Kim, Leonard, E-mail: kimlh@umdnj.edu [Department of Radiation Oncology, Cancer Institute of New Jersey, Robert Wood Johnson Medical School, University of Medicine and Dentistry of New Jersey, New Brunswick, NJ (United States); Narra, Venkat; Yue, Ning [Department of Radiation Oncology, Cancer Institute of New Jersey, Robert Wood Johnson Medical School, University of Medicine and Dentistry of New Jersey, New Brunswick, NJ (United States)
2013-07-01
Recent studies have reported potentially clinically meaningful dose differences when heterogeneity correction is used in breast balloon brachytherapy. In this study, we report on the relationship between heterogeneity-corrected and -uncorrected doses for 2 commonly used plan evaluation metrics: maximum point dose to skin surface and maximum point dose to ribs. Maximum point doses to skin surface and ribs were calculated using TG-43 and Varian Acuros for 20 patients treated with breast balloon brachytherapy. The results were plotted against each other and fit with a zero-intercept line. Max skin dose (Acuros) = max skin dose (TG-43) ? 0.930 (R{sup 2} = 0.995). The average magnitude of difference from this relationship was 1.1% (max 2.8%). Max rib dose (Acuros) = max rib dose (TG-43) ? 0.955 (R{sup 2} = 0.9995). The average magnitude of difference from this relationship was 0.7% (max 1.6%). Heterogeneity-corrected maximum point doses to the skin surface and ribs were proportional to TG-43-calculated doses. The average deviation from proportionality was 1%. The proportional relationship suggests that a different metric other than maximum point dose may be needed to obtain a clinical advantage from heterogeneity correction. Alternatively, if maximum point dose continues to be used in recommended limits while incorporating heterogeneity correction, institutions without this capability may be able to accurately estimate these doses by use of a scaling factor.
A new maximum power point tracking system
W. J. A. Teulings; J. C. Marpinard; A. Capel; D. O'Sullivan
1993-01-01
In power systems involving a load, a battery and a solar array, MPPT (maximum power point tracking) is a promising principle to extract the maximum amount of energy from the solar array and distribute it to the battery and loads. A digital hill-climbing control strategy combined with a bidirectional current mode power cell is presented that makes it possible to
Maximum tolerated dose: clinical endpoint for a bygone era?
Chris H. Takimoto
2009-01-01
The maximum tolerated dose (MTD) has been the classically recommended phase II dose for cytotoxic chemotherapy anticancer\\u000a agents. However, the development of molecular targeted therapies with highly specific mechanisms of action has raised questions\\u000a about the paradigm of dosing at the MTD. Inhibition of the molecular target may occur at dose levels substantially below those\\u000a producing dose limiting toxicities. The
Individual Module Maximum Power Point Tracking for Thermoelectric Generator Systems
Schaltz, Erik
Individual Module Maximum Power Point Tracking for Thermoelectric Generator Systems Casper Vadstrup of Thermo Electric Generator (TEG) systems a power converter is often inserted between the TEG system
Simplified maximum power point controller for PV installations
D. B. Snyman; J. H. R. Enslin
1993-01-01
A new low-cost, simplified control strategy, based on the positive feedback of the output current in a maximum power point tracking (MPPT) converter, is introduced. Cost effective MPPT reduces the energy cost of renewable energy generators by optimizing the utilization of the renewable energy source. Maximum power point tracking for relative small photovoltaic (PV) power systems, with battery back-up, is
Savannah River Site radioiodine atmospheric releases and offsite maximum doses
Marter, W.L.
1990-11-01
Radioisotopes of iodine have been released to the atmosphere from the Savannah River Site since 1955. The releases, mostly from the 200-F and 200-H Chemical Separations areas, consist of the isotopes, I-129 and 1-131. Small amounts of 1-131 and 1-133 have also been released from reactor facilities and the Savannah River Laboratory. This reference memorandum was issued to summarize our current knowledge of releases of radioiodines and resultant maximum offsite doses. This memorandum supplements the reference memorandum by providing more detailed supporting technical information. Doses reported in this memorandum from consumption of the milk containing the highest I-131 concentration following the 1961 1-131 release incident are about 1% higher than reported in the reference memorandum. This is the result of using unrounded 1-131 concentrations of I-131 in milk in this memo. It is emphasized here that this technical report does not constitute a dose reconstruction in the same sense as the dose reconstruction effort currently underway at Hanford. This report uses existing published data for radioiodine releases and existing transport and dosimetry models.
Maximum likelihood point cloud acquisition from a mobile platform
Todor Stoyanov; Achim J. Lilienthal
2009-01-01
This paper describes an approach to acquire locally consistent range data scans from a moving sensor platform. Data from a vertically mounted rotating laser scanner and odometry position estimates are fused and used to estimate maximum likelihood point clouds. An estimation algorithm is applied to reduce the accumulated error after a full rotation of the range finder. A configuration consisting
Multiple Test Procedures for Identifying the Minimum Effective and Maximum Safe Doses of a Drug
Tamhane, Ajit C.
Multiple Test Procedures for Identifying the Minimum Effective and Maximum Safe Doses of a Drug of a drug by finding its minimum effective and maximum safe doses (MINED and MAXSD). The MINED is the lowest dose that exceeds the mean efficacy of the zero dose by a specified threshold, and the MAXSD
Maximum likelihood estimation for cytogenetic dose-response curves
E. L Frome; R. J. DuFrain
1983-01-01
In vitro dose-response curves are used to describe the relation between the yield of dicentric chromosome aberrations and radiation dose for human lymphocytes. The dicentric yields follow the Poisson distribution, and the expected yield depends on both the magnitude and the temporal distribution of the dose for low LET radiation. A general dose-response model that describes this relation has been
Maximum likelihood estimation for cytogenetic dose-response curves
E. L. Frome; R. J. DuFrain
1986-01-01
In vitro dose-response curves are used to describe the relation between chromosome aberrations and radiation dose for human lymphocytes. The lymphocytes are exposed to low-LET radiation, and the resulting dicentric chromosome aberrations follow the Poisson distribution. The expected yield depends on both the magnitude and the temporal distribution of the dose. A general dose-response model that describes this relation has
A maximum power point tracking algorithm for photovoltaic applications
NASA Astrophysics Data System (ADS)
Nelatury, Sudarshan R.; Gray, Robert
2013-05-01
The voltage and current characteristic of a photovoltaic (PV) cell is highly nonlinear and operating a PV cell for maximum power transfer has been a challenge for a long time. Several techniques have been proposed to estimate and track the maximum power point (MPP) in order to improve the overall efficiency of a PV panel. A strategic use of the mean value theorem permits obtaining an analytical expression for a point that lies in a close neighborhood of the true MPP. But hitherto, an exact solution in closed form for the MPP is not published. This problem can be formulated analytically as a constrained optimization, which can be solved using the Lagrange method. This method results in a system of simultaneous nonlinear equations. Solving them directly is quite difficult. However, we can employ a recursive algorithm to yield a reasonably good solution. In graphical terms, suppose the voltage current characteristic and the constant power contours are plotted on the same voltage current plane, the point of tangency between the device characteristic and the constant power contours is the sought for MPP. It is subject to change with the incident irradiation and temperature and hence the algorithm that attempts to maintain the MPP should be adaptive in nature and is supposed to have fast convergence and the least misadjustment. There are two parts in its implementation. First, one needs to estimate the MPP. The second task is to have a DC-DC converter to match the given load to the MPP thus obtained. Availability of power electronics circuits made it possible to design efficient converters. In this paper although we do not show the results from a real circuit, we use MATLAB to obtain the MPP and a buck-boost converter to match the load. Under varying conditions of load resistance and irradiance we demonstrate MPP tracking in case of a commercially available solar panel MSX-60. The power electronics circuit is simulated by PSIM software.
Power and Sample Size Determination for a Stepwise Test Procedure for Finding the Maximum Safe Dose
Tamhane, Ajit C.
Power and Sample Size Determination for a Stepwise Test Procedure for Finding the Maximum Safe Dose This paper addresses the problem of power and sample size calculation for a stepwise multiple test procedure functions, respectively. The sample sizes necessary on the zero dose control and each of the positive doses
An approximate, maximum terminal velocity descent to a point
Eisler, G.R.; Hull, D.G.
1987-01-01
No closed form control solution exists for maximizing the terminal velocity of a hypersonic glider at an arbitrary point. As an alternative, this study uses neighboring extremal theory to provide a sampled data feedback law to guide the vehicle to a constrained ground range and altitude. The guidance algorithm is divided into two parts: 1) computation of a nominal, approximate, maximum terminal velocity trajectory to a constrained final altitude and computation of the resulting unconstrained groundrange, and 2) computation of the neighboring extremal control perturbation at the sample value of flight path angle to compensate for changes in the approximate physical model and enable the vehicle to reach the on-board computed groundrange. The trajectories are characterized by glide and dive flight to the target to minimize the time spent in the denser parts of the atmosphere. The proposed on-line scheme successfully brings the final altitude and range constraints together, as well as compensates for differences in flight model, atmosphere, and aerodynamics at the expense of guidance update computation time. Comparison with an independent, parameter optimization solution for the terminal velocity is excellent. 6 refs., 3 figs.
Design of optimum Maximum Power Point Tracking algorithm for solar panel
A. Thenkani; N. Senthil Kumar
2011-01-01
It is important to track the maximum power point of the Photovoltaic panel, as the electrical power supplied by solar array depends on insolation, temperature and load. Maximum Power Point Tracking ( MPPT) is an Power electronic system that operates the photovoltaic modules to produce maximum power. MPPT varies the electrical operating point of the modules and enables them to
Datta, D; Singh, Sanjay; Johnson, B E; Kushwaha, H S
2008-01-01
Data collection and its analysis in the field of nuclear safety is an important task in the sense that it powers the improvement of safety as well as reliability of the plant. Thus, occupational exposure data analysis is presented to measure the safety or reliability of radiation protection of a given facility. It also is required as a basic input in making decisions on radiation protection regulations and recommendations. A common practice in radiation protection is to record a zero for observation below minimum detection limit (MDL) doses, which leads to an underestimation of true doses and overestimation of the dose-response relationship. Exposure data (both external and internal) are collected by monitoring each individual and this kind of monitoring generally is graded as low-level monitoring. So, in such low-level monitoring, the occurrence of exposure below MDL invites statistical complications for estimating mean and variance because the data are generally censored, i.e observations below MDL are marked. In Type I censoring, the point of censoring (e.g. the detection limit) is 'fixed' a priori for all observations and the number of the censored observations varies. In Type II censoring, the number of censored observations is fixed a priori, and the point of censoring vary. The methodology generally followed in estimating mean and variance with these censored data was the replacement of missing dose by half the MDL. In this paper, authors have used the maximum likelihood estimation (MLE) approach for the estimation of mean and standard deviation. A computer code BDLCENSOR has been developed in which all these MLE-based advanced algorithms are implemented. In addition to the MLE-based method, an expectation maximisation algorithm has also been implemented. The code is written using Visual BASIC 6.0. The paper describes the details of the algorithms adopted for handling such censored data to estimate bias free mean and standard deviation. PMID:18083720
Hamby, D.M.
1994-02-01
An EXCEL{reg_sign} spreadsheet has been developed that, when combined with the PC version of XOQDOQ, will generate estimates of maximum individual dose from routine atmospheric releases of radionuclides. The spreadsheet, MAXINE, utilizes a variety of atmospheric dispersion factors to calculate radiation dose as recommended by the US Nuclear Regulatory Commission in Regulatory Guide 1.109 [USNRC 1977a]. The methodology suggested herein includes use of both the MAXINE spreadsheet and the PC version of XOQDOQ.
Maximum Power Point Tracking Control for Photovoltaic System Using Adaptive Neuro-Fuzzy
Paris-Sud XI, Université de
Maximum Power Point Tracking Control for Photovoltaic System Using Adaptive Neuro- Fuzzy "ANFIS Adaptive Neuro- Fuzzy "ANFIS". The PV array has an optimum operating point to generate maximum power conventional controller like Adaptive Neuro-Fuzzy "ANFIS" and fuzzy logic controller is proposed and simulated
Maximum-Power-Point Tracking Method of Photovoltaic Using Only Single Current Sensor
Fujimoto, Hiroshi
» «Solar cell systems» Abstract This paper describes a novel strategy of maximum-power-point trackingMaximum-Power-Point Tracking Method of Photovoltaic Using Only Single Current Sensor Toshihiko-2188, Japan Phone: +81-258-47-9510, Fax: +81-258-47-9500 e-mail: tnoguchi@vos.nagaokaut.ac.jp URL: pelab
Rae-Young Kim; Jih-Sheng Lai
2007-01-01
A boost-cascaded-with-buck converter based power conditioning system employing a seamless mode transfer maximum power point tracking controller is proposed to maximize energy production of a thermoelectric generator while balancing the vehicle battery charging, alternator output power, and vehicle load. When a maximum power point exceeds a load demand, the proposed controller switches to a power matching mode seamlessly by a
THE MINIMUM AND MAXIMUM NUMBER OF RATIONAL POINTS ON JACOBIAN SURFACES OVER FINITE FIELDS
Paris-Sud XI, Université de
THE MINIMUM AND MAXIMUM NUMBER OF RATIONAL POINTS ON JACOBIAN SURFACES OVER FINITE FIELDS SAFIA HALOUI Abstract. We give some bounds on the numbers of rational points on abelian varieties and jacobians of rational points on jacobians varieties of dimension 2. 1. Introduction We are interested in the number
Submodule Integrated Distributed Maximum Power Point Tracking for Solar Photovoltaic Applications
Pilawa-Podgurski, Robert C. N.
This paper explores the benefits of distributed power electronics in solar photovoltaic applications through the use of submodule integrated maximum power point trackers (MPPT). We propose a system architecture that provides ...
A novel maximum power point tracker for PV panels using switching frequency modulation
K. K. Tse; M. T. Ho; Henry S.-H. Chung; S. Y. Hui
2002-01-01
A novel technique for efficiently extracting maximum power from photovoltaic (PV) panels is presented. The power conversion stage, which is connected between a PV panel and a load or bus, is a SEPIC or Cuk converter or their derived circuits operating in discontinuous inductor-current or capacitor-voltage mode. A method of locating the maximum power point (MPP) is based on injecting
Comparison of maximum power point control methods for thermoelectric power generator
H. Nagayoshi; T. Kajikawa; T. Sugiyama
2002-01-01
This paper describes the comparison of operating point control methods such as maximum power point tracking control (MPPT) and a constant voltage control applied to the thermoelectric devices. To experimentally evaluate the power control methods, a one-chip micro controller controlled DC-DC converter was inserted between the thermoelectric module and a load. The derived power from the module by constant voltage
Kwong, Kenneth K.; Wu, Ona; Chan, Suk-Tak; Nelissen, Koen; Kholodov, Mykhaylo; Chesler, David A.
2011-01-01
Time of arrival (TOA) of a bolus of contrast agent to the tissue voxel is a reference time point critical for the Early Time Points Perfusion Imaging Method (ET) to make relative cerebral blood flow (rCBF) maps. Due to the low contrast to noise (CNR) condition at TOA, other useful reference time points known as relative time of arrival data points (rTOA) are investigated. Candidate rTOA's include the time to reach the maximum derivative, the maximum second derivative, and the maximum fractional derivative. Each rTOA retains the same relative time distance from TOA for all tissue flow levels provided that ET's basic assumption is met, namely, no contrast agent has a chance to leave the tissue before the time of rTOA. The ET's framework insures that rCBF estimates by different orders of the derivative are theoretically equivalent to each other and monkey perfusion imaging results supported the theory. In rCBF estimation, maximum values of higher order fractional derivatives may be used to replace the maximum derivative which runs a higher risk of violating ET's assumption. Using the maximum values of the derivative of orders ranging from 1 to 1.5 to 2, estimated rCBF results were found to demonstrate a gray-white matter ratio of approximately 3, a number consistent with flow ratio reported in the literature. PMID:21600995
Improved lung dose calculation using tissue--maximum ratios in the Batho correction
El-Khatib, E.; Battista, J.J.
1984-05-01
We have reexamined the Batho power law for computing the dose within and beyond lung irradiated with small and large fields of cobalt-60 and 6-MV x rays. Using slab phantoms consisting of two materials, agreement between calculated and measured doses was within 2% inside lung for 6-MV x irradiation, but much poorer (9%) for cobalt-60 irradiation. For cobalt-60 irradiation, tissue--air ratios (TARs) were used initially in the Batho equation, while for 6-MV x rays, tissue--maximum ratios (TMRs) were used. When we substituted TMR values instead of TAR values for cobalt-60, we found marked improvement by nearly 5% in the accuracy of dose calculated within lung. This was confirmed by numerical comparison of the Batho expression with an analytic solution of the primary and first-scattered radiation. We therefore encourage the use of TMRs for cobalt-60 radiation, expecially for larger radiation fields, and provide measured data tables for field sizes up to 50 x 50 cm/sup 2/, and depths up to 30 cm. In addition to unifying the dosimetry for all megavoltage irradiation, this approach improves the accuracy of doses calculated within lung.
Review of the maximum power point tracking algorithms for stand-alone photovoltaic systems
V. Salas; E. Olías; A. Barrado; A. Lázaro
2006-01-01
A survey of the algorithms for seeking the maximum power point (MPP) is proposed. As has been shown, there are many ways of distinguishing and grouping methods that seek the MPP from a photovoltaic (PV) generator. However, in this article they are grouped as either direct or nondirect methods. The indirect methods (“quasi seeks”) have the particular feature that the
Artificial Neural Network Maximum Power Point Tracker for Solar Electric Vehicle
Theodore Amissah Ocran; Junyi Cao; Binggang Cao; Xinghua Sun
2005-01-01
This paper proposes an artificial neural network maximum power point tracker (MPPT) for solar electric vehicles. The MPPT is based on a highly efficient boost converter with insulated gate bipolar transistor (IGBT) power switch. The reference voltage for MPPT is obtained by artificial neural network (ANN) with gradient descent momentum algorithm. The tracking algorithm changes the duty-cycle of the converter
N. Srighakollapu; P. S. Sensarma
2008-01-01
This paper proposes a control strategy for variable speed wind energy conversion system (WECS), incorporating maximum power point tracking (MPPT) algorithm, using direct driven permanent magnet synchronous generator (PMSG). The generator is operated in the speed control mode below the base speed by controlling the terminal voltage using three phase front-end active-rectifier feeding power to the DC bus. The voltage
Simplified feed-forward control of the maximum power point in PV installations
J. H. R. Enslin; D. B. Snyman
1992-01-01
A novel simplified control strategy, based on the positive feedback of a maximum power point tracking (MPPT) converter output current, is introduced. Cost-effective MPPT reduces the energy cost from renewable energy generators by optimizing the utilization of the renewable energy source. MPPT for relative small photovoltaic (PV) systems, with battery back-up, is achieved by maximization of the output current to
A Control Method for Maximum Power Point Tracking in Stand-Alone-Type PV Generation Systems
NASA Astrophysics Data System (ADS)
Itako, Kazutaka; Mori, Takeaki
In this paper, a new control method for maximum power point tracking (MPPT) in stand-alone-type PV generaton systems is proposed. In this control method, the operations detecting the maximum power point and tracking its point are alternately carried out by using a step-up DC—DC converter. This method requires neither the measurement of temperature and insolation level nor PV array model. In a stand-alone-type application with a battery load, the design method for the boost inductance L of the step-up DC—DC converter is described, and the experimental results show that the use of the proposed MPPT control increases the PV generated energy by 14.8% compared to the conventional system.
Brenner, David Jonathan
Breast radiotherapy in the prone position primarily reduces the maximum out-of-field measured dose advantages of prone position breast radiotherapy in terms of the radiation exposure to out-of-field organs) was to the treatment volume, the more dose spar- ing was seen for prone vs supine positioning. Breast radiotherapy
Maximum likelihood estimation of proton irradiated field and deposited dose distribution
Inaniwa, Taku; Kohno, Toshiyuki; Yamagata, Fumiko; Tomitani, Takehiro; Sato, Shinji; Kanazawa, Mitsutaka; Kanai, Tatsuaki; Urakabe, Eriko [Department of Energy Sciences, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama 226-8502 (Japan); Department of Accelerator and Medical Physics, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555 (Japan); Proton Therapy Division, Shizuoka Cancer Center Research Institute, 1007 Shimonagakubo, Nagaizumi-cho, Suntou-gun, Shizuoka Prefecture 411-8777 (Japan)
2007-05-15
In proton therapy, it is important to evaluate the field irradiated with protons and the deposited dose distribution in a patient's body. Positron emitters generated through fragmentation reactions of target nuclei can be used for this purpose. By detecting the annihilation gamma rays from the positron emitters, the annihilation gamma ray distribution can be obtained which has information about the quantities essential to proton therapy. In this study, we performed irradiation experiments with mono-energetic proton beams of 160 MeV and the spread-out Bragg peak beams to three kinds of targets. The annihilation events were detected with a positron camera for 500 s after the irradiation and the annihilation gamma ray distributions were obtained. In order to evaluate the range and the position of distal and proximal edges of the SOBP, the maximum likelihood estimation (MLE) method was applied to the detected distributions. The evaluated values with the MLE method were compared with those estimated from the measured dose distributions. As a result, the ranges were determined with the difference between the MLE range and the experimental range less than 1.0 mm for all targets. For the SOBP beams, the positions of distal edges were determined with the difference less than 1.0 mm. On the other hand, the difference amounted to 7.9 mm for proximal edges.
NASA Astrophysics Data System (ADS)
Choi, Jang-Hwan; Constantin, Dragos; Fahrig, Rebecca
2015-03-01
The mean dose over the central phantom plane (i.e., z = 0, dose maximum image) is useful in that it allows us to compare radiation dose levels across different CT scanners and acquisition protocols. The mean dose from a conventional CT scan with table translation is typically estimated by weighted CTDI (CTDIW). However, conventional CTDIW has inconsistent performance, depending on its weighting coefficients ("1/2 and 1/2" or "1/3 and 2/3") and acquisition protocols. We used a Monte Carlo (MC) model based on Geant4 (GEometry ANd Tracking) to generate dose profiles in the central plane of the CTDI phantom. MC simulations were carried out for three different sizes of z-collimator and different tube voltages (80, 100, or 120 kVp), a tube current of 80 mA, and an exposure time of 25 ms. We derived optimal weighting coefficients by taking the integral of the radial dose profiles. The first-order linear equation and the quadratic equation were used to fit the dose profiles along the radial direction perpendicular to the central plane, and the fitted profiles were revolved about the Z-axis to compute the mean dose (i.e., total volume under the fitted profiles/the central plane area). The integral computed using the linear equation resulted in the same equation as conventional CTDIW, and the integral computed using the quadratic equation resulted in a new CTDIW (CTDIMW) that incorporates different weightings ("2/3 and 1/3") and the middle dose point instead of the central dose point. Compared to the results of MC simulations, our new CTDIMW showed less error than the previous CTDIW methods by successfully incorporating the curvature of the dose profiles regardless of acquisition protocols. Our new CTDIMW will also be applicable to the AAPM-ICRU phantom, which has a middle dose point.
TS Fuzzy Maximum Power Point Tracking Control of Solar Power Generation Systems
Chian-Song Chiu
2010-01-01
This paper presents maximum power point tracking (MPPT) control for stand-alone solar power generation systems via the Takagi-Sugeno (T-S) fuzzy-model-based approach. In detail, we consider a dc\\/dc buck converter to regulate the output power of the photovoltaic panel array. First, the system is represented by the T-S fuzzy model. Next, in order to reduce the number of measured signals, a
Lawrence K. Letting; Josiah L. Munda; Yskandar Hamam
\\u000a This chapter presents the design and optimization of a fuzzy logic controller (FLC) with a minimum rule base for maximum power\\u000a point tracking in photovoltaic (PV) systems. A strategy for automated design and optimization of the FLC using genetic algorithms\\u000a is proposed. An optimal Takagi-Sugeno FLC with a rule base of only 9-rules is realized and compared to the conventional
Maximum loadability of power systems using interior point nonlinear optimization method
G. D. Irisarri; X. Wang; J. Tong; S. Mokhtari
1997-01-01
This paper proposes a nonlinear optimization interior point (IP) method for the determination of maximum loadability in a power system. Details of the implementation of pure primal-dual and predictor-corrector primal-dual IP algorithms are presented. It is shown that most of the computational effort of the algorithm is taken by the formation and factorization of the augmented Hessian matrix of the
Maximum loadability of power systems using interior point non-linear optimization method
G. D. Irisarri; X. Wang; J. Tong; S. Mokhtari
1997-01-01
This paper proposes a non-linear optimization Interior Point (IP) method for the determination of maximum loadability in a power system. Details of the implementation of pure primal-dual and predictor-corrector primal-dual IP algorithms are presented. It is shown that most of the computational effort of the algorithm is taken by the formation and factorization of the augmented Hessian matrix of the
Rae-Young Kim; Jih-Sheng Lai
2008-01-01
A boost-cascaded-with-buck converter-based power conditioning system employing a seamless mode transfer maximum power point tracking controller is proposed to maximize energy production of a thermoelectric generator while balancing a vehicle battery, alternator output power, and vehicle load. When a vehicle battery is fully charged, the proposed controller switches to a power matching mode seamlessly by a dual loop control system,
A novel maximum power point tracking algorithms for stand-alone photovoltaic system
Shiqiong Zhou; Longyun Kang; Jing Sun; Guifang Guo; Bo Cheng; Binggang Cao; Yiping Tang
2010-01-01
A novel control algorithm, namely subsection adaptive hill climbing method (SSAHC), for seeking the maximum power point (MPP)\\u000a of a photovoltaic (PV) panel for any temperature and solar radiation level is proposed. The algorithm is thus a combination\\u000a of the subsection and adaptive hill climbing methods. In this algorithm, the characteristic curve of power-voltage of PV panel\\u000a was divided into
NASA Astrophysics Data System (ADS)
Park, Hyunbin; Sim, Minseob; Kim, Shiho
2015-06-01
We propose a way of achieving maximum power and power-transfer efficiency from thermoelectric generators by optimized selection of maximum-power-point-tracking (MPPT) circuits composed of a boost-cascaded-with-buck converter. We investigated the effect of switch resistance on the MPPT performance of thermoelectric generators. The on-resistances of the switches affect the decrease in the conversion gain and reduce the maximum output power obtainable. Although the incremental values of the switch resistances are small, the resulting difference in the maximum duty ratio between the input and output powers is significant. For an MPPT controller composed of a boost converter with a practical nonideal switch, we need to monitor the output power instead of the input power to track the maximum power point of the thermoelectric generator. We provide a design strategy for MPPT controllers by considering the compromise in which a decrease in switch resistance causes an increase in the parasitic capacitance of the switch.
Calculation of photon energy deposition kernels and electron dose point kernels in water.
Mainegra-Hing, Ernesto; Rogers, D W O; Kawrakow, Iwan
2005-03-01
Effects of changes in the physics of EGSnrc compared to EGS4/PRESTA on energy deposition kernels for monoenergetic photons and on dose point kernels for beta sources in water are investigated. In the diagnostic energy range, Compton binding corrections were found to increase the primary energy fraction up to 4.5% at 30 keV with a corresponding reduction of the scatter component of the kernels. Rayleigh scattered photons significantly increase the scatter component of the kernels and reduce the primary energy fraction with a maximum 12% reduction also at 30 keV where the Rayleigh cross section in water has its maximum value. Sampling the photo-electron angular distribution produces a redistribution of the energy deposited by primaries around the interaction site causing differences of up to 2.7 times in the backscattered energy fraction at 20 keV. Above the pair production threshold, the dose distribution versus angle of the primary dose component is significantly different from the EGS4 results. This is related to the more accurate angular sampling of the electron-positron pair direction in EGSnrc as opposed to using a fixed angle approximation in default EGS4. Total energy fractions for photon beams obtained with EGSnrc and EGS4 are almost the same within 0.2%. This fact suggests that the estimate of the total dose at a given point inside an infinite homogeneous water phantom irradiated by broad beams of photons will be very similar for kernels calculated with both codes. However, at interfaces or near boundaries results can be very different especially in the diagnostic energy range. EGSnrc calculated kernels for monoenergetic electrons (50 keV, 100 keV, and 1 MeV) and beta spectra (32P and 90Y) are in excellent agreement with reported EGS4 values except at 1 MeV where inclusion of spin effects in EGSnrc produces an increase of the effective range of electrons. Comparison at 1 MeV with an ETRAN calculation of the electron dose point kernel shows excellent agreement. PMID:15839340
R. Michael Tuttle; Rebecca Leboeuf; Richard J. Robbins; Rebecca Qualey; Keith Pentlow; Steven M. Larson; Chee Y. Chan
Although 131I-iodine (RAI) therapy is a mainstay in the treatment of metastatic thyroid cancer, there is controversy regarding the maximum activity that can safely be administered without dosi- metric determination of the maximum tolerable activity (MTA). At most institutions, a fixed empiric dosing strategy is often used, with administered activities ranging from 5.55 to 9.25 GBq (150-250 mCi). In our
NASA Technical Reports Server (NTRS)
Appelbaum, J.; Singer, S.
1989-01-01
A calculation of the starting torque ratio of permanent magnet, series, and shunt-excited dc motors powered by solar cell arrays is presented for two cases, i.e., with and without a maximum-power-point tracker (MPPT). Defining motor torque magnification by the ratio of the motor torque with an MPPT to the motor torque without an MPPT, a magnification of 3 for the permanent magnet motor and a magnification of 7 for both the series and shunt motors are obtained. The study also shows that all motor types are less sensitive to solar insolation variation in systems including MPPTs as compared to systems without MPPTs.
Analysis of photon beam exit dose using photon point kernels
M. K. Woo
1994-01-01
The Monte Carlo method is used to analyse the dose fall-off at the exit surface of a megavoltage photon beam. The convolution\\/superposition method of dose calculation using Monte-Carlo-generated homogeneous photon kernels is shown to be in error for exit dose calculation. Instead, photon kernels that incorporate modelling of the exit surface were generated, also using Monte Carlo, to analyse the
Dong H Shin; Michael S McCracken; Rick E Bendel; Robert Pearlman; Mark S Juzych; Bret A Hughes; Laura L Schulz; Chaesik Kim; Nam H Baek
1999-01-01
ObjectiveTo assess the efficacy of latanoprost additive therapy in patients with intraocular pressure (IOP) out of control while taking maximum-tolerated medications and to determine whether pilocarpine therapy has a dose-dependent adverse effect on the efficacy of latanoprost therapy.
Bustamante, Fabián E.
Multiple Test Procedures for Identifying the Minimum Effective and Maximum Safe Doses of a Drug Effective and Maximum Safe Doses of a Drug AjitC. TAMHANEand Brent R. LOGAN We addressthe problemof determiningthe therapeuticwindow of a drugby findingits minimumeffective and maximumsafe doses (MINED and MAXSD
Validation of a dose-point kernel convolution technique for internal dosimetry
H. B. Giap; D. J. Macey; J. E. Bayouth; A. L. Boyer
1995-01-01
The objective of this study was to validate a dose-point kernel convolution technique that provides a three-dimensional (3D) distribution of absorbed dose from a 3D distribution of the radionuclide 131I. A dose-point kernel for the penetrating radiations was calculated by a Monte Carlo simulation and cast in a 3D rectangular matrix. This matrix was convolved with the 3D activity map
Maximum Power Point tracking charge controllers for telecom applications -- Analysis and economics
Wills, R.H. [Advanced Energy Systems, Inc., Wilton, NH (United States)
1997-12-31
Simple charge controllers connect photovoltaic modules directly to the battery bank resulting in a significant power loss if the battery bank voltage differs greatly from the PV Maximum Power Point (MPP) voltage. Recent modeling work at AES has shown that dc-dc converter type MPP tracking charge controllers can deliver more than 30% more energy from PV modules to the battery when the PV modules are cool and the battery state of charge is low--this is typically both the worst case condition (i.e., winter) and also the design condition that determines the PV array size. Economic modeling, based on typical telecom system installed costs shows benefits of more than $3/Wp for MPPT over conventional charge controllers in this application--a value that greatly exceeds the additional cost of the dc-dc converter.
The research on the algorithm of maximum power point tracking in photo voltaic array of solar car
Xiujuan Ma; Yude Sun; Jiayu Wu; Shiqiang Liu
2009-01-01
Combined with the practical working environment of the vehicle photovoltaic cell plate on the electric vehicle, according to the engineering mathematic model of photovoltaic cell, the output characteristics is nonlinear, and the maximum power is on one point. Adopting the improved conductance increment method, the maximum power tracking rate and accuracy are enhanced.
K. K. Tse; Billy M. T. Ho; Henry Shu-Hung Chung; S. Y. Ron Hui
2004-01-01
A comparative study of the maximum power point trackers using a switching-frequency modulation scheme (SFMS) for photovoltaic panels is presented. Some commonly used dc\\/dc converters, which are applied for the power conversion stage of those trackers, will be examined. Method of locating the maximum power point (MPP) is based on injecting a small-signal sinusoidal perturbation into the switching frequency of
Kenji Kobayashi; Ichiro Takano; Yoshio Sawada
2004-01-01
A photovoltaic array shows relatively low output power density, and has a greatly drooping Current-Voltage (I-V) characteristic. Therefore, Maximum Power Point Tracking (MPPT) control is used to maximize the output power of the array. Many papers have been reported in relation to MPPT. However, the Current-Power (I-P) curve sometimes shows multi-local maximum points mode under non-uniform insolation conditions. The operating
Noppadol Khaehintung; P. Sirisuk
2007-01-01
This paper presents the development of maximum power point tracking (MPPT) using an adjustable self-organizing fuzzy logic controller (SOFLC) for a solar-powered traffic light equipment (SPTLE) with an integrated maximum power point tracking (MPPT) system on a low-cost microcontroller. The proposed system is integrated with a boost converter for realizing of high performance SPTLE, whose adaptability properties are very attractive
K. Kobayashi; I. Takano; Y. Sawada
2003-01-01
A photovoltaic (PV) array shows relatively low output power density, and has a greatly drooping current-voltage (I-V) characteristic. Therefore, maximum power point tracking (MPPT) control is used to maximize the output power of the PV array. Many papers have been reported in relation to MPPT. However, the current-power (I-P) curve sometimes shows multilocal maximum points mode under nonuniform insolation conditions.
Point kernels and superposition methods for scatter dose calculations in brachytherapy
Åsa K. Carlsson; Anders Ahnesjö
2000-01-01
Point kernels have been generated and applied for calculation of scatter dose distributions around monoenergetic point sources for photon energies ranging from 28 to 662 keV. Three different approaches for dose calculations have been compared: a single-kernel superposition method, a single-kernel superposition method where the point kernels are approximated as isotropic and a novel `successive-scattering' superposition method for improved modelling
Wu, J; Liu, Y L; Chang, S J; Chao, M M; Tsai, S Y; Huang, D E
2012-11-01
Monte Carlo (MC) simulation has been commonly used in the dose evaluation of radiation accidents and for medical purposes. The accuracy of simulated results is affected by the particle-tracking algorithm, cross-sectional database, random number generator and statistical error. The differences among MC simulation software packages must be validated. This study simulated the dose point kernel (DPK) and the cellular S-values of monoenergetic electrons ranging from 0.01 to 2 MeV and the radionuclides of (90)Y, (177)Lu and (103 m)Rh, using Fluktuierende Kaskade (FLUKA) and MC N-Particle Transport Code Version 5 (MCNP5). A 6-?m-radius cell model consisting of the cell surface, cytoplasm and cell nucleus was constructed for cellular S-value calculation. The mean absolute percentage errors (MAPEs) of the scaled DPKs, simulated using FLUKA and MCNP5, were 7.92, 9.64, 4.62, 3.71 and 3.84 % for 0.01, 0.1, 0.5, 1 and 2 MeV, respectively. For the three radionuclides, the MAPEs of the scaled DPKs were within 5 %. The maximum deviations of S(N?N), S(N?Cy) and S(N?CS) for the electron energy larger than 10 keV were 6.63, 6.77 and 5.24 %, respectively. The deviations for the self-absorbed S-values and cross-dose S-values of the three radionuclides were within 4 %. On the basis of the results of this study, it was concluded that the simulation results are consistent between FLUKA and MCNP5. However, there is a minor inconsistency for low energy range. The DPK and the cellular S-value should be used as the quality assurance tools before the MC simulation results are adopted as the gold standard. PMID:22923242
NASA Astrophysics Data System (ADS)
Manikandan, S.; Kaushik, S. C.
2015-04-01
Thermoelectric generator (TEG) operated thermoelectric cooler (TEC) is a highly compatible combination for low-cooling power application. The conventional TEG-TEC combined systems have low operating efficiency and low cooling power because maximum power output from the TEG is not fully utilized. This paper proposes and analyses the combined system with maximum power point tracking technique (MPPT) to maximize the cooling power and overall efficiency. This paper also presents the effect of TEG, TEC source temperature and the effect of heat transfer area in the performance of the combined system. The thermodynamic models of the combined system are developed in MATLAB simulink environment with temperature dependent material properties and analysed for variable operating temperatures. It has been found that, in the irreversible thermodynamic model of the combined system with MPPT, when the hot and cold side of TEG and TEC are kept at a temperature difference of 150 K and 10 K respectively, the power output of TEG increases from 20.49 W to 43.92 W, cooling power of TEC increases from 32.66 W to 46.51 W and the overall combined system efficiency increases from 2.606% to 4.375% respectively when compared with the irreversible combined system without MPPT. The characteristics improvements obtained by this practice in the combined system for the above mentioned operating conditions is also true for other range of operating temperatures. It is also been observed that the external irreversibilities decreases the cooling power and the overall system efficiency of the combined system by 36.49% and by 16.9% respectively.
Point kernels and superposition methods for scatter dose calculations in brachytherapy
NASA Astrophysics Data System (ADS)
Carlsson, Åsa K.; Ahnesjö, Anders
2000-02-01
Point kernels have been generated and applied for calculation of scatter dose distributions around monoenergetic point sources for photon energies ranging from 28 to 662 keV. Three different approaches for dose calculations have been compared: a single-kernel superposition method, a single-kernel superposition method where the point kernels are approximated as isotropic and a novel `successive-scattering' superposition method for improved modelling of the dose from multiply scattered photons. An extended version of the EGS4 Monte Carlo code was used for generating the kernels and for benchmarking the absorbed dose distributions calculated with the superposition methods. It is shown that dose calculation by superposition at and below 100 keV can be simplified by using isotropic point kernels. Compared to the assumption of full in-scattering made by algorithms currently in clinical use, the single-kernel superposition method improves dose calculations in a half-phantom consisting of air and water. Further improvements are obtained using the successive-scattering superposition method, which reduces the overestimates of dose close to the phantom surface usually associated with kernel superposition methods at brachytherapy photon energies. It is also shown that scatter dose point kernels can be parametrized to biexponential functions, making them suitable for use with an effective implementation of the collapsed cone superposition algorithm.
Validation of a dose point kernal convolution technique for iodine-131 internal dosimetry
H. B. Giap; D. J. Macey; J. E. Bayouth
1994-01-01
The objective of this study was to validate a dose point kernel convolution technique, which provides a 3-D distribution of absorbed dose from a 3-D distribution of activity of I-131. Traditionally, S-factors provided by the MIRD committee have been used to provide one average absorbed dose to each organ of interest. Inaccuracy in the MIRD method is due to assumptions
Gamma dose from a cylindrical source obtained by point kernel and MCNP
N. Tsoulfanidis; B. Shrestha
1994-01-01
This paper discusses the generation of an algorithm, based on the point kernel technique, for the calculation of the dose rate at various distances from a cylindrical gamma source and the use of the MCNP code for verification of the algorithm along with the fluence-to-dose conversion factor used.
Gamma dose from a cylindrical source obtained by point kernel and MCNP
Tsoulfanidis, N.; Shrestha, B. [Univ. of Missouri, Rolla, MO (United States)
1994-12-31
This paper discusses the generation of an algorithm, based on the point kernel technique, for the calculation of the dose rate at various distances from a cylindrical gamma source and the use of the MCNP code for verification of the algorithm along with the fluence-to-dose conversion factor used.
Quan Li; Peter Wolfs
2007-01-01
For solar and electric vehicles a highly distributed maximum power point tracking (MPPT) scheme is preferred. A maximum power point tracker has been previously presented for a single triple junction cell. The Texas Instruments MSP430 microprocessor, which is designed for 1.8-V applications, provides the tracking intelligence. However, the maximum power point (MPP) cell voltages of other cell types under different
Gangopadhyay, Noopur; Shah, Manjool; Skolnick, Gary B; Patel, Kamlesh B; Naidoo, Sybill D; Woo, Albert S
2014-07-01
The esthetic success of sagittal synostosis reconstruction is measured by cephalic index (CI). This limited measure does not fully account for the abnormal head shape in sagittal synostosis. In this retrospective study, we investigate a new objective measure, point of maximum width (PMW) of the skull from a vertex view, to determine where the head is widest for children with sagittal synostosis as compared with normal controls. Preoperative computed tomography (CT) scans of 27 children with sagittal synostosis and 14 postoperative CT scans at least 8 months after surgery were obtained. Normal CT scans were matched for age, sex, and race. Three-dimensional renderings were standardized for orientation. Mean (SE) PMW in patients with sagittal synostosis was 53% (1%) compared with 57% (1%) in controls (P < 0.001). Mean (SE) CI in patients with sagittal synostosis was 66.8% (0.8%) compared with 83.3% (1.0%) in controls (P < 0.001). The correlation between PMW and CI was weak in both controls (r2 = 0.002, P = 0.824) and uncorrected cases (r2 = 0.083, P = 0.145). After surgical correction, both CI and PMW significantly improved. Mean (SE) PMW in patients after surgical release of sagittal synostosis was 58% (1%) compared with 58% (1%) in controls (P = 0.986). The PMW is not a surrogate for CI but is a novel, valid measure of skull shape, which aids in quantifying the widest region of the skull. It is significantly more anterior in children with sagittal synostosis and exhibits a consistent posterior shift along the cranium after surgery, showing no difference compared with healthy children. PMID:25006901
Gangopadhyay, Noopur; Shah, Manjool; Skolnick, Gary B; Patel, Kamlesh B; Naidoo, Sybill D; Woo, Albert S
2014-01-01
The aesthetic success of sagittal synostosis reconstruction is measured by cephalic index (CI). This limited measure does not fully account for the abnormal head shape in sagittal synostosis. In this retrospective study, we investigate a new objective measure, point of maximum width (PMW) of the skull from a vertex view, to determine where the head is widest for children with sagittal synostosis as compared to normal controls. Preoperative CT scans of 27 children with sagittal synostosis and 14 postoperative CT scans at least 8 months after surgery were obtained. Normal CT scans were matched for age, gender, and race. Three-dimensional renderings were standardized for orientation. Average PMW in patients with sagittal synostosis was 53% ± 1% compared to 57% ± 1% in controls (p<0.001). Average CI in patients with sagittal synostosis was 66.8% ± 0.8% compared to 83.3% ± 1.0% in controls (p<0.001). The correlation between PMW and CI was weak in both controls (R2=0.002, p=0.824) and uncorrected cases (R2=0.083, p=0.145). After surgical correction, both CI and PMW significantly improved. Average PMW in patients after surgical release of sagittal synostosis was 58% ± 1% compared to 58% ± 1% in controls (p=0.986). PMW is not a surrogate for CI but is a novel, valid measure of skull shape, which aids in quantifying the widest region of the skull. PMW is significantly more anterior in children with sagittal synostosis and exhibits a consistent posterior shift along the cranium after surgery, showing no difference compared to healthy children. PMID:25006901
Point kernel sup 1 H(n,. gamma. ) sup 2 H dose calculations in BNCT
Niemkiewicz, J.; Gupta, N.; Blue, T.E. (Ohio State Univ., Columbus (United States))
1992-01-01
Boron neutron capture therapy (BNCT) is a potential treatment modality for the fatal brain glioblastoma multiforme. Successful BNCT will require calculation of the expected relative biological effectiveness dose distribution in the patient's head prior to treatment. The method most often proposed for calculating dose distributions in BNCT is the Monte Carlo simulation technique. However, Monte Carlo calculations require a large amount of computer time to achieve good statistics if the dose is determined at many points within the head. In BNCT, a significant amount of radiation dose is deposited by 2.2-MeV gamma rays produced in the hydrogen capture interaction {sup 1}H(n,{gamma}){sup 2}H. To develop a faster calculational system, the absorbed dose deposited by these gamma rays was determined by the faster point kernel method and compared with Monte Carlo calculated results.
On a Triangle with the Maximum Area in a Planar Point Set
Urrutia, Jorge
between the maximum area of an empty triangle with vertices in P and the area of the convex hull of P. 1 the area of the convex hull of Q by A(Q). We evaluate the ratio between the maximum area of an empty divides the boundary of the convex hull of Pn into three chains AB, BC and CA, with p, q and r edges
Chao, R.M.; Ko, S.H.; Lin, I.H. [Department of Systems and Naval Mechatronics Engineering, National Cheng Kung University, Tainan, Taiwan 701 (China); Pai, F.S. [Department of Electronic Engineering, National University of Tainan (China); Chang, C.C. [Department of Environment and Energy, National University of Tainan (China)
2009-12-15
The historically high cost of crude oil price is stimulating research into solar (green) energy as an alternative energy source. In general, applications with large solar energy output require a maximum power point tracking (MPPT) algorithm to optimize the power generated by the photovoltaic effect. This work aims to provide a stand-alone solution for solar energy applications by integrating a DC/DC buck converter to a newly developed quadratic MPPT algorithm along with its appropriate software and hardware. The quadratic MPPT method utilizes three previously used duty cycles with their corresponding power outputs. It approaches the maximum value by using a second order polynomial formula, which converges faster than the existing MPPT algorithm. The hardware implementation takes advantage of the real-time controller system from National Instruments, USA. Experimental results have shown that the proposed solar mechatronics system can correctly and effectively track the maximum power point without any difficulties. (author)
Takashi Watanabe; Toshiya Yoshida; Katsumi Ohniwa
2004-01-01
This paper discusses a new control strategy for photovoltaic power generation systems with consideration of dynamic characteristics of the photovoltaic cells. The controller estimates internal currents of an equivalent circuit for the cells. This estimated, or the virtual current and the actual voltage of the cells are fed to a conventional Maximum-Power-Point-Tracking (MPPT) controller. Consequently, this MPPT controller still tracks
Dylan D. C. Lu; R. H. Chu; S. Sathiakumar; V. G. Agelidis
2007-01-01
This paper introduces a solar photovoltaic (PV) system suitable for undergraduate engineering education and training. The system consists of a buck converter using a simple maximum power point tracking (MPPT) method. Constant voltage control method is used for the approximate tracking and is implemented by analogue circuits. The circuit simplicity helps students to appreciate the benefit of MPPT in a
Chun-Yu Hsieh; Chih-Yu Yang; Fu-Kuei Feng; Ke-Horng Chen
2010-01-01
A low cost analog MPPT technique is proposed in this paper for high power efficiency in photovoltaic systems. A wide-range current multiplier, which tracks the maximum power point (MPP) in the solar system, is implemented to detect the power slope condition of solar panels. Experiment results show the proposed technique can rapidly track the MPP with a high tracking effectiveness
An InteriorPoint Algorithm for the MaximumVolume Ellipsoid Problem \\Lambda
Zhang, Yin
15 Yin Zhang Department of Computational and applied Mathematics Rice University Houston, Texas 77005 frameworks for applying interiorpoint methods. We propose a practical interiorpoint algorithm based on onebreaking work [8], the area of interiorpoint methods has matured considerably, as evidenced by a string
Ikeda, A.; Nishimura, K.; Koyama, H.; Tsukino, M.; Mishima, M.; Izumi, T.
1996-01-01
BACKGROUND: Although the bronchodilating effect of inhaled anticholinergics has been established in patients with chronic obstructive pulmonary disease (COPD), their effects on exercise capacity are still controversial. Previous studies have suggested that the standard dosage hardly affects exercise tolerance, whereas higher doses might elicit an improvement. The aim of the present study was to determine the dose of ipratropium bromide aerosol that improves exercise performance using progressive cycle ergometry in patients with stable COPD. METHODS: Twenty men with stable COPD of mean (SD) age 69.2 (4.6) years and forced expiratory volume in one second (FEV1) 1.00 (0.37) 1 were studied in a randomised double blind manner. Each patient received ipratropium bromide in doses of 240 micrograms, 160 micrograms, 80 micrograms, 40 micrograms, and placebo from a metered dose inhaler (MDI) with an InspirEase spacer on five separate days. Spirometric parameters were assessed before and at 30, 60, 90, and 120 minutes after each inhalation, and pulse rate and blood pressure were also measured immediately before each spirometric measurement. Symptom limited progressive (20 watts/min) cycle ergometer exercise tests were performed 90 minutes after each inhalation. RESULTS: Ipratropium bromide in doses of 160 micrograms and 240 micrograms produced a greater increase in FEV1 than 40 micrograms or 80 micrograms ipratropium bromide at all time points. Doses of 160 micrograms and 240 micrograms ipratropium bromide also produced greater increases in maximal work load and maximal oxygen consumption than placebo, whereas 40 micrograms and 80 micrograms ipratropium bromide did not. There was a weak correlation between the change in FEV1 and the change in maximal work load (r = 0.45). No differences were found in pulse rate or blood pressure between the treatment and placebo groups, and no side effects were noted throughout the study. CONCLUSIONS: A dose of at least four times the standard dose of ipratropium bromide from an MDI with a spacer device was necessary to improve maximal cycle exercise capacity in patients with stable COPD. Although the data from cycle ergometry cannot be directly applied to exercise performed during day to day activities, it is conceivable that the recommended doses of ipratropium bromide do not elicit the optimal clinical benefits. PMID:8658369
Point dose calculations using an analytical pencil beam kernel for IMRT plan checking
NASA Astrophysics Data System (ADS)
Watanabe, Yoichi
2001-04-01
A method to verify the monitor units for a treatment plan is to calculate point doses, possibly at the isocentre, by using a simple calculation method. This verification is recommended to find mistakes in the treatment plan. Treatment plans for intensity modulated radiation therapy are no exception. The method should employ a simple physical model and a dose calculation algorithm, which is different from the method used for the treatment plan. Our approach uses a convolution algorithm and an analytical pencil beam kernel with eight parameters. The model is intuitive and simple. At the same time, the method is so general that it can be applied to both step-and-shoot and sliding-window techniques. The results of applications to actual treatment plans show that the calculated total isocentre doses are accurate within ±2% of planned doses for six-field prostate plans when calculation points are in a uniform dose region. Head and neck cases show a slightly larger difference than prostate cases. When calculation points are located in a region of high dose gradient, however, the difference could be greater than 5%.
Suitability of point kernel dose calculation techniques in brachytherapy treatment planning.
Lakshminarayanan, Thilagam; Subbaiah, K V; Thayalan, K; Kannan, S E
2010-04-01
Brachytherapy treatment planning system (TPS) is necessary to estimate the dose to target volume and organ at risk (OAR). TPS is always recommended to account for the effect of tissue, applicator and shielding material heterogeneities exist in applicators. However, most brachytherapy TPS software packages estimate the absorbed dose at a point, taking care of only the contributions of individual sources and the source distribution, neglecting the dose perturbations arising from the applicator design and construction. There are some degrees of uncertainties in dose rate estimations under realistic clinical conditions. In this regard, an attempt is made to explore the suitability of point kernels for brachytherapy dose rate calculations and develop new interactive brachytherapy package, named as BrachyTPS, to suit the clinical conditions. BrachyTPS is an interactive point kernel code package developed to perform independent dose rate calculations by taking into account the effect of these heterogeneities, using two regions build up factors, proposed by Kalos. The primary aim of this study is to validate the developed point kernel code package integrated with treatment planning computational systems against the Monte Carlo (MC) results. In the present work, three brachytherapy applicators commonly used in the treatment of uterine cervical carcinoma, namely (i) Board of Radiation Isotope and Technology (BRIT) low dose rate (LDR) applicator and (ii) Fletcher Green type LDR applicator (iii) Fletcher Williamson high dose rate (HDR) applicator, are studied to test the accuracy of the software. Dose rates computed using the developed code are compared with the relevant results of the MC simulations. Further, attempts are also made to study the dose rate distribution around the commercially available shielded vaginal applicator set (Nucletron). The percentage deviations of BrachyTPS computed dose rate values from the MC results are observed to be within plus/minus 5.5% for BRIT LDR applicator, found to vary from 2.6 to 5.1% for Fletcher green type LDR applicator and are up to -4.7% for Fletcher-Williamson HDR applicator. The isodose distribution plots also show good agreements with the results of previous literatures. The isodose distributions around the shielded vaginal cylinder computed using BrachyTPS code show better agreement (less than two per cent deviation) with MC results in the unshielded region compared to shielded region, where the deviations are observed up to five per cent. The present study implies that the accurate and fast validation of complicated treatment planning calculations is possible with the point kernel code package. PMID:20589118
Development, Testing, and Application of a Beta Radiation Point Source Dose Distribution Function
NASA Astrophysics Data System (ADS)
Khalifeh, Abdulnasser
Present calculational techniques to determine beta radiation dose rates from sources of known characteristics in various source-receptor geometries are confined to desk -top type dose estimations of doses in infinite homogeneous media or relatively complicated methods to be applied to cases where activity is on or in other material separated from the dose medium of concern. This dissertation has concentrated on the development, testing, and applications of a new point source dose distribution function for assessing dose from beta-emitting radionuclides when beta radiation is transported through multiple media; both theoretical analyses and experimental measurements have been carried out. Measurements have been made using P-32, TI-204, and Pm-147 beta-emitting sources, and fabricated metallic particles of Co-60 with known thickness of material absorbers (including mica, mylar, polyethylene, aluminum foil, carbon, and polystyrene foam) between the respective source and an air extrapolation ionization chamber. Results of the measurements have been used to modify the analytical equation of the point source dose rate function, as necessary, to account for discrepancies between results predicted by the function and results from measurements.
Stand-alone photovoltaic energy storage system with maximum power point tracking
V. A. Pacheco; L. C. Freitas; E. A. A. Coelho; V. J. Farias
2003-01-01
This digests deals with the study of a stand-alone photovoltaic system, which is able to extract the maximum power from photovoltaic array for all solar intensity conditions and to provide output voltage regulation. The proposed system consists of a DC-DC converter in combination with battery energy storage in a simple structure. Operating principle and control strategy are described. Digital simulation
Effect of tissue inhomogeneity on dose distribution of point sources of low-energy electrons.
Kwok, C S; Bialobzyski, P J; Yu, S K; Prestwich, W V
1990-01-01
Perturbation in dose distributions of point sources of low-energy electrons at planar interfaces of cortical bone (CB) and red marrow (RM) was investigated experimentally and by Monte Carlo codes EGS and the TIGER series. Ultrathin LiF thermoluminescent dosimeters were used to measure the dose distributions of point sources of 204Tl and 147Pm in RM. When the point sources were at 12 mg/cm2 from a planar interface of CB and RM equivalent plastics, dose enhancement ratios in RM averaged over the region 0-12 mg/cm2 from the interface were measured to be 1.08 +/- 0.03 (SE) and 1.03 +/- 0.03 (SE) for 204Tl and 147Pm, respectively. The Monte Carlo codes predicted 1.05 +/- 0.02 and 1.01 +/- 0.02 for the two nuclides, respectively. However, EGS gave consistently 3% higher dose in the dose scoring region than the TIGER series when point sources of monoenergetic electrons up to 0.75 MeV energy were considered in the homogeneous RM situation or in the CB and RM heterogeneous situation. By means of the TIGER series, it was demonstrated that aluminum, which is normally assumed to be equivalent to CB in radiation dosimetry, leads to an overestimation of backscattering of low-energy electrons in soft tissue at a CB-soft-tissue interface by as much as a factor of 2. PMID:2233564
Radiography simulation based on point-kernel model and dose buildup factors.
Marinkovi?, Predrag; Ili?, Radovan
2009-01-01
Three-dimensional point-kernel multiple scatter model for radiography simulation, based on dose X-ray buildup factors, is proposed and validated to Monte Carlo simulation. This model embraces nonuniform attenuation in object of imaging (patient body tissue). Photon multiple scattering is treated as in the point-kernel integration gamma ray shielding problems via scatter voxels. First order Compton scattering is described by means of Klein-Nishina formula. Photon multiple scattering is accounted by using dose buildup factors. The proposed model is convenient in those situations where more exact techniques, like Monte Carlo, are not time consuming acceptable. PMID:19644212
P. F. Siy; J. T. Carter; L. R. DAddario; D. A. Loeber
1991-01-01
The MITRE Corporation has performed in-flux radiation testing of the Texas Instruments TMS320C30 32-bit floating point digital signal processor in both total dose and dose rate radiation environments. This test effort has provided data relating to the applicability of the TMS320C30 in systems with total dose and\\/or dose rate survivability requirements. In order to accomplish these tests, the MITRE Corporation
A two-dimensional point-kernel model for dose calculations in a glovebox array
Kornreich, D.E.; Dooley, D.E.
1999-06-01
An associated paper details a model of a room containing gloveboxes using the industry standard dose equivalent (dose) estimation tool MCNP. Such tools provide an excellent means for obtaining relatively reliable estimates of radiation transport in a complicated geometric structure. However, creating the input deck that models the complicated geometry is equally complicated. Therefore, an alternative tool is desirable that provides reasonable accurate dose estimates in complicated geometries for use in engineering-scale dose analyses. In the past, several tools that use the point-kernel model for estimating doses equivalent have been constructed (those referenced are only a small sample of similar tools). This new tool, the Photon and Neutron Dose Equivalent Model Of Nuclear materials Integrated with an Uncomplicated geometry Model (PANDEMONIUM), combines point-kernel and diffusion theory calculation routines with a simple geometry construction tool. PANDEMONIUM uses Visio{trademark} to draw a glovebox array in the room, including hydrogenous shields, sources and detectors. This simplification in geometric rendering limits the tool to two-dimensional geometries (and one-dimensional particle transport calculations).
Charles R. Sullivan; Matthew J. Powers
1993-01-01
A maximum power point tracker for photovoltaic arrays is presented. Components are optimized for weight\\/power-loss tradeoff in a solar-powered vehicle, resulting in over 97% efficiency. The control circuit uses a robust auto-oscillation method. Measurement and multiplication of array voltage and current is shown to be unnecessary, and the control is based only on output current measurement. Multiple local maxima arising
N. Khaehintung; P. Sirisuk
2004-01-01
This paper presents the development of maximum power point tracking (MPPT) using a fuzzy logic controller (FLC). By applying the synthetic fuzzy inference algorithm, the relation between input and output of FLC can be effectively stored in a memory-limited lookup table (LUT). As a consequence, the controller can be efficiently implemented on a low-cost 16F872 RISC microcontroller. A practical system
T. Lissitchkov; G. Arnaudov; D. Peytchev; Kh. Merkle
2006-01-01
Purpose: Bendamustine hydrochloride, an anti-neoplastic agent with unique mechanism of action, is known to cause impressive remissions\\u000a in relapsed nonHodgkin’s lymphoma and chronic lymphocytic leukaemia (CLL). Optimal bendamustine dosing for CLL patients had\\u000a not been finally established and a phase I\\/II study was conducted to determine the maximum tolerated dose (MTD) and dose limiting\\u000a toxicity (DLT) of bendamustine. Methods: The
Penetrative Rayleigh-Bénard convection in water near its maximum density point
NASA Astrophysics Data System (ADS)
Large, E.; Andereck, C. D.
2014-09-01
The presence of a density maximum in water near 4 °C significantly modifies the nature and onset conditions of convective flows due to imposed temperature differences. In the present study, vertical temperature gradients are imposed upon a horizontal, rectangular layer of water, with the top and bottom surfaces maintained above and below the maximum density temperature, respectively. In such an arrangement, convection beginning in the lower, unstable portion of the layer (as small as 1/3 of the layer height) may penetrate into the upper, stable region. The resulting convection patterns are visualized using schlieren or shadowgraph techniques along multiple visual axes. The measured onset conditions and observed patterns are discussed in the context of preceding predictions and experimental observations in similar penetrative systems. As expected from the non-Boussinesq nature of water in this temperature range, convection sets in at temperature differences below those predicted by linear stability theory when the unstable portion of the layer is sufficiently small. The conduction-convection transition is also hysteretic in nature. At onset, the convection pattern consists of parallel, transverse rolls due to the boundary conditions of the fluid chamber. When the unstable portion of the layer is significantly less than half of the fluid layer height, the convective motion is found to penetrate only partway into the upper stable region, within which weakly counter-rotating motions are driven. At higher Rayleigh numbers, the fluid undergoes secondary transitions to either hexagonal cellular or longitudinal roll states which are visualized for the first time. Pattern heights and wavenumbers were measured in some instances, establishing qualitative (in general) and quantitative (over some parameter ranges) agreement with linear theory.
NASA Astrophysics Data System (ADS)
Watanabe, Takashi; Yoshida, Toshiya; Ohniwa, Katsumi
This paper discusses a new control strategy for photovoltaic power generation systems with consideration of dynamic characteristics of the photovoltaic cells. The controller estimates internal currents of an equivalent circuit for the cells. This estimated, or the virtual current and the actual voltage of the cells are fed to a conventional Maximum-Power-Point-Tracking (MPPT) controller. Consequently, this MPPT controller still tracks the optimum point even though it is so designed that the seeking speed of the operating point is extremely high. This system may suit for applications, which are installed in rapidly changeable insolation and temperature-conditions e.g. automobiles, trains, and airplanes. The proposed method is verified by experiment with a combination of this estimating function and the modified Boehringer's MPPT algorithm.
Effect of tissue inhomogeneity on dose distribution of point sources of low-energy electrons
Kwok, C.S. (Hamilton Regional Cancer Centre, Ontario Cancer Foundation, Hamilton, Ontario (Canada) McMaster University, Hamilton, Ontario (Canada)); Bialobzyski, P.J.; Yu, S.K.; Prestwich, W.V. (McMaster University, Hamilton, Ontario (Canada))
1990-09-01
Perturbation in dose distributions of point sources of low-energy electrons at planar interfaces of cortical bone (CB) and red marrow (RM) was investigated experimentally and by Monte Carlo codes EGS and the TIGER series. Ultrathin LiF thermoluminescent dosimeters were used to measure the dose distributions of point sources of {sup 204}Tl and {sup 147}Pm in RM. When the point sources were at 12 mg/cm{sup 2} from a planar interface of CB and RM equivalent plastics, dose enhancement ratios in RM averaged over the region 0--12 mg/cm{sup 2} from the interface were measured to be 1.08{plus minus}0.03 (SE) and 1.03{plus minus}0.03 (SE) for {sup 204}Tl and {sup 147}Pm, respectively. The Monte Carlo codes predicted 1.05{plus minus}0.02 and 1.01{plus minus}0.02 for the two nuclides, respectively. However, EGS gave consistently 3% higher dose in the dose scoring region than the TIGER series when point sources of monoenergetic electrons up to 0.75 MeV energy were considered in the homogeneous RM situation or in the CB and RM heterogeneous situation. By means of the TIGER series, it was demonstrated that aluminum, which is normally assumed to be equivalent to CB in radiation dosimetry, leads to an overestimation of backscattering of low-energy electrons in soft tissue at a CB--soft-tissue interface by as much as a factor of 2.
Rondanelli, Mariangela; Monteferrario, Francesca; Faliva, Milena Anna; Perna, Simone; Antoniello, Neldo
2013-08-30
According to the American Diabetes Association and the Adult Treatment Panel III, the starting point for treating metabolic syndrome (MS) is a change of lifestyle. In addition, action on the main symptoms of MS by means of dietary supplements, can be helpful in view of the chronic course of the disease. The term 'phytosterols' refers to sterols and stanols composed of lipophilic triterpenes, a family that is widely distributed in the plant kingdom and whose cholesterol-lowering properties have been amply demonstrated. In the light of the recent literature, the key points for maximum effectiveness and safety of sterols are the following. (A) Plant sterols should be taken with meals: clinical trials have shown that when plant sterols are consumed close to mealtimes, low-density lipoprotein cholesterol may decrease by 9.4%, while when they are taken between meals, the reduction is about 6%. (B) The optimal dosage is 2-2.5 g day(-1) in a single dose. More than 3 g day(-1) has not been found to have any additional beneficial effect and increases the risk of side effects. (C) The food matrix used to dissolve the phytosterols should contain a certain amount of fat. A milk-based matrix appears optimal from this point of view. PMID:23584958
Inge Skaale; Dean J Patterson; Howard Pullen
2001-01-01
A maximum power point tracker for a very high efficiency, compound curve photovoltaic array for a solar powered vehicle is presented. Using an open loop algorithm to achieve maximum power point tracking, synchronous rectification to improve the overall circuit efficiency in a boost converter, and optimising the components according to a weight\\/power-loss trade-off, greater than 98% efficiency is achieved.
Calculation of photon energy deposition kernels and electron dose point kernels in water
Ernesto Mainegra-Hing; D. W. O. Rogers; Iwan Kawrakow
2005-01-01
Eects of changes in the physics of EGSnrc compared to EGS4\\/PRESTA on energy deposition kernels for monoenergetic photons and on dose point kernels for beta sources in water are investigated. In the diagnostic energy range, Compton binding corrections were found to increase the primary energy fraction up to 4.5% at 30 keV with a corresponding reduction of the scatter component
Calculation of electron Dose Point Kernel in water with GEANT4 for medical application
M. Moralles; F. F. Sene; J. R. Martinelli; E. Okuno
2009-01-01
The rapid insertion of new technologies in medical physics in the last years, especially in nuclear medicine, has been followed by a great development of faster Monte Carlo algorithms. GEANT4 is a Monte Carlo toolkit that contains the tools to simulate the problems of particle transport through matter. In this work, GEANT4 was used to calculate the dose-point-kernel (DPK) for
Optimized point dose measurement: An effective tool for QA in intensity-modulated radiotherapy
Kumar, Alok; Mukherjee, Gautam; Yadav, Girigesh; Pandey, Vinod; Bhattacharya, Kalyan
2007-01-01
In some cases of Intensity-modulated radiotherapy (IMRT) point dose measurement, there exists significant deviation between calculated and measured dose at isocenter, sometimes greater than ±3%. This may be because IMRT fields generate complex profiles at the reference point. The deviation arises due to lack of lateral electronic equilibrium for small fields, and other factors such as leakage and scatter contribution. Measurements were done using 0.125-cc ion chamber and Universal IMRT phantom (both from PTW-Freiburg). The aim is to find a suitable point of measurement for the chamber to avoid discrepancy between calculated and measured dose. Various beam profiles were generated in the plane of the chamber for each field by implementing patient plan on the IMRT phantom. The profiles show that for the fields which are showing deviation, the ion chamber lies in the steep-gradient region. To rectify the problem, the TPS (Treatment Planning System) calculated dose is found out at various points in the measurement plane of the chamber at isocenter. The necessary displacement to the chamber, as noted from the TPS, was given to obtain the optimum result. Twenty cases were studied for optimization, whose percentage deviation was more than ±3%. The results were well within tolerance criteria of ±3% after optimization. The mean percentage deviation value for the 20 cases studied, with standard deviation of 2.33 under 95% confidence interval, was found out to be 2.10% ± 1.14. Those cases that have significant variation even after optimization are further studied with film dosimetry. PMID:21224925
NASA Astrophysics Data System (ADS)
Gudowska, I.; Brahme, A.; Andreo, P.; Gudowski, W.; Kierkegaard, J.
1999-09-01
The absorbed dose due to photonuclear reactions in soft tissue, lung, breast, adipose tissue and cortical bone has been evaluated for a scanned bremsstrahlung beam of end point 50 MeV from a racetrack accelerator. The Monte Carlo code MCNP4B was used to determine the photon source spectrum from the bremsstrahlung target and to simulate the transport of photons through the treatment head and the patient. Photonuclear particle production in tissue was calculated numerically using the energy distributions of photons derived from the Monte Carlo simulations. The transport of photoneutrons in the patient and the photoneutron absorbed dose to tissue were determined using MCNP4B; the absorbed dose due to charged photonuclear particles was calculated numerically assuming total energy absorption in tissue voxels of 1 cm3. The photonuclear absorbed dose to soft tissue, lung, breast and adipose tissue is about (0.11-0.12)±0.05% of the maximum photon dose at a depth of 5.5 cm. The absorbed dose to cortical bone is about 45% larger than that to soft tissue. If the contributions from all photoparticles (n, p, 3He and 4He particles and recoils of the residual nuclei) produced in the soft tissue and the accelerator, and from positron radiation and gammas due to induced radioactivity and excited states of the nuclei, are taken into account the total photonuclear absorbed dose delivered to soft tissue is about 0.15±0.08% of the maximum photon dose. It has been estimated that the RBE of the photon beam of 50 MV acceleration potential is approximately 2% higher than that of conventional 60Co radiation.
J L BEDFORD; V N HANSEN; S WEBB; Surrey SM
A formula for the calculation of tissue-maximum ratio (TMR) from percentage depth dose (PDD) and peak scatter factor (PSF) is derived from first principles using a simple geometric model for the case when the field size for PDD and PSF is defined at the surface. The derivation is carried out in two ways: (a) taking field size for PDD and
Nakagawa, Akiko; Ohno, Tatsuya; Noda, Shin-ei; Kubo, Nobuteru; Kuwako, Keiko; Saitoh, Jun-Ichi; Nakano, Takashi
2014-07-01
We investigated the rectal dose-sparing effect and tumor control of a point A dose-reduced plan in patients with Stage I-II cervical cancer (?4 cm) arising from a small-sized uterus. Between October 2008 and August 2011, 19 patients with Stage I-II cervical cancer (?4 cm) were treated with external beam radiotherapy (EBRT) for the pelvis and CT-guided brachytherapy. Seven patients were treated with brachytherapy with standard loading of source-dwell positions and a fraction dose of 6 Gy at point A (conventional brachy-plan). The other 12 patients with a small uterus close to the rectum or small intestine were treated with brachytherapy with a point A dose-reduction to match D2cc of the rectum and <6 Gy as the dose constraint ('point A dose-reduced plan') instead of the 6-Gy plan at point A ('tentative 6-Gy plan'). The total doses from EBRT and brachytherapy were added up and normalized to a biological equivalent dose of 2 Gy per fraction (EQD2). The median doses to the high-risk clinical target volume (HR-CTV) D90 in the conventional brachy-plan, tentative 6-Gy plan and point A dose-reduced plan were 62 GyEQD2, 80 GyEQD2 and 64 GyEQD2, respectively. The median doses of rectal D2cc in the corresponding three plans were 42 GyEQD2, 62 GyEQD2 and 51 GyEQD2, respectively. With a median follow-up period of 35 months, three patients developed Grade-1 late rectal complications and no patients developed local recurrence. Our preliminary results suggested that CT-guided brachytherapy using an individualized point A dose-reduced plan might be useful for reducing late rectal complications while maintaining primary tumor control. PMID:24566721
Beta dose point kernels for radionuclides of potential use in radioimmunotherapy
W. V. Prestwich; J. Nunes; C. S. Kwok
1989-01-01
Beta dose point kernels for Â³Â²P, â¶â·Cu, â¹Â°Y, Â¹Â³Â¹I, Â¹â¸â¶Re, and Â¹â¸â¸Re nuclides appropriate for radioimmunotherapy are calculated based upon Monte Carlo results. The calculations are shown to differ significantly from values based upon solutions to the electron transport equation. Agreement with experiment for Â³Â²P is found to be improved for the former as compared with the latter. Values of
F. A. Deeney; J. P. O’Leary; B. Cronin; D. M. O’Leary
2008-01-01
Unlike the situation for ionic aqueous solutions, the relationship between the density maximum temperature Tmd and solute concentration for aqueous solutions of primary alcohols is known to be strongly non-linear. Using our recent theory for the existence of the maximum density in water in terms of quantum zero point energy effects, we explain why this is so. We also explain
Janicki, Christian; Seuntjens, Jan
2004-04-01
Dose-point-kernel (DPK) functions are used extensively for the dosimetry of gamma and beta emitters in many physical problems. These functions are usually obtained from Monte Carlo simulations where the energy deposited in concentric spherical shells around a point source is tallied. The energy scored in a spherical shell divided by the shell mass is taken as the dose at some effective radius R(eff) of the shell. The effective radius R(eff), defined as the distance of a hypothetical zero-thickness scoring region from the source, can be evaluated in different ways for a finite thickness scoring region. For a shell thickness that is very small compared to the distance from the origin, this exact evaluation method becomes unimportant and the arithmetic mean is usually an accurate estimator for R(eff). However, accurately determining R(eff) can be problematic for the innermost regions when the radial dose function D(r) varies considerably over the finite spherical shell thickness. In this work, a new method for determining R(eff) is introduced which yields consistent results for any shell thickness, thus improving on previous Monte Carlo calculations for DPKs at or near the origin. Dimensionless DPK functions for monoenergetic electrons were reevaluated using EGSnrc with an emphasis on accuracy and consistency near the origin using our new method for determining R(eff). These improved functions were implemented in a software code to calculate the DPKs for an exhaustive list of 546 beta emitters, thus extending the compilation from previous works. PMID:15124998
2013-01-01
Background The receptor kinase inhibitor toceranib phosphate (Palladia) was approved for use in dogs in 2009 using a dose of 3.25 mg/kg administered every other day. Preliminary data suggests that lower doses of toeceranib may be associated with a reduced adverse event profile while maintaining sufficient drug exposure to provide biologic activity. The purpose of this study was to determine the Cmax of toceranib in dogs with solid tumors receiving 2.5-2.75 mg/kg every other day and to document the adverse events associated with this dose rate. Secondary objectives included determination of plasma VEGF concentrations in treated dogs and response to therapy. Results Dogs with solid tumors were administered toceranib at an intended target dose ranging from 2.5-2.75 mg/kg every other day and plasma samples were obtained for analysis of toceranib and VEGF plasma concentrations on days 0, 7, 14 and 30 of the study at 6 and 8 hours post drug administration. Additionally, plasma samples were obtained at 0, 1, 2, 6, 8, and 12 hours from dogs on day 30 for confirmation of Cmax. Response to therapy was assessed using standard RECIST criteria and adverse events were characterized using the VCOG-CTCAE. Toceranib administered at doses between 2.4-2.9 mg/kg every other day resulted in an average 6–8 hr plasma concentration ranging from 100–120 ng/ml, well above the 40 ng/ml concentration associated with target inhibition. Plasma VEGF concentrations increased significantly over the 30 day treatment period indicating that VEGFR2 inhibition was likely achieved in the majority of dogs. The lower doses of toceranib used in this study were associated with a substantially reduced adverse event profile compared to the established label dose of 3.25 mg/kg EOD. Conclusions Doses of toceranib ranging from 2.4-2.9 mg/kg every other day provide drug exposure considered sufficient for target inhibition while resulting in an adverse event profile substantially reduced from that associated with the label dose of toceranib. This lower dose range of toceranib should be considered for future use in dogs with cancer. PMID:24079884
Paris-Sud XI, Université de
1 Dose Point Kernels in liquid water:1 an intra-comparison between GEANT4-DNA and a variety water, the simulation of electron Dose Point Kernels remains the27 preferential test. In this work: Dose Point Kernel; Geant4-DNA; Monte Carlo codes; liquid water.134 135 136 PACS: 87.53.Bn; 02.70.Ss; 87
NASA Astrophysics Data System (ADS)
Favarel, C.; Champier, D.; Bédécarrats, J. P.; Kousksou, T.; Strub, F.
2012-06-01
According to the International Energy Agency, 1.4 billion people are without electricity in the poorest countries and 2.5 billion people rely on biomass to meet their energy needs for cooking in developing countries. The use of cooking stoves equipped with small thermoelectric generator to provide electricity for basic needs (LED, cell phone and radio charging device) is probably a solution for houses far from the power grid. The cost of connecting every house with a landline is a lot higher than dropping thermoelectric generator in each house. Thermoelectric generators have very low efficiency but for isolated houses, they might become really competitive. Our laboratory works in collaboration with plane`te-bois (a non governmental organization) which has developed energy-efficient multifunction (cooking and hot water) stoves based on traditional stoves designs. A prototype of a thermoelectric generator (Bismuth Telluride) has been designed to convert a small part of the energy heating the sanitary water into electricity. This generator can produce up to 10 watts on an adapted load. Storing this energy in a battery is necessary as the cooking stove only works a few hours each day. As the working point of the stove varies a lot during the use it is also necessary to regulate the electrical power. An electric DC DC converter has been developed with a maximum power point tracker (MPPT) in order to have a good efficiency of the electronic part of the thermoelectric generator. The theoretical efficiency of the MMPT converter is discussed. First results obtained with a hot gas generator simulating the exhaust of the combustion chamber of a cooking stove are presented in the paper.
NASA Astrophysics Data System (ADS)
Huang, Yu
Solar energy becomes one of the major alternative renewable energy options for its huge abundance and accessibility. Due to the intermittent nature, the high demand of Maximum Power Point Tracking (MPPT) techniques exists when a Photovoltaic (PV) system is used to extract energy from the sunlight. This thesis proposed an advanced Perturbation and Observation (P&O) algorithm aiming for relatively practical circumstances. Firstly, a practical PV system model is studied with determining the series and shunt resistances which are neglected in some research. Moreover, in this proposed algorithm, the duty ratio of a boost DC-DC converter is the object of the perturbation deploying input impedance conversion to achieve working voltage adjustment. Based on the control strategy, the adaptive duty ratio step size P&O algorithm is proposed with major modifications made for sharp insolation change as well as low insolation scenarios. Matlab/Simulink simulation for PV model, boost converter control strategy and various MPPT process is conducted step by step. The proposed adaptive P&O algorithm is validated by the simulation results and detail analysis of sharp insolation changes, low insolation condition and continuous insolation variation.
Calculation of electron Dose Point Kernel in water with GEANT4 for medical application
NASA Astrophysics Data System (ADS)
Guimarães, C. C.; Moralles, M.; Sene, F. F.; Martinelli, J. R.; Okuno, E.
2009-06-01
The rapid insertion of new technologies in medical physics in the last years, especially in nuclear medicine, has been followed by a great development of faster Monte Carlo algorithms. GEANT4 is a Monte Carlo toolkit that contains the tools to simulate the problems of particle transport through matter. In this work, GEANT4 was used to calculate the dose-point-kernel (DPK) for monoenergetic electrons in water, which is an important reference medium for nuclear medicine. The three different physical models of electromagnetic interactions provided by GEANT4—Low Energy, Penelope and Standard—were employed. To verify the adequacy of these models, the results were compared with references from the literature. For all energies and physical models, the agreement between calculated DPKs and reported values is satisfactory.
Calculation of electron Dose Point Kernel in water with GEANT4 for medical application
Guimaraes, C. C.; Sene, F. F.; Martinelli, J. R. [Centro de Ciencia e Tecnologia de Materiais, IPEN/CNEN, CEP 05422-970, SP (Brazil); Moralles, M. [Centro do Reator de Pesquisas, IPEN/CNEN, CEP 05422-970, SP (Brazil); Okuno, E. [Instituto de Fisica, USP, Rua do Matao, Travessa R, 187. CEP 05508-090, SP (Brazil)
2009-06-03
The rapid insertion of new technologies in medical physics in the last years, especially in nuclear medicine, has been followed by a great development of faster Monte Carlo algorithms. GEANT4 is a Monte Carlo toolkit that contains the tools to simulate the problems of particle transport through matter. In this work, GEANT4 was used to calculate the dose-point-kernel (DPK) for monoenergetic electrons in water, which is an important reference medium for nuclear medicine. The three different physical models of electromagnetic interactions provided by GEANT4 - Low Energy, Penelope and Standard - were employed. To verify the adequacy of these models, the results were compared with references from the literature. For all energies and physical models, the agreement between calculated DPKs and reported values is satisfactory.
Implementing dosimetry in GATE: dose-point kernel validation with GEANT4 4.8.1.
Ferrer, Ludovic; Chouin, Nicolas; Bitar, Abdalkader; Lisbona, Albert; Bardiès, Manuel
2007-02-01
GATE is a recent Monte Carlo code, based on GEANT4, and used in nuclear medicine mainly for imaging and detector design. Our goal was to implement dosimetry within GATE (i.e., combining the excellent potential of Gate for image modeling with GEANT4 dosimetric capabilities. The latest release of GEANT4 (4.8.1) completely revised the electron multiple scattering propagation algorithm. In this work, we calculated dose point kernels (DPK) for 0.01, 0.05, 0.1, 1, and 3 MeV monoenergetic electrons. We then compared our results with data obtained with another Monte Carlo code (MCNPX) or from the reference publication from Berger and Seltzer. To facilitate comparison, all calculated dose distributions were scaled to the corresponding R(CSDA), as given by the ESTAR NIST web database. Some GEANT4 parameters (i.e., Stepmax), or the shell thickness, had to be adjusted in order to achieve good agreement for energies below 1 MeV. For all energies except 10 keV, calculated DPKs do not differ significantly from the reference, as assessed by a Kolmogorov-Smirnov test. This preliminary step allowed us to consider the integration of GEANT4 dosimetric capabilities within the Gate framework. PMID:17461728
Mohammad H. Pourgholami; Michael Szwajcer; Melvin Chin; Winston Liauw; Jonathan Seef; Peter Galettis; David L. Morris; Matthew Links
2010-01-01
Purpose Albendazole is a potential anticancer agent that is currently under development for the treatment of cancer. We carried out\\u000a a dose-finding phase I study of oral albendazole in patients with advanced malignancies.\\u000a \\u000a \\u000a \\u000a Patients and methods Thirty-six patients with refractory solid tumors were enrolled. Albendazole was given orally on a day 1–14 of a 3 weekly cycle,\\u000a starting at 400 mg BD with dose
Weber, Lars; Nilsson, Per
2002-01-01
Dose calculations with a collapsed cone algorithm implemented in a clinical treatment planning system have been studied. The algorithm has been evaluated in homogeneous as well as in heterogeneous media, and the results have been compared to measurements and Monte Carlo simulations. Commonly encountered clinical beam configurations as well as more complex geometries have been pursued to test the limitations of the model. The results show that the accuracy level reached allows for clinical use. Some situations, e.g., large wedge beams and dose calculations in the build up region, not specific to the collapsed cone model, show deviations (outside +/- 3%) compared to measurements. PMID:11958648
Spiegler, P.
1981-09-01
As part of the assessment of the potential radiological consequences of the proposed Waste Isolation Pilot Plant (WIPP), this report evaluates the post-closure radiation dose commitments associated with a possible breach event which involves dissolution of the repository by groundwaters and subsequent transport of the nuclear waste through an aquifer to a well assumed to exist at a point 3 miles downstream from the repository. The concentrations of uranium and plutonium isotopes at the well are based on the nuclear waste inventory presently proposed for WIPP and basic assumptions concerning the transport of waste as well as treatment to reduce the salinity of the water. The concentrations of U-233, Pu-239, and Pu-240, all radionuclides originally emplaced as waste in the repository, would exceed current EPA drinking water limits. The concentrations of U-234, U-235, and U-236, all decay products of plutonium isotopes originally emplaced as waste, would be well below current EPA drinking water limits. The 50-year dose commitments from one year of drinking treated water contaminated with U-233 or Pu-239 and Pu-240 were found to be comparable to a one-year dose from natural background. The 50-year dose commitments from one year of drinking milk would be no more than about 1/5 the dose obtained from ingestion of treated water. These doses are considered upper bounds because of several very conservative assumptions which are discussed in the report.
S. T. Yang; X. Z. Hu; Z. M. Wu
2011-01-01
The maximum fracture load of a notched concrete beam has been related to the local fracture energy at the cohesive crack tip region analytically in this paper, and then the correlation between the size effects on the maximum fracture loads and the RILEM specific fracture energy is established. Two extreme conditions have been established, namely zero crack-tip bridging with zero
Sang Hyun Cho; Warren D. Reece; Chan-Hyeong Kim
2004-01-01
Dose calculations around electron-emitting metallic spherical sources were performed up to the X90 distance of each electron energy ranging from 0.5 to 3.0MeV using the MCNP 4C Monte Carlo code and the dose point kernel (DPK) method with the DPKs rescaled using the linear range ratio and physical density ratio, respectively. The results show that the discrepancy between the MCNP
Sang Hyun Cho; Warren D. Reece; Chan-Hyeong Kim
2004-01-01
Dose calculations around electron-emitting metallic spherical sources were performed up to the X90 distance of each electron energy ranging from 0.5 to 3.0MeV using the MCNP 4C Monte Carlo code and the dose point kernel (DPK) method with the DPKs rescaled using the linear range ratio and physical density ratio, respectively. The results show that the discrepancy between the MCNP
Chen, Reuven
Simulation of the Nonlinear Dose Dependence of Stabilized Point Defects This article has been Contact us My IOPscience #12;Simulation of the Nonlinear Dose Dependence of Stabilized Point Defects R Redwood Scientific Incorporated, Pacifica, CA94044-4300, USA e-mail: chenr@tau.ac.il Abstract. The dose
Underbrink, A.G.; Sparrow, A.H.
1973-01-01
From effects of neutron irradiation upon cell function; Neuherberg, F.R. Germany (22 Oct 1973). Procedures are described for irradiating Tradescantia cuttings with neutrons and x rays. Stamen hairs were scored for various mutations. Results are discussed under the following headings: experimental end points and RBE; influence of dose on RBE; effect of dose rate on RBE; influence of neutron energy on RBE; the RBE of 3.9 GeV nitrogen ions; the influence of hypoxia (OER); and the influence of chromosome volume and ploidy level on RBE; pollen abortion data. Graphs are presented to show survival curves for stamen hairs after neutron and x irradiation and neutron and x-ray dose-response curves for pink mutants, blue giant cells. and colorless mutants. (HLW)
Zhen, Xin; Chen, Haibin; Yan, Hao; Zhou, Linghong; Mell, Loren K; Yashar, Catheryn M; Jiang, Steve; Jia, Xun; Gu, Xuejun; Cervino, Laura
2015-04-01
Deformable image registration (DIR) of fractional high-dose-rate (HDR) CT images is challenging due to the presence of applicators in the brachytherapy image. Point-to-point correspondence fails because of the undesired deformation vector fields (DVF) propagated from the applicator region (AR) to the surrounding tissues, which can potentially introduce significant DIR errors in dose mapping. This paper proposes a novel segmentation and point-matching enhanced efficient DIR (named SPEED) scheme to facilitate dose accumulation among HDR treatment fractions. In SPEED, a semi-automatic seed point generation approach is developed to obtain the incremented fore/background point sets to feed the random walks algorithm, which is used to segment and remove the AR, leaving empty AR cavities in the HDR CT images. A feature-based 'thin-plate-spline robust point matching' algorithm is then employed for AR cavity surface points matching. With the resulting mapping, a DVF defining on each voxel is estimated by B-spline approximation, which serves as the initial DVF for the subsequent Demons-based DIR between the AR-free HDR CT images. The calculated DVF via Demons combined with the initial one serve as the final DVF to map doses between HDR fractions. The segmentation and registration accuracy are quantitatively assessed by nine clinical HDR cases from three gynecological cancer patients. The quantitative analysis and visual inspection of the DIR results indicate that SPEED can suppress the impact of applicator on DIR, and accurately register HDR CT images as well as deform and add interfractional HDR doses. PMID:25790059
Botta, F.; Mairani, A.; Battistoni, G.; Cremonesi, M.; Di Dia, A.; Fasso, A.; Ferrari, A.; Ferrari, M.; Paganelli, G.; Pedroli, G.; Valente, M. [Medical Physics Department, European Institute of Oncology, Via Ripamonti 435, 20141 Milan (Italy); Istituto Nazionale di Fisica Nucleare (I.N.F.N.), Via Celoria 16, 20133 Milan (Italy); Medical Physics Department, European Institute of Oncology, Via Ripamonti 435, 20141 Milan (Italy); Jefferson Lab, 12000 Jefferson Avenue, Newport News, Virginia 23606 (United States); CERN, 1211 Geneva 23 (Switzerland); Medical Physics Department, European Institute of Oncology, Milan (Italy); Nuclear Medicine Department, European Institute of Oncology, Via Ripamonti 435, 2014 Milan (Italy); Medical Physics Department, European Institute of Oncology, Via Ripamonti 435, 20141 Milan (Italy); FaMAF, Universidad Nacional de Cordoba and CONICET, Cordoba, Argentina C.P. 5000 (Argentina)
2011-07-15
Purpose: The calculation of patient-specific dose distribution can be achieved by Monte Carlo simulations or by analytical methods. In this study, fluka Monte Carlo code has been considered for use in nuclear medicine dosimetry. Up to now, fluka has mainly been dedicated to other fields, namely high energy physics, radiation protection, and hadrontherapy. When first employing a Monte Carlo code for nuclear medicine dosimetry, its results concerning electron transport at energies typical of nuclear medicine applications need to be verified. This is commonly achieved by means of calculation of a representative parameter and comparison with reference data. Dose point kernel (DPK), quantifying the energy deposition all around a point isotropic source, is often the one. Methods: fluka DPKs have been calculated in both water and compact bone for monoenergetic electrons (10{sup -3} MeV) and for beta emitting isotopes commonly used for therapy ({sup 89}Sr, {sup 90}Y, {sup 131}I, {sup 153}Sm, {sup 177}Lu, {sup 186}Re, and {sup 188}Re). Point isotropic sources have been simulated at the center of a water (bone) sphere, and deposed energy has been tallied in concentric shells. fluka outcomes have been compared to penelope v.2008 results, calculated in this study as well. Moreover, in case of monoenergetic electrons in water, comparison with the data from the literature (etran, geant4, mcnpx) has been done. Maximum percentage differences within 0.8{center_dot}R{sub CSDA} and 0.9{center_dot}R{sub CSDA} for monoenergetic electrons (R{sub CSDA} being the continuous slowing down approximation range) and within 0.8{center_dot}X{sub 90} and 0.9{center_dot}X{sub 90} for isotopes (X{sub 90} being the radius of the sphere in which 90% of the emitted energy is absorbed) have been computed, together with the average percentage difference within 0.9{center_dot}R{sub CSDA} and 0.9{center_dot}X{sub 90} for electrons and isotopes, respectively. Results: Concerning monoenergetic electrons, within 0.8{center_dot}R{sub CSDA} (where 90%-97% of the particle energy is deposed), fluka and penelope agree mostly within 7%, except for 10 and 20 keV electrons (12% in water, 8.3% in bone). The discrepancies between fluka and the other codes are of the same order of magnitude than those observed when comparing the other codes among them, which can be referred to the different simulation algorithms. When considering the beta spectra, discrepancies notably reduce: within 0.9{center_dot}X{sub 90}, fluka and penelope differ for less than 1% in water and less than 2% in bone with any of the isotopes here considered. Complete data of fluka DPKs are given as Supplementary Material as a tool to perform dosimetry by analytical point kernel convolution. Conclusions: fluka provides reliable results when transporting electrons in the low energy range, proving to be an adequate tool for nuclear medicine dosimetry.
Botta, F; Di Dia, A; Pedroli, G; Mairani, A; Battistoni, G; Fasso, A; Ferrari, A; Ferrari, M; Paganelli, G
2011-06-01
The calculation of patient-specific dose distribution can be achieved by Monte Carlo simulations or by analytical methods. In this study, fluka Monte Carlo code has been considered for use in nuclear medicine dosimetry. Up to now, fluka has mainly been dedicated to other fields, namely high energy physics, radiation protection, and hadrontherapy. When first employing a Monte Carlo code for nuclear medicine dosimetry, its results concerning electron transport at energies typical of nuclear medicine applications need to be verified. This is commonly achieved by means of calculation of a representative parameter and comparison with reference data. Dose point kernel (DPK), quantifying the energy deposition all around a point isotropic source, is often the one.Methods: fluka DPKs have been calculated in both water and compact bone for monoenergetic electrons (10–3 MeV) and for beta emitting isotopes commonly used for therapy (89Sr, 90Y, 131I, 153Sm, 177Lu, 186Re, and 188Re). Point isotropic sources have been simulated at the center of a water (bone) sphere, and deposed energy has been tallied in concentric shells. fluka outcomes have been compared to penelope v.2008 results, calculated in this study as well. Moreover, in case of monoenergetic electrons in water, comparison with the data from the literature (etran, geant4, mcnpx) has been done. Maximum percentage differences within 0.8·RCSDA and 0.9·RCSDA for monoenergetic electrons (RCSDA being the continuous slowing down approximation range) and within 0.8·X90 and 0.9·X90 for isotopes (X90 being the radius of the sphere in which 90% of the emitted energy is absorbed) have been computed, together with the average percentage difference within 0.9·RCSDA and 0.9·X90 for electrons and isotopes, respectively.Results: Concerning monoenergetic electrons, within 0.8·RCSDA (where 90%–97% of the particle energy is deposed), fluka and penelope agree mostly within 7%, except for 10 and 20 keV electrons (12% in water, 8.3% in bone). The discrepancies between fluka and the other codes are of the same order of magnitude than those observed when comparing the other codes among them, which can be referred to the different simulation algorithms. When considering the beta spectra, discrepancies notably reduce: within 0.9·X90, fluka and penelope differ for less than 1% in water and less than 2% in bone with any of the isotopes here considered. Complete data of fluka DPKs are given as Supplementary Material as a tool to perform dosimetry by analytical point kernel convolution.Conclusions: fluka provides reliable results when transporting electrons in the low energy range, proving to be an adequate tool for nuclear medicine dosimetry.
A two-dimensional point-kernel model for dose calculations in a glove-box array
Kornreich, D.E.; Dooley, D.E.
1999-07-01
An associated paper details a model of a room containing glove boxes using the industry standard dose equivalent (dose) estimation tool MCNP. Such tools provide an excellent means for obtaining relatively reliable estimates of radiation transport in a complicated geometric structure. However, creating the input deck that models the complicated geometry is equally complicated. Therefore, an alternative tool is desirable that provides reasonably accurate dose estimates in complicated geometries for use in engineering-scale dose analyses. In the past, several tools that use the point-kernel model for estimating doses equivalent have been constructed (those referenced are only a small sample of similar tools). This new tool, the Photon And Neutron Dose Equivalent Model Of Nuclear materials Integrated with an Uncomplicated geometry Model (PANDEMONIUM), combines point-kernel and diffusion theory calculation routines with a geometry construction tool. PANDEMONIUM uses Visio to draw a glove-box array in the room, including hydrogenous shields, sources, and detectors. This simplification in geometric rendering limits the tool to two-dimensional geometries (and one-dimensional particle transport calculations).
Timothy H. Boyer
2002-10-30
By numerical calculation, the Planck spectrum with zero-point radiation is shown to satisfy a natural maximum-entropy principle whereas alternative choices of spectra do not. Specifically, if we consider a set of conducting-walled boxes, each with a partition placed at a different location in the box, so that across the collection of boxes the partitions are uniformly spaced across the volume, then the Planck spectrum correspond to that spectrum of random radiation (having constant energy kT per normal mode at low frequencies and zero-point energy (1/2)hw per normal mode at high frequencies) which gives maximum uniformity across the collection of boxes for the radiation energy per box. The analysis involves Casimir energies and zero-point radiation which do not usually appear in thermodynamic analyses. For simplicity, the analysis is presented for waves in one space dimension.
Johnson
1960-01-01
A general analytic expression for the relation length ( lambda ) of fast ; neutron dose rate or flux is derived from the AlbertWelton type point fission ; kernel. The application of the expression for lambda and additional ; characteristics which can be derived from lt are described. As an example of ; application, a graph is plotted of lambda
Bhandare, N. [University of Florida (United States)
2014-06-01
Purpose: To estimate and compare the doses received by the obturator, external and internal iliac lymph nodes and point Methods: CT-MR fused image sets of 15 patients obtained for each of 5 fractions of HDR brachytherapy using tandem and ring applicator, were used to generate treatment plans optimized to deliver a prescription dose to HRCTV-D90 and to minimize the doses to organs at risk (OARs). For each set of image, target volume (GTV, HRCTV) OARs (Bladder, Rectum, Sigmoid), and both left and right pelvic lymph nodes (obturator, external and internal iliac lymph nodes) were delineated. Dose-volume histograms (DVH) were generated for pelvic nodal groups (left and right obturator group, internal and external iliac chains) Per fraction DVH parameters used for dose comparison included dose to 100% volume (D100), and dose received by 2cc (D2cc), 1cc (D1cc) and 0.1 cc (D0.1cc) of nodal volume. Dose to point B was compared with each DVH parameter using 2 sided t-test. Pearson correlation were determined to examine relationship of point B dose with nodal DVH parameters. Results: FIGO clinical stage varied from 1B1 to IIIB. The median pretreatment tumor diameter measured on MRI was 4.5 cm (2.7– 6.4cm).The median dose to bilateral point B was 1.20 Gy ± 0.12 or 20% of the prescription dose. The correlation coefficients were all <0.60 for all nodal DVH parameters indicating low degree of correlation. Only 2 cc of obturator nodes was not significantly different from point B dose on t-test. Conclusion: Dose to point B does not adequately represent the dose to any specific pelvic nodal group. When using image guided 3D dose-volume optimized treatment nodal groups should be individually identified and delineated to obtain the doses received by pelvic nodes.
Sachin Jain; Vivek Agarwal
2007-01-01
This paper proposes a high performance, single-stage inverter topology for grid connected PV systems. The proposed configuration can not only boost the usually low photovoltaic (PV) array voltage, but can also convert the solar dc power into high quality ac power for feeding into the grid, while tracking the maximum power from the PV array. Total harmonic distortion of the
A two-dimensional point-kernel model for dose calculations in a glovebox array
D. E. Kornreich; D. E. Dooley
1999-01-01
An associated paper details a model of a room containing gloveboxes using the industry standard dose equivalent (dose) estimation tool MCNP. Such tools provide an excellent means for obtaining relatively reliable estimates of radiation transport in a complicated geometric structure. However, creating the input deck that models the complicated geometry is equally complicated. Therefore, an alternative tool is desirable that
Point kernel sup 1 H(n,. gamma. ) sup 2 H dose calculations in BNCT
J. Niemkiewicz; N. Gupta; T. E. Blue
1992-01-01
Boron neutron capture therapy (BNCT) is a potential treatment modality for the fatal brain glioblastoma multiforme. Successful BNCT will require calculation of the expected relative biological effectiveness dose distribution in the patient's head prior to treatment. The method most often proposed for calculating dose distributions in BNCT is the Monte Carlo simulation technique. However, Monte Carlo calculations require a large
Liu, Yi-Ching; Lee, Kuo-Wei; Sheu, Rong-Jiun
2015-07-01
This study investigated radiation exposures from nuclear medicine patients by systematically comparing the dose rates calculated using various source models, ranging from simplified point, line, and cylinder sources to high-quality anthropomorphic phantoms. Three widely used radionuclides, Tc, F, and I, were considered in these source models with uniform or organ-dependent distributions. Conducting Monte Carlo simulations with anthropomorphic phantoms is a realistic but time-consuming approach. The point source model is simple but too conservative, overestimating dose rates by approximately a factor of 2 at a distance of 30 cm and by 30-40% at 1 m. Both the line and cylinder source models provided improved estimates, reducing the overestimation of dose rates to 10-20% at distances of interest. The line source model was comparable to the cylinder source model because of the offset of two competing effects (i.e., attenuation and buildup) caused by the source volume. The influence of various photon energies and cylinder sizes on the result of compensating errors was examined to evaluate the effective range of the line source model. The line source model, which is relatively easy to implement and predicts slightly conservative dose rates, is considered the most practical method for calculating dose rates near radioactive patients. An application of the line source model to 51 post-thyroidectomy patients in Taiwan was demonstrated. The consistency between calculations and measurements was satisfactory after considering the room-scattering effect. PMID:26011499
2012-01-01
Purpose To evaluate the influence of the maximum involvement of biopsy core (MIBC) on outcome for prostate cancer patients treated with dose-escalated external beam radiotherapy (EBRT). Methods and materials The outcomes of 590 men with localized prostate cancer treated with EBRT (?75?Gy) at a single institution were retrospectively analyzed. The influence of MIBC on freedom from biochemical failure (FFBF), freedom from metastasis (FFM), cause-specific survival (CSS), and overall survival (OS) was compared to other surrogates for biopsy tumor volume, including the percentage of positive biopsy cores (PPC) and the total percentage of cancer volume (PCV). Results MIBC correlated with PSA, T-stage, Gleason score, NCCN risk group, PPC, PCV, and treatment related factors. On univariate analysis, MIBC was prognostic for all endpoints except OS; with greatest impact in those with Gleason scores of 8–10. However, on multivariate analysis, MIBC was only prognostic for FFBF (hazard ratio [HR] 1.9, p?=?0.008), but not for FFM (p?=?0.19), CSS (p?=?0.16), and OS (p?=?0.99). Conclusions In patients undergoing dose-escalated EBRT, MIBC had the greatest influence in those with Gleason scores of 8–10 but provided no additional prognostic data as compared to PPC and PCV, which remain the preferable prognostic variables in this patient population. PMID:22852797
Reichstetter, Sandra; Castillo, Gerardo M.; Rubinstein, Israel; Nishimoto-Ashfield, Akiko; Lai, ManShun; Jones, Cynthia C.; Banjeree, Aryamitra; Lyubimov, Alex; Bloedow, Duane C.; Bogdanov, Alexei; Bolotin, Elijah M.
2013-01-01
Purpose To determine and compare pharmacokinetics and toxicity of two nanoformulations of Vasoactive Intestinal Peptide (VIP). Methods VIP was formulated using a micellar (Sterically Stabilized Micelles, SSM) and a polymer-based (Protected Graft Copolymer, PGC) nanocarrier at various loading percentages. VIP binding to the nanocarriers, pharmacokinetics, blood pressure, blood chemistry, and acute maximum tolerated dose (MTD) of the formulations after injection into BALB/c mice were determined. Results Both formulations significantly extend in vivo residence time compared to unformulated VIP. Formulation toxicity is dependent on loading percentage, showing major differences between the two carrier types. Both formulations increase in vivo potency of unformulated VIP and show acute MTDs at least 140 times lower than unformulated VIP, but still at least 100 times higher than the anticipated highest human dose, 1–5 ?g/kg. These nanocarriers prevented a significant drop in arterial blood pressure compared to unformulated VIP. Conclusions While both carriers enhance in vivo residence time compared to unformulated VIP and reduce the drop in blood pressure immediately after injection, PGC is the excipient of choice to extend residence time and improve the safety of potent therapeutic peptides such as VIP. PMID:23224976
A. Hald
1949-01-01
1. Introduction.The two cases where a normal distribution is “truncated” at a known point have been treated by R. A. Fisher (1) and W. L. Stevens (2), respectively. Fisher treated the case in which all record is omitted of observations below a given value, while Stevens treated the case in which the frequency of observations below a given value is
Three-dimensional point localisation in low-dose X-ray images using stereo-photogrammetry
T. S. Douglas; C. L. Vaughan; S. M. Wynne
2004-01-01
A stereo-photogrammetric method for three-dimensional reconstruction of points in low-dose digital X-ray images obtained using\\u000a a scanner with similar imaging geometry to that of computed tomography scan projection radiography, was analysed. A calibration\\u000a frame containing 25 radio-opaque markers with known three-dimensional locations was scanned, and the accuracy of reconstruction\\u000a of the marker positions under varying control point configurations and separation
Therriault-Proulx, François; Archambault, Louis; Beaulieu, Luc; Beddar, Sam
2013-01-01
Purpose The goal of this study was to develop a novel multi-point plastic scintillation detector (mPSD) capable of measuring the dose accurately at multiple positions simultaneously using a single optical transmission line. Methods A 2-point mPSD used a band-pass approach that included splitters, color filters, and an EMCCD camera. The 3-point mPSD was based on a new full-spectrum approach, in which a spectrograph was coupled to a CCD camera. Irradiations of the mPSDs and of an ion chamber were performed with a 6-MV photon beam at various depths and lateral positions in a water tank. Results For the 2-point mPSD, the average relative differences between mPSD and ion chamber measurements for the depth-dose were 2.4±1.6% and 1.3±0.8% for BCF-60 and BCF-12, respectively. For the 3-point mPSD, the average relative differences over all conditions were 2.3±1.1%, 1.6±0.4%, and 0.32±0.19% for BCF-60, BCF-12, and BCF-10, respectively. Conclusions This study demonstrates the practical feasibility of mPSDs. This type of detector could be very useful for pre-treatment quality assurance applications as well as an accurate tool for real-time in vivo dosimetry. PMID:23060069
Christos Bousis; Dimitris Emfietzoglou; Panagiotis Hadjidoukas; Hooshang Nikjoo; Anand Pathak
2011-01-01
The spatial distribution of absorbed energy in irradiated matter can be conveniently described by dose-point-kernel (DPK) distributions that characterize the average energy deposition around single charged-particle tracks during their slowing down process. In the present work, electron DPKs in liquid water in the energy range from 100eV to 10keV are presented based on Monte Carlo simulation of electron transport in
Point kernel technique for calculating dose rates due to cobalt-60 hot particles
M. J. Thornhill; J. T. McCarthy; R. R. Morrissette; B. N. Leach
1989-01-01
This paper reports on a computer code called BETA that has been developed by health physicists at the Vermont Yankee Nuclear Power Station which accounts for the mass and size of hot particles of Cobalt-60, and therefore corrects the Loevinger-based dose calculation for self-absorption.
Kinhikar, R. A.; Pandey, V. P.; Jose, Rojas K.; Mahantshetty, U.; Dhote, D. S.; Deshpande, D. D.; Shrivastava, S. K.
2013-01-01
The objective of this work was to investigate and quantify the effect of sharp edges of the phantom on the point dose measurement during patient-specific dosimetry with Rapid Arc (RA). Ten patients with carcinoma of prostate were randomly selected for this dosimetric study. Rapid Arc plans were generated with 6 MV X-rays in the Eclipse (v 8.6.14) with single arc (clockwise). Dosimetry verification plans were generated for two phantoms (cylindrical and rectangular). The cylindrical phantom was solid water (diameter 34 cm) and the rectangular phantom was a water phantom (25 cm × 25 cm × 10 cm). These phantoms were pre-scanned in computed tomography (CT) machine with cylindrical ionization chamber (FC65) in place. The plans were delivered with Novalis Tx linear accelerator with 6 MV X-rays for both the phantoms separately. The measured dose was compared with the planned dose for both the phantoms. Mean percentage deviation between measured and planned doses was found to be 4.19 (SD 0.82) and 3.63 (SD 0.89) for cylindrical and rectangular phantoms, respectively. No significant dosimetric variation was found due to the geometry (sharp edges) of the phantom. The sharp edges of the phantom do not perturb the patient specific Rapid Arc dosimetry significantly. PMID:24049321
Kinhikar, R A; Pandey, V P; Jose, Rojas K; Mahantshetty, U; Dhote, D S; Deshpande, D D; Shrivastava, S K
2013-07-01
The objective of this work was to investigate and quantify the effect of sharp edges of the phantom on the point dose measurement during patient-specific dosimetry with Rapid Arc (RA). Ten patients with carcinoma of prostate were randomly selected for this dosimetric study. Rapid Arc plans were generated with 6 MV X-rays in the Eclipse (v 8.6.14) with single arc (clockwise). Dosimetry verification plans were generated for two phantoms (cylindrical and rectangular). The cylindrical phantom was solid water (diameter 34 cm) and the rectangular phantom was a water phantom (25 cm × 25 cm × 10 cm). These phantoms were pre-scanned in computed tomography (CT) machine with cylindrical ionization chamber (FC65) in place. The plans were delivered with Novalis Tx linear accelerator with 6 MV X-rays for both the phantoms separately. The measured dose was compared with the planned dose for both the phantoms. Mean percentage deviation between measured and planned doses was found to be 4.19 (SD 0.82) and 3.63 (SD 0.89) for cylindrical and rectangular phantoms, respectively. No significant dosimetric variation was found due to the geometry (sharp edges) of the phantom. The sharp edges of the phantom do not perturb the patient specific Rapid Arc dosimetry significantly. PMID:24049321
NASA Astrophysics Data System (ADS)
Cho, Sang Hyun; Reece, Warren D.; Kim, Chan-Hyeong
2004-03-01
Dose calculations around electron-emitting metallic spherical sources were performed up to the X90 distance of each electron energy ranging from 0.5 to 3.0 MeV using the MCNP 4C Monte Carlo code and the dose point kernel (DPK) method with the DPKs rescaled using the linear range ratio and physical density ratio, respectively. The results show that the discrepancy between the MCNP and DPK results increases with the atomic number of the source (i.e., heterogeneity in source-target geometry), regardless of the rescaling method used. The observed discrepancies between the MCNP and DPK results were up to 100% for extreme cases such as a platinum source immersed in water.
McBride, Carl; Noya, Eva G; Vega, Carlos; 10.1039/C2CP42393F
2012-01-01
The melting point of ice Ih, as well as the temperature of maximum density (TMD) in the liquid phase, has been computed using the path integral Monte Carlo method. Two new models are introduced; TIP4PQ_D2O and TIP4PQ_T2O which are specifically designed to study D2O and T2O respectively. We have also used these models to study the "competing quantum effects" proposal of Habershon, Markland and Manolopoulos; the TIP4PQ/2005, TIP4PQ/2005 (D2O) and TIP4PQ/2005 (T2O) models are able to study the isotopic substitution of hydrogen for deuterium or tritium whilst constraining the geometry, while the TIP4PQ_D2O and TIP4PQ_T2O models, where the O-H bond lengths are progressively shortened, permit the study of the influence of geometry (and thus dipole moment) on the isotopic effects. For TIP4PQ_D2O - TIP4PQ/2005 we found a melting point shift of 4.9 K (experimentally the value is 3.68K) and a TMD shift of 6K (experimentally 7.2K). For TIP4PQ_T2O - TIP4PQ/2005 we found a melting point shift of 5.2 K (experimentally the ...
NASA Astrophysics Data System (ADS)
Mangini, Colby D.
Hot particle' skin dosimetry calculations are commonly performed using homogeneous dose-point kernels (DPK) in conjunction with scaling and backscatter models to account for non-homogeneous geometries. A new scaling model for determining the actual DPK for beta-particles transmitted by a high- Z source material has been developed. The model is based on a determination of the amount of mono-energetic electron absorption that occurs in a given source thickness through the use of EGSnrc (Electron Gamma Shower) Monte Carlo simulations. Integration over a particular beta spectrum provides the betaparticle DPK following self-absorption as a function of source thickness and radial depth in water, thereby accounting for spectral hardening that may occur in higher-Z materials. Beta spectra of varying spectral shapes and endpoint energies were used to test our model for select source materials with 7.42 < Z ? 94. A new volumetric backscatter model has also been developed. This model corrects for beta-particle backscattering that occurs both in the source medium and in the atmosphere surrounding the source. Hot particle backscatter factors are constructed iteratively through selective integration of point-source backscatter factors over a given source geometry. Selection criteria are based on individual source-point positions within the source and determine which, if any, backscatter factors are used. The new scaling model and backscatter model were implemented into the DPK-based code VARSKIN 4 for extensive dose testing and verification. Verification results were compared to equivalent Monte Carlo simulations. The results demonstrate that significant improvements can be made to DPK-based models when dealing with high-Z volumetric sources in non-homogeneous geometries.
Výborný, P; Si?áková, S; Veselá Flórová, Z
2014-06-01
The author calculated the daily dose of Benzalkonium Chloride (BAC) in eye drops used in glaucoma treatment from the patients point of view, which means the real amount of BAC applied in the conjunctival sac. The information about BAC concentration in 1 milliliter (mL) do not offer sufficient picture about real circumstances, because the size of the drop, especially after the introducing of the use of generic products in clinical practice in specific anti-glaucomatic drugs, differs significantly. The daily dose of BAC may have substantial significance in the patients treatment tolerance. The overview of BAC daily dose in single therapeutic groups and drugs follows: betablockers: Timo-COMOD 0, Arutimol 2.6, Vistagan 2.8, Timolol-POS 3.0, Arteoptic 3.7, Betoptic S 4.8, Timoptol MSD 6.3, Betoptic 10.0; alpha-mimetics: Alphagan 3.5, Luxfen 3.5, Aruclonin 7.1; derivates of prostaglandine, prostamides: Taflotan 0, Monopost 0, Lumigan 1.4, Unilat 3.1, Travatan 3.9, Latanoprost Apotex 4.3, Rescula 5.8, Latanoprost POS 5.9, Xalatan 6.0, Latanoprost Ratiopharm 6.0, Latanoprost Actavis 6.0, Latanoprost Arrow 6.0, Arulatan 5.4, Latalux 6.0, Glaucotens 6.0, Xaloptic 6.0, Solusin 6.1; carboanhydrase inhibitors: Batidor 3.8, Azopt 4.8, Trusopt 5.4, Oftidor 8.1; fixed combinations: Ganfort 1.4, Dorzolamid/timolol TEVA 2.8, Combigan 3.2, Duotrav 4.3, Cosopt 5.6, Xalacom 6.0, Glaucotima 6.0, Latanoprost/timolol Apotex 6.3, Azarga 6.4, Dorzogen Combi 6.5, and Dozotima 8.8 µl. PMID:25032794
Dose point kernel for boron-11 decay and the cellular S values in boron neutron capture therapy.
Ma, Yunzhi; Geng, JinPeng; Gao, Song; Bao, Shanglian
2006-12-01
The study of the radiobiology of boron neutron capture therapy is based on the cellular level dosimetry of boron-10's thermal neutron capture reaction 10B(n,alpha)7Li, in which one 1.47 MeV helium-4 ion and one 0.84 MeV lithium-7 ion are spawned. Because of the chemical preference of boron-10 carrier molecules, the dose is heterogeneously distributed in cells. In the present work, the (scaled) dose point kernel of boron-11 decay, called 11B-DPK, was calculated by GEANT4 Monte Carlo simulation code. The DPK curve drops suddenly at the radius of 4.26 microm, the continuous slowing down approximation (CSDA) range of a lithium-7 ion. Then, after a slight ascending, the curve decreases to near zero when the radius goes beyond 8.20 microm, which is the CSDA range of a 1.47 MeV helium-4 ion. With the DPK data, S values for nuclei and cells with the boron-10 on the cell surface are calculated for different combinations of cell and nucleus sizes. The S value for a cell radius of 10 microm and a nucleus radius of 5 microm is slightly larger than the value published by Tung et al. [Appl. Radiat. Isot. 61, 739-743 (2004)]. This result is potentially more accurate than the published value since it includes the contribution of a lithium-7 ion as well as the alpha particle. PMID:17278826
Jenkins, T; Coutts, L V; Dunlop, D G; Oreffo, R O C; Cooper, C; Harvey, N C; Thurner, P J
2015-02-01
Reference Point Indentation (RPI) is a novel microindentation tool that has emerging clinical potential for the assessment of fracture risk as well as use as a laboratory tool for straight-forward mechanical characterisation of bone. Despite increasing use of the tool, little research is available to advise the set-up of testing protocols or optimisation of testing parameters. Here we consider five such parameters: maximum load, sample orientation, mode of use, sample preparation and measurement spacing, to investigate how they affect the Indentation Distance Increase (IDI), the most published measurement parameter associated with the RPI device. The RPI tool was applied to bovine bone; indenting in the proximal midshaft of five femora and human bone; indenting five femoral heads and five femoral neck samples. Based on the findings of these studies we recommend the following as the best practice. (1) Repeat measurements should be utilised to reduce the coefficient of variation (e.g. 8-15 repeats to achieve a 5-10% error, however the 3-5 measurements used here gives a 15-20% error). (2) IDI is dependent on maximum load (r=0.45 on the periosteal surface and r=0.94 on the machined surface, p<0.05), mode of use (i.e. comparing the device held freehand compared to fixed in its stand, p=0.04) and surface preparation (p=0.004) so these should be kept consistent throughout testing. Though sample orientation appears to have minimal influence on IDI (p>0.05), care should also be taken in combining measurements from different orientations. (3) The coefficient of variation is higher (p=0.04) when holding the device freehand, so it should ideally be kept supported in its stand. (4) Removing the periosteum (p=0.04) and machining the surface of the bone (p=0.08) reduces the coefficient of variation, so should be performed where practical. (5) There is a hyperbolic relationship between thickness and IDI (p<0.001) with a sample thickness 10 fold greater than the maximum indentation depth recommended, to ensure a representative measurement. (6) Measurement spacing does not appear to influence the IDI (p>0.05), so it can be as low as 500 µm. By following these recommendations, RPI users can minimise the potential confounding effects associated with the variables investigated here and reduce the coefficient of variation, hence achieving more consistent testing. This optimisation of the technique enhances both the clinical and laboratory potential of the tool. PMID:25455607
Dose point kernel for boron-11 decay and the cellular S values in boron neutron capture therapy
Ma Yunzhi; Geng Jinpeng; Gao Song; Bao Shanglian [Research Center for Tumor Diagnosis and Radiotherapy Physics and Laboratory of Medical Physics and Engineering, Peking University, Beijing 100871 (China); Department of Nuclear Physics, Chinese Institute of Atomic Energy, Beijing, 102413 (China); Research Center for Tumor Diagnosis and Radiotherapy Physics and Laboratory of Medical Physics and Engineering, Peking University, Beijing 100871 (China)
2006-12-15
The study of the radiobiology of boron neutron capture therapy is based on the cellular level dosimetry of boron-10's thermal neutron capture reaction {sup 10}B(n,{alpha}){sup 7}Li, in which one 1.47 MeV helium-4 ion and one 0.84 MeV lithium-7 ion are spawned. Because of the chemical preference of boron-10 carrier molecules, the dose is heterogeneously distributed in cells. In the present work, the (scaled) dose point kernel of boron-11 decay, called {sup 11}B-DPK, was calculated by GEANT4 Monte Carlo simulation code. The DPK curve drops suddenly at the radius of 4.26 {mu}m, the continuous slowing down approximation (CSDA) range of a lithium-7 ion. Then, after a slight ascending, the curve decreases to near zero when the radius goes beyond 8.20 {mu}m, which is the CSDA range of a 1.47 MeV helium-4 ion. With the DPK data, S values for nuclei and cells with the boron-10 on the cell surface are calculated for different combinations of cell and nucleus sizes. The S value for a cell radius of 10 {mu}m and a nucleus radius of 5 {mu}m is slightly larger than the value published by Tung et al. [Appl. Radiat. Isot. 61, 739-743 (2004)]. This result is potentially more accurate than the published value since it includes the contribution of a lithium-7 ion as well as the alpha particle.
NASA Astrophysics Data System (ADS)
Salazar, F. J. T.; Masdemont, J. J.; Gómez, G.; Macau, E. E.; Winter, O. C.
2014-11-01
Assume a constellation of satellites is flying near a given nominal trajectory around L4 or L5 in the Earth-Moon system in such a way that there is some freedom in the selection of the geometry of the constellation. We are interested in avoiding large variations of the mutual distances between spacecraft. In this case, the existence of regions of zero and minimum relative radial acceleration with respect to the nominal trajectory will prevent from the expansion or contraction of the constellation. In the other case, the existence of regions of maximum relative radial acceleration with respect to the nominal trajectory will produce a larger expansion and contraction of the constellation. The goal of this paper is to study these regions in the scenario of the Circular Restricted Three Body Problem by means of a linearization of the equations of motion relative to the periodic orbits around L4 or L5. This study corresponds to a preliminar planar formation flight dynamics about triangular libration points in the Earth-Moon system. Additionally, the cost estimate to maintain the constellation in the regions of zero and minimum relative radial acceleration or keeping a rigid configuration is computed with the use of the residual acceleration concept. At the end, the results are compared with the dynamical behavior of the deviation of the constellation from a periodic orbit.
NASA Astrophysics Data System (ADS)
Bousis, Christos; Emfietzoglou, Dimitris; Hadjidoukas, Panagiotis; Nikjoo, Hooshang; Pathak, Anand
2011-07-01
The spatial distribution of absorbed energy in irradiated matter can be conveniently described by dose-point-kernel (DPK) distributions that characterize the average energy deposition around single charged-particle tracks during their slowing down process. In the present work, electron DPKs in liquid water in the energy range from 100 eV to 10 keV are presented based on Monte Carlo simulation of electron transport in the continuous-slowing-down-approximation (csda). Elastic collisions are individually simulated using the screened Rutherford formula, whereas the energy loss from inelastic interactions is determined from stopping power (SP) theory. Along with the standard Bethe SP formula we examine different empirical expressions of general-use which are meant to improve the performance of the Bethe formula at low electron energies. Comparison is also made with a recent Bethe-type parametric expression obtained from a dielectric optical data model of liquid water. Our findings indicate that for electron energies below ?1 keV the discrepancies between the DPKs calculated by the general-purpose SP formulae become apparent. Moreover, the results obtained by the empirical expressions compare rather poorly with those from the dielectric model over the entire energy range examined.
Choi, Brian S.; Alberti, Dona B.; Schelman, William R.; Kolesar, Jill M.; Thomas, James P.; Marnocha, Rebecca; Eickhoff, Jens C.; Ivy, S. Percy; Wilding, George; Holen, Kyle D.
2010-01-01
Purpose 3-AP is a ribonucleotide reductase inhibitor and has been postulated to act synergistically with other chemotherapeutic agents. This study was conducted to determine the toxicity and antitumor activity of 3-AP with irinotecan. Correlative studies included pharmacokinetics and the effects of ABCB1 and UGT1A1 polymorphisms. Methods The treatment plan consisted of irinotecan on day 1 with 3-AP on days 1-3 of a 21-day cycle. Starting dose was irinotecan 150 mg/m2 and 3-AP 85 mg/m2/d. Polymorphisms of ABCB1 were evaluated by pyrosequencing. Drug concentrations were determined by HPLC. Results Twenty-three patients were enrolled, 10 men and 13 women. Tumor types included 7 patients with pancreatic cancer, 4 with lung cancer, 2 with cholangiocarcinoma, 2 with mesothelioma, 2 with ovarian cancer, and 6 with other malignancies. Two patients experienced dose-limiting toxicity (DLT) at dose level 1, requiring amendment of the dose escalation scheme. Maximal tolerated dose (MTD) was determined to be 3-AP 60 mg/m2/d and irinotecan 200 mg/m2. DLTs consisted of hypoxia, leukopenia, fatigue, infection, thrombocytopenia, dehydration and ALT elevation. One partial response in a patient with refractory non-small cell lung cancer was seen. Genotyping suggests that patients with wild-type ABCB1 have a higher rate of grade 3 or 4 toxicity than those with ABCB1 mutations. Conclusions The MTD for this combination was 3-AP 60 mg/m2/d on days 1-3 and irinotecan 200 mg/m2 on day 1 every 21 days. Antitumor activity in a patient with refractory non-small cell lung cancer was noted at level 1. PMID:20127092
Nikolic, Boris; Khosa, Faisal; Lin, Pei-Jan Paul; Khan, Atif N.; Sarwar, Sheryar; Yam, Chun-Shan; Court, Laurence E.; Raptopoulos, Vassilios; Clouse, Melvin E.
2012-01-01
OBJECTIVE The purpose of this article is to estimate the absorbed radiation dose in radiosensitive organs during coronary MDCT angiography using 320-MDCT and to determine the effects of tube voltage variation and heart rate (HR) control on absorbed radiation dose. MATERIALS AND METHODS Semiconductor field effect transistor detectors were used to measure absorbed radiation doses for the thyroid, midbreast, breast, and midlung in an anthropomorphic phantom at 100, 120, and 135 kVp at two different HRs of 60 and 75 beats per minute (bpm) with a scan field of view of 320 mm, 400 mA, 320 × 0.5 mm detectors, and 160 mm collimator width (160 mm range). The paired Student’s t test was used for data evaluation. RESULTS At 60 bpm, absorbed radiation doses for 100, 120, and 135 kVp were 13.41 ± 3.59, 21.7 ± 4.12, and 29.28 ± 5.17 mGy, respectively, for midbreast; 11.76 ± 0.58, 18.86 ± 1.06, and 24.82 ± 1.45 mGy, respectively, for breast; 12.19 ± 2.59, 19.09 ± 3.12, and 26.48 ± 5.0 mGy, respectively, for lung; and 0.37 ± 0.14, 0.69 ± 0.14, and 0.92 ± 0.2 mGy, respectively, for thyroid. Corresponding absorbed radiation doses for 75 bpm were 38.34 ± 2.02, 59.72 ± 3.13, and 77.8 ± 3.67 mGy for midbreast; 26.2 ± 1.74, 44 ± 1.11, and 52.84 ± 4.07 mGy for breast; 38.02 ± 1.58, 58.89 ± 1.68, and 78 ± 2.93 mGy for lung; and 0.79 ± 0.233, 1.04 ± 0.18, and 2.24 ± 0.52 mGy for thyroid. Absorbed radiation dose changes were significant for all organs for both tube voltage reductions as well as for HR control from 75 to 60 bpm at all tube voltage settings (p < 0.05). The absorbed radiation doses for the calcium score protocol were 11.2 ± 1.4 mGy for midbreast, 9.12 ± 0.48 mGy for breast, 10.36 ± 1.3 mGy for lung, and 0.4 ± 0.05 mGy for thyroid. CONCLUSION CT angiography with 320-MDCT scanners results in absorbed radiation doses in radiosensitive organs that compare favorably to those previously reported. Significant dose reductions can be achieved by tube voltage reductions and HR control. PMID:21098194
A two-dimensional point-kernel model for dose calculations in a glove-box array
D. E. Kornreich; D. E. Dooley
1999-01-01
An associated paper details a model of a room containing glove boxes using the industry standard dose equivalent (dose) estimation tool MCNP. Such tools provide an excellent means for obtaining relatively reliable estimates of radiation transport in a complicated geometric structure. However, creating the input deck that models the complicated geometry is equally complicated. Therefore, an alternative tool is desirable
Jonathan A. Freedman; David L. G. Noakes
2002-01-01
The most massive teleost, the ocean sunfish(Mola mola), is an order of magnitude smaller than the largest cartilaginous fish,the whale shark (Rhincodon typus), and issignificantly smaller than several other extantelasmobranch species. Possible reasons for this discrepancy in maximum size include:anatomical, physiological, ecological, and life-history\\/ontogenetic constraints. Weexamined life-history traits and growth ratesas the most likely constraints on maximum teleostsize. For pelagic
NASA Astrophysics Data System (ADS)
Maloy, Stuart A.; James, M. R.; Romero, T. J.; Toloczko, M. B.; Kurtz, R. J.; Kimura, A.
2005-05-01
The NLF series of steels are reduced activation ferritic-martensitic (RAFM) steels that are a part of the Japanese program to produce a suitable reduced activation ferritic-martensitic steel for the ITER project. Published reports on the NLF steels after about 35 dpa at 400 °C by Kurishita et al., indicate that these steels have similar strength and better ductility than other RAFM steels such as the JLF steels and F82H irradiated at 400 °C to similar doses. The tensile properties of NLF steels irradiated at ?400 °C to doses as high as 67 dpa are presented here. Tensile tests were conducted at a strain rate of 5 × 10-4 s-1 at 25, 400 °C, and 500 °C. Variations in irradiation temperature in the range of 390-430 °C had a relatively small, but definite effect on the tensile properties for tests conducted at 25, 400, and 500 °C. The strongest hardening is observed for specimens irradiated at 390 °C, and very little hardening is observed for specimens irradiated at 430 °C. Strain rate jump tests were performed on NLF-0 and NLF-1 at 400 °C after irradiation to 52 dpa. The rate sensitivity, m, is quite low, 0.003-0.005 and does not appear to be affected by irradiation at 52 dpa for an irradiation temperature of 430 °C.
Some considerations for modeling doses from radionuclides transported through groundwater
Robert D. Waters; Marilyn M. Gruebel
1998-01-01
Analysts typically incorporate into groundwater pathway models for low-level radioactive waste a simplified approach for the buildup and decay of radioactive progeny during environmental transport. The inventory is transported to the exposure point, with doses calculated there for the parent and progeny based on predicted concentrations of the parent radionuclides. This approach generally provides conservative values because maximum combined doses
Some Considerations for modeling doses from radionuclides transported through groundwater
Robert D. Waters; Marilyn M. Gruebel
1998-01-01
Analysts typically incorporate into groundwater pathway models for low-level radioactive waste a simplified approach for the buildup and decay of radioactive progeny during environmental transport. The inventory is transported to the exposure point, with doses calculated there for the parent and progeny based on predicted concentrations of the parent radionuclides. This approach generally provides conservative values because maximum combined doses
Julio F. Almansa; Rafael Guerrero; Feras M. O. Al-Dweri; Marta Anguiano; Antonio M. Lallena
2007-01-01
Monte Carlo calculations using the codes PENELOPE and GEANT4 have been performed to characterize the dosimetric properties of monoenergetic photon point sources in water. The dose rate in water has been calculated for energies of interest in brachytherapy, ranging between 10keV and 2MeV. A comparison of the results obtained using the two codes with the available data calculated with other
Julio F. Almansa; Rafael Guerrero; Feras M. O. Al-Dweri; Marta Anguiano; Antonio M. Lallena
2007-01-01
Monte Carlo calculations using the codes PENELOPE and GEANT4 have been performed to characterize the dosimetric properties of monoenergetic photon point sources in water. The dose rate in water has been calculated for energies of interest in brachytherapy, ranging between 10 keV and 2 MeV. A comparison of the results obtained using the two codes with the available data calculated
F. Botta; M. Cremonesi; A. Di Dia; G. Pedroli; A. Mairani; G. Battistoni; A. Fassò; A. Ferrari; M. Ferrari; G. Paganelli; M. Valente
2011-01-01
The calculation of patient-specific dose distribution can be achieved by Monte Carlo simulations or by analytical methods. In this study, fluka Monte Carlo code has been considered for use in nuclear medicine dosimetry. Up to now, fluka has mainly been dedicated to other fields, namely high energy physics, radiation protection, and hadrontherapy. When first employing a Monte Carlo code for
Dose point kernel for boron-11 decay and the cellular S values in boron neutron capture therapy
Yunzhi Ma; Jinpeng Geng; Song Gao; Shanglian Bao
2006-01-01
The study of the radiobiology of boron neutron capture therapy is based on the cellular level dosimetry of boron-10's thermal neutron capture reaction Â¹Â°B(n,Î±)â·Li, in which one 1.47 MeV helium-4 ion and one 0.84 MeV lithium-7 ion are spawned. Because of the chemical preference of boron-10 carrier molecules, the dose is heterogeneously distributed in cells. In the present work, the
Imam, Md Tarique; Venkateshan, S P; Tandon, Monika; Saha, Nilanjan; Pillai, K K
2011-12-01
The authors compared US Food and Drug Administration (FDA) and 9 pharmacologically guided approaches (PGAs; simple allometry, maximum life span potential [MLP], brain weight, rule of exponent [ROE], two 2-sp methods and 3 one-sp methods) to determine the maximum recommended starting dose (MRSD) for first-in-human clinical trials in adult healthy men using 10 drugs. The ROE method as suggested by Mahmood and Balian1 gave the best prediction accuracy for a pharmacokinetic (PK) parameter. Values derived from clearance were consistently better than volume of distribution (Vd)-based methods and had lower root mean square error (RMSE) values. A pictorial method evaluation chart was developed based on fold errors for simultaneous evaluation of various methods. The one-sp method (rat) and the US FDA methods gave the highest prediction accuracy and low RMSE values, and the 2-sp methods gave the least prediction accuracy with high RMSE values. The ROE method gave more consistent predictions for PK parameters than other allometric methods. Despite this, the MRSD predictions were not better than US FDA methods, probably indicating that across-species variation in clearance may be higher than variation in no observed adverse effect level (NOAEL) and that PGA methods may not be consistently better than the NOAEL based methods. PMID:21415286
Papadimitroulas, Panagiotis; Loudos, George; Nikiforidis, George C.; Kagadis, George C. [Department of Medical Physics, School of Medicine, University of Patras, Rion, GR 265 04 (Greece) and Department of Medical Instruments Technology, Technological Educational institute of Athens, Ag. Spyridonos Street, Egaleo GR 122 10, Athens (Greece); Department of Medical Instruments Technology, Technological Educational institute of Athens, Ag. Spyridonos Street, Egaleo GR 122 10, Athens (Greece); Department of Medical Physics, School of Medicine, University of Patras, Rion, GR 265 04 (Greece)
2012-08-15
Purpose: GATE is a Monte Carlo simulation toolkit based on the Geant4 package, widely used for many medical physics applications, including SPECT and PET image simulation and more recently CT image simulation and patient dosimetry. The purpose of the current study was to calculate dose point kernels (DPKs) using GATE, compare them against reference data, and finally produce a complete dataset of the total DPKs for the most commonly used radionuclides in nuclear medicine. Methods: Patient-specific absorbed dose calculations can be carried out using Monte Carlo simulations. The latest version of GATE extends its applications to Radiotherapy and Dosimetry. Comparison of the proposed method for the generation of DPKs was performed for (a) monoenergetic electron sources, with energies ranging from 10 keV to 10 MeV, (b) beta emitting isotopes, e.g., {sup 177}Lu, {sup 90}Y, and {sup 32}P, and (c) gamma emitting isotopes, e.g., {sup 111}In, {sup 131}I, {sup 125}I, and {sup 99m}Tc. Point isotropic sources were simulated at the center of a sphere phantom, and the absorbed dose was stored in concentric spherical shells around the source. Evaluation was performed with already published studies for different Monte Carlo codes namely MCNP, EGS, FLUKA, ETRAN, GEPTS, and PENELOPE. A complete dataset of total DPKs was generated for water (equivalent to soft tissue), bone, and lung. This dataset takes into account all the major components of radiation interactions for the selected isotopes, including the absorbed dose from emitted electrons, photons, and all secondary particles generated from the electromagnetic interactions. Results: GATE comparison provided reliable results in all cases (monoenergetic electrons, beta emitting isotopes, and photon emitting isotopes). The observed differences between GATE and other codes are less than 10% and comparable to the discrepancies observed among other packages. The produced DPKs are in very good agreement with the already published data, which allowed us to produce a unique DPKs dataset using GATE. The dataset contains the total DPKs for {sup 67}Ga, {sup 68}Ga, {sup 90}Y, {sup 99m}Tc, {sup 111}In, {sup 123}I, {sup 124}I, {sup 125}I, {sup 131}I, {sup 153}Sm, {sup 177}Lu {sup 186}Re, and {sup 188}Re generated in water, bone, and lung. Conclusions: In this study, the authors have checked GATE's reliability for absorbed dose calculation when transporting different kind of particles, which indicates its robustness for dosimetry applications. A novel dataset of DPKs is provided, which can be applied in patient-specific dosimetry using analytical point kernel convolution algorithms.
Liang, X; Morrill, S; Hardee, M; Han, E; Penagaricano, J; Zhang, X; Vaneerat, R [University of Arkansas Medical Science, Little Rock, AR (United States)
2014-06-01
Purpose: To evaluate the point dose variations between Ir-192 HDR treatments on two consecutive days using a single tandem-ovoid insertion without replanning in cervical cancer patients. Methods: This study includes eleven cervical cancer patients undergoing HDR brachytherapy with a prescribed dose of 28 Gy in 4 fractions. Each patient had two tandemovoid insertions one week apart. Each insertion was treated on consecutive days with rescanning and replanning prior to each treatment. To study the effect of no replanning for day 2 treatments, the day 1 plan dwell position and dwell time with decay were applied to the day 2 CT dataset. The point dose variations on the prescription point H (defined according to American Brachytherapy Society), and normal tissue doses at point B, bladder, rectum and vaginal mucosa (based on ICRU Report 38) were obtained. Results: Without replanning, the mean point H dose variation was 4.6 ± 10.7% on the left; 2.3 ± 2.9% on the right. The mean B point variation was 3.8 ± 4.9% on the left; 3.6 ± 4.7% on the right. The variation in the left vaginal mucosal point was 12.2 ± 10.7%; 9.5 ± 12.5% on the right; the bladder point 5.5 ± 7.4%; and the rectal point 7.9 ± 9.1%. Conclusion: Without replanning, there are variations both in the prescription point and the normal tissue point doses. The latter can vary as much as 10% or more. This is likely due to the steep dose gradient from brachytherapy compounded by shifts in the positions of the applicator in relationship to the patients anatomy. Imaging prior to each treatment and replanning ensure effective and safe brachytherapy are recommended.
NSDL National Science Digital Library
Siegrist, Kyle
This material introduces the basic theory of maximum likelihood estimation by discussing the likelihood function, the log likelihood function, and maximizing these functions using calculus. Several exercises ask students to derive certain estimators, while others have students compare the behavior of those estimators with other possibilities through the use of various JAVA applets. The applets use the same control features: the sliders set the parameter values, the Â?Stop #Â? drop down menu sets the number of samples taken, the Â?Update #Â? drop down menu sets how often the graph and tables update during the experiment, the single arrow takes one sample, the double arrow runs the full experiment, the square stops the experiment, and the back arrow resets the applet. This page is one lesson from the Virtual Laboratories in Statistics.
NASA Astrophysics Data System (ADS)
Almansa, Julio F.; Guerrero, Rafael; Al-Dweri, Feras M. O.; Anguiano, Marta; Lallena, Antonio M.
2007-05-01
Monte Carlo calculations using the codes PENELOPE and GEANT4 have been performed to characterize the dosimetric properties of monoenergetic photon point sources in water. The dose rate in water has been calculated for energies of interest in brachytherapy, ranging between 10 keV and 2 MeV. A comparison of the results obtained using the two codes with the available data calculated with other Monte Carlo codes is carried out. A ?2-like statistical test is proposed for these comparisons. PENELOPE and GEANT4 show a reasonable agreement for all energies analyzed and distances to the source larger than 1 cm. Significant differences are found at distances from the source up to 1 cm. A similar situation occurs between PENELOPE and EGS4.
Cord Dose Specification and Validation for Stereotactic Body Radiosurgery of Spine
Li Shidong [Department of Radiation Oncology, Henry Ford Health System, Detroit, MI (United States) and Department of Radiation Oncology, Temple University Hospital, Philadelphia, PA (United States)], E-mail: Shidong.Li@thus.temple.edu; Liu Yan; Chen Qing; Jin Jianyue [Department of Radiation Oncology, Henry Ford Health System, Detroit, MI (United States) Department of Radiation Oncology, Temple University Hospital, Philadelphia, PA (United States)
2009-01-01
Effective dose to a portion of the spinal cord in treatment segment, rather than the maximum point dose in the cord surface, was set as the dose limit in stereotactic-body radiosurgery (SBRS) of spine. Such a cord dose specification is sensitive to the volume size and position errors. Thus, we used stereotactic image guidance to minimize phantom positioning errors and compared the results of a 0.6-cm{sup 3} Farmer ionization chamber and a 0.01-cm{sup 3} compact ionization chamber to determine the detector size effect on 9 SBRS cases. The experimental errors ranging from 2% to 7% were estimated by the deviation of the mean dose in plans to the chamber with spatial displacements of 0.5 mm. The mean and measured doses for the large chamber to individual cases were significantly ({approx}17%) higher than the doses with the compact chamber placed at the same point. Our experimental results shown that the mean doses to the volume of interest could represent the measured cord doses. For the 9 patients, the mean doses to 10% of the cord were about 10 Gy, while the maximum cord doses varied from 11.6 to 17.6 Gy. The mean dose, possibly correlated with the cord complication, provided us an alternative and reliable cord dose specification in SBRS of spine.
Direct measurement of a patient's entrance skin dose during pediatric cardiac catheterization
Sun, Lue; Mizuno, Yusuke; Iwamoto, Mari; Goto, Takahisa; Koguchi, Yasuhiro; Miyamoto, Yuka; Tsuboi, Koji; Chida, Koichi; Moritake, Takashi
2014-01-01
Children with complex congenital heart diseases often require repeated cardiac catheterization; however, children are more radiosensitive than adults. Therefore, radiation-induced carcinogenesis is an important consideration for children who undergo those procedures. We measured entrance skin doses (ESDs) using radio-photoluminescence dosimeter (RPLD) chips during cardiac catheterization for 15 pediatric patients (median age, 1.92 years; males, n = 9; females, n = 6) with cardiac diseases. Four RPLD chips were placed on the patient's posterior and right side of the chest. Correlations between maximum ESD and dose–area products (DAP), total number of frames, total fluoroscopic time, number of cine runs, cumulative dose at the interventional reference point (IRP), body weight, chest thickness, and height were analyzed. The maximum ESD was 80 ± 59 (mean ± standard deviation) mGy. Maximum ESD closely correlated with both DAP (r = 0.78) and cumulative dose at the IRP (r = 0.82). Maximum ESD for coiling and ballooning tended to be higher than that for ablation, balloon atrial septostomy, and diagnostic procedures. In conclusion, we directly measured ESD using RPLD chips and found that maximum ESD could be estimated in real-time using angiographic parameters, such as DAP and cumulative dose at the IRP. Children requiring repeated catheterizations would be exposed to high radiation levels throughout their lives, although treatment influences radiation dose. Therefore, the radiation dose associated with individual cardiac catheterizations should be analyzed, and the effects of radiation throughout the lives of such patients should be followed. PMID:24968708
Salguero, Francisco J.; Saleh-Sayah, Nahla K.; Yan Chenyu; Siebers, Jeffrey V. [Department of Radiation Oncology, Virginia Commonwealth University, Richmond, Virginia, 23298 (United States)
2011-01-15
Purpose: This article presents a general procedural framework to assess the point-by-point precision in mapped dose associated with the intrinsic uncertainty of a deformable image registration (DIR) for any arbitrary patient. Methods: Dose uncertainty is obtained via a three-step process. In the first step, for each voxel in an imaging pair, a cluster of points is obtained by an iterative DIR procedure. In the second step, the dispersion of the points due to the imprecision of the DIR method is used to compute the spatial uncertainty. Two different ways to quantify the spatial uncertainty are presented in this work. Method A consists of a one-dimensional analysis of the modules of the position vectors, whereas method B performs a more detailed 3D analysis of the coordinates of the points. In the third step, the resulting spatial uncertainty estimates are used in combination with the mapped dose distribution to compute the point-by-point dose standard deviation. The process is demonstrated to estimate the dose uncertainty induced by mapping a 62.6 Gy dose delivered on maximum exhale to maximum inhale of a ten-phase four-dimensional lung CT. Results: For the demonstration lung image pair, the standard deviation of inconsistency vectors is found to be up to 9.2 mm with a mean {sigma} of 1.3 mm. This uncertainty results in a maximum estimated dose uncertainty of 29.65 Gy if method A is used and 21.81 Gy for method B. The calculated volume with dose uncertainty above 10.00 Gy is 602 cm{sup 3} for method A and 1422 cm{sup 3} for method B. Conclusions: This procedure represents a useful tool to evaluate the precision of a mapped dose distribution due to the intrinsic DIR uncertainty in a patient. The procedure is flexible, allowing incorporation of alternative intrinsic error models.
Lee, Seung Heon; Lee, Kyu Chan; Choi, Jinho; Ahn, So Hyun; Lee, Seok Ho; Sung, Ki Hoon; Kil, Se Hee
2015-01-01
Background. The aim of the study was to investigate whether biologically effective dose (BED) based on linear-quadratic model can be used to estimate spinal cord tolerance dose in spine stereotactic body radiation therapy (SBRT) delivered in 4 or more fractions. Patients and methods. Sixty-three metastatic spinal lesions in 47 patients were retrospectively evaluated. The most frequently prescribed dose was 36 Gy in 4 fractions. In planning, we tried to limit the maximum dose to the spinal cord or cauda equina less than 50% of prescription or 45 Gy2/2. BED was calculated using maximum point dose of spinal cord. Results. Maximum spinal cord dose per fraction ranged from 2.6 to 6.0 Gy (median 4.3 Gy). Except 4 patients with 52.7, 56.4, 62.4, and 67.9 Gy2/2, equivalent total dose in 2-Gy fraction of the patients was not more than 50 Gy2/2 (12.1–67.9, median 32.0). The ratio of maximum spinal cord dose to prescription dose increased up to 82.2% of prescription dose as epidural spinal cord compression grade increased. No patient developed grade 2 or higher radiation-induced spinal cord toxicity during follow-up period of 0.5 to 53.9 months. Conclusions. In fractionated spine SBRT, BED can be used to estimate spinal cord tolerance dose, provided that the dose per fraction to the spinal cord is moderate, e.g. < 6.0 Gy. It appears that a maximum dose of up to 45–50 Gy2/2 to the spinal cord is tolerable in 4 or more fractionation regimen.
SU-E-T-113: Dose Distribution Using Respiratory Signals and Machine Parameters During Treatment
Imae, T; Haga, A; Saotome, N; Kida, S; Nakano, M; Takeuchi, Y; Shiraki, T; Yano, K; Yamashita, H; Nakagawa, K; Ohtomo, K [University of Tokyo Hospital, Bunkyou-ku, Tokyo (Japan)
2014-06-01
Purpose: Volumetric modulated arc therapy (VMAT) is a rotational intensity-modulated radiotherapy (IMRT) technique capable of acquiring projection images during treatment. Treatment plans for lung tumors using stereotactic body radiotherapy (SBRT) are calculated with planning computed tomography (CT) images only exhale phase. Purpose of this study is to evaluate dose distribution by reconstructing from only the data such as respiratory signals and machine parameters acquired during treatment. Methods: Phantom and three patients with lung tumor underwent CT scans for treatment planning. They were treated by VMAT while acquiring projection images to derive their respiratory signals and machine parameters including positions of multi leaf collimators, dose rates and integrated monitor units. The respiratory signals were divided into 4 and 10 phases and machine parameters were correlated with the divided respiratory signals based on the gantry angle. Dose distributions of each respiratory phase were calculated from plans which were reconstructed from the respiratory signals and the machine parameters during treatment. The doses at isocenter, maximum point and the centroid of target were evaluated. Results and Discussion: Dose distributions during treatment were calculated using the machine parameters and the respiratory signals detected from projection images. Maximum dose difference between plan and in treatment distribution was ?1.8±0.4% at centroid of target and dose differences of evaluated points between 4 and 10 phases were no significant. Conclusion: The present method successfully evaluated dose distribution using respiratory signals and machine parameters during treatment. This method is feasible to verify the actual dose for moving target.
Maximum-Likelihood Stereo Correspondence using Field
MacLean, W. James
estimation. 1 Introduction Stereo vision makes use of two images from different view points to construct) motion-compensated stereo estimation. 2 Maximum-Likelihood Stereo Vision Dense stereo correspondence mayMaximum-Likelihood Stereo Correspondence using Field Programmable Gate Arrays Siraj Sabihuddin & W
Francesco Locatelli; Umberto Buoncristiani; Bernard Canaud; Hans Kohler; Thierry Petitclerc; Pietro Zucchelli; Ospedale A. Manzoni; CHU Montpellier; Schwerpunkt Nephrologie
2004-01-01
Background. From the beginning of the dialysis era, the issue of optimal dialysis dose and frequency has been a central topic in the delivery of dialysis treatment. Methods. We undertook a discussion to achieve a consensus on key points relating to dialysis dose and frequency, focusing on the relationships with clinical and patient outcomes. Results. Traditionally, dialysis adequacy has been
Organ and effective dose reduction in adult chest CT using abdominal lead shielding
Iball, G R; Brettle, D S
2011-01-01
Objectives The purpose of this study was to evaluate and compare organ and effective dose savings that could be achieved using conventional lead aprons and a new, custom-designed shield as out-of-plane shielding devices during chest CT scans. Methods Thermoluminescent dosimeters were used to measure doses throughout the abdomen and pelvis during CT scans of the chest of a RANDO phantom. Dose measurements were made with no shielding, with lead aprons and with the new shield around the abdomen and pelvis in order to quantify the achievable organ and effective dose reductions. Results Average dose savings in the 10 phantom sections ranged from 5% to 78% with the highest point dose saving of 93% being found in the mid-pelvis. When shielding was used, the maximum measured organ dose reduction was a 72% dose saving to the testes. Significant dose savings were found throughout the abdomen and pelvis, which contributed to an effective dose saving of 4% that was achieved over and above the dose savings obtained through conventional optimisation strategies. This could yield significant population dose savings and reductions in collective radiation risk. Conclusion In this study significant organ and effective dose reductions have been achieved through the use of abdominal shielding during chest CT examinations and it is therefore recommended that out-of-plane patient shielding devices should be used for all chest CT scans and potentially for every CT scan, irrespective of body part. PMID:22011831
Maximum a Posteriori Maximum Entropy Signal Denoising
NASA Astrophysics Data System (ADS)
Seghouane, Abd-Krim; Knockaert, Luc
2007-11-01
When fitting wavelet based models, shrinkage of the empirical wavelet coefficients is an effective tool for signal denoising. Based on different approaches, different shrinkage functions have been proposed in the literature. The shrinkage functions derived using Bayesian estimation theory depend on the prior used on the wavelet coefficients. However, no simple and direct method exists for the choice of the prior. In this paper a new method based on maximum entropy considerations is proposed for the construction of the prior on the wavelet coefficients. The new shrinkage function is obtained by coupling this prior to maximum a posteriori arguments. A comparison with classical shrinkage functions is given in a simulation example of image denoising in order to illustrate the effectiveness of the proposed thresholding method.
Total Maximum Daily Load Program
NSDL National Science Digital Library
The Environmental Protection Agency (EPA) provides this informative resource on Total Maximum Daily Loads (TMDL). A term used to discuss water quality, TMDL refers to "a calculation of the maximum amount of a pollutant that a water body can receive and still meet water quality standards." The TMDL Program Website offers background information on TMDLs (including FAQs), a National Overview of Impaired Waters in the US, and two standard presentations on TMDLs (HTML and Power Point). The heart of the site, however, is the interactive map of the US, which allows users access to each state's TMDL Program. Within each state, watershed names and maps, as well as source information (Water body, Parameter of Concern, Priority for TMDL Development), are provided.
A silicon strip detector dose magnifying glass for IMRT dosimetry
Wong, J. H. D.; Carolan, M.; Lerch, M. L. F.; Petasecca, M.; Khanna, S.; Perevertaylo, V. L.; Metcalfe, P.; Rosenfeld, A. B. [Centre for Medical Radiation Physics, University of Wollongong, New South Wales 2522 (Australia) and Faculty of Medicine, University of Malaya, Kuala Lumpur 50603 (Malaysia); Centre for Medical Radiation Physics, University of Wollongong, New South Wales 2522 (Australia) and Illawarra Cancer Care Centre, Wollongong Hospital, New South Wales 2500 (Australia); Centre for Medical Radiation Physics, University of Wollongong, New South Wales 2522 (Australia); St. George Cancer Care Centre, Kogarah, Sydney, New South Wales 2217 (Australia); SPA BIT, 01034 Kiev (Ukraine); Centre for Medical Radiation Physics, University of Wollongong, New South Wales 2522 (Australia)
2010-02-15
Purpose: Intensity modulated radiation therapy (IMRT) allows the delivery of escalated radiation dose to tumor while sparing adjacent critical organs. In doing so, IMRT plans tend to incorporate steep dose gradients at interfaces between the target and the organs at risk. Current quality assurance (QA) verification tools such as 2D diode arrays, are limited by their spatial resolution and conventional films are nonreal time. In this article, the authors describe a novel silicon strip detector (CMRP DMG) of high spatial resolution (200 {mu}m) suitable for measuring the high dose gradients in an IMRT delivery. Methods: A full characterization of the detector was performed, including dose per pulse effect, percent depth dose comparison with Farmer ion chamber measurements, stem effect, dose linearity, uniformity, energy response, angular response, and penumbra measurements. They also present the application of the CMRP DMG in the dosimetric verification of a clinical IMRT plan. Results: The detector response changed by 23% for a 390-fold change in the dose per pulse. A correction function is derived to correct for this effect. The strip detector depth dose curve agrees with the Farmer ion chamber within 0.8%. The stem effect was negligible (0.2%). The dose linearity was excellent for the dose range of 3-300 cGy. A uniformity correction method is described to correct for variations in the individual detector pixel responses. The detector showed an over-response relative to tissue dose at lower photon energies with the maximum dose response at 75 kVp nominal photon energy. Penumbra studies using a Varian Clinac 21EX at 1.5 and 10.0 cm depths were measured to be 2.77 and 3.94 mm for the secondary collimators, 3.52 and 5.60 mm for the multileaf collimator rounded leaf ends, respectively. Point doses measured with the strip detector were compared to doses measured with EBT film and doses predicted by the Philips Pinnacle treatment planning system. The differences were 1.1%{+-}1.8% and 1.0%{+-}1.6%, respectively. They demonstrated the high temporal resolution capability of the detector readout system, which will allow one to investigate the temporal dose pattern of IMRT and volumetric modulated arc therapy (VMAT) deliveries. Conclusions: The CMRP silicon strip detector dose magnifying glass interfaced to a TERA ASIC DAQ system has high spatial and temporal resolution. It is a novel and valuable tool for QA in IMRT dose delivery and for VMAT dose delivery.
Beta doses to spherical grains
B. J. Brennan
2003-01-01
The classic paper of Mejdahl (1979) on beta doses to quartz grains has been a standard reference for many years. In this paper we present an update of the data for beta doses to spherical quartz grains from internal and external natural sources, using dose point kernels based on modern spectra and Monte Carlo calculations. The differences from the Mejdahl
Akleev, A V; Dimov, G P; Varfolomeeva, T A
2012-01-01
The purpose of this study is a retrospective estimation of the influence of dose and dose rate of the red bone marrow chronic radiation exposure in combination with various modifying factors (gender, age, comorbidity) on the frequency of deviations from normal values of the results of peripheral blood investigation in humans exposed on the Techa River. The results of investigation show that humans chronically exposed to radiation can develop marked changes in the cellular composition of peripheral blood characterized by a tendency to cytopenia (signs of the decompensation of hemopoiesis). The tendency to cytopenia can be identified earlier in the lymphoid germ, and later in platelet and erythroid lines. A high lability of granulocytes under the influence of various, often infectious, factors is the cause of the lack of statistically significant differences in terms of frequency of neutropenia. Several non-radiation factors (gender, age, health status) in combination with radiation exposure could have a modifying influence on hematopoiesis, which contributed to the disruption of adaptation processes and the development of conditions characterized by a tendency to cytopenias in exposed individuals. The red bone marrow dose rate reduction resulted in a gradual decrease in the frequency of erythrocytopenia, thrombocytopenia, neutropenia and lymphocytopenia in the group of exposed population. Increased frequencies of erythrocytosis, thrombocytosis, lymphocytosis, monocytosis and neutrophilia were observed when the median dose rate was reduced to the level of 0.024 Gy/year (in the year 1956), which could be regarded as activation of regenerative processes in hematopoiesis. PMID:22690575
3D Dose Verification Using Tomotherapy CT Detector Array
Sheng Ke, E-mail: ks2mc@virginia.edu [Department of Radiation Oncology, University of Virginia, Charlottesville, VA (United States); Jones, Ryan; Yang Wensha; Saraiya, Siddharth; Schneider, Bernard [Department of Radiation Oncology, University of Virginia, Charlottesville, VA (United States); Chen Quan; Sobering, Geoff; Olivera, Gustavo [TomoTherapy, Inc., Madison, WI (United States); Read, Paul [Department of Radiation Oncology, University of Virginia, Charlottesville, VA (United States)
2012-02-01
Purpose: To evaluate a three-dimensional dose verification method based on the exit dose using the onboard detector of tomotherapy. Methods and Materials: The study included 347 treatment fractions from 24 patients, including 10 prostate, 5 head and neck (HN), and 9 spinal stereotactic body radiation therapy (SBRT) cases. Detector sonograms were retrieved and back-projected to calculate entrance fluence, which was then forward-projected on the CT images to calculate the verification dose, which was compared with ion chamber and film measurement in the QA plans and with the planning dose in patient plans. Results: Root mean square (RMS) errors of 2.0%, 2.2%, and 2.0% were observed comparing the dose verification (DV) and the ion chamber measured point dose in the phantom plans for HN, prostate, and spinal SBRT patients, respectively. When cumulative dose in the entire treatment is considered, for HN patients, the error of the mean dose to the planning target volume (PTV) varied from 1.47% to 5.62% with a RMS error of 3.55%. For prostate patients, the error of the mean dose to the prostate target volume varied from -5.11% to 3.29%, with a RMS error of 2.49%. The RMS error of maximum doses to the bladder and the rectum were 2.34% (-4.17% to 2.61%) and 2.64% (-4.54% to 3.94%), respectively. For the nine spinal SBRT patients, the RMS error of the minimum dose to the PTV was 2.43% (-5.39% to 2.48%). The RMS error of maximum dose to the spinal cord was 1.05% (-2.86% to 0.89%). Conclusions: An excellent agreement was observed between the measurement and the verification dose. In the patient treatments, the agreement in doses to the majority of PTVs and organs at risk is within 5% for the cumulative treatment course doses. The dosimetric error strongly depends on the error in multileaf collimator leaf opening time with a sensitivity correlating to the gantry rotation period.
Li, Heng; Park, Peter; Liu, Wei; Matney, Jason; Liao, Zhongxing; Balter, Peter; Li, Yupeng; Zhang, Xiaodong; Li, Xiaoqiang; Zhu, X. Ronald
2013-01-01
Purpose: The objective of this study was to quantify respiratory motion-induced dose uncertainty at the planning stage for step-and-shoot intensity-modulated radiation therapy (IMRT) using an analytical technique. Methods: Ten patients with stage II/III lung cancer who had undergone a planning four-dimensional (4D) computed tomographic scan and step-and-shoot IMRT planning were selected with a mix of motion and tumor size for this retrospective study. A step-and-shoot IMRT plan was generated for each patient. The maximum and minimum doses with respiratory motion were calculated for each plan, and the mean deviation from the 4D dose was calculated, taking delivery time, fractionation, and patient breathing cycle into consideration. Results: For all patients evaluated in this study, the mean deviation from the 4D dose in the planning target volume (PTV) was <2.5%, with a standard deviation <1.2%, and maximum point dose variation from the 4D dose was <6.2% in the PTV assuming delivery dose rate of 200 MU/min and patient breathing cycle of 8 s. The motion-induced dose uncertainty is a function of motion, fractionation, MU (plan modulation), dose rate, and patient breathing cycle. Conclusions: Respiratory motion-induced dose uncertainty varies from patient to patient. Therefore, it is important to evaluate the dose uncertainty on a patient-specific basis, which could be useful for plan evaluation and treatment strategy determination for selected patients. PMID:24320498
Li, Heng; Park, Peter; Liu, Wei; Matney, Jason; Balter, Peter; Zhang, Xiaodong; Li, Xiaoqiang; Zhu, X. Ronald [Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, Texas 77030 (United States)] [Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, Texas 77030 (United States); Liao, Zhongxing [Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas 77030 (United States)] [Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas 77030 (United States); Li, Yupeng [Applied Research, Varian Medical Systems, Palo Alto, California 94304 (United States)] [Applied Research, Varian Medical Systems, Palo Alto, California 94304 (United States)
2013-12-15
Purpose: The objective of this study was to quantify respiratory motion-induced dose uncertainty at the planning stage for step-and-shoot intensity-modulated radiation therapy (IMRT) using an analytical technique.Methods: Ten patients with stage II/III lung cancer who had undergone a planning four-dimensional (4D) computed tomographic scan and step-and-shoot IMRT planning were selected with a mix of motion and tumor size for this retrospective study. A step-and-shoot IMRT plan was generated for each patient. The maximum and minimum doses with respiratory motion were calculated for each plan, and the mean deviation from the 4D dose was calculated, taking delivery time, fractionation, and patient breathing cycle into consideration.Results: For all patients evaluated in this study, the mean deviation from the 4D dose in the planning target volume (PTV) was <2.5%, with a standard deviation <1.2%, and maximum point dose variation from the 4D dose was <6.2% in the PTV assuming delivery dose rate of 200 MU/min and patient breathing cycle of 8 s. The motion-induced dose uncertainty is a function of motion, fractionation, MU (plan modulation), dose rate, and patient breathing cycle.Conclusions: Respiratory motion-induced dose uncertainty varies from patient to patient. Therefore, it is important to evaluate the dose uncertainty on a patient-specific basis, which could be useful for plan evaluation and treatment strategy determination for selected patients.
Spline-based procedures for dose-finding studies with active control
Helms, Hans-Joachim; Benda, Norbert; Zinserling, Jörg; Kneib, Thomas; Friede, Tim
2015-01-01
In a dose-finding study with an active control, several doses of a new drug are compared with an established drug (the so-called active control). One goal of such studies is to characterize the dose–response relationship and to find the smallest target dose concentration d*, which leads to the same efficacy as the active control. For this purpose, the intersection point of the mean dose–response function with the expected efficacy of the active control has to be estimated. The focus of this paper is a cubic spline-based method for deriving an estimator of the target dose without assuming a specific dose–response function. Furthermore, the construction of a spline-based bootstrap CI is described. Estimator and CI are compared with other flexible and parametric methods such as linear spline interpolation as well as maximum likelihood regression in simulation studies motivated by a real clinical trial. Also, design considerations for the cubic spline approach with focus on bias minimization are presented. Although the spline-based point estimator can be biased, designs can be chosen to minimize and reasonably limit the maximum absolute bias. Furthermore, the coverage probability of the cubic spline approach is satisfactory, especially for bias minimal designs. © 2014 The Authors. Statistics in Medicine Published by John Wiley & Sons Ltd. PMID:25319931
Benchmarking for maximum value.
Baldwin, Ed
2009-03-01
Speaking at the most recent Healthcare Estates conference, Ed Baldwin, of international built asset consultancy EC Harris LLP, examined the role of benchmarking and market-testing--two of the key methods used to evaluate the quality and cost-effectiveness of hard and soft FM services provided under PFI healthcare schemes to ensure they are offering maximum value for money. PMID:19344004
NSDL National Science Digital Library
Kristine DeLong
In this activity for undergraduates, students explore the CLIMAP (Climate: Long-Range Investigation, Mapping and Prediction) model results for differences between the modern and the Last Glacial Maximum (LGM) and discover the how climate and vegetation may have changed in different regions of the Earth based on scientific data.
The contribution from transit dose for 192Ir HDR brachytherapy treatments
NASA Astrophysics Data System (ADS)
Fonseca, G. P.; Landry, G.; Reniers, B.; Hoffmann, A.; Rubo, R. A.; Antunes, P. C. G.; Yoriyaz, H.; Verhaegen, F.
2014-04-01
Brachytherapy treatment planning systems that use model-based dose calculation algorithms employ a more accurate approach that replaces the TG43-U1 water dose formalism and adopt the TG-186 recommendations regarding composition and geometry of patients and other relevant effects. However, no recommendations were provided on the transit dose due to the source traveling inside the patient. This study describes a methodology to calculate the transit dose using information from the treatment planning system (TPS) and considering the source's instantaneous and average speed for two prostate and two gynecological cases. The trajectory of the 192Ir HDR source was defined by importing applicator contour points and dwell positions from the TPS. The transit dose distribution was calculated using the maximum speed, the average speed and uniform accelerations obtained from the literature to obtain an approximate continuous source distribution simulated with a Monte Carlo code. The transit component can be negligible or significant depending on the speed profile adopted, which is not clearly reported in the literature. The significance of the transit dose can also be due to the treatment modality; in our study interstitial treatments exhibited the largest effects. Considering the worst case scenario the transit dose can reach 3% of the prescribed dose in a gynecological case with four catheters and up to 11.1% when comparing the average prostate dose for a case with 16 catheters. The transit dose component increases by increasing the number of catheters used for HDR brachytherapy, reducing the total dwell time per catheter or increasing the number of dwell positions with low dwell times. This contribution may become significant (>5%) if it is not corrected appropriately. The transit dose cannot be completely compensated using simple dwell time corrections since it may have a non-uniform distribution. An accurate measurement of the source acceleration and maximum speed should be incorporated in clinical practice or provided by the manufacturer to determine the transit dose component with high accuracy.
Finding Maximum Length Tours Under Polyhedral Norms
Alexander Barvinok; David S. Johnson; Gerhard J. Woeginger; Russell Woodroofe
1998-01-01
We consider the traveling salesman problem when the cities are points in IRdfor some fixed d and distances are computed according to a polyhedral norm. Weshow that for any such norm, the problem of finding a tour of maximum lengthcan be solved in polynomial time. If arithmetic operations are assumed to takeunit time, our algorithms run in time O(nf+1), where
Introduction to maximum entropy
Sivia, D.S.
1988-01-01
The maximum entropy (MaxEnt) principle has been successfully used in image reconstruction in a wide variety of fields. We review the need for such methods in data analysis and show, by use of a very simple example, why MaxEnt is to be preferred over other regularizing functions. This leads to a more general interpretation of the MaxEnt method, and its use is illustrated with several different examples. Practical difficulties with non-linear problems still remain, this being highlighted by the notorious phase problem in crystallography. We conclude with an example from neutron scattering, using data from a filter difference spectrometer to contrast MaxEnt with a conventional deconvolution. 12 refs., 8 figs., 1 tab.
Campanelli, Manuela; Lousto, Carlos O; Zlochower, Yosef; Merritt, David
2007-06-01
Recent calculations of gravitational radiation recoil generated during black-hole binary mergers have reopened the possibility that a merged binary can be ejected even from the nucleus of a massive host galaxy. Here we report the first systematic study of gravitational recoil of equal-mass binaries with equal, but counteraligned, spins parallel to the orbital plane. Such an orientation of the spins is expected to maximize the recoil. We find that recoil velocity (which is perpendicular to the orbital plane) varies sinusoidally with the angle that the initial spin directions make with the initial linear momenta of each hole and scales up to a maximum of approximately 4000 km s-1 for maximally rotating holes. Our results show that the amplitude of the recoil velocity can depend sensitively on spin orientations of the black holes prior to merger. PMID:17677894
Dose Calculations for [131I] Meta-Iodobenzylguanidine-Induced Bystander Effects
Gow, M. D.; Seymour, C. B.; Boyd, M.; Mairs, R. J.; Prestiwch, W. V.; Mothersill, C. E.
2014-01-01
Targeted radiotherapy is a potentially useful treatment for some cancers and may be potentiated by bystander effects. However, without estimation of absorbed dose, it is difficult to compare the effects with conventional external radiation treatment. Methods: Using the Vynckier – Wambersie dose point kernel, a model for dose rate evaluation was created allowing for calculation of absorbed dose values to two cell lines transfected with the noradrenaline transporter (NAT) gene and treated with [131I]MIBG. Results: The mean doses required to decrease surviving fractions of UVW/NAT and EJ138/NAT cells, which received medium from [131I]MIBG-treated cells, to 25 – 30% were 1.6 and 1.7 Gy respectively. The maximum mean dose rates achieved during [131I]MIBG treatment were 0.09 – 0.75 Gy/h for UVW/NAT and 0.07 – 0.78 Gy/h for EJ138/NAT. These were significantly lower than the external beam gamma radiation dose rate of 15 Gy/h. In the case of control lines which were incapable of [131I]MIBG uptake the mean absorbed doses following radiopharmaceutical were 0.03 – 0.23 Gy for UVW and 0.03 – 0.32 Gy for EJ138. Conclusion: [131I]MIBG treatment for ICCM production elicited a bystander dose-response profile similar to that generated by external beam gamma irradiation but with significantly greater cell death. PMID:24659931
Investigation of 1-cm dose equivalent for photons behind shielding materials
Hirayama, Hideo (National Lab. for High Energy Physics, Tsukuba, Ibaraki (Japan)); Tanaka, Shun-ichi (Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan))
1991-03-01
The ambient dose equivalent at 1-cm depth, assumed equivalent to the 1-cm dose equivalent in practical dose estimations behind shielding slabs of water, concrete, iron or lead for normally incident photons having various energies was calculated by using conversion factors for a slab phantom. It was compared with the 1-cm depth dose calculated with the Monte Carlo code EGS4. It was concluded from this comparison that the ambient dose equivalent calculated by using the conversion factors for the ICRU sphere could be used for the evaluation of the 1-cm dose equivalent for the sphere phantom within 20% errors. Average and practical conversion factors are defined as the conversion factors from exposure to ambient dose equivalent in a finite slab or an infinite one, respectively. They were calculated with EGS4 and the discrete ordinates code PALLAS. The exposure calculated with simple estimation procedures such as point kernel methods can be easily converted to ambient dose equivalent by using these conversion factors. The maximum value between 1 and 30 mfp can be adopted as the conversion factor which depends only on material and incident photon energy. This gives the ambient dose equivalent on the safe side. 13 refs., 7 figs., 2 tabs.
Estimation Of Organ Doses From Solar Particle Events For Future Space Exploration Missions
NASA Technical Reports Server (NTRS)
Kim, Myung-Hee; Cucinotta, Francis A.
2006-01-01
Radiation protection practices define the effective dose as a weighted sum of equivalent dose over major organ sites for radiation cancer risks. Since a crew personnel dosimeter does not make direct measurement of the effective dose, it has been estimated with skin-dose measurements and radiation transport codes for ISS and STS missions. If sufficient protection is not provided near solar maximum, the radiation risk can be significant due to exposure to sporadic solar particle events (SPEs) as well as to the continuous galactic cosmic radiation (GCR) on future exploratory-class and long-duration missions. For accurate estimates of overall fatal cancer risks from SPEs, the specific doses at various blood forming organs (BFOs) were considered, because proton fluences and doses vary considerably across marrow regions. Previous estimates of BFO doses from SPEs have used an average body-shielding distribution for the bone marrow based on the computerized anatomical man model (CAM). With the development of an 82-point body-shielding distribution at BFOs, the mean and variance of SPE doses in the major active marrow regions (head and neck, chest, abdomen, pelvis and thighs) will be presented. Consideration of the detailed distribution of bone marrow sites is one of many requirements to improve the estimation of effective doses for radiation cancer risks.
The Radiation Dose-Response of the Human Spinal Cord
Schultheiss, Timothy E. [Department of Radiation Oncology, City of Hope Cancer Center, Duarte, CA (United States)], E-mail: schultheiss@coh.org
2008-08-01
Purpose: To characterize the radiation dose-response of the human spinal cord. Methods and Materials: Because no single institution has sufficient data to establish a dose-response function for the human spinal cord, published reports were combined. Requisite data were dose and fractionation, number of patients at risk, number of myelopathy cases, and survival experience of the population. Eight data points for cervical myelopathy were obtained from five reports. Using maximum likelihood estimation correcting for the survival experience of the population, estimates were obtained for the median tolerance dose, slope parameter, and {alpha}/{beta} ratio in a logistic dose-response function. An adequate fit to thoracic data was not possible. Hyperbaric oxygen treatments involving the cervical cord were also analyzed. Results: The estimate of the median tolerance dose (cervical cord) was 69.4 Gy (95% confidence interval, 66.4-72.6). The {alpha}/{beta} = 0.87 Gy. At 45 Gy, the (extrapolated) probability of myelopathy is 0.03%; and at 50 Gy, 0.2%. The dose for a 5% myelopathy rate is 59.3 Gy. Graphical analysis indicates that the sensitivity of the thoracic cord is less than that of the cervical cord. There appears to be a sensitizing effect from hyperbaric oxygen treatment. Conclusions: The estimate of {alpha}/{beta} is smaller than usually quoted, but values this small were found in some studies. Using {alpha}/{beta} = 0.87 Gy, one would expect a considerable advantage by decreasing the dose/fraction to less than 2 Gy. These results were obtained from only single fractions/day and should not be applied uncritically to hyperfractionation.
Siauw, Ko-Ay Timmy
2012-01-01
of needles, the prostate size of the patient, dosimetry, anddosimetry robustness was evaluated. For each patient, adosimetry in our results show no dose points received this dose level for any patient.
A heterogeneous algorithm for PDT dose optimization for prostate
NASA Astrophysics Data System (ADS)
Altschuler, Martin D.; Zhu, Timothy C.; Hu, Yida; Finlay, Jarod C.; Dimofte, Andreea; Wang, Ken; Li, Jun; Cengel, Keith; Malkowicz, S. B.; Hahn, Stephen M.
2009-02-01
The object of this study is to develop optimization procedures that account for both the optical heterogeneity as well as photosensitizer (PS) drug distribution of the patient prostate and thereby enable delivery of uniform photodynamic dose to that gland. We use the heterogeneous optical properties measured for a patient prostate to calculate a light fluence kernel (table). PS distribution is then multiplied with the light fluence kernel to form the PDT dose kernel. The Cimmino feasibility algorithm, which is fast, linear, and always converges reliably, is applied as a search tool to choose the weights of the light sources to optimize PDT dose. Maximum and minimum PDT dose limits chosen for sample points in the prostate constrain the solution for the source strengths of the cylindrical diffuser fibers (CDF). We tested the Cimmino optimization procedures using the light fluence kernel generated for heterogeneous optical properties, and compared the optimized treatment plans with those obtained using homogeneous optical properties. To study how different photosensitizer distributions in the prostate affect optimization, comparisons of light fluence rate and PDT dose distributions were made with three distributions of photosensitizer: uniform, linear spatial distribution, and the measured PS distribution. The study shows that optimization of individual light source positions and intensities are feasible for the heterogeneous prostate during PDT.
Narayan, Samir [Department of Radiation Oncology, University of California Davis Medical Center, Sacramento, CA (United States)], E-mail: narayans@trinity-health.org; Lehmann, Joerg [Department of Radiation Oncology, University of California Davis Medical Center, Sacramento, CA (United States); Coleman, Matthew A. [Lawrence Livermore National Laboratory, Livermore, CA (United States); Vaughan, Andrew; Yang, Claus Chunli [Department of Radiation Oncology, University of California Davis Medical Center, Sacramento, CA (United States); Enepekides, Danny; Farwell, Gregory [Department of Otolaryngology, University of California Davis Medical Center, Sacramento, CA (United States); Purdy, James A.; Laredo, Grace [Department of Radiation Oncology, University of California Davis Medical Center, Sacramento, CA (United States); Nolan, Kerry A.S.; Pearson, Francesca S. [Lawrence Livermore National Laboratory, Livermore, CA (United States); Vijayakumar, Srinivasan [Department of Radiation Oncology, University of California Davis Medical Center, Sacramento, CA (United States)
2008-11-01
Purpose: We conducted a clinical study to correlate oral cavity dose with clinical mucositis, perform in vivo dosimetry, and determine the feasibility of obtaining buccal mucosal cell samples in patients undergoing head-and-neck radiation therapy. The main objective is to establish a quantitative dose response for clinical oral mucositis. Methods and Materials: Twelve patients undergoing radiation therapy for head-and-neck cancer were prospectively studied. Four points were chosen in separate quadrants of the oral cavity. Calculated dose distributions were generated by using AcQPlan and Eclipse treatment planning systems. MOSFET dosimeters were used to measure dose at each sampled point. Each patient underwent buccal sampling for future RNA analysis before and after the first radiation treatment at the four selected points. Clinical and functional mucositis were assessed weekly according to National Cancer Institute Common Toxicity Criteria, Version 3. Results: Maximum and average doses for sampled sites ranged from 7.4-62.3 and 3.0-54.3 Gy, respectively. A cumulative point dose of 39.1 Gy resulted in mucositis for 3 weeks or longer. Mild severity (Grade {<=} 1) and short duration ({<=}1 week) of mucositis were found at cumulative point doses less than 32 Gy. Polymerase chain reaction consistently was able to detect basal levels of two known radiation responsive genes. Conclusions: In our sample, cumulative doses to the oral cavity of less than 32 Gy were associated with minimal acute mucositis. A dose greater than 39 Gy was associated with longer duration of mucositis. Our technique for sampling buccal mucosa yielded sufficient cells for RNA analysis using polymerase chain reaction.
Gadan, M; Crawley, V; Thorp, S; Miller, M
2009-07-01
As a part of the project concerning the irradiation of a section of the human liver left lobe, a preliminary estimation of the expected dose was performed. To obtain proper input values for the calculation, neutron flux and gamma dose rate characterization were carried out using adequate portions of cow or pig liver covered with demineralized water simulating the preservation solution. Irradiations were done inside a container specially designed to fulfill temperature preservation of the organ and a reproducible irradiation position (which will be of importance for future planification purposes). Implantable rhodium based self-powered neutron detectors were developed to obtain neutron flux profiles both external and internal. Implantation of SPND was done along the central longitudinal axis of the samples, where lowest flux is expected. Gamma dose rate was obtained using a neutron shielded graphite ionization chamber moved along external surfaces of the samples. The internal neutron profile resulted uniform enough to allow for a single and static irradiation of the liver. For dose estimation, irradiation condition was set in order to obtain a maximum of 15 Gy-eq in healthy tissue. Additionally, literature reported boron concentrations of 47 ppm in tumor and 8 ppm in healthy tissue and a more conservative relationship (30/10 ppm) were used. To make a conservative estimation of the dose the following considerations were done: i). Minimum measured neutron flux inside the sample (approximately 5 x 10(9) n cm-2 s-1) was considered to calculate dose in tumor. (ii). Maximum measured neutron flux (considering both internal as external profiles) was used to calculate dose in healthy tissue (approximately 8.7 x 10(9) n cm-2 s-1). (iii). Maximum measured gamma dose rate (approximately 13.5 Gy h-1) was considered for both tumor and healthy tissue. Tumor tissue dose was approximately 69 Gy-eq for 47 ppm of (10)B and approximately 42 Gy-eq for 30 ppm, for a maximum dose of 15 Gy-eq in healthy tissue. As can be seen from these results, even for the most conservative case, minimum tumor dose will be acceptable from the treatment point of view, which shows that the irradiation conditions at this facility have quite good characteristics for the proposed irradiation. PMID:19394239
Shin, Dongho; Yoon, Myonggeun [Research Institute and Hospital, National Cancer Center, Ilsandong-gu, Goyang (Korea, Republic of); Park, Sung Yong [Research Institute and Hospital, National Cancer Center, Ilsandong-gu, Goyang (Korea, Republic of)], E-mail: cool_park@ncc.re.kr; Park, Dong Hyun; Lee, Se Byeong; Kim, Dae Yong; Cho, Kwan Ho [Research Institute and Hospital, National Cancer Center, Ilsandong-gu, Goyang (Korea, Republic of)
2007-01-01
Intensity-modulated radiation therapy (IMRT) is one of the most complex applications of radiotherapy that requires patient-specific quality assurance (QA). Here, we describe a novel method of 3-dimensional (3D) dose-verification using 12 acrylic slabs in a 3D phantom (30 x 30 x 12 cm{sup 3}) with extended dose rate (EDR2) films, which is both faster than conventionally used methods, and clinically useful. With custom-written software modules written in Microsoft Excel Visual Basic Application, the measured and planned dose distributions for the axial, coronal, and sagittal planes were superimposed by matching their origins, and the point doses were compared at all matched positions. Then, an optimization algorithm was used to correct the detected setup errors. The results show that this optimization method significantly reduces the average maximum dose difference by 7.73% and the number of points showing dose differences of more than 5% by 8.82% relative to the dose differences without an optimization. Our results indicate that the dose difference was significantly decreased with optimization and this optimization method is statistically reliable and effective. The results of 3D optimization are discussed in terms of various patient-specific QA data obtained from statistical analyses.
Environmental Radiation Dose on the Moon
K. Hayatsu; S. Kobayashi; N. Yamashita; M. Hareyama; K. Sakurai; N. Hasebe
2008-01-01
Ambient dose equivalent on the lunar surface is estimated as contribution from galactic cosmic rays, secondary neutrons and gamma rays from the lunar surface. Since the cosmic ray flux on the lunar surface varies with the phase of the solar activity, radiation doses on the surface are calculated of the three cases of this activity; the maximum, the minimum and
Bayesian estimation of dose thresholds
NASA Technical Reports Server (NTRS)
Groer, P. G.; Carnes, B. A.
2003-01-01
An example is described of Bayesian estimation of radiation absorbed dose thresholds (subsequently simply referred to as dose thresholds) using a specific parametric model applied to a data set on mice exposed to 60Co gamma rays and fission neutrons. A Weibull based relative risk model with a dose threshold parameter was used to analyse, as an example, lung cancer mortality and determine the posterior density for the threshold dose after single exposures to 60Co gamma rays or fission neutrons from the JANUS reactor at Argonne National Laboratory. The data consisted of survival, censoring times and cause of death information for male B6CF1 unexposed and exposed mice. The 60Co gamma whole-body doses for the two exposed groups were 0.86 and 1.37 Gy. The neutron whole-body doses were 0.19 and 0.38 Gy. Marginal posterior densities for the dose thresholds for neutron and gamma radiation were calculated with numerical integration and found to have quite different shapes. The density of the threshold for 60Co is unimodal with a mode at about 0.50 Gy. The threshold density for fission neutrons declines monotonically from a maximum value at zero with increasing doses. The posterior densities for all other parameters were similar for the two radiation types.
Radiation dose delivery verification in the treatment of carcinoma-cervix
NASA Astrophysics Data System (ADS)
Shrotriya, D.; Kumar, S.; Srivastava, R. N. L.
2015-06-01
The accurate dose delivery to the clinical target volume in radiotherapy can be affected by various pelvic tissues heterogeneities. An in-house heterogeneous woman pelvic phantom was designed and used to verify the consistency and computational capability of treatment planning system of radiation dose delivery in the treatment of cancer cervix. Oncentra 3D-TPS with collapsed cone convolution (CCC) dose calculation algorithm was used to generate AP/PA and box field technique plan. the radiation dose was delivered by Primus Linac (Siemens make) employing high energy 15 MV photon beam by isocenter technique. A PTW make, 0.125cc ionization chamber was used for direct measurements at various reference points in cervix, bladder and rectum. The study revealed that maximum variation between computed and measured dose at cervix reference point was 1% in both the techniques and 3% and 4% variation in AP/PA field and 5% and 4.5% in box technique at bladder and rectum points respectively.
Digital tomosynthesis mammography using a parallel maximum likelihood reconstruction method
Meleis, Waleed
Digital tomosynthesis mammography using a parallel maximum likelihood reconstruction method Tao Wu tomosynthesis mammography. Tomosynthesis mammography acquires 11 low-dose projections of a breast by moving an x are retrospectively reconstructed from a single scan. Tomosynthesis mammography has been investigated to solve
The myth of mean dose as a surrogate for radiation risk?
NASA Astrophysics Data System (ADS)
Samei, Ehsan; Li, Xiang; Chen, Baiyu; Reiman, Robert
2010-04-01
The current estimations of risk associated with medical imaging procedures rely on assessing the organ dose via direct measurements or simulation. Each organ dose is assumed to be homogeneous, a representative sample or mean of which is weighted by a corresponding tissue weighting factor provided by ICRP publication 103. The weighted values are summed to provide Effective Dose (ED), the most-widely accepted surrogate for population radiation risk. For individual risk estimation, one may employ Effective Risk (ER), which further incorporates gender- and age-specific risk factors. However, both the tissue-weighting factors (as used by ED) and the risk factors (as used by ER) were derived (mostly from the atomic bomb survivor data) under the assumption of a homogeneous dose distribution within each organ. That assumption is significantly violated in most medical imaging procedures. In chest CT, for example, superficial organs (eg, breasts) demonstrate a heterogeneous distribution while organs on the peripheries of the irradiation field (eg, liver) possess a nearly discontinuous dose profile. Projection radiography and mammography involve an even wider range of organ dose heterogeneity spanning up to two orders of magnitude. As such, mean dose or point measured dose values do not reflect the maximum energy deposited per unit volume of the organ, and therefore, effective dose or effective risk, as commonly computed, can misrepresent irradiation risk. In this paper, we report the magnitude of the dose heterogeneity in both CT and projection x-ray imaging, provide an assessment of its impact on irradiation risk, and explore an alternative model-based approach for risk estimation for imaging techniques involving heterogeneous organ dose distributions.
Chantal Ginestet; Claude Malet; Alan Cohen; Frederic Lafay; Christian Carrie
2000-01-01
Purpose: Analysis of dose specification of tissue heterogeneities.Methods and Materials: Three-dimensional dose distribution analyses of 30 patients with localized prostate cancer were reviewed with and without tissue heterogeneity correction. The number of monitor units for each portal entrance (more than 300 different fields) was calculated and the impact of targeting and number of portal entrances was also integrated.Results: The presence
Minimal Length, Friedmann Equations and Maximum Density
Adel Awad; Ahmed Farag Ali
2014-06-14
Inspired by Jacobson's thermodynamic approach[gr-qc/9504004], Cai et al [hep-th/0501055,hep-th/0609128] have shown the emergence of Friedmann equations from the first law of thermodynamics. We extend Akbar--Cai derivation [hep-th/0609128] of Friedmann equations to accommodate a general entropy-area law. Studying the resulted Friedmann equations using a specific entropy-area law, which is motivated by the generalized uncertainty principle (GUP), reveals the existence of a maximum energy density closed to Planck density. Allowing for a general continuous pressure $p(\\rho,a)$ leads to bounded curvature invariants and a general nonsingular evolution. In this case, the maximum energy density is reached in a finite time and there is no cosmological evolution beyond this point which leaves the big bang singularity inaccessible from a spacetime prospective. The existence of maximum energy density and a general nonsingular evolution is independent of the equation of state and the spacial curvature $k$. As an example we study the evolution of the equation of state $p=\\omega \\rho$ through its phase-space diagram to show the existence of a maximum energy which is reachable in a finite time.
NAIRAS aircraft radiation model development, dose climatology, and initial validation
Mertens, Christopher J; Meier, Matthias M; Brown, Steven; Norman, Ryan B; Xu, Xiaojing
2013-01-01
[1] The Nowcast of Atmospheric Ionizing Radiation for Aviation Safety (NAIRAS) is a real-time, global, physics-based model used to assess radiation exposure to commercial aircrews and passengers. The model is a free-running physics-based model in the sense that there are no adjustment factors applied to nudge the model into agreement with measurements. The model predicts dosimetric quantities in the atmosphere from both galactic cosmic rays (GCR) and solar energetic particles, including the response of the geomagnetic field to interplanetary dynamical processes and its subsequent influence on atmospheric dose. The focus of this paper is on atmospheric GCR exposure during geomagnetically quiet conditions, with three main objectives. First, provide detailed descriptions of the NAIRAS GCR transport and dosimetry methodologies. Second, present a climatology of effective dose and ambient dose equivalent rates at typical commercial airline altitudes representative of solar cycle maximum and solar cycle minimum conditions and spanning the full range of geomagnetic cutoff rigidities. Third, conduct an initial validation of the NAIRAS model by comparing predictions of ambient dose equivalent rates with tabulated reference measurement data and recent aircraft radiation measurements taken in 2008 during the minimum between solar cycle 23 and solar cycle 24. By applying the criterion of the International Commission on Radiation Units and Measurements (ICRU) on acceptable levels of aircraft radiation dose uncertainty for ambient dose equivalent greater than or equal to an annual dose of 1 mSv, the NAIRAS model is within 25% of the measured data, which fall within the ICRU acceptable uncertainty limit of 30%. The NAIRAS model predictions of ambient dose equivalent rate are generally within 50% of the measured data for any single-point comparison. The largest differences occur at low latitudes and high cutoffs, where the radiation dose level is low. Nevertheless, analysis suggests that these single-point differences will be within 30% when a new deterministic pion-initiated electromagnetic cascade code is integrated into NAIRAS, an effort which is currently underway.
Power controller design for maximum power tracking in solar installations
Eugene V. Solodovnik; Shengyi Liu; Roger A. Dougal
2004-01-01
A state space approach to the design of a maximum power point (MPP) tracking system for photovoltaic energy conversion is presented. The problem of optimal-power control of a nonlinear time-varying system is reduced to an ordinary problem of dynamic system stability in state space by applying MPP conditions in controller design. The resulting tracking system searches for the reference point
Haney, J
2015-07-01
Dose-dependent changes in target tissue absorption have important implications for determining the most defensible approach for developing a cancer-based oral toxicity factor for hexavalent chromium (CrVI). For example, mouse target tissue absorption per unit dose is an estimated 10-fold lower at the CrVI dose corresponding to the federal maximum contaminant level (MCL) than at the USEPA draft oral slope factor (SFo) point of departure dose. This decreasing target tissue absorption as doses decrease to lower, more environmentally-relevant doses is inconsistent with linear low-dose extrapolation. The shape of the dose-response curve accounting for this toxicokinetic phenomenon would clearly be non-linear. Furthermore, these dose-dependent differences in absorption indicate that the magnitude of risk overestimation by a linear low-dose extrapolation approach (e.g., SFo) increases and is likely to span one or perhaps more orders of magnitude as it is used to predict risk at progressively lower, more environmentally-relevant doses. An additional apparent implication is that no single SFo can reliably predict risk across potential environmental doses (e.g., doses corresponding to water concentrations?the federal MCL). A non-linear approach, consistent with available mode of action data, is most scientifically defensible for derivation of an oral toxicity factor for CrVI-induced carcinogenesis. PMID:25910675
Akleev, A V; Dimov, G P; Varfolomeeva, T A
2012-01-01
Residents of the Techa riverside villages chronically exposed to ionizing radiation (the average dose rate in 1951-1956 was 0.047 Gy/year, the maximum reached 2.44 Gy/year) developed marked changes in the cellular composition of peripheral blood. The maximum reduction of peripheral blood counts occurred in the years 1951-1953, after which the beginning of the restoration of cellularity to the control level was observed. The dose rate at this point (1956) was about 0.02 Gy/year. The factors of radiation and non-radiation nature (gender, the age at the onset of exposure, health related disorders) in different combinations affect the number of peripheral blood cells. The influence of dose rate of a chronic radiation exposure on a platelet count takes precedence over other factors. The factors of gender and dose rate determine the number of erythrocytes in exposed persons. The changes accompanying the health status and dose rate significantly affect the number of neutrophils. The influence of comorbidity, age and dose rate on the number of monocytes was noted. A lymphocyte count was mainly determined by the age at the onset of exposure and concomitant diseases. A joint influence of chronic radiation exposure and concomitant diseases increases a mutual action on erythro- and thrombocytopoiesis. The decrease of the dose rate was followed by a gradual predominance of the somatic disease influence on leukocyte (neutrophils, lymphocytes and monocytes) counts. PMID:22690574
Tissue-phantom ratios from percentage depth doses.
Bjärngard, B E; Zhu, T C; Ceberg, C
1996-05-01
When converting fractional (percentage) depth doses to tissue-phantom ratios, one must use a factor that accounts for the different source-to-point distances. Two minor correction factors are also involved. One is the ratio of total to primary dose at the two different distances from the source, for the same depth and field size. This factor is usually ignored. It was determined experimentally that this can introduce up to 1.5% error at 6 MV. The second correction factor reflects differences related to scattered photons and electrons at the depth of normalization in the two geometries. This correction is accounted for in published conversion procedures. It was found to be less than 1% provided the normalization depth is sufficient for electron equilibrium, which occurs first well beyond the depth of maximum dose. One may avoid electron-equilibrium problems by using an interim normalization depth that provides electron equilibrium with some margin, renormalizing to a shallower depth if desired. With this precaution, the accuracy when measured fractional depth doses were converted to tissue-phantom ratios was comparable to that of directly measured tissue-phantom ratios even when the correction factors were ignored. PMID:8724733
NOTE: On biologically conformal boost dose optimization
NASA Astrophysics Data System (ADS)
Alber, M.; Paulsen, F.; Eschmann, S. M.; Machulla, H. J.
2003-01-01
A method is described that allows the inclusion of biological imaging data in the optimization of intensity-modulated radiotherapy to produce dose boosts that conform with target subvolumes of potentially reduced radiosensitivity. The biological image (e.g. PET, fMRI, etc) is transformed into a dose efficiency distribution using a piecewise linear calibration function with a prescribed maximum boost factor. Instead of dose alone, the cost function of the optimization algorithm depends on the product of the physical dose times dose efficiency. An example case of a base-of-tongue tumour which was imaged with the hypoxia tracer fluoro-misonidazole is presented, showing the excellent capability of IMRT to produce dose distributions that conform to spatially variable dose prescriptions.
Electron dose rate and photon contamination in electron arc therapy
Marina Pla; Ervin B. Podgorsak; Conrado Pla
1989-01-01
The electron dose rate at the depth of dose maximum dmax and the photon contamination are discussed as a function of several parameters of the rotational electron beam. A pseudoarc technique with an angular increment of 10 degrees and a constant number of monitor units per each stationary electron field was used in our experiments. The electron dose rate is
Monte Carlo-based revised values of dose rate constants at discrete photon energies
Selvam, T. Palani; Shrivastava, Vandana; Chourasiya, Ghanashyam; Babu, D. Appala Raju
2014-01-01
Absorbed dose rate to water at 0.2 cm and 1 cm due to a point isotropic photon source as a function of photon energy is calculated using the EDKnrc user-code of the EGSnrc Monte Carlo system. This code system utilized widely used XCOM photon cross-section dataset for the calculation of absorbed dose to water. Using the above dose rates, dose rate constants are calculated. Air-kerma strength Sk needed for deriving dose rate constant is based on the mass-energy absorption coefficient compilations of Hubbell and Seltzer published in the year 1995. A comparison of absorbed dose rates in water at the above distances to the published values reflects the differences in photon cross-section dataset in the low-energy region (difference is up to 2% in dose rate values at 1 cm in the energy range 30–50 keV and up to 4% at 0.2 cm at 30 keV). A maximum difference of about 8% is observed in the dose rate value at 0.2 cm at 1.75 MeV when compared to the published value. Sk calculations based on the compilation of Hubbell and Seltzer show a difference of up to 2.5% in the low-energy region (20–50 keV) when compared to the published values. The deviations observed in the values of dose rate and Sk affect the values of dose rate constants up to 3%. PMID:24600166
Lee, Choonik; Jung, Jae Won; Pelletier, Christopher; Pyakuryal, Anil; Lamart, Stephanie; Kim, Jong Oh; Lee, Choonsik
2015-03-21
Organ dose estimation for retrospective epidemiological studies of late effects in radiotherapy patients involves two challenges: radiological images to represent patient anatomy are not usually available for patient cohorts who were treated years ago, and efficient dose reconstruction methods for large-scale patient cohorts are not well established. In the current study, we developed methods to reconstruct organ doses for radiotherapy patients by using a series of computational human phantoms coupled with a commercial treatment planning system (TPS) and a radiotherapy-dedicated Monte Carlo transport code, and performed illustrative dose calculations. First, we developed methods to convert the anatomy and organ contours of the pediatric and adult hybrid computational phantom series to Digital Imaging and Communications in Medicine (DICOM)-image and DICOM-structure files, respectively. The resulting DICOM files were imported to a commercial TPS for simulating radiotherapy and dose calculation for in-field organs. The conversion process was validated by comparing electron densities relative to water and organ volumes between the hybrid phantoms and the DICOM files imported in TPS, which showed agreements within 0.1 and 2%, respectively. Second, we developed a procedure to transfer DICOM-RT files generated from the TPS directly to a Monte Carlo transport code, x-ray Voxel Monte Carlo (XVMC) for more accurate dose calculations. Third, to illustrate the performance of the established methods, we simulated a whole brain treatment for the 10?year-old male phantom and a prostate treatment for the adult male phantom. Radiation doses to selected organs were calculated using the TPS and XVMC, and compared to each other. Organ average doses from the two methods matched within 7%, whereas maximum and minimum point doses differed up to 45%. The dosimetry methods and procedures established in this study will be useful for the reconstruction of organ dose to support retrospective epidemiological studies of late effects in radiotherapy patients. PMID:25715852
NASA Astrophysics Data System (ADS)
Kan, M. W. K.; Cheung, J. Y. C.; Leung, L. H. T.; Lau, B. M. F.; Yu, P. K. N.
2011-01-01
Nasopharyngeal tumors are commonly treated with intensity-modulated radiotherapy techniques. For photon dose calculations, problems related to loss of lateral electronic equilibrium exist when small fields are used. The anisotropic analytical algorithm (AAA) implemented in Varian Eclipse was developed to replace the pencil beam convolution (PBC) algorithm for more accurate dose prediction in an inhomogeneous medium. The purpose of this study was to investigate the accuracy of the AAA for predicting interface doses for intensity-modulated stereotactic radiotherapy boost of nasopharyngeal tumors. The central axis depth dose data and dose profiles of phantoms with rectangular air cavities for small fields were measured using a 6 MV beam. In addition, the air-tissue interface doses from six different intensity-modulated stereotactic radiotherapy plans were measured in an anthropomorphic phantom. The nasopharyngeal region of the phantom was especially modified to simulate the air cavities of a typical patient. The measured data were compared to the data calculated by both the AAA and the PBC algorithm. When using single small fields in rectangular air cavity phantoms, both AAA and PBC overestimated the central axis dose at and beyond the first few millimeters of the air-water interface. Although the AAA performs better than the PBC algorithm, its calculated interface dose could still be more than three times that of the measured dose when a 2 × 2 cm2 field was used. Testing of the algorithms using the anthropomorphic phantom showed that the maximum overestimation by the PBC algorithm was 20.7%, while that by the AAA was 8.3%. When multiple fields were used in a patient geometry, the dose prediction errors of the AAA would be substantially reduced compared with those from a single field. However, overestimation of more than 3% could still be found at some points at the air-tissue interface.
A {gamma} dose distribution evaluation technique using the k-d tree for nearest neighbor searching
Yuan Jiankui; Chen Weimin [ICT Radiotherapy, Livingston, New Jersey 07039 (United States) and Northeast Radiation Oncology Center, Dunmore, Pennsylvania 18509 (United States); ICT Radiotherapy, Livingston, New Jersey 07039 (United States)
2010-09-15
Purpose: The authors propose an algorithm based on the k-d tree for nearest neighbor searching to improve the {gamma} calculation time for 2D and 3D dose distributions. Methods: The {gamma} calculation method has been widely used for comparisons of dose distributions in clinical treatment plans and quality assurances. By specifying the acceptable dose and distance-to-agreement criteria, the method provides quantitative measurement of the agreement between the reference and evaluation dose distributions. The {gamma} value indicates the acceptability. In regions where {gamma}{<=}1, the predefined criterion is satisfied and thus the agreement is acceptable; otherwise, the agreement fails. Although the concept of the method is not complicated and a quick naieve implementation is straightforward, an efficient and robust implementation is not trivial. Recent algorithms based on exhaustive searching within a maximum radius, the geometric Euclidean distance, and the table lookup method have been proposed to improve the computational time for multidimensional dose distributions. Motivated by the fact that the least searching time for finding a nearest neighbor can be an O(log N) operation with a k-d tree, where N is the total number of the dose points, the authors propose an algorithm based on the k-d tree for the {gamma} evaluation in this work. Results: In the experiment, the authors found that the average k-d tree construction time per reference point is O(log N), while the nearest neighbor searching time per evaluation point is proportional to O(N{sup 1/k}), where k is between 2 and 3 for two-dimensional and three-dimensional dose distributions, respectively. Conclusions: Comparing with other algorithms such as exhaustive search and sorted list O(N), the k-d tree algorithm for {gamma} evaluation is much more efficient.
Principles of maximum entropy and maximum caliber in statistical physics
NASA Astrophysics Data System (ADS)
Pressé, Steve; Ghosh, Kingshuk; Lee, Julian; Dill, Ken A.
2013-07-01
The variational principles called maximum entropy (MaxEnt) and maximum caliber (MaxCal) are reviewed. MaxEnt originated in the statistical physics of Boltzmann and Gibbs, as a theoretical tool for predicting the equilibrium states of thermal systems. Later, entropy maximization was also applied to matters of information, signal transmission, and image reconstruction. Recently, since the work of Shore and Johnson, MaxEnt has been regarded as a principle that is broader than either physics or information alone. MaxEnt is a procedure that ensures that inferences drawn from stochastic data satisfy basic self-consistency requirements. The different historical justifications for the entropy S=-?ipilog?pi and its corresponding variational principles are reviewed. As an illustration of the broadening purview of maximum entropy principles, maximum caliber, which is path entropy maximization applied to the trajectories of dynamical systems, is also reviewed. Examples are given in which maximum caliber is used to interpret dynamical fluctuations in biology and on the nanoscale, in single-molecule and few-particle systems such as molecular motors, chemical reactions, biological feedback circuits, and diffusion in microfluidics devices.
The 1988 Solar Maximum Mission event list
NASA Technical Reports Server (NTRS)
Dennis, B. R.; Licata, J. P.; Tolbert, A. K.
1992-01-01
Information on solar burst and transient activity observed by the Solar Maximum Mission (SMM) during 1988 pointed observations is presented. Data from the following SMM experiments are included: (1) gamma ray spectrometer; (2) hard x ray burst spectrometer; (3) flat crystal spectrometers; (4) bent crystal spectrometer; (5) ultraviolet spectrometer polarimeter; and (6) coronagraph/polarimeter. Correlative optical, radio, and Geostationary Operational Environmental Satellite (GOES) x ray data are also presented. Where possible, bursts, or transients observed in the various wavelengths were grouped into discrete flare events identified by unique event numbers. Each event carries a qualifier denoting the quality or completeness of the observation. Spacecraft pointing coordinates and flare site angular displacement values from sun center are also included.
The 1980 solar maximum mission event listing
NASA Technical Reports Server (NTRS)
Speich, D. M.; Nelson, J. J.; Licata, J. P.; Tolbert, A. K.
1991-01-01
Information is contained on solar burst and transient activity observed by the Solar Maximum Mission (SMM) during 1980 pointed observations. Data from the following SMM experiments are included: (1) Gamma Ray Spectrometer, (2) Hard X-Ray Burst Spectrometer, (3) Hard X-Ray Imaging Spectrometer, (4) Flat Crystal Spectrometer, (5) Bent Crystal Spectrometer, (6) Ultraviolet Spectrometer and Polarimeter, and (7) Coronagraph/Polarimeter. Correlative optical, radio, and Geostationary Operational Environmental Satellite (GOES) x ray data are also presented. Where possible, bursts or transients observed in the various wavelengths were grouped into discrete flare events identified by unique event numbers. Each event carries a qualifier denoting the quality or completeness of the observations. Spacecraft pointing coordinates and flare site angular displacement values from Sun center are also included.
The 1989 Solar Maximum Mission event list
NASA Technical Reports Server (NTRS)
Dennis, B. R.; Licata, J. P.; Tolbert, A. K.
1992-01-01
This document contains information on solar burst and transient activity observed by the Solar Maximum Mission (SMM) during 1989 pointed observations. Data from the following SMM experiments are included: (1) Gamma Ray Spectrometer, (2) Hard X-Ray Burst Spectrometer, (3) Flat Crystal Spectrometer, (4) Bent Crystal Spectrometer, (5) Ultraviolet Spectrometer Polarimeter, and (6) Coronagraph/Polarimeter. Correlative optical, radio, and Geostationary Operational Satellite (GOES) X-ray data are also presented. Where possible, bursts or transients observed in the various wavelengths were grouped into discrete flare events identified by unique event numbers. Each event carries a qualifier denoting the quality or completeness of the observations. Spacecraft pointing coordinates and flare site angular displacement values from sun center are also included.
Parameterization of solar flare dose
Lamarche, Anne Helene
1995-01-01
of the proton transport through a given shield to obtain the dose to astronauts, the Baryon transport code, BRYNTRN, will be used. This code, developed at NASA Langley Research Center, can be used to solve the fundamental Boltzmann transport equation... at another part of the solar system. NASA's Solar Maximum Mission (SMM) answered many questions about proton acceleration sites (Chupp, 1987). Since proton storms generally outlast flares by many hours, it seems unclear whether they originate in similarly...
Appendix F Internal Dose Estimates from NTS Fallout F-1 #12;Radiation Dose to the Population;TABLE OF CONTENTS Page F- Part I. Estimates of Dose .................................................................................................................7 General system of dose calculation
Carver, R [Mary Bird Perkins Cancer Center, Baton Rouge, LA (United States); Popple, R; Benhabib, S [UniversityAlabama Birmingham, Birmingham, AL (United Kingdom); Antolak, J [Mayo Clinic, Rochester, MN (United States); Sprunger, C [Louisiana State University, Baton Rouge, LA (United States); Hogstrom, K [Mary Bird Perkins Cancer Center, Baton Rouge, LA (United States); Louisiana State University, Baton Rouge, LA (United States)
2014-06-01
Purpose: To evaluate the accuracy of electron dose distribution calculated by the Varian Eclipse electron Monte Carlo (eMC) algorithm for use with recent commercially available bolus electron conformal therapy (ECT). Methods: eMC-calculated electron dose distributions for bolus ECT have been compared to those previously measured for cylindrical phantoms (retromolar trigone and nose), whose axial cross sections were based on the mid-PTV CT anatomy for each site. The phantoms consisted of SR4 muscle substitute, SR4 bone substitute, and air. The bolus ECT treatment plans were imported into the Eclipse treatment planning system and calculated using the maximum allowable histories (2×10{sup 9}), resulting in a statistical error of <0.2%. Smoothing was not used for these calculations. Differences between eMC-calculated and measured dose distributions were evaluated in terms of absolute dose difference as well as distance to agreement (DTA). Results: Results from the eMC for the retromolar trigone phantom showed 89% (41/46) of dose points within 3% dose difference or 3 mm DTA. There was an average dose difference of ?0.12% with a standard deviation of 2.56%. Results for the nose phantom showed 95% (54/57) of dose points within 3% dose difference or 3 mm DTA. There was an average dose difference of 1.12% with a standard deviation of 3.03%. Dose calculation times for the retromolar trigone and nose treatment plans were 15 min and 22 min, respectively, using 16 processors (Intel Xeon E5-2690, 2.9 GHz) on a Varian Eclipse framework agent server (FAS). Results of this study were consistent with those previously reported for accuracy of the eMC electron dose algorithm and for the .decimal, Inc. pencil beam redefinition algorithm used to plan the bolus. Conclusion: These results show that the accuracy of the Eclipse eMC algorithm is suitable for clinical implementation of bolus ECT.
Park, J [Dept. of Pediatrics, Molecular Imaging Program at Stanford, Stanford University, Stanford, CA (United States); Research Institute of Biomedical Engineering, The Catholic University of Korea, Seoul (Korea, Republic of); Park, H [Dept. of Radiation Oncology, Ajou University School of Medicine, Suwon (Korea, Republic of); Lee, J [Konkuk University Medical Center, Seoul (Korea, Republic of); Kang, S; Lee, M; Suh, T [Research Institute of Biomedical Engineering, The Catholic University of Korea, Seoul (Korea, Republic of); Dept. of Biomedical Engineering, The Catholic University of Korea, Seoul (Korea, Republic of); Lee, B [Dept. of Bio-Convergence Engineering, Korea University, Seoul (Korea, Republic of); Dept. of Radiation Oncology, Sun Medical Center, Daejeon (Korea, Republic of)
2014-06-01
Purpose: Dosimetric effect and discrepancy according to the rectum definition methods and dose perturbation by air cavity in an endo-rectal balloon (ERB) were verified using rectal-wall (Rwall) dose maps considering systematic errors in dose optimization and calculation accuracy in intensity-modulated radiation treatment (IMRT) for prostate cancer patients. Methods: When the inflated ERB having average diameter of 4.5 cm and air volume of 100 cc is used for patient, Rwall doses were predicted by pencil-beam convolution (PBC), anisotropic analytic algorithm (AAA), and AcurosXB (AXB) with material assignment function. The errors of dose optimization and calculation by separating air cavity from the whole rectum (Rwhole) were verified with measured rectal doses. The Rwall doses affected by the dose perturbation of air cavity were evaluated using a featured rectal phantom allowing insert of rolled-up gafchromic films and glass rod detectors placed along the rectum perimeter. Inner and outer Rwall doses were verified with reconstructed predicted rectal wall dose maps. Dose errors and extent at dose levels were evaluated with estimated rectal toxicity. Results: While AXB showed insignificant difference of target dose coverage, Rwall doses underestimated by up to 20% in dose optimization for the Rwhole than Rwall at all dose range except for the maximum dose. As dose optimization for Rwall was applied, the Rwall doses presented dose error less than 3% between dose calculation algorithm except for overestimation of maximum rectal dose up to 5% in PBC. Dose optimization for Rwhole caused dose difference of Rwall especially at intermediate doses. Conclusion: Dose optimization for Rwall could be suggested for more accurate prediction of rectal wall dose prediction and dose perturbation effect by air cavity in IMRT for prostate cancer. This research was supported by the Leading Foreign Research Institute Recruitment Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science, ICT and Future Planning (MSIP) (Grant No. 200900420)
Local hardness equalization and the principle of maximum hardness.
Gázquez, José L; Vela, Alberto; Chattaraj, Pratim K
2013-06-01
The chemical potential, hardness, and hyperhardnesses equalization principles are used to show that the leading term associated with charge transfer in the total interaction energy among the fragments in which a molecule is divided is directly proportional to minus the hardness of the molecule in its ground state, as established by the principle of maximum hardness. The additional terms in the interaction energy, associated with the changes in the external potential of the fragments, provide explanation for deviations between the point of maximum hardness and the point of minimum energy. It is also found that the dual descriptor plays a very important role in hardness equalization. PMID:23758354
ERIC Educational Resources Information Center
Greenslade, Thomas B., Jr.
1985-01-01
Discusses a series of experiments performed by Thomas Hope in 1805 which show the temperature at which water has its maximum density. Early data cast into a modern form as well as guidelines and recent data collected from the author provide background for duplicating Hope's experiments in the classroom. (JN)
Maximum Chemical and Physical Hardness
Ralph G. Pearson
1999-01-01
Density functional theory (DFT) is briefly reviewed, especially concepts such as the electronic chemical potential and the hardness of the electron density function. There is much evidence, and a mathematical proof, that this chemical hardness is a maximum for an equilibrium system. The proof is based on a combination of statistical mechanics, the fluctuation-dissipation theorem, and correlation functions. In MO
Estimation of External Dose by Car-Borne Survey in Kerala, India
Hosoda, Masahiro; Tokonami, Shinji; Omori, Yasutaka; Sahoo, Sarata Kumar; Akiba, Suminori; Sorimachi, Atsuyuki; Ishikawa, Tetsuo; Nair, Raghu Ram; Jayalekshmi, Padmavathy Amma; Sebastian, Paul; Iwaoka, Kazuki; Akata, Naofumi; Kudo, Hiromi
2015-01-01
A car-borne survey was carried out in Kerala, India to estimate external dose. Measurements were made with a 3-in × 3-in NaI(Tl) scintillation spectrometer from September 23 to 27, 2013. The routes were selected from 12 Panchayats in Karunagappally Taluk which were classified into high level, mid-level and low level high background radiation (HBR) areas. A heterogeneous distribution of air kerma rates was seen in the dose rate distribution map. The maximum air kerma rate, 2.1 ?Gy/h, was observed on a beach sand surface. 232Th activity concentration for the beach sand was higher than that for soil and grass surfaces, and the range of activity concentration was estimated to be 0.7–2.3 kBq/kg. The contribution of 232Th to air kerma rate was over 70% at the measurement points with values larger than 0.34 ?Gy/h. The maximum value of the annual effective dose in Karunagappally Taluk was observed around coastal areas, and it was estimated to be 13 mSv/y. More than 30% of all the annual effective doses obtained in this survey exceeded 1 mSv/y. PMID:25885680
Molecular Size as the Main Determinant of Solute Maximum Flux Across the Skin
Beatrice M. Magnusson; Yuri G. Anissimov; Sheree E. Cross; Michael S. Roberts
2004-01-01
One of the most important determinants of dermatological and systemic penetration after topical application is the delivery or flux of solutes into or through the skin. The maximum dose of solute able to be delivered over a given period of time and area of application is defined by its maximum flux (Jmax, mol per cm2 per h) from a given
Effect of caffeine on oxidative stress during maximum incremental exercise.
Olcina, Guillermo J; Muñoz, Diego; Timón, Rafael; Caballero, M Jesús; Maynar, Juan I; Córdova, Alfredo; Maynar, Marcos
2006-01-01
Caffeine (1,3,7-trimethylxanthine) is an habitual substance present in a wide variety of beverages and in chocolate-based foods and it is also used as adjuvant in some drugs. The antioxidant ability of caffeine has been reported in contrast with its pro- oxidant effects derived from its action mechanism such as the systemic release of catecholamines. The aim of this work was to evaluate the effect of caffeine on exercise oxidative stress, measuring plasma vitamins A, E, C and malonaldehyde (MDA) as markers of non enzymatic antioxidant status and lipid peroxidation respectively. Twenty young males participated in a double blind (caffeine 5mg·kg- 1 body weight or placebo) cycling test until exhaustion. In the exercise test, where caffeine was ingested prior to the test, exercise time to exhaustion, maximum heart rate, and oxygen uptake significantly increased, whereas respiratory exchange ratio (RER) decreased. Vitamins A and E decreased with exercise and vitamin C and MDA increased after both the caffeine and placebo tests but, regarding these particular variables, there were no significant differences between the two test conditions. The results obtained support the conclusion that this dose of caffeine enhances the ergospirometric response to cycling and has no effect on lipid peroxidation or on the antioxidant vitamins A, E and C. Key PointsCaffeine ingestion may improve maximal aerobic performance in non trained men.Cellular oxidative damage is not altered by caffeine ingestion in maximal aerobic exercises.Antioxidant response to exercise, vitamins A, E and C, is not modified by caffeine action in maximal aerobic efforts. PMID:24357958
Maximum cooling and maximum efficiency of thermoacoustic refrigerators
NASA Astrophysics Data System (ADS)
Tartibu, L. K.
2015-06-01
This work provides valid experimental evidence on the difference between design for maximum cooling and maximum efficiency for thermoacoustic refrigerators. In addition, the influence of the geometry of the honeycomb ceramic stack on the performance of thermoacoustic refrigerators is presented as it affects the cooling power. Sixteen cordierite honeycomb ceramic stacks with square cross sections having four different lengths of 26, 48, 70 and 100 mm are considered. Measurements are taken at six different locations of the stack hot ends from the pressure antinode, namely 100, 200, 300, 400, 500 and 600 mm respectively. Measurement of temperature difference across the stack ends at steady state for different stack geometries are used to compute the cooling load and the coefficient of performance. The results obtained with atmospheric air showed that there is a distinct optimum depending on the design goal.
Dose finding with continuous outcome in phase I oncology trials.
Wang, Yunfei; Ivanova, Anastasia
2015-01-01
The goal of a phase I clinical trial in oncology is to find a dose with acceptable dose-limiting toxicity rate. Often, when a cytostatic drug is investigated or when the maximum tolerated dose is defined using a toxicity score, the main endpoint in a phase I trial is continuous. We propose a new method to use in a dose-finding trial with continuous endpoints. The new method selects the right dose on par with other methods and provides more flexibility in assigning patients to doses in the course of the trial when the rate of accrual is fast relative to the follow-up time. PMID:25408518
Skin dose from radionuclide contamination on clothing
Taylor, D.C.; Hussein, E.M.A. [Univ. of New Brunswick, Fredericton (Canada); Yuen, P.S. [AECL, Chalk River, Ontario (Canada)
1997-06-01
Skin dose due to radio nuclide contamination on clothing is calculated by Monte Carlo simulation of electron and photon radiation transport. Contamination due to a hot particle on some selected clothing geometries of cotton garment is simulated. The effect of backscattering in the surrounding air is taken into account. For each combination of source-clothing geometry, the dose distribution function in the skin, including the dose at tissue depths of 7 mg cm{sup -2} and 1,000 Mg cm{sup -2}, is calculated by simulating monoenergetic photon and electron sources. Skin dose due to contamination by a radionuclide is then determined by proper weighting of & monoenergetic dose distribution functions. The results are compared with the VARSKIN point-kernel code for some radionuclides, indicating that the latter code tends to under-estimate the dose for gamma and high energy beta sources while it overestimates skin dose for low energy beta sources. 13 refs., 4 figs., 2 tabs.
Dose uncertainties in photon pencil kernel calculations at off-axis positions.
Olofsson, Jörgen; Nyholm, Tufve; Ahnesjö, Anders; Karlsson, Mikael
2006-09-01
The purpose of this study was to investigate the specific problems associated with photon dose calculations in points located at a distance from the central beam axis. These problems are related to laterally inhomogeneous energy fluence distributions and spectral variations causing a lateral shift in the beam quality, commonly referred to as off-axis softening (OAS). We have examined how the dose calculation accuracy is affected when enabling and disabling explicit modeling of these two effects. The calculations were performed using a pencil kernel dose calculation algorithm that facilitates modeling of OAS through laterally varying kernel properties. Together with a multi-source model that provides the lateral energy fluence distribution this generates the total dose output, i.e., the dose per monitor unit, at an arbitrary point of interest. The dose calculation accuracy was evaluated through comparisons with 264 measured output factors acquired at 5, 10, and 20 cm depth in four different megavoltage photon beams. The measurements were performed up to 18 cm from the central beam axis, inside square fields of varying size and position. The results show that calculations including explicit modeling of OAS were considerably more accurate, up to 4%, than those ignoring the lateral beam quality shift. The deviations caused by simplified head scatter modeling were smaller, but near the field edges additional errors close to 1% occurred. When enabling full physics modeling in the dose calculations the deviations display a mean value of -0.1%, a standard deviation of 0.7%, and a maximum deviation of -2.2%. Finally, the results were analyzed in order to quantify and model the inherent uncertainties that are present when leaving the central beam axis. The off-axis uncertainty component showed to increase with both off-axis distance and depth, reaching 1% (1 standard deviation) at 20 cm depth. PMID:17022238
Dose uncertainties in photon pencil kernel calculations at off-axis positions
Olofsson, Joergen; Nyholm, Tufve; Ahnesjoe, Anders; Karlsson, Mikael [Department of Radiation Sciences, Radiation Physics, Umeaa University, SE-901 87 Umeaa (Sweden); Department of Radiation Sciences, Radiation Physics, Umeaa University, SE-901 87 Umeaa , Sweden, Nucletron Scandinavia AB, PO Box 1704, SE-751 47 Uppsala, Sweden, and Department of Oncology, Radiology and Clinical Immunology, Uppsala University (Sweden); Department of Radiation Sciences, Radiation Physics, Umeaa University, SE-901 87 Umeaa (Sweden)
2006-09-15
The purpose of this study was to investigate the specific problems associated with photon dose calculations in points located at a distance from the central beam axis. These problems are related to laterally inhomogeneous energy fluence distributions and spectral variations causing a lateral shift in the beam quality, commonly referred to as off-axis softening (OAS). We have examined how the dose calculation accuracy is affected when enabling and disabling explicit modeling of these two effects. The calculations were performed using a pencil kernel dose calculation algorithm that facilitates modeling of OAS through laterally varying kernel properties. Together with a multisource model that provides the lateral energy fluence distribution this generates the total dose output, i.e., the dose per monitor unit, at an arbitrary point of interest. The dose calculation accuracy was evaluated through comparisons with 264 measured output factors acquired at 5, 10, and 20 cm depth in four different megavoltage photon beams. The measurements were performed up to 18 cm from the central beam axis, inside square fields of varying size and position. The results show that calculations including explicit modeling of OAS were considerably more accurate, up to 4%, than those ignoring the lateral beam quality shift. The deviations caused by simplified head scatter modeling were smaller, but near the field edges additional errors close to 1% occurred. When enabling full physics modeling in the dose calculations the deviations display a mean value of -0.1%, a standard deviation of 0.7%, and a maximum deviation of -2.2%. Finally, the results were analyzed in order to quantify and model the inherent uncertainties that are present when leaving the central beam axis. The off-axis uncertainty component showed to increase with both off-axis distance and depth, reaching 1% (1 standard deviation) at 20 cm depth.
Failure-probability driven dose painting
Vogelius, Ivan R.; Håkansson, Katrin; Due, Anne K.; Aznar, Marianne C.; Berthelsen, Anne K.; Kristensen, Claus A.; Rasmussen, Jacob; Specht, Lena; Bentzen, Søren M.
2013-01-01
Purpose: To demonstrate a data-driven dose-painting strategy based on the spatial distribution of recurrences in previously treated patients. The result is a quantitative way to define a dose prescription function, optimizing the predicted local control at constant treatment intensity. A dose planning study using the optimized dose prescription in 20 patients is performed. Methods: Patients treated at our center have five tumor subvolumes from the center of the tumor (PET positive volume) and out delineated. The spatial distribution of 48 failures in patients with complete clinical response after (chemo)radiation is used to derive a model for tumor control probability (TCP). The total TCP is fixed to the clinically observed 70% actuarial TCP at five years. Additionally, the authors match the distribution of failures between the five subvolumes to the observed distribution. The steepness of the dose–response is extracted from the literature and the authors assume 30% and 20% risk of subclinical involvement in the elective volumes. The result is a five-compartment dose response model matching the observed distribution of failures. The model is used to optimize the distribution of dose in individual patients, while keeping the treatment intensity constant and the maximum prescribed dose below 85 Gy. Results: The vast majority of failures occur centrally despite the small volumes of the central regions. Thus, optimizing the dose prescription yields higher doses to the central target volumes and lower doses to the elective volumes. The dose planning study shows that the modified prescription is clinically feasible. The optimized TCP is 89% (range: 82%–91%) as compared to the observed TCP of 70%. Conclusions: The observed distribution of locoregional failures was used to derive an objective, data-driven dose prescription function. The optimized dose is predicted to result in a substantial increase in local control without increasing the predicted risk of toxicity. PMID:23927314
Failure-probability driven dose painting
Vogelius, Ivan R.; Håkansson, Katrin; Due, Anne K.; Aznar, Marianne C.; Kristensen, Claus A.; Rasmussen, Jacob; Specht, Lena [Department of Radiation Oncology, Rigshospitalet, University of Copenhagen, Copenhagen 2100 (Denmark)] [Department of Radiation Oncology, Rigshospitalet, University of Copenhagen, Copenhagen 2100 (Denmark); Berthelsen, Anne K. [Department of Radiation Oncology, Rigshospitalet, University of Copenhagen, Copenhagen 2100, Denmark and Department of Clinical Physiology, Nuclear Medicine and PET, Rigshospitalet, University of Copenhagen, Copenhagen 2100 (Denmark)] [Department of Radiation Oncology, Rigshospitalet, University of Copenhagen, Copenhagen 2100, Denmark and Department of Clinical Physiology, Nuclear Medicine and PET, Rigshospitalet, University of Copenhagen, Copenhagen 2100 (Denmark); Bentzen, Søren M. [Department of Radiation Oncology, Rigshospitalet, University of Copenhagen, Copenhagen 2100, Denmark and Departments of Human Oncology and Medical Physics, University of Wisconsin, Madison, Wisconsin 53792 (United States)] [Department of Radiation Oncology, Rigshospitalet, University of Copenhagen, Copenhagen 2100, Denmark and Departments of Human Oncology and Medical Physics, University of Wisconsin, Madison, Wisconsin 53792 (United States)
2013-08-15
Purpose: To demonstrate a data-driven dose-painting strategy based on the spatial distribution of recurrences in previously treated patients. The result is a quantitative way to define a dose prescription function, optimizing the predicted local control at constant treatment intensity. A dose planning study using the optimized dose prescription in 20 patients is performed.Methods: Patients treated at our center have five tumor subvolumes from the center of the tumor (PET positive volume) and out delineated. The spatial distribution of 48 failures in patients with complete clinical response after (chemo)radiation is used to derive a model for tumor control probability (TCP). The total TCP is fixed to the clinically observed 70% actuarial TCP at five years. Additionally, the authors match the distribution of failures between the five subvolumes to the observed distribution. The steepness of the dose–response is extracted from the literature and the authors assume 30% and 20% risk of subclinical involvement in the elective volumes. The result is a five-compartment dose response model matching the observed distribution of failures. The model is used to optimize the distribution of dose in individual patients, while keeping the treatment intensity constant and the maximum prescribed dose below 85 Gy.Results: The vast majority of failures occur centrally despite the small volumes of the central regions. Thus, optimizing the dose prescription yields higher doses to the central target volumes and lower doses to the elective volumes. The dose planning study shows that the modified prescription is clinically feasible. The optimized TCP is 89% (range: 82%–91%) as compared to the observed TCP of 70%.Conclusions: The observed distribution of locoregional failures was used to derive an objective, data-driven dose prescription function. The optimized dose is predicted to result in a substantial increase in local control without increasing the predicted risk of toxicity.
Solar maximum: solar array degradation
Miller, T.
1985-08-01
The 5-year in-orbit power degradation of the silicon solar array aboard the Solar Maximum Satellite was evaluated. This was the first spacecraft to use Teflon R FEP as a coverglass adhesive, thus avoiding the necessity of an ultraviolet filter. The peak power tracking mode of the power regulator unit was employed to ensure consistent maximum power comparisons. Telemetry was normalized to account for the effects of illumination intensity, charged particle irradiation dosage, and solar array temperature. Reference conditions of 1.0 solar constant at air mass zero and 301 K (28 C) were used as a basis for normalization. Beginning-of-life array power was 2230 watts. Currently, the array output is 1830 watts. This corresponds to a 16 percent loss in array performance over 5 years. Comparison of Solar Maximum Telemetry and predicted power levels indicate that array output is 2 percent less than predictions based on an annual 1.0 MeV equivalent election fluence of 2.34 x ten to the 13th power square centimeters space environment.
Antonio Peinado; Jonathan Hammond; Andrew Scott
2011-01-01
Pharmaceutical companies are progressively adopting and introducing the principles of Quality by Design with the main purpose of assurance and built-in quality throughout the whole manufacturing process. Within this framework, a Partial Least Square (PLS) model, based on Near Infrared (NIR) spectra and humidity determinations, was built in order to determine in-line the drying end point of a fluidised bed
Technical basis for dose reconstruction
Anspaugh, L.R.
1996-01-31
The purpose of this paper is to consider two general topics: technical considerations of why dose-reconstruction studies should or should not be performed and methods of dose reconstruction. The first topic is of general and growing interest as the number of dose-reconstruction studies increases, and one asks the question whether it is necessary to perform a dose reconstruction for virtually every site at which, for example, the Department of Energy (DOE) has operated a nuclear-related facility. And there is the broader question of how one might logically draw the line at performing or not performing dose-reconstruction (radiological and chemical) studies for virtually every industrial complex in the entire country. The second question is also of general interest. There is no single correct way to perform a dose-reconstruction study, and it is important not to follow blindly a single method to the point that cheaper, faster, more accurate, and more transparent methods might not be developed and applied.
el Dareer, S M; Kalin, J R; Tillery, K F; Hill, D L
1988-01-01
The disposition of 2-(2-quinolyl)-1,3-indandione (D. C. yellow #11, DCY) in male Fischer rats dosed intravenously or by feeding was determined. For rats given [14C]DCY in the feed (0.00044-0.41% of the diet), recovery of radioactivity during the 24-h dosing period and the 72-h period thereafter ranged from 89.1 to 93.9% for feces and from 4.98 to 6.25 for urine. Tissues contained only trace amounts. Following intravenous dosing with [14C]DCY (0.93 mg/kg), radioactivity distributed readily into most tissues; maximum amounts were present at 5 min, the earliest time of assay. Maximum amounts of radioactivity in fat, skin, and gut tissue, however, were present at 30 min after dosing. These three tissues also had relatively long alpha phases for the elimination of radioactivity. In 24 h after intravenous dosing, rats excreted 81.1% of the dose in the feces and 16.0% of the dose in the urine. For rats fitted with biliary cannulas, 54.5% of the dose, all of which was metabolites of [14C]DCY, was recovered in the bile in 4 h. Associated with the rapid and extensive biliary excretion of metabolites of intravenously administered [14C]DCY was the appearance of large amounts of radioactivity in the feces and also, at intermediate time points, in the liver, gut contents, and gut tissue. In conclusion, rats rapidly distribute, metabolize, and excrete [14C]DCY. PMID:3351983
Radiological Dose Assessment 8 2010 SITE ENVIRONMENTAL REPORT8-1
Radiological Dose Assessment 8 2010 SITE ENVIRONMENTAL REPORT8-1 DRAFT The radiological dose, and local regulations and the public is protected. The potential radiological dose to members of the public is calculated at the site boundary as the maximum dose that could be received by a hypothetical individual
Radiological Dose Assessment 8 2011 Site environmental report8-1
Radiological Dose Assessment 8 2011 Site environmental report8-1 BNL's annual radiological dose and local regulations, and that the public is protected. The potential radiological dose to members of the public is calculated at the site boundary as the maximum dose that could be received by a hypothetical
Radiological Dose Assessment 8 2012 SITE ENVIRONMENTAL REPORT8-1
Radiological Dose Assessment 8 2012 SITE ENVIRONMENTAL REPORT8-1 BNL's annual radiological dose, state, and local regulations, and that the public is protected. The potential radiological dose to members of the public is calculated at an off-site location closest to emission source as the maximum dose
NASA Astrophysics Data System (ADS)
Maigne, L.; Perrot, Y.; Schaart, D. R.; Donnarieix, D.; Breton, V.
2011-02-01
The GATE Monte Carlo simulation platform based on the GEANT4 toolkit has come into widespread use for simulating positron emission tomography (PET) and single photon emission computed tomography (SPECT) imaging devices. Here, we explore its use for calculating electron dose distributions in water. Mono-energetic electron dose point kernels and pencil beam kernels in water are calculated for different energies between 15 keV and 20 MeV by means of GATE 6.0, which makes use of the GEANT4 version 9.2 Standard Electromagnetic Physics Package. The results are compared to the well-validated codes EGSnrc and MCNP4C. It is shown that recent improvements made to the GEANT4/GATE software result in significantly better agreement with the other codes. We furthermore illustrate several issues of general interest to GATE and GEANT4 users who wish to perform accurate simulations involving electrons. Provided that the electron step size is sufficiently restricted, GATE 6.0 and EGSnrc dose point kernels are shown to agree to within less than 3% of the maximum dose between 50 keV and 4 MeV, while pencil beam kernels are found to agree to within less than 4% of the maximum dose between 15 keV and 20 MeV.
The Maximum Traveling Salesman Problem Under Polyhedral Norms
Alexander I. Barvinok; David S. Johnson; Gerhard J. Woeginger; Russell Woodroofe
1998-01-01
. We consider the traveling salesman problem when the citiesare points in Rdfor some fixed d and distances are computed accordingto a polyhedral norm. We show that for any such norm, the problem offinding a tour of maximum length can be solved in polynomial time. Ifarithmetic operations are assumed to take unit time, our algorithms runin time O(nf \\\\Gamma2log n),
VEHICLE DYNAMICS MODEL FOR PREDICTING MAXIMUM TRUCK ACCELERATION LEVELS
Rakha, Hesham A.
VEHICLE DYNAMICS MODEL FOR PREDICTING MAXIMUM TRUCK ACCELERATION LEVELS by Hesham Rakha1 , Member, Setti, and Van Aerde 2 ABSTRACT The paper presents a simple vehicle dynamics model for estimating and deceleration behavior contradicts basic vehicle dynamics. It is not clear at this point if this difference
Marty, Mary S.
2013-01-01
Life-stage-dependent toxicity and dose-dependent toxicokinetics (TK) were evaluated in Sprague Dawley rats following dietary exposure to 2,4-dichlorophenoxyacetic acid (2,4-D). 2,4-D renal clearance is impacted by dose-dependent saturation of the renal organic anion transporter; thus, this study focused on identifying inflection points of onset of dietary nonlinear TK to inform dose selection decisions for toxicity studies. Male and female rats were fed 2,4-D-fortified diets at doses to 1600 ppm for 4-weeks premating, <2 weeks during mating, and to test day (TD) 71 to parental (P1) males and to P1 females through gestation/lactation to TD 96. F1 offspring were exposed via milk with continuing diet exposure until postnatal day (PND) 35. As assessed by plasma area under the curve for the time-course plasma concentration, nonlinear TK was observed ?1200 ppm (63mg/kg/day) for P1 males and between 200 and 400 ppm (14–27mg/kg/day) for P1 females. Dam milk and pup plasma levels were higher on lactation day (LD) 14 than LD 4. Relative to P1 adults, 2,4-D levels were higher in dams during late gestation/lactation and postweaning pups (PND 21–35) and coincided with elevated intake of diet/kg body weight. Using conventional maximum tolerated dose (MTD) criteria based on body weight changes for dose selection would have resulted in excessive top doses approximately 2-fold higher than those identified incorporating critical TK data. These data indicate that demonstration of nonlinear TK, if present at dose levels substantially above real-world human exposures, is a key dose selection consideration for improving the human relevance of toxicity studies compared with studies employing conventional MTD dose selection strategies. PMID:24105888
Dose reconstruction in deforming lung anatomy: Dose grid size effects and clinical implications
Rosu, Mihaela; Chetty, Indrin J.; Balter, James M.; Kessler, Marc L.; McShan, Daniel L.; Ten Haken, Randall K. [Department of Radiation Oncology, University of Michigan, Ann Arbor, Michigan 48109-0010 (United States)
2005-08-15
In this study we investigated the accumulation of dose to a deforming anatomy (such as lung) based on voxel tracking and by using time weighting factors derived from a breathing probability distribution function (p.d.f.). A mutual information registration scheme (using thin-plate spline warping) provided a transformation that allows the tracking of points between exhale and inhale treatment planning datasets (and/or intermediate state scans). The dose distributions were computed at the same resolution on each dataset using the Dose Planning Method (DPM) Monte Carlo code. Two accumulation/interpolation approaches were assessed. The first maps exhale dose grid points onto the inhale scan, estimates the doses at the 'tracked' locations by trilinear interpolation and scores the accumulated doses (via the p.d.f.) on the original exhale data set. In the second approach, the 'volume' associated with each exhale dose grid point (exhale dose voxel) is first subdivided into octants, the center of each octant is mapped to locations on the inhale dose grid and doses are estimated by trilinear interpolation. The octant doses are then averaged to form the inhale voxel dose and scored at the original exhale dose grid point location. Differences between the interpolation schemes are voxel size and tissue density dependent, but in general appear primarily only in regions with steep dose gradients (e.g., penumbra). Their magnitude (small regions of few percent differences) is less than the alterations in dose due to positional and shape changes from breathing in the first place. Thus, for sufficiently small dose grid point spacing, and relative to organ motion and deformation, differences due solely to the interpolation are unlikely to result in clinically significant differences to volume-based evaluation metrics such as mean lung dose (MLD) and tumor equivalent uniform dose (gEUD). The overall effects of deformation vary among patients. They depend on the tumor location, field size, volume expansion, tissue heterogeneity, and direction of tumor displacement with respect to the beam, and are more likely to have an impact on serial organs (such as esophagus), rather than on large parallel organs (such as lung)
NASA Astrophysics Data System (ADS)
Hansen, J.
2007-12-01
A climate tipping point, at least as I have used the phrase, refers to a situation in which a changing climate forcing has reached a point such that little additional forcing (or global temperature change) is needed to cause large, relatively rapid, climate change. Present examples include potential loss of all Arctic sea ice and instability of the West Antarctic and Greenland ice sheets. Tipping points are characterized by ready feedbacks that amplify the effect of forcings. The notion that these may be runaway feedbacks is a misconception. However, present "unrealized" global warming, due to the climate system's thermal inertia, exacerbates the difficulty of avoiding global warming tipping points. I argue that prompt efforts to slow CO2 emissions and absolutely reduce non-CO2 forcings are both essential if we are to avoid tipping points that would be disastrous for humanity and creation, the planet as civilization knows it.
NASA Technical Reports Server (NTRS)
Savage, M.; Mackulin, M. J.; Coe, H. H.; Coy, J. J.
1991-01-01
Optimization procedures allow one to design a spur gear reduction for maximum life and other end use criteria. A modified feasible directions search algorithm permits a wide variety of inequality constraints and exact design requirements to be met with low sensitivity to initial guess values. The optimization algorithm is described, and the models for gear life and performance are presented. The algorithm is compact and has been programmed for execution on a desk top computer. Two examples are presented to illustrate the method and its application.
Azcona, J [Department of Radiation Physics, Clinica Universidad de Navarra (Spain); Burguete, J [Universidad de Navarra, Pamplona, Navarra (Spain)
2014-06-01
Purpose: To obtain the pencil beam kernels that characterize a megavoltage photon beam generated in a FFF linac by experimental measurements, and to apply them for dose calculation in modulated fields. Methods: Several Kodak EDR2 radiographic films were irradiated with a 10 MV FFF photon beam from a Varian True Beam (Varian Medical Systems, Palo Alto, CA) linac, at the depths of 5, 10, 15, and 20cm in polystyrene (RW3 water equivalent phantom, PTW Freiburg, Germany). The irradiation field was a 50 mm diameter circular field, collimated with a lead block. Measured dose leads to the kernel characterization, assuming that the energy fluence exiting the linac head and further collimated is originated on a point source. The three-dimensional kernel was obtained by deconvolution at each depth using the Hankel transform. A correction on the low dose part of the kernel was performed to reproduce accurately the experimental output factors. The kernels were used to calculate modulated dose distributions in six modulated fields and compared through the gamma index to their absolute dose measured by film in the RW3 phantom. Results: The resulting kernels properly characterize the global beam penumbra. The output factor-based correction was carried out adding the amount of signal necessary to reproduce the experimental output factor in steps of 2mm, starting at a radius of 4mm. There the kernel signal was in all cases below 10% of its maximum value. With this correction, the number of points that pass the gamma index criteria (3%, 3mm) in the modulated fields for all cases are at least 99.6% of the total number of points. Conclusion: A system for independent dose calculations in modulated fields from FFF beams has been developed. Pencil beam kernels were obtained and their ability to accurately calculate dose in homogeneous media was demonstrated.
The use of modified single pencil beam dose kernels to improve IMRT dose calculation accuracy.
Bergman, Alanah M; Otto, Karl; Duzenli, Cheryl
2004-12-01
Intensity modulated radiation therapy (IMRT) is used to deliver highly conformal radiation doses to tumors while sparing nearby sensitive tissues. Discrepancies between calculated and measured dose distributions have been reported for regions of high dose gradients corresponding to complex radiation fluence patterns. For the single pencil beam convolution dose calculation algorithm, the ability to resolve areas of high dose structure is partly related to the shape of the pencil beam dose kernel (similar to how a photon detector's point spread function relates to imaging resolution). Improvements in dose calculation accuracy have been reported when the treatment planning system (TPS) is recommissioned using high-resolution measurement data as input. This study proposes to improve the dose calculation accuracy for IMRT planning by modifying clinical dose kernel shapes already present in the TPS, thus avoiding the need to reacquire higher resolution commissioning data. The in-house optimization program minimizes a cost-function based on a two-dimensional composite dose subtraction/distance-to-agreement (gamma) analysis. The final modified kernel shapes are reintroduced into the treatment planning system and improvements to the dose calcula tion accuracy for complex IMRT dose distributions evaluated. The central kernel value (radius =0 cm) has the largest effect on the dose calculation resolution and is the focus of this study. PMID:15651610
The use of modified single pencil beam dose kernels to improve IMRT dose calculation accuracy
Bergman, Alanah M.; Otto, Karl; Duzenli, Cheryl [Physics and Astronomy, University of British Columbia, Vancouver, British Columbia, Canada and Medical Physics, BC Cancer Agency-Vancouver Centre, Vancouver, British Columbia (Canada); Medical Physics, BC Cancer Agency-Vancouver Centre, Vancouver, British Columbia (Canada); Medical Physics, BC Cancer Agency-Fraser Valley Centre, Surrey, British Columbia (Canada)
2004-12-01
Intensity modulated radiation therapy (IMRT) is used to deliver highly conformal radiation doses to tumors while sparing nearby sensitive tissues. Discrepancies between calculated and measured dose distributions have been reported for regions of high dose gradients corresponding to complex radiation fluence patterns. For the single pencil beam convolution dose calculation algorithm, the ability to resolve areas of high dose structure is partly related to the shape of the pencil beam dose kernel (similar to how a photon detector's point spread function relates to imaging resolution). Improvements in dose calculation accuracy have been reported when the treatment planning system (TPS) is recommissioned using high-resolution measurement data as input. This study proposes to improve the dose calculation accuracy for IMRT planning by modifying clinical dose kernel shapes already present in the TPS, thus avoiding the need to reacquire higher resolution commissioning data. The in-house optimization program minimizes a cost-function based on a two-dimensional composite dose subtraction/distance-to-agreement (gamma) analysis. The final modified kernel shapes are reintroduced into the treatment planning system and improvements to the dose calculation accuracy for complex IMRT dose distributions evaluated. The central kernel value (radius=0 cm) has the largest effect on the dose calculation resolution and is the focus of this study.
Calculation of external dose from distributed source
Kocher
1986-01-01
This paper discusses a relatively simple calculational method, called the point kernel method (Fo68), for estimating external dose from distributed sources that emit photon or electron radiations. The principles of the point kernel method are emphasized, rather than the presentation of extensive sets of calculations or tables of numerical results. A few calculations are presented for simple source geometries as
Absorbed Dose and Dose Equivalent Calculations for Modeling Effective Dose
NASA Technical Reports Server (NTRS)
Welton, Andrew; Lee, Kerry
2010-01-01
While in orbit, Astronauts are exposed to a much higher dose of ionizing radiation than when on the ground. It is important to model how shielding designs on spacecraft reduce radiation effective dose pre-flight, and determine whether or not a danger to humans is presented. However, in order to calculate effective dose, dose equivalent calculations are needed. Dose equivalent takes into account an absorbed dose of radiation and the biological effectiveness of ionizing radiation. This is important in preventing long-term, stochastic radiation effects in humans spending time in space. Monte carlo simulations run with the particle transport code FLUKA, give absorbed and equivalent dose data for relevant shielding. The shielding geometry used in the dose calculations is a layered slab design, consisting of aluminum, polyethylene, and water. Water is used to simulate the soft tissues that compose the human body. The results obtained will provide information on how the shielding performs with many thicknesses of each material in the slab. This allows them to be directly applicable to modern spacecraft shielding geometries.
Karlsson, Kristin, E-mail: kristin.karlsson@karolinska.se [Department of Medical Physics, Karolinska University Hospital, Stockholm (Sweden); Department of Oncology-Pathology, Karolinska Institute, Stockholm (Sweden); Nyman, Jan [Department of Oncology, Sahlgrenska University Hospital, Gothenburg (Sweden); Baumann, Pia; Wersäll, Peter [Department of Oncology, Radiumhemmet, Karolinska University Hospital, Stockholm (Sweden); Department of Oncology-Pathology, Karolinska Institute, Stockholm (Sweden); Drugge, Ninni [Department of Radiation Physics, Sahlgrenska University Hospital, Gothenburg (Sweden); Gagliardi, Giovanna [Department of Medical Physics, Karolinska University Hospital, Stockholm (Sweden); Department of Oncology-Pathology, Karolinska Institute, Stockholm (Sweden); Johansson, Karl-Axel [Department of Radiation Physics, Sahlgrenska University Hospital, Gothenburg (Sweden); Persson, Jan-Olov [Statistical Research Group, Mathematical Statistics, Stockholm University, Stockholm (Sweden); Rutkowska, Eva [Physics Department, Clatterbridge Cancer Centre, Wirral (United Kingdom); Tullgren, Owe [Department of Oncology, Radiumhemmet, Karolinska University Hospital, Stockholm (Sweden); Department of Oncology-Pathology, Karolinska Institute, Stockholm (Sweden); Lax, Ingmar [Department of Medical Physics, Karolinska University Hospital, Stockholm (Sweden); Department of Oncology-Pathology, Karolinska Institute, Stockholm (Sweden)
2013-11-01
Purpose: To evaluate the dose–response relationship between radiation-induced atelectasis after stereotactic body radiation therapy (SBRT) and bronchial dose. Methods and Materials: Seventy-four patients treated with SBRT for tumors close to main, lobar, or segmental bronchi were selected. The association between incidence of atelectasis and bronchial dose parameters (maximum point-dose and minimum dose to the high-dose bronchial volume [ranging from 0.1 cm{sup 3} up to 2.0 cm{sup 3}]) was statistically evaluated with survival analysis models. Results: Prescribed doses varied between 4 and 20 Gy per fraction in 2-5 fractions. Eighteen patients (24.3%) developed atelectasis considered to be radiation-induced. Statistical analysis showed a significant correlation between the incidence of radiation-induced atelectasis and minimum dose to the high-dose bronchial volumes, of which 0.1 cm{sup 3} (D{sub 0.1cm3}) was used for further analysis. The median value of D{sub 0.1cm3} (?/? = 3 Gy) was EQD{sub 2,LQ} = 147 Gy{sub 3} (range, 20-293 Gy{sub 3}). For patients who developed atelectasis the median value was EQD{sub 2,LQ} = 210 Gy{sub 3}, and for patients who did not develop atelectasis, EQD{sub 2,LQ} = 105 Gy{sub 3}. Median time from treatment to development of atelectasis was 8.0 months (range, 1.1-30.1 months). Conclusion: In this retrospective study a significant dose–response relationship between the incidence of atelectasis and the dose to the high-dose volume of the bronchi is shown.
Nonlinear dose dependence of TL and LM-OSL within the one trap-one center model
Chen, Reuven
Nonlinear dose dependence of TL and LM-OSL within the one trap-one center model R. Chen a,*, V of numerical simulation of dose dependence of the TL maximum under similar conditions. In some cases, the TL. Different sublinear dose-dependence functions of the trap occupancy and the maximum TL are demonstrated
Haluska, Paul; Menefee, Michael; Plimack, Elizabeth R.; Rosenberg, Jonathan; Northfelt, Donald; LaVallee, Theresa; Shi, Li; Yu, Xiang-Qing; Burke, Patricia; Huang, Jaiqi; Viner, Jaye; McDevitt, Jennifer; LoRusso, Patricia
2015-01-01
Purpose This phase I, multicenter, open-label, single-arm, dose-escalation, and dose-expansion study evaluated the safety, tolerability, and antitumor activity of MEDI-573 in adults with advanced solid tumors refractory to standard therapy or for which no standard therapy exists. Experimental Design Patients received MEDI-573 in 1 of 5 cohorts (0.5, 1.5, 5, 10, or 15 mg/kg) dosed weekly or 1 of 2 cohorts (30 or 45 mg/kg) dosed every 3 weeks. Primary end points included the MEDI-573 safety profile, maximum tolerated dose (MTD), and optimal biologic dose (OBD). Secondary end points included MEDI-573 pharmacokinetics (PK), pharmacodynamics, immunogenicity, and antitumor activity. Results In total, 43 patients (20 with urothelial cancer) received MEDI-573. No dose-limiting toxicities were identified, and only 1 patient experienced hyperglycemia related to treatment. Elevations in levels of insulin and/or growth hormone were not observed. Adverse events observed in >10% of patients included fatigue, anorexia, nausea, diarrhea, and anemia. PK evaluation demonstrated that levels of MEDI-573 increased with dose at all dose levels tested. At doses >5 mg/kg, circulating levels of insulin-like growth factor (IGF)-I and IGFII were fully suppressed. Of 39 patients evaluable for response, none experienced partial or complete response and 13 had stable disease as best response. Conclusions The MTD of MEDI-573 was not reached. The OBD was 5 mg/kg weekly or 30 or 45 mg/kg every 3 weeks. MEDI-573 showed preliminary antitumor activity in a heavily pretreated population and had a favorable tolerability profile, with no notable perturbations in metabolic homeostasis. PMID:25024259
System for Memorizing Maximum Values
NASA Technical Reports Server (NTRS)
Bozeman, Richard J., Jr. (Inventor)
1996-01-01
The invention discloses a system capable of memorizing maximum sensed values. The system includes conditioning circuitry which receives the analog output signal from a sensor transducer. The conditioning circuitry rectifies and filters the analog signal and provides an input signal to a digital driver, which may be either liner or logarithmic. The driver converts the analog signal to discrete digital values, which in turn triggers an output signal on one of a plurality of driver output lines n. The particular output lines selected is dependent on the converted digital value. A microfuse memory device connects across the driver output lines, with n segments. Each segment is associated with one driver output line, and includes a microfuse that is blown when a signal appears on the associated driver output line.
System for memorizing maximum values
NASA Technical Reports Server (NTRS)
Bozeman, Richard J., Jr. (inventor)
1992-01-01
The invention discloses a system capable of memorizing maximum sensed values. The system includes conditioning circuitry which receives the analog output signal from a sensor transducer. The conditioning circuitry rectifies and filters the analog signal and provides an input signal to a digital driver, which may be either linear or logarithmic. The driver converts the analog signal to discrete digital values, which in turn triggers an output signal on one of a plurality of driver output lines n. The particular output lines selected is dependent on the converted digital value. A microfuse memory device connects across the driver output lines, with n segments. Each segment is associated with one driver output line, and includes a microfuse that is blown when a signal appears on the associated driver output line.
Route-to-route extrapolations are a crucial step in many risk assessments. Often the doses which result In toxicological end points in one route must be compared with doses resulting from typical environmental exposures by another route. In this case we used EPA's Dose Estimati...
Route-to-route extrapolations are a crucial step in many risk assessments. Often the doses which result In toxicological end points in one route must be compared with doses resulting from typical environmental exposures by another route. In this case we used EPA's Dose Estimati...
Calculation of dose to soft tisse from implanted beta sources
Dauffy, Lucile
1998-01-01
the spatial distribution of absorbed dose around a line of spheres. BRAIN-DOSES uses integration of Berger point kernels over the source volume, employing the scaled point kernels tabulated by Berger in 1971. This method requires calculation of the beta...
An updated dose assessment for Rongelap Island
Robison, W.L.; Conrado, C.L.; Bogen, K.T.
1994-07-01
We have updated the radiological dose assessment for Rongelap Island at Rongelap Atoll using data generated from field trips to the atoll during 1986 through 1993. The data base used for this dose assessment is ten fold greater than that available for the 1982 assessment. Details of each data base are presented along with details about the methods used to calculate the dose from each exposure pathway. The doses are calculated for a resettlement date of January 1, 1995. The maximum annual effective dose is 0.26 mSv y{sup {minus}1} (26 mrem y{sup {minus}1}). The estimated 30-, 50-, and 70-y integral effective doses are 0.0059 Sv (0.59 rem), 0.0082 Sv (0.82 rem), and 0.0097 Sv (0.97 rem), respectively. More than 95% of these estimated doses are due to 137-Cesium ({sup 137}Cs). About 1.5% of the estimated dose is contributed by 90-Strontium ({sup 90}Sr), and about the same amount each by 239+240-Plutonium ({sup 239+240}PU), and 241-Americium ({sup 241}Am).
Acetaminophen accumulation in pediatric patients after repeated therapeutic doses
M. C. Nahata; D. A. Powell; D. E. Durrell; M. A. Miller
1984-01-01
Summary Acetaminophen serum concentrations were studied in 21 infants and children with fever. The maximum serum concentrations ranged from 9.96 to 19.6 µg\\/ml after a single dose of 12–14 mg\\/kg and 13.9 to 40.1 µg\\/ml after a single dose of 22–27 mg\\/kg. Ten patients were restudied at steadystate after repeat doses had been given every 4 or 8 h for 1
Peripheral doses from pediatric IMRT
Klein, Eric E.; Maserang, Beth; Wood, Roy; Mansur, David [Department of Radiation Oncology, Washington University School of Medicine, St. Louis, Missouri 63110 (United States)
2006-07-15
Peripheral dose (PD) data exist for conventional fields ({>=}10 cm) and intensity-modulated radiotherapy (IMRT) delivery to standard adult-sized phantoms. Pediatric peripheral dose reports are limited to conventional therapy and are model based. Our goal was to ascertain whether data acquired from full phantom studies and/or pediatric models, with IMRT treatment times, could predict Organ at Risk (OAR) dose for pediatric IMRT. As monitor units (MUs) are greater for IMRT, it is expected IMRT PD will be higher; potentially compounded by decreased patient size (absorption). Baseline slab phantom peripheral dose measurements were conducted for very small field sizes (from 2 to 10 cm). Data were collected at distances ranging from 5 to 72 cm away from the field edges. Collimation was either with the collimating jaws or the multileaf collimator (MLC) oriented either perpendicular or along the peripheral dose measurement plane. For the clinical tests, five patients with intracranial or base of skull lesions were chosen. IMRT and conventional three-dimensional (3D) plans for the same patient/target/dose (180 cGy), were optimized without limitation to the number of fields or wedge use. Six MV, 120-leaf MLC Varian axial beams were used. A phantom mimicking a 3-year-old was configured per Center for Disease Control data. Micro (0.125 cc) and cylindrical (0.6 cc) ionization chambers were appropriated for the thyroid, breast, ovaries, and testes. The PD was recorded by electrometers set to the 10{sup -10} scale. Each system set was uniquely calibrated. For the slab phantom studies, close peripheral points were found to have a higher dose for low energy and larger field size and when MLC was not deployed. For points more distant from the field edge, the PD was higher for high-energy beams. MLC orientation was found to be inconsequential for the small fields tested. The thyroid dose was lower for IMRT delivery than that predicted for conventional (ratio of IMRT/cnventional ranged from 0.47-0.94) doses {approx}[0.4-1.8 cGy]/[0.9-2.9 cGy]/fraction, respectively. Prior phantom reports are for fields 10 cm or greater, while pediatric central nervous system fields range from 4 to 7 cm, and effectively much smaller for IMRT (2-6 cm). Peripheral dose in close proximity (<10 cm from the field edge) is dominated by internal scatter; therefore, field-size differences overwhelm phantom size affects and increased MU. Distant peripheral dose, dominated by head leakage, was higher than predicted, even when accounting for MUs ({approx}factor of 3) likely due to the pediatric phantom size. The ratio of the testes dose ranged from 3.3-5.3 for IMRT/conventional. PD to OAR for pediatric IMRT cannot be predicted from large-field full phantom studies. For regional OAR, doses are likely lower than predicted by existing ''large field'' data, while the distant PD is higher.
Hayes, R.B.; Haskell, E.H.; Kenner, G.H. [Utah Univ., Salt Lake City, UT (United States)
1996-01-01
Additive dose methods commonly used in electron paramagnetic resonance (EPR) dosimetry are time consuming and labor intensive. We have developed a mathematical approach for determining optimal spacing of applied doses and the number of spectra which should be taken at each dose level. Expected uncertainitites in the data points are assumed to be normally distributed with a fixed standard deviation and linearity of dose response is also assumed. The optimum spacing and number of points necessary for the minimal error can be estimated, as can the likely error in the resulting estimate. When low doses are being estimated for tooth enamel samples the optimal spacing is shown to be a concentration of points near the zero dose value with fewer spectra taken at a single high dose value within the range of known linearity. Optimization of the analytical process results in increased accuracy and sample throughput.
NASA Astrophysics Data System (ADS)
Ishmael Parsai, E.; Pearson, David; Kvale, Thomas
2007-08-01
An Elekta SL-25 medical linear accelerator (Elekta Oncology Systems, Crawley, UK) has been modelled using Monte Carlo simulations with the photon flattening filter removed. It is hypothesized that intensity modulated radiation therapy (IMRT) treatments may be carried out after the removal of this component despite it's criticality to standard treatments. Measurements using a scanning water phantom were also performed after the flattening filter had been removed. Both simulated and measured beam profiles showed that dose on the central axis increased, with the Monte Carlo simulations showing an increase by a factor of 2.35 for 6 MV and 4.18 for 10 MV beams. A further consequence of removing the flattening filter was the softening of the photon energy spectrum leading to a steeper reduction in dose at depths greater than the depth of maximum dose. A comparison of the points at the field edge showed that dose was reduced at these points by as much as 5.8% for larger fields. In conclusion, the greater photon fluence is expected to result in shorter treatment times, while the reduction in dose outside of the treatment field is strongly suggestive of more accurate dose delivery to the target.
Paton, A M; Chalmers, K E; Coomber, H; Cameron, A L
2012-01-01
Objective The aim of this study was to assess the impact of dose escalation on the proportion of patients requiring MR image-guided optimisation rather than standard Manchester-based CT-guided planning, and the level of escalation achievable. Methods 30 patients with cervical cancer treated with external beam radiotherapy and image-guided brachytherapy (IGBT) had MR images acquired at the first fraction of IGBT. Gross tumour volume and high-risk clinical target volume (HR CTV) were contoured and treatment plans retrospectively produced for a range of total 2-Gy equivalent (EQD2) prescription doses from 66 Gy?/?=10 to 90 Gy?/?=10 (HR CTV D90). Standard Manchester system-style plans were produced, prescribed to point A and then optimised where necessary with the aim of delivering at least the prescription dose to the HR CTV D90 while respecting organ-at-risk (OAR) tolerances. Results Increasing the total EQD2 from 66 Gy?/?=10 to 90 Gy?/?=10 increased the number of plans requiring optimisation from 13.3% to 90%. After optimisation, the number of plans achieving the prescription dose ranged from 93.3% (66 Gy?/?=10) to 63.3% (90 Gy?/?=10) with the mean±standard deviation for HR CTV D90 EQD2 from 78.4±12.4 Gy?/?=10 (66 Gy?/?=10) to 94.1±19.9 Gy?/?=10 (90 Gy?/?=10). Conclusion As doses are escalated, the need for non-standard optimised planning increases, while benefits in terms of increased target doses actually achieved diminish. The maximum achievable target dose is ultimately limited by proximity of OARs. Advances in knowledge This work represents a guide for other centres in determining the highest practicable prescription doses while considering patient throughput and maintaining acceptable OAR doses. PMID:23175490
Dosimetry of CBCT: methods, doses and clinical consequences
NASA Astrophysics Data System (ADS)
Sykes, J. R.; Lindsay, R.; Iball, G.; Thwaites, D. I.
2013-06-01
The use of Cone beam CT (CBCT) systems for Image Guided Radiotherapy is rapidly expanding in the developed world. With its use comes concern for the increased risks of additional radiation exposure. Quantification of the imaging dose is necessary in order to report, optimise and justify CBCT exposures. This article reviews the current methods of dose measurement and calculation including dose measurements in cylindrical phantoms, use of point dosimeters in anthropomorphic phantoms, calculation of dose using mathematical phantoms and calculation of individualised patient dose using Monte Carlo and model based techniques. Typical doses from commercial systems are reported and the clinical consequences, both risks and benefits, of using CBCT based IGRT reviewed briefly.
Baruch S. Jacobson
1993-01-01
For typical tumor-cell dose-response curves, the efficiency ratio, i.e., the ratio between the fraction of cells killed and the radiation dose administered, is a continuously decreasing function of dose. However, if the survival curve is sufficiently “shouldered”, this ratio has a maximum value at a dose greater than zero. In radiotherapy, one possible criterion for the ideal dose per session
Improved dose assessment in a nuclear reactor accident using the old and new ICRP methodologies
Yoon, Suk-Chul
1987-01-01
of interest was at a height of one meter above an infinite plane. The calculations used the point-kernel integration method (Ko79). A tabulation of dose conversion factors for external dose from contaminated ground surface, referred to as the ground plane... in the computer codes and doses were obtained for distances ranging from 0. 5 to fifty miles downwind of the release point. Exposure pathways considered included external dose due to immersion in contaminated air, internal dose from inhalation of radionuclides...
Paxton, Adam B.; Davis, Stephen D.; DeWerd, Larry A. [Department of Medical Physics, University of Wisconsin-Madison, Madison, Wisconsin 53705 (United States); Department of Medical Physics, University of Wisconsin-Madison, Madison, Wisconsin 53705 and McGill University Health Centre, Department of Medical Physics, Montreal, Quebec H3G 1A4 (Canada); Department of Medical Physics, University of Wisconsin-Madison, Madison, Wisconsin 53705 (United States)
2012-03-15
Purpose: Recent advances in the imaging of {sup 90}Y using positron emission tomography (PET) and improved uncertainty in the branching ratio for the internal pair production component of {sup 90}Y decay allow for a more accurate determination of the activity distribution of {sup 90}Y microspheres within a patient. This improved activity distribution can be convolved with the dose kernel of {sup 90}Y to calculate the dose distribution within a patient. This work investigates the effects of microsphere and surrounding material composition on {sup 90}Y dose kernels using egsnrc and mcnp5 and compares the results of these two transport codes. Methods: Monte Carlo simulations were performed with egsnrc and mcnp5 to calculate the dose rate at multiple radial distances around various {sup 90}Y sources. Point source simulations were completed with mcnp5 to determine the optimal electron transport settings for this work. After determining the optimal settings, point source simulations were completed using egsnrc (user code edknrc) and mcnp5 in water and liver [as defined by the International Commission on Radiation Units and Measurements (ICRU) Report 44]. The results were compared to ICRU Report 72 reference data. Point source simulations were also completed in water with a density of 1.06 g{center_dot}cm{sup -3} to evaluate the effect of the density of the surrounding material. Glass and resin microsphere simulations were performed with average and maximum diameter and density values (based on values given in the literature) in water and in liver. The results were compared to point source simulation results using the same transport code and in the same surrounding material. All simulations had statistical uncertainties less than 1%. Results: The optimal transport settings in mcnp5 for this work included using the energy-and step-specific algorithm (DBCN 17J 2) and ESTEP set to 10. These settings were used for all subsequent simulations with mcnp5. The point source simulations in water for both egsnrc and mcnp5 were found to agree within 2% of the ICRU 72 reference data over the investigated range. Point source simulations in liver had large differences relative to ICRU 72, approaching -60% near the maximum range of {sup 90}Y. These differences are mostly attributed to the difference in density between water (1.0 g{center_dot}cm{sup -3}) and liver (1.06 g{center_dot}cm{sup -3}). Glass and resin microsphere simulations showed a slight decrease in the dose rate near the maximum range of {sup 90}Y relative to the point source simulations. The largest relative differences were approximately -4.2% and -2.8% for the glass and resin microspheres, respectively. Agreement between the egsnrc and mcnp5 simulations results was generally good. Conclusions: The presence of the microsphere material causes slight differences in the {sup 90}Y dose kernel compared to those calculated with point sources. Large differences were seen between simulations in water and those in liver. For the most accurate calculation of the dose distribution, the density of the patient's liver should be accounted for in the calculation of the dose kernel. Lastly, due to the need to determine the optimal transport settings with mcnp5, electron transport with this code should be used with caution.
Sarkar, Biplab; Ghosh, Bhaswar; Sriramprasath; Mahendramohan, Sukumaran; Basu, Ayan; Goswami, Jyotirup; Ray, Amitabh
2010-07-01
The study was aimed to compare accuracy of monitor unit verification in intensity modulated radiation therapy (IMRT) using 6 MV photons by three different methodologies with different detector phantom combinations. Sixty patients were randomly chosen. Zero degree couch and gantry angle plans were generated in a plastic universal IMRT verification phantom and 30×30×30 cc water phantom and measured using 0.125 cc and 0.6 cc chambers, respectively. Actual gantry and couch angle plans were also measured in water phantom using 0.6 cc chamber. A suitable point of measurement was chosen from the beam profile for each field. When the zero-degree gantry, couch angle plans and actual gantry, couch angle plans were measured by 0.6 cc chamber in water phantom, the percentage mean difference (MD) was 1.35%, 2.94 % and Standard Deviation (SD) was 2.99%, 5.22%, respectively. The plastic phantom measurements with 0.125 cc chamber Semiflex ionisation chamber (SIC) showed an MD=4.21% and SD=2.73 %, but when corrected for chamber-medium response, they showed an improvement, with MD=3.38 % and SD=2.59 %. It was found that measurements with water phantom and 0.6cc chamber at gantry angle zero degree showed better conformity than other measurements of medium-detector combinations. Correction in plastic phantom measurement improved the result only marginally, and actual gantry angle measurement in a flat- water phantom showed higher deviation. PMID:20927221
Pharmacokinetics of an immunomodulating dose of levamisole in weaned pigs.
Suran, Jelena; Flajs, Dubravka; Peraica, Maja; Prevendar Crni?, Andreja; Speranda, Marcela; Boži?, Frane
2013-09-01
Levamisole has been shown to stimulate the immune response in immunocompromised humans and animals. However, its use as an adjuvant in immunocompromised weaned pigs prone to colibacillosis has only been experimentally tested but not yet officially approved. Therefore, the aim of these studies was to study the pharmacokinetics (PK) of an immunomodulating dose of levamisole in weaned pigs. For that purpose, 20 weaned crossbred pigs were divided into two treatment groups. In this parallel-design study, a single dose of levamisole (2.5 mg/kg body weight) was administered by the intramuscular (i.m.) or oral (p.o.) route. Statistically significant differences between the i.m. and p.o. routes in terminal beta rate constant (?), maximum plasma concentration (Cmax), area under the curve (AUC) for plasma concentration-time curve from time zero to infinity (AUC0-inf), area under the plasma concentration-time curve from time 0 to the last quantifiable time point (AUC0-t) were determined. Further research is needed to establish a relationship between the PK and the immunomodulating effect of levamisole in pigs. PMID:23921349
Parameterized Algorithms for Directed Maximum Leaf Problems
Krivelevich, Michael
Parameterized Algorithms for Directed Maximum Leaf Problems Noga Alon 1 , Fedor V. Fomin 2 spanning tree, then D contains one with at least (n/2) 1/5 - 1 leaves. 1 Introduction The Maximum Leaf a digraph D, the Directed Maximum Leaf OutÂBranching problem is the problem of finding an outÂbranching in D
Maximum entropy principal for transportation
Bilich, F. [University of Brasilia (Brazil); Da Silva, R. [National Research Council (Brazil)
2008-11-06
In this work we deal with modeling of the transportation phenomenon for use in the transportation planning process and policy-impact studies. The model developed is based on the dependence concept, i.e., the notion that the probability of a trip starting at origin i is dependent on the probability of a trip ending at destination j given that the factors (such as travel time, cost, etc.) which affect travel between origin i and destination j assume some specific values. The derivation of the solution of the model employs the maximum entropy principle combining a priori multinomial distribution with a trip utility concept. This model is utilized to forecast trip distributions under a variety of policy changes and scenarios. The dependence coefficients are obtained from a regression equation where the functional form is derived based on conditional probability and perception of factors from experimental psychology. The dependence coefficients encode all the information that was previously encoded in the form of constraints. In addition, the dependence coefficients encode information that cannot be expressed in the form of constraints for practical reasons, namely, computational tractability. The equivalence between the standard formulation (i.e., objective function with constraints) and the dependence formulation (i.e., without constraints) is demonstrated. The parameters of the dependence-based trip-distribution model are estimated, and the model is also validated using commercial air travel data in the U.S. In addition, policy impact analyses (such as allowance of supersonic flights inside the U.S. and user surcharge at noise-impacted airports) on air travel are performed.
Ohara, Hiroshi; Nakamura, Yuji; Watanabe, Yudai; Cao, Xin; Yamazaki, Yukiko; Izumi-Nakaseko, Hiroko; Ando, Kentaro; Yamazaki, Hiroshi; Yamazaki, Junichi; Ikeda, Takanori; Sugiyama, Atsushi
2015-07-01
Azithromycin has been reported to increase the risk of death from cardiovascular causes among patients with high baseline risk. Since the information is still limited to bridge the gap between electrophysiological properties of azithromycin in vitro and cardiac death in patients, we initially assessed its electropharmacological effects in doses of 3 and 30 mg/kg, i.v., with the halothane-anesthetized dogs (n = 4). The low dose provided 5.2 times higher than the therapeutic concentration, whereas the high dose attained 17.0 times higher. The high dose delayed the ventricular repolarization in a reverse use-dependent manner, reflecting blockade of the rapid component of delayed rectifier K(+) current, and the potency was relatively weak; namely, maximum change in QTc was +20 ms (+5.6 %). The high dose also induced the negative inotropic effect possibly through Ca(2+) channel-independent pathway. In order to clarify proarrhythmic risk, 30 mg/kg, i.v., of azithromycin was examined with the chronic atrioventricular block dogs (n = 4). Azithromycin neither induced torsade de pointes nor affected beat-to-beat variability of repolarization. Thus, azithromycin can be considered to lack proarrhythmic potential, but caution has to be paid on its use for patients with left ventricular dysfunction. PMID:25367413
Differential dose contributions on total dose distribution of (125)I brachytherapy source.
Camgöz, B; Ye?in, G; Kumru, M N
2010-01-01
This work provides an improvement of the approach using Monte Carlo simulation for the Amersham Model 6711 (125)I brachytherapy seed source, which is well known by many theoretical and experimental studies. The source which has simple geometry was researched with respect to criteria of AAPM Tg-43 Report. The approach offered by this study involves determination of differential dose contributions that come from virtual partitions of a massive radioactive element of the studied source to a total dose at analytical calculation point. Some brachytherapy seeds contain multi-radioactive elements so the dose at any point is a total of separate doses from each element. It is momentous to know well the angular and radial dose distributions around the source that is located in cancerous tissue for clinical treatments. Interior geometry of a source is effective on dose characteristics of a distribution. Dose information of inner geometrical structure of a brachytherapy source cannot be acquired by experimental methods because of limits of physical material and geometry in the healthy tissue, so Monte Carlo simulation is a required approach of the study. EGSnrc Monte Carlo simulation software was used. In the design of a simulation, the radioactive source was divided into 10 rings, partitioned but not separate from each other. All differential sources were simulated for dose calculation, and the shape of dose distribution was determined comparatively distribution of a single-complete source. In this work anisotropy function was examined also mathematically. PMID:24376927
Evaluating the accuracy of electronic pediatric drug dosing rules
Kirkendall, Eric S; Spooner, S Andrew; Logan, Judith R
2014-01-01
Objective To determine the accuracy of vendor-supplied dosing eRules for pediatric medication orders. Inaccurate or absent dosing rules can lead to high numbers of false alerts or undetected prescribing errors and may potentially compromise safety in this already vulnerable population. Materials and methods 7 months of medication orders and alerts from a large pediatric hospital were analyzed. 30 medications were selected for study across 5 age ranges and 5 dosing parameters. The resulting 750 dosing rules from a commercial system formed the study corpus and were examined for accuracy against a gold standard created from traditional clinical resources. Results Overall accuracy of the rules in the study corpus was 55.1% when the rules were transformed to fit a priori age ranges. Over a pediatric lifetime, the dosing rules were accurate an average of 57.6% of the days. Dosing rules pertaining to the newborn age range were as accurate as other age ranges on average, but exhibited more variability. Daily frequency dosing parameters showed more accuracy than total daily dose, single dose minimum, or single dose maximum. Discussion The accuracy of a vendor-supplied set of dosing eRules is suboptimal when compared with traditional dosing sources, exposing a gap between dosing rules in commercial products and actual prescribing practices by pediatric care providers. More research on vendor-supplied eRules is warranted in order to understand the effects of these products on safe prescribing in children. PMID:23813541
NSDL National Science Digital Library
Izzy
2012-02-07
Let's learn how to use the lines on graphs (the x & y axis) to plot information. Choose any of the activities below to test your knowledge of identifying the coordinates correctly. Meteoroid Coordinates Soccer Coordinates Donut Coordinates Graphing Points Save the Zogs!-Using Linear Equations Using your coordinate plane knowledge and linear equations help to rescue the Zogs! Can you find the axis for these problems too? What have you noticed about linear equations? What do the lines in linear equations look ...
Appendix H Internal Dose Estimates from Global Fallout H-1 #12;Radiation Dose to the Population. 263-MQ-008090 September 30, 2000 H-2 #12;Radiation Dose to the Population of the Continental United States from the Ingestion of Food Contaminated with Radionuclides from Nuclear Tests at the Nevada Test
Appendix G External Dose Estimates from Global Fallout G-1 #12;External Radiation Exposure exposure and whole body effective dose received by residents of the continental U.S. during the period 1953-2000 from nuclear weapons tests. Doses were calculated for tests carried out in the Pacific by the U
Appendix E External Dose Estimates from NTS Fallout E-1 #12;External Radiation Exposure and whole-body effective dose received by residents of the continental U.S. during the period 1951-1962 from for each test and for each year of testing. The average committed population dose from all NTS tests
Summary: Radiation Dose Estimates from Hanford Radioactive Material Releases to the Air and the Columbia River April 21,1994 TheTechnid Steering Panel of the Hanford - Environmental Dose Reconstruction HonfordEnvironmental DoseRecartnrczionProject,anddonot necessaii!~rcfrcnthe view ofCDC. ,: :: ::sr
Use of computer code for dose distribution studies in A 60CO industrial irradiator
NASA Astrophysics Data System (ADS)
Piña-Villalpando, G.; Sloan, D. P.
1995-09-01
This paper presents a benchmark comparison between calculated and experimental absorbed dose values tor a typical product, in a 60Co industrial irradiator, located at ININ, México. The irradiator is a two levels, two layers system with overlapping product configuration with activity around 300kCi. Experimental values were obtanied from routine dosimetry, using red acrylic pellets. Typical product was Petri dishes packages, apparent density 0.13 g/cm3; that product was chosen because uniform size, large quantity and low density. Minimum dose was fixed in 15 kGy. Calculated values were obtained from QAD-CGGP code. This code uses a point kernel technique, build-up factors fitting was done by geometrical progression and combinatorial geometry is used for system description. Main modifications for the code were related with source sumilation, using punctual sources instead of pencils and an energy and anisotropic emission spectrums were included. Results were, for maximum dose, calculated value (18.2 kGy) was 8% higher than experimental average value (16.8 kGy); for minimum dose, calculated value (13.8 kGy) was 3% higher than experimental average value (14.3 kGy).
Jin Jianyue; Drzymala, Robert; Li Zuofeng [Department of Radiation Oncology, Siteman Cancer Center, Washington University Medical Center, St. Louis, Missouri 63110 (United States)
2004-12-01
The purpose of this study is to develop a simple independent dose calculation method to verify treatment plans for Leksell Gamma Knife radiosurgery. Our approach uses the total integral dose within the skull as an end point for comparison. The total integral dose is computed using a spreadsheet and is compared to that obtained from Leksell GammaPlan registered . It is calculated as the sum of the integral doses of 201 beams, each passing through a cylindrical volume. The average length of the cylinders is estimated from the Skull-Scaler measurement data taken before treatment. Correction factors are applied to the length of the cylinder depending on the location of a shot in the skull. The radius of the cylinder corresponds to the collimator aperture of the helmet, with a correction factor for the beam penumbra and scattering. We have tested our simple spreadsheet program using treatment plans of 40 patients treated with Gamma Knife registered in our center. These patients differ in geometry, size, lesion locations, collimator helmet, and treatment complexities. Results show that differences between our calculations and treatment planning results are typically within {+-}3%, with a maximum difference of {+-}3.8%. We demonstrate that our spreadsheet program is a convenient and effective independent method to verify treatment planning irradiation times prior to implementation of Gamma Knife radiosurgery.
Distributed Maximum A Posteriori Estimation for Multi-robot Cooperative Localization
Paris-Sud XI, Université de
such as the Extended Kalman Filter (EKF) [4], Maximum Likelihood Estimation (MLE) [5], and Particle Filters [6], have while utilizing all available resources in the team, and increasing robustness to single- point failures
Maximum Power Transfer Tracking for a Photovoltaic-Supercapacitor Energy System
Pedram, Massoud
Maximum Power Transfer Tracking for a Photovoltaic-Supercapacitor Energy System Younghyun Kim.g., a supercapacitor bank). Previous maximum power point tracking (MPPT) methods do not consider the fact of a supercapacitor charging process by utilizing the MPPT technique and simultaneously considering the variable
Maximum Power Transfer Tracking in a Solar USB Charger for Smartphones
Pedram, Massoud
Maximum Power Transfer Tracking in a Solar USB Charger for Smartphones Abstract--Battery life of commercial chargers using solar power have been developed. They focus on correct functionality, but system chargers do not perform the maximum power point tracking [2], [3] of the solar panel. We exclude
Surface dose for megavoltage photon beams outside the treatment field
Starkschall, G.; St. George, F.J.; Zellmer, D.L.
1983-11-01
Measurements made on photon beams from four different radiotherapy machines have demonstrated that skin dose several centimeters outside the boundary of a treatment field may be as much as 20% of the central axis maximum dose. This surface dose has been measured for an AECL Theratron 80, Siemens Mevatron VI, Varian Clinac 20, and CGR Sagittaire for distances up to 12 cm outside the field boundary and for depths up to the depth of maximum central axis dose. This dose has also been measured as a function of field size and of source-to-skin distance. For the lower energy photon beams, this radiation is significantly attenuated in the first 2: 3 mm of tissue, while for higher energy beams, a buildup phenomenon with a d/sub max/ of 2--3 mm is observed. The magnitude of this radiation is approximately linearly dependent upon field dimension for all energies.
Tyl, Benoît; Kabbaj, Meriam; Azzam, Sara; Sologuren, Ander; Valiente, Román; Reinbolt, Elizabeth; Roupe, Kathryn; Blanco, Nathalie; Wheeler, William
2012-06-01
The effect of bilastine on cardiac repolarization was studied in 30 healthy participants during a multiple-dose, triple-dummy, crossover, thorough QT study that included 5 arms: placebo, active control (400 mg moxifloxacin), bilastine at therapeutic and supratherapeutic doses (20 mg and 100 mg once daily, respectively), and bilastine 20 mg administered with ketoconazole 400 mg. Time-matched, triplicate electrocardiograms (ECGs) were recorded with 13 time points extracted predose and 16 extracted over 72 hours post day 4 dosing. Four QT/RR corrections were implemented: QTcB; QTcF; a linear individual correction (QTcNi), the primary correction; and a nonlinear one (QTcNnl). Moxifloxacin was associated with a significant increase in QTcNi at all time points between 1 and 12 hours, inclusively. Bilastine administration at 20 mg and 100 mg had no clinically significant impact on QTc (maximum increase in QTcNi, 5.02 ms; upper confidence limit [UCL] of the 1-sided, 95% confidence interval, 7.87 ms). Concomitant administration of ketoconazole and bilastine 20 mg induced a clinically relevant increase in QTc (maximum increase in QTcNi, 9.3 ms; UCL, 12.16 ms). This result was most likely related to the cardiac effect of ketoconazole because for all time points, bilastine plasma concentrations were lower than those observed following the supratherapeutic dose. PMID:21642470
ALL-PATHWAYS DOSE ANALYSIS FOR THE PORTSMOUTH ON-SITE WASTE DISPOSAL FACILITY
Smith, F.; Phifer, M.
2014-04-10
A Portsmouth On-Site Waste Disposal Facility (OSWDF) All-Pathways analysis has been conducted that considers the radiological impacts to a resident farmer. It is assumed that the resident farmer utilizes a farm pond contaminated by the OSWDF to irrigate a garden and pasture and water livestock from which food for the resident farmer is obtained, and that the farmer utilizes groundwater from the Berea sandstone aquifer for domestic purposes (i.e. drinking water and showering). As described by FBP 2014b the Hydrologic Evaluation of Landfill Performance (HELP) model (Schroeder et al. 1994) and the Surface Transport Over Multiple Phases (STOMP) model (White and Oostrom 2000, 2006) were used to model the flow and transport from the OSWDF to the Points of Assessment (POAs) associated with the 680-ft elevation sandstone layer (680 SSL) and the Berea sandstone aquifer. From this modeling the activity concentrations radionuclides were projected over time at the POAs. The activity concentrations were utilized as input to a GoldSimTM (GTG 2010) dose model, described herein, in order to project the dose to a resident farmer over time. A base case and five sensitivity cases were analyzed. The sensitivity cases included an evaluation of the impacts of using a conservative inventory, an uncased well to the Berea sandstone aquifer, a low waste zone uranium distribution coefficient (Kd), different transfer factors, and reference person exposure parameters (i.e. at 95 percentile). The maximum base case dose within the 1,000 year assessment period was projected to be 1.5E-14 mrem/yr, and the maximum base case dose at any time less than 10,000 years was projected to be 0.002 mrem/yr. The maximum projected dose of any sensitivity case was approximately 2.6 mrem/yr associated with the use of an uncased well to the Berea sandstone aquifer. This sensitivity case is considered very unlikely because it assumes leakage from the location of greatest concentration in the 680 SSL in to the Berea sandstone aquiver over time and does not conform to standard private water well construction practices. The bottom-line is that all predicted doses from the base case and five sensitivity cases fall well below the DOE all-pathways 25 mrem/yr Performance Objective.
SU-E-T-162: Evaluation of Dose Calculation of RayStation Planning System in Heterogeneous Media
Xu, H; Yi, B; Chung, H; Prado, K; Chen, S [University of Maryland School of Medicine, Baltimore, MD (United States)
2014-06-01
Purpose: To investigate the clinical reliability of heterogeneity-based dose algorithm using RayStation treatment planning system v.4.0. Methods: The collapsed cone dose calculations in RayStation (RaySearch, Sweden) were compared with the measurements (ion chamber and EBT2 film) and with an in-house Monte Carlo algorithm. A heterogeneous multi-layer phantom and CT images of 4 lung cancer patients were used here. The phantom, composed of multiple solid water slabs and Styrofoams, was irradiated with 6MV beams perpendicular to the layers. The MLC-defined field sizes were 5×5, 10×10, 15×15 and 20×20cm{sup 2}. The chamber was positioned at center of central solid water layer, and the films were placed at interfaces of solid water and Styrofoam. The RayStation dose and Monte Carlo dose were compared by performing absolute gamma analysis (3mm/3%): 1D gamma for PDD in the phantom and 3D gamma for patient volumes receiving dose above 10% of maximum dose. Results: The point dose differences between RayStation and ion chamber measurement were smaller than 1% for all of the field sizes. Between RayStation and film measurement, 5×5cm2 field had the maximum differences : <4mm for the penumbra and <0.3mm for the field width at all Styrofoam-and-solid-water interfaces. The absolute gamma analysis showed good agreement between RayStation and Monte Carlo. For PDD along beam axis in the phantom, the 1D gamma was 95.4, 98.6, 99.6 and 99.3% for field size 5×5, 10×10, 15×15 and 20×202 respectively. For dose comparison using patient CT images, 3D gamma was > 95% for all the patients. Conclusion: With respect to ion chamber/film measurement and Monte Carlo calculation, the collapsed cone algorithm in RayStation computed reasonable dose in both phantom and patient cases. Heterogeneity-based dose calculation of RayStation is clinically acceptable in heterogeneous media.
Ingestion of Nevada Test Site fallout: internal dose estimates.
Whicker, F W; Kirchner, T B; Anspaugh, L R; Ng, Y C
1996-10-01
This paper summarizes individual and collective dose estimates for the internal organs of hypothetical yet representative residents of selected communities that received measurable fallout from nuclear detonations at the Nevada Test Site. The doses, which resulted from ingestion of local and regional food products contaminated with over 20 radionuclides, were estimated with use of the PATHWAY food-chain-transport model to provide estimates of central tendency and uncertainty. The thyroid gland received much higher doses than other internal organs and tissues. In a very few cases, infants might have received thyroid doses in excess of 1 Gy, depending on location, diet, and timing of fallout. 131I was the primary thyroid dose contributor, and fresh milk was the main exposure pathway. With the exception of the thyroid, organ doses from the ingestion pathway were much smaller (< 3%) than those from external gamma exposure to deposited fallout. Doses to residents living closest to the Nevada Test Site were contributed mainly by a few fallout events; doses to more distantly located people were generally smaller, but a greater number of events provided measurable contributions. The effectiveness of different fallout events in producing internal organ doses through ingestion varied dramatically with seasonal timing of the test, with maximum dose per unit fallout occurring for early summer depositions when milk cows were on pasture and fresh, local vegetables were used. Within specific communities, internal doses differed by age, sex, and lifestyle. Collective internal dose estimates for specific geographic areas are provided. PMID:8830749
Accurate three-dimensional dose calculation using a quantitative SPECT image for radioimmunotherapy
K. Ogawa; N. Kanbe; I. Uchida
1994-01-01
This study was carried out to obtain an accurate dose distribution for radioimmunotherapy. In the radioimmunotherapy using gamma and beta emitter, estimation of absorbed dose in target organs and critical organs is very important. In the study we developed the dose calculation method using a point kernel function obtained from Monte Carlo simulation. The three dimensional dose distribution was calculated
Beta dose calculation in human arteries for various brachytherapy seed types
Lee, Sung-Woo
2004-09-30
.). Dose increase between small arteries (0.03 cm rad.) was less significant. The dose profiles of prototype 142Pr beta brachytherapy sources were calculated using MCNP 4C Monte Carlo code as well as dose point kernel (DPK) for selected cases. Dose...
Velec, Michael, E-mail: michael.velec@rmp.uhn.on.c [Radiation Medicine Program, Princess Margaret Hospital, University Health Network, Toronto (Canada); Moseley, Joanne L. [Radiation Medicine Program, Princess Margaret Hospital, University Health Network, Toronto (Canada); Eccles, Cynthia L.; Craig, Tim; Sharpe, Michael B.; Dawson, Laura A. [Radiation Medicine Program, Princess Margaret Hospital, University Health Network, Toronto (Canada); Department of Radiation Oncology, University of Toronto, Toronto (Canada); Brock, Kristy K. [Radiation Medicine Program, Princess Margaret Hospital, University Health Network, Toronto (Canada); Department of Radiation Oncology, University of Toronto, Toronto (Canada); Department of Medical Biophysics, University of Toronto, Toronto (Canada)
2011-05-01
Purpose: To investigate the effect of breathing motion and dose accumulation on the planned radiotherapy dose to liver tumors and normal tissues using deformable image registration. Methods and Materials: Twenty-one free-breathing stereotactic liver cancer radiotherapy patients, planned on static exhale computed tomography (CT) for 27-60 Gy in six fractions, were included. A biomechanical model-based deformable image registration algorithm retrospectively deformed each exhale CT to inhale CT. This deformation map was combined with exhale and inhale dose grids from the treatment planning system to accumulate dose over the breathing cycle. Accumulation was also investigated using a simple rigid liver-to-liver registration. Changes to tumor and normal tissue dose were quantified. Results: Relative to static plans, mean dose change (range) after deformable dose accumulation (as % of prescription dose) was -1 (-14 to 8) to minimum tumor, -4 (-15 to 0) to maximum bowel, -4 (-25 to 1) to maximum duodenum, 2 (-1 to 9) to maximum esophagus, -2 (-13 to 4) to maximum stomach, 0 (-3 to 4) to mean liver, and -1 (-5 to 1) and -2 (-7 to 1) to mean left and right kidneys. Compared to deformable registration, rigid modeling had changes up to 8% to minimum tumor and 7% to maximum normal tissues. Conclusion: Deformable registration and dose accumulation revealed potentially significant dose changes to either a tumor or normal tissue in the majority of cases as a result of breathing motion. These changes may not be accurately accounted for with rigid motion.
Best, D.
1982-07-01
The history of photovoltaics (PV's) is traced from 1958 and Vanguard I to the present with emphasis on cost factors modern developments, and practical applications. Overseas applications, particularly in developing countries without electrical distribution, are pointed out. The current situation in PV's is discussed. Companies involved and current technologies are reviewed. The average single-crystal PV module is cited at $9.50/watt (peak) with an efficiency of about 10% with projections of $5.25/watt (peak) by 1986. Developments in single-crystal silicon PV modules are traced as well as polycrystalline and amorphous silicon PV modules. Other materials (cadmium sulfide, gallium arsenide, copper indium selenium, and cadmium telluride) and new approaches to the design and manufacturing of PV's are discussed. Projections of the use of PV modules in residences and utilities to the year 2000 are carried out. It is estimated that by 1990, sales in the PV industry will reach $1 billion/yr. (MJJ)
Genetic algorithm dose minimization for an operational layout.
McLawhorn, S. L. (Steve L.); Kornreich, D. E. (Drew E.); Dudziak, Donald J.
2002-01-01
In an effort to reduce the dose to operating technicians performing fixed-time procedures on encapsulated source material, a program has been developed to optimize the layout of workstations within a facility by use of a genetic algorithm. Taking into account the sources present at each station and the time required to complete each procedure, the program utilizes a point kernel dose calculation tool for dose estimates. The genetic algorithm driver employs the dose calculation code as a cost function to determine the optimal spatial arrangement of workstations to minimize the total worker dose.
Effect of jaw size in megavoltage CT on image quality and dose
Jung, Jae Hong; Cho, Kwang Hwan; Kim, Yong Ho; Moon, Seong Kwon; Min, Chul Kee; Kim, Woo Chul; Kim, Eun Seog; Chang, Ah Ram; Kim, Tae Ho; Yoon, Jai-Woong; Suh, Tae-Suk; Huh, Hyun Do [Department of Radiation Oncology, College of Medicine, Soonchunhyang University Bucheon Hospital, Bucheon 1174, Korea and Department of Biomedical Engineering and Research Institute of Biomedical Engineering, College of Medicine, Catholic University of Korea Seoul 137-701 (Korea, Republic of); Department of Radiation Oncology, College of Medicine, Soonchunhyang University Bucheon Hospital, Bucheon 1174 (Korea, Republic of); Department of Radiation Oncology, College of Medicine, Soonchunhyang University Cheonan Hospital, Cheonan 23-20 (Korea, Republic of); Department of Radiation Oncology, College of Medicine, Soonchunhyang University Seoul Hospital, Seoul 657 (Korea, Republic of); Department of Biomedical Engineering and Research Institute of Biomedical Engineering, College of Medicine, Catholic University of Korea, Seoul 505 (Korea, Republic of); Department of Radiation Oncology, College of Medicine, Inha University of Korea, Incheon 7-206 (Korea, Republic of)
2012-08-15
Purpose: Recently, the jaw size for the TomoTherapy Hi-Art II{sup Registered-Sign} (TomoTherapy Inc., Madison, WI) was reduced from 4 mm (J4) to 1 mm (J1) to improve the longitudinal (IEC-Y) resolution in megavoltage computed tomography (MVCT) images. This study evaluated the effect of jaw size on the image quality and dose, as well as the dose delivered to the lens of the eye, which is a highly radiosensitive tissue. Methods: MVCT image quality (image noise, uniformity, contrast linearity, high-contrast resolution, and full width at half-maximum) and multiple scan average dose (MSAD) were measured at different jaw sizes. A head phantom and photoluminescence glass dosimeters (PLDs) were used to measure the exposed lens dose (cGy). Different MVCT scan modes (pitch = 1, 2, and 3) and scan lengths (108 mm, 156 mm, and 204 mm) were applied in the MSAD and PLDs measurements. Results: The change in jaw size from J4 to J1 produced no change or only a slight improvement in image noise, uniformity, contrast linearity, and high-contrast resolution. However, the full-width at half-maximum reduced from approximately 7.2 at J4 to 4.5 mm at J1, which represents an enhancement in the longitudinal resolution. The MSAD at the center point changed from approximately 0.69-2.32 cGy (peripheral: 0.83-2.49 cGy) at J4 to 0.85-2.81 cGy (peripheral: 1.05-2.86 cGy) at J1. The measured lens dose increased from 0.92-3.36 cGy at J4 to 1.06-3.91 cGy at J1. Conclusions: The change in jaw size improved longitudinal resolution. The MVCT imaging dose of approximately 3.86 cGy, 1.92 cGy, and 1.22 cGy was delivered at a pitch of 1, 2, and 3, respectively, per fraction in the head and neck treatment plans. Therefore, allowance for an approximately 15% increase in lens dose over that with J4 should be provided with J1.
Radiation dose in defecography
Goei, R.; Kemerink, G. (Univ. Hospital Maastricht (Netherlands))
1990-07-01
The effective dose equivalent, as an expression of total patient risk for exposure to limited areas of the body, and gonadal doses associated with hereditary effects were estimated in 67 consecutive subjects (43 women and 24 men) who underwent defecography. With use of measured entrance exposure values and data from Monte Carlo simulations, the mean effective dose equivalent was estimated at 4.9 mSv +/- 1.6 (490 mrem +/- 160) for women and 0.6 mSv +/- 0.2 (60 mrem +/- 20) for men. The ovarian dose was 15 mSv +/- 5 (1.5 rem +/- 0.5). The testes are not within the primary beam and therefore are exposed to scattered radiation only, hence the low received dose of 0.14 mSv or less (14 mrem or less). These data indicate that defecography is among the radiologic procedures associated with a considerable, but not extreme, radiation dose.
Olsher, Richard H. (Los Alamos, NM); Hsu, Hsiao-Hua (Los Alamos, NM); Casson, William H. (Los Alamos, NM); Vasilik, Dennis G. (Los Alamos, NM); Kleck, Jeffrey H. (Menlo Park, CA); Beverding, Anthony (Foster City, CA)
1996-01-01
A neutron dose equivalent detector for measuring neutron dose capable of accurately responding to neutron energies according to published fluence to dose curves. The neutron dose equivalent meter has an inner sphere of polyethylene, with a middle shell overlying the inner sphere, the middle shell comprising RTV.RTM. silicone (organosiloxane) loaded with boron. An outer shell overlies the middle shell and comprises polyethylene loaded with tungsten. The neutron dose equivalent meter defines a channel through the outer shell, the middle shell, and the inner sphere for accepting a neutron counter tube. The outer shell is loaded with tungsten to provide neutron generation, increasing the neutron dose equivalent meter's response sensitivity above 8 MeV.
Limitations of the maximum entropy principle in devising drug input rate
G. Paintaud; C. W. Maboundou; L. Helleday; G. Alván
1995-01-01
A computer program applying the principle of maximum entropy to the analysis of drug absorption rate has been developed. Plasma concentrations of amoxicillin obtained after oral and intravenous dosing have been analysed, together with simulated data corresponding to a complex input.
Estimating landscape carrying capacity through maximum clique analysis.
Donovan, Therese M; Warrington, Gregory S; Schwenk, W Scott; Dinitz, Jeffrey H
2012-12-01
Habitat suitability (HS) maps are widely used tools in wildlife science and establish a link between wildlife populations and landscape pattern. Although HS maps spatially depict the distribution of optimal resources for a species, they do not reveal the population size a landscape is capable of supporting--information that is often crucial for decision makers and managers. We used a new approach, "maximum clique analysis," to demonstrate how HS maps for territorial species can be used to estimate the carrying capacity, N(k), of a given landscape. We estimated the N(k) of Ovenbirds (Seiurus aurocapillus) and bobcats (Lynx rufus) in an 1153-km2 study area in Vermont, USA. These two species were selected to highlight different approaches in building an HS map as well as computational challenges that can arise in a maximum clique analysis. We derived 30-m2 HS maps for each species via occupancy modeling (Ovenbird) and by resource utilization modeling (bobcats). For each species, we then identified all pixel locations on the map (points) that had sufficient resources in the surrounding area to maintain a home range (termed a "pseudo-home range"). These locations were converted to a mathematical graph, where any two points were linked if two pseudo-home ranges could exist on the landscape without violating territory boundaries. We used the program Cliquer to find the maximum clique of each graph. The resulting estimates of N(k) = 236 Ovenbirds and N(k) = 42 female bobcats were sensitive to different assumptions and model inputs. Estimates of N(k) via alternative, ad hoc methods were 1.4 to > 30 times greater than the maximum clique estimate, suggesting that the alternative results may be upwardly biased. The maximum clique analysis was computationally intensive but could handle problems with < 1500 total pseudo-home ranges (points). Given present computational constraints, it is best suited for species that occur in clustered distributions (where the problem can be broken into several, smaller problems), or for species with large home ranges relative to grid scale where resampling the points to a coarser resolution can reduce the problem to manageable proportions. PMID:23387124
Rothenberg, L N; Pentlow, K S
1992-11-01
The energy deposited in the patient by the rotating x-ray beam in computed tomography produces more uniform absorbed dose values within the section of imaged tissue than those produced in conventional radiologic procedures. The dose values within a specific section are determined by factors such as voltage, current, scan time, scan field, rotation angle, filtration, collimation, and section thickness and spacing. For routine dose determinations, a pencil ionization chamber is usually employed with a plastic phantom. Dose for a specific patient can be determined with thermoluminescent dosimeters placed on the patient. Multiple-scan procedures normally increase the dose in a specific section by less than a factor of two. Typical multiple-scan average doses are in the range of 40-60 mGy for head scans and 10-40 mGy for body scans. Integral dose, however, is directly proportional to the number of sections in an examination. When examination factors are changed to reduce dose, the image noise increases. An optimum protocol is one that results in a balance between dose and image quality. PMID:1439023
Maximum Electrical Stimulation for Urge Incontinence
Masahiro Nakamura; Tsutomu Sakurai; Hideki Sugao; Takao Sonoda
1987-01-01
Urge incontinence was controlled in 13 (62%) of 21 patients by maximum electrical stimulation which was applied to the anus or the perianal skin. The first session of maximum electrical stimulation was able to determine if this treatment would be successful. This method of patient selection for further stimulation was simple and reliable and achieved clinical success in all of
Maximum entropy principle and nonlinear stochastic oscillators
K. Sobczyk; J. Trebicki
1993-01-01
The principle of maximum entropy introduced first in physics and successfully applied in many other fields (e.g. statistics, reliability estimation, simulation) has recently been developed to analyze the systems governed by stochastic differential equations. In this paper we extend the maximum entropy method to the general class of stochastic nonlinear systems and apply it to stochastic nonlinear oscillators. To indicate
49 CFR 107.329 - Maximum penalties.
Code of Federal Regulations, 2010 CFR
2010-10-01
...the maximum civil penalty is $110,000 if the violation results in death, serious illness...minimum $495 civil penalty applies to a violation...the maximum civil penalty is $110,000 if the violation results in death, serious...
MAXIMUM LIKELIHOOD ESTIMATION FOR GENERALISED LOGISTIC DISTRIBUTIONS
Quanxi Shao
2002-01-01
Maximum likelihood estimation for the type I generalised logistic distributions is investigated. We show that the maximum likelihood estimation usually exists, except when the so-called embedded model problem occurs. A full set of embedded distributions is derived, including Gumbel distribution and a two-parameter reciprocal exponential distribution. Properties relating the embedded distributions are given. We also provide criteria to determine when
On bias in maximum likelihood estimators
K. V. Mardia; H. R. Southworth; C. C. Taylor
1999-01-01
It is well known that maximum likelihood estimators are often biased, and it is of use to estimate the expected bias so that we can reduce the mean square errors of our parameter estimates. Expressions for estimating the bias in maximum likelihood estimates have been given by Cox and Hinkley (1974), (Theoretical Statistics, Chapman & Hall, London). In this paper,
Bayesian and Maximum Likelihood Neural Networks
Nielsen, Finn Ã?rup
Bayesian and Maximum Likelihood Neural Networks Finn A ffi rup Nielsen Section for Digital Signal, 1998 OVERVIEW ffl Artificial neural networks ffl Maximum likelihood, MAP, MPL neural networks ffl Bayesian neural networks -- MCMC Bayesian neural networks \\Lambda Hybrid Monte Carlo ffl lyngby matlab
Enhanced Low Dose Rate Sensitivity at Ultra-Low Dose Rates
NASA Technical Reports Server (NTRS)
Chen, Dakai; Pease, Ronald; Forney, James; Carts, Martin; Phan, Anthony; Cox, Stephen; Kruckmeyer, Kriby; Burns, Sam; Albarian, Rafi; Holcombe, Bruce; Little, Bradley; Salzman, James; Chaumont, Geraldine; Duperray, Herve; Ouellet, Al; Buchner, Stephen; LaBel, Kenneth
2011-01-01
We have presented results of ultra-low dose rate irradiations (< or = 10 mrad(Si)/s) for a variety of radiation hardened and commercial linear bipolar devices. We observed low dose rate enhancement factors exceeding 1.5 in several parts. The worst case of dose rate enhancement resulted in functional failures, which occurred after 10 and 60 krad(Si), for devices irradiated at 0.5 and 10 mrad(Si)/s, respectively. Devices fabricated with radiation hardened processes and designs also displayed dose rate enhancement at below 10 mrad(Si)/s. Furthermore, the data indicated that these devices have not reached the damage saturation point. Therefore the degradation will likely continue to increase with increasing total dose, and the low dose rate enhancement will further magnify. The cases presented here, in addition to previous examples, illustrate the significance and pervasiveness of low dose rate enhancement at dose rates lower than 10 mrad(Si). These results present further challenges for radiation hardness assurance of bipolar linear circuits, and raise the question of whether the current standard test dose rate is conservative enough to bound degradations due to ELDRS.
The problem of permissible doses of irradiation for biota
Korogodin, V.I. [Joint Institute for Nuclear Research, Moscow (Russian Federation)
1995-07-01
The dose of acute irradiation or of chronic irradiation under which the biota`s functioning is not disturbed is suggested as a permissible dose of irradiation for biota. On the basis of many separate experiments and observations, doses of chronic irradiation 1-3 gy/year are supposed to be permissible for higher plants and animals. The irradiation tolerance of microorganisms is considerably higher. The permissible doses of irradiation for the biota and for human beings are compared. The accepted maximum tolerance dose of irradiation of 10{sup -3} gy/year for humans is determined to be groundless. We propose substituting the term {open_quotes}permissible dose.{close_quotes} 28 refs., 3 figs.
Sullivan, Terry [Brookhaven National Lab. (BNL), Upton, NY (United States). Biological, Environmental, and Climate Sciences Dept.
2014-12-02
ZionSolutions is in the process of decommissioning the Zion Nuclear Power Plant in order to establish a new water treatment plant. There is some residual radioactive particles from the plant which need to be brought down to levels so an individual who receives water from the new treatment plant dose not receive a radioactive dose in excess of 25 mrem/y?¹. The objectives of this report are: (a) To present a simplified conceptual model for release from the buildings with residual subsurface structures that can be used to provide an upper bound on contaminant concentrations in the fill material; (b) Provide maximum water concentrations and the corresponding amount of mass sorbed to the solid fill material that could occur in each building for use in dose assessment calculations; (c) Estimate the maximum concentration in a well located outside of the fill material; and (d) Perform a sensitivity analysis of key parameters.
A chronic oral reference dose for hexavalent chromium-induced intestinal cancer.
Thompson, Chad M; Kirman, Christopher R; Proctor, Deborah M; Haws, Laurie C; Suh, Mina; Hays, Sean M; Hixon, J Gregory; Harris, Mark A
2014-05-01
High concentrations of hexavalent chromium [Cr(VI)] in drinking water induce villous cytotoxicity and compensatory crypt hyperplasia in the small intestines of mice (but not rats). Lifetime exposure to such cytotoxic concentrations increases intestinal neoplasms in mice, suggesting that the mode of action for Cr(VI)-induced intestinal tumors involves chronic wounding and compensatory cell proliferation of the intestine. Therefore, we developed a chronic oral reference dose (RfD) designed to be protective of intestinal damage and thus intestinal cancer. A physiologically based pharmacokinetic model for chromium in mice was used to estimate the amount of Cr(VI) entering each intestinal tissue section (duodenum, jejunum and ileum) from the lumen per day (normalized to intestinal tissue weight). These internal dose metrics, together with corresponding incidences for diffuse hyperplasia, were used to derive points of departure using benchmark dose modeling and constrained nonlinear regression. Both modeling techniques resulted in similar points of departure, which were subsequently converted to human equivalent doses using a human physiologically based pharmacokinetic model. Applying appropriate uncertainty factors, an RfD of 0.006 mg kg(-1) day(-1) was derived for diffuse hyperplasia-an effect that precedes tumor formation. This RfD is protective of both noncancer and cancer effects in the small intestine and corresponds to a safe drinking water equivalent level of 210 µg l(-1). This concentration is higher than the current federal maximum contaminant level for total Cr (100 µg l(-1)) and well above levels of Cr(VI) in US drinking water supplies (typically ? 5 µg l(-1)). PMID:23943231
Basu, Bishan; Chakraborti, Bikramjit; Ghorai, Suman; Gupta, Phalguni; Ghosh, Sajal; Ghosh, Koushik; Jayanti, J.
2012-01-01
Purpose During intracavitary brachytherapy (ICBT) for cervical cancer, the choice of applicator system remains rather arbitrary. However, as the applicator geometry may play an important role in dose distribution, thereby improving the therapeutic ratio, this study was conducted to compare the Manchester-style and Fletcher-style applicator systems. Material and methods After completion of EBRT, 22 patients with cervical cancer (stage IIA-IIIB) underwent intracavitary brachytherapy. Two different types of applicators: Manchester-style and Fletcher-style were used for each patient for alternate insertions. The purpose was to compare the dose distribution obtained when two different applicators were applied to the same patient. CT based computerized treatment planning was done and dose was prescribed to point A. After optimization, height, width and thickness of the 100% isodose curve, as well as the 100% isodose volume were noted. Dose received by the urinary bladder and rectum were noted. Results The 100% isodose volume and its maximum width were significantly greater (P value < 0.0001 in both occasions) when Manchester-style applicator was used. However, the dose received by 0.1 cc, 1.0 cc and 2.0 cc of the urinary bladder were all significantly greater (P value < 0.0001) with the Manchester-style applicator. No significant difference was found in rectal doses. Conclusions The larger 100% isodose volume, as well as the greater width achieved with the use of Manchester-style applicator can be helpful in circumstances where the tumour is large in size. However, this must be balanced against the increased dose received by the urinary bladder. PMID:23378850
BENCHMARK DOSE SOFTWARE (BMDS)
EPA has announced the latest update to the Benchmark Dose Software (BMDS) tool which is used to facilitate the application of benchmark dose (BMD) methods to EPA hazardous pollutant risk assessments. This latest version (1.4.1b) contains seventeen (17) different models that ar...
Antic, V; Ciraj-Bjelac, O; Rehani, M; Aleksandric, S; Arandjic, D; Ostojic, M
2013-01-01
Workers involved in interventional cardiology procedures receive high eye lens dose if protection is not used. Currently, there is no suitable method for routine use for the measurement of eye dose. Since most angiography machines are equipped with suitable patient dosemeters, deriving factors linking staff eye doses to the patient doses can be helpful. In this study the patient kerma-area product, cumulative dose at an interventional reference point and eye dose in terms of Hp(3) of the cardiologists, nurses and radiographers for interventional cardiology procedures have been measured. Correlations between the patient dose and the staff eye dose were obtained. The mean eye dose was 121 µSv for the first operator, 33 µSv for the second operator/nurse and 12 µSv for radiographer. Normalised eye lens doses per unit kerma-area product were 0.94 µSv Gy?¹ cm?² for the first operator, 0.33 µSv Gy?¹ cm?² for the second operator/nurse and 0.16 µSv Gy?¹ cm?² for radiographers. Statistical analysis indicated that there is a weak but significant (p < 0.01) correlation between the eye dose and the kerma-area product for all three staff categories. These values are based on a local practice and may provide useful reference for other studies for validation and for wider utilisation in assessing the eye dose using patient dose values. PMID:23152146
Calculation of external dose from distributed source
Kocher, D.C.
1986-01-01
This paper discusses a relatively simple calculational method, called the point kernel method (Fo68), for estimating external dose from distributed sources that emit photon or electron radiations. The principles of the point kernel method are emphasized, rather than the presentation of extensive sets of calculations or tables of numerical results. A few calculations are presented for simple source geometries as illustrations of the method, and references and descriptions are provided for other caluclations in the literature. This paper also describes exposure situations for which the point kernel method is not appropriate and other, more complex, methods must be used, but these methods are not discussed in any detail.
A Dose–Response Study for I-125 Prostate Implants
Richard G Stock; Nelson N Stone; Andrea Tabert; Christopher Iannuzzi; J. Keith DeWyngaert
1998-01-01
Purpose: No dose–response study has ever been performed for I-125 prostate implants using modern techniques of implant evaluation and modern treatment outcome end points. The amount of activity per volume implanted was increased over time based on review of postimplant dosimetry. This resulted in different delivered dose levels. This study explores the relationship between dose, biochemical failure, and biopsy results.Materials
Investigation of the spatial resolution of an online dose verification device
Asuni, G.; Rickey, D. W.; McCurdy, B. M. C. [Division of Medical Physics, CancerCare Manitoba, 675 McDermot Avenue, Winnipeg, Manitoba R3E 0V9 (Canada) and Department of Physics and Astronomy, University of Manitoba, Winnipeg, Manitoba R3T 2N2 (Canada); Division of Medical Physics, CancerCare Manitoba, 675 McDermot Avenue, Winnipeg, Manitoba R3E 0V9 (Canada); Department of Physics and Astronomy, University of Manitoba, Winnipeg, Manitoba R3T 2N2 (Canada) and Department of Radiology, University of Manitoba, Winnipeg, Manitoba R3A 1R9 (Canada)
2012-02-15
Purpose: The aim of this work is to characterize a new online dose verification device, COMPASS transmission detector array (IBA Dosimetry, Schwarzenbruck, Germany). The array is composed of 1600 cylindrical ionization chambers of 3.8 mm diameter, separated by 6.5 mm center-to-center spacing, in a 40 x 40 arrangement. Methods: The line spread function (LSF) of a single ion chamber in the detector was measured with a narrow slit collimator for a 6 MV photon beam. The 0.25 x 10 mm{sup 2} slit was formed by two machined lead blocks. The LSF was obtained by laterally translating the detector in 0.25 mm steps underneath the slit over a range of 24 mm and taking a measurement at each step. This measurement was validated with Monte Carlo simulation using BEAMnrc and DOSXYZnrc. The presampling modulation transfer function (MTF), the Fourier transform of the line spread function, was determined and compared to calculated (Monte Carlo and analytical) MTFs. Two head-and-neck intensity modulated radiation therapy (IMRT) fields were measured using the device and were used to validate the LSF measurement. These fields were simulated with the BEAMnrc Monte Carlo model, and the Monte Carlo generated incident fluence was convolved with the 2D detector response function (derived from the measured LSF) to obtain calculated dose. The measured and calculated dose distributions were then quantitatively compared using {chi}-comparison criteria of 3% dose difference and 3 mm distance-to-agreement for in-field points (defined as those above the 10% maximum dose threshold). Results: The full width at half-maximum (FWHM) of the measured detector response for a single chamber is 4.3 mm, which is comparable to the chamber diameter of 3.8 mm. The pre-sampling MTF was calculated, and the resolution of one chamber was estimated as 0.25 lp/mm from the first zero crossing. For both examined IMRT fields, the {chi}-comparison between measured and calculated data show good agreement with 95.1% and 96.3% of in-field points below {chi} of 1.0 for fields 1 and 2, respectively (with an average {chi} of 0.29 for IMRT field 1 and 0.24 for IMRT field 2). Conclusions: The LSF for a new novel online detector has been measured at 6 MV using a narrow slit technique, and this measurement has been validated by Monte Carlo simulation. The detector response function derived from line spread function has been applied to recover measured IMRT fields. The results have shown that the device measures IMRT fields accurately within acceptable tolerance.
Zhang, Y; Zhang, J; Hu, Q; Tie, J; Wu, H [Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education), Department of Radiotherapy, Peking University Cancer Hospital ' Institute, Beijing (China); Deng, J [Department of Therapeutic Radiology, Yale University, New Haven, CT (United States)
2014-06-01
Purpose: To investigate the possibility of applying optimized scanning protocols for pediatric CT simulation by quantifying the dosimetric inaccuracy introduced by using a fixed HU to density conversion. Methods: The images of a CIRS electron density reference phantom (Model 062) were acquired by a Siemens CT simulator (Sensation Open) using the following settings of tube voltage and beam current: 120 kV/190mA (the reference protocol used to calibrate CT for our treatment planning system (TPS)); Fixed 190mA combined with all available kV: 80, 100, and 140; fixed 120 kV and various current from 37 to 444 mA (scanner extremes) with interval of 30 mA. To avoid the HU uncertainty of point sampling in the various inserts of known electron densities, the mean CT numbers of the central cylindrical volume were calculated using DICOMan software. The doses per 100 MU to the reference point (SAD=100cm, Depth=10cm, Field=10X10cm, 6MV photon beam) in a virtual cubic phantom (30X30X30cm) were calculated using Eclipse TPS (calculation model: AcurosXB-11031) by assigning the CT numbers to HU of typical materials acquired by various protocols. Results: For the inserts of densities less than muscle, CT number fluctuations of all protocols were within the tolerance of 10 HU as accepted by AAPM-TG66. For more condensed materials, fixed kV yielded stable HU with any mA combination where largest disparities were found in 1750mg/cc insert: HU{sub reference}=1801(106.6cGy), HU{sub minimum}=1799 (106.6cGy, error{sub dose}=0.00%), HU{sub maximum}=1815 (106.8cGy, error{sub dose}=0.19%). Yet greater disagreements were observed with increasing density when kV was modified: HU{sub minimum}=1646 (104.5cGy, error{sub dose}=- 1.97%), HU{sub maximum}=2487 (116.4cGy, error{sub dose}=9.19%) in 1750mg/cc insert. Conclusion: Without affecting treatment dose calculation, personalized mA optimization of CT simulator can be conducted by fixing kV for a better cost-effectiveness of imaging dose and quality especially for children. Unless recalibrated, kV should be constant for all anatomical sites if diagnostic CT scanner is used as a simulator. This work was partially supported by Capital Medical Development Scientific Research Fund of China.
BENCHMARK DOSE TECHNICAL GUIDANCE DOCUMENT (EXTERNAL REVIEW DRAFT)
The purpose of this document is to provide guidance for the Agency on the application of the benchmark dose approach in determining the point of departure (POD) for health effects data, whether a linear or nonlinear low dose extrapolation is used. The guidance includes discussion...
Correction of CT artifacts and its influence on Monte Carlo dose calculations
Bazalova, Magdalena; Beaulieu, Luc; Palefsky, Steven; Verhaegen, Frank [Medical Physics Department, McGill University, Montreal General Hospital, 1650 Cedar Avenue, Montreal, Quebec, H3G1A4 (Canada); Department de Physique, de Genie Physique et d'Optique, Universite Laval, Quebec City, Quebec, G1K7P4 (Canada) and Department de Radio-Oncologie, Hotel Dieu de Quebec, Centre Hospitalier Universitaire de Quebec, Quebec City, Quebec, G1R2J6 (Canada); Medical Physics Department, McGill University, Montreal General Hospital, 1650 Cedar Avenue, Montreal, Quebec, H3G1A4 (Canada)
2007-06-15
Computed tomography (CT) images of patients having metallic implants or dental fillings exhibit severe streaking artifacts. These artifacts may disallow tumor and organ delineation and compromise dose calculation outcomes in radiotherapy. We used a sinogram interpolation metal streaking artifact correction algorithm on several phantoms of exact-known compositions and on a prostate patient with two hip prostheses. We compared original CT images and artifact-corrected images of both. To evaluate the effect of the artifact correction on dose calculations, we performed Monte Carlo dose calculation in the EGSnrc/DOSXYZnrc code. For the phantoms, we performed calculations in the exact geometry, in the original CT geometry and in the artifact-corrected geometry for photon and electron beams. The maximum errors in 6 MV photon beam dose calculation were found to exceed 25% in original CT images when the standard DOSXYZnrc/CTCREATE calibration is used but less than 2% in artifact-corrected images when an extended calibration is used. The extended calibration includes an extra calibration point for a metal. The patient dose volume histograms of a hypothetical target irradiated by five 18 MV photon beams in a hypothetical treatment differ significantly in the original CT geometry and in the artifact-corrected geometry. This was found to be mostly due to miss-assignment of tissue voxels to air due to metal artifacts. We also developed a simple Monte Carlo model for a CT scanner and we simulated the contribution of scatter and beam hardening to metal streaking artifacts. We found that whereas beam hardening has a minor effect on metal artifacts, scatter is an important cause of these artifacts.
Molter, Christine M; Barbosa, Lorraine; Johnson, Shawn; Knych, Heather K; Chinnadurai, Sathya K; Wack, Raymund F
2015-03-01
Information regarding analgesics in pinnipeds is limited. This study aimed to establish the pharmacokinetic parameters of a single subcutaneous dose of sustained release buprenorphine (Buprenorphine SR) in juvenile northern elephant seals (Mirounga angustirostris) with regard to its potential to provide long-lasting analgesia that requires infrequent dosing. Seals (n=26) were administered a single dose of sustained release buprenorphine at 0.12 mg/kg s.c. Blood samples were collected from the extradural intervertebral vein at 0 hr and at three or four of the following time points: 0.5, 1, 2, 6, 12, 24, 36, 48, 60, 96, 120, and 144 hr. Seals were examined daily for systemic and local adverse reactions. Plasma was analyzed by liquid chromatography tandem-mass spectrometry for buprenorphine and norbuprenorphine concentrations. A noncompartmental analysis for pharmacokinetic parameters was calculated using standard methods and equations. An average maximum concentration of 1.21 ng/ml (0.3-2.9 ng/ml) was detected 12 hr postadministration. Concentrations were quantifiable up to 144 hr postadministration but were below those expected to provide analgesia in some other species. No systemic adverse effects were noted in healthy seals receiving sustained release buprenorphine. Cellulitis or abscesses at the injection site were observed in 6/26 (23%) seals between 24 and 168 hr postadministration. Adverse local effects suggest that this drug should be used with caution in northern elephant seals. PMID:25831576
Modelling lateral beam quality variations in pencil kernel based photon dose calculations.
Nyholm, T; Olofsson, J; Ahnesjö, A; Karlsson, M
2006-08-21
Standard treatment machines for external radiotherapy are designed to yield flat dose distributions at a representative treatment depth. The common method to reach this goal is to use a flattening filter to decrease the fluence in the centre of the beam. A side effect of this filtering is that the average energy of the beam is generally lower at a distance from the central axis, a phenomenon commonly referred to as off-axis softening. The off-axis softening results in a relative change in beam quality that is almost independent of machine brand and model. Central axis dose calculations using pencil beam kernels show no drastic loss in accuracy when the off-axis beam quality variations are neglected. However, for dose calculated at off-axis positions the effect should be considered, otherwise errors of several per cent can be introduced. This work proposes a method to explicitly include the effect of off-axis softening in pencil kernel based photon dose calculations for arbitrary positions in a radiation field. Variations of pencil kernel values are modelled through a generic relation between half value layer (HVL) thickness and off-axis position for standard treatment machines. The pencil kernel integration for dose calculation is performed through sampling of energy fluence and beam quality in sectors of concentric circles around the calculation point. The method is fully based on generic data and therefore does not require any specific measurements for characterization of the off-axis softening effect, provided that the machine performance is in agreement with the assumed HVL variations. The model is verified versus profile measurements at different depths and through a model self-consistency check, using the dose calculation model to estimate HVL values at off-axis positions. A comparison between calculated and measured profiles at different depths showed a maximum relative error of 4% without explicit modelling of off-axis softening. The maximum relative error was reduced to 1% when the off-axis softening was accounted for in the calculations. PMID:16885628
Modelling lateral beam quality variations in pencil kernel based photon dose calculations
NASA Astrophysics Data System (ADS)
Nyholm, T.; Olofsson, J.; Ahnesjö, A.; Karlsson, M.
2006-08-01
Standard treatment machines for external radiotherapy are designed to yield flat dose distributions at a representative treatment depth. The common method to reach this goal is to use a flattening filter to decrease the fluence in the centre of the beam. A side effect of this filtering is that the average energy of the beam is generally lower at a distance from the central axis, a phenomenon commonly referred to as off-axis softening. The off-axis softening results in a relative change in beam quality that is almost independent of machine brand and model. Central axis dose calculations using pencil beam kernels show no drastic loss in accuracy when the off-axis beam quality variations are neglected. However, for dose calculated at off-axis positions the effect should be considered, otherwise errors of several per cent can be introduced. This work proposes a method to explicitly include the effect of off-axis softening in pencil kernel based photon dose calculations for arbitrary positions in a radiation field. Variations of pencil kernel values are modelled through a generic relation between half value layer (HVL) thickness and off-axis position for standard treatment machines. The pencil kernel integration for dose calculation is performed through sampling of energy fluence and beam quality in sectors of concentric circles around the calculation point. The method is fully based on generic data and therefore does not require any specific measurements for characterization of the off-axis softening effect, provided that the machine performance is in agreement with the assumed HVL variations. The model is verified versus profile measurements at different depths and through a model self-consistency check, using the dose calculation model to estimate HVL values at off-axis positions. A comparison between calculated and measured profiles at different depths showed a maximum relative error of 4% without explicit modelling of off-axis softening. The maximum relative error was reduced to 1% when the off-axis softening was accounted for in the calculations.
5 CFR 534.203 - Maximum stipends.
Code of Federal Regulations, 2014 CFR
2014-01-01
...Personnel 1 2014-01-01 2014-01-01 ...OTHER SYSTEMS Student-Employees... First year college undergraduate... Fourth year college undergraduate...maximum money amount in each...agency may pay a student-employee...
Code of Federal Regulations, 2012 CFR
2012-01-01
...CERTIFICATION: AIRMEN OTHER THAN FLIGHT CREWMEMBERS Air Traffic Control Tower Operators § 65.47 Maximum hours. Except in an emergency, a certificated air traffic control tower operator must be relieved of all duties...
Code of Federal Regulations, 2014 CFR
2014-01-01
...CERTIFICATION: AIRMEN OTHER THAN FLIGHT CREWMEMBERS Air Traffic Control Tower Operators § 65.47 Maximum hours. Except in an emergency, a certificated air traffic control tower operator must be relieved of all duties...
Code of Federal Regulations, 2010 CFR
2010-01-01
...CERTIFICATION: AIRMEN OTHER THAN FLIGHT CREWMEMBERS Air Traffic Control Tower Operators § 65.47 Maximum hours. Except in an emergency, a certificated air traffic control tower operator must be relieved of all duties...
Code of Federal Regulations, 2011 CFR
2011-01-01
...CERTIFICATION: AIRMEN OTHER THAN FLIGHT CREWMEMBERS Air Traffic Control Tower Operators § 65.47 Maximum hours. Except in an emergency, a certificated air traffic control tower operator must be relieved of all duties...
Code of Federal Regulations, 2013 CFR
2013-01-01
...CERTIFICATION: AIRMEN OTHER THAN FLIGHT CREWMEMBERS Air Traffic Control Tower Operators § 65.47 Maximum hours. Except in an emergency, a certificated air traffic control tower operator must be relieved of all duties...
On the efficiency at maximum cooling power
NASA Astrophysics Data System (ADS)
Apertet, Y.; Ouerdane, H.; Michot, A.; Goupil, C.; Lecoeur, Ph.
2013-08-01
The efficiency at maximum power (EMP) of heat engines operating as generators is one corner stone of finite-time thermodynamics, the Curzon-Ahlborn efficiency \\eta_CA being considered as a universal upper bound. Yet, no valid counterpart to \\eta_CA has been derived for the efficiency at maximum cooling power (EMCP) for heat engines operating as refrigerators. In this letter we analyse the reasons of the failure to obtain such a bound and we demonstrate that, despite the introduction of several optimisation criteria, the maximum cooling power condition should be considered as the genuine equivalent of maximum power condition in the finite-time thermodynamics frame. We then propose and discuss an analytic expression for the EMCP in the specific case of exoreversible refrigerators.
Incremental Network Design with Maximum Flows
2013-12-21
Dec 21, 2013 ... Incremental Network Design with Maximum Flows. Thomas ... optimization problems capturing that feature and combining two types of ...... The following computational tools were used to develop and analyze the formulations.
A real time dose monitoring and dose reconstruction tool for patient specific VMAT QA and delivery
Tyagi, Neelam; Yang Kai; Gersten, David; Yan Di [Department of Radiation Oncology, William Beaumont Hospital, 3601 West Thirteen Mile Road, Royal Oak, Michigan 48073 (United States)
2012-12-15
Purpose: To develop a real time dose monitoring and dose reconstruction tool to identify and quantify sources of errors during patient specific volumetric modulated arc therapy (VMAT) delivery and quality assurance. Methods: The authors develop a VMAT delivery monitor tool called linac data monitor that connects to the linac in clinical mode and records, displays, and compares real time machine parameters with the planned parameters. A new measure, called integral error, keeps a running total of leaf overshoot and undershoot errors in each leaf pair, multiplied by leaf width, and the amount of time during which the error exists in monitor unit delivery. Another tool reconstructs Pinnacle{sup 3} Trade-Mark-Sign format delivered plan based on the saved machine logfile and recalculates actual delivered dose in patient anatomy. Delivery characteristics of various standard fractionation and stereotactic body radiation therapy (SBRT) VMAT plans delivered on Elekta Axesse and Synergy linacs were quantified. Results: The MLC and gantry errors for all the treatment sites were 0.00 {+-} 0.59 mm and 0.05 {+-} 0.31 Degree-Sign , indicating a good MLC gain calibration. Standard fractionation plans had a larger gantry error than SBRT plans due to frequent dose rate changes. On average, the MLC errors were negligible but larger errors of up to 6 mm and 2.5 Degree-Sign were seen when dose rate varied frequently. Large gantry errors occurred during the acceleration and deceleration process, and correlated well with MLC errors (r= 0.858, p= 0.0004). PTV mean, minimum, and maximum dose discrepancies were 0.87 {+-} 0.21%, 0.99 {+-} 0.59%, and 1.18 {+-} 0.52%, respectively. The organs at risk (OAR) doses were within 2.5%, except some OARs that showed up to 5.6% discrepancy in maximum dose. Real time displayed normalized total positive integral error (normalized to the total monitor units) correlated linearly with MLC (r= 0.9279, p < 0.001) and gantry errors (r= 0.742, p= 0.005). There is a strong correlation between total integral error and PTV mean (r= 0.683, p= 0.015), minimum (r= 0.6147, p= 0.033), and maximum dose (r= 0.6038, p= 0.0376). Conclusions: Errors may exist during complex VMAT planning and delivery. Linac data monitor is capable of detecting and quantifying mechanical and dosimetric errors at various stages of planning and delivery.
Paithankar, Karthik S.; Garman, Elspeth F.
2010-01-01
The program RADDOSE is widely used to compute the dose absorbed by a macromolecular crystal during an X-ray diffraction experiment. A number of factors affect the absorbed dose, including the incident X-ray flux density, the photon energy and the composition of the macromolecule and of the buffer in the crystal. An experimental dose limit for macromolecular crystallography (MX) of 30?MGy at 100?K has been reported, beyond which the biological information obtained may be compromised. Thus, for the planning of an optimized diffraction experiment the estimation of dose has become an additional tool. A number of approximations were made in the original version of RADDOSE. Recently, the code has been modified in order to take into account fluorescent X-ray escape from the crystal (version 2) and the inclusion of incoherent (Compton) scattering into the dose calculation is now reported (version 3). The Compton cross-section, although negligible at the energies currently commonly used in MX, should be considered in dose calculations for incident energies above 20?keV. Calculations using version 3 of RADDOSE reinforce previous studies that predict a reduction in the absorbed dose when data are collected at higher energies compared with data collected at 12.4?keV. Hence, a longer irradiation lifetime for the sample can be achieved at these higher energies but this is at the cost of lower diffraction intensities. The parameter ‘diffraction-dose efficiency’, which is the diffracted intensity per absorbed dose, is revisited in an attempt to investigate the benefits and pitfalls of data collection using higher and lower energy radiation, particularly for thin crystals. PMID:20382991
Li Shidong [Department of Radiation Oncology, Henry Ford Health System, Detroit, Michigan (United States)]. E-mail: sli1@hfhs.org; Aref, Ibrahim [Department of Radiation Oncology, Henry Ford Health System, Detroit, Michigan (United States); Walker, Eleanor [Department of Radiation Oncology, Henry Ford Health System, Detroit, Michigan (United States); Movsas, Benjamin [Department of Radiation Oncology, Henry Ford Health System, Detroit, Michigan (United States)
2007-03-15
Purpose: To determine the effects of the prescription depth, cylinder size, treatment length, tip space, and curved end on high-dose-rate vaginal brachytherapy (HDR-VBT) of endometrial cancer. Methods and Materials: Treatment plans were prescribed and optimized based on points at the cylinder surface or at 0.5-cm depth. Cylinder sizes ranging from 2 to 4 cm in diameter, and treatment lengths ranging from 3 to 8 cm were used. Dose points in various depths were precisely defined along the cylinder dome. The given dose and dose uniformity to a depth of interest were measured by the mean dose (MD) and standard deviation (SD), respectively, among the dose points belonging to the depth. Dose fall-off beyond the 0.5 cm treatment depth was determined by the ratio of MD at 0.75-cm depth to MD at 0.5-cm depth. Results: Dose distribution varies significantly with different prescriptions. The surface prescription provides more uniform doses at all depths in the target volume, whereas the 0.5-cm depth prescription creates larger dose variations at the cylinder surface. Dosimetric uncertainty increases significantly (>30%) with shorter tip space. Extreme hot (>150%) and cold spots (<60%) occur if no optimization points were placed at the curved end. Conclusions: Instead of prescribing to a depth of 0.5 cm, increasing the dose per fraction and prescribing to the surface with the exact surface points around the cylinder dome appears to be the optimal approach.
Comparison of organ dose and dose equivalent for human phantoms of CAM vs. MAX
NASA Astrophysics Data System (ADS)
Kim, Myung-Hee Y.; Qualls, Garry D.; Slaba, Tony C.; Cucinotta, Francis A.
2010-04-01
For the evaluation of organ dose and dose equivalent of astronauts on space shuttle and the International Space Station (ISS) missions, the CAMERA models of CAM (Computerized Anatomical Male) and CAF (Computerized Anatomical Female) of human tissue shielding have been implemented and used in radiation transport model calculations at NASA. One of new human geometry models to meet the “reference person” of International Commission on Radiological Protection (ICRP) is based on detailed Voxel (volumetric and pixel) phantom models denoted for male and female as MAX (Male Adult voXel) and FAX (Female Adult voXel), respectively. We compared the CAM model predictions of organ doses to those of MAX model, since the MAX model represents the male adult body with much higher fidelity than the CAM model currently used at NASA. Directional body-shielding mass was evaluated for over 1500 target points of MAX for specified organs considered to be sensitive to the induction of stochastic effects. Radiation exposures to solar particle event (SPE), trapped protons, and galactic cosmic ray (GCR) were assessed at the specific sites in the MAX phantom by coupling space radiation transport models with the relevant body-shielding mass. The development of multiple-point body-shielding distributions at each organ made it possible to estimate the mean and variance of organ doses at the specific organ. For the estimate of doses to the blood forming organs (BFOs), data on active marrow distributions in adult were used to weight the bone marrow sites over the human body. The discrete number of target points of MAX organs resulted in a reduced organ dose and dose equivalent compared to the results of CAM organs especially for SPE, and should be further investigated. Differences of effective doses between the two approaches were found to be small (<5%) for GCR.
On minimizing maximum transient energy growth
James F. Whidborne; John McKernan; Anthony J. Steer
2005-01-01
Abstract The problem of minimizing the maximum,transient energy growth is considered. This problem has importance in some fluid flow control problems and other classes of non-linear systems. Conditions for the existence of static controllers that restrict the maximum,transient energy growth to unity are established. An explicit parametrization of all linear controllers ensuring monotonic decrease of the transient energy is derived.
Maximum-likelihood refinement for coherent diffractive imaging
NASA Astrophysics Data System (ADS)
Thibault, P.; Guizar-Sicairos, M.
2012-06-01
We introduce the application of maximum-likelihood (ML) principles to the image reconstruction problem in coherent diffractive imaging. We describe an implementation of the optimization procedure for ptychography, using conjugate gradients and including preconditioning strategies, regularization and typical modifications of the statistical noise model. The optimization principle is compared to a difference map reconstruction algorithm. With simulated data important improvements are observed, as measured by a strong increase in the signal-to-noise ratio. Significant gains in resolution and sensitivity are also demonstrated in the ML refinement of a reconstruction from experimental x-ray data. The immediate consequence of our results is the possible reduction of exposure, or dose, by up to an order of magnitude for a reconstruction quality similar to iterative algorithms currently in use.
Andrews, David W. [Department of Neurologic Surgery, Thomas Jefferson University (United States)], E-mail: david.andrews@jefferson.edu; Werner-Wasik, Maria; Den, Robert B. [Department of Radiation Oncology, Thomas Jefferson University (United States); Paek, Sun Ha [Department of Neurosurgery, Seoul National University (Korea, Republic of); Downes-Phillips, Beverly [Department of Neurologic Surgery, Thomas Jefferson University (United States); Willcox, Thomas O. [Department of Otolaryngology, Head and Neck Surgery, Thomas Jefferson University (United States); Bednarz, Greg; Maltenfort, Mitchel; Evans, James J. [Department of Neurologic Surgery, Thomas Jefferson University (United States); Curran, Walter J. [Department of Radiation Oncology, Thomas Jefferson University (United States)
2009-06-01
Purpose: To describe our initial experience of fractionated stereotactic radiotherapy dose reduction comparing two dose cohorts with examination of tumor control rates and serviceable hearing preservation rates. Methods and Materials: After institutional review board approval, we initiated a retrospective chart review to study the hearing outcomes and tumor control rates. All data were entered into a JMP, version 7.01, statistical spreadsheet for analysis. Results: A total of 89 patients with serviceable hearing had complete serial audiometric data available for analysis. The higher dose cohort included 43 patients treated to 50.4 Gy with a median follow-up (latest audiogram) of 53 weeks and the lower dose cohort included 46 patients treated to 46.8 Gy with a median follow-up of 65 weeks. The tumor control rate was 100% in both cohorts, and the pure tone average was significantly improved in the low-dose cohort (33 dB vs. 40 dB, p = 0.023, chi-square). When the patient data were analyzed at comparable follow-up points, the actuarial hearing preservation rate was significantly longer for the low-dose cohort than for the high-dose cohort (165 weeks vs. 79 weeks, p = .0318, log-rank). Multivariate analysis revealed the dose cohort (p = 0.0282) and pretreatment Gardner-Robertson class (p = 0.0215) to be highly significant variables affecting the hearing outcome. Conclusion: A lower total dose at 46.8 Gy was associated with a 100% local control tumor rate and a greater hearing preservation rate. An additional dose reduction is justified to achieve the optimal dose that will yield the greatest hearing preservation rate without compromising tumor control for these patients.
40 CFR 141.65 - Maximum residual disinfectant levels.
Code of Federal Regulations, 2010 CFR
2010-07-01
...PROGRAMS (CONTINUED) NATIONAL PRIMARY DRINKING WATER REGULATIONS National Primary Drinking Water Regulations: Maximum Contaminant Levels and Maximum Residual Disinfectant Levels § 141.65 Maximum residual disinfectant levels. (a) Maximum...
24 CFR 941.306 - Maximum project cost.
Code of Federal Regulations, 2012 CFR
2012-04-01
...2012-04-01 2012-04-01 false Maximum project cost. 941.306 Section 941.306 Housing...Application and Proposal § 941.306 Maximum project cost. (a) Calculation of maximum project cost. The maximum project cost...
24 CFR 941.306 - Maximum project cost.
Code of Federal Regulations, 2010 CFR
2010-04-01
...2010-04-01 2010-04-01 false Maximum project cost. 941.306 Section 941.306 Housing...Application and Proposal § 941.306 Maximum project cost. (a) Calculation of maximum project cost. The maximum project cost...
24 CFR 941.306 - Maximum project cost.
Code of Federal Regulations, 2011 CFR
2011-04-01
...2011-04-01 2011-04-01 false Maximum project cost. 941.306 Section 941.306 Housing...Application and Proposal § 941.306 Maximum project cost. (a) Calculation of maximum project cost. The maximum project cost...
24 CFR 941.306 - Maximum project cost.
Code of Federal Regulations, 2013 CFR
2013-04-01
...2013-04-01 2013-04-01 false Maximum project cost. 941.306 Section 941.306 Housing...Application and Proposal § 941.306 Maximum project cost. (a) Calculation of maximum project cost. The maximum project cost...
The 1984 - 1987 Solar Maximum Mission event list
NASA Technical Reports Server (NTRS)
Dennis, B. R.; Licata, J. P.; Nelson, J. J.; Tolbert, A. K.
1992-01-01
Information on solar burst and transient activity observed by the Solar Maximum Mission (SMM) during 1984-1987 pointed observations is presented. Data from the following SMM experiments are included: (1) gamma ray spectrometer; (2) hard x-ray burst spectrometer; (3) flat crystal spectrometer; (4) bent crystal spectrometer; (5) ultraviolet spectrometer polarimeter; and (6) coronograph/polarimeter. Correlative optical, radio, and Geostationary Operational Environmental Satellite (GOES) x ray data are also presented. Where possible, bursts or transients observed in the various wavelengths were grouped into discrete flare events identified by unique event numbers. Each event carries a qualifier denoting the quality or completeness of the observations. Spacecraft pointing coordinates and flare site angular displacement values from sun center are also included.
Sandra Boom; Krishna Talluri; Luc Janssens; Bart Remmerie; Marc De Meulder; Stefaan Rossenu; Nancy van Osselaer; Marielle Eerdekens; Adriaan Cleton
2009-01-01
Paliperidone extended-release tablet (paliperidone ER) is a centrally active dopamine D2- and serotonergic 5-HT2A-receptor antagonist that is registered for the treatment of schizophrenia. The controlled rate of release of paliperidone from the ER formulation is designed to have a slower absorption rate, which results in gradual ascending plasma concentrations with observed maximum plasma concentrations occurring at 24 hours after dosing
NASA Technical Reports Server (NTRS)
Brenner, D. J.; Hall, E. J.
1992-01-01
There is now a substantial body of evidence for end points such as oncogenic transformation in vitro, and carcinogenesis and life shortening in vivo, suggesting that dose protraction leads to an increase in effectiveness relative to a single, acute exposure--at least for radiations of medium linear energy transfer (LET) such as neutrons. Table I contains a summary of the pertinent data from studies in which the effect is seen. [table: see text] This phenomenon has come to be known as the "inverse dose rate effect," because it is in marked contrast to the situation at low LET, where protraction in delivery of a dose of radiation, either by fractionation or low dose rate, results in a decreased biological effect; additionally, at medium and high LET, for radiobiological end points such as clonogenic survival, the biological effectiveness is independent of protraction. The quantity and quality of the published reports on the "inverse dose rate effect" leaves little doubt that the effect is real, but the available evidence indicates that the magnitude of the effect is due to a complex interplay between dose, dose rate, and radiation quality. Here, we first summarize the available data on the inverse dose rate effect and suggest that it follows a consistent pattern in regard to dose, dose rate, and radiation quality; second, we describe a model that predicts these features; and, finally, we describe the significance of the effect for radiation protection.
Acetaminophen dosing for children
Taking acetaminophen (Tylenol) can help children with colds and fever feel better. As with all drugs, it is important to give children the correct dose. Acetaminophen is safe when taken as directed. But taking ...
Bremsstrahlung doses from natural uranium ingots.
Anderson, Jeri L; Hertel, Nolan E
2005-01-01
In the past, some privately owned commercial facilities in the United States were involved in producing or processing radioactive materials used in the production of atomic weapons. Seven different geometrical objects, representative of the configurations of natural uranium metal potentially encountered by workers at these facilities, are modelled to determine gamma ray and bremsstrahlung dose rates. The dose rates are calculated using the MCNP5 code and also by using the MICROSHIELD point-kernel code. Both gamma ray and bremsstrahlung dose rates are calculated and combined to obtain a total dose rate. The two methods were found to be in good agreement despite differences in modelling assumptions and method differences. Computed total dose rates on the surface of these objects ranged from approximately 51-84 microSv h(-1) and 17-95 microSv h(-1) using the MCNP5 and the MICROSHIELD modeling, respectively. The partitioning of the computed dose rates between gamma rays and bremsstrahlung were the same order of magnitude for each object. PMID:16381733
Benedict, Michael S.; Thorn, Michael D.; Lawrence, Laura E.; Cammarata, Sue K.; Sun, Eugene
2015-01-01
A randomized, double-blind, placebo-controlled, 4-period crossover study was conducted in 52 healthy adults to assess the effect of delafloxacin on the corrected QT (QTc) interval. The QT interval, corrected for heart rate using Fridericia's formula (QTcF), was determined predose and at 0.5, 1, 1.25, 1.5, 1.75, 2, 2.5, 3, 4, 5, 6, 12, 18, and 24 h after dosing with delafloxacin at 300 mg intravenously (i.v.; therapeutic), delafloxacin at 900 mg i.v. (supratherapeutic), moxifloxacin at 400 mg orally (p.o.; positive control), and placebo. The pharmacokinetic profile of delafloxacin was also evaluated. At each time point after delafloxacin administration, the upper limit of the 90% confidence interval (CI) for the placebo-corrected change from the predose baseline in QTcF (??QTcF) was less than 10 ms (maximum, 3.9 ms at 18 h after dosing), indicating an absence of a clinically meaningful increase in the QTc interval. The lower limit of the 90% CI of ??QTcF for moxifloxacin versus placebo was longer than 5 ms at all 5 time points selected for assay sensitivity analysis, demonstrating that the study was adequately sensitive to assess QTc prolongation. There was no positive relationship between delafloxacin plasma concentrations and ??QTcF. Treatment-emergent adverse events (AEs) were more frequent among subjects receiving a single supratherapeutic dose of 900 mg delafloxacin. There were no deaths, serious AEs, or AEs leading to study discontinuation and no clinically meaningful abnormalities in laboratory values or vital signs observed at any time point after any dose of the study drug. PMID:25845864
Melting Point, Boiling Point, and Symmetry
Robert Abramowitz; Samuel H. Yalkowsky
1990-01-01
The relationship between the melting point of a compound and its chemical structure remains poorly understood. The melting point of a compound can be related to certain of its other physical chemical properties. The boiling point of a compound can be determined from additive constitutive properties, but the melting point can be estimated only with the aid of nonadditive constitutive
The estimation of galactic cosmic ray penetration and dose rates
NASA Technical Reports Server (NTRS)
Burrell, M. O.; Wright, J. J.
1972-01-01
This study is concerned with approximation methods that can be readily applied to estimate the absorbed dose rate from cosmic rays in rads - tissue or rems inside simple geometries of aluminum. The present work is limited to finding the dose rate at the center of spherical shells or behind plane slabs. The dose rate is calculated at tissue-point detectors or for thin layers of tissue. This study considers cosmic-rays dose rates for both free-space and earth-orbiting missions.
Evaluation of shipping doses and compositions for vitrified waste
Shapiro, A. [Cincinnati Univ., OH (United States). Dept. of Nuclear Engineering; Vogel, R. [Fernald Environmental Restoration Management Corp., Cincinnati, OH (United States)
1996-06-01
Shipments of radioactive materials must adhere to dose limits specified in the Code of Federal Regulations. This paper discusses methods for evaluating shipping doses of vitrified waste. A methodology was developed for evaluating the change in vitrification composition required to maintain shipping dose rates within limits. The point kernel codes QAD and Microshield were used to evaluate dose equivalent rates from specified waste forms and radioactivity measurements. The Origen code was utilized to provide the gamma-ray activity as a function of time from isotopic activity measurements. This gamma-ray activity served as source input for QAD. Microshield developed its own source from the given isotopic activities.
Russo, James K. [Department of Radiation Oncology, Hollings Cancer Center, Medical University of South Carolina, Charleston, South Carolina (United States); Armeson, Kent E. [Division of Biostatistics and Epidemiology, Hollings Cancer Center, Medical University of South Carolina, Charleston, South Carolina (United States); Richardson, Susan, E-mail: srichardson@radonc.wustl.edu [Department of Radiation Oncology, Mallinckrodt Institute of Radiology, Washington University School of Medicine, St. Louis, Missouri (United States)
2012-05-01
Purpose: To evaluate bladder and rectal doses using two-dimensional (2D) and 3D treatment planning for vaginal cuff high-dose rate (HDR) in endometrial cancer. Methods and Materials: Ninety-one consecutive patients treated between 2000 and 2007 were evaluated. Seventy-one and 20 patients underwent 2D and 3D planning, respectively. Each patient received six fractions prescribed at 0.5 cm to the superior 3 cm of the vagina. International Commission on Radiation Units and Measurements (ICRU) doses were calculated for 2D patients. Maximum and 2-cc doses were calculated for 3D patients. Organ doses were normalized to prescription dose. Results: Bladder maximum doses were 178% of ICRU doses (p < 0.0001). Two-cubic centimeter doses were no different than ICRU doses (p = 0.22). Two-cubic centimeter doses were 59% of maximum doses (p < 0.0001). Rectal maximum doses were 137% of ICRU doses (p < 0.0001). Two-cubic centimeter doses were 87% of ICRU doses (p < 0.0001). Two-cubic centimeter doses were 64% of maximum doses (p < 0.0001). Using the first 1, 2, 3, 4 or 5 fractions, we predicted the final bladder dose to within 10% for 44%, 59%, 83%, 82%, and 89% of patients by using the ICRU dose, and for 45%, 55%, 80%, 85%, and 85% of patients by using the maximum dose, and for 37%, 68%, 79%, 79%, and 84% of patients by using the 2-cc dose. Using the first 1, 2, 3, 4 or 5 fractions, we predicted the final rectal dose to within 10% for 100%, 100%, 100%, 100%, and 100% of patients by using the ICRU dose, and for 60%, 65%, 70%, 75%, and 75% of patients by using the maximum dose, and for 68%, 95%, 84%, 84%, and 84% of patients by using the 2-cc dose. Conclusions: Doses to organs at risk vary depending on the calculation method. In some cases, final dose accuracy appears to plateau after the third fraction, indicating that simulation and planning may not be necessary in all fractions. A clinically relevant level of accuracy should be determined and further research conducted to address this issue.
Cell development obeys maximum Fisher information
B. R. Frieden; R. A. Gatenby
2014-04-29
Eukaryotic cell development has been optimized by natural selection to obey maximal intracellular flux of messenger proteins. This, in turn, implies maximum Fisher information on angular position about a target nuclear pore complex (NPR). The cell is simply modeled as spherical, with cell membrane (CM) diameter 10 micron and concentric nuclear membrane (NM) diameter 6 micron. The NM contains about 3000 nuclear pore complexes (NPCs). Development requires messenger ligands to travel from the CM-NPC-DNA target binding sites. Ligands acquire negative charge by phosphorylation, passing through the cytoplasm over Newtonian trajectories toward positively charged NPCs (utilizing positive nuclear localization sequences). The CM-NPC channel obeys maximized mean protein flux F and Fisher information I at the NPC, with first-order delta I = 0 and approximate 2nd-order delta I = 0 stability to environmental perturbations. Many of its predictions are confirmed, including the dominance of protein pathways of from 1-4 proteins, a 4nm size for the EGFR protein and the approximate flux value F =10^16 proteins/m2-s. After entering the nucleus, each protein ultimately delivers its ligand information to a DNA target site with maximum probability, i.e. maximum Kullback-Liebler entropy HKL. In a smoothness limit HKL approaches IDNA/2, so that the total CM-NPC-DNA channel obeys maximum Fisher I. Thus maximum information approaches non-equilibrium, one condition for life.
Feygelman, Vladimir; Zhang, Geoffrey; Hunt, Dylan; Opp, Daniel [Department of Radiation Oncology, Moffitt Cancer Center, Tampa, Florida 33612 (United States); Stambaugh, Cassandra [Department of Physics, University of South Florida, Tampa, Florida 33612 (United States); Wolf, Theresa K. [Live Oak Technologies LLC, Kirkwood, Missouri 63122 (United States); Nelms, Benjamin E. [Canis Lupus LLC, Merrimac, Wisconsin 53561 (United States)
2013-02-15
Purpose: To present a framework for measurement-guided VMAT dose reconstruction to moving patient voxels from a known motion kernel and the static phantom data, and to validate this perturbation-based approach with the proof-of-principle experiments. Methods: As described previously, the VMAT 3D dose to a static patient can be estimated by applying a phantom measurement-guided perturbation to the treatment planning system (TPS)-calculated dose grid. The fraction dose to any voxel in the presence of motion, assuming the motion kernel is known, can be derived in a similar fashion by applying a measurement-guided motion perturbation. The dose to the diodes in a helical phantom is recorded at 50 ms intervals and is transformed into a series of time-resolved high-density volumetric dose grids. A moving voxel is propagated through this 4D dose space and the fraction dose to that voxel in the phantom is accumulated. The ratio of this motion-perturbed, reconstructed dose to the TPS dose in the phantom serves as a perturbation factor, applied to the TPS fraction dose to the similarly situated voxel in the patient. This approach was validated by the ion chamber and film measurements on four phantoms of different shape and structure: homogeneous and inhomogeneous cylinders, a homogeneous cube, and an anthropomorphic thoracic phantom. A 2D motion stage was used to simulate the motion. The stage position was synchronized with the beam start time with the respiratory gating simulator. The motion patterns were designed such that the motion speed was in the upper range of the expected tumor motion (1-1.4 cm/s) and the range exceeded the normally observed limits (up to 5.7 cm). The conformal arc plans for X or Y motion (in the IEC 61217 coordinate system) consisted of manually created narrow (3 cm) rectangular strips moving in-phase (tracking) or phase-shifted by 90 Degree-Sign (crossing) with respect to the phantom motion. The XY motion was tested with the computer-derived VMAT MLC sequences. For all phantoms and plans, time-resolved (10 Hz) ion chamber dose was collected. In addition, coronal (XY) films were exposed in the cube phantom to a VMAT beam with two different starting phases, and compared to the reconstructed motion-perturbed dose planes. Results: For the X or Y motions with the moving strip and geometrical phantoms, the maximum difference between perturbation-reconstructed and ion chamber doses did not exceed 1.9%, and the average for any motion pattern/starting phase did not exceed 1.3%. For the VMAT plans on the cubic and thoracic phantoms, one point exhibited a 3.5% error, while the remaining five were all within 1.1%. Across all the measurements (N = 22), the average disagreement was 0.5 {+-} 1.3% (1 SD). The films exhibited {gamma}(3%/3 mm) passing rates {>=}90%. Conclusions: The dose to an arbitrary moving voxel in a patient can be estimated with acceptable accuracy for a VMAT delivery, by performing a single QA measurement with a cylindrical phantom and applying two consecutive perturbations to the TPS-calculated patient dose. The first one accounts for the differences between the planned and delivered static doses, while the second one corrects for the motion.
Point kernel option in MCNP at the Hanford Site
L. L. Carter; R. J. Morford; S. M. Frederickson; K. Hillesland
1994-01-01
A modified version of MCNP (MCNPH at the Hanford Site) allows the user the option to make point kernel calculations of photon tissue dose rates. This point kernel approach uses the full source and three-dimensional geometry capabilities of a Monte Carlo code and allows for switching between point kernel and full transport with only one change in the input file.
EPR dose reconstruction for bone-seeking 90Sr.
Ignatiev, E A; Lyubashevskii, N M; Shishkina, E A; Romanyukha, A A
1999-08-01
The results of the EPR dose reconstruction in calcified tissues of dog injected with 90Sr are presented. It has been established that there is no essential difference in the values of doses absorbed in tooth tissues of teeth in symmetric positions in the mouth, whereas a significant difference occurs in the values of absorbed doses in teeth in non-symmetric positions. In the case of 90Sr internal exposure the dose reconstruction in crown dentine plays an important role. It has been found that its quantity is close to the dose in diaphyseal cortical bone of the femur, dose at the endosteal bone surface and in femural fatty marrow. The fact that these values exceed doses absorbed in tooth enamel points out the predominant contribution of internal exposure. The highest absorbed doses have been observed in metaphyseal trabecular femur bones, tooth alveolar bone walls, and cortical and trabecular vertebra that can be considered as suitable candidates for biomarkers of internal 90Sr exposure for post-mortal autopsy. The satisfactory correlation has been found between the doses reconstructed in calcified dog tissues and the doses measured by EPR in alanine dosimeters fixed in (or nearby) the sites of autopsy of bones/teeth. The experiments provide support for the view that EPR retrospective dosimetry with calcified tissues for internal exposure is unique in providing useful information on the doses obtained. PMID:10376327
Connection between maximum-work and maximum-power thermal cycles
NASA Astrophysics Data System (ADS)
Gonzalez-Ayala, Julian; Arias-Hernandez, L. A.; Angulo-Brown, F.
2013-11-01
A new connection between maximum-power Curzon-Ahlborn thermal cycles and maximum-work reversible cycles is proposed. This linkage is built through a mapping between the exponents of a class of heat transfer laws and the exponents of a family of heat capacities depending on temperature. This connection leads to the recovery of known results and to a wide and interesting set of results for a class of thermal cycles. Among other results it was found that it is possible to use analytically closed expressions for maximum-work efficiencies to calculate good approaches to maximum-power efficiencies. Behind the proposed connection is an interpretation of endoreversibility hypothesis. Additionally, we suggest that certain reversible maximum-work cycles depending on working substance can be used as reversible landmarks for FTT maximum-power cycles, which also depend on working substance properties.
Filyushkin, I.V.; Bragin, Yu.N.; Khandogina, E.K.
1989-09-01
Presented are the results of an investigation of the dose-response relationship for the yield of chromosome aberrations in peripheral blood lymphocytes of persons with some hereditary diseases which represent the high risk group with respect to the increased incidence of malignant tumors and decreased life span. Despite substantially different absolute radiosensitivities of chromosomes, the variations of the alpha/beta ratio determining the extrapolation of experimental dose-response relationships to low doses did not prove to be too high, the mean deviation from the control being 15%. This points to the possible practical use of the dose-response relationships averaged over the human population as a whole.
Depth dose characteristics of electron beams at extended SSDS.
Gunhan, Basri; Karaçam, Songül; Koca, Ayse; Demir, Bayram; Emre, Dervis; Akin, Nil
The purpec: of this study is to investigate the behaviour of the percent depth dose curves (%DD) and surface doses of electronbeams at extended Source-to Surface Distances (SSDS). A (GE) Saturne 42 linear accelerator was used in this study, which produces dual photon energies of 6 and 15 MV as well as eight electron energies ranging between 4.5 and 21 MeV. The % Depth Dose curves were geneated with water scanning equipment at 6, 9, and 15 MeV for 4x4 cm(2) and 20x20 cm(2) field sizes at SSDS of 100 cm, 108 cm, and 115 cm. According to the measurements from surface to the depth of dose maximum the surface dose increased for all of the electron energies studied at extended SSDS for small field sizes. On the other hand for larger field sizes the surface doses decreased at extended SSDS. It was also observed that the increase in the surface dose diminished as the field size approached to 10x10cm(2) then the surface dose started decreasing at extended SSDS as the field sizes increased. Extended SSDS have no observable effect on the tail portion of the depth dose curves. PMID:18348849
L. M. McDowell-Boyer; F. R. ODonnell
1978-01-01
Potential radiation doses from the distribution, use, repair, and disposal of timepieces containing tritium (H-3) or promethium-147 (Pm-147) in radioluminous paint were estimated for the United States population. Under typical conditions, a maximum annual whole-body dose from H-3 of 0.9 mrem\\/year was estimated for repairmen, while a maximum of 0.3 mrem\\/ year was estimated for watch wearers from Pm-147. The
Density estimation by maximum quantum entropy
Silver, R.N.; Wallstrom, T.; Martz, H.F.
1993-11-01
A new Bayesian method for non-parametric density estimation is proposed, based on a mathematical analogy to quantum statistical physics. The mathematical procedure is related to maximum entropy methods for inverse problems and image reconstruction. The information divergence enforces global smoothing toward default models, convexity, positivity, extensivity and normalization. The novel feature is the replacement of classical entropy by quantum entropy, so that local smoothing is enforced by constraints on differential operators. The linear response of the estimate is proportional to the covariance. The hyperparameters are estimated by type-II maximum likelihood (evidence). The method is demonstrated on textbook data sets.
SD of maximum Stem Diameter (in cm)
Schierup, Mikkel Heide
SD of maximum Stem Diameter (in cm) 1,4 - 13,3 13,4 - 14,8 14,9 - 15,6 15,7 - 16,5 16,6 - 17,3 17,8 12,9 - 14,3 14,4 - 16,1 16,2 - 30,0 Mean of maximum Stem Diameter (in cm) 0,0 - 13,3 13,4 - 14,5 14 look quite similar. Mean of Stem Height, Stem Diameter and Leaf Number seem to show higher values
SU-E-T-259: Particle Swarm Optimization in Radial Dose Function Fitting for a Novel Iodine-125 Seed
Wu, X [University of Alabama at Birmingham, Birmingham, Al (United States); Duan, J; Popple, R; Huang, M; Shen, S; Brezovich, I [University of Alabama Birmingham, Birmingham, AL (United States); Cardan, R [UAB University of Alabama, Birmingham, Birmingham, AL (United States); Benhabib, S [University of Alabama at Birmingham, Birmingham, AL (United States)
2014-06-01
Purpose: To determine the coefficients of bi- and tri-exponential functions for the best fit of radial dose functions of the new iodine brachytherapy source: Iodine-125 Seed AgX-100. Methods: The particle swarm optimization (PSO) method was used to search for the coefficients of the biand tri-exponential functions that yield the best fit to data published for a few selected radial distances from the source. The coefficients were encoded into particles, and these particles move through the search space by following their local and global best-known positions. In each generation, particles were evaluated through their fitness function and their positions were changed through their velocities. This procedure was repeated until the convergence criterion was met or the maximum generation was reached. All best particles were found in less than 1,500 generations. Results: For the I-125 seed AgX-100 considered as a point source, the maximum deviation from the published data is less than 2.9% for bi-exponential fitting function and 0.2% for tri-exponential fitting function. For its line source, the maximum deviation is less than 1.1% for bi-exponential fitting function and 0.08% for tri-exponential fitting function. Conclusion: PSO is a powerful method in searching coefficients for bi-exponential and tri-exponential fitting functions. The bi- and tri-exponential models of Iodine-125 seed AgX-100 point and line sources obtained with PSO optimization provide accurate analytical forms of the radial dose function. The tri-exponential fitting function is more accurate than the bi-exponential function.
Fluence-to-dose confusion regarding external stochastic dose determination within the DOE complex.
Shores, E. F. (Erik F.); Brown, T. H. (Thomas H.)
2002-01-01
The Department of Energy's (DOE) occupational radiation protection dose limits are specified in 10 CFR 835 (hereafter referred to as 'regulation'). Ambiguity in the regulation regarding designation of dose and fluence-to-dose conversion factors leads to confusion and disagreement regarding the appropriate choice of conversion factors. Three primary dose quantities of relevance are absorbed dose, D, quality factor, Q, and the product of those, called dose equivalent, H. The modifier Q is intended to express the long-term fatal cancer causing potential of different radiation types and generally increases with energy for neutrons. For photons, Q is close to unity regardless of energy. In principle, H could be estimated by incorporating a phantom and relevant Q values in a radiation-transport model. In practice, this would entail too much model complexity and computer time. The evaluator of H instead relies on pre-calculated energy-dependent fluence-to-dose conversion factors. Three primary sets of fluence-to-dose conversion factors are commonly used to determine stochastic dose for neutrons and photons: (1) ANSI/ANS-6.1.1-1977 that incorporates the NCRP-38 data for neutrons and sets based on Claiborne and Wells for photons, (2) ANSI/ANS -6.1.1-1991 that are based on and nearly identical to the neutron and photon sets in ICRP -51, and (3) neutron and photon sets in ICRP-74. The first set is maximum H values in a 30-cm diameter cylinder phantom for neutrons and in a 30-cm thick slab phantom for photons. The second set is effective dose equivalent, HE, derived from an anthropomorphic phantom by summing the products of tissue dose equivalents, HT, and tissue weighting factors, w{sub T}. The third set is effective dose, E, also derived from an anthropomorphic phantom by summing the products of H{sub T} and w{sub T}. E is functionally identical to H{sub E} except H{sub T} is the product of D and the radiation weighting factor, w{sub R}, which is similar in meaning to Q.
Cebra, C K; Smith, C C; Stang, B V; Tornquist, S J
2014-08-01
In order to investigate whether exenatide could be used to stimulate glucose clearance and insulin secretion in alpacas without causing colic signs, six healthy adult alpacas were injected once a day with increasing subcutaneous doses. A follow-up intravenous glucose injection was given to induce hyperglycemia, and serial blood samples were collected to measure plasma concentrations of glucose, insulin, triglycerides, beta-hydroxybutyrate, and nonesterified fatty acids. The exenatide doses used were saline control (no drug), and 0.02, 0.05, or 0.1 mcg/kg injected subcutaneously. Alpacas had significantly lower plasma glucose concentrations and higher insulin concentrations on all treatment days compared with the control day, but the increase in insulin was significantly greater and lasted significantly longer when the alpacas received the two higher dosages. Two of the alpacas developed mild colic signs at the 0.05 mcg/kg dose and were not evaluated at the highest dose. Based on these findings, the 0.05 mcg/kg dose appears to offer the greatest stimulation of insulin secretion and glucose clearance without excessive risk or severity of complications. PMID:24479825
Russell, Kellie R.; Carlsson Tedgren, Aasa K.; Ahnesjoe, Anders [Nucletron Scandinavia AB, Box 1704, SE-751 47 Uppsala (Sweden); Medical Radiation Physics, Karolinska Institute and Stockholm University, P.O. Box 260, SE-171 76 Stockholm (Sweden) and Swedish Radiation Protection Authority, SE-171 16 Stockholm (Sweden); Nucletron Scandinavia AB, Box 1704, SE-751 47 Uppsala (Sweden) and Department of Oncology, Radiology and Clinical Immunology, Uppsala University (Sweden)
2005-09-15
In brachytherapy, tissue heterogeneities, source shielding, and finite patient/phantom extensions affect both the primary and scatter dose distributions. The primary dose is, due to the short range of secondary electrons, dependent only on the distribution of material located on the ray line between the source and dose deposition site. The scatter dose depends on both the direct irradiation pattern and the distribution of material in a large volume surrounding the point of interest, i.e., a much larger volume must be included in calculations to integrate many small dose contributions. It is therefore of interest to consider different methods for the primary and the scatter dose calculation to improve calculation accuracy with limited computer resources. The algorithms in present clinical use ignore these effects causing systematic dose errors in brachytherapy treatment planning. In this work we review a primary and scatter dose separation formalism (PSS) for brachytherapy source characterization to support separate calculation of the primary and scatter dose contributions. We show how the resulting source characterization data can be used to drive more accurate dose calculations using collapsed cone superposition for scatter dose calculations. Two types of source characterization data paths are used: a direct Monte Carlo simulation in water phantoms with subsequent parameterization of the results, and an alternative data path built on processing of AAPM TG43 formatted data to provide similar parameter sets. The latter path is motivated of the large amounts of data already existing in the TG43 format. We demonstrate the PSS methods using both data paths for a clinical {sup 192}Ir source. Results are shown for two geometries: a finite but homogeneous water phantom, and a half-slab consisting of water and air. The dose distributions are compared to results from full Monte Carlo simulations and we show significant improvement in scatter dose calculations when the collapsed-cone kernel-superposition algorithm is used compared to traditional table based calculations. The PSS source characterization method uses exponential fit functions derived from one-dimensional transport theory to describe both the primary and scatter dose contributions. We present data for the PSS characterization method to different {sup 192}Ir, {sup 137}Cs, and {sup 60}Cs brachytherapy sources. We also show how TG43 formatted data can be derived from our data to serve traditional treatment planning systems, as to enable for a gradual transfer to algorithms that provides improved modeling of heterogeneities in brachytherapy treatment planning.
Russell, Kellie R; Tedgren, Asa K Carlsson; Ahnesjö, Anders
2005-09-01
In brachytherapy, tissue heterogeneities, source shielding, and finite patient/phantom extensions affect both the primary and scatter dose distributions. The primary dose is, due to the short range of secondary electrons, dependent only on the distribution of material located on the ray line between the source and dose deposition site. The scatter dose depends on both the direct irradiation pattern and the distribution of material in a large volume surrounding the point of interest, i.e., a much larger volume must be included in calculations to integrate many small dose contributions. It is therefore of interest to consider different methods for the primary and the scatter dose calculation to improve calculation accuracy with limited computer resources. The algorithms in present clinical use ignore these effects causing systematic dose errors in brachytherapy treatment planning. In this work we review a primary and scatter dose separation formalism (PSS) for brachytherapy source characterization to support separate calculation of the primary and scatter dose contributions. We show how the resulting source characterization data can be used to drive more accurate dose calculations using collapsed cone superposition for scatter dose calculations. Two types of source characterization data paths are used: a direct Monte Carlo simulation in water phantoms with subsequent parameterization of the results, and an alternative data path built on processing of AAPM TG43 formatted data to provide similar parameter sets. The latter path is motivated of the large amounts of data already existing in the TG43 format. We demonstrate the PSS methods using both data paths for a clinical 192Ir source. Results are shown for two geometries: a finite but homogeneous water phantom, and a half-slab consisting of water and air. The dose distributions are compared to results from full Monte Carlo simulations and we show significant improvement in scatter dose calculations when the collapsed-cone kernel-superposition algorithm is used compared to traditional table based calculations. The PSS source characterization method uses exponential fit functions derived from one-dimensional transport theory to describe both the primary and scatter dose contributions. We present data for the PSS characterization method to different 192Ir, 137Cs, and 60Cs brachytherapy sources. We also show how TG43 formatted data can be derived from our data to serve traditional treatment planning systems, as to enable for a gradual transfer to algorithms that provides improved modeling of heterogeneities in brachytherapy treatment planning. PMID:16266087
Uppsala Universitet
Turning point Getting started To use clickers the program TurningPoint is used. TurningPoint is compatible with Powerpoint and to access TurningPoints functions simple open any powerpoint file through TurningPoint. You don't need to create the presentation in TurningPoint, apart from the questions. You can
Aravind Kalaiah; Amitabh Varshney
2001-01-01
We present a novel point rendering primitive, called Differential Point (DP), that captures the local differential geometry in the vicinity of a sam- pled point. This is a more general point representation that, for the cost of a few additional bytes, packs much more information per point than the traditional point-based models. This information is used to efficiently render the
Statistical variability and confidence intervals for planar dose QA pass rates
Bailey, Daniel W.; Nelms, Benjamin E.; Attwood, Kristopher; Kumaraswamy, Lalith; Podgorsak, Matthew B. [Department of Physics, State University of New York at Buffalo, Buffalo, New York 14260 (United States) and Department of Radiation Medicine, Roswell Park Cancer Institute, Buffalo, New York 14263 (United States); Canis Lupus LLC, Merrimac, Wisconsin 53561 (United States); Department of Biostatistics, Roswell Park Cancer Institute, Buffalo, New York 14263 (United States); Department of Radiation Medicine, Roswell Park Cancer Institute, Buffalo, New York 14263 (United States); Department of Radiation Medicine, Roswell Park Cancer Institute, Buffalo, New York 14263 (United States); Department of Molecular and Cellular Biophysics and Biochemistry, Roswell Park Cancer Institute, Buffalo, New York 14263 (United States) and Department of Physiology and Biophysics, State University of New York at Buffalo, Buffalo, New York 14214 (United States)
2011-11-15
Purpose: The most common metric for comparing measured to calculated dose, such as for pretreatment quality assurance of intensity-modulated photon fields, is a pass rate (%) generated using percent difference (%Diff), distance-to-agreement (DTA), or some combination of the two (e.g., gamma evaluation). For many dosimeters, the grid of analyzed points corresponds to an array with a low areal density of point detectors. In these cases, the pass rates for any given comparison criteria are not absolute but exhibit statistical variability that is a function, in part, on the detector sampling geometry. In this work, the authors analyze the statistics of various methods commonly used to calculate pass rates and propose methods for establishing confidence intervals for pass rates obtained with low-density arrays. Methods: Dose planes were acquired for 25 prostate and 79 head and neck intensity-modulated fields via diode array and electronic portal imaging device (EPID), and matching calculated dose planes were created via a commercial treatment planning system. Pass rates for each dose plane pair (both centered to the beam central axis) were calculated with several common comparison methods: %Diff/DTA composite analysis and gamma evaluation, using absolute dose comparison with both local and global normalization. Specialized software was designed to selectively sample the measured EPID response (very high data density) down to discrete points to simulate low-density measurements. The software was used to realign the simulated detector grid at many simulated positions with respect to the beam central axis, thereby altering the low-density sampled grid. Simulations were repeated with 100 positional iterations using a 1 detector/cm{sup 2} uniform grid, a 2 detector/cm{sup 2} uniform grid, and similar random detector grids. For each simulation, %/DTA composite pass rates were calculated with various %Diff/DTA criteria and for both local and global %Diff normalization techniques. Results: For the prostate and head/neck cases studied, the pass rates obtained with gamma analysis of high density dose planes were 2%-5% higher than respective %/DTA composite analysis on average (ranging as high as 11%), depending on tolerances and normalization. Meanwhile, the pass rates obtained via local normalization were 2%-12% lower than with global maximum normalization on average (ranging as high as 27%), depending on tolerances and calculation method. Repositioning of simulated low-density sampled grids leads to a distribution of possible pass rates for each measured/calculated dose plane pair. These distributions can be predicted using a binomial distribution in order to establish confidence intervals that depend largely on the sampling density and the observed pass rate (i.e., the degree of difference between measured and calculated dose). These results can be extended to apply to 3D arrays of detectors, as well. Conclusions: Dose plane QA analysis can be greatly affected by choice of calculation metric and user-defined parameters, and so all pass rates should be reported with a complete description of calculation method. Pass rates for low-density arrays are subject to statistical uncertainty (vs. the high-density pass rate), but these sampling errors can be modeled using statistical confidence intervals derived from the sampled pass rate and detector density. Thus, pass rates for low-density array measurements should be accompanied by a confidence interval indicating the uncertainty of each pass rate.
WAGGONER, L.O.
2000-05-16
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 smart things that protect the worker but do not hinder him while the task is being accomplished. In addition, we should not demand that large amounts of money be spent for equipment that has marginal value in order to save a few millirem. We have broken the handout into sections that should simplify the presentation. Time, distance, shielding, and source reduction are methods used to reduce dose and are covered in Part I on work execution. We then look at operational considerations, radiological design parameters, and discuss the characteristics of personnel who deal with ALARA. This handout should give you an overview of what it takes to have an effective dose reduction program.
Maximum union-free subfamilies Choongbum Lee
Fox, Jacob
Maximum union-free subfamilies Jacob Fox Choongbum Lee Benny Sudakov Abstract An old problem of Moser asks: how large of a union-free subfamily does every family of m sets have? A family of sets is called union-free if there are no three distinct sets in the family such that the union of two
Maximum terminal velocity of relativistic rocket
G. Vulpetti
1985-01-01
The maximum terminal velocity problem of the classical propulsion is extended to a relativistic rocket assumed broken down into active mass, inert mass and gross payload. A fraction of the active mass is converted into energy shared between inert mass and active mass residual. Significant effects are considered. State and co-state equations are carried out to find the exhaust speed
Maximum Homologous Crossover for Linear Genetic Programming
Paris-Sud XI, Université de
Maximum Homologous Crossover for Linear Genetic Programming Michael Defoin Platel1,2 , Manuel Fitness problem, for Linear Genetic Programming. Two variants of the new crossover operator are described of deleterious crossovers. 1 Introduction The role played by crossover in the Genetic Programming (GP
5 CFR 534.203 - Maximum stipends.
Code of Federal Regulations, 2012 CFR
2012-01-01
... Maximums by grade and step 1 L-A Below high school graduation GS-1-1 (minus 3 steps). L-1 First year college...with persons afflicted with leprosy are increased above the rates prescribed in paragraph (a) of this section to the...
5 CFR 534.203 - Maximum stipends.
Code of Federal Regulations, 2013 CFR
2013-01-01
... Maximums by grade and step 1 L-A Below high school graduation GS-1-1 (minus 3 steps). L-1 First year college...with persons afflicted with leprosy are increased above the rates prescribed in paragraph (a) of this section to the...
Original article Inequality of maximum a posteriori
Boyer, Edmond
for the genetic evaluation of breeding animals. A logical step would be to use an animal model as well to describeOriginal article Inequality of maximum a posteriori estimators with equivalent sire and animal models for threshold traits M Mayer University of Nairobi, Department of Animal Production, PO Box 29053
Weak Scale From the Maximum Entropy Principle
Yuta Hamada; Hikaru Kawai; Kiyoharu Kawana
2015-03-28
The theory of multiverse and wormholes suggests that the parameters of the Standard Model are fixed in such a way that the radiation of the $S^{3}$ universe at the final stage $S_{rad}$ becomes maximum, which we call the maximum entropy principle. Although it is difficult to confirm this principle generally, for a few parameters of the Standard Model, we can check whether $S_{rad}$ actually becomes maximum at the observed values. In this paper, we regard $S_{rad}$ at the final stage as a function of the weak scale ( the Higgs expectation value ) $v_{h}$, and show that it becomes maximum around $v_{h}={\\cal{O}}(300\\text{GeV})$ when the dimensionless couplings in the Standard Model, that is, the Higgs self coupling, the gauge couplings, and the Yukawa couplings are fixed. Roughly speaking, we find that the weak scale is given by \\begin{equation} v_{h}\\sim\\frac{T_{BBN}^{2}}{M_{pl}y_{e}^{5}},\
Weak Scale From the Maximum Entropy Principle
Hamada, Yuta; Kawana, Kiyoharu
2015-01-01
The theory of multiverse and wormholes suggests that the parameters of the Standard Model are fixed in such a way that the radiation of the $S^{3}$ universe at the final stage $S_{rad}$ becomes maximum, which we call the maximum entropy principle. Although it is difficult to confirm this principle generally, for a few parameters of the Standard Model, we can check whether $S_{rad}$ actually becomes maximum at the observed values. In this paper, we regard $S_{rad}$ at the final stage as a function of the weak scale ( the Higgs expectation value ) $v_{h}$, and show that it becomes maximum around $v_{h}={\\cal{O}}(300\\text{GeV})$ when the dimensionless couplings in the Standard Model, that is, the Higgs self coupling, the gauge couplings, and the Yukawa couplings are fixed. Roughly speaking, we find that the weak scale is given by \\begin{equation} v_{h}\\sim\\frac{T_{BBN}^{2}}{M_{pl}y_{e}^{5}},\
Comparing maximum pressures in internal combustion engines
NASA Technical Reports Server (NTRS)
Sparrow, Stanwood W; Lee, Stephen M
1922-01-01
Thin metal diaphragms form a satisfactory means for comparing maximum pressures in internal combustion engines. The diaphragm is clamped between two metal washers in a spark plug shell and its thickness is chosen such that, when subjected to explosion pressure, the exposed portion will be sheared from the rim in a short time.
ccsd00003341, On nonparametric maximum likelihood
Algorithm; Mix- tures of Probability Measures; Repeated Measurements Data; Longitudinal Data. Subject Classi value f(S i ; T i ). This kind of data is known as repeated measurements, or called longitudinal since of Pfanzagl related to mixtures [23, 24]. Keywords: Inverse Problems; Nonlinear Models; Maximum Likelihood; EM
Maximum entropy analysis of hydraulic pipe networks
NASA Astrophysics Data System (ADS)
Waldrip, Steven H.; Niven, Robert K.; Abel, Markus; Schlegel, Michael
2014-12-01
A Maximum Entropy (MaxEnt) method is developed to infer mean external and internal flow rates and mean pressure gradients (potential differences) in hydraulic pipe networks, without or with sufficient constraints to render the system deterministic. The proposed method substantially extends existing methods for the analysis of flow networks (e.g. Hardy-Cross), applicable only to deterministic networks.
Maximum entropy analysis of flow networks
NASA Astrophysics Data System (ADS)
Niven, Robert K.; Abel, Markus; Schlegel, Michael; Waldrip, Steven H.
2014-12-01
This study examines a generalised maximum entropy (MaxEnt) analysis of a flow network, involving flow rates and potential differences on the network, connected by resistance functions. The analysis gives a generic derivation based on an explicit form of the resistance functions. Accounting for the constraints also leads to an extended form of Gibbs' phase rule, applicable to flow networks.
Predicting maximum lake depth from surrounding topography.
Hollister, Jeffrey W; Milstead, W Bryan; Urrutia, M Andrea
2011-01-01
Information about lake morphometry (e.g., depth, volume, size, etc.) aids understanding of the physical and ecological dynamics of lakes, yet is often not readily available. The data needed to calculate measures of lake morphometry, particularly lake depth, are usually collected on a lake-by-lake basis and are difficult to obtain across broad regions. To span the gap between studies of individual lakes where detailed data exist and regional studies where access to useful data on lake depth is unavailable, we developed a method to predict maximum lake depth from the slope of the topography surrounding a lake. We use the National Elevation Dataset and the National Hydrography Dataset - Plus to estimate the percent slope of surrounding lakes and use this information to predict maximum lake depth. We also use field measured maximum lake depths from the US EPA's National Lakes Assessment to empirically adjust and cross-validate our predictions. We were able to predict maximum depth for ?28,000 lakes in the Northeastern United States with an average cross-validated RMSE of 5.95 m and 5.09 m and average correlation of 0.82 and 0.69 for Hydrological Unit Code Regions 01 and 02, respectively. The depth predictions and the scripts are openly available as supplements to this manuscript. PMID:21984945
Maximum rotation frequency of strange stars
Zdunik, J.L.; Haensel, P. (Nicolaus Copernicus Astronomical Center, Polish Academy of Sciences, Bartycka 18, PL-00-716 Warsaw (Poland))
1990-07-15
Using the MIT bag model of strange-quark matter, we calculate the maximum angular frequency of the uniform rotation of strange stars. After studying a broad range of the MIT bag-model parameters, we obtain an upper bound of 12.3 kHz.
Maximum Possible Transverse Velocity in Special Relativity.
ERIC Educational Resources Information Center
Medhekar, Sarang
1991-01-01
Using a physical picture, an expression for the maximum possible transverse velocity and orientation required for that by a linear emitter in special theory of relativity has been derived. A differential calculus method is also used to derive the expression. (Author/KR)
Effect of tissue inhomogeneity on beta dose distribution of Â³Â²P
Cheuk S. Kwok; M. Irfan; M. K. Woo; W. V. Prestwich
1987-01-01
In a homogeneous medium of soft tissue the radiation dose distribution due to a nonuniformly distributed beta source can be calculated by convolution of the beta dose point kernel of the nuclide with the source distribution. A possible extension of the technique to the calculation of the dose distribution in heterogeneous media involving relatively simple geometric interfaces requires the knowledge
Measurement and Analysis of Gamma-Ray Dose Distribution in Actual Ship
Hisao YAMAKOSHI; Kohtaro UEKI; Masaya NAKATA
1983-01-01
Gamma-ray dose distribution was measured in an actual ship to study applicability of point kernel method popularly applied to the calculation of ?-ray dose distribution in ships which have usually compartmentalized structures. Measured distribution was used to verify applicability of Monte Carlo method to the analysis of ?-ray dose distribution in the ship. Monte Carlo method was proved to be
NASA Astrophysics Data System (ADS)
Nadhir, Ahmad; Naba, Agus; Hiyama, Takashi
An optimal control for maximizing extraction of power in variable-speed wind energy conversion system is presented. Intelligent gradient detection by fuzzy inference system (FIS) in maximum power point tracking control is proposed to achieve power curve operating near optimal point. Speed rotor reference can be adjusted by maximum power point tracking fuzzy controller (MPPTFC) such that the turbine operates around maximum power. Power curve model can be modelled by using adaptive neuro fuzzy inference system (ANFIS). It is required to simply well estimate just a few number of maximum power points corresponding to optimum generator rotor speed under varying wind speed, implying its training can be done with less effort. Using the trained fuzzy model, some estimated maximum power points as well as their corresponding generator rotor speed and wind speed are determined, from which a linear wind speed feedback controller (LWSFC) capable of producing optimum generator speed can be obtained. Applied to a squirrel-cage induction generator based wind energy conversion system, MPPTFC and LWSFC could maximize extraction of the wind energy, verified by a power coefficient stay at its maximum almost all the time and an actual power line close to a maximum power efficiency line reference.
Low-Dose Carcinogenicity Studies
One of the major deficiencies of cancer risk assessments is the lack of low-dose carcinogenicity data. Most assessments require extrapolation from high to low doses, which is subject to various uncertainties. Only 4 low-dose carcinogenicity studies and 5 low-dose biomarker/pre-n...
ERIC Educational Resources Information Center
Titze, Ingo R.
2006-01-01
Purpose: Maximum flow declination rate (MFDR) in the glottis is known to correlate strongly with vocal intensity in voicing. This declination, or negative slope on the glottal airflow waveform, is in part attributable to the maximum area declination rate (MADR) and in part to the overall inertia of the air column of the vocal tract (lungs to…
NASA Astrophysics Data System (ADS)
Area, María C.; Calvo, Ana M.; Felissia, Fernando E.; Docters, Andrea; Miranda, María V.
2014-03-01
The aim of this study was to evaluate the effects of dose and dose rate of gamma irradiation on the physical properties of commercial papers commonly used in libraries and archives to optimize the irradiation conditions. Three different brands of paper of different fiber compositions were treated, using a 32 factorial design with four replicates of the center point, with doses ranging from 2 to 11 kGy and dose rates between 1 and 11 kGy/h. Chemical, mechanical and optical properties were determined on the samples. With some differences between the different kinds of papers, tensile strength, elongation, TEA, and air resistance were in general, unaffected by the treatment. The minimum loss of tear resistance and brightness were obtained with doses in the range 4-6 kGy at any dose rate for all three kinds of paper. These conditions are ideal to remove insects and sufficient to eliminate fungus.
K. P. Smith; D. L. Blunt; G. P. Williams; C. L. Tebes
1996-01-01
A preliminary radiological dose assessment of equipment decontamination, subsurface disposal, landspreading, equipment smelting, and equipment burial was conducted to address concerns regarding the presence of naturally occurring radioactive materials (NORM) in production waste streams. The assessment estimated maximum individual dose equivalents for workers and the general public. Sensitivity analyses of certain input parameters also were conducted. On the basis of
Low-Power Maximum Power Point Tracker with Digital Control for Thermophotovoltaic Generators
Pilawa, Robert
This paper describes the design, optimization, and evaluation of the power electronics circuitry for a low-power portable thermophotovotaic (TPV) generator system. TPV system is based on a silicon micro-reactor design and ...
Microcontroller Servomotor for Maximum Effective Power Point for Solar Cell System
Al-Khalidy, M.; Al-Rawi, O.; Noaman, N.
2010-01-01
system coast. The proposed automatic servo control system based on PIC microcontroller which is used to control the photovoltaic (PV) modules. This servo system will track the sun rays in order to get MPP during the day using direct radiation. A photo...
Highly Accurate Maximum Likelihood Laser Mapping by Jointly Optimizing Laser Points and Robot Poses
Teschner, Matthias
. In robotics, the problem is known as simultaneous localization and mapping (SLAM), and it has been deeply the estimated maps greatly improves the localization accuracy of robots. The results furthermore suggest that the accuracy of the resulting map can exceed the resolution of the laser sensors used. I. INTRODUCTION
Data required for testicular dose calculation during radiotherapy of seminoma
Mazonakis, Michalis; Kokona, Georgiana; Varveris, Haralambos; Damilakis, John; Gourtsoyiannis, Nicholas [Department of Medical Physics, University Hospital of Iraklion, 71110 Iraklion (Greece); Department of Radiotherapy, Faculty of Medicine, University of Crete, 71409 Iraklion (Greece); Department of Medical Physics, Faculty of Medicine, University of Crete, 71409 Iraklion (Greece); Department of Radiology, Faculty of Medicine, University of Crete, 71409 Iraklion (Greece)
2006-07-15
The purpose of this study was to provide the required data for the direct calculation of testicular dose resulting from radiotherapy in patients with seminoma. Paraortic (PA) treatment fields and dog-leg (DL) portals including paraortic and ipsilateral pelvic nodes were simulated on a male anthropomorphic phantom equipped with an artificial testicle. Anterior and posterior irradiations were performed for five different PA and DL field dimensions. Dose measurements were carried out using a calibrated ionization chamber. The dependence of testicular dose upon the distance separating the testicle from the treatment volume and upon the tissue thickness at the entrance point of the beam was investigated. A clamshell lead shield was used to reduce testicular dose. The scattered dose to testicle was measured in nine patients using thermoluminescent dosimeters. Phantom and patient exposures were generated with a 6 MV x-ray beam. Linear and nonlinear regression analysis was employed to obtain formulas describing the relation between the radiation dose to an unshielded and/or shielded testicle with the field size and the distance from the inferior field edge. Correction factors showing the variation of testicular dose with the patient thickness along beam axis were found. Bland-Altman statistical analysis showed that testicular dose obtained by the proposed calculation method may differ from the measured dose value by less than 25%. The current study presents a method providing reasonable estimations of testicular dose for individual patients undergoing PA or DL radiotherapy.
Interior Point Decoding for Linear Vector Channels
Tadashi Wadayama
2007-01-01
In this paper, a novel decoding algorithm for low- density parity-check (LDPC) codes based on convex optimization is presented. The decoding algorithm, called interior point decod- ing, is designed for linear vector channels. The linear vector channels include many practically important channels such as inter symbol interference channels and partial response channels. It is shown that the maximum likelihood decoding
ERIC Educational Resources Information Center
Penfield, Randall D.
2007-01-01
The standard error of the maximum likelihood ability estimator is commonly estimated by evaluating the test information function at an examinee's current maximum likelihood estimate (a point estimate) of ability. Because the test information function evaluated at the point estimate may differ from the test information function evaluated at an…
Patient-specific dose calculation methods for high-dose-rate iridium-192 brachytherapy
NASA Astrophysics Data System (ADS)
Poon, Emily S.
In high-dose-rate 192Ir brachytherapy, the radiation dose received by the patient is calculated according to the AAPM Task Group 43 (TG-43) formalism. This table-based dose superposition method uses dosimetry parameters derived with the radioactive 192Ir source centered in a water phantom. It neglects the dose perturbations caused by inhomogeneities, such as the patient anatomy, applicators, shielding, and radiographic contrast solution. In this work, we evaluated the dosimetric characteristics of a shielded rectal applicator with an endocavitary balloon injected with contrast solution. The dose distributions around this applicator were calculated by the GEANT4 Monte Carlo (MC) code and measured by ionization chamber and GAFCHROMIC EBT film. A patient-specific dose calculation study was then carried out for 40 rectal treatment plans. The PTRAN_CT MC code was used to calculate the dose based on computed tomography (CT) images. This study involved the development of BrachyGUI, an integrated treatment planning tool that can process DICOM-RT data and create PTRAN_CT input initialization files. BrachyGUI also comes with dose calculation and evaluation capabilities. We proposed a novel scatter correction method to account for the reduction in backscatter radiation near tissue-air interfaces. The first step requires calculating the doses contributed by primary and scattered photons separately, assuming a full scatter environment. The scatter dose in the patient is subsequently adjusted using a factor derived by MC calculations, which depends on the distances between the point of interest, the 192Ir source, and the body contour. The method was validated for multicatheter breast brachytherapy, in which the target and skin doses for 18 patient plans agreed with PTRAN_CT calculations better than 1%. Finally, we developed a CT-based analytical dose calculation method. It corrects for the photon attenuation and scatter based upon the radiological paths determined by ray tracing. The scatter dose is again adjusted using our scatter correction technique. The algorithm was tested using phantoms and actual patient plans for head-and-neck, esophagus, and MammoSite breast brachytherapy. Although the method fails to correct for the changes in lateral scatter introduced by inhomogeneities, it is a major improvement over TG-43 and is sufficiently fast for clinical use.
William L. Robison; Cynthia L. Conrado; Kenneth T. Bogen
1999-01-01
On March 1, 1954, radioactive fallout from the nuclear test at Bikini Atoll code-named BRAVO was deposited on Utirik Atoll which lies about 187 km (300 miles) east of Bikini Atoll. The residents of Utirik were evacuated three days after the fallout started and returned to their atoll in May 1954. In this report we provide a final dose assessment
Skin dose mapping for fluoroscopically guided interventions
Johnson, Perry B.; Borrego, David; Balter, Stephen; Johnson, Kevin; Siragusa, Daniel; Bolch, Wesley E. [Biomedical Engineering, University of Florida, Gainesville, Florida 32611 (United States); Radiology, Columbia University Medical Center, New York, New York 10032 (United States); Radiology, University of Florida, Jacksonville, Florida 32209 (United States); Radiology, Division of Vascular Interventional Radiology, University of Florida, Jacksonville, Florida 32209 (United States); Biomedical Engineering, University of Florida, Gainesville, Florida 32611 (United States)
2011-10-15
Purpose: To introduce a new skin dose mapping software system for interventional fluoroscopy dose assessment and to analyze the benefits and limitations of patient-phantom matching. Methods: In this study, a new software system was developed for visualizing patient skin dose during interventional fluoroscopy procedures. The system works by translating the reference point air kerma to the location of the patient's skin, which is represented by a computational model. In order to orient the model with the x-ray source, geometric parameters found within the radiation dose structured report (RDSR) are used along with a limited number of in-clinic measurements. The output of the system is a visual indication of skin dose mapped onto an anthropomorphic model at a resolution of 5 mm. In order to determine if patient-dependent and patient-sculpted models increase accuracy, peak skin dose was calculated for each of 26 patient-specific models and compared with doses calculated using an elliptical stylized model, a reference hybrid model, a matched patient-dependent model and one patient-sculpted model. Results were analyzed in terms of a percent difference using the doses calculated using the patient-specific model as the true standard. Results: Anthropometric matching, including the use of both patient-dependent and patient-sculpted phantoms, was shown most beneficial for left lateral and anterior-posterior projections. In these cases, the percent difference using a reference model was between 8 and 20%, using a patient-dependent model between 7 and 15%, and using a patient-sculpted model between 3 and 7%. Under the table tube configurations produced errors less than 5% in most situations due to the flattening affects of the table and pad, and the fact that table height is the main determination of source-to-skin distance for these configurations. In addition to these results, several skin dose maps were produced and a prototype display system was placed on the in-clinic monitor of an interventional fluoroscopy system. Conclusions: The skin dose mapping program developed in this work represents a new tool that, as the RDSR becomes available through automated export or real-time streaming, can provide the interventional physician information needed to modify behavior when clinically appropriate. The program is nonproprietary and transferable, and also functions independent to the software systems already installed on the control room workstation. The next step will be clinical implementation where the workflow will be optimized along with further analysis of real-time capabilities.
Effects of Proton Radiation Dose, Dose Rate and Dose Fractionation on Hematopoietic Cells in Mice
Ware, J. H.; Sanzari, J.; Avery, S.; Sayers, C.; Krigsfeld, G.; Nuth, M.; Wan, X. S.; Rusek, A.; Kennedy, A. R.
2012-01-01
The present study evaluated the acute effects of radiation dose, dose rate and fractionation as well as the energy of protons in hematopoietic cells of irradiated mice. The mice were irradiated with a single dose of 51.24 MeV protons at a dose of 2 Gy and a dose rate of 0.05–0.07 Gy/min or 1 GeV protons at doses of 0.1, 0.2, 0.5, 1, 1.5 and 2 Gy delivered in a single dose at dose rates of 0.05 or 0.5 Gy/min or in five daily dose fractions at a dose rate of 0.05 Gy/min. Sham-irradiated animals were used as controls. The results demonstrate a dose-dependent loss of white blood cells (WBCs) and lymphocytes by up to 61% and 72%, respectively, in mice irradiated with protons at doses up to 2 Gy. The results also demonstrate that the dose rate, fractionation pattern and energy of the proton radiation did not have significant effects on WBC and lymphocyte counts in the irradiated animals. These results suggest that the acute effects of proton radiation on WBC and lymphocyte counts are determined mainly by the radiation dose, with very little contribution from the dose rate (over the range of dose rates evaluated), fractionation and energy of the protons. PMID:20726731
Pharmacokinetic profiles of ciprofloxacin after single intravenous and oral doses.
Lettieri, J T; Rogge, M C; Kaiser, L; Echols, R M; Heller, A H
1992-01-01
Ciprofloxacin was administered to 12 healthy male volunteers at doses of 300 and 400 mg intravenously (i.v.) and 500 and 750 mg orally in a randomized, double-blind, single-dose, four-period crossover study. On each treatment day, each subject received both oral and i.v. formulations, one of which was a placebo. Blood and urine samples were obtained through 24 h postdose. By each dosing route, the pharmacokinetic profiles were dose proportional. The 400-mg i.v. dose was equivalent to the 500-mg oral dose with respect to the area under the concentration-time curve and was equivalent to the 750-mg oral dose with respect to the maximum concentration of ciprofloxacin in serum. The oral bioavailability was 78.0%. The steady-state volume of distribution averaged 178 liters, and the terminal half-life in serum after i.v. dosing was approximately 4.3 h. Renal clearance accounted for approximately 60% of total body clearance. No significant adverse events were associated with either route of administration. PMID:1510426
Proxy-assisted TCP maximum receive window control in split-TCP capable GEO satellite networks
M. Karaliopoulos; R. Tafazolli; B. Evans
In this paper we focus on proxy-aware split-capable satellite networks. In addition to the well-reported performance enhancement, the split connection mechanism provides additional flexibility with respect to the treatment of TCP traffic. Having as a starting point an analytical framework drawing on fixed-point approximations, we introduce an algorithm for the active control of the TCP maximum receive window of the
Efficient Algorithms for Computing the Maximum Distance Between Two Finite Planar Sets
Binay K. Bhattacharya; Godfried T. Toussaint
1983-01-01
An O(n log n) algorithm is presented for computing the maximum euclidean distancebetween two finite planar sets of n points. When the n points form the verticesof simple polygons this complexity can be reduced to O(n). The algorithm isempirically compared to the brute-force method as well as an alternate O(n2) algorithm.Both the O(n log n) and O(n2) algorithms run in
Effect of high dose ramipril with or without indomethacin on glomerular selectivity
Roberto Pisoni; Piero Ruggenenti; Fabio Sangalli; Maria Serena Lepre; Andrea Remuzzi; Giuseppe Remuzzi
2002-01-01
Effect of high dose ramipril with or without indomethacin on glomerular selectivity.BackgroundDespite the accumulating evidence of their efficacy, angiotensin-converting enzyme inhibitors (ACEi) still provide imperfect renoprotection. Up-titration above conventional doses and combined therapy with other antiproteinuric agents may serve to achieve renoprotection in patients at risk of rapid disease progression.MethodsThe effect of maximum tolerated ACEi doses (ramipril 15 mg\\/day, range
Dose Rate Upset Investigations on the Xilinx Virtex IV Field Programmable Gate Arrays
Alonzo Vera; Daniel Llamocca; Marios Pattichis; William Kemp; Walter Shedd; David Alexander; James Lyke
2007-01-01
The following paper describes the results of ionizing dose rate investigations into upset, supply photocurrent, latch-up, and burnout susceptibility of the Xilinx Virtex IV XC4VFX12. All investigations were performed on a commercial version of the device. The maximum no-upset dose rate was 2.8times108 rad(Si)\\/s. Photocurrent amplitudes as a function of dose rate were recorded.
K. Vera; L. Djafari; S. Faivre; J.-S. Guillamo; K. Djazouli; M. Osorio; F. Parker; C. Cioloca; B. Abdulkarim; J.-P. Armand; E. Raymond
2004-01-01
2 \\/day on days 1-5 every 4 weeks. In this study, a new alternative dose-dense regimen of temozolomide was explored in patients with recurrent brain tumors. Patients and methods: In this study, we evaluated the safety, dose-limiting toxicity, maximum tolerated dose, recommended dose and activity of temozolomide given on days 1-3 and 14-16 every 28 days (one cycle). The starting
Maximum-entropy description of animal movement.
Fleming, Chris H; Suba??, Yi?it; Calabrese, Justin M
2015-03-01
We introduce a class of maximum-entropy states that naturally includes within it all of the major continuous-time stochastic processes that have been applied to animal movement, including Brownian motion, Ornstein-Uhlenbeck motion, integrated Ornstein-Uhlenbeck motion, a recently discovered hybrid of the previous models, and a new model that describes central-place foraging. We are also able to predict a further hierarchy of new models that will emerge as data quality improves to better resolve the underlying continuity of animal movement. Finally, we also show that Langevin equations must obey a fluctuation-dissipation theorem to generate processes that fall from this class of maximum-entropy distributions when the constraints are purely kinematic. PMID:25871054
Pareto versus lognormal: A maximum entropy test
NASA Astrophysics Data System (ADS)
Bee, Marco; Riccaboni, Massimo; Schiavo, Stefano
2011-08-01
It is commonly found that distributions that seem to be lognormal over a broad range change to a power-law (Pareto) distribution for the last few percentiles. The distributions of many physical, natural, and social events (earthquake size, species abundance, income and wealth, as well as file, city, and firm sizes) display this structure. We present a test for the occurrence of power-law tails in statistical distributions based on maximum entropy. This methodology allows one to identify the true data-generating processes even in the case when it is neither lognormal nor Pareto. The maximum entropy approach is then compared with other widely used methods and applied to different levels of aggregation of complex systems. Our results provide support for the theory that distributions with lognormal body and Pareto tail can be generated as mixtures of lognormally distributed units.
MAXIMUM LIKELIHOOD ESTIMATION FOR SOCIAL NETWORK DYNAMICS.
Snijders, Tom A B; Koskinen, Johan; Schweinberger, Michael
2010-06-01
A model for network panel data is discussed, based on the assumption that the observed data are discrete observations of a continuous-time Markov process on the space of all directed graphs on a given node set, in which changes in tie variables are independent conditional on the current graph. The model for tie changes is parametric and designed for applications to social network analysis, where the network dynamics can be interpreted as being generated by choices made by the social actors represented by the nodes of the graph. An algorithm for calculating the Maximum Likelihood estimator is presented, based on data augmentation and stochastic approximation. An application to an evolving friendship network is given and a small simulation study is presented which suggests that for small data sets the Maximum Likelihood estimator is more efficient than the earlier proposed Method of Moments estimator. PMID:25419259
A Maximum Radius for Habitable Planets.
Alibert, Yann
2015-09-01
We compute the maximum radius a planet can have in order to fulfill two constraints that are likely necessary conditions for habitability: 1- surface temperature and pressure compatible with the existence of liquid water, and 2- no ice layer at the bottom of a putative global ocean, that would prevent the operation of the geologic carbon cycle to operate. We demonstrate that, above a given radius, these two constraints cannot be met: in the Super-Earth mass range (1-12 Mearth), the overall maximum that a planet can have varies between 1.8 and 2.3 Rearth. This radius is reduced when considering planets with higher Fe/Si ratios, and taking into account irradiation effects on the structure of the gas envelope. PMID:26159097
Finding maximum colorful subtrees in practice.
Rauf, Imran; Rasche, Florian; Nicolas, François; Böcker, Sebastian
2013-04-01
In metabolomics and other fields dealing with small compounds, mass spectrometry is applied as a sensitive high-throughput technique. Recently, fragmentation trees have been proposed to automatically analyze the fragmentation mass spectra recorded by such instruments. Computationally, this leads to the problem of finding a maximum weight subtree in an edge-weighted and vertex-colored graph, such that every color appears, at most once in the solution. We introduce new heuristics and an exact algorithm for this Maximum Colorful Subtree problem and evaluate them against existing algorithms on real-world and artificial datasets. Our tree completion heuristic consistently scores better than other heuristics, while the integer programming-based algorithm produces optimal trees with modest running times. Our fast and accurate heuristic can help determine molecular formulas based on fragmentation trees. On the other hand, optimal trees from the integer linear program are useful if structure is relevant, for example for tree alignments. PMID:23509858
Maximum Entropy Analysis of Queueing Network Models
Demetres D. Kouvatsos
1993-01-01
The principle of Maximum Entropy (ME) provides a consistent method of inference for estimating the form of an unknown discrete-state probability distribution, based on information expressed in terms of true expected values. In this tutorial paper entropy maximisation is used to characterise product-form approximations and resolution algorithms for arbitrary continuous-time and discrete-time Queueing Network Models (QNMs) at equilibrium under Repetitive-Service
Maximum entropy and Bayesian methods. Proceedings.
NASA Astrophysics Data System (ADS)
Grandy, W. T., Jr.; Schick, L. H.
This volume contains a selection of papers presented at the Tenth Annual Workshop on Maximum Entropy and Bayesian Methods. The thirty-six papers included cover a wide range of applications in areas such as economics and econometrics, astronomy and astrophysics, general physics, complex systems, image reconstruction, and probability and mathematics. Together they give an excellent state-of-the-art overview of fundamental methods of data analysis.
Maximum Correntropy Criterion for Robust Face Recognition
Ran He; Wei-Shi Zheng; Bao-Gang Hu
2011-01-01
In this paper, we present a sparse correntropy framework for computing robust sparse representations of face images for recognition. Compared with the state-of-the-art l 1 norm-based sparse representation classifier (SRC), which assumes that noise also has a sparse representation, our sparse algorithm is developed based on the maximum correntropy criterion, which is much more insensitive to outliers. In order to
THEORETICAL ESTIMATE OF MAXIMUM POSSIBLE NUCLEAR EXPLOSION
Bethe
1950-01-01
The maximum nuclear accident which could occur in a Na-cooled, Be moderated, Pu and power producing reactor is estimated theoretically. (T.R.H.) 2O82 Results of nuclear calculations for a variety of compositions of fast, heterogeneous, sodium-cooled, U-235-fueled, plutonium- and power-producing reactors are reported. Core compositions typical of plate-, pin-, or wire-type fuel elements and with uranium as metal, alloy, and oxide
49 CFR 230.24 - Maximum allowable stress.
Code of Federal Regulations, 2010 CFR
2010-10-01
... 2010-10-01 false Maximum allowable stress. 230.24 Section 230.24 Transportation...STANDARDS Boilers and Appurtenances Allowable Stress § 230.24 Maximum allowable stress. (a) Maximum allowable stress value....
49 CFR 230.24 - Maximum allowable stress.
Code of Federal Regulations, 2014 CFR
2014-10-01
... 2014-10-01 false Maximum allowable stress. 230.24 Section 230.24 Transportation...STANDARDS Boilers and Appurtenances Allowable Stress § 230.24 Maximum allowable stress. (a) Maximum allowable stress value....
49 CFR 230.24 - Maximum allowable stress.
Code of Federal Regulations, 2012 CFR
2012-10-01
... 2012-10-01 false Maximum allowable stress. 230.24 Section 230.24 Transportation...STANDARDS Boilers and Appurtenances Allowable Stress § 230.24 Maximum allowable stress. (a) Maximum allowable stress value....
49 CFR 230.24 - Maximum allowable stress.
Code of Federal Regulations, 2011 CFR
2011-10-01
... 2011-10-01 false Maximum allowable stress. 230.24 Section 230.24 Transportation...STANDARDS Boilers and Appurtenances Allowable Stress § 230.24 Maximum allowable stress. (a) Maximum allowable stress value....
49 CFR 230.24 - Maximum allowable stress.
Code of Federal Regulations, 2013 CFR
2013-10-01
... 2013-10-01 false Maximum allowable stress. 230.24 Section 230.24 Transportation...STANDARDS Boilers and Appurtenances Allowable Stress § 230.24 Maximum allowable stress. (a) Maximum allowable stress value....
14 CFR 375.23 - Maximum allowable weights.
Code of Federal Regulations, 2010 CFR
2010-01-01
... false Maximum allowable weights. 375.23 Section 375...375.23 Maximum allowable weights. Foreign civil aircraft...in the United States on the basis of foreign airworthiness certificates...limitations on maximum certificated weights prescribed or authorized...
30 CFR 56.19062 - Maximum acceleration and deceleration.
Code of Federal Regulations, 2010 CFR
2010-07-01
... 2010-07-01 false Maximum acceleration and deceleration. 56.19062 Section...Procedures § 56.19062 Maximum acceleration and deceleration. Maximum normal operating acceleration and deceleration shall not exceed...
30 CFR 56.19062 - Maximum acceleration and deceleration.
Code of Federal Regulations, 2014 CFR
2014-07-01
... 2014-07-01 false Maximum acceleration and deceleration. 56.19062 Section...Procedures § 56.19062 Maximum acceleration and deceleration. Maximum normal operating acceleration and deceleration shall not exceed...
30 CFR 56.19062 - Maximum acceleration and deceleration.
Code of Federal Regulations, 2012 CFR
2012-07-01
... 2012-07-01 false Maximum acceleration and deceleration. 56.19062 Section...Procedures § 56.19062 Maximum acceleration and deceleration. Maximum normal operating acceleration and deceleration shall not exceed...
30 CFR 57.19062 - Maximum acceleration and deceleration.
Code of Federal Regulations, 2011 CFR
2011-07-01
... 2011-07-01 false Maximum acceleration and deceleration. 57.19062 Section...Procedures § 57.19062 Maximum acceleration and deceleration. Maximum normal operating acceleration and deceleration shall not exceed...
30 CFR 56.19062 - Maximum acceleration and deceleration.
Code of Federal Regulations, 2011 CFR
2011-07-01
... 2011-07-01 false Maximum acceleration and deceleration. 56.19062 Section...Procedures § 56.19062 Maximum acceleration and deceleration. Maximum normal operating acceleration and deceleration shall not exceed...
30 CFR 57.19062 - Maximum acceleration and deceleration.
Code of Federal Regulations, 2010 CFR
2010-07-01
... 2010-07-01 false Maximum acceleration and deceleration. 57.19062 Section...Procedures § 57.19062 Maximum acceleration and deceleration. Maximum normal operating acceleration and deceleration shall not exceed...
30 CFR 56.19062 - Maximum acceleration and deceleration.
Code of Federal Regulations, 2013 CFR
2013-07-01
... 2013-07-01 false Maximum acceleration and deceleration. 56.19062 Section...Procedures § 56.19062 Maximum acceleration and deceleration. Maximum normal operating acceleration and deceleration shall not exceed...
30 CFR 57.19062 - Maximum acceleration and deceleration.
Code of Federal Regulations, 2013 CFR
2013-07-01
... 2013-07-01 false Maximum acceleration and deceleration. 57.19062 Section...Procedures § 57.19062 Maximum acceleration and deceleration. Maximum normal operating acceleration and deceleration shall not exceed...
30 CFR 57.19062 - Maximum acceleration and deceleration.
Code of Federal Regulations, 2014 CFR
2014-07-01
... 2014-07-01 false Maximum acceleration and deceleration. 57.19062 Section...Procedures § 57.19062 Maximum acceleration and deceleration. Maximum normal operating acceleration and deceleration shall not exceed...
30 CFR 57.19062 - Maximum acceleration and deceleration.
Code of Federal Regulations, 2012 CFR
2012-07-01
... 2012-07-01 false Maximum acceleration and deceleration. 57.19062 Section...Procedures § 57.19062 Maximum acceleration and deceleration. Maximum normal operating acceleration and deceleration shall not exceed...
40 CFR 143.3 - Secondary maximum contaminant levels.
Code of Federal Regulations, 2010 CFR
2010-07-01
...2010-07-01 false Secondary maximum contaminant levels. 143.3 Section 143.3 ...REGULATIONS § 143.3 Secondary maximum contaminant levels. The secondary maximum contaminant levels for public water systems are...
40 CFR 35.2205 - Maximum allowable project cost.
Code of Federal Regulations, 2011 CFR
2011-07-01
...2011-07-01 false Maximum allowable project cost. 35.2205 Section 35.2205...35.2205 Maximum allowable project cost. (a) Grants awarded on or...regulation, the maximum allowable project cost will be the sum of: (1)...
40 CFR 35.2205 - Maximum allowable project cost.
Code of Federal Regulations, 2013 CFR
2013-07-01
...2013-07-01 false Maximum allowable project cost. 35.2205 Section 35.2205...35.2205 Maximum allowable project cost. (a) Grants awarded on or...regulation, the maximum allowable project cost will be the sum of: (1)...
40 CFR 35.2205 - Maximum allowable project cost.
Code of Federal Regulations, 2010 CFR
2010-07-01
...2010-07-01 false Maximum allowable project cost. 35.2205 Section 35.2205...35.2205 Maximum allowable project cost. (a) Grants awarded on or...regulation, the maximum allowable project cost will be the sum of: (1)...
40 CFR 35.2205 - Maximum allowable project cost.
Code of Federal Regulations, 2012 CFR
2012-07-01
...2012-07-01 false Maximum allowable project cost. 35.2205 Section 35.2205...35.2205 Maximum allowable project cost. (a) Grants awarded on or...regulation, the maximum allowable project cost will be the sum of: (1)...
40 CFR 35.2205 - Maximum allowable project cost.
Code of Federal Regulations, 2014 CFR
2014-07-01
...2014-07-01 false Maximum allowable project cost. 35.2205 Section 35.2205...35.2205 Maximum allowable project cost. (a) Grants awarded on or...regulation, the maximum allowable project cost will be the sum of: (1)...
24 CFR 886.108 - Maximum annual contract commitment.
Code of Federal Regulations, 2010 CFR
2010-04-01
...Maximum annual contract commitment. (a) Number of units assisted. Based...in the project. All units currently assisted...to such conversion. Units assisted under section...Maximum annual Contract commitment. The maximum...
40 CFR 141.13 - Maximum contaminant levels for turbidity.
Code of Federal Regulations, 2010 CFR
2010-07-01
... false Maximum contaminant levels for turbidity. 141.13 Section 141.13 Protection...141.13 Maximum contaminant levels for turbidity. The maximum contaminant levels for turbidity are applicable to both community...
Mars surface radiation exposure for solar maximum conditions and 1989 solar proton events
NASA Technical Reports Server (NTRS)
Simonsen, Lisa C.; Nealy, John E.
1992-01-01
The Langley heavy-ion/nucleon transport code, HZETRN, and the high-energy nucleon transport code, BRYNTRN, are used to predict the propagation of galactic cosmic rays (GCR's) and solar flare protons through the carbon dioxide atmosphere of Mars. Particle fluences and the resulting doses are estimated on the surface of Mars for GCR's during solar maximum conditions and the Aug., Sep., and Oct. 1989 solar proton events. These results extend previously calculated surface estimates for GCR's at solar minimum conditions and the Feb. 1956, Nov. 1960, and Aug. 1972 solar proton events. Surface doses are estimated with both a low-density and a high-density carbon dioxide model of the atmosphere for altitudes of 0, 4, 8, and 12 km above the surface. A solar modulation function is incorporated to estimate the GCR dose variation between solar minimum and maximum conditions over the 11-year solar cycle. By using current Mars mission scenarios, doses to the skin, eye, and blood-forming organs are predicted for short- and long-duration stay times on the Martian surface throughout the solar cycle.
Motion-encoded dose calculation through fluence/sinogram modification
Lu, Weiguo; Olivera, Gustavo H.; Mackie, Thomas R. [TomoTherapy Inc., 1240 Deming Way, Madison, Wisconsin 53717 (United States); TomoTherapy Inc., 1240 Deming Way, Madison, Wisconsin 53717 and University of Wisconsin-Madison, 1300 University Avenue, Madison, Wisconsin, 53705 (United States)
2005-01-01
Conventional radiotherapy treatment planning systems rely on a static computed tomography (CT) image for planning and evaluation. Intra/inter-fraction patient motions may result in significant differences between the planned and the delivered dose. In this paper, we develop a method to incorporate the knowledge of intra/inter-fraction patient motion directly into the dose calculation. By decomposing the motion into a parallel (to beam direction) component and perpendicular (to beam direction) component, we show that the motion effects can be accounted for by simply modifying the fluence distribution (sinogram). After such modification, dose calculation is the same as those based on a static planning image. This method is superior to the 'dose-convolution' method because it is not based on 'shift invariant' assumption. Therefore, it deals with material heterogeneity and surface curvature very well. We test our method using extensive simulations, which include four phantoms, four motion patterns, and three plan beams. We compare our method with the 'dose-convolution' and the 'stochastic simulation' methods (gold standard). As for the homogeneous flat surface phantom, our method has similar accuracy as the 'dose-convolution' method. As for all other phantoms, our method outperforms the 'dose-convolution'. The maximum motion encoded dose calculation error using our method is within 4% of the gold standard. It is shown that a treatment planning system that is based on 'motion-encoded dose calculation' can incorporate random and systematic motion errors in a very simple fashion. Under this approximation, in principle, a planning target volume definition is not required, since it already accounts for the intra/inter-fraction motion variations and it automatically optimizes the cumulative dose rather than the single fraction dose.
Estimation of the Dose and Dose Rate Effectiveness Factor
NASA Technical Reports Server (NTRS)
Chappell, L.; Cucinotta, F. A.
2013-01-01
Current models to estimate radiation risk use the Life Span Study (LSS) cohort that received high doses and high dose rates of radiation. Transferring risks from these high dose rates to the low doses and dose rates received by astronauts in space is a source of uncertainty in our risk calculations. The solid cancer models recommended by BEIR VII [1], UNSCEAR [2], and Preston et al [3] is fitted adequately by a linear dose response model, which implies that low doses and dose rates would be estimated the same as high doses and dose rates. However animal and cell experiments imply there should be curvature in the dose response curve for tumor induction. Furthermore animal experiments that directly compare acute to chronic exposures show lower increases in tumor induction than acute exposures. A dose and dose rate effectiveness factor (DDREF) has been estimated and applied to transfer risks from the high doses and dose rates of the LSS cohort to low doses and dose rates such as from missions in space. The BEIR VII committee [1] combined DDREF estimates using the LSS cohort and animal experiments using Bayesian methods for their recommendation for a DDREF value of 1.5 with uncertainty. We reexamined the animal data considered by BEIR VII and included more animal data and human chromosome aberration data to improve the estimate for DDREF. Several experiments chosen by BEIR VII were deemed inappropriate for application to human risk models of solid cancer risk. Animal tumor experiments performed by Ullrich et al [4], Alpen et al [5], and Grahn et al [6] were analyzed to estimate the DDREF. Human chromosome aberration experiments performed on a sample of astronauts within NASA were also available to estimate the DDREF. The LSS cohort results reported by BEIR VII were combined with the new radiobiology results using Bayesian methods.
Tensor distance based multilinear locality-preserved maximum information embedding.
Liu, Yang; Liu, Yan; Chan, Keith C C
2010-11-01
This brief paper presents a unified framework for tensor-based dimensionality reduction (DR) with a new tensor distance (TD) metric and a novel multilinear locality-preserved maximum information embedding (MLPMIE) algorithm. Different from traditional Euclidean distance, which is constrained by the orthogonality assumption, TD measures the distance between data points by considering the relationships among different coordinates. To preserve the natural tensor structure in low-dimensional space, MLPMIE directly works on the high-order form of input data and iteratively learns the transformation matrices. In order to preserve the local geometry and to maximize the global discrimination simultaneously, MLPMIE keeps both local and global structures in a manifold model. By integrating TD into tensor embedding, TD-MLPMIE performs tensor-based DR through the whole learning procedure, and achieves stable performance improvement on various standard datasets. PMID:20876016
Test images for the maximum entropy image restoration method
NASA Technical Reports Server (NTRS)
Mackey, James E.
1990-01-01
One of the major activities of any experimentalist is data analysis and reduction. In solar physics, remote observations are made of the sun in a variety of wavelengths and circumstances. In no case is the data collected free from the influence of the design and operation of the data gathering instrument as well as the ever present problem of noise. The presence of significant noise invalidates the simple inversion procedure regardless of the range of known correlation functions. The Maximum Entropy Method (MEM) attempts to perform this inversion by making minimal assumptions about the data. To provide a means of testing the MEM and characterizing its sensitivity to noise, choice of point spread function, type of data, etc., one would like to have test images of known characteristics that can represent the type of data being analyzed. A means of reconstructing these images is presented.
Absorbed Gamma-Ray Doses due to Natural Radionuclides in Building Materials
Aguiar, Vitor A. P.; Medina, Nilberto H. [Instituto de Fisica, Universidade de Sao Paulo, SP (Brazil); Moreira, Ramon H.; Silveira, Marcilei A. G. [Departamento de Fisica, Centro Universitario da FEI, Sao Bernardo do Campo, SP (Brazil)
2010-05-21
This work is devoted to the application of high-resolution gamma-ray spectrometry in the study of the effective dose coming from naturally occurring radionuclides, namely {sup 40}K, {sup 232}Th and {sup 238}U, present in building materials such as sand, cement, and granitic gravel. Four models were applied to estimate the effective dose and the hazard indices. The maximum estimated effective dose coming from the three reference rooms considered is 0.90(45) mSv/yr, and maximum internal hazard index is 0.77(24), both for the compact clay brick reference room. The principal gamma radiation sources are cement, sand and bricks.
Control strategy for maximum anaerobic co-digestion performance.
García-Gen, Santiago; Rodríguez, Jorge; Lema, Juan M
2015-09-01
A control strategy for optimising the performance of anaerobic co-digestion in terms of methane productivity, digestate quality and process stability is presented. A linear programming approach is adopted to calculate the feeding of multiple substrates for maximum methane productivity, subjected to restrictions based on experimental and heuristic knowledge. Process stability is quantitatively assessed by an empirical diagnosis function comparing alkalinity ratio measurements against reference values (outputs between (-1,1]). A second empirical diagnosis function is defined to compare methane flow rate measurements against a reference value of maximum capacity (outputs between (0,1]). A variable-gain control function (outputs between (-1,1]), derived from the diagnosis functions, is defined to determine the quantitative change applied to the most active constraint of the substrate blend optimisation problem leading to a new set-point of feeding substrates blend. The control strategy works in a closed-loop architecture under which the process performance for each blend of substrates is continuously assessed. The system was successfully validated in a 1 m(3) hybrid Upflow Anaerobic Sludge Blanket - Anaerobic Filter (UASB-AF) reactor, treating blends of substrates (gelatine, glycerine and pig manure supernatant) at OLR values between 0.71 and 6.33 gCOD/L d over a period of 210 days at mesophilic conditions. PMID:26001824
Radiation Dose-Volume Effects in the Spinal Cord
Kirkpatrick, John P., E-mail: jkirk@radonc.duke.ed [Department of Radiation Oncology, Duke University Medical Center, Durham, NC (United States); Kogel, Albert J. van der [Department of Radiation Oncology, Radboud University Nijmegen Medical Centre, Nijmegen (Netherlands); Schultheiss, Timothy E. [Department of Radiation Physics, City of Hope Cancer Center, Duarte, CA (United States)
2010-03-01
Dose-volume data for myelopathy in humans treated with radiotherapy (RT) to the spine is reviewed, along with pertinent preclinical data. Using conventional fractionation of 1.8-2 Gy/fraction to the full-thickness cord, the estimated risk of myelopathy is <1% and <10% at 54 Gy and 61 Gy, respectively, with a calculated strong dependence on dose/fraction (alpha/beta = 0.87 Gy.) Reirradiation data in animals and humans suggest partial repair of RT-induced subclinical damage becoming evident about 6 months post-RT and increasing over the next 2 years. Reports of myelopathy from stereotactic radiosurgery to spinal lesions appear rare (<1%) when the maximum spinal cord dose is limited to the equivalent of 13 Gy in a single fraction or 20 Gy in three fractions. However, long-term data are insufficient to calculate a dose-volume relationship for myelopathy when the partial cord is treated with a hypofractionated regimen.
Dose rate, dose-equivalent rate, and quality factor in SLS-1
NASA Technical Reports Server (NTRS)
Badhwar, G. D.; Braby, L. A.; Cucinotta, F. A.; Atwell, W.
1992-01-01
A tissue-equivalent proportional counter (TEPC) sensitive to the lineal energy range of 0.26-300 keV micrometer-1 was flown on STS-40 (39 degrees x 278 km x 296 km) inside the Spacelab. This instrument was previously flown on STS-31 but was modified to provide a finer resolution at lower lineal energies to better map the South Atlantic Anomaly (SAA) protons. The instrument was turned on 6 June 1991, and operated for 7470 min (124.5 h). The flight duration was characterized by a very large number of X-ray solar flares and enhanced magnetic field fluctuations; however, no significant dose from the solar particles was measured at the location of this instrument. The flight data can be separated into trapped and galactic cosmic radiation parts. The dose rate, dose-equivalent rate and quality factor for trapped radiation were 4.21 +/- 0.03 mrad day-1, 7.72 +/- 0.05 mrem day-1, and 1.83 +/- 0.1, respectively. The dose rate, dose-equivalent rate, and quality factor for galactic cosmic radiation were 5.34 +/- 0.03 mrad day-1, 14.63 +/- 0.06 mrem day-1, and 2.74 +/- 0.1, respectively. The overall quality factor for the flight was 2.38. The dose from the GCR is higher than from SAA protons because of the high inclination and low altitude of this flight. The AP8MAX model of the trapped radiation gives a dose rate of 2.43 mrad day-1 and a quality factor of 1.77. The CREME solar maximum model of galactic cosmic radiation gives a dose rate of 2.54 mrad day-1 and a quality factor of 2.91. Thus the AP8MAX model underestimates the dose by a factor of 1.8 whereas the CREME model leads to an underestimation of the dose by a factor of 2. A comparison of the LET spectra using the AP8MAX model and galactic cosmic radiation transport codes shows only a qualitative agreement.
Federal Register 2010, 2011, 2012, 2013, 2014
2012-04-03
...Maximum Reactor Power Level, Florida Power & Light Company, Turkey Point, Units 3 and 4...and DPR-41, issued to Florida Power & Light Company (FPL or the licensee) for operation...nuclear reactor is a Westinghouse pressurized light-water reactor with three steam...
Li-Chuan Chen; A. Allen Bradley
2006-01-01
Because of limitations in sampling of atmospheric moisture, surface humidity is used to estimate atmospheric moisture availability for probable maximum precipitation (PMP) estimation. In practice, a pseudoadiabatic moisture profile is assumed to estimate precipitable water from surface 12-hour persisting dew point. This assumption was evaluated for the central United States using surface and upper air observations. The results show that
Three-Dimensional Compton Imaging Using List-Mode Maximum Likelihood Expectation Maximization
Shawn R. Tornga; Mohini W. Rawool Sullivan; John P. Sullivan
2009-01-01
Compton imaging is a gamma ray imaging technique that has many possible applications including homeland security and medical imaging. Using the Compton scattering formula the origin of a scattered gamma-ray can be localized to a point on the surface of a cone using a minimum of two position and energy measurements. List-mode Maximum likelihood expectation maximization (MLEM) is an iterative
To quantify explosiveness, we also measured the maximum change in C as one
Anlage, Steven
· To quantify explosiveness, we also measured the maximum change in C as one edge is added, or C product rule. · The competitive rule on directed networks has a less explosive transition than the same rule on undirected networks even though its transition point is delayed even further. Explosive
Filters, Random Fields and Maximum Entropy (FRAME): Towards a Unified Theory for Texture Modeling
Song Chun Zhu; Ying Nian Wu; David Mumford
1998-01-01
This article presents a statistical theory for texture modeling. This theory combines filtering theory and Markov random field modeling through the maximum entropy principle, and interprets and clarifies many previous concepts and methods for texture analysis and synthesis from a unified point of view. Our theory characterizes the ensemble of images I with the same texture appearance by a probability
Maximum Feedrate Interpolator for Multi-axis CNC Machining with Jerk Constraints
Paris-Sud XI, Université de
Maximum Feedrate Interpolator for Multi-axis CNC Machining with Jerk Constraints X. Beudaert, S name@lurpa.ens-cachan.fr Abstract A key role of the CNC is to perform the feedrate interpolation which for the next point along the path is computed. Examples and comparisons with an industrial CNC demonstrate
On the Relationships between Sum Score Based Estimation and Joint Maximum Likelihood Estimation
ERIC Educational Resources Information Center
del Pino, Guido; San Martin, Ernesto; Gonzalez, Jorge; De Boeck, Paul
2008-01-01
This paper analyzes the sum score based (SSB) formulation of the Rasch model, where items and sum scores of persons are considered as factors in a logit model. After reviewing the evolution leading to the equality between their maximum likelihood estimates, the SSB model is then discussed from the point of view of pseudo-likelihood and of…
Edward Shaw; Charles Scott; Luis Souhami; Robert Dinapoli; Robert Kline; Jay Loeffler; Nancy Farnan
2000-01-01
Purpose: To determine the maximum tolerated dose of single fraction radiosurgery in patients with recurrent previously irradiated primary brain tumors and brain metastases.Methods and Materials: Adults with cerebral or cerebellar solitary non-brainstem tumors ? 40 mm in maximum diameter were eligible. Initial radiosurgical doses were 18 Gy for tumors ? 20 mm, 15 Gy for those 21–30 mm, and 12
Molecular clock fork phylogenies: closed form analytic maximum likelihood solutions.
Chor, Benny; Snir, Sagi
2004-12-01
Maximum likelihood (ML) is increasingly used as an optimality criterion for selecting evolutionary trees, but finding the global optimum is a hard computational task. Because no general analytic solution is known, numeric techniques such as hill climbing or expectation maximization (EM) are used in order to find optimal parameters for a given tree. So far, analytic solutions were derived only for the simplest model-three-taxa, two-state characters, under a molecular clock. Quoting Ziheng Yang, who initiated the analytic approach,"this seems to be the simplest case, but has many of the conceptual and statistical complexities involved in phylogenetic estimation."In this work, we give general analytic solutions for a family of trees with four-taxa, two-state characters, under a molecular clock. The change from three to four taxa incurs a major increase in the complexity of the underlying algebraic system, and requires novel techniques and approaches. We start by presenting the general maximum likelihood problem on phylogenetic trees as a constrained optimization problem, and the resulting system of polynomial equations. In full generality, it is infeasible to solve this system, therefore specialized tools for the molecular clock case are developed. Four-taxa rooted trees have two topologies-the fork (two subtrees with two leaves each) and the comb (one subtree with three leaves, the other with a single leaf). We combine the ultrametric properties of molecular clock fork trees with the Hadamard conjugation to derive a number of topology dependent identities. Employing these identities, we substantially simplify the system of polynomial equations for the fork. We finally employ symbolic algebra software to obtain closed formanalytic solutions (expressed parametrically in the input data). In general, four-taxa trees can have multiple ML points. In contrast, we can now prove that each fork topology has a unique(local and global) ML point. PMID:15764563
Victor De Oliveira; Marco A. R. Ferreira
2011-01-01
This work describes a Gaussian Markov random field model that includes several previously proposed models, and studies properties\\u000a of its maximum likelihood (ML) and restricted maximum likelihood (REML) estimators in a special case. Specifically, for models\\u000a where a particular relation holds between the regression and precision matrices of the model, we provide sufficient conditions\\u000a for existence and uniqueness of ML
Winter, Helen; Egizi, Erica; Murray, Stephen; Erondu, Ngozi; Ginsberg, Ann; Rouse, Doris J; Severynse-Stevens, Diana; Pauli, Elliott
2015-02-01
This study assessed the effects of rifapentine or rifampin on the pharmacokinetics of a single dose of bedaquiline and its M2 metabolite in healthy subjects using a two-period single-sequence design. In period 1, subjects received a single dose of bedaquiline (400 mg), followed by a 28-day washout. In period 2, subjects received either rifapentine (600 mg) or rifampin (600 mg) from day 20 to day 41, as well as a single bedaquiline dose (400 mg) on day 29. The pharmacokinetic profiles of bedaquiline and M2 were compared over 336 h after the administration of bedaquiline alone and in combination with steady-state rifapentine or rifampin. Coadministration of bedaquiline with rifapentine or rifampin resulted in lower bedaquiline exposures. The geometric mean ratios (GMRs) and 90% confidence intervals (CIs) for the maximum observed concentration (Cmax), area under the concentration-time curve to the last available concentration time point (AUC0-t), and AUC extrapolated to infinity (AUC0-inf) of bedaquiline were 62.19% (53.37 to 72.47), 42.79% (37.77 to 48.49), and 44.52% (40.12 to 49.39), respectively, when coadministered with rifapentine. Similarly, the GMRs and 90% CIs for the Cmax, AUC0-t, and AUC0-inf of bedaquiline were 60.24% (51.96 to 69.84), 41.36% (37.70 to 45.36), and 47.32% (41.49 to 53.97), respectively, when coadministered with rifampin. The Cmax, AUC0-t, and AUC0-inf of M2 were also altered when bedaquiline was coadministered with rifapentine or rifampin. Single doses of bedaquiline, administered alone or with multiple doses of rifapentine or rifampin, were well tolerated, with no safety concerns related to coadministration. Daily administration of rifapentine to patients with tuberculosis presents the same drug interaction challenges as rifampin and other rifamycins. Strong inducers of the cytochrome P450 isoenzyme CYP3A4 should be avoided when considering the use of bedaquiline. (This study is registered at clinicaltrials.gov under identifier NCT02216331.). PMID:25512422
Ng, Pamela; Incekol, Diana; Lee, Roy; Paisley, Emma; Dara, Celina; Brandle, Ian; Kaufman, Marina; Chen, Christine; Trudel, Suzanne; Tiedemann, Rodger; Reece, Donna; Kukreti, Vishal
2015-08-01
Subcutaneous injection is now commonly used as a standard for bortezomib administration. The bortezomib (Velcade®) product monograph recommends that intravenous injections be prepared at a concentration of 1?mg/mL, while subcutaneous injections may be prepared at a concentration of 2.5?mg/mL. Many institutions and subcutaneous administration guidelines use 2?mL as the maximum volume for subcutaneous injection. Using 2?mL as the maximum volume for injection would mean that many patients receiving bortezomib will receive two injections during each visit with common dosing parameters. In this prospective study evaluating a change to subcutaneous administration, bortezomib 1?mg/mL was administered subcutaneously at a higher maximum of 3?mL per injection site. For 57 individual patients, 339 doses were administered. Skin reactions were noted in 42% with all reactions being Grade 1 or 2. Patients tolerated subcutaneous injections well and only four patients were switched back to intravenous route. This is the first time that subcutaneous bortezomib of a volume up to a maximum of 3?mL (bortezomib 3?mg) per injection site has been reported. This higher single dose is well tolerated with limited skin reactions, no significant hypotension and facilitates ease of administration with only 5 patients needing two injections per visit. If the maximum volume for injection was kept at 2?mL, a total of 46 patients would have received two injections per visit. PMID:24781451
Estimating maximum performance: effects of intraindividual variation.
Adolph, Stephen C; Pickering, Trevor
2008-04-01
Researchers often estimate the performance capabilities of animals using a small number of trials per individual. This procedure inevitably underestimates maximum performance, but few studies have examined the magnitude of this effect. In this study we explored the effects of intraindividual variation and individual sample size on the estimation of locomotor performance parameters. We measured sprint speed of the lizard Sceloporus occidentalis at two temperatures (20 degrees C and 35 degrees C), obtaining 20 measurements per individual. Speed did not vary temporally, indicating no training or fatigue effects. About 50% of the overall variation in speed at each temperature was due to intraindividual variation. While speed was repeatable, repeatability decreased slightly with increasing separation between trials. Speeds at 20 degrees C and 35 degrees C were positively correlated, indicating repeatability across temperatures as well. We performed statistical sampling experiments in which we randomly drew a subset of each individual's full set of 20 trials. As expected, the sample's maximum speed increased with the number of trials per individual; for example, five trials yielded an estimate averaging 89% of the true maximum. The number of trials also influenced the sample correlation between mean speeds at 20 degrees C and 35 degrees C; for example, five trials yielded a correlation coefficient averaging 90% of the true correlation. Therefore, intraindividual variation caused underestimation of maximal speed and the correlation between speeds across temperatures. These biases declined as the number of trials per individual increased, and depended on the magnitude of intraindividual variation, as illustrated by running sampling experiments that used modified data sets. PMID:18375858
Effect of Body Habitus on Radiation Dose During CT Fluoroscopy-Guided Spine Injections.
Viola, Ronald J; Nguyen, Giao B; Yoshizumi, Terry T; Stinnett, Sandra S; Hoang, Jenny K; Kranz, Peter G
2014-10-31
This study investigated the degree to which body habitus influences radiation dose during CT fluoroscopy (CTF)-guided lumbar epidural steroid injections (ESI). An anthropomorphic phantom containing metal oxide semiconductor field effect transistor (MOSFET) detectors was scanned at two transverse levels to simulate upper and lower lumbar CTF-guided ESI. Circumferential layers of adipose-equivalent material were sequentially added to model patients of three sizes: small (cross-sectional dimensions 25×30 cm), average (34×39 cm), and oversize (43×48 cm). Point dose rates to skin and internal organs within the CTF beam were measured. Scattered point dose rates 5 cm from the radiation beam were also measured. Direct point dose rates to the internal organs ranged from 0.05-0.11 mGy/10mAs in the oversized phantom, and from 0.18-0.43 mGy/10mAs in the small phantom. Skin direct point dose rates ranged from 0.69-0.71 mGy/10mAs in the oversized phantom and 0.88-0.94 mGy/10mAs in the small phantom. This represents a 180-310% increase in organ point dose rates and 24-36% increase in skin point dose rates in the small habitus compared with the oversize habitus. Scatter point dose rates increased by 83-117% for the small compared to the oversize phantom. Decreasing body habitus results in substantial increases in direct organ and skin point doses as well as scattered dose during simulated CTF-guided procedures. Failure to account for individual variations in body habitus will result in inaccurate dose estimation and inappropriate choice of tube current in CTF-guided procedures. PMID:25363254
Y. Suita; S. Tadakuma
2006-01-01
This paper describes driving performance of solar energy powered vehicle for a solar car rally. The first topic is to present one of the maximum power point tracking (MPPT) control for the vehicle which have been proposed by authors. This novel control based vehicle is estimated from the view point of energy consumption, optimal speed and the total running distance
The sun and heliosphere at solar maximum.
Smith, E J; Marsden, R G; Balogh, A; Gloeckler, G; Geiss, J; McComas, D J; McKibben, R B; MacDowall, R J; Lanzerotti, L J; Krupp, N; Krueger, H; Landgraf, M
2003-11-14
Recent Ulysses observations from the Sun's equator to the poles reveal fundamental properties of the three-dimensional heliosphere at the maximum in solar activity. The heliospheric magnetic field originates from a magnetic dipole oriented nearly perpendicular to, instead of nearly parallel to, the Sun's rotation axis. Magnetic fields, solar wind, and energetic charged particles from low-latitude sources reach all latitudes, including the polar caps. The very fast high-latitude wind and polar coronal holes disappear and reappear together. Solar wind speed continues to be inversely correlated with coronal temperature. The cosmic ray flux is reduced symmetrically at all latitudes. PMID:14615526
A spherical dose model for radiosurgery plan optimization
NASA Astrophysics Data System (ADS)
Cho, Paul S.; Gorkem Kuterdem, H.; Marks, Robert J., II
1998-10-01
Conventional 3D dose calculations for stereotactic radiosurgery involve integration of individual static beams comprising a set of arcs. For iterative optimization of multiple isocentre treatment, which requires repetitive dose calculations at a large number of sample points, the conventional method is too slow. To overcome this problem spherically symmetric dose distributions are assumed. The authors describe a spherical dose model derived from a parametrized convolution of the collimator width and a dose spread kernel. The method is fast and easy to implement requiring just a single empirically derived value. Furthermore, the model is differentiable with respect to the parameters to be optimized. This property is useful when the optimization strategies rely on gradient information.
New model for dwelling dose calculation using Monte Carlo integration.
Allam, K A
2009-02-01
A new methodology and computer model using Monte Carlo simulation for indoor dose calculation are developed. A room model of six rectangular slabs of finite thickness with door or window in each slab was used. Point-kernel photon transport model with self-absorption correction was applied for dose calculations. New software was designed and programmed using Pascal programming language, which was evaluated for standard room design. The calculated dose due to natural radionuclides in the concert walls has differences from the average model results of 0.21% for (238)U, 12.3% for (232)Th and 13.9% for (40)K; and the variability of specific dose rate with changing position density and composition of walls was studied. The new model has more flexibility for real dose calculation of any room structure and tailing, which is not given in the published models. PMID:19287012
Kessaris, N.; Nori, D. (Booth Memorial Medical Center, Flushing, NY (United States))
1993-03-20
The purpose of this study is twofold: First, to measure the dose distribution along the anterior and posterior rectal wall, compare them to the prescribed dose and establish the rectal length receiving the maximum dose. Second, to carry out in-phantom dose measurements in order to confirm that the dose planned is in fact the dose delivered. The dose distribution along the anterior and posterior rectal wall was measured for a group of 25 gynecologic cases treated with a vaginal cylinder, using the MicroSelectron High Dose Rate system. The method of measurement employed flexible vinyl rectal probes (1 or 2 cm diameter). Two fine plastic tubes, each containing 15 thermoluminescent dosimeters rods, were attached along the probe on opposite sides to measure the anterior and posterior rectal wall dose distributions. The dose distribution exhibited a sharp peak covering a rectal length from one to two centimeters. The peak doses for the anterior rectal wall ranged from 60% to 110% of prescribed dose. In-phantom measurements used layers of phantom material that contained a special source tube for the Iridium-192 source as well as thermoluminescent dosimeter tube(s) positioned at 1 cm distance from the source tube. The afterloader was programmed to deliver 300 cGy at 1 cm along its treatment length. The thermoluminescent dosimeter measurements showed good agreement with the doses expected on the basis of the treatment plan. 12 refs., 6 figs.
Sulieman, Abdelmoneim; Paroutoglou, Georgios; Kapsoritakis, Andreas; Kapatenakis, Anargeyros; Potamianos, Spiros; Vlychou, Marianna; Theodorou, Kiki
2011-01-01
Background/Aim: Endoscopic retrograde cholangiopancreatography (ERCP) is associated with a considerable radiation exposure for patients and staff. While optimization of the radiation dose is recommended, few studies have been published. The purpose of this study has been to measure patient and staff radiation dose, to estimate the effective dose and radiation risk using digital fluoroscopic images. Entrance skin dose (ESD), organ and effective doses were estimated for patients and staff. Materials and Methods: Fifty-seven patients were studied using digital X-ray machine and thermoluminescent dosimeters (TLD) to measure ESD at different body sites. Organ and surface dose to specific radiosensitive organs was carried out. The mean, median, minimum, third quartile and the maximum values are presented due to the asymmetry in data distribution. Results: The mean ESD, exit and thyroid surface dose were estimated to be 75.6 mGy, 3.22 mGy and 0.80 mGy, respectively. The mean effective dose for both gastroenterologist and assistant is 0.01 mSv. The mean patient effective dose was 4.16 mSv, and the cancer risk per procedure was estimated to be 2 × 10-5 Conclusion: ERCP with fluoroscopic technique demonstrate improved dose reduction, compared to the conventional radiographic based technique, reducing the surface dose by a factor of 2, without compromising the diagnostic findings. The radiation absorbed doses to the different organs and effective doses are relatively low. PMID:21196649
Faraone, Stephen V.; Spencer, Thomas J.; Kollins, Scott H.; Glatt, Stephen J.; Goodman, David
2012-01-01
Objective To explore dose–response effects of lisdexamfetamine dimesylate (LDX) treatment for ADHD. Method This was a 4-week, randomized, double-blinded, placebo-controlled, parallel-group, forced-dose titration study in adult participants, aged 18 to 55 years, meeting Diagnostic and Statistical Manual of Mental Disorders (4th ed., text rev.) criteria for ADHD. Results Nearly all participants assigned to an LDX dose achieved their assigned dose with the exception of about 4% of participants assigned to the 50 mg or 14% assigned to the 70 mg doses. Higher doses of LDX led to greater improvements in ADHD-rating scale scores, independent of prior pharmacotherapy. This was evident for both inattentive and hyperactive–impulsive symptoms. The authors found some evidence for an interaction between LDX dose and baseline severity of ADHD symptoms. Conclusion For LDX doses between 30 and 70 mg/d, the dose–response efficacy effect for LDX is not affected by prior pharmacotherapy, but patients with a greater severity of illness may benefit more from higher doses, especially for hyperactive–impulsive symptoms. The results do not provide information about doses above 70 mg/d, which is the maximum approved dose of LDX and the highest dose studied in ADHD clinical trials. PMID:21527575
Inhalation Anthrax: Dose Response and Risk Analysis
Thran, Brandolyn; Morse, Stephen S.; Hugh-Jones, Martin; Massulik, Stacey
2008-01-01
The notion that inhalation of a single Bacillus anthracis spore is fatal has become entrenched nearly to the point of urban legend, in part because of incomplete articulation of the scientific basis for microbial risk assessment, particularly dose-response assessment. Risk analysis (ie, risk assessment, risk communication, risk management) necessitates transparency: distinguishing scientific facts, hypotheses, judgments, biases in interpretations, and potential misinformation. The difficulty in achieving transparency for biothreat risk is magnified by misinformation and poor characterization of both dose-response relationships and the driving mechanisms that cause susceptibility or resistance to disease progression. Regrettably, this entrenchment unnecessarily restricts preparedness planning to a single response scenario: decontaminate until no spores are detectable in air, water, or on surfaces—essentially forcing a zero-tolerance policy inconsistent with the biology of anthrax. We present evidence about inhalation anthrax dose-response relationships, including reports from multiple studies documenting exposures insufficient to cause inhalation anthrax in laboratory animals and humans. The emphasis of the article is clarification about what is known from objective scientific evidence for doses of anthrax spores associated with survival and mortality. From this knowledge base, we discuss the need for future applications of more formal risk analysis processes to guide development of alternative non-zero criteria or standards based on science to inform preparedness planning and other risk management activities. PMID:18582166
Dose of Prophylactic Platelet Transfusions and Prevention of Hemorrhage
Slichter, Sherrill J.; Kaufman, Richard M.; Assmann, Susan F.; McCullough, Jeffrey; Triulzi, Darrell J.; Strauss, Ronald G.; Gernsheimer, Terry B.; Ness, Paul M.; Brecher, Mark E.; Josephson, Cassandra D.; Konkle, Barbara A.; Woodson, Robert D.; Ortel, Thomas L.; Hillyer, Christopher D.; Skerrett, Donna L.; McCrae, Keith R.; Sloan, Steven R.; Uhl, Lynne; George, James N.; Aquino, Victor M.; Manno, Catherine S.; McFarland, Janice G.; Hess, John R.; Leissinger, Cindy; Granger, Suzanne
2010-01-01
BACKGROUND We conducted a trial of prophylactic platelet transfusions to evaluate the effect of platelet dose on bleeding in patients with hypoproliferative thrombocytopenia. METHODS We randomly assigned hospitalized patients undergoing hematopoietic stem-cell transplantation or chemotherapy for hematologic cancers or solid tumors to receive prophylactic platelet transfusions at a low dose, a medium dose, or a high dose (1.1×1011, 2.2×1011, or 4.4×1011 platelets per square meter of body-surface area, respectively), when morning platelet counts were 10,000 per cubic millimeter or lower. Clinical signs of bleeding were assessed daily. The primary end point was bleeding of grade 2 or higher (as defined on the basis of World Health Organization criteria). RESULTS In the 1272 patients who received at least one platelet transfusion, the primary end point was observed in 71%, 69%, and 70% of the patients in the low-dose group, the medium-dose group, and the high-dose group, respectively (differences were not significant). The incidences of higher grades of bleeding, and other adverse events, were similar among the three groups. The median number of platelets transfused was significantly lower in the low-dose group (9.25×1011) than in the medium-dose group (11.25×1011) or the high-dose group (19.63×1011) (P = 0.002 for low vs. medium, P<0.001 for high vs. low and high vs. medium), but the median number of platelet transfusions given was significantly higher in the low-dose group (five, vs. three in the medium-dose and three in the high-dose group; P<0.001 for low vs. medium and low vs. high). Bleeding occurred on 25% of the study days on which morning platelet counts were 5000 per cubic millimeter or lower, as compared with 17% of study days on which platelet counts were 6000 to 80,000 per cubic millimeter (P<0.001). CONCLUSIONS Low doses of platelets administered as a prophylactic transfusion led to a decreased number of platelets transfused per patient but an increased number of transfusions given. At doses between 1.1×1011 and 4.4×1011 platelets per square meter, the number of platelets in the prophylactic transfusion had no effect on the incidence of bleeding. (ClinicalTrials.gov number, NCT00128713.) PMID:20164484
Determining the optimal dose in the development of anticancer agents.
Mathijssen, Ron H J; Sparreboom, Alex; Verweij, Jaap
2014-05-01
Identification of the optimal dose remains a key challenge in drug development. For cytotoxic drugs, the standard approach is based on identifying the maximum tolerated dose (MTD) in phase I trials and incorporating this to subsequent trials. However, this strategy does not take into account important aspects of clinical pharmacology. For targeted agents, the dose-effect relationships from preclinical studies are less obvious, and it is important to change the way these agents are developed to avoid recommending drug doses for different populations without evidence of differential antitumour effects in different diseases. The use of expanded cohorts in phase I trials to better define MTD and refine dose optimization should be further explored together with a focus on efficacy rather than toxicity-based predictions. Another key consideration in dose optimization is related to interindividual pharmacokinetic variability. High variability in intra-individual pharmacokinetics has been observed for many orally-administered drugs, especially those with low bioavailability, which might complicate identification of dose-effect relationships. End-organ dysfunction, interactions with other prescription drugs, herbal supplements, adherence, and food intake can influence pharmacokinetics. It is important these variables are identified during early clinical trials and considered in the development of further phase II and subsequent large-scale phase III studies. PMID:24663127
Use Dose Bricks Concept to Implement Nasopharyngeal Carcinoma Treatment Planning
Wu, Jia-Ming; Yu, Tsan-Jung; Yeh, Shyh-An; Chao, Pei-Ju; Huang, Chih-Jou
2014-01-01
Purpose. A “dose bricks” concept has been used to implement nasopharyngeal carcinoma treatment plan; this method specializes particularly in the case with bell shape nasopharyngeal carcinoma case. Materials and Methods. Five noncoplanar fields were used to accomplish the dose bricks technique treatment plan. These five fields include (a) right superior anterior oblique (RSAO), (b) left superior anterior oblique (LSAO), (c) right anterior oblique (RAO), (d) left anterior oblique (LAO), and (e) superior inferior vertex (SIV). Nondivergence collimator central axis planes were used to create different abutting field edge while normal organs were blocked by multileaf collimators in this technique. Results. The resulting 92% isodose curves encompassed the CTV, while maximum dose was about 115%. Approximately 50% volume of parotid glands obtained 10–15% of total dose and 50% volume of brain obtained less than 20% of total dose. Spinal cord receives only 5% from the scatter dose. Conclusions. Compared with IMRT, the expenditure of planning time and costing, “dose bricks” may after all be accepted as an optional implementation in nasopharyngeal carcinoma conformal treatment plan; furthermore, this method also fits the need of other nonhead and neck lesions if organ sparing and noncoplanar technique can be executed. PMID:24967395
Quantification of Proton Dose Calculation Accuracy in the Lung
Grassberger, Clemens; Daartz, Juliane; Dowdell, Stephen; Ruggieri, Thomas; Sharp, Greg; Paganetti, Harald
2014-01-01
Purpose Quantify the accuracy of a clinical proton treatment planning system (TPS) as well as Monte Carlo (MC) based dose calculation through measurements. Assess the clinical impact in a cohort of patients with tumors located in the lung. Methods A lung phantom and ion chamber array were used to measure the dose to a plane through a tumor embedded in lung and to determine the distal fall-off of the proton beam. Results were compared with TPS and MC calculations. Dose distributions in 19 patients (54 fields total) were simulated using MC and compared to the TPS algorithm. Results MC increases dose calculation accuracy in lung tissue compared to the TPS and reproduces dose measurements in the target to within ±2%. The average difference between measured and predicted dose in a plane through the center of the target is 5.6% for the TPS and 1.6% for MC. MC recalculations in patients show a mean dose to the clinical target volume on average 3.4% lower than the TPS, exceeding 5% for small fields. For large tumors MC also predicts consistently higher V5 and V10 to the normal lung, due to a wider lateral penumbra, which was also observed experimentally. Critical structures located distal to the target can show large deviations, though this effect is very patient-specific. Range measurements show that MC can reduce range uncertainty by a factor ~2: the average(maximum) difference to the measured range is 3.9mm(7.5mm) for MC and 7mm(17mm) for the TPS in lung tissue. Conclusion Integration of Monte Carlo dose calculation techniques into the clinic would improve treatment quality in proton therapy for lung cancer by avoiding systematic overestimation of target dose and underestimation of dose to normal lung. Additionally, the ability to confidently reduce range margins would benefit all patients through potentially lower toxicity. PMID:24726289
Paton, J; Jardine, E; McNeill, E; Beaton, S; Galloway, P; Young, D; Donaldson, M
2006-01-01
Background and Aims Clinical adrenal insufficiency has been reported with doses of inhaled fluticasone proprionate (FP) >400??g/day, the maximum dose licensed for use in children with asthma. Following two cases of serious adrenal insufficiency (one fatal) attributed to FP, adrenal function was evaluated in children receiving FP outwith the licensed dose. Methods Children recorded as prescribed FP ?500??g/day were invited to attend for assessment. Adrenal function was measured using the low dose Synacthen test (500?ng/1.73?m2 intravenously) and was categorised as: biochemically normal (peak cortisol response >500?nmol/l); impaired (peak cortisol ?500?nmol/l); or flat (peak cortisol ?500?nmol/l with increment of <200?nmol/l and basal morning cortisol <200?nmol/l). Results A total of 422 children had been receiving FP alone or in combination with salmeterol; 202 were not investigated (137 FP within license; 24 FP discontinued); 220 attended and 217 (age 2.6–19.3 years) were successfully tested. Of 194 receiving FP ?500??g/day, six had flat responses, 82 impaired responses, 104 were normal, and in 2 the LDST was unsuccessful. Apart from the index child, the other five with flat responses were asymptomatic; a further child with impairment (peak cortisol 296?nmol/l) had encephalopathic symptoms with borderline hypoglycaemia during an intercurrent illness. The six with flat responses and the symptomatic child were all receiving FP doses of ? 1000??g/day. Conclusion Overall, flat adrenal responses in association with FP occurred in 2.8% of children tested, all receiving ?1000??g/day, while impaired responses were seen in 39.6%. Children on above licence FP doses should have adrenal function monitoring as well as a written plan for emergency steroid replacement. PMID:16556614
Dourson, Michael; Reichard, John; Nance, Patricia; Burleigh-Flayer, Heather; Parker, Ann; Vincent, Melissa; McConnell, Ernest E
2014-04-01
1,4-Dioxane is found in consumer products and is used as a solvent in manufacturing. Studies in rodents show liver tumors to be consistently reported after chronic oral exposure. However, there were differences in the reporting of non-neoplastic lesions in the livers of rats and mice. In order to clarify these differences, a reread of mouse liver slides from the 1978 NCI bioassay on 1,4-dioxane in drinking water was conducted. This reread clearly identified dose-related non-neoplastic changes in the liver; specifically, a dose-related increase in the hypertrophic response of hepatocytes, followed by necrosis, inflammation and hyperplastic hepatocellular foci. 1,4-Dioxane does not cause point mutations, DNA repair, or initiation. However, it appears to promote tumors and stimulate DNA synthesis. Using EPA Guidelines (2005), the weight of the evidence suggests that 1,4-dioxane causes liver tumors in rats and mice through cytotoxicity followed by regenerative hyperplasia. Specific key events in this mode of action are identified. A Reference Dose (RfD) of 0.05mg/kgday is proposed to protect against regenerative liver hyperplasia based on a benchmark dose (BMD) approach. Based on this RfD, a maximum contaminant level goal of 350?g/L is proposed using a default relative source contribution for water of 20%. PMID:24491968
Janssen, Caroline H. C.; Kuijpers, Dirkjan; van Dijkman, Paul R. M.; Overbosch, Jelle; Willems, Tineke P.; Oudkerk, Matthijs
2007-01-01
Purpose of this study was to assess the additional value of first pass myocardial perfusion imaging during peak dose of dobutamine stress Cardiac-MR (CMR). Dobutamine Stress CMR was performed in 115 patients with an inconclusive diagnosis of myocardial ischemia on a 1.5 T system (Magnetom Avanto, Siemens Medical Systems). Three short-axis cine and grid series were acquired during rest and at increasing doses of dobutamine (maximum 40 ?g/kg/min). On peak dose dobutamine followed immediately by a first pass myocardial perfusion imaging sequence. Images were graded according to the sixteen-segment model, on a four point scale. Ninety-seven patients showed no New (Induced) Wall Motion Abnormalities (NWMA). Perfusion imaging showed absence of perfusion deficits in 67 of these patients (69%). Perfusion deficits attributable to known previous myocardial infarction were found in 30 patients (31%). Eighteen patients had NWMA, indicative for myocardial ischemia, of which 14 (78%) could be confirmed by a corresponding perfusion deficit. Four patients (22%) with NWMA did not have perfusion deficits. In these four patients NWMA were caused by a Left Bundle Branch Block (LBBB). They were free from cardiac events during the follow-up period (median 13.5 months; range 6–20). Addition of first-pass myocardial perfusion imaging during peak-dose dobutamine stress CMR can help to decide whether a NWMA is caused by myocardial ischemia or is due to an (inducible) LBBB, hereby preventing a false positive wall motion interpretation. PMID:17566871
Dose Calculation Evolution for Internal Organ Irradiation in Humans
Jimenez V, Reina A. [Universidad Central de Venezuela, Hospital Domingo Luciani, IVSS, Caracas, 1070 (Venezuela)
2007-10-26
The International Commission of Radiation Units (ICRU) has established through the years, a discrimination system regarding the security levels on the prescription and administration of doses in radiation treatments (Radiotherapy, Brach therapy, Nuclear Medicine). The first level is concerned with the prescription and posterior assurance of dose administration to a point of interest (POI), commonly located at the geometrical center of the region to be treated. In this, the effects of radiation around that POI, is not a priority. The second level refers to the dose specifications in a particular plane inside the patient, mostly the middle plane of the lesion. The dose is calculated to all the structures in that plane regardless if they are tumor or healthy tissue. In this case, the dose is not represented by a point value, but by level curves called 'isodoses' as in a topographic map, so you can assure the level of doses to this particular plane, but it also leave with no information about how this values go thru adjacent planes. This is why the third level is referred to the volumetrical description of doses so these isodoses construct now a volume (named 'cloud') that give us better assurance about tissue irradiation around the volume of the lesion and its margin (sub clinical spread or microscopic illness). This work shows how this evolution has resulted, not only in healthy tissue protection improvement but in a rise of tumor control, quality of life, better treatment tolerance and minimum permanent secuelae.
Nationwide measurements of cosmic-ray dose rates throughout Japan.
Nagaoka, K; Hiraide, I; Sato, K; Nakamura, T
2008-01-01
Cosmic-ray dose rates on the ground were measured throughout Japan. Neutron dose rates were measured as ambient dose equivalent rates (H*(10)) at 240 points using high-sensitivity neutron REM counters. In addition, cosmic rays directly ionising plus photon components were measured with an ionisation chamber. Time variation due to solar modulation during this study was corrected based on the results of sequential measurements. The effects of altitude, geomagnetic latitude, rainfall and snowfall on the neutron dose rate were inferred from the measured results. The mean value of the neutron dose rates (H*(10)) measured at 47 points of prefectural capitals in Japan was 4.0 nSv h(-1). The value corrected for the energy response of the REM counter was 6.4 nSv h(-1), corresponding to 4.8 nSv h(-1) as an effective dose (ISO). The mean value of the cosmic ray directly ionising plus photon components as an effective dose was 31 nSv h(-1). PMID:19151128
TOPICAL REVIEW: Dose calculations for external photon beams in radiotherapy
NASA Astrophysics Data System (ADS)
Ahnesjö, Anders; Mania Aspradakis, Maria
1999-11-01
Dose calculation methods for photon beams are reviewed in the context of radiation therapy treatment planning. Following introductory summaries on photon beam characteristics and clinical requirements on dose calculations, calculation methods are described in order of increasing explicitness of particle transport. The simplest are dose ratio factorizations limited to point dose estimates useful for checking other more general, but also more complex, approaches. Some methods incorporate detailed modelling of scatter dose through differentiation of measured data combined with various integration techniques. State-of-the-art methods based on point or pencil kernels, which are derived through Monte Carlo simulations, to characterize secondary particle transport are presented in some detail. Explicit particle transport methods, such as Monte Carlo, are briefly summarized. The extensive literature on beam characterization and handling of treatment head scatter is reviewed in the context of providing phase space data for kernel based and/or direct Monte Carlo dose calculations. Finally, a brief overview of inverse methods for optimization and dose reconstruction is provided.
Better Algorithms and Bounds for Directed Maximum Leaf Problems
Krivelevich, Michael
Better Algorithms and Bounds for Directed Maximum Leaf Problems Noga Alon 1 , Fedor V. Fomin 2 of Mathematical Sciences Chennai, 600 017, India saket@imsc.res.in Abstract. The Directed Maximum Leaf Out Maximum Leaf OutÂBranching problem is to find an outÂbranching in a given digraph with the maximum number
Maximum entropy, Nonadditive entropies and Biology
NASA Astrophysics Data System (ADS)
Presse, Steve
2014-03-01
Gibbs once presciently noted that the elegance and simplicity of the principles of statistical physics were worthy of independent development outside of thermodynamics. Biophysical systems -from the single cell to the single protein level- provide an ideal framework in which to test and apply far-from-equilibrium generalizations of statistical physics. Here we discuss two theoretical topics at the intersection of statistical physics and biology. First, we will describe a recipe for deriving, from first principles, probabilistic equations of motion from limited biophysical single particle tracking data. That is, we will show that maximum entropy principles can be used to determine the most likely statistical weights of trajectories from an ensemble of allowed system trajectories. For instance, using this reasoning, we can show under what circumstances Markov processes and chemical master equations rigorously follow from the data. Second, we will explore the logical implications of using a principle other than maximum entropy to select models (e.g. a model could be a trajectory ensemble in conformational space of a biomolecule) from non-equilibrium biophysical data. In particular, we will show that nonadditive entropy maximization can lead to biophysical models with features that go beyond what is warranted by the data.
Maximum power configuration for multireservoir chemical engines
NASA Astrophysics Data System (ADS)
Xia, Shaojun; Chen, Lingen; Sun, Fengrui
2009-06-01
A model of a multireservoir isothermal endoreversible chemical engine is put forward in this paper. Optimal control theory is used to determine the optimal configuration of the multireservoir isothermal endoreversible chemical engine for maximum power output. The optimal cycle consists of two constant chemical potential branches and two instantaneous constant mass-flux branches, which is independent of the number of mass reservoirs and the mass transfer law. The results show that, in order to obtain the maximum power output, some mass reservoirs should never connect to the working fluid in the mass transfer processes. A numerical example is provided for a linear mass transfer law three-mass-reservoir chemical engine. The effects of the potential changes of the intermediate mass reservoir on the optimal configuration of the chemical engine and the performance corresponding to the optimal configuration are analyzed. The obtained results are compared with those obtained for a multireservoir endoreversible heat engine. The object studied in this paper is general, and the results could provide some guidelines for optimal design and operation of real chemical engines.
Coulot, J; Ricard, M; Aubert, B
2003-08-21
Internal radiotherapy is currently focusing on beta emitters such as 90Y or 131I because of their high-energy emissions. However, conventional dosimetric methods (MIRD) are known to be limited for such applications. They are unable to take into account microscopic radionuclide distribution because standardized anthropomorphic phantoms are used, and absorbed dose is calculated at the organ level. New tools are therefore required for dose assessment at cellular and tissue level (10-100 microm). The purpose of this study was to validate, at this scale, a Monte Carlo usercode (DOSE3D), based on the MORSE combinatorial geometry package and the EGS code system. Dose point-kernel calculations in water were compared to those published by Cross et al and Simpkin and Mackie. They confirm that DOSE3D is a reliable tool for cellular dosimetry in various geometric configurations. PMID:12974576
NASA Astrophysics Data System (ADS)
Coulot, J.; Ricard, M.; Aubert, B.
2003-08-01
Internal radiotherapy is currently focusing on beta emitters such as 90Y or 131I because of their high-energy emissions. However, conventional dosimetric methods (MIRD) are known to be limited for such applications. They are unable to take into account microscopic radionuclide distribution because standardized anthropomorphic phantoms are used, and absorbed dose is calculated at the organ level. New tools are therefore required for dose assessment at cellular and tissue level (10-100 µm). The purpose of this study was to validate, at this scale, a Monte Carlo usercode (DOSE3D), based on the MORSE combinatorial geometry package and the EGS code system. Dose point-kernel calculations in water were compared to those published by Cross et al and Simpkin and Mackie. They confirm that DOSE3D is a reliable tool for cellular dosimetry in various geometric configurations.
A Bayesian dose-finding design for drug combination clinical trials based on the logistic model.
Riviere, Marie-Karelle; Yuan, Ying; Dubois, Frédéric; Zohar, Sarah
2014-01-01
In early phase dose-finding cancer studies, the objective is to determine the maximum tolerated dose, defined as the highest dose with an acceptable dose-limiting toxicity rate. Finding this dose for drug-combination trials is complicated because of drug-drug interactions, and many trial designs have been proposed to address this issue. These designs rely on complicated statistical models that typically are not familiar to clinicians, and are rarely used in practice. The aim of this paper is to propose a Bayesian dose-finding design for drug combination trials based on standard logistic regression. Under the proposed design, we continuously update the posterior estimates of the model parameters to make the decisions of dose assignment and early stopping. Simulation studies show that the proposed design is competitive and outperforms some existing designs. We also extend our design to handle delayed toxicities. PMID:24828456
Clinical experience with EPID dosimetry for prostate IMRT pre-treatment dose verification
McDermott, L. N.; Wendling, M.; Asselen, B. van; Stroom, J.; Sonke, J.-J.; Herk, M. van; Mijnheer, B. J. [Department of Radiation Oncology, Netherlands Cancer Institute-Antoni van Leeuwenhoek Hospital, Amsterdam (Netherlands)
2006-10-15
The aim of this study was to demonstrate how dosimetry with an amorphous silicon electronic portal imaging device (a-Si EPID) replaced film and ionization chamber measurements for routine pre-treatment dosimetry in our clinic. Furthermore, we described how EPID dosimetry was used to solve a clinical problem. IMRT prostate plans were delivered to a homogeneous slab phantom. EPID transit images were acquired for each segment. A previously developed in-house back-projection algorithm was used to reconstruct the dose distribution in the phantom mid-plane (intersecting the isocenter). Segment dose images were summed to obtain an EPID mid-plane dose image for each field. Fields were compared using profiles and in two dimensions with the {gamma} evaluation (criteria: 3%/3 mm). To quantify results, the average {gamma} ({gamma}{sub avg}), maximum {gamma} ({gamma}{sub max}), and the percentage of points with {gamma}<1(P{sub {gamma}}{sub lt1}) were calculated within the 20% isodose line of each field. For 10 patient plans, all fields were measured with EPID and film at gantry set to 0 deg. . The film was located in the phantom coronal mid-plane (10 cm depth), and compared with the back-projected EPID mid-plane absolute dose. EPID and film measurements agreed well for all 50 fields, with <{gamma}{sub avg}>=0.16, <{gamma}{sub max}>=1.00, and
=100%. Based on these results, film measurements were discontinued for verification of prostate IMRT plans. For 20 patient plans, the dose distribution was re-calculated with the phantom CT scan and delivered to the phantom with the original gantry angles. The planned isocenter dose (plan{sub iso}) was verified with the EPID (EPID{sub iso}) and an ionization chamber (IC{sub iso}). The average ratio, =98.7%. Seven plans revealed under-dosage in individual fields ranging from 5% to 16%, occurring at small regions of overlapping segments or along the junction of abutting segments (tongue-and-groove side). Test fields were designed to simulate errors and gave similar results. The agreement was improved after adjusting an incorrectly set tongue-and-groove width parameter in the treatment planning system (TPS), reducing <{gamma}{sub max}> from 2.19 to 0.80 for the test field. Mid-plane dose distributions determined with the EPID were consistent with film measurements in a slab phantom for all IMRT fields. Isocenter doses of the total plan measured with an EPID and an ionization chamber also agreed. The EPID can therefore replace these dosimetry devices for field-by-field and isocenter IMRT pre-treatment verification. Systematic errors were detected using EPID dosimetry, resulting in the adjustment of a TPS parameter and alteration of two clinical patient plans. One set of EPID measurements (i.e., one open and transit image acquired for each segment of the plan) is sufficient to check each IMRT plan field-by-field and at the isocenter, making it a useful, efficient, and accurate dosimetric tool.
Nieder, Carsten [Department of Radiation Oncology, Klinikum rechts der Isar, Technical University of Munich, Munich (Germany)]. E-mail: cnied@hotmail.com; Grosu, Anca L. [Department of Radiation Oncology, Klinikum rechts der Isar, Technical University of Munich, Munich (Germany); Stark, Sybille [Department of Radiation Oncology, Klinikum rechts der Isar, Technical University of Munich, Munich (Germany); Wiedenmann, Nicole [Department of Experimental Radiation Oncology, University of Texas M.D. Anderson Cancer Center, Houston, TX (United States); Busch, Raymonde [Institute for Medical Statistics and Epidemiology, Klinikum rechts der Isar, Technical University of Munich, Munich (Germany); Kneschaurek, Peter [Department of Radiation Oncology, Klinikum rechts der Isar, Technical University of Munich, Munich (Germany); Molls, Michael [Department of Radiation Oncology, Klinikum rechts der Isar, Technical University of Munich, Munich (Germany)
2006-03-15
Purpose: To examine retrospectively the maximum dose to the large skull base/intracranial arteries in fractionated stereotactic radiotherapy (FSRT) and intensity-modulated radiotherapy (IMRT), because of the potential risk of perfusion disturbances. Methods and Materials: Overall, 56 patients with tumors adjacent to at least one major artery were analyzed. Our strategy was to perform FSRT with these criteria: 1.8 Gy per fraction, planning target volume (PTV) enclosed by the 95% isodose, maximum dose 107%. Dose limits were applied to established organs at risk, but not the vessels. If FSRT planning failed to meet any of these criteria, IMRT was planned with the same objectives. Results: In 31 patients (median PTV, 23 cm{sup 3}), the FSRT plan fulfilled all criteria. No artery received a dose {>=}105%. Twenty-five patients (median PTV, 39 cm{sup 3}) needed IMRT planning. In 11 of 25 patients (median PTV, 85 cm{sup 3}), no plan satisfying all our criteria could be calculated. Only in this group, moderately increased maximum vessel doses were observed (106-110%, n = 7, median PTV, 121 cm{sup 3}). The median PTV dose gradient was 29% (significantly different from the 14 patients with satisfactory IMRT plans). Three of the four patients in this group had paranasal sinus tumors. Conclusion: The doses to the major arteries should be calculated in IMRT planning for critical tumor locations if a dose gradient >13% within the PTV can not be avoided because the PTV is large or includes air cavities.
NASA Astrophysics Data System (ADS)
Giles, David Matthew
Cone beam computed tomography (CBCT) is a recent development in radiotherapy for use in image guidance. Image guided radiotherapy using CBCT allows visualization of soft tissue targets and critical structures prior to treatment. Dose escalation is made possible by accurately localizing the target volume while reducing normal tissue toxicity. The kilovoltage x-rays of the cone beam imaging system contribute additional dose to the patient. In this study a 2D reference radiochromic film dosimetry method employing GAFCHROMIC(TM) model XR-QA film is used to measure point skin doses and dose profiles from the Elekta XVI CBCT system integrated onto the Synergy linac. The soft tissue contrast of the daily CBCT images makes adaptive radiotherapy possible in the clinic. In order to track dose to the patient or utilize on-line replanning for adaptive radiotherapy the CBCT images must be used to calculate dose. A Hounsfield unit calibration method for scatter correction is investigated for heterogeneity corrected dose calculation in CBCT images. Three Hounsfield unit to density calibration tables are used for each of four cases including patients and an anthropomorphic phantom, and the calculated dose from each is compared to results from the clinical standard fan beam CT. The dose from the scan acquisition is reported and the effect of scan geometry and total output of the x-ray tube on dose magnitude and distribution is shown. The ability to calculate dose with CBCT is shown to improve with the use of patient specific density tables for scatter correction, and for high beam energies the calculated dose agreement is within 1%.
Single dose tetracycline in cholera.
Islam, M R
1987-01-01
A randomised clinical trial was carried out to explore the efficacy of single dose tetracycline therapy in cholera. One hundred and eighteen adult patients were assigned to receive either tetracycline in a single 1 g, or a single 2 g dose, or tetracycline 500 mg every six hours four times, or no antibiotics as controls. The means of total liquid stool volumes after treatment were lower in the single 1 g dose group (168.0 +/- 20.9 ml/kg), in single 2 g dose group (229.5 +/- 45.6 ml/kg), and multiple dose group (214 +/- 28.5 ml/kg), than in the control group (499.1 +/- 56.5 ml/kg) (p less than 0.05). Similarly, the means of durations of diarrhoea and intravenous fluid requirements were significantly lower in the single dose and multiple dose tetracycline groups, than in the controls (p less than 0.05). The mean durations of excretion of Vibrio cholerae were significantly shortened from 3.9 +/- 0.2 days in the control group to 1.9 +/- 0.2 days in single 1 g dose, to 2.2 +/- 0.4 days in single 2 g dose and 1.3 +/- 0.1 days in multiple dose groups, respectively (p less than 0.05). Three patients in the single 1 g dose group and two patients in single 2 g dose group had clinical relapses with excretion of V cholerae during the relapses, but this was not significantly more frequent than that in the multiple dose group (p greater than 0.05). These findings suggest that although multiple dose tetracycline therapy remains the best choice, a single dose of either 1 g or 2 g tetracycline appears to be a reasonable alternative for the treatment of cholera as an adjunct to rehydration therapy. PMID:3311904
Zi-Niu Wu
2013-10-02
For many natural process of growth, with the growth rate independent of size due to Gibrat law and with the growth process following a log-normal distribution, the ratio between the time (D) for maximum value and the time (L) for maximum growth rate (inflexion point) is then equal to the square root of the base of the natural logarithm (e^{1/2}). On the logarithm scale this ratio becomes one half ((1/2)). It remains an open question, due to lack of complete data for various cases with restricted growth, whether this e^{1/2} ratio can be stated as e^{1/2}-Law. Two established examples already published, one for an epidemic spreading and one for droplet production, support however this ratio. Another example appears to be the height of humain body. For boys the maximum height occurs near 23 years old while the maximum growth rate is at the age near 14, and there ratio is close to e^{1/2}. The main theoretical base to obtain this conclusion is problem independent, provided the growth process is restricted, such as public intervention to control the spreading of communicable epidemics, so that an entropy is associated with the process and the role of dissipation, representing the mechanism of intervention, is maximized. Under this formulation the principle of maximum rate of entropy production is used to make the production process problem independent.
Haney, J
2015-02-01
The mouse dose at the lowest water concentration used in the National Toxicology Program hexavalent chromium (CrVI) drinking water study (NTP, 2008) is about 74,500 times higher than the approximate human dose corresponding to the 35-city geometric mean reported in EWG (2010) and over 1000 times higher than that based on the highest reported tap water concentration. With experimental and environmental doses differing greatly, it is a regulatory challenge to extrapolate high-dose results to environmental doses orders of magnitude lower in a meaningful and toxicologically predictive manner. This seems particularly true for the low-dose extrapolation of results for oral CrVI-induced carcinogenesis since dose-dependent differences in the dose fraction absorbed by mouse target tissues are apparent (Kirman et al., 2012). These data can be used for a straightforward adjustment of the USEPA (2010) draft oral slope factor (SFo) to be more predictive of risk at environmentally-relevant doses. More specifically, the evaluation of observed and modeled differences in the fraction of dose absorbed by target tissues at the point-of-departure for the draft SFo calculation versus lower doses suggests that the draft SFo be divided by a dose-specific adjustment factor of at least an order of magnitude to be less over-predictive of risk at more environmentally-relevant doses. PMID:25445295
Elisabeth I. Heath; Keith Bible; Robert E. Martell; Daniel C. Adelman; Patricia M. LoRusso
2008-01-01
Summary \\u000a Purpose: SNS-032, (formerly BMS-387032) is a potent and selective inhibitor of cyclin-dependent kinases (CDK) 2, 7 and 9. The primary\\u000a objective of the study was to establish the maximum tolerated dose (MTD), the maximum administered dose (MAD), dose limiting\\u000a toxicity (DLT), and the recommended phase 2 dose for SNS-032 when administered as a weekly 1-h infusion. The secondary objective
Vibration and acoustic radiation from point excited spherical shells
E. H. Wong; S. I. Hayek
1982-01-01
Two thin aluminum spherical shells were excited by an impedance head at the apex, simulating a mechanical point excitation. The driving point admittance frequency spectra of the shells when excited in air were recorded and at each maximum, the mode shape at resonance was plotted. These measurements were repeated when the shell was suspended in a large water tank. The
Dahle, Jostein [Department of Radiation Biology, Norwegian Radium Hospital, Montebello, Oslo (Norway)], E-mail: jostein.dahle@rr-research.no; Bruland, Oyvind S. [University of Oslo and Department of Oncology, Norwegian Radium Hospital, Montebello, Oslo (Norway); Larsen, Roy H. [Department of Radiation Biology, The Norwegian Radium Hospital, Montebello, Oslo (Norway)
2008-09-01
Purpose: To determine the relative biologic effects (RBE) of {alpha}-particle radiation from {sup 227}Th-rituximab and of {beta}-radiation from {sup 90}Y-tiuexetan-ibritumomab (Zevalin) compared with external beam X-radiation in the Raji lymphoma xenograft model. Methods and Materials: Radioimmunoconjugates were administered intravenously in nude mice with Raji lymphoma xenografts at different levels of activity. Absorbed dose to tumor was estimated by separate biodistribution experiments for {sup 227}Th-rituximab and Zevalin. Tumor growth was measured two to three times per week after injection or X-radiation. Treatment-induced increase in growth delay to reach tumor volumes of 500 and 1,000 mm{sup 3}, respectively, was used as an end point. Results: The absorbed radiation dose-rate in tumor was slightly more than 0.1 Gy/d for the first week following injection of {sup 227}Th-rituximab, and thereafter gradually decreased to 0.03 Gy/d at 21 days after injection. For treatment with Zevalin the maximum dose-rate in tumor was achieved already 6 h after injection (0.2 Gy/d), and thereafter decreased to 0.01 Gy/d after 7 days. The relative biologic effect was between 2.5 and 7.2 for {sup 227}Th-rituximab and between 1 and 1.3 for Zevalin. Conclusions: Both at low doses and low-dose-rates, the {sup 227}Th-rituximab treatment was more effective per absorbed radiation dose unit than the two other treatments. The considerable effect at low doses suggests that the best way to administer low-dose-rates, {alpha}-emitting radioimmunoconjugates is via multiple injections.
Das, Mini; Gifford, Howard C.; O'Connor, J. Michael; Glick, Stephen J.
2011-01-01
We examined the application of an iterative penalized maximum likelihood (PML) reconstruction method for improved detectability of microcalcifications (MCs) in digital breast tomosynthesis (DBT). Localized receiver operating characteristic (LROC) psychophysical studies with human observers and 2D image slices were conducted to evaluate the performance of this reconstruction method and to compare its performance against the commonly used Feldkamp FBP algorithm. DBT projections were generated using rigorous computer simulations that included accurate modeling of the noise and detector blur. Acquisition dose levels of 0.7, 1.0 and 1.5 mGy in a 5-cm-thick compressed breast were tested. The defined task was to localize and detect MC clusters consisting of seven MCs. The individual MC diameter was 150 ?m. Compressed-breast phantoms derived from CT images of actual mastectomy specimens provided realistic background structures for the detection task. Four observers each read 98 test images for each combination of reconstruction method and acquisition dose. All observers performed better with the PML images than with the FBP images. With the acquisition dose of 0.7 mGy, the average areas under the LROC curve (AL) for the PML and FBP algorithms were 0.69 and 0.43, respectively. For the 1.0-mGy dose, the values of AL were 0.93 (PML) and 0.7 (FBP), while the 1.5-mGy dose resulted in areas of 1.0 and 0.9 respectively for the PML and FBP algorithms. A 2D analysis of variance applied to the individual observer areas showed statistically significant differences (at a significance level of 0.05) between the reconstruction strategies at all three dose levels. There were no significant differences in observer performance for any of the dose levels. PMID:21041158
High-dose midazolam infusion for refractory status epilepticus
Fernandez, Andres; Lantigua, Hector; Lesch, Christine; Shao, Belinda; Foreman, Brandon; Schmidt, J. Michael; Hirsch, Lawrence J.; Mayer, Stephan A.
2014-01-01
Objective: This study compares 2 treatment protocols allowing low vs high continuous IV midazolam (cIV-MDZ) doses. Methods: We compared adults with refractory status epilepticus treated with a protocol allowing for high-dose cIV-MDZ (n = 100; 2002–2011) with those treated with the previous lower-dose cIV-MDZ (n = 29; 1996–2000). We collected data on baseline characteristics, cIV-MDZ doses, seizure control, hospital course, and outcome. Results: Median maximum cIV-MDZ dose was 0.4 mg/kg/h (interquartile range [IQR] 0.2, 1.0) for the high-dose group and 0.2 mg/kg/h (IQR 0.1, 0.3) for the low-dose group (p < 0.001) with similar duration of infusion. Median time from status epilepticus onset to cIV-MDZ start was 1 day (IQR 1, 3) for the high-dose group and 2 days (IQR 1, 5) for the low-dose group (p = 0.016). “Withdrawal seizures” (occurring within 48 hours of discontinuation of cIV-MDZ) were less frequent in the high-dose group (15% vs 64%, odds ratio 0.10, 95% confidence interval 0.03–0.27). “Ultimate cIV-MDZ failure” (patients requiring change to a different cIV antiepileptic medication) and hospital complications were not different between groups. Hypotension was more frequent with higher cIV-MDZ doses but was not associated with worse outcome. Discharge mortality was lower in the high-dose group (40% vs 62%, odds ratio 0.34, 95% confidence interval 0.13–0.92 in multivariate analysis). Conclusions: High-dose cIV-MDZ treatment of refractory status epilepticus can be performed safely, is associated with a lower seizure rate after cIV-MDZ discontinuation, and may be associated with lower mortality than traditional lower-dose protocols. Classification of evidence: This study provides Class III evidence that midazolam at higher infusion rates is associated with a reduction in seizure recurrence within 48 hours after discontinuation and may be associated with lower mortality. PMID:24363133
Diffusivity Maximum in a Reentrant Nematic Phase
Stieger, Tillmann; Mazza, Marco G.; Schoen, Martin
2012-01-01
We report molecular dynamics simulations of confined liquid crystals using the Gay–Berne–Kihara model. Upon isobaric cooling, the standard sequence of isotropic–nematic–smectic A phase transitions is found. Upon further cooling a reentrant nematic phase occurs. We investigate the temperature dependence of the self-diffusion coefficient of the fluid in the nematic, smectic and reentrant nematic phases. We find a maximum in diffusivity upon isobaric cooling. Diffusion increases dramatically in the reentrant phase due to the high orientational molecular order. As the temperature is lowered, the diffusion coefficient follows an Arrhenius behavior. The activation energy of the reentrant phase is found in reasonable agreement with the reported experimental data. We discuss how repulsive interactions may be the underlying mechanism that could explain the occurrence of reentrant nematic behavior for polar and non-polar molecules. PMID:22837730
Measurement of doses to the extremities of nuclear medicine staff
NASA Astrophysics Data System (ADS)
Shousha, Hany A.; Farag, Hamed; Hassan, Ramadan A.
Medical uses of ionizing radiation now represent>95% of all man-made radiation exposure, and is the largest single radiation source after natural background radiation. Therefore, it is important to quantify the amount of radiation received by occupational individuals to optimize the working conditions for staff, and further, to compare doses in different departments to ensure compatibility with the recommended standards. For some groups working with unsealed sources in nuclear medicine units, the hands are more heavily exposed to ionizing radiation than the rest of the body. A personal dosimetry service runs extensively in Egypt. But doses to extremities have not been measured to a wide extent. The purpose of this study was to investigate the equivalent radiation doses to the fingers for five different nuclear medicine staff occupational groups for which heavy irradiation of the hands was suspected. Finger doses were measured for (1) nuclear medicine physicians, (2) technologists, (3) nurses and (4) physicists. The fifth group contains three technicians handling 131I, while the others handled 99mTc. Each staff member working with the radioactive material wore two thermoluminescent dosimeters (TLDs) during the whole testing period, which lasted from 1 to 4 weeks. Staff performed their work on a regular basis throughout the month, and mean annual doses were calculated for these groups. Results showed that the mean equivalent doses to the fingers of technologist, nurse and physicist groups were 30.24±14.5, 30.37±17.5 and 16.3±7.7 ?Sv/GBq, respectively. Equivalent doses for the physicians could not be calculated per unit of activity because they did not handle the radiopharmaceuticals directly. Their doses were reported in millisieverts (mSv) that accumulated in one week. Similarly, the dose to the fingers of individuals in Group 5 was estimated to be 126.13±38.2 ?Sv/GBq. The maximum average finger dose, in this study, was noted in the technologists who handled therapeutic 131I (2.5 mSv). In conclusion, the maximum expected annual dose to extremities is less than the annual limit (500 mSv/y).
ALLDOS: a computer program for calculation of radiation doses from airborne and waterborne releases
Strenge, D.L.; Napier, B.A.; Peloquin, R.A.; Zimmerman, M.G.
1980-10-01
The computer code ALLDOS is described and instructions for its use are presented. ALLDOS generates tables of radiation doses to the maximum individual and the population in the region of the release site. Acute or chronic release of radionuclides may be considered to airborne and waterborne pathways. The code relies heavily on data files of dose conversion factors and environmental transport factors for generating the radiation doses. A source inventory data library may also be used to generate the release terms for each pathway. Codes available for preparation of the dose conversion factors are described and a complete sample problem is provided describing preparation of data files and execution of ALLDOS.