated values of parameters producing highest degree of correlation between experimental data and mathematical model. Written in FORTRAN 77.

Everhart, Joel L.; Badavi, Forooz F.

1989-01-01

193

Technical basis for internal dosimetry at Hanford  

SciTech Connect

The Hanford Internal Dosimetry Program, administered by Pacific Northwest Laboratory for the US Department of Energy, provides routine bioassay monitoring for employees who are potentially exposed to radionuclides in the workplace. This report presents the technical basis for routine bioassay monitoring and the assessment of internal dose at Hanford. The radionuclides of concern include tritium, corrosion products ({sup 58}Co, {sup 60}Co, {sup 54}Mn, and {sup 59}Fe), strontium, cesium, iodine, europium, uranium, plutonium, and americium,. Sections on each of these radionuclides discuss the sources and characteristics; dosimetry; bioassay measurements and monitoring; dose measurement, assessment, and mitigation and bioassay follow-up treatment. 78 refs., 35 figs., 115 tabs.

Sula, M.J.; Carbaugh, E.H.; Bihl, D.E.

1991-07-01

194

Technical basis for internal dosimetry at Hanford  

SciTech Connect

The Hanford Internal Dosimetry Program, administered by Pacific Northwest Laboratory for the US Department of Energy, provides routine bioassay monitoring for employees who are potentially exposed to radionuclides in the workplace. This report presents the technical basis for routine bioassay monitoring and the assessment of internal dose at Hanford. The radionuclides of concern include tritium, corrosion products (/sup 58/Co, /sup 60/Co, /sup 54/Mn, and /sup 59/Fe), strontium, cesium, iodine, europium, uranium, plutonium, and americium. Sections on each of these radionuclides discuss the sources and characteristics; dosimetry; bioassay measurements and monitoring; dose measurement, assessment, and mitigation; and bioassay follow-up treatment. 64 refs., 42 figs., 118 tabs.

Sula, M.J.; Carbaugh, E.H.; Bihl, D.E.

1989-04-01

195

Applicability of Topaz Composites to Electron Dosimetry  

NASA Astrophysics Data System (ADS)

Thermoluminescent dosimetric topaz properties have been investigated and the results have shown that this mineral presents characteristics of a good dosimeter mainly in doses evaluation in radiotherapy with photons beams in radiotherapy. Typical applications of thermoluminescent dosimeters in radiotherapy are: in vivo dosimetry on patients (either as a routine quality assurance procedure or for dose monitoring in special cases); verification of treatment techniques; dosimetry audits; and comparisons among hospitals. The mean aim of this work was to evaluate the efficiency of topaz-Teflon pellets as thermoluminescent dosimeters in high-energy electron beams used to radiotherapy. Topaz-Teflon pellets were used as TLD.

Bomfim, K. S.; Souza, D. N.

2010-11-01

196

SNL RML recommended dosimetry cross section compendium  

SciTech Connect

A compendium of dosimetry cross sections is presented for use in the characterization of fission reactor spectrum and fluence. The contents of this cross section library are based upon the ENDF/B-VI and IRDF-90 cross section libraries and are recommended as a replacement for the DOSCROS84 multigroup library that is widely used by the dosimetry community. Documentation is provided on the rationale for the choice of the cross sections selected for inclusion in this library and on the uncertainty and variation in cross sections presented by state-of-the-art evaluations.

Griffin, P.J.; Kelly, J.G.; Luera, T.F. [Sandia National Labs., Albuquerque, NM (United States)] [Sandia National Labs., Albuquerque, NM (United States); VanDenburg, J. [Science and Engineering Associates, Inc., Albuquerque, NM (United States)] [Science and Engineering Associates, Inc., Albuquerque, NM (United States)

1993-11-01

197

Recent progresses in tritium radioecology and dosimetry  

SciTech Connect

In this paper, some aspects of recent progress in tritium radioecology and dosimetry are presented, with emphasis on atmospheric releases to terrestrial ecosystems. The processes involved in tritium transfer through the environment are discussed, together with the current status of environmental tritium models. Topics include the deposition and reemission of HT and HTO, models for the assessment of routine and accidental HTO emissions, a new approach to modeling the dynamics of tritium in mammals, the dose consequences of tritium releases and aspects of human dosimetry. The need for additional experimental data is identified, together with the attributes that would be desirable in the next generation of tritium codes. (authors)

Galeriu, D. [National Inst. for Physics and Nuclear Engineering Horia Hulubei, 407 Atomistilor St., Bucharest-Magurele, RO-077125 (Romania); Davis, P. [Atomic Energy of Canada Limited AECL, Chalk River Laboratories, Chalk River, ON K0J 1J0 (Canada); Raskob, W. [Institut fuer Kern und Energietechnik IKET, Bau 433, Forschungszentrum Karlsruhe - Technik und Umwelt, Postfach 3640, D-76021 Karlsruhe (Germany); Melintescu, A. [National Inst. for Physics and Nuclear Engineering Horia Hulubei, 407 Atomistilor St., Bucharest-Magurele, RO-077125 (Romania)

2008-07-15

198

Thermoluminescence and Thermoluminescent Dosimetry, v. 1  

SciTech Connect

This work is a comprehensive, in-depth review and guide to the fields of thermoluminescence and thermoluminescent dosimetry. Three up-to-date volumes contain useful tables, illustrations, formulas and references to aid researchers in radiation and nuclear science, dosimetry and solid state physics. Volume I concentrates on the basics of thermoluminescence (TL) study. It provides a general introduction, explains models of TL trapping, recombination centers and kinetics, outlines the complexity of the TL mechanism, and discusses important TL and dosimetric characteristics of commonly used TLD materials.

Horowitz, Y.S.

1984-01-01

199

Thermoluminescence and Thermoluminescent Dosimetry, v. 2  

SciTech Connect

This work is a comprehensive, in-depth review and guide to the fields of thermoluminescence and thermoluminescent dosimetry. Three up-to-date volumes contain useful tables, illustrations, formulas and references to aid researchers in radiation and nuclear science, dosimetry and solid state physics. Volume II provides the first comprehensive review of phototransferred TL to appear in literature. It also examines the TL dose response, the use of TLDs in various radiation fields, and the general cavity theory. The concepts of track structure theory are introduced.

Horowitz, Y.S.

1984-01-01

200

Radioluminescence dosimetry by scintillating fiber optics: the open challenges  

NASA Astrophysics Data System (ADS)

In the last decade, the interest in scintillating fiber optics for ionizing radiation monitoring is constantly increasing. Among the fields of possible applications of these sensors, radiation therapy represents a driving force for the research and development of new devices. In fact, the small dimensions of fiber optics based detectors, together with their realtime response, make these systems extremely promising both in quality assurance measurements of intensity modulated radiotherapy beams, and in in-vivo dosimetry. On the other hand, two specific aspects might represent limiting factors: (i) the "stem effect", that is the spurious luminescence originating as a consequence of the irradiation of the light guide, and (ii) the "memory effect", that is the radioluminescence sensitivity increase during prolonged exposition to ionizing radiation, typical of many scintillating materials. These two issues, representing the main challenges to face for the effective use of scintillating fiber as dosimeters in radiotherapy, were studied considering amorphous silica matrices prepared by sol-gel method and doped with europium. The origin of the stem effect was investigated by means of spectral measurements of the doped fibers irradiated with Xrays and electrons of different energies, field sizes and orientations. New approaches for removing the stem effect on the basis of the radioluminescent spectral analysis are presented and discussed. Furthermore, the causes and phenomenology of the memory effect are described, considering also the effect of dose accumulation with different dose rates and energies of ionizing radiation.

Veronese, Ivan; Cantone, Marie Claire; Chiodini, Norberto; De Mattia, Cristina; Fasoli, Mauro; Mones, Eleonora; Vedda, Anna

2013-09-01

201

Reference dosimetry using radiochromic film.  

PubMed

The objectives of this study are to identify and quantify factors that influence radiochromic film dose response and to determine whether such films are suitable for reference dosimetry. The influence of several parameters that may introduce systematic dose errors when performing reference dose measurements were investigated. The effect of the film storage temperature was determined by comparing the performance of three lots of GAFCHROMIC EBT2 films stored at either 4ºC or room temperature. The effect of high (> 80%) or low (< 20%) relative humidity was also determined. Doses measured in optimal conditions with EBT and EBT2 films were then compared with an A12 ionization chamber measurement. Intensity-modulated radiation therapy quality controls using EBT2 films were also performed in reference dose. The results obtained using reference dose measurements were compared with those obtained using relative dose measurements. Storing the film at 4ºC improves the stability of the film over time, but does not eliminate the noncatalytic film development, seen as a rise in optical density over time in the absence of radiation. Relative humidity variations ranging from 80% to 20% have a strong impact on the optical density and could introduce dose errors of up to 15% if the humidity were not controlled during the film storage period. During the scanning procedure, the film temperature influences the optical density that is measured. When controlling for these three parameters, the dose differences between EBT or EBT2 and the A12 chamber are found to be within ± 4% (2? level) over a dose range of 20-350 cGy. Our results also demonstrate the limitation of the Anisotropic Analytical Algorithm for dose calculation of highly modulated treatment plans. PMID:23149793

Girard, Frédéric; Bouchard, Hugo; Lacroix, Frédéric

2012-01-01

202

Clarification Procedure for Gels  

NASA Technical Reports Server (NTRS)

Procedure developed to obtain transparent gels with consistencies suitable for crystal growth, by replacing sodium ions in silicate solution with potassium ions. Clarification process uses cation-exchange resin to replace sodium ions in stock solution with potassium ions, placed in 1M solution of soluble potassium salt. Slurry stirred for several hours to allow potassium ions to replace all other cations on resin. Supernatant solution decanted through filter, and beads rinsed with distilled water. Rinsing removes excess salt but leaves cation-exchange beads fully charged with potassium ions.

Barber, Patrick G.; Simpson, Norman R.

1987-01-01

203

High transparent shape memory gel  

NASA Astrophysics Data System (ADS)

Gels are a new material having three-dimensional network structures of macromolecules. They possess excellent properties as swellability, high permeability and biocompatibility, and have been applied in various fields of daily life, food, medicine, architecture, and chemistry. In this study, we tried to prepare new multi-functional and high-strength gels by using Meso-Decoration (Meso-Deco), one new method of structure design at intermediate mesoscale. High-performance rigid-rod aromatic polymorphic crystals, and the functional groups of thermoreversible Diels-Alder reaction were introduced into soft gels as crosslinkable pendent chains. The functionalization and strengthening of gels can be realized by meso-decorating the gels' structure using high-performance polymorphic crystals and thermoreversible pendent chains. New gels with good mechanical properties, novel optical properties and thermal properties are expected to be developed.

Gong, Jin; Arai, Masanori; Kabir, M. H.; Makino, Masato; Furukawa, Hidemitsu

2014-03-01

204

Gel for retarding water flow  

SciTech Connect

A process is described for forming, in situ, a gel in a porous structure comprising: introducing an effective amount of a gel-forming composition into pores of a porous structure; and allowing the gel-forming composition to form a gel in the pores. The thusly formed gel is capable of being formed by reacting an aqueous solution comprising a first substance selected from the group consisting of polyvinyl alcohols, polyvinyl alcohol copolymers, and mixtures thereof. A second substance comprises aldehyde operable for effecting a crosslinking reaction with the first substance, wherein the total amount of aldehyde is from about 0.005 to about 2.5% of the weight of the gel.

Marrocco, M.L.

1987-05-12

205

Polyoxometalate-based Supramolecular Gel  

PubMed Central

Self-assemblyings of surfactant-encapsulated Wells-Dawson polyoxometalates (SEPs) nanobuilding blocks in butanone and esters yielded supramolecular gels showing thermo and photo responsive properties. The gels can be further polymerized if unsaturated esters were used and subsequently electrospinned into nanowires and non-woven mats. The as-prepared non-woven mats have a Young's modulus as high as 542.55?MPa. It is believed that this supramolecular gel is a good platform for polyoxometalates processing. PMID:23666013

He, Peilei; Xu, Biao; Liu, Huiling; He, Su; Saleem, Faisal; Wang, Xun

2013-01-01

206

Polyoxometalate-based Supramolecular Gel  

NASA Astrophysics Data System (ADS)

Self-assemblyings of surfactant-encapsulated Wells-Dawson polyoxometalates (SEPs) nanobuilding blocks in butanone and esters yielded supramolecular gels showing thermo and photo responsive properties. The gels can be further polymerized if unsaturated esters were used and subsequently electrospinned into nanowires and non-woven mats. The as-prepared non-woven mats have a Young's modulus as high as 542.55 MPa. It is believed that this supramolecular gel is a good platform for polyoxometalates processing.

He, Peilei; Xu, Biao; Liu, Huiling; He, Su; Saleem, Faisal; Wang, Xun

2013-05-01

207

Electrically controlled polymeric gel actuators  

DOEpatents

Electrically controlled polymeric gel actuators or synthetic muscles are described capable of undergoing substantial expansion and contraction when subjected to changing pH environments, temperature, or solvent. The actuators employ compliant containers for the gels and their solvents. The gels employed may be cylindrical electromechanical gel fibers such as polyacrylamide fibers or a mixture of poly vinyl alcohol-polyacrylic acid arranged in a parallel aggregate and contained in an electrolytic solvent bath such as salt water. The invention includes smart, electrically activated devices exploiting this phenomenon. These devices are capable of being manipulated via active computer control as large displacement actuators for use in adaptive structure such as robots. 11 figures.

Adolf, D.B.; Shahinpoor, M.; Segalman, D.J.; Witkowski, W.R.

1993-10-05

208

Gel polymer electrolytes for batteries  

DOEpatents

Nanostructured gel polymer electrolytes that have both high ionic conductivity and high mechanical strength are disclosed. The electrolytes have at least two domains--one domain contains an ionically-conductive gel polymer and the other domain contains a rigid polymer that provides structure for the electrolyte. The domains are formed by block copolymers. The first block provides a polymer matrix that may or may not be conductive on by itself, but that can soak up a liquid electrolyte, thereby making a gel. An exemplary nanostructured gel polymer electrolyte has an ionic conductivity of at least 1.times.10.sup.-4 S cm.sup.-1 at 25.degree. C.

Balsara, Nitash Pervez; Eitouni, Hany Basam; Gur, Ilan; Singh, Mohit; Hudson, William

2014-11-18

209

2015 Radiation Epidemiology and Dosimetry Course  

Cancer.gov

Mark your calendars for the 2015 Radiation Epidemiology and Dosimetry Course, offered by the Radiation Epidemiology Branch, part of NCI's Division of Cancer Epidemiology and Genetics (DCEG). World renowned radiation experts will discuss basic principles and the most up-to-date thinking about the health effects of radiation exposure.

210

DOSIMETRY MODELING OF INHALED TOXIC REACTIVE GASES  

EPA Science Inventory

The report focuses on the physical, chemical and biological processes and factors involved in the absorption of reactive gases. Emphasis is placed on the importance of these factors in developing dosimetry models, special consideration being given to the role of lung fluids and t...

211

Distribution effectiveness for space radiation dosimetry  

NASA Technical Reports Server (NTRS)

A simplified risk basis and a theory of hematological response are presented and applied to the problem of dosimetry in the manned space program. Unlike previous studies, the current work incorporates radiation exposure distribution effects into its definition of dose equivalent. The fractional cell lethality model for prediction of hematological response is integral in the analysis.

Wilson, J. W.

1975-01-01

212

Dosimetry implant for treating restenosis and hyperplasia  

DOEpatents

The present invention discloses a method of selectively providing radiation dosimetry to a subject in need of such treatment. The radiation is applied by an implant comprising a body member and .sup.117mSn electroplated at selected locations of the body member, emitting conversion electrons absorbed immediately adjacent selected locations while not affecting surrounding tissue outside of the immediately adjacent area.

Srivastava, Suresh; Gonzales, Gilbert R; Howell, Roger W; Bolch, Wesley E; Adzic, Radoslav

2014-09-16

213

Dosimetry Calculations Using Markov Chain Monte  

Microsoft Academic Search

SUMMARY A new numerical method for solving the inverse problem of in- ternal dosimetry is described. The new method uses Markov Chain Monte Carlo and the Metropolis algorithm. Multiple intake amounts, biokinetic types, and times of intake are determined from bioas- say data by integrating over the Bayesian posterior distribution. The method appears definitive, but its application requires a large

Guthrie Miller; Harry F. Martz; Tom T. Little; Ray Guilmette

214

A-bomb survivor dosimetry update  

SciTech Connect

A-bomb survivor data have been generally accepted as applicable. Also, the initial radiations have tended to be accepted as the dominant radiation source for all survivors. There was general acceptance of the essential reliability of both the biological effects data and the causative radiation dose values. There are considerations casting doubt on these acceptances, but very little quantification of th implied uncertainties has been attempted. The exception was A-bomb survivor dosimetry, where free-field kerma values for initial radiations were thought to be accurate to about 30%, and doses to individual survivors were treated as effectively error-free. In 1980, a major challenge to the accepted A-bomb survivor dosimetry was announced, and was quickly followed by a succession of explanations and displays showing the soundness of that challenge. In fact, a complete replacement set of free-field kerma values was provided which was suitable for use in constructing an entire new dosimetry for Hiroshima and Nagasaki. The new values showed many changes greater than the accepted 30% uncertainty. An approximate new dosimetry was indeed constructed, and used to convert existing leukemia cause-and-effect data from the old to the new dose values, by way of assessing the impact. (ERB)

Loewe, W.E.

1982-06-01

215

BNCT treatments - a human dosimetry evaluation  

SciTech Connect

This paper summarizes a comprehensive calculational study that provides an assessment of the radiation dose received by a glioblastoma multiforme patient treated by boron neutron capture therapy in Japan in mid-1993. This work is an extension of an earlier dosimetry evaluation of a different patient and uses a similar methodology to calculate the radiation doses.

Storr, G.J. [ANSTO, Menai (Australia); Wheeler, F.J. [Idaho National Engineering Lab., Idaho Falls, ID (United States)

1994-12-31

216

Personnel radiation dosimetry symposium: program and abstracts  

SciTech Connect

The purpose was to provide applied and research dosimetrists with sufficient information to evaluate the status and direction of their programs relative to the latest guidelines and techniques. A technical program was presented concerning experience, requirements, and advances in gamma, beta, and neutron personnel dosimetry.

Not Available

1984-10-01

217

Dosimetry of an Implantable 252 Californium Source  

SciTech Connect

The radiation dose from 252 Californium needles designed for use as a source of neutrons for radiotherapy has been measured. The dosimetry information presented in this paper will enable clinical studies of neutron radiotherapy with 252 Californium needles to be planned and begun.

Oliver, G.D. Jr.

2001-08-29

218

Protocol for emergency EPR dosimetry in fingernails  

Technology Transfer Automated Retrieval System (TEKTRAN)

There is an increased need for after-the fact dosimetry because of the high risk of radiation exposures due to terrorism or accidents. In case of such an event, a method is needed to make measurements of dose in a large number of individuals rapidly and with sufficient accuracy to facilitate effect...

219

Development of A-bomb survivor dosimetry  

SciTech Connect

An all important datum in risk assessment is the radiation dose to individual survivors of the bombings in Hiroshima and Nagasaki. The first set of dose estimates for survivors was based on a dosimetry system developed in 1957 by the Oak Ridge National Laboratory (ORNL). These Tentative 1957 Doses (T57D) were later replaced by a more extensive and refined set of Tentative 1965 Doses (T65D). The T65D system of dose estimation for survivors was also developed at ORNL and served as a basis for risk assessment throughout the 1970s. In the late 1970s, it was suggested that there were serious inadequacies with the T65D system, and these inadequacies were the topic of discussion at two symposia held in 1981. In early 1983, joint US- Japan research programs were established to conduct a thorough review of all aspects of the radiation dosimetry for the Hiroshima and Nagasaki A-bomb survivors. A number of important contributions to this review were made by ORNL staff members. The review was completed in 1986 and a new Dosimetry System 1986 (DS86) was adopted for use. This paper discusses the development of the various systems of A-bomb survivor dosimetry, and the status of the current DS86 system as it is being applied in the medical follow-up studies of the A-bomb survivors and their offspring.

Kerr, G.D.

1995-12-31

220

From ``micro`` to ``macro`` internal dosimetry  

SciTech Connect

Radiation dose is the amount of radiation energy deposited per unit mass of absorbing tissue. Internal dosimetry applies to assessments of dose to internal organs from penetrating radiation sources outside the body and from radionuclides taken into the body. Dosimetry is essential for correlating energy deposition with biological effects that are observed when living tissues are irradiated. Dose-response information provides the basis for radiation protection standards and risk assessment. Radiation interactions with living matter takes place on a microscopic scale, and the manifestation of damage may be evident at the cellular, multi-cellular, and even organ levels of biological organization. The relative biological effectiveness of ionization radiation is largely determined by the spatial distribution of energy deposition events within microscopic as well as macroscopic biological targets of interest. The spatial distribution of energy imparted is determined by the spatial distribution of radionuclides and properties of the emitted charged-particle radiation involved. The nonuniformity of energy deposition events in microscopic volumes, particularly from high linear energy transfer (LET) radiation, results in large variations in the amount of energy imparted to very small volumes or targets. Microdosimetry is the study of energy deposition events at the cellular level. Macrodosimetry is a term for conventional dose averaging at the tissue or organ level. In between is a level of dosimetry sometimes referred to as multi-cellular dosimetry. The distinction between these terms and their applications in assessment of dose from internally deposited radionuclides is described.

Fisher, D.R.

1994-06-01

221

Proton-beam radiation therapy dosimetry standardization  

SciTech Connect

Beams of protons have been used for radiation therapy applications for over 40 years. In the last decade the number of facilities treating patients and the total number of patients being treated has begun go grow rapidly. Due to the limited and experimental nature of the early programs, dosimetry protocols tended to be locally defined. With the publication of the AAPM Task Group 20 report {open_quotes}Protocol for Dosimetry of Heavy Charged Particles{close_quotes} and the {open_quotes}European Code of Practice for Proton-Beam Dosimetry{close_quotes} the practice of determining dose in proton-beam therapy was somewhat unified. The ICRU has also recently commissioned a report on recommendations for proton-beam dosimetry. There have been three main methods of determining proton dose; the Faraday cup technique, the ionization chamber technique, and the calorimeter technique. For practical reasons the ionization chamber technique has become the most widely used. However, due to large errors in basic parameters (e.g., W-value) is also has a large uncertainty for absolute dose. It has been proposed that the development of water calorimeter absorbed dose standards would reduce the uncertainty in absolute proton dose as well as the relative dose between megavoltage X-ray beams and proton beams. The advantages and disadvantages are discussed.

Gall, K.P.

1995-12-31

222

A feasibility study using radiochromic films for fast neutron 2D passive dosimetry  

NASA Astrophysics Data System (ADS)

The objective of this paper is threefold: (1) to establish sensitivity of XRQA and EBT radiochromic films to fast neutron exposure; (2) to develop a film response to radiation dose calibration curve and (3) to investigate a two-dimensional (2D) film dosimetry technique for use in establishing an experimental setup for a radiobiological irradiation of mice and to assess the dose to the mice in this setup. The films were exposed to a 10 MeV neutron beam via the 2H(d,n)3He reaction. The XRQA film response was a factor of 1.39 greater than EBT film response to the 10 MeV neutron beam when exposed to a neutron dose of 165 cGy. A film response-to-soft tissue dose calibration function was established over a range of 0-10 Gy and had a goodness of fit of 0.9926 with the calibration data. The 2D film dosimetry technique estimated the neutron dose to the mice by measuring the dose using a mouse phantom and by placing a piece of film on the exterior of the experimental mouse setup. The film results were benchmarked using Monte Carlo and aluminum (Al) foil activation measurements. The radiochromic film, Monte Carlo and Al foil dose measurements were strongly correlated, and the film within the mouse phantom agreed to better than 7% of the externally mounted films. These results demonstrated the potential application of radiochromic films for passive 2D neutron dosimetry.

Brady, Samuel L.; Gunasingha, Rathnayaka; Yoshizumi, Terry T.; Howell, Calvin R.; Crowell, Alexander S.; Fallin, Brent; Tonchev, Anton P.; Dewhirst, Mark W.

2010-09-01

223

Fitting Pulsar Wind Tori  

E-print Network

CXO imaging has shown that equatorial tori, often with polar jets, are very common in young pulsar wind nebulae (PWNe). These structures are interesting both for what they reveal about the relativistic wind itself and for the (nearly) model-independent measurement of the neutron star spin orientation they provide. The later is a particularly valuable probe of pulsar emission models and of neutron star physics.We describe here a procedure for fitting simple 3-D torus models to the X-ray data which provides robust estimates of the geometric parameters. An application to 6 PWN tori gives orientations, PWN shock scales and post-shock wind speeds along with statistical errors. We illustrate the use of these data by commenting on the implications for kick physics and for high energy beaming models.

C. -Y. Ng; Roger W. Romani

2003-10-06

224

SE-FIT  

NASA Technical Reports Server (NTRS)

The mathematical theory of capillary surfaces has developed steadily over the centuries, but it was not until the last few decades that new technologies have put a more urgent demand on a substantially more qualitative and quantitative understanding of phenomena relating to capillarity in general. So far, the new theory development successfully predicts the behavior of capillary surfaces for special cases. However, an efficient quantitative mathematical prediction of capillary phenomena related to the shape and stability of geometrically complex equilibrium capillary surfaces remains a significant challenge. As one of many numerical tools, the open-source Surface Evolver (SE) algorithm has played an important role over the last two decades. The current effort was undertaken to provide a front-end to enhance the accessibility of SE for the purposes of design and analysis. Like SE, the new code is open-source and will remain under development for the foreseeable future. The ultimate goal of the current Surface Evolver Fluid Interface Tool (SEFIT) development is to build a fully integrated front-end with a set of graphical user interface (GUI) elements. Such a front-end enables the access to functionalities that are developed along with the GUIs to deal with pre-processing, convergence computation operation, and post-processing. In other words, SE-FIT is not just a GUI front-end, but an integrated environment that can perform sophisticated computational tasks, e.g. importing industry standard file formats and employing parameter sweep functions, which are both lacking in SE, and require minimal interaction by the user. These functions are created using a mixture of Visual Basic and the SE script language. These form the foundation for a high-performance front-end that substantially simplifies use without sacrificing the proven capabilities of SE. The real power of SE-FIT lies in its automated pre-processing, pre-defined geometries, convergence computation operation, computational diagnostic tools, and crash-handling capabilities to sustain extensive computations. SE-FIT performance is enabled by its so-called file-layer mechanism. During the early stages of SE-FIT development, it became necessary to modify the original SE code to enable capabilities required for an enhanced and synchronized communication. To this end, a file-layer was created that serves as a command buffer to ensure a continuous and sequential execution of commands sent from the front-end to SE. It also establishes a proper means for handling crashes. The file layer logs input commands and SE output; it also supports user interruption requests, back and forward operation (i.e. undo and redo), and others. It especially enables the batch mode computation of a series of equilibrium surfaces and the searching of critical parameter values in studying the stability of capillary surfaces. In this way, the modified SE significantly extends the capabilities of the original SE.

Chen, Yongkang; Weislogel, Mark; Schaeffer, Ben; Semerjian, Ben; Yang, Lihong; Zimmerli, Gregory

2012-01-01

225

An evaluation of the dosimetric performance characteristics of N-vinylpyrrolidone-based polymer gels  

NASA Astrophysics Data System (ADS)

The aim of this work was to investigate the dosimetric performance properties of the N-vinylpyrrolidone argon (VIPAR) based polymer gel as a dosimetric tool in clinical radiotherapy. VIPAR gels with a larger concentration of gelatin than the standard recipe were manufactured and irradiated up to 68 Gy using a 6 and 18 MV linear accelerator. Using MRI, the R2-dose response was recorded at different imaging sessions within a 34 day time period post-irradiation. The R2-dose response was found to be linear between 5 and 68 Gy. Although dose sensitivity did not show significant variation with time, the measured R2-dose values showed an increasing trend, which was less evident beyond 17 days. At one day post-irradiation, calculated dose standard uncertainties at 20 Gy and 56 Gy were 2.2% and 1.7%, providing a dose resolution of 0.45 Gy and 0.97 Gy, respectively. Although these values fulfilled the 2% limit of ICRU, when gels were imaged at one day post-irradiation, it was shown that the temporal evolution of the R2 values deteriorated the per cent standard uncertainty and the dose resolution by ~57%, when imaged 17 days post-irradiation. Variation in the coagulation temperature of the gels did not impact the R2-dose sensitivity. This study has shown that the VIPAR gel has the properties of a dosimetric tool required in clinical radiotherapy, especially in applications where a wide dose dynamic range is employed. For results with the lowest per cent uncertainty and the optimum dose resolution, the dosimetry gels used in this work should be MR scanned at one day post-irradiation. Furthermore, a preliminary study on the R2-dose response of a new normoxic N-vinylpyrrolidone-based polymer gel showed that it could potentially replace the traditional VIPAR gel formulation, while preserving the wide dynamic dose response inherent to that monomer.

Papadakis, A. E.; Maris, T. G.; Zacharopoulou, F.; Pappas, E.; Zacharakis, G.; Damilakis, J.

2007-08-01

226

Statement of Fitness for Work  

E-print Network

Statement of Fitness for Work ­ the fit note explained This guide explains what you should do when your health affects your ability to work. It replaces the sick note. The main difference is that the fit note allows your doctor to advise you on how you may be able to return to work. Work can

Davies, Christopher

227

Nanocrystal/sol-gel nanocomposites  

SciTech Connect

The present invention is directed to solid composites including colloidal nanocrystals within a sol-gel host or matrix and to processes of forming such solid composites. The present invention is further directed to alcohol soluble colloidal nanocrystals useful in formation of sol-gel based solid composites

Petruska, Melissa A. (Los Alamos, NM); Klimov, Victor L. (Los Alamos, NM)

2012-06-12

228

Nanocrystal/sol-gel nanocomposites  

DOEpatents

The present invention is directed to solid composites including colloidal nanocrystals within a sol-gel host or matrix and to processes of forming such solid composites. The present invention is further directed to alcohol soluble colloidal nanocrystals useful in formation of sol-gel based solid composites.

Petruska, Melissa A. (Los Alamos, NM); Klimov, Victor L. (Los Alamos, NM)

2007-06-05

229

Multiple phases of protien gels  

Microsoft Academic Search

A multiple phase transition was observed in gels made by covalently cross-linking proteins in either native or denatured state. The enzymatic activity of the gels prepared from native alpha-chymotrypsin was determined for each of the multiple phases. The reversibility of the swelling degrees and the enzymatic reaction rates upon phase transition suggests that the protein is at a free energy

Masahiko Annaka; Toyoichi Tanaka

1994-01-01

230

Electromechanical nonionic gels  

NASA Astrophysics Data System (ADS)

The electrically induced bending of nonionic polyvinyl alcohol gels, bending over 90° within 100 ms, is the fastest motion in the field of electroactuation of polymers. This rapid bending produces initial mechanical vibrations followed by a durable displacement that contrasts highly with the relaxation observed with elastomer- and polyelectrolyte-based actuators. Here, we characterize the bending process using video imaging and laser detecting technology and establish a physical model for the electromechanical conversion, based on our observation of an induced solvent migration. Our results show excellent agreement between the measurements and calculations. This study provides general rules for understanding the electrically induced bending of isotropic dielectrics and may also shed light on nonmuscular biological engines.

Zheng, J.; Xu, C.; Hirai, T.

2008-02-01

231

Artifacts suppression in optical CT for gel dosimeters by iterative reconstruction  

NASA Astrophysics Data System (ADS)

Optical CT has been considered as an important and promising readout method for 3D gel dosimetry. However, tomographic image qualities are often corrupted by artifacts such as streaks and rings, which are induced by projection discontinuities and magnified by FBP reconstruction. These artifacts will surely deteriorate the accuracy and precision of dose measurement. In this paper, we performed a preliminary study on our in-house optical CT scanner using an iterative algorithm instead of the commonly used FBP for image reconstruction. Comparative analysis of the results validates the proposed method in artifacts suppression and image quality improvement when the convergent process is properly controlled.

Yi, Du; Xiangang, Wang; Xincheng, Xiang

2015-01-01

232

Living bacteria in silica gels  

NASA Astrophysics Data System (ADS)

The encapsulation of enzymes within silica gels has been extensively studied during the past decade for the design of biosensors and bioreactors. Yeast spores and bacteria have also been recently immobilized within silica gels where they retain their enzymatic activity, but the problem of the long-term viability of whole cells in an inorganic matrix has never been fully addressed. It is a real challenge for the development of sol-gel processes. Generic tests have been performed to check the viability of Escherichia coli bacteria in silica gels. Surprisingly, more bacteria remain culturable in the gel than in an aqueous suspension. The metabolic activity of the bacteria towards glycolysis decreases slowly, but half of the bacteria are still viable after one month. When confined within a mineral environment, bacteria do not form colonies. The exchange of chemical signals between isolated bacteria rather than aggregates can then be studied, a point that could be very important for 'quorum sensing'.

Nassif, Nadine; Bouvet, Odile; Noelle Rager, Marie; Roux, Cécile; Coradin, Thibaud; Livage, Jacques

2002-09-01

233

Collapse of Gels in an Electric Field  

Microsoft Academic Search

An infinitesimal change in electric potential across a polyelectrolyte gel produces a discrete, reversible volume change. The volume of the collapsed gel can be several hundred times smaller than that of the swollen gel.

Toyoichi Tanaka; Izumi Nishio; Shao-Tang Sun; Shizue Ueno-Nishio

1982-01-01

234

Sonication-triggered instantaneous gel-to-gel transformation.  

PubMed

Two new peptide-based isomers containing cholesterol and naphthalic groups have been designed and synthesized. We found that the position of L-alanine in the linker could tune the gelation properties and morphologies. The molecule with the L-alanine residue positioned in the middle of the linker (1b) shows better gelation behavior than that with L-alanine directly linked to the naphthalimido moiety (1a). As a result, a highly thermostable organogel of 1b with a unique core-shell structure was obtained at high temperature and pressure in acetonitrile. Moreover, the gels of 1a and 1b could undergo an instantaneous gel-to-gel transition triggered by sonication. Ultrasound could break the core-shell microsphere of 1b and the micelle structure of 1a into entangled fibers. By studying the mechanism of the sonication-triggered gel-to-gel transition process of these compounds, it can be concluded that ultrasound has a variety of effects on the morphology, such as cutting, knitting, unfolding, homogenizing, and even cross-linking. Typically, ultrasound can cleave and homogenize pi-stacking and hydrophobic interactions among the gel molecules and then reshape the morphologies to form a new gel. This mechanism of morphology transformation triggered by sonication might be attractive in the field of material storage and controlled release. PMID:20572172

Yu, Xudong; Liu, Qian; Wu, Junchen; Zhang, Mingming; Cao, Xinhua; Zhang, Song; Wang, Qi; Chen, Liming; Yi, Tao

2010-08-01

235

Cascade analysis of mixed gels of xanthan and locust bean gum  

Microsoft Academic Search

The gel properties of xanthan (XG)–locust bean gum (LBG) mixtures were investigated. The concentration and temperature dependence of gel modulus, as well as the composition dependence of critical gelling concentration, were analyzed using a cascade model. The number of cross-linking sites per molecule for XG and LBG, fXG and fLBG, is determined by fitting experimental data to the model. The values

Ching-Feng Mao; Syang-Peng Rwei

2006-01-01

236

NMR relaxometry measurements of Fricke gel dosimeters exposed to neutrons  

NASA Astrophysics Data System (ADS)

Fricke infused gel matrices offer several features making them suitable for dosimetric applications; among these there are tissue equivalence, low cost and ease of preparation. Their nuclear magnetic resonance (NMR) relaxation properties can be used as a radiation detector for the dosimetry of beams used in cancer therapy. In recent years neutron capture therapy has been resumed for the treatment of various types of cancer and it requires three-dimensional mapping of the neutron fields. In this work, we investigated this particular application through NMR relaxometry and MR imaging of Fricke gels exposed to neutrons. We analyzed both the R1 and R2 relaxation rates, which relate to the longitudinal T1 and transversal T2 relaxation times. In particular, we found that the relaxation rate R2 does not depend on the neutron fluence, whereas the relaxation rate R1 increases linearly with the fluence. The magnetic resonance imaging acquisitions showed that T1-weighted images allow the characterization of samples exposed to different neutron fluences.

Marrale, Maurizio; Brai, Maria; Longo, Anna; Gallo, Salvatore; Tomarchio, Elio; Tranchina, Luigi; Gagliardo, Cesare; D'Errico, Francesco

2014-11-01

237

How do monomeric components of a polymer gel dosimeter respond to ionising radiation: A steady-state radiolysis towards preparation of a 3D polymer gel dosimeter  

NASA Astrophysics Data System (ADS)

Ionising radiation-induced reactions of aqueous single monomer solutions and mixtures of poly(ethylene glycol) diacrylate (PEGDA) and N, N'-methylenebisacrylamide (Bis) in a steady-state condition are presented below and above gelation doses in order to highlight reactions in irradiated 3D polymer gel dosimeters, which are assigned for radiotherapy dosimetry. Both monomers are shown to undergo radical polymerisation and cross-linking, which result in the measured increase in molecular weight and radius of gyration of the formed polydisperse polymer coils. The formation of nanogels was also observed for Bis solutions at a low concentration. In the case of PEGDA-Bis mixtures, co-polymerisation is suggested as well. At a sufficiently high radiation dose, the formation of a polymer network was observed for both monomers and their mixture. For this reason a sol-gel analysis for PEGDA and Bis was performed gravimetrically and a proposition of an alternative to this method employing a nuclear magnetic resonance technique is made. The two monomers were used for preparation of 3D polymer gel dosimeters having the acronyms PABIG and PABIG nx. The latter is presented for the first time in this work and is a type of the formerly established PABIG polymer gel dosimeter. The elementary characteristics of the new composition are presented, underlining the ease of its preparation, low dose threshold, and slightly increased sensitivity but lower quasi-linear range of dose response in comparison to PABIG.

Kozicki, Marek

2011-12-01

238

Carbon Nanotube and Carbon Fibre Based Radiation Dosimetry.  

E-print Network

??The principle of radiobiology and, hence, clinical outcomes in radiotherapy are inherently dependent on accurate radiation dosimetry. Over the last few decades, ionization chambers, thermoluminescence… (more)

Ma, Jiazhi

2008-01-01

239

Hanford External Dosimetry Technical Basis Manual PNL-MA-842  

SciTech Connect

The Hanford External Dosimetry Technical Basis Manual PNL-MA-842 documents the design and implementation of the external dosimetry system used at Hanford. The manual describes the dosimeter design, processing protocols, dose calculation methodology, radiation fields encountered, dosimeter response characteristics, limitations of dosimeter design under field conditions, and makes recommendations for effective use of the dosimeters in the field. The manual describes the technical basis for the dosimetry system in a manner intended to help ensure defensibility of the dose of record at Hanford and to demonstrate compliance with 10 CFR 835, DOELAP, DOE-RL, ORP, PNSO, and Hanford contractor requirements. The dosimetry system is operated by PNNL’s Hanford External Dosimetry Program which provides dosimetry services to all Hanford contractors. The primary users of this manual are DOE and DOE contractors at Hanford using the dosimetry services of PNNL. Development and maintenance of this manual is funded directly by DOE and DOE contractors. Its contents have been reviewed and approved by DOE and DOE contractors at Hanford through the Hanford Personnel Dosimetry Advisory Committee which is chartered and chaired by DOE-RL and serves as means of coordinating dosimetry practices across contractors at Hanford. This manual was established in 1996. Since inception, it has been revised many times and maintained by PNNL as a controlled document with controlled distribution. Rev. 0 marks the first revision to be released through PNNL’s Electronic Records & Information Capture Architecture (ERICA) database.

Rathbone, Bruce A.

2005-02-25

240

TransFit: Finite element analysis data fitting software  

NASA Technical Reports Server (NTRS)

The Advanced X-Ray Astrophysics Facility (AXAF) mission support team has made extensive use of geometric ray tracing to analyze the performance of AXAF developmental and flight optics. One important aspect of this performance modeling is the incorporation of finite element analysis (FEA) data into the surface deformations of the optical elements. TransFit is software designed for the fitting of FEA data of Wolter I optical surface distortions with a continuous surface description which can then be used by SAO's analytic ray tracing software, currently OSAC (Optical Surface Analysis Code). The improved capabilities of Transfit over previous methods include bicubic spline fitting of FEA data to accommodate higher spatial frequency distortions, fitted data visualization for assessing the quality of fit, the ability to accommodate input data from three FEA codes plus other standard formats, and options for alignment of the model coordinate system with the ray trace coordinate system. TransFit uses the AnswerGarden graphical user interface (GUI) to edit input parameters and then access routines written in PV-WAVE, C, and FORTRAN to allow the user to interactively create, evaluate, and modify the fit. The topics covered include an introduction to TransFit: requirements, designs philosophy, and implementation; design specifics: modules, parameters, fitting algorithms, and data displays; a procedural example; verification of performance; future work; and appendices on online help and ray trace results of the verification section.

Freeman, Mark

1993-01-01

241

Evaluation of respirator fit training by quantitative fit testing  

E-print Network

protected with a given respi- rator, and to select the best fitting respirator available . In all fit tests us1ng a challenge aerosol to detect facepiece leakage, the respirator must be equipped with air purify1ng cartridges that eff1- ciently remove... the aerosol from the amb1ent air. Oualitative Fit Tests In a qualitative fit test (OLFT), the respirator wearer is nor- mallyy exposed to an 1 rr 1 tant smoke or an odorous vapor . If the test subject cannot detect penetration of the test agent...

Chute, Daniel Otis

2012-06-07

242

NuFit: nutrition and fitness CBPR program evaluation.  

PubMed

The present study combines community-based participatory research (CBPR) and peer education to create NuFit, a nutrition and fitness curriculum, adapted by community and student peer leaders for Latino and African-American high-school students in Chicago. The purpose of this pilot study was to assess the feasibility and efficacy of the NuFit curriculum to improve the knowledge, attitudes, and behaviors regarding nutrition and fitness for minority and adolescent student populations. The NuFit curriculum improved students' short-term self-reported behaviors and attitudes around nutrition and fitness. The NuFit curriculum shows promise as one mechanism to help prevent and combat childhood obesity by fostering healthy attitudes and behaviors during the critical developmental stage of adolescence. Involvement of and collaboration between community stakeholders and youth appeared to increase the likelihood of NuFit's cultural relevance and sustainability. More work is necessary to evaluate the long-term effects of NuFit. PMID:24702662

McKinney, Chelsea; Bishop, Virginia; Cabrera, Kathy; Medina, Roxane; Takawira, Desire; Donate, Nilmari; Rodriguez, Jose Luis; Guevara, Beti

2014-01-01

243

Validation of the IRDF-2002 dosimetry library  

NASA Astrophysics Data System (ADS)

A Data Development Project was instigated by the International Atomic Energy Agency (IAEA) to update the library of dosimetry cross-sections "International Reactor Dosimetry File: IRDF-2002" and this was completed recently. Thermal capture cross-sections and resonance integrals were compared against the database of integral constants for neutron activation analysis in a validation exercise; this new IRDF-2002 file was also used in the analysis of several benchmark experiments performed at the Frascati Neutron Generator (FNG), ENEA, Frascati, and in the ASPIS facility, AEA Technology, Winfrith. The results exhibited good consistency and improved the "calculation/experiment" ratios. Reduction of some uncertainties in the new IRDF-2002 file is supported by the analysis. Inclusion of pointwise cross-section data is an important enhancement of the library for the Monte Carlo methods, as well as for codes using multigroup data for cases where self-shielding of the resonances is important.

Kodeli, I.; Trkov, A.

2007-07-01

244

Absolute and relative dosimetry for ELIMED  

NASA Astrophysics Data System (ADS)

The definition of detectors, methods and procedures for the absolute and relative dosimetry of laser-driven proton beams is a crucial step toward the clinical use of this new kind of beams. Hence, one of the ELIMED task, will be the definition of procedures aiming to obtain an absolute dose measure at the end of the transport beamline with an accuracy as close as possible to the one required for clinical applications (i.e. of the order of 5% or less). Relative dosimetry procedures must be established, as well: they are necessary in order to determine and verify the beam dose distributions and to monitor the beam fluence and the energetic spectra during irradiations. Radiochromic films, CR39, Faraday Cup, Secondary Emission Monitor (SEM) and transmission ionization chamber will be considered, designed and studied in order to perform a fully dosimetric characterization of the ELIMED proton beam.

Cirrone, G. A. P.; Cuttone, G.; Candiano, G.; Carpinelli, M.; Leonora, E.; Lo Presti, D.; Musumarra, A.; Pisciotta, P.; Raffaele, L.; Randazzo, N.; Romano, F.; Schillaci, F.; Scuderi, V.; Tramontana, A.; Cirio, R.; Marchetto, F.; Sacchi, R.; Giordanengo, S.; Monaco, V.

2013-07-01

245

Trigeminal neuralgia treatment dosimetry of the Cyberknife  

SciTech Connect

There are 2 Cyberknife units at Stanford University. The robot of 1 Cyberknife is positioned on the patient's right, whereas the second is on the patient's left. The present study examines whether there is any difference in dosimetry when we are treating patients with trigeminal neuralgia when the target is on the right side or the left side of the patient. In addition, we also study whether Monte Carlo dose calculation has any effect on the dosimetry. We concluded that the clinical and dosimetric outcomes of CyberKnife treatment for trigeminal neuralgia are independent of the robot position. Monte Carlo calculation algorithm may be useful in deriving the dose necessary for trigeminal neuralgia treatments.

Ho, Anthony [Department of Radiation Oncology, Stanford University, Stanford, CA (United States); Lo, Anthony T., E-mail: tonyho22003@yahoo.com [Department of Radiation Oncology, Stanford University, Stanford, CA (United States); Dieterich, Sonja; Soltys, Scott G.; Gibbs, Iris C. [Department of Radiation Oncology, Stanford University, Stanford, CA (United States); Chang, Steve G.; Adler, John R. [Department of Neurosurgery, Stanford University, Stanford, CA (United States)

2012-04-01

246

Passive particle dosimetry. [silver halide crystal growth  

NASA Technical Reports Server (NTRS)

Present methods of dosimetry are reviewed with emphasis on the processes using silver chloride crystals for ionizing particle dosimetry. Differences between the ability of various crystals to record ionizing particle paths are directly related to impurities in the range of a few ppm (parts per million). To understand the roles of these impurities in the process, a method for consistent production of high purity silver chloride, and silver bromide was developed which yields silver halides with detectable impurity content less than 1 ppm. This high purity silver chloride was used in growing crystals with controlled doping. Crystals were grown by both the Czochalski method and the Bridgman method, and the Bridgman grown crystals were used for the experiments discussed. The distribution coefficients of ten divalent cations were determined for the Bridgman crystals. The best dosimeters were made with silver chloride crystals containing 5 to 10 ppm of lead; other impurities tested did not produce proper dosimeters.

Childs, C. B.

1977-01-01

247

Absolute and relative dosimetry for ELIMED  

SciTech Connect

The definition of detectors, methods and procedures for the absolute and relative dosimetry of laser-driven proton beams is a crucial step toward the clinical use of this new kind of beams. Hence, one of the ELIMED task, will be the definition of procedures aiming to obtain an absolute dose measure at the end of the transport beamline with an accuracy as close as possible to the one required for clinical applications (i.e. of the order of 5% or less). Relative dosimetry procedures must be established, as well: they are necessary in order to determine and verify the beam dose distributions and to monitor the beam fluence and the energetic spectra during irradiations. Radiochromic films, CR39, Faraday Cup, Secondary Emission Monitor (SEM) and transmission ionization chamber will be considered, designed and studied in order to perform a fully dosimetric characterization of the ELIMED proton beam.

Cirrone, G. A. P.; Schillaci, F.; Scuderi, V. [INFN, Laboratori Nazionali del Sud, Via Santa Sofia 62, Catania, Italy and Institute of Physics Czech Academy of Science, ELI-Beamlines project, Na Slovance 2, Prague (Czech Republic)] [INFN, Laboratori Nazionali del Sud, Via Santa Sofia 62, Catania, Italy and Institute of Physics Czech Academy of Science, ELI-Beamlines project, Na Slovance 2, Prague (Czech Republic); Cuttone, G.; Candiano, G.; Musumarra, A.; Pisciotta, P.; Romano, F. [INFN, Laboratori Nazionali del Sud, Via Santa Sofia 62, Catania (Italy)] [INFN, Laboratori Nazionali del Sud, Via Santa Sofia 62, Catania (Italy); Carpinelli, M. [INFN Sezione di Cagliari, c/o Dipartimento di Fisica, Università di Cagliari, Cagliari (Italy)] [INFN Sezione di Cagliari, c/o Dipartimento di Fisica, Università di Cagliari, Cagliari (Italy); Leonora, E.; Randazzo, N. [INFN-Sezione di Catania, Via Santa Sofia 64, Catania (Italy)] [INFN-Sezione di Catania, Via Santa Sofia 64, Catania (Italy); Presti, D. Lo [INFN-Sezione di Catania, Via Santa Sofia 64, Catania, Italy and Università di Catania, Dipartimento di Fisica e Astronomia, Via S. Sofia 64, Catania (Italy)] [INFN-Sezione di Catania, Via Santa Sofia 64, Catania, Italy and Università di Catania, Dipartimento di Fisica e Astronomia, Via S. Sofia 64, Catania (Italy); Raffaele, L. [INFN, Laboratori Nazionali del Sud, Via Santa Sofia 62, Catania, Italy and INFN-Sezione di Catania, Via Santa Sofia 64, Catania (Italy)] [INFN, Laboratori Nazionali del Sud, Via Santa Sofia 62, Catania, Italy and INFN-Sezione di Catania, Via Santa Sofia 64, Catania (Italy); Tramontana, A. [INFN, Laboratori Nazionali del Sud, Via Santa Sofia 62, Catania, Italy and Università di Catania, Dipartimento di Fisica e Astronomia, Via S. Sofia 64, Catania (Italy)] [INFN, Laboratori Nazionali del Sud, Via Santa Sofia 62, Catania, Italy and Università di Catania, Dipartimento di Fisica e Astronomia, Via S. Sofia 64, Catania (Italy); Cirio, R.; Sacchi, R.; Monaco, V. [INFN, Sezione di Torino, Via P.Giuria, 1 10125 Torino, Italy and Università di Torino, Dipartimento di Fisica, Via P.Giuria, 1 10125 Torino (Italy)] [INFN, Sezione di Torino, Via P.Giuria, 1 10125 Torino, Italy and Università di Torino, Dipartimento di Fisica, Via P.Giuria, 1 10125 Torino (Italy); Marchetto, F.; Giordanengo, S. [INFN, Sezione di Torino, Via P.Giuria, 1 10125 Torino (Italy)] [INFN, Sezione di Torino, Via P.Giuria, 1 10125 Torino (Italy)

2013-07-26

248

DEVELOPMENTS AND TRENDS IN BIOEQUIVALENT DOSIMETRY.  

PubMed

Significant progress in radiobiology has refined the understanding of radiation-induced biological response at the cellular level and challenged the conventional application of a macroscopic description of radiation action to dosimetry in favour of a microscopic approach. Pioneering experiments, which investigated the stochastics of energy deposition from ionising radiations in volumes of cellular dimensions, contributed to the recognition of microdosimetry as a new scientific discipline. The first quantitative applications of Monte Carlo track structure simulations in radiobiology, however, supported evidence for target sizes of particular biological importance being in the nanometre regime. Bioequivalent dosimetry attempts to link particular features of the response of physical detectors with biological endpoints, exploiting clusters of multiple ionisations within nanometre scales in solid-state, gas- and water-filled devices. This approach supports the continued development of new concepts and quantities in radiation protection to permit evaluation of the biological effectiveness of radiations of different quality independently of dose and dose rate. PMID:25183836

Hajek, M

2014-09-01

249

The polyGeVero® software for fast and easy computation of 3D radiotherapy dosimetry data  

NASA Astrophysics Data System (ADS)

The polyGeVero® software package was elaborated for calculations of 3D dosimetry data such as the polymer gel dosimetry. It comprises four workspaces designed for: i) calculating calibrations, ii) storing calibrations in a database, iii) calculating dose distribution 3D cubes, iv) comparing two datasets e.g. a measured one with a 3D dosimetry with a calculated one with the aid of a treatment planning system. To accomplish calculations the software was equipped with a number of tools such as the brachytherapy isotopes database, brachytherapy dose versus distance calculation based on the line approximation approach, automatic spatial alignment of two 3D dose cubes for comparison purposes, 3D gamma index, 3D gamma angle, 3D dose difference, Pearson's coefficient, histograms calculations, isodoses superimposition for two datasets, and profiles calculations in any desired direction. This communication is to briefly present the main functions of the software and report on the speed of calculations performed by polyGeVero®.

Kozicki, Marek; Maras, Piotr

2015-01-01

250

Progress with the NCT international dosimetry exchange.  

PubMed

The international collaboration that was organized to undertake a dosimetry exchange for purposes of combining clinical data from different facilities conducting neutron capture therapy has continued since its founding at the 9th ISNCT symposium in October 2000. The thrust towards accumulating physical dosimetry data for comparison between different participants has broadened to include facilities in Japan and the determination of spectral descriptions of different beams. Retrospective analysis of patient data from the Brookhaven Medical Research Reactor is also being considered for incorporation into this study to increase the pool of available data. Meanwhile the next essential phase of comparing measurements of visiting dosimetry groups with treatment plan calculations from the host institutes has commenced. Host centers from Petten, Finland and the Czech Republic in Europe and MIT in the USA have applied the regular calculations and clinical calibrations from their current clinical studies, to generate treatment plans in the large standard phantom used for measurements by visiting participants. These data have been exchanged between the participants and scaling factors to relate the separate dose components between the different institutes are being determined. Preliminary normalization of measured and calculated dosimetry for patients is nearing completion to enable the physical radiation doses that comprise a treatment prescription at a host institute to be directly related to the corresponding measured doses of a visiting group. This should serve as an impetus for the direct comparison of patient data although the clinical requirements for achieving this need to be clearly defined. This may necessitate more extensive comparisons of treatment planning calculations through the solution of test problems and clarification regarding the question of dose specification from treatment calculations in general. PMID:15308159

Binns, P J; Riley, K J; Harling, O K; Auterinen, I; Marek, M; Kiger, W S

2004-11-01

251

Faraday dosimetry characteristics of PIII doping processes  

Microsoft Academic Search

A Faraday cup dosimetry system was developed and characterized to address the issues of plasma immersion ion implantation (PIII) dose measurements. Pure ion current was measured by using an electrostatic suppression mechanism combined with high-bandwidth fiber-optic electronics to isolate high-voltage pulses and eliminate the primary and secondary electron and displacement currents. The ion-current waveform measured by the Faraday cup was

Shu Qin; Michael P. Bradley; Peter L. Kellerman

2003-01-01

252

Radiochromic film dosimetry for clinical proton beams  

Microsoft Academic Search

Depth doses and lateral profiles for proton beams with energies of 100–250 MeV were measured with a high-sensitivity GafChromic™ MD-55 film, which requires no post-irradiation development. The exposed MD-55 films were evaluated with the RIT 113 film dosimetry system. Depth doses measured with MD-55 film were compared with those obtained with a plane-parallel ionization chamber. The GafChromic™ film was found

Stanislav M. Vatnitsky

1997-01-01

253

Update on GI Radiopharmaceuticals and Dosimetry Estimates  

PubMed Central

The gold standard technique for measuring gastric emptying is scintigraphy using radiolabeled test meals. Recently, a standardized radiolabeled solid meal has been proposed and adopted by many centers. There is still a need for alternative meals and several such meals with demonstrated radiolabel stability have been evaluated in small numbers of subjects. Updated radiation dosimetry associated with these meals has been calculated for adult males and adult females with normal GI transit as well as transit abnormalities. PMID:22293168

Knight, Linda C.

2011-01-01

254

Adhesive, elastomeric gel impregnating composition  

DOEpatents

An improved capacitor roll with alternating film and foil layers is impregnated with an adhesive, elastomeric gel composition. The gel composition is a blend of a plasticizer, a polyol, a maleic anhydride that reacts with the polyol to form a polyester, and a catalyst for the reaction. The impregnant composition is introduced to the film and foil layers while still in a liquid form and then pressure is applied to aid with impregnation. The impregnant composition is cured to form the adhesive, elastomeric gel. Pressure is maintained during curing.

Shaw, David Glenn (Tucson, AZ); Pollard, John Randolph (Tucson, AZ); Brooks, Robert Aubrey (Tijeras, NM)

2002-01-01

255

Acrylonitrile Butadiene Styrene (ABS) plastic based low cost tissue equivalent phantom for verification dosimetry in IMRT.  

PubMed

A novel IMRT phantom was designed and fabricated using Acrylonitrile Butadiene Styrene (ABS) plastic. Physical properties of ABS plastic related to radiation interaction and dosimetry were compared with commonly available phantom materials for dose measurements in radiotherapy. The ABS IMRT phantom has provisions to hold various types of detectors such as ion chambers, radiographic/radiochromic films, TLDs, MOSFETs, and gel dosimeters. The measurements related to pre-treatment dose verification in IMRT of carcinoma prostate were carried out using ABS and Scanditronics-Wellhoffer RW3 IMRT phantoms for five different cases. Point dose data were acquired using ionization chamber and TLD discs while Gafchromic EBT and radiographic EDR2 films were used for generating 2-D dose distributions. Treatment planning system (TPS) calculated and measured doses in ABS plastic and RW3 IMRT phantom were in agreement within +/-2%. The dose values at a point in a given patient acquired using ABS and RW3 phantoms were found comparable within 1%. Fluence maps and dose distributions of these patients generated by TPS and measured in ABS IMRT phantom were also found comparable both numerically and spatially. This study indicates that ABS plastic IMRT phantom is a tissue equivalent phantom and dosimetrically it is similar to solid/plastic water IMRT phantoms. Though this material is demonstrated for IMRT dose verification but it can be used as a tissue equivalent phantom material for other dosimetry purposes in radiotherapy. PMID:20160681

Kumar, Rajesh; Sharma, S D; Deshpande, Sudesh; Ghadi, Yogesh; Shaiju, V S; Amols, H I; Mayya, Y S

2010-01-01

256

Monochromatic minibeam radiotherapy: theoretical and experimental dosimetry for preclinical treatment plans  

NASA Astrophysics Data System (ADS)

Monochromatic x-ray minibeam radiotherapy is a new radiosurgery approach based on arrays of submillimetric interlaced planar x-ray beams. The aim of this study was to characterize the dose distributions obtained with this new modality when being used for preclinical trials. Monte Carlo simulations were performed in water phantoms. Percentage depth-dose curves and dose profiles were computed for single incidences and interleaved incidences of 80 keV planar x-ray minibeam (0.6 × 5 mm) arrays. Peak to valley dose ratios were also computed at various depths for an increasing number of minibeams. 3D experimental polymer gel (nPAG) dosimetry measurements were performed using MRI devices designed for small animal imaging. These very high spatial resolution (50 µm) dose maps were compared to the simulations. Preclinical minibeams dose distributions were fully characterized. Experimental dosimetry correlated well with Monte Carlo calculations (Student t-tests: p > 0.1). F98 tumor-bearing rats were also irradiated with interleaved minibeams (80 keV, prescribed dose: 25 Gy). This associated preclinical trial serves as a proof of principle of the technique. The mean survival time of irradiated glioma-bearing rats increased significantly, when compared to the untreated animals (59.6 ± 2.8 days versus 28.25 ± 0.75 days, p < 0.001).

Deman, P.; Vautrin, M.; Stupar, V.; Barbier, E. L.; Elleaume, H.; Esteve, F.; Adam, J. F.

2011-07-01

257

Software tool for portal dosimetry research.  

PubMed

This paper describes a software tool developed for research into the use of an electronic portal imaging device (EPID) to verify dose for intensity modulated radiation therapy (IMRT) beams. A portal dose image prediction (PDIP) model that predicts the EPID response to IMRT beams has been implemented into a commercially available treatment planning system (TPS). The software tool described in this work was developed to modify the TPS PDIP model by incorporating correction factors into the predicted EPID image to account for the difference in EPID response to open beam radiation and multileaf collimator (MLC) transmitted radiation. The processes performed by the software tool include; i) read the MLC file and the PDIP from the TPS, ii) calculate the fraction of beam-on time that each point in the IMRT beam is shielded by MLC leaves, iii) interpolate correction factors from look-up tables, iv) create a corrected PDIP image from the product of the original PDIP and the correction factors and write the corrected image to file, v) display, analyse, and export various image datasets. The software tool was developed using the Microsoft Visual Studio.NET framework with the C# compiler. The operation of the software tool was validated. This software provided useful tools for EPID dosimetry research, and it is being utilised and further developed in ongoing EPID dosimetry and IMRT dosimetry projects. PMID:18946980

Vial, P; Hunt, P; Greer, P B; Oliver, L; Baldock, C

2008-09-01

258

In vivo dosimetry in external beam radiotherapy  

SciTech Connect

In vivo dosimetry (IVD) is in use in external beam radiotherapy (EBRT) to detect major errors, to assess clinically relevant differences between planned and delivered dose, to record dose received by individual patients, and to fulfill legal requirements. After discussing briefly the main characteristics of the most commonly applied IVD systems, the clinical experience of IVD during EBRT will be summarized. Advancement of the traditional aspects of in vivo dosimetry as well as the development of currently available and newly emerging noninterventional technologies are required for large-scale implementation of IVD in EBRT. These new technologies include the development of electronic portal imaging devices for 2D and 3D patient dosimetry during advanced treatment techniques, such as IMRT and VMAT, and the use of IVD in proton and ion radiotherapy by measuring the decay of radiation-induced radionuclides. In the final analysis, we will show in this Vision 20/20 paper that in addition to regulatory compliance and reimbursement issues, the rationale for in vivo measurements is to provide an accurate and independent verification of the overall treatment procedure. It will enable the identification of potential errors in dose calculation, data transfer, dose delivery, patient setup, and changes in patient anatomy. It is the authors' opinion that all treatments with curative intent should be verified through in vivo dose measurements in combination with pretreatment checks.

Mijnheer, Ben [Department of Radiation Oncology, Netherlands Cancer Institute-Antoni van Leeuwenhoek Hospital, Amsterdam 1066 CX (Netherlands); Beddar, Sam [Department of Radiation Physics, University of Texas MD Anderson Cancer Center, Houston, Texas 77030 (United States); Izewska, Joanna [Division of Human Health, International Atomic Energy Agency, Vienna 1400 (Austria); Reft, Chester [Department of Radiation and Cellular Oncology, University of Chicago Medical Center, Chicago, Illinois 60637 (United States)

2013-07-15

259

Development and optimization of a 2-hydroxyethylacrylate MRI polymer gel dosimeter  

NASA Astrophysics Data System (ADS)

In this study, radiation induced changes in a polymer gel dosimeter manufactured using 2-hydroxyethylacrylate (HEA) and N,N'-methylene-bisacrylamide (BIS) were investigated using magnetic resonance imaging (MRI) and FT-Raman spectroscopy. The variation in magnetic resonance relaxation time (T2) with absorbed dose was modelled assuming fast exchange of magnetization. Overall good agreement between the model and experimental data was obtained. However, comparison with FT-Raman data suggests that not all the protons attached to the polymer contribute to the relaxation process. Furthermore, for certain compositions improved agreement with experimental data was achieved when a lower fraction of polymer protons available for exchange with water was assumed in the low dose region. This indicates that the T2 value is influenced by the composition and topology of the formed polymer, which may vary with absorbed dose. The concept of percentage dose resolution (DpDgr,%) was introduced to enable optimization of gel compositions for use in relative dosimetry applications. This concept was applied to demonstrate the effects of varying the gelatine concentration, the total fraction of monomer/crosslinker (%T) and the relative fraction of crosslinker (%C) on gel performance in HEA gels as well as compare the performance of HEA and a standard polyacrylamide gel (PAG). The percentage dose resolution was improved for all HEA gels compared to the PAG dosimeter containing 3% acrylamide and 3% BIS. Increasing the total concentration of monomer was shown to have the largest single effect. In the range of doses of interest for clinical radiation therapy, DpDgr,% for the optimal HEA gel (4% HEA, 4% BIS) was lower than 2.3%, compared to 3.8% for the PAG dosimeter.

Gustavsson, H.; Bäck, S. Å. J.; Lepage, M.; Rintoul, L.; Baldock, C.

2004-01-01

260

PHYSICAL FITNESS AND ACADEMIC ACHIEVEMENT  

Microsoft Academic Search

Grissom JB. Physical Fitness And Academic Achievement. JEPonline 2005;8(1):11-25 . The purpose of this study was to evaluate the relationship between physical fitness and academic achievement. To do so, scores on the FITNESSGRAM®, a physical fitness test, were compared to reading and mathematics scores on the Stanford Achievement Test 9th edition, a standardized norm-referenced achievement test. Subjects were all 5th,

Robert Robergs; Grissom JB

261

DNA gel particles: an overview.  

PubMed

A general understanding of interactions between DNA and oppositely charged compounds forms the basis for developing novel DNA-based materials, including gel particles. The association strength, which is altered by varying the chemical structure of the cationic cosolute, determines the spatial homogeneity of the gelation process, creating DNA reservoir devices and DNA matrix devices that can be designed to release either single- (ssDNA) or double-stranded (dsDNA) DNA. This review covers recent developments on the topic of DNA gel particles formed in water-water emulsion-type interfaces. The degree of DNA entrapment, particle morphology, swelling/dissolution behavior and DNA release responses are discussed as functions of the nature of the cationic agent used. On the basis of designing DNA gel particles for therapeutic purposes, recent studies on the determination of the surface hydrophobicity and the hemolytic and the cytotoxic assessments of the obtained DNA gel particles have been also reported. PMID:24119768

Morán, M Carmen; Vinardell, M Pilar; Infante, M Rosa; Miguel, M Graça; Lindman, Björn

2014-03-01

262

Dosimetry for Small and Nonstandard Fields  

NASA Astrophysics Data System (ADS)

The proposed small and non-standard field dosimetry protocol from the joint International Atomic Energy Agency (IAEA) and American Association of Physicist in Medicine working group introduces new reference field conditions for ionization chamber based reference dosimetry. Absorbed dose beam quality conversion factors (kQ factors) corresponding to this formalism were determined for three different models of ionization chambers: a Farmer-type ionization chamber, a thimble ionization chamber, and a small volume ionization chamber. Beam quality correction factor measurements were made in a specially developed cylindrical polymethyl methacrylate (PMMA) phantom and a water phantom using thermoluminescent dosimeters (TLDs) and alanine dosimeters to determine dose to water. The TLD system for absorbed dose to water determination in high energy photon and electron beams was fully characterized as part of this dissertation. The behavior of the beam quality correction factor was observed as it transfers the calibration coefficient from the University of Wisconsin Accredited Dosimetry Calibration Laboratory (UWADCL) 60Co reference beam to the small field calibration conditions of the small field formalism. TLD-determined beam quality correction factors for the calibration conditions investigated ranged from 0.97 to 1.30 and had associated standard deviations from 1% to 3%. The alanine-determined beam quality correction factors ranged from 0.996 to 1.293. Volume averaging effects were observed with the Farmer-type ionization chamber in the small static field conditions. The proposed small and non-standard field dosimetry protocols new composite-field reference condition demonstrated its potential to reduce or remove ionization chamber volume dependancies, but the measured beam quality correction factors were not equal to the standard CoP's kQ, indicating a change in beam quality in the small and non-standard field dosimetry protocols new composite-field reference condition relative to the standard broad beam reference conditions. The TLD- and alanine-determined beam quality correction factors in the composite-field reference conditions were approximately 3% greater and differed by more than one standard deviation from the published TG-51 kQ values for all three chambers.

Junell, Stephanie L.

263

Agarose Gel Electrophoresis of RNA  

Microsoft Academic Search

\\u000a Gel electrophoresis is one of the most important techniques currently available for the fractionation of RNA. The experimental\\u000a procedure is relatively simple, but nevertheless achieves very reproducible results and high resolution. RNA is a polyanion\\u000a and will therefore migrate toward the positive electrode in an electric field. If the migration occurs through a gel matrix\\u000a of carefully chosen pore size,

Robert J. Slater

264

NLINEAR - NONLINEAR CURVE FITTING PROGRAM  

NASA Technical Reports Server (NTRS)

A common method for fitting data is a least-squares fit. In the least-squares method, a user-specified fitting function is utilized in such a way as to minimize the sum of the squares of distances between the data points and the fitting curve. The Nonlinear Curve Fitting Program, NLINEAR, is an interactive curve fitting routine based on a description of the quadratic expansion of the chi-squared statistic. NLINEAR utilizes a nonlinear optimization algorithm that calculates the best statistically weighted values of the parameters of the fitting function and the chi-square that is to be minimized. The inputs to the program are the mathematical form of the fitting function and the initial values of the parameters to be estimated. This approach provides the user with statistical information such as goodness of fit and estimated values of parameters that produce the highest degree of correlation between the experimental data and the mathematical model. In the mathematical formulation of the algorithm, the Taylor expansion of chi-square is first introduced, and justification for retaining only the first term are presented. From the expansion, a set of n simultaneous linear equations are derived, which are solved by matrix algebra. To achieve convergence, the algorithm requires meaningful initial estimates for the parameters of the fitting function. NLINEAR is written in Fortran 77 for execution on a CDC Cyber 750 under NOS 2.3. It has a central memory requirement of 5K 60 bit words. Optionally, graphical output of the fitting function can be plotted. Tektronix PLOT-10 routines are required for graphics. NLINEAR was developed in 1987.

Everhart, J. L.

1994-01-01

265

Pre-Cast Gel Electrophoresis Guide  

E-print Network

Novex® Pre-Cast Gel Electrophoresis Guide Version B January 27, 2003 IM-1002 Novex® Pre-Cast Gel Electrophoresis Guide General information and protocols for using Novex® pre-cast gels www.invitrogen.com tech.....................................................................................................................1 Novex® Pre-Cast Gels

Kirschner, Marc W.

266

Surface grafted chitosan gels. Part II. Gel formation and characterization.  

PubMed

Responsive biomaterial hydrogels attract significant attention due to their biocompatibility and degradability. In order to make chitosan based gels, we first graft one layer of chitosan to silica, and then build a chitosan/poly(acrylic acid) multilayer using the layer-by-layer approach. After cross-linking the chitosan present in the polyelectrolyte multilayer, poly(acrylic acid) is partly removed by exposing the multilayer structure to a concentrated carbonate buffer solution at a high pH, leaving a surface-grafted cross-linked gel. Chemical cross-linking enhances the gel stability against detachment and decomposition. The chemical reaction between gluteraldehyde, the cross-linking agent, and chitosan was followed in situ using total internal reflection Raman (TIRR) spectroscopy, which provided a molecular insight into the complex reaction mechanism, as well as the means to quantify the cross-linking density. The amount of poly(acrylic acid) trapped inside the surface grafted films was found to decrease with decreasing cross-linking density, as confirmed in situ using TIRR, and ex situ by Fourier transform infrared (FTIR) measurements on dried films. The responsiveness of the chitosan-based gels with respect to pH changes was probed by quartz crystal microbalance with dissipation (QCM-D) and TIRR. Highly cross-linked gels show a small and fully reversible behavior when the solution pH is switched between pH 2.7 and 5.7. In contrast, low cross-linked gels are more responsive to pH changes, but the response is fully reversible only after the first exposure to the acidic solution, once an internal restructuring of the gel has taken place. Two distinct pKa's for both chitosan and poly(acrylic acid), were determined for the cross-linked structure using TIRR. They are associated with populations of chargeable groups displaying either a bulk like dissociation behavior or forming ionic complexes inside the hydrogel film. PMID:25006685

Liu, Chao; Thormann, Esben; Claesson, Per M; Tyrode, Eric

2014-07-29

267

The use of normoxic polymer gel for measuring dose distributions of 1, 4 and 30 mm cones  

NASA Astrophysics Data System (ADS)

This study demonstrates the use of normoxic polymer gel for measuring dose distributions of small fields that lack lateral electronic equilibrium. Two different types of normoxic polymer gel, MAGAT and PAGAT, are studied in a larger field (10 cm×10 cm) and 1, 4 and 30 mm cones to obtain cone factors, dose profiles and percentage depth doses. These results were then compared to KODAK XV film measurements and BEAMnrc Monte Carlo simulations. The results show that the sensitivity of PAGAT gel is 0.090±0.074 s-1 Gy-1, which may not be suitable for small-field dosimetry with a 0.3 mm resolution scanned using a 3 T MR imager in a dose range lower than 2.5 Gy. There are good agreements between cone factors estimated using KODAK XV film and MAGAT gel. In a dose profile comparison, good dose agreement among MAGAT gel, XV film and MC simulation can be seen in the central area for a 30 mm cone. In penumbra, the distance to agreement is at most 1.2 mm (4 pixel), and less than 0.3 mm (1 pixel) for 4 and 1 mm cones. In a percentage depth dose comparison, there were good agreements between MAGAT and MC up to a depth of 8 cm. Possible factors for gel uncertainty such as MRI magnetic field inhomogeneity and temperature were also investigated.

Lee, C. C.; Wu, J. F.; Chang, K. P.; Chu, C. H.; Wey, S. P.; Liu, H. L.; Tung, C. J.; Wu, S. W.; Chao, T. C.

2014-11-01

268

Portal dosimetry for VMAT using integrated images obtained during treatment  

SciTech Connect

Purpose: Portal dosimetry provides an accurate and convenient means of verifying dose delivered to the patient. A simple method for carrying out portal dosimetry for volumetric modulated arc therapy (VMAT) is described, together with phantom measurements demonstrating the validity of the approach. Methods: Portal images were predicted by projecting dose in the isocentric plane through to the portal image plane, with exponential attenuation and convolution with a double-Gaussian scatter function. Appropriate parameters for the projection were selected by fitting the calculation model to portal images measured on an iViewGT portal imager (Elekta AB, Stockholm, Sweden) for a variety of phantom thicknesses and field sizes. This model was then used to predict the portal image resulting from each control point of a VMAT arc. Finally, all these control point images were summed to predict the overall integrated portal image for the whole arc. The calculated and measured integrated portal images were compared for three lung and three esophagus plans delivered to a thorax phantom, and three prostate plans delivered to a homogeneous phantom, using a gamma index for 3% and 3 mm. A 0.6 cm{sup 3} ionization chamber was used to verify the planned isocentric dose. The sensitivity of this method to errors in monitor units, field shaping, gantry angle, and phantom position was also evaluated by means of computer simulations. Results: The calculation model for portal dose prediction was able to accurately compute the portal images due to simple square fields delivered to solid water phantoms. The integrated images of VMAT treatments delivered to phantoms were also correctly predicted by the method. The proportion of the images with a gamma index of less than unity was 93.7% ± 3.0% (1SD) and the difference between isocenter dose calculated by the planning system and measured by the ionization chamber was 0.8% ± 1.0%. The method was highly sensitive to errors in monitor units and field shape, but less sensitive to errors in gantry angle or phantom position. Conclusions: This method of predicting integrated portal images provides a convenient means of verifying dose delivered using VMAT, with minimal image acquisition and data processing requirements.

Bedford, James L., E-mail: James.Bedford@icr.ac.uk; Hanson, Ian M.; Hansen, Vibeke Nordmark [Joint Department of Physics, The Institute of Cancer Research and The Royal Marsden NHS Foundation Trust, Downs Road, Sutton, Surrey SM2 5PT (United Kingdom)] [Joint Department of Physics, The Institute of Cancer Research and The Royal Marsden NHS Foundation Trust, Downs Road, Sutton, Surrey SM2 5PT (United Kingdom)

2014-02-15

269

Fitting Surge Functions to Data  

ERIC Educational Resources Information Center

The problem of fitting a surge function to a set of data such as that for a drug response curve is considered. A variety of different techniques are applied, including using some fundamental ideas from calculus, the use of a CAS package, and the use of Excel's regression features for fitting a multivariate linear function to a set of transformed…

Gordon, Sheldon P.

2006-01-01

270

Classifier Fitness Based on Accuracy  

Microsoft Academic Search

In many classifier systems, the classifier strength parameter serves as a predictor of future payoff and as the classifier's fitness for the genetic algorithm. We investigate a classifier system, XCS, in which each classifier maintains a prediction of expected payoff, but the classifier's fitness is given by a measure of the prediction's accuracy. The system executes the genetic algorithm in

Stewart W. Wilson

1995-01-01

271

TG69: Radiographic film for megavoltage beam dosimetry  

Microsoft Academic Search

TG-69 is a task group report of the AAPM on the use of radiographic film for dosimetry. Radiographic films have been used for radiation dosimetry since the discovery of x-rays and have become an integral part of dose verification for both routine quality assurance and for complex treatments such as soft wedges (dynamic and virtual), intensity modulated radiation therapy (IMRT),

Sujatha Pai; Indra J. Das; James F. Dempsey; Kwok L. Lam; Thomas J. Losasso; Arthur J. Olch; Jatinder R. Palta; Lawrence E. Reinstein; Dan Ritt; Ellen E. Wilcox

2007-01-01

272

Dosimetry of Heterogeneously Distributed Radionuclides with Applications to Radioimmunotherapy  

Microsoft Academic Search

The dosimetry of internally deposited radionuclides has been investigated for applications to radioimmunotherapy. The assumptions inherent in the MIRD method of dose calculation are shown to be inappropriate to the task of dosimetry for nonuniformly distributed radionuclides emitting lowly penetrating radiations. A method using the concept of dose point kernels has been developed, expanding the MIRD method to regions of

Douglas John Simpkin

1991-01-01

273

Automatic in vivo portal dosimetry of all treatments  

NASA Astrophysics Data System (ADS)

At our institution EPID (electronic portal imaging device) dosimetry is routinely applied to perform in vivo dose verification of all patient treatments with curative intent since January 2008. The major impediment of the method has been the amount of work required to produce and inspect the in vivo dosimetry reports (a time-consuming and labor-intensive process). In this paper we present an overview of the actions performed to implement an automated in vivo dosimetry solution clinically. We reimplemented the EPID dosimetry software and modified the acquisition software. Furthermore, we introduced new tools to periodically inspect the record-and-verify database and automatically run the EPID dosimetry software when needed. In 2012, 95% of our 3839 treatments scheduled for in vivo dosimetry were analyzed automatically (27?633 portal images of intensity-modulated radiotherapy (IMRT) fields, 5551 portal image data of VMAT arcs, and 2003 portal images of non-IMRT fields). The in vivo dosimetry verification results are available a few minutes after delivery and alerts are immediately raised when deviations outside tolerance levels are detected. After the clinical introduction of this automated solution, inspection of the detected deviations is the only remaining work. These newly developed tools are a major step forward towards full integration of in vivo EPID dosimetry in radiation oncology practice.

Olaciregui-Ruiz, I.; Rozendaal, R.; Mijnheer, B.; van Herk, M.; Mans, A.

2013-11-01

274

Dosimetry Methods of Fast Neutron Using the Semiconductor Diodes  

NASA Astrophysics Data System (ADS)

Semiconductor detectors based on a silicon pin diode are frequently used in the detection of different nuclear radiations. For the detection and dosimetry of fast neutrons, these silicon detectors are coupled with a fast neutron converter. Incident neutrons interact with the converter and produce charged particles that can deposit their energy in the detectors and produce a signal. In this study, three methods are introduced for fast neutron dosimetry by using the silicon detectors, which are: recoil proton spectroscopy, similarity of detector response function with conversion function, and a discriminator layer. Monte Carlo simulation is used to calculate the response of dosimetry systems based on these methods. In the different doses of an 241Am-Be neutron source, dosimetry responses are evaluated. The error values of measured data for dosimetry by these methods are in the range of 15-25%. We find fairly good agreement in the 241Am-Be neutron sources.

H. Zaki, Dizaji; Kakavand, T.; F. Abbasi, Davani

2014-01-01

275

Thixotropic gel for vadose zone remediation  

DOEpatents

A thixotropic gel suitable for use in subsurface bioremediation is provided along with a process of using the gel. The thixotropic gel provides a non-migrating injectable substrate that can provide below ground barrier properties. In addition, the gel components provide for a favorable environment in which certain contaminants are preferentially sequestered in the gel and subsequently remediated by either indigenous or introduced microorganisms.

Rhia, Brian D. (Augusta, GA)

2011-03-01

276

In vivo dosimetry in the urethra using alanine/ESR during 192Ir HDR brachytherapy of prostate cancer—a phantom study  

NASA Astrophysics Data System (ADS)

A phantom study for dosimetry in the urethra using alanine/ESR during 192Ir HDR brachytherapy of prostate cancer is presented. The measurement method of the secondary standard of the Physikalisch-Technische Bundesanstalt had to be slightly modified in order to be able to measure inside a Foley catheter. The absorbed dose to water response of the alanine dosimetry system to 192Ir was determined with a reproducibility of 1.8% relative to 60Co. The resulting uncertainty for measurements inside the urethra was estimated to be 3.6%, excluding the uncertainty of the dose rate constant ?. The applied dose calculated by a treatment planning system is compared to the measured dose for a small series of 192Ir HDR irradiations in a gel phantom. The differences between the measured and applied dose are well within the limits of uncertainty. Therefore, the method is considered to be suitable for measurements in vivo.

Anton, Mathias; Wagner, Daniela; Selbach, Hans-Joachim; Hackel, Thomas; Hermann, Robert Michael; Hess, Clemens Friedrich; Vorwerk, Hilke

2009-05-01

277

Normoxic polyacrylamide gel doped with iodine: response versus X-ray energy.  

PubMed

The basis of Synchrotron Stereotactic Radio-Therapy (SSRT) is the incorporation of high atomic number atoms (iodine, for example) into the tumour mass followed by an irradiation with a monochromatic, low energy, X-ray beam from a synchrotron source. The purpose of the present study was to determine whether polymer gel dosimetry could be used to measure the enhancement of absorbed energy induced by the iodine in the media. We have used a standard nPAG formulation, loaded with NaI and the irradiations were performed either with monochromatic X-rays at the ESRF medical beamline or with a conventional 6 MV X-ray beam from a linear accelerator at the Grenoble University Hospital. We observed sensitivity increase with iodine loaded gels irradiated at low energies, in good agreement with the theoretical iodine dose-enhancement. As expected, the response of the iodine-doped polymer gel was not increased after irradiation with mega-voltage X-rays. We demonstrate in this study that polymer gel dosimeters can be used for measuring dose-enhancement due to iodine presence in SSR treatment. PMID:18602237

Gastaldo, Jérôme; Boudou, Caroline; Lamalle, Laurent; Troprès, Irène; Corde, Stéphanie; Sollier, Albéric; Rucka, Günther; Elleaume, Hélène

2008-12-01

278

Dosimetric characterization of CyberKnife radiosurgical photon beams using polymer gels  

SciTech Connect

Dose distributions registered in water equivalent, polymer gel dosimeters were used to measure the output factors and off-axis profiles of the radiosurgical photon beams employed for CyberKnife radiosurgery. Corresponding measurements were also performed using a shielded silicon diode commonly employed for CyberKnife commissioning, the PinPoint ion chamber, and Gafchromic EBT films, for reasons of comparison. Polymer gel results of this work for the output factors of the 5, 7.5, and 10 mm diameter beams are (0.702{+-}0.029), (0.872{+-}0.039), and (0.929{+-}0.041), respectively. Comparison of polymer gel and diode measurements shows that the latter overestimate output factors of the two small beams (5% for the 5 mm beam and 3% for the 7.5 mm beams). This is attributed to the nonwater equivalence of the high atomic number silicon material of the diode detector. On the other hand, the PinPoint chamber is found to underestimate output factors up to 10% for the 5 mm beam due to volume averaging effects. Polymer gel and EBT film output factor results are found in close agreement for all beam sizes, emphasizing the importance of water equivalence and fine detector sensitive volume for small field dosimetry. Relative off-axis profile results are in good agreement for all dosimeters used in this work, with noticeable differences observed only in the PinPoint estimate of the 80%-20% penumbra width, which is relatively overestimated.

Pantelis, E.; Antypas, C.; Petrokokkinos, L.; Karaiskos, P.; Papagiannis, P.; Kozicki, M.; Georgiou, E.; Sakelliou, L.; Seimenis, I. [Medical Physics Department, Iatropolis - Magnitiki Tomografia Clinic and Diagnostic Center, Ethnikis Antistaseos 54-56, Chalandri, 152 31, Athens (Greece); Nuclear and Particle Physics Section, Physics Department, University of Athens, Panepistimioupolis, Ilisia, 157 71 Athens (Greece) and Institute of Accelerating Systems and Applications (IASA), PO Box 17214, GR-10024 Athens (Greece); Medical Physics Laboratory, Medical School, University of Athens, 75 Mikras Asias, 115 27 Athens (Greece); Faculty of Textile Engineering and Marketing, Department of Textile Finishing, Technical University of Lodz, Zeromskiego 116, 90-543 Lodz (Poland); Medical Physics Laboratory, Medical School, University of Athens, 75 Mikras Asias, 115 27 Athens (Greece); Nuclear and Particle Physics Section, Physics Department, University of Athens, Panepistimioupolis, Ilisia, 157 71 Athens (Greece) and Institute of Accelerating Systems and Applications (IASA), PO Box 17214, GR-10024 Athens (Greece); Medical Diagnostic Center Ayios Therissos, 92 Troodous Avenue, Strovolos, Nicosia (Cyprus)

2008-06-15

279

Electrical characterization of gel collected from shark electrosensors  

NASA Astrophysics Data System (ADS)

To investigate the physical mechanism of the electric sense, we present an initial electrical characterization of the glycoprotein gel that fills the electrosensitive organs of marine elasmobranchs (sharks, skates, and rays). We have collected samples of this gel, postmortem, from three shark species, and removed the majority of dissolved salts in one sample via dialysis. Here we present the results of dc conductivity measurements, low-frequency impedance spectroscopy, and electrophoresis. Electrophoresis shows a range of large protein-based molecules fitting the expectations of glycoproteins, but the gels of different species exhibit little similarity. The electrophoresis signature is unaffected by thermal cycling and measurement currents. The dc data were collected at various temperatures, and at various electric and magnetic fields, showing consistency with the properties of seawater. The impedance data collected from a dialyzed sample, however, show large values of static permittivity and a loss peak corresponding to an unusually long relaxation time, about 1 ms. The exact role of the gel is still unknown, but our results suggest its bulk properties are well matched to the sensing mechanism, as the minimum response time of an entire electric organ is on the order of 5 ms.

Brown, Brandon R.; Hutchison, John C.; Hughes, Mary E.; Kellogg, Douglas R.; Murray, Royce W.

2002-06-01

280

Fitting Polynomial Equations to Curves and Surfaces  

NASA Technical Reports Server (NTRS)

FIT is computer program for interactively determining least-squares polynomial equations that fit user-supplied data. Finds leastsquares fits for functions of two independent variables. Interactive graphical and editing capabilities in FIT enables user to control polynomial equations to be fitted to data arising from most practical applications. FIT written in FORTRAN and COMPASS.

Arbuckle, P. D.; Sliwa, S. M.; Tiffany, S. H.

1986-01-01

281

Capillary fracture of soft gels  

NASA Astrophysics Data System (ADS)

A liquid droplet resting on a soft gel substrate can deform that substrate to the point of material failure, whereby fractures develop on the gel surface that propagate outwards from the contact line in a starburst pattern. In this paper, we characterize (i) the initiation process, in which the number of arms in the starburst is controlled by the ratio of the surface tension contrast to the gel's elastic modulus, and (ii) the propagation dynamics showing that once fractures are initiated they propagate with a universal power law L?t3/4. We develop a model for crack initiation by treating the gel as a linear elastic solid and computing the deformations within the substrate from the liquid-solid wetting forces. The elastic solution shows that both the location and the magnitude of the wetting forces are critical in providing a quantitative prediction for the number of fractures and, hence, an interpretation of the initiation of capillary fractures. This solution also reveals that the depth of the gel is an important factor in the fracture process, as it can help mitigate large surface tractions; this finding is confirmed with experiments. We then develop a model for crack propagation by considering the transport of an inviscid fluid into the fracture tip of an incompressible material and find that a simple energy-conservation argument can explain the observed material-independent power law. We compare predictions for both linear elastic and neo-Hookean solids, finding that the latter better explains the observed exponent.

Bostwick, Joshua B.; Daniels, Karen E.

2013-10-01

282

USF/Russian dosimetry on STS-57  

NASA Technical Reports Server (NTRS)

The major purpose of this experiment was to conduct an international comparison of passive dosimetry methods in space. Two APD's were flown in the charged particle directional spectrometer (CPDS)/tissue equivalent proportional counter (TEPC) locker on the space shuttle during the STS-57 mission. Due to placement, the shielding and radiation environment of the APD's were nearly the same and the dosimeters distributed in the two boxes can be considered equally exposed. The dosimeter types included plastic nuclear track detectors (PNTD's), thermoluminescent detectors (TLD), nuclear emulsions, and thermal/resonance neutron detectors (TRND's). The USF dosimeters included PNTD's, TLD's, and TRND's, while the Russian dosimeters included PNTD's, TLD's, and nuclear emulsions.

1995-01-01

283

Neutron dosimetry of the Little Boy device  

SciTech Connect

Neutron dose rates at several angular locations and at distances out to 0.5 mile have been measured during critical operation of the Little Boy replica. We used modified remmetes and thermoluminescent dosimetry techniques for the measurements. The present status of our analysis is presented including estimates of the neutron-dose-relaxation length in air and the variation of the neutron-to-gamma-ray dose ratio with distance from the replica. These results are preliminary and are subject to detector calibration measurements.

Pederson, R.A.; Plassmann, E.A.

1984-01-01

284

Kinematic Fitting of Detached Vertices  

SciTech Connect

The eg3 experiment at the Jefferson Lab CLAS detector aims to determine the existence of the $\\Xi_{5}$ pentaquarks and investigate the excited $\\Xi$ states. Specifically, the exotic $\\Xi_{5}^{--}$ pentaquark will be sought by first reconstructing the $\\Xi^{-}$ particle through its weak decays, $\\Xi^{-}\\to\\pi^{-}\\Lambda$ and $\\Lambda\\to\\pi^{-}$. A kinematic fitting routine was developed to reconstruct the detached vertices of these decays, where confidence level cuts on the fits are used to remove background events. Prior to fitting these decays, the exclusive reaction $\\gamma D\\rightarrow pp\\pi^{-}$ was studied in order to correct the track measurements and covariance matrices of the charged particles. The $\\Lambda\\rightarrow p\\pi^{-}$ and $\\Xi^{-}\\to\\pi^{-}\\Lambda$ decays were then investigated to demonstrate that the kinematic fitting routine reconstructs the decaying particles and their detached vertices correctly.

Paul Mattione

2007-05-01

285

Physical Fitness Testing and Rewards.  

ERIC Educational Resources Information Center

Fitness testing programs with award systems began in 1958 and proved to be extremely popular. Award programs for students with disabilities are described. The need for award systems for all handicapped students is stressed. (MT)

Stein, Julian U.

1988-01-01

286

Copolymers For Capillary Gel Electrophoresis  

DOEpatents

This invention relates to an electrophoresis separation medium having a gel matrix of at least one random, linear copolymer comprising a primary comonomer and at least one secondary comonomer, wherein the comonomers are randomly distributed along the copolymer chain. The primary comonomer is an acrylamide or an acrylamide derivative that provides the primary physical, chemical, and sieving properties of the gel matrix. The at least one secondary comonomer imparts an inherent physical, chemical, or sieving property to the copolymer chain. The primary and secondary comonomers are present in a ratio sufficient to induce desired properties that optimize electrophoresis performance. The invention also relates to a method of separating a mixture of biological molecules using this gel matrix, a method of preparing the novel electrophoresis separation medium, and a capillary tube filled with the electrophoresis separation medium.

Liu, Changsheng (State College, PA); Li, Qingbo (State College, PA)

2005-08-09

287

Assessing the fitness landscape revolution  

Microsoft Academic Search

According to Pigliucci and Kaplan, there is a revolution underway in how we understand fitness landscapes. Recent models suggest\\u000a that a perennial problem in these landscapes—how to get from one peak across a fitness valley to another peak—is, in fact,\\u000a non-existent. In this paper I assess the structure and the extent of Pigliucci and Kaplan’s proposed revolution and argue\\u000a for

Brett Calcott

2008-01-01

288

A feasibility study using radiochromic films for fast neutron 2D passive dosimetry  

PubMed Central

The objective of this paper is threefold: (1) to establish sensitivity of XRQA and EBT radiochromic films to fast neutron exposure; (2) to develop a film response to radiation dose calibration curve and (3) to investigate a two-dimensional (2D) film dosimetry technique for use in establishing an experimental setup for a radiobiological irradiation of mice and to assess the dose to the mice in this setup. The films were exposed to a 10 MeV neutron beam via the 2H(d,n)3He reaction. The XRQA film response was a factor of 1.39 greater than EBT film response to the 10 MeV neutron beam when exposed to a neutron dose of 165 cGy. A film response-to-soft tissue dose calibration function was established over a range of 0–10 Gy and had a goodness of fit of 0.9926 with the calibration data. The 2D film dosimetry technique estimated the neutron dose to the mice by measuring the dose using a mouse phantom and by placing a piece of film on the exterior of the experimental mouse setup. The film results were benchmarked using Monte Carlo and aluminum (Al) foil activation measurements. The radiochromic film, Monte Carlo and Al foil dose measurements were strongly correlated, and the film within the mouse phantom agreed to better than 7% of the externally mounted films. These results demonstrated the potential application of radiochromic films for passive 2D neutron dosimetry. PMID:20693612

Brady, Samuel L; Gunasingha, Rathnayaka; Yoshizumi, Terry T; Howell, Calvin R; Crowell, Alexander S; Fallin, Brent; Tonchev, Anton P; Dewhirst, Mark W

2013-01-01

289

A feasibility study using radiochromic films for fast neutron 2D passive dosimetry.  

PubMed

The objective of this paper is threefold: (1) to establish sensitivity of XRQA and EBT radiochromic films to fast neutron exposure; (2) to develop a film response to radiation dose calibration curve and (3) to investigate a two-dimensional (2D) film dosimetry technique for use in establishing an experimental setup for a radiobiological irradiation of mice and to assess the dose to the mice in this setup. The films were exposed to a 10 MeV neutron beam via the (2)H(d,n)(3)He reaction. The XRQA film response was a factor of 1.39 greater than EBT film response to the 10 MeV neutron beam when exposed to a neutron dose of 165 cGy. A film response-to-soft tissue dose calibration function was established over a range of 0-10 Gy and had a goodness of fit of 0.9926 with the calibration data. The 2D film dosimetry technique estimated the neutron dose to the mice by measuring the dose using a mouse phantom and by placing a piece of film on the exterior of the experimental mouse setup. The film results were benchmarked using Monte Carlo and aluminum (Al) foil activation measurements. The radiochromic film, Monte Carlo and Al foil dose measurements were strongly correlated, and the film within the mouse phantom agreed to better than 7% of the externally mounted films. These results demonstrated the potential application of radiochromic films for passive 2D neutron dosimetry. PMID:20693612

Brady, Samuel L; Gunasingha, Rathnayaka; Yoshizumi, Terry T; Howell, Calvin R; Crowell, Alexander S; Fallin, Brent; Tonchev, Anton P; Dewhirst, Mark W

2010-09-01

290

Fitting Cosmological Data CMB Model  

NSDL National Science Digital Library

The Cosmic Microwave Background (CMB) radiation measurements offer some of the most powerful constraints in cosmology for supporting the accelerated expansion of the universe (cosmic acceleration). Rather than fitting a model to the entire dataset, we fit a model to three parameters that represent specific features of the CMB. The simulation allows users to compare and fit theoretical models of cosmology with recent CMB data sets to confirm the accelerated expansion of the universe. This modeling allows the user to vary cosmological parameters within a particular class of dark energy cosmological models to fit a particular cosmological data set. The user can plot several theoretical curves with the data to compare different models. The values of these parameters, for a particular model, determine the physical description and evolution of the universe. The EJS Fitting Cosmological Data CMB model was created using Easy Java Simulations (EJS) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the ejs_FittingCosmologicalDataCMB.jar file will run the program if Java is installed. You can modify this simulation if you have EJS by right-clicking within the plot and selecting Open Ejs Model from the pop-up menu item.

Moldenhauer, Jacob; Stone, Keenan; Engelhardt, Larry

2012-09-10

291

TG-69: Radiographic film for megavoltage beam dosimetry  

SciTech Connect

TG-69 is a task group report of the AAPM on the use of radiographic film for dosimetry. Radiographic films have been used for radiation dosimetry since the discovery of x-rays and have become an integral part of dose verification for both routine quality assurance and for complex treatments such as soft wedges (dynamic and virtual), intensity modulated radiation therapy (IMRT), image guided radiation therapy (IGRT), and small field dosimetry like stereotactic radiosurgery. Film is convenient to use, spatially accurate, and provides a permanent record of the integrated two dimensional dose distributions. However, there are several challenges to obtaining high quality dosimetric results with film, namely, the dependence of optical density on photon energy, field size, depth, film batch sensitivity differences, film orientation, processing conditions, and scanner performance. Prior to the clinical implementation of a film dosimetry program, the film, processor, and scanner need to be tested to characterize them with respect to these variables. Also, the physicist must understand the basic characteristics of all components of film dosimetry systems. The primary mission of this task group report is to provide guidelines for film selection, irradiation, processing, scanning, and interpretation to allow the physicist to accurately and precisely measure dose with film. Additionally, we present the basic principles and characteristics of film, processors, and scanners. Procedural recommendations are made for each of the steps required for film dosimetry and guidance is given regarding expected levels of accuracy. Finally, some clinical applications of film dosimetry are discussed.

Pai, Sujatha; Das, Indra J.; Dempsey, James F.; Lam, Kwok L.; LoSasso, Thomas J.; Olch, Arthur J.; Palta, Jatinder R.; Reinstein, Lawrence E.; Ritt, Dan; Wilcox, Ellen E. [Radiation Therapy Department, Memorial Hermann Hospital, Houston, Texas 77024 (United States); Department of Radiation Oncology, University of Pennsylvania, Philadelphia, Pennsylvania 19104 (United States); Department of Radiation Oncology, University of Florida, Gainesville, Florida 32610 (United States); Department of Radiation Oncology, University of Michigan, Ann Arbor, Michigan 48109 (United States); Medical Physics Department, Memorial Sloan-Kettering Cancer Center, New York, New York 10021 (United States); Radiation Oncology Program, Childrens Hospital of LA, Los Angeles, California 90027 (United States); Department of Radiation Oncology, University of Florida, Gainesville, Florida 32610 (United States); Radiation Oncology Department, SUNY Stony Brook University Hospital, Stony Brook, New York 11794 (United States); Radiological Imaging Technology, Inc., Colorado Springs, Colorado 80907 (United States); Radiation Oncology Department, St. Francis Hospital, Hartford, Connecticut 06105 (United States)

2007-06-15

292

Clinical radionuclide therapy dosimetry: the quest for the “Holy Gray”  

PubMed Central

Introduction Radionuclide therapy has distinct similarities to, but also profound differences from external radiotherapy. Review This review discusses techniques and results of previously developed dosimetry methods in thyroid carcinoma, neuro-endocrine tumours, solid tumours and lymphoma. In each case, emphasis is placed on the level of evidence and practical applicability. Although dosimetry has been of enormous value in the preclinical phase of radiopharmaceutical development, its clinical use to optimise administered activity on an individual patient basis has been less evident. In phase I and II trials, dosimetry may be considered an inherent part of therapy to establish the maximum tolerated dose and dose–response relationship. To prove that dosimetry-based radionuclide therapy is of additional benefit over fixed dosing or dosing per kilogram body weight, prospective randomised phase III trials with appropriate end points have to be undertaken. Data in the literature which underscore the potential of dosimetry to avoid under- and overdosing and to standardise radionuclide therapy methods internationally are very scarce. Developments In each section, particular developments and insights into these therapies are related to opportunities for dosimetry. The recent developments in PET and PET/CT imaging, including micro-devices for animal research, and molecular medicine provide major challenges for innovative therapy and dosimetry techniques. Furthermore, the increasing scientific interest in the radiobiological features specific to radionuclide therapy will advance our ability to administer this treatment modality optimally. PMID:17268773

Bodei, L.; Giammarile, F.; Linden, O.; Luster, M.; Oyen, W. J. G.; Tennvall, J.

2007-01-01

293

Tracer diffusion in colloidal gels  

E-print Network

Computer simulations were done of the mean square displacement (MSD) of tracer particles in colloidal gels formed by diffusion or reaction limited aggregation of hard spheres. The diffusion coefficient was found to be determined by the volume fraction accessible to the spherical tracers ($\\phi_a$) independent of the gel structure or the tracer size. In all cases, critical slowing down was observed at $\\phi_a\\approx 0.03$ and was characterized by the same scaling laws reported earlier for tracer diffusion in a Lorentz gas. Strong heterogeneity of the MSD was observed at small $\\phi_a$ and was related to the size distribution of pores.

Sujin Babu; Jean Christophe Gimel; Taco Nicolai

2007-05-09

294

Tracer diffusion in colloidal gels.  

PubMed

Computer simulations were done of the mean square displacement (MSD) of tracer particles in colloidal gels formed by diffusion or reaction limited aggregation of hard spheres. The diffusion coefficient was found to be determined by the volume fraction accessible to the spherical tracers (phi a) independent of the gel structure or the tracer size. In all cases, critical slowing down was observed at phi a approximately 0.03 and was characterized by the same scaling laws reported earlier for tracer diffusion in a Lorentz gas. Strong heterogeneity of the MSD was observed at small phi a and was related to the size distribution of pores. PMID:18171042

Babu, Sujin; Gimel, Jean Christophe; Nicolai, Taco

2008-01-24

295

Gelatin gels in deuterium oxide  

Microsoft Academic Search

Gelatin gels formed in D2O have greater rigidity than gels of equal concentration formed in H2O. In D2O the junction zones (regions of collagen triple helix structure) were smaller (i.e. involved fewer amino acid residues) than in H2O. The contribution per amino acid residue to the free energy of formation of junction zones was ?0.51kJ\\/mol in D2O compared with ?0.34kJ\\/mol

David Oakenfull; Alan Scott

2003-01-01

296

Screening effect on nanostructure of charged gel  

NASA Astrophysics Data System (ADS)

Charge screening effects on nanostructures of N-isopropylacrylamide-sodium acrylate (NIPA-SA) and -acrylic acid (NIPA-AAc) gels are investigated with small-angle neutron scattering. The NIPA-SA and NIPA-AAc gels with low water content exhibit microphase separations with different dimensions. The dehydrated NIPA-SA gel also makes the microphase separation but the dehydrated NIPA-AAc gel does not. These results indicate that ionic circumstance around charged bases strongly affects the nanostructures both of the dehydrated gel and the gel with low water content.

Sugiyama, Masaaki; Annaka, Masahiko; Hino, Masahiro; Fukunaga, Toshiharu; E. Vigild, Martin; Hara, Kazuhiro

2004-07-01

297

Proton Diffusion and T1Relaxation in Polyacrylamide Gels: A Unified Approach Using Volume Averaging  

NASA Astrophysics Data System (ADS)

The structure of polyacrylamide gels was studied using proton spin-lattice relaxation and PFG diffusion methods. Polyacrylamide gels, with total polymer concentrations ranging from 0.25 to 0.35 g/ml and crosslinker concentrations from 0 to 10% by weight, were studied. The data showed no effect of the crosslinker concentration on the diffusion of water molecules. The Ogston-Morris and Mackie-Meares models fit the general trends observed for water diffusion in gels. The diffusion coefficients from the volume averaging method also fit the data, and this theory was able to account for the effects of water-gel interactions that are not accounted for in the other two theories. The averaging theory also did not require the physically unrealistic assumption, required in the other two theories, that the acrylamide fibers are of similar size to water molecules. Contrary to the diffusion data, T1relaxation measurements showed a significant effect of crosslinker concentration on the relaxation of water in gels. The model developed using the Bloch equations and the volume averaging method described the effects of water adsorption on the gel medium on both the diffusion coefficients and the relaxation measurements. In the proposed model the gel medium was assumed to consist of three phases (i.e., bulk water, uncrosslinked acrylamide fibers, and a bisacrylamide crosslinker phase). The effects of the crosslinker concentration were accounted for by introducing the proton partition coefficient, Keq, between the bulk water and crosslinker phase. The derived relaxation equations were successful in fitting the experimental data. The partition coefficient, Keq, decreased significantly as the crosslinker concentration increased from 5 to 10% by weight. This trend is consistent with the idea that bisacrylamide tends to form hydrophobic regions with increasing crosslinker concentration.

Penke, Brigita; Kinsey, Stephen; Gibbs, Stephen J.; Moerland, Timothy S.; Locke, Bruce R.

1998-06-01

298

Hanford External Dosimetry Technical Basis Manual PNL-MA-842  

SciTech Connect

The Hanford External Dosimetry Technical Basis Manual PNL-MA-842 documents the design and implementation of the external dosimetry system used at Hanford. The manual describes the dosimeter design, processing protocols, dose calculation methodology, radiation fields encountered, dosimeter response characteristics, limitations of dosimeter design under field conditions, and makes recommendations for effective use of the dosimeters in the field. The manual describes the technical basis for the dosimetry system in a manner intended to help ensure defensibility of the dose of record at Hanford and to demonstrate compliance with 10 CFR 835, DOELAP, DOE-RL, ORP, PNSO, and Hanford contractor requirements. The dosimetry system is operated by PNNL’s Hanford External Dosimetry Program (HEDP) which provides dosimetry services to all Hanford contractors. The primary users of this manual are DOE and DOE contractors at Hanford using the dosimetry services of PNNL. Development and maintenance of this manual is funded directly by DOE and DOE contractors. Its contents have been reviewed and approved by DOE and DOE contractors at Hanford through the Hanford Personnel Dosimetry Advisory Committee (HPDAC) which is chartered and chaired by DOE-RL and serves as means of coordinating dosimetry practices across contractors at Hanford. This manual was established in 1996. Since inception, it has been revised many times and maintained by PNNL as a controlled document with controlled distribution. The first revision to be released through PNNL’s Electronic Records & Information Capture Architecture (ERICA) database was designated Revision 0. Revision numbers that are whole numbers reflect major revisions typically involving changes to all chapters in the document. Revision numbers that include a decimal fraction reflect minor revisions, usually restricted to selected chapters or selected pages in the document.

Rathbone, Bruce A.

2009-08-28

299

Dosimetry of inhaled radon and thoron progeny  

SciTech Connect

This chapter reviews recent developments in modeling doses received by lung tissues, with particular emphasis on application of ICRP`s new dosimetric model of the respiratory tract for extrapolating to other environments the established risks from exposure to radon progeny in underground mines. Factors discussed include: (1) the influence of physical characteristics of radon progeny aerosols on dose per unit exposure, e.g., the unattached fraction, and the activity-size distributions of clustered and attached progeny; (2) the dependence of dose on breathing rate, and on the exposed subject (man, woman or child); (3) the variability of dose per unit exposure in a home when exposure is expressed in terms of potential {alpha} energy or radon gas concentration; (4) the comparative dosimetry of thoron progeny; and (5) the effects of air-cleaning on lung dose. Also discussed is the apparent discrepancy between lung cancer risk estimates derived purely from dosimetry and the lung cancer incidence observed in the epidemiological studies of radon-exposed underground miners. Application of ICRP`s recommended risk factors appears to overestimate radon lung-cancer risk for miners by a factor of three. ``Normalization`` of the calculated effective dose is therefore needed, at least for {alpha} dose from radon and thoron progeny, in order to obtain a realistic estimate of lung cancer risk.

James, A.C.

1994-06-01

300

Eleventh DOE workshop on personnel neutron dosimetry  

SciTech Connect

Since its formation, the Office of Health (EH-40) has stressed the importance of the exchange of information related to and improvements in neutron dosimetry. This Workshop was the eleventh in the series sponsored by the Department of Energy (DOE). It provided a forum for operational personnel at DOE facilities to discuss current issues related to neutron dosimetry and for leading investigators in the field to discuss promising approaches for future research. A total of 26 papers were presented including the keynote address by Dr. Warren K. Sinclair, who spoke on, ``The 1990 Recommendations of the ICRP and their Biological Background.`` The first several papers discussed difficulties in measuring neutrons of different energies and ways of compensating or deriving correction factors at individual facilities. Presentations were also given by the US Navy and Air Force. Current research in neutron dosimeter development was the subject of the largest number of papers. These included a number on the development of neutron spectrometers. Selected papers were processed separately for inclusion in the Energy Science and Technology Database.

Not Available

1991-12-31

301

Investigation of the dosimetry of chest tomosynthesis  

NASA Astrophysics Data System (ADS)

Chest tomosynthesis has recently been introduced to healthcare as a low-dose alternative to CT or as a tool for improved diagnostics in chest radiography with only a modest increase in radiation dose to the patient. However, no detailed description of the dosimetry for this type of examination has been presented. The aim of this work was therefore to investigate the dosimetry of chest tomosynthesis. The chest tomosynthesis examination was assumed to be performed using a stationary detector and a vertically moving x-ray tube, exposing the patient from different angles. The Monte Carlo based computer software PCXMC was used to determine the effective dose delivered to a standard-sized patient from various angles using different assumptions of the distribution of the effective dose over the different projections. The obtained conversion factors between input dose measures and effective dose for chest tomosynthesis for different angular intervals were then compared with the horizontal projection. The results indicate that the error introduced by using conversion factors for the PA projection in chest radiography for estimating the effective dose of chest tomosynthesis is small for normally sized patients, especially if a conversion factor between KAP and effective dose is used.

Svalkvist, Angelica; Zachrisson, Sara; Månsson, Lars Gunnar; Båth, Magnus

2009-02-01

302

Dosimetry of two new interstitial brachytherapy sources  

NASA Astrophysics Data System (ADS)

With increased demand for low 103Pd (palladium) seed sources, to treat prostate and eye cancers, new sources have been designed and introduced. This article presents the two new palladium brachytherapy sources, IR03-103Pd and IR04-103Pd that have been developed at Nuclear Science and Technology Research Institute. The dosimetry parameters such as the dose rate constant ?, the radial dose function g(r), and the anisotropy function F(r,?), around the sources have been characterized using Version 5 Monte Carlo radiation transport code in accordance with the update AAPM Task Group No. 43 report (TG-43U1). The results indicated the dose rate constant of 0.689±0.02 and 0.667±0.02 cGy h-1 U-1 for the IR03-103Pd and IR04-103Pd sources respectively, which are in acceptable agreement with other commercial seeds. The calculated results were compared with published results for those of other source manufacturers. However, they show an acceptable dose distribution, using for clinical applications is pending experimental dosimetry.

Saidi, Pooneh; Sadeghi, Mahdi

2011-01-01

303

The importance of 3D dosimetry  

NASA Astrophysics Data System (ADS)

Radiation therapy has been getting progressively more complex for the past 20 years. Early radiation therapy techniques needed only basic dosimetry equipment; motorized water phantoms, ionization chambers, and basic radiographic film techniques. As intensity modulated radiation therapy and image guided therapy came into widespread practice, medical physicists were challenged with developing effective and efficient dose measurement techniques. The complex 3-dimensional (3D) nature of the dose distributions that were being delivered demanded the development of more quantitative and more thorough methods for dose measurement. The quality assurance vendors developed a wide array of multidetector arrays that have been enormously useful for measuring and characterizing dose distributions, and these have been made especially useful with the advent of 3D dose calculation systems based on the array measurements, as well as measurements made using film and portal imagers. Other vendors have been providing 3D calculations based on data from the linear accelerator or the record and verify system, providing thorough evaluation of the dose but lacking quality assurance (QA) of the dose delivery process, including machine calibration. The current state of 3D dosimetry is one of a state of flux. The vendors and professional associations are trying to determine the optimal balance between thorough QA, labor efficiency, and quantitation. This balance will take some time to reach, but a necessary component will be the 3D measurement and independent calculation of delivered radiation therapy dose distributions.

Low, Daniel

2015-01-01

304

Effect of processor temperature on film dosimetry  

SciTech Connect

Optical density (OD) of a radiographic film plays an important role in radiation dosimetry, which depends on various parameters, including beam energy, depth, field size, film batch, dose, dose rate, air film interface, postexposure processing time, and temperature of the processor. Most of these parameters have been studied for Kodak XV and extended dose range (EDR) films used in radiation oncology. There is very limited information on processor temperature, which is investigated in this study. Multiple XV and EDR films were exposed in the reference condition (d{sub max.}, 10 Multiplication-Sign 10 cm{sup 2}, 100 cm) to a given dose. An automatic film processor (X-Omat 5000) was used for processing films. The temperature of the processor was adjusted manually with increasing temperature. At each temperature, a set of films was processed to evaluate OD at a given dose. For both films, OD is a linear function of processor temperature in the range of 29.4-40.6 Degree-Sign C (85-105 Degree-Sign F) for various dose ranges. The changes in processor temperature are directly related to the dose by a quadratic function. A simple linear equation is provided for the changes in OD vs. processor temperature, which could be used for correcting dose in radiation dosimetry when film is used.

Srivastava, Shiv P. [Department of Radiation Oncology, Reid Hospital and Health Care Services, Richmond, IN (United States); Das, Indra J., E-mail: idas@iupui.edu [Department of Radiation Oncology, Indiana University School of Medicine, Indianapolis, IN (United States)

2012-07-01

305

Molecular simulation of the swelling of polyelectrolyte gels by monovalent and divalent counterions  

PubMed Central

Permanently crosslinked polyelectrolyte gels are known to undergo discontinuous first-order volume phase transitions, the onset of which may be caused by a number of factors. In this study we examine the volumetric properties of such polyelectrolyte gels in relation to the progressive substitution of monovalent counterions by divalent counterions as the gels are equilibrated in solvents of different dielectric qualities. We compare the results of coarse-grained molecular dynamics simulations of polyelectrolyte gels with previous experimental measurements by others on polyacrylate gels. The simulations show that under equilibrium conditions there is an approximate cancellation between the electrostatic contribution and the counterion excluded-volume contribution to the osmotic pressure in the gel-solvent system; these two contributions to the osmotic pressure have, respectively, energetic and entropic origins. The finding of such a cancellation between the two contributions to the osmotic pressure of the gel-solvent system is consistent with experimental observations that the swelling behavior of polyelectrolyte gels can be described by equations of state for neutral gels. Based on these results, we show and explain that a modified form of the Flory–Huggins model for nonionic polymer solutions, which accounts for neither electrostatic effects nor counterion excluded-volume effects, fits both experimental and simulated data for polyelectrolyte gels. The Flory–Huggins interaction parameters obtained from regression to the simulation data are characteristic of ideal polymer solutions, whereas the experimentally obtained interaction parameters, particularly that associated with the third virial coefficient, exhibit a significant departure from ideality, leading us to conclude that further enhancements to the simulation model, such as the inclusion of excess salt, the allowance for size asymmetric electrolytes, or the use of a distance-dependent solvent dielectricity model, may be required. Molecular simulations also reveal that the condensation of divalent counterions onto the polyelectrolyte network backbone occurs preferentially over that of monovalent counterions. PMID:19045224

Yin, De-Wei; Horkay, Ferenc; Douglas, Jack F.; de Pablo, Juan J.

2008-01-01

306

Molecular simulation of the swelling of polyelectrolyte gels by monovalent and divalent counterions.  

PubMed

Permanently crosslinked polyelectrolyte gels are known to undergo discontinuous first-order volume phase transitions, the onset of which may be caused by a number of factors. In this study we examine the volumetric properties of such polyelectrolyte gels in relation to the progressive substitution of monovalent counterions by divalent counterions as the gels are equilibrated in solvents of different dielectric qualities. We compare the results of coarse-grained molecular dynamics simulations of polyelectrolyte gels with previous experimental measurements by others on polyacrylate gels. The simulations show that under equilibrium conditions there is an approximate cancellation between the electrostatic contribution and the counterion excluded-volume contribution to the osmotic pressure in the gel-solvent system; these two contributions to the osmotic pressure have, respectively, energetic and entropic origins. The finding of such a cancellation between the two contributions to the osmotic pressure of the gel-solvent system is consistent with experimental observations that the swelling behavior of polyelectrolyte gels can be described by equations of state for neutral gels. Based on these results, we show and explain that a modified form of the Flory-Huggins model for nonionic polymer solutions, which accounts for neither electrostatic effects nor counterion excluded-volume effects, fits both experimental and simulated data for polyelectrolyte gels. The Flory-Huggins interaction parameters obtained from regression to the simulation data are characteristic of ideal polymer solutions, whereas the experimentally obtained interaction parameters, particularly that associated with the third virial coefficient, exhibit a significant departure from ideality, leading us to conclude that further enhancements to the simulation model, such as the inclusion of excess salt, the allowance for size asymmetric electrolytes, or the use of a distance-dependent solvent dielectricity model, may be required. Molecular simulations also reveal that the condensation of divalent counterions onto the polyelectrolyte network backbone occurs preferentially over that of monovalent counterions. PMID:19045224

Yin, De-Wei; Horkay, Ferenc; Douglas, Jack F; de Pablo, Juan J

2008-10-21

307

Dosimetry of Auger emitters: Physical and phenomenological approaches  

SciTech Connect

Recent radiobiological studies have demonstrated that Auger cascades can cause severe biological damage contrary to expectations based on conventional dosimetry. Several determinants govern these effects, including the nature of the Auger electron spectrum; localized energy deposition; cellular geometry; chemical form of the carrier; cellular localization, concentration, and subcellular distribution of the radionuclide. Conventional dosimetry is inadequate in that these considerations are ignored. Our results provide the basis for biophysical approaches toward subcellular dosimetry of Auger emitters in vitro and in vivo. 12 refs., 7 figs., 2 tabs.

Sastry, K.S.R.; Howell, R.W.; Rao, D.V.; Mylavarapu, V.B.; Kassis, A.I.; Adelstein, S.J.; Wright, H.A.; Hamm, R.N.; Turner, J.E.

1987-01-01

308

Investigation of 3D dosimetry for an anthropomorphic spine phantom  

NASA Astrophysics Data System (ADS)

A new dosimetry insert for the Radiological Physics Center's spine phantom was designed to hold a specially molded dosimeter. The phantom was irradiated with the traditional insert loaded with radiochromic film and TLD, and then with the new 3D dosimetry insert. A comparison with the calculated dose distribution showed that PRESAGE® dosimeter, as well as the film and TLD system, agreed to within ±2mm. Further analysis of the 3D dosimeter, including a measured dose volume histogram, demonstrated the advantages of 3D dosimetry in a clinical environment.

Grant, R.; Ibbott, G.; Yang, J.; Adamovics, J.; Followill, D.

2013-06-01

309

Formulation and evaluation of in situ gelling thermoreversible mucoadhesive gel of fluconazole.  

PubMed

The purpose of the present study was to develop ophthalmic gel formulations of fluconazole. Intraocular delivery of topically applied drugs such as fluconazole is hampered by elimination of the solution due to tear turnover, so an in situ gelling thermoreversible mucoadhesive gel was formulated. Thermoreversible mucoadhesive gels were prepared using the cold method along with poloxamer 407 and different mucoadhesive polymers such as hydroxy ethyl cellulose (HEC), hydroxy propyl methyl cellulose (HPMC) K4M, and polyvinyl pyrrolidone (PVP) K30. Gels were evaluated for physical parameters like appearance, gelation temperature, pH, spreadability, drug content, gel strength, bioadhesion, and in vitro permeation. A modified device (modified K-C diffusion cell with a sheep's eye corneal membrane as a diffusion membrane) was used for evaluation of drug permeation through a sheep's corneal membrane. The formulated gels were transparent, uniform in consistency, and had spreadability with a pH range of 6.8 to 7.3. Satisfactory bioadhesion on the sheep's corneal surface and good gel strength were also observed. Diffusion studies have shown that a matrix is the best-fit model. As the concentration of mucoadhesive agent increases, the rate of permeation decreases. The order of drug permeation through the membrane was HEC > PVP K30 > HPMC K4M. This study found that a thermoreversible polymer and mucoadhesive polymers can be effectively used to prolong residence time. PMID:22495461

Gonjari, I D; Hosmani, A H; Karmarkar, A B; Godage, A S; Kadam, S B; Dhabale, P N

2009-02-01

310

Elasticity of c*Gels  

Microsoft Academic Search

A junction affine network model is solved for chains following a Redner des Cloizeaux distribution. In a gel at c^* the network strands behave as isolated chains. In a good solvent their elastic properties cannot be obtained from Gaussian statistics as in the classical models of rubber elasticity. Instead the Redner-des Cloizeaux distribution is employed, which is known to be

Ralf Everaers

1995-01-01

311

Gel Electrophoresis Lab: Paternity Case  

NSDL National Science Digital Library

This lab activity from the Biotechnology Alliance for Suncoast Biology Educators provides instructions for conducting a gel electrophoresis lab. Students will try to solve a paternity case with this activity by obtaining a DNA fingerprint from each potential father, the mother and the child. This activity may be downloaded in PDF file format. A data collection sheet and student questions are also included.

2013-07-05

312

Fitting Cosmological Supernovae Data Model  

NSDL National Science Digital Library

The Fitting Cosmological Supernovae Data Model allows users to compare and fit cosmological models with recent supernovae type Ia datasets to confirm the accelerated expansion of the universe. The 2011 Nobel Prize in Physics was awarded for the discovery of the cosmic acceleration using Supernovae Type Ia. This simulation allows the user to vary cosmological parameters within a particular class of dark energy cosmological models to fit a particular supernovae dataset. The simulation can plot several theoretical curves with the supernovae data to compare different models. The values of these parameters, for a particular model, determine the physical description and evolution of the universe. The Fitting Cosmological Supernovae Data Model model was created using Easy Java Simulations (EJS) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the ejs_Fitting_Cosmological_Models_Supernovae.jar file will run the program if Java is installed. You can modify this simulation if you have EJS by right-clicking within the plot and selecting âOpen Ejs Modelâ from the pop-up menu item.

Moldenhauer, Jacob; Engelhardt, Larry; Stone, Keenan

2011-12-08

313

Water sorption and physical properties of locust bean gum–pectin–starch composite gel dried using different drying methods  

Microsoft Academic Search

Locust bean gum–pectin–starch gel was dried with four different drying methods: air, vacuum, freeze and microwave vacuum drying to a moisture content of about 3–5% on wet basis. The effect of the drying method on water sorption properties of dried gel was evaluated at 25°C. Three different equations proposed in the literature (GAB, Oswin, Hasley) were used to fit the

Jaya Sundaram; Timothy D. Durance

2008-01-01

314

Calculating Percent Gel For Process Control  

NASA Technical Reports Server (NTRS)

Reaction state of thermosetting resin tracked to assure desired properties. Rate of gel determined as function of temperature by measuring time to gel of part of graphite fabric impregnated with Hexcel R120 (or equivalent) phenolic resin.

Webster, Charles Neal; Scott, Robert O.

1988-01-01

315

Regenerative medicine: Noodle gels for cells  

NASA Astrophysics Data System (ADS)

Heating and cooling of peptide amphiphile suspensions converts disorganized nanofibres into liquid-crystalline nanofibre bundles that gel on addition of salts. The noodle-shaped strings of gel can entrap and align cells.

Deming, Timothy J.

2010-07-01

316

Obtaining, Maintaining, and Advancing Your Fitness Certification  

ERIC Educational Resources Information Center

Public awareness of health, fitness, and exercise has increased and the fitness industry has expanded in recent years. Yet, ironically, the health of our nation continues to deteriorate. Now more than ever there is the need for qualified fitness professionals to help individuals to improve or maintain health and fitness. Since fitness

Pierce, Patricia; Herman, Susan

2004-01-01

317

Implementation of Health Fitness Exercise Programs.  

ERIC Educational Resources Information Center

This monograph includes the following articles to aid in implementation of fitness concepts: (1) "Trends in Physical Fitness: A Personal Perspective" (H. Harrison Clarke); (2) "A Total Health-Fitness Life-Style" (Steven N. Blair); (3) "Objectives for the Nation--Physical Fitness and Exercise" (Jack H. Wilmore); (4) "A New Physical Fitness Test"…

Cundiff, David E., Ed.

318

Determining the fitness consequences of antipredation behavior  

E-print Network

offspring (i.e., fitness). Although in theory the fitness consequences of any antipredation behavior can and therefore greater probability of producing offspring (i.e., fitness). Although in theory the fit- nessReview Determining the fitness consequences of antipredation behavior Johan Lind and Will Cresswell

319

Results for NRPB dosimetry services in the 2000 EURADOS trial performance test. National Radiolgical Protection Board. European Radiation Dosimetry Group.  

PubMed

During 2000 a trial performance test for individual monitoring services in Europe was organised by the European Radiation Dosimetry Group (EURADOS), covering whole-body beta/photon, whole-body neutron and extremity beta/photon dosimetry for both monoenergetic and simulated workplace fields. The UK National Radiological Protection Board (NRPB), which supplies routine dosemeters to some 50,000 wearers in the UK and overseas, participated in this trial performance test. This paper presents the results obtained for the NRPB whole-body TLD, neutron (PADC) and extremity dosimetry services and comments on their performance in comparison with the overall results. PMID:12382744

Gilvin, P J; Dunderdale, J; Perkins, D K

2002-01-01

320

Comparison of Real-Time Intraoperative Ultrasound-Based Dosimetry With Postoperative Computed Tomography-Based Dosimetry for Prostate Brachytherapy  

SciTech Connect

Purpose: To evaluate whether real-time intraoperative ultrasound (US)-based dosimetry can replace conventional postoperative computed tomography (CT)-based dosimetry in prostate brachytherapy. Methods and Materials: Between December 2001 and November 2002, 82 patients underwent {sup 103}Pd prostate brachytherapy. An interplant treatment planning system was used for real-time intraoperative transrectal US-guided treatment planning. The dose distribution was updated according to the estimated seed position to obtain the dose-volume histograms. Postoperative CT-based dosimetry was performed a few hours later using the Theraplan-Plus treatment planning system. The dosimetric parameters obtained from the two imaging modalities were compared. Results: The results of this study revealed correlations between the US- and CT-based dosimetry. However, large variations were found in the implant-quality parameters of the two modalities, including the doses covering 100%, 90%, and 80% of the prostate volume and prostate volumes covered by 100%, 150%, and 200% of the prescription dose. The mean relative difference was 38% and 16% for doses covering 100% and 90% of the prostate volume and 10% and 21% for prostate volumes covered by 100% and 150% of the prescription dose, respectively. The CT-based volume covered by 200% of the prescription dose was about 30% greater than the US-based one. Compared with CT-based dosimetry, US-based dosimetry significantly underestimated the dose to normal organs, especially for the rectum. The average US-based maximal dose and volume covered by 100% of the prescription dose for the rectum was 72 Gy and 0.01 cm{sup 3}, respectively, much lower than the 159 Gy and 0.65 cm{sup 3} obtained using CT-based dosimetry. Conclusion: Although dosimetry using intraoperative US-based planning provides preliminary real-time information, it does not accurately reflect the postoperative CT-based dosimetry. Until studies have determined whether US-based dosimetry or postoperative CT-based dosimetry can better predict patient outcomes, the American Brachytherapy Society recommendation of CT-based postimplant dosimetry should remain the standard of care.

Nag, Subir [Department of Radiation Medicine, Ohio State University, Columbus, OH (United States); Kaiser Permanente Radiation Oncology, Santa Clara, CA (United States); Shi Peipei [Department of Radiation Medicine, Ohio State University, Columbus, OH (United States); Department of Statistics, Case Western Reserve University, Cleveland, OH (United States); Liu Bingren [Department of Radiation Medicine, Ohio State University, Columbus, OH (United States); Department of Radiation Oncology, University of Rochester School of Medicine and Dentistry, Rochester, NY (United States); Gupta, Nilendu [Department of Radiation Medicine, Ohio State University, Columbus, OH (United States); Bahnson, Robert R. [Department of Urologic Surgery, Ohio State University, Columbus, OH (United States); Wang, Jian Z. [Department of Radiation Medicine, Ohio State University, Columbus, OH (United States)], E-mail: wang.993@osu.edu

2008-01-01

321

Energy absorption buildup factors, exposure buildup factors and Kerma for optically stimulated luminescence materials and their tissue equivalence for radiation dosimetry  

NASA Astrophysics Data System (ADS)

Optically stimulated luminescence (OSL) materials are sensitive dosimetric materials used for precise and accurate dose measurement for low-energy ionizing radiation. Low dose measurement capability with improved sensitivity makes these dosimeters very useful for diagnostic imaging, personnel monitoring and environmental radiation dosimetry. Gamma ray energy absorption buildup factors and exposure build factors were computed for OSL materials using the five-parameter Geometric Progression (G-P) fitting method in the energy range 0.015-15 MeV for penetration depths up to 40 mean free path. The computed energy absorption buildup factor and exposure buildup factor values were studied as a function of penetration depth and incident photon energy. Effective atomic numbers and Kerma relative to air of the selected OSL materials and tissue equivalence were computed and compared with that of water, PMMA and ICRU standard tissues. The buildup factors and kerma relative to air were found dependent upon effective atomic numbers. Buildup factors determined in the present work should be useful in radiation dosimetry, medical diagnostics and therapy, space dosimetry, accident dosimetry and personnel monitoring.

Singh, Vishwanath P.; Badiger, N. M.

2014-11-01

322

Optically characterizing collagen gels made with different cell types  

NASA Astrophysics Data System (ADS)

The ability of optical imaging techniques such as optical coherence tomography (OCT) to non-destructively characterize tissue-engineered constructs has generated enormous interest recently. Collagen gels are 3D structures that represent a simple common model of many engineered tissues that contain 2 primary scatterers: collagen and cells. We are testing the ability of OCT data to characterize the remodeling of such collagen-based constructs by 3 different types of cells: vascular smooth muscle cells (SMCs), endothelial cells (ECs), and osteoblasts (OBs). Collagen gels were prepared with SMCs, ECs, and OBs with a seeding density of 1×106 cells/ml; additionally, acellular controls were also prepared. The disk-shaped constructs were allowed to remodel in the incubator for 5 days, with OCT imaging occurring on days 1 and 5. From the OCT data, the attenuation and reflectivity were evaluated by fitting the data to a theoretical model that relates the tissue optical properties (scattering coefficient and anisotropy factor) and imaging conditions to the OCT signal. The degree of gel compaction was determined from the volume of the culture medium that feeds the constructs. We found that gel compaction (relative to the acellular control) occurred in the SMC constructs, but not in the OB or EC constructs. The optical property data showed that at day 5 the SMC constructs had an overall higher reflectivity (lower g) relative to day 1, whereas there was no obvious change in reflectivity of the EC, OB constructs and acellular controls relative to day 1. Moreover, there was a difference in the attenuation of the OB constructs on day 5 relative to day 1, but not in the other constructs. The apparent decrease in anisotropy observed in the SMC constructs, but not in the OB and EC constructs and acellular controls, suggests that OCT is sensitive to the remodeling of the collagen matrix that accompanies gel compaction, and can offer highly localized information on the construct microstructure. The apparent increase in the scattering coefficient of the OB constructs is believed to be caused by a higher rate of proliferation by these cell types relative to the others. Overall, these results suggest that the optical properties of collagen gels contain information on both cell number and collagen gel microstructure.

Levitz, David; Choudhury, Niloy; Vartanian, Keri; Hinds, Monica T.; Hanson, Stephen R.; Jacques, Steven L.

2009-02-01

323

Albedo neutron dosimetry in Germany: regulations and performance.  

PubMed

Personal neutron dosimetry has been performed in Germany using albedo dosemeters for >20 y. This paper describes the main principles, the national standards, regulations and recommendations, the quality management and the overall performance, giving some examples. PMID:24639589

Luszik-Bhadra, M; Zimbal, A; Busch, F; Eichelberger, A; Engelhardt, J; Figel, M; Frasch, G; Günther, K; Jordan, M; Martini, E; Haninger, T; Rimpler, A; Seifert, R

2014-12-01

324

DOSIMETRY OF OZONE AND NITROGEN DIOXIDE IN MAN AND ANIMALS  

EPA Science Inventory

Agreement between experimental data on maximum morphological damage and maximal predicated tissue does offers promise that mathematical dosimetry models can contribute to a better understanding of effective doses in animal studies and their correspondence to human exposure levels...

325

Retrospective dosimetry analyses of reactor vessel cladding samples  

SciTech Connect

Reactor pressure vessel cladding samples for Ringhals Units 3 and 4 in Sweden were analyzed using retrospective reactor dosimetry techniques. The objective was to provide the best estimates of the neutron fluence for comparison with neutron transport calculations. A total of 51 stainless steel samples consisting of chips weighing approximately 100 to 200 mg were removed from selected locations around the pressure vessel and were sent to Pacific Northwest National Laboratory for analysis. The samples were fully characterized and analyzed for radioactive isotopes, with special interest in the presence of Nb-93m. The RPV cladding retrospective dosimetry results will be combined with a re-evaluation of the surveillance capsule dosimetry and with ex-vessel neutron dosimetry results to form a comprehensive 3D comparison of measurements to calculations performed with 3D deterministic transport code. (authors)

Greenwood, L. R.; Soderquist, C. Z. [Battelle Pacific Northwest National Laboratory, Richland, WA 99352 (United States); Fero, A. H. [Westinghouse Electric Company, Cranberry Twp., PA 16066 (United States)

2011-07-01

326

Gamma-ray dosimetry measurements of the Little Boy replica  

SciTech Connect

We present the current status of our gamma-ray dosimetry results for the Little Boy replica. Both Geiger-Mueller and thermoluminescent detectors were used in the measurements. Future work is needed to test assumptions made in data analysis.

Plassmann, E.A.; Pederson, R.A.

1984-01-01

327

Review of retrospective dosimetry techniques for external ionising radiation exposures.  

PubMed

The current focus on networking and mutual assistance in the management of radiation accidents or incidents has demonstrated the importance of a joined-up approach in physical and biological dosimetry. To this end, the European Radiation Dosimetry Working Group 10 on 'Retrospective Dosimetry' has been set up by individuals from a wide range of disciplines across Europe. Here, established and emerging dosimetry methods are reviewed, which can be used immediately and retrospectively following external ionising radiation exposure. Endpoints and assays include dicentrics, translocations, premature chromosome condensation, micronuclei, somatic mutations, gene expression, electron paramagnetic resonance, thermoluminescence, optically stimulated luminescence, neutron activation, haematology, protein biomarkers and analytical dose reconstruction. Individual characteristics of these techniques, their limitations and potential for further development are reviewed, and their usefulness in specific exposure scenarios is discussed. Whilst no single technique fulfils the criteria of an ideal dosemeter, an integrated approach using multiple techniques tailored to the exposure scenario can cover most requirements. PMID:21183550

Ainsbury, E A; Bakhanova, E; Barquinero, J F; Brai, M; Chumak, V; Correcher, V; Darroudi, F; Fattibene, P; Gruel, G; Guclu, I; Horn, S; Jaworska, A; Kulka, U; Lindholm, C; Lloyd, D; Longo, A; Marrale, M; Monteiro Gil, O; Oestreicher, U; Pajic, J; Rakic, B; Romm, H; Trompier, F; Veronese, I; Voisin, P; Vral, A; Whitehouse, C A; Wieser, A; Woda, C; Wojcik, A; Rothkamm, K

2011-11-01

328

Raman spectroscopy of blue gel pen inks  

Microsoft Academic Search

Raman spectroscopy is becoming a tool of major importance in forensic science. It is a non-invasive, non-destructive analytical method allowing samples to be examined without any preparation. This paper demonstrates the use of the technique as a general tool for gel pen inks analysis. For this purpose, 55 blue gel pen inks, of different brands and models representative of gel

Williams David Mazzella; Patrick Buzzini

2005-01-01

329

Advanced gel propulsion controls for kill vehicles  

Microsoft Academic Search

A gel propulsion control concept for tactical applications is reviewed, and the status of the individual component technologies currently under development at the Aerojet Propulsion Division is discussed. It is concluded that a gel propellant Divert and Attitude Control Subsystem (DACS) provides a safe, insensitive munitions compliant alternative to current liquid Theater Missile Defense (TMD) DACS approaches. The gel kill

W. K. Yasuhara; A. Olson; S. Finato

1993-01-01

330

Spring-loaded polymeric gel actuators  

DOEpatents

Spring-loaded electrically controllable polymeric gel actuators are disclosed. The polymeric gels can be polyvinyl alcohol, polyacrylic acid, or polyacrylamide, and are contained in an electrolytic solvent bath such as water plus acetone. The action of the gel is mechanically biased, allowing the expansive and contractile forces to be optimized for specific applications.

Shahinpoor, Mohsen (Albuquerque, NM)

1995-01-01

331

Food gels: Gelling process and new applications  

Microsoft Academic Search

Food gels are viscoelastic substances and several gelled products are manufactured throughout the world. The gelling agents in foods are usually polysaccharides and proteins. In food gels, the polymer molecules are not cross-linked by covalent bonds with the exception of disulphide bonds in some protein gels. Instead, the molecules are held together by a combination of weak inter-molecular forces like

SOUMYA BANERJEE; SUVENDU BHATTACHARYA

2011-01-01

332

Food Gels: Gelling Process and New Applications  

Microsoft Academic Search

Food gels are viscoelastic substances and several gelled products are manufactured throughout the world. The gelling agents in foods are usually polysaccharides and proteins. In food gels, the polymer molecules are not cross-linked by covalent bonds with the exception of disulphide bonds in some protein gels. Instead, the molecules are held together by a combination of weak inter-molecular forces like

Soumya Banerjee; Suvendu Bhattacharya

2012-01-01

333

A clarified gel for crystal growth  

NASA Technical Reports Server (NTRS)

A procedure for preparing clarified sodium silicate gels suitable for crystal growth is described. In the method described here, the silicate stock is clarified by pretreating it with cation exchange resins before preparing the gels. Also, a modified recipe is proposed for preparing gels to achieve improved transparency.

Barber, P. G.; Simpson, N. R.

1985-01-01

334

Spring-loaded polymeric gel actuators  

DOEpatents

Spring-loaded electrically controllable polymeric gel actuators are disclosed. The polymeric gels can be polyvinyl alcohol, polyacrylic acid, or polyacrylamide, and are contained in an electrolytic solvent bath such as water plus acetone. The action of the gel is mechanically biased, allowing the expansive and contractile forces to be optimized for specific applications. 5 figs.

Shahinpoor, M.

1995-02-14

335

Pro-Q Diamond Phosphoprotein Gel Stain  

E-print Network

Pro-Q Diamond Phosphoprotein Gel Stain In-gel Detection Technology for Protein Phosphorylation and phosphoproteomics, the Pro-Q Diamond phos- phoprotein gel stain is a breakthrough technology that provides a simple phosphoproteins, the Pro-Q Diamond signal is linear over three orders of magnitude and the strength of the signal

Lebendiker, Mario

336

Reassignment of boundaries requiring personal dosimetry at a nuclear facility  

E-print Network

) portion of the site were not provided dosimetry, but all workers who entered the Unit 2 (nuclear plant) side of the site, at any time regardless of work assignment, were provided dosimetry along with the security identification badge. Visitors who... thermoluminescent dosimeters (TLD's) as the primary dosimeter (the primary dosimeter is the one used to determine the "official" dose reported on records). These dosimeters (badges) are exchanged once every calendar quarter (i. e. , January 1, April 1, July 1...

Fulmer, Philip Clark

1990-01-01

337

Thermoluminescent Dosimetry: A Preliminary Study for microCT Applications  

SciTech Connect

Preliminary measurements for microCT dosimetry are reported in this work, using TLD-100 crystals (1x1x1 mm3) within a solid water phantom specially designed with approximate dimensions of a mouse. A dose dependence as a function of radial distance and position along the axis of the phantom was found. Because of the smaller doses used in this work we can say that it is feasible to perform dosimetry measurements with high accuracy using TLD-100 microcubes.

Montano Garcia, C.; Rodriguez-Villafuerte, M.; Martinez-Davalos, A.; Brandan, M. E.; Ruiz-Trejo, C. [Instituto de Fisica, UNAM, A.P.20-364, 01000, Mexico City (Mexico)

2006-09-08

338

Dosimetry for the approval of food irradiation processes  

NASA Astrophysics Data System (ADS)

The use of accurate and precise radiation dosimetry to control the food irradiation process for regulatory purposes is discussed. The various procedures required to establish a thorough dosimetric control, such as commissioning the irradiation facility, process validation and routine control are described. It is concluded that, coupled with an administrative inventory control, dosimetry can provide the guarantee that the process has been correctly applied and regulatory release of irradiated food can be based on accurate and reproducible absorbed dose measurements.

Miller, A.; Chadwick, K. H.

339

Accidental neutron dosimetry with human hair  

NASA Astrophysics Data System (ADS)

Human hair contains sulfur, which can be activated by fast neutrons. The 32S(n,p)32P reaction with a threshold of 2.5 MeV was used for fast neutron dose estimation. It is a very important parameter for individual dose reconstruction with regards to the heterogeneity of the neutron transfer to the human body. Samples of human hair were irradiated in a radial channel of a training reactor VR-1. 32P activity in hair was measured both, directly by means of a proportional counter, and as ash dispersed in a liquid scintillator. Based on neutron spectrum estimation, a relationship between the neutron dose and induced activity was derived. The experiment verified the practical feasibility of this dosimetry method in cases of criticality accidents or malevolent acts with nuclear materials.

Ekendahl, Daniela; Be?ková, V?ra; Zdychová, Vlasta; Bulánek, Boris; Prouza, Zden?k; Štefánik, Milan

2014-11-01

340

Advanced Semiconductor Dosimetry in Radiation Therapy  

NASA Astrophysics Data System (ADS)

Modern radiation therapy is very conformal, resulting in a complexity of delivery that leads to many small radiation fields with steep dose gradients, increasing error probability. Quality assurance in delivery of such radiation fields is paramount and requires real time and high spatial resolution dosimetry. Semiconductor radiation detectors due to their small size, ability to operate in passive and active modes and easy real time multichannel readout satisfy many aspects of in vivo and in a phantom quality assurance in modern radiation therapy. Update on the recent developments and improvements in semiconductor radiation detectors and their application for quality assurance in radiation therapy, based mostly on the developments at the Centre for Medical Radiation Physics (CMRP), University of Wollongong, is presented.

Rosenfeld, Anatoly B.

2011-05-01

341

Novel approaches in radon and thoron dosimetry  

NASA Astrophysics Data System (ADS)

This report presents some novel approaches for radon/radon progeny and thoron measurements that can help to resolve some long-lasting problems in dosimetry, but which are not yet part of the common practice. The focus is in two directions: The use of CDs/DVDs as radon and thoron detectors and the employment of grab-sampling and/or integrated radon progeny measurements for diagnostic of the air conditions related to mitigation and indoor ventilation. The potential of these approaches is illustrated by several successful applications: (1) Study of the 222Rn distribution in large buildings and identification of places with radon problem; (2) Radon and thoron monitoring in underground mines; (3) Radon measurements in natural waters, including directly in the water source; (4) Grab sampling 222Rn progeny measurements for the purposes of pre- and post-mitigation diagnostic; (5) Integrated measurements of individual 222Rn short-lived decay products for diagnostic of indoor ventilation conditions.

Pressyanov, D.; Dimitrov, D.; Dimitrova, I.; Georgiev, S.; Mitev, K.

2014-07-01

342

Dosimetry for photodynamic therapy of endometrial tissue  

NASA Astrophysics Data System (ADS)

Hysterectomy is the most common major operation performed in the United States with dysfunctional uterine bleeding as one of the major indications. The clinical needs for simple and safe endometrial destruction are essential. Photodynamic therapy (PDT) may offer a simple and cost effective solution for the treatment of dysfunctional uterine bleeding. The dosimetry is discussed for the case of topical application of photosensitizer. This technique might be the method of preference because undesired side effects such as skin photosensitization that is typical for systemically injected photosensitizers, can be avoided. Effective PDT requires a sufficient amount of light delivered to the targeted tissue in a reasonable period of time. A trifurcated optical applicator consisting of three cylindrical diffusing fibers has been constructed, and this applicator can deliver a typical required optical dose of about 50-100 J/cm2 to the full depth of the endometrium for an exposure time of 10-20 minutes.

Svaasand, Lars O.; Fehr, Mathias K.; Madsen, Sten; Tadir, Yona; Tromberg, Bruce J.

1995-05-01

343

Boron dose determination for BNCT using Fricke and EPR dosimetry  

SciTech Connect

In Boron Neutron Capture Therapy (BNCT) the dominant dose delivered to the tumor is due to {alpha} and {sup 7}Li charged particles resulting from a neutron capture by {sup 10}B and is referred to herein as the boron dose. Boron dose is directly attributable to the following two independent factors, one boron concentration and the neutron capture energy dependent cross section of boron, and two the energy spectrum of the neutrons that interact with boron. The neutron energy distribution at a given point is dictated by the incident neutron energy distribution, the depth in tissue, geometrical factors such as beam size and patient`s dimensions. To account for these factors can be accommodated by using Monte Carlo theoretical simulations. However, in conventional experimental BNCT dosimetry, e.g., using TLDs or ionization chambers, it is only possible to estimate the boron dose. To overcome some of the limitations in the conventional dosimetry, modifications in ferrous sulfate dosimetry (Fricke) and Electron Paramagnetic Resonance (EPR) dosimetry in alanine, enable to measure specifically boron dose in a mixed gamma neutron radiation fields. The boron dose, in either of the dosimeters, is obtained as a difference between measurements with boronated and unboronated dosimeters. Since boron participates directly in the measurements, the boron dosimetry reflects the true contribution, integral of the neutron energy spectrum with boron cross section, of the boron dose to the total dose. Both methods are well established and used extensively in dosimetry, they are presented briefly here.

Wielopolski, L. [Brookhaven National Lab., Upton, NY (United States); Ciesielski, B. [Medical Academy, Gdansk (Poland). Dept. of Physics and Biophysics

1995-02-01

344

Personnel neutron dosimetry using electrochemically etched CR-39 foils  

SciTech Connect

A personnel neutron dosimetry system has been developed based on the electrochemical etching of CR-39 plastic at elevated temperatures. The doses obtained using this dosimeter system are more accurate than those obtained using other dosimetry systems, especially when varied neutron spectra are encountered. This Cr-39 dosimetry system does not have the severe energy dependence that exists with albedo neutron dosimeters or the fading and reading problems encountered with NTA film. The dosimetry system employs an electrochemical etch procedure that be used to process large numbers of Cr-39 dosimeters. The etch procedure is suitable for operations where the number of personnel requires that many CR-39 dosimeters be processed. Experience shows that one full-time technician can etch and evaluate 2000 foils per month. The energy response to neutrons is fairly flat from about 80 keV to 3.5 MeV, but drops by about a factor of three in the 13 to 16 MeV range. The sensitivity of the dosimetry system is about 7 tracks/cm/sup 2//mrem, with a background equivalent to about 8 mrem for new CR-39 foils. The limit of sensitivity is approximately 10 mrem. The dosimeter has a significant variation in directional dependence, dropping to about 20% at 90/sup 0/. This dosimeter has been used for personnel neutron dosimetry at the Lawrence Livermore National Laboratory for more tha 18 months. 6 refs., 23 figs., 2 tabs.

Hankins, D.E.; Homann, S.; Westermark, J.

1986-09-17

345

Specific issues in small animal dosimetry and irradiator calibration  

PubMed Central

Purpose In response to the increased risk of radiological terrorist attack, a network of Centers for Medical Countermeasures against Radiation (CMCR) has been established in the United States, focusing on evaluating animal model responses to uniform, relatively homogenous whole- or partial-body radiation exposures at relatively high dose rates. The success of such studies is dependent not only on robust animal models but on accurate and reproducible dosimetry within and across CMCR. To address this issue, the Education and Training Core of the Duke University School of Medicine CMCR organised a one-day workshop on small animal dosimetry. Topics included accuracy in animal dosimetry accuracy, characteristics and differences of cesium-137 and X-ray irradiators, methods for dose measurement, and design of experimental irradiation geometries for uniform dose distributions. This paper summarises the information presented and discussed. Conclusions Without ensuring accurate and reproducible dosimetry the development and assessment of the efficacy of putative countermeasures will not prove successful. Radiation physics support is needed, but is often the weakest link in the small animal dosimetry chain. We recommend: (i) A user training program for new irradiator users, (ii) subsequent training updates, and (iii) the establishment of a national small animal dosimetry center for all CMCR members. PMID:21961967

Yoshizumi, Terry; Brady, Samuel L.; Robbins, Mike E.; Bourland, J. Daniel

2013-01-01

346

A physical dosimetry intercomparison for BNCT.  

PubMed

An intercomparison of physical dosimetry methods used at the Massachusetts Institute of Technology (MIT) and Brookhaven National Laboratory was completed to enable retrospective analysis of BNCT trials. Measurements were performed under reference conditions pertinent to clinical irradiations at the epithermal neutron beam facility of the Brookhaven Medical Research Reactor (BMRR) using procedures developed at MIT during similar trials. Thermal neutron flux was determined from gold foil activation experiments and good agreement was found between the depth profiles measured in-phantom by the two groups. At a depth of 3.5 cm where the measured flux is greatest, the ratio of the MIT/BMRR measurements is 1.01+/-0.10 if the same reporting procedures are applied. Photon and fast neutron absorbed dose rates were assessed using ionization chambers with separate graphite and A-150 plastic walls. Measurement of the in-phantom photon depth dose component agreed favorably with that previously reported by the BMRR group using thermoluminescent dosimeters. At a depth of 3.5 cm the ratio of the MIT measurements to those made by the BMRR group was 0.89+/-0.12. In-air measurements of the fast neutron and photon absorbed dose rates agreed within the limits of experimental uncertainty. Additional studies were performed in the ellipsoidal water phantom regularly used for beam characterizations at MIT. No significant differences in the thermal neutron flux measured in either a solid PMMA cube or an ellipsoidal shaped water phantom were observed on the central axis of the beam. This study confirms the reproducibility and uniformity of dosimetry measurements performed by the two independent groups undertaking BNCT trials in the USA and provides the physical data necessary to compare BMRR treatment protocols with those applied at Harvard-MIT. PMID:12033586

Riley, Kent J; Binns, Peter J; Greenberg, Dennis D; Harling, Otto K

2002-05-01

347

Real-time volumetric scintillation dosimetry  

NASA Astrophysics Data System (ADS)

The goal of this brief review is to review the current status of real-time 3D scintillation dosimetry and what has been done so far in this area. The basic concept is to use a large volume of a scintillator material (liquid or solid) to measure or image the dose distributions from external radiation therapy (RT) beams in three dimensions. In this configuration, the scintillator material fulfills the dual role of being the detector and the phantom material in which the measurements are being performed. In this case, dose perturbations caused by the introduction of a detector within a phantom will not be at issue. All the detector configurations that have been conceived to date used a Charge-Coupled Device (CCD) camera to measure the light produced within the scintillator. In order to accurately measure the scintillation light, one must correct for various optical artefacts that arise as the light propagates from the scintillating centers through the optical chain to the CCD chip. Quenching, defined in its simplest form as a nonlinear response to high-linear energy transfer (LET) charged particles, is one of the disadvantages when such systems are used to measure the absorbed dose from high-LET particles such protons. However, correction methods that restore the linear dose response through the whole proton range have been proven to be effective for both liquid and plastic scintillators. Volumetric scintillation dosimetry has the potential to provide fast, high-resolution and accurate 3D imaging of RT dose distributions. Further research is warranted to optimize the necessary image reconstruction methods and optical corrections needed to achieve its full potential.

Beddar, S.

2015-01-01

348

Validation of high-resolution 3D patient QA for proton PBS and IMPT using laser CT of improved polymer gel dosimeters  

NASA Astrophysics Data System (ADS)

Laser CT scanning of LET-independent BANG3-Pro2® polymer gel dosimeters has recently shown potential in proton dosimetry. However, raw materials' impurities impart some variability. This study aimed to validate a new method of compensating for this variability, and to validate the suitability of the improved dosimeter for patient-specific QA in pencil beam scanning (PBS) and IMPT. Six modifications of the BANG3-Pro2® gel dosimeter were analysed for their sensitivity to proton dose and to LET. One formulation was selected for a clinical QA feasibility study, in which one composite IMPT plan, two single-field IMPT plans, and one SFUD plan were delivered to identical gel phantoms. New commercial VOLQATM software (beta version) was used for data analysis. Both validations were successful.

Cardin, A.; Ding, X.; Kassaee, A.; Lin, L.; Maryanski, M. J.; Avery, S.

2015-01-01

349

Sports Potentials for Physical Fitness.  

ERIC Educational Resources Information Center

This report, one of a series on research into specific physical activities and their efficacy in improving and maintaining physical fitness, examines sport participation and the potential it has for developing muscular strength, muscular endurance, and circulatory-respiratory endurance. The activities consist primarily of the following twelve…

Clarke, H. Harrison, Ed.

1978-01-01

350

Physical Therapist Assistant Fitness Lab.  

ERIC Educational Resources Information Center

Colby Community College's (CCC) Fitness Lab was established to provide the Physical Therapist Assistant (PTA) Program with a learning laboratory in which students can practice classroom-acquired skills, while at the same time promoting the physical, emotional, social, and intellectual well-being of CCC students and staff, and community members. A…

Backstrom, Kurt; And Others

351

Current Issues in Flexibility Fitness.  

ERIC Educational Resources Information Center

Physical activity is extremely important in maintaining good health. Activity is not possible without a certain amount of flexibility. This report discusses issues related to flexibility fitness. Flexibility is a property of the musculoskeletal system that determines the range of motion achievable without injury to the joints. Static flexibility…

Knudson, Duane V.; Magnusson, Peter; McHugh, Malachy

2000-01-01

352

Fitting Cosmological Data Baryon Model  

NSDL National Science Digital Library

The 1998 discovery of the cosmic acceleration with supernovae was recently awarded the 2011 Nobel Prize in Physics. Measurements of the baryon acoustic oscillations (BAO), as standard rulers, support this accelerated expansion of the universe (cosmic acceleration). The simulation allows users to compare and fit theoretical models of cosmology with recent BAO data sets to confirm the accelerated expansion of the universe. This modeling allows the user to vary cosmological parameters within a particular class of dark energy cosmological models to fit a particular cosmological data set. The user can plot several theoretical curves with the data to compare different models. The values of these parameters, for a particular model, determine the physical description and evolution of the universe. The Fitting Cosmological Data Baryon Model was created using Easy Java Simulations (EJS) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the ejs_FittingCosmologicalDataBaryon.jar file will run the program if Java is installed. You can modify this simulation if you have EJS by right-clicking within the plot and selecting âOpen Ejs Modelâ from the pop-up menu item.

Moldenhauer, Jacob; Stone, Keenan; Engelhardt, Larry

2012-09-07

353

Fitting Cosmological Data Hz Model  

NSDL National Science Digital Library

The 1998 discovery of the cosmic acceleration with supernovae was recently awarded the 2011 Nobel Prize in Physics. Direct and indirect measurements of the Hubble Parameter, H(z), support this accelerated expansion of the universe (cosmic acceleration). The simulation allows users to compare and fit theoretical models of cosmology with recent Hubble Parameter data sets to confirm the accelerated expansion of the universe. This modeling allows the user to vary cosmological parameters within a particular class of dark energy cosmological models to fit a particular cosmological data set. The user can plot several theoretical curves with the data to compare different models. The values of these parameters, for a particular model, determine the physical description and evolution of the universe. The EJS Fitting Cosmological Data Hz Model was created using Easy Java Simulations (EJS) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the ejs_FittingCosmologicalDataHz.jar file will run the program if Java is installed. You can modify this simulation if you have EJS by right-clicking within the plot and selecting Open Ejs Model from the pop-up menu item.

Moldenhauer, Jacob; Stone, Keenan; Engelhardt, Larry

2012-09-07

354

Forming of seamless pipe fittings  

Microsoft Academic Search

Analysis and results of the high temperature forming of seamless pipe fittings produced at a local factory are presented in this work. The studies were conducted by recording the thermal evolution in different parts of the piece as it was being forged, which was done by placing a series of type K thermocouples within the part and logging the data

Andrés Rodr??guez; Margarita Mezzetti; Peter Fodor; Rafael Colás

2002-01-01

355

Orifice fittings and meter tubes  

SciTech Connect

Various methods and designs of orifice fittings and meter tubes exist. The incorporation of these designs depend on process conditions, piping configurations, economics, and other considerations. Within the incorporation of these designs are the specifications of the orifice meter standards set forth by the AGA and the API. This will ensure reliable and accurate fluid measurement.

Ragsdale, J. [Daniel Industries, Inc., Tulsa, OK (United States)

1995-12-01

356

Fv: Interactive FITS file editor  

NASA Astrophysics Data System (ADS)

Fv is an easy-to-use graphical program for viewing and editing any FITS format image or table. The Fv software is small, completely self-contained and runs on Windows PCs, most Unix platforms and Mac OS-X. Fv also provides a portal into the Hera data analysis service from the HEASARC.

Pence, William; Chai, Pan

2012-05-01

357

A dosimetric study of small photon fields using polymer gel and Gafchromic EBT films  

SciTech Connect

The use of small field sizes is increasingly becoming important in radiotherapy particularly since the introduction of stereotactic radiosurgery and intensity-modulated radiation therapy techniques. The reliable measurement of delivered dose from such fields with conventional dosimeters, such as ionization chambers, is a challenging task. In this work, methacrylic and ascorbic acid in gelatin initiated by copper polymer gel dosimeters are employed to measure dose in 3 dimensions. Field sizes of 5 × 5 mm{sup 2}, 10 × 10 mm{sup 2}, 20 × 20 mm{sup 2}, and 30 × 30 mm{sup 2} are investigated for a 6-MV x-rays. The results show an agreement with Gafchromic film, with some variation in measured doses near the edge of the fields, where the film data decrease more rapidly than the other methods. Dose penumbra widths obtained with gel dosimeters and Gafchormic film were generally in agreement with each other. The results of this work indicate that polymer gel dosimetry could be invaluable for the quantification of the 3-dimensional dose distribution in small field size.

Hassani, Hossein [Department of Medical Radiation Engineering, Science and Research Branch, Islamic Azad University, Tehran (Iran, Islamic Republic of); Nedaie, Hassan Ali, E-mail: Nedaieha@sina.tums.ac.ir [Cancer Research Center, Tehran University of Medical Sciences, Tehran (Iran, Islamic Republic of); Zahmatkesh, Mohammad Hassan [Department of Medical Physics, Shahid Beheshti university of Medical Sciences, Tehran (Iran, Islamic Republic of); Shirani, Kaveh [Department of Medical Radiation Engineering, Science and Research Branch, Islamic Azad University, Tehran (Iran, Islamic Republic of)

2014-04-01

358

Elasticity of c*-Gels  

NASA Astrophysics Data System (ADS)

A junction affine network model is solved for chains following a Redner des Cloizeaux distribution. In a gel at c^* the network strands behave as isolated chains. In a good solvent their elastic properties cannot be obtained from Gaussian statistics as in the classical models of rubber elasticity. Instead the Redner-des Cloizeaux distribution is employed, which is known to be an excellent approximation to the end to end distance distribution of flexible polymer chains in a good solvent. The implications of using non-linear entropic springs, the role of fluctuations and the quality of the affine approximation are worked out for a Flory-Rehner model. The applicability to swollen networks and the elasticity of two dimensional c^*-gels are briefly discussed.

Everaers, Ralf

1995-10-01

359

Fluctuations in strained polymer gels  

SciTech Connect

Following the recent observations of butterfly-like isointensity patterns in neutron scattering from stretched gels, swollen rubbers and mixtures of molten polymers. The authors represent a Landau-de Gennes theory of coupled strain and concentration fluctuations in such systems. This paper shows that while {open_quotes}anomalous{close_quotes} patterns with fluctuations enhanced along the deformation axis appear in systems that exhibit linear elasticity at strains or order unity. {open_quotes}Normal{close_quotes} patterns result when nonlinear effects are important. The magnitude of the asymmetry is proportional to the strength of the coupling between concentration and strain and to the concentration dependence of the elastic moduli. These effects also play an important role in understanding the swelling of polymer gels.

Rabin, Y.; Pekarski, P. [Bar-Ilan Univ., Ramat-Gan (Israel); Bruinsma, R. [Univ. of California, Los Angeles, CA (United States)

1993-12-31

360

Morphology of biaxially stretched triblock copolymer gels using SAXS  

NASA Astrophysics Data System (ADS)

Gels of styrenic triblock copolymers swollen by a low-volatility, midblock-selective oil behave as high-strain, low-field dielectric elastomers in the design of electroactive polymeric actuators. A standard configuration of such devices involves stretching, or ``prestraining,'' the elastomer film biaxially. However, little is known about the effect of biaxial prestrain on copolymer morphology. In this study, small-angle X-ray scattering (SAXS) is used to probe the nanostructure of gels composed of poly[styrene-b-(ethylene-co-butylene)-b-styrene] and mineral oil by systematically changing the concentration of polymer from 5 to 30 wt% and the biaxial prestrain from 0 to 300%. In the azimuthally integrated intensity profiles, the form factor due to scattering from polystyrene microdomains correlates strongly with polymer concentration and does not change with the applied prestrain, indicating that the polystyrene crosslinks remain as polydisperse spheres. The structure factor data correlates with prestrain, and is fitted using the Percus-Yevick approximation for interacting spheres. While a hard sphere interaction model is sufficient for unstrained gels, we resort to a square shoulder hard sphere potential for strained samples.

Krishnan, Arjun; Ghosh, Tushar; Spontak, Richard

2009-03-01

361

Hylan gel composition for percutaneous embolization.  

PubMed

Viscoelastic, pseudoplastic, radiopaque injectable hylan gel for percutaneous embolization was developed and evaluated by in vitro and in vivo tests. The embolization gel is composed of cross-linked hylan (hyaluronan, hyaluronate), tantalum, microcrystalline cellulose, hexamethonium chloride, and thrombin. Upon delivery through small-lumen catheters to the appropriate vascular site, the gel induces formation of a solid blood/gel coagulum. Results from animal studies (rat aorta, rabbit auricular artery) demonstrate that formation of complete and long-lasting arterial blockage is readily achievable without complications due to blood flow, partial vessel obstruction, uncontrolled polymerization, or movement of the gel or its components (specifically thrombin and hexamethonium chloride) into the circulation. Microscopic evaluation indicates that arterial occlusion initially occurs as a result of the injected gel and formed fibrin; at 7 weeks and beyond, arteries are occluded by injected gel, inflammatory cells and fibrosis (scar tissue). PMID:1874755

Larsen, N E; Leshchiner, E A; Parent, E G; Hendrikson-Aho, J; Balazs, E A; Hilal, S K

1991-06-01

362

A Person-Environment Fit Approach to Volunteerism: Volunteer Personality Fit and Culture Fit as Predictors of Affective Outcomes  

Microsoft Academic Search

This study employed a person-environment (P-E) fit approach to explaining volunteer satisfaction, affective commitment, and turnover intentions. It was hypothesized that personality fit would explain additional variance in volunteer affective outcomes above and beyond motives to volunteer. This hypothesis was supported. Personality fit but not culture fit was related to satisfaction and affective commitment. Volunteer turnover intentions were predicted by

Annelies E. M. Van Vianen; Bernard A. Nijstad; Olga F. Voskuijl

2008-01-01

363

Intercomparison of small biomolecules by gel filtration and small angle scattering  

SciTech Connect

This paper describes how small angle neutron scattering (SANS) can be used to confirm that gel filtration results are free of dimerization effects. After characterization by analytical gel filtration, concentrated solutions (in heavy water, D2O) of a cobra neurotoxin, a cytotoxin, and a cytotoxin analog are studied by SANS. Small differences in shape are shown to be discernible by means of least-square fits to ellipsoidal models. The parallel axis theorem is then invoked to assess dimerization levels statistically. The results are briefly discussed on the basis of function in relation to structure.

Martel, P.; Stepanik, T.M.; Szabo, A.G. (Atomic Energy of Canada Limited, Chalk River Nuclear Laboratories, Ontario (Canada))

1990-05-01

364

Funtools: FITS Users Need Tools  

NASA Astrophysics Data System (ADS)

Funtools is a "minimal buy-in" FITS library and utility package developed at the the High Energy Astrophysics Division of SAO. The Funtools library provides simplified access to a wide array of file types: standard astronomical FITS images and binary tables, raw arrays and binary event lists, and even tables of ASCII column data. A sophisticated region filtering library (compatible with ds9) filters images and tables using boolean operations between geometric shapes, support world coordinates, etc. Funtools also supports advanced capabilities such as optimized data searching using index files. Because Funtools consists of a library and a set of user programs, it is most appropriately built from source. Funtools has been ported to Solaris, Linux, LinuxPPC, SGI, Alpha OSF1, Mac OSX (darwin) and Windows 98/NT/2000/XP. Once the source code tar file is retrieved, Funtools can be built and installed easily using standard commands.

Mandel, Eric; Murray, Stephen S.; Roll, John

2011-12-01

365

Musculoskeletal Fitness and Risk of Mortality.  

ERIC Educational Resources Information Center

Quantified the relationship between musculoskeletal fitness and all-cause mortality in Canada, using measures of musculoskeletal fitness (situps, pushups, grip strength, and sit- and-reach trunk flexibility) from adult male and female participants in the Canadian Fitness Survey. Results indicated that some components of musculoskeletal fitness,…

Katzmarzyk, Peter T.; Craig, Cora L.

2002-01-01

366

Youth Physical Fitness: Ten Key Concepts  

ERIC Educational Resources Information Center

The promotion of physical fitness has been a key objective of physical education for more than a century. During this period, physical education has evolved to accommodate changing views on fitness and health. The purpose of this article is to discuss issues with fitness assessment and fitness education central to the new Presidential Youth…

Corbin, Charles B.; Welk, Gregory J.; Richardson, Cheryl; Vowell, Catherine; Lambdin, Dolly; Wikgren, Scott

2014-01-01

367

Aging, Mental Retardation and Physical Fitness.  

ERIC Educational Resources Information Center

This fact sheet uses a question-and-answer format to provide an overview of what physical fitness is and how it relates to people with mental retardation. Questions address the following topics: the fitness movement; a definition of physical fitness; the different components of physical fitness (muscle strength and endurance, flexibility, body…

Rimmer, James H.

368

Decomposing the seasonal fitness decline.  

PubMed

Seasonal fitness declines are common, but the relative contribution of different reproductive components to the seasonal change in the production of reproductive young, and the component-specific drivers of this change is generally poorly known. We used long-term data (17 years) on breeding time (i.e. date of first egg laid) in northern wheatears (Oenanthe oenanthe) to investigate seasonal reproductive patterns and estimate the relative contributions of reproductive components to the overall decline in reproduction, while accounting for factors potentially linked to seasonal declines, i.e. individual and habitat quality. All reproductive components-nest success (reflecting nest predation rate), clutch size, fledging success and recruitment success-showed a clear decline with breeding time whereas subsequent adult survival did not. A non-linear increase in nest predation rate caused nest success to decline rapidly early in the season and level off at ~80% success late in the breeding season. The combined seasonal decline in all reproductive components caused the mean production of recruits per nest to drop from around 0.7-0.2; with the relative contribution greatest for recruitment success which accounted for ~50% of the decline. Our data suggest that changing environmental conditions together with effects of nest predation have strong effects on the seasonal decline in fitness. Our demonstration of the combined effects of all reproductive components and their relative contribution shows that omitting data from later stages of breeding (recruitment) can greatly underestimate seasonal fitness declines. PMID:24013387

Öberg, Meit; Pärt, Tomas; Arlt, Debora; Laugen, Ane T; Low, Matthew

2014-01-01

369

Mathematical modeling of drug release profiles for modified hydrophobic HPMC based gels.  

PubMed

Hydroxypropyl methylcellulose (HPMC) is now available in modified hydrophobic forms (Sangelose). In this paper, the effect of viscosity grade and HPMC concentration on in vitro release kinetics of a topically applied drug were studied using gel formulations of a nonsteroidal anti-inflammatory drug (NSAID), diclofenac potassium (DP), with different viscosity grades of the polymer (60L, 60 M, 90 M for hydrophobic HPMC and 50 cPs for conventional hydrophilic HPMC) in different proportions. It was found that hydrophobic HPMC-based gels having a higher viscosity and lower polymer concentration release a notably higher amount of drug compared with hydrophilic HPMC-based gels containing a higher concentration of polymer but with lower viscosity. For gels, the suitability of different common empirical (zero-order, first-order, and Higuchi), and semi-empirical (Ritger-Peppas and Peppas-Sahlin) models, and some new statistical (logistic, log-logistic, Weibull, Gumbel, and generalized extreme value distribution) models to describe the drug release profile were tested through non-linear least-square curve fitting. A general purpose mathematical analysis tool MATLAB was used. Further, instead of the widely used transformed linear fit method, direct fitting was used in the paper to avoid any form of truncation and transformation errors. The results revealed that the log-logistic distribution, amongst all the models investigated, was the best fit for hydrophobic formulations. For hydrophilic ones, the semi-empirical models and Weibull distribution worked best, although log-logistic also showed a close fit. The shape parameter for the log-logistic and Weibull distribution conveys vital information about the rate of release and helps improve understanding of drug release profiles. PMID:22512085

Ghosal, K; Chandra, A; Rajabalaya, R; Chakraborty, S; Nanda, A

2012-02-01

370

EANM Dosimetry Committee guidelines for bone marrow and whole-body dosimetry  

Microsoft Academic Search

Introduction  The level of administered activity in radionuclide therapy is often limited by haematological toxicity resulting from the\\u000a absorbed dose delivered to the bone marrow. The purpose of these EANM guidelines is to provide advice to scientists and clinicians\\u000a on data acquisition and data analysis related to bone-marrow and whole-body dosimetry.\\u000a \\u000a \\u000a \\u000a \\u000a Materials and methods  The guidelines are divided into sections “Data acquisition”

Cecilia Hindorf; Gerhard Glatting; Carlo Chiesa; Ola Lindén; Glenn Flux

2010-01-01

371

Bacterial cellulose gels with high mechanical strength.  

PubMed

A composite structure was formed between polyethylene glycol diacrylate (PEGDA) and bacterial cellulose (BC) gels swollen in polyethylene glycol (PEG) as a solvent (BC/PEG gel) to improve the mechanical strength of the gels. The mechanical strength under compression and the rheostatic properties of the gels were evaluated. The compression test results indicated that the mechanical strength of the gels depended on the weight percent of cross-linked PEGDA in the gel, the chain length between the cross-linking points, and the cross-linking density of PEGDA polymers. The PEGDA polymers around the cellulose fibers were resistant to pressure; thus, the BC/PEG-PEGDA gel was stronger than the BC/PEG gel under compression. The results of transmittance measurements and thermomechanical analysis showed that the rheostatic properties of the gels were retained even after composite structure formation. BC/PEG-PEGDA gels, which are expected to be biocompatible, may be useful for clinical applications as a soft material. PMID:25492172

Numata, Yukari; Sakata, Tadanori; Furukawa, Hidemitsu; Tajima, Kenji

2015-02-01

372

Metal-silica sol-gel materials  

NASA Technical Reports Server (NTRS)

The present invention relates to a single phase metal-silica sol-gel glass formed by the co-condensation of a transition metal with silicon atoms where the metal atoms are uniformly distributed within the sol-gel glass as individual metal centers. Any transition metal may be used in the sol-gel glasses. The present invention also relates to sensor materials where the sensor material is formed using the single phase metal-silica sol-gel glasses. The sensor materials may be in the form of a thin film or may be attached to an optical fiber. The present invention also relates to a method of sensing chemicals using the chemical sensors by monitoring the chromatic change of the metal-silica sol-gel glass when the chemical binds to the sensor. The present invention also relates to oxidation catalysts where a metal-silica sol-gel glass catalyzes the reaction. The present invention also relates to a method of performing oxidation reactions using the metal-silica sol-gel glasses. The present invention also relates to organopolymer metal-silica sol-gel composites where the pores of the metal-silica sol-gel glasses are filled with an organic polymer polymerized by the sol-gel glass.

Stiegman, Albert E. (Inventor)

2002-01-01

373

Generative force of self-oscillating gel.  

PubMed

We succeeded in measuring the generative force of a self-oscillating polymer gel in an aqueous solution comprising the three substrates of the Belousov-Zhabotinsky (BZ) reaction (malonic acid, sodium bromate, and nitric acid) under constant temperature. In this study, we developed an apparatus with a microforce sensor for measuring the generative force of small-sized gels (1 mm(3)). The self-oscillating polymer gel directly converts the chemical energy of the BZ reaction into mechanical work. It was determined that the generative force of the self-oscillating gel was 972 Pa, and the period of self-oscillation was 480 s at 18 °C. We demonstrated that the generative force of the gel was about a hundredth the generative force of a muscle in the body. We analyzed the time dependence of the color change in the self-oscillating polymer gel. The color of the gel changed periodically owing to the cyclic change in the redox state of the Ru moiety, induced by the BZ reaction. The peaks of the waveforms of the generative force and color change were almost identical. This result showed that the generative force was synchronized with the periodical change in the oxidation number of the Ru catalytic moiety in the gel. To understand a theoretical basis for the generative force of a self-oscillating gel, we considered a general theory that is based on the volume phase transition of gel and the two-parameter Oregonator model of the BZ reaction. PMID:24524539

Hara, Yusuke; Mayama, Hiroyuki; Morishima, Keisuke

2014-03-01

374

Evaluation of the breast absorbed dose distribution using the Fricke Xylenol Gel  

NASA Astrophysics Data System (ADS)

During a breast cancer radiotherapy treatment, several issues have to be taken into account, among them, hot spots, gradient of doses delivered over the breast, as well as in the lungs and the heart. The present work aims to apply the Fricke Xylenol Gel (FXG) dosimeter in the study of these issues, using a CCD camera to analyse the dose deposited distribution. Thus, the CCD was used to capture the images of different cuvettes that were filled with FXG and irradiated considering analogous setups employed in breast cancer radiotherapy treatments. Thereafter, these pictures where processed in a MatLab routine and the spatial dose distributions could be evaluated. These distributions were compared with the ones that were obtained from dedicated treatment planning's softwares. According to the results obtained, the FXG, allied with the CCD system, has shown to be a complementary tool in dosimetry, helping to prevent possible complications during breast cancer treatments.

Czelusniak, C.; Del Lama, L. S.; Moreira, M. V.; De Almeida, A.

2010-11-01

375

Improved dosimetry techniques for intravascular brachytherapy  

NASA Astrophysics Data System (ADS)

Coronary artery disease leads to the accumulation of atheromatous plaque leading to coronary stenosis. Coronary intervention techniques such as balloon angioplasty and atherectomy are used to address coronary stenosis and establish a stable lumen thus enhancing blood flow to the myocardium. Restenosis or re-blockage of the arteries is a major limitation of the above mentioned interventional techniques. Neointimal hyperplasia or proliferation of cells in response to the vascular injury as a result of coronary intervention is considered to be one of the major causes of restenosis. Recent studies indicated that irradiation of the coronary lesion site, with radiation doses ranging from 15 to 30 Gy, leads to diminishing neointimal hyperplasia with subsequent reduction in restenosis. The radiation dose is given by catheter-based radiation delivery systems using beta-emitters 90Sr/90Y, 32P and gamma-emitting 192Ir among others. However the dose schema used for dose prescription for these sources are relatively simplistic, and are based on calculations using uniform homogenous water or tissue media and simple cylinder geometry. Stenotic coronary vessels are invariably lined with atheromatous plaque of heterogeneous composition, the radiation dose distribution obtained from such dosimetry data can cause significant variations in the actual dose received by a given patient. Such discrepancies in dose calculation can introduce relatively large uncertainties in the limits of dose window for effective and safe application of intravascular brachytherapy, and consequently in the clinical evaluation of the efficacy of this modality. In this research study we investigated the effect of different geometrical and material heterogeneities, including residual plaque, catheter non-centering, lesion eccentricity and cardiac motion on the radiation dose delivered at the lesion site. Correction factors including dose perturbation factors and dose variation factors have been calculated using Monte Carlo-based radiation transport code MCNP and tabulated for a range of different coronary geometries and different radionuclides. A new technique using imaging techniques such as intravascular ultrasound and angiography to assess dosimetry for realistic coronary arteries is also introduced. The results indicate the need for accurate assessment of post-intervention clinical measurements such as minimal lumen diameter and residual plaque burden and incorporating them into dose calculations.

Sehgal, Varun

376

Hanford External Dosimetry Technical Basis Manual PNL-MA-842  

SciTech Connect

The Hanford External Dosimetry Technical Basis Manual PNL-MA-842 documents the design and implementation of the external dosimetry system used at Hanford. The manual describes the dosimeter design, processing protocols, dose calculation methodology, radiation fields encountered, dosimeter response characteristics, limitations of dosimeter design under field conditions, and makes recommendations for effective use of the dosimeters in the field. The manual describes the technical basis for the dosimetry system in a manner intended to help ensure defensibility of the dose of record at Hanford and to demonstrate compliance with 10 CFR 835, DOELAP, DOE-RL, ORP, PNSO, and Hanford contractor requirements. The dosimetry system is operated by PNNL’s Hanford External Dosimetry Program (HEDP) which provides dosimetry services to all Hanford contractors. The primary users of this manual are DOE and DOE contractors at Hanford using the dosimetry services of PNNL. Development and maintenance of this manual is funded directly by DOE and DOE contractors. Its contents have been reviewed and approved by DOE and DOE contractors at Hanford through the Hanford Personnel Dosimetry Advisory Committee (HPDAC) which is chartered and chaired by DOE-RL and serves as means of coordinating dosimetry practices across contractors at Hanford. This manual was established in 1996. Since inception, it has been revised many times and maintained by PNNL as a controlled document with controlled distribution. Rev. 0 marks the first revision to be released through PNNL’s Electronic Records & Information Capture Architecture (ERICA) database. Revision numbers that are whole numbers reflect major revisions typically involving changes to all chapters in the document. Revision numbers that include a decimal fraction reflect minor revisions, usually restricted to selected chapters or selected pages in the document. Revision Log: Rev. 0 (2/25/2005) Major revision and expansion. Rev. 0.1 (3/12/2007) Minor revision. Updated Chapters 5, 6 and 9 to reflect change in default ring calibration factor used in HEDP dose calculation software. Factor changed from 1.5 to 2.0 beginning January 1, 2007. Pages on which changes were made are as follows: 5.23, 5.69, 5.78, 5.80, 5.82, 6.3, 6.5, 6.29, 9.2.

Rathbone, Bruce A.

2007-03-12

377

Hanford External Dosimetry Technical Basis Manual PNL-MA-842  

SciTech Connect

The Hanford External Dosimetry Technical Basis Manual PNL-MA-842 documents the design and implementation of the external dosimetry system used at the U.S. Department of Energy (DOE) Hanford site. The manual describes the dosimeter design, processing protocols, dose calculation methodology, radiation fields encountered, dosimeter response characteristics, limitations of dosimeter design under field conditions, and makes recommendations for effective use of the dosimeters in the field. The manual describes the technical basis for the dosimetry system in a manner intended to help ensure defensibility of the dose of record at Hanford and to demonstrate compliance with requirements of 10 CFR 835, the DOE Laboratory Accreditation Program, the DOE Richland Operations Office, DOE Office of River Protection, DOE Pacific Northwest Office of Science, and Hanford’s DOE contractors. The dosimetry system is operated by the Pacific Northwest National Laboratory (PNNL) Hanford External Dosimetry Program which provides dosimetry services to PNNL and all Hanford contractors. The primary users of this manual are DOE and DOE contractors at Hanford using the dosimetry services of PNNL. Development and maintenance of this manual is funded directly by DOE and DOE contractors. Its contents have been reviewed and approved by DOE and DOE contractors at Hanford through the Hanford Personnel Dosimetry Advisory Committee which is chartered and chaired by DOE-RL and serves as means of coordinating dosimetry practices across contractors at Hanford. This manual was established in 1996. Since its inception, it has been revised many times and maintained by PNNL as a controlled document with controlled distribution. The first revision to be released through PNNL’s Electronic Records & Information Capture Architecture database was designated Revision 0. Revision numbers that are whole numbers reflect major revisions typically involving significant changes to all chapters in the document. Revision numbers that include a decimal fraction reflect minor revisions, usually restricted to selected chapters or selected pages in the document. Maintenance and distribution of controlled hard copies of the manual by PNNL was discontinued beginning with Revision 0.2.

Rathbone, Bruce A.

2011-04-04

378

Hanford External Dosimetry Technical Basis Manual PNL-MA-842  

SciTech Connect

The Hanford External Dosimetry Technical Basis Manual PNL-MA-842 documents the design and implementation of the external dosimetry system used at the U.S. Department of Energy (DOE) Hanford site. The manual describes the dosimeter design, processing protocols, dose calculation methodology, radiation fields encountered, dosimeter response characteristics, limitations of dosimeter design under field conditions, and makes recommendations for effective use of the dosimeters in the field. The manual describes the technical basis for the dosimetry system in a manner intended to help ensure defensibility of the dose of record at Hanford and to demonstrate compliance with requirements of 10 CFR 835, the DOE Laboratory Accreditation Program, the DOE Richland Operations Office, DOE Office of River Protection, DOE Pacific Northwest Office of Science, and Hanford’s DOE contractors. The dosimetry system is operated by the Pacific Northwest National Laboratory (PNNL) Hanford External Dosimetry Program which provides dosimetry services to PNNL and all Hanford contractors. The primary users of this manual are DOE and DOE contractors at Hanford using the dosimetry services of PNNL. Development and maintenance of this manual is funded directly by DOE and DOE contractors. Its contents have been reviewed and approved by DOE and DOE contractors at Hanford through the Hanford Personnel Dosimetry Advisory Committee which is chartered and chaired by DOE-RL and serves as means of coordinating dosimetry practices across contractors at Hanford. This manual was established in 1996. Since its inception, it has been revised many times and maintained by PNNL as a controlled document with controlled distribution. The first revision to be released through PNNL’s Electronic Records & Information Capture Architecture database was designated Revision 0. Revision numbers that are whole numbers reflect major revisions typically involving significant changes to all chapters in the document. Revision numbers that include a decimal fraction reflect minor revisions, usually restricted to selected chapters or selected pages in the document. Maintenance and distribution of controlled hard copies of the manual by PNNL was discontinued beginning with Revision 0.2.

Rathbone, Bruce A.

2010-04-01

379

Student Perceptions of an Online Medical Dosimetry Program  

SciTech Connect

The University of Wisconsin-La Crosse offers the first online medical dosimetry program in the nation. There is no data to research a program of this type. This research consisted of the evaluation of other distance education programs including health profession programs in addition to face-to-face medical dosimetry programs. There was a need to collect and analyze student perceptions of online learning in medical dosimetry. This research provided a guide for future implementation by other programs as well as validated the University of Wisconsin-La Crosse program. Methodology used consisted of an electronic survey sent to all previous and currently enrolled students in the University of Wisconsin-La Crosse medical dosimetry program. The survey was both quantitative and qualitative in demonstrating attitudinal perceptions of students in the program. Quantitative data was collected and analyzed using a 5-point Likert scale. Qualitative data was gathered based on the open-ended responses and the identifying themes from the responses. The results demonstrated an overall satisfaction with this program, the instructor, and the online courses. Students felt a sense of belonging to the courses and the program. Considering that a majority of the students had never taken an online course previously, the students felt there were no technology issues. Future research should include an evaluation of board exam statistics for students enrolled in the online and face-to-face medical dosimetry programs.

Lenards, Nishele, E-mail: lenards.nish@uwlax.ed [Department of Health Professions/College of Science and Health, Medical Dosimetry Program, University of Wisconsin-La Crosse, La Crosse, WI (United States)

2011-07-01

380

Neutron dosimetry for a general 252Cf brachytherapy source.  

PubMed

This paper extends previous work to characterize neutron dosimetry in the vicinity of 252Cf brachytherapy sources. A general source is examined with an arbitrary length, diameter, and encapsulation using Monte Carlo methods. Fast neutron dosimetry and thermal neutron fluence rates were determined in a variety of clinically relevant media of varying dimensions. Applicator Tube, point source, high dose rate VariSource, and high dose rate muSelectron source geometries were analyzed. Fast neutron dosimetry was relatively independent of encapsulation thickness for an assortment of encapsulation materials less than 2 mm thick. Large variations in phantom size made minimal differences in the fast neutron dose close to the source. Specific source geometries were compared with dosimetry obtained from a simplified point model. The consequence of these results is a convenient means of accurately predicting clinical fast neutron dosimetry characteristics around a general 252Cf brachytherapy source in a variety of media without requiring neutron transport. Thermal neutron fluence rates were determined for a variety of source encapsulation materials, encapsulation thicknesses, and phantom sizes. At a distance of 3 cm from the source center, the thermal neutron fluence rate for a 30 cm diameter phantom was a 2.65 times greater than for a 10 cm diameter water phantom. These results demonstrate 252Cf thermal neutron fluence rate is relatively independent of encapsulation thickness and composition, yet highly dependent on hydrogen mass density and phantom size for phanta with diameters <30 cm. PMID:11190964

Rivard, M J

2000-12-01

381

Automated apparatus for producing gradient gels  

DOEpatents

Apparatus for producing a gradient gel which serves as a standard medium for a two-dimensional analysis of proteins, the gel having a density gradient along its height formed by a variation in gel composition, with the apparatus including first and second pumping means each including a plurality of pumps on a common shaft and driven by a stepping motor capable of providing small incremental changes in pump outputs for the gel ingredients, the motors being controlled, by digital signals from a digital computer, a hollow form or cassette for receiving the gel composition, means for transferring the gel composition including a filler tube extending near the bottom of the cassette, adjustable horizontal and vertical arms for automatically removing and relocating the filler tube in the next cassette, and a digital computer programmed to automatically control the stepping motors, arm movements, and associated sensing operations involving the filling operation.

Anderson, Norman L. (Clarendon Hills, IL)

1986-01-01

382

Automated apparatus for producing gradient gels  

DOEpatents

Apparatus for producing a gradient gel which serves as a standard medium for a two-dimensional analysis of proteins, the gel having a density gradient along its height formed by a variation in gel composition, with the apparatus including first and second pumping means each including a plurality of pumps on a common shaft and driven by a stepping motor capable of providing small incremental changes in pump outputs for the gel ingredients, the motors being controlled, by digital signals from a digital computer, a hollow form or cassette for receiving the gel composition, means for transferring the gel composition including a filler tube extending near the bottom of the cassette, adjustable horizontal and vertical arms for automatically removing and relocating the filler tube in the next cassette, and a digital computer programmed to automatically control the stepping motors, arm movements, and associated sensing operations involving the filling operation.

Anderson, N.L.

1983-11-10

383

Active gel model of amoeboid cell motility  

NASA Astrophysics Data System (ADS)

We develop a model of amoeboid cell motility based on active gel theory. Modeling the motile apparatus of a eukaryotic cell as a confined layer of finite length of poroelastic active gel permeated by a solvent, we first show that, due to active stress and gel turnover, an initially static and homogeneous layer can undergo a contractile-type instability to a polarized moving state in which the rear is enriched in gel polymer. This agrees qualitatively with motile cells containing an actomyosin-rich uropod at their rear. We find that the gel layer settles into a steadily moving, inhomogeneous state at long times, sustained by a balance between contractility and filament turnover. In addition, our model predicts an optimal value of the gel-substrate adhesion leading to maximum layer speed, in agreement with cell motility assays. The model may be relevant to motility of cells translocating in complex, confining environments that can be mimicked experimentally by cell migration through microchannels.

Callan-Jones, A. C.; Voituriez, R.

2013-02-01

384

Monochromatic beam characterization for Auger electron dosimetry and radiotherapy.  

PubMed

Dosimetry for Auger electron radiotherapy using monochromatic photon beams requires knowledge of beam characteristics. This study characterized a 35-keV photon beam generated at the LSU/CAMD synchrotron. Beam energy was measured by Compton spectroscopy and Si640c powder diffraction. Photon spatial distribution and virtual source position were measured using radiochromic film. Central-axis fluence was determined from Compton scattering measurements and application of the Klein-Nishina cross-section with percent polarization fit to results at 2-4 scattering angles. Broad-beam fluence was combined with MCNP5 Monte Carlo dose per fluence calculations to generate dose versus depth in a polymethylmethacrylate phantom, which was compared to ionization chamber and radiochromic film depth-dose measurements. For 22-41 keV beams, diffraction-based and Compton-based energy measurements agreed to within -0.1+/-0.3 and 0.6+/-0.3 keV, respectively, of monochromator calibrated energies. At 35 eV and 0.66 cm depth, dose uniformity over 80% of the 2.8 cm x 2.5 cm beam varied from 105 to 78% of the central-axis value horizontally and from 90 to 100% vertically. Narrow-beam divergence yielded vertical and horizontal virtual source-to-surface distances of 3.8+/-0.2 and 15.7+/-1.0m, respectively. Incident fluence rates for a 35-keV beam (100 mA ring current) ranged from 1.181+/-0.011 x 10(11) to 3.053+/-0.004 x 10(11)photons cm(-2)s(-1) with approximately 100% polarization in the horizontal plane. Ion chamber and film dose measurements underestimated MCNP5-based dose by an average of 6.4+/-0.8 and 9.1+/-0.8%, respectively, over measured depths. These practical beam characterization methods should allow subsequent Monte Carlo dose calculations needed for planning future radiotherapy studies. Although simulated and measured depth-dose curves agree well in shape, improvement in absolute dose is desirable. PMID:18599232

Dugas, Joseph P; Oves, Scott D; Sajo, Erno; Matthews, Kenneth L; Ham, Kyungmin; Hogstrom, Kenneth R

2008-12-01

385

The cytogenetic dosimetry of recent accidental overexposure.  

PubMed

When accidental exposure to ionizing radiations is suspected, optimal choice of a treatment strategy requires, in addition to information about the clinical signs and physical dosimetry, a determination by biological parameters of the dose received. The scoring of unstable chromosomal aberrations in peripheral blood lymphocytes is the current reference method. Preparation of these samples depends on the goal sought--an exact assessment of several irradiations or rapid triage in the case of a large-scale accident. Moreover, some adaptation may be necessary if the irradiation is either heterogenous or not recent. Despite the robustness and adaptability of this procedure, conventional cytogenetics remains a tedious and time-consuming technique, and it requires specialized staff. Scoring micronuclei in binucleated lymphocytes may be an easier, simpler altemative to a dicentric assay. This paper, which is based on the experience acquired by the IPSN in recent years in expert assessment of suspected radiations, has as its goal to provide a succinct technical guideline of these different approaches, as they are adapted to suspected recent irradiation and triage. PMID:11441964

Voisin, P; Benderitter, M; Claraz, M; Chambrette, V; Sorokine-Durm, I; Delbos, M; Durand, V; Leroy, A; Paillole, N

2001-05-01

386

Mayak worker dosimetry study: an overview.  

PubMed

The Mayak Production Association (MPA) was the first plutonium production plant in the former Soviet Union. Workers at the MPA were exposed to relatively large internal radiation intakes and external radiation exposures, particularly in the early years of plant operations. This paper describes the updated dosimetry database, "Doses-2005." Doses-2005 represents a significant improvement in the determination of absorbed organ dose from external radiation and plutonium intake for the original cohort of 18,831 Mayak workers. The methods of dose reconstruction of absorbed organ doses from external radiation uses: 1) archive records of measured dose and worker exposure history, 2) measured energy and directional response characteristics of historical Mayak film dosimeters, and 3) calculated dose conversion factors for Mayak Study-defined exposure scenarios using Monte Carlo techniques. The methods of dose reconstruction for plutonium intake uses two revised models developed from empirical data derived from bioassay and autopsy cases and/or updates from prevailing or emerging International Commission on Radiological Protection models. Other sources of potential significant exposure to workers such as medical diagnostic x-rays, ambient onsite external radiation, neutron radiation, intake of airborne effluent, and intake of nuclides other than plutonium were evaluated to determine their impact on the dose estimates. PMID:17693770

Vasilenko, E K; Khokhryakov, V F; Miller, S C; Fix, J J; Eckerman, K; Choe, D O; Gorelov, M; Khokhryakov, V V; Knyasev, V; Krahenbuhl, M P; Scherpelz, R I; Smetanin, M; Suslova, K; Vostrotin, V

2007-09-01

387

Calibration facility for environment dosimetry instruments  

NASA Astrophysics Data System (ADS)

In the last ten years, the nuclear activities, as well as the major nuclear events (see Fukushima accident) had an increasing impact on the environment, merely by contamination with radioactive materials. The most conferment way to quickly identify the presence of some radioactive elements in the environment, is to measure the dose-equivalent rate H. In this situation, information concerning the values of H due only to the natural radiation background must exist. Usually, the values of H due to the natural radiation background, are very low (˜10-9 - 10-8 Sv/h). A correct measurement of H in this range involve a performing calibration of the measuring instruments in the measuring range corresponding to the natural radiation background lead to important problems due to the presence of the natural background itself the best way to overlap this difficulty is to set up the calibration stand in an area with very low natural radiation background. In Romania, we identified an area with such special conditions at 200 m dept, in a salt mine. This paper deals with the necessary requirements for such a calibration facility, as well as with the calibration stand itself. The paper includes also, a description of the calibration stand (and images) as well as the radiological and metrological parameters. This calibration facilities for environment dosimetry is one of the few laboratories in this field in Europe.

Bercea, Sorin; Celarel, Aurelia; Cenusa, Constantin

2013-12-01

388

Personnel neutron dosimetry using CR-39 foils  

SciTech Connect

We are using CR-39 foils for personnel nuetron dosimetry at the Lawrence Livermore National Laboratory. We have developed a three-step electrochemical etching procedure that includes low-frequency electrochemical etching at low frequency and at elevated temperatures. Our first etching step is at 60 Hz, 3000 V for 5 hours in a 60/sup 0/C oven using 6.5 N KOH. The second etching step consists of an additional 23-minute etch at 60/sup 0/C, 2.0 kHz, and 3000 V, which increases the track size and makes them relatively uniform in size. The final step is a 15-minute post etch at 60/sup 0/C, which gives the tracks a smoother appearance. The foils are etched in etch chambers that can etch up to 24 foils. Several of these chambers can be used simultaneously with a single power supply. These chambers are rugged and have been used daily for over a year. 8 refs., 6 figs., 1 tab.

Hankins, D.E.; Homann, S.; Westermark, J.

1987-01-13

389

Intraoperative dynamic dosimetry for prostate implants  

NASA Astrophysics Data System (ADS)

This paper describes analytic tools in support of a paradigm shift in brachytherapy treatment planning for prostate cancer - a shift from standard pre-planning to intraoperative planning using dosimetric feedback based on the actual deposited seed positions within the prostate. The method proposed is guided by several desiderata: (a) bringing both planning and evaluation in the operating room (i.e. make post-implant evaluation superfluous) therefore making rectifications - if necessary - still achievable; (b) making planning and implant evaluation consistent by using the same imaging system (ultrasound); and (c) using only equipment commonly found in a hospital operating room. The intraoperative dosimetric evaluation is based on the fusion between ultrasound images and 3D seed coordinates reconstructed from fluoroscopic projections. Automatic seed detection and registration of the fluoroscopic and ultrasound information, two of the three key ingredients needed for the intraoperative dynamic dosimetry optimization (IDDO), are explained in detail. The third one, the reconstruction of 3D coordinates from projections, was reported in a previous article. The algorithms were validated using a custom-designed phantom with non-radioactive (dummy) seeds. Also, fluoroscopic images were taken at the conclusion of an actual permanent prostate implant and compared with data on the same patient obtained from radiographic-based post-implant evaluation. To offset the effect of organ motion the comparison was performed in terms of the proximity function of the two seed distributions. The agreement between the intra- and post-operative seed distributions was excellent.

Todor, D. A.; Zaider, M.; Cohen, G. N.; Worman, M. F.; Zelefsky, M. J.

2003-05-01

390

Biological dosimetry by interphase chromosome painting  

NASA Technical Reports Server (NTRS)

Both fluorescence in situ hybridization of metaphase spreads with whole-chromosome probes and premature chromosome condensation in interphase nuclei have been used in the past to estimate the radiation dose to lymphocytes. We combined these techniques to evaluate the feasibility of using painted interphase chromosomes for biodosimetry. Human peripheral lymphocytes were exposed to gamma rays and fused to mitotic Chinese hamster cells either immediately after irradiation or after 8 h incubation at 37 degrees C. Interphase or metaphase human chromosomes were hybridized with a composite probe specific for human chromosomes 3 and 4. The dose-response curve for fragment induction immediately after irradiation was linear; these results reflected breakage frequency in the total genome in terms of DNA content per chromosome. At 8 h after irradiation, the dose-response curve for chromosome interchanges, the prevalent aberration in interphase chromosomes, was linear-quadratic and similar to that observed for metaphase chromosomes. These results suggest that painting prematurely condensed chromosomes can be useful for biological dosimetry when blood samples are available shortly after the exposure, or when interphase cells are to be scored instead of mitotic cells.

Durante, M.; George, K.; Yang, T. C.

1996-01-01

391

Western Blot Protocol 1. Cast Gel  

E-print Network

resolution gel (recipe) and mix Make stacking gel (recipe) à diwater--acrylamide/bis Add 7.5ml of res gel __________________________ul in plates and rock 1hr. (Could stop here and put in 4 o over night.) ***SAVE AB*** Add 10ml ______________________________ul à Rock 30 min. / pour out milk Add 10ml milkà rock 10 min. / pour out Repeat Wash with 15ml

Ye, Jianping

392

Performance evaluation of an improved optical computed tomography polymer gel dosimeter system for 3D dose verification of static and dynamic phantom deliveries  

SciTech Connect

The performance of a next-generation optical computed tomography scanner (OCTOPUS-5X) is characterized in the context of three-dimensional gel dosimetry. Large-volume (2.2 L), muscle-equivalent, radiation-sensitive polymer gel dosimeters (BANG-3) were used. Improvements in scanner design leading to shorter acquisition times are discussed. The spatial resolution, detectable absorbance range, and reproducibility are assessed. An efficient method for calibrating gel dosimeters using the depth-dose relationship is applied, with photon- and electron-based deliveries yielding equivalent results. A procedure involving a preirradiation scan was used to reduce the edge artifacts in reconstructed images, thereby increasing the useful cross-sectional area of the dosimeter by nearly a factor of 2. Dose distributions derived from optical density measurements using the calibration coefficient show good agreement with the treatment planning system simulations and radiographic film measurements. The feasibility of use for motion (four-dimensional) dosimetry is demonstrated on an example comparing dose distributions from static and dynamic delivery of a single-field photon plan. The capability to visualize three-dimensional dose distributions is also illustrated.

Lopatiuk-Tirpak, O.; Langen, K. M.; Meeks, S. L.; Kupelian, P. A.; Zeidan, O. A.; Maryanski, M. J. [Department of Radiation Oncology, M. D. Anderson Cancer Center Orlando, Orlando, Florida 32806 (United States); MGS Research, Inc., Madison, Connecticut 06443 (United States)

2008-09-15

393

21 CFR 866.4900 - Support gel.  

Code of Federal Regulations, 2014 CFR

...AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES IMMUNOLOGY AND MICROBIOLOGY DEVICES Immunology Laboratory Equipment and Reagents § 866.4900 Support gel. (a)...

2014-04-01

394

21 CFR 866.4900 - Support gel.  

Code of Federal Regulations, 2011 CFR

...AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES IMMUNOLOGY AND MICROBIOLOGY DEVICES Immunology Laboratory Equipment and Reagents § 866.4900 Support gel. (a)...

2011-04-01

395

21 CFR 866.4900 - Support gel.  

Code of Federal Regulations, 2012 CFR

...AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES IMMUNOLOGY AND MICROBIOLOGY DEVICES Immunology Laboratory Equipment and Reagents § 866.4900 Support gel. (a)...

2012-04-01

396

21 CFR 866.4900 - Support gel.  

Code of Federal Regulations, 2010 CFR

...AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES IMMUNOLOGY AND MICROBIOLOGY DEVICES Immunology Laboratory Equipment and Reagents § 866.4900 Support gel. (a)...

2010-04-01

397

21 CFR 866.4900 - Support gel.  

Code of Federal Regulations, 2013 CFR

...AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES IMMUNOLOGY AND MICROBIOLOGY DEVICES Immunology Laboratory Equipment and Reagents § 866.4900 Support gel. (a)...

2013-04-01

398

Food gels: gelling process and new applications.  

PubMed

Food gels are viscoelastic substances and several gelled products are manufactured throughout the world. The gelling agents in foods are usually polysaccharides and proteins. In food gels, the polymer molecules are not cross-linked by covalent bonds with the exception of disulphide bonds in some protein gels. Instead, the molecules are held together by a combination of weak inter-molecular forces like hydrogen bonds, electrostatic forces, Van der Waals forces, and hydrophobic interactions. Polysaccharides including hydrocolloids are strongly hydrated in aqueous medium but they tend to have less ordered structures. The mechanism of gelation depends on the nature of the gelling agent(s) and on the conditions of gel formation like the temperature, the presence of ions, the pH, and the concentration of gelling agents, etc. Characterization of gels can be performed in several ways of which rheological measurements are frequently practiced. Multi-component or mixed gel system is an important area of interest in which two or more gelling components are simultaneously used to achieve certain specific structural and functional characteristics. We here discuss about the different gels and gelling agents, the characterization of gels, and the mechanism of gelation with an emphasis on mixed or multi-component gels that would have significant commercial applications. PMID:22332597

Banerjee, Soumya; Bhattacharya, Suvendu

2012-01-01

399

Conducting Polymer Electrodes for Gel Electrophoresis  

PubMed Central

In nearly all cases, electrophoresis in gels is driven via the electrolysis of water at the electrodes, where the process consumes water and produces electrochemical by-products. We have previously demonstrated that ?-conjugated polymers such as poly(3,4-ethylenedioxythiophene) (PEDOT) can be placed between traditional metal electrodes and an electrolyte to mitigate electrolysis in liquid (capillary electroosmosis/electrophoresis) systems. In this report, we extend our previous result to gel electrophoresis, and show that electrodes containing PEDOT can be used with a commercial polyacrylamide gel electrophoresis system with minimal impact to the resulting gel image or the ionic transport measured during a separation. PMID:24586761

Bengtsson, Katarina; Nilsson, Sara; Robinson, Nathaniel D.

2014-01-01

400

Gel catalysts that switch on and off.  

PubMed

We report development of a polymer gel with a catalytic activity that can be switched on and off when the solvent composition is changed. The gel consists of two species of monomers. The major component, N-isopropylacrylamide, makes the gel swell and shrink in response to a change in composition of ethanol/water mixtures. The minor component, vinylimidazole, which is capable of catalysis, is copolymerized into the gel network. The reaction rate for catalytic hydrolysis of p-nitrophenyl caprylate was small when the gel was swollen. In contrast, when the gel was shrunken, the reaction rate increased 5 times. The activity changes discontinuously as a function of solvent composition, thus the catalysis can be switched on and off by an infinitesimal change in solvent composition. The kinetics of catalysis by the gel in the shrunken state is well described by the Michaelis-Menten formula, indicating that the absorption of the substrate by the hydrophobic environment created by the N-isopropylacrylamide polymer in the shrunken gel is responsible for enhancement of catalytic activity. In the swollen state, the rate vs. active site concentration is linear, indicating that the substrate absorption is not a primary factor determining the kinetics. Catalytic activity of the gel is studied for substrates with various alkyl chain lengths; of those studied the switching effect is most pronounced for p-nitrophenyl caprylate. PMID:10954747

Wang, G; Kuroda, K; Enoki, T; Grosberg, A; Masamune, S; Oya, T; Takeoka, Y; Tanaka, T

2000-08-29

401

Tissue simulating gel for medical research  

NASA Technical Reports Server (NTRS)

A tissue simulating gel and a method for preparing the tissue simulating gel are disclosed. The tissue simulating gel is prepared by a process using water, gelatin, ethylene glycol, and a cross-linking agent. In order to closely approximate the characteristics of the type of tissue being simulated, other material has been added to change the electrical, sound conducting, and wave scattering properties of the tissue simulating gel. The result of the entire process is a formulation that will not melt at the elevated temperatures involved in hyperthermia medical research. Furthermore, the tissue simulating gel will not support mold or bacterial growth, is of a sufficient mechanical strength to maintain a desired shape without a supporting shell, and is non-hardening and non-drying. Substances have been injected into the tissue simulating gel prior to the setting-up thereof just as they could be injected into actual tissue, and the tissue simulating gel is translucent so as to permit visual inspection of its interior. A polyurethane spray often used for coating circuit boards can be applied to the surface of the tissue simulating gel to give a texture similar to human skin, making the tissue simulating gel easier to handle and contributing to its longevity.

Companion, John A. (Inventor)

1991-01-01

402

Production and characterization of spodumene dosimetric pellets prepared by a sol-gel route  

NASA Astrophysics Data System (ADS)

Spodumene is an aluminosilicate that has shown good results for high-dose TL dosimetry for beta or gamma rays. Due to its chemical composition (LiAlSi2O6) it has potential to be used as a neutron dosimeter. The synthetic spodumene is usually produced by solid state reaction and conventional sol-gel, whose shortcomings arise from the need to employ high temperatures and high cost reagents, respectively. Proteic sol-gel method is promising, because it can reduce production costs and the possibility of environmental contamination. This work reports the production of the spodumene by the proteic sol-gel method using edible unflavored gelatin as a precursor. The product is characterized physically and morphologically, and investigated its applicability as a TL dosimeter. Two sets of samples were prepared using different sources of silicon, one with TEOS (Si(OC3H5)4) and one with SILICA (SiO2). The materials produced were characterized by X-ray diffraction, differential thermal analysis and thermogravimetry in order to evaluate the structural properties, as well as possible changes in physical or chemical properties depending on the temperature. The production of spodumene was successful, with generation of the crystals in the ?-phase with tetragonal structure. Sintered pellets produced from these crystals were irradiated with a 90Sr-90Y source and their TL glow curves were evaluated. Although the samples prepared by the proteic sol-gel method with TEOS presented a lower forming temperature, the samples produced with SILICA showed higher sensitivity to radiation.

Lima, H. R. B. R.; Nascimento, D. S.; Bispo, G. F. C.; Teixeira, V. C.; Valério, M. E. G.; Souza, S. O.

2014-11-01

403

Two-dimensional gel electrophoresis image registration using block-matching techniques and deformation models.  

PubMed

Block-matching techniques have been widely used in the task of estimating displacement in medical images, and they represent the best approach in scenes with deformable structures such as tissues, fluids, and gels. In this article, a new iterative block-matching technique-based on successive deformation, search, fitting, filtering, and interpolation stages-is proposed to measure elastic displacements in two-dimensional polyacrylamide gel electrophoresis (2D-PAGE) images. The proposed technique uses different deformation models in the task of correlating proteins in real 2D electrophoresis gel images, obtaining an accuracy of 96.6% and improving the results obtained with other techniques. This technique represents a general solution, being easy to adapt to different 2D deformable cases and providing an experimental reference for block-matching algorithms. PMID:24613260

Rodriguez, Alvaro; Fernandez-Lozano, Carlos; Dorado, Julian; Rabuñal, Juan R

2014-06-01

404

Principles of Gel Permeation Chromatography  

NSDL National Science Digital Library

Principles of Gel Permeation Chromatography presents the principles of gel permeation chromatography (GPC) for students in introductory undergraduate courses of chemistry and biochemistry. These principles are presented in four sections: Introduction, Real Lab, Virtual Lab, and Microscopic Model. The Introduction and Real Lab sections present a brief view of the basic experimental apparatus typically used in laboratory GPC in order to provide a concrete connection of the real process of separation. The basic elements of column chromatography, emphasizing the stationary and mobile phases, are presented in the Introduction, followed by a sequence of pictures and texts describing major steps in GPC analysis in the Real Lab section. The Virtual Lab section is a simulator. Three samples are available for a virtual GPC experiment: sample 1, containing hemoglobin; sample 2, containing methylene blue; and sample 3, containing both methylene blue and hemoglobin. Each sample undergoes a virtual separation run, which is dynamically represented in three ways in the software: a virtual column, the collected fractions, and a virtual chromatogram. This threefold representation allows the simultaneous view of key aspects of the process to demonstrate the correlation between the experimental procedure and the resulting chromatogram.

405

Introduction Observations PSF fitting Photometry Results Defocused PSF-fitting Photometry  

E-print Network

Introduction Observations PSF fitting Photometry Results Defocused PSF-fitting Photometry Ro Parviainen Defocused PSF-fitting Photometry #12;Introduction Observations PSF fitting Photometry Results 1 Introduction The light curve Defocused PSF 2 Observations Observations 3 PSF fitting Photometry PSF model 1 PSF

Pinfield, David J.

406

Dosimetry and cross section measurements at RTNS II  

SciTech Connect

Numerous measurements have been conducted at TRNS-II in order to map the neutron field for materials irradiations, to measure activation cross sections, and to measure helium production cross sections. Experiments of up to two weeks duration irradiated large numbers of activation dosimetry and helium samples both close to the source and throughout the target room. Many other samples have been irradiated in piggy-back positions over periods lasting many months. All of these experiments fall into four main classes, namely, fluence-mapping, activation dosimetry, the production of long-lived isotopes, and helium generation measurements. Radiometric dosimetry and activation cross section measurements were performed at Argonne National Laboratory; helium production was measured at Rockwell International Corporation. This paper briefly summarizes the principal results of our measurements at RTNS-II; references are given for more detailed publications. 14 refs., 4 figs.

Greenwood, L.R.; Kneff, D.W.

1987-01-01

407

Topical Review: Optically stimulated luminescence (OSL) dosimetry in medicine  

NASA Astrophysics Data System (ADS)

This paper reviews fundamental and practical aspects of optically stimulated luminescence (OSL) dosimetry pertaining to applications in medicine, having particularly in mind new researchers and medical physicists interested in gaining familiarity with the field. A basic phenomenological model for OSL is presented and the key processes affecting the outcome of an OSL measurement are discussed. Practical aspects discussed include stimulation modalities (continuous-wave OSL, pulsed OSL and linear modulation OSL), basic experimental setup, available OSL readers, optical fiber systems and basic properties of available OSL dosimeters. Finally, results from the recent literature on applications of OSL in radiotherapy, radiodiagnostics and heavy charged particle dosimetry are discussed in light of the theoretical and practical framework presented in this review. Open questions and future challenges in OSL dosimetry are highlighted as a guide to the research needed to further advance the field.

Yukihara, E. G.; McKeever, S. W. S.

2008-10-01

408

Instability of viscous flow over a deformable two-layered gel: Experiments and theory  

NASA Astrophysics Data System (ADS)

The instability of the flow of a viscous fluid past a soft, two-layered gel is probed using experiments, and the observations are compared with results from a linear stability analysis. The experimental system consists of the rotating top plate of a rheometer and its stationary bottom plate on which the two-layer gel is placed. When the flow between the top plate and the two-layer gel is viscometric (i.e., laminar), the viscosity obtained from the rheometer is a measure of the material property of the fluid. However, after a critical shear stress, there is a sudden increase in apparent viscosity, indicating that the flow has undergone an instability due to the deformable nature of the two-layer gel. Experiments are carried out to quantify how the critical value of fluid shear stress required to destabilize the flow varies as a function of ratio of solid to fluid layer thickness, and the ratio of the shear moduli of the two gels. A linear stability analysis is carried out for plane Couette flow of a Newtonian fluid past the two-layered gel, by assuming the two solid layers to be elastic neo-Hookean materials. In order to compare the experimental and theoretical results, the effective shear modulus (Geff, defined by H /Geff=H1/G1+H2/G2) of the two-layer gel is found to be useful, where H =H1+H2. Here, Hi and Gi (i =1,2), respectively, denote the thickness and shear modulus of each layer. Results for the nondimensional parameter ?eff=?V/(dGeff) (V is the velocity of the top plate; ? is fluid viscosity, d is the fluid thickness) as a function of solid to fluid thickness H /d obtained from the stability analysis agree well with experimental observations, without any fitting parameters. In general, we find that the flow is more unstable if the softer gel is adjacent to the fluid flow compared to the case when it is not. This suggests that the instability is more interfacial in nature and is crucially dependent on the relative placement of the two layers, and not just on the effective modulus of the two-layer gel. We further show that the theoretical and experimental data for two-layer gels can be suitably collapsed onto the results obtained for a single-gel layer.

Neelamegam, R.; Giribabu, D.; Shankar, V.

2014-10-01

409

EURADOS trial performance test for neutron personal dosimetry.  

PubMed

This paper reports on the results of a neutron trial performance test sponsored by the European Commission and organised by EURADOS. As anticipated, neutron dosimetry results were very dependent on the dosemeter type and the dose calculation algorithm. Fast neutron fields were generally well measured, but particular problems were noted in the determination of intermediate energy fields and large incident angles, demonstrating the difficulties of neutron personal dosimetry. Of particular concern from a radiological protection point of view was the large number of results underestimating personal dose equivalent. A considerable over-response was noted in a few cases. PMID:11586722

Bordy, J M; Stadtmann, H; Ambrosi, P; Bartlett, D T; Christensen, P; Colgan, T; Hyvönen, H

2001-01-01

410

Current state of the art brachytherapy treatment planning dosimetry algorithms.  

PubMed

Following literature contributions delineating the deficiencies introduced by the approximations of conventional brachytherapy dosimetry, different model-based dosimetry algorithms have been incorporated into commercial systems for (192)Ir brachytherapy treatment planning. The calculation settings of these algorithms are pre-configured according to criteria established by their developers for optimizing computation speed vs accuracy. Their clinical use is hence straightforward. A basic understanding of these algorithms and their limitations is essential, however, for commissioning; detecting differences from conventional algorithms; explaining their origin; assessing their impact; and maintaining global uniformity of clinical practice. PMID:25027247

Papagiannis, P; Pantelis, E; Karaiskos, P

2014-09-01

411

Personal nuclear accident dosimetry at Sandia National Laboratories  

SciTech Connect

DOE installations possessing sufficient quantities of fissile material to potentially constitute a critical mass, such that the excessive exposure of personnel to radiation from a nuclear accident is possible, are required to provide nuclear accident dosimetry services. This document describes the personal nuclear accident dosimeter (PNAD) used by SNL and prescribes methodologies to initially screen, and to process PNAD results. In addition, this report describes PNAD dosimetry results obtained during the Nuclear Accident Dosimeter Intercomparison Study (NAD23), held during 12-16 June 1995, at Los Alamos National Laboratories. Biases for reported neutron doses ranged from -6% to +36% with an average bias of +12%.

Ward, D.C.; Mohagheghi, A.H. [Sandia National Labs., Albuquerque, NM (United States); Burrows, R. [Nuclear Regulatory Commission, Lisle, IL (United States). Division of Nuclear Material Safety

1996-09-01

412

Hanford Internal Dosimetry Program Manual, PNL-MA-552  

SciTech Connect

This manual is a guide to the services provided by the Hanford Internal Dosimetry Program (IDP), which is operated by the Pacific Northwest National Laboratory.( ) for the U.S. Department of Energy Richland Operations Office, Office of River Protection and their Hanford Site contractors. The manual describes the roles of and relationships between the IDP and the radiation protection programs of the Hanford Site contractors. Recommendations and guidance are also provided for consideration in implementing bioassay monitoring and internal dosimetry elements of radiation protection programs.

Carbaugh, Eugene H.; Bihl, Donald E.; Maclellan, Jay A.

2009-09-24

413

Computational high-resolution heart phantoms for medical imaging and dosimetry simulations  

NASA Astrophysics Data System (ADS)

Cardiovascular disease in general and coronary artery disease (CAD) in particular, are the leading cause of death worldwide. They are principally diagnosed using either invasive percutaneous transluminal coronary angiograms or non-invasive computed tomography angiograms (CTA). Minimally invasive therapies for CAD such as angioplasty and stenting are rendered under fluoroscopic guidance. Both invasive and non-invasive imaging modalities employ ionizing radiation and there is concern for deterministic and stochastic effects of radiation. Accurate simulation to optimize image quality with minimal radiation dose requires detailed, gender-specific anthropomorphic phantoms with anatomically correct heart and associated vasculature. Such phantoms are currently unavailable. This paper describes an open source heart phantom development platform based on a graphical user interface. Using this platform, we have developed seven high-resolution cardiac/coronary artery phantoms for imaging and dosimetry from seven high-quality CTA datasets. To extract a phantom from a coronary CTA, the relationship between the intensity distribution of the myocardium, the ventricles and the coronary arteries is identified via histogram analysis of the CTA images. By further refining the segmentation using anatomy-specific criteria such as vesselness, connectivity criteria required by the coronary tree and image operations such as active contours, we are able to capture excellent detail within our phantoms. For example, in one of the female heart phantoms, as many as 100 coronary artery branches could be identified. Triangular meshes are fitted to segmented high-resolution CTA data. We have also developed a visualization tool for adding stenotic lesions to the coronaries. The male and female heart phantoms generated so far have been cross-registered and entered in the mesh-based Virtual Family of phantoms with matched age/gender information. Any phantom in this family, along with user-defined stenoses, can be used to obtain clinically realistic projection images with the Monte Carlo code penMesh for optimizing imaging and dosimetry.

Gu, Songxiang; Gupta, Rajiv; Kyprianou, Iacovos

2011-09-01

414

Cardiovascular Fitness Levels among American Workers  

PubMed Central

Objective To explore cardiovascular fitness in 40 occupations using a nationally-representative 3 sample of the U.S. population. Methods Respondents aged 18–49 (n=3,354) from the 1999–2004 NHANES were evaluated for 5 cardiovascular fitness and classified into low, moderate, and high levels. Comparisons were 6 made among occupations. Results Of all U.S. workers, 16% had low, 36% moderate, and 48% high cardiovascular 8 fitness. Administrators, Health occupations, Wait staff, Personal services, and Agricultural 9 occupations had a lesser percentage of workers with low cardiovascular fitness compared to all 10 others. Sales workers, Administrative support, and Food preparers had a higher percentage of 11 workers with low cardiovascular fitness compared to all others. Conclusions Cardiovascular fitness varies significantly across occupations, and those with limited physical activity have higher percentages of low cardiovascular fitness. Workplace strategies are needed to promote cardiovascular fitness among high-risk occupations. PMID:21915067

Lewis, John E.; Clark, John D.; LeBlanc, William G.; Fleming, Lora E.; Cabán-Martinez, Alberto J.; Arheart, Kristopher L.; Tannenbaum, Stacey L.; Ocasio, Manuel A.; Davila, Evelyn P.; Kachan, Diana; McCollister, Kathryn; Dietz, Noella; Bandiera, Frank C.; Clarke, Tainya C.; Lee, David J.

2011-01-01

415

14 CFR 31.43 - Fitting factor.  

Code of Federal Regulations, 2011 CFR

...and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT AIRWORTHINESS STANDARDS: MANNED FREE BALLOONS Design Construction § 31.43 Fitting factor. (a) A fitting factor of at least 1.15 must be used in...

2011-01-01

416

14 CFR 31.43 - Fitting factor.  

Code of Federal Regulations, 2013 CFR

...and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT AIRWORTHINESS STANDARDS: MANNED FREE BALLOONS Design Construction § 31.43 Fitting factor. (a) A fitting factor of at least 1.15 must be used in...

2013-01-01

417

14 CFR 31.43 - Fitting factor.  

Code of Federal Regulations, 2014 CFR

...and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT AIRWORTHINESS STANDARDS: MANNED FREE BALLOONS Design Construction § 31.43 Fitting factor. (a) A fitting factor of at least 1.15 must be used in...

2014-01-01

418

14 CFR 31.43 - Fitting factor.  

Code of Federal Regulations, 2010 CFR

...and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT AIRWORTHINESS STANDARDS: MANNED FREE BALLOONS Design Construction § 31.43 Fitting factor. (a) A fitting factor of at least 1.15 must be used in...

2010-01-01

419

14 CFR 31.43 - Fitting factor.  

Code of Federal Regulations, 2012 CFR

...and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT AIRWORTHINESS STANDARDS: MANNED FREE BALLOONS Design Construction § 31.43 Fitting factor. (a) A fitting factor of at least 1.15 must be used in...

2012-01-01

420

Association Between Physical Fitness and Dementia  

MedlinePLUS

The Association Between Physical Fitness and Dementia The full report is titled “The Association Between Midlife Cardiorespiratory Fitness Levels and Later-Life Dementia. A Cohort Study.” It is in ...

421

49 CFR 195.118 - Fittings.  

Code of Federal Regulations, 2012 CFR

... PIPELINE SAFETY TRANSPORTATION OF HAZARDOUS LIQUIDS BY PIPELINE Design Requirements § 195.118 Fittings. (a) Butt-welding type fittings must meet the marking, end preparation, and the bursting strength requirements of ASME/ANSI...

2012-10-01

422

49 CFR 195.118 - Fittings.  

Code of Federal Regulations, 2010 CFR

... PIPELINE SAFETY TRANSPORTATION OF HAZARDOUS LIQUIDS BY PIPELINE Design Requirements § 195.118 Fittings. (a) Butt-welding type fittings must meet the marking, end preparation, and the bursting strength requirements of ASME/ANSI...

2010-10-01

423

49 CFR 195.118 - Fittings.  

Code of Federal Regulations, 2013 CFR

... PIPELINE SAFETY TRANSPORTATION OF HAZARDOUS LIQUIDS BY PIPELINE Design Requirements § 195.118 Fittings. (a) Butt-welding type fittings must meet the marking, end preparation, and the bursting strength requirements of ASME/ANSI...

2013-10-01

424

49 CFR 195.118 - Fittings.  

Code of Federal Regulations, 2011 CFR

... PIPELINE SAFETY TRANSPORTATION OF HAZARDOUS LIQUIDS BY PIPELINE Design Requirements § 195.118 Fittings. (a) Butt-welding type fittings must meet the marking, end preparation, and the bursting strength requirements of ASME/ANSI...

2011-10-01

425

A Novel Way to Promote Youth Fitness.  

ERIC Educational Resources Information Center

Basic steps in organizing and implementing Fun and Fitness Day are outlined. This event, jointly planned by local schools and Triton College, provided 1800 elementary students with health-related fitness testing and a day of fun and competition. (IAH)

Crum, Tom

1989-01-01

426

Beta-dosimetry studies at LLNL  

SciTech Connect

This paper summarizes three beta-dosimetry studies made recently at the Lawrence Livermore National Laboratory. The first study was to determine the beta-gamma exposure rates at the Los Alamos Godiva IV Critical Assembly. The beta spectra from the assembly were evaluated using absorption curves and the beta-gamma dose-rate ratios were determined at various distances from the assembly. A comparison was made of the doses determined using two types of TLD personnel dosimeters and a film badge. The readings of an Eberline RO-7 instrument and the dose rates determined by TLDs were compared. Shielding provided by various metals, gloves, and clothing were measured. The second study was to determine the beta energy response of the Eberline RO-7 instrument based on measurements made with the PTB beta sources. This study required additional calibration points for the PTB sources which were made using extrapolation chamber measurements. The third study resulted in two techniques to determine the beta energy (E/sub max/) from the readings of this-window portable survey instruments. Both techniques are based on the readings obtained using aluminium filters. One technique is for field application, requires one filter, and provides a quick estimate of the beta energy in three energy groups: < 0.5 MeV, 0.5 MeV to 1.5 MeV and > 1.5 MeV. The second technique is more complex requiring measurements with two or three filters, but gives the beta energy and the approximate shape of the beta spectrum. 9 references, 6 figures.

Hankins, D.E.

1983-01-01

427

Activities at the NEA for Dosimetry Applications  

NASA Astrophysics Data System (ADS)

The Nuclear Energy Agency (NEA) is a specialised agency within the Organisation for Economic Co-operation and Development (OECD) that assists its member countries in maintaining and further developing, through international co-operation, the scientific and technological use of nuclear energy for peaceful purposes. The main role of the NEA is the collection, validation and distribution of basic nuclear data, computer codes covering the areas of nuclear research and engineering, and experimental data. The activities linked to dosimetry applications are described in this paper, such as those of the Working Party on international nuclear data Evaluation Co-operation (WPEC) established at the NEA to promote the exchange of nuclear data evaluations, measurements, nuclear model calculations and validation. Collection, validation, and distribution of the computer codes and nuclear data libraries will be presented and, in particular, the Joint Evaluated Fusion and Fission (JEFF) library project. For the verification of activation and transport nuclear data, as well as computational methods, several integral experimental databases are collected and distributed by the Data Bank, for example the Shielding Integral Benchmark Archive Database (SINBAD), the International Criticality Safety Benchmark Experiments Project (ICSBEP) and the International Reactor Physics Experiments (IRPhE). Another important activity at the NEA is the collection of experimental differential nuclear reaction data for the EXFOR database. A recent WPEC project emphasizes the need for a coherent format that could be used for computer code calculations and improved validation of experimental data. JANIS is a graphical visualization tool that has been found to be useful for checking the content of EXFOR.

Henriksson, H.; Kodeli, I.

2009-08-01

428

Renewable Energy in Fitness Centers  

SciTech Connect

All military installations have goals for implementing renewable energy projects, but not all have abundant solar energy or have massive feedstock for a large biomass plant. They must build up their renewable portfolio one project at it a time where they make the most sense – most of the time through small projects on specific buildings. During the last few years, Pacific Northwest National Laboratory (PNNL) provided project support to Army Installation Management Command Southeast Region (IMCOM-Southeast) installations. One of the building types visited, the physical fitness center (PFC), almost always yield project ideas. The building lends itself to a number of different technologies, and the high traffic nature is the perfect place to craft an educational message for users and demonstrate an installation’s commitment to sustainable energy development.

Chvala, William D.

2009-09-30

429

Hanford External Dosimetry Technical Basis Manual PNL-MA-842  

SciTech Connect

The Hanford External Dosimetry Technical Basis Manual PNL-MA-842 documents the design and implementation of the external dosimetry system used at Hanford. The manual describes the dosimeter design, processing protocols, dose calculation methodology, radiation fields encountered, dosimeter response characteristics, limitations of dosimeter design under field conditions, and makes recommendations for effective use of the dosimeters in the field. The manual describes the technical basis for the dosimetry system in a manner intended to help ensure defensibility of the dose of record at Hanford and to demonstrate compliance with 10 CFR 835, DOELAP, DOE-RL, ORP, PNSO, and Hanford contractor requirements. The dosimetry system is operated by PNNL’s Hanford External Dosimetry Program (HEDP) which provides dosimetry services to all Hanford contractors. The primary users of this manual are DOE and DOE contractors at Hanford using the dosimetry services of PNNL. Development and maintenance of this manual is funded directly by DOE and DOE contractors. Its contents have been reviewed and approved by DOE and DOE contractors at Hanford through the Hanford Personnel Dosimetry Advisory Committee (HPDAC) which is chartered and chaired by DOE-RL and serves as means of coordinating dosimetry practices across contractors at Hanford. This manual was established in 1996. Since its inception, it has been revised many times and maintained by PNNL as a controlled document with controlled distribution. The first revision to be released through PNNL’s Electronic Records & Information Capture Architecture (ERICA) database was designated Revision 0. Revision numbers that are whole numbers reflect major revisions typically involving significant changes to all chapters in the document. Revision numbers that include a decimal fraction reflect minor revisions, usually restricted to selected chapters or selected pages in the document. Maintenance and distribution of controlled hard copies of the manual by PNNL was discontinued beginning with Revision 0.2. Revision Log: Rev. 0 (2/25/2005) Major revision and expansion. Rev. 0.1 (3/12/2007) Updated Chapters 5, 6 and 9 to reflect change in default ring calibration factor used in HEDP dose calculation software. Factor changed from 1.5 to 2.0 beginning January 1, 2007. Pages on which changes were made are as follows: 5.23, 5.69, 5.78, 5.80, 5.82, 6.3, 6.5, 6.29, and 9.2. Rev 0.2 (8/28/2009) Updated Chapters 3, 5, 6, 8 and 9. Chapters 6 and 8 were significantly expanded. References in the Preface and Chapters 1, 2, 4, and 7 were updated to reflect updates to DOE documents. Approved by HPDAC on 6/2/2009. Rev 1.0 (1/1/2010) Major revision. Updated all chapters to reflect the Hanford site wide implementation on January 1, 2010 of new DOE requirements for occupational radiation protection. The new requirements are given in the June 8, 2007 amendment to 10 CFR 835 Occupational Radiation Protection (Federal Register, June 8, 2007. Title 10 Part 835. U.S., Code of Federal Regulations, Vol. 72, No. 110, 31904-31941). Revision 1.0 to the manual replaces ICRP 26 dosimetry concepts and terminology with ICRP 60 dosimetry concepts and terminology and replaces external dose conversion factors from ICRP 51 with those from ICRP 74 for use in measurement of operational quantities with dosimeters. Descriptions of dose algorithms and dosimeter response characteristics, and field performance were updated to reflect changes in the neutron quality factors used in the measurement of operational quantities.

Rathbone, Bruce A.

2010-01-01

430

Morphology and COâ uptake in Tobermorite gel  

Microsoft Academic Search

Tobermorite gels have been synthesized in various degrees of crystallinity by a number of techniques. In this article, it is shown that a tobermorite gel may absorb carbon dioxide from the atmosphere to a level over 20% COâ by wt, with virtually no change in morphology. The marked changes in crystallinity and infrared absorption which occur during this process are

T. Baird; A. G. Cairns-Smith; D. S. Snell

1975-01-01

431

Alumina precursors produced by gel combustion  

Microsoft Academic Search

Alumina precursor produced by a gel combustion method using aluminum nitrate and citric acid as raw materials was investigated. Thermodynamic calculation of the combustion reaction shows that as the citrate-to-nitrate ratio ? increases, the enthalpy of reaction and adiabatic flame temperatures also increase. The DSC analysis indicates that the combustion temperature of the gel decreases, as the citrate content in

Jiang Li; Yusong Wu; Yubai Pan; Jingkun Guo

2007-01-01

432

A Simple Vertical Slab Gel Electrophoresis Apparatus.  

ERIC Educational Resources Information Center

Describes an inexpensive, easily constructed, and safe vertical slab gel kit used routinely for sodium dodecyl sulphate-polyacrylamide gel electrophoresis research and student experiments. Five kits are run from a single transformer. Because toxic solutions are used, students are given plastic gloves and closely supervised during laboratory…

Carter, J. B.; And Others

1983-01-01

433

Drying compressed natural gas with silica gel  

Microsoft Academic Search

In order to determine the feasibility of using the heat of compressed natural gas to regenerate the sorbent, an investigation of gas drying with silica gel at 20 MPa and regeneration of the silica gel at relatively low temperature in a pilot unit was performed. Prior to this drying method, in automotive gas-filling compressor stations, compressed natural gas was subjected

G. V. Vyalkina; Z. A. Nabutovskii; V. I. Popov; E. N. Torevskii

1986-01-01

434

Microporous gel electrolyte Li-ion battery  

Microsoft Academic Search

This paper describes the fabrication and performance of microporous gel electrolyte (MGE) Li-ion batteries. Fabrication of the MGE battery includes three steps: (1) making a microporous membrane separator by the phase inversion method, (2) activating the battery with a liquid electrolyte, and (3) forming MGE in situ by cycling the battery. The MGE contains three phases: liquid electrolyte, gel electrolyte,

S. S. Zhang; K. Xu; D. L. Foster; M. H. Ervin; T. R. Jow

2004-01-01

435

Sol-gel kinetics by NMR  

SciTech Connect

The chemical synthesis of advanced ceramic and glass materials by the sol-gel process has become an area of increasing activity in the field of material science. The sol-gel process provides a means to prepare homogeneous, high purity materials with tailored chemical and physical properties. This paper surveyed the nuclear magnetic resonance (NMR) studies of silicon-based sol-gel kinetics. A review of the various models which have been used to analyze the chemical kinetics of various sol-gel systems was presented. The utility of NMR spectroscopy was demonstrated in investigating the influence that various reaction conditions have on the reaction pathways by which sol-gel derived materials are synthesized. By observing in a direct fashion the chemical pathway of the sol-gel, it is often possible to relate the final properties of the material to the formulation and reaction conditions of the sol-gel. The study of reaction kinetics by NMR is expected to play an increasingly important role in understanding sol-gel processing and material properties. 1