bluuebunny/crossref_metadata_2025 huggingface dataset:
How to Treat Hypertension in Patients With Coronary Heart Disease disease.
Authors: Moser Marvin , Wright Jackson T. , Victor Ronald G. , Handler Joel
Published: May 2008

Following a hypertension symposium in Los Angeles in October 2007, a panel was convened to discuss how to treat hypertension in patients with coronary artery disease or with evidence of multiple major risk factors for coronary heart disease. Marvin Moser, MD, Clinical Professor of Medicine at the Yale University School of Medicine, New Haven, CT, moderated the discussion. Jackson T. Wright Jr, MD, PhD, Professor of Medicine, Program Director of William T. Dahms Clinical Research, and Director of the Clinical Hypertension Program at Case Western Reserve University, Cleveland, OH; Ronald G. Victor, MD, Professor and Division Chief, Hypertension, University of Texas Southwestern Medical Center, Dallas, TX; and Joel Handler, MD, Hypertension Lead, Care Management Institute, Kaiser Permanente, Anaheim, CA, participated in the discussion.
COPD ‘diagnosis’ based on spirometric reference equations
Authors: Olofson Jan , Bake Björn , Tengelin Maria Nilsson , Houltz Birgitta
Published: May 2008

Introduction:  Chronic obstructive pulmonary disease (COPD) is suspected if the ratio between forced expired volume in 1 s (FEV1) and forced vital capacity is below 0.7 after bronchodilatation, according to the Global Initiative for Chronic Obstructive Lung Disease (GOLD). As this ratio varies with age and gender, the lower limit of normality (LLN) of appropriate reference equations appears more adequate.

Objectives:  To study the prevalences of suspected COPD according to the GOLD criterion and various reference equations in a well‐defined population sample.

Methods:  Spirometries obtained in a random population sample of 598 men, 50 or 60 years of age, were analysed. The prevalences of suspected COPD were calculated according to the GOLD criterion and the LLNs of four Nordic and two European reference equations.

Results:  The GOLD criterion resulted in prevalences of COPD of 9.3% and 23.7% in the 50‐ and 60‐year‐old never‐smokers, respectively. Depending on the reference equation, the calculated prevalences of COPD varied between 9.3% and 23.4% and 12.0% and 39.1% among all of the 50‐ and 60‐year‐old men, respectively.

Conclusions:  The GOLD criterion is inadequate because of substantial overestimation in 60‐year‐old never‐smokers. LLNs of the various reference equations are unreliable because of obvious lack of consistency. Spirometric criteria for airway obstruction, and suspicion of COPD, therefore need to be revised.

Please cite this paper as: Olofson J, Bake B, Tengelin MN and Houltz B. COPD ‘diagnosis’ based on spirometric reference equations. The Clinical Respiratory Journal 2008; 2: 214–219.
How Are Basic Belief‐Forming Methods Justified?
Authors: ENOCH DAVID , SCHECHTER JOSHUA
Published: May 2008

In this paper, we present an account of in virtue of what thinkers are justified in employing certain basic belief‐forming methods. The guiding idea is inspired by Reichenbach’s work on induction. There are certain projects in which thinkers are rationally required to engage. Thinkers are epistemically justified in employing a belief‐forming method that is indispensable for successfully engaging in such a project. We present a detailed account based on this intuitive thought, and address objections to it. We conclude by commenting on the implications that our account may have for other important epistemological debates.
Contextualism and the Factivity Problem
Authors: BAUMANN PETER
Published: May 2008

Epistemological contextualism ‐ the claim that the truth‐value of knowledge‐attributions can vary with the context of the attributor ‐ has recently faced a whole series of objections. The most serious one, however, has not been discussed much so far: the factivity objection. In this paper, I explain what the objection is and present three different versions of the objection. I then show that there is a good way out for the contextualist. However, in order to solve the problem the contextualist has to accept a relationalist version of contextualism.
Extended Green's Solution for the Stresses in an Infinite Plate With Two Equal or Unequal Circular Holes
Authors: Hoang Son K. , Abousleiman Younane N.
Published: May 2008

The distribution of stress in an isotropic and infinitely large plate perforated by circular holes has long attracted attention from both mathematical and engineering standpoints. Unfortunately, almost all existing solutions are only applicable to stress-free conditions at the boundary of the holes, which is not always the case in engineering applications. In an attempt to cover a wider range of applications, this paper presents the exact explicit solution for the stress distribution in an infinite plate containing two equal/unequal circular holes subjected to general in-plane stresses at infinity and internal pressures inside the holes, following the approach proposed by Green (1940, “General Bi-Harmonic Analysis for a Plate Containing Circular Holes,” Proc. R. Soc. London, Ser. A, 176(964), pp. 121–139). The newly derived general solution has been verified not only with published solutions for special cases but also qualitatively with a comparable experimental testing program. In addition, some numerical examples are also provided to offer insight into the complexity of the interplay of parameters.
The Effects of
Vibrations on Particle Motion in a Viscous Fluid
Cell
Authors: Hassan Samer , Kawaji Masahiro
Published: May 2008

The effects of small vibrations on particle motion in a viscous fluid cell have been investigated experimentally and theoretically. A steel particle was suspended by a thin wire at the center of a fluid cell, and the cell was vibrated horizontally using an electromagnetic actuator and an air bearing stage. The vibration-induced particle amplitude measurements were performed for different fluid viscosities (58.0cP and 945cP), and cell vibration amplitudes and frequencies. A viscous fluid model was also developed to predict the vibration-induced particle motion. This model shows the effect of fluid viscosity compared to the inviscid model, which was presented earlier by Hassan et al. (2004, “The Effects of Vibrations on Particle Motion in an Infinite Fluid Cell,” ASME J. Appl. Mech., 73(1), pp. 72–78) and validated using data obtained for water. The viscous model with modified drag coefficients is shown to predict well the particle amplitude data for the fluid viscosities of 58.5cP and 945cP. While there is a resonance frequency corresponding to the particle peak amplitude for oil (58.0cP), this phenomenon disappeared for glycerol (945cP). This disappearance of resonance phenomenon is explained by referring to the theory of mechanical vibrations of a mass-spring-damper system. For the sinusoidal particle motion in a viscous fluid, the effective drag force has been obtained, which includes the virtual mass force, drag force proportional to the velocity, and the Basset or history force terms.
Dynamic Biaxial Plastic Buckling of Circular Shells
Authors: Abdul-Latif A. , Baleh R.
Published: May 2008

Of particular interest is the experimental study of the complex dynamic plastic buckling of circular metallic shells and their energy absorption capacity. Initially proposed by Baleh and Abdul-Latif (2006), “Quasi-Stalic Biaxial Plastic Buckling of Tubular Structures used as an Energy Absorber,” ASME J. Appl. Mech., 74, pp. 638–635, the novel idea, which aims to enhance the strength properties of materials, is extended for studying the biaxial plastic dynamic buckling behavior of circular shells. It can be assumed that changes in local deformation mechanisms, which reflect this enhancement in the strength properties, are mainly governed by the loading path complexity. The question of whether the performance of dynamic axially crushed tubes could be further improved by using the developed device (the absorption par compression-torsion plastique (ACTP)) generating a biaxial loading path (combined compression and torsion) from a uniaxial loading. A key point emerging from this study is that the structure impact response (i.e., the plastic flow mechanism and the absorbed energy) is influenced by the loading rate coupled with the biaxial loading complexity. In this study, three different metallic circular shells made from copper, aluminum, and mild steel, having distinct geometrical parameters, are extensively investigated. The obtained results show that the higher the biaxial loading complexity provided by the ACTP applied, the greater the energy absorbed by the copper, aluminum, and mild-steel structures. Thus, it is easy to demonstrate that the enhancement in the energy absorption, notably in the case of aluminum, is higher than 150%, in favor of the most complicated loading path (i.e., biaxial 45deg case) compared to the classical uniaxial case. Moreover, the deformation mode for the tested materials is slightly sensitive to the torsion amplitude in dynamic loading, contrary to the quasistatic one.
Three-Dimensional Constitutive Creep/Relaxation Model of Carbon Cathode Materials
Authors: Picard D. , Fafard M. , Soucy G. , Bilodeau J.-F.
Published: May 2008

In order to adequately simulate the behavior of a Hall–Héroult electrolysis cell, a finite element model must take into account the properties of each material forming the cell structure and those contained in it. However, there is some lack of full knowledge of the mechanical behavior of these materials, e.g., the long term viscoelastic (creep/relaxation) behavior of the carbon cathode. In this present paper, a three-dimensional viscoelastic model is devised and proposed, being ready to be implemented in a finite element code. This 3D viscoelastic model was developed from the thermodynamics of irreversible processes, where the selection of the model’s internal variables was based on a phenomenological approach. The model has been developed at a particular reference state; therefore, the model parameters are represented by constant constitutive tensors. The model’s particular parameters were identified for three different types of cathode carbon, i.e., semigraphitic, graphitic, and graphitized.
Anniversary Paper: AAPM Education Council: Looking back or looking forward
Authors: Mower Herbert W. , Yester Michael J.
Published: May 2008

As we celebrate the 50th year of the American Association of Physicists in Medicine (AAPM), what better time to look back at our development as well as to look forward to the opportunities that lie ahead. Here the authors will review some of the achievements of the Education Council and show how the activities are helping to shape the future educational goals and opportunities of the AAPM and the medical physics profession. Much of the work of the Education Council is carried out by the various committees and subcommittees that make up the Council or have a liaison relationship with the Council.
Normalized maximum intensity time ratio maps and morphological descriptors for assessment of malignancy in MR mammography
Authors: Ertas Gokhan , Gulcur H. Ozcan , Tunaci Mehtap
Published: May 2008

Effectiveness of morphological descriptors based on normalized maximum intensity‐time ratio (nMITR) maps generated using a pixel moving mask on dynamic contrast‐enhanced magnetoresistance (MR) mammograms are studied for assessment of malignancy. After a rough indication of volume of interest on the nMITR maps, lesions are automatically segmented. Two‐dimensional (2D) convexity, normalized complexity, extent, and eccentricity as well as three‐dimensional (3D) versions of these descriptors and contact surface area ratio are computed. On a data set consisting of dynamic contrast‐enhanced MR DCE‐MR mammograms from 51 women that contain 26 benign and 32 malignant lesions, 3D convexity, complexity, and extent are found to reflect aggressiveness of malignancy better than 2D descriptors. Contact surface area ratio which is easily adaptable to different imaging resolutions is found to be the most significant and accurate descriptor ( sensitivity, specificity, positive predictive values, and negative predictive values).
Potential use of P‐32 ophthalmic applicator: Monte Carlo simulations for design and dosimetry
Authors: Park Yang Kyun , Ye Sung‐Joon , Kim Il Han , Wee Won Ryang , Kim Mee Kum , Han Hyon Soo , Son Kwang‐Jae , Park Ul Jae
Published: May 2008

Postoperative ‐irradiation after pterygium excision has been considered a valuable therapeutic procedure to reduce the recurrence rate. Recently, it was reported that ‐irradiation also substantially reduced the risk of surgical failure after glaucoma surgery. Pure ‐irradiation using a applicator has been almost exclusively used for this purpose. As an alternative to ‐irradiation, we propose treatment with betas of a source. While has a lower maximum energy than , it has an average energy comparable to that of . Furthermore, it can be produced easily in a nuclear reactor by neutron activation and is considered a less hazardous material. Monte Carlo simulations for the dosimetry of proposed applicators were performed using the MCNP5 code. The structure and dimension of the applicators were based on those of the applicators currently available, while medical plastic encapsulation and liquid source were chosen to enhance ‐dose to the surface of the conjunctiva. The applicator showed that the surface dose distribution (up to depth) is very similar to that of . However, beyond depth, the doses decrease with depths more rapidly than doses. In order to achieve the same surface dose rate, the required activity is about three times that for a applicator. We conclude that the proposed applicator can deliver therapeutic doses to the target lesion while sparing the lens better than the applicator. The activity required to deliver therapeutic doses can be produced in a reactor available at the Korea Atomic Energy Research Institute.
Magnetic field distribution in the presence of paramagnetic plates in magnetic resonance imaging: A combined numerical and experimental study
Authors: Mertens Philipp , Machann Juergen , Mueller‐Bierl Bernd , Steidle Guenter , Bellemann Matthias E. , Schick Fritz
Published: May 2008

The amount and geometric distribution of paramagnetic components in tissue is considered as the basis of ‐weighted magnetic resonance imaging (MRI). Such techniques are routinely applied for assessment of iron in parenchymal organs such as the liver (hemosiderosis). Furthermore, susceptibility sensitive MRI is discussed as an alternative method to x‐ray techniques for quantitative assessment of paramagnetic spongy bone components in patients with osteoporosis. The presented work is dedicated to systematically examining the possible influences of macroscopic arrangements of paramagnetic plates on the magnetic field. In a theoretical approach magnetic field distribution was simulated applying decomposition of the plates in single dipoles. Plate size and distances between parallel plates, as well as plate orientation with respect to the static field, were varied for these numerical simulations. Experiments on corresponding plate arrangements were carried out on a whole body MR scanner using the field‐sensitive MR sequence technique for field mapping. Further examinations were carried out on a bone preparation of the femur, where maps were measured and analyzed on a pixel‐by‐pixel basis at two orientations with respect to the static field. A series of experiments were performed using isotropic and anisotropic volume elements in three‐dimensional gradient echo sequences. Resulting magnetic field distributions in the experimentally recorded field maps were in good agreement with the numerical simulations. Field distortions dominated in areas close to the plates and especially near the edges. Those areas showed strong local field gradients, leading to pronounced signal dephasing effects. The examination of the bone preparations revealed different values for identical regions in the bone when the orientation of the bone or the pixel geometry was changed with respect to the magnetic field. Those effects amounted to nearly 70% ( versus in a region of interest in the femur) for 90° rotation of the femur in the magnetic fields. The orientation of anisotropic picture elements with constant size also showed a strong influence on the derived value (up to 80%, increasing with anisotropy of picture elements).
The DosiMap, a new 2D scintillating dosimeter for IMRT quality assurance: Characterization of two Čerenkov discrimination methods
Authors: Frelin A‐M. , Fontbonne J‐M. , Ban G. , Colin J. , Labalme M. , Batalla A. , Vela A. , Boher P. , Braud M. , Leroux T.
Published: May 2008

New radiation therapy techniques such as IMRT present significant efficiency due to their highly conformal dose distributions. A consequence of the complexity of their dose distributions (high gradients, small irradiation fields, low dose distribution, …) is the requirement for better precision quality assurance than in classical radiotherapy in order to compare the conformation of the delivered dose with the planned dose distribution and to guarantee the quality of the treatment. Currently this control is mostly performed by matrices of ionization chambers, diode detectors, dosimetric films, portal imaging, or dosimetric gels. Another approach is scintillation dosimetry, which has been developed in the last 15 years mainly through scintillating fiber devices. Despite having many advantages over other methods it is still at an experimental level for routine dosimetry because the Čerenkov radiation produced under irradiation represents an important stem effect. A new 2D water equivalent scintillating dosimeter, the DosiMap, and two different Čerenkov discrimination methods were developed with the collaboration of the Laboratoire de Physique Corpusculaire of Caen, the Comprehensive Cancer Center François Baclesse, and the ELDIM Co., in the frame of the MAESTRO European project. The DosiMap consists of a plastic scintillating sheet placed inside a transparent polystyrene phantom. The light distribution produced under irradiation is recorded by a CCD camera. Our first Čerenkov discrimination technique is subtractive. It uses a chessboard pattern placed in front of the scintillator, which provides a background signal containing only Čerenkov light. Our second discrimination technique is colorimetric. It performs a spectral analysis of the light signal, which allows the unfolding of the Čerenkov radiation and the scintillation. Tests were carried out with our DosiMap prototype and the performances of the two discrimination methods were assessed. The comparison of the dose measurements performed with the DosiMap and with dosimetric films for three different irradiation configurations showed discrepancies smaller than for a 2 mm spatial resolution. Two innovative discrimination solutions were demonstrated to separate the scintillation from the Čerenkov radiation. It was also shown that the DosiMap, which is water equivalent, fast, and user friendly, is a very promising tool for radiotherapy quality assurance.
LiF:Mg,Ti TLD response as a function of photon energy for moderately filtered x‐ray spectra in the range of 20–250 kVp relative to
Authors: Nunn A. A. , Davis S. D. , Micka J. A. , DeWerd L. A.
Published: May 2008

The response of LiF:Mg,Ti thermoluminescent dosimeters (TLDs) as a function of photon energy was determined using irradiations with moderately filtered x‐ray beams in the energy range of 20–250 kVp relative to the response to irradiations with photons. To determine if the relative light output from LiF:Mg,Ti TLDs per unit air kerma as a function of photon energy can be predicted using calculations such as Monte Carlo (MC) simulations, measurements from the x‐ray beam irradiations were compared with MC calculated results, similar to the methodology used by Davis et al. [Radiat. Prot. Dosim. 106, 33–43 (2003)]. TLDs were irradiated in photon beams with well‐known air kerma rates using the National Institute of Standards and Technology traceable M‐series x‐ray beams in the range of 20–250 kVp. For each x‐ray beam, several sets of TLDs were irradiated for times corresponding to different air kerma levels to take into account any dose nonlinearity. TLD light output was then compared to that from several sets of TLDs irradiated at similar corresponding air kerma levels using a irradiator. The MC code MCNP5 was used to account for photon scatter and attenuation in the holder and TLDs and was used to calculate the predicted relative TLD light output per unit air kerma for irradiations with each of the experimentally used photon beams. The measured relative TLD response as a function of photon energy differed by up to from the MC calculations. We conclude that MC calculations do not accurately predict the relative response of TLDs as a function of photon energy, consistent with the conclusions of Davis et al. [Radiat. Prot. Dosim. 106, 33–43 (2003)]. This is likely due to complications in the solid state physics of the thermoluminescence process that are not incorporated into the simulation.
An investigation of the accuracy of an IMRT dose distribution using two‐ and three‐dimensional dosimetry techniques
Authors: Oldham Mark , Sakhalkar Harshad , Guo Pengyi , Adamovics John
Published: May 2008

Complex dose delivery techniques like intensity‐modulated radiation therapy (IMRT) require dose measurement in three dimensions for comprehensive validation. Previously, we demonstrated the feasibility of the “PRESAGE™/optical‐computed tomography (CT)” system for the three‐dimensional verification of simple open beam dose distributions where the planning system was known to be accurate. The present work extends this effort and presents the first application of the PRESAGE™/optical‐CT system for the verification of a complex IMRT distribution. A highly modulated 11 field IMRT plan was delivered to a cylindrical PRESAGE™ dosimeter (16 cm in diameter and 11 cm in height), and the dose distribution was readout using a commercial scanning‐laser optical‐CT scanner. Comparisons were made with independent GAFCHROMIC® EBT film measurements, and the calculated dose distribution from a commissioned treatment planning system (ECLIPSE®). Isodose plots, dose profiles, gamma maps, and dose‐volume histograms were used to evaluate the agreement. The isodose plots and dose profiles from the PRESAGE™/optical‐CT system were in excellent agreement with both the EBT measurements and the ECLIPSE® calculation at all points except within 3 mm of the outer edge of the dosimeter where an edge artifact occurred. Excluding this 3 mm rim, gamma map comparisons show that all three distributions mutually agreed to within a 3% (dose difference) and 3 mm (distance‐to‐agreement) criteria. A 96% gamma pass ratio was obtained between the PRESAGE™ and ECLIPSE® distributions over the entire volume excluding this rim. In conclusion, for the complex IMRT plan studied, and in the absence of inhomogeneities, the ECLIPSE® dose calculation was found to agree with both independent measurements, to within 3%, 3 mm gamma criteria.
Prostate intrafraction motion evaluation using kV fluoroscopy during treatment delivery: A feasibility and accuracy study
Authors: Adamson Justus , Wu Qiuwen
Published: May 2008

Margin reduction for prostate radiotherapy is limited by uncertainty in prostate localization during treatment. We investigated the feasibility and accuracy of measuring prostate intrafraction motion using kV fluoroscopy performed simultaneously with radiotherapy. Three gold coils used for target localization were implanted into the patient's prostate gland before undergoing hypofractionated online image‐guided step‐and‐shoot intensity modulated radiation therapy (IMRT) on an Elekta Synergy linear accelerator. At each fraction, the patient was aligned using a cone‐beam computed tomography (CBCT), after which the IMRT treatment delivery and fluoroscopy were performed simultaneously. In addition, a post‐treatment CBCT was acquired with the patient still on the table. To measure the intrafraction motion, we developed an algorithm to register the fluoroscopy images to a reference image derived from the post‐treatment CBCT, and we estimated coil motion in three‐dimensional (3D) space by combining information from registrations at different gantry angles. We also detected the MV beam turning on and off using MV scatter incident in the same fluoroscopy images, and used this information to synchronize our intrafraction evaluation with the treatment delivery. In addition, we assessed the following: the method to synchronize with treatment delivery, the dose from kV imaging, the accuracy of the localization, and the error propagated into the 3D localization from motion between fluoroscopy acquisitions. With and a bowtie filter implemented, the coils could be localized with the gantry at both and with the MV beam off, and at with the MV beam on when multiple fluoroscopy frames were averaged. The localization in two‐dimensions for phantom and patient measurements was performed with submillimeter accuracy. After backprojection into 3D the patient localization error was , , and in the right‐left (RL), anterior‐posterior (AP), and superior‐inferior (SI) axes, respectively. Simulations showed that while oscillating (stationary) motion cannot be effectively represented in 3D, linearly drifting (nonstationary) motion is detectable with good accuracy. These results show that measuring prostate intrafraction motion using a single kV imager during radiotherapy is feasible and can be performed with acceptable accuracy.
Geometric calibration for a dual tube/detector micro‐CT system
Authors: Johnston Samuel M. , Johnson G. Allan , Badea Cristian T.
Published: May 2008

The authors describe a dual tube/detector micro‐computed tomography (micro‐CT) system that has the potential to improve temporal resolution and material contrast in small animal imaging studies. To realize this potential, it is necessary to precisely calibrate the geometry of a dual micro‐CT system to allow the combination of projection data acquired with each individual tube/detector in a single reconstructed image. The authors present a geometric calibration technique that uses multiple projection images acquired with the two imaging chains while rotating a phantom containing a vertical array of regularly spaced metallic beads. The individual geometries of the imaging chains are estimated from the phantom projection images using analytical methods followed by a refinement procedure based on nonlinear optimization. The geometric parameters are used to create the cone beam projection matrices required by the reconstruction process for each imaging chain. Next, a transformation between the two projection matrices is found that allows the combination of projection data in a single reconstructed image. The authors describe this technique, test it with a series of computer simulations, and then apply it to data collected from their dual tube/detector micro‐CT system. The results demonstrate that the proposed technique is accurate, robust, and produces images free of misalignment artifacts.
Tumor trailing strategy for intensity‐modulated radiation therapy of moving targets
Authors: Trofimov Alexei , Vrancic Christian , Chan Timothy C. Y. , Sharp Gregory C. , Bortfeld Thomas
Published: May 2008

Internal organ motion during the course of radiation therapy of cancer affects the distribution of the delivered dose and, generally, reduces its conformality to the targeted volume. Previously proposed approaches aimed at mitigating the effect of internal motion in intensity‐modulated radiation therapy (IMRT) included expansion of the target margins, motion‐correlated delivery (e.g., respiratory gating, tumor tracking), and adaptive treatment plan optimization employing a probabilistic description of motion. We describe and test the tumor trailing strategy, which utilizes the synergy of motion‐adaptive treatment planning and delivery methods. We regard the (rigid) target motion as a superposition of a relatively fast cyclic component (e.g., respiratory) and slow aperiodic trends (e.g., the drift of exhalation baseline). In the trailing approach, these two components of motion are decoupled and dealt with separately. Real‐time motion monitoring is employed to identify the “slow” shifts, which are then corrected by applying setup adjustments. The delivery does not track the target position exactly, but trails the systematic trend due to the delay between the time a shift occurs, is reliably detected, and, subsequently, corrected. The “fast” cyclic motion is accounted for with a robust motion‐adaptive treatment planning, which allows for variability in motion parameters (e.g., mean and extrema of the tidal volume, variable period of respiration, and expiratory duration). Motion‐surrogate data from gated IMRT treatments were used to provide probability distribution data for motion‐adaptive planning and to test algorithms that identified systematic trends in the character of motion. Sample IMRT fields were delivered on a clinical linear accelerator to a programmable moving phantom. Dose measurements were performed with a commercial two‐dimensional ion‐chamber array. The results indicate that by reducing intrafractional motion variability, the trailing strategy enhances relevance and applicability of motion‐adaptive planning methods, and improves conformality of the delivered dose to the target in the presence of irregular motion. Trailing strategy can be applied to respiratory‐gated treatments, in which the correction for the slow motion can increase the duty cycle, while robust probabilistic planning can improve management of the residual motion within the gate window. Similarly, trailing may improve the dose conformality in treatment of patients who exhibit detectable target motion of low amplitude, which is considered insufficient to provide a clinical indication for the use of respiratory‐gated treatment (e.g., peak‐to‐peak motion of less than 10 mm). The mechanical limitations of implementing tumor trailing are less rigorous than those of real‐time tracking, and the same technology could be used for both.
Dynamic conformal arc therapy: Transmitted signal in vivo dosimetry
Authors: Piermattei Angelo , Stimato Gerardina , Gaudino Diego , Ramella Sara , D'Angelillo Rolando Maria , Cellini Francesco , Trodella Lucio , D'Onofrio Guido , Grimaldi Luca , Cilla Savino , Fidanzio Andrea , Placidi Elisa , Azario Luigi
Published: May 2008

A method for the determination of the in vivo isocenter dose, , has been applied to the dynamic conformal arc therapy (DCAT) for thoracic tumors. The method makes use of the transmitted signal, , measured at different gantry angles, , by a small ion chamber positioned on the electronic portal imaging device. The in vivo method is implemented by a set of correlation functions obtained by the ratios between the transmitted signal and the midplane dose in a solid phantom, irradiated by static fields. The in vivo dosimetry at the isocenter for the DCAT requires the convolution between the signals, , and the dose reconstruction factors, , that depend on the patient's anatomy and on its tissue inhomogeneities along the beam central axis in the direction. The factors are obtained by processing the patient's computed tomography scan. The method was tested by taking measurements in a cylindrical phantom and in a Rando Alderson phantom. The results show that the difference between the convolution calculations and the phantom measurements is within . The in vivo dosimetry of the stereotactic DCAT for six lung tumors, irradiated with three or four arcs, is reported. The isocenter dose up to 17 Gy per therapy fraction was delivered on alternating days for three fractions. The agreement obtained in this pilot study between the total in vivo dose and the planned dose at the isocenter is . The method has been applied on the DCAT obtaining a more extensive monitoring of possible systematic errors, the effect of which can invalidate the current therapy which uses a few high‐dose fractions.
Improving accuracy of electron density measurement in the presence of metallic implants using orthovoltage computed tomography
Authors: Yang Ming , Virshup Gary , Mohan Radhe , Shaw Chris C. , Zhu X. Ronald , Dong Lei
Published: May 2008

The goal of this study was to evaluate the improvement in electron density measurement and metal artifact reduction using orthovoltage computed tomography (OVCT) imaging compared with conventional kilovoltage CT (KVCT). For this study, a bench‐top system was constructed with adjustable x‐ray tube voltage up to 320 kVp. A commercial tissue‐characterization phantom loaded with inserts of various human tissue substitutes was imaged using 125 kVp (KVCT) and 320 kVp (OVCT) x rays. Stoichiometric calibration was performed for both KVCT and OVCT imaging using the Schneider method. The metal inserts—titanium rods and aluminum rods—were used to study the impact of metal artifacts on the electron‐density measurements both inside and outside the metal inserts. It was found that the relationships between Hounsfield units and relative electron densities (to water) were more predictable for OVCT than KVCT. Unlike KVCT, the stoichiometric calibration for OVCT was insensitive to the use of tissue substitutes for direct electron density calibration. OVCT was found to significantly reduce metal streak artifacts. Errors in electron‐density measurements within uniform tissue substitutes were reduced from 42% (maximum) and 18% (root‐mean‐square) in KVCT to 12% and 2% in OVCT, respectively. Improvements were also observed inside the metal implants. For the detectors optimized for KVCT, the imaging dose is almost doubled for OVCT for the image quality comparable to KVCT. OVCT may be a good option for high‐precision radiotherapy treatment planning, especially for patients with metal implants and especially for charged particle therapy, such as proton therapy.
Proton and Charged Particle Radiotherapy
Authors: Newhauser Wayne
Published: May 2008

Proton and Charged Particle Radiotherapy DeLaney Thomas F. and Kooy Hanne M. Lippincott Williams & Wilkins, Philadelphia, PA, USA, September 2007. $179.00, Hardcover 320 pp., ISBN 978‐0‐7817‐6552‐7.
Labeling Fish with an Activable Element
Authors: Michibata Hitoshi , Hori Reiji
Published: May 2008

An activable element was administrated for labeling fish, Oryzias latipes, by injecting samarium, one of the rare earth elements, into the abdominal cavity. The fish were killed at intervals varying from 1 to 600 d after the injection and exposed to a beam of thermal neutrons in a nuclear reactor. It was possible to distinguish the difference between labeled and unlabeled fish by the detection of 153Sm produced by (n, γ) reaction. The level of samarium detected remained almost constant even about 2 yr after the last injection. The second experiment using larger fish, Carassius auratus, revealed that samarium was retained in the internal organs.Key words: fish marking, activable tracer, activation analysis, samarium, Oryzias latipes, Carassius auratus
Intracellular Composition and Net Release Rates of Free Amino Acids in Daphnia magna
Authors: Gardner Wayne S. , Miller III Warren H.
Published: May 2008

Excretion of free amino acids and ammonia by Daphnia magna was measured by examining in vitro changes in concentration of the two forms of nitrogen over 4–6 h. Mean weight-specific amino acid release rate (± SE) for 32 healthy daphnids was 0.13 ± 0.03 nmol (mg dry wt)−1∙h−1 as compared with a mean ammonia excretion rate of 21 ± 2 nmol (mg dry wt)−1∙h−1. Net removal from solution was observed when low levels of amino acids (2 nmol/8 mL) were added to the water before incubation, indicating that measured net release rates could be reduced by amino acid uptake. Toxic levels (0.5 mg∙L−1) of lead, arsenic, Kepone, toxaphene, malathion, or pentachlorophenol, added to stress the animals, did not significantly affect release rates of amino acids or ammonia, but the addition of copper (as CuSO4) increased amino acid release by daphnids and hindered microbial removal of amino acids from incubation waters. Amino acids released from copper-exposed animals were similar in composition to those in intracellular amino acid pools of D. magna, suggesting that diffusion across cell membranes may have been the mechanism for amino acid release.Key words: amino acids, ammonia, cladocera, contaminants, copper, Daphnia, excretion, free amino acids, stress, zooplankton
Adsorption and Desorption of Permethrin and Other Pesticides on Glass and Plastic Materials used in Bioassay Procedures
Authors: Sharom M. S. , Solomon K. R.
Published: May 2008

Laboratory studies were conducted to determine the adsorption and desorption of permethrin on glass and several plastic materials that may be used for the construction of limnocorrals. The insecticide was substantially adsorbed on polyethylene, polyvinylchloride, glass, and Teflon. Adsorbed permethrin was not easily desorbed from polyethylene and polyvinylchloride by several water rinses. Increased adsorption of the insecticide was observed with increasing temperatures. A study on the adsorption of several herbicides of various water solubilities indicated that trifluralin was adsorbed to glass and that there was no general relationship between adsorption of the herbicide on polyvinylchloride and water solubility.Key words: permethrin, bioassay, adsorption, desorption
Phosphorus Kinetics in Lake Superior: Light Intensity and Phosphate Uptake in Algae
Authors: Nalewajko C. , Lee K. , Shear H.
Published: May 2008

Epilimnetic phytoplankton in Lake Superior in September, 1979, had low Ik values (75–190 μE∙m−2∙s−1), low N/P ratios (8 to 13:1) and 32PO4–P uptake kinetics that were not consistent with a state of extreme phosphorus limitation. Parallel laboratory experiments with Chlorella pyrenoidosa indicated that phosphorus content per cell was higher and uptake rates of phosphate were lower in cells grown under low light (57 μE∙m−2∙s−1) than those under high light (340 μE∙m−2∙s−1). Maximum 32PO4 uptake occurred at about 50–60 μE∙m−2∙s−1 in both cultures indicating 32PO4 uptake kinetics are light dependent at very low light levels, below or close to their Ik values. It appears that light and not phosphorus limited phytoplankton growth in Lake Superior at the time of our experiments. Antecedent solar radiation prior to our experiments coupled with complete mixing of the top 20–25 m of the Lake possibly resulted in a low light-adapted phytoplankton population. We suggest that phosphorus control need not be the correct management strategy to maintain oligotrophy in Lake Superior. Key words: phosphorus, kinetics, light, primary production, mixing, management
Multivariate Analysis as a Means of Comparing Growth in Fish
Authors: Bernard David R.
Published: May 2008

The Hotelling's T2 is described as a test for differences between like von Bertalanffy growth parameters estimated from two fish groups when these parameters are correlated. Equations to calculate T2 are presented as are equations to modify T2 to an F statistic for use in testing. Simultaneous confidence intervals and critical F values are described to separate effects of parameters on observed differences in growth. Assumptions made by the T2 technique are discussed, as are ways in which any bias caused by violating these assumptions is lessened. Two numerical examples concerning growth differences among groups of Pacific ocean perch (Sebastes alutus) are provided. Growth of male and of female perch captured off the Columbia River is different with L∞ being the most statistically significant parameter and t0 the least. Growth of male perch captured off Vancouver Island and off the Columbia River is also different with only L∞ statistically significant.Key words: Hotelling's T2, multivariate statistics, Pacific ocean perch, von Bertalanffy, growth
Uptake of Waterborne Methylmercury by Rainbow Trout (Salmo gairdneri) in Relation to Oxygen Consumption and Methylmercury Concentration
Authors: Rodgers D. W. , Beamish F. W. H.
Published: May 2008

Oxygen consumption and uptake of waterborne methylmercury were measured for rainbow trout (Salmo gairdneri) forced to swim at sustained swimming speeds at 10 and 20 °C. The concentrations of methylmercury used (< 8 μg Hg∙L−1) did not affect oxygen consumption. The log of mass specific oxygen consumption increased linearly with relative swimming speed. Standard metabolic rates were significantly different (P < 0.05) at 10 and 20 °C (111 and 192 mg O2∙kg−1∙h−1, respectively) but the rate of increase in oxygen consumption with swimming speed was not significantly different between temperatures. The rate of methylmercury uptake was positively correlated with both oxygen consumption and methylmercury concentration. Multiple linear regression equations relating the logs of rate of methylmercury uptake, rate of oxygen consumption, and methylmercury concentration at 10 and 20 °C were contiguous and a single equation described the relationship at both temperatures. The efficiency of methylmercury uptake relative to oxygen was ~0.25 at both temperatures. Assuming an oxygen percent utilization of 33%, the percent utilization of methylmercury from water was ~8%.Key words: methylmercury, uptake, respiration, oxygen consumption, rainbow trout, bioaccumulation, pollutant
Prediction of Egg Development and Mortality Rates in Capelin (Mallotus viliosus) from Meteorological, Hydrographic, and Biological Factors
Authors: Frank Kenneth T. , Leggett William C.
Published: May 2008

We studied the factors governing in situ egg development and mortality rates in beach spawning capelin (Mallotus villosus). Time to hatching was strongly influenced by the average incubation temperature which varied between years and between cohorts in a single year, and between positions on the beach (high, mid, low tide zone). Average incubation temperatures were determined by a complex of variables which included water temperature, maximum and minimum air temperature, and hours of sunlight. Mortality rates were both spatially and temporally variable. Over 70% of the temporal and spatial variance in egg mortality was attributed to the interacting effects of egg density, water temperature, maximum and minimum air temperature, hours of sunlight, rainfall, and tidal amplitude. Multivariate equations for predicting egg mortality as a function of these variables are given. The principal climatic and hydrographic variables influencing egg mortality vary only slightly over a 7° range of latitude encompassing the main spawning sites of the eastern Newfoundland and southern Labrador coasts. The potential thus exists for synchronous year to year changes in egg mortality over this spawning range as a result of annual variations in climate and hydrographic conditions. Such synchronous changes may contribute to the substantial year to year fluctuations in capelin year-class strength.Key words: capelin, Mallotus viliosus; development, mortality, meteorology, hydrology, temperature, intertidal zone, year-class, egg, beach spawning
Elimination of Hexachlorobenzene (HCB) by Rainbow Trout (Salmo gairdneri), and an Examination of its Kinetics in Lake Ontario Salmonids
Authors: Niimi A. J. , Cho C. Y.
Published: May 2008

Subadult rainbow trout (Salmo gairdneri) were fed diets containing hexachlorobenzene (HCB) to establish mean body burdens of 225 and 440 μg HCB per fish. They were sampled after 0, 24, 55, and 110 d to estimate the rate of elimination. The biological half-life or T[Formula: see text] of HCB for trout under the prescribed laboratory conditions was estimated to be at least 7 mo, and perhaps as long as several years. T[Formula: see text] was calculated using body burden or μg HCB per fish, and tissue concentrations or μg/kg HCB. Estimates of T[Formula: see text] derived from tissue concentrations ranged from 61 to 117 d, but this was shown to be due to a relative increase in body weight over the study period. The implications of increasing body weight on kinetics measurements are discussed, and an equation is presented that adjusts for changes in body weight where estimates of T[Formula: see text] are calculated using tissue concentrations.The results of this and other studies on HCB were used to examine the kinetics of HCB in salmonids collected from Lake Ontario. Using the information derived from laboratory studies on rainbow trout, good agreement was achieved between the expected level and that monitored in field samples of rainbow trout, but only a fair agreement was suggested for lake trout (Salvelinus namaycush) and coho salmon (Oncorhynchus kisutch). Differences in the HCB kinetics of these species may be attributed to body weight, age, and perhaps feeding habits. Concentrations of HCB reported in field sampling programs generally range from 1 to 100 μg/kg in fish, and it is suggested that these levels are primarily due to the limited availability of HCB in the Lake Ontario environment.Key words: contaminants, hexachlorobenzene (HCB), half-life, elimination, depuration, rainbow trout, Salmo gairdneri; Lake Ontario
Initial Colonization of Artificial Substrate: Community Development and Structure Studied by Scanning Electron Microscopy
Authors: Hudon Christiane , Bourget Edwin
Published: May 2008

The initial phases of subtidal and intertidal community development were observed using scanning electron microscopy on samples from plastic panels immersed monthly in the St. Lawrence Estuary.Bacteria and diatom populations were quantitatively evaluated on samples collected from May to November, 1978. The pattern of immersion and/or periodical emersion according to the level greatly influenced the community structure. Subtidal panels (−5.0 m) were rapidly colonized by bacteria while diatoms settled 2–7 wk later, depending on the season. Cocconeis spp. and Amphora spp. were the major diatom colonizers until mid-August. In September, Synedra tabulata settled on the panels. Until mid-September, all dominant species formed well-defined, generally monospecific clumps. In contrast with Cocconeis spp. and Amphora spp., which lie horizontally on the surface, S. tabulata, which is needlelike in shape, formed erect fan-shaped colonies. Other late invaders possessed a mucus stalk, raising themselves from the surface and thus better utilizing the vertical dimension. Clump overlap and increased species interactions occurred with higher cell densities. In the intertidal zone bacteria settled after 8–12 wk while Achnanthes brevipes var. parvula appeared after 20 wk, the only diatom species able to resist semidiurnal emersion. The ability of the panels to retain water through detritus and irregularities is probably the main factor allowing the development of this community. Panels emersed only at spring tides (monthly) were rapidly colonized by bacteria, and heavy diatom settlement occurred within 4 wk. Successive monthly emersions eliminated or strongly reduced diatom populations, which were replaced by filamentous (Ectocarpaceae) algae. The three types of communities are compared and the strategic advantage of upright forms is discussed in relation to population density, light availability, and detrital cover.Key words: St. Lawrence Estuary, artificial substrate, community structure, community development, Cocconeis spp., Synedra tabulata. Amphora spp., diatoms