bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dynamics of Axially Accelerating Beams With an Intermediate Support
Authors: Bağdatli S. M. , Özkaya E. , Öz H. R. 
Published: April 2011

Abstract
The transverse vibrations of an axially accelerating Euler–Bernoulli beam resting on simple supports are investigated. The supports are at the ends, and there is a support in between. The axial velocity is a sinusoidal function of time varying about a constant mean speed. Since the supports are immovable, the beam neutral axis is stretched during the motion, and hence, nonlinear terms are introduced to the equations of motion. Approximate analytical solutions are obtained using the method of multiple scales. Natural frequencies are obtained for different locations of the support other than end supports. The effect of nonlinear terms on natural frequency is calculated for different parameters. Principal parametric resonance occurs when the velocity fluctuation frequency is equal to approximately twice of natural frequency. By performing stability analysis of solutions, approximate stable and unstable regions were identified. Effects of axial velocity and location of intermediate support on the stability regions have been investigated.
An alternating focused ultrasound system for thermal therapy studies in small animals
Authors: Chen Xin , Novák Petr , Benson Donald G. , Webber Jessica S. , Hennings Leah , Shafirstein Gal , Corry Peter M. , Griffin Robert J. , Moros Eduardo G. 
Published: April 2011

Purpose:To develop an alternating focused ultrasound system (AFUS) for preclinical studies of thermal and acoustic responses of tumors in small animal models. This work was motivated by the need of noninvasively creating relatively small spheroidal thermal lesions in small targets (e.g., a murine tumor) without damaging the surrounding tissues.Methods:The AFUS consists of two lead zirconate titanate (PZT‐4) spherically curved ultrasound transducers with focal zones crossing each other at a 90° angle. The transducers were independently powered following a programed alternating firing scheme. Before the device design and construction, an acoustic and biothermal model was developed to simulate the ultrasound pressure field and the resulting temperature and thermal dose distributions. A shape factor, sphericity, to quantify the roundness of the lesions was calculated based on the 240 equivalent minutes at thermal dose contours. A prototype of the AFUS was constructed with two identical transducers of an operating frequency of 2.25 MHz, 38 mm in diameter, and ‐number equal to 1.33. To evaluate the performance of the AFUS experimentally, a series of heating in polyacrylamide phantoms, ex vivo porcine liver tissues, and in implanted mouse tumors fibrosarcoma (FSaII) in vivo was conducted. In these experimental cases, the sphericity was calculated and compared based on the visible lesion (a marked change in coloration).Results:As shown in the simulations, the lesions induced in polyacrylamide phantoms,ex vivo porcine liver tissues, and in vivo mouse tumors, the sphericities of the lesions yielded by AFUS heating were approximately 50% higher than those of single focused ultrasound heating as long as moderate intensities were used and the duty cycle pulses were distributed equally among the transducers.Conclusions:The AFUS is a device capable of noninvasively creating spheroidal thermal lesions in small targets such as murine tumors.
Comparison of 250 MHz electron spin echo and continuous wave oxygen EPR imaging methods for in vivo applications
Authors: Epel Boris , Sundramoorthy Subramanian V. , Barth Eugene D. , Mailer Colin , Halpern Howard J. 
Published: April 2011

Purpose:The authors compare two electron paramagnetic resonance imaging modalities at 250 MHz to determine advantages and disadvantages of those modalities forin vivo oxygen imaging.Methods:Electron spin echo (ESE) and continuous wave (CW) methodologies were used to obtain three‐dimensional images of a narrow linewidth, water soluble, nontoxic oxygen‐sensitive trityl molecule OX063in vitro and in vivo. The authors also examined sequential images obtained from the same animal injected intravenously with trityl spin probe to determine temporal stability of methodologies.Results:A study of phantoms with different oxygen concentrations revealed a threefold advantage of the ESE methodology in terms of reduced imaging time and more precise oxygen resolution for samples with less than 70 torr oxygen partial pressure. Above , CW performed better. The images produced by both methodologies showed distributions with similar mean values. However, ESE images demonstrated superior performance in low regions while missing voxels in high regions.Conclusions:ESE and CW have different areas of applicability. ESE is superior for hypoxia studies in tumors.
Subzone based magnetic resonance elastography using a Rayleigh damped material model
Authors: Van Houten Elijah E.W. , Viviers D. vR. , McGarry M. D.J. , Perriñez P. R. , Perreard I. I. , Weaver J. B. , Paulsen K. D. 
Published: April 2011

Purpose:Recently, the attenuating behavior of soft tissue has been addressed in magnetic resonance elastography by the inclusion of a damping mechanism in the methods used to reconstruct the resulting mechanical property image. To date, this mechanism has been based on a viscoelastic model for material behavior. Rayleigh, orproportional, damping provides a more generalized model for elastic energy attenuation that uses two parameters to characterize contributions proportional to elastic and inertial forces. In the case of time‐harmonic vibration, these two parameters lead to both the elastic modulus and the density being complex valued (as opposed to the case of pure viscoelasticity, where only the elastic modulus is complex valued).Methods:This article presents a description of Rayleigh damping in the time‐harmonic case, discussing the differences between this model and the viscoelastic damping models. In addition, the results from a subzone based Rayleigh damped elastography study of gelatin and tofu phantoms are discussed, along with preliminary results fromin vivo breast data.Results:Both the phantom and the tissue studies presented here indicate a change in the Rayleigh damping structure, described asRayleigh composition, between different material types, with tofu and healthy tissue showing lower Rayleigh composition values than gelatin or cancerous tissue.Conclusions:It is possible that Rayleigh damping elastography and the concomitant Rayleigh composition images provide a mechanism for differentiating tissue structure in addition to measuring elastic stiffness and attenuation. Such information could be valuable in the use of Rayleigh damped magnetic resonance elastography as a diagnostic imaging tool.
Normal tissue dose conformality measures to guide radiotherapy fractionation decisions
Authors: Myerson Robert J. 
Published: April 2011

Purpose:To determine conditions under which hypofractionation could be favorable for a normal tissue—even if tumor exceeds the normal tissue's .Methods:The hypofractionation sufficiency condition (HSC) for an organ is defined as a dose conformality constraint such that, if satisfied, a family of tumor control probability isoeffective fractionation schemes will showdecreasing normal tissue complication probability with decreasing number of fractions.Results:In the extended equivalent uniform dose (EUD) model [obtained by replacing dose with linear quadratic (LQ) 2 Gy equivalent dose], the HSC for a normal organ is proven to be satisfied if a suitably weighted average of the relative dose [hypofractionation sufficiency index (HSI)] is less than the ratio of normal tissue to tumor . The HSI is determined solely by dose distribution and the normal tissue volume factor, “.” If the HSC is satisfied for every normal tissue of concern, then there is a therapeutic gain with hypofractionation. The corresponding multifractionation sufficiency condition (therapeutic gain with increasing number of fractions) and multifractionation sufficiency index (MSI) are also derived. A sample clinical case is presented.Conclusions:Within the context of the LQ/EUD models, conformality measures (HSI and MSI) can be used to inform fractionation decisions.
Optimization of a parallel hole collimator/CdZnTe gamma‐camera architecture for scintimammography
Authors: Robert Charlotte , Montémont Guillaume , Rebuffel Véronique , Verger Loïck , Buvat Irène 
Published: April 2011

Purpose:Small field‐of‐view CdZnTe (CZT) gamma cameras are increasingly studied for breast lesion detection to complement mammography or ultrasonographic findings. However, in classical collimation configurations, they remain limited by the trade‐off between spatial resolution and sensitivity. The HiSens architecture was proposed to overcome these limitations. Using an accurate 3D localization of the interactions inside the detector, this architecture leads to a gain in sensitivity without loss in spatial resolution. In this article, the relevance of the HiSens architecture for planar scintimammography is studied.Methods:A detective quantum efficiency (DQE) computation method is developed and used to optimize the dimensioning of a parallel hole collimator dedicated to scintimammography. Based on the DQE curves, the impact of the collimator‐to‐detector distance is studied. Two algorithms are proposed to combine data acquired with different collimator‐to‐detector distances.Results:It is shown that CZT detector virtual pixelization increases system sensitivity by 3.3 while preserving a standard LEHR spatial resolution. The introduction of a gap between the CZT detector and the collimator is useful to modulate the DQE curve shape. The combination of data acquired using different gaps in the image formation process leads to enhanced restoration of the frequency content of the images, resulting in image contrast and spatial resolution improvements.Conclusions:Acquisition duration or injected activity could be markedly reduced if the HiSens architecture with an appropriate collimator‐detector gap were used.
An analysis of confidence limit calculations used in AAPM Task Group No. 119
Authors: Knill Cory , Snyder Michael 
Published: April 2011

Purpose:The report issued by AAPM Task Group No. 119 outlined a procedure for evaluating the effectiveness of IMRT commissioning. The procedure involves measuring gamma pass‐rate indices for IMRT plans of standard phantoms and determining if the results fall within a confidence limit set by assuming normally distributed data. As stated in the TG report, the assumption of normally distributed gamma pass rates is a convenient approximation for commissioning purposes, but may not accurately describe the data. Here the authors attempt to better describe gamma pass‐rate data by fitting it to different distributions. The authors then calculate updated confidence limits using those distributions and compare them to those derived using TG No. 119 method.Methods:Gamma pass‐rate data from 111 head and neck patients are fitted using the TG No. 119 normal distribution, a truncated normal distribution, and a Weibull distribution. Confidence limits to 95% are calculated for each and compared. A more general analysis of the expected differences between the TG No. 119 method of determining confidence limits and a more time‐consuming curve fitting method is performed.Results:The TG No. 119 standard normal distribution does not fit the measured data. However, due to the small range of measured data points, the inaccuracy of the fit has only a small effect on the final value of the confidence limits. The confidence limits for the 111 patient plans are within 0.1% of each other for all distributions. The maximum expected difference in confidence limits, calculated using TG No. 119's approximation and a truncated distribution, is 1.2%.Conclusions:A three‐parameter Weibull probability distribution more accurately fits the clinical gamma index pass‐rate data than the normal distribution adopted by TG No. 119. However, the sensitivity of the confidence limit on distribution fit is low outside of exceptional circumstances.
Similarity evaluation in a content‐based image retrieval (CBIR) CADx system for characterization of breast masses on ultrasound images
Authors: Cho Hyun‐chong , Hadjiiski Lubomir , Sahiner Berkman , Chan Heang‐Ping , Helvie Mark , Paramagul Chintana , Nees Alexis V. 
Published: April 2011

Purpose:The authors are developing a content‐based image retrieval (CBIR) CADx system to assist radiologists in characterization of breast masses on ultrasound images. In this study, the authors compared seven similarity measures to be considered for the CBIR system. The similarity between the query and the retrieved masses was evaluated based on radiologists' visual similarity assessments.Methods:The CADx system retrieves masses that are similar to a query mass from a reference library based on computer‐extracted features using a ‐nearest neighbor approach. Among seven similarity measures evaluated for the CBIR system, four similarity measures including linear discriminant analysis (LDA), Bayesian neural network (BNN), cosine similarity measure (Cos), and Euclidean distance (ED) similarity measure were compared by radiologists' visual assessment. For LDA and BNN, the features of a query mass were combined first into a malignancy score and then masses with similar scores were retrieved. For Cos and ED, similar masses were retrieved based on the normalized dot product and the Euclidean distance, respectively, between two feature vectors. For the observer study, three most similar masses were retrieved for a given query mass with each method. All query‐retrieved mass pairs were mixed and presented to the radiologists in random order. Three Mammography Quality Standards Act (MQSA) radiologists rated the similarity between each pair using a nine‐point similarity scale ( dissimilar, similar). The accuracy of the CBIR CADx system using the different similarity measures to characterize malignant and benign masses was evaluated by ROC analysis.Results:The BNN measure used with the classifier provided slightly higher performance for classification of malignant and benign masses ( values of 0.87) than those with the LDA, Cos, and ED measures ( of 0.86, 0.84, and 0.81, respectively). The average similarity ratings of all radiologists for LDA, BNN, Cos, and ED were 4.71, 4.95, 5.18, and 5.32, respectively. The with the ED measures retrieved masses of significantly higher similarity than LDA and BNN.Conclusions:Similarity measures using the resemblance of individual features in the multidimensional feature space can retrieve visually more similar masses than similarity measures using the resemblance of the classifier scores. A CBIR system that can most effectively retrieve similar masses to the query may not have the best .
Assessing software upgrades, plan properties and patient geometry using intensity modulated radiation therapy (IMRT) complexity metrics
Authors: McGarry Conor K. , Chinneck Candice D. , O'Toole Monica M. , O'Sullivan Joe M , Prise Kevin M. , Hounsell Alan R. 
Published: April 2011

Purpose:The aim of this study is to compare the sensitivity of different metrics to detect differences in complexity of intensity modulated radiation therapy (IMRT) plans following upgrades, changes to planning parameters, and patient geometry. Correlations between complexity metrics are also assessed.Method:A program was developed to calculate a series of metrics used to describe the complexity of IMRT fields using monitor units (MUs) and multileaf collimator files: Modulation index (MI), modulation complexity score (MCS), and plan intensity map variation (PIMV). Each metric, including the MUs, was used to assess changes in beam complexity for six prostate patients, following upgrades in the inverse planning optimization software designed to incorporate direct aperture optimization (DAO). All beams were delivered to a 2D ionization chamber array and compared to those calculated using gamma analysis. Each complexity metric was then calculated for all beams, on a different set of six prostate IMRT patients, to assess differences between plans calculated using different minimum field sizes and different maximum segment numbers. Different geometries, including CShape, prostate, and head and neck phantoms, were also assessed using the metrics. Correlations between complexity metrics were calculated for 20 prostate IMRT patients.Results:MU, MCS, MI, and PIMV could all detect reduced complexity following an upgrade to the optimization leaf sequencer, although only MI and MCS could detect a reduction in complexity when one‐step optimization (DAO) was employed rather than two‐step optimization. All metrics detected a reduction in complexity when the minimum field size was increased from 1 to 4 cm and all apart from PIMV detected reduced complexity when the number of segments was significantly reduced. All metrics apart from MI showed differences in complexity depending on the treatment site. Significant correlations exist between all metrics apart from MI and PIMV for prostate IMRT patients. Treatment deliverability appeared to be more correlated with MI and MCS than MU or PIMV.Conclusions:The application of complexity metrics in the IMRT treatment planning process has been demonstrated. Complexity of treatment plans can vary for different inverse planning software versions and can depend on planning parameters and the treatment site. MCS is most suitable for inclusion within the cost function to limit complexity in IMRT optimization due to its sensitivity to complexity changes and correlation to treatment deliverability.
Oblique incidence effects in direct x‐ray detectors: A first‐order approximation using a physics‐based analytical model
Authors: Badano Aldo , Freed Melanie , Fang Yuan 
Published: April 2011

Purpose:The authors describe the modifications to a previously developed analytical model of indirect CsI:Tl‐based detector response required for studying oblique x‐ray incidence effects in direct semiconductor‐based detectors. This first‐order approximation analysis allows the authors to describe the associated degradation in resolution in direct detectors and compare the predictions to the published data for indirect detectors.Methods:The proposed model is based on a physics‐based analytical description developed by Freed et al. [“A fast, angle‐dependent, analytical model of CsI detector response for optimization of 3D x‐ray breast imaging systems,” Med. Phys. 37(6), 2593–2605 (2010)] that describes detector response functions for indirect detectors and oblique incident x rays. The model, modified in this work to address direct detector response, describes the dependence of the response with x‐ray energy, thickness of the transducer layer, and the depth‐dependent blur and collection efficiency.Results:The authors report the detector response functions for indirect and direct detector models for typical thicknesses utilized in clinical systems for full‐field digital mammography ( for indirect CsI:Tl and for ‐Se direct detectors). The results suggest that the oblique incidence effect in a semiconductor detector differs from that in indirect detectors in two ways: The direct detector model produces a sharper overall PRF compared to the response corresponding to the indirect detector model for normal x‐ray incidence and a larger relative increase in blur along the x‐ray incidence direction compared to that found in indirect detectors with respect to the response at normal incidence angles.Conclusions:Compared to the effect seen in indirect detectors, the direct detector model exhibits a sharper response at normal x‐ray incidence and a larger relative increase in blur along the x‐ray incidence direction with respect to the blur in the orthogonal direction. The results suggest that the oblique incidence effect in direct detectors can be considered to be caused mostly by the geometry of the path where the x‐ray beam and its secondary particles deposit energy in the semiconductor layer.
Republished review: The world through a lens: the vision of Sir Harold Ridley
Authors: Moore D B , Harris A , Siesky B 
Published: April 2011

ABSTRACT
Sir Harold Ridley is recognised today as the inventor of intraocular lens implantation, one the most successful and common procedures in all of surgery. His story, however, is not largely one of triumph and public accolade. This paper reviews Ridley's invention of the intraocular lens and highlights the struggles he faced after his discovery.
Republished paper: Meta-analysis of the effect of comprehensive smoke-free legislation on acute coronary events
Authors: Mackay D F , Irfan M O , Haw S , Pell J P 
Published: April 2011

ABSTRACT

Objective
To assess the evidence for a reduced risk of acute coronary events following comprehensive smoke-free legislation.

Methods
Two independent systematic reviews were undertaken using PubMed, Embase and Science Direct with no date restrictions imposed. Meta-analysis was undertaken using a random effects model to obtain a pooled estimate of the relative risk. Linear regression was used to examine possible bias and meta-regression was used to investigate possible causes of heterogeneity.

Main outcome measure
Acute coronary events.

Results
The 17 eligible studies (10 from North America, 6 from Europe and 1 from Australasia) provided 35 estimates of effect size. Apart from five subgroup analyses, all of the published results suggested a reduction in the incidence of acute coronary events following the introduction of smoke-free legislation. Meta-analysis produced a pooled estimate of the relative risk of 0.90 (95% CI 0.86 to 0.94). There was significant heterogeneity (overall I2=95.1%, p&lt;0.001) but there was no evidence of small study bias (p=0.714). On univariate random effects meta-regression analysis, studies with longer data collection following legislation produced greater estimates of risk reduction and remained significant after adjustment for other study characteristics (adjusted coefficient −0.005, 95% CI −0.007 to −0.002, multiplicity adjusted p=0.006).

Conclusions
There is now a large body of evidence supporting a reduction in acute coronary events following the implementation of comprehensive smoke-free legislation, with the effect increasing over time from implementation. Countries that have not yet adopted smoke-free legislation should be encouraged to do so.
Coordinating e-health systems with TuCSoN semantic tuple centres
Authors: Nardini Elena , Omicini Andrea , Viroli Mirko , Schumacher Michael I. 
Published: April 2011

Open and distributed application scenarios like e-Health systems mandate for new coordination models and technologies. In particular, they require middleware providing coordination and security services modelled with abstractions promoting run-time observability and adaptation.
Along this line, in this paper we describe the architecture of the TuCSoN coordination infrastructure, and show its application to an e-Health application scenario.