bluuebunny/crossref_metadata_2025 huggingface dataset:
Drivers Behind Farmers’ Willingness to Terminate Arable Land Use Contracts
Authors: Gao Jia , Strijker Dirk , Song Ge , Li Shiping
Published: February 2017

The shortage of land resources has become a serious problem in China's rapid urbanisation. A recognised method for solving arable land resource shortage problems is to encourage marginal farmers to terminate their arable land use contracts with the government so that they can be transferred to farmers with better prospects. This paper analyses the drivers behind farmers’ willingness to terminate their arable land use contracts based on survey data from agricultural households in Guanzhong, Shaanxi Province, China, using a multivariable logistic model. Results show that households led by male householders, with large families, fewer agricultural labourers, more plots of land, including family members with non‐agricultural skills training and including family members who are covered by rural residents’ health insurance, are more likely to terminate their contracts.
Bending the rules, breaking the rules: How corruption and lobbying affect the investment market selection of Swedish firms
Authors: Thede Susanna , Gustafson Nils‐Åke
Published: February 2017

There is stark evidence that many policies which influence firm gains from engaging in FDI (such as tax and trade policies) are targeted by lobbying groups and that corruption can be an important determinant of market attractiveness. The scarce research that exists on firm behaviour, corruption and lobbying shows that these activities can be regarded as alternative, and interdependent, influence forms. This paper provides the novel contribution of investigating how the market infiltration of corruption and lobbying affects the firm's investment decision. We identify the interdependent effects using census data for Swedish manufacturing firms that allows a complete identification of the firm's market selection. Our results reveal that these private–public sector links influence the firm's investment decision differently, as market selection is deterred by corruption and stimulated by lobbying, and that they function as substitutes. We show that the stimulating lobbying effect largely can be attributed to its interdependency with corruption, which suggests that firms are more shielded from corruption in lobbying environments. Further investigation reveals that the corruption and lobbying effects are not always representative of larger firms: The largest firms are undeterred by corruption in markets where lobbying forms an integral part of the business environment and larger firms are not stimulated by lobbying in markets largely void of corruption.
Reviewer Acknowledgements
Authors: Smith Robert
Published: February 2017

Journal of Education and Training Studies (JETS) would like to acknowledge the following reviewers for their assistance with peer review of manuscripts for this issue. Many authors, regardless of whether JETS publishes their work, appreciate the helpful feedback provided by the reviewers. Their comments and suggestions were of great help to the authors in improving the quality of their papers. Each of the reviewers listed below returned at least one review for this issue.Reviewers for Volume 5, Number 3 Angela Lee, UNC Pembroke, USAAnne M. Hornak, Central Michigan University, USACagla Atmaca, Pamukkale University, TurkeyChosang Tendhar, Baylor College of Medicine, USADana Badau, University of Medicine and Pharmacy of Targu Mures, RomaniaDavid A. Compton, Wingate University, USAErica D. Shifflet-Chila, Michigan State University, USAFahrettin Sanal, Necmettin Erbakan University, TurkeyHyesoo Yoo, Virginia Tech., USAJeyavel Sundaramoorthy, Gulbarga University Campus, IndiaJill M. Feldman, Westat, USAJosé D Badia, University of Valencia, SpainKun Li, Duke University, USALorna T. Enerva, Polytechnic University of the Philippines, PhilippinesMaria Pavlis Korres, Hellenic Open University, GreeceMaurizio Sajeva, Natural Resources Institute Finland, FinlandMeral Seker, Cukurova University, TurkeyMin Gui, Wuhan University, ChinaNicole Celestine, The University of Western Australia, AustraliaNiveen M. Zayed, MENA College of Management, JordanRichard H. Martin, Mercer University, USARichard Penny, University of Washington Bothell, USARufaidah Kamal Abdulmajeed, Baghdad University, IraqRui Manuel Carreteiro, National Institute of Psychology and Neurosciences, PortugalSahin Gök, Gelisim University, TurkeySamah Mohammed Fahim, Suez University, EgyptSenem Seda Şahenk Erkan, Marmara University, TurkeyShengnan Liu, Ocean University of China, ChinaSimona Savelli, Università degli Studi Guglielmo Marconi, ItalySisi Liu, The Education University of Hong Kong, Hong KongSuzan Kavanoz, Yıldız Technical University, TurkeyTürker Sezer, Abant İzzet Baysal University, TurkeyYalçın Dilekli, Aksaray University, TurkeyYerlan Seisenbekov, Kazakh National Pedagogical University, KazakhstanYi Lu, American Institute for Research, USAYüksel Çırak, Inonu University, TurkeyZeynep Kurtulmus, Gazi University, Turkey Robert SmithEditorial AssistantOn behalf of,The Editorial Board of Journal of Education and Training StudiesRedfame Publishing9450 SW Gemini Dr. #99416Beaverton, OR 97008, USAURL: http://jets.redfame.com
Linear and non‐linear contributions to oxygen transport and utilization during moderate random exercise in humans
Authors: Beltrame T. , Hughson R. L.
Published: February 2017

New Findings

What is the central question of this study?

The pulmonary oxygen uptake () data used to study the muscle aerobic system dynamics during moderate‐exercise transitions is classically described as a mono‐exponential function controlled by a complex interaction of the oxygen delivery–utilization balance. This elevated complexity complicates the acquisition of relevant information regarding aerobic system dynamics based on data during a varying exercise stimulus.

What is the main finding and its importance?

The elevated complexity of dynamics is a consequence of a multiple‐order interaction between muscle oxygen uptake and circulatory distortion. Our findings challenge the use of a first‐order function to study the influences of the oxygen delivery–utilization balance over the dynamics.

The assumption of aerobic system linearity implies that the pulmonary oxygen uptake () dynamics during exercise transitions present a first‐order characteristic. The main objective of this study was to test the linearity of the oxygen delivery–utilization balance during random moderate exercise. The cardiac output () and deoxygenated haemoglobin concentration ([HHb]) were measured to infer the central and local O2 availability, respectively. Thirteen healthy men performed two consecutive pseudorandom binary sequence cycling exercises followed by an incremental protocol. The system input and the outputs , [HHb] and were submitted to frequency‐domain analysis. The linearity of the variables was tested by computing the ability of the response at a specific frequency to predict the response at another frequency. The predictability levels were assessed by the coefficient of determination. In a first‐order system, a participant who presents faster dynamics at a specific frequency should also present faster dynamics at any other frequency. All experimentally obtained variables (, [HHb] and ) presented a certainly degree of non‐linearity. The local O2 availability, evaluated by the ratio /[HHb], presented the most irregular behaviour. The overall [HHb] kinetics were faster than and kinetics. In conclusion, the oxygen delivery–utilization balance behaved as a non‐linear phenomenon. Therefore, the elevated complexity of the pulmonary oxygen uptake dynamics is governed by a complex multiple‐order interaction between the oxygen delivery and utilization systems.
Cardiac sympathetic innervation, from a different point of (re)view
Authors: Zaglia Tania , Mongillo Marco
Published: February 2017

The audience of basic and clinical scientists is familiar with the notion that the sympathetic nervous system controls heart function during stresses. However, evidence indicates that the neurogenic control of the heart spans from the maintenance of housekeeping functions in resting conditions to the recruitment of maximal performance, in the fight‐or‐flight responses, across a whole range of intermediate states. To perform such sophisticated functions, sympathetic ganglia integrate both peripheral and central inputs, and transmit information to the heart via ‘motor’ neurons, directly interacting with target cardiomyocytes. To date, the dynamics and mode of communication between these two cell types, which determine how neuronal information is adequately translated into the wide spectrum of cardiac responses, are still blurry. By combining the anatomical and structural information brought to light by recent imaging technologies and the functional evidence in cellular systems, we focus on the interface between neurons and cardiomyocytes, and advocate the existence of a specific ‘neuro‐cardiac junction’, where sympathetic neurotransmission occurs in a ‘quasi‐synaptic’ way. The properties of such junctional‐type communication fit well with those of the physiological responses elicited by the cardiac sympathetic nervous system, and explain its ability to tune heart function with precision, specificity and elevated temporal resolution.

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Assessment of Thermal Damage During Skin Tumor Treatment Using Thermal Wave Model: A Realistic Approach
Authors: Verma A. K. , Rath P. , Mahapatra S. K.
Published: February 2017

In this study, a three-layered skin tissue has been modeled to assess the heat transfer characteristics in laser skin tumor–tissue interaction. A finite-volume-based two-dimensional numerical bioheat transfer model has been put together to study the damage prediction of healthy tissues by considering both Fourier and non-Fourier laws. The combination of the bioheat transfer equation with Fourier law forms the parabolic equation (Pennes model) and with the non-Fourier equation forms the hyperbolic equation (thermal wave model). In this paper, the laser source is provided on the outer layer of the skin to dismantle the undesired tumor region exemplified as inhomogeneity (tumor) present in the intermediate layer. Heat input through the laser source is on until it reaches the tumor-killing criteria. The heat transport equation has been discretized by the finite volume method (FVM). The finite-volume-based numerical model is developed in such a way that the non-Fourier model predictions can be obtained through conventional Fourier-based solver. The central difference scheme is adopted for discretizing the spatial derivative terms. An implicit scheme is applied to treat the transient terms in the model. For few cases of the hyperbolic problems, certain limitation for a chosen implicit scheme has also been addressed in this paper. The results are validated with the existing literatures. The evaluated results are based on both the Fourier and the non-Fourier model, to investigate the temperature distribution and thermal damage by ensuring irreversible thermal damage in the whole tumor region placed in the dermis layer. Thermal damage of the healthy tissue is found to be more in the time scale of the thermal wave model.
The Postbuckling Behavior of Planar Elastica Constrained by a Deformable Wall
Authors: Katz Shmuel , Givli Sefi
Published: February 2017

Attributed to its significance in a wide range of practical applications, the post-buckling behavior of a beam with lateral constraints has drawn much attention in the last few decades. Despite the fact that, in reality, the lateral constraints are often flexible or deformable, vast majority of studies have considered fixed and rigid lateral constraints. In this paper, we make a step toward bridging this gap by studying the post-buckling behavior of a planar beam that is laterally constrained by a deformable wall. Unfortunately, the interaction with a compliant wall prevents derivation of closed-form analytical solutions. Nevertheless, careful examination of the governing equations of a simplified model reveals general properties of the solution, and let us identify the key features that govern the behavior. Specifically, we construct universal “solution maps” that do not depend on the mode number and enable simple and easy prediction of the contact conditions and of the mode-switching force (the force at which the system undergoes instantaneous transition from one equilibrium configuration (or mode) to another). The predictions of the mathematical model are validated against finite element (FE) simulations.
Seepage Monitoring of an Embankment Dam Based on Hydro-Thermal Coupled Analysis
Authors: Song Chung R. , Yosef Tewodros Y.
Published: February 2017

Distributed temperature sensing (DTS)-based fiber optic sensors are widely used for monitoring spatially continuous temperature distribution in structures. In this research, hydro-thermal (H-T) coupled analysis is used to monitor seepage conditions in an embankment dam. Variably saturated two-dimensional heat transport (VS2DHI), a computer code developed by the U.S. Geological Survey, was used for this coupled analysis. From the coupled analysis, the temperature profile for a dam with an artificially generated crack clearly showed the location of the crack. In addition, it turned out that the temperature change in the dam took much longer than the seepage time due to the additional time required for heat transfer. The study shows that temperature variation in the dam is comparable to the seepage condition with time delay for heat transfer. This study also shows the possibility that temperature data may serve as a tool to diagnose prior seepage conditions and past incidents of a dam.
Remote Determination of Time-Dependent Stiffness of Surface-Degrading-Polymer Scaffolds Via Synchrotron-Based Imaging
Authors: Bawolin N. K. , Chen X. B.
Published: February 2017

Surface-degrading polymers have been widely used to fabricate scaffolds with the mechanical properties appropriate for tissue regeneration/repair. During their surface degradation, the material properties of polymers remain approximately unchanged, but the scaffold geometry and thus mechanical properties vary with time. This paper presents a novel method to determine the time-dependent mechanical properties, particularly stiffness, of scaffolds from the geometric changes captured by synchrotron-based imaging, with the help of finite element analysis (FEA). Three-dimensional (3D) tissue scaffolds were fabricated from surface-degrading polymers, and during their degradation, the tissue scaffolds were imaged via the synchrotron-based imaging to characterize their changing geometry. On this basis, the stiffness behavior of scaffolds was estimated from the FEA, and the results obtained were compared to the direct measurements of scaffold stiffness from the load–displacement material testing. The comparison illustrates that the Young's moduli estimated from the FEA and characterized geometry are in agreement with the ones of direct measurements. The developed method of estimating the mechanical behavior was also demonstrated effective with a nondegrading scaffold that displays the nonlinear stress–strain behavior. The in vivo monitoring of Young's modulus by morphology characterization also suggests the feasibility of characterizing experimentally the difference between in vivo and in vitro surface degradation of tissue engineering constructs.
Nonlinear, Phase-Based Oscillator to Generate and Assist Periodic Motions
Authors: De la Fuente Juan , Sugar Thomas G. , Redkar Sangram
Published: February 2017

Oscillatory behavior is important for tasks, such as walking and running. We are developing methods for wearable robotics to add energy to enhance or vary the oscillatory behavior based on the system's phase angle. We define a nonlinear oscillator using a forcing function based on the sine and cosine of the system's phase angle that can modulate the amplitude and frequency of oscillation. This method is based on the state of the system and does not use off-line trajectory planning. The behavior of a limit cycle is shown using the Poincaré–Bendixson criterion. Linear and rotational models are simulated using our phase controller. The method is implemented and tested to control a pendulum.
Battery State of Health Monitoring by Estimation of Side Reaction Current Density Via Retrospective-Cost Subsystem Identification
Authors: Zhou Xin , Bernstein Dennis S. , Stein Jeffrey L. , Ersal Tulga
Published: February 2017

This paper introduces a new method to monitor battery state of health (SOH). In particular, the side reaction current density is estimated as a direct SOH indicator for the first time and its estimation is formulated as an inaccessible subsystem identification problem, where the battery health subsystem is treated as an inaccessible subsystem with the side reaction current density as the output. Inaccessibility in this context refers to the fact that the inputs and outputs of the subsystem are not measurable in situ. This subsystem is identified using retrospective-cost subsystem identification (RCSI) algorithm, and the output of the identified battery health subsystem provides an estimate for the side reaction current density. Using an example parameter set for a LiFePO4 battery, simulations are performed to obtain estimates under various current profiles. These simulations show promising results in identifying the battery health subsystem and estimating the side reaction current density with RCSI under ideal conditions. Robustness of the algorithm under nonideal conditions is analyzed. Estimation of the side reaction current density using RCSI is shown to be sensitive to nonideal conditions that cause errors in the measurement or estimation of the battery voltage. A method for quantitatively assessing the impact of nonideal conditions on the side reaction current estimation accuracy is provided. The proposed estimation technique, including the method for estimating the side reaction current density using RCSI and the framework analyzing its robustness, can also be applied to other parameter sets and other battery chemistries to monitor the SOH change resulting from any electrochemical-based degradation mechanism that consumes cyclable Li-ions.
Two-Scale Command Shaping for Reducing Powertrain Vibration During Engine Restart
Authors: Justin Wilbanks J. , Leamy Michael J.
Published: February 2017

This paper introduces a two-scale command shaping strategy for reducing vibrations in conventional and hybrid electric vehicle (HEV) powertrains during engine restart. The approach introduces no additional system components and thus few additional costs. The torque profile from an electric machine (EM) is tailored to start the internal combustion engine (ICE) while minimizing residual vibrations. It is shown that the tailored EM torque profile, composed of a linear combination of constant and time-varying components, results in significant mitigation of powertrain vibrations and smoother ICE startup. The time-varying EM torque component is calculated using an analytical ICE model and a perturbation technique for separating scales, which isolates the ICE nonlinear response. Command shaping is then applied to the linear problem at the remaining scale. Simulation results suggest a promising and straightforward technique for reducing vibrations and improving drivability during ICE restart. Furthermore, two-scale command shaping may also be useful in mitigating other HEV-related drivability issues associated with powertrain mode changes (e.g., blending of hybrid power sources, engaging and disengaging of clutches, etc.).
An Exploratory Investigation of the Mechanical Properties of the Nanostructured Porous Materials Deposited by Laser-Induced Chemical Solution Synthesis
Authors: Peng Cheng , Richard Liu C. , Voothaluru Rohit , Ou Chun-Yu , Liu Zhikun
Published: February 2017

Laser-induced chemical solution synthesis has been recently developed as a new generic method to create porous nanostructured materials for complex and miniaturized devices. The material made by this approach is successfully demonstrated for electrochemical catalytic, nanoscale powders, protective coatings, and other applications. One question has therefore been raised: What are the mechanical properties of the porous materials deposited by the laser-induced chemical solution synthesis? This paper has attempted to explore the mechanical properties of such porous nanostructured materials deposited by this new nanomanufacturing method. This process also offers an innovative opportunity to study the strength of a very simple bonding in additive manufacturing. A thin-film of copper nanoparticles is deposited on copper substrates; then, the microstructure of the deposited film is characterized by scanning electron microscope (SEM), and mechanical properties are investigated by a variety of experiments, such as microhardness test, nano-indentation test, bending test, and adhesion test. The mechanical properties of substrates with surface deposition have been shown to have adequate bond strength (>60 g/mm) to allow effective usage in intended applications. Based on the test results, statistical regression and significant tests have also been carried out. A new model for the nano-indentation of the porous coating (film) is proposed. The empirical results have shown that the effect of coating thickness is more prominent on mechanical properties in the case of thick coating deposition.
Dependence of brain DTI maps of fractional anisotropy and mean diffusivity on the number of diffusion weighting directions
Authors: Giannelli Marco , Cosottini Mirco , Michelassi Maria Chiara , Lazzarotti Guido , Belmonte Gina , Bartolozzi Carlo , Lazzeri Mauro
Published: February 2017

The rotational variance dependence of diffusion tensor imaging (DTI) derived parameters on the number of diffusion weighting directions (N) has been investigated by several Monte Carlo simulation studies. However, the dependence of fractional anisotropy (FA) and mean diffusivity (MD) maps on N, in terms of accuracy and contrast between different anatomical structures, has not been assessed in detail. This experimental study further investigated in vivo the effect of the number of diffusion weighting directions on DTI maps of FA and MD. Human brain FA and MD maps of six healthy subjects were acquired at 1.5T with varying N (6, 11, 19, 27, 55). Then, FA and MD mean values in high and low anisotropy segmented brain regions were measured. Moreover, the contrast‐to‐signal variance ratio between the main white matter and the surrounding regions was calculated. Analysis of variance showed that and significantly depend on N. In particular, FAL decreased (6%–11%) with N, whereas (1.6%–2.5%) and (4%–6.5%) increased with and did not significantly depend on N. Unlike MD values, FA values significantly vary with N. It is noteworthy that the observed variation is opposite in low and high anisotropic regions. In clinical studies, the effect of N may represent a confounding variable for anisotropy measurements and the employment of DTI acquisition schemes with high allows an increased CVR and a better visualization of white matter structures in FA maps.

PACS number: 87.61.Tg, 82.56.Lz
A grid to facilitate physics staffing justification
Authors: Klein Eric E.
Published: February 2017

Justification of clinical physics staffing levels is difficult due to the lack of direction as how to equate clinical needs with the staffing levels and competency required. When a physicist negotiates staffing requests to administration, she/he often refers to American College of Radiology staffing level suggestions, and resources such as the Abt studies. This approach is often met with questions as to how to fairly derive the time it takes to perform tasks. The result is often insufficient and/or inexperienced staff handling complex and cumbersome tasks. We undertook development of a staffing justification grid to equate the clinical needs to the quantity and quality of staffing required. The first step is using the Abt study, customized to the clinical setting, to derive time per task multiplied by the anticipated number of such tasks. Inclusion of vacation, meeting, and developmental time may be incorporated along with allocated time for education and administration. This is followed by mapping the tasks to the level of competency/experience needed. For example, in an academic setting the faculty appointment levels correlate with experience. Non‐staff personnel, such as IMRT QA technicians or clerical staff, should also be part of the equation. By using the staffing justification grid, we derived strong documentation to justify a substantial budget increase. The grid also proved useful when our clinical demands changed. Justification for physics staffing can be significantly strengthened with a properly developed data‐based time and work analysis. A staffing grid is presented, along with a development methodology that facilitated our justification. Though our grid is for a large academic facility, the methodology can be extended to a non‐academic setting, and to a smaller scale. This grid method not only equates the clinical needs with the quantity of staffing, but can also help generate the personnel budget, based on the type of staff and personnel required. The grid is easily adaptable when changes to the clinical environment change, such as an increase in IMRT or IGRT applications.

PACS number: 87.55.tm, 87.55.Qr
Helical tomotherapy in the radiotherapy treatment of Hodgkin's disease ‐ a feasibility study
Authors: Vlachaki Maria T. , Kumar Sanath
Published: February 2017

Radiation therapy for advanced Hodgkin's disease often requires large fields and may result in significant exposure of normal tissues to ionizing radiation. In long‐term survivors, this may increase the risk for late toxicity including secondary malignancies. 3D CRT has been successfully used to treat this disease but treatment delivery is often complex requiring matching of photon with electron beams, and utilization of field‐in‐field techniques and of partial transmission blocks. HT is an arc‐rotational intensity modulated radiation therapy technique proven to achieve superior target dose conformality and sharp dose gradients around critical normal tissues. HT, however, has also been associated with higher volumes of low‐dose regions in normal tissues and, therefore, higher integral dose. The present study was undertaken to compare the dosimetry of 3D CRT to HT in a pediatric patient with advanced HD. Clinical target volume (CTV) included bilateral lower cervical and supraclavicular areas, mediastinum, bilateral hili, left axilla and bilateral diaphragmatic lymph nodes. The planning target volume (PTV) was derived by circumferentially expanding the CTV by 1 cm. Whole lung and heart irradiation was also planned due to bilateral pleural and pericardial effusions. The prescribed radiation dose was 21 Gy to the PTV and 10.5 Gy to the whole lung and heart. Target coverage was comparable for both plans. The minimum, maximum, and mean PTV doses were 18.61 Gy, 22.45 Gy and 21.52 Gy with 3D CRT and 19.85 Gy, 22.36 Gy and 21.39 Gy with HT, respectively. HT decreased mean normal tissue dose by 21.6% and 20.07% for right and left breast, 20.40% for lung, 30.78% for heart, and 22.74% for the thyroid gland. Integral dose also decreased with HT by 46.50%. HT results in significant dosimetric gain related to normal tissue sparing compared to 3D CRT. Further studies are warranted to evaluate clinical applications of HT in patients with HD.

PACS number: 87.53.Kn
Comparison of a 3D multi‐group particle transport code with Monte Carlo for intercavitary brachytherapy of the cervix uteri
Authors: Gifford Kent A. , Wareing Todd A. , Failla Gregory , Horton John L. , Eifel Patricia J. , Mourtada Firas
Published: February 2017

A patient dose distribution was calculated by a 3D multi‐group particle transport code for intracavitary brachytherapy of the cervix uteri and compared to previously published Monte Carlo results. A Cs‐137 LDR intracavitary brachytherapy CT data set was chosen from our clinical database. MCNPX version 2.5.c, was used to calculate the dose distribution. A 3D multi‐group particle transport code, Attila version 6.1.1 was used to simulate the same patient. Each patient applicator was built in SolidWorks, a mechanical design package, and then assembled with a coordinate transformation and rotation for the patient. The SolidWorks exported applicator geometry was imported into Attila for calculation. Dose matrices were overlaid on the patient CT data set. Dose volume histograms and point doses were compared. The MCNPX calculation required 14.8 hours, whereas the Attila calculation required 22.2 minutes on a 1.8 GHz AMD Opteron CPU. Agreement between Attila and MCNPX dose calculations at the ICRU 38 points was within . Calculated doses to the 2 cc and 5 cc volumes of highest dose differed by not more than between the two codes. Dose and DVH overlays agreed well qualitatively. Attila can calculate dose accurately and efficiently for this Cs‐137 CT‐based patient geometry. Our data showed that a three‐group cross‐section set is adequate for Cs‐137 computations. Future work is aimed at implementing an optimized version of Attila for radiotherapy calculations.

PACS number: 87.53.Jw
Analysis of RapidArc optimization strategies using objective function values and dose‐volume histograms
Authors: Oliver Mike , Gagne Isabelle , Popescu Carmen , Ansbacher Will , Beckham Wayne A.
Published: February 2017

RapidArc is a novel treatment planning and delivery system that has recently been made available for clinical use. Included within the Eclipse treatment planning system are a number of different optimization strategies that can be employed to improve the quality of the final treatment plan. The purpose of this study is to systematically assess three categories of strategies for four phantoms, and then apply proven strategies to clinical head and neck cases. Four phantoms were created within Eclipse with varying shapes and locations for the planning target volumes and organs at risk. A baseline optimization consisting of a single 359.8° arc with collimator at 45° was applied to all phantoms. Three categories of strategies were assessed and compared to the baseline strategy. They include changing the initialization parameters, increasing the total number of control points, and increasing the total optimization time. Optimization log files were extracted from the treatment planning system along with final dose‐volume histograms for plan assessment. Treatment plans were also generated for four head and neck patients to determine whether the results for phantom plans can be extended to clinical plans. The strategies that resulted in a significant difference from baseline were: changing the maximum leaf speed prior to optimization , increasing the total number of segments by adding an arc , and increasing the total optimization time by either continuing the optimization or adding time to the optimization by pausing the optimization . The reductions in objective function values correlated with improvements in the dose‐volume histogram (DVH). The addition of arcs and pausing strategies were applied to head and neck cancer cases, which demonstrated similar benefits with respect to the final objective function value and DVH. Analysis of the optimization log files is a useful way to intercompare treatment plans that have the same dose‐volume objectives and importance values. The results for clinical head and neck plans were consistent with phantom plans.

PACS number: 87.55.x, 87.55.D, 87.55.de 87.55.dk
Establishing radiation therapy treatment planning effects involving implantable pacemakers and implantable cardioverter‐defibrillators
Authors: Gossman Michael S. , Graves‐Calhoun Alison R. , Wilkinson Jeffrey D.
Published: February 2017

Recent improvements to the functionality and stability of implantable pacemakers and cardioverter‐defibrillators involve changes that include efficient battery power consumption and radiation hardened electrical circuits. Manufacturers have also pursued MRI‐compatibility for these devices. While such newer models of pacemakers and cardioverter‐defibrillators are similar in construction to previously marketed devices – even for the recent MRI‐compatible designs currently in clinical trials – there is increased interest now with regard to radiation therapy dose effects when a device is near or directly in the field of radiation. Specifically, the limitation on dose to the device from therapeutic radiation beams is being investigated for a possible elevation in limiting dose above 200 cGy. We present here the first‐ever study that evaluates dosimetric effects from implantable pacemakers and implantable cardioverter‐defibrillators in high energy X‐ray beams from a medical accelerator. Treatment plan simulations were analyzed for four different pacemakers and five different implantable cardioverter‐defibrillators and intercompared with direct measurements from a miniature ionization chamber in water. All defibrillators exhibited the same results and all pacemakers were seen to display the same consequences, within only a deviation for all X‐ray energies studied. Attenuation, backscatter, and lateral scatter were determined to be , 2.1% and 1.5% at 6 MV, and , 3.1% and 5.1% at 18 MV for the defibrillator group. For the pacemaker group, this research showed results of , 2.8% and 2.5% at 6 MV, and , 3.4% and 5.7% at 18 MV, respectively. Limited results were discovered from scattering processes through computer modeling. Strong verification from measurements was concluded with respect to simulating attenuation characteristics. For IP and ICD leads, measured dose changes were less than 4%, existing as attenuation processes only, and invariant with regard to X‐ray energy.

PACS number: 87.53.Bn, 87.53.Dq, 87.53.Tf, 87.66.Jj
Stereotactic body radiation therapy (SBRT) and respiratory gating in lung cancer: dosimetric and radiobiological considerations
Authors: Herman Tania De La Fuente , Vlachaki Maria T. , Herman Terence S. , Hibbitts Kerry , Stoner Julie A. , Ahmad Salahuddin
Published: February 2017

The purpose of this study was to assess the impact of respiratory gating on tumor and normal tissue dosimetry in patients treated with SBRT for early stage non‐small cell lung cancer (NSCLC). Twenty patients with stage I NSCLC were studied. Treatment planning was performed using four‐dimensional computed tomography (4D CT) with free breathing (Plan I), near‐end inhalation (Plan II), and near‐end exhalation (Plan III). The prescription dose was 60 Gy in three fractions. The tumor displacement was most pronounced for lower peripheral lesions (average 7.0 mm, range 4.1–14.3 mm) when compared to upper peripheral (average 2.4 mm, range 1.0–5.1 mm) or central lesions (average 2.9 mm, range 1.0–4.1 mm). In this study, the pencil beam convolution (PBC) algorithm with modified Batho power law for tissue heterogeneity was used for dose calculation. There were no significant differences in tumor and normal tissue dosimetry among the three gated plans. Tumor location however, significantly influenced tumor doses because of the necessity of respecting normal tissue constraints of centrally located structures. For plans I, II and III, average doses to central lesions were lower as compared with peripheral lesions by 4.88 Gy, 8.24 Gy and 6.93 Gy for minimum PTV and 0.98, 1.65 and 0.87 Gy for mean PTV dose, respectively. As a result, the mean single fraction equivalent dose (SFED) values were also lower for central compared to peripheral lesions. In addition, central lesions resulted in higher mean doses for lung, esophagus, and ipsilateral bronchus by 1.24, 1.93 and 7.75 Gy, respectively. These results indicate that the tumor location is the most important determinant of dosimetric optimization of SBRT plans. Respiratory gating proved unhelpful in the planning of these patients with severe COPD.

PACS numbers: 87.55.‐x, 87.55.kd, 87.90.+y
Clinical implications of adopting Monte Carlo treatment planning for CyberKnife
Authors: Sharma Subhash C. , Ott Joseph T. , Williams Jamone B. , Dickow Danny
Published: February 2017

It is documented that well‐modeled Monte Carlo dose calculation algorithms are more accurate than traditional correction‐based algorithms or convolution algorithms at predicting dose distributions delivered to heterogeneous volumes. This increased accuracy has clinical implications for CyberKnife, particularly when comparing dose distributions between the ray‐tracing and Monte Carlo algorithms. Differences between ray‐tracing and Monte Carlo calculations are exacerbated for highly heterogeneous volumes and small field sizes. In this study, the anthropomorphic thorax phantom from the Radiological Physics Center was used to validate the accuracy of the CyberKnife Monte Carlo dose calculation algorithm. Retrospective comparisons of dose distributions calculated by ray‐tracing and Monte Carlo were made for a selection of CyberKnife treatment plans; comparisons were based on target coverage and conformality. For highly heterogeneous cases, such as those involving the lungs, the ray‐tracing algorithm consistently overestimated the target dose and coverage. In our sample of lung treatment plans, the average target coverage for ray‐tracing calculations was 97.7%, while for Monte Carlo, the average coverage dropped to 69.2%. In each plan comparison, the same beam orientations and monitor units were used for both calculations. Significant changes in conformality were also observed. Isodose prescription lines and subsequent target coverage selected for treatment plans calculated with the ray‐tracing algorithm may be different from comparable treatment plans calculated with Monte Carlo, and as such, may have clinical implications for dose prescriptions.

PACS number: 87.53.Wz
Dose perturbation due to the polysulfone cap surrounding a Fletcher‐Williamson colpostat
Authors: Price Michael J. , Kry Stephen F. , Eifel Patricia J. , Salehpour Mohammad , Mourtada Firas
Published: February 2017

We conducted a Monte Carlo evaluation of the dosimetric impact of the polysulfone cap used with the Fletcher‐Williamson (FW) colpostat for high‐dose rate and pulsed‐dose rate intracavitary brachytherapy. Polysulfone caps with diameters of 30 mm, 25 mm, 20 mm, and 16 mm (mini‐ovoid) were simulated, and the absorbed dose rate in surrounding water was calculated and compared to the dose rate calculated for a bare source in water. The dose perturbation depended on the cap diameter, distance away from the cap surface, and angular position around the cap. The largest dose rate reductions were found to be where the cap is thickest, in the general direction of the tumor bed. The range of perturbation mainly from the polysulfone cap over all depths and cap diameters was (dose enhancement) to (dose reduction); this perturbation is separate from the well‐documented attenuation of the rectal and bladder tungsten shields of the colpostat. Based on the impact of the polysulfone cape, the FW colpostat cap's material composition should be modified to reduce this dosimetric effect, or brachytherapy treatment planning dose algorithms should be improved to account for this perturbation.

PACS numbers: 87.10.Rt 87.53.‐j 87.53.Bn 87.53.Jw
Initial dosimetric evaluation of SmartArc – a novel VMAT treatment planning module implemented in a multi‐vendor delivery chain
Authors: Feygelman Vladimir , Zhang Geoffrey , Stevens Craig
Published: February 2017

We performed an initial dosimetric evaluation of SmartArc – a novel VMAT planning module for the Philips Pinnacle treatment planning system. It was implemented in a multi‐vendor environment, with the other two major components of the delivery chain being MOSAIQ record and verify system (IMPAC Medical Systems, Sunnyvale, CA) and a Trilogy linac (Varian Medical Systems, Palo Alto, CA). A test suite of structure sets and dose objectives provided by the AAPM for multi‐institutional comparison of IMRT dosimetry was used. A total of fifty plans were successfully delivered. The effect of control point spacing on dosimetric accuracy was investigated. When calculated with the 4° spacing, the overall mean point dose errors measured with an ion chamber were and for the PTV and OAR, respectively. The γ(3%, 3 mm) passing rate, measured for absolute dose with a biplanar diode array, was (range 94.5–99.9%). Ninety percent of the passing rate values were above 97.7%. With the 6° control point spacing, the highly modulated plans exhibited large dosimetric errors (e.g. γ(3%, 3 mm) passing rates below 90% and ion chamber point dose errors of 6–12%), while the results were still acceptable for the simpler cases. The data show that the practical accuracy of the small‐arc approximation, which is at the heart of VMAT dose calculations, depends not only on the control point spacing, but also on the size and relative position of the MLC openings corresponding to the consecutive control points. The effect of the minimum allowed separation between the opposing leaves was found to be minimal. It appears that 4° control point spacing may be a good compromise between calculation speed and accuracy. However each institution is encouraged to establish its own treatment planning guidelines based on the case complexity and acceptable error level.

PACS number: 87.55Qr
Future trends in the supply and demand for radiation oncology physicists
Authors: Mills Michael D. , Thornewill Judah , Esterhay Robert J.
Published: February 2017

Significant controversy surrounds the 2012 / 2014 decision announced by the Trustees of the American Board of Radiology (ABR) in October of 2007. According to the ABR, only medical physicists who are graduates of a Commission on Accreditation of Medical Physics Education Programs, Inc. (CAMPEP) accredited academic or residency program will be admitted for examination in the years 2012 and 2013. Only graduates of a CAMPEP accredited residency program will be admitted for examination beginning in the year 2014. An essential question facing the radiation oncology physics community is an estimation of supply and demand for medical physicists through the year 2020. To that end, a Demand & Supply dynamic model was created using STELLA software. Inputs into the model include: a) projected new cancer incidence and prevalence 1990–2020; b) AAPM member ages and retirement projections 1990–2020; c) number of ABR physics diplomates 1990–2009; d) number of patients per Qualified Medical Physicist from Abt Reports I (1995), II (2002) and III (2008); e) non‐CAMPEP physicists trained 1990–2009 and projected through 2014; f) CAMPEP physicists trained 1993–2008 and projected through 2014; and g) working Qualified Medical Physicists in radiation oncology in the United States (1990–2007). The model indicates that the number of qualified medical physicists working in radiation oncology required to meet demand in 2020 will be 150–175 per year. Because there is some elasticity in the workforce, a portion of the work effort might be assumed by practicing medical physicists. However, the minimum number of new radiation oncology physicists (ROPs) required for the health of the profession is estimated to be 125 per year in 2020. The radiation oncology physics community should plan to build residency programs to support these numbers for the future of the profession.

PACS numbers: 87.90.+y, 87.53.‐j
Evaluation of fluence‐smoothing feature for three IMRT planning systems
Authors: Anker Christopher J. , Wang Brian , Tobler Matt , Chapek Julie , Shrieve Dennis C. , Hitchcock Ying J. , Salter Bill J.
Published: February 2017

Commercially available intensity‐modulated radiation therapy (IMRT) inverse treatment planning systems (ITPS) typically include a smoothing function which allows the user to vary the complexity of delivered beam fluence patterns. This study evaluated the behavior of three ITPSs when varying smoothing parameters. We evaluated four cases treated with IMRT in our clinic: sinonasal carcinoma (SNC), glioblastoma multiforme (GBM), base of tongue carcinoma (BOT), and prostate carcinoma (PST). Varian Eclipse v6.5, BrainLAB BrainScan v5.31, and Nomos Corvus v6.2 ITPSs were studied for the SNC, GBM, and PST sites. Only Eclipse and Corvus were studied for BOT due to field size constraints of the BrainLAB MM3 collimator. For each ITPS, plans were first optimized using vendor‐recommended default “smoothing” values. Treatment plans were then reoptimized, exploring various smoothing values. Key metrics recorded included a delivery complexity (DC) metric and the Ian Paddick Conformality Index (IPCI). Results varied widely by vendor with regard to the impact of smoothing on complexity and conformality. Plans run on the Corvus ITPS showed the logically anticipated increase in DC as smoothing was decreased, along with associated improved organ‐at‐risk (OAR) sparing. Both Eclipse and BrainScan experienced an expected trend for increased DC as smoothing was decreased. However, this increase did not typically result in appreciably improved OAR sparing. For Eclipse and Corvus, and to a much lesser extent BrainScan, increases in smoothing decreased DC but eventually caused unacceptable losses in plan conformality. Depending on the ITPS, potential benefits from optimizing fluence smoothing levels can be significant, allowing for increases in either efficiency or conformality. Because of variability in smoothing function behavior by ITPS, it is important that users familiarize themselves with the effects of varying smoothing parameters for their respective ITPS. Based on the experience gained here, we provide recommended workflows for each ITPS to best exploit the fluence‐smoothing features of the system.

PACS numbers: 87.56.bd, 87.56.N‐
Dosimetric assessment of rigid setup error by CBCT for HN‐IMRT
Authors: Worthy Danielle , Wu Qiuwen
Published: February 2017

Dose distributions in HN‐IMRT are complex and may be sensitive to the treatment uncertainties. The goals of this study were to evaluate: 1) dose differences between plan and actual delivery and implications on margin requirement for HN‐IMRT with rigid setup errors; 2) dose distribution complexity on setup error sensitivity; and 3) agreement between average dose and cumulative dose in fractionated radiotherapy. Rigid setup errors for HN‐IMRT patients were measured using cone‐beam CT (CBCT) for 30 patients and 896 fractions. These were applied to plans for 12 HN patients who underwent simultaneous integrated boost (SIB) IMRT treatment. Dose distributions were recalculated at each fraction and summed into cumulative dose. Measured setup errors were scaled by factors of 2–4 to investigate margin adequacy. Two plans, direct machine parameter optimization (DMPO) and fluence only (FO), were available for each patient to represent plans of different complexity. Normalized dosimetric indices, conformity index (CI) and conformation number (CN) were used in the evaluation. It was found that current 5 mm margins are more than adequate to compensate for rigid setup errors, and that standard margin recipes overestimate margins for rigid setup error in SIB HN‐IMRT because of differences in acceptance criteria used in margin evaluation. The CTV‐to‐PTV margins can be effectively reduced to 1.9 mm and 1.5 mm for CTV1 and CTV2. Plans of higher complexity and sharper dose gradients are more sensitive to setup error and require larger margins. The CI and CN are not recommended for cumulative dose evaluation because of inconsistent definition of target volumes used. For fractionated radiotherapy in HN‐IMRT, the average fractional dose does not represent the true cumulative dose received by the patient through voxel‐by‐voxel summation, primarily due to the setup error characteristics, where the random component is larger than systematic and different target regions get underdosed at each fraction.

PACS numbers: 87.53.Kn, 87.53.Tf.