bluuebunny/crossref_metadata_2025 huggingface dataset:
Optimal use of topical corticosteroids in inflammatory skin diseases
Authors: Giannotti B.
Published: February 2011

The optimal use of topical corticosteroids (TC) in the treatment of inflammatory disorders of the skin is related to a number of factors concerning the drug on the one hand (potency, pharmacological properties, formulation), and the patient on the other hand (type and phase of the disease, characteristics of the lesion, site to be treated, age and general conditions). The careful balance between drug and disease/patient allows the establishment of a simple series of gold standard guidelines for TC treatment.
A Brief History of the Berlin Mission Society in South Africa
Authors: Pakendorf Gunther
Published: February 2011

The Berlin Mission Society (BMS) was one of four German Protestant mission societies active in 19th and 20th century South Africa. Born out of the tradition of Pietism in Germany and at the time of evangelical revival after the Napoleonic wars, the BMS sent its first missionaries to South Africa in 1834; it was formally disbanded in 1972. After an initial period of hardship and disappointments, it experienced an upsurge in its activities after 1859, which lasted up to World War One. In the latter half of the 19th century, the BMS was moderately represented in the Free State, the Eastern Cape and Natal and had a very strong presence in the northern and eastern parts of the Transvaal Boer republic. Events in Europe between 1914 and 1945 affected mission work negatively and made contact between the Board in Berlin and the missionaries in South Africa difficult, at times even impossible. The post‐1945 period was fraught with problems resulting from the division of Germany and its former capital, Berlin; global challenges resulting from the Cold War and decolonisation in Africa; and lastly, the racial policies of the apartheid government. The BMS was part of the broad evangelical mission movement and was thus barely distinct from other societies. Yet, both its Pietist and Lutheran heritage and its relative distance from the colonial powers that be resulted in its characteristic emphasis on spiritual inwardness, its uncompromising stand on puritanical values such as morality, hard work and self‐discipline and its difficulties with urban cosmopolitanism – and ultimately also in its inability to speak and act decisively against injustice and racial discrimination.
Writing the Worlds of Our Fathers and Mothers: The Fall and Rise of American Jewish Labor History
Authors: Breitzer Susan Roth
Published: February 2011

American Jewish labor history stands out as a place where labor, immigration, Jewish, and other specialties meet and interact – often uneasily. The changing fortunes of this area of study have not always coincided with those of American Jewish history, which was established as a field well in advance of the rise of the new social history. As a result, American Jewish labor history became marginalized just as American Jewish history as a field had become mainstream enough to become comfortably critical as opposed to self‐consciously celebratory. Part of the reason for this has been a relatively narrow geographic and chronological focus, as well as an emphasis on institutions and lack of attention to (or even dismissiveness) of gender issues. Additionally, the focus has traditionally been more celebratory and memoiristic than critical, due to the fact that most of the earliest published histories have been written by former activists. In addition, the general narrative, popularized by Irving Howe’s The World of our Fathers has made the Lower East Side tailor the symbol and stereotype of the Jewish worker. In the last decade, however, more critical approaches, as well crossover scholarship from the fields of women’s, immigration, and labor history, have resulted in the study themes and topics that have been previously ignored or slighted, as well as new approaches that incorporate gender, social history, and comparative perspectives and challenge long‐accepted conventional wisdom.
Cavotricuspid Isthmus Ablation Guided by Electroanatomic Mapping in a Patient with a Mechanical Tricuspid Valve Replacement After a Total Correction of Tetralogy of Fallot
Authors: LI CHENG‐HUNG , LIN YENN‐JIANG , CHEN SHIH‐ANN
Published: February 2011

Cavotricuspid Isthmus Ablation Guided by Electroanatomic Mapping. Atrial arrhythmias are a common sequel after surgery for congenital heart disease, and often eventually cause late morbidity and mortality. Nowadays, percutaneous catheter ablation of atrial flutter (AFL) is widely practised, and is highly successful and safe. Patients with a tricuspid valve replacement (TVR) represent a distinct group for whom the appropriate nonpharmacologic therapy for AFL has not yet been established. We report a case of a 55‐year‐old woman with a history of a total correction of tetralogy of Fallot (ToF) who developed AFL before and after receiving a tricuspid valve prosthesis. Based on the results of the activation mapping, counterclockwise and clockwise AFL were identified. Completion of a cavotricuspid isthmus (CTI) line on the atrial side successfully terminated the AFL, with resumption of sinus rhythm. Guided by a 3D mapping system, CTI ablation is feasible and safe in patients with a prosthetic tricuspid valve. (J Cardiovasc Electrophysiol, Vol. 22, pp. 938‐940, August 2011)
Impact of Patent Foramen Ovale on Left Atrial Linear Lesions in the Context of Atrial Fibrillation Ablation
Authors: MIYAZAKI SHINSUKE , SHAH ASHOK J. , NAULT ISABELLE , WRIGHT MATTHEW , JADIDI AMIR S. , FORCLAZ ANDREI , LIU XINGPENG , LINTON NICK , XHAËT OLIVIER , RIVARD LENA , DERVAL NICOLAS , SACHER FRÉDÉRIC , HOCINI MÉLÈZE , JAÏS PIERRE , HAÏSSAGUERRE MICHEL
Published: February 2011

Impact of PFO on LA Linear Ablation. Introduction: We investigated the impact of the mode of left atrial (LA) access via patent foramen ovale (PFO) versus transseptal (TS) puncture on LA linear lesions during atrial fibrillation (AF) ablation.

Methods and Results: We investigated 139 (PFO: 25) consecutive patients who underwent mitral isthmus (MI) and/or LA roof linear ablation. Technical endpoint was completeness of linear lesions and duration of radiofrequency (RF) application. During the initial procedure, complete MI and LA roof blocks were created in 13 of 19 (68%) and 14 of 17 (82%) patients in the PFO group, and in 57 of 94 (61%) and 54 of 70 (74%) patients in the TS group, respectively (P = NS). There was no significant difference in RF durations at MI (11.1 ± 8.9 and 15.1 ± 7.6 minutes, P = 0.11), and LA roof (10.1 ± 3.5 and 8.3 ± 5.0 minutes, P = 0.21) between the 2 groups. Among 28 patients who underwent repeat linear ablation, complete MI and LA roof blocks were created in 3 of 4 (75%) and 0 of 1 (0%) patients in the PFO group, and in 16 of 21 (76%) and 7 of 10 (70%) patients in the TS group, respectively (P = NS). There was no significant difference in RF durations at MI (15.3 ± 8.3 and 19.5 ± 18.3 minutes, P = 0.71), and LA roof (19.0 and 10.3 ± 5.4 minutes, P = 0.19) between the 2 groups. Clinical outcomes at 12 months were also similar.

Conclusion: There were no significant differences in the procedural success rates, durations of RF application, 12‐month clinical outcomes, and complication rates of LA linear ablation between the PFO and TS groups. Accessing the LA via a PFO is not an unfavorable approach toward LA linear ablation. (J Cardiovasc Electrophysiol, Vol. 22, pp. 846‐850, August 2011)
Underpaid and overworked: A cross‐national perspective on care workers
Authors: RAZAVI Shahra , STAAB Silke
Published: February 2011

This article defines paid care work and explains why it has become an important arena for research and policy. Drawing on cross‐national and country‐level analyses of selected occupations, it highlights three findings: first, the employment situation of care workers often mirrors broader, country‐specific labour market conditions and problems; second, the State's role as an employer of care workers is changing as governments increasingly outsource such work; and third, social policy regimes also shape opportunities for and conditions of care employment. It concludes that both care workers and care recipients are likely to benefit from improved employment conditions of care work.
Love of God and Neighbor: Living Charity in Aquinas’ Ethics
Authors: Clark Meghan J.
Published: February 2011

The purpose of this paper is to examine the role of charity in the moral life by focusing on the nature of charity and its requirements. What does it mean to say that someone has charity? Through an examination of the virtue of charity: subject, object and order, I will establish the necessary way in which charity functions as love of neighbor, including the love of God through love of neighbor. Focusing then on love of neighbor, I will examine what, for Aquinas, is constitutive of living charity through mercy, beneficence and almsgiving. Throughout, I will argue that one cannot have charity without living charity through love of neighbor.
A novel ErbB2 epitope targeted by human antitumor immunoagents
Authors: Troise Fulvia , Monti Maria , Merlino Antonello , Cozzolino Flora , Fedele Carmine , Russo Krauss Irene , Sica Filomena , Pucci Piero , D’Alessio Giuseppe , De Lorenzo Claudia
Published: February 2011

Two novel human antitumor immunoconjugates, engineered by fusion of a single‐chain antibody fragment against human ErbB2 receptor, termed Erbicin, with either a human RNase or the Fc region of a human IgG1, are selectively cytotoxic for ErbB2‐positive cancer cells in vitro and in vivo. These Erbicin‐derived immunoagents (EDIAs) do not show the most negative properties of Herceptin, the only humanized mAb against ErbB2 used in the therapy of breast carcinoma: cardiotoxicity and the inability to act on resistant tumors. These differences are probably attributable to the different ErbB2 epitopes recognized by EDIAs and Herceptin, respectively, as we have previously reported that they induce different signaling mechanisms that control tumor and cardiac cell viability. Thus, to accurately identify the novel epitope recognized by EDIAs, three independent and complementary methodologies were used. They gave coherent results, which are reported here: EDIAs bind to a different ErbB2 epitope than Herceptin and the other human/humanized antibodies against ErbB2 reported so far. The epitope has been successfully located in region 122–195 of extracellular domain I. These findings could lead to the identification of novel epitopes on ErbB2 that could be used as potential therapeutic targets to mitigate anti‐ErbB2‐associated cardiotoxicity and eventually overcome resistance.
Models for the clustering of far-infrared and submillimetre selected galaxies
Authors: Short Jo , Coles Peter
Published: February 2011

We discuss and compare two alternative models for the two-point angular correlation function of galaxies detected through the submillimetre emission using the Herschel Space Observatory. The first, now-standard Halo Model, which represents the angular correlations as arising from one-halo and two-halo contributions, is flexible but complex and rather unwieldy. The second model is based on a much simpler approach: we incorporate a fitting function method to estimate the matter correlation function with approximate model of the bias inferred from the estimated redshift distribution to find the galaxy angular correlation function. We find that both models give a good account of the shape of the correlation functions obtained from published preliminary studies of the Herschel Multi-tiered Extragalactic Survey (HerMES) and the Herschel-Astrophysical Terahertz Large Area Survey (H-ATLAS) performed using Herschel, and yield consistent estimates of the minimum halo mass within which the submillimetre galaxies must reside. We note also that both models predict an inflection in the correlation function at intermediate angular scales, so the presence of the feature in the measured correlation function does not unambiguously indicate the presence of intra-halo correlations. The primary barrier to more detailed interpretation of these clustering measurements lies in the substantial uncertainty surrounding the redshift distribution of the sources.
Mind‐wandering While Reading: Attentional Decoupling, Mindless Reading and the Cascade Model of Inattention
Authors: Smallwood Jonathan
Published: February 2011

When the mind wanders to unrelated thoughts and feelings while reading, the eyes often continue to scan the words without due attention to their meaning. This mindless reading, similar to states such as daydreaming or absentminded lapses, is a state of decoupled processing in which attention to ongoing perceptual information is reduced often in favor of the active consideration of internally generated thoughts and feelings. Normal reading involves a complex interaction between bottom‐up representations of the text that is being read and top‐down representations of the more general context that help to keep the readers mind on what they are doing. Since states of decoupling involve a reduced processing of sensory information, the coupling between the reader and the text breaks down during mindless reading. This reduced external coupling is one reason why mind‐wandering during reading has significant implications for reading comprehension. Following the presentation of a model of the decoupled state and a specific consideration of mind‐wandering during reading, five key unresolved issues for future research in mindless reading are identified.
Functionally Localizing Language‐Sensitive Regions in Individual Subjects With fMRI: A Reply to Grodzinsky’s Critique of Fedorenko and Kanwisher (2009)
Authors: Fedorenko Evelina , Kanwisher Nancy
Published: February 2011

In Fedorenko and Kanwisher (F&K 2009), we argued that defining regions of interest functionally in individual subjects may lead to a clearer picture of the functional architecture of the language system because it affords higher sensitivity and selectivity. Grodzinsky (2010) takes issue with two aspects of the F&K paper. First, he argues that the picture of the neural basis of language that has emerged from previous work is not as murky as F&K argue, with the implication that perhaps a new method is not needed. And second, he raises some concerns with the individual‐subjects functional localization approach and argues instead for the use of probabilistic cytoarchitectonic maps (e.g., Amunts et al. 1999). In the current manuscript, we respond to both of Grodzinsky’s points. Regarding the first point, we stand by our assessment of the brain basis of language literature, and argue that many core questions related to functional specialization remain unanswered. We explain why we remain unconvinced by Grodzinsky’s example of Broca’s area (or a portion of it) as a region with a well‐understood functional profile. Regarding the concerns that Grodzinsky raises with respect to the use of functional localizers in investigating the language system, we respond to the main comments and refer the reader to Fedorenko et al. (2010) where the remaining concerns are addressed (with both data and argumentation). Finally, we point out that the probabilistic cytoarchitectonic maps that Grodzinsky advocates have some of the same limitations as other group‐based methods. We conclude that the individual‐subjects functional localization approach, advocated in F&K, holds promise for better understanding the brain basis of language by enabling a detailed characterization of language‐sensitive regions with respect to their role in both linguistic and non‐linguistic processes.
Leveraging Motivational Mindsets to Foster Positive Interracial Interactions
Authors: Murphy Mary C. , Richeson Jennifer A. , Molden Daniel C.
Published: February 2011

As the United States becomes increasingly diverse, interracial contact will become considerably less rare. Much research has suggested that interracial interactions are often stressful and uncomfortable for both Whites and racial minorities. Bringing together several bodies of research, the present article outlines a motivational perspective on the dynamics of intergroup contact. To this end, we consider the roles of three motivational mindsets that have the potential to shape interactions to be less cognitively depleting and more enjoyable for both interactants. In particular, we consider the effects of (i) approach and avoidance motivation (Handbook of Motivation and Cognition: Foundation of Social Behavior, 1990, New York: Guilford Press), (ii) promotion and prevention regulatory focus (American Psychologist, 52, 1997, 1280), and (iii) learning and performance goals (Psychological Review, 95, 1988, 256) in shaping the dynamics of interracial contact. We suggest that investigations into these motivational mindsets will offer further insight into how and why interracial interactions go awry and will assist in the development of strategies and interventions that facilitate more smooth and enjoyable contact experiences.
Positivism and ‘Functional Theory’ in the Thought of Karl Polanyi, 1907–1922
Authors: Dale Gareth
Published: February 2011

Karl Polanyi is the author of a modern social science classic, The Great Transformation, as well as a number of well‐known and widely debated essays collected in Trade and Market in the Early Empires and Primitive, Archaic and Modern Economies. These texts were researched and written either during his second exile in 1930s Britain or in wartime or post‐war North America. Not so well known, however, are his Hungarian writings from the 1910s. Until recently, very few of these had been republished or translated, although this is in the process of being rectified [Gareth Dale (forthcoming): Karl Polanyi: The Hungarian Writings]. With reference to new translations of his Hungarian writings, to interviews with his daughter, Kari Polanyi‐Levitt, as well as to biographical essays by György Litván, Évá Gábor, Endre Kiss, and Zoltán Horváth, this article explores his early influences, drawing attention in particular to his flirtation with and then violent reaction against philosophical materialism and ‘objectivist’ sociology, his appreciation of Ernst Mach’s positivism, and his adherence to the ‘functional theory’ of contemporary Guild Socialism.
The Role of Social Networks in Getting a Job
Authors: Trimble Lindsey B. , Kmec Julie A.
Published: February 2011

This article reviews recent research on the effects of social networks on access to job information and getting a job in the United States. Drawing on network ties from friends, family members, acquaintances, employers, or coworkers can improve the job search because individuals gain access to and make use of their network’s social capital. While this job searching strategy can result in a successful job search for some, not all job seekers benefit from reliance on social networks. We spotlight research that documents how reliance on social networks as a means to find work can actually maintain sex and racial/ethnic inequality at work. We discuss research documenting the important role social networks play in the job acquisition process. The last half of this review focuses on several new developments in the literature that promise to further our understanding of social networks’ lasting effects on employment outcomes.
The maintenance of offspring diversity in response to land use: sexual and asexual recruitment in an alpine meadow on the Tibetan Plateau
Authors: Li Wei , Wu Gao‐Lin , Zhang Ge‐Fei , Du Guo‐Zhen
Published: February 2011

Human activities have caused dramatic land use changes, impacting plant community composition, diversity and function. Fertilization and grazing are the two most common land use modes in grasslands. To understand the effects of grazing and fertilization on sexual and asexual recruitment in alpine grasslands, we conducted a demographic field investigation of species recruitment in an alpine meadow on the Tibetan Plateau. Grazing and fertilization had different effects on the quantity and diversity of sexual and asexual recruitment. Sexual recruitment increased significantly in grazed plots, but decreased significantly in fertilized plots. Asexual recruitment increased significantly in fertilized plots, but decreased significantly in grazed plots. For functional groups, grazing significantly reduced offspring recruitment of graminoids, but significantly increased offspring recruitment of forbs and legumes; fertilization significantly reduced offspring recruitment of forbs and legumes, but significantly increased offspring recruitment of graminoids. Furthermore, offspring diversity from sexual recruitment was significantly higher than from asexual recruitment in grazed plots, and as compared to non‐grazed and fertilized grasslands. Our studies indicate that moderate grazing disturbance has positive effects on seedling recruitment and offspring diversity, and fertilization has negative effects on offspring diversity, but may significantly increase asexual recruitment.
The taxonomic value of leaf anatomy and trichome morphology of the genus Cyclotrichium (Lamiaceae) in Turkey
Authors: SatIl Fatih , Kaya Ayla , Dirmenci Tuncay
Published: February 2011

The genus Cyclotrichium (Boiss.) Manden. & Scheng. is represented by six species in Turkey: C. glabrescens, C. leucotrichum, C. longiflorum, C. niveum, C. origanifolium and C. stamineum. They are aromatic perennial subshrubs used as spices or herbal teas in traditional Turkish medicine. The leaf anatomy and tomentum morphology of leaves and calyces of Cyclotrichium species in Turkey was investigated by scanning electron microscopy (SEM) and light microscopy (LM). The investigated species have equifacial (C. niveum, C. origanifolium) or bifacial leaves (C. glabressens, C. leucotrichum, C. longiflorum, C. stamineum). All species have peltate and capitate glandular, and simple (all species) or branched (C. niveum) eglandular trichomes and diacytic stomata. Peltate trichomes consist of a basal cell embedded in the epidermis, a stalk cell, and a broad 12 (–13)‐celled secretory head arranged in two concentric circles. The capitate trichomes observed in Cyclotrichium can be grouped into five types, differing in structure and size. They consist of either a pear‐shaped or globose unicellular head and uni‐or bicellular stalk, or a bicellular head and bicellular stalk. The density of peltate, capitate and eglandular trichomes differs between species. Peltate trichomes are densely spaced only on the calyx and on the leaf surface of C. niveum and C. origanifolium and on the abaxial leaf surface of C. longiflorum and C. stamineum. The significance of trichome architecture for taxonomy in Cyclotrichium and Lamiaceae in general is discussed.
Forced Convection Boundary Layer Flow Past Nonisothermal Thin Needles in Nanofluids
Authors: Grosan T. , Pop I.
Published: February 2011

The classical problem of forced convection boundary layer flow and heat transfer past a needle with variable wall temperature using nanofluids is theoretically studied. The similarity equations are solved numerically for two types of metallic or nonmetallic, such as copper (Cu) and alumina (Al2O3) nanoparticles in the based fluid of water with the Prandtl number Pr=7 to investigate the effect of the solid volume fraction parameter ϕ of the fluid and heat transfer characteristics. The skin friction coefficient, Nusselt number, and the velocity and temperature profiles are presented and discussed. It is found that the solid volume fraction affects the fluid flow and heat transfer characteristics.
Plasma-enhanced chemical vapor deposition synthesis of silica-silicone nanolaminates using a single precursor
Authors: Patel Rakhi P. , Wolden Colin A.
Published: February 2011

Plasma-enhanced chemical vapor deposition was used to deposit silica, silicone, and silica/silicone nanolaminates at room temperature using hexamethyldisiloxane (HMDSO). The rate and composition of the individual constituents may be tuned by appropriate control of parameters including the O2/HMDSO ratio and rf power. The organic content of silicone films was maximized at moderate plasma power, while carbon-free silica required high power and excess O2. Transparent silica-silicone nanolaminates were formed on polymer substrates with varying composition. Digital control over nanolaminate structure and composition was demonstrated through transmission electron microscopy imaging and spectroscopic ellipsometry. The mechanical properties of the hybrid nanolaminates tend to be closer to that of silicone, which is advantageous for applications on flexible substrates.
Quality assurance of U.S.‐guided external beam radiotherapy for prostate cancer: Report of AAPM Task Group 154
Authors: Molloy Janelle A. , Chan Gordon , Markovic Alexander , McNeeley Shawn , Pfeiffer Doug , Salter Bill , Tome Wolfgang A.
Published: February 2011

Task Group 154 (TG154) of the American Association of Physicists in Medicine (AAPM) was created to produce a guidance document for clinical medical physicists describing recommended quality assurance (QA) procedures for ultrasound (U.S.)‐guided external beam radiotherapy localization. This report describes the relevant literature, state of the art, and briefly summarizes U.S. imaging physics. Simulation, treatment planning and treatment delivery considerations are presented in order to improve consistency and accuracy. User training is emphasized in the report and recommendations regarding peer review are included. A set of thorough, yet practical, QA procedures, frequencies, and tolerances are recommended. These encompass recommendations to ensure both spatial accuracy and image quality.
The central electrode correction factor for high‐Z electrodes in small ionization chambers
Authors: Muir B. R. , Rogers D. W. O.
Published: February 2011

Purpose:

Recent Monte Carlo calculations of beam quality conversion factors for ion chambers that use high‐Z electrodes [B. R. Muir and D. W. O. Rogers, Med. Phys., – (2010)] have shown large deviations of values from values calculated using the same techniques as the TG‐51 and TRS‐398 protocols. This report investigates the central electrode correction factor, , for these chambers.

Methods:

Ionization chambers are modeled and is calculated using the EGSnrc user code egs_chamber for three cases: in photon and electron beams under reference conditions; as a function of distance from an iridium‐192 point source in a water phantom; and as a function of depth in a water phantom on which a 200 kVp x‐ray source or 6 MV beam is incident.

Results:

In photon beams, differences of up to 3% between calculations for a chamber with a high‐Z electrode and those used by TG‐51 for a 1 mm diameter aluminum electrode are observed. The central electrode correction factor for a given value of the beam quality specifier is different depending on the amount of filtration of the photon beam. However, in an unfiltered 6 MV beam, , varies by only 0.3% for a chamber with a high‐Z electrode as the depth is varied from 1 to 20 cm in water. The difference between calculations for chambers with high‐Z electrodes and TG‐51 values for a chamber with an aluminum electrode is up to 0.45% in electron beams. The central electrode correction, which is roughly proportional to the chambers absorbed dose sensitivity, is found to be large and variable as a function of distance for chambers with high‐Z and aluminum electrodes in low‐energy photon fields.

Conclusions:

In this work, ionization chambers that employ high‐Z electrodes have been shown to be problematic in various situations. For beam quality conversion factors, the ratio of in a beam quality to that in a Co‐60 beam is required; for some chambers, is significantly different from current dosimetry protocol values because of central electrode effects. It would be best for manufacturers to avoid producing ion chambers that use high‐Z electrodes.
Stochastic formulation of patient positioning using linac‐mounted cone beam imaging with prior knowledge
Authors: Hoegele W. , Loeschel R. , Dobler B. , Hesser J. , Koelbl O. , Zygmanski P.
Published: February 2011

Purpose:

In this work, a novel stochastic framework for patient positioning based on linac‐mounted CB projections is introduced. Based on this formulation, the most probable shifts and rotations of the patient are estimated, incorporating interfractional deformations of patient anatomy and other uncertainties associated with patient setup.

Methods:

The target position is assumed to be defined by and is stochastically determined from positions of various features such as anatomical landmarks or markers in CB projections, i.e., radiographs acquired with a CB‐CT system. The patient positioning problem of finding the target location from CB projections is posed as an inverse problem with prior knowledge and is solved using a Bayesian maximuma posteriori (MAP) approach. The prior knowledge is three‐fold and includes the accuracy of an initial patient setup (such as in‐room laser and skin marks), the plasticity of the body (relative shifts between target and features), and the feature detection error in CB projections (which may vary depending on specific detection algorithm and feature type). For this purpose, MAP estimators are derived and a procedure of using them in clinical practice is outlined. Furthermore, a rule of thumb is theoretically derived, relating basic parameters of the prior knowledge (initial setup accuracy, plasticity of the body, and number of features) and the parameters of CB data acquisition (number of projections and accuracy of feature detection) to the expected estimation accuracy.

Results:

MAP estimation can be applied to arbitrary features and detection algorithms. However, to experimentally demonstrate its applicability and to perform the validation of the algorithm, a water‐equivalent, deformable phantom with features represented by six 1 mm chrome balls were utilized. These features were detected in the cone beam projections (XVI, Elekta Synergy®) by a local threshold method for demonstration purposes only. The accuracy of estimation (strongly varying for different plasticity parameters of the body) agreed with the rule of thumb formula. Moreover, based on this rule of thumb formula, about 20 projections for 6 detectable features seem to be sufficient for a target estimation accuracy of 0.2 cm, even for relatively large feature detection errors with standard deviation of 0.5 cm and spatial displacements of the features with standard deviation of 0.5 cm.

Conclusions:

The authors have introduced a general MAP‐based patient setup algorithm accounting for different sources of uncertainties, which are utilized as the prior knowledge in a transparent way. This new framework can be further utilized for different clinical sites, as well as theoretical developments in the field of patient positioning for radiotherapy.
Comparative imaging study in ultrasound, MRI, CT, and DSA using a multimodality renal artery phantom
Authors: King Deirdre M. , Fagan Andrew J. , Moran Carmel M. , Browne Jacinta E.
Published: February 2011

Purpose:

A range of anatomically realistic multimodality renal artery phantoms consisting of vessels with varying degrees of stenosis was developed and evaluated using four imaging techniques currently used to detect renal artery stenosis (RAS). The spatial resolution required to visualize vascular geometry and the velocity detection performance required to adequately characterize blood flow in patients suffering from RAS are currently ill‐defined, with the result that no one imaging modality has emerged as a gold standard technique for screening for this disease.

Methods:

The phantoms, which contained a range of stenosis values (0%, 30%, 50%, 70%, and 85%), were designed for use with ultrasound, magnetic resonance imaging, x‐ray computed tomography, and x‐ray digital subtraction angiography. The construction materials used were optimized with respect to their ultrasonic speed of sound and attenuation coefficient, MR relaxometry properties, and Hounsfield number/x‐ray attenuation coefficient, with a design capable of tolerating high‐pressure pulsatile flow. Fiducial targets, incorporated into the phantoms to allow for registration of images among modalities, were chosen to minimize geometric distortions.

Results:

High quality distortion‐free images of the phantoms with good contrast between vessel lumen, fiducial markers, and background tissue to visualize all stenoses were obtained with each modality. Quantitative assessments of the grade of stenosis revealed significant discrepancies between modalities, with each underestimating the stenosis severity for the higher‐stenosed phantoms (70% and 85%) by up to 14%, with the greatest discrepancy attributable to DSA.

Conclusions:

The design and construction of a range of anatomically realistic renal artery phantoms containing varying degrees of stenosis is described. Images obtained using the main four diagnostic techniques used to detect RAS were free from artifacts and exhibited adequate contrast to allow for quantitative measurements of the degree of stenosis in each phantom. Such multimodality phantoms may prove useful in evaluating current and emerging US, MRI, CT, and DSA technology.
Metal artifact reduction in x‐ray computed tomography (CT) by constrained optimization
Authors: Zhang Xiaomeng , Wang Jing , Xing Lei
Published: February 2011

Purpose:

The streak artifacts caused by metal implants have long been recognized as a problem that limits various applications of CT imaging. In this work, the authors propose an iterative metal artifact reduction algorithm based on constrained optimization.

Methods:

After the shape and location of metal objects in the image domain is determined automatically by the binary metal identification algorithm and the segmentation of “metal shadows” in projection domain is done, constrained optimization is used for image reconstruction. It minimizes a predefined function that reflectsa priori knowledge of the image, subject to the constraint that the estimated projection data are within a specified tolerance of the available metal‐shadow‐excluded projection data, with image non‐negativity enforced. The minimization problem is solved through the alternation of projection‐onto‐convex‐sets and the steepest gradient descent of the objective function. The constrained optimization algorithm is evaluated with a penalized smoothness objective.

Results:

The study shows that the proposed method is capable of significantly reducing metal artifacts, suppressing noise, and improving soft‐tissue visibility. It outperforms the FBP‐type methods and ART and EM methods and yields artifacts‐free images.

Conclusions:

Constrained optimization is an effective way to deal with CT reconstruction with embedded metal objects. Although the method is presented in the context of metal artifacts, it is applicable to general “missing data” image reconstruction problems.
Scaling law for noise variance and spatial resolution in differential phase contrast computed tomography
Authors: Chen Guang‐Hong , Zambelli Joseph , Li Ke , Bevins Nicholas , Qi Zhihua
Published: February 2011

Purpose:

The noise variance versus spatial resolution relationship in differential phase contrast (DPC) projection imaging and computed tomography (CT) are derived and compared to conventional absorption‐based x‐ray projection imaging and CT.

Methods:

The scaling law for DPC‐CT is theoretically derived and subsequently validated with phantom results from an experimental Talbot–Lau interferometer system.

Results:

For the DPC imaging method, the noise variance in the differential projection images follows the same inverse‐square law with spatial resolution as in conventional absorption‐based x‐ray imaging projections. However, both in theory and experimental results, in DPC‐CT the noise variance scales with spatial resolution following an inverse linear relationship with fixed slice thickness.

Conclusions:

The scaling law in DPC‐CT implies a lesser noise, and therefore dose, penalty for moving to higher spatial resolutions when compared to conventional absorption‐based CT in order to maintain the same contrast‐to‐noise ratio.
Quality assurance of volumetric modulated arc therapy: Evaluation and comparison of different dosimetric systems
Authors: Masi L. , Casamassima F. , Doro R. , Francescon P.
Published: February 2011

Purpose:

To compare and evaluate different dosimetric techniques and devices for the QA of VMAT plans created by two treatment planning systems (TPSs).

Methods:

A total of 50 VMAT plans were optimized for treatment of anatomical sites of various complexities by two TPSs which use rather different approaches to VMAT optimization. Dosimetric plan verifications were performed both as part of commissioning and as patient specific QA of clinical treatments. Absolute point doses were measured for all plans by a micro ion chamber inserted in a dedicated water‐filled cylindrical phantom. Delivered dose distributions were verified by four techniques based on different detectors: radiographic and gafchromic films, two systems based on 2D diode arrays and an ion chamber array. Gamma index analysis with various tolerance levels (3%, 3 mm and 3%, 2 mm) was used to analyze differences between calculated and delivered doses. Sensitivity to possible delivery errors was also evaluated for three of the considered devices introducing ±3 mm shifts along the three directions and a 3° gantry offset.

Results:

Ion chamber measured point doses were within 3% of calculated ones for 48 out of 50 values. For delivered dose distribution, the average fraction of passed gamma values using 3% and 3 mm criteria was above 95% for both TPSs and all detectors except gafchromic film which yielded on average of 91.4%. For 49 out of 50 plans, a pass‐rate above 94% was obtained by at least one of the four techniques. Shrinking the tolerance to 3% and 2 mm, the average pass‐rate by all detectors (except film) was still above 95% for one of the two TPSs, but lower for the other one. The detector sensitivity to 3 mm shifts and to gantry angle offset was strongly plan and partially detector dependent: the obtained pass‐rate reduction ranged from 2% to 30%.

Conclusions:

The presented results for VMAT plans QA assess the reliability of the delivered doses for both TPSs. The slightly lower pass‐rate obtained for one of the considered TPS can be attributed to a higher level of complexity of the optimized plans. The results by different dosimetric techniques are coherent, apart from a few measurements by gafchromic films. The detector sensitivity to delivery errors, being strongly plan dependent, is not easy to evaluate.
Application of thermography for the assessment of allergen‐induced skin reactions
Authors: Rokita Eugeniusz , Rok Tomasz , Tatoń Grzegorz
Published: February 2011

Purpose:

The allergic response is commonly identified and assessed by skin testing. The usual method to quantify skin reactions is to mark wheal and erythema regions and assess the surfaces affected by the reactions; however, subjective interpretation of the outcome may cause errors. Skin thermography supplemented by a mathematical model based on the pathophysiology of heat generation was evaluated as a novel, objective, and sensitive indicator of the skin prick test result.

Methods:

TH measurements were performed simultaneously with routine skin prick tests for 24 patients. Eight allergens and control (histamine) were examined. Thermographic images of both forearms were acquired every 70 s from 0 to 910 s after skin prick and analyzed with the use of dedicated software. The introduction of potential allergens and histamine at sites on the skin induces a complex sequence of events known as the local inflammatory response. The crucial steps of the process have been considered in the model. In the model, the authors assumed that the reaction takes place in the thin skin layer and that histamine is the principal mediator of the allergic reaction. Histamine penetrates the skin and binds to receptors of nearby capillaries and venules. The engorged vessels are, in turn, responsible for skin redness and an increase in skin temperature.

Results:

The model parameters were determined by fitting the analytical solutions to the spatiotemporal distributions of the differences between measured and baseline temperatures. The model reproduces experimental data very well. The coefficient of determination ranged from 0.805 to 0.995. Seven model parameters were tested to find the optimal marker of the intensity and kinetics of the allergic reaction. The parameter which quantifies a release of histamine after allergen injection has appeared to be the best indicator of the allergen‐induced response. The parameter correlates with the routine assessment based on wheal and erythema areas (correlation).

Conclusions:

It was demonstrated that the thermographic measurements supplemented by the mathematical model offer a new approach to the quantification of allergen‐induced skin reactions. Despite the applied simplifications, the proposed model reflected properly the mechanism of heat generation during skin prick test. Moreover, the continuous recording of the skin temperature represents an additional possibility to investigate the mechanism of the allergic reaction.
Characterization of image quality and image‐guidance performance of a preclinical microirradiator
Authors: Clarkson R. , Lindsay P. E. , Ansell S. , Wilson G. , Jelveh S. , Hill R. P. , Jaffray D. A.
Published: February 2011

Purpose:

To assess image quality and image‐guidance capabilities of a cone‐beam CT based small‐animal image‐guided irradiation unit (micro‐IGRT).

Methods:

A micro‐IGRT system has been developed in collaboration with the authors' laboratory as a means to study the radiobiological effects of conformal radiation dose distributions in small animals. The system, the X‐Rad 225Cx, consists of a 225 kVp x‐ray tube and a flat‐panel amorphous silicon detector mounted on a rotational C‐arm gantry and is capable of both fluoroscopic x‐ray and cone‐beam CT imaging, as well as image‐guided placement of the radiation beams. Image quality (voxel noise, modulation transfer, CT number accuracy, and geometric accuracy characteristics) was assessed using water cylinder and micro‐CT test phantoms. Image guidance was tested by analyzing the dose delivered to radiochromic films fixed to BB's through the end‐to‐end process of imaging, targeting the center of the BB, and irradiation of the film/BB in order to compare the offset between the center of the field and the center of the BB. Image quality and geometric studies were repeated over a 5–7 month period to assess stability.

Results:

CT numbers reported were found to be linear and the noise for images of homogeneous water phantom was 30 HU at imaging doses of approximately 1 cGy (to water). The presampled MTF at 50% and 10% reached 0.64 and , respectively. Targeting accuracy by means of film irradiations was shown to have a mean displacement error of , with standard deviations of [0.02, 0.20, 0.17] mm. The system has proven to be stable over time, with both the image quality and image‐guidance performance being reproducible for the duration of the studies.

Conclusions:

The micro‐IGRT unit provides soft‐tissue imaging of small‐animal anatomy at acceptable imaging doses. The geometric accuracy and targeting systems permit dose placement with submillimeter accuracy and precision. The system has proven itself to be stable over 2 yr of routine laboratory use and provides a platform for the exploration of targeted radiation effects in small‐animal models.
Aperture modulated, translating bed total body irradiation
Authors: Hussain Amjad , Villarreal‐Barajas Jose Eduardo , Dunscombe Peter , Brown Derek W.
Published: February 2011

Purpose:

Total body irradiation (TBI) techniques aim to deliver a uniform radiation dose to a patient with an irregular body contour and a heterogeneous density distribution to within ±10% of the prescribed dose. In the current article, the authors present a novel, aperture modulated, translating bed TBI (AMTBI) technique that produces a high degree of dose uniformity throughout the entire patient.

Methods:

The radiation beam is dynamically shaped in two dimensions using a multileaf collimator (MLC). The irregular surface compensation algorithm in the Eclipse™ treatment planning system is used for fluence optimization, which is performed based on penetration depth and internal inhomogeneities. Two optimal fluence maps (AP and PA) are generated and beam apertures are created to deliver these optimal fluences. During treatment, the patient/phantom is translated on a motorized bed close to the floor (source to bed distance: 204.5 cm) under a stationary radiation beam with 0° gantry angle. The bed motion and dynamic beam apertures are synchronized.

Results:

The AMTBI technique produces a more homogeneous dose distribution than fixed open beam translating bed TBI. In phantom studies, the dose deviation along the midline is reduced from 10% to less than 5% of the prescribed dose in the longitudinal direction. Dose to the lung is reduced by more than 15% compared to the unshielded fixed open beam technique. At the lateral body edges, the dose received from the open beam technique was 20% higher than that prescribed at umbilicus midplane. With AMTBI the dose deviation in this same region is reduced to less than 3% of the prescribed dose. Validation of the technique was performed using thermoluminescent dosimeters in a Rando® phantom. Agreement between calculation and measurement was better than 3% in all cases.

Conclusions:

A novel, translating bed, aperture modulated TBI technique that employs dynamically shaped MLC defined beams is shown to improve dose uniformity in three dimensions. In comparison with the fixed open beam TBI technique, homogeneity of dose distribution is greatly improved.
Is Weisskoff model valid for the correction of contrast agent extravasation with combined and effects in dynamic susceptibility contrast MRI?
Authors: Liu Ho‐Ling , Wu Yi‐Ying , Yang Wei‐Shan , Chen Chih‐Feng , Lim Kun‐Eng , Hsu Yuan‐Yu
Published: February 2011

Purpose:

The Weisskoff model has been widely applied for correcting the effect of the contrast agent leakage in the measured dynamic susceptibility contrast (DSC)‐MRI signals. This study aimed to modify the Weisskoff model for the inclusion of both and effects of the contrast agent extravasation.

Methods:

A two‐compartment model was proposed and implemented into the original Weisskoff model to describe the combined and effects from the contrast agent leakage in the measured DSC‐MRI signals. A computer simulation was performed to evaluate the dependence of versus dominance on imaging parameter, field strength, baseline , and severity of the leakage. The modified Weisskoff model was employed to correct the relative cerebral blood volume (rCBV) maps in three patients with brain tumors to demonstrate its use.

Results:

The resultant equation had the same mathematical form as the original model, but with a different expression for the fitting constant. This new parameter can be of either a positive or a negative value. Results of the computer simulation showed more probable dominance with longer TE, higher field strength, shorter baseline , and greater extraction of the contrast agent. Clinical data were well fitted by the model, with a positive indicating dominance and underestimated rCBV and a negative indicating dominance and overestimated rCBV. The values of normal‐appearing brain tissues were distributed in a much smaller range than the values of enhancing tumors. The ratios of corrected over uncorrected normalized CBV (nCBV) for gray matter (GM) were in the range between 1.04 and 1.05, meaning that the nCBV remained rather stable before and after correction. The ratios for the tumors were 0.65, 0.42, and 2.81, either much smaller or greater than the ratios for GM.

Conclusions:

This study proposed a modified Weisskoff model that was able to explain both and dominant effects of the contrast agent extravasation in DSC‐MRI. Further development is needed to make the parameter a quantitative indicator of the vessel permeability.