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1

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.

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

2010-01-01

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

NMR mechanisms in gel dosimetry  

NASA Astrophysics Data System (ADS)

Nuclear magnetic resonance was critical to the development of gel dosimetry, as it established the potential for three dimensional dosimetry with chemical dosimeter systems through magnetic resonance imaging [1]. In the last two decades MRI has served as the gold standard for imaging, while NMR relaxometry has played an important role in the development and understanding of the behaviour of new gel dosimetry systems. Therefore, an appreciation of the relaxation mechanisms determining the NMR behaviour of irradiated gel dosimeters is important for a full comprehension of a considerable component of the literature on gel dosimetry. A number of excellent papers have presented this important theory, this brief review will highlight some of the salient points made previously [1-5]. The spin relaxation of gel dosimeters (which determines the dose dependence in most conventional MR imaging) is determined principally by the protons on water molecules in the system. These water protons exist in different environments, or groups (see Figure 1): on bulk water, on water hydrating the chemical species that are being modified under irradiation, and on water hydrating the gel matrix used to spatially stabilize the dosimeter (e.g., gelatin, agarose, etc). The spin relaxation depends on the inherent relaxation rate of each spin group, that is, on the relaxation rate which would be observed for the specific group if it were isolated. Also, the different water environments are not isolated from each other, and the observed relaxation rate also depends on the rate of exchange of magnetization between the groups, and on the fraction of protons in each group. In fact, the water exchanges quickly between the environments, so that relaxation is in what is usually termed the fast exchange regime. In the limit of fast exchange, the relaxation of the water protons is well characterized by a single exponential and hence by a single apparent relaxation rate. In irradiated gel dosimeters this observed rate is a function of the absorbed dose. In this review I will first develop the fast exchange model for the spin lattice relaxation Fricke gel dosimeter system, as this is conceptually the simpler system. Fundamental concepts such as relaxivity (which specifies the ability of some species to enhance the relaxation of water protons) and chemical yield will be presented. The linear dose relationship for Fricke gel dosimeters, and the reduced dose sensitivity of Fricke dosimeters containing chelators, will be explained. The model will then be extended to the spin-spin relaxation of polymer gel systems and the main differences discussed. The reasons for the enhanced dose sensitivy and dynamic range for spin-spin (R2) rather than spin-lattice (R1) relaxation will be presented.

Schreiner, L. J.

2009-05-01

4

MAGIC Gel Dosimetry  

NASA Astrophysics Data System (ADS)

Proton therapy has proven a very successful tool in treating certain tumors, but a three dimensional view of this fact has not yet been clearly demonstrated. In this experiment we have used MAGIC (Methacrylic and Ascorbic Acid in Gelatin Initiated by Copper) gel to represent brain tissue and gone through normal treatment planning for an Acoustic Neuroma to show the three dimensional dose distributions associated with such a tumor.

Mifflin, Rachel; Shahnazi, Kambiz; Jesseph, Rick

2008-10-01

5

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

2013-08-22

6

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

7

TOPICAL REVIEW: Polymer gel dosimetry  

Microsoft Academic Search

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

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

2010-01-01

8

Polymer gel dosimetry using computed tomography  

NASA Astrophysics Data System (ADS)

Polymer gel dosimeter (PGD) is a type of integrating chemical dosimeter that, with the use of a suitable phantom, can be used for evaluation of the absorbed dose (dose distribution) deposited into a polymer gel by various irradiation modalities.Using suitable compounds of gel and appropriate parameters affecting the quality of the final image, evaluation using computed tomography (CT) should become a more advantageous alternative to magnetic resonance (MR), which is the most frequently applied method for the purposes of polymer gel dosimetry so far.In our work, several compositions of polymer gels (PG) were tested; evaluation was made via CT and MR, and values of dose and relative dose resolution were calculated. The optimal protocol for CT imaging and comparison of results from CT and MR are discussed.

Ornová, D.; Šemnická, J.; Sp?vá?ek, V.; Kon?ek, O.

2011-10-01

9

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

10

PREFACE: The 5th International Conference on Radiotherapy Gel Dosimetry (DOSGEL 2008)  

Microsoft Academic Search

The International Conference on Radiotherapy Gel Dosimetry (DOSGEL) is held every two years. Its purpose is to bring together basic science and clinical researchers, medical physicists and clinicians from around the world to discuss the state-of-the-art of the gel dosimetry technique and to set the directions and trends for its future improvements. Gel dosimetry can be broadly defined as using

Thomas G. Maris; Evangelos Pappas

2009-01-01

11

On the reliability of 3D gel dosimetry  

NASA Astrophysics Data System (ADS)

Gel dosimetry has a unique role to play in safeguarding conformal radiotherapy treatments as it covers the whole treatment chain and provides the radiation oncologist with the integrated dose distribution in 3D. A major obstacle that has hindered the wider dissemination of polymer gel dosimetry in radiotherapy centres is the lack of confidence in the reliability of the measured dose. Discrepancies in dose response of small versus large polymer gel dosimeters have been reported and although several hypothesis for these discrepancies have been postulated, the actual contribution of these error sources to the overall inaccuracy of the dose maps has not been determined. Several gel dosimetry research groups have chosen to use an internal calibration of gel dosimeters. In this study, the inter-and intra-batch reproducibility of the current state-of-the-art 3D gel dosimeters has been assessed. It is demonstrated that with a carefully designed scanning set-up, the overall accuracy that can be obtained with an independent calibration is well within 5% of all pixels.

De Deene, Y.; Vandecasteele, J.

2013-06-01

12

Small Photon Field Dosimetry using Gel  

Microsoft Academic Search

Small photon fields which were originally used for Stereotactic irradiation are currently being used increasingly in modern\\u000a radiotherapy such as IMRT, Tomotherapy and CyberKnife etc. The dosimetry of these small photon fields for commissioning is\\u000a a challenging task due to issues such as radiation field perturbation, volume averaging effects and lateral electronic disequilibrium.\\u000a In this work we have measured total

Paul B Ravindran

13

Magnetization transfer imaging for polymer gel dosimetry  

Microsoft Academic Search

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

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

2002-01-01

14

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

15

Investigations in x-ray computed tomography polyacrylamide gel dosimetry  

NASA Astrophysics Data System (ADS)

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 PAG with an overall goal to improve 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. Systems for irradiating and imaging gels are designed and tested and dose response reproducibility is established. 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 that occurs per unit polymer yield is highest for gels with low and high concentrations of crosslinking molecule (%C) and the dose response sensitivity is linearly dependent on the total concentration of monomer in the gel. The second study investigates strategies for minimizing noise in x-ray CT polymer gel dosimetry and assesses system performance. Specifically, the effects of phantom design, scanning technique and image voxel size on image noise are investigated. This work leads to the establishment of a method of predicting image noise for any given CT imaging protocol. Image uniformity is also assessed, in the context of noise levels in gel dosimetry. The effect of scanning protocol on imaging time is established and the dose resolution achievable with an optimized system is calculated given voxel size and imaging time constraints. These results, when compared with published values for MRI and optical CT gel dosimetry indicate that CT dose resolution (e.g. 5%, 1 x 1 x 3 mm3 voxels), is still not at the level of the best MRI or optical CT techniques, however fast imaging times makes the rapid acquisition of volumetric data most feasible with x-ray CT. The third study investigates the potential of image filtering for improved dose resolution in CT gel dosimetry. CT image noise is characterized as Gaussian distributed and independent of signal strength and filters for reducing spatially invariant noise are investigated: mean, median, midpoint, adaptive mean, alpha-trimmed mean, sigma mean and a relatively new filter called SUSAN. The filters are tested on a CT image of a PAG irradiated with a clinically relevant dose distribution. Filter performance varies greatly in both achieved dose resolution and affects on the spatial distribution of dose. The ADAPTIVE and SUSAN filters provide the best overall performance, more than halving the dose resolution without significantly distorting the spatial distribution of dose. In summary, this thesis provides new insight into the fundamental nature of PAG density to dose response, develops strategies for minimizing image noise and quantifies system performance and demonstrates that digital image filtering is an effective tool to provide additional improvements to dose resolution.

Hilts, Michelle Louise

16

Radiological properties of MAGIC normoxic polymer gel dosimetry  

NASA Astrophysics Data System (ADS)

For a polymer gel dosimeter to be of use in radiation dosimetry, it should display water-equivalent radiological properties. In this study, the radiological properties of the MAGIC (Methacrylic and Ascorbic acid in Gelatin Initiated by Copper) normoxic polymer gels were investigated. The mass density (?) was determined based on Archimedes' principle. The weight fraction of elemental composition and the effective atomic number (Zeff) were calculated. The electron density was also measured with 90° scattering angle at room temperature. The linear attenuation coefficient (?) of unirradiated gel, irradiated gel, and water were determined using Am-241 based on narrow beam geometry. Monte Carlo simulation was used to calculate the depth doses response of MAGIC gel and water for 6MV photon beam. The weight fractions of elements composition of MAGIC gel were close to that for water. The mass density was found to be 1027 ± 2 kg m-3, which is also very close to mass density of muscle tissue (1030 kg m-3) and 2.7% higher than that of water. The electron density (?e) and atomic number (Zeff) were found to be 3.43 × 1029 e m-3 and 7.105, respectively. The electron density measured was 2.6% greater than that for water. The atomic number was very close to that for water. The prepared MAGIC gel was found to be water equivalent based on the study of element composition, mass density, electron density and atomic number. The linear attenuation coefficient of unirradiated gel was very close to that of water. The ? of irradiated gel was found to be linear with dose 2-40 Gy. The depth dose response for MAGIC gel from a 6 MV photon beam had a percentage dose difference to water of less than 1%. Therefore it satisfies the criteria to be a good polymer gel dosimeter for radiotherapy.

Aljamal, M.; Zakaria, A.; Shamsuddin, S.

2013-04-01

17

Fricke gel dosimetry in boron neutron capture therapy.  

PubMed

Gel dosimetry allows three-dimensional (3D) measurement of absorbed dose in tissue-equivalent dosemeter phantoms. Gel phantoms are imaged using optical techniques. In neutron capture therapy (NCT), properly designed gel dosemeters can give 3D dose distributions, due to the various components of the secondary radiation, in phantoms exposed in the thermal or epithermal column of a nuclear reactor. In addition to the therapeutic dose arising from the reaction 10B(n,alpha)7Li, the other dose components are also obtainable, i.e. the gamma dose (due to reactor background and to the reaction 1H(n,gamma)2H of thermal neutrons with hydrogen, the dose due to protons emitted in the reaction 14N(n,p)14C of thermal neutrons with nitrogen and the dose due to recoil protons resulting from elastic scattering of epithermal neutrons. PMID:12382781

Gambarini, G; Birattari, C; Colombi, C; Pirola, L; Rosi, G

2002-01-01

18

Technical considerations for implementation of x-ray CT polymer gel dosimetry  

NASA Astrophysics Data System (ADS)

Gel dosimetry is the most promising 3D dosimetry technique in current radiation therapy practice. X-ray CT has been shown to be a feasible method of reading out polymer gel dosimeters and, with the high accessibility of CT scanners to cancer hospitals, presents an exciting possibility for clinical implementation of gel dosimetry. In this study we report on technical considerations for implementation of x-ray CT polymer gel dosimetry. Specifically phantom design, CT imaging methods, imaging time requirements and gel dose response are investigated. Where possible, recommendations are made for optimizing parameters to enhance system performance. The dose resolution achievable with an optimized system is calculated given voxel size and imaging time constraints. Results are compared with MRI and optical CT polymer gel dosimetry results available in the literature.

Hilts, M.; Jirasek, A.; Duzenli, C.

2005-04-01

19

Monte Carlo verification of gel dosimetry measurements for stereotactic radiotherapy.  

PubMed

The quality assurance of stereotactic radiotherapy and radiosurgery treatments requires the use of small-field dose measurements that can be experimentally challenging. This study used Monte Carlo simulations to establish that PAGAT dosimetry gel can be used to provide accurate, high-resolution, three-dimensional dose measurements of stereotactic radiotherapy fields. A small cylindrical container (4 cm height, 4.2 cm diameter) was filled with PAGAT gel, placed in the parietal region inside a CIRS head phantom and irradiated with a 12-field stereotactic radiotherapy plan. The resulting three-dimensional dose measurement was read out using an optical CT scanner and compared with the treatment planning prediction of the dose delivered to the gel during the treatment. A BEAMnrc/DOSXYZnrc simulation of this treatment was completed, to provide a standard against which the accuracy of the gel measurement could be gauged. The three-dimensional dose distributions obtained from Monte Carlo and from the gel measurement were found to be in better agreement with each other than with the dose distribution provided by the treatment planning system's pencil beam calculation. Both sets of data showed close agreement with the treatment planning system's dose distribution through the centre of the irradiated volume and substantial disagreement with the treatment planning system at the penumbrae. The Monte Carlo calculations and gel measurements both indicated that the treated volume was up to 3 mm narrower, with steeper penumbrae and more variable out-of-field dose, than predicted by the treatment planning system. The Monte Carlo simulations allowed the accuracy of the PAGAT gel dosimeter to be verified in this case, allowing PAGAT gel to be utilized in the measurement of dose from stereotactic and other radiotherapy treatments, with greater confidence in the future. PMID:22572565

Kairn, T; Taylor, M L; Crowe, S B; Dunn, L; Franich, R D; Kenny, J; Knight, R T; Trapp, J V

2012-05-09

20

Monte Carlo verification of gel dosimetry measurements for stereotactic radiotherapy  

NASA Astrophysics Data System (ADS)

The quality assurance of stereotactic radiotherapy and radiosurgery treatments requires the use of small-field dose measurements that can be experimentally challenging. This study used Monte Carlo simulations to establish that PAGAT dosimetry gel can be used to provide accurate, high-resolution, three-dimensional dose measurements of stereotactic radiotherapy fields. A small cylindrical container (4 cm height, 4.2 cm diameter) was filled with PAGAT gel, placed in the parietal region inside a CIRS head phantom and irradiated with a 12-field stereotactic radiotherapy plan. The resulting three-dimensional dose measurement was read out using an optical CT scanner and compared with the treatment planning prediction of the dose delivered to the gel during the treatment. A BEAMnrc/DOSXYZnrc simulation of this treatment was completed, to provide a standard against which the accuracy of the gel measurement could be gauged. The three-dimensional dose distributions obtained from Monte Carlo and from the gel measurement were found to be in better agreement with each other than with the dose distribution provided by the treatment planning system's pencil beam calculation. Both sets of data showed close agreement with the treatment planning system's dose distribution through the centre of the irradiated volume and substantial disagreement with the treatment planning system at the penumbrae. The Monte Carlo calculations and gel measurements both indicated that the treated volume was up to 3 mm narrower, with steeper penumbrae and more variable out-of-field dose, than predicted by the treatment planning system. The Monte Carlo simulations allowed the accuracy of the PAGAT gel dosimeter to be verified in this case, allowing PAGAT gel to be utilized in the measurement of dose from stereotactic and other radiotherapy treatments, with greater confidence in the future. Experimental aspects of this work were originally presented at the Engineering and Physical Sciences in Medicine Conference (EPSM-ABEC), Melbourne, 2010.

Kairn, T.; Taylor, M. L.; Crowe, S. B.; Dunn, L.; Franich, R. D.; Kenny, J.; Knight, R. T.; Trapp, J. V.

2012-06-01

21

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

22

Investigation of ultrasonic properties of MAGIC gels for pulse-echo gel dosimetry  

NASA Astrophysics Data System (ADS)

Ultrasound has been proposed as an alternative 3D method to read out dosimetric gels. The ultrasonic properties of MAGIC gel are investigated in relation to producing a dosimetry system based on a pulse-echo technique. The sound speed, attenuation coefficient, and density of MAGIC gel were measured over a range of temperatures and doses. A nonlinear relationship between ultrasonic attenuation and dose was observed, with the attenuation below 10 Gy being approximately constant. The sound speed was 1550.3 ± 1.5 m s-1 at 25 °C with a dose sensitivity of 0.14 ± 0.03 m s-1 Gy-1 both properties changed with temperature and were 1535.4 ± 0.8 m s-1 and -0.08 ± 0.01 m s-1 Gy-1 respectively at 15 °C. The density also varied with temperature and dose, and was 1028.9 ± 0.3 kg m-3 with a dose sensitivity of 0.178 ± 0.004 kg m-3 Gy-1 at 26 °C. The characteristic acoustic impedance of MAGIC gel was calculated to be 1.596 × 106 kg m2 s-1 at 0 Gy and 25 °C. The dose sensitivities measured indicate that changes to the characteristic acoustic impedance caused by irradiation are small, and therefore a reflector that has a similar characteristic acoustic impedance is required to maximise sensitivity of the pulse-echo technique. A suitable material has been developed and the reflection characteristics of the interface between MAGIC gel and the reflector are also temperature dependent. It is concluded that temperature management will be central to the development of any practical pulse-echo dosimetry system.

Atkins, T. J.; Humphrey, V. F.; Duck, F. A.; Tooley, M. A.

2010-11-01

23

MAGAT gel dosimetry for its application in small field treatment techniques  

Microsoft Academic Search

Purpose of this work is to present the role of in-house manufactured MAGAT gel for treatment verification in small field dosimetric techniques such as Gammaknife (GK) and intensity-modulated radiation therapy (IMRT). Magnetic resonance imaging (MRI) is one of the most extensively used imaging technique for polymer gel dosimetry hence we used this method for gel evaluation. Different MR scanners and

N. Gopishankar; S. Vivekanandhan; S. S. Kale; G. K. Rath; S. Senthil Kumaran; Sanjay Thulkar; V. Subramani; M. A. Laviraj; R. K. Bisht; A. K. Mahapatra

2010-01-01

24

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

25

Three-dimensional radiation dosimetry for gamma knife using a gel dosimeter  

NASA Astrophysics Data System (ADS)

The use of three-dimensional radiation dosimetry has been limited. With the use of water phantoms and ionization chambers, it has been possible to determine three dimensional dose distributions on a gross scale for cobalt 60 and linear accelerator sources. This method has been somewhat useful for traditional radiotherapy. There is, however, a need for more precise dosimetry, particularly with stereotactic radiosurgery. Most gamma knife facilities use either thermoluminescant dosimetry or film, neither of which provides three dimensional dose distributions. To overcome this limitation, we have developed a gel dosimetry system that relies on the production of a ferric ion-xylenol orange colored complex. This work demonstrates the use of laser light and a detector to quantify radiation-induced colorimetric changes in absorbance for the gel dosimeter. The absorbance has been reconstructed by the back projection technique to demonstrate the applicability of the gel dosimeter to gamma knife 3D-dose distributions.

Hussain, Kazi Muazzam

26

Monte Carlo verification of polymer gel dosimetry applied to radionuclide therapy: a phantom study  

Microsoft Academic Search

This study evaluates the dosimetric performance of the polymer gel dosimeter 'Methacrylic and Ascorbic acid in Gelatin, initiated by Copper' and its suitability for quality assurance and analysis of I-131-targeted radionuclide therapy dosimetry. Four batches of gel were manufactured in-house and sets of calibration vials and phantoms were created containing different concentrations of I-131-doped gel. Multiple dose measurements were made

J. I. Gear; E. Charles-Edwards; M. Partridge; G. D. Flux

2011-01-01

27

Polymer gel - TPS radiotherapy dosimetry GeVero® software for ionizing radiation absorbed dose 3D distribution calculations  

NASA Astrophysics Data System (ADS)

Implementation of polymer gel dosimetry in radiotherapy departments calls for: easily manufactured gel dosimeters of required physical-chemical properties, set-up procedures of irradiation, adaptation of three-dimensional scanning procedures and instruments as well as fast tool for calculation of 3D absorbed dose distribution in the polymer gel dosimeters and comparison with another treatment planning system calculated dose distribution. These challenges resulted in several propositions in polymer gel dosimetry area. In this work, however, a summary of results on construction of polymer gel dosimetry software facilitating usually laborious 3D dose distributions data processing is provided.

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

2009-05-01

28

The application of polymer gel dosimeters to dosimetry for targeted radionuclide therapy  

NASA Astrophysics Data System (ADS)

There is a lack of standardized methodology to perform dose calculations for targeted radionuclide therapy and at present no method exists to objectively evaluate the various approaches employed. The aim of the work described here was to investigate the practicality and accuracy of calibrating polymer gel dosimeters such that dose measurements resulting from complex activity distributions can be verified. Twelve vials of the polymer gel dosimeter, 'MAGIC', were uniformly mixed with varying concentrations of P-32 such that absorbed doses ranged from 0 to 30 Gy after a period of 360 h before being imaged on a magnetic resonance scanner. In addition, nine vials were prepared and irradiated using an external 6 MV x-ray beam. Magnetic resonance transverse relaxation time, T2, maps were obtained using a multi-echo spin echo sequence and converted to R2 maps (where T2 = 1/R2). Absorbed doses for P-32 irradiated gel were calculated according to the medical internal radiation dose schema using EGSnrc Monte Carlo simulations. Here the energy deposited in cylinders representing the irradiated vials was scored. A relationship between dose and R2 was determined. Effects from oxygen contamination were present in the internally irradiated vials. An increase in O2 sensitivity over those gels irradiated externally was thought to be a result of the longer irradiation period. However, below the region of contamination dose response appeared homogenous. Due do a drop-off of dose at the periphery of the internally irradiated vials, magnetic resonance ringing artefacts were observed. The ringing did not greatly affect the accuracy of calibration, which was comparable for both methods. The largest errors in calculated dose originated from the initial activity measurements, and were approximately 10%. Measured R2 values ranged from 5-35 s-1 with an average standard deviation of 1%. A clear relationship between R2 and dose was observed, with up to 40% increased sensitivity for internally irradiated gels. Curve fits to the calibration data followed a single exponential function. The correlation coefficients for internally and externally irradiated gels were 0.991 and 0.985, respectively. With the ability to accurately calibrate internally dosed polymer gels, this technology shows promise as a means to evaluate dosimetry methods, particularly in cases of non-uniform uptake of a radionuclide.

Gear, J. I.; Flux, G. D.; Charles-Edwards, E.; Partridge, M.; Cook, G.; Ott, R. J.

2006-07-01

29

Investigations in x-ray computed tomography polyacrylamide gel dosimetry  

Microsoft Academic Search

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

Michelle Louise Hilts

2005-01-01

30

Gamma Knife relative dosimetry using VIP polymer gel and EBT radiochromic films  

NASA Astrophysics Data System (ADS)

The VIP polymer gel-MRI method and EBT Gafchromic films were employed to obtain relative dosimetry results for the Gamma Knife (GK) radiation fields of 4 mm and 18 mm nominal diameter. Results are compared to the corresponding calculations of GammaPlan Treatment Planning System (TPS) in the form of 1D profiles and 2D distributions. Measured and planned relative dosimetry datasets are found in close agreement within experimental uncertainties. A corresponding agreement is shown for Dose Volume Histogram (DVH) results that are available only through the application of the polymer gel method.

Moutsatsos, A.; Petrokokkinos, L.; Zourari, K.; Papagiannis, P.; Karaiskos, P.; Dardoufas, K.; Damilakis, J.; Seimenis, I.; Georgiou, E.

2009-05-01

31

PREFACE: The 5th International Conference on Radiotherapy Gel Dosimetry (DOSGEL 2008)  

NASA Astrophysics Data System (ADS)

The International Conference on Radiotherapy Gel Dosimetry (DOSGEL) is held every two years. Its purpose is to bring together basic science and clinical researchers, medical physicists and clinicians from around the world to discuss the state-of-the-art of the gel dosimetry technique and to set the directions and trends for its future improvements. Gel dosimetry can be broadly defined as using a gel that can react to the absorption of ionizing radiation, and that can retain this information which can subsequently be retrieved by an external imaging modality. Examples of radiation-sensitive gels include, but are not limited to, polymer gel dosimeters, Fricke gel dosimeters and others. Imaging modalities that are of general use in this field are (in alphabetical order) magnetic resonance imaging (MRI), optical light computed tomography and x-ray computed tomography. This volume comprises the proceedings of the 5th International Conference on Radiotherapy Gel Dosimetry (DOSGEL 2008). The conference, organised by the University of Crete, Medical Physics Department, took place in Hersonissos, Crete, Greece from 29 September to 3 October 2008. The meeting aimed to continue the series of biannual DOSGEL conferences and focused on the promotion of gel dosimetry techniques by setting the trends for their future improvements. The main scientific session topics of DOSGEL 2008 were the following: Chemistry and fundamental properties of polymer gel dosimeters Gel dosimetry with Optical Computed Tomography Gel dosimetry with Magnetic Resonance Imaging Gel dosimetry with other than Optical CT and MR scan Techniques Other 3D dosimeters Gel dosimetry applications Local Organizing Committee Thomas G Maris (University of Crete, Greece, Chairman DOSGEL 2008) John Damilakis (University of Crete, Greece) Evangelos Pappas (University of Crete, Greece) Antonios Papadakis (University of Crete, Greece) Fotini Zacharopoulou (University of Crete, Greece) John Stratakis (University of Crete, Greece) Pantelis Karaiskos (University of Athens, Greece) Panos Papagiannis (University of Athens, Greece) Scientific Committee President: Yves De Deene (Ghent University, Belgium) Sven Back (Lund University, Sweden) Clive Baldock (University of Sydney, Australia) David Bonnett (Kent Oncology Center, UK) Simon Doran (University of Surrey, UK) Cheryl Duzenli (University of British Columbia, Canada) Geoffrey Ibbott (Colorado State University, USA) Andrew Jirasek (University of Victoria, Canada) Kevin Jordan (University of Western Ontario, Canada) Martin Lepage (Universite de Sherbrooke, Canada) Mark Oldham (Duke University, USA) L John Schreiner (Kingston Regional Cancer Centre, Canada) Acknowledgements The local organising committee wishes to express its gratitude to all participants for their activities at DOSGEL 2008 and for creating such a friendly and inspiring environment. Special thanks are due to all the speakers, for preparing and presenting their talks, and for many valuable discussions. We also give thanks to all members of the scientific committee who, acting as referees, improved significantly the scientific quality of this proceedings volume. We would also like to thank all chairmen for their efficient leading of sessions. On Behalf of the local organizing committee of DOSGEL 2008 Thomas G Maris and Evangelos Pappas Editors Conference photograph

Maris, Thomas G.; Pappas, Evangelos

2009-07-01

32

MAGIC-f Gel in Nuclear Medicine Dosimetry: study in an external beam of Iodine-131  

NASA Astrophysics Data System (ADS)

MAGIC-f gel applicability in Nuclear Medicine dosimetry was investigated by exposure to a 131I source. Calibration was made to provide known absorbed doses in different positions around the source. The absorbed dose in gel was compared with a Monte Carlo Simulation using PENELOPE code and a thermoluminescent dosimetry (TLD). Using MRI analysis for the gel a R2-dose sensitivity of 0.23 s-1Gy-1was obtained. The agreement between dose-distance curves obtained with Monte Carlo simulation and TLD was better than 97% and for MAGIC-f and TLD was better than 98%. The results show the potential of polymer gel for application in nuclear medicine where three dimensional dose distribution is demanded.

Schwarcke, M.; Marques, T.; Garrido, C.; Nicolucci, P.; Baffa, O.

2010-11-01

33

Relaxometry changes in a gel dosimetry phantom due to continued RF exposure  

Microsoft Academic Search

This study investigates the potential alteration in relaxation times in phantoms used for MRI gel-dosimetry due to their continued RF exposure from the MRI scanner used in the measurement process. The work quantifies these changes and establishes a tolerance for the image acquisition time as well as mapping the spatial distribution of these effects.

Gary P. Liney; Mark J. Godber; Andrew D. Wilson; John W. Goodby; Lindsay W. Turnbull

2009-01-01

34

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

35

Evaluation of the potential for diacetylenes as reporter molecules in 3D micelle gel dosimetry.  

PubMed

Radiochromic micelle gel dosimeters are promising for three-dimensional (3D) radiation dosimetry because they can be read out by optical CT techniques and they have superior spatial stability compared to polymer and Fricke gel dosimeters. This study evaluates the use of diacetylenes as reporter molecules in micelle gel dosimeters. Several gels containing pentacosa-10,12-diynoic acid (PCDA) emulsified using sodium dodecyl sulfate (SDS) changed from colourless to blue upon irradiation. Unfortunately, all phantoms that experienced a colour change were turbid and would be unsuitable for 3D dosimetry. Two techniques (use of organic solvent and aqueous-phase additives) were successful in increasing colloidal stability to prevent the turbidity problem, but none of the resulting transparent gels changed colour in response to radiation. Transparent PCDA emulsions were prepared using NaOH solutions with no SDS or other emulsifier, but these transparent emulsions also did not change colour. Only turbid gels and emulsions with precipitated particles responded to radiation. These results indicate that the colour change was due to the oligomerization within precipitated PCDA crystals, and that liquid-phase emulsified PCDA did not undergo oligomerization. As a result, PCDA is not suitable for use in micelle gel dosimeters, and other radiochromic reporter molecules will need to be identified. PMID:23322115

Nasr, A T; Olding, T; Schreiner, L J; McAuley, K B

2013-01-16

36

In-phantom dosimetry for BNCT with Fricke and normoxic-polymer gels  

NASA Astrophysics Data System (ADS)

Measurements of in-phantom dose distributions and images are important for Boron Neutron Capture Therapy treatment planning. The method for spatial determination of absorbed doses in thermal or epithermal neutron fields, based on Fricke-xylenol-orange-infused gel dosimeters in form of layers, has revealed to be very reliable, as gel layer dosimeters give the possibility of obtaining spatial dose distributions and measurements of each dose contribution in neutron fields, by means of a properly studied procedure. Quite recently, BNCT has been applied to treat liver metastases; in this work the results of in-phantom dosimetry for explanted liver in BNCT treatments are described. Moreover, polyacrylamide gel (PAG) dosimeters in which a polymerization process appears as a consequence of absorbed dose, have been recently tested, because of their characteristic absence of diffusion. In fact, due to the diffusion of ferric ions, Fricke-gel dosimeters require prompt analysis after exposure to avoid spatial information loss. In this work the preliminary results of a study about the reliability of polymer gel in BNCT dosimetry are also discussed. Gel layers have been irradiated in a phantom exposed in the thermal column of the TRIGA MARK II reactor (Pavia). The results obtained with the two kinds of gel dosimeter have been compared.

Gambarini, G.; Agosteo, S.; Carrara, M.; Gay, S.; Mariani, M.; Pirola, L.; Vanossi, E.

2006-05-01

37

Relative output factor measurements of a 5 mm diameter radiosurgical photon beam using polymer gel dosimetry  

SciTech Connect

Besides the fine spatial resolution inherent in polymer gel-magnetic resonance imaging (MRI) dosimetry, the method also features the potential for multiple measurements of varying sensitive volume in a single experiment by integrating results in MRI voxels of finite dimensions (i.e., in plane resolution by slice thickness). This work exploits this feature of polymer gel dosimetry to propose an experimental technique for relative output factor (OF) measurements of small radiosurgical beams. Two gel vials were irradiated with a 5 and 30 mm diameter 6 MV radiosurgery beam and MR scanned with the same slice thickness and three different in plane resolutions. Using this experimental data set, 5 mm OF measurements with the PinPoint ion chamber are simulated by integrating results over a sensitive volume equal to that of the chamber. Results are found in agreement within experimental uncertainties with actual PinPoint measurements verifying the validity of the proposed experimental procedure. The polymer gel data set is subsequently utilized for OF measurements of the 5 mm beam with varying sensitive volume to discuss the magnitude of detector volume averaging effects. Seeking to correct for volume averaging, results are extrapolated to zero sensitive volume yielding a 5 mm OF measurement of (0.66{+-}5%). This result compares reasonably with corresponding ionometric and radiographic film measurements of this work and corresponding, limited, data in the literature. Overall, results suggest that polymer gel dosimetry coupled with the proposed experimental procedure helps overcome not only tissue-equivalence and beam perturbation implications but also volume averaging and positioning uncertainties which constitute the main drawback in small radiosurgical beam dosimetry.

Pappas, E.; Petrokokkinos, L.; Angelopoulos, A.; Maris, T.G.; Kozicki, M.; Dalezios, I.; Kouloulias, V. [Nuclear and Particle Physics Section, Physics Department, University of Athens, Panepistimioupolis, Ilisia, 157 71 Athens (Greece); Radiology Section, Medical Physics Department, MRI Unit, University Hospital of Heraklion, 711 10 Stavrakia-Heraklion, Crete (Greece); Faculty of Textile Engineering, Technical University of Lodz, Zeromskiego St 116, 90-543 Lodz, Poland and Institute of Applied Radiation Chemistry, Technical University of Lodz, Wroblewskiego Street 15, 93-590 Lodz (Poland); Department of Biomedical Engineering, University General Hospital 'Attikon', 1 Rimini Street, 124 62, Chaidari, Athens (Greece); Department of Electrical Engineering and Computer Science, National Technical University of Athens, 9 Hroon Polytechniou Street, 157 73 Athens (Greece)

2005-06-15

38

Development and Characterization of NMR Measurements for Polymer Gel Dosimetry  

NASA Astrophysics Data System (ADS)

Polymer gel dosimeters are systems of water, gelatin, and monomers which form polymers upon irradiation. The gelatin matrix retains dose distribution in 3D form, facilitating truly integrated measurements of complex dose plans for radiation therapy. Polymer gels have two proton pools coupled by exchange: free solvent protons and bound polymerized macromolecular protons. Measuring magnetization transfer (MT) and relaxation affords useful insights into particle rigidity and chemical exchange effects on relaxation in polymer gels. Polymer gel dose response has been previously quantified with several techniques, most often in terms of MRI parameters, usually at field strengths of 1.5 T and below. The research described here investigates the dose response of a revised MAGIC gel dosimeter via both high-field imaging and simpler nuclear magnetic resonance (NMR) spectroscopy. This includes both transverse and longitudinal relaxation rates (R2 and R1) and quantitative MT parameters. We investigated estimating polymer molecular weight for a given applied dose using the Rouse model and R2 data from the imaging study. Finally, we began development of NMR methods for studying dose response, requiring adaption of NMR experiments to accommodate for radiation damping.

Kwong, Zachary; Whitney, Heather

2012-03-01

39

Application of polymer-gel dosimetry in stereotactic radiosurgery  

NASA Astrophysics Data System (ADS)

Stereotactic irradiation with the Leksell gamma knife (Elekta Instrument AB, Stockholm, Sweden) is one of the primary methods used for the stereotactic radiosurgery treatment of intracranial lesions. To assure the quality of the whole treatment procedure a proper dosimetric system is required. The polymer-gel dosimeter evaluated by nuclear magnetic resonance (NMR) is a promising tool to satisfy this requirement. The purpose of this study was to investigate the use of polymer-gel dosimeter as a dosimetric tool for the quality control of stereotactic radiosurgery procedures performed by the Leksell gamma knife.

Novotny, J., Jr.; Spevacek, V.; Dvorak, P.; Hrbacek, J.; Novotny, J.; Tlachacova, D.; Schmitt, M.; Vymazal, J.; Tintera, J.; Cechak, T.

2004-01-01

40

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

Microsoft Academic Search

The accuracy of the Leksell GammaPlan registered , 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

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

2007-01-01

41

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

42

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

2011-07-06

43

Feasibility of quantitative PET/CT dosimetry for proton therapy using polymer gels  

NASA Astrophysics Data System (ADS)

A feasibility study of proton beam PET/CT off-line quantitative dosimetry using polymer gels is presented. A newly developed proton-sensitive polymer gel dosimeter (BANG(®)3-Pro2) is used as a dosimeter and a tissue-equivalent phantom medium for this study. We explore a new approach to correlating measured proton 3-dimensional (3D) dose distributions directly to measured positron emission from in the gel medium using PET/CT imaging. A large cylindrical volume (2.2 Litres) of the gel was irradiated with a clinical modulated proton beam using irregular-shaped aperture geometry. The gel was imaged in a nearby PET/CT unit immediately (<3 min) after irradiation. Dose distribution in the gel was generated using an optical tomography scanning system. Direct 3D spatial comparison of dose and positron emission distributions was then performed. Profiles along the beam path show that the distal fall-off of the dose is nearly 2 cm deeper than the activity profile which is comparable to previous studies with plastic phantoms and Monte Carlo simulations of activity distributions. Planar PET and dose distributions at depth and perpendicular to beam axis show a strong one-to-one spatial correlation. This phantom study demonstrates that the gel medium could be potentially useful for quantifying various physical factors that can influence the PET activity range verification method in patients.

Zeidan, O. A.; Hsi, W. C.; Lopatiuk-Tirpak, O.; Sriprisan, S. I.; Meeks, S. L.; Kupelian, P. A.; Li, Z.; Palta, J. R.

2010-11-01

44

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

SciTech Connect

The accuracy of the Leksell GammaPlan registered , 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 N{sub 2} 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 registered 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 registered 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.

Isbakan, Fatih; Uelgen, Yekta; Bilge, Hatice; Ozen, Zeynep; Agus, Onur; Buyuksarac, Bora [Institute of Biomedical Engineering, Bogazici University, Istanbul (Turkey); Institute of Radiation Oncology, Istanbul University, Istanbul (Turkey); Radiation Oncology Department, Marmara University Hospital, Istanbul (Turkey); Institute of Biomedical Engineering, Bogazici University, Istanbul (Turkey)

2007-05-15

45

Three-dimensional dosimetry of small megavoltage radiation fields using radiochromic gels and optical CT scanning  

NASA Astrophysics Data System (ADS)

The dosimetry of small fields as used in stereotactic radiotherapy, radiosurgery and intensity-modulated radiation therapy can be challenging and inaccurate due to partial volume averaging effects and possible disruption of charged particle equilibrium. Consequently, there exists a need for an integrating, tissue equivalent dosimeter with high spatial resolution to avoid perturbing the radiation beam and artificially broadening the measured beam penumbra. In this work, radiochromic ferrous xylenol-orange (FX) and leuco crystal violet (LCV) micelle gels were used to measure relative dose factors (RDFs), percent depth dose profiles and relative lateral beam profiles of 6 MV x-ray pencil beams of diameter 28.1, 9.8 and 4.9 mm. The pencil beams were produced via stereotactic collimators mounted on a Varian 2100 EX linear accelerator. The gels were read using optical computed tomography (CT). Data sets were compared quantitatively with dosimetric measurements made with radiographic (Kodak EDR2) and radiochromic (GAFChromic® EBT) film, respectively. Using a fast cone-beam optical CT scanner (Vista™), corrections for diffusion in the FX gel data yielded RDFs that were comparable to those obtained by minimally diffusing LCV gels. Considering EBT film-measured RDF data as reference, cone-beam CT-scanned LCV gel data, corrected for scattered stray light, were found to be in agreement within 0.5% and -0.6% for the 9.8 and 4.9 mm diameter fields, respectively. The validity of the scattered stray light correction was confirmed by general agreement with RDF data obtained from the same LCV gel read out with a laser CT scanner that is less prone to the acceptance of scattered stray light. Percent depth dose profiles and lateral beam profiles were found to agree within experimental error for the FX gel (corrected for diffusion), LCV gel (corrected for scattered stray light), and EBT and EDR2 films. The results from this study reveal that a three-dimensional dosimetry method utilizing optical CT-scanned radiochromic gels allows for the acquisition of a self-consistent volumetric data set in a single exposure, with sufficient spatial resolution to accurately characterize small fields.

Babic, Steven; McNiven, Andrea; Battista, Jerry; Jordan, Kevin

2009-04-01

46

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

47

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

48

On the validity of 3D polymer gel dosimetry: II. physico-chemical effects.  

PubMed

This study quantifies some major physico-chemical factors that influence the validity of MRI (PAGAT) polymer gel dosimetry: temperature history (pre-, during and post-irradiation), oxygen exposure (post-irradiation) and volumetric effects (experiment with phantom in which a small test tube is inserted). Present results confirm the effects of thermal history prior to irradiation. By exposing a polymer gel sample to a linear temperature gradient of ?2.8 °C cm?¹ and following the dose deviation as a function of post-irradiation time new insights into temporal variations were added. A clear influence of the temperature treatment on the measured dose distribution is seen during the first hours post-irradiation (resulting in dose deviations up to 12%). This effect diminishes to 5% after 54 h post-irradiation. Imposing a temperature offset (maximum 6 °C for 3 h) during and following irradiation on a series of calibration phantoms results in only a small dose deviation of maximum 4%. Surprisingly, oxygen diffusing in a gel dosimeter up to 48 h post-irradiation was shown to have no effect. Volumetric effects were studied by comparing the dose distribution in a homogeneous phantom compared to the dose distribution in a phantom in which a small test tube was inserted. This study showed that the dose measured inside the test tube was closer to the ion chamber measurement in comparison to the reference phantom without test tube by almost 7%. It is demonstrated that physico-chemical effects are not the major causes for the dose discrepancies encountered in the reproducibility study discussed in the concurrent paper (Vandecasteele and De Deene 2013a Phys. Med. Biol. 58 19-42). However, it is concluded that these physico-chemical effects are important factors that should be addressed to further improve the dosimetric accuracy of 3D MRI polymer gel dosimetry. PMID:23221322

Vandecasteele, Jan; De Deene, Yves

2012-12-06

49

On the validity of 3D polymer gel dosimetry: II. Physico-chemical effects  

NASA Astrophysics Data System (ADS)

This study quantifies some major physico-chemical factors that influence the validity of MRI (PAGAT) polymer gel dosimetry: temperature history (pre-, during and post-irradiation), oxygen exposure (post-irradiation) and volumetric effects (experiment with phantom in which a small test tube is inserted). Present results confirm the effects of thermal history prior to irradiation. By exposing a polymer gel sample to a linear temperature gradient of ˜2.8 °C cm-1 and following the dose deviation as a function of post-irradiation time new insights into temporal variations were added. A clear influence of the temperature treatment on the measured dose distribution is seen during the first hours post-irradiation (resulting in dose deviations up to 12%). This effect diminishes to 5% after 54 h post-irradiation. Imposing a temperature offset (maximum 6 °C for 3 h) during and following irradiation on a series of calibration phantoms results in only a small dose deviation of maximum 4%. Surprisingly, oxygen diffusing in a gel dosimeter up to 48 h post-irradiation was shown to have no effect. Volumetric effects were studied by comparing the dose distribution in a homogeneous phantom compared to the dose distribution in a phantom in which a small test tube was inserted. This study showed that the dose measured inside the test tube was closer to the ion chamber measurement in comparison to the reference phantom without test tube by almost 7%. It is demonstrated that physico-chemical effects are not the major causes for the dose discrepancies encountered in the reproducibility study discussed in the concurrent paper (Vandecasteele and De Deene 2013a Phys. Med. Biol. 58 19-42). However, it is concluded that these physico-chemical effects are important factors that should be addressed to further improve the dosimetric accuracy of 3D MRI polymer gel dosimetry. Both authors contributed equally to this study.

Vandecasteele, Jan; De Deene, Yves

2013-01-01

50

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

51

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.

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

2010-01-01

52

An x-ray CT polymer gel dosimetry prototype: I. Remnant artefact removal  

NASA Astrophysics Data System (ADS)

In this study a new x-ray CT polymer gel dosimetry (PGD) filtering technique is presented for the removal of (i) remnant ring and streak artefacts, and (ii) ‘structured’ noise in the form of minute, intrinsic gel density fluctuations. It is shown that the noise present within x-ray CT PGD images is not purely stochastic (pixel by pixel) in nature, but rather is ‘structured’, and hence purely stochastic-based noise-removal filters fail in removing this significant, unwanted noise component. The remnant artefact removal (RAR) technique is based on a class of signal stripping (i.e. baseline-estimation) algorithms typically used in the estimation of unwanted non-uniform baselines underlying spectral data. Here the traditional signal removal algorithm is recast, whereby the ‘signal’ that is removed is the structured noise and remnant artefacts, leaving the desired polymer gel dose distribution. The algorithm is extended to 2D and input parameters are optimized for PGD images. RAR filter results are tested on (i) synthetic images with measured gel background images added, in order to accurately represent actual noise present in PGD images, and (ii) PGD images of a three-field gel irradiation. RAR results are compared to a top-performing noise filter (adaptive mean, AM), used in previous x-ray CT PGD studies. It is shown that, in all cases, the RAR filter outperforms the AM filter, particularly in cases where either (i) a low-dose gel image has been acquired or (ii) the signal-to-noise ratio of the PG image is low, as in the case when a low number of image averages are acquired within a given experiment. Guidelines for the implementation of the RAR filter are given.

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

2012-05-01

53

Characteristics of a new polymer gel for high-dose gradient dosimetry using a micro optical CT scanner  

Microsoft Academic Search

The properties of a new polymer gel with two sensitivities, made specifically for high-dose-gradient dosimetry, were investigated. The measurements were performed at NIST using a 1cm×1cm calibrated 60Co field, and a 1cm active diameter 90Sr\\/90Y beta particle source. A high-resolution laser CT scanner was used to quantify the response. The results show that the high-sensitivity gel responds linearly to the

G. Massillon-JL; R. Minniti; C. G. Soares; M. J. Maryanski; S. Robertson

2010-01-01

54

Magnetization transfer proportion: a simplified measure of dose response for polymer gel dosimetry  

PubMed Central

The response to radiation of polymer gel dosimeters has most often been described by measuring the nuclear magnetic resonance transverse relaxation rate as a function of dose. This approach is highly dependent upon the choice of experimental parameters, such as the echo spacing time for Carr-Purcell-Meiboom-Gill-type pulse sequences, and is difficult to optimize in imaging applications where a range of doses are applied to a single gel, as is typical for practical uses of polymer gel dosimetry. Moreover, errors in computing dose can arise when there are substantial variations in the radiofrequency (B1) field or resonant frequency, as may occur for large samples. Here we consider the advantages of using magnetization transfer imaging as an alternative approach and propose the use of a simplified quantity, the magnetization transfer proportion (MTP), to assess doses. This measure can be estimated through two simple acquisitions and is more robust in the presence of some sources of system imperfections. It also has a dependence upon experimental parameters that is independent of dose, allowing simultaneous optimization at all dose levels. The MTP is shown to be less susceptible to B1 errors than are CPMG measurements of R2. The dose response can be optimized through appropriate choices of the power and offset frequency of the pulses used in magnetization transfer imaging.

Whitney, Heather M; Gochberg, Daniel F; Gore, John C

2009-01-01

55

Evaluation of the dose enhancement of iodinated compounds by polyacrylamide gel dosimetry  

NASA Astrophysics Data System (ADS)

In this study, polyacrylamide gel (PAG) dosimetry is used to quantitatively assess the efficiency of radiation sensitizers. The local dose enhancement caused by the K-edge absorption of certain atoms such as bromine and iodine can be employed to increase the damage to neighboring molecules and cells. Clonogenic assays can assess the radiation survival of cells to evaluate the efficiency of radiation sensitizers, but this technique requires reliable cell growth in culture media and is time consuming. Our purpose is to use PAG dosimetry to investigate the sensitizing potential of radiation sensitizers such as iodinated compounds. Incorporation of iodinated radiation sensitizers such as NaI and an iodinated contrast agent leads to a quantifiable dose enhancement ratio. When irradiated at low energy (~40 keV), the dose enhancement ratio of the iodinated contrast agent at concentrations of 0.01 (3.5 mg ml-1), 0.05 (6 mg ml-1) and 0.1 (12 mg ml-1) M are 1.16 ± 0.02, 1.39 ± 0.03 and 1.82 ± 0.04, respectively. No dose enhancement was observed when the samples were irradiated with 1.25 MeV gamma photons.

Meesat, Ridthee; Jay-Gerin, Jean-Paul; Khalil, Abdelouahed; Lepage, Martin

2009-10-01

56

Characteristics of a new polymer gel for high-dose gradient dosimetry using a micro optical CT scanner.  

PubMed

The properties of a new polymer gel with two sensitivities, made specifically for high-dose-gradient dosimetry, were investigated. The measurements were performed at NIST using a 1cmx1cm calibrated (60)Co field, and a 1cm active diameter (90)Sr/(90)Y beta particle source. A high-resolution laser CT scanner was used to quantify the response. The results show that the high-sensitivity gel responds linearly to the absorbed dose for doses from 0.5 up to 15Gy, while the low-sensitivity one is linear up to 225Gy. For both radiation types, the gel response remains stable in time up to a month after the irradiation. The response of the gel was found to have no dose rate dependence for dose rates ranging from 3.7 to 15mGy/s. Within the measurement uncertainty, the gel response is more sensitive for beta particles than high energy photons. PMID:19775899

Massillon-JL, G; Minniti, R; Soares, C G; Maryanski, M J; Robertson, S

2009-09-03

57

Measurement of the absorbed dose distribution near an 192Ir intravascular brachytherapy seed using a high-spatial-resolution gel dosimetry system  

Microsoft Academic Search

The absorbed dose distribution at sub-millimeter distances from the Best single 192Ir intravascular brachytherapy seed was measured using a high-spatial-resolution gel dosimetry system. Two gel phantoms from the same batch were used; one for the seed irradiation and one for calibration. Since the response of this gel is energy independent for photons between 20 and 1250 keV, the gel was

G Massillon-JL; R Minniti; M G Mitch; C G Soares

2012-01-01

58

Three-dimensional dose verification for intensity modulated radiation therapy using optical CT based polymer gel dosimetry  

SciTech Connect

Dose distributions generated from intensity-modulated-radiation-therapy (IMRT) treatment planning present high dose gradient regions in the boundaries between the target and the surrounding critical organs. Dose accuracy in these areas can be critical, and may affect the treatment. With the increasing use of IMRT in radiotherapy, there is an increased need for a dosimeter that allows for accurate determination of three-dimensional (3D) dose distributions with high spatial resolution. In this study, polymer gel dosimetry and an optical CT scanner have been employed to implement 3D dose verification for IMRT. A plastic cylinder of 17 cm diameter and 12 cm height, filled with BANG registered 3 polymer gels (MGS Research, Inc., Madison, CT) and modified to optimal dose-response characteristics, was used for IMRT dose verification. The cylindrical gel phantom was immersed in a 24x24x20 cm water tank for an IMRT irradiation. The irradiated gel sample was then scanned with an optical CT scanner (MGS Research Inc., Madison, CT) utilizing a single He-Ne laser beam and a single photodiode detector. Similar to the x-ray CT process, filtered back-projection was used to reconstruct the 3D dose distribution. The dose distributions measured from the gel were compared with those from the IMRT treatment planning system. For comparative dosimetry, a solid water phantom of 24x24x20 cm, having the same geometry as the water tank for the gel phantom, was used for EDR2 film and ion chamber measurements. Root mean square (rms) deviations for both dose difference and distance-to-agreement (DTA) were used in three-dimensional analysis of the dose distribution comparison between treatment planning calculations and the gel measurement. Comparison of planar dose distributions among gel dosimeter, film, and the treatment planning system showed that the isodose lines were in good agreement on selected planes in axial, coronal, and sagittal orientations. Absolute point-dose verification was performed with ion chamber measurements at four different points, varying from 48% to 110% of the prescribed dose. The measured and calculated doses were found to agree to within 4.2% at all measurement points. For the comparison between the gel measurement and treatment planning calculations, rms deviations were 2%-6% for dose difference and 1-3 mm for DTA, at 60%-110% doses levels. The results from this study show that optical CT based polymer gel dosimetry has the potential to provide a high resolution, accurate, three-dimensional tool for IMRT dose distribution verification.

Wuu Chengshie; Xu, Y. [Department of Radiation Oncology, Columbia University, New York, New York 10032 (United States)

2006-05-15

59

Cone beam optical computed tomography for gel dosimetry I: scanner characterization  

NASA Astrophysics Data System (ADS)

The ongoing development of easily accessible, fast optical readout tools promises to remove one of the barriers to acceptance of gel dosimetry as a viable tool in cancer clinics. This paper describes the characterization of a number of basic properties of the Vista™ cone beam CCD-based optical scanner, which can obtain high resolution reconstructed data in less than 20 min total imaging and reconstruction time. The suitability of a filtered back projection cone beam reconstruction algorithm is established for optically absorbing dosimeters using this scanner configuration. The system was then shown to be capable of imaging an optically absorbing media-filled 1 L polyethylene terephthalate (PETE) jar dosimeter to a reconstructed voxel resolution of 0.5 × 0.5 × 0.5 mm3. At this resolution, more than 60% of the imaged volume in the dosimeter exhibits minimal spatial distortion, a measurement accuracy of 3-4% and the mean to standard deviation signal-to-noise ratio greater than 100 over an optical absorption range of 0.06-0.18 cm-1. An inter-day scan precision of 1% was demonstrated near the upper end of this range. Absorption measurements show evidence of stray light perturbation causing artifacts in the data, which if better managed would improve the accuracy of optical readout. Cone beam optical attenuation measurements of scattering dosimeters, on the other hand, are nonlinearly affected by angled scatter stray light. Scatter perturbation leads to significant cupping artifacts and other inaccuracies that greatly limit the readout of scattering polymer gel dosimeters with cone beam optical CT.

Olding, Tim; Holmes, Oliver; Schreiner, L. John

2010-05-01

60

Initial investigation of a novel light-scattering gel phantom for evaluation of optical CT scanners for radiotherapy gel dosimetry.  

PubMed

There is a need for stable gel materials for phantoms used to validate optical computerized tomography (CT) scanners used in conjunction with radiation-induced polymerizing gel dosimeters. Phantoms based on addition of light-absorbing dyes to gelatine to simulate gel dosimeters have been employed. However, to more accurately simulate polymerizing gels one requires phantoms that employ light-scattering colloidal suspensions added to the gel. In this paper, we present the initial results of using an optical CT scanner to evaluate a novel phantom in which radiation-exposed polymer gels are simulated by the addition of colloidal suspensions of varying turbidity. The phantom may be useful as a calibration transfer standard for polymer gel dosimeters. The tests reveal some phenomena peculiar to light-scattering gels that need to be taken into account when calibrating polymer gel dosimeters. PMID:17473358

Bosi, Stephen; Naseri, Pourandokht; Puran, Alicia; Davies, Justin; Baldock, Clive

2007-05-01

61

Optical CT scanner for in-air readout of gels for external radiation beam 3D dosimetry.  

PubMed

Optical CT scanners for a 3D readout of externally irradiated radiosensitive hydrogels currently require the use of a refractive index (RI) matching liquid bath to obtain suitable optical ray paths through the gel sample to the detector. The requirement for a RI matching liquid bath has been negated by the design of a plastic cylindrical gel container that provides parallel beam geometry through the gel sample for the majority of the projection. The design method can be used for various hydrogels. Preliminary test results for the prototype laser beam scanner with ferrous xylenol-orange gel show geometric distortion of 0.2 mm maximum, spatial resolution limited to beam spot size of about 0.4 mm and 0.8% noise (1 SD) for a uniform irradiation. Reconstruction of a star pattern irradiated through the cylinder walls demonstrates the suitability for external beam applications. The extremely simple and cost-effective construction of this optical CT scanner, together with the simplicity of scanning gel samples without RI matching fluid increases the feasibility of using 3D gel dosimetry for clinical external beam dose verifications. PMID:22644104

Ramm, Daniel; Rutten, Thomas P; Shepherd, Justin; Bezak, Eva

2012-05-30

62

Artefacts in multi-echo T2 imaging for high-precision gel dosimetry: II. Analysis of B1-field inhomogeneity.  

PubMed

In BANG gel dosimetry, the spin-spin relaxation rate, R2 = 1/T2, is related to radiation dose that has been delivered to a gel phantom. R2 is calculated by fitting the pixel intensities of a set of differently T2-weighted base images. The accuracy that is aimed for in this quantitative MR application is about 5% relative to the maximum dose. In a conventional imaging MR scanner, however, several imaging artefacts may perturb the final dose map. These deviations manifest themselves as either a deformation of the dose map or an inaccuracy of the dose pixel value. Inaccuracies in the dose maps are caused by both spatial and temporal deviations in signal intensities during scanning. This study deals with B1-field inhomogeneities as a source of dose inaccuracy. First, the influence of B1-field inhomogeneities on slice profiles is investigated using a thin-slice phantom. Secondly, a FLASH sequence is used to map the B1-field by assessing the effective flip angle in each voxel of a homogeneous phantom. In addition, both experiments and computer simulations revealed the effects of B1 field inhomogeneities on the measured R2. This work offers a method to correct R2 maps for B1 -field inhomogeneities. PMID:10943921

De Deenet, Y; De Wagter, C; De Neve, W; Achten, E

2000-07-01

63

Investigation of a 2D two-point maximum entropy regularization method for signal-to-noise ratio enhancement: application to CT polymer gel dosimetry  

NASA Astrophysics Data System (ADS)

This study presents a new method of image signal-to-noise ratio (SNR) enhancement by utilizing a newly developed 2D two-point maximum entropy regularization method (TPMEM). When utilized as an image filter, it is shown that 2D TPMEM offers unsurpassed flexibility in its ability to balance the complementary requirements of image smoothness and fidelity. The technique is evaluated for use in the enhancement of x-ray computed tomography (CT) images of irradiated polymer gels used in radiation dosimetry. We utilize a range of statistical parameters (e.g. root-mean square error, correlation coefficient, error histograms, Fourier data) to characterize the performance of TPMEM applied to a series of synthetic images of varying initial SNR. These images are designed to mimic a range of dose intensity patterns that would occur in x-ray CT polymer gel radiation dosimetry. Analysis is extended to a CT image of a polymer gel dosimeter irradiated with a stereotactic radiation therapy dose distribution. Results indicate that TPMEM performs strikingly well on radiation dosimetry data, significantly enhancing the SNR of noise-corrupted images (SNR enhancement factors >15 are possible) while minimally distorting the original image detail (as shown by the error histograms and Fourier data). It is also noted that application of this new TPMEM filter is not restricted exclusively to x-ray CT polymer gel dosimetry image data but can in future be extended to a wide range of radiation dosimetry data.

Jirasek, A.; Matthews, Q.; Hilts, M.; Schulze, G.; Blades, M. W.; Turner, R. F. B.

2006-05-01

64

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

65

New radiochromic gel for 3D dosimetry based on Turnbull blue: basic properties  

Microsoft Academic Search

The recently developed new radiochromic gel dosimeter based on Turnbull blue dye formed by irradiation (the TBG dosimeter) does not exhibit dose pattern degradation due to diffusion effects as observed in the Fricke-gel dosimeter with xylenol orange incorporated into the gel matrix (the FXG dosimeter). The TBG dosimeter can be easily prepared and its optical properties enable evaluation of the

Jaroslav Solc; Václav Spevácek

2009-01-01

66

Preliminary dosimetry investigation of Tc-99m diagnostic radionuclide by NIPAM gel dosimeter  

NASA Astrophysics Data System (ADS)

The N-isopropylacrylamide (NIPAM) gel dosimeter was investigated as a suitable material for measuring absorbed doses from radionuclide sources. In this study, NIPAM gel dosimeter was used to evaluate the dose distributions of the Tc-99m radionuclide in NIPAM gel. The accumulated radioactivity range of the Tc-99m NIPAM gel is from approximately 0 MBq to 13.6 MBq (about 0.37 mCi). The NIPAM gel dosimeter with high stability and high-dose linear and non-energy dependent properties can provide various radiopharmaceutical activity intensities in the conduct of dose assessment in nuclear medicine, thereby producing the most promising dose verification tools.

Huang, You-Ruei; Chang, Yuan-Jen; Hsieh, Ling-Ling; Yu, Bi-Wei; Chu, Chien-Hau; Hsieh, Bor-Tsung

2013-06-01

67

Calibration and conformational studies in radiation dosimetry using polymer gel dosimeters  

Microsoft Academic Search

The polymer gel dosimeter made its debut in the early 90's and dosimetrists and medical physicists alike were excited about the prospect of using the gel dosimeter as an effective and useful three-dimensional modeling tool. Research in the early to mid-90's brought on better polymer mixtures with greater sensitivity and shelf life. Nearly a decade later, these gels are not

Richard L. Cardenas

2001-01-01

68

Preliminary investigation of PAGAT polymer gel radionuclide dosimetry of Tc-99m  

NASA Astrophysics Data System (ADS)

PAGAT polymer gel was investigated as a suitable dosimeter materials for measuring absorbed dose from the unsealed source radionuclide Tc-99m. Differing amounts of Tc-99m over the range of 25-5000 MBq were introduced into a normoxic polymer gel mixture (PAGAT) in sealed nitrogen-filled P6 glass vials. After irradiation the gels were evaluated using MRI more than 48 hours after preparation to allow for radioactive decay. The dose delivered to the vial was also calculated empirically. R2 versus total activity curves were obtained over a number of experiments and these were used to evaluate the relationship between the amount of gel polymerization and the dose deposited by the radionuclide. A linear response up to 1000 MBq (corresponding to 20Gy) was displayed and was still behaving monotonically at 5000 MBq. Polymer gels offer the potential to measure radiation dose three-dimensionally using MRI.

Braun, Kelly; Bailey, Dale; Hill, Brendan; Baldock, Clive

2009-05-01

69

NIPAM polymer gel dosimetry for IMRT four-field box irradiation using optical-CT scanner  

NASA Astrophysics Data System (ADS)

The study assessed the dosimetric characteristics of the N-isopropylacrylamide (NIPAM) polymer gel dosimeter. Experiments on the intra-dosimeter consistency and reproducibility of NIPAM polymer gels were performed. A cylindrical NIPAM gel phantom measuring 10 cm (diameter) by 10 cm (height) by 3 mm (thickness) was irradiated using the four-field box treatment with a field size of 3 cm × 3 cm. A fast, optical computerized tomography scanner was used to scan the gel phantoms. The results showed that the dose profiles were consistent at various depths. The isodose lines agreed quantitatively with the calculated TPS dose and the measured NIPAM polymer gel dose within the 30 to 90 percentage isodose lines. In addition, the Gamma pass rates were determined to be 94.9%, 95.2%, and 95.7% at depths of 40 mm, 45 mm, and 50 mm, respectively, using 5% dose difference and 5 mm distance-to-agreement criteria. Using the same Gamma criteria, the Gamma pass rates were 95.1%, 95.3%, and 95.7% for the three replicated. The results indicated that the NIPAM polymer gel dosimeter was stable and reliable. The dosimetric characteristics highlighted the potential of NIPAM polymer gel dosimeter in radiotherapy.

Yao, C. H.; Hsu, W. T.; Hsu, S. M.; Ma, P. Y. L.; Hsieh, B. T.; Chang, Y. J.

2013-06-01

70

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

71

New radiochromic gel for 3D dosimetry based on Turnbull blue: basic properties.  

PubMed

The recently developed new radiochromic gel dosimeter based on Turnbull blue dye formed by irradiation (the TBG dosimeter) does not exhibit dose pattern degradation due to diffusion effects as observed in the Fricke-gel dosimeter with xylenol orange incorporated into the gel matrix (the FXG dosimeter). The TBG dosimeter can be easily prepared and its optical properties enable evaluation of the gel's response using the cone-beam optical computed tomography technique. The preparation procedure is described in the paper along with the basic characteristics of the gel, including dose response, dose sensitivity, ageing under different storage conditions, diffusion rates of Turnbull blue and gel density. The measurement of diffusion is described in more detail. The same method was applied to the FXG dosimeter for direct comparison. It was found that the diffusion coefficient of the TBG dosimeter stored at 24 degrees C is less than 4 x 10(-3) mm(2) h(-1) (1sigma confidence level), compared to the value of 7.3 x 10(-1) mm(2) h(-1) (1sigma) of the FXG dosimeter measured at the same temperature. Although the TBG dosimeter is less sensitive than the FXG dosimeter, its diffusion coefficient is practically negligible and, therefore, it offers large potential as a three-dimensional dosimeter for applications encompassing sharp dose gradients such as high-dose-rate brachytherapy. PMID:19652291

Solc, Jaroslav; Spevácek, Václav

2009-08-04

72

MRI-based polymer gel dosimetry for validating plans with multiple matrices in Gamma Knife stereotactic radiosurgery.  

PubMed

One of treatment planning techniques with Leksell GammaPlan (LGP) for Gamma Knife stereotactic radiosurgery (GKSRS) uses multiple matrices with multiple dose prescriptions. Computational complexity increases when shots are placed in multiple matrices with different grid sizes. Hence, the experimental validation of LGP calculated dose distributions is needed for those cases. For the current study, we used BANG3 polymer gel contained in a head-sized glass bottle to simulate the entire treatment process of GKSRS. A treatment plan with three 18 mm shots and one 8 mm shot in separate matrices was created with LGP. The prescribed maximum dose was 8 Gy to three shots and 16 Gy to one of the 18 mm shots. The 3D dose distribution recorded in the gel dosimeter was read using a Siemens 3T MRI scanner. The scanning parameters of a CPMG pulse sequence with 32 equidistant echoes were as follows: TR = 7 s, echo step = 13.6 ms, field-of-view = 256 mm × 256 mm, and pixel size = 1 mm × 1 mm. Interleaved acquisition mode was used to obtain 15 to 45 2-mm-thick slices. Using a calibration relationship between absorbed dose and the spin-spin relaxation rate (R2), we converted R2 images to dose images. MATLAB-based in-house programs were used for R2 estimation and dose comparison. Gamma-index analysis for the 3D data showed gamma values less than unity for 86% of the voxels. Through this study we accomplished the first application of polymer gel dosimetry for a true comparison between measured 3D dose distributions and LGP calculations for plans using multiple matrices for multiple targets. PMID:21587176

Gopishankar, N; Watanabe, Yoichi; Subbiah, Vivekanandhan

2011-01-31

73

The application of polymer gel dosimeters to dosimetry for targeted radionuclide therapy  

Microsoft Academic Search

There is a lack of standardized methodology to perform dose calculations for targeted radionuclide therapy and at present no method exists to objectively evaluate the various approaches employed. The aim of the work described here was to investigate the practicality and accuracy of calibrating polymer gel dosimeters such that dose measurements resulting from complex activity distributions can be verified. Twelve

J. I. Gear; G. D. Flux; E. Charles-Edwards; M. Partridge; G. Cook; R. J. Ott

2006-01-01

74

Dosimetric comparison between three dimensional treatment planning system, Monte Carlo simulation and gel dosimetry in nasopharynx phantom for high dose rate brachytherapy.  

PubMed

Purpose: For the treatment of nasopharnx carcinoma (NPC) using brachytherapy methods and high-energy photon sources are common techniques. In the common three dimensional (3D) treatments planning, all of the computed tomography images are assumed homogeneous. This study presents the results of Monte Carlo calculations for non-homogeneous nasopharynx phantom, MAGICA normoxic gel dosimetry and 3D treatment planning system (TPS). Materials and Methods: The head phantom was designed with Plexiglas cylinder, head bone, and nasopharynx brachytherapy silicon applicator. For the simulations, version 5 of the Monte Carlo N-particle transport code (MCNP5) was used. 3D treatment planning was performed in Flexiplan software. A normoxic radiosensitive polymer gel was fabricated under normal atmospheric conditions and poured into test tubes (for calibration curve) and the head phantom. In addition, the head phantom was irradiated with Flexitron afterloader brachytherapy machine with 192 Ir source. To obtain calibration curves, 11 dosimeters were irradiated with dose range of 0-2000 cGy. Evaluations of dosimeters were performed on 1.5T scanner. Results: Two-dimensional iso-dose in coronal plan at distances of z = +0.3, -0.3 cm was calculated. There was a good accordance between 3D TPS and MCNP5 simulation and differences in various distances were between 2.4% and 6.1%. There was a predictable accordance between MAGICA gel dosimetry and MCNP5 simulation and differences in various distances were between 5.7% and 7.4%. Moreover, there was an acceptable accordance between MAGICA gel dosimetry and MCNP5 data and differences in various distances were between 5.2% and 9.4%. Conclusion: The sources of differences in this comparison are divided to calculations variation and practical errors that was added in experimental dosimetry. The result of quality assurance of nasopharynx high dose rate brachytherapy is consistent with international standards. PMID:24125974

Fazli, Zeynab; Sadeghi, Mahdi; Zahmatkesh, M H; Mahdavi, Seied Rabei; Tenreiro, Claudio

75

The use of gel dosimetry to measure the 3D dose distribution of a 90Sr\\/90Y intravascular brachytherapy seed  

Microsoft Academic Search

Absorbed dose distributions in 3D imparted by a single 90Sr\\/90Y beta particle seed source of the type used for intravascular brachytherapy were investigated. A polymer gel dosimetry medium was used as a dosemeter and phantom, while a special high-resolution laser CT scanner with a spatial resolution of 100 µm in all dimensions was used to quantify the data. We have

G Massillon-JL; R Minniti; M G Mitch; M J Maryanski; C G Soares

2009-01-01

76

Indigenously developed multipurpose acrylic head phantom for verification of IMRT using film and gel dosimetry.  

PubMed

The purpose of this study was to validate the newly designed acrylic phantom for routine dosimetric purpose in radiotherapy. The phantom can be used to evaluate and compare the calculated dose and measured dose using film and gel dosimetric methods. In this study, a doughnut-shaped planning target volume (8.54 cm3) and inner organ at risk (0.353 cm3) were delineated for an IMRT test plan using the X-ray CT image of the phantom. The phantom consists of acrylic slabs which are integrated to form a human head with a hole in the middle where several dosimetric inserts can be positioned for measurement. An inverse planning with nine coplanar intensity-modulated fields was created using Pinnacle TPS. For the film analysis, EBT2 film, flatbed scanner, in-house developed MATLAB codes and ImageJ software were used. The 3D dose distribution recorded in the MAGAT gel dosimeter was read using a 1.5 T MRI scanner. Scanning parameters were CPMG pulse sequence with 8 equidistant echoes, TR = 5600, echo step = 22 ms, pixel size = 0.5 × 0.5, slice thickness = 2 mm. Using a calibration relationship between absorbed dose and spin-spin relaxation rate (R2), R2 images were converted to dose images. The dose comparison was accomplished using in-house MATLAB-based graphical user interface named "IMRT3DCMP". For gel measurement dose grid from the TPS was extracted and compared with the measured dose grid of the gel. Gamma index analysis of film measurement for the tolerance criteria of 2%/2mm, 1%/1 mm showed more than 90% voxels pass rate. Gamma index analysis of 3D gel measurement data showed more than 90% voxels pass rate for different tolerance criteria of 2%/2 mm and 1%/1 mm. Overall both 2D and 3D measurement were in close agreement with the Pinnacle TPS calculated dose. The phantom designed is cost-effective and the results are promising, but further investigation is required to validate the phantom with other 3D conformal techniques for dosimetric purpose. PMID:23470932

Gopishankar, N; Vivekanandhan, S; Rath, G K; Laviraj, M A; Senthilkumaran, S; Kale, S S; Thulkar, S; Bisht, R K; Subramani, V

2013-03-04

77

Experimental 3D dosimetry around a high-dose-rate clinical 192Ir source using a polyacrylamide gel (PAG) dosimeter  

Microsoft Academic Search

It is well known that the experimental dosimetry of brachytherapy sources presents a challenge. Depending on the particular dosimeter used, measurements can suffer from poor spatial resolution (ion chambers), lack of 3D information (film) or errors due to the presence of the dosimeter itself distorting the radiation flux. To avoid these problems, we have investigated the dosimetry of a clinical

M. McJury; P. D. Tapper; V. P. Cosgrove; P. S. Murphy; S. Griffin; M. O. Leach; S. Webb; M. Oldham

1999-01-01

78

Mycosis Fungoides electron beam absorbed dose distribution using Fricke xylenol gel dosimetry  

NASA Astrophysics Data System (ADS)

Radiotherapy uses ionizing radiation to destroy tumor cells. The absorbed dose control in the target volume is realized through radiation sensors, such as Fricke dosimeters and radiochromic film, which permit to realize bi-dimensional evaluations at once and because of that, they will be used in this study as well. Among the several types of cancer suitable for ionizing radiation treatment, the Mycosis Fungoides, a lymphoma that spreads on the skin surface and depth, requires for its treatment total body irradiation by high-energy electrons. In this work the Fricke xylenol gel (FXG) was used in order to obtain information about the absorbed dose distribution induced by the electron interactions with the irradiated tissues and to control this type of treatment. FXG can be considered as an alternative dosimeter, since up to now only films have been used. FXG sample cuvettes, simulating two selected tomos (cranium and abdomen) of the Rando anthropomorphic phantom, were positioned along with radiochromic films for comparison. The phantom was subjected to Stanford total body irradiation using 6 MeV electrons. Tomographic images were acquired for both dosimeters and evaluated through horizontal and vertical profiles along the tomographic centers. These profiles were obtained through a Matlab routine developed for this purpose. From the obtained results, one could infer that, for a superficial and internal patient irradiation, the FXG dosimeter showed an absorbed dose distribution similar to the one of the film. These results can validate the FXG dosimeter as an alternative dosimeter for the Mycosis Fungoides treatment planning.

da Silveira, Michely C.; Sampaio, Francisco G. A.; Petchevist, Paulo C. D.; de Oliveira, André L.; Almeida, Adelaide De

2011-12-01

79

Fitness  

MedlinePLUS

... responsibilities. So don’t wait — get fit today! Content last updated July 24, 2013 top Twitter Facebook About this site Mission Statement Privacy Policy For the Media Contact Us This site is owned and maintained by the Office on Women's Health in the Office of the Assistant Secretary for Health ...

80

An evaluation of the TSE MR sequence for time efficient data acquisition in polymer gel dosimetry of applications involving high doses and steep dose gradients  

SciTech Connect

The use of magnetic resonance imaging as a readout method for polymer gel dosimetry commonly involves long imaging sessions, particularly when high spatial resolution is required in all three dimensions, for the investigation of dose distributions with steep dose gradients and stringent dose delivery specifications. In this work, a volume selective turbo spin echo (TSE) pulse sequence is compared to the established Carr-Purcell-Meiboom-Gill (CPMG) multiecho acquisition with regard to providing accurate dosimetric results in significantly reduced imaging times. Polyethylene glycol diacrylate based (PABIG) gels were irradiated and subsequently scanned to obtain R2 relaxation rate measurements, using a CPMG multiecho sequence and a dual echo TSE utilizing an acceleration (turbo) factor of 64. R2 values, plotted against corresponding Monte Carlo dose calculations, provided calibration data of PABIG gels dose response over a wide dose range. A linear R2 versus dose relationship was demonstrated for both sequences with TSE results presenting reduced dose sensitivity. Although TSE data were found to deviate from linearity at lower doses compared to CPMG data, a relatively wide dynamic dose range of response extending up to approximately 100 Gy was observed for both sequences. The TSE and CPMG sequences were evaluated with a brachytherapy irradiation using a high dose rate {sup 192}Ir source and a gamma knife stereotactic radiosurgery irradiation with a single 4 mm collimator helmet shot. Dosimetric results obtained with the TSE and CPMG are shown to compare equally well with the expected dose distributions for these irradiations. The 60-fold scan time reduction achieved with TSE implies that this sequence could prove to be a useful tool for the introduction of polymer gel dosimetry in clinical radiation therapy applications involving high doses and steep dose gradients.

Baras, P.; Seimenis, I.; Sandilos, P.; Vlahos, L.; Bieganski, T.; Georgiou, E.; Pantelis, E.; Papagiannis, P.; Sakelliou, L. [Philips Hellas Medical Systems, 44 Kifissias Ave., Maroussi 151 25, Athens (Greece); Department of Radiology, Medical School, University of Athens, Areteion Hospital, 76 Vas. Sofias Ave., 115 28 Athens (Greece) and Medical Physics Department, Hygeia Hospital, Kiffisias Avenue, 24 Erythrou Stavrou, Marousi, 151 23, Athens (Greece); Department of Radiology, Mother's Memorial Hospital, Rzgowska 281/289, 93-388, Lodz (Poland); Medical Physics Department, 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)

2005-11-15

81

On the accuracy of monomer/polymer gel dosimetry in the proximity of a high-dose-rate 192Ir source  

NASA Astrophysics Data System (ADS)

The aim of this work was to investigate the applicability of MR-based polymer gel dosimetry to measure the absorbed dose distribution at short distance from an iridium-192 brachytherapy point source. In this paper, different methodological problems that may result in significant errors in the measured dose distribution are discussed. First of all the extent to which physico-chemical mechanisms alter the dose response is discussed. The most important among these are the oxygen permeability of the catheter material and monomer-diffusion-related effects during irradiation. The effect of oxygen on the dose-R2 curve has been determined quantitatively and an oxygen map is performed using a well-defined external irradiation beam. The effect of diffusion of monomer during irradiation has been simulated. Another contribution of errors is related to magnetic susceptibility differences between the catheter and the gel during scanning the irradiated gel. The magnetic field distortion has been mapped by using both an experimental MRI technique and by simulation. Moreover, in constructing a dose-versus-distance curve by polar averaging, the sensitivity to the exact distance between source and point of measurement and to partial volume effects is illustrated. An optimization program is proposed to determine the location of the source on a sub-pixel scale.

DeDeene, Y.; Reynaert, N.; DeWagter, C.

2001-11-01

82

Effects of phantom volume and shape on the accuracy of MRI BANG gel dosimetry using BANG3TM  

Microsoft Academic Search

Complex radiotherapy techniques call for three-dimensional dosimetric methods with high spatial resolution. Radiation-sensitive polymer gel systems (e.g. commercially available BANGTM gel), read using MRI T2 mapping, offer a promising solution. A series of calibration test tubes is traditionally used to calculate the dose delivered to a larger, differently shaped volume of gel. In this work, we investigated the implicit assumption

N D MacDougall; M E Miquel; S F Keevil

2007-01-01

83

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

Microsoft Academic Search

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\\/dm³. Both nuclear magnetic resonance (NMR)

Yves de Deene; Koen Vergote; Carolien Claeys; Carlos De Wagter

2006-01-01

84

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

Microsoft Academic Search

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

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

2010-01-01

85

MAGAT gel and EBT2 film-based dosimetry for evaluating source plugging-based treatment plan in Gamma Knife stereotactic radiosurgery.  

PubMed

This work illustrates a procedure to assess the overall accuracy associated with Gamma Knife treatment planning using plugging. The main role of source plugging or blocking is to create dose falloff in the junction between a target and a critical structure. We report the use of MAGAT gel dosimeter for verification of an experimental treatment plan based on plugging. The polymer gel contained in a head-sized glass container simulated all major aspects of the treatment process of Gamma Knife radiosurgery. The 3D dose distribution recorded in the gel dosimeter was read using a 1.5T MRI scanner. Scanning protocol was: CPMG pulse sequence with 8 equidistant echoes, TR = 7 s, echo step = 14 ms, pixel size = 0.5mm × 0.5mm, and slice thickness of 2 mm. Using a calibration relationship between absorbed dose and spin-spin relaxation rate (R2), we converted R2 images to dose images. Volumetric dose comparison between treatment planning system (TPS) and gel measurement was accomplished using an in-house MATLAB-based program. The isodose overlay of the measured and computed dose distribution on axial planes was in close agreement. Gamma index analysis of 3D data showed more than 94% voxel pass rate for different tolerance criteria of 3%/2 mm, 3%/1 mm and 2%/2 mm. Film dosimetry with GAFCHROMIC EBT 2 film was also performed to compare the results with the calculated TPS dose. Gamma index analysis of film measurement for the same tolerance criteria used for gel measurement evaluation showed more than 95% voxel pass rate. Verification of gamma plan calculated dose on account of shield is not part of acceptance testing of Leksell Gamma Knife (LGK). Through this study we accomplished a volumetric comparison of dose distributions measured with a polymer gel dosimeter and Leksell GammaPlan (LGP) calculations for plans using plugging. We propose gel dosimeter as a quality assurance (QA) tool for verification of plug-based planning. PMID:23149780

Natanasabapathi, Gopishankar; Subbiah, Vivekanandhan; Kale, Shashank Sharad; Rath, Goura Kishor; Senthilkumaran, S; Thulkar, Sanjay; Subramani, Vellaiyan; Laviraj, M A; Bisht, Raj Kishor; Mahapatra, A K

2012-11-08

86

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

87

A simple modification of TG-43 based brachytherapy dosimetry with improved fitting functions: application to the selectSeed source.  

PubMed

A variation of TG-43 protocol for seeds with cylindrical symmetry aiming at a better description of the radial and anisotropy functions is proposed. The TG-43 two dimensional formalism is modified by introducing a new anisotropy function. Also new fitting functions that permit a more robust description of the radial and anisotropy functions than usual polynomials are studied. The relationship between the new anisotropy function and the anisotropy factor included in the one-dimensional TG-43 formalism is analyzed. The new formalism is tested for the (125)I Nucletron selectSeed brachytherapy source, using Monte Carlo simulations performed with PENELOPE. The goodness of the new parameterizations is discussed. The results obtained indicate that precise fits can be achieved, with a better description than that provided by previous parameterizations. Special care has been taken in the description and fitting of the anisotropy factor near the source. The modified formalism shows advantages with respect to the usual one in the description of the anisotropy functions. The new parameterizations obtained can be easily implemented in the clinical planning calculation systems, provided that the ratio between geometry factors is also modified according to the new dose rate expression. PMID:22698855

Juan-Senabre, Xavier J; Porras, Ignacio; Lallena, Antonio M

2012-06-12

88

Monte Carlo verification of gel dosimetry measurements for stereotactic radiotherapyExperimental aspects of this work were originally presented at the Engineering and Physical Sciences in Medicine Conference (EPSM-ABEC), Melbourne, 2010  

Microsoft Academic Search

The quality assurance of stereotactic radiotherapy and radiosurgery treatments requires the use of small-field dose measurements that can be experimentally challenging. This study used Monte Carlo simulations to establish that PAGAT dosimetry gel can be used to provide accurate, high-resolution, three-dimensional dose measurements of stereotactic radiotherapy fields. A small cylindrical container (4 cm height, 4.2 cm diameter) was filled with

T Kairn; M L Taylor; S B Crowe; L Dunn; R D Franich; J Kenny; R T Knight; J V Trapp

2012-01-01

89

Measurement of the absorbed dose distribution near an 192Ir intravascular brachytherapy seed using a high-spatial-resolution gel dosimetry system  

NASA Astrophysics Data System (ADS)

The absorbed dose distribution at sub-millimeter distances from the Best single 192Ir intravascular brachytherapy seed was measured using a high-spatial-resolution gel dosimetry system. Two gel phantoms from the same batch were used; one for the seed irradiation and one for calibration. Since the response of this gel is energy independent for photons between 20 and 1250 keV, the gel was calibrated using a narrowly collimated 60Co gamma-ray beam (cross-sectional area ˜1 cm2). A small format laser computed tomography scanner was used to acquire the data. The measurements were carried out with a spatial resolution of 100 µm in all dimensions. The seed was calibrated at NIST in terms of air-kerma strength. The absorbed dose rate as well as the radial dose function, gL(r), was measured for radial distances between 0.6 and 12.6 mm from the seed center. The dose rate constant was measured, yielding a value of ? = (1.122 ± 0.032) cGy h-1 U-1, which agrees with published data within the measurement uncertainty. For distances between 0.6 and 1.5 mm, gL(r) decreases from a maximum value of 1.06 down to 1.00; between 1.5 and 6.7 mm, an enhancement is clearly observed with a maximum value around 1.24 and beyond 6.7 mm, gL(r) has an approximately constant value around 1.0, which suggests that this seed can be considered as a point source only at distances larger than 6.7 mm. This latter observation agrees with data for the same seed reported previously using Gafchromic film MD-55-2. Additionally, published Monte Carlo (MC) calculations have predicted the observed behavior of the radial dose function resulting from the absorbed dose contributions of beta particles and electrons emitted by the 192Ir seed. Nonetheless, in the enhancement region, MC underestimates the dose by approximately 20%. This work suggests that beta particles and electrons emitted from the seed make a significant contribution to the total absorbed dose delivered at distances near the seed center (less than 6 mm) and therefore cannot be neglected, given the dimensions of blood vessel walls.

Massillon-JL, G.; Minniti, R.; Mitch, M. G.; Soares, C. G.

2012-06-01

90

Measurement of the absorbed dose distribution near an 192Ir intravascular brachytherapy seed using a high-spatial-resolution gel dosimetry system.  

PubMed

The absorbed dose distribution at sub-millimeter distances from the Best single (192)Ir intravascular brachytherapy seed was measured using a high-spatial-resolution gel dosimetry system. Two gel phantoms from the same batch were used; one for the seed irradiation and one for calibration. Since the response of this gel is energy independent for photons between 20 and 1250 keV, the gel was calibrated using a narrowly collimated (60)Co gamma-ray beam (cross-sectional area ~1 cm(2)). A small format laser computed tomography scanner was used to acquire the data. The measurements were carried out with a spatial resolution of 100 µm in all dimensions. The seed was calibrated at NIST in terms of air-kerma strength. The absorbed dose rate as well as the radial dose function, g(L)(r), was measured for radial distances between 0.6 and 12.6 mm from the seed center. The dose rate constant was measured, yielding a value of ? = (1.122 ± 0.032) cGy h(-1) U(-1), which agrees with published data within the measurement uncertainty. For distances between 0.6 and 1.5 mm, g(L)(r) decreases from a maximum value of 1.06 down to 1.00; between 1.5 and 6.7 mm, an enhancement is clearly observed with a maximum value around 1.24 and beyond 6.7 mm, g(L)(r) has an approximately constant value around 1.0, which suggests that this seed can be considered as a point source only at distances larger than 6.7 mm. This latter observation agrees with data for the same seed reported previously using Gafchromic film MD-55-2. Additionally, published Monte Carlo (MC) calculations have predicted the observed behavior of the radial dose function resulting from the absorbed dose contributions of beta particles and electrons emitted by the (192)Ir seed. Nonetheless, in the enhancement region, MC underestimates the dose by approximately 20%. This work suggests that beta particles and electrons emitted from the seed make a significant contribution to the total absorbed dose delivered at distances near the seed center (less than 6 mm) and therefore cannot be neglected, given the dimensions of blood vessel walls. PMID:22572625

Massillon-JL, G; Minniti, R; Mitch, M G; Soares, C G

2012-05-10

91

The use of gel dosimetry to measure the 3D dose distribution of a 90Sr/90Y intravascular brachytherapy seed.  

PubMed

Absorbed dose distributions in 3D imparted by a single (90)Sr/(90)Y beta particle seed source of the type used for intravascular brachytherapy were investigated. A polymer gel dosimetry medium was used as a dosemeter and phantom, while a special high-resolution laser CT scanner with a spatial resolution of 100 microm in all dimensions was used to quantify the data. We have measured the radial dose function, g(L)(r), observing that g(L)(r) increases to a maximum value and then decreases as the distance from the seed increases. This is in good agreement with previous data obtained with radiochromic film and thermoluminescent dosemeters (TLDs), even if the TLDs underestimate the dose at distances very close to the seed. Contrary to the measurements, g(L)(r) calculated through Monte Carlo simulations and reported previously steadily decreases without a local maximum as a function of the distance from the seed. At distances less than 1.5 mm, differences of more than 20% are observed between the measurements and the Monte Carlo calculations. This difference could be due to a possible underestimation of the energy absorbed into the seed core and encapsulation in the Monte Carlo simulation, as a consequence of the unknown precise chemical composition of the core and its respective density for this seed. The results suggest that g(L)(r) can be measured very close to the seed with a relative uncertainty of about 1% to 2%. The dose distribution is isotropic only at distances greater than or equal to 2 mm from the seed and is almost symmetric, independent of the depth. This study indicates that polymer gel coupled with the special small format laser CT scanner are valid and accurate methods for measuring the dose distribution at distances close to an intravascular brachytherapy seed. PMID:19242054

Massillon-Jl, G; Minniti, R; Mitch, M G; Maryanski, M J; Soares, C G

2009-02-25

92

Radiation dosimetry  

Microsoft Academic Search

This book consists of five papers on the following topics: bioeffect dosimetry in radiation therapy; a comparison of national and international megavoltage calibration protocols; recent advances in electron and photon dosimetry; microdosimetry and its application to biological processes; and ultraviolet radiation dosimetry and measurement.

Orton

1985-01-01

93

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

94

ESR Dosimetry  

NASA Astrophysics Data System (ADS)

ESR dosimetry is widely used for several applications such as dose assessment in accidents, medical applications and sterilization of food and other materials. In this work the dosimetric properties of natural and synthetic Hydroxyapatite, Alanine, and 2-Methylalanine are presented. Recent results on the use of a K-Band (24 GHz) ESR spectrometer in dosimetry are also presented.

Baffa, Oswaldo; Kinoshita, Angela; Chen Abrego, Felipe; Dos Santos, Adevailton Bernardo; Rossi, Bruno; Graeff, Carlos

2004-09-01

95

(Neutron dosimetry)  

Microsoft Academic Search

The traveler attended the Sixth Symposium on Neutron Dosimetry during October 12--14, 1987, at the Gesellschaft fur Strahlen-und Umweltforschung in Neuherberg, Federal Republic of Germany. This conference included a very comprehensive program with technical presentations in all areas of neutron dosimetry including several currently controversial topics such as quality factors, passive personnel dosimeters, bubble detectors, and survey instruments. The conference

Swaja

1987-01-01

96

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

97

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

98

NMR relaxation enhancement in gels polymerized and cross-linked by ionizing radiation: a new approach to 3D dosimetry by MRI.  

PubMed

A new type of tissue-equivalent medium for magnetic resonance imaging of the dose distributions produced by ionizing radiation has been developed. Agarose gel is infused with acrylamide and N,N'-methylene-bis-acrylamide (Bis) comonomers, which are readily polymerized by free radical initiators in de-aerated aqueous solutions. Polymerization and cross-linking induced locally by free radical products of water radiolysis increase the rate of water proton spin relaxation gradually up to doses of about 15 Gy. The slopes of the dose-response curves at 64 MHz are 0.015 and 0.28 s-1 Gy-1 for R1 and R2, respectively. The agarose matrix as well as the high (50% by weight) relative concentration of the cross-linker (Bis) per total comonomer limit the spread of polymerization so that the spatial distribution of the radiation dose is faithfully represented in the resultant spatial distribution of relaxation rates. The gel can be imaged with conventional magnetic resonance imaging devices with high spatial resolution and accuracy. In addition, due to the well established effect of the precipitation of insoluble agglomerates of highly cross-linked acrylamide, the optical turbidity of the gel increases gradually with the absorbed dose. This may provide an additional means of visualizing the dose distribution in three dimensions. The major advantage of the acrylamide-Bis-agarose gels over those that depend on ionic chemical dosimeters, for example, Fricke-infused gels, lies in the lack of diffusion of radiation-induced chemical changes subsequent to or concurrent with irradiation. PMID:8455435

Maryanski, M J; Gore, J C; Kennan, R P; Schulz, R J

1993-01-01

99

Epid Dosimetry  

SciTech Connect

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. [Dept.Radiation Oncology, Calvary Mater Newcastle Hospital, Locked Bag 7, Hunter Region Mail Centre, Newcastle, NSW 2310 (Australia); Mathematical and Physical Sciences, University of Newcastle, Callaghan, NSW 2298 (Australia); Vial, Philip [Dept Medical Physics, Liverpool and Macarthur Cancer Therapy Centre, Liverpool, NSW 2170 (Australia); School of Physics, University of Sydney, Camperdown, NSW 2050 (Australia)

2011-05-05

100

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

101

(Neutron dosimetry)  

SciTech Connect

The traveler attended the Sixth Symposium on Neutron Dosimetry during October 12--14, 1987, at the Gesellschaft fur Strahlen-und Umweltforschung in Neuherberg, Federal Republic of Germany. This conference included a very comprehensive program with technical presentations in all areas of neutron dosimetry including several currently controversial topics such as quality factors, passive personnel dosimeters, bubble detectors, and survey instruments. The conference was attended by more than 200 people form about 15 countries including many recognized experts in radiation dosimetry, radiobiology, and microdosimetry. The traveler presented a paper containing results of neutron personnel dosimetry research studies conducted since 1974 at the Oak Ridge National Laboratory. During the symposium, the traveler discussed possible future collaborative research efforts with personnel from facilities associated with the Commission of European Communities in areas concerning neutron spectrometry and passive dosimeter testing. These discussions were continued during a visit to the Atomic Energy Authority Laboratories in Harwell, United Kingdom, on October 15, 1987. Through the conference attendance and discussions with dosimetry researchers, the traveler gained information concerning directions and philosophies in neutron dosimetry and made preliminary plans for future cooperative research efforts which will be directly related to DOE programs.

Swaja, R.E.

1987-10-28

102

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

PubMed

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. PMID:19673199

Pourfallah, Tayyeb Allahverdi; Allahverdi, Mahmoud; Alam, Nader Riahi; Ay, Mohammad-Reza; Zahmatkesh, Mohammad-Hasan

2009-07-01

103

(Biological dosimetry)  

SciTech Connect

The traveler participated in an International Symposium on Trends in Biological Dosimetry and presented an invited paper entitled, Adducts in sperm protamine and DNA vs mutation frequency.'' The purpose of the Symposium was to examine the applicability of new methods to study quantitatively the effects of xenobiotic agents (radiation and chemicals) on molecular, cellular and organ systems, with special emphasis on human biological dosimetry. The general areas covered at the meeting included studies on parent compounds and metabolites; protein adducts; DNA adducts; gene mutations; cytogenetic end-points and reproductive methods.

Sega, G.A.

1990-11-06

104

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

105

Dosimetry in modern radiation therapy: limitations and needs  

NASA Astrophysics Data System (ADS)

This paper extends the motivation for gel dosimetry beyond the discussion of solely radiation measurement and presents a broad review of the developments in modern conformal radiation therapy using intensity modulation, image guidance and adaptive processes.

Schreiner, L. John

2006-12-01

106

(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

107

Radiation dosimetry  

Microsoft Academic Search

This article summarized the basic facts about the measurement of ionizing radiation, usually referred to as radiation dosimetry. The article defines the common radiation quantities and units; gives typical levels of natural radiation and medical exposures; and describes the most important biological effects of radiation and the methods used to measure radiation. Finally, a proposal is made for a new

1991-01-01

108

Neutron personnel dosimetry  

NASA Astrophysics Data System (ADS)

The current state of the art in neutron personnel dosimetry is reviewed. Topics covered include dosimetry needs and alternatives, current dosimetry approaches, personnel monitoring devices, calibration strategies, and future developments.

Griffith, R. V.

1981-06-01

109

X-ray computer tomography, ultrasound and vibrational spectroscopic evaluation techniques of polymer gel dosimeters  

NASA Astrophysics Data System (ADS)

Since Gore et al published their paper on Fricke gel dosimetry, the predominant method of evaluation of both Fricke and polymer gel dosimeters has been magnetic resonance imaging (MRI). More recently optical computer tomography (CT) has also been a favourable evaluation method. Other techniques have been explored and developed as potential evaluation techniques in gel dosimetry. This paper reviews these other developments.

Baldock, Clive

2004-01-01

110

CONFORMANCE IMPROVEMENT USING GELS  

Microsoft Academic Search

This report describes work performed during the third and final year of the project, ''Conformance Improvement Using Gels.'' Corefloods revealed throughput dependencies of permeability reduction by polymers and gels that were much more prolonged during oil flow than water flow. This behavior was explained using simple mobility ratio arguments. A model was developed that quantitatively fits the results and predicts

Randall S. Seright

2004-01-01

111

Fibrin glue does not improve the fixation of press-fitted cell-free collagen gel plugs in an ex vivo cartilage repair model  

Microsoft Academic Search

Purpose  Adequate graft fixation over a certain time period is necessary for successful cartilage repair and permanent integration\\u000a of the graft into the surrounding tissue. The aim of the present study was to test the primary stability of a new cell-free\\u000a collagen gel plug (CaReS®-1S) with two different graft fixation techniques over a simulated early postoperative period.\\u000a \\u000a \\u000a \\u000a \\u000a Methods  Isolated chondral lesions (11 mm

Turgay Efe; Alexander Füglein; Thomas J. Heyse; Thomas Stein; Nina Timmesfeld; Susanne Fuchs-Winkelmann; Jan Schmitt; Jürgen R. J. Paletta; Markus D. Schofer

112

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

113

Breast dosimetry.  

PubMed

The estimation of the absorbed dose to the breast is an important part of the quality control of the mammographic examination. Knowledge of breast dose is essential for the design and performance assessment of mammographic imaging systems. This review gives a historical introduction to the measurement of breast dose. The mean glandular dose (MGD) is introduced as an appropriate measure of breast dose. MGD can be estimated from measurements of the incident air kerma at the surface of the breast and the application of an appropriate conversion factor. Methods of calculating and measuring this conversion factor are described and the results discussed. The incident air kerma itself may be measured for patients or for a test phantom simulating the breast. In each case the dose may be determined using TLD measurements, or known exposure parameters and measurements of tube output. The methodology appropriate to each case is considered and the results from sample surveys of breast dose are presented. Finally the various national protocols for breast dosimetry are compared. PMID:10028637

Dance, D R; Skinner, C L; Carlsson, G A

1999-01-01

114

Evaluation of the dosimetric performance of BANG3® polymer gel  

NASA Astrophysics Data System (ADS)

New radiotherapy techniques call for three-dimensional dosimetric methods with high spatial resolution. Radiation sensitive gels read out using MRI T2 mapping provide an extremely promising option, and commercially available BANG® polymer gels provide a convenient route into gel dosimetry. Gel dosimetry is dependent on the ability to calibrate gel response against radiation dose. This in turn is dependent on the reproducibility of response both between gels irradiated to the same dose and for a single gel sample over time. This study aims to evaluate the performance of a commercially available BANG® gel. Our experimental arrangement gave excellent precision of radiation delivery (<0.2%) and reproducibility of T2 measurement (<0.5%). Seven groups of 10 test tubes containing BANG3® gel were irradiated in 0.5 Gy steps between 0 and 3 Gy. A further four groups of four samples were irradiated in 2 Gy steps between 4 and 10 Gy. The gel samples were identical and derived from the same manufacturing batch. MR imaging was carried out four days after irradiation and then at weekly intervals for four weeks. Short-term variation in gel response can readily be corrected using reference samples. Longer term systematic drift of the gel calibration curve was observed relative to reference samples prepared in-house for quality assurance purposes. This implies that read-out of the calibration gels and dosimetry phantom must be performed at the same time after irradiation, or errors of up to 25% may be incurred. Precision of gel response did not change significantly over time. The observation of significantly different T2 values both prior to irradiation and following irradiation to the same dose (variation up to 15%) illustrates the current difficulties associated with BANG3® gel calibration and constrains the practical utility of these commercially available gels for clinical radiation dosimetry.

MacDougall, N. D.; Miquel, M. E.; Wilson, D. J.; Keevil, S. F.; Smith, M. A.

2005-04-01

115

Thin film tritium dosimetry  

DOEpatents

The present invention provides a method for tritium dosimetry. A dosimeter comprising a thin film of a material having relatively sensitive RITAC-RITAP dosimetry properties is exposed to radiation from tritium, and after the dosimeter has been removed from the source of the radiation, the low energy electron dose deposited in the thin film is determined by radiation-induced, thermally-activated polarization dosimetry techniques.

Moran, Paul R. (Madison, WI)

1976-01-01

116

Mental Fitness  

Microsoft Academic Search

The author explores Andie Knutson's plea for a more appropriate term to describe the positive aspects of mental health and suggest the term mental fitness. She provides the definition of fitness and explains that this concept of mental fitness carries much of the connotation we are groping for. It forms an excellent counterpart for the late President Kennedy's program for

Dorothea McCarthy

1964-01-01

117

Absolute dose verifications in small photon fields using BANGTM gel  

NASA Astrophysics Data System (ADS)

Polymer gel dosimeters change their magnetic resonance (MR) and optical properties with the absorbed dose when irradiated and are suitable for narrow photon beam dosimetry in radiosurgery. Such dosimeters enable relative and absolute 3D dose verifications in order to check the entire treatment chain from imaging to dose application during commissioning and quality assurance. For absolute 3D dose verifications in radiosurgery using Gamma Knife B, commercially available BANGTM Gels (BANG 25 Gy and BANG 3 Gy) together with dedicated phantoms were chosen in order to determine the potential of absolute gel dosimetry in radiosurgery.

Scheib, S. G.; Schenkel, Y.; Gianolini, S.

2004-01-01

118

RADIATION POLYMERIZATION DOSIMETRY  

Microsoft Academic Search

Quantitative studies of the high energy radiation photo sensitivity of ; certain liquid monomer-polymers have indicated a possible solution to the problem ; of high level dosimetry. Investigations of the relation between absorbed dose ; and factors which influence sensitivity have led to the development of a ; dependable system of radiation polymerization dosimetry. Changes in the ; composition of

F. E. Hoecker; I. W. Watkins; J. T. Han

1958-01-01

119

CONFORMANCE IMPROVEMENT USING GELS  

SciTech Connect

This report describes work performed during the third and final year of the project, ''Conformance Improvement Using Gels.'' Corefloods revealed throughput dependencies of permeability reduction by polymers and gels that were much more prolonged during oil flow than water flow. This behavior was explained using simple mobility ratio arguments. A model was developed that quantitatively fits the results and predicts ''clean up'' times for oil productivity when production wells are returned to service after application of a polymer or gel treatment. X-ray computed microtomography studies of gels in strongly water-wet Berea sandstone and strongly oil-wet porous polyethylene suggested that oil penetration through gel-filled pores occurs by a gel-dehydration mechanism, rather than gel-ripping or gel-displacement mechanisms. In contrast, analysis of data from the University of Kansas suggests that the gel-ripping or displacement mechanisms are more important in more permeable, strongly water-wet sandpacks. These findings help to explain why aqueous gels can reduce permeability to water more than to oil under different conditions. Since cement is the most commonly used material for water shutoff, we considered when gels are preferred over cements. Our analysis and experimental results indicated that cement cannot be expected to completely fill (top to bottom) a vertical fracture of any width, except near the wellbore. For vertical fractures with apertures less than 4 mm, the cement slurry will simply not penetrate very far into the fracture. For vertical fractures with apertures greater than 4 mm, the slurry may penetrate a substantial distance into the bottom part of the fracture. However, except near the wellbore, the upper part of the fracture will remain open due to gravity segregation. We compared various approaches to plugging fractures using gels, including (1) varying polymer content, (2) varying placement (extrusion) rate, (3) using partially formed gels, (4) using combinations of high and low molecular weight (Mw) polymers, (5) using secondary crosslinking reactions, (6) injecting un-hydrated polymer particles, and (7) incorporating particulates. All of these methods showed promise in some aspects, but required performance improvements in other aspects. All materials investigated to date showed significant performance variations with fracture width. High pressure gradients and limited distance of penetration are common problems in tight fractures. Gravity segregation and low resistance to breaching are common problems in wide fractures. These will be key issues to address in future work. Although gels can exhibit disproportionate permeability reduction in fractures, the levels of permeability reduction for oil flow are too high to allow practical exploitation in most circumstances. In contrast, disproportionate permeability reduction provided by gels that form in porous rock (adjacent to the fractures) has considerable potential in fractured systems.

Randall S. Seright

2004-09-30

120

Thermoluminescence in medical dosimetry.  

PubMed

Thermoluminescence dosimetry (TLD) is applied worldwide for personal and medical dosimetry. TLD method has resulted in many interesting findings in medicine as TL dosimeters have many relevant advantages such as high sensitivity, small physical size, tissue equivalence, etc. The main characteristics of various TL materials used in radiation measurements and their practical consequences are overviewed: well defined TL glow curve, batch homogeneity, signal stability after irradiation, precision and accuracy, response with dose, and influence of energy. In this paper a brief summary of the advances in the application of thermally stimulated luminescence (TSL) to dosimetry in radiation therapy application is presented. PMID:22633888

Rivera, T

2012-04-30

121

Curve Fitting  

NSDL National Science Digital Library

Created by John Michel for the Connected Curriculum Project, the purpose of this module is to extend the concept of fitting a least squares line to allow fitting more complex functions, including those in which the model parameters do not appear linearly. This is part of a larger collection of learning modules hosted by Duke University.

Michel, John

2010-06-08

122

Thorium metabolism and dosimetry.  

National Technical Information Service (NTIS)

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 presen...

J. R. Johnson R. L. Hill A. Birchall N. S. Jarvis

1994-01-01

123

Optically stimulated luminescence dosimetry  

Microsoft Academic Search

Models and the conceptual framework necessary for an understanding of optically stimulated luminescence (OSL) are described. Examples of various OSL readout schemes are described, along with examples of the use of OSL in radiation dosimetry.

Stephen W. S. McKeever

2001-01-01

124

The dosimetry of ionizing radiation. Volume 1  

Microsoft Academic Search

This book discusses the papers on dosimetry of ionizing radiation. The topics covered are: theoretical basis for dosimetry; fundamentals of microdosimetry; dosimetry of external radiation beams of photon and electron radiation; beam characteristics dosimetry of nuclear particles; measurement and dosimetry of radioactivity in the environment; and internal dosimetry for radiation protection.

K. R. Kase; B. E. Bjarngard; F. H. Attix

1985-01-01

125

Practical CT dosimetry  

SciTech Connect

The dose from computed tomography (CT) examinations is not negligible from a radiation safety standpoint. Occasionally, one encounters a case in which an unsuspected pregnant woman undergoes a CT pelvic scan, and the radiologist is required to estimate the dose to the fetus. This article addresses practical methods of CT dosimetry with a specific discussion on fetal dose estimate. Three methods are described: (1) the use of a dose chart, (2) the pencil ionization chamber method, and (3) the thermoluminescence dosimetry (TLD) method.

Yoshizumi, T.T.; Suneja, S.K.; Teal, J.S. (Howard Univ. Hospital, Washington, DC (USA))

1989-07-01

126

Chemical Dosimetry of Ionizing Radiations.  

National Technical Information Service (NTIS)

This volume generalizes the theoretical and experimental material that has been accumulated during recent years in the field of chemical dosimetry. Attention is focused on the justification for the use of chemical-dosimetry methods to solve problems that ...

A. M. Kabakchi Y. I. Lavrentovich V. V. Penkovskii

1966-01-01

127

Optical analysis of gel dosimeters: Comparison of Fricke and normoxic polymer gels  

NASA Astrophysics Data System (ADS)

The dosimetry method based on optical analysis of gel layers has been experienced utilising both Fricke and polymer (normoxic) gels. The aim of the work was that of investigating the potentiality of a normoxic polymer gel and of performing a further verification of the reliability of Fricke gel dosimeters. Optical absorbance was measured, both with a spectrophotometer and by imaging light transmittance detected with a CCD camera. The results of the study of sensitivity, linearity of the response and reproducibility of the polymer gel dosimeter have shown acceptable performances, except for doses below 2 Gy. The linearity range extends up to 20 Gy. On the other side, dose images and profiles have shown noticeable differences when compared to those calculated or measured with ionisation chambers or Fricke gel dosimeters. Such Fricke dosimeters have given further confirmation of their reliability.

Gambarini, G.; Carrara, M.; Mariani, M.; Pirola, L.; Tomatis, S.; Valente, M.; Vanossi, E.

2007-10-01

128

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.

Science, American A.

2009-01-01

129

Inclusive fitness  

Microsoft Academic Search

Although the prisoner's dilemma (PD) has been used extensively to study reciprocal altruism, here we show that the n-player prisoner's dilemma (NPD) is also central to two other prominent theories of the evolution of altruism: inclusive fitness and multilevel selection. An NPD model captures the essential factors for the evolution of altruism directly in its parameters and integrates important aspects

Andy Gardner; Martin Zwick

2011-01-01

130

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

131

Optically stimulated luminescence dosimetry  

NASA Astrophysics Data System (ADS)

Optically Stimulated Luminescence (OSL) dosimetry is attractive to the health physics and dosimetry community due to its all-optical character, fast data acquisition and the avoidance of heating the detector. Until recently there was no luminescent material sensitive enough to radiation, and at the same time suitable for stimulation with visible light, for use in this application. However, anion-deficient aluminum oxide doped with carbon (Al2O3:C) appears to be not only an extremely sensitive thermoluminescence (TL) material, but is also well-suited to OSL applications. Several OSL readout protocols have been suggested, including cw-OSL, pulsed OSL (POSL), and 'delayed' OSL (DOSL). The paper discusses the physical mechanisms that give rise to the OSL signals and the dependence of these signals upon absorbed dose. Example applications of the use of OSL from Al2O3:C in environmental radiation and ultraviolet-B dosimetry are discussed.

McKeever, Stephen W.

1999-02-01

132

Practical CT dosimetry.  

PubMed

The dose from computed tomography (CT) examinations is not negligible from a radiation safety standpoint. Occasionally, one encounters a case in which an unsuspected pregnant woman undergoes a CT pelvic scan, and the radiologist is required to estimate the dose to the fetus. This article addresses practical methods of CT dosimetry with a specific discussion on fetal dose estimate. Three methods are described: (1) the use of a dose chart, (2) the pencil ionization chamber method, and (3) the thermoluminescence dosimetry (TLD) method. PMID:2762539

Yoshizumi, T T; Suneja, S K; Teal, J S

133

Practical CT dosimetry  

Microsoft Academic Search

The dose from computed tomography (CT) examinations is not negligible from a radiation safety standpoint. Occasionally, one encounters a case in which an unsuspected pregnant woman undergoes a CT pelvic scan, and the radiologist is required to estimate the dose to the fetus. This article addresses practical methods of CT dosimetry with a specific discussion on fetal dose estimate. Three

T. T. Yoshizumi; S. K. Suneja; J. S. Teal

1989-01-01

134

Proton dosimetry intercomparison  

Microsoft Academic Search

Background and purpose: Methods for determining absorbed dose in clinical proton beams are based on dosimetry protocols provided by the AAPM and the ECHED. Both groups recommend the use of air-filled ionization chambers calibrated in terms of exposure or air kerma in a 60Co beam when a calorimeter or Faraday cup dosimeter is not available. The set of input data

S. Vatnitsky; J. Siebers; D. Miller; M. Moyers; M. Schaefer; D. Jones; S. Vynckier; Y. Hayakawa; S. Delacroix; U. Isacsson; J. Medin; A. Kacperek; A. Lomax; A. Coray; H. Kluge; J. Heese; L. Verhey; I. Daftari; K. Gall; G. Lam; T. Beck; G. Hartmann

1996-01-01

135

Neutron Exposure Parameters for the Dosimetry Capsule in the Heavy-Section Steel Irradiation Program Tenth Irradiation Series  

SciTech Connect

This report describes the computational methodology for the least-squares adjustment of the dosimetry data from the HSSI 10.OD dosimetry capsule with neutronics calculations. It presents exposure rates at each dosimetry location for the neutron fluence greater than 1.0 MeV, fluence greater than 0.1 MeV, and displacements per atom. Exposure parameter distributions are also described in terms of three- dimensional fitting functions. When fitting functions are used it is suggested that an uncertainty of 6% (1 o) should be associated with the exposure rate values. The specific activity of each dosimeter at the end of irradiation is listed in the Appendix.

C.A. Baldwin; F.B.K. Kam; I. Remec

1998-10-01

136

In vivo dosimetry for IMRT  

SciTech Connect

In vivo dosimetry has a well established role in the quality assurance of 2D radiotherapy and 3D conformal radiotherapy. The role of in vivo dosimetry for IMRT is not as well established. IMRT introduces a range of technical issues that complicate in vivo dosimetry. The first decade or so of IMRT implementation has largely relied upon pre-treatment phantom based dose verification. During that time, several new devices and techniques for in vivo dosimetry have emerged with the promise of providing the ultimate form of IMRT dose verification. Solid state dosimeters continue to dominate the field of in vivo dosimetry in the IMRT era. In this report we review the literature on in vivo dosimetry for IMRT, with an emphasis on clinical evidence for different detector types. We describe the pros and cons of different detectors and techniques in the IMRT setting and the roles that they are likely to play in the future.

Vial, Philip [Department of Medical Physics, Liverpool Cancer Therapy Centre (Australia); Institute of Medical Physics, School of Physics, University of Sydney (Australia)

2011-05-05

137

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

138

Dosimetry with diamond detectors  

Microsoft Academic Search

In this paper we present the dosimetry analysis in terms of stability and repeatability of the signal and dose rate dependence of a synthetic single crystal diamond grown by Chemical Vapor Deposition (CVD) technique. The measurements carried out by 5MeV X-ray photons beam show very promising results, even if the dose rate detector response points out that the charge trapping

G. Gervino; C. Marino; F. Silvestri; A. Lavagno; F. Truc

2010-01-01

139

Cosmic Ray Dosimetry  

NASA Astrophysics Data System (ADS)

Radiation levels at aircraft cruising altitudes are twenty times higher than at sea level. Thus, on average, a typical airline pilot receives a larger annual radiation dose than some one working in nuclear industry. The main source of this radiation is from galactic cosmic radiation, high energy particles generated by exploding stars within our own galaxy. In this work we study cosmic rays dosimetry at various aviation altitudes using the PARMA model.

Si Belkhir, F.; Attallah, R.

2010-10-01

140

NSUSY fits  

NASA Astrophysics Data System (ADS)

We perform a global fit to Higgs signal-strength data in the context of light stops in Natural SUSY. In this case, the Wilson coefficients of the higher dimensional operators mediating gg ? h and h ? ??, given by c g , c ? , are related by c g = 3 (1 + 3 ? s /(2?)) c ? /8. We examine this predictive scenario in detail, combining Higgs signal-strength constraints with recent precision measurements of m W , Br( overline{B} ? X s ?) constraints and direct collider bounds on weak scale SUSY, finding regions of parameter space that are consistent with all of these constraints. However it is challenging for the allowed parameter space to reproduce the observed Higgs mass value with sub-TeV stops. We discuss some of the direct stop discovery prospects and show how Higgs search data can be used to exclude light stop parameter space difficult to probe by direct collider searches. We determine the current status of such indirect exclusions and estimate their reach by the end of the 8 TeV LHC run.

Espinosa, José R.; Grojean, Christophe; Sanz, Verónica; Trott, Michael

2012-12-01

141

MAGIC polymer gel for dosimetric verification in boron neutron capture therapy.  

PubMed

Radiation sensitive polymer gels are among the most promising three-dimensional dose verification tools developed to date. Polymer gel dosimeter known by the acronym MAGIC has been tested for evaluation of its use in boron neutron capture (BNCT) dosimetry. We irradiated a large (diameter 10 cm, length 20 cm) cylindrical gel phantom in the epithermal neutron beam of the Finnish BNCT facility at the FiR 1 nuclear reactor. Neutron irradiation was simulated with a Monte Carlo radiation transport code MCNP. Gel samples from the same production batch were also irradiated with 6 MV photons from a medical linear accelerator to compare dose response in the two different types of beams. Irradiated gel phantoms were imaged using MRI to determine their relaxation rate R2 maps. The measured and normalized dose distribution in the epithermal neutron beam was compared to the dose distribution calculated by computer simulation. The results support the feasibility MAGIC gel in BNCT dosimetry. PMID:17592463

Uusi-Simola, Jouni; Heikkinen, Sami; Kotiluoto, Petri; Serén, Tom; Seppälä, Tiina; Auterinen, Iiro; Savolainen, Sauli

2007-04-30

142

Study of Fricke gel dosimeter response for different gel quality  

NASA Astrophysics Data System (ADS)

The Fricke xylenol gel (FXG) dosimeter has been studied for application in radiotherapy because it is capable of to measure the spatial distribution of radiation doses. The dosimetry is based on the oxidation of ferrous (Fe2+) to ferric (Fe3+) ions radiation induced, related to the radiation dose. The gel material usually employed is the 300 Bloom gelatin, which is imported and very expensive in Brazil. Aiming to analyze the viability of to use a locally produced and low cost gel material, in this work the spectrophotometric responses of FXG solutions prepared using 270 Bloom gelatin commercially available and 300 Bloom gelatin imported were compared. The absorption spectra of solutions prepared with 5% by weight 270 and 300 Bloom gelatins non-irradiated and irradiated with 60Co gamma radiation in the dose range between 0.5 and 100 Gy were analysed, the dose-response curves were evaluated and the useful dose range was established. The obtained results indicate that the FXG solution prepared with 270 Bloom gelatin presents good performance, similar to that presented by the FXG solution prepared with 300 Bloom gelatin and its use can be recommended owing to the low cost and the availability in local market.

Cavinato, C. C.; Campos, L. L.

2010-11-01

143

Design of radiosensitive gels and phantoms for irradiation assessment using MRI measurement: case of glottic cancer  

Microsoft Academic Search

Chemical dosimetry is a technique allowing tridimensional assessment of dose in radiotherapy. Magnetic resonance imaging provides 3D dose mapping of irradiated gels. Those gels are composed of an aqueous gel matrix containing radiosensitive compounds such as ferrous ions that are radio-oxidized or vinyl monomers that polymerize. There are specific requirements about soft-tissue equivalence that don't necessarily matched with MRI requirements,

Isabelle Rousselle; Jean Rousseau; Bernard Castelain; Thieny Sarrazin; Xavier Marchandise; David Gibon

1997-01-01

144

Hamiltonian inclusive fitness: a fitter fitness concept.  

PubMed

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

2013-10-16

145

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

146

Interspecies Dosimetry of Reactive Gases.  

National Technical Information Service (NTIS)

The development of dosimetry models that can provide a description of the uptake and distribution of inhaled compounds throughout the body and the availability of animal toxicological data are integral components for a full evaluation of potential risks a...

F. J. Miller J. H. Overton T. R. Gerrity R. C. Graham

1987-01-01

147

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

148

Cf252 physics and dosimetry  

Microsoft Academic Search

At the request of an ad hoc committee on the dosimetry of californium-252 medical neutron sources, the author in 1971-1972 conducted a review of the dosimetry data then available and prepared a status report which was subsequently published. The committee was convened by the Cf-252 Biomedical Advisory Panel of the U.S. Atomic Energy Commission's Div. of Biology and Medicine. The

1986-01-01

149

Fifth international radiopharmaceutical dosimetry symposium  

SciTech Connect

This meeting was held to exchange information on how to get better estimates of the radiation absorbed dose. There seems to be a high interest of late in patient dosimetry; discussions were held in the light of revised risk estimates for radiation. Topics included: Strategies of Dose Assessment; Dose Estimation for Radioimmunotherapy; Dose Calculation Techniques and Models; Dose Estimation for Positron Emission Tomography (PET); Kinetics for Dose Estimation; and Small Scale Dosimetry and Microdosimetry. (VC)

Watson, E.E.; Schlafke-Stelson, A.T. (eds.)

1992-05-01

150

Medical dosimetry in Hungary  

NASA Astrophysics Data System (ADS)

Radiation exposure of medical staff during cardiological and radiological procedures was investigated. The exposure of medical staff is directly connected to patient exposure. The aim of this study was to determine the distribution of doses on uncovered part of body of medical staff using LiF thermoluminescent (TL) dosimeters in seven locations.Individual Kodak film dosimeters (as authorized dosimetry system) were used for the assessment of medical staff's effective dose. Results achieved on dose distribution measurements confirm that wearing only one film badge under the lead apron does not provide enough information on the personal dose.The value of estimated annual doses on eye lens and extremities (fingers) were in good correlation with international publications.

Turák, O.; Osvay, M.; Ballay, L.

2012-09-01

151

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

152

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

153

Large deformation analysis of gellan gels  

NASA Astrophysics Data System (ADS)

Gellan gel, a typical polysaccharide gel, is ruptured with different deformation behaviors from gelatin gel or rubber. It exhibits both strain hardening and softening; hardening is observed for moderate strain and softening occurs for larger strain. From the analyses of stress-strain curves of gellan gels, we propose forms of strain energy function. The fit with the proposed equation was excellent, while the existing models fail because they consider only one of hardening or softening effect. Furthermore, these equations are shown to be capable of extracting the hardening and softening effects separately from the observed stress-strain curves. By using these fitting equations, the concentration dependences of hardening and softening are investigated. It is shown that the degrees of hardening and softening both increase with increasing gellan concentration.

Kawai, Shinnosuke; Nitta, Yoko; Nishinari, Katsuyoshi

2007-08-01

154

Progress towards an alanine\\/ESR therapy level reference dosimetry service at NPL  

Microsoft Academic Search

This paper describes work being carried out at the National Physical Laboratory towards the establishment of an alanine reference dosimetry service for radiotherapy applications. A precision fused quartz holder has been constructed to allow precise positioning of alanine dosimeters in the ESR cavity. A novel method of signal analysis based on spectrum fitting has been developed to minimize the effect

P. H. G. Sharpe; K. Rajendran; J. P. Sephton

1996-01-01

155

Testosterone Gel REMS  

Center for Drug Evaluation (CDER)

Text VersionPage 1. Initial REMS Approval: 02/2012 Testosterone Gel CIII Drug Class and Formulation: Testosterone Gel Products ... use of testosterone gel. II. ... More results from www.fda.gov/downloads/drugs/drugsafety

156

10 CFR 35.630 - Dosimetry equipment.  

Code of Federal Regulations, 2010 CFR

...2010-01-01 2010-01-01 false Dosimetry equipment. 35.630 Section 35...Stereotactic Radiosurgery Units § 35.630 Dosimetry equipment. (a) Except for low...manufacturer, a licensee shall have a calibrated dosimetry system available for use. To...

2010-01-01

157

10 CFR 35.630 - Dosimetry equipment.  

Code of Federal Regulations, 2010 CFR

...2009-01-01 2009-01-01 false Dosimetry equipment. 35.630 Section 35...Stereotactic Radiosurgery Units § 35.630 Dosimetry equipment. (a) Except for low...manufacturer, a licensee shall have a calibrated dosimetry system available for use. To...

2009-01-01

158

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.

159

Status of Dosimetry and Activation Data.  

National Technical Information Service (NTIS)

The need for and the status of dosimetry and activation nuclear data libraries will be presented. Each of the major library systems in the world will be covered. Besides the traditional long-lived fission reactor dosimetry sets, new dosimetry sets contain...

F. M. Mann

1987-01-01

160

Introduction to Radiological Physics and Radiation Dosimetry  

Microsoft Academic Search

A straightforward presentation of the broad concepts underlying radiological physics and radiation dosimetry for the graduate-level student. Covers photon and neutron attenuation, radiation and charged particle equilibrium, interactions of photons and charged particles with matter, radiotherapy dosimetry, as well as photographic, calorimetric, chemical, and thermoluminescence dosimetry. Includes many new derivations, such as Kramers X-ray spectrum, as well as topics that

Frank Herbert Attix

1987-01-01

161

A Pretty Good Fit  

ERIC Educational Resources Information Center

|We often look for a best-fit function to a set of data. This article describes how a "pretty good" fit might be better than a "best" fit when it comes to promoting conceptual understanding of functions. In a pretty good fit, students design the function themselves rather than choosing it from a menu; they use appropriate variable names; and they…

Erickson, Tim

2008-01-01

162

Photostimulable storage phosphor dosimetry  

SciTech Connect

The feasibility of employing alkaline earth sulfide based photostimulable storage phosphors for relative dosimetry in radiation oncology has been investigated. The dosimetric characteristics, radiologic characteristics, and spacial sensitivity of calcium sulfide and strontium sulfide based phosphors were determined. Dosimetric characteristics were explored by cavity theory calculation, Monte Carlo simulation, and physical measurement. Dosimetric characteristics obtained with cavity theory and Monte Carlo simulations agree well. The dose perturbation of the phosphor base materials were comparable to those produced by clinical dosimeter materials over the energy region employed in radiation oncology. Dose perturbation in regions downstream of the phosphor were measured with a variety of clinical dosimeters and compared with simulation results. The results of the measurements and simulations agreed within the uncertainty levels of the simulations and the measurements. Radiological characteristics of sensitivity, fading, dose response, dose rate response, and energy dependence of response were studied with an experimental phosphor output reader. Relative sensitivity was found to be dependent upon the mass thickness of phosphor layer. Fading was quantified for the calcium sulfide phosphor, with a half time of 2300 minutes. The strontium sulfide sample exhibited some fading, however, the regression lines yielded low correlation coefficients. A linear dose response over the range of doses employed in radiation oncology was obtained for both phosphors. No significant dose rate dependence of response was measured for the phosphors. The phosphor's energy dependence of response paralleled the dose perturbation relative to water predicted by cavity theory and simulations. Spatial sensitivity was demonstrated with an experimental phosphor scanner.

Frye, D.M.D.

1993-01-01

163

Dosimetry of pulsed radiation  

SciTech Connect

International Commission on Radiation Units and Measurements (ICRU) Report 34 provides guidance on the special procedures to be followed in measuring the radiation dose from sources such as linear accelerators, betatrons, synchrotrons, or field-emission impulse generators. These sources deliver their output impulses within the range 10/sup -9/ to 10/sup -6/ seconds, spaced at least a few milliseconds apart. Condenser discharge machines with field-emission cathodes deliver much larger pulses, usually singly or at very low frequency, and with a pulse duration much less than a microsecond. The report provides information on certain precautions and the selection of calibration constants needed to permit the use of methods of dosimetry employed for measuring continuous radiation from constant potential x-ray sources or from gamma-ray sources. Treated are measurements using ionization chambers, chemical dosimeters, calorimeters and solid state devices. The aim of the report is to guide those who have to measure pulsed radiation to the most convenient and accurate system for their particular problem.

Not Available

1983-01-01

164

Fast neutron dosimetry  

SciTech Connect

During 1988--1990 the magnetic resonance dosimetry project was completed, as were the 250 MeV proton shielding measurements. The first cellular experiment using human cells in vitro at the 1 GeV electron storage ring was also accomplished. More detail may be found in DOE Report {number sign}DOE/EV/60417-002 and the open literature cited in the individual progress subsections. We report Kinetic Energy Released in Matter (KERMA), factor measurements in several elements of critical importance to neutron radiation therapy and radiation protection for space habitation and exploration for neutron energies below 30 MeV. The results of this effort provide the only direct measurements of the oxygen and magnesium kerma factors above 20 MeV neutron energy, and the only measurements of the iron kerma factor above 15 MeV. They provide data of immediate relevance to neutron radiotherapy and impose strict criteria for normalizing and testing nuclear models used to calculate kerma factors at higher neutron energies.

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

1991-01-01

165

Taurine for EPR dosimetry.  

PubMed

EPR dosimetry is characterized by its non-destructive read-out and the possibility of dose archival. Here, taurine is proposed as a radiation dosimeter using EPR spectroscopy. The EPR spectrum of taurine was studied and assigned, and changes in the taurine EPR spectrum as a result of the change in both modulation amplitude and microwave power were quantified. For gamma radiation, the energy absorption coefficient and the collision mass stopping power of taurine were compared to the corresponding values of soft tissue and alanine, in addition to calculation of effective atomic numbers. The response of taurine to gamma radiation doses in the range from 0.1 to 50 kGy was investigated, as well as that in the range from 1.0 to 20.0 Gy using numerically enhanced EPR taurine spectra. Both response curves showed a linear behavior. In addition, the time dependence of radiation-induced radicals was studied for short (during the first 6 h after irradiation) and long (during about 3 months after irradiation) time periods, and a reasonable degree of stability of the taurine radicals was observed. It is concluded that taurine is a promising dosimeter, which is characterized by its simple spectrum, radical stability, and wide range of linear response to gamma radiation. PMID:22526915

Maghraby, A; Mansour, A; Tarek, E

2012-04-18

166

Preliminary Investigation of the Dosimetric Properties of 'RadGel'  

NASA Astrophysics Data System (ADS)

A preliminary investigation into the efficacy of a new 3D dosimetry material, RadGelTM, for verification of radiation therapy dose distributions is presented. Small volumes of RadGelTM were found to exhibit a linear, reproducible response to dose. A gradual increase in optical-density (OD) with time was observed, suggesting scanning should be completed within 18 hours to keep a linear correlation of R2 > 0.99. A larger 10 cm diameter volume of RadGelTM was irradiated with a rotationally symmetric "spoke" plan designed to rigorously evaluate scanner/dosimeter combined performance. The dosimeter was imaged with the Duke Mid-sized Optical-CT Scanner (DMOS). Promising OD and corresponding dose maps were obtained. Edge artefacts were observed and are suspected to be exacerbated by the particular container used in this early study. Further studies will evaluate new containers and methods for refractive matching at the gel-container-fluid interface.

Newton, J. R.; Thomas, A.; Appleby, A.; Marsden, C.; Christman, E. A.; Wolodzko, J. G.; Oldham, M.

2010-11-01

167

The radiation dosimetry of Re-186 HEDP  

SciTech Connect

Patients suffering from metastatic bone cancer may be offered some relief of bone pain by several palliative agents currently under study. One such agent is Re-186 HEDP (etidronate). We gathered biodistribution data from 27 patients receiving this agent for palliation of bone pain. Skeletal activity was estimated as that portion of administered activity not recovered in urine or measured in kidneys or extracellular fluid (ECF) space. Activity in kidneys was estimated through scintigraphic imaging. Activity in urine and blood were estimated by direct counting of samples; activity in ECF was approximated as blood activity divided by the plasmacrit, multiplied by 0.2 times body weight. All retention data were fit to a sum of exponentials for estimation of residence times. Activity in the urinary bladder contents was estimated from the urinary excretion data using the dynamic bladder model of Cloutier et al. Estimated residence times were kidneys 0.538 hr, bone 33.3 hr (divided evenly between cortical and trabecular bone for dosimetry purposes), urinary bladder contents 1.18 hr, and remainder of body 6.52hr. Radiation dose estimates were developed, using the MIRDOSE 3 software. Radiation dose estimates for bone surfaces and red marrow are 1.9 and 0.82 mGy/MBq, respectively. The estimate for the urinary bladder wall is 0.57 mGy/MBq. Most other organs` estimates were around 0.02 mGy/MBq. The new marrow dose model presented in MIRDOSE 3 was used to look at the distribution of marrow dose in different bones, and to develop a dose-volume histogram. These data should be used as the basis for the radiation dosimetry of this agent.

Stabin, M.G. [Oak Ridge Inst. for Science and Education, TN (United States); Graham, M.C.; Scher, H.J. [Memorial Sloan-Kettering Cancer Center, NY (United States)

1995-05-01

168

Anniversary Paper: Fifty years of AAPM involvement in radiation dosimetry  

Microsoft Academic Search

This article reviews the involvement of the AAPM in various aspects of radiation dosimetry over its 50 year history, emphasizing the especially important role that external beam dosimetry played in the early formation of the organization. Topics covered include the AAPM's involvement with external beam and x-ray dosimetry protocols, brachytherapy dosimetry, primary standards laboratories, accredited dosimetry chains, and audits for

J. F. Williamson; S. M. Seltzer; D. W. O. Rogers; C.-M. Ma; G. Ibbott

2008-01-01

169

Open issues in reactor dosimetry  

Microsoft Academic Search

The need for more energy in a worldwide scope, as well as the necessity to reduce emission, diversification of energy sources and to preserve the environment equilibrium has renewed the expectations of nuclear energy. Programmes for construction of 3rd and 4th generation reactors, modernization of existing nuclear power plants (NPP), and plant life extension are being developed worldwide. Reactor dosimetry

A. Ballesteros; L. Debarberis; W. Voorbraak; J. Wagemans; P. D’hondt

2010-01-01

170

Family Activities for Fitness  

ERIC Educational Resources Information Center

|This article discusses how families can increase family togetherness and improve physical fitness. The author provides easy ways to implement family friendly activities for improving and maintaining physical health. These activities include: walking, backyard games, and fitness challenges.|

Grosse, Susan J.

2009-01-01

171

Youth Physical Fitness Awards.  

ERIC Educational Resources Information Center

|The article explores theoretical and practical factors that support or challenge the effectiveness of various awards programs intended to motivate improvement in youth fitness, motivate youth to take fitness tests, and encourage active lifestyles. (Author/CB)|

Corbin, Charles B.; And Others

1988-01-01

172

Fitness for Kids  

MedlinePLUS

... Fitness Inactivity in front of a computer or television contributes to children being out of shape. Fitness ... org/topic.cfm?topic=A00038) Weightbearing Exercise for Women and Girls Weightbearing Exercise for Women and Girls ( ...

173

Dosimetry for ion beam radiotherapy.  

PubMed

Recently, ion beam radiotherapy (including protons as well as heavier ions) gained considerable interest. Although ion beam radiotherapy requires dose prescription in terms of iso-effective dose (referring to an iso-effective photon dose), absorbed dose is still required as an operative quantity to control beam delivery, to characterize the beam dosimetrically and to verify dose delivery. This paper reviews current methods and standards to determine absorbed dose to water in ion beam radiotherapy, including (i) the detectors used to measure absorbed dose, (ii) dosimetry under reference conditions and (iii) dosimetry under non-reference conditions. Due to the LET dependence of the response of films and solid-state detectors, dosimetric measurements are mostly based on ion chambers. While a primary standard for ion beam radiotherapy still remains to be established, ion chamber dosimetry under reference conditions is based on similar protocols as for photons and electrons although the involved uncertainty is larger than for photon beams. For non-reference conditions, dose measurements in tissue-equivalent materials may also be necessary. Regarding the atomic numbers of the composites of tissue-equivalent phantoms, special requirements have to be fulfilled for ion beams. Methods for calibrating the beam monitor depend on whether passive or active beam delivery techniques are used. QA measurements are comparable to conventional radiotherapy; however, dose verification is usually single field rather than treatment plan based. Dose verification for active beam delivery techniques requires the use of multi-channel dosimetry systems to check the compliance of measured and calculated dose for a representative sample of measurement points. Although methods for ion beam dosimetry have been established, there is still room for developments. This includes improvement of the dosimetric accuracy as well as development of more efficient measurement techniques. PMID:20952816

Karger, Christian P; Jäkel, Oliver; Palmans, Hugo; Kanai, Tatsuaki

2010-10-15

174

10 CFR 835.1304 - Nuclear accident dosimetry.  

Code of Federal Regulations, 2010 CFR

...2009-01-01 false Nuclear accident dosimetry. 835.1304 Section 835.1304...Situations § 835.1304 Nuclear accident dosimetry. (a) Installations possessing...possible, shall provide nuclear accident dosimetry for those individuals. (b)...

2009-01-01

175

10 CFR 835.1304 - Nuclear accident dosimetry.  

Code of Federal Regulations, 2010 CFR

...2010-01-01 false Nuclear accident dosimetry. 835.1304 Section 835.1304...Situations § 835.1304 Nuclear accident dosimetry. (a) Installations possessing...possible, shall provide nuclear accident dosimetry for those individuals. (b)...

2010-01-01

176

Isopropanol-based polymer gel dosimeters for use with x-ray CT imaging  

NASA Astrophysics Data System (ADS)

We report on investigations aimed at increasing the dose response sensitivity and resolution in x-ray CT imaging of polymer gel dosimeters (PGD). We incorporate isopropanol as co-solvent into the gel formulation and show that this incorporation increases dose sensitivity and dose resolution of x-ray CT imaged gel dosimeters. These gels are reproducible in response and stable post-irradiation. We apply the system to a simple 1L gel test case where 2 separate irradiations are used to generate a dose response calibration curve. A third irradiation (3-field) is then calibrated and compared to treatment planning predictions. Results indicate that isopropanol-based PGDs are promising formulations for x-ray CT gel dosimetry and that this current system outperforms previous attempts at dose reconstruction using x-ray CT imaging of PGDs.

Jirasek, A.; Hilts, M.; McAuley, K.

2010-11-01

177

Unexplained overexposures on physical dosimetry reported by biological dosimetry.  

PubMed

The Medical Service of the Radiation Protection Service from the University Hospital La Fe (Valencia, Spain), carries out medical examinations of the workers occupationally exposed to ionising radiation. The Biological Dosimetry Laboratory is developing its activity since 2001. Up to now, the activities have been focused in performing biological dosimetry studies of Interventionists workers from La Fe Hospital. Recently, the Laboratory has been authorized by the Health Authority in the Valencian Community. Unexplained overexposures of workers and patients are also studied. Workers suspected of being overexposed to ionising radiation were referred for investigation by cytogenetic analysis. Two of these were from Hospitals of the Valencian Community and one belonged to an uranium mine from Portugal. Hospital workers had a physical dose by thermoluminiscence dosimeters (TLD) that exceeded the established limit. The worker of the uranium mine received a dose from a lost source of Cesium 137 with an activity of 170 mCi. All three cases showed normal values after the hematological analysis. Finally, the aim of this study consist to determine whether the dose showed by the dosimeter is reliable or not. In the case of workers that wore dosimeter, it is concluded that the doses measured by dosimeter are not corresponding to real doses. Hospital worker with a physical dose of 2.6 Sv and 0.269 Sv had an estimated absorbed dose by biological dosimetry of 0.076 Gy (0-0.165 Gy) and 0 Gy (0-0.089 Gy), respectively. In case of the mine worker an estimated absorbed dose of 0.073 Gy (0-0.159 Gy) was obtained by biological dosimetry. In all cases we used the odds ratio to present the results due to a very low frequency of observed aberrations [1]. PMID:19964943

Montoro, A; Almonacid, M; Villaescusa, J I; Verdu, G

2009-01-01

178

Running an Agarose Gel  

NSDL National Science Digital Library

This video adapted from the University of Leicester provides step-by-step instructions for loading samples into an agarose gel and then running the gel to separate DNA molecules according to their size.

Foundation, Wgbh E.

2011-11-07

179

Dosimetry User's Perspective on Covariance Needs  

SciTech Connect

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. [Nuclear Technologies Department, Sandia National Laboratories, Albuquerque, NM 87185-1146 (United States)], E-mail: pjgriff@sandia.gov

2008-12-15

180

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

181

Gel drying methods.  

PubMed

For some instances, protein gels need to be dried after SDS-PAGE, for example, if autoradiography should be performed from radioactive-labeled proteins after their separation on SDS-polyacrylamide gels. Another reason may be to simply store the gel in the laboratory book. Aside from expensive commercial solutions, especially for storage of the dried gel in the lab book, the simple and cheap drying protocol here presented may be sufficient. PMID:22585507

Stamova, Slava; Michalk, Irene; Bartsch, Holger; Bachmann, Michael

2012-01-01

182

Film dosimetry of clinical electron beams  

SciTech Connect

Film dosimetry is used widely to obtain relative dose distributions of clinical electron beams in phantoms. Nevertheless, measurement results obtained with film dosimetry may lack precision and reliability. In this paper well defined and reproducible methods in film dosimetry are discussed. By application of these methods, film dosimetry appears to be adequate in measuring relative dose distributions of clinically applied electron beams, with an accuracy of 1% to 2% of the dose maximum, in water and plastics as well as in heterogeneously composed material.

van Battum, L.J.; Huizenga, H. (Dr. Daniel den Hoed Cancer Centre, Rotterdam (Netherland))

1990-01-01

183

Non-diffusing photochromic gel for optical computed tomography phantoms  

NASA Astrophysics Data System (ADS)

This study examines photochromic response in radiation sensitive hydrogels. Genipin, crosslinked, gelatin gel can support high resolution images because the chromophores do not diffuse. A low power, 633 nm He-Ne laser was used to write lines into the gels by a photobleaching reaction. Optical cone-beam computed tomography (CBCT) scans mapped the high resolution images in 3D with 0.25 mm voxel resolution. A straight line was written into a deformed gel and then readout in its relaxed, initial shape. The curved, photo-bleached line demonstrated deformable 3D dosimetry is possible with this system to the balloon edge. High resolution, photochromic images provide key information for characterizing optical CT scanners and 3D dosimeters. Many, ionizing radiation, dosimeter materials demonstrate either a photochromic or photothermal response, allowing this approach to be widely used in quantitative 3D scanning.

Jordan, K.

2013-06-01

184

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

185

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

186

Mutation Accumulation, Performance, Fitness  

Microsoft Academic Search

SYNOPSIS. The morphology-performance-fitness paradigm is usually explored by determining whether nat- ural or ''phenotypically engineered'' variation among individuals in morphology (physiology) or perfor- mance covaries with an index of fitness such as survival. Here we study between-line covariation between performance and fitness for 44 lines of flies that had undergone mutation accumulation (in the absence of natural selection) on the

RAYMOND B. HUEY; W. G ILCHRIST; K IMIORA WARD; L ISA MAVES; DAVID PEPIN; DAVID HOULE

2003-01-01

187

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

188

Modelling of the inhomogeneous interior of polymer gels  

NASA Astrophysics Data System (ADS)

A simple model has been investigated to elucidate the mean squared displacement (MSD) of probe molecules in cross-linked polymer gels. In the model, we assume that numerous cavities distribute in the inhomogeneous interior of a gel, and probe molecules are confined within these cavities. The individual probe molecules trapped in a gel are treated as Brownian particles confined to a spherical harmonic potential. The harmonic potential is chosen to model the effective potential experienced by the probe particle in the cavity of a gel. Each field strength is corresponding to the characteristic of one type of effective cavity. Since the statistical distribution of different effective cavity sizes is unknown, several distribution functions are examined. Meanwhile, the calculated averaged MSDs are compared to the experimental data by Nisato et al (2000 Phys. Rev. E 61 2879). We find that the theoretical results of the MSD are sensitive to the shape of the distribution function. For low cross-linked gels, the best fit is obtained when the interior cavities of a gel follow a bimodal distribution. Such a result may be attributed to the presence of at least two distinct classes of cavity in gels. For high cross-linked gels, the cavities in the gel can be depicted by a single-modal uniform distribution function, suggesting that the range of cavity sizes becomes smaller. These results manifest the voids inside a gel, and the shape of distribution functions may provide the insight into the inhomogeneous interior of a gel.

Shew, Chwen-Yang; Iwaki, Takafumi

2006-04-01

189

New water equivalent liquid scintillation solutions for 3D dosimetry.  

PubMed

Despite recent advances in radiochromic film and gel dosimetry techniques, radiation therapy still lacks an efficient, accurate, and convenient dose measurement method capable of measuring the dose simultaneously over a plane or a volume (3D). A possibility for creating such a 3D method based on observing scintillation photons emitted from an irradiated volume was recently reported [A. S. Kirov et al., Med. Phys. 26, 1069 (1999)]. In the present article, we investigate the potential to use a liquid scintillation solution (LS) as a dose sensitive media and, simultaneously, as a water equivalent phantom material which fills the measurement volume. We show that matching water density in addition to energy absorption properties is important for using the LS solution as a phantom. Through a parametric study of the LS attenuation and absorption coefficients as well as Monte Carlo dose calculations and scintillation efficiency measurements we developed novel LS materials. For the new solutions, the calculated dose in LS is within 8% of the dose to water for depths up to 5 cm for photons having energies between 30 keV and 2 MeV. The new LS solutions, which are loaded with a Si containing compound, retain more than 85% of the scintillation efficiency of the unloaded solutions and exhibit high localization of the scintillation process. The new LS solutions are superior with respect to efficiency and water equivalence to plastic scintillator materials used in dosimetry and may be used apart from the mentioned 3D method. PMID:10841423

Kirov, A S; Shrinivas, S; Hurlbut, C; Dempsey, J F; Binns, W R; Poblete, J L

2000-05-01

190

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.

Liao, David

191

Facing Up To Fitness  

PubMed Central

Becoming fit means preparing ourselves to cope more effectively with environmental stresses. Exercise programs represent one approach to the fitness struggle. There are alternatives for those who find regular exercise unappealing - Yoga, biofeedback training or self hypnosis. At the moment these techniques appear unscientific and spooky - but they work.

Schatz, Douglas

1974-01-01

192

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

193

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

194

Youth Physical Fitness Awards  

Microsoft Academic Search

For more than 20 years national awards have been given to youth who have met predetermined standards on physical fitness test batteries. These awards were established to motivate improvements in youth fitness, to motivate youth to want to take fimess tests, and to encourage active lifestyles. Recently questions have been raised as to the effectiveness of these award schemes. Theoretical

Charles B. Corbin; James R. Whitehead; Peter Y. Lovejoy

1988-01-01

195

ACSM Fit Society Page  

MedlinePLUS

... Page include (click title to view): 2013 -- Overhauling Fitness: Breaking Plateaus 2013 -- Youth Sports Health and Safety 2012 -- Injury Management and Recovery 2012 -- On the Move 2012 -- Managing Chronic Disease 2012 -- DIY ... Fitness Assessment & Injury Prevention 2009 -- Strength Training 2009 -- Menopause ...

196

Fitness and Americans.  

ERIC Educational Resources Information Center

This document makes a number of observations about physical fitness in America. Among them are: (1) the symptoms of aging (fat accumulation, lowered basal metabolic rate, loss of muscular strength, reduction in motor fitness, reduction in work capacity, etc.) are not the result of disease but disuse; (2) society conditions the individual to…

Nordholm, Catherine R.

197

Fitness in Disguise  

ERIC Educational Resources Information Center

|Physical fitness activities are often viewed as monotonous and tedious, so they fail to motivate students to become more physically active. This tedium could be relieved by using a "learning as play" strategy, widely used in other academic disciplines. This article describes how to incorporate fitness into a variety of games so that students do…

Williams, Neil F.; Germain, Jenna

2008-01-01

198

Visualizing fitness landscapes  

PubMed Central

Fitness landscapes are a classical concept for thinking about the relationship between genotype and fitness. However, because the space of genotypes is typically high-dimensional, the structure of fitness landscapes can be difficult to understand and the heuristic approach of thinking about fitness landscapes as low-dimensional, continuous surfaces may be misleading. Here I present a rigorous method for creating low-dimensional representations of fitness landscapes. The basic idea is to plot the genotypes in a manner that reflects the ease or difficulty of evolving from one genotype to another. Such a layout can be constructed using the eigenvectors of the transition matrix describing the evolution of a population on the fitness landscape when mutation is weak. In addition, the eigendecomposition of this transition matrix provides a new, high-level view of evolution on a fitness landscape. I demonstrate these techniques by visualizing the fitness landscape for selection for the amino acid serine and by visualizing a neutral network derived from the RNA secondary structure genotype-phenotype map.

McCandlish, David M.

2013-01-01

199

Fits of hyperon data  

NASA Astrophysics Data System (ADS)

Precision fits of the baryon semileptonic decay data and the baryon magnetic moments are discussed. Two versions of the spectrum generating group model are compared with the conventional cabibbo model, which gives poor fits if rates and symmetries are used. Two versions of the bag model are also tested.

Bohm, A.

1981-09-01

200

Aufgaben und Genauigkeit der klinischen Dosimetrie  

NASA Astrophysics Data System (ADS)

In diesem Kapitel werden die Aufgaben der klinischen Dosimetrie für die verschiedenen radiologischen Disziplinen zusammengestellt. Die wichtigste Aufgabe ist die Messung der im bestrahlten Medium entstandenen Energiedosis für die verschiedenen Strahlungsquellen. Die am weitesten verbreitete dazu verwendete Methode ist die Dosismessung mit gasgefüllten Ionisationskammern. Im zweiten Teil des Kapitels werden die Genauigkeitsanforderungen der klinischen Dosimetrie diskutiert.

Krieger, Hanno

201

Air density correction in ionization dosimetry  

Microsoft Academic Search

Air density must be taken into account when ionization dosimetry is performed with unsealed ionization chambers. The German dosimetry protocol DIN 6800-2 states an air density correction factor for which current barometric pressure and temperature and their reference values must be known. It also states that differences between air density and the attendant reference value, as well as changes in

G. Christ; O. S. Dohm; E. Schüle; S. Gaupp; M. Martin

2004-01-01

202

Biological dosimetry: Cytometric approaches to mammalian systems  

Microsoft Academic Search

Biological dosimetry carries the concept one step further by describing dose in terms of a defined biological response. For mutagens this might take the form of induced mutations, for clastogens of induced chromosome aberrations, for ionizing radiation of changes in circulating blood cells, for a reproductive toxin of altered sperm or decreased fertility. Such dosimetry has two general functions: a

W. G. Eisert; M. L. Mendelson

1984-01-01

203

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.

204

Dosimetry for human exposures and radiological impact  

Microsoft Academic Search

In Health Physics Division annual progress report for period ending July ; 31, 1573. Topics include the Japanese dosimetry program, in utero exposure of A-; bomb survivors, thermal neutron fluence distributions, dose and fluence in ; isotropic and nonwiform fields of radiation, ICRU neutron dosimetry ; intercomparison, and improvements in nitrocellulose film. (WHK);

G. D. Kerr; T. D. Jones; J. S. Cheka; H. W. Dickson; W. F. Fox; S. B. Lupica; D. G. Willhoit; J. J. Shonka; S. L. Chu

1973-01-01

205

40 years of development in radiation dosimetry  

Microsoft Academic Search

A brief historical survey is given. The topics discussed include: the use of condenser chambers in the 1940s; refinements to Bragg-Gray theory in 1955; the adoption by the ICRU in the 1950s of new quantities; the introduction of pulsed accelerators in the 1950s; ionisation dosimetry; calorimetry; chemical dosimetry.

J. W. Boag

1984-01-01

206

Recent achievements in external radiation dosimetry  

Microsoft Academic Search

Some of the more relevant recent achievements and developments in the field of external radiation dosimetry are reviewed in this presentation. Among them, topics related to personal dosimetry, as the relative role of active and passive methods and the features of some recently proposed new methods. Electronic personal dosemeters and Optically Stimulated Luminescence, OSL, have already accredited their adequacy for

Antonio Delgado

207

A novel dosimetry system for computed tomography using phototransistor  

Microsoft Academic Search

Computed tomography (CT) dosimetry normally uses an ionization chamber 100mm long to estimate the computed tomography dose index (CTDI), however some reports have already indicated that small devices could replace the long ion chamber to improve quality assurance procedures in CT dosimetry. This paper presents a novel dosimetry system based in a commercial phototransistor evaluated for CT dosimetry. Three detector

C. M. S. Magalhães; M. L. Sobrinho; D. N. Souza; J. Antônio Filho; E. F. da Silva; L. A. P. Santos

208

Physical Fitness: Questions Teachers Ask.  

ERIC Educational Resources Information Center

Answers teachers' questions about physical fitness, emphasizing children's physical fitness, why people believe children are unfit, children's activity levels, heredity and maturation in fitness testing, test results, adequate fitness, activity, and participation, how long it takes children to get fit, reward systems, current fitness testing, and…

Pangrazi, Robert P.; Corbin, Charles B.

1993-01-01

209

GENII: The Hanford Environmental Radiation Dosimetry Software System: Volume 2, Users' manual: Hanford Environmental Dosimetry Upgrade Project  

Microsoft Academic Search

The Hanford Environmental Dosimetry Upgrade Project was undertaken to incorporate the internal dosimetry models recommended by the International Commission on Radiological Protection (ICRP) in updated versions of the environmental pathway analysis models used at Hanford. The resulting second generation of Hanford environmental dosimetry computer codes is compiled in the Hanford Environmental Dosimetry System (Generation II, or GENII). The purpose of

B. A. Napier; R. A. Peloquin; D. L. Strenge; J. V. Ramsdell

1988-01-01

210

GENII (Generation II): The Hanford Environmental Radiation Dosimetry Software System: Volume 3, Code maintenance manual: Hanford Environmental Dosimetry Upgrade Project  

Microsoft Academic Search

The Hanford Environmental Dosimetry Upgrade Project was undertaken to incorporate the internal dosimetry models recommended by the International Commission on Radiological Protection (ICRP) in updated versions of the environmental pathway analysis models used at Hanford. The resulting second generation of Hanford environmental dosimetry computer codes is compiled in the Hanford Environmental Dosimetry System (Generation II, or GENII). This coupled system

B. A. Napier; R. A. Peloquin; D. L. Strenge; J. V. Ramsdell

1988-01-01

211

Monte Carlo Simulation of MAGIC-f gel for Radiotherapy using PENELOPE  

NASA Astrophysics Data System (ADS)

MAGIC-f gel has been shown as a suitable dosimeter for different techniques in radiotherapy due to its characteristics of water equivalence (effective atomic number of 7.41) and a spatial resolution better than 1mm. One way to predict the gel results is the use of simulations through PENELOPE Monte Carlo code. This simulation code was used to simulate the MAGIC-f gel and its use for dosimetry in conventional and conformal radiotherapy. The results obtained from the simulation were compared with experimental values. Comparisons from simulation and experimental values show mean differences of 2.88 % and 3.75% for conventional and conformal, respectively. This study shows that PENELOPE code can be simulate the components of the MAGIC- f gel to study and predict the gel response.

Alva, M.; Pianoschi, T.; Marques, T.; Santanna M, M.; Baffa, O.; Nicolucci, P.

2010-11-01

212

GOSSIP: SED fitting code  

NASA Astrophysics Data System (ADS)

GOSSIP fits the electro-magnetic emission of an object (the SED, Spectral Energy Distribution) against synthetic models to find the simulated one that best reproduces the observed data. It builds-up the observed SED of an object (or a large sample of objects) combining magnitudes in different bands and eventually a spectrum; then it performs a chi-square minimization fitting procedure versus a set of synthetic models. The fitting results are used to estimate a number of physical parameters like the Star Formation History, absolute magnitudes, stellar mass and their Probability Distribution Functions.

Franzetti, Paolo; Scodeggio, Marco

2012-10-01

213

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".

214

Anniversary Paper: Fifty years of AAPM involvement in radiation dosimetry  

SciTech Connect

This article reviews the involvement of the AAPM in various aspects of radiation dosimetry over its 50 year history, emphasizing the especially important role that external beam dosimetry played in the early formation of the organization. Topics covered include the AAPM's involvement with external beam and x-ray dosimetry protocols, brachytherapy dosimetry, primary standards laboratories, accredited dosimetry chains, and audits for machine calibrations through the Radiological Physics Center.

Ibbott, G.; Ma, C.-M.; Rogers, D. W. O.; Seltzer, S. M.; Williamson, J. F. [Radiological Physics Center, University of M. D. Anderson Cancer Center, Houston, Texas 77030-4009 (United States); Fox Chase Cancer Center, Philadelphia, Pennsylvania 19111 (United States); Ottawa Carleton Institute of Physics, Carleton University Campus, Ottawa K1S 5B6 (Canada); Radiation Interactions and Dosimetry Group, NIST, Gaithersburg, Maryland 20899-8460 (United States); Virginia Commonwealth University, Richmond, Virginia 23298 (United States)

2008-04-15

215

Anniversary paper: fifty years of AAPM involvement in radiation dosimetry.  

PubMed

This article reviews the involvement of the AAPM in various aspects of radiation dosimetry over its 50 year history, emphasizing the especially important role that external beam dosimetry played in the early formation of the organization. Topics covered include the AAPM's involvement with external beam and x-ray dosimetry protocols, brachytherapy dosimetry, primary standards laboratories, accredited dosimetry chains, and audits for machine calibrations through the Radiological Physics Center. PMID:18491537

Ibbott, G; Ma, C-M; Rogers, D W O; Seltzer, S M; Williamson, J F

2008-04-01

216

Water equivalence of NIPAM based polymer gel dosimeters with enhanced sensitivity for x-ray CT  

NASA Astrophysics Data System (ADS)

Two new formulations of N-isopropylacrylamide (NIPAM) based three dimensional (3D) gel dosimeters have recently been developed with improved sensitivity to x-ray CT readout, one without any co-solvent and the other one with isopropanol co-solvent. The water equivalence of the NIPAM gel dosimeters was investigated using different methods to calculate their radiological properties including: density, electron density, number of electrons per grams, effective atomic number, photon interaction probabilities, mass attenuation and energy absorption coefficients, electron collisional, radiative and total mass stopping powers and electron mass scattering power. Monte Carlo modelling was also used to compare the dose response of these gel dosimeters with water for kilovoltage and megavoltage x-ray beams and for megavoltage electron beams. We found that the density and electron density of the co-solvent free gel dosimeter are more water equivalent with less than a 2.6% difference compared to a 5.7% difference for the isopropanol gel dosimeter. Both the co-solvent free and isopropanol solvent gel dosimeters have lower effective atomic numbers than water, differing by 2.2% and 6.5%, respectively. As a result, their photoelectric absorption interaction probabilities are up to 6% and 19% different from water, respectively. Compton scattering and pair production interaction probabilities of NIPAM gel with isopropanol differ by up to 10% from water while for the co-solvent free gel, the differences are 3%. Mass attenuation and energy absorption coefficients of the co-solvent free gel dosimeter and the isopropanol gel dosimeter are up to 7% and 19% lower than water, respectively. Collisional and total mass stopping powers of both gel dosimeters differ by less than 2% from those of water. The dose response of the co-solvent free gel dosimeter is water equivalent (with <1% discrepancy) for dosimetry of x-rays with energies <100 keV while the discrepancy increases (up to 5%) for the isopropanol gel dosimeter over the same energy range. For x-ray beams over the energy range 180 keV-18 MV, both gel dosimeters have less than 2% discrepancy with water. For megavoltage electron beams, the dose differences with water reach 7% and 14% for the co-solvent free gel dosimeter and the isopropanol gel dosimeter, respectively. Our results demonstrate that for x-ray beam dosimetry with photon energies higher than 100 keV and megavoltage electron beams, correction factors are needed for both NIPAM gels to be used as water equivalent dosimeters.

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

2013-10-01

217

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…

Vogel, Ryan M.; Feldman, Daniel C.

2009-01-01

218

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

219

Quenching correction for volumetric scintillation dosimetry of proton beams.  

PubMed

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. 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. 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. 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

2012-12-21

220

Quenching correction for volumetric scintillation dosimetry of proton beams  

NASA Astrophysics Data System (ADS)

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. 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. 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. 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.

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

2013-01-01

221

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

222

[The application of non-annealing thermoluminescent dosimetry (TLD)].  

PubMed

Conventional use of Thermoluminescence (TL) in radiation dosimetry is very time-consuming. It requires repeating the procedures of preheating and annealing. In an attempt to simplify these procedures, we conducted an experiment of non-annealing TL dosimetry. This article reports the experiment's results. We adopted Lithium Fluoride (LiF) chip (TLD-100) in polystyrene under the exposure of Co-60, and the result was taken by HAR-SHAW-4000 TL reading system. The TL response was analyzed, including linearity, reproducibility and fading test. Because non-annealing TL response was greatly influenced by residual electron, TLD calibration curves were separated into two parts: (1) high dose region (HDR, 50-1500 cGy); (2) low dose region (LDR, 0-50 cGy). When TL dosimeters were exposed to a single high does (about 500 cGy), the HDR could be reproduced within 3% and fit a good linearity. For LDR, we had to give up the tail of glow curve in the high temperature region. We could then get good linearity and reproducibility. Furthermore, fading of non-annealing was apparently larger than annealing. We could control the fading of non-annealing was apparently larger than annealing. We could control the fading influence within 1% by taking the TL reading one hour after exposure. On the other hand, a combination of photon and electron exposure was also performed by non-annealing TL dosimetry. The results were compatible with Co-60 exposure in the same system. PMID:8339153

Wu, J M; Chen, C S; Lan, R H

1993-06-01

223

Senior Community Fitness Program.  

National Technical Information Service (NTIS)

The paper summarizes the senior fitness program, which was offered by the Carbondale Young Men's Christian Association (YMCA) to the residents of Greenfield and Scott Townships in Pennsylvania. Seventeen people were evaluated, and of these 10 performed bo...

L. Dean

1985-01-01

224

Exercise and Physical Fitness  

MedlinePLUS

... Increase your chances of living longer Fitting regular exercise into your daily schedule may seem difficult at ... fine. The key is to find the right exercise for you. It should be fun and should ...

225

Health physics research reactor reference dosimetry  

SciTech Connect

Reference neutron dosimetry is developed for the Health Physics Research Reactor (HPRR) in the new operational configuration directly above its storage pit. This operational change was physically made early in CY 1985. The new reference dosimetry considered in this document is referred to as the 1986 HPRR reference dosimetry and it replaces any and all HPRR reference documents or papers issued prior to 1986. Reference dosimetry is developed for the unshielded HPRR as well as for the reactor with each of five different shield types and configurations. The reference dosimetry is presented in terms of three different dose and six different dose equivalent reporting conventions. These reporting conventions cover most of those in current use by dosimetrists worldwide. In addition to the reference neutron dosimetry, this document contains other useful dosimetry-related data for the HPRR in its new configuration. These data include dose-distance measurements and calculations, gamma dose measurements, neutron-to-gamma ratios, ''9-to-3 inch'' ratios, threshold detector unit measurements, 56-group neutron energy spectra, sulfur fluence measurements, and details concerning HPRR shields. 26 refs., 11 figs., 31 tabs.

Sims, C.S.; Ragan, G.E.

1987-06-01

226

Fast neutron dosimetry: Progress summary  

SciTech Connect

The purpose was to investigate the radiological physics and biology of very low energy photons derived from a 1-GeV electron synchrotron storage ring. An extensive beam line and irradiation apparatus was designed, developed, and constructed. Dosimetry measurements required invention and testing of a miniature absolute calorimeter and a cell irradiation fixture suitable for scanning exposures under computer control. Measurements of the kerma factors of oxygen, aluminum and silicon for 14-20 MeV neutrons. Custom designed miniature proportional counters of cylindrical symmetry were employed in these determinations. The oxygen kerma factor was found significantly lower than values calculated from microscopic cross sections. We also tested Mg and Fe walled conventional spherical counters. The direct neutron-counting gas interaction is significant enough for these counters that a correction is needed. We also investigated the application of Nuclear Magnetic Resonance spectroscopy to radiation dosimetry. Our purpose was to take advantage of recent development of very high-field magnets, complex RF-pulse techniques for solvent suppression, and improved spectral analysis techniques.

DeLuca, P.M. Jr.

1988-01-01

227

Introduction to Radiological Physics and Radiation Dosimetry  

NASA Astrophysics Data System (ADS)

A straightforward presentation of the broad concepts underlying radiological physics and radiation dosimetry for the graduate-level student. Covers photon and neutron attenuation, radiation and charged particle equilibrium, interactions of photons and charged particles with matter, radiotherapy dosimetry, as well as photographic, calorimetric, chemical, and thermoluminescence dosimetry. Includes many new derivations, such as Kramers X-ray spectrum, as well as topics that have not been thoroughly analyzed in other texts, such as broad-beam attenuation and geometrics, and the reciprocity theorem. Subjects are layed out in a logical sequence, making the topics easier for students to follow. Supplemented with numerous diagrams and tables.

Attix, Frank Herbert

1987-04-01

228

CONFORMANCE IMPROVEMENT USING GELS  

SciTech Connect

This technical progress report describes work performed from September 1, 2003, through February 29, 2004, for the project, ''Conformance Improvement Using Gels.'' We examined the properties of several ''partially formed'' gels that were formulated with a combination of high and low molecular weight HPAM polymers. After placement in 4-mm-wide fractures, these gels required about 25 psi/ft for brine to breach the gel (the best performance to date in fractures this wide). After this breach, stabilized residual resistance factors decreased significantly with increased flow rate. Also, residual resistance factors were up to 9 times greater for water than for oil. Nevertheless, permeability reduction factors were substantial for both water and oil flow. Gel with 2.5% chopped fiberglass effectively plugged 4-mm-wide fractures if a 0.5-mm-wide constriction was present. The ability to screen-out at a constriction appears crucial for particulate incorporation to be useful in plugging fractures. In addition to fiberglass, we examined incorporation of polypropylene fibers into gels. Once dispersed in brine or gelant, the polypropylene fibers exhibited the least gravity segregation of any particulate that we have tested to date. In fractures with widths of at least 2 mm, 24-hr-old gels (0.5% high molecular weight HPAM) with 0.5% fiber did not exhibit progressive plugging during placement and showed extrusion pressure gradients similar to those of gels without the fiber. The presence of the fiber roughly doubled the gel's resistance to first breach by brine flow. The breaching pressure gradients were not as large as for gels made with high and low molecular weight polymers (mentioned above). However, their material requirements and costs (i.e., polymer and/or particulate concentrations) were substantially lower than for those gels. A partially formed gel made with 0.5% HPAM did not enter a 0.052-mm-wide fracture when applying a pressure gradient of 65 psi/ft. This result suggests a lower limit of fracture width for entry of formed or partially formed gels (when reasonable pressure gradients are applied). In unfractured porous rock, we investigated the time dependence of oil and water permeabilities during various cycles of oil and water injection after placement of a Cr(III)-acetate-HPAM gel. Permeability to water stabilized rapidly (within 1 pore volume, PV), while permeability to oil stabilized gradually over the course of 100 PV. The behavior was surprisingly insensitive to core material (strongly water-wet Berea sandstone and strongly oil-wet porous polyethylene), core permeability (740 to 10,000 md), and applied pressure gradient (10 to 100 psi/ft).

Randall S. Seright

2004-03-01

229

Mutation accumulation, performance, fitness.  

PubMed

The morphology-performance-fitness paradigm is usually explored by determining whether natural or "phenotypically engineered" variation among individuals in morphology (physiology) or performance covaries with an index of fitness such as survival. Here we study between-line covariation between performance and fitness for 44 lines of flies that had undergone mutation accumulation (in the absence of natural selection) on the second chromosome for 62 generations, plus 13 control lines. These mutation accumulation (MA) lines were known to have reduced competitive fitness and life history scores, and to have positive between-line covariances among life history traits. We measured several performance traits of larvae and adults (and a life history trait), examined covariances among those trait means, and also examined covariances of traits with competitive fitness. MA lines had significantly lower performances than did control lines in most traits. However, because control lines had been unknowingly contaminated, a conclusion that MA reduces performance must be tentative. Correlations among performance traits were highly variable in sign, suggesting that MA does not negatively affect all traits equivalently. Even so, correlation matrices for MA and for control lines were very similar. In bivariate comparisons, only one performance trait (a "get-a-grip index," which measures the ability of a falling fly to catch itself on baffles) was positively correlated with competitive fitness. Multivariate analyses again suggested the importance primarily of get-a-grip. Two main patterns emerge from this study. First, MA negatively affects diverse aspects of physiological performance, but does so differentially across traits. Second, except for GAG, MA-induced variation in performance is at best weakly correlated with competitive fitness. PMID:21680447

Huey, Raymond B; Gilchrist, George W; Ward, Kimiora; Maves, Lisa; Pepin, David; Houle, David

2003-07-01

230

Dosimetry using HS GafChromic films the influence of readout light on sensitivity of dosimetry  

NASA Astrophysics Data System (ADS)

Various forms of Gafchromic films that are increasingly used for dosimetry in radiotherapy offer the prospect of reproducible and accurate high-resolution two-dimensional dose measurements, but there are many unresolved issues regarding the optimal choice of densitometric procedure used for the film's optical density (OD) readout. There are conflicting requirements for scanners (sensitivity, availability, price) and commercial document scanners appears to be a reasonable option, hence we analyzed the measured sublinear dose response of these scanners. Using measured film absorption spectra we were able to make quantitative distinction between various factors affecting the sublinearity and to demonstrate that the dose response curve can be predicted for any selected light source used for scanning. We also used the commercial narrow bandpass filters in conjunction with document scanners to investigate whether such an inexpensive option can improve their sensitivity, but results were not encouraging. Finally, we analyzed the suitability of proposed fitting equations for the calibration of the dose response and found that their reliability largely depends on the dose range used for the calibration.

Še?erov, Bojana; Dakovi?, Marko; Borojevi?, Nenad; Ba?i?, Goran

2011-03-01

231

Optical properties of HITC and oxazine-1-doped sol-gel gel glasses  

NASA Astrophysics Data System (ADS)

The lifetime of the near-infrared emission of oxazine-1 and 1,1',3,3,3',3'- hexamethylindotrycarbocyanine iodide (HITC) into gel-glasses prepared from TMOS or TEOS are studied by variable frequency phase and modulation data. Analysis of the lifetime by a fitting procedure to an assumed model revealed two lifetimes with a low value of the reduced chi-squared for the studied doped gel-glasses. The longer lifetime is attributed to the adsorbed species, while the shorter to species which are affected by the remaining solvent in the pores. The contributions of these species to the total fluroescence are also resolved.

del Monte, Francisco; Levy, David

1994-10-01

232

A comparison of next-fit, first-fit, and best-fit  

Microsoft Academic Search

“Next-fit” allocation differs from first-fit in that a first-fit allocator commences its search for free space at a fixed end of memory, whereas a next-fit allocator commences its search wherever it previously stopped searching. This strategy is called “modified first-fit” by Shore [2] and is significantly faster than the first-fit allocator. To evaluate the relative efficiency of next-fit (as well

Carter Bays

1977-01-01

233

Fitting Cosmological Data Package  

NSDL National Science Digital Library

The EJS Fitting Cosmological Data Launcher package includes several cosmological fitting simulations for five different observations of the expansion, all of which support a cosmic acceleration. The launcher allows users to choose which simulation to use to compare and fit theoretical models of cosmology with recent supernovae, gamma-ray bursts, the Hubble Parameter, baryon acoustic oscillations, and the 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 Launcher package was created using Easy Java Simulations (EJS) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the ejs_CosmoEJS.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; Shuler, Zeke; Engelhardt, Larry

2012-09-10

234

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

235

Fitness Testing Athletes  

PubMed Central

Fitness testing of athletes can be subdivided into tests of body build, strength, aerobic power, and tests specific to the athletic event. World class athletes seem to fall into specific body types for the individual events. The top athlete usually has very little of the endomorphic characteristics and should be lean. Strength testing should be used more frequently as weight and isometric training techniques are used by many athletes and coaches without specific goals. The aerobic power of many national class athletes may be only 10-30 percent above that of the general population, and high values were found only in cyclists and distance runners. It is emphasized that the scores of fitness tests are specific for each test and do not necessarily correlate at all with athletic performance which is also specific. Despite this limitation, fitness tests do have a place in athletics and should be utilized more fully and with more understanding by coaches and athletes. Imagesp48-a

Cumming, Gordon R.

1970-01-01

236

Coloring the FITS Universe  

NASA Astrophysics Data System (ADS)

A new, freely-available accessory for Adobe's widely-used Photoshop image editing software makes it much more convenient to produce presentable images directly from FITS data. It merges a fully-functional FITS reader with an intuitive user interface and includes fully interactive flexibility in scaling data. Techniques for producing attractive images from astronomy data using the FITS plugin will be presented, including the assembly of full-color images. These techniques have been successfully applied to producing colorful images for public outreach with data from the Hubble Space Telescope and other major observatories. Now it is much less cumbersome for students or anyone not experienced with specialized astronomical analysis software, but reasonably familiar with digital photography, to produce useful and attractive images.

Levay, Z. G.

2004-12-01

237

Model fitting tutorial  

NASA Astrophysics Data System (ADS)

The purpose of this tutorial is not to describe the theory of model fitting, but to focus on practical aspects and to learn how to work around difficulties. For practice, we use LITpro, a software currently developed within the JMMC research group. LITpro is based on a modified Levenberg-Marquardt algorithm and its architecture allows a flexible implementation of complex models and fits with heterogeneous data. Through the analyzis of an example of a fit on simulated interferometric data, we learn how to deal with degeneracies and how to tackle the problem of local minima, with tools provided by LITpro. The web-site of the Jean-Marie Mariotti Center is http://www.mariotti.fr.

Tallon-Bosc, I.; Tallon, M.; Thiébaut, E.; Béchet, C.

2007-10-01

238

Report on high energy neutron dosimetry workshop  

SciTech Connect

The workshop was called to assess the performance of neutron dosimetry per the responses from ten DOE accelerator facilities to an Office of Energy Research questionnaire regarding implementation of a personnel dosimetry requirement in DRAFT DOE 5480.ACC, Safety of Accelerator Facilities''. The goals of the workshop were to assess the state of dosimetry at high energy accelerators and if such dosimetry requires improvement, to reach consensus on how to proceed with such improvements. There were 22 attendees, from DOE Programs and contract facilities, DOE, Office of Energy Research (ER), Office of Environmental Safety and Health (EH), Office of Fusion Energy, and the DOE high energy accelerator facilities. A list of attendees and the meeting agenda are attached. Copies of the presentations are also attached.

Alvar, K.R.; Gavron, A.

1993-01-27

239

Report on high energy neutron dosimetry workshop  

SciTech Connect

The workshop was called to assess the performance of neutron dosimetry per the responses from ten DOE accelerator facilities to an Office of Energy Research questionnaire regarding implementation of a personnel dosimetry requirement in DRAFT DOE 5480.ACC, ``Safety of Accelerator Facilities``. The goals of the workshop were to assess the state of dosimetry at high energy accelerators and if such dosimetry requires improvement, to reach consensus on how to proceed with such improvements. There were 22 attendees, from DOE Programs and contract facilities, DOE, Office of Energy Research (ER), Office of Environmental Safety and Health (EH), Office of Fusion Energy, and the DOE high energy accelerator facilities. A list of attendees and the meeting agenda are attached. Copies of the presentations are also attached.

Alvar, K.R.; Gavron, A.

1993-01-27

240

Dosimetrie retrospective (ou auto-dosimetrie): application au parc electronucleaire francais. (Retrospective dosimetry (or self dosimetry): Application to French Nuclear Power Plants).  

National Technical Information Service (NTIS)

In this text we give the dosimetry principle on irradiated materials such baffle screw, pressure vessel and control element cans. This measure, made by gammametry, is based on the steel activation and comparison with calculated measures by Actige code. 4 ...

R. Lloret

1993-01-01

241

Radon Progeny Dosimetry in the Rat Lung.  

National Technical Information Service (NTIS)

Deposition, mucociliary clearance, and dosimetry for the inhalation of radon progeny in the rat lung have been simulated for a variety of inhalation conditions. Computations indicate that the exposure-dose conversion factor for the rat lung is approximate...

W. Hofmann M. G. Menache R. C. Graham

1993-01-01

242

Dosimetry and Protection from Ionizing Radiation.  

National Technical Information Service (NTIS)

Consideration is given to different methods of ionizing radiation dosimetry and simplified methods for design of shielding for gamma radiation, for neutron radiation and for design of shielding in a nuclear reactor.

B. P. Golubev

1967-01-01

243

Dosimetry Techniques Applied to Thermoluminescent Age Estimation.  

National Technical Information Service (NTIS)

The reliability and the ease of the field application of the measuring techniques of natural radioactivity dosimetry are studied. The natural radioactivity in minerals in composed of the internal dose deposited by alpha and beta radiations issued from the...

H. Erramli

1986-01-01

244

Nonlinearity of dose responses in thermoluminescence dosimetry.  

National Technical Information Service (NTIS)

All of dose responses in thermoluminescence (TL) dosimetry can be described by a dose response function derived from statistical Poisson distribution. Two characteristic parameters in this function, one hit factor R and characteristic dose D(sub 0), can b...

Luo Daling Zhang Chunxiang

1995-01-01

245

Film badge dosimetry in atmospheric nuclear tests  

SciTech Connect

This book is divided into the following sections: Basic Principles of Film Badge Dosimetry; Radiation source terms in atmospheric testing; Use of film badge in atmospheric nuclear testing; Quantification of Personnel Film badge uncertainties; Uncertainty analysis by individual test series.

Not Available

1989-01-01

246

Quantum Data Fitting  

NASA Astrophysics Data System (ADS)

We provide a new quantum algorithm that efficiently determines the quality of a least-squares fit over an exponentially large data set by building upon an algorithm for solving systems of linear equations efficiently (Harrow et al., Phys. Rev. Lett. 103, 150502 (2009)). In many cases, our algorithm can also efficiently find a concise function that approximates the data to be fitted and bound the approximation error. In cases where the input data is a pure quantum state, the algorithm can be used to provide an efficient parametric estimation of the quantum state and therefore can be applied as an alternative to full quantum state tomography given a fault tolerant quantum computer.

Wiebe, Nathan

2013-03-01

247

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.

Roberts, Donna

248

Multigroup processing ENDF/B dosimetry covariances  

SciTech Connect

The methodology of multigroup processing of ENDF/B dosimetry covariance (uncertainty) information is discussed, with specific references to the ERRORR covariance module of the NJOY nuclear data processing system. Also discussed is the recent application of ERRORR to the generation of a 137-group, 35-material covariance library for dosimetry applications, and a compact format for storing and transmitting fine-group covariance libraries is introduced.

Muir, D.W.; MacFarlane, R.E.; Boicourt, R.M.

1982-01-01

249

Linking the Fits, Fitting the Links: Connecting Different Types of PO Fit to Attitudinal Outcomes  

ERIC Educational Resources Information Center

|In this paper we explore the linkages among various types of person-organization (PO) fit and their effects on employee attitudinal outcomes. We propose and test a conceptual model which links various types of fits--objective fit, perceived fit and subjective fit--in a hierarchical order of cognitive information processing and relate them to…

Leung, Aegean; Chaturvedi, Sankalp

2011-01-01

250

Agarose Gel Demos  

NSDL National Science Digital Library

This video, presented by WGBH, is a great overview of how to prepare Agarose gel for electrophoresis. The video goes in-depth with the finer points including how to insert the pipette as to not disturb the gel and get the best results. This video would be useful for anyone in biochemistry or molecular biology fields. This video would also be helpful for instructors looking to provide their students with an overview on how to prepare Agarose gel. Educators will also find a background essay, discussion questions, and standards alignment for the material.

2010-09-15

251

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

252

Mentoring that Fits  

ERIC Educational Resources Information Center

Beginning teachers enter the classroom with diverse backgrounds, training, expectations, and needs. Yet too often, write the authors, induction programs resemble a one-size-fits-all poncho rather than a well-tailored coat. Reviewing the research, the authors write that high-quality mentors, a focus on improving instruction, and allocated time are…

Grossman, Pam; Davis, Emily

2012-01-01

253

Action Plan for Fitness.  

ERIC Educational Resources Information Center

By completing a short worksheet, physical education students can develop and practice a five-step fitness plan that is appropriate for elementary through college students. The steps include: selecting an appropriate goal and listing costs and benefits, assessing progress, creating a supportive environment, using supportive self-messages, and…

Lottes, Christine R.

1997-01-01

254

Kids Weigh to Fitness.  

ERIC Educational Resources Information Center

A description is given of a program that provides preventive measures to check obesity in children and young people. The 24-week program is divided into two parts--a nutrition component and an exercise component. At the start and end of the program, tests are given to assess the participants' height, weight, body composition, fitness level, and…

Maione, Mary Jane

255

Langley Fitness Center.  

National Technical Information Service (NTIS)

NASA Langley recognizes the importance of healthy employees by committing itself to offering a complete fitness program. The scope of the program focuses on promoting overall health and wellness in an effort to reduce the risks of illness and disease and ...

1993-01-01

256

Wheel of Fitness  

NSDL National Science Digital Library

In this fun activity for any size group, early elementary learners complete physical challenges while playing a game. Learners add new challenges to the "wheel of fitness" that they want to try. During this activity, learners practice their counting skills and discover new ways to get moving. This lesson plan includes extensions, questions to ask learners, and a sample wheel.

Houston, Children'S M.

2007-01-01

257

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

258

Directory of Fitness Certifications.  

ERIC Educational Resources Information Center

|This article discusses the need for certification of fitness instructors in the aerobic dance/dance-exercise industry and presents results of a survey of 18 agencies that certify instructors. Survey data has been compiled and published. An excerpt is included which lists organizations, training, certification and renewal procedures, publications,…

Parks, Janet B.

1990-01-01

259

Goodness of Fit  

Microsoft Academic Search

This study addresses the fit between social work education and practice in health care. A random sample of NASW members identifying with health care (N = 179) responded to a mail survey about the utility of core knowledge and roles that we had identified by reviewing seven commonly used health care social work texts. Quantitative data revealed knowledge and roles

Laura Bronstein; Pamela Kovacs; Alex Vega

2007-01-01

260

Progressive Human Skeleton Fitting  

Microsoft Academic Search

Abstract This paper proposes a method,to fit a skeleton or stick- model to a blob to determine the pose of a person in an image. The input is a binary image representing the sil- houette of a person and the ouput is a stick-model co- herent with the pose of the person in this image. A torso model is first

J Er Ome Vignola

261

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

262

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

263

EPIDUO Gel Labeling  

Center for Biologics Evaluation and Research (CBER)

Text Version... treated with EPIDUO Gel were dry skin, contact ... of topical products with a strong drying effect can ... Weather extremes, such as wind or cold, may be ... More results from www.fda.gov/downloads/advisorycommittees/committeesmeetingmaterials

264

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

265

Active DNA gels  

NASA Astrophysics Data System (ADS)

Research into the mechanics and fluctuations of living cells has revealed the key role played by the cytoskeleton, a gel of stiff filaments driven out of equilibrium by force-generating motor proteins. Inspired by the extraordinary mechanical functions that the cytoskeleton imparts to the cell, we sought to create an artificial gel with similar characteristics. We identified DNA, and DNA-based motor proteins, as functional counterparts to the constituents of the cytoskeleton. We used DNA selfassembly to create a gel, and characterized its fluctuations and mechanics both before and after activation by the motor. We found that certain aspects of the DNA gel quantitatively match those of cytoskeletal networks, indicating the universal features of motor-driven, non-equilibrium networks.

Saleh, Omar A.; Fygenson, Deborah K.; Bertrand, Olivier J. N.; Park, Chang Young

2013-02-01

266

Multicomponent biopolymer gels  

Microsoft Academic Search

The structure—property relationship and application of multicomponent protein—polysaccharide and polysaccharide 1—polysaccharide 2 gels are considered. Attention is focused on gels based on mixed solutions of gelatin with dextran, human serum albumin, sodium caseinate, ovalbumin, agarose, methylcellulose, calcium alginate or sodium alginate. The thermodynamic incompatibility of and the formation of complexes by food hydrocolloids greatly affect mechanical and other physicochemical properties

D. V. Zasypkin; E. E. Braudo; V. B. Tolstoguzov

1997-01-01

267

Fluorescent staining of gels.  

PubMed

Certain transition metal complexes show intensive fluorescence when bound to proteins. They can be used to stain gels after electrophoresis with a sensitivity approaching that of silver staining, but in a much simpler and more reproducible procedure. Stains can be prepared easily and at a fraction of the cost of commercially available reagents.Hydrophobic dyes can be used to stain gels without fixing; they do not interfere with later blotting or electro-elution. PMID:22585519

Buxbaum, Engelbert

2012-01-01

268

Gels with magnetic properties  

Microsoft Academic Search

Materials producing strain in magnetic field are known as magnetoelastic or magneto strictive materials. A new type has been\\u000a developed by preparing magnetic field sensitive gels, called ferrogels. Single domain, magnetic particles of colloidal size\\u000a are incorporated into chemically cross-linked polyvinyl-alcohol hydrogels. The finely distributed colloidal particles having\\u000a superparamgnetic behavior couple the shape of the gel to the nonuniform external

L. Barsi; A. Biiki; D. Szabó; M. Zrinyi

269

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

270

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

271

Radiochromic Gel dosimeter (FXG) chemical yield determination for dose measurements standardization  

NASA Astrophysics Data System (ADS)

Different gel dosimetry techniques have been proposed as methods for three dimensional dose distribution measurements. Gel dosimeters were proposed for radiotherapy dosimetry at which the calibration of any dose-measuring technique is the main requirement for its proper practical application. The standardisation of the technique requires the establishment of a method for the calibration of each type of these gel materials. The aim of this study is to determine the chemical yield for the radiochromic "Ferrous-sulphate and Xelenol-orange Gelatin" (FXG) gel. Using standard absorbed dose to water protocol, the radiation field is calibrated first; then a standard Fricke solution dosimeter is calibrated. The obtained chemical yield for Fricke is G(Fe3+) = 1.68×106 [mol. J-1]. Finally, FXG dosimeter was calibrated against the standard Fricke solution before calculating the system chemical yield and comparing its value with Fricke system. The results show that square.G (FXG) = 6093.1 [m2. J-1] = 19.5×square.G (Fricke). Compared with the Fricke system, the FXG dosimeter has much higher sensitivity. Additionally, the overall accuracy and reproducibility of the gel detector was also comparable to those reported for Fricke solution. However, the FXG dosimeter properties could be improved further through the establishment of a defined manufacturing procedures and calibration method; as well as precise selection of sensitive materials and radiation effects evaluation techniques.

Bero, M. A.; Zahili, M.

2009-05-01

272

Evaluation of dose delivery accuracy of gamma knife using MRI polymer gel dosimeter in an inhomogeneous phantom  

NASA Astrophysics Data System (ADS)

Polymer gel dosimetry is still the only dosimetry method for directly measuring three-dimensional dose distributions. MRI Polymer gel dosimeters are tissue equivalent and can act as a phantom material. Because of high dose response sensitivity, the MRI was chosen as readout device. In this study dose profiles calculated with treatment-planning software (LGP) and measurements with the MR polymer gel dosimeter for single-shot irradiations were compared. A custom-built 16 cm diameter spherical plexiglas head phantom was used in this study. Inside the phantom, there is a cubic cutout for insertion of gel phantoms and another cutout for inserting the inhomogeneities. The phantoms were scanned with a 1.5T MRI (Siemens syngo MR 2004A 4VA25A) scanner. The multiple spin-echo sequence with 32 echoes was used for the MRI scans. Calibration relations between the spin-spin relaxation rate and the absorbed dose were obtained by using small cylindrical vials, which were filled with the PAGAT polymer gel from the same batch as for the spherical phantom. 1D and 2D data obtained using gel dosimeter for homogeneous and inhomogeneous phantoms were compared with dose obtained using LGP calculation. The distance between relative isodose curves obtained for homogeneous phantom and heterogeneous phantoms exceed the accepted total positioning error (>±2mm). The findings of this study indicate that dose measurement using PAGAT gel dosimeter can be used for verifying dose delivering accuracy in GK unit in presence of inhomogeneities.

Pourfallah T, A.; Alam N, Riahi; M, Allahverdi; M, Ay; M, Zahmatkesh

2009-05-01

273

The stability of liquid-filled matrix ionization chamber electronic portal imaging devices for dosimetry purposes.  

PubMed

This study was performed to determine the stability of liquid-filled matrix ionization chamber (LiFi-type) electronic portal imaging devices (EPID) for dosimetric purposes. The short- and long-term stability of the response was investigated, as well as the importance of factors influencing the response (e.g., temperature fluctuations, radiation damage, and the performance of the electronic hardware). It was shown that testing the performance of the electronic hardware as well as the short-term stability of the imagers may reveal the cause of a poor long-term stability of the imager response. In addition, the short-term stability was measured to verify the validity of the fitted dose-response curve immediately after beam startup. The long-term stability of these imagers could be considerably improved by correcting for room temperature fluctuations and gradual changes in response due to radiation damage. As a result, the reproducibility was better than 1% (1 SD) over a period of two years. The results of this study were used to formulate recommendations for a quality control program for portal dosimetry. The effect of such a program was assessed by comparing the results of portal dosimetry and in vivo dosimetry using diodes during the treatment of 31 prostate patients. The improvement of the results for portal dosimetry was consistent with the deviations observed with the reproducibility tests in that particular period. After a correction for the variation in response of the imager, the average difference between the measured and prescribed dose during the treatment of prostate patients was -0.7%+/-1.5% (1 SD), and -0.6%+/-1.1% (1 SD) for EPID and diode in vivo dosimetry, respectively. It can be concluded that a high stability of the response can be achieved for this type of EPID by applying a rigorous quality control program. PMID:15124999

Louwe, R J W; Tielenburg, R; van Ingen, K M; Mijnheer, B J; van Herk, M B

2004-04-01

274

Memory Allocation with Lazy Fits  

Microsoft Academic Search

Dynamic memory allocation is an important part of modern pro- gramming languages. It is important that it be done fast without wasting too much memory. Memory allocation using lazy fits is introduced, where pointer increments, which is very fast, is used as the primary allocation method and where conventional fits such as best fit or first fit are used as

Yoo C. Chung; Soo-Mook Moon

2000-01-01

275

Memory allocation with lazy fits  

Microsoft Academic Search

Dynamic memory allocation is an important part of modern programming languages. It is important that it be done fast without wasting too much memory. Memory allocation using lazy fits is introduced, where pointer increments, which is very fast, is used as the primary allocation method and where conventional fits such as best fit or first fit are used as backup.

Yoo C. Chung; Soo-Mook Moon

2001-01-01

276

Chandra FITS Dictionary  

NASA Astrophysics Data System (ADS)

Well-defined data and metadata specifications are fundamental for the operation of large observing facilities. We have collected the complete body of FITS keywords, as used in Chandra data products, into a dictionary database that provides easy access to their use and meaning. We present an account of the functionality of the dictionary, as well as a description of the database design and details of the tools which display the dictionary.

Winkelman, S. L.; Rots, A. H.; Michaud, K.; Blecksmith, S. E.

2004-07-01

277

Technical Basis Document for PFP Area Monitoring Dosimetry Program  

SciTech Connect

This document describes the phantom dosimetry used for the PFP Area Monitoring program and establishes the basis for the Plutonium Finishing Plant's (PFP) area monitoring dosimetry program in accordance with the following requirements: Title 10, Code of Federal Regulations (CFR), part 835, ''Occupational Radiation Protection'' Part 835.403; Hanford Site Radiological Control Manual (HSRCM-1), Part 514; HNF-PRO-382, Area Dosimetry Program; and PNL-MA-842, Hanford External Dosimetry Technical Basis Manual.

COOPER, J.R.

2000-04-17

278

Fitting the phenomenological MSSM  

SciTech Connect

We perform a global Bayesian fit of the phenomenological minimal supersymmetric standard model (pMSSM) to current indirect collider and dark matter data. The pMSSM contains the most relevant 25 weak-scale MSSM parameters, which are simultaneously fit using 'nested sampling' Monte Carlo techniques in more than 15 years of CPU time. We calculate the Bayesian evidence for the pMSSM and constrain its parameters and observables in the context of two widely different, but reasonable, priors to determine which inferences are robust. We make inferences about sparticle masses, the sign of the {mu} parameter, the amount of fine-tuning, dark matter properties, and the prospects for direct dark matter detection without assuming a restrictive high-scale supersymmetry breaking model. We find the inferred lightest CP-even Higgs boson mass as an example of an approximately prior-independent observable. This analysis constitutes the first statistically convergent pMSSM global fit to all current data.

AbdusSalam, Shehu S.; Allanach, Benjamin C. [DAMTP, Center for Mathematical Sciences, Wilberforce Road, Cambridge CB3 0WA (United Kingdom); Quevedo, Fernando [DAMTP, Center for Mathematical Sciences, Wilberforce Road, Cambridge CB3 0WA (United Kingdom); CERN, PH-TH, CH-1211, Geneva 23 (Switzerland); Feroz, Farhan; Hobson, Mike [Cavendish Laboratory, JJ Thomson Avenue, Cambridge CB3 0HE (United Kingdom)

2010-05-01

279

CONFORMANCE IMPROVEMENT USING GELS  

SciTech Connect

This technical progress report describes work performed from June 20 through December 19, 2001, for the project, ''Conformance Improvement Using Gels''. Interest has increased in some new polymeric products that purport to substantially reduce permeability to water while causing minimum permeability reduction to oil. In view of this interest, we are currently studying BJ's Aqua Con. Results from six corefloods revealed that the Aqua Con gelant consistently reduced permeability to water more than that to oil. However, the magnitude of the disproportionate permeability reduction varied significantly for the various experiments. Thus, as with most materials tested to date, the issue of reproducibility and control of the disproportionate permeability remains to be resolved. Concern exists about the ability of gels to resist washout after placement in fractures. We examined whether a width constriction in the middle of a fracture would cause different gel washout behavior upstream versus downstream of the constriction. Tests were performed using a formed Cr(III)-acetate-HPAM gel in a 48-in.-long fracture with three sections of equal length, but with widths of 0.08-, 0.02-, and 0.08-in., respectively. The pressure gradients during gel extrusion (i.e., placement) were similar in the two 0.08-in.-wide fracture sections, even though they were separated by a 0.02-in.-wide fracture section. The constriction associated with the middle fracture section may have inhibited gel washout during the first pulse of brine injection after gel placement. However, during subsequent phases of brine injection, the constriction did not inhibit washout in the upstream fracture section any more than in the downstream section.

Randall S. Seright

2002-02-28

280

Tooth enamel as a detector material for retrospective EPR dosimetry  

Microsoft Academic Search

Different methods of spectra evaluation and dose reconstruction in retrospective EPR dosimetry with tooth enamel have been compared in this study. Experiments with teeth irradiated with known doses have shown that dosimetry above 1 Gy using a dose effect curve is, with a standard deviation of 10%, the best method. As a second result it is shown that dosimetry down

S. Egersdörfer; A. Wieser; A. Müller

1996-01-01

281

Personnel neutron dosimetry using electrochemically etched CR39 foils  

Microsoft Academic Search

This report describes a personnel neutron dosimetry system based on the electrochemical etching of CR-39 plastic at elevated temperatures. The CR-39 dosimetry system has several advantages: the doses obtained using this system are more accurate than those from other dosimetry systems, especially when varied neutron spectra are encountered; CR-39 does not have the severe energy dependence that exists with albedo

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

1987-01-01

282

Personnel neutron dosimetry using electrochemically etched CR39 foils  

Microsoft Academic Search

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

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

1986-01-01

283

The dose distribution of low dose rate Cs137 in intracavitary brachytherapy: comparison of Monte Carlo simulation, treatment planning calculation and polymer gel measurement  

Microsoft Academic Search

In this study, the dose distribution delivered by low dose rate Cs-137 brachytherapy sources was investigated using Monte Carlo (MC) techniques and polymer gel dosimetry. The results obtained were compared with a commercial treatment planning system (TPS). The 20 mm and the 30 mm diameter Selectron vaginal applicator set (Nucletron) were used for this study. A homogeneous and a heterogeneous---with

M. Fragoso; P. A. Love; F. Verhaegen; C. Nalder; A. M. Bidmead; M. Leach; S. Webb

2004-01-01

284

Dosimetry and Risk Assessment: Fundamental Concepts  

SciTech Connect

Radiation dosimetry is important for characterizing radiation exposures and for risk assessment. In a medical setting, dosimetry is important for evaluating the safety of administered radiopharmaceuticals and for planning the safe administration of therapeutic radionuclides. Environmental dosimetry helps establish the safety of radionuclide releases from electric power production and other human activities. Internal and external dosimetry help us understand the consequences of radiation exposure. The absorbed dose is the fundamental quantity in radiation dosimetry from which all other operational values in radiation protection are obtained. Equivalent dose to tissue and effective dose to the whole body are derivatives of absorbed dose and constructs of risk. Mathematical systems supported by computer software facilitate dose calculations and make it possible to estimate internal dose based on bioassay or other biokinetic data. Risk coefficients for radiation-induced cancer rely primarily on data from animal studies and long-term observations of the Hiroshima and Nagasaki bomb survivors. Low-dose research shows that mechanisms of radiation interactions with tissue are dose-dependent, but the resulting biological effects are not necessarily linear with absorbed dose. Thus, the analysis of radiation effects and associated risks must account for the influences of microscopic energy distributions at the cellular level, dose-rate, cellular repair of sub-lethal radiation damage, and modifying factors such as bystander effects, adaptive response, and genomic instability.

Fisher, Darrell R.

2005-12-29

285

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

286

DNA Electrophoresis in Agarose Gels: Mobility vs. Length Dependence  

Microsoft Academic Search

Over the years, many different models have been applied to the migration of DNA fragments during gel electrophoresis. These models have been limited to describing DNA motion over specific size ranges. We propose a frictional and charge based model relating the electrophoretic mobility to length that fits data for DNA fragment lengths from 100 base pairs (bp) to 50 kilobase

Afshin Beheshti; David van Winkle; Randolph Rill

2001-01-01

287

Neutron dosimetry for low dose rate Cf252 AT sources and adherence to recent clinical dosimetry protocol for brachytherapy  

Microsoft Academic Search

In 1995, the American Association of Physicists in Medicine Task Group 43 (AAPM TG-43) published a protocol obsoleting all mixed-field radiation dosimetry for Cf-252. Recommendations for a new brachytherapy dosimetry formalism made by this Task Group favor quantification of source strength in terms of air kerma rather than apparent Curies or other radiation units. Additionally, representation of this dosimetry data

M. J. Rivard; J. G. Wierzbicki; F. Van den Heuvel; R. C. Martin

1997-01-01

288

An internal dosimetry intercomparison study  

SciTech Connect

Pacific Northwest Laboratory performed a study to evaluate the consistency of internal dosimetry assessments. A total of eleven laboratories, including DOE sites and NRC licensees, participated in this intercomparison study. Participants were asked to respond to five actual exposure scenarios, previously used in a similar European study. The participating dosimetrists assessed the data of the test scenarios and calculated results in terms of estimated radionuclide intake and the resulting internal doses. To maintain confidentiality, results are given without identifying any site. Except for one scenario, the results showed that the standard deviation of the final results on committed effective dose equivalent for each exposure scenario was about 30-50% of the mean value, giving a consistency slightly greater variant than that of the European study. The discrepancies can be attributed to variations in (1) the interpretation and statistical treatment of the bioassay data; (2) the biokinetic models applied; and (3) the computational tools used. This represents a preliminary study; further intercomparison testing is needed to fully evaluate the problem of dose-assessment inconsistency. 13 refs., 10 tabs.

Hui, T.E.; Fisher, D.R.; McDonald, J.C. [Pacific Northwest Lab., Richland, WA (United States); Loesch, R.M. [Dept. of Energy, Washington, DC (United States); Raddatz, C. [Nuclear Regulatory Commission, Washington, DC (United States)

1994-09-01

289

Surface tension-induced gel fracture. Part 1. Fracture of agar gels.  

PubMed

This work involves an experimental investigation of the spreading of liquids on gel layers in the presence of surfactants. Of primary interest is the instability that accompanies the cracking of gels through the deposition and subsequent spreading of a drop of surfactant solution on their surfaces. This instability manifests itself via the shaping of crack-like spreading "arms", in formations that resemble starbursts. The main aim of this study is to elucidate the complex interactions between spreading surfactants and underlying gels and to achieve a fundamental understanding of the mechanism behind the observed phenomenon of the cracking pattern formation. By spreading SDS and Silwet L-77 surfactant solutions on the surfaces of agar gels, the different ways that system parameters such as the surfactant chemistry and concentration and the gel strength can affect the morphology and dynamics of the starburst patterns are explored. The crack propagation dynamics is fitted to a power law by measuring the temporal evolution of the length of the spreading arms that form each one of the observed patterns. The values of the exponent of the power law are within the predicted limits for Marangoni-driven spreading on thick layers. Therefore, Marangoni stresses, induced by surface tension gradients between the spreading surfactant and the underlying gel layer, are identified to be the main driving force behind these phenomena, whereas gravitational forces were also found to play an important role. A mechanism that involves the "unzipping" of the gel in a manner perpendicular to the direction of the largest surface tension gradient is proposed. This mechanism highlights the important role of the width of the arms in the process; it is demonstrated that a cracking pattern is formed only within the experimental conditions that allow S/?w to be greater than G', where S is the spreading coefficient, ?w is the change in the width of the crack, and G' is the storage modulus of the substrate. PMID:22512657

Spandagos, Constantinos; Goudoulas, Thomas B; Luckham, Paul F; Matar, Omar K

2012-04-26

290

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

291

Small Field: dosimetry in electron disequilibrium region  

NASA Astrophysics Data System (ADS)

Small fields are more commonly used for radiation therapy because of the development of IMRT, stereotactic radiosurgery, and other special equipments such as Cyberknife and Tomotherapy. The dosimetry in the sub-centimeter field can result in substantial uncertainties because of the presence of electron disequilibrium due to the large dose gradients in the field. It is further complicated by the introduction of various radiation detectors, which usually perturb the conditions of disequilibrium. Hence additional corrections are required to maintain the dosimetric accuracy previously achieved for standard radiation dosimetry. A review of small field dosimetry provides some insights into the methods to characterize the detector convolution kernel and other methods to characterize detector perturbation effect.

Zhu, Timothy C.

2010-11-01

292

Occupational radiation protection dosimetry in Nigeria.  

PubMed

The general features of occupational radiation protection dosimetry in Nigeria within the period 1990-1999 have been summarised. About 640 personnel, representing about 25% of the estimated number of radiation workers in Nigeria, were monitored by the TL dosimetry technique during the period, with the majority being the personnel of the teaching hospitals across the country. Most private establishments, especially the X ray diagnostic centres, operate without dosimetry coverage or supervision by a regulatory authority. The weighted mean of the annual effective dose ranged between 0 and 28.97 mSv with the upper limit of collective effective dose being 18.47 man.Sv per year. The individual risk estimate due to this is about 1.5 x 10(-3) per year and this was among the medical personnel. The value could be more if all radiation workers in the country were monitored. PMID:11468807

Farai, I P; Obed, R I

2001-01-01

293

Solar cell window fitting  

SciTech Connect

A window fitting is described comprising: (a) a frame structure dimensioned to fit in a window opening of a building; (b) a pair of transparent panes supported by the frame structure in substantially parallel disposition with respect to each other to define a space there between; a window blind secured to the frame structure so as to be disposed in the space between the transparent panes, the window blind comprising a plurality of slats mounted in generally parallel disposition with respect to each other for substantially simultaneous rotation of the slats so that each of the slats moves through an angular range from a CLOSED configuration in which the slats overlap each other so as to block passage of sunlight through the window opening to a fully OPEN configuration in which a maximum amount of sunlight can pass through the window opening; (d) a plurality of solar-chargeable batteries for storing electrical energy, the batteries being mounted on the slats; (e) a plurality of solar cells mounted on the batteries so as to be exposed to sunlight incident upon the slats, the batteries thereby being sandwiched between the solar cells and the slats, the solar cells being electrically connected to the batteries so that the batteries can be electrically charged by the solar cells; and means for removing from the batteries the stored electrical energy that has been generated by the solar cells.

Gillard, C.W.

1993-06-22

294

Return to fitness.  

PubMed

The cornerstone of personal health is prevention. The concept of exercise as medicine is a lesson I have preached throughout my career, both with my patients in my private practice as well as through my years working with athletes at all levels including the Philadelphia 76ers basketball team and the Pennsylvania Ballet. It is also a message I relayed as a Special Advisor to the President's Council on Physical Fitness and Sports (PCPFS) during the first Bush administration, working closely with my old friend-and fitness advocate and visionary himself-Governor Arnold Schwarzenegger, who served as Chairman to the PCPFS. Arnold's impact on our nation's health was an extremely positive one that was felt in communities from coast-to-coast. Exercise, activity, and prevention were key components of his prescription for change and improved health for our country. He has also always personally inspired me to see my role as a physician and "healer" in a much broader context. PMID:20048467

Dinubile, Nicholas A

2008-12-01

295

A position-sensitive superheated emulsion chamber for three-dimensional photon dosimetry.  

PubMed

A position-sensitive detector chamber is introduced for the three-dimensional (3D) dosimetry of photon-emitting brachytherapy sources. The detector is based on an extremely fine suspension of monochloropentafluoroethane droplets emulsified in a gel. The droplets are highly superheated at room temperature and their evaporation can be triggered by photon interactions, leading to the formation of microscopic bubbles. Thus, when photon-emitting brachytherapy sources are inserted into the detector, bubble distributions form around them, enabling visualization of the radiation field. The tissue-equivalent emulsifier gel is highly viscous and keeps the bubbles immobilized at the location of their formation. Bubbles can then be imaged by nuclear magnetic resonance or optical scanning techniques. After the imaging, the detector can be pressurized in order to recondense the bubbles to the liquid phase. In a few minutes, the device is annealed and ready to be used again for repeated measurements improving the counting statistics. The photon sensitivity of the monochloropentafluoroethane droplets was determined with highly filtered, quasi-monochromatic x-ray beams and radionuclide gamma sources. The air-kerma response presents a broad maximum at low energies, due to the relatively high effective atomic number of the halocarbon molecule. A prototype chamber was built and successfully tested: bubble distributions deriving from the insertion of a 125I source were imaged by means of a slice-selective 3D gradient-echo technique. These experiments confirm the potential and viability of this new approach to 3D photon dosimetry. PMID:9623646

d'Errico, F; Nath, R; Lamba, M; Holland, S K

1998-05-01

296

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

297

A parameterization method and application in breast tomosynthesis dosimetry.  

PubMed

Purpose: To present a parameterization method based on singular value decomposition (SVD), and to provide analytical parameterization of the mean glandular dose (MGD) conversion factors from eight references for evaluating breast tomosynthesis dose in the Mammography Quality Standards Act (MQSA) protocol and in the UK, European, and IAEA dosimetry protocols.Methods: MGD conversion factor is usually listed in lookup tables for the factors such as beam quality, breast thickness, breast glandularity, and projection angle. The authors analyzed multiple sets of MGD conversion factors from the Hologic Selenia Dimensions quality control manual and seven previous papers. Each data set was parameterized using a one- to three-dimensional polynomial function of 2-16 terms. Variable substitution was used to improve accuracy. A least-squares fit was conducted using the SVD.Results: The differences between the originally tabulated MGD conversion factors and the results computed using the parameterization algorithms were (a) 0.08%-0.18% on average and 1.31% maximum for the Selenia Dimensions quality control manual, (b) 0.09%-0.66% on average and 2.97% maximum for the published data by Dance et al. [Phys. Med. Biol. 35, 1211-1219 (1990); ibid. 45, 3225-3240 (2000); ibid. 54, 4361-4372 (2009); ibid. 56, 453-471 (2011)], (c) 0.74%-0.99% on average and 3.94% maximum for the published data by Sechopoulos et al. [Med. Phys. 34, 221-232 (2007); J. Appl. Clin. Med. Phys. 9, 161-171 (2008)], and (d) 0.66%-1.33% on average and 2.72% maximum for the published data by Feng and Sechopoulos [Radiology 263, 35-42 (2012)], excluding one sample in (d) that does not follow the trends in the published data table.Conclusions: A flexible parameterization method is presented in this paper, and was applied to breast tomosynthesis dosimetry. The resultant data offer easy and accurate computations of MGD conversion factors for evaluating mean glandular breast dose in the MQSA protocol and in the UK, European, and IAEA dosimetry protocols. Microsoft Excel™ spreadsheets are provided for the convenience of readers. PMID:24007174

Li, Xinhua; Zhang, Da; Liu, Bob

2013-09-01

298

Third conference on radiation protection and dosimetry  

SciTech Connect

This conference has been designed with the objectives of promoting communication among applied, research, regulatory, and standards personnel involved in radiation protection and providing them with sufficient information to evaluate their programs. To partly fulfill these objectives, a technical program consisting of more than 75 invited and contributed oral presentations encompassing all aspects of radiation protection has been prepared. General topics include external dosimetry, internal dosimetry, instruments, regulations and standards, accreditation and test programs, research advances, and applied program experience. This publication provides a summary of the technical program and a collection of abstracts of the oral presentations.

Not Available

1991-01-01

299

Practical neutron dosimetry at high energies  

SciTech Connect

Dosimetry at high energy particle accelerators is discussed with emphasis on physical measurements which define the radiation environment and provide an immutable basis for the derivation of any quantities subsequently required for risk evaluation. Results of inter-laboratory dosimetric comparisons are reviewed and it is concluded that a well-supported systematic program is needed which would make possible detailed evaluations and inter-comparisons of instruments and techniques in well characterized high energy radiation fields. High-energy dosimetry is so coupled with radiation transport that it is clear their study should proceed concurrently.

McCaslin, J.B.; Thomas, R.H.

1980-10-01

300

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

301

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

302

Spinodal decomposition in gels  

Microsoft Academic Search

We construct a Ginzburg-Landau model for gels undergoing spinodal decomposition in terms of the polymer volume fraction and a deformation tensor. We numerically demonstrate that the domain growth is extremely slowed down in late stages, where the surface tension force, which drives the coarsening in usual fluids, is cancelled by the elastic force. The patterns closely resemble those observed in

A. Onuki; S. Puri

1999-01-01

303

[Pharmaceutical hydrophilic gels].  

PubMed

From the pharmacopoeial standpoint, gels, together with ointments, creams, pastes, cataplasmata, and medicated plasters, rank among the group of topical semisolid preparations applied to the skin. They are bicoherent systems composed of the internal phase made of a polymer producing a coherent three-dimensional net-like structure, which fixes the liquid vehicle as the external phase. Intermolecular forces bind the molecules of the solvent to a polymeric net, thus decreasing the mobility of these molecules and producing a structured system with increased viscosity. The physical and chemical bonds binding the particles of the internal phase provide a relatively stable structure, which can originate by swelling of solid polymers, or by decreasing the solubility of the polymer in a solution. An important group of gels used in pharmacy are hydrophylic gels, or hydrogels, usually made of hydrophyilc polymers, which under certain conditions and polymer concentration, jellify. Attention of pharmaceutical research now concentrates primarily on hydrophilic gels, as this dosage form seems to be prospective for the development of modern drugs based on systems with prolonged and controlled release of active ingredients. PMID:15895965

Chalupová, Z; Masteiková, R; Savickas, A

2005-03-01

304

Dose verification of single shot gamma knife applications using VIPAR polymer gel and MRI  

NASA Astrophysics Data System (ADS)

This work describes an experimental procedure with potential to assess the overall accuracy associated with gamma knife clinical applications, from patient imaging and dosimetry planning to patient positioning and dose delivery using the automated positioning system of a Leksell Gamma Knife model C. The VIPAR polymer gel-MRI dosimetry method is employed due to its inherent three-dimensional feature and linear dose response over the range of gamma knife applications. Different polymer gel vials were irradiated with single shot gamma knife treatment plans using each of the four available collimator helmets to deliver a maximum dose of 30 Gy. Percentage relative dose results are presented not only in the form of one-dimensional profiles but also planar isocontours and isosurfaces in three dimensions. Experimental results are compared with corresponding Gammaplan treatment planning system calculations as well as acceptance test radiochromic film measurements. A good agreement, within the experimental uncertainty, is observed between measured and expected dose distributions. This experimental uncertainty is of the order of one imaging pixel in the MRI gel readout session (<1 mm) and allows for the verification of single shot gamma knife applications in terms of acceptance specifications for precision in beam alignment and accuracy. Averaging net R2 results in the dose plateau of the 4 mm and 18 mm collimator irradiated gel vials, which were MR scanned in the same session, provides a crude estimate of the 4 mm output factor which agrees within errors with the default value of 0.870.

Karaiskos, P.; Petrokokkinos, L.; Tatsis, E.; Angelopoulos, A.; Baras, P.; Kozicki, M.; Papagiannis, P.; Rosiak, J. M.; Sakelliou, L.; Sandilos, P.; Vlachos, L.

2005-03-01

305

Dosimetry Control: Technic and methods. Proceedings of the international workshop 'Actual problems of dosimetry'.  

National Technical Information Service (NTIS)

There is a number of unsolved problems of both dosimetric and radiometric control, questions of the biological dosimetry, reconstruction of dozes of irradiation of the population at radiation incidents, which require coordination of efforts of scientists ...

A. A. Milyutin A. M. Lyutsko E. F. Konoplya V. A. Chudakov V. B. Nesterenko

1997-01-01

306

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

2012-11-08

307

Beyond model fitting SEDs  

NASA Astrophysics Data System (ADS)

Extracting star formation histories from spectra is a process plagued by numerous degeneracies among the parameters that contribute to the definition of the underlying stellar populations. Traditional approaches to overcome such degeneracies involve carefully defined line strength or spectral fitting procedures. However, all these methods rely on comparisons with population synthesis models. This paper illustrates alternative approaches based on the statistical properties of the information that can be extracted from uniformly selected samples of observed spectra, without any prior reference to modelling. Such methods are more useful with large datasets, such as surveys, where the information from thousands of spectra can be exploited to classify galaxies. An illustrative example is presented on the classification of early-type galaxies with optical spectra from the Sloan Digital Sky Survey.

Ferreras, Ignacio

2012-08-01

308

Functional Fitness of Older Adults  

Microsoft Academic Search

The purpose of this study is to compare differences in the functional fitness of a group of older adults to determine if they are aging successfully, to analyze the differences in functional fitness between females and males, and to determine differences in four categories by sex. Participants were placed into four categories based on senior fitness test (SFT) scores. More

Linda D. Wilkin; Bryan L. Haddock

2011-01-01

309

Personality Correlates of Physical Fitness  

Microsoft Academic Search

In this article, I examine the relation between personality and physical fitness. One group (N = 97) of male adults completed the Hogan Personality Inventory and five nationally recognized physical fitness batteries. A second group (N = 35) completed the Minnesota Multiphasic Personality Inventory and a set of medical and physical performance assessments. Results indicate that physical fitness must be

Joyce Hogan

1989-01-01

310

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

311

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

312

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

313

System for Gel Electrophoretic Immunoassay.  

National Technical Information Service (NTIS)

A micro-analytical platform for performing electrophoresis-based immunoassays was developed by integrating photopolymerized cross-linked polyacrylamide gels within a microfluidic device. The microfluidic immunoassays are performed by gel electrophoretic s...

A. E. Herr A. K. Singh D. J. Throckmorton

2005-01-01

314

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

315

Use of Superheated Liquids in Neutron Dosimetry.  

National Technical Information Service (NTIS)

Ways of increasing (up to several hours) the time of liquid existence in a superheated state are investigated and a possiblity of applying superheated liquids for neutron dosimetry is indicated. It is experimentally proved that a total-wave neutron detect...

N. S. Smirnova M. M. Belyukov Y. N. Martynyuk S. V. Malinovskij A. K. Salomatov

1987-01-01

316

HIFX Electron-Beam Dosimetry System.  

National Technical Information Service (NTIS)

The U.S. Army Research Laboratory has developed a dosimetry system for use with the High-intensity Flash X-ray (HIFX) facility and the custom low-noise test fixture used to perform radiation tests of integrated circuits in vacuum. When the flash x-ray is ...

G. K. Ovrebo S. M. Blomquist S. R. Murrill

1994-01-01

317

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

318

Numerical dosimetry dedicated to children RF exposure  

Microsoft Academic Search

Children are more and more using wireless communication systems. This growth has strengthened public concern and has highlighted the need to assess the radio frequency (RF) exposure of children. In dosimetry, taking advantage of the improvement of High Performance Calculation systems, great efforts have been carried out to improve the numerical tools and human models used to assess the Specific

Joe Wiart; Abdelhamid Hadjem; Nadège Varsier; Emmanuelle Conil

319

Neutron dosimetry using an electret albedo dosimeter  

Microsoft Academic Search

The method of albedo dosimetry can provide a measure of individual dose in stray neutron fields at nuclear power plants. Calculated and measured neutron sensitivities of a simple albedo dosimeter based on the utilization of the (n, ?) reaction on boron within the sensitive chamber volume of an electret ionization chamber are presented. It is noted that, for practical use

H. Seifert; B. Dorschel; J. Pawelke

1991-01-01

320

Recent Progress in Californium-252 Dosimetry.  

National Technical Information Service (NTIS)

Studies are being conducted on increasing the accuracy of dose determinations in irradiated animals with small implanted tumors. Three experimental methods of in-phantom dosimetry are being employed in this work since any one method thus far has not led t...

L. H. Lanzl M. Rozenfeld D. Bednarek R. Oswald F. Moser

1976-01-01

321

Computational Techniques of Electromagnetic Dosimetry for Humans  

NASA Astrophysics Data System (ADS)

There has been increasing public concern about the adverse health effects of human exposure to electromagnetic fields. This paper reviews the rationale of international safety guidelines for human protection against electromagnetic fields. Then, this paper also presents computational techniques to conduct dosimetry in anatomically-based human body models. Computational examples and remaining problems are also described briefly.

Hirata, Akimasa; Fujiwara, Osamu

322

Development of A-bomb survivor dosimetry  

Microsoft Academic Search

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

Kerr

1995-01-01

323

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

324

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...

325

Borate-gum gel breakers  

Microsoft Academic Search

This is a delayed action gel breaker for borate-gum gels. Water-base fracturing fluid is widely used in hydraulic fracturing operations. Borate ions and certain natural gums having cis di-diol groups or adjcent cis hydroxyl units form a gel in water to produce a satisfactory fracturing fluid. The gel must retain its high viscosity and particle suspending qualities from 1 to

R. E. Wyant; T. K. Perkins; T. F. Moore

1964-01-01

326

Phase Transitions in Ionic Gels  

Microsoft Academic Search

The polymer network of a gel, under certain conditions, undergoes a discrete transition in equilibrium volume with changes in solvent composition or temperature. This Letter demonstrates that ionization of the gel network plays an essential role in the phase transition. The volume collapse is also observed when the pH within the gel is varied.

Toyoichi Tanaka; David Fillmore; Shao-Tang Sun; Izumi Nishio; Gerald Swislow; Arati Shah

1980-01-01

327

TOPICAL REVIEW Dosimetry for ion beam radiotherapy  

NASA Astrophysics Data System (ADS)

Recently, ion beam radiotherapy (including protons as well as heavier ions) gained considerable interest. Although ion beam radiotherapy requires dose prescription in terms of iso-effective dose (referring to an iso-effective photon dose), absorbed dose is still required as an operative quantity to control beam delivery, to characterize the beam dosimetrically and to verify dose delivery. This paper reviews current methods and standards to determine absorbed dose to water in ion beam radiotherapy, including (i) the detectors used to measure absorbed dose, (ii) dosimetry under reference conditions and (iii) dosimetry under non-reference conditions. Due to the LET dependence of the response of films and solid-state detectors, dosimetric measurements are mostly based on ion chambers. While a primary standard for ion beam radiotherapy still remains to be established, ion chamber dosimetry under reference conditions is based on similar protocols as for photons and electrons although the involved uncertainty is larger than for photon beams. For non-reference conditions, dose measurements in tissue-equivalent materials may also be necessary. Regarding the atomic numbers of the composites of tissue-equivalent phantoms, special requirements have to be fulfilled for ion beams. Methods for calibrating the beam monitor depend on whether passive or active beam delivery techniques are used. QA measurements are comparable to conventional radiotherapy; however, dose verification is usually single field rather than treatment plan based. Dose verification for active beam delivery techniques requires the use of multi-channel dosimetry systems to check the compliance of measured and calculated dose for a representative sample of measurement points. Although methods for ion beam dosimetry have been established, there is still room for developments. This includes improvement of the dosimetric accuracy as well as development of more efficient measurement techniques.

Karger, Christian P.; Jäkel, Oliver; Palmans, Hugo; Kanai, Tatsuaki

2010-11-01

328

The effects of small field dosimetry on the biological models used in evaluating IMRT dose distributions  

NASA Astrophysics Data System (ADS)

The primary goal in radiation oncology is to deliver lethal radiation doses to tumors, while minimizing dose to normal tissue. IMRT has the capability to increase the dose to the targets and decrease the dose to normal tissue, increasing local control, decrease toxicity and allow for effective dose escalation. This advanced technology does present complex dose distributions that are not easily verified. Furthermore, the dose inhomogeneity caused by non-uniform dose distributions seen in IMRT treatments has caused the development of biological models attempting to characterize the dose-volume effect in the response of organized tissues to radiation. Dosimetry of small fields can be quite challenging when measuring dose distributions for high-energy X-ray beams used in IMRT. The proper modeling of these small field distributions is essential in reproducing accurate dose for IMRT. This evaluation was conducted to quantify the effects of small field dosimetry on IMRT plan dose distributions and the effects on four biological model parameters. The four biological models evaluated were: (1) the generalized Equivalent Uniform Dose (gEUD), (2) the Tumor Control Probability (TCP), (3) the Normal Tissue Complication Probability (NTCP) and (4) the Probability of uncomplicated Tumor Control (P+). These models are used to estimate local control, survival, complications and uncomplicated tumor control. This investigation compares three distinct small field dose algorithms. Dose algorithms were created using film, small ion chamber, and a combination of ion chamber measurements and small field fitting parameters. Due to the nature of uncertainties in small field dosimetry and the dependence of biological models on dose volume information, this examination quantifies the effects of small field dosimetry techniques on radiobiological models and recommends pathways to reduce the errors in using these models to evaluate IMRT dose distributions. This study demonstrates the importance of valid physical dose modeling prior to the use of biological modeling. The success of using biological function data, such as hypoxia, in clinical IMRT planning will greatly benefit from the results of this study.

Cardarelli, Gene A.

329

Molecular Evolution under Fitness Fluctuations  

NASA Astrophysics Data System (ADS)

Molecular evolution is a stochastic process governed by fitness, mutations, and reproductive fluctuations in a population. Here, we study evolution where fitness itself is stochastic, with random switches in the direction of selection at individual genomic loci. As the correlation time of these fluctuations becomes larger than the diffusion time of mutations within the population, fitness changes from an annealed to a quenched random variable. We show that the rate of evolution has its maximum in the crossover regime, where both time scales are comparable. Adaptive evolution emerges in the quenched fitness regime (evidence for such fitness fluctuations has recently been found in genomic data). The joint statistical theory of reproductive and fitness fluctuations establishes a conceptual connection between evolutionary genetics and statistical physics of disordered systems.

Mustonen, Ville; Lässig, Michael

2008-03-01

330

Got Fitness? Addressing Student Fitness Needs within Secondary Physical Education  

ERIC Educational Resources Information Center

|Feeling trapped within your daily teaching routine? Are the same curricular activities getting you down, or worse yet ... your students? Perhaps you and your students are craving an injection of new and fun fitness activities designed for the secondary level. The development of health-related fitness has long been associated with primary…

Banks, Aaron; Reimann, Bonnie

2007-01-01

331

Factors influencing alginate gel biocompatibility.  

PubMed

Alginate remains the most popular polymer used for cell encapsulation, yet its biocompatibility is inconsistent. Two commercially available alginates were compared, one with 71% guluronate (HiG), and the other with 44% (IntG). Both alginates were purified, and their purities were verified. After 2 days in the peritoneal cavity of C57BL/6J mice, barium (Ba)-gel and calcium (Ca)-gel beads of IntG alginate were clean, while host cells were adhered to beads of HiG alginate. IntG gel beads, however, showed fragmentation in vivo while HiG gel beads stayed firm. The physicochemical properties of the sodium alginates and their gels were thoroughly characterized. The intrinsic viscosity of IntG alginate was 2.5-fold higher than that of HiG alginate, suggesting a greater molecular mass. X-ray photoelectron spectroscopy indicated that both alginates were similar in elemental composition, including low levels of counterions in all gels. The wettabilities of the alginates and gels were also identical, as measured by contact angles of water on dry films. Ba-gel beads of HiG alginate resisted swelling and degradation when immersed in water, much more than the other gel beads. These results suggest that the main factors contributing to the biocompatibility of gels of purified alginate are the mannuronate/guluronate content and/or intrinsic viscosity. PMID:21523903

Tam, Susan K; Dusseault, Julie; Bilodeau, Stéphanie; Langlois, Geneviève; Hallé, Jean-Pierre; Yahia, L'Hocine

2011-04-26

332

Dosimetry requirements derived from the sterilization standards  

NASA Astrophysics Data System (ADS)

The main standards for radiation sterilization, ISO 11137 and EN 552, rest the documentation for the properly executed sterilization process on dosimetry. Both standards describe general requirements to the dosimetry system: The dose measurements must be traceable to national standards, the uncertainty of the dose measurement and the environmental influences must be known. This paper discusses how to obtain and maintain traceability and how to document measurement uncertainty. The implication of these requirements in the process control of radiation sterilization are further discussed. Known and documented uncertainty limits of the dose measurements can be used to specify process control limits. This is also useful, for example, when dose setting experiments are carried out according to the methods described in ISO 11137, where product samples shall be irradiated within narrow limits.

Miller, Arne

1998-06-01

333

Holographic interferometry in radiation dosimetry, microprocessor assisted  

NASA Astrophysics Data System (ADS)

In this paper the applications of holographic interferometry to ionizing radiation dosimetry are presented. The determination of the accurate value of dose delivered by an ionizing radiation source (released energy per mass unit) is a complex problem which imposes different solutions depending on the experimental parameters and it is solved with a double exposure holographic interferometric method associated with an optoelectronic interface and Z-80 microprocessor. The method can determine the integral absorbed dose as well as the tridimensional distribution of dose in a given volume. The paper presents some results obtained in radiation dosimetry. Different transparent liquids were used as ionizing radiation transducers. Integral dose and spatial dose-distribution were recorded for equivalent tissue liquids and blood plasma. Boundary phenomena, during a irradiation of successive layers of liquids having different atomic numbers, were investigated.

Nicolau, Silvia; Sporea, Dan G.; Niculescu, V. I.

1999-08-01

334

Argentine intercomparison programme for personal dosimetry.  

PubMed

An Intercomparison Programme is being carried out in Argentina for individual monitoring services. The programme was designed to test, on a voluntary basis, the performance of the laboratories that provide individual monitoring services for X and gamma radiation fields in the range from low-level dose up to 100 mSv. Irradiations were performed in full accordance with ISO 4037-3 recommendations by the Regional Reference Centre for Dosimetry (CRRD), belonging to Atomic Energy Commission (CNEA) and the Physical Dosimetry Laboratory of the Nuclear Regulatory Authority (ARN). At the same time, several items have been asked to each participant pertaining to the action range, the detectors' characteristics, the laboratory procedures, the existence of an algorithm and its use for the dosemeter evaluation. In this study the evolution of the laboratories' performance throughout the programme, based on ISO 14146 acceptance criteria, is shown. PMID:17848382

Gregori, B N; Papadópulos, S B; Saraví, M; Kunst, J J

2007-09-11

335

An investigation of false positive dosimetry results  

SciTech Connect

The Waste Isolation Pilot Plant (WIPP) is a facility designed for the demonstration of the safe disposal of transuranic waste. Currently, the radiation source term is confined to sealed calibration and check sources since WIPP has not received waste for disposal. For several years the WIPP Dosimetry Group has operated a Harshaw Model 8800C reader to analyze Harshaw 8801-7776 thermoluminescent cards (3 TLD-700 and 1 TLD-600) with 8805 holder. The frequency of false positive results for quarterly dosimeter exchanges is higher than desired by the Dosimetry Group management. Initial observations suggested that exposure to intense ambient sunlight may be responsible for the majority of the false positive readings for element 3. A study was designed to investigate the possibility of light leaking through the holder and inducing a signal in element 3. This paper discusses the methods and results obtained, with special emphasis placed on recommendations to reduce the frequency of light-induced false positive readings.

Lewandowski, M.A.; Davis, S.A.; Goff, T.E.; Wu, C.F.

1996-12-31

336

Techniques for radiation measurements: microdosimetry and dosimetry.  

PubMed

Experimental microdosimetry is concerned with the determination of radiation quality and how this can be specified in terms of the distribution of energy deposition arising from the interaction of a radiation field with a particular target site. This paper discusses various techniques that have been developed to measure radiation energy deposition over the three orders of magnitude of site-size; nanometer, micrometer and millimetre, which radiation biology suggests is required to fully account for radiation quality. Inevitably, much of the discussion will concern the use of tissue-equivalent proportional counters and variants of this device, but other technologies that have been studied, or are under development, for their potential in experimental microdosimetry are also covered. Through an examination of some of the quantities used in radiation metrology and dosimetry the natural link with microdosimetric techniques will be shown and the particular benefits of using microdosimetric methods for dosimetry illustrated. PMID:17223638

Waker, A J

2007-01-12

337

Aspects of retrospective ESR dosimetry (invited paper).  

PubMed

A review is given on the major technological and methodological aspects of retrospective ESR dosimetry with tooth enamel. Topics include the collection and preparation of samples, the evaluation, treatment and interpretation of the ESR signals, and the procedure of dose reconstruction. Two pathways are described to differentiate between doses from different internal and external sources. They are based on dose comparisons as evaluated from different tooth issues or from dose vs age dependencies obtained by ESR dosimetry from populations with different exposure conditions. The concepts given are illustrated by recently achieved ESR doses that were reconstructed from teeth of radiation workers and members of the public of the Southern Urals region, Russia. PMID:9022187

Romanyukha, A A; Regulla, D F

338

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

339

Beta-particle dosimetry in radiation synovectomy  

Microsoft Academic Search

Beta-particle dosimetry of various radionuclides used in the treatment of rheumatoid arthritis was estimated using Monte Carlo radiation transport simulation coupled with experiments using reactor-produced radionuclides and radiachromic film dosimeters inserted into joint phantoms and the knees of cadavers. Results are presented as absorbed dose factors (cGy-cm2\\/MBq-s) versus depth in a mathematical model of the rheumatoid joint which includes regions

L. S. Johnson; J. C. Yanch; S. Shortkroff; C. L. Barnes; A. I. Spitzere; C. B. Sledge

1995-01-01

340

Exercise Prescription for Physical Fitness.  

ERIC Educational Resources Information Center

Examines current guidelines for physical fitness, noting issues that may influence the updating of the American College of Sports Medicine exercise statement. Differences between exercise prescription for fitness and physical activity for health are discussed, noting the importance of designing individualized programs with appropriate levels of…

Pollock, Michael L.; And Others

1995-01-01

341

The Two Faces of Fitness  

Microsoft Academic Search

Biologists came to see that this limit on the concept of fitness is theoretically unjustified. Fitness is relevant to evolution because of the process of natural selection. Selection has an impact on the traits that determine how likely it is for an organism to survive from the egg stage to adulthood, but it equally has an impact on the traits

Elliott Sober

342

Fantastic Disc Activities for Fitness  

ERIC Educational Resources Information Center

Disc activities are an excellent elementary content area for both skill and fitness enhancement. They may occur through progressive skill and drill practice, small sided-game examples, modifications of traditional disc activities appropriate to large groups, and with adjustments designed to increase activity and fitness levels. For games in this…

Griffin, Michael R.; Johnson, Romona; Thomas, Jessica; Spell, Melissa; Popham, John; Croft, Brent; Umpleby, Albert; Verbel, Eric

2005-01-01

343

Fantastic Disc Activities for Fitness  

ERIC Educational Resources Information Center

|Disc activities are an excellent elementary content area for both skill and fitness enhancement. They may occur through progressive skill and drill practice, small sided-game examples, modifications of traditional disc activities appropriate to large groups, and with adjustments designed to increase activity and fitness levels. For games in this…

Griffin, Michael R.; Johnson, Romona; Thomas, Jessica; Spell, Melissa; Popham, John; Croft, Brent; Umpleby, Albert; Verbel, Eric

2005-01-01

344

Exercise Prescription for Physical Fitness.  

ERIC Educational Resources Information Center

|Examines current guidelines for physical fitness, noting issues that may influence the updating of the American College of Sports Medicine exercise statement. Differences between exercise prescription for fitness and physical activity for health are discussed, noting the importance of designing individualized programs with appropriate levels of…

Pollock, Michael L.; And Others

1995-01-01

345

Properties of Symmetric Fitness Functions  

Microsoft Academic Search

The properties of symmetric fitness functions are investigated. We show that the search spaces obtained from symmetric functions have the zero-correlation structures between fitness and distance. It is also proven that symmetric functions induce a class of the hardest problems in terms of the epistasis variance and its variants. These analyses suggest that the existing quantitative measures cannot discriminate among

Sung-soon Choi; Yung-keun Kwon; Byung-Ro Moon

2007-01-01

346

Motivating Students in Fitness Activities  

ERIC Educational Resources Information Center

|Physical educators have a responsibility to motivate students to develop personal fitness. This is a critical concept as physical education is the only part of the curriculum capable of meeting the health needs of students regarding physical activity. Current physical educators must promote fitness in ways that motivate students to engage in…

Wilkinson, Carol; Hunter, Mike

2008-01-01

347

Physical Fitness in Secondary Education.  

ERIC Educational Resources Information Center

The secondary curriculum provides the student a transitional period between childhood and adulthood. Physical fitness objectives at this level should enhance dynamic health through physical activity for all individuals rather than for elite performers only. Suggestions are offered to help physical educators accomplish fitness goals. (DF)

Franks, B. Don

1984-01-01

348

Pilot Fitness and Airplane Crashes  

Microsoft Academic Search

With the growing conviction that the pilot is an important factor in the increasing number of airplane crashes, it seems that more attention should be paid to fitness in the selection of pilots and to making sure that they are fit for service at all times when they are called upon to render service. It is strange indeed that so

C. E. Ferree; G. Rand

1938-01-01

349

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

350

FITS Liberator: Image processing software  

NASA Astrophysics Data System (ADS)

The ESA/ESO/NASA FITS Liberator makes it possible to process and edit astronomical science data in the FITS format to produce stunning images of the universe. Formerly a plugin for Adobe Photoshop, the current version of FITS Liberator is a stand-alone application and no longer requires Photoshop. This image processing software makes it possible to create color images using raw observations from a range of telescopes; the FITS Liberator continues to support the FITS and PDS formats, preferred by astronomers and planetary scientists respectively, which enables data to be processed from a wide range of telescopes and planetary probes, including ESO's Very Large Telescope, the NASA/ESA Hubble Space Telescope, NASA's Spitzer Space Telescope, ESA's XMM-Newton Telescope and Cassini-Huygens or Mars Reconnaissance Orbiter.

Lindberg Christensen, Lars; Holm Nielsen, Lars; Nielsen, Kaspar K.; Johansen, Teis; Hurt, Robert; de Martin, David

2012-06-01

351

Bayesian Methods for Radiation Detection and Dosimetry  

SciTech Connect

We performed work in three areas: radiation detection, external and internal radiation dosimetry. In radiation detection we developed Bayesian techniques to estimate the net activity of high and low activity radioactive samples. These techniques have the advantage that the remaining uncertainty about the net activity is described by probability densities. Graphs of the densities show the uncertainty in pictorial form. Figure 1 below demonstrates this point. We applied stochastic processes for a method to obtain Bayesian estimates of 222Rn-daughter products from observed counting rates. In external radiation dosimetry we studied and developed Bayesian methods to estimate radiation doses to an individual with radiation induced chromosome aberrations. We analyzed chromosome aberrations after exposure to gammas and neutrons and developed a method for dose-estimation after criticality accidents. The research in internal radiation dosimetry focused on parameter estimation for compartmental models from observed compartmental activities. From the estimated probability densities of the model parameters we were able to derive the densities for compartmental activities for a two compartment catenary model at different times. We also calculated the average activities and their standard deviation for a simple two compartment model.

Peter G. Groer

2002-09-29

352

Sensitivity studies associated with dosimetry experiment interpretation  

SciTech Connect

Document available in abstract form only, full text of document follows: Interpretation of reactor dosimetry experiments with C/E comparison requires precise knowledge of parameters involved in modeling. Some parameters have more weight than others on the calculated values. So, sensitivity studies should be conducted to verify the importance of these parameters. The conclusions of these studies are used to refine the experiment modeling, or to correct uncertainty calculations. The results of these sensitivity studies allow a post-irradiation analysis, which can justify the discarding of some atypical C/M values. Derived uncertainties may be improved by the sensitivity analyses. Beyond classical parameters as geometry or composition, this paper describes some specific sensitivity studies conducted for dosimetry irradiation in reactor, and presents conclusions. These studies are based on dosimeters irradiated in the EOLE reactor facility at Cadarache CEA center. Conclusions drawn from these studies are generic and can be applied to any dosimetry study. Calculations performed for these studies were realized using TRIPOLI-4 Monte Carlo code. (authors)

Bourganel, S.; Soldevila, M. [CEA/DANS/DM2S/SERMA, CEA Saclay, 91191, Gif sur Yvette (France); Ferrer, A.; Gregoire, G.; Destouches, C.; Beretz, D. [CEA/DEN-CAD/DER/SPEX, CEA Cadarache, F13108, Saint Paul lez Durance (France)

2011-07-01

353

In vivo dosimetry in external beam radiotherapy.  

PubMed

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. PMID:23822404

Mijnheer, Ben; Beddar, Sam; Izewska, Joanna; Reft, Chester

2013-07-01

354

DNA Electrophoresis in Agarose Gels: Mobility vs. Length Dependence  

NASA Astrophysics Data System (ADS)

Over the years, many different models have been applied to the migration of DNA fragments during gel electrophoresis. These models have been limited to describing DNA motion over specific size ranges. We propose a frictional and charge based model relating the electrophoretic mobility to length that fits data for DNA fragment lengths from 100 base pairs (bp) to 50 kilobase pairs (kbp). Excellent fits have been obtained from both published sources and experiments we have performed, with agarose gel concentrations of 0.5% to 1.5%. The length range of DNA for which the model works spans the range where a DNA fragment behaves like a semi-rigid rod to best described as a random coil polymer

Beheshti, Afshin; van Winkle, David; Rill, Randolph

2001-03-01

355

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.

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

2013-01-01

356

Inexpensive and safe DNA gel electrophoresis using household materials.  

PubMed

Gel electrophoresis is the single most important molecular biology technique and it is central to life sciences research, but it is often too expensive for the secondary science classroom or homeschoolers. A simple safe low-cost procedure is described here that uses household materials to construct and run DNA gel electrophoresis. Plastic containers are fitted with aluminum foil electrodes and 9-V batteries to run food-grade agar-agar gels using aquarium pH buffers and then stained with gentian violet. This activity was tested in a high school biology classroom with significantly positive responses on postactivity reflective surveys. The electrophoresis activity addresses several Life Science Content Standard C criteria, including aspects of cell biology, genetics, and evolution. It also can be used to teach aspects of motion and force in the physical science classroom. PMID:22615228

Ens, S; Olson, A B; Dudley, C; Ross, N D; Siddiqi, A A; Umoh, K M; Schneegurt, M A

2012-02-15

357

Magnetic resonance imaging of microbubbles in a superheated emulsion chamber for brachytherapy dosimetry.  

PubMed

This paper describes development of magnetic resonance imaging (MRI) techniques for three-dimensional (3D) imaging of a position-sensitive detector for brachytherapy dosimetry. The detector is a 0.5 l chamber containing an emulsion of halocarbon-115 droplets in a tissue-equivalent glycerin-based gel. The halocarbon droplets are highly superheated and expand into vapor microbubbles upon irradiation. Brachytherapy sources can be inserted into the superheated emulsion chamber to create distributions of bubbles. Three-dimensional MRI of the chamber is then performed. A 3D gradient-echo technique was optimized for spatial resolution and contrast between bubbles and gel. Susceptibility gradients at the interfaces between bubbles and gel are exploited to enhance contrast so microscopic bubbles can be imaged using relatively large voxel sizes. Three-dimensional gradient-echo images are obtained with an isotropic resolution of 300 microns over a 77 mm x 77 mm x 9.6 mm field-of-view in an imaging time of 14 min. A post-processing technique was developed to semi-automatically segment the bubbles from the images and to assess dose distributions based on the measured bubble densities. Relative dose distributions are computed from MR images for a 125I brachytherapy source and the results compare favorably to relative radial dose distributions calculated as recommended by Task Group 43 of the American Association of Physicists in Medicine. PMID:9874823

Lamba, M; Holland, S K; Elson, H; d'Errico, F; Nath, R

1998-12-01

358

Electrically controlled polymeric gel actuators  

DOEpatents

Electrically controlled polymeric gel actuators or synthetic muscles 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.

Adolf, Douglas B. (Albuquerque, NM); Shahinpoor, Mohsen (Albuquerque, NM); Segalman, Daniel J. (Albuquerque, NM); Witkowski, Walter R. (Albuquerque, NM)

1993-01-01

359

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

360

Fit-testing for firefighters.  

PubMed

When fit-testing firefighters who may be required to wear an SCBA unit in the positive pressure mode for IDLH or structural firefighting applications, use these guidelines. 1. The firefighter shall be allowed to pick the most acceptable respirator from a sufficient number of respirator models and sizes so the respirator is acceptable to, and correctly fits, the firefighter. 2. Before a firefighter may be required to use the SCBA, he/she must be fit-tested with the same make, model, style, and size of respirator that will be used. If different makes, models, styles, and sizes of facepieces are used, the firefighter must be fit-tested for each. 3. Based on current interpretations and guidance, OSHA requires firefighters to be quantitatively or qualitatively fit-tested while in the negative pressure mode. 4. Quantitative fit-testing of these respirators shall be accomplished by modifying the facepiece to allow sampling inside the facepiece and breathing zone of the user, midway between the nose and mouth. This requirement shall be accomplished by installing a permanent sampling probe onto a surrogate facepiece or by using a sampling adapter designed to temporarily provide a means of sampling air from inside the facepiece. 5. Qualitative fit-testing can be accomplished by converting the user's actual facepiece into a negative pressure respirator with appropriate filters or by using an identical negative pressure air-purifying respirator facepiece with the same sealing surfaces as a surrogate for the SCBA facepiece. 6. If after passing the fit-test the firefighter subsequently determines the fit of the respirator is unacceptable, he/she shall be given a reasonable opportunity to select a different respirator facepiece and be retested. 7. The new standard requires initial and at least annual fit-testing using quantitative or qualitative fit-testing protocols. 8. Additional fit-testing may be required whenever physical changes to the employee occur that may affect respirator fit, such as facial scarring, dental changes, cosmetic surgery, or an obvious change in body weight. PMID:9891408

Brickman, C P

1999-01-01

361

IEC-based hearing aid fitting  

Microsoft Academic Search

We propose a hearing aid fitting method based on an interactive evolutionary computation (IEC). First, we identify the problems with current hearing aid fitting methods and propose an IEC fitting method to improve the fitting process with completely different approach from that of conventional fitting methods. Then, we design an experimental hearing aid system and evaluate the IEC fitting method.

H. Takagi; M. Ohsaki

1999-01-01

362

Breast in vivo dosimetry by EPID.  

PubMed

An electronic portal imaging device (EPID) is an effective detector for in vivo transit dosimetry. In fact, it supplies two-dimensional information, does not require special efforts to be used during patient treatment, and can supply data in real time. In the present paper, a new procedure has been proposed to improve the EPID in vivo dosimetry accuracy by taking into account the patient setup variations. The procedure was applied to the breast tangential irradiation for the reconstruction of the dose at the breast midpoint, Dm. In particular, the patient setup variations were accounted for by comparing EPID images versus digitally reconstructed radiographies. In this manner, EPID transit signals were obtained corresponding to the geometrical projections of the breast midpoint on the EPID for each therapy session. At the end, the ratios R between D(m) and the doses computed by the treatment planning system (TPS) at breast midpoints, D(m,TPS), were determined for 800 therapy sessions of 20 patients. Taking into account the method uncertainty, tolerance levels equal to ± 5% have been determined for the ratio R.The improvement of in vivo dosimetry results obtained (taking into account patient misalignment) has been pointed out comparing the R values obtained with and with-out considering patient setup variations. In particular, when patient misalignments were taken into account, the R values were within ± 5% for 93% of the checks; when patient setup variations were not taken into account, the R values were within ± 5% in 72% of the checks. This last result points out that the transit dosimetry method overestimates the dose discrepancies if patient setup variations are not taken into account for dose reconstruction. In this case, larger tolerance levels have to be adopted as a trade-off between workload and ability to detect errors, with the drawback being that some errors (such as the ones in TPS implementation or in beam calibration) cannot be detected, limiting the in vivo dosimetry efficacy.The paper also reports preliminary results about the possibility of reconstructing a dose profile perpendicular to the beam central axis reaching from the apex to the lung and passing through the middle point of the breast by an algorithm, similar to the one used for dose reconstruction at breast midpoint. In particular, the results have shown an accuracy within ± 3% for the dose profile reconstructed in the breast (excluding the interface regions) and an underestimation of the lung dose. PMID:21081886

Fidanzio, Andrea; Greco, Francesca; Mameli, Alessandra; Azario, Luigi; Balducci, Mario; Gambacorta, Maria Antonietta; Frascino, Vincenzo; Cilla, Savino; Sabatino, Domenico; Piermattei, Angelo

2010-09-02

363

Dosimetric verification of complex radiotherapy with a 3D optically based dosimetry system: Dose painting and target tracking.  

PubMed

Abstract Background. The increasing complexity of radiotherapy (RT) has motivated research into three-dimensional (3D) dosimetry. In this study we investigate the use of 3D dosimetry with polymerizing gels and optical computed tomography (optical CT) as a verification tool for complex RT: dose painting and target tracking. Materials and Methods. For the dose painting studies, two dosimeters were irradiated with a seven-field intensity modulated radiotherapy (IMRT) plan with and without dose prescription based on a hypoxia image dataset of a head and neck patient. In the tracking experiments, two dosimeters were irradiated with a volumetric modulated arc therapy (VMAT) plan with and without clinically measured prostate motion and a third with both motion and target tracking. To assess the performance, 3D gamma analyses were performed between measured and calculated stationary dose distributions. Results. Gamma pass-rates of 95.3% and 97.3% were achieved for the standard and dose-painted IMRT plans. Gamma pass-rates of 91.4% and 54.4% were obtained for the stationary and moving dosimeter, respectively, while tracking increased the pass-rate for the moving dosimeter to 90.4%. Conclusions. This study has shown that the 3D dosimetry system can reproduce and thus verify complex dose distributions, also when influenced by motion. PMID:23957684

Skyt, Peter S; Petersen, Jørgen B B; Yates, Esben S; Poulsen, Per R; Ravkilde, Thomas L; Balling, Peter; Muren, Ludvig P

2013-08-19

364

Difference gel electrophoresis.  

PubMed

DIGE is a protein labelling and separation technique allowing quantitative proteomics of two or more samples by optical fluorescence detection of differentially labelled proteins that are electrophoretically separated on the same gel. DIGE is an alternative to quantitation by MS-based methodologies and can circumvent their analytical limitations in areas such as intact protein analysis, (linear) detection over a wide range of protein abundances and, theoretically, applications where extreme sensitivity is needed. Thus, in quantitative proteomics DIGE is usually complementary to MS-based quantitation and has some distinct advantages. This review describes the basics of DIGE and its unique properties and compares it to MS-based methods in quantitative protein expression analysis. PMID:19003860

Timms, John F; Cramer, Rainer

2008-12-01

365

Electrostatic forces in muscle and cylindrical gel systems  

SciTech Connect

Repulsive pressure has been measured as a function of lattice spacing in gels of tobacco mosaic virus (TMV) and in the filament lattice of vertebrate striated muscle. External pressures up to ten atm have been applied to these lattices by an osmotic stress method. Numerical solutions to the Poisson-Boltzmann equation in hexagonal lattices have been obtained and compared to the TMV and muscle data. The theoretical curves using values for kappa calculated from the ionic strength give a good fit to experimental data from TMV gels, and an approximate fit to that from the muscle lattice, provided that a charge radius for the muscle thick filaments of approx. 16 nm is assumed. Variations in ionic strength, sarcomere length and state of the muscle give results which agree qualitatively with the theory, though a good fit between experiment and theory in the muscle case will clearly require consideration of other types of forces. We conclude that Poisson-Boltzmann theory can provide a good first approximation to the long-range electrostatic forces operating in such biological gel systems.

Millman, B.M.; Nickel, B.G.

1980-10-01

366

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

367

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

PubMed

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). PMID:21719951

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

2011-06-30

368

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

2009-12-17

369

Use of the GATE Monte Carlo package for dosimetry applications  

NASA Astrophysics Data System (ADS)

One of the roles for Monte Carlo (MC) simulation studies is in the area of dosimetry. A number of different codes dedicated to dosimetry applications are available and widely used today, such as MCNP, EGSnrc and PTRAN. However, such codes do not easily facilitate the description of complicated 3D sources or emission tomography systems and associated data flow, which may be useful in different dosimetry application domains. Such problems can be overcome by the use of specific MC codes such as GATE (GEANT4 Application to Tomographic Emission), which is based on Geant4 libraries, providing a scripting interface with a number of advantages for the simulation of SPECT and PET systems. Despite this potential, its major disadvantage is in terms of efficiency involving long execution times for applications such as dosimetry. The strong points and disadvantages of GATE in comparison to other dosimetry specific codes are discussed and illustrated in terms of accuracy, efficiency and flexibility. A number of features, such as the use of voxelised and moving sources, as well as developments such as advanced visualization tools and the development of dose estimation maps allowing GATE to be used for dosimetry applications are presented. In addition, different examples from dosimetry applications with GATE are given. Finally, future directions with respect to the use of GATE for dosimetry applications are outlined.

Visvikis, D.; Bardies, M.; Chiavassa, S.; Danford, C.; Kirov, A.; Lamare, F.; Maigne, L.; Staelens, S.; Taschereau, R.

2006-12-01

370

[Instrumental radiofrequency electromagnetic radiation dosimetry: general principals and modern methodology].  

PubMed

The modern experimental radiofrequency electromagnetic field dosimetry approach has been considered. The main principles of specific absorbed rate measurement are analyzed for electromagnetic field biological effect assessment. The general methodology of specific absorbed rate automated dosimetry system applied to establish the compliance of radiation sources with the safety standard requirements (maximum permissible levels and base restrictions) is described. PMID:22891551

Perov, S Iu; Kudriashov, Iu B; Rubtsova, N B

371

Comparison of uncertainty metrics for calculated dosimetry activities  

SciTech Connect

Various metrics are formulated for the uncertainty of calculated neutron activities for dosimetry reactions. The correlations between the uncertainty metrics are examined. The uncertainty data are presented for the dosimetry reactions and can be used to guide the selection of sensors used in spectrum determinations.

Griffin, P.J.

1996-02-01

372

Hanford External Dosimetry Technical Basis Manual PNL-MA-842  

Microsoft Academic Search

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

Rathbone; Bruce A

2010-01-01

373

Evaluation of commercial silicon diode for electron dosimetry  

Microsoft Academic Search

Ionization chambers have been widely used as the reference detector for measurements of photon and electron beams. However, advances in silicon planar technology have allowed the use of silicon diodes in spectrometry and dosimetry of radiations. The aim of this study is to evaluate the response of a PIN silicon diode for electron dosimetry. The diode selected for this study

H. J. Khoury; H. Schelin; D. Soboll; N. Lunelli; C. Baptista

2007-01-01

374

a Decade of Dosimetry for Magnox Reactor Plants  

Microsoft Academic Search

This paper reviews the reactor dosimetry program that has supported steel pressure vessel integrity assessments for magnox power plants over the last ten years. The dosimetry program has aimed to achieve consistent:. • calculated and measured fast and thermal neutron doses. • data for surveillance specimens and reactor pressure vessels. Throughout the program, the flux measurements on the plants have

T. A. Lewis; D. A. Thornton

2003-01-01

375

Fricke Dosimetry in Low Dose Range for Food Irradiation.  

National Technical Information Service (NTIS)

In order to establish a suitable method of dosimetry in low dose range on food irradiation, the precision limit of the Fricke dosimeter (ferrous sulfate dosimeter) and the effect of water purification on Fricke dosimetry were investigated. At the dose ran...

T. Kume H. Tachibana M. Takehisa

1982-01-01

376

[Comments on the current state of thermoluminescent dosimetry instrumentation].  

PubMed

Due to the essential improvement of evaluation equipment, thermoluminescent dosimetry has found more and more practical use during the last decades. This study describes the measuring technique of TL dosimetry, presents some individual components of modern measuring units and indicates some further amelioration possibilities. PMID:3975941

Oberhofer, M

1985-02-01

377

GENII: The Hanford Environmental Radiation Dosimetry Software System: Volume 1, Conceptual representation  

Microsoft Academic Search

The Hanford Environmental Dosimetry Upgrade Project was undertaken to incorporate the internal dosimetry models recommended by the International Commission on Radiological Protection (ICRP) in updated versions of the environmental pathway analysis models used at Hanford. The resulting second generation of Hanford environmental dosimetry computer codes is compiled in the Hanford Environmental Dosimetry System (Generation II, or GENII). The purpose of

B. A. Napier; R. A. Peloquin; D. L. Strenge; J. V. Ramsdell

1988-01-01

378

Physical Fitness of Women Marines.  

National Technical Information Service (NTIS)

The proposed Jewett physical fitness test battery for WMs was evaluated, found consistent with recommendations made in the literature, and administered to 167 WMs. Intercorrelations of the scores demonstrated that each test event measured a separate facto...

P. J. Rasch J. W. Hamby

1967-01-01

379

Fitting of Lower Extremity Prosthetics.  

National Technical Information Service (NTIS)

The research was to discover the relationships between pressure and temperature distribution in the stump of amputees and to determine whether measurement of these parameters would be helpful in the fitting of lower extremity prostheses. The use of thermo...

D. W. Lewis R. McLaughlin

1973-01-01

380

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

381

EDITORIAL: Special issue on radiation dosimetry Special issue on radiation dosimetry  

Microsoft Academic Search

This special issue of Metrologia on radiation dosimetry is the second in a trilogy on the subject of ionizing radiation measurements, a field that is overseen by Sections I, II and III of the CIPM's Consultative Committee for Ionizing Radiation (CCRI). The work of Section II, on radionuclide metrology, was covered in issue 44(4), published in 2007, and that of

Peter Sharpe

2009-01-01

382

Athletic Shoe Fit and Modifications  

Microsoft Academic Search

\\u000a Whether treating professional athletes or weekend warriors, it is critical to select the right shoes and get the correct fit.\\u000a Some foot-care professionals fit patients themselves, while others refer patients out to stores that decide what is best.\\u000a Either way, patients’ needs are best served by the sports medicine specialist assessing the functional biomechanics of the\\u000a lower extremity, identifying structural

Josh White

383

fpack: FITS Image Compression Program  

NASA Astrophysics Data System (ADS)

fpack is a utility program for optimally compressing images in the FITS data format. The associated funpack program will restore the compressed file back to its original state. These programs may be run from the host operating system command line and are analogous to the gzip and gunzip utility programs, except that they are specifically optimized for FITS format images and offer a wider choice of compression options. fpack uses the tiled image compression convention for storing the compressed images. This convention can in principle support any number of of different compression algorithms; currently GZIP, Rice, Hcompress, and the IRAF pixel list compression algorithms have been implemented. The main advantages of fpack compared to the commonly used technique of externally compressing the whole FITS file with gzip are: 1. It is generally faster and offers better compression than gzip. 2. The FITS header keywords remain uncompressed for fast access. 3. Each HDU of a multi-extension FITS file is compressed separately, so it is not necessary to uncompress the entire file to read a single image in a multi-extension file. 4. Dividing the image into tiles before compression enables faster access to small subsections of the image. 5. The compressed image is itself a valid FITS file and can be manipulated by other general FITS utility software. 6. Lossy compression can be used for much higher compression in cases where it is not necessary to exactly preserve the original image. 7. The CHECKSUM keywords are automatically updated to help verify the integrity of the files. 8. Software that supports the tiled image compression technique can directly read and write the FITS images in their compressed form.

Seaman, Rob; Pence, William; White, Rick

2010-10-01

384

Silicone gel including antimicrobial agent.  

PubMed

Silicone gel sheets containing Ofloxacin (OFLX), that provide a continual drug delivery system from a wound dressing to the wound so as to prevent infection and to promote healing, are described. It was found that silicone gel sheets without added medication did not inhibit microbial growth but that gel sheets containing 0.02% and 0.2% of OFLX had a positive antimicrobial effect against Staphylococcus aureus and Pseudomonas aeruginosa in a dose-dependent fashion in vitro. Further, this antimicrobial efficacy was greatly increased in a silicone gel sheet that contained 0.02% of OFLX and an additional 10% of silicone oil. In animal experiments, a silicone gel sheet containing OFLX prevented microbiol growth and promoted rapid epithelialisation in wounds to which Staphylococcus aureus had been applied, whereas wounds covered only with OpSite all resulted in continued infection. PMID:2107010

Sawada, Y; Suzuki, T; Hatayama, I; Sone, K

1990-01-01

385

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

386

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

387

The effects of a tea tree oil-containing gel on plaque and chronic gingivitis  

Microsoft Academic Search

Background: This clinical study assessed the effects of topically applied tea tree oil (TTO)-containing gel on dental plaque and chronic gingivitis. Methods: This was a double-blind, longitudinal, non-crossover study in 49 medically fit non-smokers (24 males and 25 females) aged 18-60 years with severe chronic gingivitis. Subjects were randomly assigned to three groups and given either TTO-gel (2.5 per cent),

S. Soukoulis; R. Hirsch

2004-01-01

388

Neutron dosimetry for low dose rate Cf-252 AT sources and adherence to recent clinical dosimetry protocol for brachytherapy  

SciTech Connect

In 1995, the American Association of Physicists in Medicine Task Group 43 (AAPM TG-43) published a protocol obsoleting all mixed-field radiation dosimetry for Cf-252. Recommendations for a new brachytherapy dosimetry formalism made by this Task Group favor quantification of source strength in terms of air kerma rather than apparent Curies or other radiation units. Additionally, representation of this dosimetry data in terms of radial dose functions, anisotropy functions, geometric factors, and dose rate constants are in an angular and radial (spherical) coordinate system as recommended, rather than the along-away dosimetry data (Cartesian coordinate system) currently available. This paper presents the initial results of calculated neutron dosimetry in a water phantom for a Cf-252 applicator tube (AT) type medical source soon available from Oak Ridge National Laboratory (ORNL).

Rivard, M.J.; Wierzbicki, J.G.; Van den Heuvel, F. [Wayne State Univ., Detroit, MI (United States). Dept. of Radiation Oncology; Martin, R.C. [Oak Ridge National Lab., TN (United States). Chemical Technology Div.

1997-12-01

389

Bouncing gel balls: Impact of soft gels onto rigid surface  

NASA Astrophysics Data System (ADS)

After being thrown onto a solid substrate, very soft spherical gels bounce repeatedly. Separate rheological measurements suggest that these balls can be treated as nearly elastic. The Hertz contact deformation expected in the static (elastic) limit was observed only at very small impact velocities. For larger velocities, the gel ball deformed into flattened forms like a pancake. We measured the size of the gel balls at the maximal deformation and the contact time as a function of velocities for samples different in the original spherical radius and the Young modulus. The experimental results revealed a number of scaling relations. To interpret these relations, we developed scaling arguments to propose a physical picture.

Tanaka, Y.; Yamazaki, Y.; Okumura, K.

2003-07-01

390

Improving neutron dosimetry using bubble detector technology  

SciTech Connect

Providing accurate neutron dosimetry for a variety of neutron energy spectra is a formidable task for any dosimetry system. Unless something is known about the neutron spectrum prior to processing the dosimeter, the calculated dose may vary greatly from that actually encountered; that is until now. The entrance of bubble detector technology into the field of neutron dosimetry has eliminated the necessity of having an a priori knowledge of the neutron energy spectra. Recently, a new approach in measuring personnel neutron dose equivalent was developed at Oak Ridge National Laboratory. By using bubble detectors in combination with current thermoluminescent dosimeters (TLDs) as a Combination Personnel Neutron Dosimeter (CPND), not only is it possible to provide accurate dose equivalent results, but a simple four-interval neutron energy spectrum is obtained as well. The components of the CPND are a Harshaw albedo TLD and two bubble detectors with theoretical energy thresholds of 100 key and 1500 keV. Presented are (1) a synoptic history surrounding emergence of bubble detector technology, (2) a brief overview of the current theory on mechanisms of interaction, (3) the data and analysis process involved in refining the response functions, (4) performance evaluation of the original CPND and a reevaluation of the same data under the modified method, (5) the procedure used to determine the reference values of component fluence and dose equivalent for field assessment, (6) analysis of the after-modification results, (7) a critique of some currently held assumptions, offering some alternative explanations, and (8) thoughts concerning potential applications and directions for future research.

Buckner, M.A.

1993-02-01

391

Dosimetry challenges for implementing emerging technologies.  

PubMed

During the last 10 years, radiation therapy technologies have gone through major changes, mainly related introduction of sophisticated delivery and imaging techniques to improve the target localization accuracy and dose conformity. While implementation of these emerging technologies such as image-guided SRS/SBRT, IMRT/IMAT, IGRT, 4D motion management, and special delivery technologies showed substantial clinical gains for patient care, many other factors, such as training/quality, efficiency/efficacy, and cost/effectiveness etc. remain to be challenging. This talk will address technical challenges for dosimetry verification of implementing these emerging technologies in radiation therapy. PMID:21617745

Yin, Fang-Fang; Oldham, Mark; Cai, Jing; Wu, Qiuwen

2010-01-01

392

The next decade in external dosimetry  

SciTech Connect

As the radiation protection community moves through the last half of the '80s and into the next decade, we can expect the requirements for external dosimetry to become increasingly more restrictive and demanding. As in other health protection fields, growing regulatory and legal pressures, together with a natural evolution in philosophy, require the health physicist to display an increasing degree of accountability, rigor, and professionalism. The good news is that, for the most part, the technology necessary to solve many of the problems will be available or not far behind. This paper describes anticipated technology. 66 refs., 10 figs.

Griffith, R.V.

1986-10-01

393

An efficient approach to routine TL dosimetry.  

PubMed

A new labour-saving protocol for clinical dosimetric measurements based on the thermoluminescence (TL) of lithium fluoride is presented. The accuracy of dose measurements resulting from the application of this protocol is examined with particular emphasis on the linearity, reproducibility, and fading of TL response. It is shown that the technique described here is capable of yielding an accuracy of +/- 5% at the 95% confidence level for doses in excess of 1cGy. This study establishes that adoption of the protocol can result in significant savings in labour whilst maintaining a level of accuracy that is adequate for clinical dosimetry. PMID:8311914

McGhee, P; Humphreys, S; Dunscombe, P

1993-01-01

394

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.

395

North Carolina Children and Youth Fitness Study.  

ERIC Educational Resources Information Center

Discusses results from the North Carolina Children and Youth Fitness Study as they relate to national fitness norms, addresses questions concerning youth fitness levels at state and national levels, encourages states to organize similar statewide studies, and compares results from North Carolina's fitness testing with Healthy People 2000 fitness

Davis, Kathryn L.; And Others

1994-01-01

396

Fit Effect of Motorcycle Helmet  

NASA Astrophysics Data System (ADS)

Optimized assessment of the adequacy of fit conditions between a motorcycle helmet and head size in relation to prevention of head injury remains unclear and is complicated by wide variations in the size and shape characteristics of helmet and wearer’s heads. A finite element model (LS-DYNA3D) based on realistic geometric features of a motorcycle helmet was established to simulate the standard shock absorption test for evaluating the dynamic response and fit effects of a helmet. The model was used to simulate crown, rear and side sites impacts of the helmet. The peak acceleration and Head Injury Criterion (HIC) were employed to assess the protective performance of the helmet against head injuries. The results show that this helmet model had various dynamic responses at different impact sites due to its geometric shape, but that the impact-absorbing capability did not vary markedly within these sites. The fit conditions between the headform and the helmet dramatically affected the assessment of the impact-absorbing capability of the helmet in the standard shock absorption test. However, for a motorcyclist, the helmet fit would have only minor influence on the protection against head injuries. This observation suggests that a better fitting helmet with stable fixation should provide more protection against head injury.

Chang, Li-Tung; Chang, Chih-Han; Chang, Guan-Liang

397

Fitting Cosmological Data Compilation Model  

NSDL National Science Digital Library

The 1998 discovery of the cosmic acceleration with supernovae was recently awarded the 2011 Nobel Prize in Physics. More observations continue to support this accelerated expansion of the universe (cosmic acceleration). The EJS âFitting Cosmological Data Compilationâ model includes several cosmological surveys for five different observations of the expansion, all of which support a cosmic acceleration. The simulation allows users to compare and fit theoretical models of cosmology with recent supernovae, gamma-ray bursts, the Hubble Parameter, baryon acoustic oscillations, and the 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 âFitting Cosmological Data Compilationâ 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_Data_Compilation.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; Shuler, Zeke; Engelhardt, Larry

2012-08-27

398

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

399

Introduction to Agarose Gel Electrophoresis  

NSDL National Science Digital Library

In this module, developed as part of Cornell's Learning Initiative in Medicine and Bioengineering (CLIMB), students are introduced to the concepts of gel electrophoresis without requiring all the equipment needed to run a full gel electrophoresis experiment. The goal is to have students understand how gels are made for DNA separation and how altering the composition can affect the experimental parameters. This module contains a teacher's guide, classroom activity, and suggestions for extended activities. This lab is a precursor to Cornellâs Institute for Biology Teachers labâs entitled DNA Profiling â Paternity Testing, which is linked within the teacher's guide. CLIMB is part of the NSF GK-12 program.

Bioengineering, Climb: C.

400

Physical fitness in lignite miners.  

PubMed

The purpose of this study was to determine physical fitness level of lignite miners in the Czech Republic. The authors have examined a representative group of 152 active lignite miners by bicycle spiroergometry. The duration of employment in coal mines ranged between 5 and 32 years. The average age was 43.1 +/- 4.7 years. The miners had an average peak oxygen consumption 2.9 +/- 0.5 l.min-1, corresponding to 99.7 +/- 20.4% of the predicted maximal oxygen consumption. Physical fitness of lignite miners was comparable with reference values for healthy men in Czech population. The level of physical fitness did not correlate with the length of exposure to underground work. PMID:7698905

Brhel, P; Homolka, P; Kratochvílová, J; Bärtlová, E

1994-01-01

401

The Soldier Fitness Tracker: Global Delivery of Comprehensive Soldier Fitness  

ERIC Educational Resources Information Center

Carefully implemented technology strategies are vital to the success of large-scale initiatives such as the U.S. Army's Comprehensive Soldier Fitness (CSF) program. Achieving the U.S. Army's vision for CSF required a robust information technology platform that was scaled to millions of users and that leveraged the Internet to enable global reach.…

Fravell, Mike; Nasser, Katherine; Cornum, Rhonda

2011-01-01

402

The Soldier Fitness Tracker: Global Delivery of Comprehensive Soldier Fitness  

ERIC Educational Resources Information Center

|Carefully implemented technology strategies are vital to the success of large-scale initiatives such as the U.S. Army's Comprehensive Soldier Fitness (CSF) program. Achieving the U.S. Army's vision for CSF required a robust information technology platform that was scaled to millions of users and that leveraged the Internet to enable global reach.…

Fravell, Mike; Nasser, Katherine; Cornum, Rhonda

2011-01-01

403

Effect of processor temperature on film dosimetry.  

PubMed

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(max.), 10 × 10 cm(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°C (85-105°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. PMID:21925862

Srivastava, Shiv P; Das, Indra J

2011-09-16

404

Internal dosimetry verification and validation database.  

PubMed

Simulated-data internal dosimetry cases for use in intercomparison exercises or as a software verification and validation tool have been published on the internet (www.lanl.gov/bayesian/software Bayesian software package II). A user may validate their internal dosimetry code or method using this simulated bioassay data. Or, the user may choose to try out the Los Alamos National Laboratory codes ID and UF, which are also supplied. A Poisson-lognormal model of data uncertainty is assumed. A collection of different possible models for each nuclide (e.g. solubility types and particle sizes) are used. For example, for 238Pu, 14 different biokinetic models or types (8 inhalation, 4 wound and 2 ingestion) are assumed. Simulated data are generated for all the assumed biokinetic models, both for incidents, where the time of intake is known, and for non-incidents, where it is not. For the dose calculations, the route of intake, but not the biokinetic model, is considered to be known. The object is to correctly calculate the known true dose from simulated data covering a period of time. A 'correct' result has been defined in two ways: (1) that the credible limits of the calculated dose include the correct dose and (2) that the calculated dose is within a factor of 2 of the correct dose. PMID:18325930

Miller, G; Bertelli, L; Little, T; Guilmette, R A

2008-03-06

405

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

406

Proton therapy dosimetry using positron emission tomography  

PubMed Central

Protons deposit most of their kinetic energy at the end of their path with no energy deposition beyond the range, making proton therapy a valuable option for treating tumors while sparing surrounding tissues. It is imperative to know the location of the dose deposition to ensure the tumor, and not healthy tissue, is being irradiated. To be able to extract this information in a clinical situation, an accurate dosimetry measurement system is required. There are currently two in vivo methods that are being used for proton therapy dosimetry: (1) online or in-beam monitoring and (2) offline monitoring, both using positron emission tomography (PET) systems. The theory behind using PET is that protons experience inelastic collisions with atoms in tissues resulting in nuclear reactions creating positron emitters. By acquiring a PET image following treatment, the location of the positron emitters in the patient, and therefore the path of the proton beam, can be determined. Coupling the information from the PET image with the patient’s anatomy, it is possible to monitor the location of the tumor and the location of the dose deposition. This review summarizes current research investigating both of these methods with promising results and reviews the limitations along with the advantages of each method.

Studenski, Matthew T; Xiao, Ying

2010-01-01

407

Performance evaluation of MRI-based PAGAT polymer gel dosimeter in an inhomogeneous phantom using EGSnrc code on a Co-60 machine.  

PubMed

Relative isodose curves were obtained using PAGAT gel dosimeter on homogeneous and inhomogeneous phantoms. Distance-to-agreement (DTA) was calculated between simulated and measured values for both the homogeneous and inhomogeneous phantoms. All DTAs except one passed the acceptance criterion (+/-5 dose variation for selected isodose levels). Results of this study also showed the ability of the Monte Carlo modeling to provide accurate dosimetry, and revealed that the dose response of PAGAT polymer gel is dependent on the method of fabrication. PMID:18951810

Pourfallah, Tayyeb Allahverdi; Allahverdi, Mahmoud; Alam, Nader Riahi; Ay, Mohammad-Reza; Zahmatkesh, Mohammad-Hasan; Ibbott, Geoffrey S

2008-09-21

408

48 CFR 752.7033 - Physical fitness.  

Code of Federal Regulations, 2010 CFR

...2009-10-01 2009-10-01 false Physical fitness. 752.7033 Section 752...Contract Clauses 752.7033 Physical fitness. For use in all USAID contracts...involving performance overseas. Physical Fitness (JUL 1997) (The...

2009-10-01

409

48 CFR 752.7033 - Physical fitness.  

Code of Federal Regulations, 2010 CFR

...2010-10-01 2010-10-01 false Physical fitness. 752.7033 Section 752...Contract Clauses 752.7033 Physical fitness. For use in all USAID contracts...involving performance overseas. Physical Fitness (JUL 1997) (The...

2010-10-01

410

A Futuristic Alternative: Campus Fitness Programming.  

ERIC Educational Resources Information Center

The components of a prescription physical fitness program include a physical examination, fitness and dietary assessment, consultations to determine the fitness and diet prescriptions, instructional sessions, and periodic reviews of the individual's prescription. (CJ)

Mueller, C. E.; Oatey, Jennifer Sue

1980-01-01

411

10 CFR 26.406 - Fitness monitoring.  

Code of Federal Regulations, 2013 CFR

...2013-01-01 2013-01-01 false Fitness monitoring. 26.406 Section 26...Energy NUCLEAR REGULATORY COMMISSION FITNESS FOR DUTY PROGRAMS FFD Program for Construction § 26.406 Fitness monitoring. (a) The...

2013-01-01

412

10 CFR 26.406 - Fitness monitoring.  

Code of Federal Regulations, 2010 CFR

...2010-01-01 2010-01-01 false Fitness monitoring. 26.406 Section 26...Energy NUCLEAR REGULATORY COMMISSION FITNESS FOR DUTY PROGRAMS FFD Program for Construction § 26.406 Fitness monitoring. (a) The...

2010-01-01

413

a Decade of Dosimetry for Magnox Reactor Plants  

NASA Astrophysics Data System (ADS)

This paper reviews the reactor dosimetry program that has supported steel pressure vessel integrity assessments for magnox power plants over the last ten years. The dosimetry program has aimed to achieve consistent:. • calculated and measured fast and thermal neutron doses. • data for surveillance specimens and reactor pressure vessels. Throughout the program, the flux measurements on the plants have been judged essential for any doses where a high degree of confidence is required. The work to support operation is now largely complete and the dosimetry is being extended to assess radioactive inventories as part of the decommissioning process.

Lewis, T. A.; Thornton, D. A.

2003-06-01

414

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

415

A Modified Polyacrylamide Gel Slicer.  

National Technical Information Service (NTIS)

The polyacrylamide gel slicer described by Goldberger in 1968 contained two critical parts which are no longer commercially available. Design changes are presented which allow for construction of this device at reduced cost, using readily available parts....

G. L. Moore C. D. Purpura

1970-01-01

416

Aqueous Acrylamide Gel Duplicating Material.  

National Technical Information Service (NTIS)

An aqueous acrylamide gel duplicating material was developed by modification of a commercially available acrylamide material. A synthetic calcium silicate was added for purposes of lowering the per cent strain from 35 to 24 per cent. A potassium alignate ...

E. R. Dootz R. G. Craig F. A. Peyton

1967-01-01

417

Mathematical modelling of response of polymer gel dosimeters to brachytherapy radiation  

NASA Astrophysics Data System (ADS)

A dynamic partial differential equation (PDE) model is used to simulate effects of a single Ir192 brachytherapy seed on the amount and composition of polymer formed during polyacrylamide gel (PAG) dosimetry. Simulations are conducted for a point-source brachytherapy seed placed at the center of a 6%T 50% C anoxic PAG phantom. The seed is removed after one minute, but polymerization is simulated up to a final time of 24 hours. Simulation results indicate that changes occur in both the mass of polymer formed per unit dose and in the crosslink density as a function of the radial distance from the brachytherapy seed. For example, at a distance of 5 mm from the seed, 41 mg of polymer form per Gy of radiation absorbed (after 24 hours), whereas at a larger distance of 5 cm from the seed 75 mg of polymer form per Gy. The polymer that forms near the seed is predicted to have a higher level of crosslinking than the polymer that forms further away. These results suggest potential calibration problems that may occur during brachytherapy dosimetry using polymer gels.

Nasr, A. T.; Chain, J. N. M.; Schreiner, L. J.; McAuley, K. B.

2010-11-01

418

Polysaccharide gel with multiple emulsion  

Microsoft Academic Search

The aim of the present work was to investigate the possibility of using a semicrystalline oil phase in W\\/O\\/W to modify the release of encapsulated hydrophilic compounds from polysaccharide gels with embedded multiple emulsions.l-Tryptophan was enclosed within the W1-phase of an W1\\/O\\/W2-emulsion, which itself was homogeneously distributed in a Ca2+-alginate gel with maltodextrin (D.E. 6.5) as a bulking agent. Various

Julia Weiss; Inta Scherze; Gerald Muschiolik

2005-01-01

419

Adjustable-angle pipe fitting  

DOEpatents

This invention pertains to a pipe fitting for joining two pipes at a desired, preselected angle and comprises a curved section of pipe with a generally circular cross-section. One end of the curved pipe is preferably furnished with a bell fitting. The other end is adapted to be inserted into the bell of another pipe fitting. The surface of the pipe is marked with circumferential lines spaced at several-degree intervals, the lines corresponding to the angle of the bend which will result if the pipe is cut along that line. The outer diameter of the pipe is closely controlled to be the same throughout its length as the outer diameter of a straight pipe, so the cut end can be inserted into the bell of another fitting without further treatment, and the radius of curvature of the pipe is larger than a standard street elbow, preferably three to ten times the diameter of the pipe. Thus, a cut approximately perpendicular to the axial centerline can be made at any point along the length of the pipe to form an elbow of any desired angle.

Kronberg, J.W.

1991-01-01

420

Adjustable-angle pipe fitting  

DOEpatents

This invention pertains to a pipe fitting for joining two pipes at a desired, preselected angle and comprises a curved section of pipe with a generally circular cross-section. One end of the curved pipe is preferably furnished with a bell fitting. The other end is adapted to be inserted into the bell of another pipe fitting. The surface of the pipe is marked with circumferential lines spaced at several-degree intervals, the lines corresponding to the angle of the bend which will result if the pipe is cut along that line. The outer diameter of the pipe is closely controlled to be the same throughout its length as the outer diameter of a straight pipe, so the cut end can be inserted into the bell of another fitting without further treatment, and the radius of curvature of the pipe is larger than a standard street elbow, preferably three to ten times the diameter of the pipe. Thus, a cut approximately perpendicular to the axial centerline can be made at any point along the length of the pipe to form an elbow of any desired angle.

Kronberg, J.W.

1991-12-31

421

Aromatherapy for sports and fitness  

Microsoft Academic Search

The article describes the use of aromatherapy for achieving excellence in sports and fitness. Aromatherapy is the science of holistic approach for taking care of the body and mind using pleasant smelling of botanical oils. It has been extensively studied and found to be one of the fastest growing areas of alternative medicine. There have been numerous studies showing different

Preeti Sharma; Tilak R Meena

2010-01-01

422

Keeping Fit and Staying Alive.  

ERIC Educational Resources Information Center

Provides (1) background information on the many ways birds keep fit and are adapted to survive; (2) student activities on this topic; and (3) ready-to-copy materials (a game, worksheet, and coloring pages). Each activity includes an objective, recommended age level(s), subject area(s), list of materials needed, and procedures. (JN)

NatureScope, 1985

1985-01-01

423

Fitting and using growth curves  

Microsoft Academic Search

A technique is presented for fitting and analyzing growth patterns using Gompertz, power, and exponential curves. Data collection involves measuring growth rate as a function of size. This is useful because growth rates at many different sizes can be measured at the same time, which removes the effect of environmental change from the observed growth pattern. Using size instead of

Karl W. Kaufmann

1981-01-01

424

The Health and Fitness Challenge.  

ERIC Educational Resources Information Center

"Health and Fitness Challenge" program was implemented using the "social marketing model" to raise awareness of health education and related services to students. Collaboration between faculty, student affairs professionals, and students occurred from design through evaluation. The primary goal of bringing students, faculty and staff together was…

Snelling, Anastasia M.

1999-01-01

425

Fit Effect of Motorcycle Helmet  

Microsoft Academic Search

Optimized assessment of the adequacy of fit conditions between a motorcycle helmet and head size in relation to prevention of head injury remains unclear and is complicated by wide variations in the size and shape characteristics of helmet and wearer's heads. A finite element model (LS-DYNA3D) based on realistic geometric features of a motorcycle helmet was established to simulate the

Li-Tung Chang; Chih-Han Chang; Guan-Liang Chang

2001-01-01

426

Coaches as Fitness Role Models  

ERIC Educational Resources Information Center

|The lack of physical activity, low fitness levels, and elevated obesity rates as high as 32% of today's youth are well documented. Many strategies and grants have been developed at the national, regional, and local levels to help counteract these current trends. Strategies have been developed and implemented for schools, households (parents), and…

Nichols, Randall; Zillifro, Traci D.; Nichols, Ronald; Hull, Ethan E.

2012-01-01

427

Physical Performance, Fitness and Diet.  

ERIC Educational Resources Information Center

|This book deals principally with the relationships between diet, fitness, and physical work capacity. The extreme nutritional states of obesity and chronic food deprivation are considered, and the effect of supplementation and modification of normal dietaries on work capacity are discussed. Figures and data tables provide information regarding…

Young, Donald R.

428

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

429

Monotone piecewise cubic data fitting  

SciTech Connect

This paper describes PCHLS, an algorithm for least squares fitting of a monotone piecewise cubic function to data. It extends the piecewise cubic Hermite interpolation package PCHIP to situations in which the data are noisy or are adequately represented by far fewer cubic pieces than data points. 6 refs., 5 figs.

Fritsch, F.N.

1988-07-01

430

Regulatory fit and health behavior  

Microsoft Academic Search

Everyone prefers health to ill-health, though some worry more about ill health than others and for others abstract health concerns seem to pale compared with the prospect of immediate hedonic pleasures. Two studies (n = 90, n = 70) utilized a ‘fit’ in self-regulatory focus approach (Higgins, 2000) to describe when and how worrying about health (versus focus on hedonic

Ayse K. Uskul; Johannes Keller; Daphna Oyserman

2008-01-01

431

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

432

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

433

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

434

10 CFR 35.2630 - Records of dosimetry equipment used with remote afterloader units, teletherapy units, and gamma...  

Code of Federal Regulations, 2010 CFR

... 2009-01-01 false Records of dosimetry equipment used with remote afterloader... Records § 35.2630 Records of dosimetry equipment used with remote afterloader...intercomparison, and comparisons of its dosimetry equipment done in accordance...

2009-01-01

435

10 CFR 35.2630 - Records of dosimetry equipment used with remote afterloader units, teletherapy units, and gamma...  

Code of Federal Regulations, 2010 CFR

... 2010-01-01 false Records of dosimetry equipment used with remote afterloader... Records § 35.2630 Records of dosimetry equipment used with remote afterloader...intercomparison, and comparisons of its dosimetry equipment done in accordance...

2010-01-01

436

Application of Chandrasekhar`s method to a radiation dosimetry problem  

SciTech Connect

In the last several years we have been developing a simplified electron transport model to calculate energy deposition profiles in multilayered structures irradiated by X rays and gamma rays. This model was implemented in a rapidly running algorithm MULTILAYER, for an IBM-compatible personal computer suitable for radiation-hardened electronics and dosimetry applications. In particular, we have been seeking to model the dose enhancement phenomenon near material interfaces for which experimental results were reported by Wall and Burke. In Refs. 1, 2, and 3, a simple one-group S{sub 2} transport model is described. This rod model arose as an extension of a semi-empirical model developed by Burke and Garth which was, in turn, based on exponential fits to Monte Carlo calculations of dose profiles at gold/silicon interfaces at photon energies from 10 to 2000 keV.

Woolf, S.; Garth, J.C.

1994-12-31

437

External dosimetry in the aftermath of a radiological terrorist event.  

PubMed

This paper reviews external dosimetry in emergency preparedness planning for a potential terrorist release of radioactive material in a densely populated area. The radiation dose received by response workers and members of the public is needed to understand health risks. The existing framework for dosimetry of routinely occupationally exposed workers is not directly applicable to all emergency workers who would respond to a radiological terrorist event. Emergency preparedness plans incorporate various old and new dosimetry technologies, including quartz fibre electrets, electronic dosemeters, personnel badges and wallet cards. Environmental monitoring and dose calculations are the usual methods for determining public dose. However, during the late-phase response, after removable contamination has been eliminated, it may be easier and more straightforward to provide individual dosimetry for members of the public who may be moving through a city with varying contamination areas. Doing so could allow resumption of normal activities earlier and promote confidence in reusing the site. PMID:16606662

Klemic, Gladys A; Bailey, Paul D; Miller, Kevin M; Monetti, Matthew A

2006-04-10

438

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

439

Thermoluminescence Dosimetry Environmental Monitoring System. Features and Performance.  

National Technical Information Service (NTIS)

In this report, characteristics and performances of an environmental monitoring system with thermoluminescence dosimetry are presented. Most of the work deals with the main physical parameters necessary for measurements of ambiental dose. At the end of th...

S. Bortoluzzi

1989-01-01

440

Proceedings of the third conference on radiation protection and dosimetry  

SciTech Connect

The Third Conference on Radiation Protection and Dosimetry was held during October 21--24, 1991, at the Sheraton Plaza Hotel in Orlando, Florida. This meeting was designed with the objectives of promoting communication among applied, research, regulatory, and standards personnel involved in radiation protection, and providing them with sufficient information to evaluate their programs. To meet these objectives, a technical program consisting of more than 75 invited and contributed oral presentations encompassing all aspects of radiation protection was prepared. General topics considered in the technical session included external dosimetry, internal dosimetry, instruments, accident dosimetry, regulations and standards, research advances, and applied program experience. In addition, special sessions were held to afford attendees the opportunity to make short presentations of recent work or to discuss topics of general interest. Individual reports are processed separately on the database.

Swaja, R.E.; Sims, C.S.; Casson, W.H. [eds.

1991-10-01

441

Proceedings of the third conference on radiation protection and dosimetry.  

National Technical Information Service (NTIS)

The Third Conference on Radiation Protection and Dosimetry was held during October 21--24, 1991, at the Sheraton Plaza Hotel in Orlando, Florida. This meeting was designed with the objectives of promoting communication among applied, research, regulatory,...

R. E. Swaja C. S. Sims W. H. Casson

1991-01-01

442

Proceedings of the Third Conference on Radiation Protection and Dosimetry  

NASA Astrophysics Data System (ADS)

The Third Conference on Radiation Protection and Dosimetry was held during October 21-24, 1991, at the Sheraton Plaza Hotel in Orlando, Florida. This meeting was designed with the objectives of promoting communication among applied, research, regulatory, and standards personnel involved in radiation protection, and providing them with sufficient information to evaluate their programs. To meet these objectives, a technical program consisting of more than 75 invited and contributed oral presentations encompassing all aspects of radiation protection was prepared. General topics considered in the technical session included external dosimetry, internal dosimetry, instruments, accident dosimetry, regulations and standards, research advances, and applied program experience. In addition, special sessions were held to afford attendees the opportunity to make short presentations of recent work or to discuss topics of general interest. Individual reports are processed separately on the database.

Swaja, R. E.; Sims, C. S.; Casson, W. H.

1991-10-01

443

Dosimetry and Temperature Aspects of Mobile-Phone Exposures  

Microsoft Academic Search

\\u000a Dosimetric assessment is an import subject in studying the effects from exposure to wireless communication devices. It provides\\u000a a quantitative measure for epidemiological studies and in the development of exposure guidelines. Dosimetry may be accomplished\\u000a either numerically or experimentally, or by a combination of both since each technique has its own advantages and drawbacks.\\u000a While numerical dosimetry forms the focus

Paolo Bernardi; Stefano Pisa; Marta Cavagnaro; Emanuel Piuzzi; James C. Lin

444

ESR and ESR microscopy in geosciences and radiation dosimetry  

Microsoft Academic Search

ESR and its microscopic imaging (microscopy) have found new applications in interdisciplinary fields related with geosciences\\u000a and with radiation dosimetry. Geological, archaeological and forensic dating has been made through paleo-dosimetry of natural\\u000a radiation and chemical reactions of both radical formation and valency changes. ESR microscopy, especially the simple scanning\\u000a method has a potentiality to be used in various fields. New

M. Ikeya

1994-01-01

445

Plastic scintillation dosimetry: optimization of light collection efficiency  

Microsoft Academic Search

Practical contemporary radiotherapy dosimetry systems used for dose measurement and verification are ionization chambers (which typically have at least a 0.1 cm3 air cavity volume), thermoluminescent dosimeters (TLDs) and silicon diodes. However, during the last decade, there has been an increased interest in scintillation dosimetry using small water-equivalent plastic scintillators, due to their favourable characteristics when compared with other more

A Sam Beddar; Susan Law; Natalka Suchowerska; T Rockwell Mackie

2003-01-01

446

Towards four dimensional (4D) dosimetry for radiation-therapy  

NASA Astrophysics Data System (ADS)

The development of accurate and convenient dosimetry tools with the capacity to comprehensively verify advanced four-dimensional treatments is an important and urgent goal for radiation therapy physi