Dose Reduction Study in Vaginal Balloon Packing Filled With Contrast for HDR Brachytherapy Treatment

International Nuclear Information System (INIS)

Saini, Amarjit S.; Zhang, Geoffrey G.; Finkelstein, Steven E.; Biagioli, Matthew C.

2011-01-01

Purpose: Vaginal balloon packing is a means to displace organs at risk during high dose rate brachytherapy of the uterine cervix. We tested the hypothesis that contrast-filled vaginal balloon packing reduces radiation dose to organs at risk, such as the bladder and rectum, in comparison to water- or air-filled balloons. Methods and Materials: In a phantom study, semispherical vaginal packing balloons were filled with air, saline solution, and contrast agents. A high dose rate iridium-192 source was placed on the anterior surface of the balloon, and the diode detector was placed on the posterior surface. Dose ratios were taken with each material in the balloon. Monte Carlo (MC) simulations, by use of the MC computer program DOSXYZnrc, were performed to study dose reduction vs. balloon size and contrast material, including commercially available iodine- and gadolinium-based contrast agents. Results: Measured dose ratios on the phantom with the balloon radius of 3.4 cm were 0.922 ± 0.002 for contrast/saline solution and 0.808 ± 0.001 for contrast/air. The corresponding ratios by MC simulations were 0.895 ± 0.010 and 0.781 ± 0.010. The iodine concentration in the contrast was 23.3% by weight. The dose reduction of contrast-filled balloon ranges from 6% to 15% compared with water-filled balloon and 11% to 26% compared with air-filled balloon, with a balloon size range between 1.4 and 3.8 cm, and iodine concentration in contrast of 24.9%. The dose reduction was proportional to the contrast agent concentration. The gadolinium-based contrast agents showed less dose reduction because of much lower concentrations in their solutions. Conclusions: The dose to the posterior wall of the bladder and the anterior wall of the rectum can be reduced if the vaginal balloon is filled with contrast agent in comparison to vaginal balloons filled with saline solution or air.

Radiation dose-reduction strategies in thoracic CT.

Science.gov (United States)

Moser, J B; Sheard, S L; Edyvean, S; Vlahos, I

2017-05-01

Modern computed tomography (CT) machines have the capability to perform thoracic CT for a range of clinical indications at increasingly low radiation doses. This article reviews several factors, both technical and patient-related, that can affect radiation dose and discusses current dose-reduction methods relevant to thoracic imaging through a review of current techniques in CT acquisition and image reconstruction. The fine balance between low radiation dose and high image quality is considered throughout, with an emphasis on obtaining diagnostic quality imaging at the lowest achievable radiation dose. The risks of excessive radiation dose reduction are also considered. Inappropriately low dose may result in suboptimal or non-diagnostic imaging that may reduce diagnostic confidence, impair diagnosis, or result in repeat examinations incurring incremental ionising radiation exposure. Copyright © 2016 The Royal College of Radiologists. Published by Elsevier Ltd. All rights reserved.

Dose reduction strategies for cardiac CT

International Nuclear Information System (INIS)

Midgley, S.M.; Einsiedel, P.; Langenberg, F.; Lui, E.

2010-01-01

Full text: Recent advances in CT technology have produced brighter X-ray sources. gantries capable of increased rotation speeds, faster scintil lation materials arranged into multiple rows of detectors, and associated advances in 3D reconstruction methods. These innovations have allowed multi-detector CT to be turned to the diagnosis of cardiac abnormalities and compliment traditional imaging techniques such as coronary angiography. This study examines the cardiac imaging solution offered by the Siemens Somatom Definition Dual Source 64 slice CT scanner. Our dose reduction strategies involve optimising the data acquisition protocols according to diagnostic task, patient size and heart rate. The relationship between scan parameters, image quality and patient dose is examined and verified against measurements with phantoms representing the standard size patient. The dose reduction strategies are reviewed with reference to survey results of patient dose. Some cases allow the insertion of shielding to protect radiosensitive organs, and results are presented to quantify the dose saving.

Dose-reduction techniques for high-dose worker groups in nuclear power plants

International Nuclear Information System (INIS)

Khan, T.A.; Baum, J.W.; Dionne, B.J.

1991-03-01

This report summarizes the main findings of a study of the extent of radiation dose received by special work groups in the nuclear power industry. Work groups which chronically get large doses were investigated, using information provided by the industry. The tasks that give high doses to these work groups were examined and techniques described that were found to be particularly successful in reducing dose. Quantitative information on the extent of radiation doses to various work groups shows that significant numbers of workers in several critical groups receive doses greater than 1 and even 2 rem per year, particularly contract personnel and workers at BWR-type plants. The number of radiation workers whose lifetime dose is greater than their age is much less. Although the techniques presented would go some way in reducing dose, it is likely that a sizeable reduction to the high-dose work groups may require development of new dose-reduction techniques as well as major changes in procedures. 10 refs., 26 tabs

Dose reduction and optimization studies (ALARA) at nuclear power facilities

International Nuclear Information System (INIS)

Baum, J.W.; Meinhold, C.B.

1983-01-01

Brookhaven National Laboratory (BNL) has been commissioned by the Nuclear Regulatory Commission (NRC) to study dose-reduction techniques and effectiveness of as low as reasonably achievable (ALARA) planning at LWR plants. These studies have the following objectives: identify high-dose maintenance tasks; identify dose-reduction techniques; examine incentives for dose reduction; evaluate cost-effectiveness and optimization of dose-reduction techniques; and compile an ALARA handbook on data, engineering modifications, cost-effectiveness calculations, and other information of interest to ALARA practioners

Radiation dose reduction in chest CT—Review of available options

International Nuclear Information System (INIS)

Kubo, Takeshi; Ohno, Yoshiharu; Kauczor, Hans Ulrich; Hatabu, Hiroto

2014-01-01

Highlights: • The present status of proliferating CT examinations was presented. • Technical improvements of CT scanners for radiation dose reduction were reviewed. • Advantage and disadvantage of methods for CT radiation dose reduction were discussed. • Evidences for safety of CT radiation dose reduction were reviewed. - Abstract: Computed tomography currently accounts for the majority of radiation exposure related to medical imaging. Although technological improvement of CT scanners has reduced the radiation dose of individual examinations, the benefit was overshadowed by the rapid increase in the number of CT examinations. Radiation exposure from CT examination should be kept as low as reasonably possible for patient safety. Measures to avoid inappropriate CT examinations are needed. Principles and information on radiation dose reduction in chest CT are reviewed in this article. The reduction of tube current and tube potential are the mainstays of dose reduction methods. Study results indicate that routine protocols with reduced tube current are feasible with diagnostic results comparable to conventional standard dose protocols. Tube current adjustment is facilitated by the advent of automatic tube current modulation systems by setting the appropriate image quality level for the purpose of the examination. Tube potential reduction is an effective method for CT pulmonary angiography. Tube potential reduction often requires higher tube current for satisfactory image quality, but may still contribute to significant radiation dose reduction. Use of lower tube potential also has considerable advantage for smaller patients. Improvement in image production, especially the introduction of iterative reconstruction methods, is expected to lower radiation dose significantly. Radiation dose reduction in CT is a multifaceted issue. Understanding these aspects leads to an optimal solution for various indications of chest CT

Radiation dose reduction in chest CT—Review of available options

Energy Technology Data Exchange (ETDEWEB)

Kubo, Takeshi, E-mail: tkubo@kuhpkyoto-u.ac.jp [Department of Diagnostic Imaging and Nuclear Medicine, Kyoto University Graduate School of Medicine, 54 Shogoin Kawahara-cho, Sakyo-ku, Kyoto 606-8507 (Japan); Ohno, Yoshiharu, E-mail: yosirad@kobe-u.ac.jp [Department of Radiology, Kobe University Graduate School of Medicine, 7-5-2, Kusunoki-cho, Chuo-ku, Kobe 650-0017 (Japan); Kauczor, Hans Ulrich, E-mail: hu.kauczor@med.uni-heidelberg.de [Diagnostic and Interventional Radiology, University Clinic Heidelberg, Im Neuenheimer Feld 110, D-69120 Heidelberg (Germany); Hatabu, Hiroto, E-mail: hhatabu@partners.org [Department of Radiology, Brigham and Women' s Hospital, 75 Francis Street, Boston, MA 02115 (United States)

2014-10-15

Highlights: • The present status of proliferating CT examinations was presented. • Technical improvements of CT scanners for radiation dose reduction were reviewed. • Advantage and disadvantage of methods for CT radiation dose reduction were discussed. • Evidences for safety of CT radiation dose reduction were reviewed. - Abstract: Computed tomography currently accounts for the majority of radiation exposure related to medical imaging. Although technological improvement of CT scanners has reduced the radiation dose of individual examinations, the benefit was overshadowed by the rapid increase in the number of CT examinations. Radiation exposure from CT examination should be kept as low as reasonably possible for patient safety. Measures to avoid inappropriate CT examinations are needed. Principles and information on radiation dose reduction in chest CT are reviewed in this article. The reduction of tube current and tube potential are the mainstays of dose reduction methods. Study results indicate that routine protocols with reduced tube current are feasible with diagnostic results comparable to conventional standard dose protocols. Tube current adjustment is facilitated by the advent of automatic tube current modulation systems by setting the appropriate image quality level for the purpose of the examination. Tube potential reduction is an effective method for CT pulmonary angiography. Tube potential reduction often requires higher tube current for satisfactory image quality, but may still contribute to significant radiation dose reduction. Use of lower tube potential also has considerable advantage for smaller patients. Improvement in image production, especially the introduction of iterative reconstruction methods, is expected to lower radiation dose significantly. Radiation dose reduction in CT is a multifaceted issue. Understanding these aspects leads to an optimal solution for various indications of chest CT.

Occupational dose reduction developments and data collected at nuclear power plants

International Nuclear Information System (INIS)

Dionne, B.J.; Baum, J.W.

1984-01-01

Occupational dose reduction developments and data collected at nuclear power plants have been described. Written descriptions of repetitive high dose jobs, their collective dose equivalent ranges and list of dose reduction techniques will aid in reducing collective dose equivalents from these dose-reduction targets. Knowing which components contribute to high maintenance or repair dose will aid in reducing routine maintenance collective dose equivalents. The radwaste dose reduction improvements will aid in reducing radwaste operations collective dose equivalent and reduce the number of radwaste workers who exceed their administrative dose limits. The identification and rating of managers' and workers' ALARA incentives will provide the basis for recommendations to improve dose reduction incentives. Lastly, the identification and rating of the key components of an ALARA program will aid in the development and coordination of the nuclear station ALARA programs

Radiation dose reduction in pediatric CT

International Nuclear Information System (INIS)

Robinson, A.E.; Hill, E.P.; Harpen, M.D.

1986-01-01

The relationship between image noise and radiation dose was investigated in computed tomography (CT) images of a pediatric abdomen phantom. A protocol which provided a minimum absorbed dose consistent with acceptable image noise criteria was determined for a fourth generation CT scanner. It was found that pediatric abdominal CT scans could maintain diagnostic quality with at least a 50% reduction in dose from the manufacturers' suggested protocol. (orig.)

Cost-effectiveness of reduction of off-site dose

International Nuclear Information System (INIS)

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

1988-03-01

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

Dose reduction factors from a radioactive cloud for large buildings

International Nuclear Information System (INIS)

Grand, J. le; Roux, Y.

1986-01-01

A set of complex and accurate computer codes has been established to determine the transport of photons emitted from a radioactive cloud through various media. The geometrical and physical description of large buildings with various numbers of floors and rooms can be done by the user. The codes can calculate, in any room or apartment, the characteristics of the photon fields (photon flux, energy flux and distribution, direction distribution) and whole-body absorbed dose rates in a phantom standing or lying on the floor. The dose reduction factor is then the quotient of the mean absorbed dose rate in the apartment to the absorbed dose rate in the phantom standing on the ground outdoors. Applications to several modern multistorey buildings are presented. The results show the influence of various parameters such as density and composition of building materials, the fraction of the external building surface containing apertures and initial photon energy. (author)

Reduction of radiation doses on patients. Practice cases

International Nuclear Information System (INIS)

Ruiz Perez de Villar, M.J.; Llorca Diaz, A.L.; Vano Carruana, E.

1993-01-01

The percentages of patient dose reduction achieved in chest, abdomen, lumbar spine and pelvis imaging as a result of the quality controls applied to X-ray generators and tubes are presented. Dosimetry was done with lithium fluoride thermoluminescent crystals. The absorbed doses were measured before and after the quality controls and were compared with reference doses provided by the European Community and by the Medical Physics department of the Universidad Complutense in Madrid. The procedures applied in the quality controls of generators and tubes were noninvasive. In chest studies, the reductions in dose ranged between 60 and 80%. In studies of abdomen, lumbar column and pelvis, it was possible to reduce the absorbed dose by 35%. (Author)

Sci-Thur PM – Brachytherapy 05: Surface Collimation Applied to Superficial Flap High Dose-Rate Brachytherapy

Energy Technology Data Exchange (ETDEWEB)

Liu, Derek; Sabondjian, Eric; Lawrence, Kailin; Sankreacha, Raxa [University of Toronto, Carlo Fidani Peel Regional Cancer Center, Carlo Fidani Peel Regional Cancer Center, University of Toronto (Canada)

2016-08-15

Purpose: To apply surface collimation for superficial flap HDR skin brachytherapy utilizing common clinical resources and to demonstrate the potential for OAR dose reduction within a clinically relevant setting. Methods: Two phantom setups were used. 3 mm lead collimation was applied to a solid slab phantom to determine appropriate geometries relating to collimation and dwell activation. The same collimation was applied to the temple of an anthropomorphic head phantom to demonstrate lens dose reduction. Each setup was simulated and planned to deliver 400 cGy to a 3 cm circular target to 3 mm depth. The control and collimated irradiations were sequentially measured using calibrated radiochromic films. Results: Collimation for the slab phantom attenuated the dose beyond the collimator opening, decreasing the fall-off distances by half and reducing the area of healthy skin irradiated. Target coverage can be negatively impacted by a tight collimation margin, with the required margin approximated by the primary beam geometric penumbra. Surface collimation applied to the head phantom similarly attenuated the surrounding normal tissue dose while reducing the lens dose from 84 to 68 cGy. To ensure consistent setup between simulation and treatment, additional QA was performed including collimator markup, accounting for collimator placement uncertainties, standoff distance verification, and in vivo dosimetry. Conclusions: Surface collimation was shown to reduce normal tissue dose without compromising target coverage. Lens dose reduction was demonstrated on an anthropomorphic phantom within a clinical setting. Additional QA is proposed to ensure treatment fidelity.

Sci-Thur PM – Brachytherapy 05: Surface Collimation Applied to Superficial Flap High Dose-Rate Brachytherapy

International Nuclear Information System (INIS)

Liu, Derek; Sabondjian, Eric; Lawrence, Kailin; Sankreacha, Raxa

2016-01-01

Purpose: To apply surface collimation for superficial flap HDR skin brachytherapy utilizing common clinical resources and to demonstrate the potential for OAR dose reduction within a clinically relevant setting. Methods: Two phantom setups were used. 3 mm lead collimation was applied to a solid slab phantom to determine appropriate geometries relating to collimation and dwell activation. The same collimation was applied to the temple of an anthropomorphic head phantom to demonstrate lens dose reduction. Each setup was simulated and planned to deliver 400 cGy to a 3 cm circular target to 3 mm depth. The control and collimated irradiations were sequentially measured using calibrated radiochromic films. Results: Collimation for the slab phantom attenuated the dose beyond the collimator opening, decreasing the fall-off distances by half and reducing the area of healthy skin irradiated. Target coverage can be negatively impacted by a tight collimation margin, with the required margin approximated by the primary beam geometric penumbra. Surface collimation applied to the head phantom similarly attenuated the surrounding normal tissue dose while reducing the lens dose from 84 to 68 cGy. To ensure consistent setup between simulation and treatment, additional QA was performed including collimator markup, accounting for collimator placement uncertainties, standoff distance verification, and in vivo dosimetry. Conclusions: Surface collimation was shown to reduce normal tissue dose without compromising target coverage. Lens dose reduction was demonstrated on an anthropomorphic phantom within a clinical setting. Additional QA is proposed to ensure treatment fidelity.

Towards tracer dose reduction in PET studies: Simulation of dose reduction by retrospective randomized undersampling of list-mode data.

Science.gov (United States)

Gatidis, Sergios; Würslin, Christian; Seith, Ferdinand; Schäfer, Jürgen F; la Fougère, Christian; Nikolaou, Konstantin; Schwenzer, Nina F; Schmidt, Holger

2016-01-01

Optimization of tracer dose regimes in positron emission tomography (PET) imaging is a trade-off between diagnostic image quality and radiation exposure. The challenge lies in defining minimal tracer doses that still result in sufficient diagnostic image quality. In order to find such minimal doses, it would be useful to simulate tracer dose reduction as this would enable to study the effects of tracer dose reduction on image quality in single patients without repeated injections of different amounts of tracer. The aim of our study was to introduce and validate a method for simulation of low-dose PET images enabling direct comparison of different tracer doses in single patients and under constant influencing factors. (18)F-fluoride PET data were acquired on a combined PET/magnetic resonance imaging (MRI) scanner. PET data were stored together with the temporal information of the occurrence of single events (list-mode format). A predefined proportion of PET events were then randomly deleted resulting in undersampled PET data. These data sets were subsequently reconstructed resulting in simulated low-dose PET images (retrospective undersampling of list-mode data). This approach was validated in phantom experiments by visual inspection and by comparison of PET quality metrics contrast recovery coefficient (CRC), background-variability (BV) and signal-to-noise ratio (SNR) of measured and simulated PET images for different activity concentrations. In addition, reduced-dose PET images of a clinical (18)F-FDG PET dataset were simulated using the proposed approach. (18)F-PET image quality degraded with decreasing activity concentrations with comparable visual image characteristics in measured and in corresponding simulated PET images. This result was confirmed by quantification of image quality metrics. CRC, SNR and BV showed concordant behavior with decreasing activity concentrations for measured and for corresponding simulated PET images. Simulation of dose

The Effect of Aquaplast on Surface Dose of Photon Beam

International Nuclear Information System (INIS)

Oh, Do Hoon; Bae, Hoon Sik

1995-01-01

Purpose : To evaluate the effect on surface dose due to Aquaplast used for immobilizing the patients with head and neck cancers in photon beam radiotherapy. Materials and Methods : To assess surface and buildup region dose for 6MV X-ray from linear accelerator(Siemens Mevatron 6740), we measured percent ionization value with the Markus chamber model 30-329 manufactured by PTW Frieburg and Capintec electrometer, model WK92. For measurement of surface ionization value, the chamber was embedded in 25 X 25 X 3 cm 3 acrylic phantom and set on 25 X 25 X 5 cm 3 , polystyrene phantom to allow adequate scattering. The measurements of percent depth ionization were made by placing the polystyrene layers of appropriate thickness over the chamber. The measurements were taken at 10 cm SSD for 5 X 5 cm 2 , 10 X 10 cm 2 , and 15 X 15 cm 2 field sizes, respectively. Placing the layer of Aquaplast over the chamber, the same procedures were repeated. We evaluated two types o Aquaplast: 1.6mm layer of original Aquaplast(manufactured by WFR Aquaplast Corp.) and transformed Aquaplast similar to moulded one for immobilizing the patients practically. We also measured surface ionization values with blocking tray in presence or absence of transformed Aquaplast. In calculating percent depth dose, we used the formula suggested by Gerbi and khan to correct over response of the Markus chamber. Results : The surface doses for open fields of 5 X 5 cm 2 , 10 X 10 cm 2 , 15 X 15 cm 2 were 7.9%, 13.6%, and 18.7% respectively. He original Aquaplast increased the surface doses upto 38.4%, 43.6% and 47.4% respectively. There were little differences in percent depth dose values beyond the depth of Dmax. Increasing field size, the blocking tray caused increase of the surface dose by 0.2%, 1.7%, 3.0% without Aquaplast, 0.2%, 1.9%, 3.7% with transformed Aquaplast, respectively. Conclusion : The original and transformed Aquaplast increased the surface dose moderately. The percent depth doses beyond Dmax

Reduction of uterus dose in clinical thoracic computed tomography

International Nuclear Information System (INIS)

Danova, D.; Keil, B.; Kaestner, B.; Klose, K.J.; Heverhagen, J.T.; Wulff, J.; Fiebich, M.; Zink, K.

2010-01-01

Purpose: The aim of this study was to investigate the potential dose reduction in the uterus as a result of lead apron protection during thoracic CT scans. Moreover, the distribution of the radiation dose in the uterus was determined in order to obtain information about the ratio of internally and externally scattered radiation. Materials and Methods: The uterus doses during thoracic CT were determined by measuring organ doses using an Alderson-RANDO registered -Phantom and thermoluminescent dosimeters. A 0.25 mm lead equivalent protective apron was used to shield the abdominal area. Three measurement conditions were evaluated: without lead apron, covered with lead apron and wrapped with lead apron. The uterus dose with and without shielding describes the mean value and standard deviation of all examinations and all measurement points in the organ. Results: The uterus dose by thoracic CT was measured to be approximately 66.5 ± 3.1 μGy. If the abdomen is covered with a 0.25 mm Pb equivalent lead apron in the front area and on both sides, the uterus dose is reduced to 49.4 ± 2.8 μGy (26 % reduction, p < 0.001). If a lead apron is wrapped around the abdomen, providing 0.50 mm Pb shielding in the anterior section due to overlap, and 0.25 mm Pb in the posterior section and on both sides, the uterus dose is reduced even more to 43.8 ± 2.5 μGy (34 % reduction, p < 0.001). The dose distribution when the lead apron covers the abdomen shows that the shielding is effective for the scatter radiation that comes from the anterior part. Moreover, the wrapped apron protects the uterus from all directions and is even more effective for dose reduction than the covering apron. Conclusion: Our findings demonstrate that protective aprons are an effective dose reduction technique without additional costs and little effect on patient examination time. (orig.)

Skin dose reduction by a clinically viable magnetic deflector

International Nuclear Information System (INIS)

Butson, M.J.; Carolan, M.; Metcalfe, J.N.; University of Wollongong, NSW; Mathur, J.N.; Yu, P.; Young, E.; Kan, M.; City University of Hong Kong, Kowloon

1997-01-01

A variable magnetic deflector which attaches onto the treatment head of a linear accelerator has reduced skin dose by as much as 65% for 6MV x-rays. The magnetic deflector is constructed from Neodymium Iron Boron (NdFeB) rare earth magnets. It weighs approximately 15 kg and is designed to easily fit onto the accessory mount of a clinical linear accelerator. All field sizes are attainable up to 35 cm x 35 cm at 100 cm SSD. The gap between the magnetic poles can be adjusted, providing the highest field strength for each field size. Magnetic field strengths up to 0.55 Tesla are attainable. For a 6MV x-ray beam with a 10 mm perspex block tray, surface dose is reduced from 29% to 14% and from 59% to 37% for a 20 cm x 20 cm and 35 cm x 35 cm field size, respectively. Results at varying SSD's have shown at least 10 cm of space must be allowed between the magnets and patient for adequate reduction of skin dose through removal of electron contaminants. (authors)

Securing safe and informative thoracic CT examinations—Progress of radiation dose reduction techniques

Energy Technology Data Exchange (ETDEWEB)

Kubo, Takeshi, E-mail: tkubo@kuhp.kyoto-u.ac.jp [Department of Diagnostic Imaging and Nuclear Medicine, Kyoto University Graduate School of Medicine, 54 Shogoin Kawahara-cho, Sakyo-ku, Kyoto 606-8507 (Japan); Ohno, Yoshiharu [Division of Functional and Diagnostic Imaging Research, Department of Radiology, Kobe University Graduate School of Medicine, 7-5-2 Kusunoki-cho, Chuo-ku, Kobe 650-0017 (Japan); Advanced Biomedical Imaging Research Center, Kobe University Graduate School of Medicine, 7-5-2 Kusunoki-cho, Chuo-ku, Kobe 650-0017 (Japan); Seo, Joon Beom [Department of Radiology, University of Ulsan College of Medicine, Asan Medical Center, 88 Olympic-ro 43-gil, Songpa-gu, Seoul 05505 (Korea, Republic of); Yamashiro, Tsuneo [Department of Radiology, Graduate School of Medical Science, University of the Ryukyus, 207 Uehara, Nishinara, Okinawa 903-0215 (Japan); Kalender, Willi A. [Institute of Medical Physics, Friedrich-Alexander-University Erlangen-Nürnberg, Henkestr. 91, 91052 Erlangen (Germany); Lee, Chang Hyun [Department of Radiology, Seoul National University Hospital, 28 Yeongeon-dong, Jongno-gu, Seoul (Korea, Republic of); Lynch, David A. [Department of Radiology, National Jewish Health, 1400 Jackson St, A330 Denver, Colorado 80206 (United States); Kauczor, Hans-Ulrich [Diagnostic and Interventional Radiology, University Hospital Heidelberg, Im Neuenheimer Feld 400, 69120 Heidelberg (Germany); Translational Lung Research Center Heidelberg (TLRC), Member of the German Center for Lung Research (DZL), Im Neuenheimer Feld 400, 69120 Heidelberg (Germany); Hatabu, Hiroto, E-mail: hhatabu@partners.org [Center for Pulmonary Functional Imaging, Department of Radiology, Brigham and Women' s Hospital, 75 Francis Street, Boston, MA 02115 (United States)

2017-01-15

Highlights: • Various techniques have led to substantial radiation dose reduction of chest CT. • Automatic modulation of tube current has been shown to reduce radiation dose. • Iterative reconstruction makes significant radiation dose reduction possible. • Processing time is a limitation for full iterative reconstruction, currently. • Validation of diagnostic accuracy is desirable for routine use of low dose protocols. - Abstract: The increase in the radiation exposure from CT examinations prompted the investigation on the various dose-reduction techniques. Significant dose reduction has been achieved and the level of radiation exposure of thoracic CT is expected to reach the level equivalent to several chest X-ray examinations. With more scanners with advanced dose reduction capability deployed, knowledge on the radiation dose reduction methods has become essential to clinical practice as well as academic research. This article reviews the history of dose reduction techniques, ongoing changes brought by newer technologies and areas of further investigation.

Identification of dose-reduction techniques for BWR and PWR repetitive high-dose jobs

International Nuclear Information System (INIS)

Dionne, B.J.; Baum, J.W.

1984-01-01

As a result of concern about the apparent increase in collective radiation dose to workers at nuclear power plants, this project will provide information to industry in preplanning for radiation protection during maintenance operations. This study identifies Boiling Water Reactor (BWR) and Pressurized Water Reactor (PWR) repetitive jobs, and respective collective dose trends and dose reduction techniques. 3 references, 2 tables

Employee dose reduction at British Nuclear Fuels plc

International Nuclear Information System (INIS)

Fishwick, A.H.; Finlayson, J.L.; James, R.D.

1992-01-01

Average work force doses in uranium fuel fabrication plants are a small percentage (about 6 % or 3 mSv pa) of UK regulatory limits. In uranium metal casting, and uranium oxide production plants, doses are somewhat higher than the average. Dose reduction methods have, however, resulted in these being reduced to 20 %, or less, of the same limit. Major future investment should reduce doses in oxide production plants to about the current average level. (author)

Skin dose reduction by a clinically viable magnetic deflector

Energy Technology Data Exchange (ETDEWEB)

Butson, M.J.; Carolan, M.; Metcalfe, J.N. [Illawarra Cancer Centre, NSW (Australia). Department of Radiotherapy]|[University of Wollongong, NSW (Australia). Department of Physics; Mathur, J.N. [University of Wollongong, NSW (Australia). Department of Physics; Yu, P.; Young, E. [City University of Hong Kong, Kowloon (Hong Kong). Department of Physics; Kan, M. [Hong Kong Polytechnic University, Kowloon (Hong Kong). Department of Optometry and Radiography]|[City University of Hong Kong, Kowloon (Hong Kong). Department of Physics

1997-06-01

A variable magnetic deflector which attaches onto the treatment head of a linear accelerator has reduced skin dose by as much as 65% for 6MV x-rays. The magnetic deflector is constructed from Neodymium Iron Boron (NdFeB) rare earth magnets. It weighs approximately 15 kg and is designed to easily fit onto the accessory mount of a clinical linear accelerator. All field sizes are attainable up to 35 cm x 35 cm at 100 cm SSD. The gap between the magnetic poles can be adjusted, providing the highest field strength for each field size. Magnetic field strengths up to 0.55 Tesla are attainable. For a 6MV x-ray beam with a 10 mm perspex block tray, surface dose is reduced from 29% to 14% and from 59% to 37% for a 20 cm x 20 cm and 35 cm x 35 cm field size, respectively. Results at varying SSD`s have shown at least 10 cm of space must be allowed between the magnets and patient for adequate reduction of skin dose through removal of electron contaminants. (authors). 14 refs., 6 figs.

Radiographic film: surface dose extrapolation techniques

International Nuclear Information System (INIS)

Cheung, T.; Yu, P.K.N.; Butson, M.J.; Cancer Services, Wollongong, NSW; Currie, M.

2004-01-01

Full text: Assessment of surface dose delivered from radiotherapy x-ray beams for optimal results should be performed both inside and outside the prescribed treatment fields An extrapolation technique can be used with radiographic film to perform surface dose assessment for open field high energy x-ray beams. This can produce an accurate 2 dimensional map of surface dose if required. Results have shown that surface % dose can be estimated within ±3% of parallel plate ionisation chamber results with radiographic film using a series of film layers to produce an extrapolated result. Extrapolated percentage dose assessment for 10cm, 20cmand 30cm square fields was estimated to be 15% ± 2%, 29% ± 3% and 38% ± 3% at the central axis and relatively uniform across the treatment field. Corresponding parallel plate ionisation chamber measurement are 16%, 27% and 37% respectively. Surface doses are also measured outside the treatment field which are mainly due to scattered electron contamination. To achieve this result, film calibration curves must be irradiated to similar x-ray field sizes as the experimental film to minimize quantitative variations in film optical density caused by varying x-ray spectrum with field size. Copyright (2004) Australasian College of Physical Scientists and Engineers in Medicine

GARDEC, Estimation of dose-rates reduction by garden decontamination

International Nuclear Information System (INIS)

Togawa, Orihiko

2006-01-01

1 - Description of program or function: GARDEC estimates the reduction of dose rates by garden decontamination. It provides the effect of different decontamination Methods, the depth of soil to be considered, dose-rate before and after decontamination and the reduction factor. 2 - Methods: This code takes into account three Methods of decontamination : (i)digging a garden in a special way, (ii) a removal of the upper layer of soil, and (iii) covering with a shielding layer of soil. The dose-rate conversion factor is defined as the external dose-rate, in the air, at a given height above the ground from a unit concentration of a specific radionuclide in each soil layer

Reduction of radiation dose during the complex explorations using additional filter in pediatric patients

International Nuclear Information System (INIS)

Minguez, C.; Espana, M. L.; Castro, P.; Sevillano, D.; Lopez Franco, P.

2006-01-01

The aim of this study is to investigate the influence on image contrast, tube load and effective dose in paediatric fluoroscopy using added filtration. A Philips Omnidiagnosti is used in Nino Jesus Hospital and was therefore chosen for radiation dose measurements. The phantom consisted of varying methacrylate thickness to represent different patients sizes. All measurements were performed in automatic mode. For each exposure and additional filtration added the following data was recorded: tube voltage, tube current, air kerma rate on phantom surface and brightness on the image monitor. An 2026 electrometer (Radical Corporation) in conjunction with a model 2025-60 ion chamber were used for entrance dose measurements and the luxometer IL-400A (International Light) was used for brightness measurements on the image monitor: Evaluation of image quality was performed using a Leeds TOR TVF test object. Finally, the program PCXMC 1.5 based on the Monte Carlo method was used for calculating organ doses and the effective dose in fluoroscopy examinations. By increasing the filtration of the x-ray tube 1st Entrance radiation exposure can be decreased 58%, organ dose up to 40%, and effective dose up to 44%. 2nd The tube load increased up to 33%. 3rd Significant dose reduction is achievable without compromising image quality. The use of additional filtration in paediatric fluoroscopy should be evaluated taking into account dose reduction, additional tube loading and the possibility of some deterioration in image quality. (Author)

SU-F-T-325: On the Use of Bolus in Dosimetry and Dose Reduction for Pacemaker and Defibrillator

International Nuclear Information System (INIS)

Liu, W; Kenneth, R; Higgins, S; Nath, R; Zhu, D; Trumpore, S; Chen, Z

2016-01-01

Purpose: Special attention is required in planning and administering radiation therapy to patients with cardiac implantable electronic devices (CIEDs), such as pacemaker and defibrillator. The range of dose to CIEDs that can induce malfunction is very large among CIEDs. Significant defects have been reported at dose as low as 0.15Gy. Failures causing discomfort have been reported at dose as low as 0.05Gy. Therefore, accurate estimation of dose to CIED and dose reduction are both important even if the dose is expected to be less than the often-used 2Gy limit. We investigate the use of bolus in in vivo dosimetry for CIEDs. Methods: In our clinic, high-energy beams (>10MV) are not used for patients with CIED due to neutron production. Solid water phantom measurements of out-of-field dose for a 6MV beam were performed using parallel plate chamber at different depth with and without 2cm bolus covering the chamber. In vivo dosimetry at skin surface above the pacemaker was performed with and without bolus for 3 patients with pacemaker <5cm from the field edge. Results: Chamber measured dose at depth ∼1 to 1.5cm below the skin surface, where the CIED is normally located, was reduced by ∼6% – 20% with bolus. The dose reduction became smaller at deeper depth. In vivo dosimetry at skin surface also yielded ∼20% – 60% lower dose when using bolus for the 3 patients. In general, TPS calculation underestimated the dose. The dose measured with bolus is closer to the dose at the depth of the pacemaker and less affected by contaminant electrons and linac head leakage. Conclusion: In vivo CIED dose measurements should be performed with 1 to 2cm bolus covering the dosimeter on the skin above the CIED for more accurate CIED dose estimation. The use of bolus also reduces the dose delivered to CIED.

SU-F-T-325: On the Use of Bolus in Dosimetry and Dose Reduction for Pacemaker and Defibrillator

Energy Technology Data Exchange (ETDEWEB)

Liu, W; Kenneth, R; Higgins, S; Nath, R [Yale University School of Medicine, New Haven, CT (United States); Zhu, D [Saint Thomas Hospital, Murfreesboro, TN (United States); Trumpore, S [Yale-New Haven Hospital, New Haven, CT (United States); Chen, Z [Yale New Haven Hospital, New Haven, CT (United States)

2016-06-15

Purpose: Special attention is required in planning and administering radiation therapy to patients with cardiac implantable electronic devices (CIEDs), such as pacemaker and defibrillator. The range of dose to CIEDs that can induce malfunction is very large among CIEDs. Significant defects have been reported at dose as low as 0.15Gy. Failures causing discomfort have been reported at dose as low as 0.05Gy. Therefore, accurate estimation of dose to CIED and dose reduction are both important even if the dose is expected to be less than the often-used 2Gy limit. We investigate the use of bolus in in vivo dosimetry for CIEDs. Methods: In our clinic, high-energy beams (>10MV) are not used for patients with CIED due to neutron production. Solid water phantom measurements of out-of-field dose for a 6MV beam were performed using parallel plate chamber at different depth with and without 2cm bolus covering the chamber. In vivo dosimetry at skin surface above the pacemaker was performed with and without bolus for 3 patients with pacemaker <5cm from the field edge. Results: Chamber measured dose at depth ∼1 to 1.5cm below the skin surface, where the CIED is normally located, was reduced by ∼6% – 20% with bolus. The dose reduction became smaller at deeper depth. In vivo dosimetry at skin surface also yielded ∼20% – 60% lower dose when using bolus for the 3 patients. In general, TPS calculation underestimated the dose. The dose measured with bolus is closer to the dose at the depth of the pacemaker and less affected by contaminant electrons and linac head leakage. Conclusion: In vivo CIED dose measurements should be performed with 1 to 2cm bolus covering the dosimeter on the skin above the CIED for more accurate CIED dose estimation. The use of bolus also reduces the dose delivered to CIED.

Dose reduction - the radiologist's view

International Nuclear Information System (INIS)

Russell, J.G.B.

1984-01-01

The magnitude of the exposure to ionising radiation dominates radiological practice in only three fields, i.e. foetal radiography, mammography and computed tomography. The balance between risk and benefit are briefly examined. The types of hazard considered are carcinogenesis, genetic injury and organogenesis. Ways of achieving a reduction of the dose to the patient are also briefly discussed. (U.K.)

Optimal dose reduction in computed tomography methodologies predicted from real-time dosimetry

Science.gov (United States)

Tien, Christopher Jason

Over the past two decades, computed tomography (CT) has become an increasingly common and useful medical imaging technique. CT is a noninvasive imaging modality with three-dimensional volumetric viewing abilities, all in sub-millimeter resolution. Recent national scrutiny on radiation dose from medical exams has spearheaded an initiative to reduce dose in CT. This work concentrates on dose reduction of individual exams through two recently-innovated dose reduction techniques: organ dose modulation (ODM) and tube current modulation (TCM). ODM and TCM tailor the phase and amplitude of x-ray current, respectively, used by the CT scanner during the scan. These techniques are unique because they can be used to achieve patient dose reduction without any appreciable loss in image quality. This work details the development of the tools and methods featuring real-time dosimetry which were used to provide pioneering measurements of ODM or TCM in dose reduction for CT.

Trend of collective dose and dose reduction measures of Mitsubishi Electric Corporation workers in nuclear power plants

International Nuclear Information System (INIS)

Yamato, I.; Nakayama, T.; Shimokawa, F.; Yamamoto, T.

1996-01-01

MELCO has supplied the reactor instrumentation control system, reactor coolant pump motors, turbine generator and central control system for the pressurized water type nuclear power plant. For the legal periodical inspection and repair work, MELCO has also received orders for the periodical inspection for 23 power plants (including 4 plants under construction) of 5 electric power companies, and executed the inspection work from the view point of preventive maintenance. The annual dose for MELCO's workers is liable to be decreased in spite of increased number of plants. The dose for new plant in particular is 50, or less as compared with that for conventional plant. This is because the measures taken for the conventional plant against the dose reduction is reflected upon the new plant. The dose reduction measures are taken for each system for which order was received. Such measures are mainly intended to improve the work procedures and equipment for reduction of work time in the radioactive area and to arrange the working process, so as to perform the work in such period when the dose level at the working environment is low. To enhance the workers' consciousness for reduction of dose, MELCO provided the workers with dose predictive training, and let them aware of such items known at the tool box briefing (TBX), which could realize the dose reduction for workers. MELCO has been positively promoting the activity to arrange the desirable work environment for extermination of 3Ks (giken, gitsui, titanai) or 3Ds (dangerous, difficult, dirty) including protection against radiation in corporation with electric power companies. (author)

Regulatory actions towards dose reduction at Atucha 1 NPS

International Nuclear Information System (INIS)

Spano, F.; Curti, A.R.; Telleria, D.M.; Rudelli, M.D.

1998-01-01

Atucha 1, a nuclear power plant designed in the late sixties, is in commercial operation since June 1974. In some internal components such as the coolant channels, the station has Stellite-6, a high cobalt content alloy (up to 60%) for hard-facing application. The erosion and corrosion processes on the surfaces of the piping components of the primary coolant and moderator systems generate a varied type of particles oxides called 'crud'. The crud and cobalt 60 produced by neutron activation of cobalt are transferred by the water along the circuit of the coolant and moderator systems, producing deposits on internal surfaces. The cobalt deposits are dominant in radiation fields at working locations. For years, the Authority allowed a considerable number of station workers incurring doses near the limit since that installation had been built previously to introduction of the optimisation concept by ICRP publication 26. The recommendations included in ICRP publication 60 made more than difficult the radiological situation at the Atucha 1. For the facility, to comply with the new limit established by the Authority in January 1995, meant to carry out a substantial modification of the radiological conditions, specially the radiation fields due to cobalt 60. Some options to reduce individual and collective doses were analysed by the Authority. To carry out the evaluation of the deposit mechanisms and the real activity level of cobalt 60, a model of compartments connected by means of constant transfer coefficients was designed. It was concluded that there was a necessity to the change of coolant channels by new ones free of cobalt. It has been shown experimentally that radiation fields and occupational doses were reduced, due to the replacement programme carried out by the utility, in a similar way to the model predictions. At present after more than three years from the beginning of the application of the new limits, and after carrying out partially the tasks for the

Digital chest radiography: collimation and dose reduction

DEFF Research Database (Denmark)

Debess, Jeanne; Johnsen, Karen Kirstine; Vejle-Sørensen, Jens Kristian

,3 mAs and SID SID of 180 centimetres using a phantom and lithium fluoride thermo luminescence dosimeter (TLD). Dose to risk organs mamma, thyroid and colon are measured at different collimations with one-centimetre steps. TLD results are used to estimate dose reduction for different collimations...... at the conference. Conclusion: Collimation improvement in basic chest radiography can reduce the radiation to female patients at chest x-ray examinations....

Dose reduction in fluoroscopy with modern DSA equipment

International Nuclear Information System (INIS)

Waggershauser, T.; Herrmann, K.; Schaetzl, M.; Reiser, M.

1995-01-01

The new Multistar T.O.P. (Siemens) is equipped with various features for dose reduction. In this study pulsed fluoroscopy was tested versus standard continuous fluoroscopy and supervisions. Fluoroscope with 3, 7.5, and 15 pulses/s in the Multistar T.O.P. were compared to standard fluoroscopy and to reduced-dose supervision in a human pelvic phantom. The skin entry dose and pelvic dose were continuously registered. The supervision mode used 58% of the dose used in continuous fluoroscopy. Pulsed fluoroscopy with 15 pulses/s required 54%, 7.5 pulses/s 27% and 3 pulses/s. These provide adequate image quality with only 10% of the standard dose. (orig./MG) [de

Extrapolated surface dose measurements using a NdFeB magnetic deflector for 6 MV x-ray beams.

Science.gov (United States)

Damrongkijudom, N; Butson, M; Rosenfeld, A

2007-03-01

Extrapolated surface dose measurements have been performed using radiographic film to measure 2-Dimensional maps of skin and surface dose with and without a magnetic deflector device aimed at reducing surface dose. Experiments are also performed using an Attix parallel plate ionisation chamber for comparison to radiographic film extrapolation surface dose analysis. Extrapolated percentage surface dose assessments from radiographic film at the central axis of a 6 MV x-ray beam with magnetic deflector for field size 10 x 10 cm2, 15 x 15 cm2 and 20 x 20 cm2 are 9 +/- 3%, 13 +/- 3% and 16 +/- 3%, these compared to 14 +/- 3%, 19 +/- 3%, and 27 +/- 3% for open fields, respectively. Results from Attix chamber for the same field size are 12 +/- 1%, 15 +/- 1% and 18 +/- 1%, these compared to 16 +/- 1%, 21 +/- 1% and 27 +/- 1% for open fields, respectively. Results are also shown for profiles measured in-plane and cross-plane to the magnetic deflector and compared to open field data. Results have shown that the surface dose is reduced at all sites within the treatment field with larger reductions seen on one side of the field due to the sweeping nature of the designed magnetic field. Radiographic film extrapolation provides an advanced surface dose assessment and has matched well with Attix chamber results. Film measurement allows for easy 2 dimensional dose assessments.

Patient dose measurement and dose reduction in East Anglia (UK)

International Nuclear Information System (INIS)

Wade, J.P.; Goldstone, K.E.; Dendy, P.P.

1995-01-01

At the end of 1990 a programme of patient dose measurements was introduced as part of the quality assurance service already provided for X ray departments throughout the East Anglian Health Region (UK). Thermoluminescence dosemeters (TLDs) were used to measure over 1200 skin entrance surface doses for four common radiographic views in 33 hospitals in both the NHS and private sector. The four views were chosen to cover a wide range of equipment and techniques. The data collected have enabled Regional reference doses to be set which, for all views considered, fall below the National Radiological Protection Board (NRPB) Reference levels. In departments which exceeded reference levels, techniques were reviewed, improvements suggested and doses re-measured, in accordance with the recommended procedure for patient dose audit. A significant finding was that, given appropriate controls, X ray departments in the private sector could achieve the same acceptably low doses as NHS departments. (Author)

SU-F-J-16: Planar KV Imaging Dose Reduction Study

Energy Technology Data Exchange (ETDEWEB)

Gershkevitsh, E; Zolotuhhin, D [North Estonia Medical Centre, Tallinn (Estonia)

2016-06-15

Purpose: IGRT has become an indispensable tool in modern radiotherapy with kV imaging used in many departments due to superior image quality and lower dose when compared to MV imaging. Many departments use manufacturer supplied protocols for imaging which are not always optimised between image quality and radiation dose (ALARA). Methods: Whole body phantom PBU-50 (Kyoto Kagaku ltd., Japan) for imaging in radiology has been imaged on Varian iX accelerator (Varian Medical Systems, USA) with OBI 1.5 system. Manufacturer’s default protocols were adapted by modifying kV and mAs values when imaging different anatomical regions of the phantom (head, thorax, abdomen, pelvis, extremities). Images with different settings were independently reviewed by two persons and their suitability for IGRT set-up correction protocols were evaluated. The suitable images with the lowest mAs were then selected. The entrance surface dose (ESD) for manufacturer’s default protocols and modified protocols were measured with RTI Black Piranha (RTI Group, Sweden) and compared. Image quality was also measured with kVQC phantom (Standard Imaging, USA) for different protocols. The modified protocols have been applied for clinical work. Results: For most cases optimized protocols reduced the ESD on average by a factor of 3(range 0.9–8.5). Further reduction in ESD has been observed by applying bow-tie filter designed for CBCT. The largest reduction in dose (12.2 times) was observed for Thorax lateral protocol. The dose was slightly increased (by 10%) for large pelvis AP protocol. Conclusion: Manufacturer’s default IGRT protocols could be optimised to reduce the ESD to the patient without losing the necessary image quality for patient set-up correction. For patient set-up with planar kV imaging the bony anatomy is mostly used and optimization should focus on this aspect. Therefore, the current approach with anthropomorphic phantom is more advantageous in optimization over standard kV quality

Surface dose extrapolation measurements with radiographic film

International Nuclear Information System (INIS)

Butson, Martin J; Cheung Tsang; Yu, Peter K N; Currie, Michael

2004-01-01

Assessment of surface dose delivered from radiotherapy x-ray beams for optimal results should be performed both inside and outside the prescribed treatment fields. An extrapolation technique can be used with radiographic film to perform surface dose assessment for open field high energy x-ray beams. This can produce an accurate two-dimensional map of surface dose if required. Results have shown that the surface percentage dose can be estimated within ±3% of parallel plate ionization chamber results with radiographic film using a series of film layers to produce an extrapolated result. Extrapolated percentage dose assessment for 10 cm, 20 cm and 30 cm square fields was estimated to be 15% ± 2%, 29% ± 3% and 38% ± 3% at the central axis and relatively uniform across the treatment field. The corresponding parallel plate ionization chamber measurements are 16%, 27% and 37%, respectively. Surface doses are also measured outside the treatment field which are mainly due to scattered electron contamination. To achieve this result, film calibration curves must be irradiated to similar x-ray field sizes as the experimental film to minimize quantitative variations in film optical density caused by varying x-ray spectrum with field size. (note)

Dose reduction by x-ray beam filtration in screen-film radiography

International Nuclear Information System (INIS)

Koedooder, C.

1986-01-01

This thesis describes experimental and theoretical aspects of dose reduction by x-ray beam filtration in screen-film radiography. The thesis deals mainly with dose reduction under the constraint of constant image quality; an analytical approach is chosen. Therefore, part of the thesis deals with the development of an algorithm to calculate patient dose and exposure for different filter materials and different tube load conditions, under the constraint of constant contrast and constant optical density. (Auth.)

Utilizing placebo mechanisms for dose reduction in pharmacotherapy.

Science.gov (United States)

Doering, Bettina K; Rief, Winfried

2012-03-01

The knowledge and systematic application of the placebo effect remains limited, although its importance to the treatment of various medical conditions has increasingly been recognized. A possible application of the placebo effect to pharmacotherapy is seen in conditioning processes that aim at a placebo-controlled dose reduction of drugs while maintaining the efficacy of the medical treatment. The pairing of a placebo and a pharmacological agent may achieve satisfactory treatment outcomes in combination with a lower dose of medication. This procedure includes classic and instrumental conditioning processes that involve both conscious and non-conscious information processing. Although recent studies have gathered preliminary evidence for the efficacy of placebo-controlled dose reduction (e.g. in psoriasis and attention deficit hyperactivity disorder [ADHD]), they have also illustrated the difficulties that are inherent to this approach. We critically review previous approaches and discuss designs for clinical trials that seem appropriate to the investigation of conditioned placebo effects in pharmacotherapy. Copyright © 2011 Elsevier Ltd. All rights reserved.

Practical methods of dose reduction to the bladder wall

International Nuclear Information System (INIS)

Smith, E.M.; Warner, G.G.

1976-01-01

The radiation dose to the bladder wall following the administration of radionuclides to patients can be reduced by a factor between 25 percent and 75 percent when the effective half-life for the radioactivity entering the urine is two hours or less. A significant but smaller reduction in dose to the gonads may also be achieved in situations where the major fraction of the administered activity is rapidly excreted in the urine. This reduction in dose is achieved by ensuring that the patient has between 50 and 150 ml of urine in his bladder when the radioactivity is injected, and is encouraged to void between one and two hours after the activity has been administered. The interrelationship of voiding schedule, effective half-life, initial urine volume, and demand urination has been analyzed in these studies. In addition, the significance of the rate of urine production and volume of urine in the bladder on the radiation dose to the bladder is demonstrated

Method for simulating dose reduction in digital mammography using the Anscombe transformation

OpenAIRE

Borges, Lucas R.; de Oliveira, Helder C. R.; Nunes, Polyana F.; Bakic, Predrag R.; Maidment, Andrew D. A.; Vieira, Marcelo A. C.

2016-01-01

Purpose: This work proposes an accurate method for simulating dose reduction in digital mammography starting from a clinical image acquired with a standard dose. Methods: The method developed in this work consists of scaling a mammogram acquired at the standard radiation dose and adding signal-dependent noise. The algorithm accounts for specific issues relevant in digital mammography images, such as anisotropic noise, spatial variations in pixel gain, and the effect of dose reduction on the d...

Gonadal dose reduction in lumbar spine radiography

International Nuclear Information System (INIS)

Moilanen, A.; Kokko, M.L.; Pitkaenen, M.

1983-01-01

Different ways to minimize the gonadal dose in lumbar spine radiography have been studied. Two hundred and fifty lumbar spine radiographs were reviewed to assess the clinical need for lateral L5/S1 projection. Modern film/screen combinations and gonadal shielding of externally scattered radiation play a major role in the reduction of the genetic dose. The number of exposures should be minimized. Our results show that two projections, anteroposterior (AP) and lateral, appear to be sufficient in routine radiography of the lumbar spine. (orig.)

Dose reduction using a dynamic, piecewise-linear attenuator

Energy Technology Data Exchange (ETDEWEB)

Hsieh, Scott S., E-mail: sshsieh@stanford.edu [Department of Radiology, Stanford University, Stanford, California 94305 and Department of Electrical Engineering, Stanford University, Stanford, California 94305 (United States); Fleischmann, Dominik [Department of Radiology, Stanford University, Stanford, California 94305 (United States); Pelc, Norbert J. [Department of Radiology, Stanford University, Stanford, California 94305 and Department of Bioengineering, Stanford University, Stanford, California 94305 (United States)

2014-02-15

Purpose: The authors recently proposed a dynamic, prepatient x-ray attenuator capable of producing a piecewise-linear attenuation profile customized to each patient and viewing angle. This attenuator was intended to reduce scatter-to-primary ratio (SPR), dynamic range, and dose by redistributing flux. In this work the authors tested the ability of the attenuator to reduce dose and SPR in simulations. Methods: The authors selected four clinical applications, including routine full field-of-view scans of the thorax and abdomen, and targeted reconstruction tasks for an abdominal aortic aneurysm and the pancreas. Raw data were estimated by forward projection of the image volume datasets. The dynamic attenuator was controlled to reduce dose while maintaining peak variance by solving a convex optimization problem, assuminga priori knowledge of the patient anatomy. In targeted reconstruction tasks, the noise in specific regions was given increased weighting. A system with a standard attenuator (or “bowtie filter”) was used as a reference, and used either convex optimized tube current modulation (TCM) or a standard TCM heuristic. The noise of the scan was determined analytically while the dose was estimated using Monte Carlo simulations. Scatter was also estimated using Monte Carlo simulations. The sensitivity of the dynamic attenuator to patient centering was also examined by shifting the abdomen in 2 cm intervals. Results: Compared to a reference system with optimized TCM, use of the dynamic attenuator reduced dose by about 30% in routine scans and 50% in targeted scans. Compared to the TCM heuristics which are typically used withouta priori knowledge, the dose reduction is about 50% for routine scans. The dynamic attenuator gives the ability to redistribute noise and variance and produces more uniform noise profiles than systems with a conventional bowtie filter. The SPR was also modestly reduced by 10% in the thorax and 24% in the abdomen. Imaging with the dynamic

SU-F-T-441: Dose Calculation Accuracy in CT Images Reconstructed with Artifact Reduction Algorithm

Energy Technology Data Exchange (ETDEWEB)

Ng, C; Chan, S; Lee, F; Ngan, R [Queen Elizabeth Hospital (Hong Kong); Lee, V [University of Hong Kong, Hong Kong, HK (Hong Kong)

2016-06-15

Purpose: Accuracy of radiotherapy dose calculation in patients with surgical implants is complicated by two factors. First is the accuracy of CT number, second is the dose calculation accuracy. We compared measured dose with dose calculated on CT images reconstructed with FBP and an artifact reduction algorithm (OMAR, Philips) for a phantom with high density inserts. Dose calculation were done with Varian AAA and AcurosXB. Methods: A phantom was constructed with solid water in which 2 titanium or stainless steel rods could be inserted. The phantom was scanned with the Philips Brillance Big Bore CT. Image reconstruction was done with FBP and OMAR. Two 6 MV single field photon plans were constructed for each phantom. Radiochromic films were placed at different locations to measure the dose deposited. One plan has normal incidence on the titanium/steel rods. In the second plan, the beam is at almost glancing incidence on the metal rods. Measurements were then compared with dose calculated with AAA and AcurosXB. Results: The use of OMAR images slightly improved the dose calculation accuracy. The agreement between measured and calculated dose was best with AXB and image reconstructed with OMAR. Dose calculated on titanium phantom has better agreement with measurement. Large discrepancies were seen at points directly above and below the high density inserts. Both AAA and AXB underestimated the dose directly above the metal surface, while overestimated the dose below the metal surface. Doses measured downstream of metal were all within 3% of calculated values. Conclusion: When doing treatment planning for patients with metal implants, care must be taken to acquire correct CT images to improve dose calculation accuracy. Moreover, great discrepancies in measured and calculated dose were observed at metal/tissue interface. Care must be taken in estimating the dose in critical structures that come into contact with metals.

Dose reduction and cost-benefit analysis at Japan's Tokai No. 2 Plant

International Nuclear Information System (INIS)

Humamoto, Hisao; Suzuki, Seishiro; Taniguchi, Kazufumi

1995-01-01

In the Tokai No. 2 power plant of the Japan Atomic Power Company, about 80% of the annual dose equivalent is received during periodic maintenance outages. A project group for dose reduction was organized at the company's headquarters in 1986; in 1988, they proposed a five-year program to reduce by half the collective dose of 4 person-Sv per normal outage work. To achieve the target dose value, some dose-reduction measures were undertaken, namely, permanent radiation shielding, decontamination, automatic, operating machines, and ALARA organization. As the result, the collective dose from normal outage work was 1.6 person-Sv in 1992, which was less than the initial target value

Field experience on Zn injection on PWR plants with a view to dose rate reduction

International Nuclear Information System (INIS)

Roumiguiere, F.

2005-01-01

Operating experience acquired at PWR plants shows that zinc injection in the primary coolant at low concentration (∼5 ppb) is a very effective tool to achieve a reduction of the dose rate build-up. The beneficial effect of zinc consists on improving the protective layer characteristics of the reactor coolant system surfaces, which results in a lower pickup of activated products (Co-60, Co-58), and consequently a reduction of the associated dose rates. Zinc injection was introduced at the Unit B of the Biblis Power Station in September 1996 and at the Obrigheim Nuclear Power Station in February 1998, as a measure for reduction of radiation fields. The effectiveness of the method and its compatibility with the overall plant was examined in a rather comprehensive surveillance program at these plants. The already published data show that zinc injection did not lead to any operating restrictions or other negative effects on plants systems and components. Zinc injection is still being implemented today at these plants. Zinc injection is considered today as a mature technique and is now being successfully applied at a number of PWRs in Germany, Brazil, USA and Japan, with the support of Framatome-ANP. Several PWRs in Europe and Asia are preparing for zinc chemistry in the near future. The method is inexpensive and easy to apply. Its implementation is highly advisable in terms of the cost/benefit criterion following the ALARA principle. This paper gives an overview of the experience gathered with the method. The main subject addressed by the paper is the evolution of dose rates at the primary system and work-related doses since introduction of the method. In German PWRs with Incoloy 800 steam generator tubing material (Ni-content ∼32%), the observed reductions correspond to a decrease in dose rates of around 10 to 15% per year following, as predicted, the half-life time of 60 Co. Overall reductions in high radiation areas are now in the range of 50% after 5 years of

Proceedings of an international workshop on historic dose experience and dose reduction (ALARA) at nuclear power plants

International Nuclear Information System (INIS)

Horan, J.R.; Baum, J.W.; Dionne, B.J.

1985-06-01

Dose reduction data and experience from 28 foreign and 10 US nuclear power plants was examined to determine causes for the wide variations in occupational dose from country to country. Major topics discussed were: steam generator and refueling maintenance problems; utility and supplier ALARA programs; effectiveness of dose-reduction modifications; attitudes and training; current and future dose-reduction research. While many parameters contribute to differences of occupational doses between plants from different nations, it is clear that most US plants have higher collective dose equivalent per reactor per megawatt-year than most other countries, even for plants of similar size and age. Worldwide, Finnish and Swedish plants, both PWR and BWR, have achieved the lowest values. Major factors which contribute to low doses include: (1) minimization of cobalt in primary system components exposed to water; (2) careful plant design, layout and component segregation and shielding; (3) plant standardization; (4) selection of components and systems for increased reliability; (5) management interest and commitment; (6) minimum number of workers and in-depth worker training; (7) careful control of primary system oxygen and pH; (8) good primary system water purity to minimize corrosion product formation; (9) use of special tools and robotics; (10) decontamination and passivation of primary systems and components; and (11) extent of backfitting and mandated inspections

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

International Nuclear Information System (INIS)

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

2016-01-01

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

Determinants to dose reduction in EMCCR - in regulatory perspective

International Nuclear Information System (INIS)

Mohan, V.; Venkataraman, S.; Venkataraman, R.; Sajeev, B.S.

2006-01-01

Indian PHWRs had experienced three en masse coolant channel replacement campaigns, (EMCCR) first in RAPS-2, next in MAPS-2 and the last in MAPS-1. The campaign is already in full swing at NAPS-1. At MAPS, two EMCCR campaigns were done in a span of four years. The collective dose consumption in the MAPS-1 campaign was only about 25 % that of MAPS-2, a commendable achievement. Based on the experience of RAPS-2 and MAPS-2 campaigns, AERB - through several regulatory means- had given directives for reduction in collective dose in MAPS-1 campaign which was successfully implemented. This paper analyses and quantifies the key factors that contributed to collective dose reduction in MAPS-1 EMCCR. These factors could be put to use in the on going NAPS and forthcoming KAPS campaigns. (author)

Objective assessment of image quality and dose reduction in CT iterative reconstruction

Energy Technology Data Exchange (ETDEWEB)

Vaishnav, J. Y., E-mail: jay.vaishnav@fda.hhs.gov; Jung, W. C. [Diagnostic X-Ray Systems Branch, Office of In Vitro Diagnostic Devices and Radiological Health, Center for Devices and Radiological Health, United States Food and Drug Administration, 10903 New Hampshire Avenue, Silver Spring, Maryland 20993 (United States); Popescu, L. M.; Zeng, R.; Myers, K. J. [Division of Imaging and Applied Mathematics, Office of Science and Engineering Laboratories, Center for Devices and Radiological Health, United States Food and Drug Administration, 10903 New Hampshire Avenue, Silver Spring, Maryland 20993 (United States)

2014-07-15

Purpose: Iterative reconstruction (IR) algorithms have the potential to reduce radiation dose in CT diagnostic imaging. As these algorithms become available on the market, a standardizable method of quantifying the dose reduction that a particular IR method can achieve would be valuable. Such a method would assist manufacturers in making promotional claims about dose reduction, buyers in comparing different devices, physicists in independently validating the claims, and the United States Food and Drug Administration in regulating the labeling of CT devices. However, the nonlinear nature of commercially available IR algorithms poses challenges to objectively assessing image quality, a necessary step in establishing the amount of dose reduction that a given IR algorithm can achieve without compromising that image quality. This review paper seeks to consolidate information relevant to objectively assessing the quality of CT IR images, and thereby measuring the level of dose reduction that a given IR algorithm can achieve. Methods: The authors discuss task-based methods for assessing the quality of CT IR images and evaluating dose reduction. Results: The authors explain and review recent literature on signal detection and localization tasks in CT IR image quality assessment, the design of an appropriate phantom for these tasks, possible choices of observers (including human and model observers), and methods of evaluating observer performance. Conclusions: Standardizing the measurement of dose reduction is a problem of broad interest to the CT community and to public health. A necessary step in the process is the objective assessment of CT image quality, for which various task-based methods may be suitable. This paper attempts to consolidate recent literature that is relevant to the development and implementation of task-based methods for the assessment of CT IR image quality.

Objective assessment of image quality and dose reduction in CT iterative reconstruction

International Nuclear Information System (INIS)

Vaishnav, J. Y.; Jung, W. C.; Popescu, L. M.; Zeng, R.; Myers, K. J.

2014-01-01

Purpose: Iterative reconstruction (IR) algorithms have the potential to reduce radiation dose in CT diagnostic imaging. As these algorithms become available on the market, a standardizable method of quantifying the dose reduction that a particular IR method can achieve would be valuable. Such a method would assist manufacturers in making promotional claims about dose reduction, buyers in comparing different devices, physicists in independently validating the claims, and the United States Food and Drug Administration in regulating the labeling of CT devices. However, the nonlinear nature of commercially available IR algorithms poses challenges to objectively assessing image quality, a necessary step in establishing the amount of dose reduction that a given IR algorithm can achieve without compromising that image quality. This review paper seeks to consolidate information relevant to objectively assessing the quality of CT IR images, and thereby measuring the level of dose reduction that a given IR algorithm can achieve. Methods: The authors discuss task-based methods for assessing the quality of CT IR images and evaluating dose reduction. Results: The authors explain and review recent literature on signal detection and localization tasks in CT IR image quality assessment, the design of an appropriate phantom for these tasks, possible choices of observers (including human and model observers), and methods of evaluating observer performance. Conclusions: Standardizing the measurement of dose reduction is a problem of broad interest to the CT community and to public health. A necessary step in the process is the objective assessment of CT image quality, for which various task-based methods may be suitable. This paper attempts to consolidate recent literature that is relevant to the development and implementation of task-based methods for the assessment of CT IR image quality

Comparison of image quality in head CT studies with different dose-reduction strategies

DEFF Research Database (Denmark)

Johansen, Jeppe; Nielsen, Rikke; Fink-Jensen, Vibeke

The number of multi-detector CT examinations is increasing rapidly. They allow high quality reformatted images providing accurate and precise diagnosis at maximum speed. Brain examinations are the most commonly requested studies, and although they come at a lower effective dose than body CT, can...... account to a considerable radiation dose as many patients undergo repeated studies. Therefore, various dose-reduction strategies are applied such as automated tube current and voltage modulation and recently different iterative reconstruction algorithms. However, the trade-off of all dose......-reduction maneuvers is reduction of image quality due to image noise or artifacts. The aim of our study was therefore to find the best diagnostic images with lowest possible dose. We present results of dose- and image quality optimizing strategies of brain CT examinations at our institution. We compare sequential...

Paediatric x-ray radiation dose reduction and image quality analysis.

Science.gov (United States)

Martin, L; Ruddlesden, R; Makepeace, C; Robinson, L; Mistry, T; Starritt, H

2013-09-01

Collaboration of multiple staff groups has resulted in significant reduction in the risk of radiation-induced cancer from radiographic x-ray exposure during childhood. In this study at an acute NHS hospital trust, a preliminary audit identified initial exposure factors. These were compared with European and UK guidance, leading to the introduction of new factors that were in compliance with European guidance on x-ray tube potentials. Image quality was assessed using standard anatomical criteria scoring, and visual grading characteristics analysis assessed the impact on image quality of changes in exposure factors. This analysis determined the acceptability of gradual radiation dose reduction below the European and UK guidance levels. Chest and pelvis exposures were optimised, achieving dose reduction for each age group, with 7%-55% decrease in critical organ dose. Clinicians confirmed diagnostic image quality throughout the iterative process. Analysis of images acquired with preliminary and final exposure factors indicated an average visual grading analysis result of 0.5, demonstrating equivalent image quality. The optimisation process and final radiation doses are reported for Carestream computed radiography to aid other hospitals in minimising radiation risks to children.

Paediatric x-ray radiation dose reduction and image quality analysis

International Nuclear Information System (INIS)

Martin, L; Ruddlesden, R; Mistry, T; Starritt, H; Makepeace, C; Robinson, L

2013-01-01

Collaboration of multiple staff groups has resulted in significant reduction in the risk of radiation-induced cancer from radiographic x-ray exposure during childhood. In this study at an acute NHS hospital trust, a preliminary audit identified initial exposure factors. These were compared with European and UK guidance, leading to the introduction of new factors that were in compliance with European guidance on x-ray tube potentials. Image quality was assessed using standard anatomical criteria scoring, and visual grading characteristics analysis assessed the impact on image quality of changes in exposure factors. This analysis determined the acceptability of gradual radiation dose reduction below the European and UK guidance levels. Chest and pelvis exposures were optimised, achieving dose reduction for each age group, with 7%–55% decrease in critical organ dose. Clinicians confirmed diagnostic image quality throughout the iterative process. Analysis of images acquired with preliminary and final exposure factors indicated an average visual grading analysis result of 0.5, demonstrating equivalent image quality. The optimisation process and final radiation doses are reported for Carestream computed radiography to aid other hospitals in minimising radiation risks to children. (paper)

Analysis of Cumulative Dose to Implanted Pacemaker According to Various IMRT Delivery Methods: Optimal Dose Delivery Versus Dose Reduction Strategy

Energy Technology Data Exchange (ETDEWEB)

Lee, Jeong Woo; Hong, Se Mie [Dept. of Radiation Oncology, Konkuk University Medical Center, Seoul (Korea, Republic of)

2011-11-15

Cancer patients with implanted cardiac pacemaker occasionally require radiotherapy. Pacemaker may be damaged or malfunction during radiotherapy due to ionizing radiation or electromagnetic interference. Although radiotherapy should be planned to keep the dose to pacemaker as low as possible not to malfunction ideally, current radiation treatment planning (RTP) system does not accurately calculate deposited dose to adjacent field border or area beyond irradiated fields. In terms of beam delivery techniques using multiple intensity modulated fields, dosimetric effect of scattered radiation in high energy photon beams is required to be detailed analyzed based on measurement data. The aim of this study is to evaluate dose discrepancies of pacemaker in a RTP system as compared to measured doses. We also designed dose reduction strategy limited value of 2 Gy for radiation treatment patients with cardiac implanted pacemaker. Total accumulated dose of 145 cGy based on in-vivo dosimetry was satisfied with the recommendation criteria to prevent malfunction of pacemaker in SS technique. However, the 2 mm lead shielder enabled the scattered doses to reduce up to 60% and 40% in the patient and the phantom, respectively. The SS technique with the lead shielding could reduce the accumulated scattered doses less than 100 cGy. Calculated and measured doses were not greatly affected by the beam delivery techniques. In-vivo and measured doses on pacemaker position showed critical dose discrepancies reaching up to 4 times as compared to planned doses in RTP. The current SS technique could deliver lower scattered doses than recommendation criteria, but use of 2 mm lead shielder contributed to reduce scattered doses by 60%. The tertiary lead shielder can be useful to prevent malfunction or electrical damage of implanted pacemakers during radiotherapy. It is required to estimate more accurate scattered doses of the patient or medical device in RTP to design proper dose reduction strategy.

Analysis of Cumulative Dose to Implanted Pacemaker According to Various IMRT Delivery Methods: Optimal Dose Delivery Versus Dose Reduction Strategy

International Nuclear Information System (INIS)

Lee, Jeong Woo; Hong, Se Mie

2011-01-01

Cancer patients with implanted cardiac pacemaker occasionally require radiotherapy. Pacemaker may be damaged or malfunction during radiotherapy due to ionizing radiation or electromagnetic interference. Although radiotherapy should be planned to keep the dose to pacemaker as low as possible not to malfunction ideally, current radiation treatment planning (RTP) system does not accurately calculate deposited dose to adjacent field border or area beyond irradiated fields. In terms of beam delivery techniques using multiple intensity modulated fields, dosimetric effect of scattered radiation in high energy photon beams is required to be detailed analyzed based on measurement data. The aim of this study is to evaluate dose discrepancies of pacemaker in a RTP system as compared to measured doses. We also designed dose reduction strategy limited value of 2 Gy for radiation treatment patients with cardiac implanted pacemaker. Total accumulated dose of 145 cGy based on in-vivo dosimetry was satisfied with the recommendation criteria to prevent malfunction of pacemaker in SS technique. However, the 2 mm lead shielder enabled the scattered doses to reduce up to 60% and 40% in the patient and the phantom, respectively. The SS technique with the lead shielding could reduce the accumulated scattered doses less than 100 cGy. Calculated and measured doses were not greatly affected by the beam delivery techniques. In-vivo and measured doses on pacemaker position showed critical dose discrepancies reaching up to 4 times as compared to planned doses in RTP. The current SS technique could deliver lower scattered doses than recommendation criteria, but use of 2 mm lead shielder contributed to reduce scattered doses by 60%. The tertiary lead shielder can be useful to prevent malfunction or electrical damage of implanted pacemakers during radiotherapy. It is required to estimate more accurate scattered doses of the patient or medical device in RTP to design proper dose reduction strategy.

Measurements of dose on build-up region, surface dose and outlet dose by a 10 MeV Linear accelerator

International Nuclear Information System (INIS)

Souza, C.N. de; Khoury, H.J.

1987-01-01

The dose on buildup region and the surface dose for a 10 MeV photon beam from a linear acelerator (Mevatrom-74, Siemens) is studied. The influence of the tray of polycarbonate on the surface dose is determined. (M.A.C.) [pt

TMI-2 [Three Mile Island Unit 2] reactor building dose reduction task force

International Nuclear Information System (INIS)

Daniels, R.S.

1988-01-01

In late October 1982, the director of Three Mile Island Unit 2 (TMI-2) created the dose reduction task force with the objective of identifying the principal radiological sources in the reactor building and recommending actions to minimize the dose to workers on labor-intensive projects. Members of the task force were drawn form various groups at TMI. Findings and recommendations were presented to the US Nuclear Regulatory Commission in a briefing on November 18, 1982. The task force developed a three-step approach toward dose reduction. Step 1 identified the radiological sources. Step 2 modeled the source and estimated its contribution to the general area dose rates. Step 3 recommended actions to achieve dose reductions consistent with general exposure rate goals

Intussusception reduction: Effect of air vs. liquid enema on radiation dose

Energy Technology Data Exchange (ETDEWEB)

Kaplan, Summer L.; Edgar, J.C.; Anupindi, Sudha A.; Zhu, Xiaowei [The Children' s Hospital of Philadelphia, Department of Radiology, Philadelphia, PA (United States); University of Pennsylvania, Perelman School of Medicine, Philadelphia, PA (United States); Magill, Dennise; Felice, Marc A. [University of Pennsylvania, Environmental Health and Radiation Safety, Philadelphia, PA (United States)

2017-10-15

Both air and radiopaque liquid contrast are used to reduce ileocolic intussusception under fluoroscopy. Some suggest air lowers radiation dose due to shorter procedure times. However, air enema likely lowers radiation dose regardless of fluoroscopy time due to less density over the automatic exposure control cells. We test the hypothesis that air enema reduction of ileocolic intussusception results in lower radiation dose than liquid contrast enema independent of fluoroscopy time. We describe a role for automatic exposure control in this dose difference. We retrospectively evaluated air and liquid intussusception reductions performed on a single digital fluoroscopic unit during a 26-month period. We compared patient age, weight, gender, exam time of day and year, performing radiologist(s), radiographic image acquisitions, grid and magnification use, fluoroscopy time and dose area product. We compared categorical and continuous variables statistically using chi-square and Mann-Whitney U tests, respectively. The mean dose area product was 2.7-fold lower for air enema, 1.3 ± 0.9 dGy.cm{sup 2}, than for liquid, 3.5 ± 2.5 dGy.cm{sup 2} (P<0.005). The mean fluoroscopy time was similar between techniques. The mean dose area product/min was 2.3-fold lower for air, 0.6 ± 0.2 dGy.cm{sup 2}/min, than for liquid, 1.4 ± 0.5 dGy.cm{sup 2}/min (P<0.001). No group differences were identified in other measured dose parameters. Fluoroscopic intussusception reduction using air enema uses less than half the radiation dose of liquid contrast enema. Dose savings are independent of fluoroscopy time and are likely due to automatic exposure control interaction. (orig.)

Method for simulating dose reduction in digital mammography using the Anscombe transformation

Energy Technology Data Exchange (ETDEWEB)

Borges, Lucas R., E-mail: lucas.rodrigues.borges@usp.br; Oliveira, Helder C. R. de; Nunes, Polyana F.; Vieira, Marcelo A. C. [Department of Electrical and Computer Engineering, São Carlos School of Engineering, University of São Paulo, 400 Trabalhador São-Carlense Avenue, São Carlos 13566-590 (Brazil); Bakic, Predrag R.; Maidment, Andrew D. A. [Department of Radiology, Hospital of the University of Pennsylvania, University of Pennsylvania, 3400 Spruce Street, Philadelphia, Pennsylvania 19104 (United States)

2016-06-15

Purpose: This work proposes an accurate method for simulating dose reduction in digital mammography starting from a clinical image acquired with a standard dose. Methods: The method developed in this work consists of scaling a mammogram acquired at the standard radiation dose and adding signal-dependent noise. The algorithm accounts for specific issues relevant in digital mammography images, such as anisotropic noise, spatial variations in pixel gain, and the effect of dose reduction on the detective quantum efficiency. The scaling process takes into account the linearity of the system and the offset of the detector elements. The inserted noise is obtained by acquiring images of a flat-field phantom at the standard radiation dose and at the simulated dose. Using the Anscombe transformation, a relationship is created between the calculated noise mask and the scaled image, resulting in a clinical mammogram with the same noise and gray level characteristics as an image acquired at the lower-radiation dose. Results: The performance of the proposed algorithm was validated using real images acquired with an anthropomorphic breast phantom at four different doses, with five exposures for each dose and 256 nonoverlapping ROIs extracted from each image and with uniform images. The authors simulated lower-dose images and compared these with the real images. The authors evaluated the similarity between the normalized noise power spectrum (NNPS) and power spectrum (PS) of simulated images and real images acquired with the same dose. The maximum relative error was less than 2.5% for every ROI. The added noise was also evaluated by measuring the local variance in the real and simulated images. The relative average error for the local variance was smaller than 1%. Conclusions: A new method is proposed for simulating dose reduction in clinical mammograms. In this method, the dependency between image noise and image signal is addressed using a novel application of the Anscombe

Method for simulating dose reduction in digital mammography using the Anscombe transformation.

Science.gov (United States)

Borges, Lucas R; Oliveira, Helder C R de; Nunes, Polyana F; Bakic, Predrag R; Maidment, Andrew D A; Vieira, Marcelo A C

2016-06-01

This work proposes an accurate method for simulating dose reduction in digital mammography starting from a clinical image acquired with a standard dose. The method developed in this work consists of scaling a mammogram acquired at the standard radiation dose and adding signal-dependent noise. The algorithm accounts for specific issues relevant in digital mammography images, such as anisotropic noise, spatial variations in pixel gain, and the effect of dose reduction on the detective quantum efficiency. The scaling process takes into account the linearity of the system and the offset of the detector elements. The inserted noise is obtained by acquiring images of a flat-field phantom at the standard radiation dose and at the simulated dose. Using the Anscombe transformation, a relationship is created between the calculated noise mask and the scaled image, resulting in a clinical mammogram with the same noise and gray level characteristics as an image acquired at the lower-radiation dose. The performance of the proposed algorithm was validated using real images acquired with an anthropomorphic breast phantom at four different doses, with five exposures for each dose and 256 nonoverlapping ROIs extracted from each image and with uniform images. The authors simulated lower-dose images and compared these with the real images. The authors evaluated the similarity between the normalized noise power spectrum (NNPS) and power spectrum (PS) of simulated images and real images acquired with the same dose. The maximum relative error was less than 2.5% for every ROI. The added noise was also evaluated by measuring the local variance in the real and simulated images. The relative average error for the local variance was smaller than 1%. A new method is proposed for simulating dose reduction in clinical mammograms. In this method, the dependency between image noise and image signal is addressed using a novel application of the Anscombe transformation. NNPS, PS, and local noise

Method for simulating dose reduction in digital mammography using the Anscombe transformation

International Nuclear Information System (INIS)

Borges, Lucas R.; Oliveira, Helder C. R. de; Nunes, Polyana F.; Vieira, Marcelo A. C.; Bakic, Predrag R.; Maidment, Andrew D. A.

2016-01-01

Purpose: This work proposes an accurate method for simulating dose reduction in digital mammography starting from a clinical image acquired with a standard dose. Methods: The method developed in this work consists of scaling a mammogram acquired at the standard radiation dose and adding signal-dependent noise. The algorithm accounts for specific issues relevant in digital mammography images, such as anisotropic noise, spatial variations in pixel gain, and the effect of dose reduction on the detective quantum efficiency. The scaling process takes into account the linearity of the system and the offset of the detector elements. The inserted noise is obtained by acquiring images of a flat-field phantom at the standard radiation dose and at the simulated dose. Using the Anscombe transformation, a relationship is created between the calculated noise mask and the scaled image, resulting in a clinical mammogram with the same noise and gray level characteristics as an image acquired at the lower-radiation dose. Results: The performance of the proposed algorithm was validated using real images acquired with an anthropomorphic breast phantom at four different doses, with five exposures for each dose and 256 nonoverlapping ROIs extracted from each image and with uniform images. The authors simulated lower-dose images and compared these with the real images. The authors evaluated the similarity between the normalized noise power spectrum (NNPS) and power spectrum (PS) of simulated images and real images acquired with the same dose. The maximum relative error was less than 2.5% for every ROI. The added noise was also evaluated by measuring the local variance in the real and simulated images. The relative average error for the local variance was smaller than 1%. Conclusions: A new method is proposed for simulating dose reduction in clinical mammograms. In this method, the dependency between image noise and image signal is addressed using a novel application of the Anscombe

The benefit of accounting for DQE variations in simulated dose reduction of digital radiographic systems

International Nuclear Information System (INIS)

Svalkvist, A.; Baath, M.

2010-01-01

Adding noise to clinical radiographs to simulate dose reduction can be used to investigate the relationship between dose level and clinical image quality without exposing patients to additional radiation. The purpose of the present paper was to examine the benefits of using a method that accounts for detective quantum efficiency (DQE) variations that may occur in different dose ranges in the simulated dose reduction process. A method initially intended for simulated dose reduction in tomo-synthesis was applied to extremely low-dose posterio-anterior radiographs of an anthropomorphic chest phantom, selected from a group of projection images included in a tomo-synthesis examination and compared with a previous method that do not account for DQE variations. A comparison of images simulated to be collected at a lower dose level (73% of the original dose level) and images actually collected at this lower dose level revealed that the error in the integrated normalised noise power spectrum was smaller than 4% for the method that accounts for DQE variations in the simulated dose reduction, whereas the error was larger than 20% for the previous method. This indicates that an increased validity in dose reduction simulation of digital radiographic systems is obtained with a method accounting for DQE variations. (authors)

Radiation doses in diagnostic radiology and methods for dose reduction. Report of a co-ordinated research programme (1991-1993)

Energy Technology Data Exchange (ETDEWEB)

NONE

1995-04-01

It is well recognized that diagnostic radiology is the largest contributor to the collective dose from all man-made sources of radiation. Large differences in radiation doses from the same procedures among different X ray rooms have led to the conclusion that there is a potential for dose reduction. A Co-ordinated Research Programme on Radiation Doses in Diagnostic Radiology and Methods for Dose Reduction, involving Member States with different degrees of development, was launched by the IAEA in co-operation with the CEC. This report summarizes the results of the second and final Research Co-ordination Meeting held in Vienna from 4 to 8 October 1993. 22 refs, 6 figs and tabs.

Radiation doses in diagnostic radiology and methods for dose reduction. Report of a co-ordinated research programme (1991-1993)

International Nuclear Information System (INIS)

1995-04-01

It is well recognized that diagnostic radiology is the largest contributor to the collective dose from all man-made sources of radiation. Large differences in radiation doses from the same procedures among different X ray rooms have led to the conclusion that there is a potential for dose reduction. A Co-ordinated Research Programme on Radiation Doses in Diagnostic Radiology and Methods for Dose Reduction, involving Member States with different degrees of development, was launched by the IAEA in co-operation with the CEC. This report summarizes the results of the second and final Research Co-ordination Meeting held in Vienna from 4 to 8 October 1993. 22 refs, 6 figs and tabs

Effective dose at pneumatic reduction of paediatric intussusception

International Nuclear Information System (INIS)

Heenan, S.D.; Kyriou, J.; Fitzgerald, M.; Adam, E.J.

2000-01-01

AIM: The purpose of this study was to assess screening times and resulting dose implication at pneumatic reduction of intussusception in the paediatric age group and to examine the relationship with the outcome of the procedure. MATERIALS AND METHODS: We retrospectively reviewed the case notes and departmental records of 143 children who had undergone a total of 153 pneumatic reductions in our department over a 4-year period. Success rates, screening times and available dose-area products (DAP) were recorded. The DAPs were converted to effective dose (ED) for 77 procedures. RESULTS: A 76.5% (117/153) success rate was achieved with a recurrence rate of 6.5% and only one complication: a perforation. Screening times were recorded in 137 reductions and ranged from 15 s to 22.6 min. Although the longest screening time was associated with an unsuccessful outcome, the second longest time of 21 min was successful. This gave a DAP of 1278 cGy cm 2 and an ED of 12.73 mSv, which is equivalent to approximately 400 abdominal films for a 1-year-old. A lifetime risk of fatal cancer of one in 1000 was achieved, assuming the worst case, after a screening time of 30 min on our conventional fluoroscopy unit. CONCLUSION: Our success rate compares well with other centres. Our institution is a tertiary referral centre and the occasional long screening time may reflect the delay and complex nature of the patients referred. Persistence at air reduction may be successful and the success rate increases with delayed attempts but the risks of the increasing radiation burden must be weighed against the risks of emergency surgery and anaesthesia. Heenan, S.D. (2000)

Planning of occupational dose reduction at BWR power plant by past dose record analysis combined with on-site workers' idea analysis

International Nuclear Information System (INIS)

Konno, T.; Taira, J.; Hayashida, T.; Suzuki, A.; Hayashi, K.; Kato, S.; Ishikawa, T.; Konno, T.; Hayashi, K.

2011-01-01

In order to establish a plan for occupational dose reduction at operating plants, outage inspection works that involve high-dose exposure were selected and a determination of the major causes of high-dose exposure made by plant-by-plant comparison of doses received during inspection works. The comparison was made to investigate the relationship between exposure and the volume of objects to be inspected, working time and man-hour of each work process and ambient dose rates at work areas. In parallel with this, an analysis has also been carried out on 400 data items in a questionnaire survey conducted on relevant individuals, including foremen, radiation safety personnel, on-site workers and plant designers regarding ideas for dose reduction methods. With combination of these two analyses, matters that require improvement will be highlighted, then modification of equipment or revision of work procedures necessary for occupational dose reduction will be planned by plant designers through review. (authors)

Generative Adversarial Networks for Noise Reduction in Low-Dose CT.

Science.gov (United States)

Wolterink, Jelmer M; Leiner, Tim; Viergever, Max A; Isgum, Ivana

2017-12-01

Noise is inherent to low-dose CT acquisition. We propose to train a convolutional neural network (CNN) jointly with an adversarial CNN to estimate routine-dose CT images from low-dose CT images and hence reduce noise. A generator CNN was trained to transform low-dose CT images into routine-dose CT images using voxelwise loss minimization. An adversarial discriminator CNN was simultaneously trained to distinguish the output of the generator from routine-dose CT images. The performance of this discriminator was used as an adversarial loss for the generator. Experiments were performed using CT images of an anthropomorphic phantom containing calcium inserts, as well as patient non-contrast-enhanced cardiac CT images. The phantom and patients were scanned at 20% and 100% routine clinical dose. Three training strategies were compared: the first used only voxelwise loss, the second combined voxelwise loss and adversarial loss, and the third used only adversarial loss. The results showed that training with only voxelwise loss resulted in the highest peak signal-to-noise ratio with respect to reference routine-dose images. However, CNNs trained with adversarial loss captured image statistics of routine-dose images better. Noise reduction improved quantification of low-density calcified inserts in phantom CT images and allowed coronary calcium scoring in low-dose patient CT images with high noise levels. Testing took less than 10 s per CT volume. CNN-based low-dose CT noise reduction in the image domain is feasible. Training with an adversarial network improves the CNNs ability to generate images with an appearance similar to that of reference routine-dose CT images.

Dose and dose reduction in computed tomography; Dosis und Dosisreduktion in der Computertomografie

Energy Technology Data Exchange (ETDEWEB)

Lell, Michael [Klinikum Nuernberg (Germany). Inst. fuer Radiologie und Nuklearmedizin; Paracelsus Medical Univ. Nuernberg (Germany); Wucherer, Michael [Klinikum Nuernberg (Germany). Inst. fuer Medizinische Physik; Kachelriess, Marc [Deutsches Krebsforschungszentrum (DKFZ), Heidelberg (Germany)

2017-06-15

CT is widely used in medical imaging due to high availability, relatively low cost, and excellent diagnostic yield. Newer applications like coronary CTA, CT colonography, and CT perfusion imaging are integrated in clinical pathways. Although there is a high level of consensus that the benefits of CT exceeds the risks of radiation exposure for appropriate indications, concerns have been raised regarding the potential of cancer induction. Keeping dose as low as reasonably achievable remains the most important task. Dose reduction strategies are presented and discussed.

Dose reduction in pediatric abdominal CT: use of iterative reconstruction techniques across different CT platforms

International Nuclear Information System (INIS)

Khawaja, Ranish Deedar Ali; Singh, Sarabjeet; Otrakji, Alexi; Padole, Atul; Lim, Ruth; Nimkin, Katherine; Westra, Sjirk; Kalra, Mannudeep K.; Gee, Michael S.

2015-01-01

Dose reduction in children undergoing CT scanning is an important priority for the radiology community and public at large. Drawbacks of radiation reduction are increased image noise and artifacts, which can affect image interpretation. Iterative reconstruction techniques have been developed to reduce noise and artifacts from reduced-dose CT examinations, although reconstruction algorithm, magnitude of dose reduction and effects on image quality vary. We review the reconstruction principles, radiation dose potential and effects on image quality of several iterative reconstruction techniques commonly used in clinical settings, including 3-D adaptive iterative dose reduction (AIDR-3D), adaptive statistical iterative reconstruction (ASIR), iDose, sinogram-affirmed iterative reconstruction (SAFIRE) and model-based iterative reconstruction (MBIR). We also discuss clinical applications of iterative reconstruction techniques in pediatric abdominal CT. (orig.)

Dose reduction in pediatric abdominal CT: use of iterative reconstruction techniques across different CT platforms

Energy Technology Data Exchange (ETDEWEB)

Khawaja, Ranish Deedar Ali; Singh, Sarabjeet; Otrakji, Alexi; Padole, Atul; Lim, Ruth; Nimkin, Katherine; Westra, Sjirk; Kalra, Mannudeep K.; Gee, Michael S. [MGH Imaging, Massachusetts General Hospital, Harvard Medical School, Boston, MA (United States)

2015-07-15

Dose reduction in children undergoing CT scanning is an important priority for the radiology community and public at large. Drawbacks of radiation reduction are increased image noise and artifacts, which can affect image interpretation. Iterative reconstruction techniques have been developed to reduce noise and artifacts from reduced-dose CT examinations, although reconstruction algorithm, magnitude of dose reduction and effects on image quality vary. We review the reconstruction principles, radiation dose potential and effects on image quality of several iterative reconstruction techniques commonly used in clinical settings, including 3-D adaptive iterative dose reduction (AIDR-3D), adaptive statistical iterative reconstruction (ASIR), iDose, sinogram-affirmed iterative reconstruction (SAFIRE) and model-based iterative reconstruction (MBIR). We also discuss clinical applications of iterative reconstruction techniques in pediatric abdominal CT. (orig.)

The application of dose-reduction simulation in neonatal head CT scan

International Nuclear Information System (INIS)

Liu Yue; Peng Yun; Zeng Jinjin; Zhang Qifeng; Li Jianying

2009-01-01

Objective: To determine the effects of dose reduction on multi-slice spiral CT (MSCT) of neonatal head and assess the lowest possible radiation for acceptable clinical images. Methods: Fifty-seven newborns suspected intracranial hemorrhage were entered into the study and underwent MSCT scans. Original images at three anatomic levels (posterior fossa, basal ganglia, centrum semiovale) were collected and synthetic noise was added so as to simulate dose reductions of 25%, 40%, 50% and 70%, respectively by using the noise addition tool. A total of 855 image data sets were obtained for the 57 patients. Original and simulated dose-reduction scan images were analyzed. Image noise and image quality were assessed by two independent experienced pediatric radiologists using diagnostic acceptability score, subjective image noise score on a 5-point scale and objective noise index. Image noise was measured by respectively placing region of interest (ROI) at cerebellum, thalamus and corona radiata of 3 different slices. And the noise index and mean value was calculated. The degree of inter-observer concordance was determined by Kappa statistical analysis. The Spearman statistical correlations between the noise index and diagnostic acceptability score were performed. Results: On the images of original dose and simulated dose reductions of 25%, 40%, 50% and 70%, the diagnostic acceptability was 4.47±0.51, 3.96±0.33, 3.21±0.45, 2.92±0.32, and 1.85±0.57, respectively, the subjective image scores were 1.62±0.48, 1.99±0.48, 2.76±0.81, 3.19±0.67, and 4.27±0.54, respectively, the noise index were 1.90±0.19, 2.17±0.20. 2.44± 0.25, 2.68±0.28, and 3.37±0.39, respectively. The two radiologists had good interobserver agreement for diagnostic acceptability (K=0.860, P=0.017) and for image noise scoring(K=0.630, P=0.022). There was significant statistical correlation between image noise index and diagnostic acceptability (r= 0.826,P=0.001). At 40% dose reduction to the standard

Possible radiation dose reduction by using digital X-ray equipment

International Nuclear Information System (INIS)

Horvathova, M.; Nikodemova, D.; Prikazska, M.

2001-01-01

The radiation load of population all over the world from medical examinations clearly demonstrates the importance of the introduction of the quality assurance and quality control programmes into the activities of radiology departments. The basic aim of quality assurance program is to ensure that the radiation dose is kept as low as reasonably practicable while still providing an adequate image quality. As many other fields, the rapid development of techniques brought change-over from the conventional analogue technique to the digital technique. In this process, the conventional X-ray film is being abandoned and images are being viewed on either laser film or monitor. The main advantages of using digital equipment lay in improved image quality and diagnostic accuracy through digital image processing, reduction in patients exposure, cost reduction by reduction of the film usage, more efficient storage and retrieval of radiographic images through picture archiving. Several studies that have been conducted for comparison of various diagnostic examinations show , that there is potential for dose saving in the digital image intensifier technique. The aim of this study was to compare measured values of dose-area product for colon investigations using different X-ray equipment types, two digital and two analogue. Our material consisted of 169 randomly selected patients, 115 of them were examined with digital equipment and 54 patients with the analogue equipment. The obtained results have confirmed the dose reduction and increase of diagnostic accuracy when using the digital equipment, with the added benefit of a good image quality. (authors)

Reduction of doses to staff in a nuclear medicine department

International Nuclear Information System (INIS)

Van Every, B.

1982-01-01

Data relating to the radiation protection of staff working in the Department of Nuclear Medicine, Alfred Hospital, Victoria during the period 1977 to 1981 are examined. No member of staff received more than one tenth of the annual whole body dose limit of 5x10 4 μSv. The reduction in the total whole body dose of staff and in the technologist's individual dose is due to relocating the department, using appropriate radiation monitoring equipment, using a staff roster and making staff aware of previous doses

An epidemiological study for the reduction of population radiation dose

International Nuclear Information System (INIS)

Gamo, Makoto

1989-01-01

The correlation of tube voltage with patient exposure was studied using effective dose as an indicator of dose reduction in intraoral radiography. The results were as follows: l. The salivary gland tissues contributed the most to the effective dose of intraoral radiography. 2. In the 50 to 90 kV range, there was no appreciable correlation between tube voltage and effective dose. 3. Therefore, it was suggested that adjusting the tube voltage for maximum image quality does not effect radiation protection. 4. This study reconfirmed the fact that increases in voltages up to 90 kV reduce skin doses. (author)

Dose reduction in pulsed fluoroscopy by modifying the high-voltage pulse shape

International Nuclear Information System (INIS)

Sabau, M.N.; Phelps, G.

1988-01-01

This paper presents the dose reduction results in pulsed fluoroscopy by modifying the high-voltage pulse shape (HVPS). Since the HVPS in regular pulsed fluoroscopy has a long tail, the radiation pulse shape (RPS) is similar. Using specially designed circuitry in the high-voltage generator to produce a rectangular HVPS, and consequently a rectangular RPS, it was possible to obtain a reduction of up to 25% of patient exposure. This dose reduction obtained by cutting the long tail of RPS does not damage the image quality

Radiochromic film as a radiotherapy surface-dose detector

International Nuclear Information System (INIS)

Butson, M.J.; Metcalfe, P.E.; Wollongong Univ., NSW; Mathur, J.N.

1996-01-01

Radiochromic film is shown to be a useful surface-dose detector for radiotherapy x-ray beams. Central-axis percentage surface-dose results as measured by Gafchromic film for a 6 MVp x-ray beam produced by a Varian 2100C Linac at 100 cm SSD are 16%, 25%, 35%, 41% for 10, 20, 30 and 40 cm square field sizes, respectively. Using a simple, uniform light source and a CCD camera connected to an image analysis system, quantitative 3D surface doses are accurately attainable in real time as either numerical data, a black-and-white image or a colour-enhanced image. (Author)

Dose reduction and cost-benefit analysis at Japan`s Tokai No. 2 Plant

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Humamoto, Hisao; Suzuki, Seishiro; Taniguchi, Kazufumi [Japan Atomic Power Co., Otemachi (Japan)

1995-03-01

In the Tokai No. 2 power plant of the Japan Atomic Power Company, about 80% of the annual dose equivalent is received during periodic maintenance outages. A project group for dose reduction was organized at the company`s headquarters in 1986; in 1988, they proposed a five-year program to reduce by half the collective dose of 4 person-Sv per normal outage work. To achieve the target dose value, some dose-reduction measures were undertaken, namely, permanent radiation shielding, decontamination, automatic, operating machines, and ALARA organization. As the result, the collective dose from normal outage work was 1.6 person-Sv in 1992, which was less than the initial target value.

Review of surface dose detectors in radiotherapy

LENUS (Irish Health Repository)

O'Shea, E.

2006-11-20

Several instruments have been used to measure absorbed radiation dose under non-electronic equilibrium conditions, such as in the build-up region or near the interface between two different media, including the surface. Many of these detectors are discussed in this paper. A common method of measuring the absorbed dose distribution and electron contamination in the build-up region of high-energy beams for radiation therapy is by means of parallel-plate ionisation chambers. Thermoluminescent dosimeters (TLDs), diodes and radiographic film have also been used to obtain surface dose measurements. The diamond detector was used recently by the author in an investigation on the effects of beam-modifying devices on skin dose and it is also described in this report

Multiple cost criteria for occupational dose reduction

International Nuclear Information System (INIS)

James, J.Z.

1983-01-01

This paper describes a simple, feasible procedure for deciding if a proposed dose reduction measure is justified under ALARA, based on engineering economic principles of project feasibility analysis. Particular attention is given to the fixing of cost criteria: the importance of melding disparate objectives into a single parameter, and the distinction between a cost criterion and a cost consideration. (author)

[Examination of patient dose reduction in cardiovasucular X-ray systems with a metal filter].

Science.gov (United States)

Yasuda, Mitsuyoshi; Kato, Kyouichi; Tanabe, Nobuaki; Sakiyama, Koushi; Uchiyama, Yushi; Suzuki, Yoshiaki; Suzuki, Hiroshi; Nakazawa, Yasuo

2012-01-01

In interventional X-ray for cardiology of flat panel digital detector (FPD), the phenomenon that exposure dose was suddenly increased when a subject thickness was thickened was recognized. At that time, variable metal built-in filters in FPD were all off. Therefore, we examined whether dose reduction was possible without affecting a clinical image using metal filter (filter) which we have been conventionally using for dose reduction. About 45% dose reduction was achieved when we measured an exposure dose at 30 cm of acrylic thickness in the presence of a filter. In addition, we measured signal to noise ratio/contrast to noise ratio/a resolution limit by the visual evaluation, and there was no influence by filter usage. In the clinical examination, visual evaluation of image quality of coronary angiography (40 cases) using a 5-point evaluation scale by a physician was performed. As a result, filter usage did not influence the image quality (p=NS). Therefore, reduction of sudden increase of exposure dose was achieved without influencing an image quality by adding filter to FPD.

Initial substantial reduction in air dose rates of Cs origin and personal doses for residents owing to the Fukushima nuclear accident

International Nuclear Information System (INIS)

Yoshida, Hiroko; Saito, Junko; Hirasawa, Noriyasu; Kobayashi, Ikuo

2013-01-01

The initial substantial reduction in the air dose rate and personal dose equivalent [Hp(10)] for residents were compared between the Marumori and Kosugo regions for the period from September 2011 to September 2012 after the occurrence of the Fukushima nuclear accident. Marumori is a rural settlement, and Kosugo is a suburban city along a freeway. A similar tendency was observed in the Hp(10) results for Marumori residents and in the air dose rates for both regions: values dropped during the heavy snow season and a faster reduction in the air dose rate than the radioactive decay of 134 Cs and 137 Cs was observed after the snow had thawed. These reductions are considered to be caused by the weathering and/or migration of radionuclides down the soil column. However, neither a drop due to an accumulation of snow nor faster reduction was observed in Hp(10) for Kosugo residents. This discrepancy between the air dose rate and Hp(10) for Marumori and Kosugo residents might be caused by differences in their living environment. (author)

The need for national diagnostic reference levels: entrance surface dose measurement in intraoral radiography

International Nuclear Information System (INIS)

Mortazavi, S. M. J.; Shareghi, A.; Kavousi, A.; Ghiassi-Nejad, M.; Jafari-Zadeh, M.; Nazeri, F.; Mozdarani, H.

2004-01-01

Background: Intraoral radiographies are the most frequent X-ray examinations in humans. According to International Commission on Radiation Protection recommendations, the selection of a diagnostic reference level should be specific to a country or region. Critical organs such as thyroid gland are exposed to X-rays in intraoral radiography and these exposures should be kept as low as reasonably achievable. To assist the development of DRLs for intraoral radiography, a National Radiation Protection Department-sponsored pilot study was carried out. Materials and methods: thermoluminescent dosimetry is widely acknowledged to be the recommended method for measuring entrance surface doses. In this study, entrance surface doses was measured using LiF thermoluminescent dosimeters on the skin (either mandibular or maxillary arcs) of 40 patients. Three thermoluminescent dosimetry chips were placed on the skin of each patient. The doses were averaged for each radiography and mean entrance surface doses of all patients calculated. Results: the mean ±SD entrance surface dose at the center of the beam on the patient's skin in intraoral radiography was 1.173 ±0.606 mGy (ranged from 0.01 o 0.40 m Gy). The mean entrance surface doses for male and female patients were 1.380± 0.823, and 1.004± 0.258 respectively. No statistically significant difference was found between these means. Despite its necessity , in national level , there is no published data on the diagnostic reference levels for intraoral radiography. However, the results obtained in this study are lower than those reported by investigators in other countries. Conclusion: in IR Iran , due to lack of large scale studies, no diagnostic reference levels have been set for X-ray diagnostic procedures. Due to lack of national diagnostic reference levels, it is not possible to clarify whether in intraoral radiographies any dose reduction techniques are needed. We intend to perform similar nationwide studies to set the

Relationship medical exposure in X-ray diagnosis and loading factor and film/screen system for reduction exposure dose in Aomori. An analysis based on the results of questionnaire

International Nuclear Information System (INIS)

Kon, Masanori; Fukushi, Shouji; Oota, Fumio; Kawamura, Kouji; Shinohe, Tetsuo; Suwa, Kouki; Fujii, Kiyosuke; Yamagami, Hirofumi

2000-01-01

A fact-finding questionnaire survey on medical exposure in Aomori Prefecture was conducted in September 1998. Of the 23 exposed sites in the body investigated, exposure at 17 sites in adults was investigated in terms of the type of high-voltage generator, imaging conditions (X-ray tube voltage, electric current, exposure time, etc.), photosensitive materials and relative photosensitivity, and entrance surface doses. At 6 of the 17 exposed sites, the relationships between these technical conditions and entrance surface doses were analyzed to consider further reduction of medical exposure. The most frequently used high-voltage generators were inverter generators (about 52%). In many institutions, additional filters were utilized for high-voltage imaging of the chest. Highly sensitive green-emission materials were the most frequently used photosensitive materials (73%). These findings indicate that many institutions are attempting to reduce exposure. Entrance surface doses varied greatly among institutions: and a 100-fold difference was observed in exposure to the chest, Martius, and the pelvis. Further efforts to lower entrance surface doses are therefore necessary to reduce medical exposure. Negative correlations were observed between electric voltage, electric current, and exposure time. Examination of the relationships between entrance surface doses, electric current, and exposure time yielded positive correlations. However, the entrance surface doses may not have been properly calculated in some institutions, and examination of the relationship between the relative sensitivity of the sensitive material and entrance surface doses showed great variability in entrance surface doses between institutions. Based on the above results, it is concluded that further reduction of medical exposure is possible, not only by improving the accuracy of X-ray units/devices, but by choosing a more appropriate of conditions to perform radiography. (K.H.)

Dose reduction for snubber inspection and testing

International Nuclear Information System (INIS)

Morrison, G.M.; Cotton, S.R.

1991-01-01

This paper reports that Health physics staff members at Grand Gulf Nuclear Station have implemented several dose reduction methods for snubber inspection, testing and changeout. These methods include construction maps to permit easy location of snubbers in the drywell, painting azimuth numbers on the inside drywell wall and biological shield wall to coincide with the maps, requiring pre-job briefings for quality inspectors and craft support personnel, using job history files for work planning, using experienced inspectors and craft personnel whenever possible, designating certain craft personnel solely for snubber work, and cutting out stuck snubber pins rather than attempting intact removal. The total dose for snubber-related tasks has been significantly reduced using these methods

Evaluation of skin surface dose for head and neck cancer patients treated with intensity-modulated radiation therapy using in vivo dosimetry

International Nuclear Information System (INIS)

Kim, Yeon Sil; Lee, Dong Soo; Yoo, Mi Na; Hong, Joo Young; Yoon, Se Chul; Jang, Hong Suk

2011-01-01

Use of intensity-modulated radiation therapy (IMRT) for head and neck cancer is gradually increasing, because it could facilitate more sophsticated treatment of target volumes and reduction of acute and late sequelae. However, theoretically, there is a potential risk of increased skin surface dose resulting from multiple obliquity effects caused by multiple tangential beams. Moreover, we sometimes confronted with more skin reactions in the patients treated with IMRT than conventional techniques. In this study, we evaluated skin surface dose adjacent to the target volumes to verify whether the use of IMRT would increase the skin dose more than we predicted. This study had shown that the use of IMRT did not increase the skin surface hot point dose. The measured skin surface dose was 20 to 40 percent of the adjacent target prescription dose, and was within acceptable dose range. Our study had some limitations with small number of experimental patients and methodological problems. Potential risk of increasing skin dose with bolus effect of aquaplaster should be examined in the future trials. In addition, the accurate set-up verification should be maintained because of steep dose gradient between skin surface and target volumes within a short distance in the head and neck cancer patients.

Radiation dose reduction in fluoroscopic procedures: left varicocele embolization as a model

Energy Technology Data Exchange (ETDEWEB)

Verstandig, Anthony G.; Shraibman, Vladimir [Shaare Zedek Medical Center, Department of Radiology, Interventional Radiology Unit, POB 3235, Jerusalem (Israel); Shamieh, Bashar [St. Joseph Hospital, Department of Radiology, Jerusalem (Israel); Raveh, David [Shaare Zedek Medical Center, Infectious Diseases Unit, POB 3235, Jerusalem (Israel)

2015-06-01

To investigate the effect of a radiation reduction program on total dose, fluoroscopy dose per second corrected for body habitus and degree of collimation in left varicocele embolizations (LVE). A radiation reduction program for LVE was implemented, consisting of a technique minimizing fluoroscopy time, using low-dose presets, virtual collimation, and virtual patient positioning. Height, weight, fluoroscopy time, kerma area product (KAP) and reference air kerma (Ka,r) were recorded for 100 consecutive cases satisfying the inclusion criteria. For each patient, a device specific dose correction factor, determined using a phantom, was used to standardize the KAP to that of the cylindrical diameter of the standard man and a collimation index was derived from the KAP and Ka,r. Median fluoroscopy time was 3 minutes (mean 4.5, range 1-23.8). Median KAP was 0.54 Gy/cm{sup 2} (mean 0.82, range 0.12-6.52). There was a significant decrease in KAP/second corrected for cylindrical diameter (p < 0.001) and the collimation index (p < 0.001) over time. This study shows that a dedicated dose reduction program can achieve very low total radiation dose rates for LVE. The significant decrease in collimation index and standardized KAP per second during this study suggest a learning curve for collimation. (orig.)

The survey of the surface doses of the dental x-ray machines

International Nuclear Information System (INIS)

Lee, Jae Seo; Kang, Byung Cheol; Yoon, Suk Ja

2005-01-01

The purpose of this study was to investigate variability of doses with same exposure parameters and evaluate radiographic density according to the variability of doses. Twenty-eight MAX-GLS (Shinhung Co, Seoul, Korea), twenty-one D-60-S (DongSeo Med, Seoul, Korea), and eleven REX-601 (Yoshida Dental MFG, Tokyo, Japan) dental x-ray machines were selected for this study. Surface doses were measured under selected combinations of tube voltage, tube current, exposure time, and constant distance 42 cm from the focal spot to the surface of the Multi-O-meter (Unfors Instrument, Billdal, Sweden). Radiographic densities were measured on the films at maximum, minimum and mean surface doses of each brand of x-ray units. With MAX-GLS, the maximum surface doses were thirteen to fourteen times as much as the minimum surfaces doses. With D-60-S, the maximum surface doses were three to eight times as much as the minimum surface doses. With REX-601, the maximum surface doses were six to ten times as much as the minimum surface doses. The differences in radiographic densities among maximum, mean, and minimum doses were significant (p<0.01). The surface exposure doses of each x-ray machine at the same exposure parameters were different within the same manufacturer's machines.

Reduction of doses in the environment of IPEN-CNEN/SP

International Nuclear Information System (INIS)

Rodrigues, D.L.; Sanches, M.P.; Sordi, G.M.A.A.

1997-01-01

According Brazilian legislation, individual dose levels at IPEN-CNEN/SP entitle staff to receive 10% of their base salary as additional health allowance, 20 holidays per semester, and special retirement after 25 years of work. The present work presents estimates of cost due to health allowances and recommends reduction of individual dose levels for staff including non-radiological personnel

Evaluation of the impact of organ-specific dose reduction on image quality in pediatric chest computed tomography

International Nuclear Information System (INIS)

Boos, Johannes; Kroepil, Patric; Klee, Dirk; Heusch, Philipp; Schimmoeller, Lars; Schaper, Joerg; Antoch, Gerald; Lanzman, Rotem S.

2014-01-01

Organ-specific dose reduction significantly reduces the radiation exposure of radiosensitive organs. The purpose of this study was to assess the impact of a novel organ-specific dose reduction algorithm on image quality of pediatric chest CT. We included 28 children (mean age 10.9 ± 4.8 years, range 3-18 years) who had contrast-enhanced chest CT on a 128-row scanner. CT was performed at 100 kV using automated tube current modulation and a novel organ-specific dose-reduction algorithm (XCare trademark; Siemens, Forchheim, Germany). Seven children had a previous chest CT performed on a 64-row scanner at 100 kV without organ-specific dose reduction. Subjective image quality was assessed using a five-point scale (1-not diagnostic; 5-excellent). Contrast-to-noise ratio (CNR) and signal-to-noise ratio (SNR) were assessed in the descending aorta. Overall mean subjective image quality was 4.1 ± 0.6. In the subgroup of the seven children examined both with and without organ-specific dose reduction, subjective image quality was comparable (score 4.4 ± 0.5 with organ-specific dose reduction vs. 4.4 ± 0.7 without it; P > 0.05). There was no significant difference in mean signal-to-noise ratio and contrast-to-noise ratio with organ-specific dose reduction (38.3 ± 10.1 and 28.5 ± 8.7, respectively) and without the reduction (35.5 ± 8.5 and 26.5 ± 7.8, respectively) (P > 0.05). Volume computed tomography dose index (CTDI vol ) and size-specific dose estimates did not differ significantly between acquisitions with the organ-specific dose reduction (1.7 ± 0.8 mGy) and without the reduction (1.7 ± 0.8 mGy) (P > 0.05). Organ-specific dose reduction does not have an impact on image quality of pediatric chest CT and can therefore be used in clinical practice to reduce radiation dose of radiosensitive organs such as breast and thyroid gland. (orig.)

Quantification of acute vocal fold epithelial surface damage with increasing time and magnitude doses of vibration exposure.

Directory of Open Access Journals (Sweden)

Tsuyoshi Kojima

Full Text Available Because the vocal folds undergo repeated trauma during continuous cycles of vibration, the epithelium is routinely susceptible to damage during phonation. Excessive and prolonged vibration exposure is considered a significant predisposing factor in the development of vocal fold pathology. The purpose of the present study was to quantify the extent of epithelial surface damage following increased time and magnitude doses of vibration exposure using an in vivo rabbit phonation model. Forty-five New Zealand white breeder rabbits were randomized to nine groups and received varying phonation time-doses (30, 60, or 120 minutes and magnitude-doses (control, modal intensity phonation, or raised intensity phonation of vibration exposure. Scanning electron microscopy and transmission electron microscopy was used to quantify the degree of epithelial surface damage. Results revealed a significant reduction in microprojection density, microprojection height, and depth of the epithelial surface with increasing time and phonation magnitudes doses, signifying increased epithelial surface damage risk with excessive and prolonged vibration exposure. Destruction to the epithelial cell surface may provide significant insight into the disruption of cell function following prolonged vibration exposure. One important goal achieved in the present study was the quantification of epithelial surface damage using objective imaging criteria. These data provide an important foundation for future studies of long-term tissue recovery from excessive and prolonged vibration exposure.

Reduction of rectal doses by removal of gas in the rectum during vaginal cuff brachytherapy

Energy Technology Data Exchange (ETDEWEB)

Sabater, S.; Sevillano, M.M.; Andres, I.; Berenguer, R. [Complejo Hospitalario Univ. de Albacete (CHUA) (Spain). Dept. of Radiation Oncology; Machin-Hamalainen, S. [C.S. General Ricardos, Madrid (Spain); Mueller, K.; Arenas, M. [Hospital Univ. Sant Joan, Reus (Spain). Dept. of Radiation Oncology

2013-11-15

Objective: The goal of this work was to evaluate whether the volume reduction related to removal of gas in the rectum could be translated in lower doses to organs at risk (OAR) during vaginal cuff brachytherapy (VBT). Material and methods: Fourteen pairs of brachytherapy planning CT scans derived from 11 patients were re-segmented and re-planned using the same parameters. The only difference between pairs of CTs was the presence or lack of gas in the rectum. The first CT showed the basal status and the second was carried out after gas removal with a tube. A set of values derived from bladder and rectum dose-volume histograms (DVH) and dose-surface histograms (DSH) were extracted. Moreover the cylinder position related to the patient craniocaudal axis was recorded. Results: Rectum volume decreased significantly from 77.8 {+-} 45 to 55.43 {+-} 17.6 ml (p = 0.0052) after gas removal. Such volume diminution represented a significant reduction on all rectal DVH parameters analyzed except D{sub 25%} and D{sub 50%}. DSH parameter results were similar to previous ones. A nonsignificant increase of the bladder volume was observed and was associated with an increase of the DVH metrics analyzed. Conclusion: Removal of gas pockets is a simple and inexpensive maneuver that decreases rectal dose parameters on VBT, which can be translated as a better therapeutic ratio. It also suggests that other actions directed to empty the rectum could have a similar effect. (orig.)

Effect of dose reduction on the detection of mammographic lesions: A mathematical observer model analysis

International Nuclear Information System (INIS)

Chawla, Amarpreet S.; Samei, Ehsan; Saunders, Robert; Abbey, Craig; Delong, David

2007-01-01

The effect of reduction in dose levels normally used in mammographic screening procedures on the detection of breast lesions were analyzed. Four types of breast lesions were simulated and inserted into clinically-acquired digital mammograms. Dose reduction by 50% and 75% of the original clinically-relevant exposure levels were simulated by adding corresponding simulated noise into the original mammograms. The mammograms were converted into luminance values corresponding to those displayed on a clinical soft-copy display station and subsequently analyzed by Laguerre-Gauss and Gabor channelized Hotelling observer models for differences in detectability performance with reduction in radiation dose. Performance was measured under a signal known exactly but variable detection task paradigm in terms of receiver operating characteristics (ROC) curves and area under the ROC curves. The results suggested that luminance mapping of digital mammograms affects performance of model observers. Reduction in dose levels by 50% lowered the detectability of masses with borderline statistical significance. Dose reduction did not have a statistically significant effect on detection of microcalcifications. The model results indicate that there is room for optimization of dose level in mammographic screening procedures

Surface dose measurements and comparison of unflattened and flattened photon beams

Directory of Open Access Journals (Sweden)

Ashokkumar Sigamani

2016-01-01

Full Text Available The purpose of this study was to evaluate the central axis dose in the build-up region and the surface dose of a 6 MV and 10 MV flattened photon beam (FB and flattening filter free (FFF therapeutic photon beam for different square field sizes (FSs for a Varian Truebeam linear accelerator using parallel-plate ionization chamber and Gafchromic film. Knowledge of dosimetric characteristics in the build-up region and surface dose of the FFF is essential for clinical care. The dose measurements were also obtained empirically using two different commonly used dosimeters: a p-type photon semiconductor dosimeter and a cylindrical ionization chamber. Surface dose increased linearly with FS for both FB and FFF photon beams. The surface dose values of FFF were higher than the FB FSs. The measured surface dose clearly increases with increasing FS. The FFF beams have a modestly higher surface dose in the build-up region than the FB. The dependence of source to skin distance (SSD is less significant in FFF beams when compared to the flattened beams at extended SSDs.

Major cost savings associated with biologic dose reduction in patients with inflammatory arthritis.

LENUS (Irish Health Repository)

Murphy, C L

2015-01-01

The purpose of this study was to explore whether patients with Inflammatory Arthritis (IA) (Rheumatoid Arthritis (RA), Psoriatic Arthritis (PsA) or Ankylosing Spondylitis (AS)) would remain in remission following a reduction in biologic dosing frequency and to calculate the cost savings associated with dose reduction. This prospective non-blinded non-randomised study commenced in 2010. Patients with Inflammatory Arthritis being treated with a biologic agent were screened for disease activity. A cohort of those in remission according to standardized disease activity indices (DAS28 < 2.6, BASDAI < 4) was offered a reduction in dosing frequency of two commonly used biologic therapies (etanercept 50 mg once per fortnight instead of weekly, adalimumab 40 mg once per month instead of fortnightly). Patients were assessed for disease activity at 3, 6, 12, 18 and 24 months following reduction in dosing frequency. Cost saving was calculated. 79 patients with inflammatory arthritis in remission were recruited. 57% had rheumatoid arthritis (n = 45), 13% psoriatic arthritis (n = 10) and 30% ankylosing spondylitis (n = 24). 57% (n = 45) were taking etanercept and 43% (n = 34) adalimumab. The percentage of patients in remission at 24 months was 56% (n = 44). This resulted in an actual saving to the state of approximately 600,000 euro over two years. This study demonstrates the reduction in biologic dosing frequency is feasible in Inflammatory Arthritis. There was a considerable cost saving at two years. The potential for major cost savings in biologic usage should be pursued further.

Data base on dose reduction research projects for nuclear power plants

International Nuclear Information System (INIS)

Khan, T.A.; Yu, C.K.; Roecklein, A.K.

1994-05-01

This is the fifth volume in a series of reports that provide information on dose reduction research and health physics technology or nuclear power plants. The information is taken from two of several databases maintained by Brookhaven National Laboratory's ALARA Center for the Nuclear Regulatory Commission. The research section of the report covers dose reduction projects that are in the experimental or developmental phase. It includes topics such as steam generator degradation, decontamination, robotics, improvements in reactor materials, and inspection techniques. The section on health physics technology discusses dose reduction efforts that are in place or in the process of being implemented at nuclear power plants. A total of 105 new or updated projects are described. All project abstracts from this report are available to nuclear industry professionals with access to a fax machine through the ACEFAX system or a computer with a modem and the proper communications software through the ACE system. Detailed descriptions of how to access all the databases electronically are in the appendices of the report

Preemptive warfarin dose reduction after initiation of sulfamethoxazole-trimethoprim or metronidazole.

Science.gov (United States)

Powers, Anna; Loesch, Erin B; Weiland, Anthony; Fioravanti, Nicole; Lucius, David

2017-07-01

To evaluate the utility of a preemptive warfarin dose reduction at the time of initiation of either sulfamethoxazole-trimethoprim or metronidazole, a retrospective chart review of patients who received an outpatient prescription for warfarin and either sulfamethoxazole-trimethoprim and/or metronidazole from July 1, 2011 to July 1, 2015 was conducted. Clinical outcomes compared Veterans who had a warfarin dose reduction and those who did not within 120 h (5 days) of antibiotic initiation. The primary outcome compared the pre-and post-antibiotic International Normalized Ratio (INR) of patients in the intervention group (warfarin dose reduction) with those in the control group (no intervention). Secondary outcomes assessed incidence of thromboembolic and major bleeding events within 30 days of antibiotic completion. Fifty patients were assessed. Forty-nine patients had at least one follow-up appointment; 126 follow-up visits were evaluated. There was a statistically significant difference for the change in therapeutic INR at the first follow-up appointment (p = 0.029) for those patients in the control group. On average, the patients in the intervention group required fewer follow-up visits (p = 0.019). There were no statistically significant differences for the overall rate of therapeutic INR values between groups, as well as no instances of a thromboembolic or major bleeding events during the follow-up period. Clinically significant differences were observed for patients who received a preemptive warfarin dose reduction upon initiation of sulfamethoxazole-trimethoprim or metronidazole. Patients in the intervention group required fewer follow-up appointments and were more likely maintain a therapeutic INR within the 30 days following the antibiotic course. Results of this study will be presented the at Pharmacy and Therapeutics committee in an effort to seek approval for policy development to initiate a local preemptive warfarin dose adjustment as a standard

Results of comparative assessment of US and Foreign Nuclear Power Plant dose experience and dose reduction programs

International Nuclear Information System (INIS)

Baum, J.W.; Horan, J.R.; Dionne, B.J.

1984-01-01

Based on data evaluated to date it is clear that US plants have higher collective dose equivalents per reactor and per MW-y generated than most other countries. Factors which contribute to low doses include: (1) minimization of cobalt in primary system components exposed to water, (2) careful control of primary system oxygen and pH, (3) good primary system water purity to minimize corrosion product formation, (4) careful plant design, layout and component segration and shielding, (5) management interest and commitment, (6) minimum number of workers and in-depth worker training, (7) use of special tools, and (8) plant standardization. It should be pointed out that reductions in exposure are more difficult and costly in plants already built and operating. The cost-effectiveness of dose reduction efforts at US plants should be carefully evaluated before recommendations are made concerning existing plants

Dose reduction using Bismuth protectors in chest computed tomography

International Nuclear Information System (INIS)

Anaya, R.

2012-01-01

This monography is about the Dose reduction using Bismuth protectors in chest CT. The radiation protection of specific areas is necessary when the tissues or radiosensitive organs are near the path of light beam. The correct use of protection represents a challenge for the radiologist because of the time and materials required. The method used was a prospective investigatio in CHPR (TC service) and the doses was measured with TLD dosimeters. It is important to use these protectors in children hospitals.

Final design review report for K basin dose reduction project

International Nuclear Information System (INIS)

Blackburn, L.D.

1996-01-01

The strategy for reducing radiation dose originating from radionuclides absorbed in the K East Basin concrete is to raise the pool water level to provide additional shielding. This report documents a final design review for cleaning/coating basin walls and modifying other basin components where appropriate. The conclusion of this review was that the documents developed constitute an acceptable design for the Dose Reduction Project

Reduction of the dose of ionizing radiation: progressions in TC

International Nuclear Information System (INIS)

Orlacchio, A.; Costanzo, E.; Chegai, F.; Simonetti, G.

2014-01-01

The optimization of the dose of ionizing radiation in CT, it is a very important matter that can be reach avoiding unnecessary examinations, using un appropriate report KV / mAs reducing the rotation time, determining the field of study, using a high pitch using equipment that provide systems with dose reduction, through proper education of the staff that interacts with machinery and using radioprotective compounds.

Method of simulating dose reduction for digital radiographic systems

International Nuclear Information System (INIS)

Baath, M.; Haakansson, M.; Tingberg, A.; Maansson, L. G.

2005-01-01

The optimisation of image quality vs. radiation dose is an important task in medical imaging. To obtain maximum validity of the optimisation, it must be based on clinical images. Images at different dose levels can then either be obtained by collecting patient images at the different dose levels sought to investigate - including additional exposures and permission from an ethical committee - or by manipulating images to simulate different dose levels. The aim of the present work was to develop a method of simulating dose reduction for digital radiographic systems. The method uses information about the detective quantum efficiency and noise power spectrum at the original and simulated dose levels to create an image containing filtered noise. When added to the original image this results in an image with noise which, in terms of frequency content, agrees with the noise present in an image collected at the simulated dose level. To increase the validity, the method takes local dose variations in the original image into account. The method was tested on a computed radiography system and was shown to produce images with noise behaviour similar to that of images actually collected at the simulated dose levels. The method can, therefore, be used to modify an image collected at one dose level so that it simulates an image of the same object collected at any lower dose level. (authors)

Fetal shielding combined with state of the art CT dose reduction strategies during maternal chest CT

Energy Technology Data Exchange (ETDEWEB)

Chatterson, Leslie C., E-mail: lch088@mail.usask.ca [Department of Diagnostic Imaging, University of Saskatchewan (Canada); Leswick, David A.; Fladeland, Derek A. [Department of Diagnostic Imaging, University of Saskatchewan (Canada); Hunt, Megan M.; Webster, Stephen [Saskatchewan Ministry of Labour Relations and Workplace Safety (Canada); Lim, Hyun [Department of Community Health and Epidemiology, College of Medicine, University of Saskatchewan (Canada)

2014-07-15

Purpose: Custom bismuth-antimony shields were previously shown to reduce fetal dose by 53% on an 8DR (detector row) CT scanner without dynamic adaptive section collimation (DASC), automatic tube current modulation (ATCM) or adaptive statistical iterative reconstruction (ASiR). The purpose of this study is to compare the effective maternal and average fetal organ dose reduction both with and without bismuth-antimony shields on a 64DR CT scanner using DASC, ATCM and ASiR during maternal CTPA. Materials and methods: A phantom with gravid prosthesis and a bismuth-antimony shield were used. Thermoluminescent dosimeters (TLDs) measured fetal radiation dose. The average fetal organ dose and effective maternal dose were determined using 100 kVp, scanning from the lung apices to the diaphragm utilizing DASC, ATCM and ASiR on a 64DR CT scanner with and without shielding in the first and third trimester. Isolated assessment of DASC was done via comparing a new 8DR scan without DASC to a similar scan on the 64DR with DASC. Results: Average third trimester unshielded fetal dose was reduced from 0.22 mGy ± 0.02 on the 8DR to 0.13 mGy ± 0.03 with the conservative 64DR protocol that included 30% ASiR, DASC and ATCM (42% reduction, P < 0.01). Use of a shield further reduced average third trimester fetal dose to 0.04 mGy ± 0.01 (69% reduction, P < 0.01). The average fetal organ dose reduction attributable to DASC alone was modest (6% reduction from 0.17 mGy ± 0.02 to 0.16 mGy ± 0.02, P = 0.014). First trimester fetal organ dose on the 8DR protocol was 0.07 mGy ± 0.03. This was reduced to 0.05 mGy ± 0.03 on the 64DR protocol without shielding (30% reduction, P = 0.009). Shields further reduced this dose to below accurately detectable levels. Effective maternal dose was reduced from 4.0 mSv on the 8DR to 2.5 mSv on the 64DR scanner using the conservative protocol (38% dose reduction). Conclusion: ASiR, ATCM and DASC combined significantly reduce effective maternal and fetal

Fetal shielding combined with state of the art CT dose reduction strategies during maternal chest CT

International Nuclear Information System (INIS)

Chatterson, Leslie C.; Leswick, David A.; Fladeland, Derek A.; Hunt, Megan M.; Webster, Stephen; Lim, Hyun

2014-01-01

Purpose: Custom bismuth-antimony shields were previously shown to reduce fetal dose by 53% on an 8DR (detector row) CT scanner without dynamic adaptive section collimation (DASC), automatic tube current modulation (ATCM) or adaptive statistical iterative reconstruction (ASiR). The purpose of this study is to compare the effective maternal and average fetal organ dose reduction both with and without bismuth-antimony shields on a 64DR CT scanner using DASC, ATCM and ASiR during maternal CTPA. Materials and methods: A phantom with gravid prosthesis and a bismuth-antimony shield were used. Thermoluminescent dosimeters (TLDs) measured fetal radiation dose. The average fetal organ dose and effective maternal dose were determined using 100 kVp, scanning from the lung apices to the diaphragm utilizing DASC, ATCM and ASiR on a 64DR CT scanner with and without shielding in the first and third trimester. Isolated assessment of DASC was done via comparing a new 8DR scan without DASC to a similar scan on the 64DR with DASC. Results: Average third trimester unshielded fetal dose was reduced from 0.22 mGy ± 0.02 on the 8DR to 0.13 mGy ± 0.03 with the conservative 64DR protocol that included 30% ASiR, DASC and ATCM (42% reduction, P < 0.01). Use of a shield further reduced average third trimester fetal dose to 0.04 mGy ± 0.01 (69% reduction, P < 0.01). The average fetal organ dose reduction attributable to DASC alone was modest (6% reduction from 0.17 mGy ± 0.02 to 0.16 mGy ± 0.02, P = 0.014). First trimester fetal organ dose on the 8DR protocol was 0.07 mGy ± 0.03. This was reduced to 0.05 mGy ± 0.03 on the 64DR protocol without shielding (30% reduction, P = 0.009). Shields further reduced this dose to below accurately detectable levels. Effective maternal dose was reduced from 4.0 mSv on the 8DR to 2.5 mSv on the 64DR scanner using the conservative protocol (38% dose reduction). Conclusion: ASiR, ATCM and DASC combined significantly reduce effective maternal and fetal

Data base on nuclear power plant dose reduction research projects

Energy Technology Data Exchange (ETDEWEB)

Khan, T.A.; Baum, J.W.

1986-10-01

Staff at the ALARA Center of Brookhaven National Laboratory have established a data base of information about current research that is likely to result in lower radiation doses to workers. The data base, concerned primarily with nuclear power generation, is part of a project that the ALARA Center is carrying out for the Nuclear Regulatory Commission. This report describes its current status. A substantial amount of research on reducing occupational exposure is being done in the US and abroad. This research is beginning to have an impact on the collective dose expenditures at nuclear power plants. The collective radiation doses in Europe, Japan, and North America all show downward trends. A large part of the research in the US is either sponsored by the nuclear industry through joint industry organizations such as EPRI and ESEERCO or is done by individual corporations. There is also significant participation by smaller companies. The main emphasis of the research on dose reduction is on engineering approaches aimed at reducing radiation fields or keeping people out of high-exposure areas by using robotics. Effective ALARA programs are also underway at a large number of nuclear plants. Additional attention should be given to non-engineering approaches to dose reduction, which are potentially very useful and cost effective but require quantitative study and analysis based on data from nuclear power plants. 9 refs., 1 fig.

Reducing Radiation Dose in Coronary Angiography and Angioplasty Using Image Noise Reduction Technology.

Science.gov (United States)

Kastrati, Mirlind; Langenbrink, Lukas; Piatkowski, Michal; Michaelsen, Jochen; Reimann, Doris; Hoffmann, Rainer

2016-08-01

This study sought to quantitatively evaluate the reduction of radiation dose in coronary angiography and angioplasty with the use of image noise reduction technology in a routine clinical setting. Radiation dose data from consecutive 605 coronary procedures (397 consecutive coronary angiograms and 208 consecutive coronary interventions) performed from October 2014 to April 2015 on a coronary angiography system with noise reduction technology (Allura Clarity IQ) were collected. For comparison, radiation dose data from consecutive 695 coronary procedures (435 coronary angiograms and 260 coronary interventions) performed on a conventional coronary angiography system from October 2013 to April 2014 were evaluated. Patient radiation dosage was evaluated based on the cumulative dose area product. Operators and operator practice did not change between the 2 evaluated periods. Patient characteristics were collected to evaluate similarity of patient groups. Image quality was evaluated on a 5-grade scale in 30 patients of each group. There were no significant differences between the 2 evaluated groups in gender, age, weight, and fluoroscopy time (6.8 ± 6.1 vs 6.9 ± 6.3 minutes, not significant). The dose area product was reduced from 3195 ± 2359 to 983 ± 972 cGycm(2) (65%, p technology. Image quality was graded as similar between the evaluated systems (4.0 ± 0.7 vs 4.2 ± 0.6, not significant). In conclusion, a new x-ray technology with image noise reduction algorithm provides a substantial reduction in radiation exposure without the need to prolong the procedure or fluoroscopy time. Copyright © 2016 Elsevier Inc. All rights reserved.

Patient Outcomes in Dose Reduction or Discontinuation of Long-Term Opioid Therapy: A Systematic Review.

Science.gov (United States)

Frank, Joseph W; Lovejoy, Travis I; Becker, William C; Morasco, Benjamin J; Koenig, Christopher J; Hoffecker, Lilian; Dischinger, Hannah R; Dobscha, Steven K; Krebs, Erin E

2017-08-01

Expert guidelines recommend reducing or discontinuing long-term opioid therapy (LTOT) when risks outweigh benefits, but evidence on the effect of dose reduction on patient outcomes has not been systematically reviewed. To synthesize studies of the effectiveness of strategies to reduce or discontinue LTOT and patient outcomes after dose reduction among adults prescribed LTOT for chronic pain. MEDLINE, EMBASE, PsycINFO, CINAHL, and the Cochrane Library from inception through April 2017; reference lists; and expert contacts. Original research published in English that addressed dose reduction or discontinuation of LTOT for chronic pain. Two independent reviewers extracted data and assessed study quality using the U.S. Preventive Services Task Force quality rating criteria. All authors assessed evidence quality using the GRADE (Grading of Recommendations Assessment, Development and Evaluation) system. Prespecified patient outcomes were pain severity, function, quality of life, opioid withdrawal symptoms, substance use, and adverse events. Sixty-seven studies (11 randomized trials and 56 observational studies) examining 8 intervention categories, including interdisciplinary pain programs, buprenorphine-assisted dose reduction, and behavioral interventions, were found. Study quality was good for 3 studies, fair for 13 studies, and poor for 51 studies. Many studies reported dose reduction, but rates of opioid discontinuation ranged widely across interventions and the overall quality of evidence was very low. Among 40 studies examining patient outcomes after dose reduction (very low overall quality of evidence), improvement was reported in pain severity (8 of 8 fair-quality studies), function (5 of 5 fair-quality studies), and quality of life (3 of 3 fair-quality studies). Heterogeneous interventions and outcome measures; poor-quality studies with uncontrolled designs. Very low quality evidence suggests that several types of interventions may be effective to reduce or

Radiation exposure reduction technologies for a Japanese Advanced BWR (Dose Rate Reduction Experience in Shika Unit 2)

International Nuclear Information System (INIS)

Saito, Takeshi; Ichikawa, Koji; Ishimaru, Hiroshi; Aizawa, Motohiro; Sato, Yoshiteru; Morita, Shoichi

2012-09-01

Operating experiences of the advanced boiling water reactor (ABWR) have been accumulated in Japan since the first ABWRs Kashiwazaki-Kariwa NPS unit 6 and 7 came into service. Shika NPS unit 2 (Shika-2) of Hokuriku Electric Power Co. is the fourth ABWR plant in Japan. Since ABWRs have no piping of the reactor recirculation system (RRS), which is the largest source of radiation in conventional BWRs, carbon steel piping of the reactor water cleanup system (RWCU) and residual heat removal system (RHR) are the largest source in ABWRs. Therefore we have focused on reduction methods of radioactive material on carbon steel surface in order to reduce the quantity of occupational exposure in Shika-2. In Shika-2 the following methods have been adopted. Before fuel loading, alkaline pre-filming process was applied to the RWCU piping during plant startup testing. After start of operation, the feed water iron concentration control (or nickel/iron ratio control) method was applied. Furthermore, during shutdown operation the RHR system was operated when the reactor water temperature was dropped to 120 degree C with the use of condenser heat sink cooling operation. These dose rate reduction methods worked well in Shika-2 as expected. The quantity of occupational exposure at the 3 rd outage in Shika-2 was approximately 0.35 person-Sv. On the basis of the results obtained thus far, the occupational dose expected at the outage after deposition amount of radioactivity reaching the equilibrium state has been estimated to be around 0.5 person-Sv. This value is considered to be in low level compared with the worldwide statistics. (authors)

Are phantoms useful for predicting the potential of dose reduction in full-field digital mammography?

International Nuclear Information System (INIS)

Gennaro, Gisella; Katz, Luc; Souchay, Henri; Alberelli, Claudio; Maggio, Cosimo di

2005-01-01

A phantom study was performed in full-field digital mammography to investigate the opportunity and the magnitude of a possible dose reduction that would leave the image quality above the accepted thresholds associated with some classical phantoms. This preliminary work is intended to lay the groundwork for a future clinical study on the impact of dose reduction on clinical results. Three different mammography phantoms (ACR RMI 156, CIRS 11A and CDMAM 3.4) were imaged by a full-field digital mammography unit (GE Senographe 2000D) at different dose levels. Images were rated by three observers with softcopy reading and scoring methods specific to each phantom. Different types of data analysis were applied to the ACR (American College of Radiology) and the other two phantoms, respectively. With reference to the minimum acceptance score in screen/film accreditation programmes, the ACR phantom showed that about 45% dose reduction could be applied, while keeping the phantom scores above that threshold. A relative comparison was done for CIRS and CDMAM, for which no threshold is defined. CIRS scoring remained close to the reference level down to 40% dose reduction, the inter- and intra-observer variability being the main source of uncertainty. Contrast-detail curves provided by CDMAM overlapped down to 50% dose reduction, at least for object contrast values ranging between 30% and 3%. This multi-phantom study shows the potential of further reducing the dose in full-field digital mammography beyond the current values. A common dose reduction factor around 50% seems acceptable for all phantoms. However, caution is required before extrapolating the results for clinical use, given the limitations of these widely used phantoms, mainly related to their limited dynamic range and uniform background

Dose banding as an alternative to body surface area-based dosing of chemotherapeutic agents

NARCIS (Netherlands)

E. Chatelut (Etienne); M.L. White-Koning (M.); A.H.J. Mathijssen (Ron); F. Puisset (F.); S.D. Baker (Sharyn); A. Sparreboom (Alex)

2012-01-01

textabstractBackground: Dose banding is a recently suggested dosing method that uses predefined ranges (bands) of body surface area (BSA) to calculate each patients dose by using a single BSA-value per band. Thus, drugs with sufficient long-term stability can be prepared in advance. The main

SU-E-T-802: Verification of Implanted Cardiac Pacemaker Doses in Intensity-Modulated Radiation Therapy: Dose Prediction Accuracy and Reduction Effect of a Lead Sheet

Energy Technology Data Exchange (ETDEWEB)

Lee, J [Dept. of Radiation Oncology, Konkuk University Medical Center, Seoul (Korea, Republic of); Chung, J [Dept. of Radiation Oncology, Seoul National University Bundang Hospital, Seongnam (Korea, Republic of)

2015-06-15

Purpose: To verify delivered doses on the implanted cardiac pacemaker, predicted doses with and without dose reduction method were verified using the MOSFET detectors in terms of beam delivery and dose calculation techniques in intensity-modulated radiation therapy (IMRT). Methods: The pacemaker doses for a patient with a tongue cancer were predicted according to the beam delivery methods [step-and-shoot (SS) and sliding window (SW)], intensity levels for dose optimization, and dose calculation algorithms. Dosimetric effects on the pacemaker were calculated three dose engines: pencil-beam convolution (PBC), analytical anisotropic algorithm (AAA), and Acuros-XB. A lead shield of 2 mm thickness was designed for minimizing irradiated doses to the pacemaker. Dose variations affected by the heterogeneous material properties of the pacemaker and effectiveness of the lead shield were predicted by the Acuros-XB. Dose prediction accuracy and the feasibility of the dose reduction strategy were verified based on the measured skin doses right above the pacemaker using mosfet detectors during the radiation treatment. Results: The Acuros-XB showed underestimated skin doses and overestimated doses by the lead-shield effect, even though the lower dose disagreement was observed. It led to improved dose prediction with higher intensity level of dose optimization in IMRT. The dedicated tertiary lead sheet effectively achieved reduction of pacemaker dose up to 60%. Conclusion: The current SS technique could deliver lower scattered doses than recommendation criteria, however, use of the lead sheet contributed to reduce scattered doses.Thin lead plate can be a useful tertiary shielder and it could not acuse malfunction or electrical damage of the implanted pacemaker in IMRT. It is required to estimate more accurate scattered doses of the patient with medical device to design proper dose reduction strategy.

SU-E-T-802: Verification of Implanted Cardiac Pacemaker Doses in Intensity-Modulated Radiation Therapy: Dose Prediction Accuracy and Reduction Effect of a Lead Sheet

International Nuclear Information System (INIS)

Lee, J; Chung, J

2015-01-01

Purpose: To verify delivered doses on the implanted cardiac pacemaker, predicted doses with and without dose reduction method were verified using the MOSFET detectors in terms of beam delivery and dose calculation techniques in intensity-modulated radiation therapy (IMRT). Methods: The pacemaker doses for a patient with a tongue cancer were predicted according to the beam delivery methods [step-and-shoot (SS) and sliding window (SW)], intensity levels for dose optimization, and dose calculation algorithms. Dosimetric effects on the pacemaker were calculated three dose engines: pencil-beam convolution (PBC), analytical anisotropic algorithm (AAA), and Acuros-XB. A lead shield of 2 mm thickness was designed for minimizing irradiated doses to the pacemaker. Dose variations affected by the heterogeneous material properties of the pacemaker and effectiveness of the lead shield were predicted by the Acuros-XB. Dose prediction accuracy and the feasibility of the dose reduction strategy were verified based on the measured skin doses right above the pacemaker using mosfet detectors during the radiation treatment. Results: The Acuros-XB showed underestimated skin doses and overestimated doses by the lead-shield effect, even though the lower dose disagreement was observed. It led to improved dose prediction with higher intensity level of dose optimization in IMRT. The dedicated tertiary lead sheet effectively achieved reduction of pacemaker dose up to 60%. Conclusion: The current SS technique could deliver lower scattered doses than recommendation criteria, however, use of the lead sheet contributed to reduce scattered doses.Thin lead plate can be a useful tertiary shielder and it could not acuse malfunction or electrical damage of the implanted pacemaker in IMRT. It is required to estimate more accurate scattered doses of the patient with medical device to design proper dose reduction strategy

Concept for Sustainable Dose Reduction in Operating BWRs and PWRs with FSD (Full System decontamination)

Energy Technology Data Exchange (ETDEWEB)

Sempere Belda, L.; Stiepani, C.; Topf, C.

2011-07-01

Nuclear power plants experience an increase in dose rates during operation due to the build-up of the activity inventory. The activity build-up is influenced by the construction materials, past and present water chemistries, and the individual operating history of the plant. Depending on these factors the dose levels in an operating plant may reach a point in which concrete actions to reduce the overall radiation exposure become necessary. AREVA has developed the Concept for Sustainable Dose Reduction in Operating BWRs and PWRs. This is a program of joint corrective measures to minimize dose levels and keep them low for continued operation. It can be applied in plants from all constructors and designs. The concept is put into practice through the coordinated application of proven technologies, including: . Full System Decontamination to minimize the activity inventory . The formation of new, very stable protective oxides on the system surfaces including injection of depleted zinc . Introduction of advanced water chemistry for maintaining the low dose levels achieved during ongoing operation The implementation of this program is particularly interesting for plants with a long operation history, especially when considering life extension. A description of the activities involved is provided, including an approximate timeline for the implementation from the initial planning stages until completion.

Concept for Sustainable Dose Reduction in Operating BWRs and PWRs with FSD (Full System decontamination)

International Nuclear Information System (INIS)

Sempere Belda, L.; Stiepani, C.; Topf, C.

2011-01-01

Nuclear power plants experience an increase in dose rates during operation due to the build-up of the activity inventory. The activity build-up is influenced by the construction materials, past and present water chemistries, and the individual operating history of the plant. Depending on these factors the dose levels in an operating plant may reach a point in which concrete actions to reduce the overall radiation exposure become necessary. AREVA has developed the Concept for Sustainable Dose Reduction in Operating BWRs and PWRs. This is a program of joint corrective measures to minimize dose levels and keep them low for continued operation. It can be applied in plants from all constructors and designs. The concept is put into practice through the coordinated application of proven technologies, including: . Full System Decontamination to minimize the activity inventory . The formation of new, very stable protective oxides on the system surfaces including injection of depleted zinc . Introduction of advanced water chemistry for maintaining the low dose levels achieved during ongoing operation The implementation of this program is particularly interesting for plants with a long operation history, especially when considering life extension. A description of the activities involved is provided, including an approximate timeline for the implementation from the initial planning stages until completion.

Dose reduction due to the use of pulsed miction-cystourethrography in pediatrics

International Nuclear Information System (INIS)

Rettinger, Tobias

2013-01-01

The miction-cystourethrography (MCU) is the most frequently used radiographic method (30-50%) in pediatrics. The absorbed doses were significantly reduced during the last years aimed to realize the ALARA principle. The scope of the work is to study the possibility of a further dose reduction using pulsed radiation systems based on a computer-aided analysis of the dose-time curve during MCU examination.

Breast dose reduction for chest CT by modifying the scanning parameters based on the pre-scan size-specific dose estimate (SSDE)

Energy Technology Data Exchange (ETDEWEB)

Kidoh, Masafumi; Utsunomiya, Daisuke; Oda, Seitaro; Nakaura, Takeshi; Yuki, Hideaki; Hirata, Kenichiro; Namimoto, Tomohiro; Sakabe, Daisuke; Hatemura, Masahiro; Yamashita, Yasuyuki [Kumamoto University, Department of Diagnostic Radiology, Faculty of Life Sciences, Honjo, Kumamoto (Japan); Funama, Yoshinori [Kumamoto University, Department of Medical Physics, Faculty of Life Sciences, Honjo, Kumamoto (Japan)

2017-06-15

To investigate the usefulness of modifying scanning parameters based on the size-specific dose estimate (SSDE) for a breast-dose reduction for chest CT. We scanned 26 women with a fixed volume CT dose index (CTDI{sub vol}) (15 mGy) and another 26 with a fixed SSDE (15 mGy) protocol (protocol 1 and 2, respectively). In protocol 2, tube current was calculated based on the patient habitus obtained on scout images. We compared the mean breast dose and the inter-patient breast dose variability and performed linear regression analysis of the breast dose and the body mass index (BMI) of the two protocols. The mean breast dose was about 35 % lower under protocol 2 than protocol 1 (10.9 mGy vs. 16.8 mGy, p < 0.01). The inter-patient breast dose variability was significantly lower under protocol 2 than 1 (1.2 mGy vs. 2.5 mGy, p < 0.01). We observed a moderate negative correlation between the breast dose and the BMI under protocol 1 (r = 0.43, p < 0.01); there was no significant correlation (r = 0.06, p = 0.35) under protocol 2. The SSDE-based protocol achieved a reduction in breast dose and in inter-patient breast dose variability. (orig.)

Experiences of occupational dose reduction at the Fugen nuclear power station

International Nuclear Information System (INIS)

Suzuki, Kazuya; Nakao, Hiromi; Naoi, Yohsuke; Takei, Hiroaki

1992-01-01

Occupational radiation dose has been effectively suppressed by efforts against both internal and external exposure in the Fugen nuclear power station. The tritium internal dose is completely suppressed by developments of high sensitivity tritium monitors with hollow fiber radon filters, comfortable tritium protection suits, and established working procedure for equipment maintenance of the heavy water system. The internal occupational dose has been suppressed to a negligible level comparing to the external dose. The external occupational dose had increased with dose rates of the primary cooling system. Establishment of radiation work procedure for maintenance works and development of chemical decontamination has been effectively saving the external occupational dose. The chemical decontaminations carried out in 1989 and 1991 are the first applications to the whole primary cooling system of operating power stations in Japan. This paper describes these efforts and effects on occupational dose reduction in Fugen. (author)

Ambient radiation dose reduction within a newly remodeled Nuclear Medicine Department

International Nuclear Information System (INIS)

Lai, Y.C.; Chen, Y.W.; Huang, Y.F.

2008-01-01

Full text: Ambient radiation levels at the patient waiting areas have been greatly reduced after remodeling of our Nuclear Medicine Department (NMD) based on the ALARA consideration. Complete ambient radiation monitoring of our NMD before remodeling had been characterized and published earlier by the same authors elsewhere. The NMD outpatients, with an initial dose of up to 740 MBq (20 mCi) per case, may wait around and incidentally congest in one place that could cause an unexpected higher exposure level in public access areas. In this new surveillance study after remodeling, the ambient radiation time-profile, peak dose rates and daily doses have been re-evaluated by using high sensitivity, digital survey dosimeters. As a preliminary result, with our newly improved facility in operation, we have demonstrated the NMD waiting room average daily dose has dropped from about 3.0 μSv to 0.42 μSv during most of busy days in comparison. The hourly peak dose rate detected in patient waiting areas has also reduced to a factor of more than two, from maximum dose rate of 40.4 μSv/h to 15.4 μSv/h, during one worst case scenario. The great reduction of the environment dose was achieved mainly by using larger room space with thicker lead wall, from previous 2-mm to new 5-mm in lead thickness, and by increasing patient waiting rooms/areas with less chairs available in each seating location. Other NMD administrative control measure of our dose reduction program has also been emphasized in better patient routing, scheduling and less waiting time for the diagnostic patients. (author)

Radiation dose reduction: comparative assessment of publication volume between interventional and diagnostic radiology.

Science.gov (United States)

Hansmann, Jan; Henzler, Thomas; Gaba, Ron C; Morelli, John N

2017-01-01

We aimed to quantify and compare awareness regarding radiation dose reduction within the interventional radiology and diagnostic radiology communities. Abstracts accepted to the annual meetings of the Society of Interventional Radiology (SIR), the Cardiovascular and Interventional Radiological Society of Europe (CIRSE), the Radiological Society of North America (RSNA), and the European Congress of Radiology (ECR) between 2005 and 2015 were analyzed using the search terms "interventional/computed tomography" and "radiation dose/radiation dose reduction." A PubMed query using the above-mentioned search terms for the years of 2005-2015 was performed. Between 2005 and 2015, a total of 14 520 abstracts (mean, 660±297 abstracts) and 80 614 abstracts (mean, 3664±1025 abstracts) were presented at interventional and diagnostic radiology meetings, respectively. Significantly fewer abstracts related to radiation dose were presented at the interventional radiology meetings compared with the diagnostic radiology meetings (162 abstracts [1% of total] vs. 2706 [3% of total]; P radiology abstracts (range, 6-27) and 246±105 diagnostic radiology abstracts (range, 112-389) pertaining to radiation dose were presented at each meeting. The PubMed query revealed an average of 124±39 publications (range, 79-187) and 1205±307 publications (range, 829-1672) related to interventional and diagnostic radiology dose reduction per year, respectively (P radiology community over the past 10 years has not mirrored the increased volume seen within diagnostic radiology, suggesting that increased education and discussion about this topic may be warranted.

SU-E-T-577: Obliquity Factor and Surface Dose in Proton Beam Therapy

International Nuclear Information System (INIS)

Das, I; Andersen, A; Coutinho, L

2015-01-01

Purpose: The advantage of lower skin dose in proton beam may be diminished creating radiation related sequalae usually seen with photon and electron beams. This study evaluates the surface dose as a complex function of beam parameters but more importantly the effect of beam angle. Methods: Surface dose in proton beam depends on the beam energy, source to surface distance, the air gap between snout and surface, field size, material thickness in front of surface, atomic number of the medium, beam angle and type of nozzle (ie double scattering, (DS), uniform scanning (US) or pencil beam scanning (PBS). Obliquity factor (OF) is defined as ratio of surface dose in 0° to beam angle Θ. Measurements were made in water phantom at various beam angles using very small microdiamond that has shown favorable beam characteristics for high, medium and low proton energy. Depth dose measurements were performed in the central axis of the beam in each respective gantry angle. Results: It is observed that surface dose is energy dependent but more predominantly on the SOBP. It is found that as SSD increases, surface dose decreases. In general, SSD, and air gap has limited impact in clinical proton range. High energy has higher surface dose and so the beam angle. The OF rises with beam angle. Compared to OF of 1.0 at 0° beam angle, the value is 1.5, 1.6, 1,7 for small, medium and large range respectively for 60 degree angle. Conclusion: It is advised that just like range and SOBP, surface dose should be clearly understood and a method to reduce the surface dose should be employed. Obliquity factor is a critical parameter that should be accounted in proton beam therapy and a perpendicular beam should be used to reduce surface dose

Clinical validation of a dose reduction study in paediatric abdomen MSCT scanning

International Nuclear Information System (INIS)

Ciccarone, A.; Fonda, C.; Zatelli, Giovanna; Mazzocchi, S.

2008-01-01

Full text: In our previous work an individual dose adaptation in abdomen of paediatric patients has been showed at the Meyer children hospital of Florence. For each kV really feasible in our MSCT scanner, a table of mAs versus abdomen thickness and width ratio has been developed only on the basis of water cylinder phantoms. The choice of the water arise by the fact that in pediatric patient the quantity of water inside the body is major than that of adult. In this way a reduction dose has showed with respect to the ordinary paediatric scanning protocol in use before and the same image quality has been preserved in the case of an optimized CT scanning technique of a standard adult patient of height 175 cm and weight 70 kg. However these results were only theoretical because relied on water phantoms. Now this work concerns the clinical validation of our dose reduction study on phantoms. So 50 examinations were acquired with the dose reduction scanning technique and scored randomly, without knowing weight and height of patient by three radiologists. These scores were compared with that of other 50 abdomen examination before dose reduction study. The scores refers to the noise perceived by radiologist and to the diagnostic quality of radiograph. As last, a score on the low contrast tissue separation between muscle and fat and a score on visibility of structure therein have been asked to the radiologists. The same work has concerned the abdomen examinations with iodine contrast medium. In this study the score of each radiographs has been catalogued in four range of age, 0 - 1; 1 - 3; 3 - 8; 8 - 13 years. Aligned rank and Wilcoxon's signed rank tests were used for statistical analyses. The table of modulating mAs with respect to the size of patient obtained with only water phantom study has been revised so that none reduced detection in low-visibility structures like fat or muscle or liver was evident. Nevertheless a reduction in CTDI of 30 % has been reached in our new

Characterization of adaptive statistical iterative reconstruction algorithm for dose reduction in CT: A pediatric oncology perspective

International Nuclear Information System (INIS)

Brady, S. L.; Yee, B. S.; Kaufman, R. A.

2012-01-01

Purpose: This study demonstrates a means of implementing an adaptive statistical iterative reconstruction (ASiR™) technique for dose reduction in computed tomography (CT) while maintaining similar noise levels in the reconstructed image. The effects of image quality and noise texture were assessed at all implementation levels of ASiR™. Empirically derived dose reduction limits were established for ASiR™ for imaging of the trunk for a pediatric oncology population ranging from 1 yr old through adolescence/adulthood. Methods: Image quality was assessed using metrics established by the American College of Radiology (ACR) CT accreditation program. Each image quality metric was tested using the ACR CT phantom with 0%–100% ASiR™ blended with filtered back projection (FBP) reconstructed images. Additionally, the noise power spectrum (NPS) was calculated for three common reconstruction filters of the trunk. The empirically derived limitations on ASiR™ implementation for dose reduction were assessed using (1, 5, 10) yr old and adolescent/adult anthropomorphic phantoms. To assess dose reduction limits, the phantoms were scanned in increments of increased noise index (decrementing mA using automatic tube current modulation) balanced with ASiR™ reconstruction to maintain noise equivalence of the 0% ASiR™ image. Results: The ASiR™ algorithm did not produce any unfavorable effects on image quality as assessed by ACR criteria. Conversely, low-contrast resolution was found to improve due to the reduction of noise in the reconstructed images. NPS calculations demonstrated that images with lower frequency noise had lower noise variance and coarser graininess at progressively higher percentages of ASiR™ reconstruction; and in spite of the similar magnitudes of noise, the image reconstructed with 50% or more ASiR™ presented a more smoothed appearance than the pre-ASiR™ 100% FBP image. Finally, relative to non-ASiR™ images with 100% of standard dose across the

Determination of surface dose rate for cloisonne using thermoluminescent dosimeters

Energy Technology Data Exchange (ETDEWEB)

Hengyuan, Zhao; Yulian, Zhang

1985-07-01

In this paper, the measuring method and results of surface dose rate of cloisonne using CaSO/sub 4/ Dy-Teflon foil dosimeter are described. The surface dose rate of all products are below 0.015 mrad/h. These products contain 42 sorts of jewelery and 20 sets of wares (such as vases, plates, ash-trays, etc.). Most of the data fall within the range of natural background. For comparison, some jewelery from Taiwan and 3 vases from Japan are measured. The highest surface dose rate of 0.78 mrad/h is due to the necklace jewelery from Taiwan.

Reduction of patient doses in X-ray diagnosis using quality control tests on image and equipment

International Nuclear Information System (INIS)

Milu, C.; Tomulescu, V.; Sorescu, Anca; Vladareanu, M.; Olteanu, B.; Enachescu, B.; Zaharia, N.; Lesaru, M.

1997-01-01

In the frame of a research program under the contract with the International Atomic Energy Agency (IAEA), several patient dose measurements were performed using thermoluminescent dosemeters (TLDs) before and after application of Quality Control tests and patient dose reduction methods. The paper evidenced the practical influence factors (like the need of use of high voltage technique) and possibilities for dose reduction keeping the image quality. (authors)

Bioinspired surfaces for turbulent drag reduction.

Science.gov (United States)

Golovin, Kevin B; Gose, James W; Perlin, Marc; Ceccio, Steven L; Tuteja, Anish

2016-08-06

In this review, we discuss how superhydrophobic surfaces (SHSs) can provide friction drag reduction in turbulent flow. Whereas biomimetic SHSs are known to reduce drag in laminar flow, turbulence adds many new challenges. We first provide an overview on designing SHSs, and how these surfaces can cause slip in the laminar regime. We then discuss recent studies evaluating drag on SHSs in turbulent flow, both computationally and experimentally. The effects of streamwise and spanwise slip for canonical, structured surfaces are well characterized by direct numerical simulations, and several experimental studies have validated these results. However, the complex and hierarchical textures of scalable SHSs that can be applied over large areas generate additional complications. Many studies on such surfaces have measured no drag reduction, or even a drag increase in turbulent flow. We discuss how surface wettability, roughness effects and some newly found scaling laws can help explain these varied results. Overall, we discuss how, to effectively reduce drag in turbulent flow, an SHS should have: preferentially streamwise-aligned features to enhance favourable slip, a capillary resistance of the order of megapascals, and a roughness no larger than 0.5, when non-dimensionalized by the viscous length scale.This article is part of the themed issue 'Bioinspired hierarchically structured surfaces for green science'. © 2016 The Author(s).

Effects of building structures on radiation doses from routine releases of radionuclides to the atmosphere

International Nuclear Information System (INIS)

Kocher, D.C.

1978-01-01

Realistic assessments of radiation doses to the population from routine releases of radionuclides to the atmosphere require consideration of man's largely indoor environment. The effect of a building structure on radiation doses is described quantitatively by a dose reduction factor, which is the ratio of the dose to a reference individual inside a structure to the corresponding dose with no structure present. We have implemented models to estimate dose reduction factors for internal dose from inhaled radionuclides and for external photon dose from airborne and surface-deposited radionuclides. The models are particularly useful in radiological assessment applications, since dose reduction factors may readily be estimated for arbitrary mixtures and concentrations of radionuclides in the atmosphere and on the ground. The model for inhalation dose reduction factors accounts for radioactive decay, air ventilation into and out of the structure, and deposition of radionuclides on inside surfaces of the structure. External dose reduction factors are estimated using the point-kernel integration method including consideration of buildup in air and the walls of the building. The potential importance of deposition of radionuclides on inside surfaces of a structure on both inhalation and external dose reduction factors has been demonstrated. Model formulation and the assumptions used in the calculations are discussed. Results of model-parameter sensitivity studies and estimates of dose reduction factors for radionuclides occurring in routine releases from an LWR fuel reprocessing plant are presented. (author)

Surface doses under head and neck immobilisation devices

International Nuclear Information System (INIS)

Baveas, E.

2004-01-01

Full text: Methods using ion chambers, TLDs and film were developed to measure the skin-sparing properties of three head and neck immobilisation devices used in radiation therapy, viz. Sinmed multi-perforated and micro-perforated posicast thermoplastic masks (used with a supporting carbon fibre back support), and a Kablite vacuum-formed shell plastic mask (used with a Perspex back support). All measurements were performed with 6 MV beams from Elekta Precise linear accelerators. Two situations have been considered in this study. In the first situation, phantom surface doses under the flat unmoulded mask and back-support materials lying on the surface of a 'solid water' phantom were measured with parallel plate ion chambers and correlated with the physical properties of the materials. In the second situation a particular head and neck treatment technique was adopted and the treatment planned on an anthropomorphic tissue-equivalent phantom. The clinical setup consisted of a wedged pair to the right parotid, planned to deliver a reference dose of 63 Gy to the isocentre, plus an anterior supraclavicular field planned to deliver a reference dose of 50 Gy at a depth of 2 cm. The 3 immobilisation masks were each moulded to the anthropomorphic tissue-equivalent phantom. TLD chips were used to measure the phantom skin dose at a set of 18 locations under each of the 3 immobilisation masks and also without an immobilisation device. The results clearly demonstrate the extent to which the various immobilisation devices increase the surface dose. Results for the first situation are summarised. The averages of the doses recorded by the TLDs in three separate regions for the second situation are shown in Table 2. The combined results show that the areal density of the unmoulded mask materials correlates with the surface dose these materials produce before moulding, but this correlation is lost after moulding for the clinical situation considered. This change upon moulding is

Dose reduction during CT scanning in an anthropomorphic phantom by the use of a male gonad shield.

Science.gov (United States)

Price, R; Halson, P; Sampson, M

1999-05-01

Shielding the radiosensitive gonads during X-ray exposure has been advocated for plain film radiography for many years. In the UK, gonad shields are not widely employed in routine CT scanning, possibly owing to a perceived difficulty in protecting the gonads from a multidirectional X-ray source. The increasing numbers of CT scanners in the UK, with the large doses they deliver to patients, make potential dose reduction methods an important issue. This study measures the dose reduction achievable by shielding the male gonads with a lead wrap-around protection device. The reductions in dose when shielded both from direct radiation and from indirect radiation scattered from local tissues were studied. The use of the device resulted in a statistically significant reduction in the absorbed testicular dose from both direct and scattered radiation, with no increase in the dose measured in surrounding tissues. In three clinically relevant experimental protocols where the testes were not irradiated directly, the testicular absorbed dose from indirect scatter was reduced by 77-93% of the corresponding non-shielded figure. In these three experiments, image quality was unaltered by the use of the shield. A larger dose reduction was obtained when the shield was used to protect the testes from direct irradiation. However, this was achieved at the expense of considerable image degradation from streak artefact that would effectively prevent the clinical use of the device in this setting.

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

OpenAIRE

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

2017-01-01

Background: Contrast dose and radiation dose reduction in computerized tomography (CT) scan for adult has been explored successfully, but there have been few studies on the application of low-concentration contrast in pediatric abdominal CT examinations. This was a feasibility study on the use of dual-energy spectral imaging and adaptive statistical iterative reconstruction (ASiR) for the reduction of radiation dose and iodine contrast dose in pediatric abdominal CT patients with solid tumors...

Present status of brain intravascular surgery and reduction of exposure dose

International Nuclear Information System (INIS)

Sato, Kunihiko

1999-01-01

Many successful results have been obtained during the progress of angiography of which purpose has been changing from diagnosis to interventional radiography (IVR). The problem involved in IVR is the serious exposure to patients and operating staff. In the field of brain neurosurgery, use of IVR is expanding: e.g., for embolization of sick vasculature, for percutaneous transluminal angioplasty and for intra-arterial administration of therapeutic agents. When the skin doses were measured with thermoluminescence dosimeter (LiF), 409.9 and 2654.4 mGy of exposure were found in cases of 17 diagnoses and 17 IVR, respectively. Reduction of exposure was examined and discussed with angiography QC phantom and testing chart under various imaging conditions. Reduction could be attainable by reduction of fluoroscopy pulse rate and flame, and use of expanding function and filter. For protection of staff, scattering radiation doses and effects of shielding were examined with phantoms and ionization chamber survey meters to see the distribution of the radiation. For protection, it was important to make narrow the irradiation field and to use the shielding tools. (K.H.)

Impact of new technologies on dose reduction in CT

International Nuclear Information System (INIS)

Lee, Ting-Yim; Chhem, Rethy K.

2010-01-01

The introduction of slip ring technology enables helical CT scanning in the late 1980's and has rejuvenated CT's role in diagnostic imaging. Helical CT scanning has made possible whole body scanning in a single breath hold and computed tomography angiography (CTA) which has replaced invasive catheter based angiography in many cases because of its easy of operation and lesser risk to patients. However, a series of recent articles and accidents have heightened the concern of radiation risk from CT scanning. Undoubtedly, the radiation dose from CT studies, in particular, CCTA studies, are among the highest dose studies in diagnostic imaging. Nevertheless, CT has remained the workhorse of diagnostic imaging in emergent and non-emergent situations because of their ubiquitous presence in medical facilities from large academic to small regional hospitals and their round the clock accessibility due to their ease of use for both staff and patients as compared to MR scanners. The legitimate concern of radiation dose has sparked discussions on the risk vs benefit of CT scanning. It is recognized that newer CT applications, like CCTA and perfusion, will be severely curtailed unless radiation dose is reduced. This paper discusses the various hardware and software techniques developed to reduce radiation dose to patients in CT scanning. The current average effective dose of a CT study is ∼10 mSv, with the implementation of dose reduction techniques discussed herein; it is realistic to expect that the average effective dose may be decreased by 2-3 fold.

Dose reduction in spiral CT angiography of thoracic outlet syndrome by anatomically adapted tube current modulation

International Nuclear Information System (INIS)

Mastora, I.; Remy-Jardin, M.; Remy, J.; Suess, C.; Scherf, C.; Guillot, J.P.

2001-01-01

The aim of this study was to evaluate dose reduction in spiral CT angiography of the thoracic outlet by on-line tube-current control. Prospectively, 114 patients undergoing spiral CT angiography of the subclavian artery for thoracic outlet arterial syndromes were evaluated with and without tube-current modulation at the same session (scanning parameters for the two successive angiograms, one in the neutral position and one after the postural maneuver): 140 kV; 206 mA; scan time 0.75 s; collimation 3 mm; pitch = (1). The dose reduction system was applied in the neutral position in the first 92 consecutive patients and after postural maneuver in the remaining 22 consecutive patients. Dose reduction and image quality were analyzed in the overall study group (group 1; n = 114). The influence of the arm position was assessed in 44 of the 114 patients (group 2), matched by the transverse diameter of the upper thorax. The mean dose reduction was 33 % in group 1 (range 22-40 %) and 34 % in group 2 (range 26-40 %). In group 2 the only difference in image quality was a significantly higher frequency of graininess on low-dose scans compared with reference scans whatever the patient's arm position, graded as minimal in 38 of the 44 patients (86 %). When the low-dose technique was applied after postural maneuver in group 2: (a) the mean dose reduction was significantly higher (35 vs 32 % in the neutral position; p = 0.006); (b) graininess was less frequent (82 vs 91 % in the neutral position); and (c) the percentage of graininess graded as minimal was significantly higher (83 vs 70 % in the neutral position; p = 0.2027). On-line tube-current modulation enables dose reduction on high-quality, diagnostic spiral CT angiograms of the thoracic outlet and should be applied during data acquisition in the neutral position and after postural maneuver for optimal use. (orig.)

Dose reduction in spiral CT angiography of thoracic outlet syndrome by anatomically adapted tube current modulation

Energy Technology Data Exchange (ETDEWEB)

Mastora, I.; Remy-Jardin, M.; Remy, J. [Dept. of Radiology, University Center Hospital Calmette, Lille (France); Medical Research Group, Lille (France); Suess, C.; Scherf, C. [Siemens Medical Systems, Forcheim (Germany); Guillot, J.P. [Dept. of Radiology, University Center Hospital Calmette, Lille (France)

2001-04-01

The aim of this study was to evaluate dose reduction in spiral CT angiography of the thoracic outlet by on-line tube-current control. Prospectively, 114 patients undergoing spiral CT angiography of the subclavian artery for thoracic outlet arterial syndromes were evaluated with and without tube-current modulation at the same session (scanning parameters for the two successive angiograms, one in the neutral position and one after the postural maneuver): 140 kV; 206 mA; scan time 0.75 s; collimation 3 mm; pitch = (1). The dose reduction system was applied in the neutral position in the first 92 consecutive patients and after postural maneuver in the remaining 22 consecutive patients. Dose reduction and image quality were analyzed in the overall study group (group 1; n = 114). The influence of the arm position was assessed in 44 of the 114 patients (group 2), matched by the transverse diameter of the upper thorax. The mean dose reduction was 33 % in group 1 (range 22-40 %) and 34 % in group 2 (range 26-40 %). In group 2 the only difference in image quality was a significantly higher frequency of graininess on low-dose scans compared with reference scans whatever the patient's arm position, graded as minimal in 38 of the 44 patients (86 %). When the low-dose technique was applied after postural maneuver in group 2: (a) the mean dose reduction was significantly higher (35 vs 32 % in the neutral position; p = 0.006); (b) graininess was less frequent (82 vs 91 % in the neutral position); and (c) the percentage of graininess graded as minimal was significantly higher (83 vs 70 % in the neutral position; p = 0.2027). On-line tube-current modulation enables dose reduction on high-quality, diagnostic spiral CT angiograms of the thoracic outlet and should be applied during data acquisition in the neutral position and after postural maneuver for optimal use. (orig.)

Dose Reduction Techniques

CERN Document Server

Waggoner, L O

2000-01-01

As radiation safety specialists, one of the things we are required to do is evaluate tools, equipment, materials and work practices and decide whether the use of these products or work practices will reduce radiation dose or risk to the environment. There is a tendency for many workers that work with radioactive material to accomplish radiological work the same way they have always done it rather than look for new technology or change their work practices. New technology is being developed all the time that can make radiological work easier and result in less radiation dose to the worker or reduce the possibility that contamination will be spread to the environment. As we discuss the various tools and techniques that reduce radiation dose, keep in mind that the radiological controls should be reasonable. We can not always get the dose to zero, so we must try to accomplish the work efficiently and cost-effectively. There are times we may have to accept there is only so much you can do. The goal is to do the sm...

Pediatric CT: implementation of ASIR for substantial radiation dose reduction while maintaining pre-ASIR image noise.

Science.gov (United States)

Brady, Samuel L; Moore, Bria M; Yee, Brian S; Kaufman, Robert A

2014-01-01

To determine a comprehensive method for the implementation of adaptive statistical iterative reconstruction (ASIR) for maximal radiation dose reduction in pediatric computed tomography (CT) without changing the magnitude of noise in the reconstructed image or the contrast-to-noise ratio (CNR) in the patient. The institutional review board waived the need to obtain informed consent for this HIPAA-compliant quality analysis. Chest and abdominopelvic CT images obtained before ASIR implementation (183 patient examinations; mean patient age, 8.8 years ± 6.2 [standard deviation]; range, 1 month to 27 years) were analyzed for image noise and CNR. These measurements were used in conjunction with noise models derived from anthropomorphic phantoms to establish new beam current-modulated CT parameters to implement 40% ASIR at 120 and 100 kVp without changing noise texture or magnitude. Image noise was assessed in images obtained after ASIR implementation (492 patient examinations; mean patient age, 7.6 years ± 5.4; range, 2 months to 28 years) the same way it was assessed in the pre-ASIR analysis. Dose reduction was determined by comparing size-specific dose estimates in the pre- and post-ASIR patient cohorts. Data were analyzed with paired t tests. With 40% ASIR implementation, the average relative dose reduction for chest CT was 39% (2.7/4.4 mGy), with a maximum reduction of 72% (5.3/18.8 mGy). The average relative dose reduction for abdominopelvic CT was 29% (4.8/6.8 mGy), with a maximum reduction of 64% (7.6/20.9 mGy). Beam current modulation was unnecessary for patients weighing 40 kg or less. The difference between 0% and 40% ASIR noise magnitude was less than 1 HU, with statistically nonsignificant increases in patient CNR at 100 kVp of 8% (15.3/14.2; P = .41) for chest CT and 13% (7.8/6.8; P = .40) for abdominopelvic CT. Radiation dose reduction at pediatric CT was achieved when 40% ASIR was implemented as a dose reduction tool only; no net change to the magnitude

Data base on dose reduction research projects for nuclear power plants. Volume 5

Energy Technology Data Exchange (ETDEWEB)

Khan, T.A.; Yu, C.K.; Roecklein, A.K. [Brookhaven National Lab., Upton, NY (United States)

1994-05-01

This is the fifth volume in a series of reports that provide information on dose reduction research and health physics technology or nuclear power plants. The information is taken from two of several databases maintained by Brookhaven National Laboratory`s ALARA Center for the Nuclear Regulatory Commission. The research section of the report covers dose reduction projects that are in the experimental or developmental phase. It includes topics such as steam generator degradation, decontamination, robotics, improvements in reactor materials, and inspection techniques. The section on health physics technology discusses dose reduction efforts that are in place or in the process of being implemented at nuclear power plants. A total of 105 new or updated projects are described. All project abstracts from this report are available to nuclear industry professionals with access to a fax machine through the ACEFAX system or a computer with a modem and the proper communications software through the ACE system. Detailed descriptions of how to access all the databases electronically are in the appendices of the report.

Dose rate reduction using epoxy mixed lead shielding: experimental and theoretical determination of its shielding effectiveness

International Nuclear Information System (INIS)

Yadav, R.K.B.; Prasad, S.K.; Babu, K.S.; Hardiya, M.R.; Ullas, O.P.

2010-01-01

Full text: High background radiation field exists in Water Treatment Area (WTA) of Rod Cutting Building (RCB) in Cirus due to beta, gamma contamination on its floor. The high contamination on sides of wall and on floor is primarily due to deposition of activity generated during the regeneration of old mixed bed cartridges earlier (before year 1985) and presently due to deposition of contaminants by sump overflowing, wastes generated during maintenance/servicing of circulating pumps. RCB-WTA contribution to collective dose in present situation is up to 30% of the total collective dose of Cirus. Various options such as chipping of top layer of concrete floor of a sample area, in-situ placing of slab of cement and lead shot mixture were considered. In this case the man-rem consumption was high as radiation dose rate on concrete chip was 0.4 mGy/h and air activity generated was high, that too long lived with 137 Cs-as main constituent. The dose reduction factor was 1.7. In the second option the reduction in dose rate was insignificant and in-situ pouring of concrete consumed high collective dose. Hence above two options were not acceptable. Therefore the idea of tiling the contaminated floor with prefabricated epoxy mixed lead shots was accepted from ALARA point of view. It was concluded that pre-fabricated slabs of epoxy mixed lead slab of 25 mm thickness can be laid in RCB area to achieve a dose rate reduction factor of approximately five at a height of 30 cm above floor. This will result in a reduction of Person-mSv consumption in RCB by a factor of 5-10. These slabs of different thickness were fabricated outside RCB and were tested for shielding effectiveness experimentally by using radiation source and theoretically using MCNP code. Dose reduction factor of five for a point source, obtained experimentally for epoxy mixed lead shots was very near to value obtained by theoretical simulation. An extended calculation for an area source using this MCNP model gives a

Normal tissue complication probabilities: dependence on choice of biological model and dose-volume histogram reduction scheme

International Nuclear Information System (INIS)

Moiseenko, Vitali; Battista, Jerry; Van Dyk, Jake

2000-01-01

Purpose: To evaluate the impact of dose-volume histogram (DVH) reduction schemes and models of normal tissue complication probability (NTCP) on ranking of radiation treatment plans. Methods and Materials: Data for liver complications in humans and for spinal cord in rats were used to derive input parameters of four different NTCP models. DVH reduction was performed using two schemes: 'effective volume' and 'preferred Lyman'. DVHs for competing treatment plans were derived from a sample DVH by varying dose uniformity in a high dose region so that the obtained cumulative DVHs intersected. Treatment plans were ranked according to the calculated NTCP values. Results: Whenever the preferred Lyman scheme was used to reduce the DVH, competing plans were indistinguishable as long as the mean dose was constant. The effective volume DVH reduction scheme did allow us to distinguish between these competing treatment plans. However, plan ranking depended on the radiobiological model used and its input parameters. Conclusions: Dose escalation will be a significant part of radiation treatment planning using new technologies, such as 3-D conformal radiotherapy and tomotherapy. Such dose escalation will depend on how the dose distributions in organs at risk are interpreted in terms of expected complication probabilities. The present study indicates considerable variability in predicted NTCP values because of the methods used for DVH reduction and radiobiological models and their input parameters. Animal studies and collection of standardized clinical data are needed to ascertain the effects of non-uniform dose distributions and to test the validity of the models currently in use

Assessment of female breast dose for thoracic cone-beam CT using MOSFET dosimeters.

Science.gov (United States)

Sun, Wenzhao; Wang, Bin; Qiu, Bo; Liang, Jian; Xie, Weihao; Deng, Xiaowu; Qi, Zhenyu

2017-03-21

To assess the breast dose during a routine thoracic cone-beam CT (CBCT) check with the efforts to explore the possible dose reduction strategy. Metal oxide semiconductor field-effect transistor (MOSFET) dosimeters were used to measure breast surface doses during a thorax kV CBCT scan in an anthropomorphic phantom. Breast doses for different scanning protocols and breast sizes were compared. Dose reduction was attempted by using partial arc CBCT scan with bowtie filter. The impact of this dose reduction strategy on image registration accuracy was investigated. The average breast surface doses were 20.02 mGy and 11.65 mGy for thoracic CBCT without filtration and with filtration, respectively. This indicates a dose reduction of 41.8% by use of bowtie filter. It was found 220° partial arc scanning significantly reduced the dose to contralateral breast (44.4% lower than ipsilateral breast), while the image registration accuracy was not compromised. Breast dose reduction can be achieved by using ipsilateral 220° partial arc scan with bowtie filter. This strategy also provides sufficient image quality for thorax image registration in daily patient positioning verification.

Surface applicators for high dose rate brachytherapy in AIDS-related kaposi's sarcoma

International Nuclear Information System (INIS)

Evans, Michael D.C.; Yassa, Mariam; Podgorsak, Ervin B.; Roman, Ted N.; Schreiner, L. John; Souhami, Luis

1997-01-01

Purpose: The development of commercially available surface applicators using high dose rate remote afterloading devices has enabled radiotherapy centers to treat selected superficial lesions using a remote afterloading brachytherapy unit. The dosimetric parameters of these applicators, the clinical implementation of this technique, and a review of the initial patient treatment regimes are presented. Methods and Materials: A set of six fixed-diameter (1, 2, and 3 cm), tungsten/steel surface applicators is available for use with a single stepping-source (Ir-192, 370 GBq) high dose rate afterloader. The source can be positioned either in a parallel or perpendicular orientation to the treatment plane at the center of a conical aperture that sits at an SSD of approximately 15 mm and is used with a 1-mm thick removable plastic cap. The surface dose rates, percent depth dose, and off-axis ratios were measured. A custom-built, ceiling-mounted immobilization device secures the applicator on the surface of the patient's lesion during treatment. Results: Between November 1994, and September 1996, 16 AIDS-related Kaposi's sarcoma patients having a total of 120 lesions have been treated with palliative intent. Treatment sites were distributed between the head and neck, extremity, and torso. Doses ranged from 8 to 20 Gy, with a median dose of 10 Gy delivered in a single fraction. Treatments were well tolerated with minimal skin reaction, except for patients with lesions treated to 20 Gy who developed moderate/severe desquamation. Conclusion: Radiotherapy centers equipped with a high dose rate remote afterloading unit may treat small selected surface lesions with commercially available surface applicators. These surface applicators must be used with a protective cap to eliminate electron contamination. The optimal surface dose appears to be either 10 or 15 Gy depending upon the height of the lesion

Dose reduction in CT by on-line tube current control: principles and validation on phantoms and cadavers

International Nuclear Information System (INIS)

Kalender, W.A.; Wolf, H.; Suess, C.; Gies, M.; Greess, H.; Bautz, W.A.

1999-01-01

We investigated approaches to reducing the dose in CT without impairing image quality. Dose can be reduced for non-circular object cross-sections without a significant increase in noise if X-ray tube current is reduced at angular tube positions where the X-ray attenuation by the patients is small. We investigated different schemes of current modulation during tube rotation by simulation and phantom measurements. Both pre-programmed sinusoidal modulation functions and attenuation-based on-line control of the tube current were evaluated. All relevant scan parameters were varied, including constraints such as the maximum modulation amplitude. A circular, an elliptical and two oval water phantoms were used. Results were validated on six cadavers. Dose reduction of 10-45 % was obtained both in simulations and in measurements for the different non-circular phantom geometries and current modulation algorithms without an increase in pixel noise values. On-line attenuation-based control yielded higher reductions than modulation by a sinusoidal curve. The maximal dose reduction predicted by simulations could not be achieved due to limits in the modulation amplitude. In cadaver studies, a reduction of typically 20-40 % was achieved for the body and about 10 % for the head. Variations of our technique are possible; a slight increase in nominal tube current for high-attenuation projections combined with attenuation-based current modulation still yields significant dose reduction, but also a reduction in the structured noise that may obscure diagnostic details. We conclude that a significant reduction in dose can be achieved by tube current modulation without compromising image quality. Attenuation-based on-line control and a modulation amplitude of at least 90 % should be employed. (orig.)

Characterization of adaptive statistical iterative reconstruction algorithm for dose reduction in CT: A pediatric oncology perspective

Energy Technology Data Exchange (ETDEWEB)

Brady, S. L.; Yee, B. S.; Kaufman, R. A. [Department of Radiological Sciences, St. Jude Children' s Research Hospital, Memphis, Tennessee 38105 (United States)

2012-09-15

Purpose: This study demonstrates a means of implementing an adaptive statistical iterative reconstruction (ASiR Trade-Mark-Sign ) technique for dose reduction in computed tomography (CT) while maintaining similar noise levels in the reconstructed image. The effects of image quality and noise texture were assessed at all implementation levels of ASiR Trade-Mark-Sign . Empirically derived dose reduction limits were established for ASiR Trade-Mark-Sign for imaging of the trunk for a pediatric oncology population ranging from 1 yr old through adolescence/adulthood. Methods: Image quality was assessed using metrics established by the American College of Radiology (ACR) CT accreditation program. Each image quality metric was tested using the ACR CT phantom with 0%-100% ASiR Trade-Mark-Sign blended with filtered back projection (FBP) reconstructed images. Additionally, the noise power spectrum (NPS) was calculated for three common reconstruction filters of the trunk. The empirically derived limitations on ASiR Trade-Mark-Sign implementation for dose reduction were assessed using (1, 5, 10) yr old and adolescent/adult anthropomorphic phantoms. To assess dose reduction limits, the phantoms were scanned in increments of increased noise index (decrementing mA using automatic tube current modulation) balanced with ASiR Trade-Mark-Sign reconstruction to maintain noise equivalence of the 0% ASiR Trade-Mark-Sign image. Results: The ASiR Trade-Mark-Sign algorithm did not produce any unfavorable effects on image quality as assessed by ACR criteria. Conversely, low-contrast resolution was found to improve due to the reduction of noise in the reconstructed images. NPS calculations demonstrated that images with lower frequency noise had lower noise variance and coarser graininess at progressively higher percentages of ASiR Trade-Mark-Sign reconstruction; and in spite of the similar magnitudes of noise, the image reconstructed with 50% or more ASiR Trade-Mark-Sign presented a more

Practical experience of monitoring patient dose

Energy Technology Data Exchange (ETDEWEB)

McDonnell, C.; Shrimpton, P. (National Radiological Protection Board, Chilton (United Kingdom)); O' Mahoney, M. (National Radiological Protection Board, Leeds (United Kingdom)); Foster, J. (Nuffield Hospitals, Surbiton (United Kingdom))

1994-05-01

NRPB recommends the use of reference dose levels for diagnostic medical exposures as an aid to patient dose reduction, but is this approach effective This article describes the broadly encouraging experiences of one large group of hospitals in carrying out measurements of entrance surface dose on patients undergoing some common types of x-ray examination. (author).

Construction of boundary-surface-based Chinese female astronaut computational phantom and proton dose estimation

International Nuclear Information System (INIS)

Sun Wenjuan; Xie Tianwu; Liu Qian; Jia Xianghong; Xu Feng

2013-01-01

With the rapid development of China's space industry, the importance of radiation protection is increasingly prominent. To provide relevant dose data, we first developed the Visible Chinese Human adult Female (VCH-F) phantom, and performed further modifications to generate the VCH-F Astronaut (VCH-FA) phantom, incorporating statistical body characteristics data from the first batch of Chinese female astronauts as well as reference organ mass data from the International Commission on Radiological Protection (ICRP; both within 1% relative error). Based on cryosection images, the original phantom was constructed via Non-Uniform Rational B-Spline (NURBS) boundary surfaces to strengthen the deformability for fitting the body parameters of Chinese female astronauts. The VCH-FA phantom was voxelized at a resolution of 2 x 2 x 4 mm 3 for radioactive particle transport simulations from isotropic protons with energies of 5000 - 10 000 MeV in Monte Carlo N-Particle eXtended (MCNPX) code. To investigate discrepancies caused by anatomical variations and other factors, the obtained doses were compared with corresponding values from other phantoms and sex-averaged doses. Dose differences were observed among phantom calculation results, especially for effective dose with low-energy protons. Local skin thickness shifts the breast dose curve toward high energy, but has little impact on inner organs. Under a shielding layer, organ dose reduction is greater for skin than for other organs. The calculated skin dose per day closely approximates measurement data obtained in low-Earth orbit (LEO). (author)

Construction of boundary-surface-based Chinese female astronaut computational phantom and proton dose estimation

Science.gov (United States)

Sun, Wenjuan; JIA, Xianghong; XIE, Tianwu; XU, Feng; LIU, Qian

2013-01-01

With the rapid development of China's space industry, the importance of radiation protection is increasingly prominent. To provide relevant dose data, we first developed the Visible Chinese Human adult Female (VCH-F) phantom, and performed further modifications to generate the VCH-F Astronaut (VCH-FA) phantom, incorporating statistical body characteristics data from the first batch of Chinese female astronauts as well as reference organ mass data from the International Commission on Radiological Protection (ICRP; both within 1% relative error). Based on cryosection images, the original phantom was constructed via Non-Uniform Rational B-Spline (NURBS) boundary surfaces to strengthen the deformability for fitting the body parameters of Chinese female astronauts. The VCH-FA phantom was voxelized at a resolution of 2 × 2 × 4 mm3for radioactive particle transport simulations from isotropic protons with energies of 5000–10 000 MeV in Monte Carlo N-Particle eXtended (MCNPX) code. To investigate discrepancies caused by anatomical variations and other factors, the obtained doses were compared with corresponding values from other phantoms and sex-averaged doses. Dose differences were observed among phantom calculation results, especially for effective dose with low-energy protons. Local skin thickness shifts the breast dose curve toward high energy, but has little impact on inner organs. Under a shielding layer, organ dose reduction is greater for skin than for other organs. The calculated skin dose per day closely approximates measurement data obtained in low-Earth orbit (LEO). PMID:23135158

Nitrite reduction mechanism on a Pd surface.

Science.gov (United States)

Shin, Hyeyoung; Jung, Sungyoon; Bae, Sungjun; Lee, Woojin; Kim, Hyungjun

2014-11-04

Nitrate (NO3-) is one of the most harmful contaminants in the groundwater, and it causes various health problems. Bimetallic catalysts, usually palladium (Pd) coupled with secondary metallic catalyst, are found to properly treat nitrate-containing wastewaters; however, the selectivity toward N2 production over ammonia (NH3) production still requires further improvement. Because the N2 selectivity is determined at the nitrite (NO2-) reduction step on the Pd surface, which occurs after NO3- is decomposed into NO2- on the secondary metallic catalyst, we here performed density functional theory (DFT) calculations and experiments to investigate the NO2- reduction pathway on the Pd surface activated by hydrogen. Based on extensive DFT calculations on the relative energetics among ∼100 possible intermediates, we found that NO2- is easily reduced to NO* on the Pd surface, followed by either sequential hydrogenation steps to yield NH3 or a decomposition step to N* and O* (an adsorbate on Pd is denoted using an asterisk). Based on the calculated high migration barrier of N*, we further discussed that the direct combination of two N* to yield N2 is kinetically less favorable than the combination of a highly mobile H* with N* to yield NH3. Instead, the reduction of NO2- in the vicinity of the N* can yield N2O* that can be preferentially transformed into N2 via diverse reaction pathways. Our DFT results suggest that enhancing the likelihood of N* encountering NO2- in the solution phase before combination with surface H* is important for maximizing the N2 selectivity. This is further supported by our experiments on NO2- reduction by Pd/TiO2, showing that both a decreased H2 flow rate and an increased NO2- concentration increased the N2 selectivity (78.6-93.6% and 57.8-90.9%, respectively).

Immunosensing by luminescence reduction in surface-modified microstructured SU-8

Energy Technology Data Exchange (ETDEWEB)

Eravuchira, Pinkie Jacob; Baranowska, Malgorzata; Eckstein, Chris [Departament d’Enginyeria Electrònica, Elèctrica i Automàtica, Universitat Rovira i Virgili, Avda. Països Catalans 26, Tarragona 43007 (Spain); Díaz, Francesc [Departament de Química Física i Inorgànica, Universitat Rovira i Virgili, Marcelí Domingo s/n, Tarragona 43007 (Spain); Llobet, Eduard; Marsal, Lluis F. [Departament d’Enginyeria Electrònica, Elèctrica i Automàtica, Universitat Rovira i Virgili, Avda. Països Catalans 26, Tarragona 43007 (Spain); Ferré-Borrull, Josep, E-mail: josep.ferre@urv.cat [Departament d’Enginyeria Electrònica, Elèctrica i Automàtica, Universitat Rovira i Virgili, Avda. Països Catalans 26, Tarragona 43007 (Spain)

2017-01-15

Highlights: • The reduction of photoluminescence of SU-8 upon surface modification is reported. • Micropillar structuring of SU-8 surface results in an increased photoluminescence reduction rate (10% glass, 15% silicon). • Photoluminescence reduction rate can be a transduction parameter for the detection of antibody-antigen binding events. • The proposed sensing mechanism can be used to quantify small concentrations of antibody. • Lower limit of detection (LOD) of 28 μg/ml on silicon substrates and 42 μg/ml on glass substrates was achieved. - Abstract: SU-8, an epoxy based negative photoresist is extensively used as a structural material for the fabrication of microelectro-mechanical systems and in microelectronics technology. However, the possible applications of SU-8 for biosensing have not been explored much, mainly because of the photoluminescence SU-8 possesses in the near-UV and visible wavelength ranges which hinders fluorescent labelling of biorecognition events. In this study we demonstrate that photoluminescence of SU-8 can be employed itself as a sensing transduction parameter to produce a tool for immunosensing: the photoluminescence shows a systematic reduction upon modification of its surface chemistry, and in particular upon attachment of an antigen-antibody (aIgG-IgG) pair. We investigate the relation of the amount of reduction of photoluminescence on planar and microstructured surfaces, and we show that microstructuring leads to a higher reduction than a planar surface. Furthermore, we evaluated the dependence of photoluminescence reduction as a function of analyte concentration to prove that this magnitude can be applied to immunosensing.

Radiation dose reduction at a price: the effectiveness of a thyroid shield during head CT scanning

International Nuclear Information System (INIS)

Fu Qiang; Lu Tao; Zhang Ling

2008-01-01

Objective: To assess radiation dose to the thyroid in patients undergoing head CT scanning and to evaluate dose reduction to the thyroid by load shielding. Methods: A post-morterm was scanned by different model and study was undertaken to evaluate the dose reduction by thyroid lead shields and assess their practicality in a clinical setting. (a)No thyroid shields and (b) thyroid shield. One thermoluminescent dosimeters (TLDs)were placed over the thyroid gland center, A thyroid lead shield (Pb eq 0.5mm)was placed around the neck of post-morterm. Scan parameter, CTDIw and DLP were recorded. Results: (a) 0.207mSv; (b) 0.085mSv. A mean effective radiation dose reduction of 58% was seen in the shielded versus the unshielded. Conclusion: Thyroid exposure to scattered radiation from head CT scanning only once is associated with a low but not negligible risk of cancer, but accumulatived doses to the thyroid are serious, highlighting the need for increased awareness of patient radiation protection. Thyroid lead shielding yields significant radiation protection, which should be used routinely during head CT scan. (authors)

Use of a channelized Hotelling observer to assess CT image quality and optimize dose reduction for iteratively reconstructed images.

Science.gov (United States)

Favazza, Christopher P; Ferrero, Andrea; Yu, Lifeng; Leng, Shuai; McMillan, Kyle L; McCollough, Cynthia H

2017-07-01

The use of iterative reconstruction (IR) algorithms in CT generally decreases image noise and enables dose reduction. However, the amount of dose reduction possible using IR without sacrificing diagnostic performance is difficult to assess with conventional image quality metrics. Through this investigation, achievable dose reduction using a commercially available IR algorithm without loss of low contrast spatial resolution was determined with a channelized Hotelling observer (CHO) model and used to optimize a clinical abdomen/pelvis exam protocol. A phantom containing 21 low contrast disks-three different contrast levels and seven different diameters-was imaged at different dose levels. Images were created with filtered backprojection (FBP) and IR. The CHO was tasked with detecting the low contrast disks. CHO performance indicated dose could be reduced by 22% to 25% without compromising low contrast detectability (as compared to full-dose FBP images) whereas 50% or more dose reduction significantly reduced detection performance. Importantly, default settings for the scanner and protocol investigated reduced dose by upward of 75%. Subsequently, CHO-based protocol changes to the default protocol yielded images of higher quality and doses more consistent with values from a larger, dose-optimized scanner fleet. CHO assessment provided objective data to successfully optimize a clinical CT acquisition protocol.

Increased dose near the skin due to electromagnetic surface beacon transponder.

Science.gov (United States)

Ahn, Kang-Hyun; Manger, Ryan; Halpern, Howard J; Aydogan, Bulent

2015-05-08

The purpose of this study was to evaluate the increased dose near the skin from an electromagnetic surface beacon transponder, which is used for localization and tracking organ motion. The bolus effect due to the copper coil surface beacon was evaluated with radiographic film measurements and Monte Carlo simulations. Various beam incidence angles were evaluated for both 6 MV and 18 MV experimentally. We performed simulations using a general-purpose Monte Carlo code MCNPX (Monte Carlo N-Particle) to supplement the experimental data. We modeled the surface beacon geometry using the actual mass of the glass vial and copper coil placed in its L-shaped polyethylene terephthalate tubing casing. Film dosimetry measured factors of 2.2 and 3.0 enhancement in the surface dose for normally incident 6 MV and 18 MV beams, respectively. Although surface dose further increased with incidence angle, the relative contribution from the bolus effect was reduced at the oblique incidence. The enhancement factors were 1.5 and 1.8 for 6 MV and 18 MV, respectively, at an incidence angle of 60°. Monte Carlo simulation confirmed the experimental results and indicated that the epidermal skin dose can reach approximately 50% of the dose at dmax at normal incidence. The overall effect could be acceptable considering the skin dose enhancement is confined to a small area (~ 1 cm2), and can be further reduced by using an opposite beam technique. Further clinical studies are justified in order to study the dosimetric benefit versus possible cosmetic effects of the surface beacon. One such clinical situation would be intact breast radiation therapy, especially large-breasted women.

Radiation dose reduction in parasinus CT by spectral shaping

Energy Technology Data Exchange (ETDEWEB)

May, Matthias S.; Brand, Michael; Lell, Michael M.; Uder, Michael; Wuest, Wolfgang [University Hospital Erlangen, Department of Radiology, Erlangen (Germany); Sedlmair, Martin; Allmendinger, Thomas [Siemens Healthcare GmbH, Forchheim (Germany)

2017-02-15

Spectral shaping aims to narrow the X-ray spectrum of clinical CT. The aim of this study was to determine the image quality and the extent of radiation dose reduction that can be achieved by tin prefiltration for parasinus CT. All scans were performed with a third generation dual-source CT scanner. A study protocol was designed using 100 kV tube voltage with tin prefiltration (200 mAs) that provides image noise levels comparable to a low-dose reference protocol using 100 kV without spectral shaping (25 mAs). One hundred consecutive patients were prospectively enrolled and randomly assigned to the study or control group. All patients signed written informed consent. The study protocol was approved by the local Institutional Review Board and applies to the HIPAA. Subjective and objective image quality (attenuation values, image noise, and contrast-to-noise ratio (CNR)) were assessed. Radiation exposure was assessed as volumetric CT dose index, and effective dose was estimated. Mann-Whitney U test was performed for radiation exposure and for image noise comparison. All scans were of diagnostic image quality. Image noise in air, in the retrobulbar fat, and in the eye globe was comparable between both groups (all p > 0.05). CNR{sub eye} {sub globe/air} did not differ significantly between both groups (p = 0.7). Radiation exposure (1.7 vs. 2.1 mGy, p < 0.01) and effective dose (0.055 vs. 0.066 mSv, p < 0.01) were significantly reduced in the study group. Radiation dose can be further reduced by 17% for low-dose parasinus CT by tin prefiltration maintaining diagnostic image quality. (orig.)

Radiation dose reduction in parasinus CT by spectral shaping

International Nuclear Information System (INIS)

May, Matthias S.; Brand, Michael; Lell, Michael M.; Uder, Michael; Wuest, Wolfgang; Sedlmair, Martin; Allmendinger, Thomas

2017-01-01

Spectral shaping aims to narrow the X-ray spectrum of clinical CT. The aim of this study was to determine the image quality and the extent of radiation dose reduction that can be achieved by tin prefiltration for parasinus CT. All scans were performed with a third generation dual-source CT scanner. A study protocol was designed using 100 kV tube voltage with tin prefiltration (200 mAs) that provides image noise levels comparable to a low-dose reference protocol using 100 kV without spectral shaping (25 mAs). One hundred consecutive patients were prospectively enrolled and randomly assigned to the study or control group. All patients signed written informed consent. The study protocol was approved by the local Institutional Review Board and applies to the HIPAA. Subjective and objective image quality (attenuation values, image noise, and contrast-to-noise ratio (CNR)) were assessed. Radiation exposure was assessed as volumetric CT dose index, and effective dose was estimated. Mann-Whitney U test was performed for radiation exposure and for image noise comparison. All scans were of diagnostic image quality. Image noise in air, in the retrobulbar fat, and in the eye globe was comparable between both groups (all p > 0.05). CNR_e_y_e _g_l_o_b_e_/_a_i_r did not differ significantly between both groups (p = 0.7). Radiation exposure (1.7 vs. 2.1 mGy, p < 0.01) and effective dose (0.055 vs. 0.066 mSv, p < 0.01) were significantly reduced in the study group. Radiation dose can be further reduced by 17% for low-dose parasinus CT by tin prefiltration maintaining diagnostic image quality. (orig.)

SU-G-IeP3-05: Effects of Image Receptor Technology and Dose Reduction Software On Radiation Dose Estimates for Fluoroscopically-Guided Interventional (FGI) Procedures

Energy Technology Data Exchange (ETDEWEB)

Merritt, Z; Dave, J; Eschelman, D; Gonsalves, C [Thomas Jefferson University, Philadelphia, PA (United States)

2016-06-15

Purpose: To investigate the effects of image receptor technology and dose reduction software on radiation dose estimates for most frequently performed fluoroscopically-guided interventional (FGI) procedures at a tertiary health care center. Methods: IRB approval was obtained for retrospective analysis of FGI procedures performed in the interventional radiology suites between January-2011 and December-2015. This included procedures performed using image-intensifier (II) based systems which were subsequently replaced, flat-panel-detector (FPD) based systems which were later upgraded with ClarityIQ dose reduction software (Philips Healthcare) and relatively new FPD system already equipped with ClarityIQ. Post procedure, technologists entered system-reported cumulative air kerma (CAK) and kerma-area product (KAP; only KAP for II based systems) in RIS; these values were analyzed. Data pre-processing included correcting typographical errors and cross-verifying CAK and KAP. The most frequent high and low dose FGI procedures were identified and corresponding CAK and KAP values were compared. Results: Out of 27,251 procedures within this time period, most frequent high and low dose procedures were chemo/immuno-embolization (n=1967) and abscess drainage (n=1821). Mean KAP for embolization and abscess drainage procedures were 260,657, 310,304 and 94,908 mGycm{sup 2}, and 14,497, 15,040 and 6307 mGycm{sup 2} using II-, FPD- and FPD with ClarityIQ- based systems, respectively. Statistically significant differences were observed in KAP values for embolization procedures with respect to different systems but for abscess drainage procedures significant differences were only noted between systems with FPD and FPD with ClarityIQ (p<0.05). Mean CAK reduced significantly from 823 to 308 mGy and from 43 to 21 mGy for embolization and abscess drainage procedures, respectively, in transitioning to FPD systems with ClarityIQ (p<0.05). Conclusion: While transitioning from II- to FPD- based

Radiation dose reduction in digital breast tomosynthesis (DBT) by means of deep-learning-based supervised image processing

Science.gov (United States)

Liu, Junchi; Zarshenas, Amin; Qadir, Ammar; Wei, Zheng; Yang, Limin; Fajardo, Laurie; Suzuki, Kenji

2018-03-01

To reduce cumulative radiation exposure and lifetime risks for radiation-induced cancer from breast cancer screening, we developed a deep-learning-based supervised image-processing technique called neural network convolution (NNC) for radiation dose reduction in DBT. NNC employed patched-based neural network regression in a convolutional manner to convert lower-dose (LD) to higher-dose (HD) tomosynthesis images. We trained our NNC with quarter-dose (25% of the standard dose: 12 mAs at 32 kVp) raw projection images and corresponding "teaching" higher-dose (HD) images (200% of the standard dose: 99 mAs at 32 kVp) of a breast cadaver phantom acquired with a DBT system (Selenia Dimensions, Hologic, CA). Once trained, NNC no longer requires HD images. It converts new LD images to images that look like HD images; thus the term "virtual" HD (VHD) images. We reconstructed tomosynthesis slices on a research DBT system. To determine a dose reduction rate, we acquired 4 studies of another test phantom at 4 different radiation doses (1.35, 2.7, 4.04, and 5.39 mGy entrance dose). Structural SIMilarity (SSIM) index was used to evaluate the image quality. For testing, we collected half-dose (50% of the standard dose: 32+/-14 mAs at 33+/-5 kVp) and full-dose (standard dose: 68+/-23 mAs at 33+/-5 kvp) images of 10 clinical cases with the DBT system at University of Iowa Hospitals and Clinics. NNC converted half-dose DBT images of 10 clinical cases to VHD DBT images that were equivalent to full dose DBT images. Our cadaver phantom experiment demonstrated 79% dose reduction.

An education and training programme for radiological institutes: impact on the reduction of the CT radiation dose

International Nuclear Information System (INIS)

Schindera, Sebastian T.; Allmen, Gabriel von; Vock, Peter; Szucs-Farkas, Zsolt; Treier, Reto; Trueb, Philipp R.; Nauer, Claude

2011-01-01

To establish an education and training programme for the reduction of CT radiation doses and to assess this programme's efficacy. Ten radiological institutes were counselled. The optimisation programme included a small group workshop and a lecture on radiation dose reduction strategies. The radiation dose used for five CT protocols (paranasal sinuses, brain, chest, pulmonary angiography and abdomen) was assessed using the dose-length product (DLP) before and after the optimisation programme. The mean DLP values were compared with national diagnostic reference levels (DRLs). The average reduction of the DLP after optimisation was 37% for the sinuses (180 vs. 113 mGycm, P < 0.001), 9% for the brain (982 vs. 896 mGycm, P < 0.05), 24% for the chest (425 vs. 322 mGycm, P < 0.05) and 42% for the pulmonary arteries (352 vs. 203 mGycm, P < 0.001). No significant change in DLP was found for abdominal CT. The post-optimisation DLP values of the sinuses, brain, chest, pulmonary arteries and abdomen were 68%, 10%, 20%, 55% and 15% below the DRL, respectively. The education and training programme for radiological institutes is effective in achieving a substantial reduction in CT radiation dose. (orig.)

Efficacy of patient skin dose reduction by a compensating filter through of irradiation field overlaps on the area during percutaneous coronary intervention

International Nuclear Information System (INIS)

Yamasaki, Hiroyuki; Yamaguchi, Sadao; Yamamoto, Naomi; Miyagawa, Takashi; Hirose, Etsuko; Takenaka, Tatsuaki; Nakahara, Makoto

2011-01-01

Our study was involved with entrance surface dose reduction and irradiation field by the filter use of PCI, and insertion in place of an effective compensating filter to maximize entrance surface dose reduction, which we verified. The radiation dosimetry put a 6 cc ion chamber on the back side of the thorax phantom, and changed the filter of the four corners (a: upper left, b: upper right, c: lower right, d: lower left) of the monitor confirmed with fluoroscopy [(0) no filter, (1) one filter, (2) two filters]. The angle of C arm was assumed to be eight directions and 0 degrees adopted by this hospital. It was compared with a corrective rate of which one was no filter. Next, the presence of filter and irradiation field overlaps on the area in monitor in the angle of C arm was verified by this hospital's classic example. As for corrective rate, (1) becomes 0.41 and (2) become 0.25 at fluoroscopy, (1) becomes 0.26 and (2) become 0.16 at exposure. Irradiation field overlaps on the area (+) compensating filter (-) was many with d of right anterior oblique (RAO)/cranial (CAU), a of RAO and c of CAU at left coronary angiography (CAG), c of left anterior oblique (LAO) at right CAG, b of LAO/cranial (CRA) (left CAG), b of CRA (right CAG) and a and d of RAO (right CAG) at both CAG. Irradiation field overlaps on the area (+) compensating filter (+) was many with b of CRA at left CAG, a of LAO/CRA at right CAG, b of CRA (left CAG) and b of RAO (right CAG) at both CAG. When the compensating filter is used the entrance surface dose reduction effect was great. If automatic exposure control protects the part of irradiation field overlaps on the area in the range without operating excessively, the radiological risk can be reduced, and it is conceivable as useful clinical setting. (author)

Dose reduction in evacuation proctography

International Nuclear Information System (INIS)

Hare, C.; Halligan, S.; Bartram, C.I.; Gupta, R.; Walker, A.E.; Renfrew, I.

2001-01-01

The goal of this study was to reduce the patient radiation dose from evacuation proctography. Ninety-eight consecutive adult patients referred for proctography to investigate difficult rectal evacuation were studied using a digital imaging system with either a standard digital program for barium examinations, a reduced dose digital program (both with and without additional copper filtration), or Video fluoroscopy. Dose-area products were recorded for each examination and the groups were compared. All four protocols produced technically acceptable examinations. The low-dose program with copper filtration (median dose 382 cGy cm 2 ) and Video fluoroscopy (median dose 705 cGy cm 2 ) were associated with significantly less dose than other groups (p < 0.0001). Patient dose during evacuation proctography can be reduced significantly without compromising the diagnostic quality of the examination. A digital program with added copper filtration conveyed the lowest dose. (orig.)

Exposure dose to gonad and its reduction in CT examinations

International Nuclear Information System (INIS)

Suzuki, Shoichi; Menju, Mina; Nakazawa, Masato

2006-01-01

Exposure doses to gonad (ovary and uterus) due to scattering at the ordinary CT examinations of head, breast, and abdomen (liver) were measured and their reductions by the protective apron usually used in clinic were evaluated by comparison of the given and International Commission of Radiological Protection (ICRP) data for risk assessment. Multi-slice helical/scanno-helical CT for the regions under ordinary diagnostic conditions was done by the apparatus Toshiba Aquilion 16 for the human body phantom (Alderson) with or without the apron (Hagoromo) equivalent to 0.25 mm thick lead. Doses inside and outside the beam flux were measured by the thermoluminescent dosimeter, of which data were corrected by Radcal Model 300 ionization chamber. The doses in the gonad due to scattering were found to be in the range from 0.01 (head CT) to 1 (liver CT) mGy and to be reduced in 20-30% by the apron. Found dose were far smaller than the ICRP threshold values for inducing teratosis and infertality. (T.I.)

Evaluation of the Entrance Surface Dose (ESD and Radiation Dose to the Radiosensitive Organs in Pediatric Pelvic Radiography

Directory of Open Access Journals (Sweden)

Vahid Karami

2017-06-01

Full Text Available Background Patients' dosimetry is crucial in order to enhance radiation protection optimization and to deliver low radiation dose to the patients in a radiological procedure. The aim of this study was to assess the entrance surface dose (ESD and radiation dose to the radiosensitive organs in pediatric pelvic radiography. Materials and Methods The studied population included 98 pediatric patients of both genders referred to anteroposterior (AP projection of pelvic radiography. The radiation dose was directly measured using high radiosensitive cylindrical lithium fluoride thermo-luminescent dosimeters (TLD-GR200. Two TLDs were placed at the center point of the radiation field to measure the ESD of pelvis. Moreover for each patient, 2 TLDs were placed upon each eyelid, 2 TLDs upon each breast, 2 TLDs upon the surface anatomical position of the thyroid gland and finally 2 TLDs at the surface anatomical position of the gonads to measure the received dose. Results The ESD ± standard deviation for AP pelvic radiography was obtained 591.7±76 µGy. Statistically significant difference was obtained between organs located outside and inside of the radiation field with respect to dose received (P

Dose reduction using bismuth shielding during paediatric CT examinations in Slovakia

International Nuclear Information System (INIS)

Gbelcova, L.; Nikodemova, D.; Horvathova, M.

2011-01-01

Considering the massive increase of computer tomography (CT) examinations in Slovakia during the last 10 y, it can be expected that a higher radiation load may be observed in the Slovak population. Since child population is more sensitive to radiation than adult population, a monitoring has started to see how high the radiation dose is for paediatric patients during CT examinations in chosen departments in Slovakia. The CT examination of the head is one of the most frequently done examinations in Slovakian departments and that is why measurements were done to clarify how usage of bismuth shields for eyes and thyroid can affect the eye and thyroid doses. For simulation, 215 thermoluminescent dosimeters were exposed on anthropomorphic phantom of a child with and without usage of bismuth shields. The result was that only two of the three chosen departments confirmed a reduction. On the other hand, one of the departments confirmed that the reduction can be up to 56-65 %, which is significant. (authors)

Patient surface doses in computerized tomography examinations

International Nuclear Information System (INIS)

Vekic, B; Kovacevic, S.; Ranogajec-Komor, M.; Duvnjak, N.; Marusic, P.; Anic, P.; Dolencic, P.

1996-01-01

The diagnostic value of computerized tomography has increased due to very rapid technical advances in both equipment and techniques. When the CT scanners were introduced, a significant problem for the specification of the radiation dose imparted to the patient undergoing CT examination has been created. In CT, the conditions of exposure are quite different from those in conventional X-ray imaging. CT procedure involves the continuous tomography of thin layers. Some of these layers touch each other while others overlap. The radiation doses received by patients can vary considerably. In addition to the radiation from the collimated primary beam, patients are exposed to significant scattered doses in unpredictable amounts. Every effort should be made to keep these doses to a reasonable minimum, without sacrificing the image quality. The aims of this work were to determine the surface doses delivered to various organs of patients during various computerized tomography examinations (head, thorax, kidney, abdomen and pelvis). Particular attention was directed to the precise determination of doses received by the eyes (during CT of head) and gonads (during CT of pelvis and lower abdomen) since these organs can be near or even in the primary X-ray beam

Effects of indoor residence on radiation doses from routine releases of radionuclides to the atmosphere

International Nuclear Information System (INIS)

Kocher, D.C.

1980-01-01

Dose reduction factors from indoor residence during routine releases of radionuclides to the atmosphere were studied using models that are suitable for application to arbitrary source terms. Dose reduction factors for internal exposure to inhaled radionuclides account for air ventilation and deposition on inside building surfaces. Estimated internal dose reduction factors are approx. 0.2 to 0.8 for particulates and 0.07 to 0.4 for radioiodine. Dose reduction factors for external photon exposure from airborne and surface-deposited sources are based on the point-kernel integration method. Values for source terms from a fuel reprocessing plant and a hypothetical reactor accident are within a factor of 2 of the value 0.5 adopted by the US Nuclear Regulatory Commission (NRC) for population dose assessments. For the release at Three Mile Island nuclear station, however, the external dose reduction factor may be an order of magnitude less than the value adopted by the NRC

Radiation dose reduction for CT assessment of urolithiasis using iterative reconstruction. A prospective intra-individual study

Energy Technology Data Exchange (ETDEWEB)

Harder, Annemarie M. den; Willemink, Martin J.; Wessels, Frank J.; Schilham, Arnold M.R.; Leiner, Tim; Jong, Pim A. de [Utrecht University Medical Center, Department of Radiology, Utrecht (Netherlands); Doormaal, Pieter J. van; Budde, Ricardo P.J. [Erasmus Medical Center, Department of Radiology, Rotterdam (Netherlands); Lock, M.T.W.T. [University Medical Center, Department of Urology, Utrecht (Netherlands)

2018-01-15

To assess the performance of hybrid (HIR) and model-based iterative reconstruction (MIR) in patients with urolithiasis at reduced-dose computed tomography (CT). Twenty patients scheduled for unenhanced abdominal CT for follow-up of urolithiasis were prospectively included. Routine dose acquisition was followed by three low-dose acquisitions at 40%, 60% and 80% reduced doses. All images were reconstructed with filtered back projection (FBP), HIR and MIR. Urolithiasis detection rates, gall bladder, appendix and rectosigmoid evaluation and overall subjective image quality were evaluated by two observers. 74 stones were present in 17 patients. Half the stones were not detected on FBP at the lowest dose level, but this improved with MIR to a sensitivity of 100%. HIR resulted in a slight decrease in sensitivity at the lowest dose to 72%, but outperformed FBP. Evaluation of other structures with HIR at 40% and with MIR at 60% dose reductions was comparable to FBP at routine dose, but 80% dose reduction resulted in non-evaluable images. CT radiation dose for urolithiasis detection can be safely reduced by 40 (HIR)-60 (MIR) % without affecting assessment of urolithiasis, possible extra-urinary tract pathology or overall image quality. (orig.)

SU-F-T-621: Impact of Vacuum and Treatment Couch On Surface Dose in Stereotactic Body Radiation Therapy With and Without a Flattening Filter

Energy Technology Data Exchange (ETDEWEB)

Lan, HT; Lu, SH; Kuo, SH; Tsai, YC; Chen, LH; Wen, SY; Wang, CW [National Taiwan University Hospital, Taipei City, Taiwan (China)

2016-06-15

Purpose: When treating lung cancer patients with stereotactic body radiation therapy (SBRT), better immobilization is needed for accurate delivery of high-dose radiation. However, using a treatment couch (TrueBeamTM) and vacuum bag (BlueBAGTM) may increase the surface dose and skin toxicity. This study investigated the influence of couch and vacuum bag on the surface dose. Methods: The relative surface dose (D{sub 0}/DMAX) was measured in an ion-chamber (Markus-type PTW, 0.05cm{sup 3}) with a solid water phantom and SSD to 100 cm. A comprehensive comparison of different parameter settings, including the different energies (6MV-FFF, 10MV-FF, and 10MV-FFF), field sizes (3 X 3 cm{sup 2}, 5 × 5 cm{sup 2}, 8 × x cm{sup 2} , 10 × 10 cm{sup 2}, and 15 × 15 cm{sup 2}), thickness of the vacuum bag (5mm, 15mm, 30mm, 39mm and 55mm), and couch (with and without), was performed. Results: The FFF increases the surface dose as compared to FF mode. In a similar setting with field of 10 × 10 cm{sup 2}, FFF mode increases the surface dose from 26.0% to 32.8% for 6 MV, and 17.4% to 21.5% for 10 MV. When the beam passes through the couch, the surface dose increases to 3.6, 4.6, 2.9, and 3.7 times for 6 MV-FF, 10 MV-FF, 6 MV-FFF, and 10 MV-FFF, respectively. At the same energy, the surface dose increases to 3.93, 4.11, 4.23, 4.16 and 4.24 times at 5 mm, 15 mm, 30 mm, 39 mm and 55 mm thickness of the vacuum, respectively. Conclusion: Using a couch and vacuum significantly increases the surface dose. For SBRT with a superficial target close to the couch and immobilization vacuum, reduction of vacuum thickness and careful attention to skin dose in planning would be helpful in avoiding severe skin toxicity.

Investigation of the Entrance Surface Dose and Dose to Different Organs in Lumbar Spine Imaging

Science.gov (United States)

Sina, S; Zeinali, B; Karimipoorfard, M; Lotfalizadeh, F; Sadeghi, M; Zamani, E; Faghihi, R

2014-01-01

Background: Dose assessment using proper dosimeters is especially important in radiation protection optimization and imaging justification in diagnostic radiology. Objective: The aim of this study is to obtain the Entrance Skin Dose (ESD) of patients undergoing lumbar spine imaging using two thermoluminescence dosimeters TLD-100 (LiF: Mg, Ti) and GR-200 (LiF: Mg, Cu, P) and also to obtain the absorbed dose to different organs in lumbar spine imaging with several views. Methods: To measure the ESD values of the patients undergoing lumbar spine imaging, the two TLD types were put on their skin surface. The ESD values for different views of lumbar spine imaging were also measured by putting the TLDs at the surface of the Rando phantom. Several TLD chips were inserted inside different organs of Rando phantom to measure the absorbed dose to different organs in lumbar spine imaging. Results: The results indicate that there is a close agreement between the results of the two dosimeters. Based on the results of this experiment, the ESD dose of the 16 patients included in this study varied between 2.71 mGy and 26.29 mGy with the average of 11.89 mGy for TLD-100, and between 2.55 mGy and 27.41 mGy with the average of 12.32 mGy for GR-200 measurements. The ESDs obtained by putting the two types of TLDs at the surface of Rando phantom are in close agreement. Conclusion: According to the results, the GR200 has greater sensitivity than the TLD-100. PMID:25599058

Investigation of the Entrance Surface Dose and Dose to Different Organs in Lumbar Spine Imaging

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Sina S

2014-12-01

Full Text Available Background: Dose assessment using proper dosimeters is especially important in radiation protection optimization and imaging justification in diagnostic radiology. Objective: The aim of this study is to obtain the Entrance Skin Dose (ESD of patients undergoing lumbar spine imaging using two thermoluminescence dosimeters TLD-100 (LiF: Mg, Ti and GR-200 (LiF: Mg, Cu, P and also to obtain the absorbed dose to different organs in lumbar spine imaging with several views. Methods: To measure the ESD values of the patients undergoing lumbar spine imaging, the two TLD types were put on their skin surface. The ESD values for different views of lumbar spine imaging were also measured by putting the TLDs at the surface of the Rando phantom. Several TLD chips were inserted inside different organs of Rando phantom to measure the absorbed dose to different organs in lumbar spine imaging. Results: The results indicate that there is a close agreement between the results of the two dosimeters. Based on the results of this experiment, the ESD dose of the 16 patients included in this study varied between 2.71 mGy and 26.29 mGy with the average of 11.89 mGy for TLD-100, and between 2.55 mGy and 27.41 mGy with the average of 12.32 mGy for GR-200 measurements. The ESDs obtained by putting the two types of TLDs at the surface of Rando phantom are in close agreement. Conclusion: According to the results, the GR200 has greater sensitivity than the TLD-100.

Data base on dose reduction research projects for nuclear power plants: Volume 3

Energy Technology Data Exchange (ETDEWEB)

Khan, T.A.; Baum, J.W.

1989-05-01

This is the third volume in a series of reports that provide information on dose-reduction research and health physics technology for nuclear power plants. The information is taken from data base maintained by Brookhaven National Laboratory's ALARA Center for the Nuclear Regulatory Commission. This report presents information on 80 new projects, covering a wide area of activities. Projects on steam generator degradation, decontamination, robotics, improvement in reactor materials, and inspection techniques, among others, are described in the research section. The section on health physics technology includes some simple and very cost-effective projects to reduce radiation exposures. Collective dose data from the United States and other countries are also presented. In the conclusion, we suggest that although new advanced reactor design technology will eventually reduce radiation exposures at nuclear power plants to levels below serious concern, in the interim an aggressive approach to dose reduction remains necessary. 20 refs.

Utilization of radiation protection gear for absorbed dose reduction: an integrative literature review

International Nuclear Information System (INIS)

Soares, Flavio Augusto Penna; Flor, Rita de Cassia; Pereira, Aline Garcia

2011-01-01

Objective: The present study was aimed at evaluating the relation between the use of radiation protection gear and the decrease in absorbed dose of ionizing radiation, thereby reinforcing the efficacy of its use by both the patients and occupationally exposed personnel. Materials and Methods: The integrative literature review method was utilized to analyze 21 articles, 2 books, 1 thesis, 1 monograph, 1 computer program, 4 pieces of database research (Instituto Brasileiro de Geografia e Estatistica and Departamento de Informatica do Sistema Unico de Saude) and 2 sets of radiological protection guidelines. Results: Theoretically, a reduction of 86% to 99% in the absorbed dose is observed with the use of radiation protection gear. In practice, however, the reduction may achieve 88% in patients submitted to conventional radiology, and 95% in patients submitted to computed tomography. In occupationally exposed individuals, the reduction is around 90% during cardiac catheterization, and 75% during orthopedic surgery. Conclusion: According to findings of several previous pieces of research, the use of radiation protection gear is a low-cost and effective way to reduce absorbed dose both for patients and occupationally exposed individuals. Thus, its use is necessary for the implementation of effective radioprotection programs in radiodiagnosis centers. (author)

The reduction of image noise and streak artifact in the thoracic inlet during low dose and ultra-low dose thoracic CT

International Nuclear Information System (INIS)

Paul, N S; Prezelj, E; Burey, P; Menezes, R J; Blobel, J; Ursani, A; Kashani, H; Siewerdsen, J H

2010-01-01

Increased pixel noise and streak artifact reduce CT image quality and limit the potential for radiation dose reduction during CT of the thoracic inlet. We propose to quantify the pixel noise of mediastinal structures in the thoracic inlet, during low-dose (LDCT) and ultralow-dose (uLDCT) thoracic CT, and assess the utility of new software (quantum denoising system and BOOST3D) in addressing these limitations. Twelve patients had LDCT (120 kV, 25 mAs) and uLDCT (120 kV, 10 mAs) images reconstructed initially using standard mediastinal and lung filters followed by the quantum denoising system (QDS) to reduce pixel noise and BOOST3D (B3D) software to correct photon starvation noise as follows: group 1 no QDS, no B3D; group 2 B3D alone; group 3 QDS alone and group 4 both QDS and B3D. Nine regions of interest (ROIs) were replicated on mediastinal anatomy in the thoracic inlet, for each patient resulting in 3456 data points to calculate pixel noise and attenuation. QDS reduced pixel noise by 18.4% (lung images) and 15.8% (mediastinal images) at 25 mAs. B3D reduced pixel noise by ∼8% in the posterior thorax and in combination there was a 35.5% reduction in effective radiation dose (E) for LDCT (1.63-1.05 mSv) in lung images and 32.2% (1.55-1.05 mSv) in mediastinal images. The same combination produced 20.7% reduction (0.53-0.42 mSv) in E for uLDCT, for lung images and 17.3% (0.51-0.42) for mediastinal images. This quantitative analysis of image quality confirms the utility of dedicated processing software in targeting image noise and streak artifact in thoracic LDCT and uLDCT images taken in the thoracic inlet. This processing software potentiates substantial reductions in radiation dose during thoracic LDCT and uLDCT.

CT breast dose reduction with the use of breast positioning and organ-based tube current modulation.

Science.gov (United States)

Fu, Wanyi; Tian, Xiaoyu; Sturgeon, Gregory M; Agasthya, Greeshma; Segars, William Paul; Goodsitt, Mitchell M; Kazerooni, Ella A; Samei, Ehsan

2017-02-01

This study aimed to investigate the breast dose reduction potential of a breast-positioning (BP) technique for thoracic CT examinations with organ-based tube current modulation (OTCM). This study included 13 female anthropomorphic computational phantoms (XCAT, age range: 27-65 y.o., weight range: 52-105.8 kg). Each phantom was modified to simulate three breast sizes in standard supine geometry. The modeled breasts were then morphed to emulate BP that constrained the majority of the breast tissue inside the 120° anterior tube current (mA) reduction zone. The OTCM mA value was modeled using a ray-tracing program, which reduced the mA to 20% in the anterior region with a corresponding increase to the posterior region. The organ doses were estimated by a validated Monte Carlo program for a typical clinical CT system (SOMATOM Definition Flash, Siemens Healthcare). The simulated organ doses and organ doses normalized by CTDI vol were used to compare three CT protocols: attenuation-based tube current modulation (ATCM), OTCM, and OTCM with BP (OTCM BP ). On average, compared to ATCM, OTCM reduced breast dose by 19.3 ± 4.5%, whereas OTCM BP reduced breast dose by 38.6 ± 8.1% (an additional 23.8 ± 9.4%). The dose saving of OTCM BP was more significant for larger breasts (on average 33, 38, and 44% reduction for 0.5, 1, and 2 kg breasts, respectively). Compared to ATCM, OTCM BP also reduced thymus and heart dose by 15.1 ± 7.4% and 15.9 ± 6.2% respectively. In thoracic CT examinations, OTCM with a breast-positioning technique can markedly reduce unnecessary exposure to radiosensitive organs in anterior chest wall, specifically breast tissue. The breast dose reduction is more notable for women with larger breasts. © 2016 American Association of Physicists in Medicine.

Radiation dose reduction in cerebral CT perfusion imaging using iterative reconstruction

International Nuclear Information System (INIS)

Niesten, Joris M.; Schaaf, Irene C. van der; Riordan, Alan J.; Jong, Hugo W.A.M. de; Eijspaart, Daniel; Smit, Ewoud J.; Mali, Willem P.T.M.; Velthuis, Birgitta K.; Horsch, Alexander D.

2014-01-01

To investigate whether iterative reconstruction (IR) in cerebral CT perfusion (CTP) allows for 50 % dose reduction while maintaining image quality (IQ). A total of 48 CTP examinations were reconstructed into a standard dose (150 mAs) with filtered back projection (FBP) and half-dose (75 mAs) with two strengths of IR (middle and high). Objective IQ (quantitative perfusion values, contrast-to-noise ratio (CNR), penumbra, infarct area and penumbra/infarct (P/I) index) and subjective IQ (diagnostic IQ on a four-point Likert scale and overall IQ binomial) were compared among the reconstructions. Half-dose CTP with high IR level had, compared with standard dose with FBP, similar objective (grey matter cerebral blood volume (CBV) 4.4 versus 4.3 mL/100 g, CNR 1.59 versus 1.64 and P/I index 0.74 versus 0.73, respectively) and subjective diagnostic IQ (mean Likert scale 1.42 versus 1.49, respectively). The overall IQ in half-dose with high IR level was scored lower in 26-31 %. Half-dose with FBP and with the middle IR level were inferior to standard dose with FBP. With the use of IR in CTP imaging it is possible to examine patients with a half dose without significantly altering the objective and diagnostic IQ. The standard dose with FBP is still preferable in terms of subjective overall IQ in about one quarter of patients. (orig.)

Clinical meaning of radiodermatitis considering the surface dose of supervoltage electron beam

Energy Technology Data Exchange (ETDEWEB)

Hiraki, T [Kanazawa Univ. (Japan). School of Paramedicine; Rikimaru, S; Kakishita, M; Kuranishi, M

1975-12-01

In our experience using supervoltage betatron electron beam, the skin surface dose of the electron decreased when the energy became either greater or less than 18 MeV. When we considered 18 MeV to be a 100% dose, the dose with 4 MeV, which was the least amount, corresponded to 81% of the dose. The skin surface dose of 10 MeV betatron electrons or more became greater than the 90% standard tumor dose. An external irradiation of more than 10 MeV should not be applied to neoplasms of which the curative ratio is less than 1.0. Therefore another methods such as intraoperative irradiation, should be used. The surface skin dose about 4 to 6 MeV betatron postoperative irradiation, particularly after resection of breast cancer, was less than the skin dose with 10 MeV. Close care should be taken to prevent hot lesions which are caused by duplication of irradiation fields. It should be kept in mind that the late effects of hot lesions caused by electron beam irradiation with an energy of 10 MeV or more are serious.

Tungsten and carbon surface change under high dose plasma exposure

International Nuclear Information System (INIS)

Martynenko, Y.V.; Khripunov, B.I.; Petrov, V.B.

2009-01-01

Study of surface composition dynamics has been made on the LENTA linear plasma simulator. Experiments have been made on tungsten and carbon materials subjected to steady-state plasma exposure. The achieved ion doses on the surface were 10 21 ion cm -2 . WL 10 tungsten containing 1% of La2O3 oxide and titanium-doped graphite RG-T were studied. The following experimental conditions were varied in these experiments: energy of ions, surface temperature, working gas. Irradiations of tungsten WL 10 were executed in deuterium plasma at low ion energies (about 20 eV) and at 200 eV for temperatures below 340 K. Graphite RG-T was exposed at 1300 K. Elevated surface temperature (about 1050K) was also characteristic of experiments on tungsten sample under nitrogen plasma impact (simulated inter-ELMs condition). Surface microstructure modification has been observed and surface composition changes were found on the materials showing influence of high dose plasma irradiations on element redistribution in the near surface layers. (author)

Statin dose reduction with complementary diet therapy: A pilot study of personalized medicine

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Bianca Scolaro

2018-05-01

Full Text Available Objective: Statin intolerance, whether real or perceived, is a growing issue in clinical practice. Our aim was to evaluate the effects of reduced-dose statin therapy complemented with nutraceuticals. Methods: First phase: Initially, 53 type 2 diabetic statin-treated patients received a supplementation with fish oil (1.7 g EPA + DHA/day, chocolate containing plant sterols (2.2 g/day, and green tea (two sachets/day for 6 weeks. Second phase: “Good responders” to supplementation were identified after multivariate analysis (n = 10, and recruited for a pilot protocol of statin dose reduction. “Good responders” were then provided with supplementation for 12 weeks: standard statin therapy was kept during the first 6 weeks and reduced by 50% from weeks 6–12. Results: First phase: After 6 weeks of supplementation, plasma LDL-C (−13.7% ± 3.7, P = .002 and C-reactive protein (−35.5% ± 5.9, P = .03 were reduced. Analysis of lathosterol and campesterol in plasma suggested that intensity of LDL-C reduction was influenced by cholesterol absorption rate rather than its synthesis. Second phase: no difference was observed for plasma lipids, inflammation, cholesterol efflux capacity, or HDL particles after statin dose reduction when compared to standard therapy. Conclusions: Although limited by the small sample size, our study demonstrates the potential for a new therapeutic approach combining lower statin dose and specific dietary compounds. Further studies should elucidate “good responders” profile as a tool for personalized medicine. This may be particularly helpful in the many patients with or at risk for CVD who cannot tolerate high dose statin therapy. Trial registration: ClinicalTrials.gov, NCT02732223. Keywords: Atherosclerosis, Omega-3 fatty acids, Plant sterols, Polyphenols, Responders

SUDOQU, a new dose-assessment methodology for radiological surface contamination.

Science.gov (United States)

van Dillen, Teun; van Dijk, Arjan

2018-06-12

A new methodology has been developed for the assessment of the annual effective dose resulting from removable and fixed radiological surface contamination. It is entitled SUDOQU (SUrface DOse QUantification) and it can for instance be used to derive criteria for surface contamination related to the import of non-food consumer goods, containers and conveyances, e.g., limiting values and operational screening levels. SUDOQU imposes mass (activity)-balance equations based on radioactive decay, removal and deposition processes in indoor and outdoor environments. This leads to time-dependent contamination levels that may be of particular importance in exposure scenarios dealing with one or a few contaminated items only (usually public exposure scenarios, therefore referred to as the 'consumer' model). Exposure scenarios with a continuous flow of freshly contaminated goods also fall within the scope of the methodology (typically occupational exposure scenarios, thus referred to as the 'worker model'). In this paper we describe SUDOQU, its applications, and its current limitations. First, we delineate the contamination issue, present the assumptions and explain the concepts. We describe the relevant removal, transfer, and deposition processes, and derive equations for the time evolution of the radiological surface-, air- and skin-contamination levels. These are then input for the subsequent evaluation of the annual effective dose with possible contributions from external gamma radiation, inhalation, secondary ingestion (indirect, from hand to mouth), skin contamination, direct ingestion and skin-contact exposure. The limiting effective surface dose is introduced for issues involving the conservatism of dose calculations. SUDOQU can be used by radiation-protection scientists/experts and policy makers in the field of e.g. emergency preparedness, trade and transport, exemption and clearance, waste management, and nuclear facilities. Several practical examples are worked

Adaptive statistical iterative reconstruction and bismuth shielding for evaluation of dose reduction to the eye and image quality during head CT

Science.gov (United States)

Kim, Myeong Seong; Choi, Jiwon; Kim, Sun Young; Kweon, Dae Cheol

2014-03-01

There is a concern regarding the adverse effects of increasing radiation doses due to repeated computed tomography (CT) scans, especially in radiosensitive organs and portions thereof, such as the lenses of the eyes. Bismuth shielding with an adaptive statistical iterative reconstruction (ASIR) algorithm was recently introduced in our clinic as a method to reduce the absorbed radiation dose. This technique was applied to the lens of the eye during CT scans. The purpose of this study was to evaluate the reduction in the absorbed radiation dose and to determine the noise level when using bismuth shielding and the ASIR algorithm with the GE DC 750 HD 64-channel CT scanner for CT of the head of a humanoid phantom. With the use of bismuth shielding, the noise level was higher in the beam-hardening artifact areas than in the revealed artifact areas. However, with the use of ASIR, the noise level was lower than that with the use of bismuth alone; it was also lower in the artifact areas. The reduction in the radiation dose with the use of bismuth was greatest at the surface of the phantom to a limited depth. In conclusion, it is possible to reduce the radiation level and slightly decrease the bismuth-induced noise level by using a combination of ASIR as an algorithm process and bismuth as an in-plane hardware-type shielding method.

Adaptive statistical iterative reconstruction and bismuth shielding for evaluation of dose reduction to the eye and image quality during head CT

Energy Technology Data Exchange (ETDEWEB)

Kim, Myeong Seong [The Korean National Cancer Center, Goyang (Korea, Republic of); Seoul National University, Seoul (Korea, Republic of); Choi, Ji Won [Jeonju University, Jeonju (Korea, Republic of); Kim, Sun Young [Hallym University of Graduate Studies, Seoul (Korea, Republic of); The Korean National Cancer Center, Goyang (Korea, Republic of); Kweon, Dae Cheol [Shinhan University, Uijeongbu (Korea, Republic of)

2014-03-15

There is a concern regarding the adverse effects of increasing radiation doses due to repeated computed tomography (CT) scans, especially in radiosensitive organs and portions thereof, such as the lenses of the eyes. Bismuth shielding with an adaptive statistical iterative reconstruction (ASIR) algorithm was recently introduced in our clinic as a method to reduce the absorbed radiation dose. This technique was applied to the lens of the eye during CT scans. The purpose of this study was to evaluate the reduction in the absorbed radiation dose and to determine the noise level when using bismuth shielding and the ASIR algorithm with the GE DC 750 HD 64-channel CT scanner for CT of the head of a humanoid phantom. With the use of bismuth shielding, the noise level was higher in the beam-hardening artifact areas than in the revealed artifact areas. However, with the use of ASIR, the noise level was lower than that with the use of bismuth alone; it was also lower in the artifact areas. The reduction in the radiation dose with the use of bismuth was greatest at the surface of the phantom to a limited depth. In conclusion, it is possible to reduce the radiation level and slightly decrease the bismuth-induced noise level by using a combination of ASIR as an algorithm process and bismuth as an in-plane hardware-type shielding method.

CT dose reduction using Automatic Exposure Control and iterative reconstruction: A chest paediatric phantoms study.

Science.gov (United States)

Greffier, Joël; Pereira, Fabricio; Macri, Francesco; Beregi, Jean-Paul; Larbi, Ahmed

2016-04-01

To evaluate the impact of Automatic Exposure Control (AEC) on radiation dose and image quality in paediatric chest scans (MDCT), with or without iterative reconstruction (IR). Three anthropomorphic phantoms representing children aged one, five and 10-year-old were explored using AEC system (CARE Dose 4D) with five modulation strength options. For each phantom, six acquisitions were carried out: one with fixed mAs (without AEC) and five each with different modulation strength. Raw data were reconstructed with Filtered Back Projection (FBP) and with two distinct levels of IR using soft and strong kernels. Dose reduction and image quality indices (Noise, SNR, CNR) were measured in lung and soft tissues. Noise Power Spectrum (NPS) was evaluated with a Catphan 600 phantom. The use of AEC produced a significant dose reduction (p<0.01) for all anthropomorphic sizes employed. According to the modulation strength applied, dose delivered was reduced from 43% to 91%. This pattern led to significantly increased noise (p<0.01) and reduced SNR and CNR (p<0.01). However, IR was able to improve these indices. The use of AEC/IR preserved image quality indices with a lower dose delivered. Doses were reduced from 39% to 58% for the one-year-old phantom, from 46% to 63% for the five-year-old phantom, and from 58% to 74% for the 10-year-old phantom. In addition, AEC/IR changed the patterns of NPS curves in amplitude and in spatial frequency. In chest paediatric MDCT, the use of AEC with IR allows one to obtain a significant dose reduction while maintaining constant image quality indices. Copyright © 2016 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.

Retention and reduction of uranium on pyrite surface

International Nuclear Information System (INIS)

Eglizaud, N.

2006-12-01

In the hypothesis of a storage of the spent fuel in a deep geological formation, understanding the uranium dispersion in the environment is important. Pyrite is a reducing mineral present in the Callovo-Oxfordian argilites, the geological formation actually studied for such a storage. However, pyrite impact on uranium migration has already been poorly studied. The aim of the study was to understand the mechanisms of uranium(VI) retention and reduction on the pyrite surface (FeS 2 ). Solution chemistry was therefore coupled with solid spectroscopic studies (XPS and Raman spectroscopy). All uranium-pyrite interactions experiments were performed under an anoxic atmosphere, in a glove box. Pyrite dissolution under anoxic conditions releases sulfoxy-anions and iron(II), which can then be adsorbed on the pyrite surface. This adsorption was confirmed by interaction experiments using iron(II) isotopic dilution. Uranium(VI) is retained by an exchange reaction with iron(II) adsorbed on sulphur sites, with a maximal amount of sorbed uranium at pH ≥ 5.5. Cobalt(II) and europium(III) are also adsorbed on the pyrite surface above pH 5.5 confirming then that reduction is not required for species to adsorb on pyrite. When the concentration of uranium retained is lower than 4 x 10 -9 mol g -1 , an oxidation-reduction reaction leads to the formation of a uranium (VI) (IV) mixed oxide and to solid sulphur (d.o. ≥ -I). During this reaction, iron remains mostly at the +II oxidation degree. The reaction products seem to passivate the pyrite surface: at higher amounts of retained uranium, the oxidation-reduction reaction is no longer observed. The surface is saturated by the retention of (3.4 ± 0.8) x 10 -7 mol L -1 of uranium(VI). Modelling of uranium sorption at high surface coverage (≥ 4 x 10 -9 mol g -1 ) by the Langmuir model yields an adsorption constant of 8 x 10 7 L mol -1 . Finally, a great excess of uranium(VI) above the saturation concentration allows the observation of

SU-C-12A-07: Effect of Vertical Position On Dose Reduction Using X-Care

International Nuclear Information System (INIS)

Silosky, M; Marsh, R

2014-01-01

Purpose: Reduction of absorbed dose to radiosensitive tissues is an important goal in diagnostic radiology. Siemens Medical has introduced a technique (X-CARE) to lower CT dose to anterior anatomy by reducing the tube current during 80° of rotation over radiosensitive tissues. Phantom studies have shown 30-40% dose reduction when phantoms are positioned at isocenter. However, for CT face and sinus exams, the center of the head is commonly positioned below isocenter. This work investigated the effects of vertical patient positioning on dose reduction using X-CARE. Methods: A 16cm Computed Tomography Dose Index phantom was scanned on a Siemens Definition Flash CT scanner using a routine head protocol, with the phantom positioned at scanner isocenter. Optically stimulated luminescent dosimeters were placed on the anterior and posterior sides of the phantom. The phantom was lowered in increments of 2cm and rescanned, up to 8cm below isocenter. The experiment was then repeated using the same scan parameters but adding the X-CARE technique. The mean dosimeter counts were determined for each phantom position, and the difference between XCARE and routine scans was plotted as a function of distance from isocenter. Results: With the phantom positioned at isocenter, using XCARE reduced dose to the anterior side of the phantom by 40%, compared to dose when X-CARE was not used. Positioned below isocenter, anterior dose was reduced by only 20-27%. Additionally, using X-CARE at isocenter reduced dose to the anterior portion of the phantom by 45.6% compared to scans performed without X-CARE 8cm below isocenter. Conclusion: While using X-CARE substantially reduced dose to the anterior side of the phantom, this effect was diminished when the phantom was positioned below isocenter, simulating common practice for face and sinus scans. This indicates that centering the head in the gantry will maximize the effect of X-CARE

Characterization of a lead breast shielding for dose reduction in computed tomography

Energy Technology Data Exchange (ETDEWEB)

Correia, Paula Duarte; Brochi, Marco Aurelio Corte; Azevedo-Marques, Paulo Mazzoncini de, E-mail: pauladuarte@usp.br [Universidade de Sao Paulo (FM/RSP), Ribeirao Preto, SP (Brazil). Faculdade de Medicina; Granzotti, Cristiano Roberto Fabri; Santos, Yago da Silva [Universidade de Sao Paulo (FFCLRP/RSP), Ribeirao Preto, SP (Brazil). Faculdade de Filosofia, Ciencias e Letras

2014-07-15

Objective: several studies have been published regarding the use of bismuth shielding to protect the breast in computed tomography (CT) scans and, up to the writing of this article, only one publication about barium shielding was found. The present study was aimed at characterizing, for the first time, a lead breast shielding. Materials and methods: the percentage dose reduction and the influence of the shielding on quantitative imaging parameters were evaluated. Dose measurements were made on a CT equipment with the aid of specific phantoms and radiation detectors. A processing software assisted in the qualitative analysis evaluating variations in average CT number and noise on images. Results: the authors observed a reduction in entrance dose by 30% and in CTDIvol by 17%. In all measurements, in agreement with studies in the literature, the utilization of cotton fiber as spacer object reduced significantly the presence of artifacts on the images. All the measurements demonstrated increase in the average CT number and noise on the images with the presence of the shielding. Conclusion: as expected, the data observed with the use of lead shielding were of the same order as those found in the literature about bismuth shielding. (author)

Depth dose of critical organs of phantom based on surface dose exposed with Dual X-ray absorptiometry: pencil beam using TLD dosimetry

Directory of Open Access Journals (Sweden)

Ali Akbar Sharafi

2009-02-01

Full Text Available Introduction: Dual X-ray absorptiometry (DXA is one of the most widely used techniques fornon-invasive assessment of bone status. Radiation dosimetry is well established technique for pencilbeam and fan beam DXA system, for the assessment of the surface absorbed dose. No publishedassessment of the absorbed dose for the various depths of the critical organs such as the thyroid anduterus was found. Therefore, in this study, we measured the surface dose and depth dose of criticalorgans to determine the correlation between the depth dose and the surface dose.Materials and Methods: A Lunar DPX-MD (pencil beam system was used in this study. Ananthropomorphic phantom was designed. AP spine and femur scan modes were used to measure thesurface and depth doses of the thyroid left and right lobes and uterus in various deeps and scan centers.TLDs-400 were placed at the surface, near the source and also inserted at different depths in thyroidand uterus of the anthropomorphic phantom. Absorbed doses were measured on the phantom for APspine and femur scans. The correlation between the absorbed dose and the depth was found using thelinear regression analysis.Results: There was no significant correlation between the depth dose and the scan center doseexcept in the femur scan. AP spine effective dose were calculated as 0.064, 0.059, 0.061 and 0.242μSv for thyroid left, right lobes, uterus and ovary, respectively.Conclusion: It is concluded that there is significant correlation between the surface and the doseof various depths of the scanned sections.

Results of comparative assessment of US and foreign nuclear power plant dose experience and dose reduction programs

International Nuclear Information System (INIS)

Baum, J.W.; Horan, J.R.; Dionne, B.J.

1985-01-01

The objectives of this study were to determine how collective dose equivalents at US nuclear power plants compare to those of other technically advanced countries, and to evaluate factors that contribute to the differences. Fifty Health Physicists and nuclear engineers from 10 countries met at BNL May 29 - June 1, 1984 to exchange information and hold discussions on ''Historical Dose Experience and Dose Reduction (ALARA) at Nuclear Power Plants''. Results of evaluation of data from this meeting and other data from recent publications are summarized. Based on data evaluated to date it is clear that US plants have higher collective dose equivalents per reactor and per MW-yr generated than most other countries. Factors which contribute to low doses include: 1) minimization of cobalt in primary system components exposed to water, 2) careful control of primary system oxygen and pH, 3) good primary system water purity to minimize corrosion product formation, 4) careful plant design, layout and component segregation and shielding, 5) management interest and commitment, 6) minimum number of workers and in-depth worker training, 7) use of special tools, and 8) plant standardization

Pediatric cT: Implementation of ASIR for Substantial Radiation Dose Reduction While Maintaining Pre-ASIR Image Noise1

Science.gov (United States)

Brady, Samuel L.; Moore, Bria M.; Yee, Brian S.; Kaufman, Robert A.

2015-01-01

Purpose To determine a comprehensive method for the implementation of adaptive statistical iterative reconstruction (ASIR) for maximal radiation dose reduction in pediatric computed tomography (CT) without changing the magnitude of noise in the reconstructed image or the contrast-to-noise ratio (CNR) in the patient. Materials and Methods The institutional review board waived the need to obtain informed consent for this HIPAA-compliant quality analysis. Chest and abdominopelvic CT images obtained before ASIR implementation (183 patient examinations; mean patient age, 8.8 years ± 6.2 [standard deviation]; range, 1 month to 27 years) were analyzed for image noise and CNR. These measurements were used in conjunction with noise models derived from anthropomorphic phantoms to establish new beam current–modulated CT parameters to implement 40% ASIR at 120 and 100 kVp without changing noise texture or magnitude. Image noise was assessed in images obtained after ASIR implementation (492 patient examinations; mean patient age, 7.6 years ± 5.4; range, 2 months to 28 years) the same way it was assessed in the pre-ASIR analysis. Dose reduction was determined by comparing size-specific dose estimates in the pre- and post-ASIR patient cohorts. Data were analyzed with paired t tests. Results With 40% ASIR implementation, the average relative dose reduction for chest CT was 39% (2.7/4.4 mGy), with a maximum reduction of 72% (5.3/18.8 mGy). The average relative dose reduction for abdominopelvic CT was 29% (4.8/6.8 mGy), with a maximum reduction of 64% (7.6/20.9 mGy). Beam current modulation was unnecessary for patients weighing 40 kg or less. The difference between 0% and 40% ASIR noise magnitude was less than 1 HU, with statistically nonsignificant increases in patient CNR at 100 kVp of 8% (15.3/14.2; P = .41) for chest CT and 13% (7.8/6.8; P = .40) for abdominopelvic CT. Conclusion Radiation dose reduction at pediatric CT was achieved when 40% ASIR was implemented as a dose

Retention and reduction of uranium on pyrite surface; Retention et reduction de l'uranium a la surface de la pyrite

Energy Technology Data Exchange (ETDEWEB)

Eglizaud, N

2006-12-15

In the hypothesis of a storage of the spent fuel in a deep geological formation, understanding the uranium dispersion in the environment is important. Pyrite is a reducing mineral present in the Callovo-Oxfordian argilites, the geological formation actually studied for such a storage. However, pyrite impact on uranium migration has already been poorly studied. The aim of the study was to understand the mechanisms of uranium(VI) retention and reduction on the pyrite surface (FeS{sub 2}). Solution chemistry was therefore coupled with solid spectroscopic studies (XPS and Raman spectroscopy). All uranium-pyrite interactions experiments were performed under an anoxic atmosphere, in a glove box. Pyrite dissolution under anoxic conditions releases sulfoxy-anions and iron(II), which can then be adsorbed on the pyrite surface. This adsorption was confirmed by interaction experiments using iron(II) isotopic dilution. Uranium(VI) is retained by an exchange reaction with iron(II) adsorbed on sulphur sites, with a maximal amount of sorbed uranium at pH {>=} 5.5. Cobalt(II) and europium(III) are also adsorbed on the pyrite surface above pH 5.5 confirming then that reduction is not required for species to adsorb on pyrite. When the concentration of uranium retained is lower than 4 x 10{sup -9} mol g{sup -1}, an oxidation-reduction reaction leads to the formation of a uranium (VI) (IV) mixed oxide and to solid sulphur (d.o. {>=} -I). During this reaction, iron remains mostly at the +II oxidation degree. The reaction products seem to passivate the pyrite surface: at higher amounts of retained uranium, the oxidation-reduction reaction is no longer observed. The surface is saturated by the retention of (3.4 {+-} 0.8) x 10{sup -7} mol L{sup -1} of uranium(VI). Modelling of uranium sorption at high surface coverage ({>=} 4 x 10{sup -9} mol g{sup -1}) by the Langmuir model yields an adsorption constant of 8 x 10{sup 7} L mol{sup -1}. Finally, a great excess of uranium(VI) above the

Assessment of contralateral breast dose reduction in post mastectomy patients using superflab during EBRT

International Nuclear Information System (INIS)

Akanksha, S.; Athiyaman, M.; Hemalatha, A.; Kumar, H.S.

2016-01-01

Breast cancer (BC) is most common cancer in women worldwide. External beam radiotherapy (EBRT) is used as adjuvant in most post operative BC cases for loco-regional control. Present study is concerned about dose received by contralateral breast (CLB) during EBRT which results due to scatter from treatment head. Dose to CLB in 18 post operative BC patients were evaluated using CaSO_4-Dy thermoluminiscence dosimeters (TLDs) and effect of superflab is also investigated for dose reduction

SU-E-J-198: Out-Of-Field Dose and Surface Dose Measurements of MRI-Guided Cobalt-60 Radiotherapy

International Nuclear Information System (INIS)

Lamb, J; Agazaryan, N; Cao, M; Low, D; Thomas, D; Yang, Y

2015-01-01

Purpose: To measure quantities of dosimetric interest in an MRI-guided cobalt radiotherapy machine that was recently introduced to clinical use. Methods: Out-of-field dose due to photon scatter and leakage was measured using an ion chamber and solid water slabs mimicking a human body. Surface dose was measured by irradiating stacks of radiochromic film and extrapolating to zero thickness. Electron out-of-field dose was characterized using solid water slabs and radiochromic film. Results: For some phantom geometries, up to 50% of Dmax was observed up to 10 cm laterally from the edge of the beam. The maximum penetration was between 1 and 2 mm in solid water, indicating an electron energy not greater than approximately 0.4 MeV. Out-of-field dose from photon scatter measured at 1 cm depth in solid water was found to fall to less than 10% of Dmax at a distance of 1.2 cm from the edge of a 10.5 × 10.5 cm field, and less that 1% of Dmax at a distance of 10 cm from field edge. Surface dose was measured to be 8% of Dmax. Conclusion: Surface dose and out-of-field dose from the MRIguided cobalt radiotherapy machine was measured and found to be within acceptable limits. Electron out-of-field dose, an effect unique to MRI-guided radiotherapy and presumed to arise from low-energy electrons trapped by the Lorentz force, was quantified. Dr. Low is a member of the scientific advisory board of ViewRay, Inc

Field Study of Infiltration Capacity Reduction of Porous Mixture Surfaces

Directory of Open Access Journals (Sweden)

Luis A. Sañudo-Fontaneda

2014-03-01

Full Text Available Porous surfaces have been used all over the world in source control techniques to minimize flooding problems in car parks. Several studies highlighted the reduction in the infiltration capacity of porous mixture surfaces after several years of use. Therefore, it is necessary to design and develop a new methodology to quantify this reduction and to identify the hypothetical differences in permeability between zones within the same car park bay due to the influence of static loads in the parked vehicles. With this aim, nine different zones were selected in order to check this hypothesis (four points under the wheels of a standard vehicle and five points between wheels. This article presents the infiltration capacity reduction results, using the LCS permeameter, of Polymer-Modified Porous Concrete (9 bays and Porous Asphalt (9 bays surfaces in the University of Cantabria Campus parking area (Spain 5 years after their construction. Statistical analysis methodology was proposed for assessing the results. Significant differences were observed in permeability and reduction in infiltration capacity in the case of porous concrete surfaces, while no differences were found for porous asphalt depending on the measurement zone.

Application of a simple phantom in assessing the effects of dose reduction on image quality in chest radiography

International Nuclear Information System (INIS)

Egbe, N.O.; Heaton, B.; Sharp, P.F.

2010-01-01

Purpose: Firstly, to evaluate a commercial chest phantom incorporating a quasi anthropomorphic insert by comparing exposure measurements on the phantom with those of actual patients and, secondly, to assess the value of the phantom for image quality and dose optimisation. Methods: In the first part of the study entrance surface doses (ESD), Beam transmission (BT), and optical density (OD) were obtained for 77 chest radiography patients and compared with measurements made from exposures of the phantom using the respective patient exposure factors from chest examination. Differences were assessed with a student t-test, while the Pearson's linear correlation coefficient was used to test for any linear relationship. The second part assessed the applicability of the phantom to image quality studies by investigating the effect, on the clarity and detectability of lung lesions made from gelatine, of reducing patient dose below current dose levels. Clarity of linear objects of different dimensions was also studied. Lesion detectability and clarity was assessed by four observers. The possibility of extending dose reduction below current dose levels (D ref ) was assessed from comparison of doses that produced statistically significant differences in image quality from D ref . Results: Results show that, with the exception of entrance doses and beam transmission through the diaphragm (P > 0.05), differences in OD and beam transmission between patients and phantom were statistically significant (P ref produced significant changes in both clarity and detectability. Conclusion: Within limits posed by the observed differences, the phantom can be applied to image quality studies in diagnostic radiology.

No compelling evidence that sibutramine prolongs life in rodents despite providing a dose-dependent reduction in body weight

Science.gov (United States)

Smith, Daniel L.; Robertson, Henry; Desmond, Renee; Nagy, Tim R.; Allison, David B.

2010-01-01

Objective The health and longevity effects of body weight reduction resulting from exercise and caloric restriction in rodents are well known, but less is known about whether similar effects occur with weight reduction from the use of a pharmaceutical agent such as sibutramine, a serotonin-norepinephrine reuptake inhibitor. Results & Conclusion Using data from a two-year toxicology study of sibutramine in CD rats and CD-1 mice, despite a dose-dependent reduction in food intake and body weight in rats compared to controls, and a body weight reduction in mice at the highest dose, there was no compelling evidence for reductions in mortality rate. PMID:21079617

The contribution to surface dose form air scatter in mega voltage photon beams

International Nuclear Information System (INIS)

Carolan, M.G.; Butson, M.; Metcalfe, P.

1996-01-01

Full text: The minimisation of surface dose is an important requirement in radiotherapy in order to avoid undesirable skin reactions. For this reason significant effort has been expended to avoid and understand photon and electron scatter in the heads of linear accelerators which may contribute to surface dose. In this study we have examined the contribution to surface dose which arises due to scatter in the air above the patient. Experimental investigations of air contributions are difficult to design and execute. Therefore we have used Monte Carlo calculations to determine the effect that the presence of air has on surface dose. Methods: The Los Alamos Monte Carlo Neutron and Photon transport code, MCNP4A which incorporates the ETRAN electron transport code from the Integrated TIGER Series of codes was used for our simulations. The geometry used in the model was a 30 cm cube of water. The dose was tallied in cylindrical elements of 7 cm diameter along the axis of the photon beam. For the first millimetre along the beam axis in the phantom, the dose was determined at 0.1 mm increments in 0.1 mm thick volumes. For depths between 1.0 mm and 15.0 mm the dose was determined every 1 mm in 1 mm cylindrical volumes. This yields a depth dose profile with fine spatial resolution near the phantom surface. Dose was also tallied at depths of 5.0, 10.0, 15.0 and 20.0 cm. The simulations were done assuming a 6 MV photon source with a diameter of 1.5 cm, a gaussian intensity profile and a photon energy spectrum based on Mohan et al. (Med. Phys. 12 (1985) 592). No accelerator head geometry was modelled. The field size was defined by virtual collimators which were simply thin regions of zero photon importance and therefore do not contribute to photon or electron scatter. All simulations were run for sufficient particle histories (∼2x10 7 - 5x10 7 source photons) to give statistical uncertainties of ≤ 10% and in most cases ≤ 5%. Fields of size 10, 15, 20 and 25 cm were used

Patient surface doses in computerized tomography examinations

International Nuclear Information System (INIS)

Vekic, B.; Kovacevic, S.; Ranogajec Komor, M.; Duvnjak, N.; Marusic, P.; Anic, P.; Dolencic, P.

1996-01-01

Computed tomography (CT) has become a major source of the population exposure to diagnostic x-rays, and acknowledge of the doses delivered by the CT equipment has become very important. Considerable efforts should be made to keep these doses to a reasonable minimum, without sacrificing the image quality. The conditions of exposure in CT are quite different from dose in conventional x-ray imaging. This has required the development of specific techniques for assessing patient dose from CT. The aims of this work were to determine the dose delivered to various organs of patients undergoing computed tomography of abdomen, thorax, pelvis and kidney as measured on the surface of the body and to estimate the risk to the patients. Dosimetric measurements were performed at two different CT scanners (Siemens SOMATOM DR-H ver. HC-1 and Shimadzu SCT-4500TE). The dose absorbed by different organs (gonads, chest, thyroid and eye lens) and by the examined part of the body of 95 patients of various sex and age were measured with TLD-700. The doses absorbed by different organs during the diagnostic CT examination of the body depend on the technical parameters, such as the number of scan, mAs, the thickness of scans, scanning times, tube voltage and other characteristics, some of each depend on the type and severity of illness. Clinical parameters, such as patient size and composition, and patient cooperation with regard to the control and motion, also influence the dose and the image quality. The highest dose measured in this study (89.19 mGy) was delivered to kidney during CT examination of this organ. (author)

Automatic exposure control in pediatric and adult multidetector CT examinations: A phantom study on dose reduction and image quality

Energy Technology Data Exchange (ETDEWEB)

Papadakis, Antonios E.; Perisinakis, Kostas; Damilakis, John [Department of Medical Physics, Faculty of Medicine, University of Crete, P.O. Box 1352, Iraklion 71110, Crete (Greece)

2008-10-15

The aim of this study was to assess the potential of a modern x,y,z modulation-based automatic exposure control system (AEC) for dose reduction in pediatric and adult multidetector CT (MDCT) imaging and evaluate the quality of the images obtained. Five physical anthropomorphic phantoms that simulate the average individual as neonate, 1-, 5-, 10-year old child, and adult were scanned with a MDCT scanner, equipped with a modern AEC system. Dose reduction (%DR) was calculated as the percentage difference of the mean modulated and the preset tube current-time product that is prescribed for standard head and body scan protocols. The effect of the tube potential and the orientation of the topogram acquisition on dose reduction were assessed. Image quality was evaluated on the basis of image noise and signal to noise ratio (SNR). The dose reduction values achieved in pediatric phantoms were remarkably lower than those achieved for the adult. The efficiency of the AEC is decreased at 80 kVp compared to higher tube potentials and for helical scans following an anterior posterior (AP-AEC) compared to a lateral (LAT-AEC) topogram acquisition. In AP-AEC scans, the dose reduction ranged between 4.7 and 34.7% for neonate, 15.4 and 30.9% for 1 year old, 3.1 and 26.7% for 5 years old, 1.2 and 58.7% for 10 years old, and 15.5 and 57.4% for adult. In LAT-AEC scans, the corresponding dose reduction ranged between 11.0 and 36.5%, 27.2 and 35.7%, 11.3 and 35.6%, 0.3 and 67.0%, and 15.0 and 61.7%, respectively. AP-AEC scans resulted in a 17.1% and 19.7% dose increase in the thorax of neonate and the pelvis of the 10-year old phantom, respectively. The variation in the measured noise among images obtained along the scanning z axis was lower in AEC activated compared to fixed milliamperes scans. However, image noise was significantly increased (P<.001) and SNR significantly decreased (P<.001) in most AEC activated compared to fixed milliamperes scans. In conclusion, AEC resulted in a (i

SMART, Radiation Dose Rates on Cask Surface

International Nuclear Information System (INIS)

Yamakoshi, Hisao

1989-01-01

1 - Description of program or function: SMART calculates radiation dose rate at the center of each cask surface by using characteristic functions for radiation shielding ability and for radiation current back-scattered from cask wall and cask cavity of each cask, once cask-type is specified. 2 - Method of solution: Matrix Calculation

Biomimetics inspired surfaces for drag reduction and oleophobicity/philicity

Directory of Open Access Journals (Sweden)

Bharat Bhushan

2011-02-01

Full Text Available The emerging field of biomimetics allows one to mimic biology or nature to develop nanomaterials, nanodevices, and processes which provide desirable properties. Hierarchical structures with dimensions of features ranging from the macroscale to the nanoscale are extremely common in nature and possess properties of interest. There are a large number of objects including bacteria, plants, land and aquatic animals, and seashells with properties of commercial interest. Certain plant leaves, such as lotus (Nelumbo nucifera leaves, are known to be superhydrophobic and self-cleaning due to the hierarchical surface roughness and presence of a wax layer. In addition to a self-cleaning effect, these surfaces with a high contact angle and low contact angle hysteresis also exhibit low adhesion and drag reduction for fluid flow. An aquatic animal, such as a shark, is another model from nature for the reduction of drag in fluid flow. The artificial surfaces inspired from the shark skin and lotus leaf have been created, and in this article the influence of structure on drag reduction efficiency is reviewed. Biomimetic-inspired oleophobic surfaces can be used to prevent contamination of the underwater parts of ships by biological and organic contaminants, including oil. The article also reviews the wetting behavior of oil droplets on various superoleophobic surfaces created in the lab.

Surface dose measurements in and out of field. Implications for breast radiotherapy with megavoltage photon beams

Energy Technology Data Exchange (ETDEWEB)

Lonski, Peta; Kron, Tomas [Peter MacCallum Cancer Centre, Melbourne (Australia); RMIT Univ., Melbourne (Australia); Ramachandran, Prabhakar; Franich, Rick [Peter MacCallum Cancer Centre, Melbourne (Australia)

2017-07-01

This study examines the difference in surface dose between flat and flattening filter free (FFF) photon beams in the context of breast radiotherapy. The surface dose was measured for 6 MV, 6 MV FFF, 10 MV, 10 MV FFF and 18 MV photon beams using a thin window ionisation chamber for various field sizes. Profiles were acquired to ascertain the change in surface dose off-axis. Out-of-field measurements were included in a clinically representative half beam block tangential breast field. In the field centres of FFF beams the surface dose was found to be increased for small fields and decreased for large fields compared to flat beams. For FFF beams, surface dose was found to decrease off-axis and resulted in lower surface dose out-of-field compared to flat beams.

Contralateral breast dose reduction using a virtual wedge

International Nuclear Information System (INIS)

Yeo, In Hwan; Kim, Dae Yong; Kim, Tae Hyun; Shin, Kyung Hwan; Chie, Eui Kyu; Park, Won; Lim, Do Hoon; Huh, Seung Jae; Ahn, Yong Chan

2005-01-01

in a Siemens linear accelerator was found to be useful in reducing dose to the contralateral breast. Our additional finding was that the surface dose distribution from the Siemens accelerator was different from a Varian accelerator

CT dose reduction in children

International Nuclear Information System (INIS)

Vock, Peter

2005-01-01

World wide, the number of CT studies in children and the radiation exposure by CT increases. The same energy dose has a greater biological impact in children than in adults, and scan parameters have to be adapted to the smaller diameter of the juvenile body. Based on seven rules, a practical approach to paediatric CT is shown: Justification and patient preparation are important steps before scanning, and they differ from the preparation of adult patients. The subsequent choice of scan parameters aims at obtaining the minimal signal-to-noise ratio and volume coverage needed in a specific medical situation; exposure can be divided in two aspects: the CT dose index determining energy deposition per rotation and the dose-length product (DLP) determining the volume dose. DLP closely parallels the effective dose, the best parameter of the biological impact. Modern scanners offer dose modulation to locally minimise exposure while maintaining image quality. Beyond the selection of the physical parameters, the dose can be kept low by scanning the minimal length of the body and by avoiding any non-qualified repeated scanning of parts of the body. Following these rules, paediatric CT examinations of good quality can be obtained at a reasonable cost of radiation exposure. (orig.)

Optimisation of CT procedures by dose reduction in abdominal-pelvic studies of chronic patients

International Nuclear Information System (INIS)

Calvo, D.; Rodriguez, A.M.; Peinado, M.A.; Fernandez, B.; Fernandez, B.M.; Jimenez, J.R.

2006-01-01

Full text of publication follows: Objectives: CT explorations are responsible of a significant increase of collective dose during last twenty years. However, by adapting the procedures to the specific diagnostic requirements of each kind of exploration, dose values can be decreased. This can be specially interesting for chronic patients who undergo several CT controls. The aim of this research is to contrast CT image diagnostic quality by comparing those techniques commonly used in our hospital with lower dose ones. Materials and methods: In a first phase, a study on phantom has been developed to evaluate image quality variations obtained with standard a several low dose techniques. Dose reduction was quantified as well by means of C.T.D.I. w measurements on an abdominal phantom. Both aspects were taken into account to determine a dose threshold below image quality degradation was considered unacceptable from a diagnostic point of view. Subsequently, a group of 50 chronic patients under follow -up was selected to undergo a control CT but with a low dose-technique. Image diagnostic quality was compared with that of previous controls obtained using the standard technique. Three experimented radiologist carried out this evaluation over a sample of six particular slices located at the abdomen and pelvis using an ordinal scale. Such a scale gradate the confidence level of the image for each radiologist. This evaluation was repeated one and two months later without knowledge of previous results to calculate inter and intra -observer variability. Conclusions: CT studies can be carried out with a significant dose reduction preserving their diagnostic capabilities. A quantitative evaluation will be offered at the end of the study, still running. (authors)

Friction reduction using discrete surface textures: principle and design

International Nuclear Information System (INIS)

Hsu, Stephen M; Jing, Yang; Hua, Diann; Zhang, Huan

2014-01-01

There have been many reports on the use of dimples, grooves, and other surface textures to control friction in sliding interfaces. The effectiveness of surface textures in friction reduction has been demonstrated in conformal contacts under high speed low load applications such as mechanical seals and automotive water pump seals, etc., resulting in reduced friction and longer durability. For sliding components with higher contact pressures or lower speeds, conflicting results were reported. Reasons for the inconsistency may be due to the differences in texture fabrication techniques, lack of dimple size and shape uniformity, and different tester used. This paper examines the basic principles on which surface textural patterns influence friction under the three principle lubrication regimes: hydrodynamic, elastohydrodynamic, and boundary lubrication regimes. Our findings suggest that each regime requires specific dimple size, shape, depth, and areal density to achieve friction reduction. Control experiments were also conducted to explore mechanisms of friction reduction. The dimple geometric shape and the dimple's orientation with respect to the sliding direction influence friction significantly. The underlying mechanisms for friction control via textures are discussed. (paper)

The clinical meaning of radiodermatitis considering the surface dose of supervoltage electron beam

International Nuclear Information System (INIS)

Hiraki, Tatsunosuke; Rikimaru, Shigeho; Kakishita, Masao; Kuranishi, Makoto.

1975-01-01

In our experience using supervoltage betatron electron beam, the skin surface dose of the electron decreased when the energy became either greater of less than 18 MeV. When we considered 18 MeV to be a 100% dose, the dose with 4 MeV, which was the least amount, corresponded to 81% of the dose. The skin surface dose of 10 MeV betatron electrons or more became greater than the 90% standard tumor dose. An external irradiation of more than 10 MeV should not be applied to neoplasms of which the curative ratio is less than 1.0. Therefore another methods such as intraoperative irradiation, should be used. The surface skin dose about 4-6 MeV betatron postoperative irradiation, particularly after resection of breast cancer, was less than the skin dose with 10 MeV. Close care should be taken to prevent hot lesions which are caused by duplication of irradiation fields. It should be kept in mind that the late effects of hot lesions caused by electron beam irradiation with an energy of 10 MeV or more are serious. (Kashu, E.)

A consideration on internal dose evaluation and intervention based on a surface contamination concept

International Nuclear Information System (INIS)

Yasuda, H.

1997-01-01

Long-term radiation doses received by the inhabitants after the Chernobyl accident have been evaluated according to the surface contamination levels on the ground surface. The health effects have also been discussed by comparison between the surface-contaminated area and the uncontaminated control area. Selected protective measures were carried out in accordance with the contamination level of surface soil. These have been based on the 'surface contamination concept' which assumes that the radiation risk to inhabitants is proportional to the level of ground-surface contamination. The observations collected in regions around Chernobyl, however, show that the internal radiation doses to the inhabitants poorly correlate with the surface contamination level. This fact poses a question on the suitability of dose evaluations and interventions based on this concept

Evaluation of surface dose rate on C-14 scrubber and gas bag

International Nuclear Information System (INIS)

Gang, D. W.; Lee, H. S.; Lee, D. H.

2003-01-01

In CANDU(Canadian Deuterium Uranium) reactors, purge and discharge of moderator cover gas has been performed via vapor recovery system. The methods employed in C-14 removal are mainly based on reactions of CO 2 with absorber of adsorbent. In order to choose an optimum process, we should consider the characteristics of the process, such as, temperature, pressure, humidity etc. and surface dose rate on C-14 scrubber and gas bag to estimate job-related personnel doses. Assuming that the whole C-14 scrubber was completely replaced after one-cycle operation, and that its C-14 activity for one-cycle operation was 40 mCi, we calculated the surface dose rate at the six points of the C-14 scrubber. This calculation showed that the dose rate on the surface of cartridge was only 1.25μSυ/hγ because of low energy of β ray. It is concluded, therefore, that the cartridge change-out is safe because the operation of C-14 removal system causes only a small increase in dose rate

Patient dose reduction by changing the amount of {sup 18}F-FDG radiopharmaceutical injected

Energy Technology Data Exchange (ETDEWEB)

Paiva, Fernanda G. [Universidade Federal de Minas Gerais (UFMG), Belo Horizonte, MG (Brazil). Departamento de Engenharia Nuclear. Programa de Pós Graduação em Ciências e Técnicas Nucleares; Santana, Priscila C. [Universidade Federal de Minas Gerais (UFMG), Belo Horizonte, MG (Brazil). Departamento de Anatomia e Imagem; Mourão Filho, Arnaldo P., E-mail: fgpaiva92@gmail.com, E-mail: pridili@gmail.com, E-mail: apratabhz@gmail.com [Centro Federal de Educação Tecnológica de Minas Gerais (CEFET-MG), Belo Horizonte, MG (Brazil). Centro de Engenharia Biomédica

2017-07-01

Images of Positron Emission Tomography (PET) associated with Computed Tomography (CT) have important diagnostic applications, mainly for oncology. These compound tomographic devices allow the overlapping of functional images obtained from the administration of radiopharmaceuticals and anatomical images generated by X-ray beam attenuation. This work evaluated the impact of reducing the effective dose by reducing the activity injected into the patient using the ICRP 106 biokinetic model. The activity to be injected may vary according to the patient mass and the detector sensitivity. In this work was used the fixed mass of Alderson phantoms, as a standard adult, this mass is 73.5 kg for the male, and 50 kg for the female. Different values of activity to be injected were simulated, from 0.07 mCi to 0.15 mCi, and with 10 mCi, protocol used in some services. Thus, for the acquisition of PET scans, any reduction of the administered activity implies a proportional reduction of the effective dose in patient. The effective dose may vary up to 114% altering the injected activity between 0.07 and 0.15 mCi. Comparing the results found for the effective dose range using 10 mCi the effective dose may vary by up to approximately 14000%. It is expected that the PET/CT scans protocols are changed at the end of the study, so that the absorbed and effective dose received by the patient decreases. (author)

Oxygen dosing the surface of SrTiO{sub 3}

Energy Technology Data Exchange (ETDEWEB)

Dudy, L.; Scheiderer, P.; Schuetz, P.; Gabel, J.; Buchwald, M.; Sing, M.; Claessen, R. [Physikalisches Institut, Universitaet Wuerzburg (Germany); Denlinger, J.D. [Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA, 94270 (United States); Schlueter, C.; Lee, T.L. [Diamond Light Source Ltd., Didcot, Oxfordshire (United Kingdom)

2015-07-01

The highly mobile two-dimensional electron system (2DES) on the surface of the insulating SrTiO{sub 3}(STO) offers exciting perspectives for advanced material design. This 2DES resides in a depletion layer caused by oxygen deficiency of the surface. With photoemission spectroscopy, we monitor the appearance of quasi-particle weight (QP) at the Fermi energy and oxygen vacancy induced states in the band gap (IG). Both, QP and IG weight, increase and decrease respectively upon exposure to extreme ultraviolet (XUV) light and in-situ oxygen dosing. By a proper adjustment of oxygen dosing, any intermediate state can be stabilized providing full control over the charge carrier density. From a comparison of the charge carrier concentrations obtained from an analysis of core-level spectra and the Fermi-surface volume, we conclude on a spatially inhomogeneous surface electronic structure with at least two different phases.

The PA projection of the clavicle: a dose-reducing technique.

LENUS (Irish Health Repository)

Mc Entee, Mark F

2010-06-01

This study compares dose and image quality during PA and AP radiography of the clavicle. The methodology involved a cadaver-based dose and image quality study. Results demonstrate a statistically significant 56.1 % (p reductions to breast tissue and 62.3 % (p reductions in the thyroid dose with employment of PA and PA15 caudal projections. Reductions of 28.5 % (p doses to the eye were demonstrated for the PA. Differences in entrance-surface and exit doses were deemed non-significant. A 5.9 % (p reduction in overall image quality was seen with PA positioning. Reductions in image quality were evaluated to be non-significant at 95 % (AP vs PA (p dose reductions to the thyroid and breast when PA projection is chosen over the AP projection. The authors recommend the implementation of PA positioning for clavicle radiography.

SU-F-18C-12: On the Relationship of the Weighted Dose to the Surface Dose In Abdominal CT - Patient Size Dependency

Energy Technology Data Exchange (ETDEWEB)

Zhou, Y; Scott, A; Allahverdian, J [Cedars-Sinai Medical Center, Los Angeles, CA (United States)

2014-06-15

Purpose: It is possible to measure the patient surface dose non-invasively using radiolucent dosimeters. However, the patient size specific weighted dose remains unknown. We attempted to study the weighted dose to surface dose relationship as the patient size varies in abdominal CT. Methods: Seven abdomen phantoms (CIRS TE series) simulating patients from an infant to a large adult were used. Size specific doses were measured with a 100 mm CT chamber under axial scans using a Siemens Sensation 64 (mCT) and a GE 750 HD. The scanner settings were 120 kVp, 200 mAs with fully opened collimations. Additional kVps (80, 100, 140) were added depending on the phantom sizes. The ratios (r) of the weighted CT dose (Dw) to the surface dose (Ds) were related to the phantom size (L) defined as the diameter resulting the equivalent cross-sectional area. Results: The Dw versus Ds ratio (r) was fitted to a linear relationship: r = 1.083 − 0.007L (R square = 0.995), and r = 1.064 − 0.007L (R square = 0.953), for Siemens Sensation 64 and GE 750 HD, respectively. The relationship appears to be independent of the scanner specifics. Conclusion: The surface dose to the weighted dose ratio decreases linearly as the patient size increases. The result is independent of the scanner specifics. The result can be used to obtain in vivo CT dosimetry in abdominal CT.

SU-F-18C-12: On the Relationship of the Weighted Dose to the Surface Dose In Abdominal CT - Patient Size Dependency

International Nuclear Information System (INIS)

Zhou, Y; Scott, A; Allahverdian, J

2014-01-01

Purpose: It is possible to measure the patient surface dose non-invasively using radiolucent dosimeters. However, the patient size specific weighted dose remains unknown. We attempted to study the weighted dose to surface dose relationship as the patient size varies in abdominal CT. Methods: Seven abdomen phantoms (CIRS TE series) simulating patients from an infant to a large adult were used. Size specific doses were measured with a 100 mm CT chamber under axial scans using a Siemens Sensation 64 (mCT) and a GE 750 HD. The scanner settings were 120 kVp, 200 mAs with fully opened collimations. Additional kVps (80, 100, 140) were added depending on the phantom sizes. The ratios (r) of the weighted CT dose (Dw) to the surface dose (Ds) were related to the phantom size (L) defined as the diameter resulting the equivalent cross-sectional area. Results: The Dw versus Ds ratio (r) was fitted to a linear relationship: r = 1.083 − 0.007L (R square = 0.995), and r = 1.064 − 0.007L (R square = 0.953), for Siemens Sensation 64 and GE 750 HD, respectively. The relationship appears to be independent of the scanner specifics. Conclusion: The surface dose to the weighted dose ratio decreases linearly as the patient size increases. The result is independent of the scanner specifics. The result can be used to obtain in vivo CT dosimetry in abdominal CT

Optimization of filtration for reduction of lung dose from Rn decay products: Part I--Theoretical

International Nuclear Information System (INIS)

Curling, C.A.; Rudnick, S.N.; Ryan, P.B.; Moeller, D.W.

1990-01-01

A theoretical model was developed for the optimization of filter characteristics that would minimize the dose from the inhalation of Rn decay products. Modified forms of the Jacobi-Porstendorfer room model and the Jacobi-Eisfeld lung dose model were chosen for use in the mathematical simulation. Optimized parameters of the filter were the thickness, solidity, and fiber diameter. For purposes of the calculations, the room dimensions, air exchange rate, particle-size distribution and concentration, and the Rn concentration were specified. The resulting computer-aided optimal design was a thin filter (the minimum thickness used in the computer model was 0.1 mm) having low solidity (the minimum solidity used was 0.5%) and large diameter fibers (the maximum diameter used was 100 microns). The simulation implies that a significant reduction in the dose rate can be achieved using a well-designed recirculating filter system. The theoretical model, using the assumption of ideal mixing, predicts an 80% reduction in the dose rate, although inherent in this assumption is the movement of 230 room volumes per hour through the fan

Radiation dose reduction in a neonatal intensive care unit in computed radiography

International Nuclear Information System (INIS)

Frayre, A.S.; Torres, P.; Gaona, E.; Rivera, T.; Franco, J.; Molina, N.

2012-01-01

The purpose of this study was to evaluate the dose received by chest x-rays in neonatal care with thermoluminescent dosimetry and to determine the level of exposure where the quantum noise level does not affect the diagnostic image quality in order to reduce the dose to neonates. In pediatric radiology, especially the prematurely born children are highly sensitive to the radiation because of the highly mitotic state of their cells; in general, the sensitivity of a tissue to radiation is directly proportional to its rate of proliferation. The sample consisted of 208 neonatal chest x-rays of 12 neonates admitted and treated in a Neonatal Intensive Care Unit (NICU). All the neonates were preterm in the range of 28–34 weeks, with a mean of 30.8 weeks. Entrance Surface Doses (ESD) values for chest x-rays are higher than the DRL of 50 μGy proposed by the National Radiological Protection Board (NRPB). In order to reduce the dose to neonates, the optimum image quality was achieved by determining the level of ESD where level noise does not affect the diagnostic image quality. The optimum ESD was estimated for additional 20 chest x-rays increasing kVp and reducing mAs until quantum noise affects image quality. - Highlights: ► Entrance surface doses (ESD) in neonates were measured. ► Doses measured in neonates examinations were higher than those reported by literature. ► Reference levels in neonatal studies are required. ► Radiation protection optimization was proposed.

Model-based iterative reconstruction for reduction of radiation dose in abdominopelvic CT: comparison to adaptive statistical iterative reconstruction.

Science.gov (United States)

Yasaka, Koichiro; Katsura, Masaki; Akahane, Masaaki; Sato, Jiro; Matsuda, Izuru; Ohtomo, Kuni

2013-12-01

To evaluate dose reduction and image quality of abdominopelvic computed tomography (CT) reconstructed with model-based iterative reconstruction (MBIR) compared to adaptive statistical iterative reconstruction (ASIR). In this prospective study, 85 patients underwent referential-, low-, and ultralow-dose unenhanced abdominopelvic CT. Images were reconstructed with ASIR for low-dose (L-ASIR) and ultralow-dose CT (UL-ASIR), and with MBIR for ultralow-dose CT (UL-MBIR). Image noise was measured in the abdominal aorta and iliopsoas muscle. Subjective image analyses and a lesion detection study (adrenal nodules) were conducted by two blinded radiologists. A reference standard was established by a consensus panel of two different radiologists using referential-dose CT reconstructed with filtered back projection. Compared to low-dose CT, there was a 63% decrease in dose-length product with ultralow-dose CT. UL-MBIR had significantly lower image noise than L-ASIR and UL-ASIR (all pASIR and UL-ASIR (all pASIR in diagnostic acceptability (p>0.65), or diagnostic performance for adrenal nodules (p>0.87). MBIR significantly improves image noise and streak artifacts compared to ASIR, and can achieve radiation dose reduction without severely compromising image quality.

Optimal treatment scheduling of ionizing radiation and sunitinib improves the antitumor activity and allows dose reduction

International Nuclear Information System (INIS)

Kleibeuker, Esther A; Hooven, Matthijs A ten; Castricum, Kitty C; Honeywell, Richard; Griffioen, Arjan W; Verheul, Henk M; Slotman, Ben J; Thijssen, Victor L

2015-01-01

The combination of radiotherapy with sunitinib is clinically hampered by rare but severe side effects and varying results with respect to clinical benefit. We studied different scheduling regimes and dose reduction in sunitinib and radiotherapy in preclinical tumor models to improve potential outcome of this combination treatment strategy. The chicken chorioallantoic membrane (CAM) was used as an angiogenesis in vivo model and as a xenograft model with human tumor cells (HT29 colorectal adenocarcinoma, OE19 esophageal adenocarcinoma). Treatment consisted of ionizing radiation (IR) and sunitinib as single therapy or in combination, using different dose-scheduling regimes. Sunitinib potentiated the inhibitory effect of IR (4 Gy) on angiogenesis. In addition, IR (4 Gy) and sunitinib (4 days of 32.5 mg/kg per day) inhibited tumor growth. Ionizing radiation induced tumor cell apoptosis and reduced proliferation, whereas sunitinib decreased tumor angiogenesis and reduced tumor cell proliferation. When IR was applied before sunitinib, this almost completely inhibited tumor growth, whereas concurrent IR was less effective and IR after sunitinib had no additional effect on tumor growth. Moreover, optimal scheduling allowed a 50% dose reduction in sunitinib while maintaining comparable antitumor effects. This study shows that the therapeutic efficacy of combination therapy improves when proper dose-scheduling is applied. More importantly, optimal treatment regimes permit dose reductions in the angiogenesis inhibitor, which will likely reduce the side effects of combination therapy in the clinical setting. Our study provides important leads to optimize combination treatment in the clinical setting

MO-F-CAMPUS-I-04: Patient Eye-Lens Dose Reduction in Routine Brain CT Examinations Using Organ-Based Tube Current Modulation and In-Plane Bismuth Shielding

International Nuclear Information System (INIS)

Tsai, Hui-Yu; Liao, Ying-Lan; Lai, Nan-Ku; Chen, Tou-Rong; Chen, Jun-Rong

2015-01-01

Purpose: The purpose of this study is to assess eye-lens dose for patients who underwent brain CT examinations using two dose reduction Methods: organ-based tube current modulation (OBTCM) and in-plane bismuth shielding method. Methods: This study received institutional review board approval; written informed consent to participate was obtained from all patients. Ninety patients who underwent the routine brain CT examination were randomly assigned to three groups, ie. routine, OBTCM, and bismuth shield. The OBTCM technique reduced the tube current when the X-ray tube rotates in front of patients’ eye-lens region. The patients in the bismuth shield group were covered one-ply bismuth shield in the eyes’ region. Eye-lens doses were measured using TLD-100H chips and the total effective doses were calculated using CT-Expo according to the CT scanning parameters. The surface doses for patients at off-center positions were assessed to evaluate the off-centering effect. Results: Phantom measurements indicates that OBTCM technique could reduced by 26% to 28% of the surface dose to the eye lens, and increased by 25% of the surface dose at the opposed incident direction at the angle of 180°. Patients’ eye-lens doses were reduced 16.9% and 30.5% dose of bismuth shield scan and OBTCM scan, respectively compared to the routine scan. The eye-lens doses were apparently increased when the table position was lower than isocenter. Conclusion: Reducing the dose to the radiosensitive organs, such as eye lens, during routine brain CT examinations could lower the radiation risks. The OBTCM technique and in-plane bismuth shielding could be used to reduce the eye-lens dose. The eye-lens dose could be effectively reduced using OBTCM scan without interfering the diagnostic image quality. Patient position relative the CT gantry also affects the dose level of the eye lens. This study was supported by the grants from the Ministry of Science and Technology of Taiwan (MOST103-2314-B-182

Investigation of Reduction of the Uncertainty of Monte Carlo Dose Calculations in Oncor® Clinical Linear Accelerator Simulation Using the DBS Variance Reduction Technique in Monte Carlo Code BEAMnrc

Directory of Open Access Journals (Sweden)

Amin Asadi

2017-10-01

Full Text Available Purpose: To study the benefits of Directional Bremsstrahlung Splitting (DBS dose variance reduction technique in BEAMnrc Monte Carlo (MC code for Oncor® linac at 6MV and 18MV energies. Materials and Method: A MC model of Oncor® linac was built using BEAMnrc MC Code and verified by the measured data for 6MV and 18MV energies of various field sizes. Then Oncor® machine was modeled running DBS technique, and the efficiency of total fluence and spatial fluence for electron and photon, the efficiency of dose variance reduction of MC calculations for PDD on the central beam axis and lateral dose profile across the nominal field was measured and compared. Result: With applying DBS technique, the total fluence of electron and photon increased in turn 626.8 (6MV and 983.4 (6MV, and 285.6 (18MV and 737.8 (18MV, the spatial fluence of electron and photon improved in turn 308.6±1.35% (6MV and 480.38±0.43% (6MV, and 153±0.9% (18MV and 462.6±0.27% (18MV. Moreover, by running DBS technique, the efficiency of dose variance reduction for PDD MC dose calculations before maximum dose point and after dose maximum point enhanced 187.8±0.68% (6MV and 184.6±0.65% (6MV, 156±0.43% (18MV and 153±0.37% (18MV, respectively, and the efficiency of MC calculations for lateral dose profile remarkably on the central beam axis and across the treatment field raised in turn 197±0.66% (6MV and 214.6±0.73% (6MV, 175±0.36% (18MV and 181.4±0.45% (18MV. Conclusion: Applying dose variance reduction technique of DBS for modeling Oncor® linac with using BEAMnrc MC Code surprisingly improved the fluence of electron and photon, and it therefore enhanced the efficiency of dose variance reduction for MC calculations. As a result, running DBS in different kinds of MC simulation Codes might be beneficent in reducing the uncertainty of MC calculations. 

SU-E-T-196: Comparative Analysis of Surface Dose Measurements Using MOSFET Detector and Dose Predicted by Eclipse - AAA with Varying Dose Calculation Grid Size

Energy Technology Data Exchange (ETDEWEB)

Badkul, R; Nejaiman, S; Pokhrel, D; Jiang, H; Kumar, P [University of Kansas Medical Center, Kansas City, KS (United States)

2015-06-15

Purpose: Skin dose can be the limiting factor and fairly common reason to interrupt the treatment, especially for treating head-and-neck with Intensity-modulated-radiation-therapy(IMRT) or Volumetrically-modulated - arc-therapy (VMAT) and breast with tangentially-directed-beams. Aim of this study was to investigate accuracy of near-surface dose predicted by Eclipse treatment-planning-system (TPS) using Anisotropic-Analytic Algorithm (AAA)with varying calculation grid-size and comparing with metal-oxide-semiconductor-field-effect-transistors(MOSFETs)measurements for a range of clinical-conditions (open-field,dynamic-wedge, physical-wedge, IMRT,VMAT). Methods: QUASAR™-Body-Phantom was used in this study with oval curved-surfaces to mimic breast, chest wall and head-and-neck sites.A CT-scan was obtained with five radio-opaque markers(ROM) placed on the surface of phantom to mimic the range of incident angles for measurements and dose prediction using 2mm slice thickness.At each ROM, small structure(1mmx2mm) were contoured to obtain mean-doses from TPS.Calculations were performed for open-field,dynamic-wedge,physical-wedge,IMRT and VMAT using Varian-21EX,6&15MV photons using twogrid-sizes:2.5mm and 1mm.Calibration checks were performed to ensure that MOSFETs response were within ±5%.Surface-doses were measured at five locations and compared with TPS calculations. Results: For 6MV: 2.5mm grid-size,mean calculated doses(MCD)were higher by 10%(±7.6),10%(±7.6),20%(±8.5),40%(±7.5),30%(±6.9) and for 1mm grid-size MCD were higher by 0%(±5.7),0%(±4.2),0%(±5.5),1.2%(±5.0),1.1% (±7.8) for open-field,dynamic-wedge,physical-wedge,IMRT,VMAT respectively.For 15MV: 2.5mm grid-size,MCD were higher by 30%(±14.6),30%(±14.6),30%(±14.0),40%(±11.0),30%(±3.5)and for 1mm grid-size MCD were higher by 10% (±10.6), 10%(±9.8),10%(±8.0),30%(±7.8),10%(±3.8) for open-field, dynamic-wedge, physical-wedge, IMRT, VMAT respectively.For 6MV, 86% and 56% of all measured values

Dose reduction in LDR brachytherapy by implanted prostate gold fiducial markers.

Science.gov (United States)

Landry, Guillaume; Reniers, Brigitte; Lutgens, Ludy; Murrer, Lars; Afsharpour, Hossein; de Haas-Kock, Danielle; Visser, Peter; van Gils, Francis; Verhaegen, Frank

2012-03-01

The dosimetric impact of gold fiducial markers (FM) implanted prior to external beam radiotherapy of prostate cancer on low dose rate (LDR) brachytherapy seed implants performed in the context of combined therapy was investigated. A virtual water phantom was designed containing a single FM. Single and multi source scenarios were investigated by performing Monte Carlo dose calculations, along with the influence of varying orientation and distance of the FM with respect to the sources. Three prostate cancer patients treated with LDR brachytherapy for a recurrence following external beam radiotherapy with implanted FM were studied as surrogate cases to combined therapy. FM and brachytherapy seeds were identified on post implant CT scans and Monte Carlo dose calculations were performed with and without FM. The dosimetric impact of the FM was evaluated by quantifying the amplitude of dose shadows and the volume of cold spots. D(90) was reported based on the post implant CT prostate contour. Large shadows are observed in the single source-FM scenarios. As expected from geometric considerations, the shadows are dependent on source-FM distance and orientation. Large dose reductions are observed at the distal side of FM, while at the proximal side a dose enhancement is observed. In multisource scenarios, the importance of shadows appears mitigated, although FM at the periphery of the seed distribution caused underdosage (LDR brachytherapy seed implant dose distributions. Therefore, reduced tumor control could be expected from FM implanted in tumors, although our results are too limited to draw conclusions regarding clinical significance.

Reduction of radiation doses in leg lengthening procedures by means of audit and computed tomography scanogram techniques

International Nuclear Information System (INIS)

Romanowski, C.A.J.; Sprigg, A.; Underwood, A.C.

1994-01-01

Children with congenital bone dysplasias may benefit from leg lengthening procedures. Such procedures, by necessity, require frequent and regular imaging. It is necessary to minimize the total radiation dose to these patients, and particularly the dose to the gonads. In the present study, the films of 13 patients who had completed leg lengthening procedures were reviewed. The number of films was assessed together with the use of appropriate gonad shielding. In a second part of the study, thermoluminescent dosemeter measurements of radiation doses to a phantom were made for both plain radiographs (with and without gonad protection) and computed tomography (CT) scanograms. The results show that audit plays an important role in assessing radiographic practice with respect to accurate placement of gonad protection and confirm that a significant dose reduction can be accomplished by careful use of this lead shielding. Dose reduction can also be achieved by using alternative radiographic techniques such as CT scanograms. (author)

Oxidation-reduction induced roughening of platinum (111) surface

International Nuclear Information System (INIS)

You, H.; Nagy, Z.

1993-06-01

Platinum (111) single crystal surface was roughened by repeated cycles of oxidation and reduction to study dynamic evolution of surface roughening. The interface roughens progressively upon repeated cycles. The measured width of the interface was fit to an assumed pow law, W ∼t β , with β = 0.38(1). The results are compared with a simulation based on a random growth model. The fraction of the singly stepped surface apparently saturates to 0. 25 monolayer, which explains the apparent saturation to a steady roughness observed in previous studies

Impact of thermoplastic mask on X-ray surface dose calculated with Monte Carlo code

International Nuclear Information System (INIS)

Zhao Yanqun; Li Jie; Wu Liping; Wang Pei; Lang Jinyi; Wu Dake; Xiao Mingyong

2010-01-01

Objective: To calculate the effects of thermoplastic mask on X-ray surface dose. Methods: The BEAMnrc Monte Carlo Code system, designed especially for computer simulation of radioactive sources, was performed to evaluate the effects of thermoplastic mask on X-ray surface dose.Thermoplastic mask came from our center with a material density of 1.12 g/cm 2 . The masks without holes, with holes size of 0.1 cm x 0.1 cm, and with holes size of 0. 1 cm x 0.2 cm, and masks with different depth (0.12 cm and 0.24 cm) were evaluated separately. For those with holes, the material width between adjacent holes was 0.1 cm. Virtual masks with a material density of 1.38 g/cm 3 without holes with two different depths were also evaluated. Results: Thermoplastic mask affected X-rays surface dose. When using a thermoplastic mask with the depth of 0.24 cm without holes, the surface dose was 74. 9% and 57.0% for those with the density of 1.38 g/cm 3 and 1.12 g/cm 3 respectively. When focusing on the masks with the density of 1.12 g/cm 3 , the surface dose was 41.2% for those with 0.12 cm depth without holes; 57.0% for those with 0. 24 cm depth without holes; 44.5% for those with 0.24 cm depth with holes size of 0.1 cm x 0.2 cm;and 54.1% for those with 0.24 cm depths with holes size of 0.1 cm x 0.1 cm.Conclusions: Using thermoplastic mask during the radiation increases patient surface dose. The severity is relative to the hole size and the depth of thermoplastic mask. The surface dose change should be considered in radiation planning to avoid severe skin reaction. (authors)

Measurement of annual dose on porcelain using surface TLD method

International Nuclear Information System (INIS)

Xia Junding; Wang Weida; Leung, P.L.

2001-01-01

In order to improve accuracy of TL authentication test for porcelain, a method of measurement of annual dose using ultrathin (CaSO 4 :Tm) dosage layer on porcelain was studied. The TLD was placed on the part of porcelain without glaze. A comparison of measurement of annual dose for surface TLD, inside TLD and alpha counting on porcelain was made. The results show that this technique is suitable for measuring annual dose and improving accuracy of TL authentication test for both porcelain and pottery

Surface-reconstructed Cu Electrode via a Facile Electrochemical Anodization-Reduction Process for Low Overpotential CO 2 reduction

KAUST Repository

Min, Shixiong; Yang, Xiulin; Lu, Ang-Yu; Tseng, Chien-Chih; Hedhili, Mohamed N.; Lai, Zhiping; Li, Lain-Jong; Huang, Kuo-Wei

2017-01-01

A high-surface-area Cu electrode, fabricated by a simple electrochemical anodization-reduction method, exhibits high activity and selectivity for CO2 reduction at low overpotential in 0.1 M KHCO3 solution. A faradaic efficiency of 37% for HCOOH

Drag reduction in reservoir rock surface: Hydrophobic modification by SiO_2 nanofluids

International Nuclear Information System (INIS)

Yan, Yong-Li; Cui, Ming-Yue; Jiang, Wei-Dong; He, An-Le; Liang, Chong

2017-01-01

Graphical abstract: The micro-nanoscale hierarchical structures at the sandstone core surface are constructed by adsorption of the modified silica nanoparticles, which leads to the effect of drag reduction to improve the low injection rate in ultra-low permeability reservoirs. - Highlights: • A micro-nanoscale hierarchical structure is formed at the reservoir rock surface. • An inversion has happened from hydrophilic into hydrophobic modified by nanofluids. • The effect of drag reduction to improve the low injection rate is realized. • The mechanism of drag reduction induced from the modified core surface was unclosed. - Abstract: Based on the adsorption behavior of modified silica nanoparticles in the sandstone core surface, the hydrophobic surface was constructed, which consists of micro-nanoscale hierarchical structure. This modified core surface presents a property of drag reduction and meets the challenge of high injection pressure and low injection rate in low or ultra-low permeability reservoir. The modification effects on the surface of silica nanoparticles and reservoir cores, mainly concerning hydrophobicity and fine structure, were determined by measurements of contact angle and scanning electron microscopy. Experimental results indicate that after successful modification, the contact angle of silica nanoparticles varies from 19.5° to 141.7°, exhibiting remarkable hydrophobic properties. These modified hydrophobic silica nanoparticles display a good adsorption behavior at the core surface to form micro-nanobinary structure. As for the wettability of these modified core surfaces, a reversal has happened from hydrophilic into hydrophobic and its contact angle increases from 59.1° to 105.9°. The core displacement experiments show that the relative permeability for water has significantly increased by an average of 40.3% via core surface modification, with the effects of reducing injection pressure and improving injection performance of water

Studies on reduction of dosimeter used in the product dose mapping process at Sinagama Plant

International Nuclear Information System (INIS)

Sofian Ibrahim; Syuhada Ramli; Cosmos George; Zarina Mohd Nor; Kamarudin Buyong; Shahidan Yob; Nor Ishadi Ismail; Mohd Sidek Othman; Ahsanulkhaliqin Abdul Wahab; Mohd Khairul Azfar Ramli

2012-01-01

Product dose mapping is the determination of the best product loading configuration which will be used during routine sterilization. In product dose mapping, dosimeters are placed throughout products at strategic locations to determine the zones of minimum and maximum dose. On previous Sinagama's product dose mapping method, a total of 240 unit's ceric-cerous dosimeter been used for a tote. Based on the data obtained from Irradiator Dose Mapping Report in 2004 and data from recent studies, the number of dosimeter to be used in product dose mapping can be reduced to 28 units without sacrificing precision and accuracy of the dose mapping results. This also led changes of the placing dosimeter method from Plane system to Coordinate system. Reduction of 88 % on dosimeters usage will directly reduce the cost of expenses on dosimeter, time and labor. (author)

Using the benchmark dose (BMD) methodology to determine an appropriate reduction of certain ingredients in food products.

Science.gov (United States)

Bi, Jian

2010-01-01

As the desire to promote health increases, reductions of certain ingredients, for example, sodium, sugar, and fat in food products, are widely requested. However, the reduction is not risk free in sensory and marketing aspects. Over reduction may change the taste and influence the flavor of a product and lead to a decrease in consumer's overall liking or purchase intent for the product. This article uses the benchmark dose (BMD) methodology to determine an appropriate reduction. Calculations of BMD and one-sided lower confidence limit of BMD are illustrated. The article also discusses how to calculate BMD and BMDL for over dispersed binary data in replicated testing based on a corrected beta-binomial model. USEPA Benchmark Dose Software (BMDS) were used and S-Plus programs were developed. The method discussed in the article is originally used to determine an appropriate reduction of certain ingredients, for example, sodium, sugar, and fat in food products, considering both health reason and sensory or marketing risk.

Radiation Dose-rate Reduction Pattern in Well-differentiated Thyroid Cancer Treated with I-131.

Science.gov (United States)

Khan, Shahbaz Ahmad; Khan, Muhammad Saqib; Arif, Muhammad; Durr-e-Sabih; Rahim, Muhammad Kashif; Ahmad, Israr

2015-07-01

To determine the patterns of dose rate reduction in single and multiple radioiodine (I-131) therapies in cases of well differentiated thyroid cancer patients. Analytical series. Department of Nuclear Medicine and Radiation Physics, Multan Institute of Nuclear Medicine and Radiotherapy (MINAR), Multan, Pakistan, from December 2006 to December 2013. Ninety three patients (167 therapies) with well differentiated thyroid cancer treated with different doses of I-131 as an in-patient were inducted. Fifty four patients were given only single I-131 therapy dose ranging from 70 mCi (2590 MBq) to 150 mCi (5550 MBq). Thirty nine patients were treated with multiple I-131 radioisotope therapy doses ranging from 80 mCi (2960 MBq) to 250 mCi (9250 MBq). T-test was applied on the sample data showed statistically significant difference between the two groups with p-value (p < 0.01) less than 0.05 taken as significant. There were 68 females and 25 males with an age range of 15 to 80 years. Mean age of the patients were 36 years. Among the 93 cases of first time Radio Active Iodine (RAI) therapy, 59 cases (63%) were discharged after 48 hours. Among 39 patients who received RAI therapy second time or more, most were discharged earlier after achieving acceptable discharge dose rate i.e 25 µSv/hour; 2 out of 39 (5%) were discharged after 48 hours. In 58% patients, given single I-131 therapy dose, majority of these were discharged after 48 hours without any major complications. For well differentiated thyroid cancer patients, rapid dose rate reduction is seen in patients receiving second or subsequent radioiodine (RAI) therapy, as compared to first time receiving RAI therapy.

Impact of view reduction in CT on radiation dose for patients

International Nuclear Information System (INIS)

Parcero, E.; Flores, L.; Sánchez, M.G.; Vidal, V.; Verdú, G.

2017-01-01

Iterative methods have become a hot topic of research in computed tomography (CT) imaging because of their capacity to resolve the reconstruction problem from a limited number of projections. This allows the reduction of radiation exposure on patients during the data acquisition. The reconstruction time and the high radiation dose imposed on patients are the two major drawbacks in CT. To solve them effectively we adapted the method for sparse linear equations and sparse least squares (LSQR) with soft threshold filtering (STF) and the fast iterative shrinkage-thresholding algorithm (FISTA) to computed tomography reconstruction. The feasibility of the proposed methods is demonstrated numerically. - Highlights: • A method for CT reconstruction is proposed: LSQR-STF-FISTA. • Our method achieve good results in reconstruction of few-view CT. • The reconstruction of projections with Gaussian noise is possible. • Our reconstruction process allows a reduction of time in the data acquisition process. • Our reconstruction process allows a reduction in the radiation exposure in the patients.

[Fluoroscopy dose reduction of computed tomography guided chest interventional radiology using real-time iterative reconstruction].

Science.gov (United States)

Hasegawa, Hiroaki; Mihara, Yoshiyuki; Ino, Kenji; Sato, Jiro

2014-11-01

The purpose of this study was to evaluate the radiation dose reduction to patients and radiologists in computed tomography (CT) guided examinations for the thoracic region using CT fluoroscopy. Image quality evaluation of the real-time filtered back-projection (RT-FBP) images and the real-time adaptive iterative dose reduction (RT-AIDR) images was carried out on noise and artifacts that were considered to affect the CT fluoroscopy. The image standard deviation was improved in the fluoroscopy setting with less than 30 mA on 120 kV. With regard to the evaluation of artifact visibility and the amount generated by the needle attached to the chest phantom, there was no significant difference between the RT-FBP images with 120 kV, 20 mA and the RT-AIDR images with low-dose conditions (greater than 80 kV, 30 mA and less than 120 kV, 20 mA). The results suggest that it is possible to reduce the radiation dose by approximately 34% at the maximum using RT-AIDR while maintaining image quality equivalent to the RT-FBP images with 120 V, 20 mA.

Dose of Biocoagulant-Mixing Rate Combinations for Optimum Reduction of COD in Wastewater

Science.gov (United States)

Patricia, Maria Faustina; Purwono; Budihardjo, Mochamad Arief

2018-02-01

Chemical oxygen demand (COD) in domestic wastewater can be treated using flocculation-coagulation process with addition of Oyster mushroom (Pleurotus ostreatus) in powder form as biocoagulant. The fungal cell wall of Oyster mushroom comprises of chitin that is high polyelectrolyte and can be function as an absorbent of heavy metals in wastewater. The effectiveness of flocculation-coagulation process in treating wastewater depends on dose of coagulant and mixing rate. Therefore, this study aims to determine the best combination of three variation of dose of biocoagulant which are 600 mg/l, 1000 mg/l, and 2000 mg/l and mixing rate which are 100 rpm, 125 rpm, and 150 rpm that give the most reduction of COD in the wastewater. The result indicates that the combination of 1000 mg/l of biocoagulant and 100 rpm of mixing rate were found to be the most optimum combination to treat COD in the wastewater with COD reduction of 47.7%.

Dose of Biocoagulant-Mixing Rate Combinations for Optimum Reduction of COD in Wastewater

Directory of Open Access Journals (Sweden)

Faustina Patricia Maria

2018-01-01

Full Text Available Chemical oxygen demand (COD in domestic wastewater can be treated using flocculation-coagulation process with addition of Oyster mushroom (Pleurotus ostreatus in powder form as biocoagulant. The fungal cell wall of Oyster mushroom comprises of chitin that is high polyelectrolyte and can be function as an absorbent of heavy metals in wastewater. The effectiveness of flocculation-coagulation process in treating wastewater depends on dose of coagulant and mixing rate. Therefore, this study aims to determine the best combination of three variation of dose of biocoagulant which are 600 mg/l, 1000 mg/l, and 2000 mg/l and mixing rate which are 100 rpm, 125 rpm, and 150 rpm that give the most reduction of COD in the wastewater. The result indicates that the combination of 1000 mg/l of biocoagulant and 100 rpm of mixing rate were found to be the most optimum combination to treat COD in the wastewater with COD reduction of 47.7%.

Effects of adaptive statistical iterative reconstruction on radiation dose reduction and diagnostic accuracy of pediatric abdominal CT

Energy Technology Data Exchange (ETDEWEB)

Bae, Sohi; Kim, Myung-Joon; Lee, Mi-Jung [Yonsei University College of Medicine, Department of Radiology and Research Institute of Radiological Science, Severance Children' s Hospital, Seoul (Korea, Republic of); Yoon, Choon-Sik [Yonsei University College of Medicine, Department of Radiology, Gangnam Severance Hospital, Seoul (Korea, Republic of); Kim, Dong Wook; Hong, Jung Hwa [Yonsei University College of Medicine, Biostatistics Collaboration Unit, Seoul (Korea, Republic of)

2014-12-15

Since children are more radio-sensitive than adults, there is a need to minimize radiation exposure during CT exams. To evaluate the effects of adaptive statistical iterative reconstruction (ASIR) on radiation dose reduction, image quality and diagnostic accuracy in pediatric abdominal CT. We retrospectively reviewed the abdominal CT examinations of 41 children (24 boys and 17 girls; mean age: 10 years) with a low-dose radiation protocol and reconstructed with ASIR (the ASIR group). We also reviewed routine-dose abdominal CT examinations of 41 age- and sex-matched controls reconstructed with filtered-back projection (control group). Image quality was assessed objectively as noise measured in the liver, spleen and aorta, as well as subjectively by three pediatric radiologists for diagnostic acceptability using a four-point scale. Radiation dose and objective image qualities of each group were compared with the paired t-test. Diagnostic accuracy was evaluated by reviewing follow-up imaging studies and medical records in 2012 and 2013. There was 46.3% dose reduction of size-specific dose estimates in ASIR group (from 13.4 to 7.2 mGy) compared with the control group. Objective noise was higher in the liver, spleen and aorta of the ASIR group (P < 0.001). However, the subjective image quality was average or superior in 84-100% of studies. Only one image was subjectively rated as unacceptable by one reviewer. There was only one case with interpretational error in the control group and none in the ASIR group. Use of the ASIR technique resulted in greater than a 45% reduction in radiation dose without impairing subjective image quality or diagnostic accuracy in pediatric abdominal CT, despite increased objective image noise. (orig.)

Effects of adaptive statistical iterative reconstruction on radiation dose reduction and diagnostic accuracy of pediatric abdominal CT

International Nuclear Information System (INIS)

Bae, Sohi; Kim, Myung-Joon; Lee, Mi-Jung; Yoon, Choon-Sik; Kim, Dong Wook; Hong, Jung Hwa

2014-01-01

Since children are more radio-sensitive than adults, there is a need to minimize radiation exposure during CT exams. To evaluate the effects of adaptive statistical iterative reconstruction (ASIR) on radiation dose reduction, image quality and diagnostic accuracy in pediatric abdominal CT. We retrospectively reviewed the abdominal CT examinations of 41 children (24 boys and 17 girls; mean age: 10 years) with a low-dose radiation protocol and reconstructed with ASIR (the ASIR group). We also reviewed routine-dose abdominal CT examinations of 41 age- and sex-matched controls reconstructed with filtered-back projection (control group). Image quality was assessed objectively as noise measured in the liver, spleen and aorta, as well as subjectively by three pediatric radiologists for diagnostic acceptability using a four-point scale. Radiation dose and objective image qualities of each group were compared with the paired t-test. Diagnostic accuracy was evaluated by reviewing follow-up imaging studies and medical records in 2012 and 2013. There was 46.3% dose reduction of size-specific dose estimates in ASIR group (from 13.4 to 7.2 mGy) compared with the control group. Objective noise was higher in the liver, spleen and aorta of the ASIR group (P < 0.001). However, the subjective image quality was average or superior in 84-100% of studies. Only one image was subjectively rated as unacceptable by one reviewer. There was only one case with interpretational error in the control group and none in the ASIR group. Use of the ASIR technique resulted in greater than a 45% reduction in radiation dose without impairing subjective image quality or diagnostic accuracy in pediatric abdominal CT, despite increased objective image noise. (orig.)

Analysis of Surface Dose Refer to Distance between Beam Spoiler and Patient in Total Body Irradiation

International Nuclear Information System (INIS)

Choi, Jong Hwan; Kim, Jong Sik; Choi, Ji Min; Shin, Eun Hyuk; Song, Ki Won; Park, Young Hwan

2007-01-01

Total body irradiation is used to kill the total malignant cell and for immunosuppression component of preparatory regimens for bone-marrow restitution of patients. Beam spoiler is used to increase the dose to the superficial tissues. This paper finds the property of the distance between beam spoiler and patient. Set-up conditions are 6 MV-Xray, 300 MU, SAD = 400 cm, field size = 40 x 40 cm 2 . The parallel plate chamber located in surface, midpoint and exit of solid water phantom. The surface dose is measured while the distance between beam spoiler and patient is altered. Because it should be found proper distance. The solid water phantom is fixer and beam spoiler is moving. Central dose of phantom is 10.7 cGy and exit dose is 6.7 cGy. In case of distance of 50 cm to 60 cm between beam spoiler and solid water phantom, incidence dose is 14.58-14.92 cGy. Therefore, The surface dose was measured 99.4-101% with got near most to the prescription dose. In clinical case, distance between beam spoiler and patient affect surface dose. If once 50-60 cm of distance between beam spoiler and patient, surface dose of patient got near prescription dose. It would be taken distance between beam spoiler and patient into account in clinical therapy.

Monte carlo calculation of the neutron effective dose rate at the outer surface of the biological shield of HTR-10 reactor

International Nuclear Information System (INIS)

Remetti, Romolo; Andreoli, Giulio; Keshishian, Silvina

2012-01-01

Highlights: ► We deal with HTR-10, that is a helium-cooled graphite-moderated pebble bed reactor. ► We carried out Monte Carlo simulation of the core by MCNP5. ► Extensive use of MCNP5 variance reduction methods has been done. ► We calculated the trend of neutron flux within the biological shield. ► We calculated neutron effective dose at the outer surface of biological shield. - Abstract: Research on experimental reactors, such as HTR-10, provide useful data about potentialities of very high temperature gas-cooled reactors (VHTR). The latter is today rated as one of the six nuclear reactor types involved in the Generation-IV International Forum (GIF) Initiative. In this study, the MCNP5 code has been employed to evaluate the neutron radiation trend vs. the biological shield's thickness and to calculate the neutron effective dose rate at the outer surface. The reactor's geometry has been completely modeled by means of lattices and universes provided by MCNP, even though some approximations were required. Monte Carlo calculations have been performed by means of a simple PC and, as a consequence, in order to obtain acceptable run times, it was made an extensive recourse to variance reduction methods.

Occupational dose reduction at nuclear power plants: Annotated bibliography of selected readings in radiation protection and ALARA: Volume 4

International Nuclear Information System (INIS)

Khan, T.A.; Baum, J.W.

1989-06-01

This report is the fourth in the series of bibliographies supporting the efforts at the Brookhaven National Laboratory on dose reduction at nuclear power plants. Abstracts for this bibliography were selected from proceedings of technical meetings, journals, research reports and searches of the DOE's Energy Data Base. The abstracts included in this report to operational health physics as well as other subjects which have a bearing on dose reduction at nuclear power plants, such as stress corrosion, cracking, plant chemistry, use of robotics and remote devices, etc. Material on improved design, materials selection, planning and other topics which are related to dose reduction efforts are also included. The report contains 327 abstracts as well as subject and author indices. All information in the current volume is also available from the ALARA Center's bulletin board service which is accessible by personal computers with the help of a modem. The last section of the report explains the features of the bulletin board. The bulletin board will be kept up-to-date with new information and should be of help in keeping people current in the area of dose reduction

SU-E-T-329: Dosimetric Impact of Implementing Metal Artifact Reduction Methods and Metal Energy Deposition Kernels for Photon Dose Calculations

International Nuclear Information System (INIS)

Huang, J; Followill, D; Howell, R; Liu, X; Mirkovic, D; Stingo, F; Kry, S

2015-01-01

Purpose: To investigate two strategies for reducing dose calculation errors near metal implants: use of CT metal artifact reduction methods and implementation of metal-based energy deposition kernels in the convolution/superposition (C/S) method. Methods: Radiochromic film was used to measure the dose upstream and downstream of titanium and Cerrobend implants. To assess the dosimetric impact of metal artifact reduction methods, dose calculations were performed using baseline, uncorrected images and metal artifact reduction Methods: Philips O-MAR, GE’s monochromatic gemstone spectral imaging (GSI) using dual-energy CT, and GSI imaging with metal artifact reduction software applied (MARs).To assess the impact of metal kernels, titanium and silver kernels were implemented into a commercial collapsed cone C/S algorithm. Results: The CT artifact reduction methods were more successful for titanium than Cerrobend. Interestingly, for beams traversing the metal implant, we found that errors in the dimensions of the metal in the CT images were more important for dose calculation accuracy than reduction of imaging artifacts. The MARs algorithm caused a distortion in the shape of the titanium implant that substantially worsened the calculation accuracy. In comparison to water kernel dose calculations, metal kernels resulted in better modeling of the increased backscatter dose at the upstream interface but decreased accuracy directly downstream of the metal. We also found that the success of metal kernels was dependent on dose grid size, with smaller calculation voxels giving better accuracy. Conclusion: Our study yielded mixed results, with neither the metal artifact reduction methods nor the metal kernels being globally effective at improving dose calculation accuracy. However, some successes were observed. The MARs algorithm decreased errors downstream of Cerrobend by a factor of two, and metal kernels resulted in more accurate backscatter dose upstream of metals. Thus

Full dose reduction potential of statistical iterative reconstruction for head CT protocols in a predominantly pediatric population

Science.gov (United States)

Mirro, Amy E.; Brady, Samuel L.; Kaufman, Robert. A.

2016-01-01

Purpose To implement the maximum level of statistical iterative reconstruction that can be used to establish dose-reduced head CT protocols in a primarily pediatric population. Methods Select head examinations (brain, orbits, sinus, maxilla and temporal bones) were investigated. Dose-reduced head protocols using an adaptive statistical iterative reconstruction (ASiR) were compared for image quality with the original filtered back projection (FBP) reconstructed protocols in phantom using the following metrics: image noise frequency (change in perceived appearance of noise texture), image noise magnitude, contrast-to-noise ratio (CNR), and spatial resolution. Dose reduction estimates were based on computed tomography dose index (CTDIvol) values. Patient CTDIvol and image noise magnitude were assessed in 737 pre and post dose reduced examinations. Results Image noise texture was acceptable up to 60% ASiR for Soft reconstruction kernel (at both 100 and 120 kVp), and up to 40% ASiR for Standard reconstruction kernel. Implementation of 40% and 60% ASiR led to an average reduction in CTDIvol of 43% for brain, 41% for orbits, 30% maxilla, 43% for sinus, and 42% for temporal bone protocols for patients between 1 month and 26 years, while maintaining an average noise magnitude difference of 0.1% (range: −3% to 5%), improving CNR of low contrast soft tissue targets, and improving spatial resolution of high contrast bony anatomy, as compared to FBP. Conclusion The methodology in this study demonstrates a methodology for maximizing patient dose reduction and maintaining image quality using statistical iterative reconstruction for a primarily pediatric population undergoing head CT examination. PMID:27056425

Does bridging the gap between knowledge and practice help? Example of patient dose reduction in radiology

International Nuclear Information System (INIS)

Rehani, M.M.; Kaul, Rashmi; Kumar, Pratik; Berry, M.

1995-01-01

The paper is aimed at bridging the gap between knowledge and practice and evaluating the impact of this activity on reduction of patient dose. While enormous data on radiation doses in diagnostic radiology exists, there is absolute lack of information at user's level. For example, the implications on patient dose from 1cm error in x-ray field size or error of 5 kVp or 5mAs is invariably not known. We estimated that 1 cm increase in field size results in irradiation of 600-900cc of extra volume of patient which may contain sensitive tissue, 5 kVp increase results in exposure of 35-65 mR, with more effect in case of lumbar spine and abdomen x-ray and lesser for chest and D-spine, 5 mAs error results in 4-25 mR. The impact of information supply to users was evaluated and it was found that information based approach results in dose reduction to patient and improved image quality. (author). 3 refs., 4 figs., 3 tabs

Effects of ground surface decontamination on the air radiation dose rate. Results of a decontamination trial at a playground lot in a Fukushima residential area

International Nuclear Information System (INIS)

Tagawa, Akihiro

2012-01-01

The Japan Atomic Energy Agency decontaminated schools, playgrounds, swimming pools, and houses in nonevacuated, less-contaminated areas in Fukushima for environmental restoration. A small, 150 m 2 playground lot in the residential area was chosen for decontamination demonstration, which used routinely available tools and commodities to carry out the work. The surfaces of playground lot equipment, such as swings, slides, and horizontal iron bars, were completely decontaminated by brushing with water and/or detergent. Side gutters around the playground lot were cleaned by removing the mud and then brushed and washed with a high-pressure water jet (7 MPa). The air dose rate at the playground lot was dominated by radiation from the ground surface and adjacent surroundings, such as apartments and rice fields. Two or three centimeters of the surface soil contaminated with cesium was removed manually with shovels, hoes, and other gardening tools. This significantly reduced the average air dose rate of the entire playground lot from 1.5 μSv/h before decontamination to 0.6 μSv/h. These results showed that ground surface decontamination can contribute measurably to the reduction in air dose rate in relatively small areas in residential areas. (author)

Modeling dose-rate on/over the surface of cylindrical radio-models using Monte Carlo methods

International Nuclear Information System (INIS)

Xiao Xuefu; Ma Guoxue; Wen Fuping; Wang Zhongqi; Wang Chaohui; Zhang Jiyun; Huang Qingbo; Zhang Jiaqiu; Wang Xinxing; Wang Jun

2004-01-01

Objective: To determine the dose-rates on/over the surface of 10 cylindrical radio-models, which belong to the Metrology Station of Radio-Geological Survey of CNNC. Methods: The dose-rates on/over the surface of 10 cylindrical radio-models were modeled using the famous Monte Carlo code-MCNP. The dose-rates on/over the surface of 10 cylindrical radio-models were measured by a high gas pressurized ionization chamber dose-rate meter, respectively. The values of dose-rate modeled using MCNP code were compared with those obtained by authors in the present experimental measurement, and with those obtained by other workers previously. Some factors causing the discrepancy between the data obtained by authors using MCNP code and the data obtained using other methods are discussed in this paper. Results: The data of dose-rates on/over the surface of 10 cylindrical radio-models, obtained using MCNP code, were in good agreement with those obtained by other workers using the theoretical method. They were within the discrepancy of ±5% in general, and the maximum discrepancy was less than 10%. Conclusions: As if each factor needed for the Monte Carlo code is correct, the dose-rates on/over the surface of cylindrical radio-models modeled using the Monte Carlo code are correct with an uncertainty of 3%

Interdependence between body surface area and ultraviolet B dose in vitamin D production

DEFF Research Database (Denmark)

Bogh, M K B; Schmedes, Anne; Philipsen, P A

2011-01-01

Ultraviolet (UV) B radiation increases serum vitamin D level expressed as 25-hydroxyvitamin-D(3) [25(OH)D], but the relationship to body surface area and UVB dose needs investigation.......Ultraviolet (UV) B radiation increases serum vitamin D level expressed as 25-hydroxyvitamin-D(3) [25(OH)D], but the relationship to body surface area and UVB dose needs investigation....

The calculation of the surface dose in examinations following cardiac catheterization

International Nuclear Information System (INIS)

Ewen, K.

1995-01-01

It is inevitable in examinations requiring patient exposure to high doses that the investigators and medical assistants receive high wholebody doses on account of fray radiation and, occasionally, also high partial body doses (hands) on account of the useful beam range. A number of different circumstances are adding up to create this extreme situation. In this connection, a mathematical method for the calculation of the surface dose (cutaneous dose rate) is described that is based on sets of parameters commonly used in diagnostic radiology: Set I of parameters: Tube voltage - current strength of tube - distance between focus and skin; - set II of parameters: Incidence dose rate of image intensifier - distance between focus and skin -distance between image intensifier and plane of ray incidence (skin). (orig./VHE) [de

Comparison of surface doses from spot scanning and passively scattered proton therapy beams

International Nuclear Information System (INIS)

Arjomandy, Bijan; Sahoo, Narayan; Gillin, Michael; Cox, James; Lee, Andrew

2009-01-01

Proton therapy for the treatment of cancer is delivered using either passively scattered or scanning beams. Each technique delivers a different amount of dose to the skin, because of the specific feature of their delivery system. The amount of dose delivered to the skin can play an important role in choosing the delivery technique for a specific site. To assess the differences in skin doses, we measured the surface doses associated with these two techniques. For the purpose of this investigation, the surface doses in a phantom were measured for ten prostate treatment fields planned with passively scattered proton beams and ten patients planned with spot scanning proton beams. The measured doses were compared to evaluate the differences in the amount of skin dose delivered by using these techniques. The results indicate that, on average, the patients treated with spot scanning proton beams received lower skin doses by an amount of 11.8% ± 0.3% than did the patients treated with passively scattered proton beams. That difference could amount to 4 CGE per field for a prescribed dose of 76 CGE in 38 fractions treated with two equally weighted parallel opposed fields. (note)

A comparison of mantle versus involved-field radiotherapy for Hodgkin's lymphoma: reduction in normal tissue dose and second cancer risk

International Nuclear Information System (INIS)

Koh, Eng-Siew; Paul, Narinder; Hodgson, David C; Tran, Tu Huan; Heydarian, Mostafa; Sachs, Rainer K; Tsang, Richard W; Brenner, David J; Pintilie, Melania; Xu, Tony; Chung, June

2007-01-01

Hodgkin's lymphoma (HL) survivors who undergo radiotherapy experience increased risks of second cancers (SC) and cardiac sequelae. To reduce such risks, extended-field radiotherapy (RT) for HL has largely been replaced by involved field radiotherapy (IFRT). While it has generally been assumed that IFRT will reduce SC risks, there are few data that quantify the reduction in dose to normal tissues associated with modern RT practice for patients with mediastinal HL, and no estimates of the expected reduction in SC risk. Organ-specific dose-volume histograms (DVH) were generated for 41 patients receiving 35 Gy mantle RT, 35 Gy IFRT, or 20 Gy IFRT, and integrated organ mean doses were compared for the three protocols. Organ-specific SC risk estimates were estimated using a dosimetric risk-modeling approach, analyzing DVH data with quantitative, mechanistic models of radiation-induced cancer. Dose reductions resulted in corresponding reductions in predicted excess relative risks (ERR) for SC induction. Moving from 35 Gy mantle RT to 35 Gy IFRT reduces predicted ERR for female breast and lung cancer by approximately 65%, and for male lung cancer by approximately 35%; moving from 35 Gy IFRT to 20 Gy IFRT reduces predicted ERRs approximately 40% more. The median reduction in integral dose to the whole heart with the transition to 35 Gy IFRT was 35%, with a smaller (2%) reduction in dose to proximal coronary arteries. There was no significant reduction in thyroid dose. The significant decreases estimated for radiation-induced SC risks associated with modern IFRT provide strong support for the use of IFRT to reduce the late effects of treatment. The approach employed here can provide new insight into the risks associated with contemporary IFRT for HL, and may facilitate the counseling of patients regarding the risks associated with this treatment

A three-dimensional computed tomography-assisted Monte Carlo evaluation of ovoid shielding on the dose to the bladder and rectum in intracavitary radiotherapy for cervical cancer

International Nuclear Information System (INIS)

Gifford, Kent A.; Horton, John L.; Pelloski, Christopher E.; Jhingran, Anuja; Court, Laurence E.; Mourtada, Firas; Eifel, Patricia J.

2005-01-01

Purpose: To determine the effects of Fletcher Suit Delclos ovoid shielding on dose to the bladder and rectum during intracavitary radiotherapy for cervical cancer. Methods and Materials: The Monte Carlo method was used to calculate the dose in 12 patients receiving low-dose-rate intracavitary radiotherapy with both shielded and unshielded ovoids. Cumulative dose-difference surface histograms were computed for the bladder and rectum. Doses to the 2-cm 3 and 5-cm 3 volumes of highest dose were computed for the bladder and rectum with and without shielding. Results: Shielding affected dose to the 2-cm 3 and 5-cm 3 volumes of highest dose for the rectum (10.1% and 11.1% differences, respectively). Shielding did not have a major impact on the dose to the 2-cm 3 and 5-cm 3 volumes of highest dose for the bladder. The average dose reduction to 5% of the surface area of the bladder was 53 cGy. Reductions as large as 150 cGy were observed to 5% of the surface area of the bladder. The average dose reduction to 5% of the surface area of the rectum was 195 cGy. Reductions as large as 405 cGy were observed to 5% of the surface area of the rectum. Conclusions: Our data suggest that the ovoid shields can greatly reduce the radiation dose delivered to the rectum. We did not find the same degree of effect on the dose to the bladder. To calculate the dose accurately, however, the ovoid shields must be included in the dose model

Surface dose investigation of the flattening filter-free photon beams.

Science.gov (United States)

Wang, Yuenan; Khan, Mohammad K; Ting, Joseph Y; Easterling, Stephen B

2012-06-01

Flattening filter-free (FFF) x-rays can provide more efficient use of photons and a significant increase of dose rate compared with conventional flattened x-rays, features that are especially beneficial for stereotactic radiosurgery (SRS) and stereotactic body radiotherapy (SBRT). The available data on the entrance doses of the FFF photon beams remain limited. The purpose of this study was to investigate the entrance dose of FFF photons in the buildup region and to compare it with that of conventional flattened photons. A Varian TrueBeam linear accelerator has been in full clinical operation with 6-MV and 10-MV FFF and flattened x-ray photons. Entrance dose at the surface was measured using a parallel plate ionization chamber in a solid water phantom with buildup depth = 0~15 mm for 6X and 0~25 mm for 10X. Different field size (FS) patterns were created in the Eclipse Treatment Planning System by multileaf collimator (MLC) rather than jaws (FS = 2 × 2, 3 × 3, 4 × 4, 6 × 6, and 10 × 10 cm(2) by MLC and jaw size = 2.2 × 2.2, 3.2 × 3.2, 4.2 × 4.2, 6 × 6, and 10 × 10 cm(2)). The smallest FS was about four times larger than the ion chamber dimension. All buildup dose measurements were normalized to FS = 10 × 10 cm(2) at the depth of dose maximum (dmax). Good repeatability was demonstrated and surface dose increased linearly with FS for both flattened and FFF photons. The entrance dose of the FFF photons was modestly larger than that of the corresponding flattened photons for both 6X and 10X for different FS ranging from 2 × 2 cm(2) to 10 × 10 cm(2). The FFF photons have a higher entrance dose than that of the corresponding flattened photons for FS smaller than 10 × 10 cm(2). However, the difference is not substantial and may be clinically insignificant. Published by Elsevier Inc.

Fetal dose reduction in head and neck radiotherapy of a pregnant woman

International Nuclear Information System (INIS)

Moeckli, R.; Pache, G.; Valley, J.F.; Ozsahin, M.; Mirimanoff, R.O.; Azria, D.

2004-01-01

Background and purpose: a pregnant woman was referred for post-operative radiotherapy of a malignant schwannoma in the head and neck region. A best-treatment plan was devised in order to minimize the fetal dose. Material and methods: the fetal dose resulting from radiological examinations was determined according to international protocols, that resulting from radiotherapy was calculated according to recommendation 36 of the American Association of Physicists in Medicine (AAPM) Task Group. Pre-treatment dosimetry was performed with an anthropomorphic phantom. Several alternative treatment plans were evaluated. The use of a multileaf collimator (MLC) and a virtual wedge (VW) was compared to cerrobend blocks (CB) and physical wedge (PW). In-vivo dosimetry was performed using a vaginal probe containing thermoluminescent dosimeters (TLD). Results: the total fetal dose resulting from diagnostic and radiotherapy procedures was estimated to be 36 mGy. The technique based on MLC and VW was elected for patient treatment. Measurements for this configuration resulted in a fetal dose reduction of 82%. The shielding of the patient's abdomen further reduced the fetal dose by 42%. Conclusion: the use of VW and MLC for the treatment of a pregnant woman is highly recommended. Each case should be individually studied with pre-treatment and in-vivo dosimetry. (orig.)

Dose distribution considerations of medium energy electron beams at extended source-to-surface distance

International Nuclear Information System (INIS)

Saw, Cheng B.; Ayyangar, Komanduri M.; Pawlicki, Todd; Korb, Leroy J.

1995-01-01

Purpose: To determine the effects of extended source-to-surface distance (SSD) on dose distributions for a range of medium energy electron beams and cone sizes. Methods and Materials: The depth-dose curves and isodose distributions of 6 MeV, 10 MeV, and 14 MeV electron beams from a dual photon and multielectron energies linear accelerator were studied. To examine the influence of cone size, the smallest and the largest cone sizes available were used. Measurements were carried out in a water phantom with the water surface set at three different SSDs from 101 to 116 cm. Results: In the region between the phantom surface and the depth of maximum dose, the depth-dose decreases as the SSD increases for all electron beam energies. The effects of extended SSD in the region beyond the depth of maximum dose are unobservable and, hence, considered minimal. Extended SSD effects are apparent for higher electron beam energy with small cone size causing the depth of maximum dose and the rapid dose fall-off region to shift deeper into the phantom. However, the change in the depth-dose curve is small. On the other hand, the rapid dose fall-off region is essentially unaltered when the large cone is used. The penumbra enlarges and electron beam flatness deteriorates with increasing SSD

Descriptors and Thermodynamic Limitations of Electrocatalytic Carbon Dioxide Reduction on Rutile Oxide Surfaces

DEFF Research Database (Denmark)

Bhowmik, Arghya; Vegge, Tejs; Hansen, Heine Anton

2016-01-01

A detailed understanding of the electrochemical reduction of CO2 into liquid fuels on rutile metal oxide surfaces is developed by using DFT calculations. We consider oxide overlayer structures on RuO2(1 1 0) surfaces as model catalysts to elucidate the trends and limitations in the CO2 reduction...... and it defines the left leg of the activity volcano for CO2RR. HCOOH* is a key intermediate for products formed through further reduction, for example, methanediol, methanol, and methane. The surfaces that do not bind HCOOH* are selective towards formic acid (HCOOH) production, but hydrogen evolution limits...

Radiotherapy high energy surface dose measurements: effects of chamber polarity

International Nuclear Information System (INIS)

Cheung, T.; Yu, P.K.N.; Butson, M.J.; Cancer Services, Wollongong, NSW

2004-01-01

Full text: The effects of chamber polarity have been investigated for the measurement of 6MV and 18MV x-ray surface dose using a parallel plate ionization chamber. Results have shown that a significant difference in measured ionization is recorded between to polarities at 6MV and 18MV at the phantom surface. A polarity ratio ranging from 1 062 to 1 005 is seen for 6MV x-rays at the phantom surface for field sizes 5cm x 5cm to 40cm x 40cm when comparing positive to negative polarity. These ratios range from 1.024 to 1.004 for 18MV x-rays with the same field sizes. When these charge reading are compared to the D max readings of the same polarity it is found that these polarity effects are minimal for the calculation of percentage dose results with variations being less than 1% of maximum. Copyright (2004) Australasian College of Physical Scientists and Engineers in Medicine

Postimplantation Analysis Enables Improvement of Dose-Volume Histograms and Reduction of Toxicity for Permanent Seed Implantation

International Nuclear Information System (INIS)

Wust, Peter; Postrach, Johanna; Kahmann, Frank; Henkel, Thomas; Graf, Reinhold; Cho, Chie Hee; Budach, Volker; Boehmer, Dirk

2008-01-01

Purpose: To demonstrate how postimplantation analysis is useful for improving permanent seed implantation and reducing toxicity. Patients and Methods: We evaluated 197 questionnaires completed by patients after permanent seed implantation (monotherapy between 1999 and 2003). For 70% of these patients, a computed tomography was available to perform postimplantation analysis. The index doses and volumes of the dose-volume histograms (DVHs) were determined and categorized with respect to the date of implantation. Differences in symptom scores relative to pretherapeutic status were analyzed with regard to follow-up times and DVH descriptors. Acute and subacute toxicities in a control group of 117 patients from an earlier study (June 1999 to September 2001) by Wust et al. (2004) were compared with a matched subgroup from this study equaling 110 patients treated between October 2001 and August 2003. Results: Improved performance, identifying a characteristic time dependency of DVH parameters (after implantation) and toxicity scores, was demonstrated. Although coverage (volume covered by 100% of the prescription dose of the prostate) increased slightly, high-dose regions decreased with the growing experience of the users. Improvement in the DVH and a reduction of toxicities were found in the patient group implanted in the later period. A decline in symptoms with follow-up time counteracts this gain of experience and must be considered. Urinary and sexual discomfort was enhanced by dose heterogeneities (e.g., dose covering 10% of the prostate volume, volume covered by 200% of prescription dose). In contrast, rectal toxicities correlated with exposed rectal volumes, especially the rectal volume covered by 100% of the prescription dose. Conclusion: The typical side effects occurring after permanent seed implantation can be reduced by improving the dose distributions. An improvement in dose distributions and a reduction of toxicities were identified with elapsed time between

Surface-reconstructed Cu Electrode via a Facile Electrochemical Anodization-Reduction Process for Low Overpotential CO 2 reduction

KAUST Repository

Min, Shixiong

2017-03-21

A high-surface-area Cu electrode, fabricated by a simple electrochemical anodization-reduction method, exhibits high activity and selectivity for CO2 reduction at low overpotential in 0.1 M KHCO3 solution. A faradaic efficiency of 37% for HCOOH and 27% for CO production was achieved with the current density of 1.5 mA cm-2 at −0.64 V vs. RHE, much higher than that of polycrystalline Cu. The enhanced catalytic performance is a result of the formation of the high electrochemical active surface area and high density of preferred low-index facets.

Surface dose characterisation of the Varian Ir-192 HDR conical surface applicator set with a vertically orientated source

Energy Technology Data Exchange (ETDEWEB)

Buchauer, Konrad; Henke, Guido; Schiefer, Hans; Plasswilm, Ludwig [Kantonsspital St. Gallen, Department of Radiation Oncology, St. Gallen (Switzerland)

2014-12-15

Conical surface applicators with an Ir-192 high-dose-rate brachytherapy source are a common modality for the treatment of non-melanomatous skin cancer with high tumour control rates. Surface dose characterisation of the Varian Varisource GammaMed+ IX afterloader vertical type surface applicators is performed two dimensionally using high-resolution film dosimetry. The focus of this study was to determine if Varian surface applicators with a vertical source suffer from the dose distribution irregularities reported for comparable applicators. Our goal was to evaluate if the irregularities found affected treatment and dose output verification procedures. Ionisation chamber-based verification of applicator output was established according to guidelines provided by the manufacturer. For additional measurement of surface dose Gafchromic EBT3 film dosimetry was used. The term ''therapeutic dose'' was defined as 85 % of the prescribed dose level. For the 10 different applicator inserts evaluated, cold spots were observed. Mean cold spot size was 2.0 mm x 3.6 mm (± 0.6 mm). The cold spots were dosimetrically well below 85 % of the prescribed dose. The cold spot was situated 2.2 mm (1.4-2.7 mm) unilaterally from the central axis and caused general asymmetry in the dose profiles intersecting the cold spot area. A source tilt of approximately 8 (± 1 ) was determined for the source used for irradiation. A central underdosed area exceeding 15 % of the prescribed dose has not been previously reported. Source tilt was observed and found to affect clinical use and possibly treatment outcome in applicators using a vertically arranged source. Surface applicators with a vertically orientated source were subject to dose irregularities that could impact on chamber-based applicator output verification procedures. We recommend film dosimetry-backed applicator commissioning to avoid systematic errors. (orig.) [German] Konische Oberflaechenapplikatoren sind ein

Determination of skin dose reduction by lead equivalent gloves

International Nuclear Information System (INIS)

Norriza Mohd Isa; Abd Aziz Mhd Ramli

2006-01-01

Radiation protective gloves are always used in medical facilities to protect radiation workers from unnecessary radiation exposure. A study on radiation protection gloves which are produced by local company had been performed by the Medical Physics Group, MINT. The gloves were made of lead equivalent material, as the attenuating element. The gloves were evaluated in term of the percentage of skin dose reduction by using a newly developed procedure and facilities in MINT. Attenuation measurements of the gloves had been carried out using direct beams and scattered radiations of different qualities. TLD rings were fitted on finger phantom; and water phantom were used in the measurement. The result were obtained and analysed based on data supplied by manufacturer. (Author)

Direct Monte Carlo dose calculation using polygon-surface computational human model

International Nuclear Information System (INIS)

Jeong, Jong Hwi; Kim, Chan Hyeong; Yeom, Yeon Su; Cho, Sungkoo; Chung, Min Suk; Cho, Kun-Woo

2011-01-01

In the present study, a voxel-type computational human model was converted to a polygon-surface model, after which it was imported directly to the Geant4 code without using a voxelization process, that is, without converting back to a voxel model. The original voxel model was also imported to the Geant4 code, in order to compare the calculated dose values and the computational speed. The average polygon size of the polygon-surface model was ∼0.5 cm 2 , whereas the voxel resolution of the voxel model was 1.981 × 1.981 × 2.0854 mm 3 . The results showed a good agreement between the calculated dose values of the two models. The polygon-surface model was, however, slower than the voxel model by a factor of 6–9 for the photon energies and irradiation geometries considered in the present study, which nonetheless is considered acceptable, considering that direct use of the polygon-surface model does not require a separate voxelization process. (author)

Radiation dose reduction in CT with adaptive statistical iterative reconstruction (ASIR) for patients with bronchial carcinoma and intrapulmonary metastases

International Nuclear Information System (INIS)

Schäfer, M.-L.; Lüdemann, L.; Böning, G.; Kahn, J.; Fuchs, S.; Hamm, B.; Streitparth, F.

2016-01-01

Aim: To compare the radiation dose and image quality of 64-row chest computed tomography (CT) in patients with bronchial carcinoma or intrapulmonary metastases using full-dose CT reconstructed with filtered back projection (FBP) at baseline and reduced dose with 40% adaptive statistical iterative reconstruction (ASIR) at follow-up. Materials and methods: The chest CT images of patients who underwent FBP and ASIR studies were reviewed. Dose–length products (DLP), effective dose, and size-specific dose estimates (SSDEs) were obtained. Image quality was analysed quantitatively by signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) measurement. In addition, image quality was assessed by two blinded radiologists evaluating images for noise, contrast, artefacts, visibility of small structures, and diagnostic acceptability using a five-point scale. Results: The ASIR studies showed 36% reduction in effective dose compared with the FBP studies. The qualitative and quantitative image quality was good to excellent in both protocols, without significant differences. There were also no significant differences for SNR except for the SNR of lung surrounding the tumour (FBP: 35±17, ASIR: 39±22). Discussion: A protocol with 40% ASIR can provide approximately 36% dose reduction in chest CT of patients with bronchial carcinoma or intrapulmonary metastases while maintaining excellent image quality. - Highlights: • adaptive statistical iterative reconstruction in chest computed tomography scans. • patients with bronchial carcinoma or intrapulmonary metastases. • ASIR studies showed 36% reduction in effective dose compared with the FBP studies. • the qualitative and quantitative image quality was good to excellent in both protocols.

The child fluoroscopic examination in the I.I.-DR. Reduction of radiation exposure dose

International Nuclear Information System (INIS)

Endo, Takayuki

2001-01-01

This examination for I.I.-DR conditions was done for the purpose of reducing radiation exposure dose in child gastrointestinal fluoroscopy. Fluoroscopic apparatus used was Toshiba MAX-1000A with imaging recorder DDX-1000A. Dose was measured with a thimble ionization chamber Radcal Corporation Model 9015. Examinations for conditions were performed with the standard dose determined, the digital value 300, giving the plateau contrast ratio of acryl plate/barium sulfate. Reduction to about 10% dose (57 μGy/min for pulse fluoroscopy and 6.8 μGy/film for filming) relative to the usual method (764 μGy/min and 36.0 μGy/film, respectively) was found attained with additional filter of Al 0.5 mm + Cu 0.2 mm and IRIS diameter 100 with acryl thickness of 10 cm. Actual images of 6 months old baby were presented. (K.H.)

An investigation of dose changes for therapeutic kilovoltage x-ray beams with underlying lead shielding

International Nuclear Information System (INIS)

Hill, Robin; Healy, Brendan; Holloway, Lois; Baldock, Clive

2007-01-01

Kilovoltage x-ray beams are used to treat cancer on or close to the skin surface. Many clinical cases use high atomic number materials as shielding to reduce dose to underlying healthy tissues. In this work, we have investigated the effect on both the surface dose and depth doses in a water phantom with lead shielding at depth in the phantom. The EGSnrc Monte Carlo code was used to simulate the water phantom and to calculate the surface doses and depth doses using primary x-ray beam spectra derived from an analytical model. The x-ray beams were in the energy range of 75-135 kVp with field sizes of 2, 5 and 8 cm diameter. The lead sheet was located beneath the water surface at depths ranging from 0.5-7.5 cm. The surface dose decreased as the lead was positioned closer to the water surface and as the field size was increased. The variation in surface dose as a function of x-ray beam energy was only small but the maximum reduction occurred for the 100 kVp x-ray beam. For the 8 cm diameter field with the lead at 1 cm depth and using the 100 kVp x-ray beam, the surface dose was reduced to 0.898 of the surface dose in the water phantom only. Measured surface dose changes, using a Farmer-type ionization chamber, agreed with the Monte Carlo calculated doses. Calculated depth doses in water with a lead sheet positioned below the surface showed that the dose fall-off increased as the lead was positioned closer to the water surface as compared to the depth dose in the water phantom only. Monte Carlo calculations of the total x-ray beam spectrum at the water surface showed that the total fluence decreased due to a reduction in backscatter from within the water and very little backscatter from the lead. The mean energy of the x-ray spectrum varied less than 1 keV, with the lead at 1 cm beneath the water phantom surface. As the Monte Carlo calculations showed good agreement with the measured results, this method can be used to verify surface dose changes in clinical situations

Drag reduction in reservoir rock surface: Hydrophobic modification by SiO{sub 2} nanofluids

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Yan, Yong-Li, E-mail: yylhill@163.com [College of Chemistry & Chemical Engineering, Xi’an Shiyou University, Xi’an 710065 (China); Cui, Ming-Yue; Jiang, Wei-Dong; He, An-Le; Liang, Chong [Langfang Branch of Research Institute of Petroleum Exploration & Development, Langfang 065007 (China)

2017-02-28

Graphical abstract: The micro-nanoscale hierarchical structures at the sandstone core surface are constructed by adsorption of the modified silica nanoparticles, which leads to the effect of drag reduction to improve the low injection rate in ultra-low permeability reservoirs. - Highlights: • A micro-nanoscale hierarchical structure is formed at the reservoir rock surface. • An inversion has happened from hydrophilic into hydrophobic modified by nanofluids. • The effect of drag reduction to improve the low injection rate is realized. • The mechanism of drag reduction induced from the modified core surface was unclosed. - Abstract: Based on the adsorption behavior of modified silica nanoparticles in the sandstone core surface, the hydrophobic surface was constructed, which consists of micro-nanoscale hierarchical structure. This modified core surface presents a property of drag reduction and meets the challenge of high injection pressure and low injection rate in low or ultra-low permeability reservoir. The modification effects on the surface of silica nanoparticles and reservoir cores, mainly concerning hydrophobicity and fine structure, were determined by measurements of contact angle and scanning electron microscopy. Experimental results indicate that after successful modification, the contact angle of silica nanoparticles varies from 19.5° to 141.7°, exhibiting remarkable hydrophobic properties. These modified hydrophobic silica nanoparticles display a good adsorption behavior at the core surface to form micro-nanobinary structure. As for the wettability of these modified core surfaces, a reversal has happened from hydrophilic into hydrophobic and its contact angle increases from 59.1° to 105.9°. The core displacement experiments show that the relative permeability for water has significantly increased by an average of 40.3% via core surface modification, with the effects of reducing injection pressure and improving injection performance of water

MLSOIL and DFSOIL - computer codes to estimate effective ground surface concentrations for dose computations

International Nuclear Information System (INIS)

Sjoreen, A.L.; Kocher, D.C.; Killough, G.G.; Miller, C.W.

1984-11-01

This report is a user's manual for MLSOIL (Multiple Layer SOIL model) and DFSOIL (Dose Factors for MLSOIL) and a documentation of the computational methods used in those two computer codes. MLSOIL calculates an effective ground surface concentration to be used in computations of external doses. This effective ground surface concentration is equal to (the computed dose in air from the concentration in the soil layers)/(the dose factor for computing dose in air from a plane). MLSOIL implements a five compartment linear-transfer model to calculate the concentrations of radionuclides in the soil following deposition on the ground surface from the atmosphere. The model considers leaching through the soil as well as radioactive decay and buildup. The element-specific transfer coefficients used in this model are a function of the k/sub d/ and environmental parameters. DFSOIL calculates the dose in air per unit concentration at 1 m above the ground from each of the five soil layers used in MLSOIL and the dose per unit concentration from an infinite plane source. MLSOIL and DFSOIL have been written to be part of the Computerized Radiological Risk Investigation System (CRRIS) which is designed for assessments of the health effects of airborne releases of radionuclides. 31 references, 3 figures, 4 tables

Can radiation therapy treatment planning system accurately predict surface doses in postmastectomy radiation therapy patients?

International Nuclear Information System (INIS)

Wong, Sharon; Back, Michael; Tan, Poh Wee; Lee, Khai Mun; Baggarley, Shaun; Lu, Jaide Jay

2012-01-01

Skin doses have been an important factor in the dose prescription for breast radiotherapy. Recent advances in radiotherapy treatment techniques, such as intensity-modulated radiation therapy (IMRT) and new treatment schemes such as hypofractionated breast therapy have made the precise determination of the surface dose necessary. Detailed information of the dose at various depths of the skin is also critical in designing new treatment strategies. The purpose of this work was to assess the accuracy of surface dose calculation by a clinically used treatment planning system and those measured by thermoluminescence dosimeters (TLDs) in a customized chest wall phantom. This study involved the construction of a chest wall phantom for skin dose assessment. Seven TLDs were distributed throughout each right chest wall phantom to give adequate representation of measured radiation doses. Point doses from the CMS Xio® treatment planning system (TPS) were calculated for each relevant TLD positions and results correlated. There were no significant difference between measured absorbed dose by TLD and calculated doses by the TPS (p > 0.05 (1-tailed). Dose accuracy of up to 2.21% was found. The deviations from the calculated absorbed doses were overall larger (3.4%) when wedges and bolus were used. 3D radiotherapy TPS is a useful and accurate tool to assess the accuracy of surface dose. Our studies have shown that radiation treatment accuracy expressed as a comparison between calculated doses (by TPS) and measured doses (by TLD dosimetry) can be accurately predicted for tangential treatment of the chest wall after mastectomy.

Effects of a radiation dose reduction strategy for computed tomography in severely injured trauma patients in the emergency department: an observational study

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Kim Soo Hyun

2011-11-01

Full Text Available Abstract Background Severely injured trauma patients are exposed to clinically significant radiation doses from computed tomography (CT imaging in the emergency department. Moreover, this radiation exposure is associated with an increased risk of cancer. The purpose of this study was to determine some effects of a radiation dose reduction strategy for CT in severely injured trauma patients in the emergency department. Methods We implemented the radiation dose reduction strategy in May 2009. A prospective observational study design was used to collect data from patients who met the inclusion criteria during this one year study (intervention group from May 2009 to April 2010. The prospective data were compared with data collected retrospectively for one year prior to the implementation of the radiation dose reduction strategy (control group. By comparison of the cumulative effective dose and the number of CT examinations in the two groups, we evaluated effects of a radiation dose reduction strategy. All the patients met the institutional adult trauma team activation criteria. The radiation doses calculated by the CT scanner were converted to effective doses by multiplication by a conversion coefficient. Results A total of 118 patients were included in this study. Among them, 33 were admitted before May 2009 (control group, and 85 were admitted after May 2009 (intervention group. There were no significant differences between the two groups regarding baseline characteristics, such as injury severity and mortality. Additionally, there was no difference between the two groups in the mean number of total CT examinations per patient (4.8 vs. 4.5, respectively; p = 0.227. However, the mean effective dose of the total CT examinations per patient significantly decreased from 78.71 mSv to 29.50 mSv (p Conclusions The radiation dose reduction strategy for CT in severely injured trauma patients effectively decreased the cumulative effective dose of the total

Infliximab Dose Reduction Sustains the Clinical Treatment Effect in Active HLAB27 Positive Ankylosing Spondylitis: A Two-Year Pilot Study

Directory of Open Access Journals (Sweden)

Boel Mörck

2013-01-01

Full Text Available The rationale of the study was to evaluate the efficacy of infliximab (IFX treatment in patients with ankylosing spondylitis (AS and to determine whether IFX dose reduction and interval extension sustains the treatment effect. Nineteen patients were included and treated with IFX 5 mg/kg every 6 weeks for 56 weeks. All patients concomitantly received MTX with median dose 7.5 mg/weekly. During the second year, the IFX dose was reduced to 3 mg/kg every 8 weeks. Eighteen patients completed the 1-year and 15 patients the 2-year trial. The ≥50% improvement at week 16 from baseline of BASDAI was achieved in 16/19 (84% patients. Significant reductions in BASDAI, BASFI, and BASMI scores, decrease in ESR and CRP, and improvement in SF-36 were observed at weeks 16 and 56. The MRI-defined inflammatory changes in the sacroiliac joints disappeared in 10/15 patients (67% already at 16 weeks. IFX treatment effect was sustained throughout the second year after IFX dose reduction and interval extension. We conclude that IFX treatment is effective in well-established active AS and a dose reduction sustains the treatment effect. These observations are of clinical importance and open the opportunity to reduce the drug costs. This trial is registered with ClinicalTrials.gov NCT01850121.

Cardiovascular CT angiography in neonates and children: Image quality and potential for radiation dose reduction with iterative image reconstruction techniques

International Nuclear Information System (INIS)

Tricarico, Francesco; Hlavacek, Anthony M.; Schoepf, U.J.; Ebersberger, Ullrich; Nance, John W.; Vliegenthart, Rozemarijn; Cho, Young Jun; Spears, J.R.; Secchi, Francesco; Savino, Giancarlo; Marano, Riccardo; Bonomo, Lorenzo; Schoenberg, Stefan O.; Apfaltrer, Paul

2013-01-01

To evaluate image quality (IQ) of low-radiation-dose paediatric cardiovascular CT angiography (CTA), comparing iterative reconstruction in image space (IRIS) and sinogram-affirmed iterative reconstruction (SAFIRE) with filtered back-projection (FBP) and estimate the potential for further dose reductions. Forty neonates and children underwent low radiation CTA with or without ECG synchronisation. Data were reconstructed with FBP, IRIS and SAFIRE. For ECG-synchronised studies, half-dose image acquisitions were simulated. Signal noise was measured and IQ graded. Effective dose (ED) was estimated. Mean absolute and relative image noise with IRIS and full-dose SAFIRE was lower than with FBP (P < 0.001), while SNR and CNR were higher (P < 0.001). Image noise was also lower and SNR and CNR higher in half-dose SAFIRE studies compared with full-and half-dose FBP studies (P < 0.001). IQ scores were higher for IRIS, full-dose SAFIRE and half-dose SAFIRE than for full-dose FBP and higher for half-dose SAFIRE than for half-dose FBP (P < 0.05). Median weight-specific ED was 0.3 mSv without and 1.36 mSv with ECG synchronisation. The estimated ED of half-dose SAFIRE studies was 0.68 mSv. IR improves image noise, SNR, CNR and subjective IQ compared with FBP in low-radiation-dose paediatric CTA and allows further dose reductions without compromising diagnostic IQ. (orig.)

Cardiovascular CT angiography in neonates and children: Image quality and potential for radiation dose reduction with iterative image reconstruction techniques

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Tricarico, Francesco [Medical University of South Carolina, Ashley River Tower, Department of Radiology and Radiological Science, Charleston, SC (United States); Catholic University of the Sacred Heart, ' ' A. Gemelli' ' Hospital, Department of Bioimaging and Radiological Sciences, Rome (Italy); Hlavacek, Anthony M. [Medical University of South Carolina, Ashley River Tower, Department of Radiology and Radiological Science, Charleston, SC (United States); Children' s Hospital, Medical University of South Carolina, Division of Pediatric Cardiology, Charleston, SC (United States); Schoepf, U.J. [Medical University of South Carolina, Ashley River Tower, Department of Radiology and Radiological Science, Charleston, SC (United States); Children' s Hospital, Medical University of South Carolina, Division of Pediatric Cardiology, Charleston, SC (United States); Medical University of South Carolina, Division of Cardiology, Department of Medicine, Charleston, SC (United States); Ebersberger, Ullrich [Medical University of South Carolina, Ashley River Tower, Department of Radiology and Radiological Science, Charleston, SC (United States); Heart Centre Munich-Bogenhausen, Department of Cardiology and Intensive Care Medicine, Munich (Germany); Nance, John W. [Medical University of South Carolina, Ashley River Tower, Department of Radiology and Radiological Science, Charleston, SC (United States); Johns Hopkins Hospital, The Russell H. Morgan Department of Radiology and Radiological Science, Baltimore, MD (United States); Vliegenthart, Rozemarijn [Medical University of South Carolina, Ashley River Tower, Department of Radiology and Radiological Science, Charleston, SC (United States); University Medical Centre Groningen/University of Groningen, Centre for Medical Imaging - North East Netherlands, Department of Radiology, Groningen (Netherlands); Cho, Young Jun [Medical University of South Carolina, Ashley River Tower, Department of Radiology and Radiological Science, Charleston, SC (United States); Konyang University School of Medicine, Department of Radiology, Daejeon (Korea, Republic of); Spears, J.R. [Medical University of South Carolina, Ashley River Tower, Department of Radiology and Radiological Science, Charleston, SC (United States); Secchi, Francesco [Medical University of South Carolina, Ashley River Tower, Department of Radiology and Radiological Science, Charleston, SC (United States); University of Milan School of Medicine IRCCS Policlinico San Donato, Department of Medical and Surgical Sciences, Radiology Unit, Milan (Italy); Savino, Giancarlo; Marano, Riccardo; Bonomo, Lorenzo [Catholic University of the Sacred Heart, ' ' A. Gemelli' ' Hospital, Department of Bioimaging and Radiological Sciences, Rome (Italy); Schoenberg, Stefan O. [University Medical Centre Mannheim, Medical Faculty Mannheim - Heidelberg University, Institute of Clinical Radiology and Nuclear Medicine, Mannheim (Germany); Apfaltrer, Paul [Medical University of South Carolina, Ashley River Tower, Department of Radiology and Radiological Science, Charleston, SC (United States); University Medical Centre Mannheim, Medical Faculty Mannheim - Heidelberg University, Institute of Clinical Radiology and Nuclear Medicine, Mannheim (Germany)

2013-05-15

To evaluate image quality (IQ) of low-radiation-dose paediatric cardiovascular CT angiography (CTA), comparing iterative reconstruction in image space (IRIS) and sinogram-affirmed iterative reconstruction (SAFIRE) with filtered back-projection (FBP) and estimate the potential for further dose reductions. Forty neonates and children underwent low radiation CTA with or without ECG synchronisation. Data were reconstructed with FBP, IRIS and SAFIRE. For ECG-synchronised studies, half-dose image acquisitions were simulated. Signal noise was measured and IQ graded. Effective dose (ED) was estimated. Mean absolute and relative image noise with IRIS and full-dose SAFIRE was lower than with FBP (P < 0.001), while SNR and CNR were higher (P < 0.001). Image noise was also lower and SNR and CNR higher in half-dose SAFIRE studies compared with full-and half-dose FBP studies (P < 0.001). IQ scores were higher for IRIS, full-dose SAFIRE and half-dose SAFIRE than for full-dose FBP and higher for half-dose SAFIRE than for half-dose FBP (P < 0.05). Median weight-specific ED was 0.3 mSv without and 1.36 mSv with ECG synchronisation. The estimated ED of half-dose SAFIRE studies was 0.68 mSv. IR improves image noise, SNR, CNR and subjective IQ compared with FBP in low-radiation-dose paediatric CTA and allows further dose reductions without compromising diagnostic IQ. (orig.)

Pelvic X-ray examinations in follow-up of hip arthroplasty or femoral osteosynthesis – Dose reduction and quality criteria

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Kloth, Jost Karsten, E-mail: jost.kloth@med.uni-heidelberg.de [Diagnostic and Interventional Radiology, University Hospital Heidelberg, Im Neuenheimer Feld 110, D-69120 Heidelberg (Germany); Rickert, Markus, E-mail: markus.rickert@ortho.med.uni-giessen.de [Department of Orthopaedics and Orthopaedic Surgery, University Hospital Giessen and Marburg, Klinikstrasse 33, D-35392 Giessen (Germany); Gotterbarm, Tobias, E-mail: tobias.gotterbarm@med.uni-heidelberg.de [Orthopedic and Trauma Surgery, University Hospital Heidelberg, Schlierbacher Landstraße 200a, D-69118 Heidelberg (Germany); Stiller, Wolfram, E-mail: wolfram.stiller@med.uni-heidelberg.de [Diagnostic and Interventional Radiology, University Hospital Heidelberg, Im Neuenheimer Feld 110, D-69120 Heidelberg (Germany); Burkholder, Iris, E-mail: stabil@burkholder.de [Department of Nursing and Health, University of Applied Sciences of the Saarland, Goebenstrasse 40, D-66117 Saarbruecken (Germany); Kauczor, Hans-Ulrich, E-mail: hans-ulrich.kauczor@med.uni-heidelberg.de [Diagnostic and Interventional Radiology, University Hospital Heidelberg, Im Neuenheimer Feld 110, D-69120 Heidelberg (Germany); Ewerbeck, Volker, E-mail: volker.ewerbeck@med.uni-heidelberg.de [Orthopedic and Trauma Surgery, University Hospital Heidelberg, Schlierbacher Landstraße 200a, D-69118 Heidelberg (Germany); Weber, Marc-André, E-mail: marcandre.weber@med.uni-heidelberg.de [Diagnostic and Interventional Radiology, University Hospital Heidelberg, Im Neuenheimer Feld 110, D-69120 Heidelberg (Germany)

2015-05-15

Highlights: • Pelvic radiographs with speed class 400 and 800 in follow-up of hip arthroplasty were compared. • Radiographs with reduced dose (800) were not inferior to those with standard dose (400). • We recommend speed class 800 as new reference parameter in these examinations. - Abstract: Objective: Digital plain radiographs of the pelvis are frequently performed in follow-up examinations of patients who received total hip arthroplasty (THA) or osteosynthesis (OS). Thus, the purpose was to reduce the radiation dose and to determine objective quality control criteria to ensure accurate assessment. Materials and methods: Institutional review board approval was obtained. In this prospective randomized study, 289 patients underwent X-ray examination of the pelvis as follow up after receiving THA or OS with standard and reduced dose. The evaluation of the plain radiographs was conducted using the following criteria: bone–implant interface, implant–implant discrimination, implant–surface character and periarticular heterotopic ossification. Two radiologists evaluated these criteria using a score ranging from 1 (definitely assessable) to 4 (not assessable). If a single criterion had been evaluated with a score of 3 or more or more than 2 criteria with 2 points, the radiograph was scored as “not assessable“. The study was designed as non-inferiority-trial. Results: Seven (2.4%) examined X-rays were scored as not assessable. There was no statistical inferiority between the examinations with standard (0.365 mSv) or reduced dose (0.211 mSv). Reduced dose only led to limitations in the evaluation of ceramic components with low clinical impact in most scenarios. Conclusion: Plain radiography of the pelvis in patients with THA or OS can be performed with a dose reduction of about 42% without a loss of important information. The obtained quality control criteria were clinically applicable.

Calculated dose factors for the radiosensitive tissues in bone irradiated by surface-deposited radionuclides

International Nuclear Information System (INIS)

Spiers, F.W.; Whitwell, J.R.; Beddoe, A.H.

1978-01-01

The method of calculating dose factors for the haemopoietic marrow and endosteal tissues in human trabecular bone, used by Whitwell and Spiers for volume-seeking radionuclides, has been developed for the case of radionuclides which are deposited as very thin layers on bone surfaces. The Monte Carlo method is again used, but modifications to the computer program are made to allow for a surface rather than a volume source of particle emission. The principal change is the introduction of a surface-orientation factor which is shown to have a value of approximately 2, varying slightly with bone structure. Results are given for β-emitting radionuclides ranging from 171 Tm(anti Esub(β) = 0.025 MeV) to 90 Y(anti Esub(β) = 0.93 MeV), and also for the α-emitter 239 Pu. It is shown that where the particle ranges are short compared with the dimensions of the bone structures the dose factors for the surface seekers are much greater than those for the volume seekers. For long range particles the dose factors for surface- and volume-seeking radionuclides converge. Comparisons are given relating the dose factors calculated in this paper on the basis of measured bone structures to those of other workers based on single plane geometry. (author)

Analysis of surface and build up region dose for motorized wedge and omni wedge

International Nuclear Information System (INIS)

Panta, Raj Kumar; Sundarum, T.

2008-01-01

Megavoltage x-ray beam exhibits the well known phenomenon of dose build-up within the first few millimeters of incident phantom surface or skin. The skin sparing effect of high energy gamma or x-ray photon may be reduced or even lost, if the beam is contaminated with electron or low energy photons. Since skin dose in the treatment of deeply seated tumor may be a limiting factor in the delivery of tumoricidal dose due to possible complications such as erythema, desquamation, fibrosis, necrosis and epilation, the dose distribution in the build up region should be known. The objective of this study was to measure and investigate the surface and build-up region dose for 6 MV and 15 MV photon beam for Motorized wedge and Omni wedge in Precise Digital Linear Accelerator (Elekta)

Influence of bismuth shielding use in the dose CT and the imaging quality in standard brain protocol

International Nuclear Information System (INIS)

Sanchez Carnoma, G.; Urena Llinares, A.; Santos Rubio, A.; Haro Madero, G.; Herrador Cordoba, M.

2006-01-01

The purpose of this work is to evaluate the reduction of lens doses, CT dose index (CTDI) and image quality when bismuth shielding is used. Dose indexes nCDTIs,p, w were measured for a head phantom (d=16 cm) in three situations: first, without shielding, second, shielded with bismuth over the phantom surface and, last, with 2 cm between both. Four regions of interest were selected, two including the theoretical eyes position and the others 4-6 cm below them. Noise and grey level in Housfield units were also measured in all geometries. A bismuth shielding in contact or 2 cm above surface provides a dose reduction of 36% y 29% respectively. In the first case an importation of image quality appears, increasing a 55% the Housfield units in the superficial regions of interest and a growth of noise 6 times greater. Bismuth protection provides an important reduction in lens dose., in the case of dire ct incidence radiation beam. (Author)

Radiation dose reduction in medical x-ray CT via Fourier-based iterative reconstruction.

Science.gov (United States)

Fahimian, Benjamin P; Zhao, Yunzhe; Huang, Zhifeng; Fung, Russell; Mao, Yu; Zhu, Chun; Khatonabadi, Maryam; DeMarco, John J; Osher, Stanley J; McNitt-Gray, Michael F; Miao, Jianwei

2013-03-01

A Fourier-based iterative reconstruction technique, termed Equally Sloped Tomography (EST), is developed in conjunction with advanced mathematical regularization to investigate radiation dose reduction in x-ray CT. The method is experimentally implemented on fan-beam CT and evaluated as a function of imaging dose on a series of image quality phantoms and anonymous pediatric patient data sets. Numerical simulation experiments are also performed to explore the extension of EST to helical cone-beam geometry. EST is a Fourier based iterative algorithm, which iterates back and forth between real and Fourier space utilizing the algebraically exact pseudopolar fast Fourier transform (PPFFT). In each iteration, physical constraints and mathematical regularization are applied in real space, while the measured data are enforced in Fourier space. The algorithm is automatically terminated when a proposed termination criterion is met. Experimentally, fan-beam projections were acquired by the Siemens z-flying focal spot technology, and subsequently interleaved and rebinned to a pseudopolar grid. Image quality phantoms were scanned at systematically varied mAs settings, reconstructed by EST and conventional reconstruction methods such as filtered back projection (FBP), and quantified using metrics including resolution, signal-to-noise ratios (SNRs), and contrast-to-noise ratios (CNRs). Pediatric data sets were reconstructed at their original acquisition settings and additionally simulated to lower dose settings for comparison and evaluation of the potential for radiation dose reduction. Numerical experiments were conducted to quantify EST and other iterative methods in terms of image quality and computation time. The extension of EST to helical cone-beam CT was implemented by using the advanced single-slice rebinning (ASSR) method. Based on the phantom and pediatric patient fan-beam CT data, it is demonstrated that EST reconstructions with the lowest scanner flux setting of 39 m

Radiation dose reduction in medical x-ray CT via Fourier-based iterative reconstruction

International Nuclear Information System (INIS)

Fahimian, Benjamin P.; Zhao Yunzhe; Huang Zhifeng; Fung, Russell; Zhu Chun; Miao Jianwei; Mao Yu; Khatonabadi, Maryam; DeMarco, John J.; McNitt-Gray, Michael F.; Osher, Stanley J.

2013-01-01

Purpose: A Fourier-based iterative reconstruction technique, termed Equally Sloped Tomography (EST), is developed in conjunction with advanced mathematical regularization to investigate radiation dose reduction in x-ray CT. The method is experimentally implemented on fan-beam CT and evaluated as a function of imaging dose on a series of image quality phantoms and anonymous pediatric patient data sets. Numerical simulation experiments are also performed to explore the extension of EST to helical cone-beam geometry. Methods: EST is a Fourier based iterative algorithm, which iterates back and forth between real and Fourier space utilizing the algebraically exact pseudopolar fast Fourier transform (PPFFT). In each iteration, physical constraints and mathematical regularization are applied in real space, while the measured data are enforced in Fourier space. The algorithm is automatically terminated when a proposed termination criterion is met. Experimentally, fan-beam projections were acquired by the Siemens z-flying focal spot technology, and subsequently interleaved and rebinned to a pseudopolar grid. Image quality phantoms were scanned at systematically varied mAs settings, reconstructed by EST and conventional reconstruction methods such as filtered back projection (FBP), and quantified using metrics including resolution, signal-to-noise ratios (SNRs), and contrast-to-noise ratios (CNRs). Pediatric data sets were reconstructed at their original acquisition settings and additionally simulated to lower dose settings for comparison and evaluation of the potential for radiation dose reduction. Numerical experiments were conducted to quantify EST and other iterative methods in terms of image quality and computation time. The extension of EST to helical cone-beam CT was implemented by using the advanced single-slice rebinning (ASSR) method. Results: Based on the phantom and pediatric patient fan-beam CT data, it is demonstrated that EST reconstructions with the lowest

The effect of 18F-florbetapir dose reduction on region-based classification of cortical amyloid deposition

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Herholz, K.; Evans, R.; Anton-Rodriguez, J.; Hinz, R.; Matthews, J.C. [University of Manchester, Wolfson Molecular Imaging Centre and Manchester Academic Health Science Centre, Manchester, England (United Kingdom)

2014-11-15

There are specific dose recommendations for diagnostic amyloid PET imaging with 18F-florbetapir, but they may not apply to research studies using regional quantitative analysis. We, therefore, studied the effect of tracer dose reduction on the discriminative power of regional analysis. Using bootstrap resampling of list-mode data from 18F-florbetapir scans, a total of 800 images were reconstructed for four different dosage levels: 100, 50, 20, and 10 %. The effect of the injected dose on the variation of measured radiotracer uptake was determined in large cortical regions defined on co-registered and segmented magnetic resonance images. The impact of the observed variation on the discrimination between normal controls and patients with AD was then assessed using data in a cohort study described by Fleisher et al. (Arch Neurol 68(11):1404-1411, 2011). The coefficient of variance for the cortex to cerebellum uptake ratio increased from 0.9 % at full dose of 300 MBq to 2.5 % at 10 % of this dose, but was still small compared to biological variation. It, therefore, had very little impact on discrimination between AD and elderly controls. The original area under the ROC curve was 0.881, decreasing to 0.878 at 10 % of full dose. Original sensitivity for discrimination between AD and controls was 82.0 %, while specificity was 77.3 %; these decreased to 81.8 and 77.1 %, respectively, at the reduced dose. However, the number of subjects within the classification border zone between proven amyloid pathology and young healthy controls increased substantially by 7 to 14 %. A substantial reduction of tracer dose increases uncertainty at the classification border zone while still providing good discrimination between AD patients and controls when using activity data from cortical regions defined on co-registered and segmented MR scans. (orig.)

Radiation dose reduction at a price: the effectiveness of a male gonadal shield during helical CT scans

International Nuclear Information System (INIS)

Dauer, Lawrence T; Casciotta, Kevin A; Erdi, Yusuf E; Rothenberg, Lawrence N

2007-01-01

It is estimated that 60 million computed tomography (CT) scans were performed during 2006, with approximately 11% of those performed on children age 0–15 years. Various types of gonadal shielding have been evaluated for reducing exposure to the gonads. The purpose of this study was to quantify the radiation dose reduction to the gonads and its effect on image quality when a wrap-around male pediatric gonad shield was used during CT scanning. This information is obtained to assist the attending radiologist in the decision to utilize such male gonadal shields in pediatric imaging practice. The dose reduction to the gonads was measured for both direct radiation and for indirect scattered radiation from the abdomen. A 6 cm 3 ion chamber (Model 10X5-6, Radcal Corporation, Monrovia, CA) was placed on a Humanoid real bone pelvic phantom at a position of the male gonads. When exposure measurements with shielding were made, a 1 mm lead wrap-around gonadal shield was placed around the ion chamber sensitive volume. The use of the shields reduced scatter dose to the gonads by a factor of about 2 with no appreciable loss of image quality. The shields reduced the direct beam dose by a factor of about 35 at the expense of extremely poor CT image quality due to severe streak artifacts. Images in the direct exposure case are not useful due to these severe artifacts and the difficulties in positioning these shields on patients in the scatter exposure case may not be warranted by the small absolute reduction in scatter dose unless it is expected that the patient will be subjected to numerous future CT scans

Radiation dose reduction at a price: the effectiveness of a male gonadal shield during helical CT scans.

Science.gov (United States)

Dauer, Lawrence T; Casciotta, Kevin A; Erdi, Yusuf E; Rothenberg, Lawrence N

2007-03-16

It is estimated that 60 million computed tomography (CT) scans were performed during 2006, with approximately 11% of those performed on children age 0-15 years. Various types of gonadal shielding have been evaluated for reducing exposure to the gonads. The purpose of this study was to quantify the radiation dose reduction to the gonads and its effect on image quality when a wrap-around male pediatric gonad shield was used during CT scanning. This information is obtained to assist the attending radiologist in the decision to utilize such male gonadal shields in pediatric imaging practice. The dose reduction to the gonads was measured for both direct radiation and for indirect scattered radiation from the abdomen. A 6 cm3 ion chamber (Model 10X5-6, Radcal Corporation, Monrovia, CA) was placed on a Humanoid real bone pelvic phantom at a position of the male gonads. When exposure measurements with shielding were made, a 1 mm lead wrap-around gonadal shield was placed around the ion chamber sensitive volume. The use of the shields reduced scatter dose to the gonads by a factor of about 2 with no appreciable loss of image quality. The shields reduced the direct beam dose by a factor of about 35 at the expense of extremely poor CT image quality due to severe streak artifacts. Images in the direct exposure case are not useful due to these severe artifacts and the difficulties in positioning these shields on patients in the scatter exposure case may not be warranted by the small absolute reduction in scatter dose unless it is expected that the patient will be subjected to numerous future CT scans.

Editor's choice--Use of disposable radiation-absorbing surgical drapes results in significant dose reduction during EVAR procedures.

Science.gov (United States)

Kloeze, C; Klompenhouwer, E G; Brands, P J M; van Sambeek, M R H M; Cuypers, P W M; Teijink, J A W

2014-03-01

Because of the increasing number of interventional endovascular procedures with fluoroscopy and the corresponding high annual dose for interventionalists, additional dose-protecting measures are desirable. The purpose of this study was to evaluate the effect of disposable radiation-absorbing surgical drapes in reducing scatter radiation exposure for interventionalists and supporting staff during an endovascular aneurysm repair (EVAR) procedure. This was a randomized control trial in which 36 EVAR procedures were randomized between execution with and without disposable radiation-absorbing surgical drapes (Radpad: Worldwide Innovations & Technologies, Inc., Kansas City, US, type 5511A). Dosimetric measurements were performed on the interventionalist (hand and chest) and theatre nurse (chest) with and without the use of the drapes to obtain the dose reduction and effect on the annual dose caused by the drapes. Use of disposable radiation-absorbing surgical drapes resulted in dose reductions of 49%, 55%, and 48%, respectively, measured on the hand and chest of the interventionalist and the chest of the theatre nurse. The use of disposable radiation-absorbing surgical drapes significantly reduces scatter radiation exposure for both the interventionalist and the supporting staff during EVAR procedures. Copyright © 2013 European Society for Vascular Surgery. Published by Elsevier Ltd. All rights reserved.

Dose reduction in diagnostic radiology. Proceedings of the Hospital Physicists' Association meeting on 8th December 1983 at Birbeck College, London

International Nuclear Information System (INIS)

Brennen, S.E.; Putney, R.G.

1984-01-01

Nine chapters review the Proceedings of the Hospital Physicists' Association Meeting held in London in 1983 on 'Dose Reduction in Diagnostic Radiology'. Among the topics discussed were the balance between dose reduction and image quality, various procedures and techniques for keeping the dose to the patient to a minimum including the use of K-edge filtration and rare-earth intensifying screens, equipment for assessing the area exposure product in patients and the balance between radiation risk and benefit from radiographic examinations. All nine chapters are indexed separately. (U.K.)

FSD for operating NPPs as part of sustainable dose reduction - recontamination evaluation for the German PWR Grafenrheinfeld

International Nuclear Information System (INIS)

Stellwag, Bernhard; Hoffmann-Wankerl, Stephan; Schuetz, Sigrid; Jacob, Astrid

2012-09-01

Full-system decontamination (FSD) or replacement of steam generators (SG) and other large components in mature PWR plants results in large bare metal surfaces in the reactor system. The AREVA chemistry concept for sustainable dose rate reduction at such plants includes a passivation treatment for formation of high-quality oxide films in the reactor system and high pH operation in combination with zinc injection during subsequent power operation. The effectiveness of these measures has been proven by plant operation experience. The systematic evaluation of plant-specific experience is used for further optimization of the concept. These measures were also applied at the 1350 MW-class 4-loop PWR Grafenrheinfeld after an FSD with the AREVA decontamination process HP/CORD R UV in 28 th outage. The passivation treatment consisted of zinc injection during plant heat-up and parallel adjustment of a high pH value. It was carried out in the plant operation condition 'subcritical hot' for 200 hours and a pH (300 deg. C) of 7.1. During the cycle, the pH value was increased to 7.4 and zinc injection was continued. This paper evaluates the recontamination of the plant inclusive the first refueling outage since the FSD. The evaluation is based on routine chemistry and dose rate surveillance data and on the results of special measurement programs conducted at the plant before and after the FSD. Results of surface gamma activity measurements and fuel crud analyses are also described. Data is evaluated with regard to release, transport and deposition of corrosion products and nuclides in the reactor system. The plant-specific contamination sources and their pathways are outlined. Compared to the first refueling outage of the plant in 1983, the dose rate level at the main loops could be more than halved in spite of already activated core internals and crud on fuel assemblies, the in-core instrumentation and the control rods including guide assemblies and drive rods. The FSD

Dose Prediction for surface nuclear explosions: case studies for Semipalatinsk and Lop Nur tests

International Nuclear Information System (INIS)

Takada, Jun

2008-01-01

Dose prediction method RAPS after surface nuclear explosion has been developed by using the empirical dose function of USA nuclear test. This method which provides us external total dose, dose rate at any distant, at any time for any yield of nuclear explosion, is useful for radiation protection in case of nuclear events such as terrorism and nuclear war. The validity of RAPS has been confirmed by application to historical surface nuclear test explosions. The first test case study which was done for the first test explosion of the former USSR at the Semipalatinsk Nuclear Test Site on August 29th 1949, shows a good agreement with luminescence dosimetry on a brick. This dose prediction method was applied nuclear tests in Lop Nur. The results indicate dangerous nuclear radiation influences including fatal risk in the wide Uygur area. (author)

Simulated dose reduction by adding artificial noise to measured raw data: A validation study

International Nuclear Information System (INIS)

Soederberg, M.; Gunnarsson, M.; Nilsson, M.

2010-01-01

The purpose of this study was to verify and validate a noise simulation tool called Dose Tutor (VAMP GmbH) in terms of level and texture of the simulated noise. By adding artificial noise to measured computed tomography (CT) raw data, a scan acquired with a lower dose (mAs) than the actual one can be simulated. A homogeneous polyethylene phantom and an anthropomorphic chest phantom were scanned for different mAs levels, tube voltages, slice thicknesses and reconstruction kernels. The simulated noise levels were compared with the noise levels in real transverse slice images actually acquired with corresponding mAs values. In general, the noise comparisons showed acceptable agreement in magnitude (<20% deviation in pixel standard deviation). Also, the calculated noise power spectra were similar, which indicates that the noise texture is correctly reproduced. In conclusion, this study establishes that the Dose Tutor might be a useful tool for estimating the dose reduction potential for CT protocols. (authors)

SU-D-209-03: Radiation Dose Reduction Using Real-Time Image Processing in Interventional Radiology

Energy Technology Data Exchange (ETDEWEB)

Kanal, K; Moirano, J; Zamora, D; Stewart, B [University Washington, Seattle, WA (United States)

2016-06-15

Purpose: To characterize changes in radiation dose after introducing a new real-time image processing technology in interventional radiology systems. Methods: Interventional radiology (IR) procedures are increasingly complex, at times requiring substantial time and radiation dose. The risk of inducing tissue reactions as well as long-term stochastic effects such as radiation-induced cancer is not trivial. To reduce this risk, IR systems are increasingly equipped with dose reduction technologies.Recently, ClarityIQ (Philips Healthcare) technology was installed in our existing neuroradiology IR (NIR) and vascular IR (VIR) suites respectively. ClarityIQ includes real-time image processing that reduces noise/artifacts, enhances images, and sharpens edges while also reducing radiation dose rates. We reviewed 412 NIR (175 pre- and 237 post-ClarityIQ) procedures and 329 VIR (156 preand 173 post-ClarityIQ) procedures performed at our institution pre- and post-ClarityIQ implementation. NIR procedures were primarily classified as interventional or diagnostic. VIR procedures included drain port, drain placement, tube change, mesenteric, and implanted venous procedures. Air Kerma (AK in units of mGy) was documented for all the cases using a commercial radiation exposure management system. Results: When considering all NIR procedures, median AK decreased from 1194 mGy to 561 mGy. When considering all VIR procedures, median AK decreased from 49 to 14 mGy. Both NIR and VIR exhibited a decrease in AK exceeding 50% after ClarityIQ implementation, a statistically significant (p<0.05) difference. Of the 5 most common VIR procedures, all median AK values decreased, but significance (p<0.05) was only reached in venous access (N=53), angio mesenteric (N=41), and drain placement procedures (N=31). Conclusion: ClarityIQ can reduce dose significantly for both NIR and VIR procedures. Image quality was not assessed in conjunction with the dose reduction.

Effects of a radiation dose reduction strategy for computed tomography in severely injured trauma patients in the emergency department: an observational study.

Science.gov (United States)

Kim, Soo Hyun; Jung, Seung Eun; Oh, Sang Hoon; Park, Kyu Nam; Youn, Chun Song

2011-11-03

Severely injured trauma patients are exposed to clinically significant radiation doses from computed tomography (CT) imaging in the emergency department. Moreover, this radiation exposure is associated with an increased risk of cancer. The purpose of this study was to determine some effects of a radiation dose reduction strategy for CT in severely injured trauma patients in the emergency department. We implemented the radiation dose reduction strategy in May 2009. A prospective observational study design was used to collect data from patients who met the inclusion criteria during this one year study (intervention group) from May 2009 to April 2010. The prospective data were compared with data collected retrospectively for one year prior to the implementation of the radiation dose reduction strategy (control group). By comparison of the cumulative effective dose and the number of CT examinations in the two groups, we evaluated effects of a radiation dose reduction strategy. All the patients met the institutional adult trauma team activation criteria. The radiation doses calculated by the CT scanner were converted to effective doses by multiplication by a conversion coefficient. A total of 118 patients were included in this study. Among them, 33 were admitted before May 2009 (control group), and 85 were admitted after May 2009 (intervention group). There were no significant differences between the two groups regarding baseline characteristics, such as injury severity and mortality. Additionally, there was no difference between the two groups in the mean number of total CT examinations per patient (4.8 vs. 4.5, respectively; p = 0.227). However, the mean effective dose of the total CT examinations per patient significantly decreased from 78.71 mSv to 29.50 mSv (p trauma patients effectively decreased the cumulative effective dose of the total CT examinations in the emergency department. But not effectively decreased the number of CT examinations.

MO-DE-204-00: International Symposium: Patient Dose Reduction in Diagnostic Radiology

International Nuclear Information System (INIS)

2016-01-01

The main topic of the session is to show how dose optimization is being implemented in various regions of the world, including Europe, Australia, North America and other regions. A multi-national study conducted under International Atomic Energy Agency (IAEA) across more than 50 less resourced countries gave insight into patient radiation doses and safety practices in CT, mammography, radiography and interventional procedures, both for children and adults. An important outcome was the capability development on dose assessment and management. An overview of recent European projects related to CT radiation dose and optimization both to adults and children will be presented. Existing data on DRLs together with a European methodology proposed on establishing and using DRLs for paediatric radiodiagnostic imaging and interventional radiology practices will be shown. Compared with much of Europe at least, many Australian imaging practices are relatively new to the task of diagnostic imaging dose optimisation. In 2008 the Australian Government prescribed a requirement to periodically compare patient radiation doses with diagnostic reference levels (DRLs), where DRLs have been established. Until recently, Australia had only established DRLs for computed tomography (CT). Regardless, both professional society and individual efforts to improved data collection and develop optimisation strategies across a range of modalities continues. Progress in this field, principally with respect to CT and interventional fluoroscopy will be presented. In the US, dose reduction and optimization efforts for computed tomography have been promoted and mandated by several organizations and accrediting entities. This presentation will cover the general motivation, implementation, and implications of such efforts. Learning Objectives: Understand importance of the dose optimization in Diagnostic Radiology. See how this goal is achieved in different regions of the World. Learn about the global trend

MO-DE-204-00: International Symposium: Patient Dose Reduction in Diagnostic Radiology

Energy Technology Data Exchange (ETDEWEB)

NONE

2016-06-15

The main topic of the session is to show how dose optimization is being implemented in various regions of the world, including Europe, Australia, North America and other regions. A multi-national study conducted under International Atomic Energy Agency (IAEA) across more than 50 less resourced countries gave insight into patient radiation doses and safety practices in CT, mammography, radiography and interventional procedures, both for children and adults. An important outcome was the capability development on dose assessment and management. An overview of recent European projects related to CT radiation dose and optimization both to adults and children will be presented. Existing data on DRLs together with a European methodology proposed on establishing and using DRLs for paediatric radiodiagnostic imaging and interventional radiology practices will be shown. Compared with much of Europe at least, many Australian imaging practices are relatively new to the task of diagnostic imaging dose optimisation. In 2008 the Australian Government prescribed a requirement to periodically compare patient radiation doses with diagnostic reference levels (DRLs), where DRLs have been established. Until recently, Australia had only established DRLs for computed tomography (CT). Regardless, both professional society and individual efforts to improved data collection and develop optimisation strategies across a range of modalities continues. Progress in this field, principally with respect to CT and interventional fluoroscopy will be presented. In the US, dose reduction and optimization efforts for computed tomography have been promoted and mandated by several organizations and accrediting entities. This presentation will cover the general motivation, implementation, and implications of such efforts. Learning Objectives: Understand importance of the dose optimization in Diagnostic Radiology. See how this goal is achieved in different regions of the World. Learn about the global trend

The use of the eyes protection for dose reduction in CT scans of skull

International Nuclear Information System (INIS)

Mourao, Arnaldo P.; Silva, Teogenes A.; Alonso, Thessa C.

2013-01-01

The technique for imaging the brain scans of the skull by computed tomography (CT) scanning is the volume bounded by the foramen magnum and the apex of the skull. The lenses are radiosensitive tissues and CT scans of the head deposited significant doses on them, since they are in the region of incidence of the primary beam of X-rays. Thus, the variation of the dose deposited in the crystalline skull CT scans for diagnostic imaging of the brain was investigated. Cranial scans were performed using the acquisition protocol routine with or without the use of bismuth to shield the eyes. To carry out the scans we used a male anthropomorphic phantom, Alderson Rando model and dosimeters (TLD-100) were used to record the doses. These TLDs were used to record specific doses internally to the phantom in specific organs (crystalline, pituitary, thyroid, spinal cord and breasts). The scans were performed on a GE machine, model 64 Discovery channels. The data obtained allowed to observe the variation of dose in organs. The highest dose was recorded in the lens (26,18 mGy), followed by spinal cord (17,79 mGy). Comparing the doses of the two scans it was significant variation in the crystal. Scan using bismuth shield generated smaller doses in the eyes and in the eyes occurred the higher dose reduction, about 37%. The results may contribute to spread a suitable procedure for the optimization of CT scans of the skull

Effect of rare earth filtration on patient exposure, dose reduction, and image quality in oral panoramic radiology

International Nuclear Information System (INIS)

Tyndall, D.A.; Washburn, D.B.

1987-01-01

Rare earth intensifying screen material (Gd2O2S:Tb) was added to the standard Al filtration of an oral panoramic x-ray unit, resulting in a beam capable of achieving reductions in patient dose without a loss of image quality. The added rare earth filtration technique resulted in patient dose reductions of 21-56%, depending on anatomic sites, when compared to the conventional Al filtration technique. Films generated from both techniques were measured densitometrically and evaluated by a panel of practicing clinicians. Diagnostically significant differences were minimal. The results indicate that use of rare earth filters in oral panoramic radiography is an effective means of reducing exposures of dental patients to ionizing radiation

Study of the response reduction of LiF:Mg, Ti dosimeter for high dose dosimetry

Energy Technology Data Exchange (ETDEWEB)

Torkzadeh, Falamarz [Nuclear Sciences and Technology Research Institute, Tehran (Iran, Islamic Republic of). Radiation Applications Research School; AEOI, Tehran (Iran, Islamic Republic of); Faripour, Heidar [Nuclear Sciences and Technology Research Institute, Tehran (Iran, Islamic Republic of). Laser and Optics Research School; AEOI, Tehran (Iran, Islamic Republic of); Mardashti, Forough; Manouchehri, Farhad [Nuclear Sciences and Technology Research Institute, Tehran (Iran, Islamic Republic of). Radiation Applications Research School

2017-07-15

A single crystal and 5 polycrystalline samples of LiF:Mg, Ti and their pellets were prepared and investigated so as to apply thermoluminescence high gamma dose dosimetry. Three zones of single crystal with dopant concentrations of 200 ppm of Mg and 20 ppm of Ti were also used to prepare the single crystal samples. For polycrystalline samples, dopant concentrations of 0.062 mol% Mg and Ti concentrations in the range of 0.016 and 0.046 mol% were used. All the samples were exposed to gamma doses of 1 kGy to 700 kGy and their response changes were determined by a gamma dose test of about 60 mGy. According to the results obtained, the use of response reduction by curve-fitting up to about 300 kGy can be performed reliably for high dose gamma dosimetry.

Angular dependence of the MOSFET dosimeter and its impact on in vivo surface dose measurement in breast cancer treatment.

Science.gov (United States)

Qin, S; Chen, T; Wang, L; Tu, Y; Yue, N; Zhou, J

2014-08-01

The focus of this study is the angular dependence of two types of Metal Oxide Semiconductor Field Effect Transistor (MOSFET) dosimeters (MOSFET20 and OneDose/OneDosePlus) when used for surface dose measurements. External beam radiationat different gantry angles were delivered to a cubic solid water phantom with a MOSFET placed on the top surface at CAX. The long axis of the MOSFET was oriented along the gantry axis of rotation, with the dosimeter (bubble side) facing the radiation source. MOSFET-measured surface doses were compared against calibrated radiochromic film readings. It was found that both types of MOSFET dosimeters exhibited larger than previously reported angular dependence when measuring surface dose in beams at large oblique angles. For the MOSFET20 dosimeter the measured surface dose deviation against film readings was as high as 17% when the incident angle was 72 degrees to the norm of the phantom surface. It is concluded that some MOSFET dosimeters may have a strong angular dependence when placed on the surface of water-equivalent material, even though they may have an isotropic angular response when surrounded by uniform medium. Extra on-surface calibration maybe necessary before using MOSFET dosimeters for skin dose measurement in tangential fields.

Extensive reduction of surface UV radiation since 1750 in world's populated regions

Directory of Open Access Journals (Sweden)

M. M. Kvalevåg

2009-10-01

Full Text Available Human activity influences a wide range of components that affect the surface UV radiation levels, among them ozone at high latitudes. We calculate the effect of human-induced changes in the surface erythemally weighted ultra-violet radiation (UV-E since 1750. We compare results from a radiative transfer model to surface UV-E radiation for year 2000 derived by satellite observations (from Total Ozone Mapping Spectroradiometer and to ground based measurements at 14 sites. The model correlates well with the observations; the correlation coefficients are 0.97 and 0.98 for satellite and ground based measurements, respectively. In addition to the effect of changes in ozone, we also investigate the effect of changes in SO₂, NO₂, the direct and indirect effects of aerosols, albedo changes and aviation-induced contrails and cirrus. The results show an increase of surface UV-E in polar regions, most strongly in the Southern Hemisphere. Furthermore, our study also shows an extensive surface UV-E reduction over most land areas; a reduction up to 20% since 1750 is found in some industrialized regions. This reduction in UV-E over the industrial period is particularly large in highly populated regions.

Effect of various physical parameters on surface and build-up dose for 15-MV X-rays

International Nuclear Information System (INIS)

Yadav, Girigesh; Yadav, R.S.; Kumar, Alok

2010-01-01

The purpose of this study was to find out the effect of various physical parameters on the skin and build-up doses of 15-MV photon beams. The effects of field dimensions, acrylic shadow tray, focus to-skin distance (FSD) on surface and buildup dose were determined for open, motorized 60 deg wedge (MW) and blocked fields. A 'Markus' plane parallel plate chamber was used for these measurements in an Elekta (6-15MV) linear accelerator. The surface dose for MW fields was lower than the dose for an open field, but the trend reversed for large fields and higher degree wedges. With the use of an acrylic shadow tray, the surface dose increased for all field sizes, but the increase was dominant for large fields. The surface dose for blocked fields was lower than the dose for open fields. The percentage depth dose of 10 x 10 cm 2 field at surface (PDD 0 ) for open beam were 13.89%, 11.71%, and 10.74% at 80 cm, 100 cm, and 120 cm FSD, respectively. The blocking tray increased PDD 0 of 10 x 10 cm 2 field to 26.29%, 14.01%, and 11.53%, while the motorized 60 deg wedge decreased PDD 0 to 11.32%, 9.7%, and 8.9 % at these FSDs. The maximum PDD difference seen at surface (i.e. skin) for 5x5 cm 2 , 15x15 cm 2 , and 30x30 cm 2 are 0.5%, 4.6%, and 5.6% for open field and 0.9%, 4.7%, and 7.2% for motorized 60 deg wedge field, when FSDs varied from 80 cm to 120 cm. The maximum PDD difference seen at surface for 5x5 cm 2 , 15x15 cm 2 , and 30x30 cm 2 fields are 5.6%, 22.8%, and 29.6%, respectively, for a 1.0-cm perspex-blocking tray as the FSD is changed. The maximum PDD difference was seen at the surface (i.e. skin) and this decreased with increasing depth. (author)

Reduction of radiation exposure and image quality using dose reduction tool on computed tomography fluoroscopy

International Nuclear Information System (INIS)

Sakabe, Daisuke; Tochihara, Syuichi; Ono, Michiaki; Tokuda, Masaki; Kai, Noriyuki; Nakato, Kengo; Hashida, Masahiro; Funama, Yoshinori; Murazaki, Hiroo

2012-01-01

The purpose of our study was to measure the reduction rate of radiation dose and variability of image noise using the angular beam modulation (ABM) on computed tomography (CT) fluoroscopy. The Alderson-Rando phantom and the homemade phantom were used in our study. These phantoms were scanned at on-center and off-center positions at -12 cm along y-axis with and without ABM technique. Regarding the technique, the x-ray tube is turned off in a 100-degree angle sector at the center of 12 o'clock, 10 o'clock, and 2 o'clock positions during CT fluoroscopy. CT fluoroscopic images were obtained with tube voltages, 120 kV; tube current-time product per reconstructed image, 30 mAs; rotation time, 0.5 s/rot; slice thickness, 4.8 mm; and reconstruction kernel B30s in each scanning. After CT scanning, radiation exposure and image noise were measured and the image artifacts were evaluated with and without the technique. The reduction rate for radiation exposure was 75-80% with and without the technique at on-center position regardless of each angle position. In the case of the off-center position at -12 cm, the reduction rate was 50% with and without the technique. In contrast, image noise remained constant with and without the technique. Visual inspection for image artifacts almost have the same scores with and without the technique and no statistical significance was found in both techniques (p>0.05). ABM is an appropriate tool for reducing radiation exposure and maintaining image-noise and artifacts during CT fluoroscopy. (author)

Cranial CT with adaptive statistical iterative reconstruction: improved image quality with concomitant radiation dose reduction.

Science.gov (United States)

Rapalino, O; Kamalian, Shervin; Kamalian, Shahmir; Payabvash, S; Souza, L C S; Zhang, D; Mukta, J; Sahani, D V; Lev, M H; Pomerantz, S R

2012-04-01

To safeguard patient health, there is great interest in CT radiation-dose reduction. The purpose of this study was to evaluate the impact of an iterative-reconstruction algorithm, ASIR, on image-quality measures in reduced-dose head CT scans for adult patients. Using a 64-section scanner, we analyzed 100 reduced-dose adult head CT scans at 6 predefined levels of ASIR blended with FBP reconstruction. These scans were compared with 50 CT scans previously obtained at a higher routine dose without ASIR reconstruction. SNR and CNR were computed from Hounsfield unit measurements of normal GM and WM of brain parenchyma. A blinded qualitative analysis was performed in 10 lower-dose CT datasets compared with higher-dose ones without ASIR. Phantom data analysis was also performed. Lower-dose scans without ASIR had significantly lower mean GM and WM SNR (P = .003) and similar GM-WM CNR values compared with higher routine-dose scans. However, at ASIR levels of 20%-40%, there was no statistically significant difference in SNR, and at ASIR levels of ≥60%, the SNR values of the reduced-dose scans were significantly higher (P ASIR levels of ≥40% (P ASIR levels ≥60% (P ASIR in adult head CT scans reduces image noise and increases low-contrast resolution, while allowing lower radiation doses without affecting spatial resolution.

Adaptive iterative dose reduction (AIDR) 3D in low dose CT abdomen-pelvis: Effects on image quality and radiation exposure

International Nuclear Information System (INIS)

Ang, W C; Hashim, S; Karim, M K A; Bahruddin, N A; Salehhon, N; Musa, Y

2017-01-01

The widespread use of computed tomography (CT) has increased the medical radiation exposure and cancer risk. We aimed to evaluate the impact of AIDR 3D in CT abdomen-pelvic examinations based on image quality and radiation dose in low dose (LD) setting compared to standard dose (STD) with filtered back projection (FBP) reconstruction. We retrospectively reviewed the images of 40 patients who underwent CT abdomen-pelvic using a 80 slice CT scanner. Group 1 patients ( n =20, mean age 41 ± 17 years) were performed at LD with AIDR 3D reconstruction and Group 2 patients ( n =20, mean age 52 ± 21 years) were scanned with STD using FBP reconstruction. Objective image noise was assessed by region of interest (ROI) measurements in the liver and aorta as standard deviation (SD) of the attenuation value (Hounsfield Unit, HU) while subjective image quality was evaluated by two radiologists. Statistical analysis was used to compare the scan length, CT dose index volume (CTDI vol ) and image quality of both patient groups. Although both groups have similar mean scan length, the CTDI vol significantly decreased by 38% in LD CT compared to STD CT ( p <0.05). Objective and subjective image quality were statistically improved with AIDR 3D ( p <0.05). In conclusion, AIDR 3D enables significant dose reduction of 38% with superior image quality in LD CT abdomen-pelvis. (paper)

Calculation of normal tissue complication probability and dose-volume histogram reduction schemes for tissues with a critical element architecture

International Nuclear Information System (INIS)

Niemierko, Andrzej; Goitein, Michael

1991-01-01

The authors investigate a model of normal tissue complication probability for tissues that may be represented by a critical element architecture. They derive formulas for complication probability that apply to both a partial volume irradiation and to an arbitrary inhomogeneous dose distribution. The dose-volume isoeffect relationship which is a consequence of a critical element architecture is discussed and compared to the empirical power law relationship. A dose-volume histogram reduction scheme for a 'pure' critical element model is derived. In addition, a point-based algorithm which does not require precomputation of a dose-volume histogram is derived. The existing published dose-volume histogram reduction algorithms are analyzed. The authors show that the existing algorithms, developed empirically without an explicit biophysical model, have a close relationship to the critical element model at low levels of complication probability. However, it is also showed that they have aspects which are not compatible with a critical element model and the authors propose a modification to one of them to circumvent its restriction to low complication probabilities. (author). 26 refs.; 7 figs

Radiation dose reduction in CT-guided sacroiliac joint injections to levels of pulsed fluoroscopy: a comparative study with technical considerations

Directory of Open Access Journals (Sweden)

Artner J

2012-08-01

Full Text Available Juraj Artner, Balkan Cakir, Heiko Reichel, Friederike LattigDepartment of Orthopaedic Surgery, University of Ulm, RKU, GermanyBackground: The sacroiliac (SI joint is frequently the primary source of low back pain. Over the past decades, a number of different SI injection techniques have been used in its diagnosis and therapy. Despite the concerns regarding exposure to radiation, image-guided injection techniques are the preferred method to achieve safe and precise intra-articular needle placement. The following study presents a comparison of radiation doses, calculated for fluoroscopy and CT-guided SI joint injections in standard and low-dose protocol and presents the technical possibility of CT-guidance with maximum radiation dose reduction to levels of fluoroscopic-guidance for a precise intra-articular injection technique.Objective: To evaluate the possibility of dose reduction in CT-guided sacroiliac joint injections to pulsed-fluoroscopy-guidance levels and to compare the doses of pulsed-fluoroscopy-, CT-guidance, and low-dose CT-guidance for intra-articular SI joint injections.Study design: Comparative study with technical considerations.Methods: A total of 30 CT-guided intra-articular SI joint injections were performed in January 2012 in a developed low-dose mode and the radiation doses were calculated. They were compared to 30 pulsed-fluoroscopy-guided SI joint injections, which were performed in the month before, and to five injections, performed in standard CT-guided biopsy mode for spinal interventions. The statistical significance was calculated with the SPSS software using the Mann–Whitney U-Test. Technical details and anatomical considerations were provided.Results: A significant dose reduction of average 94.01% was achieved using the low-dose protocol for CT-guided SI joint injections. The radiation dose could be approximated to pulsed-fluoroscopy-guidance levels.Conclusion: Radiation dose of CT-guided SI joint injections can be

Radiation dose reduction at a price: the effectiveness of a male gonadal shield during helical CT scans

Directory of Open Access Journals (Sweden)

Erdi Yusuf E

2007-03-01

Full Text Available Abstract Background It is estimated that 60 million computed tomography (CT scans were performed during 2006, with approximately 11% of those performed on children age 0–15 years. Various types of gonadal shielding have been evaluated for reducing exposure to the gonads. The purpose of this study was to quantify the radiation dose reduction to the gonads and its effect on image quality when a wrap-around male pediatric gonad shield was used during CT scanning. This information is obtained to assist the attending radiologist in the decision to utilize such male gonadal shields in pediatric imaging practice. Methods The dose reduction to the gonads was measured for both direct radiation and for indirect scattered radiation from the abdomen. A 6 cm3 ion chamber (Model 10X5-6, Radcal Corporation, Monrovia, CA was placed on a Humanoid real bone pelvic phantom at a position of the male gonads. When exposure measurements with shielding were made, a 1 mm lead wrap-around gonadal shield was placed around the ion chamber sensitive volume. Results The use of the shields reduced scatter dose to the gonads by a factor of about 2 with no appreciable loss of image quality. The shields reduced the direct beam dose by a factor of about 35 at the expense of extremely poor CT image quality due to severe streak artifacts. Conclusion Images in the direct exposure case are not useful due to these severe artifacts and the difficulties in positioning these shields on patients in the scatter exposure case may not be warranted by the small absolute reduction in scatter dose unless it is expected that the patient will be subjected to numerous future CT scans.

Radiation dose reduction in CT with adaptive statistical iterative reconstruction (ASIR) for patients with bronchial carcinoma and intrapulmonary metastases.

Science.gov (United States)

Schäfer, M-L; Lüdemann, L; Böning, G; Kahn, J; Fuchs, S; Hamm, B; Streitparth, F

2016-05-01

To compare the radiation dose and image quality of 64-row chest computed tomography (CT) in patients with bronchial carcinoma or intrapulmonary metastases using full-dose CT reconstructed with filtered back projection (FBP) at baseline and reduced dose with 40% adaptive statistical iterative reconstruction (ASIR) at follow-up. The chest CT images of patients who underwent FBP and ASIR studies were reviewed. Dose-length products (DLP), effective dose, and size-specific dose estimates (SSDEs) were obtained. Image quality was analysed quantitatively by signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) measurement. In addition, image quality was assessed by two blinded radiologists evaluating images for noise, contrast, artefacts, visibility of small structures, and diagnostic acceptability using a five-point scale. The ASIR studies showed 36% reduction in effective dose compared with the FBP studies. The qualitative and quantitative image quality was good to excellent in both protocols, without significant differences. There were also no significant differences for SNR except for the SNR of lung surrounding the tumour (FBP: 35±17, ASIR: 39±22). A protocol with 40% ASIR can provide approximately 36% dose reduction in chest CT of patients with bronchial carcinoma or intrapulmonary metastases while maintaining excellent image quality. Copyright © 2016 The Royal College of Radiologists. Published by Elsevier Ltd. All rights reserved.

Moving back: The radiation dose received from lumbar spine quantitative fluoroscopy compared to lumbar spine radiographs with suggestions for dose reduction.

Science.gov (United States)

Mellor, F E; Thomas, P; Breen, A

2014-08-01

Quantitative fluoroscopy is an emerging technology for assessing continuous inter-vertebral motion in the lumbar spine, but information on radiation dose is not yet available. The purposes of this study were to compare the radiation dose from quantitative fluoroscopy of the lumbar spine with lumbar spine radiographs, and identify opportunities for dose reduction in quantitative fluoroscopy. Internationally reported dose area product (DAP) and effective dose data for lumbar spine radiographs were compared with the same for quantitative fluoroscopy and with data from a local hospital for functional radiographs (weight bearing AP, lateral, and/or flexion and extension) ( n  = 27). The effects of procedure time, age, weight, height and body mass index on the fluoroscopy dose were determined by multiple linear regression using SPSS v19 software (IBM Corp., Armonck, NY, USA). The effective dose (and therefore the estimated risk) for quantitative fluoroscopy is 0.561 mSv which is lower than in most published data for lumbar spine radiography. The dose area product (DAP) for sagittal (flexion + extension) quantitative fluoroscopy is 3.94 Gy cm 2 which is lower than local data for two view (flexion and extension) functional radiographs (4.25 Gy cm 2 ), and combined coronal and sagittal dose from quantitative fluoroscopy (6.13 Gy cm 2 ) is lower than for four view functional radiography (7.34 Gy cm 2 ). Conversely DAP for coronal and sagittal quantitative fluoroscopy combined (6.13 Gy cm 2 ) is higher than that published for both lumbar AP or lateral radiographs, with the exception of Nordic countries combined data. Weight, procedure time and age were independently positively associated with total dose, and height (after adjusting for weight) was negatively associated, thus as height increased, the DAP decreased.

Moving back: The radiation dose received from lumbar spine quantitative fluoroscopy compared to lumbar spine radiographs with suggestions for dose reduction

International Nuclear Information System (INIS)

Mellor, F.E.; Thomas, P.; Breen, A.

2014-01-01

Purpose: Quantitative fluoroscopy is an emerging technology for assessing continuous inter-vertebral motion in the lumbar spine, but information on radiation dose is not yet available. The purposes of this study were to compare the radiation dose from quantitative fluoroscopy of the lumbar spine with lumbar spine radiographs, and identify opportunities for dose reduction in quantitative fluoroscopy. Methods: Internationally reported dose area product (DAP) and effective dose data for lumbar spine radiographs were compared with the same for quantitative fluoroscopy and with data from a local hospital for functional radiographs (weight bearing AP, lateral, and/or flexion and extension) (n = 27). The effects of procedure time, age, weight, height and body mass index on the fluoroscopy dose were determined by multiple linear regression using SPSS v19 software (IBM Corp., Armonck, NY, USA). Results and conclusion: The effective dose (and therefore the estimated risk) for quantitative fluoroscopy is 0.561 mSv which is lower than in most published data for lumbar spine radiography. The dose area product (DAP) for sagittal (flexion + extension) quantitative fluoroscopy is 3.94 Gy cm 2 which is lower than local data for two view (flexion and extension) functional radiographs (4.25 Gy cm 2 ), and combined coronal and sagittal dose from quantitative fluoroscopy (6.13 Gy cm 2 ) is lower than for four view functional radiography (7.34 Gy cm 2 ). Conversely DAP for coronal and sagittal quantitative fluoroscopy combined (6.13 Gy cm 2 ) is higher than that published for both lumbar AP or lateral radiographs, with the exception of Nordic countries combined data. Weight, procedure time and age were independently positively associated with total dose, and height (after adjusting for weight) was negatively associated, thus as height increased, the DAP decreased

Air-spun PLA nanofibers modified with reductively sheddable hydrophilic surfaces for vascular tissue engineering: synthesis and surface modification.

Science.gov (United States)

Ko, Na Re; Sabbatier, Gad; Cunningham, Alexander; Laroche, Gaétan; Oh, Jung Kwon

2014-02-01

Polylactide (PLA) is a class of promising biomaterials that hold great promise for various biological and biomedical applications, particularly in the field of vascular tissue engineering where it can be used as a fibrous mesh to coat the inside of vascular prostheses. However, its hydrophobic surface providing nonspecific interactions and its limited ability to further modifications are challenges that need to be overcome. Here, the development of new air-spun PLA nanofibers modified with hydrophilic surfaces exhibiting reduction response is reported. Surface-initiated atom transfer radical polymerization allows for grafting pendant oligo(ethylene oxide)-containing polymethacrylate (POEOMA) from PLA air-spun fibers labeled with disulfide linkages. The resulting PLA-ss-POEOMA fibers exhibit enhanced thermal stability and improved surface properties, as well as thiol-responsive shedding of hydrophilic POEOMA by the cleavage of its disulfide linkages in response to reductive reactions, thus tuning the surface properties. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

TH-EF-BRB-03: Significant Cord and Esophagus Dose Reduction by 4π Non-Coplanar Spine Stereotactic Body Radiation Therapy and Stereotactic Radiosurgery

Energy Technology Data Exchange (ETDEWEB)

Yu, V; Tran, A; Nguyen, D; Woods, K; Cao, M; Kaprealian, T; Chin, R; Low, D; Sheng, K [UCLA, Los Angeles, CA (United States)

2016-06-15

Purpose: To demonstrate significant organ-at-risk (OAR) sparing achievable with 4π non-coplanar radiotherapy on spine SBRT and SRS patients. Methods: Twenty-five stereotactic spine cases previously treated with VMAT (n = 23) or IMRT (n = 2) were included in this study. A computer-aided-design model of a Linac with a 3D-scanned human surface was utilized to determine the feasible beam space throughout the 4π steradian and beam specific source-to-target-distances (STD) required for collision avoidance. 4π radiotherapy plans integrating beam orientation and fluence map optimization were then created using a column-generation algorithm. Twenty optimal beams were selected for each case. To evaluate the tradeoff between dosimetric benefit and treatment complexity, 4π plans including only isocentrically deliverable beams were also created. Beam angles of all standard and isocentric 4π plans were imported into Eclipse to recalculate the dose using the same calculation engine as the clinical plans for unbiased comparison. OAR and PTV dose statistics for the clinical, standard-4π, and isocentric-4π plans were compared. Results: Comparing standard-4π to clinical plans, particularly significant average percent reduction in the [mean, maximum] dose of the cord and esophagus of [41%, 21.7%], and [38.7%, 36.4%] was observed, along with global decrease in all other OAR dose statistics. The average cord volume receiving more than 50% prescription dose was substantially decreased by 76%. In addition, improved PTV coverage was demonstrated with a maximum dose reduction of 0.93% and 1.66% increase in homogeneity index (D95/D5). All isocentric-4π plans achieved dosimetric performance equivalent to that of the standard-4π plans with higher delivery complexity. Conclusion: 4π radiotherapy significantly improves stereotactic spine treatment dosimetry. With the substantial OAR dose sparing, PTV dose escalation is considerably safer. Isocentric-4π is sufficient to achieve the

Critical analysis of dose reduction trends with special reference to procedures involved in fluoroscopy

International Nuclear Information System (INIS)

Anderson, K.; Mattsson, O.

1985-01-01

Experiences of a half-year's use of dose-checking instrumentation in fluoroscopy are presented. Radiologists under training succeeded in lowering the patient dose surprisingly well - the diagnostic results remaining unchanged or even improving, because of higher image quality as a result of better diaphragming. Other factors involved in fluoroscopy are discussed. Present systems with heavy bulky intensifiers create problems for close patient contact and for the necessary manipulation, patient adjustment and application of compression. The examination will be simplified and facilitated by the use of a flat image system: proper adjustments need fewer fluoroscopic observations, and patient dose as well as examination time can be saved. Flat display principles will take over the function of the present old-fashioned intensifiers and monitors, either as single units or equipped with TV, video or digital processing accessories. A flat image system, the 'PET-scope', was tested and found to be very convenient for fluoroscopic procedures. The physical properties were studied thoroughly - the high intensification particularly gives these systems an advantage in dose reduction. New applications are possible with these light-weight low-dose units. Fluoroscopy represents a field where considerable contributions to the 'Quality Assurance' trend can be obtained. (author)

Optical microtopographic inspection of the surface of tooth subjected to stripping reduction

Science.gov (United States)

Costa, Manuel F.; Pereira, Pedro B.

2011-05-01

In orthodontics, the decreasing of tooth-size by reducing interproximal enamel surfaces (stripping) of teeth is a common procedure which allows dental alignment with minimal changes in the facial profile and no arch expansion. In order to achieve smooth surfaces, clinicians have been testing various methods and progressively improved this therapeutic technique. In order to evaluate the surface roughness of teeth subject to interproximal reduction through the five most commonly used methods, teeth were inspected by scanning electron microscopy and microtopographically measured using the optical active triangulation based microtopographer MICROTOP.06.MFC. The metrological procedure will be presented as well as the comparative results concluding on the most suitable tooth interproximal reduction method.

Reduction of exposure dose using ASiR (adaptive statistical iterative reconstruction) technique at the routine computed tomography

International Nuclear Information System (INIS)

Shibata, M.; Matsukura, R.; Akimoto, H.; Kojima, Y.; Sakamoto, T.; Matsukura, H.; Ono, Shuichi; Takai, Yoshihiro

2013-01-01

The GE 64-row CT machine, Discovery CT 750 HD, loads the ASiR and garnet detector, which are able to give a higher image quality than usual, and thus is useful for reducing the dose. The extent of the dose reduction by 750 HD was evaluated by comparison with the ordinary CT machine, GE 16-row Light Speed Ultra (LSU). Abdominal CT images acquisitioned by 750 HD during Mar-May 2011 of 112 patients (M 71/F 41, 11-85 years old) were compared with their past images by LSU. Imaging conditions like tube voltage, current, rotation time, helical pitch, slice thickness and scanning length were the same as each other except for noise index (11.3 in 750 HD vs 9.8 in LSU) with ASiR 50%, which had been adjusted to give images with the same visional quality by multiple radiological doctors and technologists. Difference of dose-length products (mGy.cm) between the two methods was analyzed with Wilcoxon t test, and significant 31.9% reduction of LSU dose was found in 750 HD acquisition. At the routine examination, imaging conditions of 750 HD should be setup on the individual patient's physique represented by parameters like BMI as the machine has an automatic exposure controlling function tending to increase the dose. (T.T.)

Modeling drag reduction and meniscus stability of superhydrophobic surfaces comprised of random roughness

Science.gov (United States)

Samaha, Mohamed A.; Tafreshi, Hooman Vahedi; Gad-el-Hak, Mohamed

2011-01-01

Previous studies dedicated to modeling drag reduction and stability of the air-water interface on superhydrophobic surfaces were conducted for microfabricated coatings produced by placing hydrophobic microposts/microridges arranged on a flat surface in aligned or staggered configurations. In this paper, we model the performance of superhydrophobic surfaces comprised of randomly distributed roughness (e.g., particles or microposts) that resembles natural superhydrophobic surfaces, or those produced via random deposition of hydrophobic particles. Such fabrication method is far less expensive than microfabrication, making the technology more practical for large submerged bodies such as submarines and ships. The present numerical simulations are aimed at improving our understanding of the drag reduction effect and the stability of the air-water interface in terms of the microstructure parameters. For comparison and validation, we have also simulated the flow over superhydrophobic surfaces made up of aligned or staggered microposts for channel flows as well as streamwise or spanwise ridges configurations for pipe flows. The present results are compared with theoretical and experimental studies reported in the literature. In particular, our simulation results are compared with work of Sbragaglia and Prosperetti, and good agreement has been observed for gas fractions up to about 0.9. The numerical simulations indicate that the random distribution of surface roughness has a favorable effect on drag reduction, as long as the gas fraction is kept the same. This effect peaks at about 30% as the gas fraction increases to 0.98. The stability of the meniscus, however, is strongly influenced by the average spacing between the roughness peaks, which needs to be carefully examined before a surface can be recommended for fabrication. It was found that at a given maximum allowable pressure, surfaces with random post distribution produce less drag reduction than those made up of

Calculation of rectal dose surface histograms in the presence of time varying deformations

International Nuclear Information System (INIS)

Roeske, John C.; Spelbring, Danny R.; Vijayakumar, S.; Forman, Jeffrey D.; Chen, George T.Y.

1996-01-01

Purpose: Dose volume (DVH) and dose surface histograms (DSH) of the bladder and rectum are usually calculated from a single treatment planning scan. These DVHs and DSHs will eventually be correlated with complications to determine parameters for normal tissue complication probabilities (NTCP). However, from day to day, the size and shape of the rectum and bladder may vary. The purpose of this study is to compare a more accurate estimate of the time integrated DVHs and DSHs of the rectum (in the presence of daily variations in rectal shape) to initial DVHs/DSHs. Methods: 10 patients were scanned once per week during the course of fractionated radiotherapy, typically accumulating a total of six scans. The rectum and bladder were contoured on each of the studies. The model used to assess effects of rectal contour deformation is as follows: the contour on a given axial slice (see figure) is boxed within a rectangle. A line drawn parallel to the AP axis through the rectangle equally partitions the box. Starting at the intersection of the vertical line and the rectal contour, points on the contour are marked off representing the same rectal dose point, even in the presence of distortion. Corresponding numbered points are used to sample the dose matrix and create a composite DSH. The model assumes uniform stretching of the rectal contour for any given axial cut, and no twist of the structure or vertical displacement. A similar model is developed for the bladder with spherical symmetry. Results: Normalized DSHs (nDSH) for each CT scan were calculated as well as the time averaged nDSH over all scans. These were compared with the nDSH from the initial planning scan. Individual nDSHs differed by 8% surface area irradiated at the 80% dose level, to as much as 20% surface area in the 70-100% dose range. DSH variations are due to position and shape changes in the rectum during different CT scans. The spatial distribution of dose is highly variable, and depends on the field

Thickened boundary layer theory for air film drag reduction on a van body surface

Science.gov (United States)

Xie, Xiaopeng; Cao, Lifeng; Huang, Heng

2018-05-01

To elucidate drag reduction mechanism on a van body surface under air film condition, a thickened boundary layer theory was proposed and a frictional resistance calculation model of the van body surface was established. The frictional resistance on the van body surface was calculated with different parameters of air film thickness. In addition, the frictional resistance of the van body surface under the air film condition was analyzed by computational fluid dynamics (CFD) simulation and different air film states that influenced the friction resistance on the van body surface were discussed. As supported by the CFD simulation results, the thickened boundary layer theory may provide reference for practical application of air film drag reduction on a van body surface.

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

International Nuclear Information System (INIS)

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

2014-01-01

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

Surface dose of X rays to patients during extracorporeal shock wave lithotripsy

International Nuclear Information System (INIS)

Jiang Qingqi; Weng Zhigeng; Feng Ming; Wang Guomin.

1990-01-01

During extracorporeal shock wave lithotripsy (ESWL), the fluoroscopy must be made to show the location and size of the stone thus the patient has to be exposed to X rays. The surface dose to patients during ESWL was measured in an investigation on 134 cases of renal lithiasis admitted in a certain hospital of Shanghai. The results show that the average skin dose equivalent for these patients was 162 mSv and the magnitude of doses was depended upon some factors such as the size and location of the stone

Dose reduction using non lineal diffusion and smoothing filters in computed radiography

International Nuclear Information System (INIS)

Sánchez, M.G.; Juste, B.; Vidal, V.; Verdú, G.; Mayo, P.; Rodenas, F.

2014-01-01

The use of Computed Radiography (CR) into clinical practice has been followed by a high increase in the number of examinations performed and overdose cases in patients, especially children in pediatric applications. Computed radiographic images are corrupted by noise because either data acquisition or data transmission. The level of this inherent noise is related with the X-ray dose exposure: lower radiation exposure involves higher noise level. The main aim of this work is to reduce the noise present in a low radiation dose CR image in order to the get a CR image of the same quality as a higher radiation exposure image. In this work, we use a non lineal diffusion filtering method to reduce the noise level in a CR, this means that we are able to reduce the exposure, milliampere-second (mAs), and the dose absorbed by the patients. In order to get an optimal result, the diffusive filter is complemented with a smoothing filter with edge detection in order to preserve edges. Therefore, the proposed method consists in obtaining a good quality CR image for diagnostic purposes by selection of lower X-ray exposure jointly with a reduction of the noise. We conclude that a good solution to minimize the dose to patients, especially children in pediatric applications, in X-ray computed radiography consists in decreasing the mAs of the X-ray exposure and then processing the image with the proposed method. - Highlights: • We have investigated the techniques to obtain the image quality to make a confident diagnosis. • We have used diffusion and smoothing filter in order to reduce the exposure. • Reducing CR doses, especially in pediatric applications. • The new CR images allow medical researchers to analyze how low dose affects the patient diagnosis

Dosimetric perturbations of a lead shield for surface and interstitial high-dose-rate brachytherapy

International Nuclear Information System (INIS)

Candela-Juan, Cristian; Granero, Domingo; Vijande, Javier; Ballester, Facundo; Perez-Calatayud, Jose; Rivard, Mark J

2014-01-01

In surface and interstitial high-dose-rate brachytherapy with either 60 Co, 192 Ir, or 169 Yb sources, some radiosensitive organs near the surface may be exposed to high absorbed doses. This may be reduced by covering the implants with a lead shield on the body surface, which results in dosimetric perturbations. Monte Carlo simulations in Geant4 were performed for the three radionuclides placed at a single dwell position. Four different shield thicknesses (0, 3, 6, and 10 mm) and three different source depths (0, 5, and 10 mm) in water were considered, with the lead shield placed at the phantom surface. Backscatter dose enhancement and transmission data were obtained for the lead shields. Results were corrected to account for a realistic clinical case with multiple dwell positions. The range of the high backscatter dose enhancement in water is 3 mm for 60 Co and 1 mm for both 192 Ir and 169 Yb. Transmission data for 60 Co and 192 Ir are smaller than those reported by Papagiannis et al (2008 Med. Phys. 35 4898–4906) for brachytherapy facility shielding; for 169 Yb, the difference is negligible. In conclusion, the backscatter overdose produced by the lead shield can be avoided by just adding a few millimetres of bolus. Transmission data provided in this work as a function of lead thickness can be used to estimate healthy organ equivalent dose saving. Use of a lead shield is justified. (paper)

Impact of dose reductions on efficacy outcome in heart transplant patients receiving enteric-coated mycophenolate sodium or mycophenolate mofetil at 12 months post-transplantation.

Science.gov (United States)

Segovia, Javier; Gerosa, Gino; Almenar, Luis; Livi, Ugolino; Viganò, Mario; Arizón, Jose Maria; Yonan, Nizar; Di Salvo, Thomas G; Renlund, Dale G; Kobashigawa, Jon A

2008-01-01

Mycophenolic acid (MPA) dose reduction is associated with increased risk of rejection and graft loss in renal transplantation. This analysis investigated the impact of MPA dose changes with enteric-coated mycophenolate sodium (EC-MPS) or mycophenolate mofetil (MMF) in de novo heart transplant recipients. In a 12-month, single-blind trial, 154 patients (EC-MPS, 78; MMF, 76) were randomized to either EC-MPS (1080 mg bid) or MMF (1500 mg bid) in combination with cyclosporine and steroids. The primary efficacy variable was the incidence of treatment failure, comprising a composite of biopsy-proven (BPAR) and treated acute rejection, graft loss or death. Significantly fewer patients receiving EC-MPS required > or =2 dose reductions than patients on MMF (26.9% vs. 42.1% of patients, p = 0.048). Accordingly, the average daily dose of EC-MPS as a percentage of the recommended dose was significantly higher than for MMF (88.4% vs. 79.0%, p = 0.016). Among patients requiring > or =1 dose reduction, the incidence of treated BPAR grade > or =3A was significantly lower with EC-MPS compared with MMF (23.4% vs. 44.0%, p = 0.032). These data suggest that EC-MPS-treated heart transplant patients are less likely to require multiple dose reductions than those on MMF which may be associated with a significantly lower risk of treated BPAR > or =3A.

Dose reduction and the application of the ALARP principle to occupational exposure at the nuclear fuel reprocessing plant at Sellafield in Cumbria

International Nuclear Information System (INIS)

Anderson, R.W.; Coates, R.

1991-01-01

This paper presents information on the application of the ALARP principle to Dose Reduction at the British Nuclear Fuels plc site at Sellafield in Cumbria. The development of the Operational methods employed to effect dose reductions on existing plants and the impact of stringent targets for new plants is described in addition to discussion of the factors initiating the change and the success of the initiatives. (Author)

Absolute and relative dose-surface and dose-volume histograms of the bladder: which one is the most representative for the actual treatment?

International Nuclear Information System (INIS)

Hoogeman, Mischa S; Peeters, Stephanie T H; Bois, Josien de; Lebesque, Joos V

2005-01-01

The purpose of this study was to quantify to what extent relative and absolute bladder dose-volume and dose-surface histograms of the planning CT scan were representative for the actual treatment. We used data of 17 patients, who each received 11 repeat CT scans and a planning CT scan. The repeat CT scans were matched on the planning CT scan by the bony anatomy. Clinical treatment plans were used to evaluate the impact of bladder filling changes on the four histogram types. The impact was quantified by calculating for this patient group the correlation coefficient between the planning histogram and the treatment histogram. We found that the absolute dose-surface histogram was the most representative one for the actual treatment

Object-based Dimensionality Reduction in Land Surface Phenology Classification

Directory of Open Access Journals (Sweden)

Brian E. Bunker

2016-11-01

Full Text Available Unsupervised classification or clustering of multi-decadal land surface phenology provides a spatio-temporal synopsis of natural and agricultural vegetation response to environmental variability and anthropogenic activities. Notwithstanding the detailed temporal information available in calibrated bi-monthly normalized difference vegetation index (NDVI and comparable time series, typical pre-classification workflows average a pixel’s bi-monthly index within the larger multi-decadal time series. While this process is one practical way to reduce the dimensionality of time series with many hundreds of image epochs, it effectively dampens temporal variation from both intra and inter-annual observations related to land surface phenology. Through a novel application of object-based segmentation aimed at spatial (not temporal dimensionality reduction, all 294 image epochs from a Moderate Resolution Imaging Spectroradiometer (MODIS bi-monthly NDVI time series covering the northern Fertile Crescent were retained (in homogenous landscape units as unsupervised classification inputs. Given the inherent challenges of in situ or manual image interpretation of land surface phenology classes, a cluster validation approach based on transformed divergence enabled comparison between traditional and novel techniques. Improved intra-annual contrast was clearly manifest in rain-fed agriculture and inter-annual trajectories showed increased cluster cohesion, reducing the overall number of classes identified in the Fertile Crescent study area from 24 to 10. Given careful segmentation parameters, this spatial dimensionality reduction technique augments the value of unsupervised learning to generate homogeneous land surface phenology units. By combining recent scalable computational approaches to image segmentation, future work can pursue new global land surface phenology products based on the high temporal resolution signatures of vegetation index time series.

Biofilm attachment reduction on bioinspired, dynamic, micro-wrinkling surfaces

International Nuclear Information System (INIS)

Epstein, Alexander K; Hong, Donggyoon; Kim, Philseok; Aizenberg, Joanna

2013-01-01

Most bacteria live in multicellular communities known as biofilms that are adherent to surfaces in our environment, from sea beds to plumbing systems. Biofilms are often associated with clinical infections, nosocomial deaths and industrial damage such as bio-corrosion and clogging of pipes. As mature biofilms are extremely challenging to eradicate once formed, prevention is advantageous over treatment. However, conventional surface chemistry strategies are either generally transient, due to chemical masking, or toxic, as in the case of leaching marine antifouling paints. Inspired by the nonfouling skins of echinoderms and other marine organisms, which possess highly dynamic surface structures that mechanically frustrate bio-attachment, we have developed and tested a synthetic platform based on both uniaxial mechanical strain and buckling-induced elastomer microtopography. Bacterial biofilm attachment to the dynamic substrates was studied under an array of parameters, including strain amplitude and timescale (1–100 mm s −1 ), surface wrinkle length scale, bacterial species and cell geometry, and growth time. The optimal conditions for achieving up to ∼ 80% Pseudomonas aeruginosa biofilm reduction after 24 h growth and ∼ 60% reduction after 48 h were combinatorially elucidated to occur at 20% strain amplitude, a timescale of less than ∼ 5 min between strain cycles and a topography length scale corresponding to the cell dimension of ∼ 1 μm. Divergent effects on the attachment of P. aeruginosa, Staphylococcus aureus and Escherichia coli biofilms showed that the dynamic substrate also provides a new means of species-specific biofilm inhibition, or inversely, selection for a desired type of bacteria, without reliance on any toxic or transient surface chemical treatments. (paper)

Biofilm attachment reduction on bioinspired, dynamic, micro-wrinkling surfaces

Science.gov (United States)

Epstein, Alexander K.; Hong, Donggyoon; Kim, Philseok; Aizenberg, Joanna

2013-09-01

Most bacteria live in multicellular communities known as biofilms that are adherent to surfaces in our environment, from sea beds to plumbing systems. Biofilms are often associated with clinical infections, nosocomial deaths and industrial damage such as bio-corrosion and clogging of pipes. As mature biofilms are extremely challenging to eradicate once formed, prevention is advantageous over treatment. However, conventional surface chemistry strategies are either generally transient, due to chemical masking, or toxic, as in the case of leaching marine antifouling paints. Inspired by the nonfouling skins of echinoderms and other marine organisms, which possess highly dynamic surface structures that mechanically frustrate bio-attachment, we have developed and tested a synthetic platform based on both uniaxial mechanical strain and buckling-induced elastomer microtopography. Bacterial biofilm attachment to the dynamic substrates was studied under an array of parameters, including strain amplitude and timescale (1-100 mm s-1), surface wrinkle length scale, bacterial species and cell geometry, and growth time. The optimal conditions for achieving up to ˜ 80% Pseudomonas aeruginosa biofilm reduction after 24 h growth and ˜ 60% reduction after 48 h were combinatorially elucidated to occur at 20% strain amplitude, a timescale of less than ˜ 5 min between strain cycles and a topography length scale corresponding to the cell dimension of ˜ 1 μm. Divergent effects on the attachment of P. aeruginosa, Staphylococcus aureus and Escherichia coli biofilms showed that the dynamic substrate also provides a new means of species-specific biofilm inhibition, or inversely, selection for a desired type of bacteria, without reliance on any toxic or transient surface chemical treatments.

SU-F-T-93: Breast Surface Dose Enhancement Using a Clinical Prone Breast Board

International Nuclear Information System (INIS)

Guerra, M; Jozsef, G

2016-01-01

Purpose: The use of specialized patient set-up devices in radiotherapy, such as prone breast boards, may have unwanted dosimetric effects. The goal of this study was to evaluate the effect of a clinically used prone breast board on skin dose due to buildup. Methods: GafChromic film (EBT3) was used for dose measurements on the surface of a solid water phantom shaped to mimic the curvature of the breast. We investigated two setup scenarios: the medial field border placed at the medial edge of the board and 1 cm contralaterally from that edge. A strip of film was taped to the medial surface of the phantom. Gantry angles varied from 10 to 30 degrees below the lateral gantry position, representing anterior oblique fields. The measurements were performed with and without the presence of the board; the ratio of their corresponding doses (dose enhancement) was evaluated. Results: For the cases where the field edge is at the edge of the board, the dose enhancement is negligible for all the tested angles. When the field edge is 1 cm inside the board, the maximum surface dose enhancement varies depending on the gantry angle between 2.2 for 30 degrees and 3.2 for 20 degrees. The length on the film at which the presence of the board is detectable (i.e. where there is dose enhancement) is longer for the shallower angles. Conclusion: Even the low-density, thin carbon fiber board with a thin soft foam pad on the top can produce significant dose enhancement on the skin in prone breast treatment due to loss of buildup. However, it happens only when the patient mid-sternum is over the board, i.e. the medial edge of the field traverses through the board and pad. Even then, the effect occurs only at the field edge, i.e. the penumbral region.

Effects of radiation dose reduction in Volume Perfusion CT imaging of acute ischemic stroke

International Nuclear Information System (INIS)

Othman, Ahmed E.; Brockmann, Carolin; Afat, Saif; Pjontek, Rastislav; Nikobashman, Omid; Brockmann, Marc A.; Wiesmann, Martin; Yang, Zepa; Kim, Changwon; Kim, Jong Hyo

2015-01-01

To examine the influence of radiation dose reduction on image quality and sensitivity of Volume Perfusion CT (VPCT) maps regarding the detection of ischemic brain lesions. VPCT data of 20 patients with suspected ischemic stroke acquired at 80 kV and 180 mAs were included. Using realistic reduced-dose simulation, low-dose VPCT datasets with 144 mAs, 108 mAs, 72 mAs and 36 mAs (80 %, 60 %, 40 % and 20 % of the original levels) were generated, resulting in a total of 100 datasets. Perfusion maps were created and signal-to-noise-ratio (SNR) measurements were performed. Qualitative analyses were conducted by two blinded readers, who also assessed the presence/absence of ischemic lesions and scored CBV and CBF maps using a modified ASPECTS-score. SNR of all low-dose datasets were significantly lower than those of the original datasets (p <.05). All datasets down to 72 mAs (40 %) yielded sufficient image quality and high sensitivity with excellent inter-observer-agreements, whereas 36 mAs datasets (20 %) yielded poor image quality in 15 % of the cases with lower sensitivity and inter-observer-agreements. Low-dose VPCT using decreased tube currents down to 72 mAs (40 % of original radiation dose) produces sufficient perfusion maps for the detection of ischemic brain lesions. (orig.)

Evaluation of dose reduction versus standard dosing for maintenance of remission in patients with spondyloarthritis and clinical remission with anti-TNF (REDES-TNF): study protocol for a randomized controlled trial.

Science.gov (United States)

Pontes, Caridad; Gratacós, Jordi; Torres, Ferran; Avendaño, Cristina; Sanz, Jesús; Vallano, Antoni; Juanola, Xavier; de Miguel, Eugenio; Sanmartí, Raimon; Calvo, Gonzalo

2015-08-20

Dose reduction schedules of tumor necrosis factor antagonists (anti-TNF) as maintenance therapy in patients with spondyloarthritis are used empirically in clinical practice, despite the lack of clinical trials providing evidence for this practice. To address this issue the Spanish Society of Rheumatology (SER) and Spanish Society of Clinical Pharmacology (SEFC) designed a 3-year multicenter, randomized, open-label, controlled clinical trial (2 years for inclusion and 1 year of follow-up). The study is expected to include 190 patients with axial spondyloarthritis on stable maintenance treatment (≥4 months) with any anti-TNF agent at doses recommended in the summary of product characteristics. Patients will be randomized to either a dose reduction arm or maintenance of the dosing regimen as per the official labelling recommendations. Randomization will be stratified according to the anti-TNF agent received before study inclusion. Patient follow-up, visit schedule, and examinations will be maintained as per normal clinical practice recommendations according to SER guidelines. The study aims to test the hypothesis of noninferiority of the dose reduction strategy compared with standard treatment. The first patients were recruited in July 2012, and study completion is scheduled for the end of April 2015. The REDES-TNF study is a pragmatic clinical trial that aims to provide evidence to support a medical decision now made empirically. The study results may help inform clinical decisions relevant to both patients and healthcare decision makers. EudraCT 2011-005871-18 (21 December 2011).

Radiation dose reduction in soft tissue neck CT using adaptive statistical iterative reconstruction (ASIR)

Energy Technology Data Exchange (ETDEWEB)

Vachha, Behroze, E-mail: bvachha@partners.org [Neuroradiology Division, Massachusetts General Hospital, Harvard Medical School, 55 Fruit Street, Boston, MA 02114 (United States); Brodoefel, Harald; Wilcox, Carol; Hackney, David B.; Moonis, Gul [Department of Radiology, Beth Israel Deaconess Medical Center, Harvard Medical School, 330 Brookline Avenue, Boston, MA 02215 (United States)

2013-12-01

Purpose: To compare objective and subjective image quality in neck CT images acquired at different tube current–time products (275 mA s and 340 mA s) and reconstructed with filtered-back-projection (FBP) and adaptive statistical iterative reconstruction (ASIR). Materials and methods: HIPAA-compliant study with IRB approval and waiver of informed consent. 66 consecutive patients were randomly assigned to undergo contrast-enhanced neck CT at a standard tube-current–time-product (340 mA s; n = 33) or reduced tube-current–time-product (275 mA s, n = 33). Data sets were reconstructed with FBP and 2 levels (30%, 40%) of ASIR-FBP blending at 340 mA s and 275 mA s. Two neuroradiologists assessed subjective image quality in a blinded and randomized manner. Volume CT dose index (CTDIvol), dose-length-product (DLP), effective dose, and objective image noise were recorded. Signal-to-noise ratio (SNR) was computed as mean attenuation in a region of interest in the sternocleidomastoid muscle divided by image noise. Results: Compared with FBP, ASIR resulted in a reduction of image noise at both 340 mA s and 275 mA s. Reduction of tube current from 340 mA s to 275 mA s resulted in an increase in mean objective image noise (p = 0.02) and a decrease in SNR (p = 0.03) when images were reconstructed with FBP. However, when the 275 mA s images were reconstructed using ASIR, the mean objective image noise and SNR were similar to those of the standard 340 mA s CT images reconstructed with FBP (p > 0.05). Subjective image noise was ranked by both raters as either average or less-than-average irrespective of the tube current and iterative reconstruction technique. Conclusion: Adapting ASIR into neck CT protocols reduced effective dose by 17% without compromising image quality.

Radiation dose reduction in soft tissue neck CT using adaptive statistical iterative reconstruction (ASIR)

International Nuclear Information System (INIS)

Vachha, Behroze; Brodoefel, Harald; Wilcox, Carol; Hackney, David B.; Moonis, Gul

2013-01-01

Purpose: To compare objective and subjective image quality in neck CT images acquired at different tube current–time products (275 mA s and 340 mA s) and reconstructed with filtered-back-projection (FBP) and adaptive statistical iterative reconstruction (ASIR). Materials and methods: HIPAA-compliant study with IRB approval and waiver of informed consent. 66 consecutive patients were randomly assigned to undergo contrast-enhanced neck CT at a standard tube-current–time-product (340 mA s; n = 33) or reduced tube-current–time-product (275 mA s, n = 33). Data sets were reconstructed with FBP and 2 levels (30%, 40%) of ASIR-FBP blending at 340 mA s and 275 mA s. Two neuroradiologists assessed subjective image quality in a blinded and randomized manner. Volume CT dose index (CTDIvol), dose-length-product (DLP), effective dose, and objective image noise were recorded. Signal-to-noise ratio (SNR) was computed as mean attenuation in a region of interest in the sternocleidomastoid muscle divided by image noise. Results: Compared with FBP, ASIR resulted in a reduction of image noise at both 340 mA s and 275 mA s. Reduction of tube current from 340 mA s to 275 mA s resulted in an increase in mean objective image noise (p = 0.02) and a decrease in SNR (p = 0.03) when images were reconstructed with FBP. However, when the 275 mA s images were reconstructed using ASIR, the mean objective image noise and SNR were similar to those of the standard 340 mA s CT images reconstructed with FBP (p > 0.05). Subjective image noise was ranked by both raters as either average or less-than-average irrespective of the tube current and iterative reconstruction technique. Conclusion: Adapting ASIR into neck CT protocols reduced effective dose by 17% without compromising image quality

Radiation dose reduction in soft tissue neck CT using adaptive statistical iterative reconstruction (ASIR).

Science.gov (United States)

Vachha, Behroze; Brodoefel, Harald; Wilcox, Carol; Hackney, David B; Moonis, Gul

2013-12-01

To compare objective and subjective image quality in neck CT images acquired at different tube current-time products (275 mAs and 340 mAs) and reconstructed with filtered-back-projection (FBP) and adaptive statistical iterative reconstruction (ASIR). HIPAA-compliant study with IRB approval and waiver of informed consent. 66 consecutive patients were randomly assigned to undergo contrast-enhanced neck CT at a standard tube-current-time-product (340 mAs; n = 33) or reduced tube-current-time-product (275 mAs, n = 33). Data sets were reconstructed with FBP and 2 levels (30%, 40%) of ASIR-FBP blending at 340 mAs and 275 mAs. Two neuroradiologists assessed subjective image quality in a blinded and randomized manner. Volume CT dose index (CTDIvol), dose-length-product (DLP), effective dose, and objective image noise were recorded. Signal-to-noise ratio (SNR) was computed as mean attenuation in a region of interest in the sternocleidomastoid muscle divided by image noise. Compared with FBP, ASIR resulted in a reduction of image noise at both 340 mAs and 275 mAs. Reduction of tube current from 340 mAs to 275 mAs resulted in an increase in mean objective image noise (p=0.02) and a decrease in SNR (p = 0.03) when images were reconstructed with FBP. However, when the 275 mAs images were reconstructed using ASIR, the mean objective image noise and SNR were similar to those of the standard 340 mAs CT images reconstructed with FBP (p>0.05). Subjective image noise was ranked by both raters as either average or less-than-average irrespective of the tube current and iterative reconstruction technique. Adapting ASIR into neck CT protocols reduced effective dose by 17% without compromising image quality. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

Reduction of Dose Delivered to Organs at Risk in Prostate Cancer Patients via Image-Guided Radiation Therapy

International Nuclear Information System (INIS)

Pawlowski, Jason M.; Yang, Eddy S.; Malcolm, Arnold W.; Coffey, Charles W.; Ding, George X.

2010-01-01

Purpose: To determine whether image guidance can improve the dose delivered to target organs and organs at risk (OARs) for prostate cancer patients treated with intensity-modulated radiotherapy (IMRT). Methods and Materials: Eight prostate cancer patients were treated with IMRT to 76 Gy at 2 Gy per fraction. Daily target localization was performed via alignment of three intraprostatic fiducials and weekly kV-cone beam computed tomography (CBCT) scans. The prostate and OARs were manually contoured on each CBCT by a single physician. Daily patient setup shifts were obtained by comparing alignment of skin tattoos with the treatment position based on fiducials. Treatment fields were retrospectively applied to CBCT scans. The dose distributions were calculated using actual treatment plans (an 8-mm PTV margin everywhere except for 6-mm posteriorly) with and without image guidance shifts. Furthermore, the feasibility of margin reduction was evaluated by reducing planning margins to 4 mm everywhere except for 3 mm posteriorly. Results: For the eight treatment plans on the 56 CBCT scans, the average doses to 98% of the prostate (D98) were 102% (range, 99-104%) and 99% (range, 45-104%) with and without image guidance, respectively. Using margin reduction, the average D98s were 100% (range, 84-104%) and 92% (range, 40-104%) with and without image guidance, respectively. Conclusions: Currently, margins used in IMRT plans are adequate to deliver a dose to the prostate with conventional patient positioning using skin tattoos or bony anatomy. The use of image guidance may facilitate significant reduction of planning margins. Future studies to assess the efficacy of decreasing margins and improvement of treatment-related toxicities are warranted.

Radiation dose reduction to the male gonads during MDCT: the effectiveness of a lead shield.

Science.gov (United States)

Hohl, Christian; Mahnken, Andreas H; Klotz, Ernst; Das, Marco; Stargardt, Achim; Mühlenbruch, Georg; Schmidt, Thorsten; Günther, Rolf W; Wildberger, Joachim E

2005-01-01

Our study was designed to quantify the effect of a standard gonad shield on the testicular radiation exposure due to scatter during routine abdominopelvic MDCT. Routine abdominopelvic MDCT was performed in 34 patients with gonadal lead shielding and 32 patients without this shielding; the testes were not exposed to the direct beam during the examination. We estimated the testicular dose administered with thermoluminescent dosimetry, taking into account each patient's body weight and body mass index (BMI). With a 1-mm lead shield, the mean testicular dose was reduced from 2.40 to 0.32 mSv, a reduction of 87%. The difference was found to be statistically significant (p Shielding the male gonads reduces the testicular radiation dose during abdominopelvic MDCT significantly and can be recommended for routine use.

SU-E-T-348: Effect of Treatment Table and Immobilization Devices On Surface Dose When Using a GRID Technique

Energy Technology Data Exchange (ETDEWEB)

Gajdos, S; Donaghue, J [Akron General Medical Center, Akron, OH (United States)

2015-06-15

Purpose: To determine the increase of surface dose of MLC-designed GRID therapy in the presence of immobilization devices and treatment table. Methods: To create a GRID field, our facility utilizes an MLC consisting of four millimeter wide leaves. The field is designed to have aperture sizes of 0.8 cm X 0.8 cm with inter-aperture distance of 3.2 cm. Gafchromic EBT3 film was placed between the surface of a solid water phantom and the immobilization device. The treatment table was also present within the beam path. The devices consist of carbon fiber exterior shell. A piece of film was also placed at maximal depth for the photon energy of 10 MV. Image files were converted to dose per a calibration curve based on the selected red channel. The surface dose to maximum dose was established by comparing the ratio of seven centrally located aperture regions-of-interest and four adjacent inter-aperture regions-of-interest were measured with the available software tools. Results: With no devices present in beam path, the ratio of surface dose to maximum dose was 11.5% ± 0.3% for aperture region and 7.0% ± 0.1% for inter-aperture region. When devices are present, the ratio of surface dose to maximum dose was 45.2% ± 0.5% and 33.8% ± 1.1%, respectively. Due to the presence of devices, the surface dose increases in aperture region by 3.8 times or in the inter-aperture region by 4.7 times. Conclusion: The purpose of using GRID technique is to deliver a single fractional dose in range of 15–20 Gy to a bulky lesion while also preserving skin tolerance. The increase of surface dose due to devices placed in beam path may increase the chance of skin toxicity in GRID therapy. Care should be used to determine best manageable patient immobilization while considering skin dose especially for posteriorly located lesions.

Radiation dose reduction with dictionary learning based processing for head CT

International Nuclear Information System (INIS)

Chen, Yang; Shi, Luyao; Hu, Yining; Luo, Limin; Yang, Jiang; Yin, Xindao; Coatrieux, Jean-Louis

2014-01-01

In CT, ionizing radiation exposure from the scan has attracted much concern from patients and doctors. This work is aimed at improving head CT images from low-dose scans by using a fast Dictionary learning (DL) based post-processing. Both Low-dose CT (LDCT) and Standard-dose CT (SDCT) nonenhanced head images were acquired in head examination from a multi-detector row Siemens Somatom Sensation 16 CT scanner. One hundred patients were involved in the experiments. Two groups of LDCT images were acquired with 50 % (LDCT50 %) and 25 % (LDCT25 %) tube current setting in SDCT. To give quantitative evaluation, Signal to noise ratio (SNR) and Contrast to noise ratio (CNR) were computed from the Hounsfield unit (HU) measurements of GM, WM and CSF tissues. A blinded qualitative analysis was also performed to assess the processed LDCT datasets. Fifty and seventy five percent dose reductions are obtained for the two LDCT groups (LDCT50 %, 1.15 ± 0.1 mSv; LDCT25 %, 0.58 ± 0.1 mSv; SDCT, 2.32 ± 0.1 mSv; P < 0.001). Significant SNR increase over the original LDCT images is observed in the processed LDCT images for all the GM, WM and CSF tissues. Significant GM–WM CNR enhancement is noted in the DL processed LDCT images. Higher SNR and CNR than the reference SDCT images can even be achieved in the processed LDCT50 % and LDCT25 % images. Blinded qualitative review validates the perceptual improvements brought by the proposed approach. Compared to the original LDCT images, the application of DL processing in head CT is associated with a significant improvement of image quality.

Radiation dose reduction without compromise to image quality by alterations of filtration and focal spot size in cerebral angiography

Energy Technology Data Exchange (ETDEWEB)

Kim, Dong Joon; Park, Min Keun; Jung, Da Eun; Kang, Jung Han; Kim, Byung Moon [Dept. of Radiology, Yonsei University College of Medicine, Seoul (Korea, Republic of)

2017-08-01

Different angiographic protocols may influence the radiation dose and image quality. In this study, we aimed to investigate the effects of filtration and focal spot size on radiation dose and image quality for diagnostic cerebral angiography using an in-vitro model and in-vivo patient groups. Radiation dose and image quality were analyzed by varying the filtration and focal spot size on digital subtraction angiography exposure protocols (1, inherent filtration + large focus; 2, inherent + small; 3, copper + large; 4, copper + small). For the in-vitro analysis, a phantom was used for comparison of radiation dose. For the in-vivo analysis, bilateral paired injections, and patient cohort groups were compared for radiation dose and image quality. Image quality analysis was performed in terms of contrast, sharpness, noise, and overall quality. In the in-vitro analysis, the mean air kerma (AK) and dose area product (DAP)/frame were significantly lower with added copper filtration (protocols 3 and 4). In the in-vivo bilateral paired injections, AK and DAP/frame were significantly lower with filtration, without significant difference in image quality. The patient cohort groups with added filtration (protocols 3 and 4) showed significant reduction of total AK and DAP/patient without compromise to the image quality. Variations in focal spot size showed no significant differences in radiation dose and image quality. Addition of filtration for angiographic exposure studies can result in significant total radiation dose reduction without loss of image quality. Focal spot size does not influence radiation dose and image quality. The routine angiographic protocol should be judiciously investigated and implemented.

Iterative methods for dose reduction and image enhancement in tomography

Science.gov (United States)

Miao, Jianwei; Fahimian, Benjamin Pooya

2012-09-18

A system and method for creating a three dimensional cross sectional image of an object by the reconstruction of its projections that have been iteratively refined through modification in object space and Fourier space is disclosed. The invention provides systems and methods for use with any tomographic imaging system that reconstructs an object from its projections. In one embodiment, the invention presents a method to eliminate interpolations present in conventional tomography. The method has been experimentally shown to provide higher resolution and improved image quality parameters over existing approaches. A primary benefit of the method is radiation dose reduction since the invention can produce an image of a desired quality with a fewer number projections than seen with conventional methods.

Data base on nuclear power plant dose reduction research projects

Energy Technology Data Exchange (ETDEWEB)

Khan, T.A.; Dionne, B.J.; Baum, J.W.

1985-12-01

This report contains project information on the research and development activities of the nuclear power industry in the area of dose reduction. It is based on a data base of information set up at the ALARA Center of Brookhaven National Laboratory. One purpose of this report is to draw attention to work in progress and to enable researchers and subscribers to obtain further information from the investigators and project managers. Information is provided on 180 projects, divided according to whether they are oriented to Engineering Research or to Health Physics Technology. The report contains indices on main category, project manager, principal investigator, sponsoring organization, contracting organization, and subject. This is an initial report. It is intended that periodic updates be issued whenever sufficient material has been accumulated.

Data base on nuclear power plant dose reduction research projects

International Nuclear Information System (INIS)

Khan, T.A.; Dionne, B.J.; Baum, J.W.

1985-12-01

This report contains project information on the research and development activities of the nuclear power industry in the area of dose reduction. It is based on a data base of information set up at the ALARA Center of Brookhaven National Laboratory. One purpose of this report is to draw attention to work in progress and to enable researchers and subscribers to obtain further information from the investigators and project managers. Information is provided on 180 projects, divided according to whether they are oriented to Engineering Research or to Health Physics Technology. The report contains indices on main category, project manager, principal investigator, sponsoring organization, contracting organization, and subject. This is an initial report. It is intended that periodic updates be issued whenever sufficient material has been accumulated

Reduction of outdoor and indoor ambient dose equivalent after decontamination in the Fukushima evacuation zones

International Nuclear Information System (INIS)

Yoshida-Ohuchi, Hiroko; Kanagami, Takashi; Naitoh, Yutaka; Kameyama, Mizuki; Hosoda, Masahiro

2017-01-01

One of the most urgent issues following the accident at the Fukushima Daiichi nuclear power plant (FDNPP) was the remediation of the land, in particular, for residential area contaminated by the radioactive materials discharged. In this study, the effect of decontamination on reduction of ambient dose equivalent outdoors and indoors was evaluated. The latter is essential for residents as most individuals spend a large portion of their time indoors. From December 2012 to November 2014, thirty-seven Japanese single-family detached wooden houses were investigated before and after decontamination in evacuation zones. Outdoor and indoor dose measurements (n=84 and 114, respectively) were collected based on in situ measurements using the NaI (Tl) scintillation surveymeter. The outdoor ambient dose equivalents [H"*(10)_o_u_t] ranged from 0.61 to 3.71 μSv h"-"1 and from 0.23 to 1.32 μSv h"-"1 before and after decontamination, respectively. The indoor ambient dose equivalents [H"*(10)"i"n] ranged from 0.29 to 2.53 μSv h"-"1 and from 0.16 to 1.22 μSv h"-"1 before and after decontamination, respectively. The values of reduction efficiency (RE), defined as the ratio by which the radiation dose has been reduced via decontamination, were evaluated as 0.47±0.13, 0.51±0.13, and 0.58±0.08 (average±σ) when H"*(10)_o_u_t <1.0 μSv h"-"1, 1.0 μSv h"-"1 < H"*(10)_o_u_t <2.0 μSv h"-"1, and 2.0 μSv h"-"1< H"*(10)_o_u_t, respectively, indicating the values of RE increased as H"*(10)_o_u_t increased. It was found that the values of RE were 0.53±0.12 outdoors and 0.41±0.09 indoors, respectively, indicating RE was larger outdoors than indoors. Indoor dose is essential as most individuals spend a large portion of their time indoors. The difference between outdoors and indoors should be considered carefully in order to estimate residents’ exposure dose before their returning home