bluuebunny/crossref_metadata_2025 huggingface dataset:
More Regulation of Industry-Supported Biomedical Research: Are We Asking the Right Questions?
Authors: Fry-Revere Sigrid , Malmstrom David Bjorn
Published: August 2009

There is no doubt that industry-sponsored biomedical research is under the microscope. Unfortunately, this new era of skepticism prematurely rushes in doubts of the ethos of science. Skepticism can lead to positive changes, but only when timely and supported by sound reasoning. Snapshot views and theories, especially those that result in costly new regulations and inefficient policies often do more harm than good. Many critics would have the reader doubt scientific integrity because they believe that the relationship between the pharmaceutical industry and biomedical research poses an unavoidable and dangerous conflict of interest. However, these conflicts are neither unavoidable nor dangerous per se.
Pharmaceutical Industry Financial Support for Medical Education: Benefit, or Undue Influence?
Authors: Brody Howard
Published: August 2009

As early as the 1960s and 1970s, astute commentators began to call into question the degree of influence that the pharmaceutical industry was exercising over all aspects of medical research, education, and practice in the U.S. More recently, a spate of books and articles demonstrates that the issue has only become more serious in the last decade or two.

My focus in this paper will be on the industry’s influence on medical education. The influence that the industry exerts on undergraduate and graduate medical education (that is, the training of medical students and residents) often occurs through the system of pharmaceutical sales representatives, who also “detail” drugs to practitioners; or through the influence that the industry exerts over medical research. I will therefore devote my attention here primarily to the system of continuing medical education (CME) by which practitioners receive information about medical advances. The pharmaceutical industry currently supports about one-half of the costs of CME in the U.S., so it seems appropriate to question the degree of industry influence over the content of CME.
Administrative Law v. Constitutional Law: The Correct Decision on FDA’s Treatment of Plan B
Authors: Shachar Carmel
Published: August 2009

In order for the Food and Drug Administration (FDA) to receive the trust and deference it needs to accomplish its mission, it must be seen as relatively impervious to political manipulation. For most of the FDA’s history, it has been seen as an institution driven by scientific expertise, not by political maneuvering. However, the FDA was increasingly criticized during the Bush administration for politicizing decisions such as rejecting an application to grant the “morning after pill,” known as Plan B, over-the-counter (OTC) status for women of all ages. After an atypical approval process, the FDA approved OTC Plan B use only for women over the age of 18. Because some groups perceive the morning after pill as a form of abortion, the politically appointed leadership of the FDA was suspected of dramatically departing from normal FDA procedures in order to ensure that the application would not be approved.
Project Overview and Emerging Themes
Authors: Connors Elenora E. , Westmoreland Timothy M.
Published: August 2009

The American public has increasingly identified health care as a key issue of concern. In order to address the multiple problems relating to the access and affordability of health care, President Obama and federal lawmakers across the political spectrum continue to call for major health reform. In any debate on health reform, a predictable set of complex policy, management, economic, and legal issues is likely to be raised. Due to the diverse interests involved, these issues could lead to a series of high-stakes policy debates. Therefore, it is critical that advocates of reform strategies anticipate such issues in order to decrease the likelihood that legally resolvable questions become barriers to substantive health reform. In an effort to frame and study legal challenges and solutions in advance of the heat of political debate, the O’Neill Institute for National and Global Health Law at Georgetown University and the Robert Wood Johnson Foundation have crafted the “Legal Solutions in Health Reform” project.
Executive Authority to Reform Health: Options and Limitations
Authors: Chugh Madhu
Published: August 2009

Presidential power has provoked increasingly vigorous debate since the turn of this century. In recent years, scholars and lawyers have been grappling with how Congress’s dictates may limit the president’s Commander-in-Chief power to detain enemy combatants at Guantanamo Bay, to fight wars abroad, and to conduct intelligence activities at home. But policymakers have not yet explored the many possibilities for invoking the president’s “Take Care” power to change health care policy.

This article explores the scope and limits of President Barack Obama’s ability to invoke his executive authority to reform health care. Specifically, it identifies ways the Obama Administration can use directives to: (1) expand Medicaid and State Children’s Health Insurance Program (SCHIP) coverage through section 1115 waivers; (2) test quality initiatives through Medicare demonstration authority; (3) expand health information technology; (4) allow drug reimportation and experiment with contracting power under Medicare; (5) enhance patient protections and private coverage requirements; (6) lift coverage restrictions on Medicaid and SCHIP; and (7) build on the health insurance program for federal employees. Consistent with the mission of the Legal Solutions in Health Reform project, this article does not endorse a particular policy. Instead of recommending “what,” it explains “how.”
Yoga Breathing, Meditation, and Longevity
Authors: Brown Richard P. , Gerbarg Patricia L.
Published: August 2009

Yoga breathing is an important part of health and spiritual practices in Indo‐Tibetan traditions. Considered fundamental for the development of physical well‐being, meditation, awareness, and enlightenment, it is both a form of meditation in itself and a preparation for deep meditation. Yoga breathing (pranayama) can rapidly bring the mind to the present moment and reduce stress. In this paper, we review data indicating how breath work can affect longevity mechanisms in some ways that overlap with meditation and in other ways that are different from, but that synergistically enhance, the effects of meditation. We also provide clinical evidence for the use of yoga breathing in the treatment of depression, anxiety, post‐traumatic stress disorder, and for victims of mass disasters. By inducing stress resilience, breath work enables us to rapidly and compassionately relieve many forms of suffering.
Wisdom and Method
Authors: Tsondu Geshe Ngawang , Dodson‐Lavelle Brooke
Published: August 2009

The focus in our discussion of longevity‐enhancement has centered on developing techniques and technologies to control the environment as well as the physical body and its functions. The Tibetan contemplative and medical sciences offer a sophisticated view of the mind‐body complex in which efforts to control the external world are insufficient without the development of “inner” technologies to train the mind. From the Tibetan perspective, training the mind is in fact essential to the realization of extraordinary levels of longevity, happiness, and optimal health.
Beyond Cell Doctrine
Authors: Theise Neil D.
Published: August 2009

Cell doctrine is the foundational paradigm of Euro‐American medicine and biology. Even without stepping outside that tradition, one may imagine alternate models of the body such as a fluid model in which cells do not exist or a model wherein cells are described as overlapping fields of molecular organization in space and time. With a complexity analysis of cell biology, we find that the existence of cells as unitary entities, as things, is contingent on the level of scale at which the body is observed. Therefore, alternate models of the body may be conceived that are specific and appropriate to other levels of scale. These ideas suggest that some bodily phenomena, particularly from Asian traditions, which have previously resisted explanation from within the cell‐based Euro‐American tradition (e.g., acupuncture) may be productively investigated with one or more of these other models. Additionally, the seemingly metaphorical concepts from Tibetan medicine of the coarse, energy, and subtle bodies may represent precise, though somewhat poetically expressed representations of the body at different levels of scale.
The Relationship between Inflammation and Regeneration in the MRL Mouse
Authors: Heber‐Katz Ellen , Gourevitch Dmitri
Published: August 2009

The matrix metalloproteinases (MMPs) have been implicated in the regenerative response in amphibians and various mammalian models of regeneration. The neutrophil response is known to bring MMPs and other proteases to the wound to promote bacterial elimination and tissue remodeling. These issues in relation to what is occurring in the MRL mouse model of regeneration/wound healing are discussed, followed by speculation as to their possible relevance for examples of the putative scarless wound healing described by some medical anthropologists and clinicians.
Longevity
Authors: Bushell William C.
Published: August 2009

This chapter briefly reviews recent psychological, physiological, molecular biological, and anthropological research which has important implications, both direct and indirect, for the recognition and understanding of the potential life span and health span enhancing effects of the basic yoga meditational regimen. This regimen consists of meditation, yogic breath control practices, physical exercises (of both a postural‐ and movement‐based, including aerobic nature), and dietary practices. While each of these component categories exhibit variations in different schools, lineages, traditions, and cultures, the focus of this chapter is primarily on basic forms of relaxation meditation and breath control, as well as postural and aerobic physical exercises (e.g., yogic prostration regimens, see below), and a standard form of yogic or ascetic diet, all of which constitute a basic form of regimen found in many if not most cultures, though with variations.
Differential brain activation during response inhibition in bipolar and attention‐deficit hyperactivity disorders
Authors: Cerullo Michael A. , Adler Caleb M. , Lamy Martine , Eliassen James C. , Fleck David E. , Strakowski Stephen M. , DelBello Melissa P.
Published: August 2009

Aim: To identify differential patterns of brain activation between adolescents with bipolar disorder and adolescents with attention‐deficit hyperactivity disorder (ADHD) to better understand the neurophysiology of both disorders. We hypothesized that subjects with ADHD would show altered activation in brain regions involved in executive and sustained attention. In contrast, we hypothesized that bipolar subjects would show altered brain activation in regions responsible for emotionally homeostasis, including the striatum and amygdala.

Methods: Functional magnetic resonance imaging was performed during a continuous performance task with a response inhibition component in 11 adolescents with bipolar disorder during a manic episode, 10 adolescents with ADHD, and 13 healthy adolescents.

Results: There were no differences in behavioural performance among the three groups. Compared with bipolar subjects, subjects with ADHD showed increased activation in the superior temporal lobe during successful response inhibition. Although bipolar subjects did not show activation differences in the striatum or amygdala compared with ADHD subjects, increased left parahippocampal activation in the bipolar group was associated with increased manic symptoms.

Conclusions: The patterns of brain activation observed in the current study support divergent patterns of neurophysiological dysfunction in individuals with bipolar disorder as compared with those with ADHD. Therefore, the impulsive behaviour seen in both disorders may be the consequence of dysfunction in different brain regions, and further research may help identify neurobiological markers that are specific to each condition.
Do premorbid impairments predict emergent ‘prodromal’ symptoms in young relatives at risk for schizophrenia?
Authors: Keshavan Matcheri S. , Eack Shaun M. , Montrose Debra M. , Abela Michelle M. , Bangalore Srihari S. , Diwadkar Vaibhav A. , Prasad Konasale M. R. ,   Rajaprabhakaran Rajarethinam
Published: August 2009

Aims:Individuals at risk for developing schizophrenia (SZ) in the future frequently exhibit subtle behavioural and neurobiological abnormalities in their childhood. A better understanding of the role of these abnormalities in predicting later onset of ‘prodromal’ symptoms or psychosis may help in early identification of SZ.

Methods:In an ongoing prospective follow‐up study of young genetically at‐risk relatives of patients with SZ, we studied the prevalence of problems in premorbid social adjustment and childhood psychopathology and examined their relationship with the presence and progression of ‘prodromal’ symptoms of SZ.

Results:Growth curve analyses showed that ‘prodromal’ symptoms, as measured by the Scale of ‘Prodromal’ Symptoms, increased during follow‐up. Premorbid maladjustment and childhood behavioural disturbances were cross‐sectionally correlated broadly with ‘prodromal’ symptomatology scores. Longitudinal analyses revealed that behavioural disturbances, but not childhood maladjustment at baseline, significantly predicted increases in ‘prodromal’ symptomatology during the 2‐year study period.

Conclusion:Premorbid behavioural disturbance and maladjustment may predict the later emergence of ‘prodromal’ symptoms. ‘Prodromal’ symptoms in young at‐risk relatives may define a subgroup worthy of follow‐up into the age of risk for psychosis in order to cost‐effectively characterize the predictors of psychotic symptoms and SZ.
Evaluation of pollen morphology as a taxonomic character for generic delimitation in Scilla s.l. (Hyacinthaceae)
Authors: Ghavami E. , Jamzad Z. , Tavasoli A.
Published: August 2009

Scilla L. s.l. (Hyacinthaceae) comprises about 100 species distributed in south Europe, the Mediterranean region, and central and western Asia with 10 species reported from Iran.

However, according to recent studies based on molecular data Scilla s.l. is not monophyletic and should be divided into several smaller genera, i.e. Fessia Speta, Othocallis Salisb., Pfosseria Speta, Prospero Salisb., Scilla s.s. and Zagrosia Speta.

In the present study the pollen grains of 13 species representing six segregate genera within Scilla s.l. were studied to evaluate the taxonomic value of pollen characters for generic delimitation. Pollen grains of all examined species were found to be monosulcate, prolate or sub‐prolate and heteropolar. Three different types of exine sculpturing were recognized: fossulate, perforate–reticulate and perforate.

In Prospero autumnale (=Scilla autumnalis) pollen exine sculpturing is fossulate. In Othocallis armena, O. mischtschenkoana, O. rosenii and O. siberica (=Scilla armena, S. mischtschenkoana, S. rosenii and S. siberica) exine sculpturing is perforate–reticulate with mainly large perforations surrounded by smaller ones. In Fessia gorganica, F. greilhuberi, F. hohenakeri, F. khorassanica and F. raewskiana (=S. gorganica, S. greilhuberi, S. hohenakeri, S. khorassanica and S. raewskiana) the exine is perforate with rather uniform perforation. Zagrosia persica (=S. persica) has the same exine type as Fessia spp. In Pfosseria, the exine is perforate with linear and circular perforations. Scilla s.s. has a perforate exine, but the perforations are not uniform and their size and shape are variable.

Our results are generally congruent with the circumscription of the new genera previously included in Scilla s.l. and show that pollen exine morphology is useful as an additional taxonomic character for the delimitation these segregate genera.
Stating and Supporting Opinions in an Interview: L1 and L2 Japanese Speakers
Authors: Iwasaki Noriko
Published: August 2009

Abstract: Stating and supporting opinions are important speech acts for language learners to develop. This article examines how speakers of Japanese as their first language (L1) state and support their opinions. Performances of second language (L2) learners of Japanese were also examined to identify the language abilities that L2 learners may need to develop. While L1 speakers often sought common ground using various mitigation devices such as ‐zyanai desu ka (“isn't the case that”), ‐yone (“y'know”), and the modal adverb yappari (“after all, as expected”), L2 learners enrolled in a 4th‐year Japanese course rarely sought common ground using these devices. In order to help L2 learners develop their ability to state and support opinions in a socioculturally appropriate way, it is important to provide guided opportunities for them to produce discourse‐level exchanges beyond sentence‐level opinion statements.
Integrating Language and Literature: Teaching Textual Analysis with Input and Output Activities and an Input‐to‐Output Approach
Authors: Weber‐Fève Stacey
Published: August 2009

Abstract: The Modern Language Association report and Profession issue from summer 2007 (Geisler et al., 2007) are highly indicative of the increasingly debated concerns in the profession surrounding (1) the traditional division of foreign language curriculum between “language” and “literature” and (2) the instruction of textual analysis (or practice of close reading) in the student‐centered literature classroom. In this article, I discuss the need in the profession to address the contemporary problems inherited from the traditional “language‐literature” divide and postulate the use of close reading as a tactic to overcome this traditional divide. This article specifically addresses the issue of “why” and “how” to teach students textual analysis meaningfully and communicatively in the foreign language classroom and then proposes and demonstrates the use of input and output activities as a pedagogical strategy.
One Right Way, Intercultural Participation, and Language Learning Anxiety: A Qualitative Analysis of Adult Online Heritage and Nonheritage Language Learners
Authors: Coryell Joellen E. , Clark M. Carolyn
Published: August 2009

Abstract: This study investigated self‐assessed anxious learners who enrolled in online Spanish courses to determine if their anxiety was mediated by the lack of face‐to‐face (F2F) and other synchronous learning interactions. Participants were enrolled in courses at two postsecondary institutions located in south‐central Texas. Narrative analysis was used to interpret the interview data. Findings indicated participants experienced language anxiety because their previous F2F and online learning experiences enforced the concept of language as performance with a focus on correctness and precision. However, intercultural respect and a desire to participate meaningfully with diverse cultural communities became a resource for our participants as they wrestled with language learning anxiety and persisted in their learning endeavors. Implications for designing online language instruction for anxious, self‐directed adults are offered.
Making Rapid Gains in Second Language Writing: A Case Study of a Third‐Year Russian Language Course
Authors: Brown N. Anthony , Bown Jennifer , Eggett Dennis L.
Published: August 2009

Abstract: This research describes a method applied in a third‐year Russian language course designed to push students' writing proficiency to the Intermediate/Advanced threshold and beyond and the findings associated therewith. The approach centered around argumentation and debate, a subject usually designed to improve students' command of logic and reasoning in their first language, but rarely found in second language curricula, much less with an emphasis on writing rather than speaking. Data supporting the researchers' claims reflect ACTFL pre‐ and post‐written proficiency test ratings, biweekly rough draft scores, and participants' responses to a language background questionnaire. Findings suggest that an emphasis on argumentation and debate and content‐based instruction proved statistically significant. In addition, participants in the treatment group benefited considerably from the inclusion of native speaker consultations.
Computational Fluid Dynamics Simulations of Intracranial Aneurysms at Varying Heart Rates: A “Patient-Specific” Study
Authors: Jiang Jingfeng , Strother Charles
Published: August 2009

Rupture of an intracranial aneurysm (IA) is frequently associated with intense physical exertion and/or emotional excitement, events that are typically also accompanied by sudden significant changes in both heart rate and blood pressure. Very few experimental studies of aneurysm hemodynamics have examined the impact on hemodynamic parameters in and around an aneurysm resulting from changes in heart rate. In order to further understanding these changes, as they relate to hemodynamic features that may contribute to rupture of an IA, we examined the characteristics of pulsatile flow in and around two “patient-specific” intracranial aneurysms at three different cardiac frequencies. Three dimensional X-ray angiographic data (3D-DSA) were used to reconstruct accurate and patient-specific aneurysm geometries. Then, computational fluid dynamics techniques were utilized to analyze the characteristics of blood flow in and around the two aneurysms. Physiologically realistic flow conditions, as measured by transcranial Doppler ultrasound, were used in the simulations. Our results showed that there were significant changes in the overall flow patterns (e.g., vortex formation and translation) associated with the changes of heart rates. In both aneurysms, the calculated wall shear stress exhibited substantial increases with an increase in heart rate. Our results suggest that the changes in local hemodynamic forces associated with variations in heart rate are dependent not only on the heart rate but also on the aneurysm geometry. This thus precludes applying our observations about the impact of variations in cardiac rate to aneurysms in general.
Prediction of Plantar Shear Stress Distribution by Artificial Intelligence Methods
Authors: Yavuz Metin , Ocak Hasan , Hetherington Vincent J. , Davis Brian L.
Published: August 2009

Shear forces under the human foot are thought to be responsible for various foot pathologies such as diabetic plantar ulcers and athletic blisters. Frictional shear forces might also play a role in the metatarsalgia observed among hallux valgus (HaV) and rheumatoid arthritis (RA) patients. Due to the absence of commercial devices capable of measuring shear stress distribution, a number of linear models were developed. All of these have met with limited success. This study used nonlinear methods, specifically neural network and fuzzy logic schemes, to predict the distribution of plantar shear forces based on vertical loading parameters. In total, 73 subjects were recruited; 17 had diabetic neuropathy, 14 had HaV, 9 had RA, 11 had frequent foot blisters, and 22 were healthy. A feed-forward neural network (NN) and adaptive neurofuzzy inference system (NFIS) were built. These systems were then applied to a custom-built platform, which collected plantar pressure and shear stress data as subjects walked over the device. The inputs to both models were peak pressure, peak pressure-time integral, and time to peak pressure, and the output was peak resultant shear. Root-mean-square error (RMSE) values were calculated to test the models’ accuracy. RMSE/actual shear ratio varied between 0.27 and 0.40 for NN predictions. Similarly, NFIS estimations resulted in a 0.28–0.37 ratio for local peak values in all subject groups. On the other hand, error percentages for global peak shear values were found to be in the range 11.4–44.1. These results indicate that there is no direct relationship between pressure and shear magnitudes. Future research should aim to decrease error levels by introducing shear stress dependent variables into the models.
Development and Verification of a High-Fidelity Computational Fluid Dynamics Model of Canine Nasal Airflow
Authors: Craven Brent A. , Paterson Eric G. , Settles Gary S. , Lawson Michael J.
Published: August 2009

The canine nasal cavity contains a complex airway labyrinth, dedicated to respiratory air conditioning, filtering of inspired contaminants, and olfaction. The small and contorted anatomical structure of the nasal turbinates has, to date, precluded a proper study of nasal airflow in the dog. This study describes the development of a high-fidelity computational fluid dynamics (CFD) model of the canine nasal airway from a three-dimensional reconstruction of high-resolution magnetic resonance imaging scans of the canine anatomy. Unstructured hexahedral grids are generated, with large grid sizes ((10–100)×106 computational cells) required to capture the details of the nasal airways. High-fidelity CFD solutions of the nasal airflow for steady inspiration and expiration are computed over a range of physiological airflow rates. A rigorous grid refinement study is performed, which also illustrates a methodology for verification of CFD calculations on complex unstructured grids in tortuous airways. In general, the qualitative characteristics of the computed solutions for the different grid resolutions are fairly well preserved. However, quantitative results such as the overall pressure drop and even the regional distribution of airflow in the nasal cavity are moderately grid dependent. These quantities tend to converge monotonically with grid refinement. Lastly, transient computations of canine sniffing were carried out as part of a time-step study, demonstrating that high temporal accuracy is achievable using small time steps consisting of 160 steps per sniff period. Here we demonstrate that acceptable numerical accuracy (between approximately 1% and 15%) is achievable with practical levels of grid resolution (∼100×106 computational cells). Given the popularity of CFD as a tool for studying flow in the upper airways of humans and animals, based on this work we recommend the necessity of a grid dependence study and quantification of numerical error when presenting CFD results in complicated airways.
A Phenomenological Approach Toward Patient-Specific Computational Modeling of Articular Cartilage Including Collagen Fiber Tracking
Authors: Pierce David M. , Trobin Werner , Trattnig Siegfried , Bischof Horst , Holzapfel Gerhard A.
Published: August 2009

To model the cartilage morphology and the material response, a phenomenological and patient-specific simulation approach incorporating the collagen fiber fabric is proposed. Cartilage tissue response is nearly isochoric and time-dependent under physiological pressure levels. Hence, a viscoelastic constitutive model capable of reproducing finite strains is employed, while the time-dependent deformation change is purely isochoric. The model incorporates seven material parameters, which all have a physical interpretation. To calibrate the model and facilitate further analysis, five human cartilage specimens underwent a number of tests. A series of magnetic resonance imaging (MRI) sequences is taken, next the cartilage surface is imaged, then mechanical indentation tests are completed at 2–7 different locations per sample, resulting in force/displacement data over time, and finally, the underlying bone surface is imaged. Imaging and mechanical testing are performed with a custom-built robotics-based testing device. Stereo reconstruction of the cartilage and subchondral bone surface is employed, which, together with the proposed constitutive model, led to specimen-specific finite element simulations of the mechanical indentation tests. The force-time response of 23 such indentation experiment simulations is optimized to estimate the mean material parameters and corresponding standard deviations. The model is capable of reproducing the deformation behavior of human articular cartilage in the physiological loading domain, as demonstrated by the good agreement between the experiment and numerical results (R2=0.95±0.03, mean±standard deviation of force-time response for 23 indentation tests). To address validation, a sevenfold cross-validation experiment is performed on the 21 experiments representing healthy cartilage. To quantify the predictive error, the mean of the absolute force differences and Pearson’s correlation coefficient are both calculated. Deviations in the mean absolute difference, normalized by the peak force, range from 4% to 90%, with 40±25%(M±SD). The correlation coefficients across all predictions have a minimum of 0.939, and a maximum of 0.993 with 0.975±0.013(M±SD), which demonstrates an excellent match of the decay characteristics. A novel feature of the proposed method is 3D sample-specific numerical tracking of the fiber fabric deformation under general loading. This feature is demonstrated by comparing the estimated fiber fabric deformation with recently published experimental data determined by diffusion tensor MRI. The proposed approach is efficient enough to enable large-scale 3D contact simulations of knee joint loading in simulations with accurate joint geometries.
Increased Microstructural Variability is Associated With Decreased Structural Strength But With Increased Measures of Structural Ductility in Human Vertebrae
Authors: Yerramshetty Janardhan , Kim Do-Gyoon , Yeni Yener N.
Published: August 2009

The lack of accuracy in the prediction of vertebral fracture risk from average density measurements, all external factors being equal, may not just be because bone mineral density (BMD) is less than a perfect surrogate for bone strength but also because strength alone may not be sufficient to fully characterize the structural failure of a vertebra. Apart from bone quantity, the regional variation of cancellous architecture would have a role in governing the mechanical properties of vertebrae. In this study, we estimated various microstructural parameters of the vertebral cancellous centrum based on stereological analysis. An earlier study indicated that within-vertebra variability, measured as the coefficient of variation (COV) of bone volume fraction (BV/TV) or as COV of finite element-estimated apparent modulus (EFE) correlated well with vertebral strength. Therefore, as an extension to our earlier study, we investigated (i) whether the relationships of vertebral strength found with COV of BV/TV and COV of EFE could be extended to the COV of other microstructural parameters and microcomputed tomography-estimated BMD and (ii) whether COV of microstructural parameters were associated with structural ductility measures. COV-based measures were more strongly associated with vertebral strength and ductility measures than average microstructural measures. Moreover, our results support a hypothesis that decreased microstructural variability, while associated with increased strength, may result in decreased structural toughness and ductility. The current findings suggest that variability-based measures could provide an improvement, as a supplement to clinical BMD, in screening for fracture risk through an improved prediction of bone strength and ductility. Further understanding of the biological mechanisms underlying microstructural variability may help develop new treatment strategies for improved structural ductility.
A New Laser Reflectance System Capable of Measuring Changing Cross-Sectional Area of Soft Tissues During Tensile Testing
Authors: Pokhai Gabriel G. , Oliver Michele L. , Gordon Karen D.
Published: August 2009

Determination of the biomechanical properties of soft tissues such as tendons and ligaments is dependent on the accurate measurement of their cross-sectional area (CSA). Measurement methods, which involve contact with the specimen, are problematic because soft tissues are easily deformed. Noncontact measurement methods are preferable in this regard, but may experience difficulty in dealing with the complex cross-sectional shapes and glistening surfaces seen in soft tissues. Additionally, existing CSA measurement systems are separated from the materials testing machine, resulting in the inability to measure CSA during testing. Furthermore, CSA measurements are usually made in a different orientation, and with a different preload, prior to testing. To overcome these problems, a noncontact laser reflectance system (LRS) was developed. Designed to fit in an Instron 8872 servohydraulic test machine, the system measures CSA by orbiting a laser transducer in a circular path around a soft tissue specimen held by tissue clamps. CSA measurements can be conducted before and during tensile testing. The system was validated using machined metallic specimens of various shapes and sizes, as well as different sizes of bovine tendons. The metallic specimens could be measured to within 4% accuracy, and the tendons to within an average error of 4.3%. Statistical analyses showed no significant differences between the measurements of the LRS and those of the casting method, an established measurement technique. The LRS was successfully used to measure the changing CSA of bovine tendons during uniaxial tensile testing. The LRS developed in this work represents a simple, quick, and accurate way of reconstructing complex cross-sectional profiles and calculating cross-sectional areas. In addition, the LRS represents the first system capable of automatically measuring changing CSA of soft tissues during tensile testing, facilitating the calculation of more accurate biomechanical properties.
Effect of sidewall passivation in BCl3∕N2 inductively coupled plasma etching of two-dimensional GaAs photonic crystals
Authors: Atlasov Kirill A. , Gallo Pascal , Rudra Alok , Dwir Benjamin , Kapon Eli
Published: August 2009

The effect of surface passivation in BCl3∕N2 inductively coupled plasma reactive-ion etching of GaAs-based photonic crystals (PhCs) was investigated. It is shown that sidewall passivation is crucial for achieving cylindrical, vertical PhC holes, where the exact shape of the hole is controlled via the N2 content in the plasma composition. The achieved quality of PhC membrane cavities was established by optical characterization of such cavities incorporating site-controlled quantum wires as integrated light source.
Secondary neutron spectra from modern Varian, Siemens, and Elekta linacs with multileaf collimators
Authors: Howell Rebecca M. , Kry Stephen F. , Burgett Eric , Hertel Nolan E. , Followill David S.
Published: August 2009

Neutrons are a by‐product of high‐energy x‐ray radiation therapy (threshold for reactions in high‐ material ). Neutron production varies depending on photon beam energy as well as on the manufacturer of the accelerator. Neutron production from modern linear accelerators (linacs) has not been extensively compared, particularly in terms of the differences in the strategies that various manufacturers have used to implement multileaf collimators (MLCs) into their linac designs. However, such information is necessary to determine neutron dose equivalents for different linacs and to calculate vault shielding requirements. The purpose of the current study, therefore, was to measure the neutron spectra from the most up‐to‐date linacs from three manufacturers: Varian 21EX operating at 15, 18, and , Siemens ONCOR operating at 15 and , and Elekta Precise operating at 15 and . Neutron production was measured by means of gold foil activation in Bonner spheres. Based on the measurements, the authors determined neutron spectra and calculated the average energy, total neutron fluence, ambient dose equivalent, and neutron source strength. The shapes of the neutron spectra did not change significantly between accelerators or even as a function of treatment energy. However, the neutron fluence, and therefore the ambient dose equivalent, did vary, increasing with increasing treatment energy. For a given nominal treatment energy, these values were always highest for the Varian linac. The current study thus offers medical physicists extensive information about the neutron production of MLC‐equipped linacs currently in operation and provides them information vital for accurate comparison and prediction of neutron dose equivalents and calculation of vault shielding requirements.
An easy method to account for light scattering dose dependence in radiochromic films
Authors: Miras Hector , Arrans Rafael
Published: August 2009

Purpose:

To date no detector can offer the unbeatable characteristics of film dosimetry in terms of spatial resolution and this is why it has been chosen by many institutions for treatment verification and, in that respect, radiochromic films are becoming increasingly popular due to their advantageous properties. It is the aim of this work to suggest an easy method to overcome one of the drawbacks in radiochromic film dosimetry associated with the scanning device, namely, the non‐uniform dose dependent response, mainly due to the light scattering effect.

Methods:

The suggested procedure consists of building four correction matrices by sequentially scanning one, two, three, and four unexposed blank films. The color level of these four matrices is compatible with four points in the calibration curve dose range. Therefore, the dose dependent correction to the scanned irradiated film will be obtained by interpolating between the four correction matrices.

Results:

The validity of the suggested method is checked against an ion chamber 2D array. The use of the proposed flattening correction improves considerably the dose agreement when compared with the cases in which no correction is applied.

Conclusions:

The method showed to be fast and easy and practically overcomes the dependence on the dose of light scattering of flatbed scanners.
Monte Carlo analysis of energy dependent anisotropy of bremsstrahlung x‐ray spectra
Authors: Kákonyi Róbert , Erdélyi Miklós , Szabó Gábor
Published: August 2009

The energy resolved emission angle dependence of x‐ray spectra was analyzed by MCNPX (Monte Carlo particle Monte Carlo) simulator. It was shown that the spectral photon flux had a maximum at a well‐defined emission angle due to the anisotropy of the bremsstrahlung process. The higher the relative photon energy, the smaller the emission angle belonging to the maximum was. The trends predicted by the Monte Carlo simulations were experimentally verified. The Monte Carlo results were compared to both the Institute of Physics and Engineering in Medicine spectra table and the SPEKCALCV1.0 code.
SPECT imaging of high energy isotopes and isotopes with high energy contaminants with rotating slat collimators
Authors: Van Holen Roel , Staelens Steven , Vandenberghe Stefaan
Published: August 2009

Purpose:

Quantitative SPECT imaging is limited by many factors, including penetration of high energy photons through the collimator. Even small peaks of high energy yield extensive contamination in the photopeak energy window. Rotating slat collimators typically offer a 40‐ to 50‐fold increase in geometric detection efficiency compared to parallel hole collimators, while the amount of high‐energy contamination is expected to remain the same. The aim of this study is to show that SPECT for isotopes with high energy peaks benefits from the use of a rotating slat collimator by significantly reducing the effect of high energy contamination.

Methods:

Monte Carlo simulations were performed for I‐123 and I‐131. The simulation of a single point source in a scattering medium was used to investigate the history of each detected photon both for the rotating slat and the parallel hole collimator. Next, realistic simulations of an image quality phantom in combination with iterative image reconstruction enabled us to study the gain in image quality which can be expected for the rotating slat collimator.

Results:

The results show that the rotating slat collimator is able to reduce the contribution of high energy photons from about 60% to about 8% of all the detected photons in the photopeak energy window. This results in a recovered contrast gain of about 25%. For I‐131, there was a reduction in contamination from 65% to 49% when using a rotating slat instead of a parallel hole collimator. This resulted in an average hot contrast improvement of 12% and average cold contrast improvement of 8% for tomographic images.

Conclusions:

Rotating slat collimators have an additional advantage regarding image quality for isotopes with high energy emissions, especially if the contamination arises from photons with energies higher than the main emission energy, due to the relatively lower number of measured collimator‐penetrating photons with respect to geometrically collimated photons.
A two‐step scheme for distortion rectification of magnetic resonance images
Authors: Baldwin Lesley N. , Wachowicz Keith , Fallone B. Gino
Published: August 2009

The aim of this work is to demonstrate a complete, robust, and time‐efficient method for distortion correction of magnetic resonance (MR) images. It is well known that MR images suffer from both machine‐related spatial distortions [gradient nonlinearity and main field inhomogeneity] and patient‐related spatial distortions (susceptibility and chemical shift artifacts), and growing interest in the area of MR‐based radiotherapy treatment planning has put new requirements on the geometric accuracy of such images. The authors present a two‐step method that combines a phantom‐based reverse gradient technique for measurement of gradient nonlinearities and a patient‐based phase difference mapping technique for measurement of inhomogeneities, susceptibility, and chemical shift distortions. The phase difference mapping technique adds only minutes to the total patient scan time and can be used to correct a variety of images of the same patient and anatomy. The technique was tested on several different phantoms, each designed to isolate one type of distortion. The mean distortion was reduced to in both gradient echo and spin echo images of a grid phantom. For the more difficult case of a highly distorted echo planar image, residual distortion was reduced to subvoxel dimensions. As a final step, the technique was implemented on patient images. The current technique is effective, time efficient, and robust and provides promise for preparing distortion‐rectified MR images for use in MR‐based treatment planning.
Technical Note: RabbitCT—an open platform for benchmarking 3D cone‐beam reconstruction algorithmsa)
Authors: Rohkohl C. , Keck B. , Hofmann H. G. , Hornegger J.
Published: August 2009

Purpose:

Fast 3D cone beam reconstruction is mandatory for many clinical workflows. For that reason, researchers and industry work hard on hardware‐optimized 3D reconstruction. Backprojection is a major component of many reconstruction algorithms that require a projection of each voxel onto the projection data, including data interpolation, before updating the voxel value. This step is the bottleneck of most reconstruction algorithms and the focus of optimization in recent publications. A crucial limitation, however, of these publications is that the presented results are not comparable to each other. This is mainly due to variations in data acquisitions, preprocessing, and chosen geometries and the lack of a common publicly available test dataset. The authors provide such a standardized dataset that allows for substantial comparison of hardware accelerated backprojection methods.

Methods:

They developed an open platform RabbitCT (www.rabbitCT.com) for worldwide comparison in backprojection performance and ranking on different architectures using a specific high resolution C‐arm CT dataset of a rabbit. This includes a sophisticated benchmark interface, a prototype implementation in C++, and image quality measures.

Results:

At the time of writing, six backprojection implementations are already listed on the website. Optimizations include multithreading using Intel threading building blocks and OpenMP, vectorization using SSE, and computation on the GPU usingCUDA 2.0.

Conclusions:

There is a need for objectively comparing backprojection implementations for reconstruction algorithms. RabbitCT aims to provide a solution to this problem by offering an open platform with fair chances for all participants. The authors are looking forward to a growing community and await feedback regarding future evaluations of novel software‐ and hardware‐based acceleration schemes.
Megavoltage planar and cone‐beam imaging with low‐ targets: Dependence of image quality improvement on beam energy and patient separation
Authors: Robar James L. , Connell Tanner , Huang Weihong , Kelly Robin G.
Published: August 2009

Purpose:

The purpose of this study is to investigate the improvement of megavoltage planar and cone‐beam CT (CBCT) image quality with the use of low atomic number external targets in the linear accelerator.

Methods:

In this investigation, two experimental megavoltage imaging beams were generated by using either 3.5 or electrons incident on aluminum targets installed above the level of the carousel in a linear accelerator (2100EX, Varian Medical, Inc., Palo Alto, CA). Images were acquired using an amorphous silicon detector panel. Contrast‐to‐noise ratio (CNR) in planar and CBCT images was measured as a function of dose and a comparison was made between the imaging beams and the standard therapy beam. Phantoms of variable diameter were used to examine the loss of contrast due to beam hardening. Porcine imaging was conducted to examine qualitatively the advantages of the low‐ target approach in CBCT.

Results:

In CBCT imaging CNR increases by factors as high as 2.4 and 4.3 for the 7.0 and beams, respectively, compared to images acquired with . Similar factors of improvement are observed in planar imaging. For the imaging beams, beam hardening causes a significant loss of the contrast advantage with increasing phantom diameter; however, for the beam and a phantom diameter of , a contrast advantage remains, with increases of contrast by factors of 1.5 and 3.4 over for bone and lung inhale regions, respectively. The spatial resolution is improved slightly in CBCT images for the imaging beams. CBCT images of a porcine cranium demonstrate qualitatively the advantages of the low‐ target approach, showing greater contrast between tissues and improved visibility of fine detail.

Conclusions:

The use of low‐ external targets in the linear accelerator improves megavoltage planar and CBCT image quality significantly. CNR may be increased by a factor of 4 or greater. Improvement of the spatial resolution is also apparent.
Multiple scattering of 13 and 20 MeV electrons by thin foils: A Monte Carlo study with GEANT, Geant4, and PENELOPE
Authors: Vilches M. , García‐Pareja S. , Guerrero R. , Anguiano M. , Lallena A. M.
Published: August 2009

Purpose:

In this work, recent results from experiments and simulations (with EGSnrc) performed by Rosset al. [Med. Phys. 35, 4121–4131 (2008)] on electron scattering by foils of different materials and thicknesses are compared to those obtained using several Monte Carlo codes.

Methods:

Three codes have been used: GEANT (version 3.21), Geant4 (version 9.1, patch03), and PENELOPE (version 2006). In the case of PENELOPE, mixed and fully detailed simulations have been carried out.

Results:

Transverse dose distributions in air have been obtained in order to compare with measurements. The detailed PENELOPE simulations show excellent agreement with experiment. The calculations performed with GEANT and PENELOPE (mixed) agree with experiment within 3% except for the Be foil. In the case of Geant4, the distributions are 5% narrower compared to the experimental ones, though the agreement is very good for the Be foil. Transverse dose distribution in water obtained with PENELOPE (mixed) is 4% wider than those calculated by Rosset al. using EGSnrc and is 1% narrower than the transverse dose distributions in air, as considered in the experiment.

Conclusions:

All the codes give a reasonable agreement (within 5%) with the experimental results for all the material and thicknesses studied.