bluuebunny/crossref_metadata_2025 huggingface dataset:
The Carnal Body: Representation, Performativity and the Rest of Us
Authors: Detamore Mathias J.
Published: March 2010

The body has long been a concern of human knowledge; where it comes from, how it develops, how it works, what it means. Since the feminist political activism and academic scholarship of the late 1960s, at least, the body has had a resurging interest in the social sciences and humanities as a location through which Enlightenment notions of a mind/body dichotomy have held the female body captive. Out of this, how the body is ‘represented’ and how the body is ‘performed’ through the ways in which we talk about ourselves has theoretically pushed the body to the fore in much academic thought and inquiry. While gender and (soon following) sexuality has been the primary impetus for reevaluating the body and its relationship to power, the body can now be found in an array of other socio‐political phenomena that render the body a site for exclusion, violence and marginality. Yet the elusiveness of the body and its difficulty at definition continues to provoke anxiety in scholars working through its problems. A recent contribution on ‘carnality’ seems to offer us a window into a more refined and nuanced understanding of the body, highlighting the inseparable interdependence between the corporeal material of the body and the subjective discourses that ‘matter forth’ the body. This essay examines the location of the body in geographical literatures and the social sciences and humanities by briefly outlining its (re)emergence in feminist literatures; locating its continuing development in geographical literatures; taking it through one particular prevailing theoretical debate (including a major geographical intervention through the work of Nigel Thrift); and supposing my own intervention working through Elizabeth Povinelli’s concept of ‘carnality’.
The New Geopolitics of Fear
Authors: Pain Rachel
Published: March 2010

This century, linked to a series of geopolitical events and phenomena, an array of new fears have come to prominence. A number of academic and popular commentators have named and analysed these fears and predicted their reach and effects on people in western countries. However, these accounts have often lacked grounding in evidence that is mounting elsewhere on the everyday sites where emotions and geopolitics meet. This paper brings together a range of evidence from social research about western fears connected to the war on/of terror. First, through examining survey evidence since 2001, I suggest that fear of terrorism in the west tends to be overblown by commentators, and that fear close to the sites of terrorism should be viewed as exceptional rather than routinised or dispersed. Second, I explore a growing body of research that shows those most affected by fear in the current geopolitical climate are marginalised minority groups. Finally, I identify recent writing on alternative geopolitics which points to some original and hopeful directions for conceptual and empirical work on fear.
Methodological Approaches for Interviewing Elites
Authors: Harvey William S.
Published: March 2010

This paper explores some of the methodological strategies for interviewing elites. The focus is on researching elite members, preparing for interviews and gaining access, as well as the associated power relationships. Examples are drawn from across the social sciences and from the author’s doctoral and postdoctoral work with over one hundred members of business elites. It is argued that researchers should be more attentive towards the following three areas. First, providing flexibility when designing research projects and conducting interviews. Second, ensuring transparency when communicating with elite members. Third, maintaining good etiquette with all participants to ensure the highest professional standards. The overall aim of the paper is to provide an introduction for those who are new to the field of interviewing elite subjects.
Lumped Conceptual Rainfall‐Runoff Models and Simple Water Balance Methods: Overview and Applications in Ungauged and Data Limited Regions
Authors: Chiew Francis H. S.
Published: March 2010

This article provides an overview of lumped conceptual rainfall‐runoff models and simple water and energy balance methods, with a focus on practical model applications to estimate runoff in gauged and ungauged catchments over large regions and to predict climate change impact on future runoff. The models are applied to a large data set across south‐eastern Australia to explore the effectiveness of the different model types under varying data availability. The conceptual rainfall‐runoff models are relatively simple tools for predicting runoff in catchments and large regions with sufficient observed streamflow data to calibrate the models. In data‐poor regions, the simple water balance methods can perform as well as the rainfall‐runoff models, particularly where only mean annual runoff estimates for broad‐scale assessments are required. Rainfall‐runoff modelling is a fairly mature science, and this article provides references to previous reviews and recent key papers, particularly on regionalisation studies to predict runoff in ungauged catchments. The study also discusses some of the more significant research areas currently being pursued as well as the use of lumped conceptual rainfall‐runoff models for climate change and land use impact studies.
Case report: Confined penetration of a duodenal ulcer causing pancreatitis
Authors: Singh T , Mendelson R
Published: March 2010

Confined penetration of a duodenal ulcer is an unusual cause of pancreatic gas and pancreatitis.
Syntrophic butyrate and propionate oxidation processes: from genomes to reaction mechanisms
Authors: Müller Nicolai , Worm Petra , Schink Bernhard , Stams Alfons J. M. , Plugge Caroline M.
Published: March 2010

In anoxic environments such as swamps, rice fields and sludge digestors, syntrophic microbial communities are important for decomposition of organic matter to CO2 and CH4. The most difficult step is the fermentative degradation of short‐chain fatty acids such as propionate and butyrate. Conversion of these metabolites to acetate, CO2, formate and hydrogen is endergonic under standard conditions and occurs only if methanogens keep the concentrations of these intermediate products low. Butyrate and propionate degradation pathways include oxidation steps of comparably high redox potential, i.e. oxidation of butyryl‐CoA to crotonyl‐CoA and of succinate to fumarate, respectively, that require investment of energy to release the electrons as hydrogen or formate. Although investigated for several decades, the biochemistry of these reactions is still not completely understood. Genome analysis of the butyrate‐oxidizing Syntrophomonas wolfei and Syntrophus aciditrophicus and of the propionate‐oxidizing Syntrophobacter fumaroxidans and Pelotomaculum thermopropionicum reveals the presence of energy‐transforming protein complexes. Recent studies indicated that S. wolfei uses electron‐transferring flavoproteins coupled to a menaquinone loop to drive butyryl‐CoA oxidation, and that S. fumaroxidans uses a periplasmic formate dehydrogenase, cytochrome b:quinone oxidoreductases, a menaquinone loop and a cytoplasmic fumarate reductase to drive energy‐dependent succinate oxidation. Furthermore, we propose that homologues of the Thermotoga maritima bifurcating [FeFe]‐hydrogenase are involved in NADH oxidation by S. wolfei and S. fumaroxidans to form hydrogen.
Molecular characterization of Hepatozoon species in a Leopard Cat (Prionailurus bengalensis) from Thailand
Authors: Salakij Chaleow , Sirinarumitr Theerapol , Tongthainun Daraka
Published: March 2010

Abstract: Hepatozoon gamonts were observed by light microscopy in neutrophils of a male, wild‐caught Leopard Cat. Complete blood counts at presentation and 6 months later were unremarkable. Serologic tests were negative for both FIV and FeLV. A partial sequence of the 18S rRNA gene from the Hepatozoon found in the cat indicated that, compared with all species examined, the protozoan had the closest relationship (99.2% sequence similarity) with the Hepatozoon of the water python (Stegonotus cucullatus). The cat was clinically healthy at last report. Although Hepatozoon has been found in another wild cat in Thailand, this is the first report in a Leopard Cat. The pathogenicity of Hepatozoon in these cats remains uncertain.
Little enhancement of meal‐induced glucagon‐like peptide 1 secretion in Japanese: Comparison of type 2 diabetes patients and healthy controls
Authors: Yabe Daisuke , Kuroe Akira , Lee Soushou , Watanabe Koin , Hyo Takanori , Hishizawa Masahiro , Kurose Takeshi , Deacon Carolyn F , Holst Jens J , Hirano Tsutomu , Inagaki Nobuya , Seino Yutaka
Published: March 2010

Although glucose‐dependent insulinotropic polypeptide (GIP) levels have been characterized previously, GLP‐1 levels in Asians remain unclear. Here, we investigate total and intact levels of GLP‐1, as well as GIP during oral glucose and meal tolerance tests (OGTT and MTT) in Japanese patients with or without type 2 diabetes (T2DM). Seventeen Japanese healthy controls and 18 age‐matched and untreated patients with T2DM of short duration participated in the present study. Fasting levels of total GPL‐1 were similar between the two groups (approximately 15 pM), and intact GLP‐1 levels were considerably low in both groups (less than 1 pM). In both groups, total GLP‐1 reached a peak 30 min after glucose ingestion (30–40 pM), whereas intact GLP‐1 levels remained low with no significant peak. In MTT, total and intact GLP‐1 showed no obvious peak. The current data indicate that intact GLP‐1 levels are considerably low in the Japanese and that meal‐induced enhancement of GLP‐1 secretion is negligible in the Japanese. (J Diabetes Invest, doi: 10.1111/j.2040‐1124.2010.00010.x, 2010)
Bifurcation Phenomena Caused by Multiple Nonlinear Vibration Absorbers
Authors: Ikeda Takashi
Published: March 2010

The characteristics of two, three, and four nonlinear vibration absorbers or nonlinear tuned mass dampers (NTMDs) attached to a structure under harmonic excitation are investigated. The frequency response curves are theoretically determined using van der Pol’s method. When the parameters of the absorbers are equal, it is found from the theoretical analysis that pitchfork bifurcations may occur on the part of the response curves, which are unstable in the multi-absorber systems, but are stable in a system with one NTMD. Multivalued steady-state solutions, such as three steady-state solutions for a dual-absorber system with different amplitudes, five steady-state solutions for a triple-absorber system, and seven steady-state solutions for a quadruple-absorber system, appear near bifurcation points. The NTMDs behave in that one of them vibrates at high amplitudes while the others vibrate at low amplitudes, even if the dimensions of the NTMDs are identical. Namely, “localization phenomenon” or “mode localization” occurs. After the pitchfork bifurcation, Hopf bifurcations may occur depending on the values of the system parameters, and amplitude- and phase-modulated motions, including chaotic vibrations, appear after the Hopf bifurcation when the excitation frequency decreases. Lyapunov exponents are numerically calculated to prove the occurrence of chaotic vibrations. Bifurcation sets are also calculated to investigate the influence of the system parameters on the response of the systems.
Fractional Order Control of Fractional Diffusion Systems Subject to Input Hysteresis
Authors: Özdemir Necati , İskender Beyza Billur
Published: March 2010

This paper concerns the control of a time fractional diffusion system defined in the Riemann–Liouville sense. It is assumed that the system is subject to hysteresis nonlinearity at its input, where the hysteresis is mathematically modeled with the Duhem operator. To compensate the effects of hysteresis nonlinearity, a fractional order Proportional+Integral+Derivative (PID) controller is designed by minimizing integral square error. For numerical computation, the Riemann–Liouville fractional derivative is approximated by the Grünwald–Letnikov approach. A set of algebraic equations arises from this approximation, which can be solved numerically. Performance of the fractional order PID controllers are analyzed in comparison with integer order PID controllers by simulation results, and it is shown that the fractional order controllers are more advantageous than the integer ones.
Operational Parameter Study of Aircraft Dynamics on the Ground
Authors: Rankin James , Krauskopf Bernd , Lowenberg Mark , Coetzee Etienne
Published: March 2010

The dynamics of passenger aircraft on the ground are influenced by the nonlinear characteristics of several components, including geometric nonlinearities, aerodynamics, and interactions at the tire-ground interface. We present a fully parameterized mathematical model of a typical passenger aircraft that includes all relevant nonlinear effects. The full equations of motion are derived from first principles in terms of forces and moments acting on a rigid airframe, and they include implementations of the local models of individual components. The overall model has been developed from and validated against an existing industry-tested SIMMECHANICS model. The key advantage of the mathematical model is that it allows for comprehensive studies of solutions and their stability with methods from dynamical systems theory, particularly, the powerful tool of numerical continuation. As a concrete example, we present a bifurcation study of how fixed-radius turning solutions depend on the aircraft’s steering angle and center of gravity position. These results are represented in a compact form as surfaces of solutions, on which we identify regions of stable turning and regions of laterally unstable solutions. The boundaries between these regions are computed directly, and they allow us to determine ranges of parameter values for safe operation. The robustness of these results under the variation in additional parameters, specifically, the engine thrust and aircraft mass, are investigated. Qualitative changes in the structure of the solutions are identified and explained in detail. Overall our results give a complete description of the possible turning dynamics of the aircraft in dependence on four parameters of operational relevance.
On Abstract Fractional Order Telegraph Equation
Authors: Herzallah Mohamed A. E. , Baleanu Dumitru
Published: March 2010

During the last decades, there has been a great deal of interest in fractional differential equations and their applications in various fields of science and engineering. In this paper, we give a new model of the abstract fractional order telegraph equation and we study the existence and uniqueness theorems of the strong and mild solutions as well as the continuation of this solution. To illustrate the obtained results, two examples were analyzed in detail.
The Dynamics of Embedded-Charge Microenergy Harvesting
Authors: Lutzer Carl V. , Ross David S.
Published: March 2010

The microelectronic devices that are ubiquitous these days are limited by the need for batteries. Various methods of harvesting ambient mechanical energy have been proposed and are being developed. Recently, Potter has developed a method for embedding charge, at high density, stably at the interfaces of dissimilar insulators. In this paper, we present and analyze dynamical system models that Potter and co-workers have used to optimize microenergy harvesters based on this novel technology.
Stability Analysis of Two-Point Mooring System in Surge Oscillation
Authors: Banik A. K. , Datta T. K.
Published: March 2010

Nonlinear surge response behavior of a multipoint mooring system under harmonic wave excitation is analyzed to investigate various instability phenomena such as bifurcation, period-doubling, and subharmonic and chaotic responses. The nonlinearity of the system arises due to nonlinear restoring force, which is modeled as a cubic polynomial. In order to trace different branches at the bifurcation point on the response curve (amplitude versus frequency of excitation plot), an arc-length continuation technique along with the incremental harmonic balance (IHBC) method is employed. The stability of the solution is investigated by the Floquet theory using Hsu’s scheme. The period-one and subharmonic solutions obtained by the IHBC method are compared with those obtained by the numerical integration of the equation of motion. Characteristics of solutions from stable to unstable zones, chaotic motion, nT solutions, etc., are identified with the help of phase plots and Poincaré map sections.
Remarks on an Optimal Linear Control Design Applied to a Nonideal and an Ideal Structure Coupled to an Essentially Nonlinear Oscillator
Authors: Chavarette Fábio Roberto , Balthazar José Manoel , Felix Jorge L. P.
Published: March 2010

This paper considers a nonlinear dynamics of a particular structure coupled (or uncoupled) to an essentially nonlinear oscillator. We used an optimal linear control design to reduce the amplitude of oscillations and to expand energy consumption, for both ideal and nonideal mathematical models.
Effect of n- and p-type dopants on patterned amorphous regrowth
Authors: Morarka S. , Rudawski N. G. , Law M. E. , Jones K. S. , Elliman R. G.
Published: March 2010

Solid-phase epitaxial regrowth for patterned amorphous regions has been known to form device degrading mask-edge defects. Prior studies have shown that orientation dependence of regrowth leads to pinching of the slow regrowing corners (111 fronts) that create these defects [K. L. Saenger et al., J. Appl. Phys. 101, 104908 (2007)]. Also, the effect of n-type and p-type dopants on regrowth is known only for 001 bulk [B. C. Johnson and J. C. McCallum, Phys. Res. B 76, 045216 (2007); J. S. Williams and R. G. Elliman, Phys. Rev. Lett. 51, 1069 (1983)]. This article studies the effect of these dopants (boron and arsenic) on the patterned amorphous regrowth to see if there is any change in the corner regrowth. The experiment was done on very low resistivity wafers (∼0.003Ωcm) so that the doping concentration was constant in the whole amorphous region and the doping was high enough to have a significant effect on the regrowth. Recent studies have also shown that local α-c interface curvature is an important factor in modeling patterned amorphous regrowth for intrinsic Si [S. Morarka et al., J. Appl. Phys. 105, 053701 (2009)]. This experiment shows the dopant-curvature relationship that is important from modeling perspective.
Dopant measurements in semiconductors with atom probe tomography
Authors: Ronsheim P. A. , Hatzistergos M. , Jin S.
Published: March 2010

The capability of atom probe tomography to make useful measurements of dopant distribution single device geometry is explored by characterizing the compositional accuracy of reconstructed data sets. The objective of this analysis is to evaluate whether atom probe can provide measurements to guide a predictive model development for diffusion in device geometry and strain conditions. Simple measurements of thin films of varying compositions show that, except for boron, all elements studied were collected and identified correctly and match secondary ion mass spectrometry reference values. Boron in silicon shows more variability and may require in situ concentration references.
Detailed simulation study of embedded SiGe and Si:C source/drain stressors in nanoscaled silicon on insulator metal oxide semiconductor field effect transistors
Authors: Flachowsky Stefan , Illgen Ralf , Herrmann Tom , Klix Wilfried , Stenzel Roland , Ostermay Ina , Naumann Andreas , Wei Andy , Höntschel Jan , Horstmann Manfred
Published: March 2010

Strained silicon techniques have become an indispensable technology feature, enabling the momentum of semiconductor scaling. Embedded silicon-germanium (eSiGe) is already widely adopted in the industry and delivers outstanding p-metal oxide semiconductor field effect transistor (MOSFET) performance improvements. The counterpart for n-MOSFET is embedded silicon-carbon (eSi:C). However, n-MOSFET performance improvement is much more difficult to achieve with eSi:C due to the challenging process integration. In this study, detailed TCAD simulations are employed to compare the efficiency of eSiGe and eSi:C stressors and to estimate their potential for performance enhancements in future nanoscaled devices with gate lengths down to 20nm. It is found that eSiGe as a stressor is superior to eSi:C in deeply scaled and highly strained devices due to its easier process integration, reduced parasitic resistance, and nonlinear effects in the silicon band structure, favoring hole mobility enhancement at high strain levels.
Simulation of asymmetric doped high performance silicon on insulator metal oxide semiconductor field effect transistors for very large scale integrated complementary metal oxide semiconductor technologies
Authors: Herrmann Tom , Flachowsky Stefan , Illgen Ralf , Klix Wilfried , Stenzel Roland , Höntschel Jan , Feudel Thomas , Horstmann Manfred
Published: March 2010

Asymmetric halo and extension implantations are examined by simulation for their usability in 45 and 32 nm technology high performance silicon on insulator metal oxide semiconductor field effect transistors (SOI-MOSFETs). Tilted halo and extension implantations from the source side show higher saturation currents and lower drain overlap and junction capacitances, which improve the intrinsic MOSFET power delay product. Furthermore the asymmetric doping profile leads to an inverter chain speed benefit. The stronger short channel effect, present in these devices, can be reduced by a low dose drain side halo implantation simultaneously maintaining a transistor performance improvement from asymmetric doping. This optimized transistor design is successfully transferred from the 45 into the 32 nm technology.
Kinetic lattice Monte Carlo simulations of interdiffusion in strained silicon germanium alloys
Authors: Chen Renyu , Dunham Scott T.
Published: March 2010

Point-defect-mediated diffusion processes are investigated in strained SiGe alloys using kinetic lattice Monte Carlo (KLMC) simulation technique. The KLMC simulator incorporates an augmented lattice domain and includes defect structures, atomistic hopping mechanisms, and the stress dependence of transition rates obtained from density functional theory calculation results. Vacancy-mediated interdiffusion in strained SiGe alloys is analyzed, and the stress effect caused by the induced strain of germanium is quantified separately from that due to germanium-vacancy binding. The results indicate that both effects have substantial impact on interdiffusion.
Reconstruction of 3D lung models from 2D planning data sets for Hodgkin's lymphoma patients using combined deformable image registration and navigator channels
Authors: Ng Angela , Nguyen Thao‐Nguyen , Moseley Joanne L. , Hodgson David C. , Sharpe Michael B. , Brock Kristy K.
Published: March 2010

Purpose:

Late complications (cardiac toxicities, secondary lung, and breast cancer) remain a significant concern in the radiation treatment of Hodgkin's lymphoma (HL). To address this issue, predictive dose‐risk models could potentially be used to estimate radiotherapy‐related late toxicities. This study investigates the use of deformable image registration (DIR) and navigator channels (NCs) to reconstruct 3D lung models from 2D radiographic planning images, in order to retrospectively calculate the treatment dose exposure to HL patients treated with 2D planning, which are now experiencing late effects.

Methods:

Three‐dimensional planning CT images of 52 current HL patients were acquired. 12 image sets were used to construct a male and a female population lung model. 23 “Reference” images were used to generate lung deformation adaptation templates, constructed by deforming the population model into each patient‐specific lung geometry using a biomechanical‐based DIR algorithm, MORFEUS. 17 “Test” patients were used to test the accuracy of the reconstruction technique by adapting existing templates using 2D digitally reconstructed radiographs. The adaptation process included three steps. First, a Reference patient was matched to a Test patient by thorax measurements. Second, four NCs (small regions of interest) were placed on the lung boundary to calculate 1D differences in lung edges. Third, the Reference lung model was adapted to the Test patient's lung using the 1D edge differences. The Reference‐adapted Test model was then compared to the 3D lung contours of the actual Test patient by computing their percentage volume overlap (POL) and Dice coefficient.

Results:

The average percentage overlapping volumes and Dice coefficient expressed as a percentage between the adapted and actual Test models were found to be and , respectively. Paired ‐tests demonstrated that the volumetric reconstruction method made a statistically significant improvement to the population lung model shape . The error in the results were also comparable to the volume overlap difference observed between inhale and exhale lung volumes during free‐breathing respiratory motion , which implies that the accuracies of the reconstruction method are within breathing constraints and would not be the confining factor in estimating normal tissue dose exposure.

Conclusions:

The result findings show that the DIR‐NC technique can achieve a high degree of reconstruction accuracy, and could be useful in approximating 3D dosimetric representations of historical 2D treatment. In turn, this could provide a better understanding of the biophysical relationship between dose‐volume exposure and late term radiotherapy effects.
The quantitative potential for breast tomosynthesis imaging
Authors: Shafer Christina M. , Samei Ehsan , Lo Joseph Y.
Published: March 2010

Purpose:

Due to its limited angular scan range, breast tomosynthesis has lower resolution in the depth direction, which may limit its accuracy in quantifying tissue density. This study assesses the quantitative potential of breast tomosynthesis using relatively simple reconstruction and image processing algorithms. This quantitation could allow improved characterization of lesions as well as image processing to present tomosynthesis images with the familiar appearance of mammography by preserving more low‐frequency information.

Methods:

All studies were based on a Siemens prototype MAMMOMAT Novation TOMO breast tomo system with a 45° total angular span. This investigation was performed using both simulations and empirical measurements. Monte Carlo simulations were conducted using the breast tomosynthesis geometry and tissue‐equivalent, uniform, voxelized phantoms with cuboid lesions of varying density embedded within. Empirical studies were then performed using tissue‐equivalent plastic phantoms which were imaged on the actual prototype system. The material surrounding the lesions was set to either fat‐equivalent or glandular‐equivalent plastic. From the simulation experiments, the effects of scatter, lesion depth, and background material density were studied. The empirical experiments studied the effects of lesion depth, background material density, x‐ray tube energy, and exposure level. Additionally, the proposed analysis methods were independently evaluated using a commercially available QA breast phantom (CIRS Model 11A). All image reconstruction was performed with a filtered backprojection algorithm. Reconstructed voxel values within each slice were corrected to reduce background nonuniformities.

Results:

The resulting lesion voxel values varied linearly with known glandular fraction (correlation coefficient ) under all simulated and empirical conditions, including for the independent tests with the QA phantom. Analysis of variance performed on the fit line parameters revealed statistically significant differences between the two different background materials and between 28 kVp and the remaining energies (26, 30, and 32 kVp) for the dense experimental phantom. However, no significant differences arose between different energies for the fatty phantom, nor for any of the many other combinations of parameters.

Conclusions:

These strong linear relationships suggest that breast tomosynthesis image voxel values, after being corrected by our outlined methods, are highly positively correlated with true tissue density. This consistent linearity implies that breast tomosynthesis imaging indeed has potential to be quantitative.
Backprojection‐filtration reconstruction without invoking a spatially varying weighting factor
Authors: Xia Dan , Cho Seungryong , Pan Xiaochuan
Published: March 2010

Purpose:

To develop a backprojection‐filtration (BPF) algorithm with improved noise properties over the existing BPF algorithm through utilizing (approximate) redundant information in circular cone‐beam or fan‐beam scans.

Methods:

The backprojection steps in the existing filtered‐backprojection (FBP) and BPF algorithms for fan‐beam and cone‐beam projections invoke spatially varying weighting factors, which may not only increase the computational load in image reconstruction but also, more importantly, result in reconstruction artifacts. Redundant information in fan‐beam projections has been exploited for eliminating the weighting factor in the existing FBP algorithm. However, the new FBP algorithm cannot be applied to image reconstruction in a region of interest from transversely truncated data. In this work, the authors identify approximate data redundancy in circular cone‐beam projections and propose a new BPF algorithm in which the approximate data redundancy is exploited for eliminating the spatially varying weighting factor in the existing BPF algorithm.

Results:

The authors have implemented and evaluated the proposed BPF algorithm in numerical studies of reconstructing 3D images from both the nontruncated and truncated projection data in a circular cone‐beam scan. The results of numerical studies demonstrate that the proposed BPF algorithm retains the resolution property of the existing BPF algorithm, and that it can also reconstruct accurately ROI images from truncated data. More importantly, the results also indicate that the proposed BPF algorithm not only is computationally more efficient but also yields generally lower image variances than the existing BPF algorithm.

Conclusions:

A BPF algorithm was proposed that not only retains the desirable properties of the existing BPF algorithm but also possesses improved computational and noise properties over the latter.
Mathematical formulation and analysis of the nonlinear system reconstruction of the online image‐guided adaptive control of hyperthermia
Authors: Cheng Kung‐Shan , Dewhirst Mark W. , Stauffer Paul F. , Das Shiva
Published: March 2010

Purpose:

A nonlinear system reconstruction can theoretically provide timely system reconstruction when designing a real‐time image‐guided adaptive control for multisource heating for hyperthermia. This clinical need motivates an analysis of the essential mathematical characteristics and constraints of such an approach.

Methods:

The implicit function theorem (IFT), the Karush–Kuhn–Tucker (KKT) necessary condition of optimality, and the Tikhonov–Phillips regularization (TPR) were used to analyze and determine the requirements of the optimal system reconstruction. Two mutually exclusive generic approaches were analyzed to reconstruct the physical system: The traditional full reconstruction and the recently suggested partial reconstruction. Rigorous mathematical analysis based on IFT, KKT, and TPR was provided for all four possible nonlinear reconstructions: (1) Nonlinear noiseless full reconstruction, (2) nonlinear noisy full reconstruction, (3) nonlinear noiseless partial reconstruction, and (4) nonlinear noisy partial reconstruction, when a class of nonlinear formulations of system reconstruction is employed.

Results:

Effective numerical algorithms for solving each of the aforementioned four nonlinear reconstructions were introduced and formal derivations and analyses were provided. The analyses revealed the necessity of adding regularization when partial reconstruction is used. Regularization provides the theoretical support for one to uniquely reconstruct the optimal system. It also helps alleviate the negative influences of unavoidable measurement noise. Both theoretical analysis and numerical examples showed the importance of having a good initial guess for accomplishing nonlinear system reconstruction.

Conclusions:

Regularization is mandatory for partial reconstruction to make it well posed. The Tikhonov–Phillips regularized Gauss–Newton algorithm has nice theoretical performance for partial reconstruction of systems with and without noise. The Levenberg–Marquardt algorithm is a more robust algorithmic option compared to the Gauss–Newton algorithm for nonlinear full reconstruction. A severe limitation of nonlinear reconstruction is the time consuming calculations required for the derivatives of temperatures to unknowns. Developing a method of model reduction or implementing a parallel algorithm can resolve this. The results provided herein are applicable to hyperthermia with blood perfusion nonlinearly depending on temperature and in the presence of thermally significant blood vessels.
Variations in tumor size and position due to irregular breathing in 4D‐CT: A simulation study
Authors: Sarker Joyatee , Chu Alan , Mui Kit , Wolfgang John A. , Hirsch Ariel E. , Chen George T. Y. , Sharp Gregory C.
Published: March 2010

Purpose:

To estimate the position and volume errors in 4D‐CT caused by irregular breathing.

Methods:

A virtual 4D‐CT scanner was designed to reproduce axial mode scans with retrospective resorting. This virtual scanner creates an artificial spherical tumor based on the specifications of the user, and recreates images that might be produced by a 4D‐CT scanner using a patient breathing waveform. 155 respiratory waveforms of patients were used to test the variability of 4D‐CT scans. Each breathing waveform was normalized and scaled to 1, 2, and 3 cm peak‐to‐peak motion, and artificial tumors with 2 and 4 cm radius were simulated for each scaled waveform. The center of mass and volume of resorted 4D‐CT images were calculated and compared to the expected values of center of mass and volume for the artificial tumor. Intrasubject variability was investigated by running the virtual scanner over different subintervals of each patient's breathing waveform.

Results:

The average error in the center of mass location of an artificial tumor was less than 2 mm standard deviation for 2 cm motion. The corresponding average error in volume was less than 4%. In the worst‐case scenarios, a center of mass error of 1.0 cm standard deviation and volume errors of 30%–60% at inhale were found. Systematic errors were observed in a subset of patients due to irregular breathing, and these errors were more pronounced when the tumor volume is smaller.

Conclusions

: Irregular breathing during 4D‐CT simulation causes systematic errors in volume and center of mass measurements. These errors are small but depend on the tumor size, motion amplitude, and degree of breathing irregularity.
Advanced statistical techniques applied to comprehensive FTIR spectra on human colonic tissues
Authors: Zwielly A. , Mordechai S. , Sinielnikov I. , Salman A. , Bogomolny E. , Argov S.
Published: March 2010

Purpose:

Colon cancer is a major public health problem due to its high disease rate and death toll worldwide. The use of FTIR microscopy in the field of cancer diagnosis has become attractive over the past 20 years. In the present study, the authors investigated the potential of FTIR microscopy to define spectral changes among normal, polyp, and cancer human colonic biopsied tissues.

Methods:

A large database of FTIR microscopic spectra was compiled from 230 human colonic biopsies. The database was divided into five subgroups: Normal, cancerous tissues, and three stages of benign colonic polyps, namely, mild, moderate, and severe polyps, which are precursors of carcinoma. All biopsied tissue sections were classified concurrently by an expert pathologist. The authors applied the principal components analysis (PCA) model to reduce the dimension of the original data size to 13 principal components.

Results:

While PCA analysis shows only partial success in distinguishing among cancer, polyp, and the normal tissues, multivariate analysis (e.g., LDA) shows a promising distinction even within the polyp subgroups.

Conclusions:

Good classification accuracy among normal, polyp, and cancer groups was achieved with a success rate of approximately 85%. These results strongly support the potential of developing FTIR microscopy as a simple, reagent‐free tool for early detection of colon cancer and, in particular, for discriminating among the benign premalignant colonic polyps having increasing degrees of dysplasia severity (mild, moderate, and severe).
Individualized computer‐aided education in mammography based on user modeling: Concept and preliminary experiments
Authors: Mazurowski Maciej A. , Baker Jay A. , Barnhart Huiman X. , Tourassi Georgia D.
Published: March 2010

Purpose:

The authors propose the framework for an individualized adaptive computer‐aided educational system in mammography that is based on user modeling. The underlying hypothesis is that user models can be developed to capture the individual error making patterns of radiologists‐in‐training. In this pilot study, the authors test the above hypothesis for the task of breast cancer diagnosis in mammograms.

Methods:

The concept of a user model was formalized as the function that relates image features to the likelihood/extent of the diagnostic error made by a radiologist‐in‐training and therefore to the level of difficulty that a case will pose to the radiologist‐in‐training (or “user”). Then, machine learning algorithms were implemented to build such user models. Specifically, the authors explored‐nearest neighbor, artificial neural networks, and multiple regression for the task of building the model using observer data collected from ten Radiology residents at Duke University Medical Center for the problem of breast mass diagnosis in mammograms. For each resident, a user‐specific model was constructed that predicts the user's expected level of difficulty for each presented case based on two BI‐RADS image features. In the experiments, leave‐one‐out data handling scheme was applied to assign each case to a low‐predicted‐difficulty or a high‐predicted‐difficulty group for each resident based on each of the three user models. To evaluate whether the user model is useful in predicting difficulty, the authors performed statistical tests using the generalized estimating equations approach to determine whether the mean actual error is the same or not between the low‐predicted‐difficulty group and the high‐predicted‐difficulty group.

Results:

When the results for all observers were pulled together, the actual errors made by residents were statistically significantly higher for cases in the high‐predicted‐difficulty group than for cases in the low‐predicted‐difficulty group for all modeling algorithms (for all methods). This indicates that the user models were able to accurately predict difficulty level of the analyzed cases. Furthermore, the authors determined that among the two BI‐RADS features that were used in this study, mass margin was the most useful in predicting individual user errors.

Conclusions:

The pilot study shows promise for developing individual user models that can accurately predict the level of difficulty that each case will pose to the radiologist‐in‐training. These models could allow for constructing adaptive computer‐aided educational systems in mammography.
A pseudoinverse deformation vector field generator and its applications
Authors: Yan C. , Zhong H. , Murphy M. , Weiss E. , Siebers J. V.
Published: March 2010

Purpose:

To present, implement, and test aself‐consistent pseudoinverse displacement vector field (PIDVF) generator, which preserves the location of information mapped back‐and‐forth between image sets.

Methods:

The algorithm is an iterative scheme based on nearest neighbor interpolation and a subsequent iterative search. Performance of the algorithm is benchmarked using a lung 4DCT data set with six CT images from different breathing phases and eight CT images for a single prostrate patient acquired on different days. A diffeomorphic deformable image registration is used to validate our PIDVFs. Additionally, the PIDVF is used to measure the self‐consistency of two nondiffeomorphic algorithms which do not use a self‐consistency constraint: The ITK Demons algorithm for the lung patient images and an in‐house B‐Spline algorithm for the prostate patient images. Both Demons and B‐Spline have been QAed through contour comparison. Self‐consistency is determined by using a DIR to generate a displacement vector field (DVF) between reference image and study image . The same DIR is used to generate . Additionally, our PIDVF generator is used to create . Back‐and‐forth mapping of a set of points (used as surrogates of contours) using and is compared to back‐and‐forth mapping performed with and . The Euclidean distances between the original unmapped points and the mapped points are used as a self‐consistency measure.

Results:

Test results demonstrate that the consistency error observed in back‐and‐forth mappings can be reduced two to nine times in point mapping and 1.5 to three times in dose mapping when the PIDVF is used in place of the B‐Spline algorithm. These self‐consistency improvements are not affected by the exchanging of and . It is also demonstrated that differences between and can be used as a criteria to check the quality of the DVF.

Conclusions:

Use of DVF and its PIDVF will improve the self‐consistency of points, contour, and dose mappings in image guided adaptive therapy.
A volumetric model‐based 2D to 3D registration method for measuring kinematics of natural knees with single‐plane fluoroscopy
Authors: Tsai Tsung‐Yuan , Lu Tung‐Wu , Chen Chung‐Ming , Kuo Mei‐Ying , Hsu Horng‐Chaung
Published: March 2010

Purpose:

Accurate measurement of the three‐dimensional (3D) rigid body and surface kinematics of the natural human knee is essential for many clinical applications. Existing techniques are limited either in their accuracy or lack more realistic experimental evaluation of the measurement errors. The purposes of the study were to develop a volumetric model‐based 2D to 3D registration method, called the weighted edge‐matching score (WEMS) method, for measuring natural knee kinematics with single‐plane fluoroscopy to determine experimentally the measurement errors and to compare its performance with that of pattern intensity (PI) and gradient difference (GD) methods.

Methods:

The WEMS method gives higher priority to matching of longer edges of the digitally reconstructed radiograph and fluoroscopic images. The measurement errors of the methods were evaluated based on a human cadaveric knee at 11 flexion positions.

Results:

The accuracy of the WEMS method was determined experimentally to be less than 0.77 mm for the in‐plane translations, 3.06 mm for out‐of‐plane translation, and 1.13° for all rotations, which is better than that of the PI and GD methods.

Conclusions:

A new volumetric model‐based 2D to 3D registration method has been developed for measuring 3Din vivo kinematics of natural knee joints with single‐plane fluoroscopy. With the equipment used in the current study, the accuracy of the WEMS method is considered acceptable for the measurement of the 3D kinematics of the natural knee in clinical applications.
Fully automatic nonrigid registration‐based local motion estimation for motion‐corrected iterative cardiac CT reconstruction
Authors: Isola Alfonso A. , Grass Michael , Niessen Wiro J.
Published: March 2010

Purpose:

Cardiac computed tomography is a rapidly emerging technique for noninvasive diagnosis of cardiovascular diseases. Nevertheless, the cardiac motion continues to be a limiting factor. Electrocardiogram‐gated cardiac computed tomography reconstruction methods yield excellent results, but these are limited in their temporal resolution due to the mechanical movement of the gantry, and lead to residual motion blurring artifacts. If the motion of the cardiac region of interest is determined, motion compensated gated reconstructions can be applied to reduce motion artifacts. In this paper it is shown that elastic image registration methods can be an accurate solution to determine the cardiac motion. A method, which combines elastic registration and iterative computed tomography reconstruction methods delivering motion‐corrected images of a chosen cardiac region of interest, is introduced.

Methods:

Using a gated four‐dimensional region of interest image data set, a fully automatic elastic image registration is applied to recover a cardiac displacement field from a reference phase to a number of phases within the RR interval. Here, a stochastic optimizer and multiresolution approach are adopted to speed up the registration process. Subsequently, motion‐compensated iterative reconstruction using the determined motion field is carried out. For the image representation volume‐adapted spherical basis functions (blobs) are used to take the volume change caused by a divergent motion vector field into account.

Results:

The method is evaluated on phantom data and on four clinical data sets at a strong cardiac motion phase. Comparing the method to standard gated iterative reconstruction results shows that motion compensation strongly improves the image quality in these phases. A qualitative and quantitative accuracy study is presented for the estimated cardiac motion field. For the first time a blob‐volume adaptation is applied on clinical data, and in the case of divergent motion it yields improved image quality.

Conclusions:

A fully automatic local cardiac motion compensated gated iterative method with volume‐adapted blobs is proposed. The method leads to excellent motion‐corrected images which outperform nonmotion corrected results in phases of strong cardiac motion. In clinical cases, a volume‐dependent blob‐footprint adaptation proves to be a good solution to take care of the change in the blob volume caused by a divergent motion field.
Monte Carlo characterization of a new Yb‐169 high dose rate source for brachytherapy application
Authors: Cazeca Mario J. , Medich David C. , Munro John J.
Published: March 2010

Purpose:

The objective was to characterize a new Yb‐169 high dose rate source for brachytherapy application.

Methods:

Monte Carlo simulations were performed using theMCNP5 F6 energy deposition tallies placed around the Yb‐169 source at different radial distances in both air‐vacuum and water environments. The calculations were based on a spherical water phantom with a radius of 50 cm. The output from the simulations was converted into radial dose rate distribution in polar coordinates surrounding the brachytherapy source.

Results:

The results from Monte Carlo simulations were used to calculate the AAPM Task Group 43 dosimetric parameters: Anisotropy function, radial dose function, air kerma strength, and dose rate constant. The results indicate a dose rate constant of , anisotropy function ranging from 0.44 to 1.00 for radial distances of 0.5–10 cm and polar angles of 0°–180°.

Conclusions:

The data from the Yb‐169 HDR source, Model M42, presented in this study show that this source compares favorably with another source of Yb‐169, Model 4140, already approved for brachytherapy treatment.