bluuebunny/crossref_metadata_2025 huggingface dataset:
Numerical and Experimental Analyses for the Aerodynamic Design of High Performance Counter-Rotating Axial Flow Fans
Authors: Cho Leesang , Choi Hyunmin , Lee Seawook , Cho Jinsoo
Published: July 2010

A study was done on the numerical and experimental analyses for the aerodynamic design of high performance of the counter rotating axial fan (CRF). Front rotor and rear rotor blades of a counter rotating axial fan are designed using the simplified meridional flow analysis method with the radial equilibrium equation and the free vortex design condition, according to design requirements. The through-flow fields and the aerodynamic characteristics of the designed rotor blades are analyzed by the matrix method and the frequency domain panel method. Fan performance curves are measured by following the standard fan testing method, KS B 6311. Three-dimensional flow fields in the CRF are analyzed by using the prism type five-hole probe. Performance characteristics of a counter-rotating axial flow fan are estimated for the variation of design parameters such as the hub to tip ratio, the taper ratio and the solidity. The effect of the hub to tip ratio on the fan efficiency is significant compared with the effects of other design parameters such as the solidity and the taper ratio. The fan efficiency is peak at the hub to tip ratio of 0.4, which is almost same point for the front rotor efficiency and rear rotor efficiency. The magnitudes of the meridional and relative velocities on the front and rear rotors are increased with the radial direction from hub to tip. This results in the reverse pressure gradient at the blade leading edges of both the front rotor and the rear rotor. Axial velocities of the CRF, which are measured by the prism type five-hole probe, are gradually increased at the mean radius due to the flow contraction effect. At the hub region, axial velocity is gradually decreased due to the flow separation and the hub vortex compare with design results. This result induces the increment of the incidence angle and the diffusion factor of the front rotor and the rear rotor.
A Micro Pump Driven by Conducting Polymer Soft Actuator Based on Polypyrrole
Authors: Naka Yoshitaka , Fuchiwaki Masaki , Tanaka Kazuhiro
Published: July 2010

Micro pumps with various driving systems have been developed and they have been carried out with experimental and numerical approaches so far. The authors propose a micro pump with soft actuators by conducting polymers as a driving source. The purpose of the present study is to develop the micro pump driven by conducting polymer soft actuator based on polypyrrole and to clarify the basic characteristics of the micro pump. Especially, we measure the flow rates, delivery heads and energy consumption of the micro pump driven by conducting polymer soft actuators and compare these results with those of the conventional micro pumps. The micro pump driven by a conducting polymer soft actuator can transport fluids in one direction without backflow by two soft actuators with opening and closing movement. Furthermore, wider ranges of flow rates are obtained with this micro pump and greater maximum delivery heads are obtained by them Moreover, the influence of the viscosity of the transport fluid was small and the micro pump driven by the conducting polymer soft actuator can transport fluid even with the viscosity that is 400 times as great as that of water in addition. The energy consumption rates of our micro pump are dramatically lower than those of the conventional micro pumps. This is because a conducting polymer soft actuator drives with a low voltage and a micro pump with low energy consumption is realized here.
Investigation of the Cooling and Underbody Flow Field on a Detailed Scale Model Passenger Car: Part 2—Effect of Ground Simulation
Authors: Landstro¨m Christoffer , Christoffersen Lasse , Lo¨fdahl Lennart
Published: July 2010

Future demands on passenger cars consist to a large extend of making them more energy efficient. Reducing the driving resistance by reducing the aerodynamic drag will be one important part in reducing fuel consumption. In most cases during passenger car development, early experimental investigations are performed in scale model wind tunnels. Considering that such models inevitably suffer from Reynolds number effects it is important to understand how this affects the test results. Investigations of the aerodynamics of a detailed scale model Volvo S60 have been performed in the aerodynamic wind tunnel at Chalmers University of Technology. The investigation aimed at increasing the understanding of how the flow field in scale model testing is affected by ground simulation and different cooling air flow configurations at different Reynolds numbers. A full width moving ground system was used in the experiments. Pressure taps were distributed between the cooling air inlets, the underbody and the vehicle base. An internal six component balance was used to measure global forces and moments. By combining the results from the measurements it was possible to increase the understanding of some of the local flow features. Results showed significant Reynolds number effects both with stationary ground as well as moving ground and rotating wheels. Global aerodynamic drag as well as front and rear axle lift was found to be affected.
Modeling In-Situ Vapor Extraction During Convective Boiling
Authors: Salakij Saran , Liburdy James A. , Pence Deborah V.
Published: July 2010

The pressure drop of convective boiling flow may be reduced by extracting vapor locally since the entire generated vapor does not have to travel through the entire channel length. In this study, the theoretical model was developed to simulate a convective boiling flow through a fractal-like branching microchannel network with vapor extraction. The fractal-like branching microchannel network has a porous membrane forming one wall of the channels. Vapor extraction occurs by applying a vacuum across the membrane. Sample predictive local conditions and global results are presented and discussed. The predicting results are classified into two groups: low inlet flow rate-low heat flux and high inlet flow rate-high heat flux. The results show that to increase extracted vapor mass flow rate, either decreasing supplying extracting pressure or increasing permeability of the porous membrane must be applied. As the amount of vapor extracting increases, the reduction in pressure drop across the channel and the exit vapor quality is achieved.
Statistical Modeling of Rarefied Gas Channel Flows
Authors: Gokaltun Seckin , Sukop Michael C. , Dulikravich George S.
Published: July 2010

Lattice Boltzmann method (LBM) and direct simulation Monte Carlo (DSMC) method are used for analysis of moderate Knudsen number phenomena. Simulation results are presented for pressure-driven isothermal rarefied channel flow at various pressure ratios. Analytical equations for non-linear pressure distribution and velocity profiles along the channel axis are used to verify the present LBM and DSMC results. We conclude that the LBM method can be used as an alternative model to DSMC simulations.
Effect of Manifold Design on Flow Distribution in Multichanneled Microfluidic Devices
Authors: Mathew B. , John T. J. , Hegab H.
Published: July 2010

The effect of channel width and channel spacing on the flow distribution in a microfluidic device with U-type manifolds is numerically analyzed in this paper. Analysis is performed for flow rates between 1 ml/min and 60 ml/min. Flow distribution in a microfluidic device with three different microchannel widths are studied: 50 μm, 100 μm, and 200 μm. Reduction in the microchannel width reduced the non-uniformity in flow rate. Moreover, the flow malidistribution increased with increase in flow rate. The RMS value of the deviation of flow rate per channel reduced from 3 ml/min to 0.3 ml/min with reduction in channel width for a total flow rate of 60 ml/min. The effect of channel spacing on flow distribution was investigated for three channel spacing of 300 μm, 100 μm, and 50 μm. Reduction in channel spacing increased nonuniformity of flow distribution. The RMS value of the deviation of flow rate per flow rate reduced from 1 ml/min to 0.6 ml/min with increase in channel spacing for the greatest flow rate. From the particular studies examined in this paper it is found channel width has a stronger influence on flow distribution than channel spacing. Moreover, proper selection of channel width and channel spacing can uniformly distribute flow.
Prediction of Droplet Size and Velocity Distribution in Spray Using Maximum Entropy Method
Authors: Ommi Fathollah , Movahednejad Ehsan , Hosseinalipour S. Mostafa , Chen Chien-Pin
Published: July 2010

The distribution of sizes and velocities of droplets initially formed in sprays is an important piece of information needed in the spray modeling, because it defines the initial condition of the spray droplets in the predictive calculations of the downstream flow fields. The early stage of the atomization process (Primary Breakup) is clearly deterministic, whereas the droplet formation stage is random and stochastic. The stochastic aspect deals with the stage of droplet formation after the liquid bulk breakup by statistical means through the maximum entropy principle (MEP) based. The MEP provided model predicts atomization process while satisfying constrain equations of mass, momentum and energy. This model is capable for considering drag force on droplets downstream through a gas field. The model prediction is compared favorably with the experimentally measured size and velocity distribution for droplets, near the liquid bulk breakup region, produced by an air-blast annular nozzle. Therefore, the present model can be used to predict the initial droplet size and velocity distribution in droplet formation region of sprays.
Core Flood Tests of In-Situ CO2 Generation Technology
Authors: Bakhtiyarov S. I.
Published: July 2010

In-situ CO2 generation technique (ISCGT) is designed to address CO2 flooding method’s shortcomings and makes CO2 flood method economical in the places where CO2 flooding is not feasible. The results of core-flood tests of in-situ CO2 generation technique are presented in this paper. The experiments were conducted to define effect of surfactants on recovery efficiency. The results demonstrated obvious advantages of the foamy system over the brine solution in order to achieve higher sweep efficiency and recovery coefficient.
Polymer Adsorption Phenomena in Porous Media Filtration Problems
Authors: Bakhtiyarov S. I. , Panakhov G. M. , Abbasov E. M. , Omrani A. N. , Bakhtiyarov A. S.
Published: July 2010

This paper represents the results of the mathematical modeling of the chemical flood process in oil reservoirs. The mathematical model of a problem resulted in solution of the differential equations in private derivatives with initial boundary conditions. In non-uniform net area the problem is replaced with a discrete problem by means of combination of obvious and implicit-difference schemes increasing accuracy order and is solved by double-sweep method. The effective decision algorithms of one-dimensional problem as adsorption and convectional diffusion equations are obtained.
Aerodynamic Design and Performance Analysis of HAWT Blades
Authors: Kulunk Emrah , Yilmaz Nadir
Published: July 2010

In this paper, a design method based on blade element momentum (BEM) theory is explained for horizontal-axis wind turbine (HAWT) blades. The method is used to optimize the chord and twist distributions of the blades. Applying this method a 100kW HAWT rotor is designed. Also a computer program is written to estimate the aerodynamic performance of the existing HAWT blades and used for the performance analysis of the designed 100kW HAWT rotor.
Numerical Study of Liquid Film Microstructure During Spin Coating of Ag Colloidal Suspension
Authors: Zhao Yongli , Ratner Albert , Marshall Jeffrey S.
Published: July 2010

A multiple time-step discrete-element approach is employed to model the transport, collision and adhesion of small silver (Ag) colloidal particles in a spin coating process. The three-dimensional (3D) particle motions are computed using a combination of fluid-induced forces and torques, and forces and torques induced by the particle collision and adhesion forces. These analysis are used to predict the final aggregate size distribution and microstructure during the non-evaporative phase of spin coating of a thin film, which is important for controlling the abrasiveness, opacity, conductivity, and other properties of the film, as well as for using the deposited particles for growing new materials (e.g., nanotubes). The computations examine the effect of adhesion potential, volume concentration, and spin speed effects on the distribution of particle aggregate sizes and their deposition during spin coating. The aggregates are observed to be primarily governed by these parameters, as has previously been observed in experiments. The results provide a fundamental understanding of the physics of thin film spin coating processes and insight in to microstructure control during the coating process.
PIV Measurement of Oscillatory Flow Field in Compliant Tube
Authors: Kolinsky J. , Matecha J. , Novotny J.
Published: July 2010

This paper deals with the 2D measurement of non-stationary flow fields in elastic tubes. The requirements of the model (transparency and tracking) were consistent with the principles of the PIV (Particle Image Velocimetry) method. In addition, the paper describes the production of elastic models, the measurement procedures and image processing. The analysis shows the main differences between the flow field measurements in rigid and elastic tubes. The flow field was measured during one period of oscillating flow under different conditions (Womersley number 5 and 7). The obtained velocity fields were formalized with normalized velocity profiles. In both cases, the fluctuation of velocity was analyzed for the whole period.
Aeroelastic Analysis of Membrane Micro Air Vehicles
Authors: Attar Peter J. , Gordnier Raymond E. , Johnston Jordan W. , Romberg William A. , Parthasarathy Ramkumar N.
Published: July 2010

The fluid and structural response of two different membrane wing Micro Air Vehicles is studied through computation and experiment. A (three) batten-reinforced fixed wing membrane micro air vehicle is used to determine the effect of membrane prestrain and fixed angle of attack on flutter and limit cycle behavior of fixed wing membrane Micro Air Vehicles. For each configuration tested, flutter and subsequent limit cycle oscillations are measured in wind tunnel tests and predicted using an aeroelastic computational model consisting of a nonlinear finite element model coupled to a vortex lattice solution of the Laplace equation and boundary conditions. Correlation between the predicted and measured onset of limit cycle oscillation is good as is the prediction of the amplitude of the limit cycle at the trailing edge of the lower membrane. A direct correlation between levels of strain and the phase of the membranes during the limit cycle is found in the computation and thought to also occur in the experiment. The second membrane wing micro air vehicle configuration is that of a plunging membrane airfoil model. This model is studied computationally using a sixth-order finite difference solution of the Navier-Stokes equations coupled to a nonlinear string finite element model. The effect, on the structural and fluid response, of plunging Strouhal number, reduced frequency and static angle of attack is examined. At two degree angle of attack, and Strouhal number of 0.2, the effect of increasing the plunging reduced frequency is to decrease the sectional lift coefficient and increase the sectional drag coefficient. At this angle of attack, minimal change in the sectional lift coefficient is found when increasing from a Strouhal number of 0.2 to 0.5 at reduced frequencies of 0.5 and 5.903, the lowest and highest values of this parameter which are studied in this work. For this angle of attack the maximum change which occurs when increasing the Strouhal number from 0.2 to 0.5 is at a reduced frequency of 1.5. When the effect of angle of attack is studied, it is found that at a Strouhal number of 0.5 and reduced frequency of 1.5 the plunging flexible model demonstrates improved lift characteristics over the fixed flexible airfoil case. The greatest improvement occurs at an angle of attack of 2 degrees followed by 10 degrees and then 6 degrees. Finally the effect on the flow characteristics of airfoil flexibility is investigated by increasing the membrane pre-strain from a nominal value of 5 percent to that of 20 percent. This increase in pre-strain results in a reduced value of sectional lift coefficient as compared the 5 percent pre-strain case at the same fixed angle of attack, Strouhal number and reduced frequency.
Kinetic model‐based factor analysis of dynamic sequences for 82‐rubidium cardiac positron emission tomography
Authors: Klein R. , Beanlands R. S. , Wassenaar R. W. , Thorn S. L. , Lamoureux M. , DaSilva J. N. , Adler A. , deKemp R. A.
Published: July 2010

Purpose:

Factor analysis has been pursued as a means to decompose dynamic cardiac PET images into different tissue types based on their unique temporal signatures to improve quantification of physiological function. In this work, the authors present a novel kinetic model‐based (MB) method that includes physiological models of factor relationships within the decomposition process. The physiological accuracy of MB decomposed cardiac PET images is evaluated using simulated and experimental data. Precision of myocardial blood flow (MBF) measurement is also evaluated.

Methods:

A gamma‐variate model was used to describe the transport of in arterial blood from the right to left ventricle, and a one‐compartment model to describe the exchange between blood and myocardium. Simulations of canine and rat heart imaging were performed to evaluate parameter estimation errors. Arterial blood sampling in rats and blood pool imaging in dogs were used to evaluate factor and structure accuracy. Variable infusion duration studies in canine were used to evaluate MB structure and global MBF reproducibility. All results were compared to a previously published minimal structure overlap (MSO) method.

Results:

Canine heart simulations demonstrated that MB has lower root‐mean‐square error (RMSE) than MSO for both factor (0.2% vs 0.5%, MB vs MSO, respectively) and structure (3.0% vs 4.7%, ) estimations, as with rat heart simulations (factors: 0.2% vs 0.9%, and structures: 3.0% vs 6.7%, ). MB blood factors compared to arterial blood samples in rats had lower RMSE than MSO (1.6% vs 2.2%, ). There was no difference in the RMSE of blood structures compared to a blood pool image in dogs (8.5% vs 8.8%, ). Myocardial structures were more reproducible with MB than with MSO ( vs 6.2%, ), as were blood structures ( vs 5.6%, ). Finally, MBF values tended to be more reproducible with MB compared to MSO ( vs 18%, ). The execution time of MB was, on average, 2.4 times shorter than MSO due to fewer free parameters.

Conclusions:

Kinetic model‐based factor analysis can be used to provide physiologically accurate decomposition of dynamic PET images, and may improve the precision of MBF quantification.
Multilevel analysis of spatiotemporal association features for differentiation of tumor enhancement patterns in breast DCE‐MRI
Authors: Lee Sang Ho , Kim Jong Hyo , Cho Nariya , Park Jeong Seon , Yang Zepa , Jung Yun Sub , Moon Woo Kyung
Published: July 2010

Purpose:

Analyzing spatiotemporal enhancement patterns is an important task for the differential diagnosis of breast tumors in dynamic contrast‐enhanced MRI (DCE‐MRI), and yet remains challenging because of complexities in analyzing the time‐series of three‐dimensional image data. The authors propose a novel approach to breast MRI computer‐aided diagnosis (CAD) using a multilevel analysis of spatiotemporal association features for tumor enhancement patterns in DCE‐MRI.

Methods:

A database of 171 cases consisting of 111 malignant and 60 benign tumors was used. Time‐series contrast‐enhanced MR images were obtained from two different types of MR scanners and protocols. The images were first registered for motion compensation, and then tumor regions were segmented using a fuzzy c‐means clustering‐based method. Spatiotemporal associations of tumor enhancement patterns were analyzed at three levels: Mapping of pixelwise kinetic features within a tumor, extraction of spatial association features from kinetic feature maps, and extraction of kinetic association features at the spatial feature level. A total of 84 initial features were extracted. Predictable values of these features were evaluated with an area under the ROC curve, and were compared between the spatiotemporal association features and a subset of simple form features which do not reflect spatiotemporal association. Several optimized feature sets were identified among the spatiotemporal association feature group or among the simple feature group based on a feature ranking criterion using a support vector machine based recursive feature elimination algorithm. A least‐squares support vector machine (LS‐SVM) classifier was used for tumor differentiation and the performances were evaluated using a leave‐one‐out testing.

Results:

Predictable values of the extracted single features ranged in 0.52–0.75. By applying multilevel analysis strategy, the spatiotemporal association features became more informative in predicting tumor malignancy, which was shown by a statistical testing in ten spatiotemporal association features. By using a LS‐SVM classifier with the optimized second and third level feature set, the CAD scheme showed of 0.88 in classification of malignant and benign tumors. When this performance was compared to the same LS‐SVM classifier with simple form features which do not reflect spatiotemporal association, there was a statistically significant difference (0.88 vs 0.79, ), suggesting that the multilevel analysis strategy yields a significant performance improvement.

Conclusions:

The results suggest that the multilevel analysis strategy characterizes the complex tumor enhancement patterns effectively with the spatiotemporal association features, which in turn leads to an improved tumor differentiation. The proposed CAD scheme has a potential for improving diagnostic performance in breast DCE‐MRI.
Fundamental properties of the delivery of volumetric modulated arc therapy (VMAT) to static patient anatomy
Authors: Rangaraj D. , Oddiraju S. , Sun B. , Santanam L. , Yang D. , Goddu S. , Papiez L.
Published: July 2010

Purpose:

The primary goal of this article is to formulate volumetric modulated arc therapy (VMAT) delivery problem and study interdependence between several parameters (beam dose rate, gantry angular speed, and MLC leaf speed) in the delivery of VMAT treatment plan. The secondary aim is to provide delivery solution and prove optimality (minimal beam on time) of the solution. An additional goal of this study is to investigate alternative delivery approaches to VMAT (like constant beam dose rate and constant gantry angular speed delivery).

Method:

The problem of the VMAT delivery is formulated as a control problem with machine constraints. The relationships between parameters of arc therapy delivery are derived under the constraint of treatment plan invariance and limitations on delivery parameters. The nonuniqueness of arc therapy delivery solutions is revealed from these relations. The most efficient delivery of arc therapy is then formulated as optimal control problem and solved by geometrical methods. A computer program is developed to find numerical solutions for deliveries of specific VMAT plan.

Results:

Explicit examples of VMAT plan deliveries are computed and illustrated with graphical representations of the variability of delivery parameters. Comparison of delivery parameters with that of Varian's delivery are shown and discussed. Alternative delivery strategies such as constant gantry angular speed delivery and constant beam dose rate delivery are formulated and solutions are provided. The treatment times for all the delivery solutions are provided.

Conclusion:

The investigations derive and prove time optimal VMAT deliveries. The relationships between delivery parameters are determined. The optimal alternative delivery strategies are discussed.
Robust optimization based upon statistical theory
Authors: Sobotta B. , Söhn M. , Alber M.
Published: July 2010

Purpose:

Organ movement is still the biggest challenge in cancer treatment despite advances in online imaging. Due to the resulting geometric uncertainties, the delivered dose cannot be predicted precisely at treatment planning time. Consequently, all associated dose metrics (e.g., EUD and maxDose) are random variables with a patient‐specific probability distribution. The method that the authors propose makes these distributions the basis of the optimization and evaluation process.

Methods:

The authors start from a model of motion derived from patient‐specific imaging. On a multitude of geometry instances sampled from this model, a dose metric is evaluated. The resulting pdf of this dose metric is termed outcome distribution. The approach optimizes the shape of the outcome distribution based on its mean and variance. This is in contrast to the conventional optimization of a nominal value (e.g., PTV EUD) computed on a single geometry instance. The mean and variance allow for an estimate of the expected treatment outcome along with the residual uncertainty. Besides being applicable to the target, the proposed method also seamlessly includes the organs at risk (OARs).

Results:

The likelihood that a given value of a metric is reached in the treatment is predicted quantitatively. This information reveals potential hazards that may occur during the course of the treatment, thus helping the expert to find the right balance between the risk of insufficient normal tissue sparing and the risk of insufficient tumor control. By feeding this information to the optimizer, outcome distributions can be obtained where the probability of exceeding a given OAR maximum and that of falling short of a given target goal can be minimized simultaneously.

Conclusions:

The method is applicable to any source of residual motion uncertainty in treatment delivery. Any model that quantifies organ movement and deformation in terms of probability distributions can be used as basis for the algorithm. Thus, it can generate dose distributions that are robust against interfraction and intrafraction motion alike, effectively removing the need for indiscriminate safety margins.
Tissue typing using ultrasound RF time series: Experiments with animal tissue samples
Authors: Moradi Mehdi , Abolmaesumi Purang , Mousavi Parvin
Published: July 2010

Purpose:

This article provides experimental evidence to show that the time series of radiofrequency (RF) ultrasound data can be used for tissue typing. It also explores the tissue typing information in RF time series. Clinical and high‐frequency ultrasound are studied.

Methods:

Bovine liver, pig liver, bovine muscle, and chicken breast were used in the experiments as the animal tissue types. In the proposed approach, the authors record RF echo signals backscattered from tissue, while the imaging probe and the tissue are stationary. This sequence of recorded RF data generates a time series of RF echoes for each spatial sample of the RF signal. The authors use spectral and fractal features of ultrasound RF time series averaged over a region of interest, along with feedforward neural networks for tissue typing. The experiments are repeated at ultrasound frequency of 6.6 and also 55 MHz. The effects of increasing power and frame rate are studied.

Results:

The methodology yielded an average two‐class classification accuracy of 95.1% when ultrasound data were acquired at 6.6 MHz and 98.1% when data were collected with a high‐frequency probe operating at 55 MHz. In four‐class classification experiments, the recorded accuracies were 78.6% and 86.5% for low and high‐frequency ultrasound data, respectively. A set of 12 texture features extracted from the B‐mode image equivalents of the RF data yields an accuracy of only 77.5% in typing the analyzed tissues. An increase in acoustic power and the frame rate of ultrasound results in an improvement in classification results.

Conclusions:

The results of this study demonstrate that RF time series can be used for ultrasound‐based tissue typing. Further investigation of the underlying physical mechanisms is necessary.
Temporal resolution improvement in cardiac CT using PICCS (TRI‐PICCS): Performance studies
Authors: Tang Jie , Hsieh Jiang , Chen Guang‐Hong
Published: July 2010

Purpose:

The recently proposed prior image constrained compressed sensing (PICCS) method has been applied in cardiac MDCT to improve the temporal resolution by approximately a factor of 2, by using projection data acquired from half of the standard short‐scan angular range to reconstruct images with improved temporal resolution. The method was referred to as temporal resolution improvement using PICCS (TRI‐PICCS). The primary purpose of this article is to study (1) the relationship between the performance of the TRI‐PICCS algorithm and the angular range of projection data used in image reconstruction; (2) the relationship between the performance of the TRI‐PICCS algorithm and the motion orientations and motion patterns of moving objects; and (3) the relationship between the performance of the TRI‐PICCS algorithm and various heart rates.

Methods:

A hybrid phantom consisting of realistic cardiac anatomy and eight moving objects with known motion profiles to simulate coronary arteries was constructed by superimposing the analytical projection data of eight simulated moving vessels to thein vivo projection data from a cardiac MDCT scan. The motion profiles of the moving objects may independently change orientations, period, and amplitude. A prior image was reconstructed using a short‐scan filtered backprojection method from a gated short‐scan data set for each given motion profile. The TRI‐PICCS method was applied to improve temporal resolution for each configuration of given motion profiles of moving objects and given active angular range specified by the target temporal resolution. To quantitatively study the performance, figures of merit were introduced to quantify signal intensity deficit, image distortion, and residual motion artifacts, respectively.

Results:

The performance of the TRI‐PICCS method is the same when the projection data are taken from 100° to 120°. The performance of the TRI‐PICCS method is independent of location and motion orientations. The performance of the TRI‐PICCS method does not significantly degrade for heart rates up to 100 bpm with a gantry rotation speed of 350 ms per rotation.

Conclusions:

The TRI‐PICCS method can be used to systematically improve temporal resolution for MDCT cardiac imaging by a factor of 2–2.3 and the performance of the TRI‐PICCS method is insensitive to motion locations and motion orientations. The TRI‐PICCS method enables a single‐source MDCT scanner with 350 ms or faster gantry speed to scan patients with heart rates as high as 100 bpm.
A method to evaluate the dose increase in CT with iodinated contrast medium
Authors: Amato Ernesto , Lizio Domenico , Settineri Nicola , Di Pasquale Andrea , Salamone Ignazio , Pandolfo Ignazio
Published: July 2010

Purpose:

The objective of this study is to develop a method to calculate the relative dose increase when a computerized tomography scan (CT) is carried out after administration of iodinated contrast medium, with respect to the same CT scan in absence of contrast medium.

Methods:

A Monte Carlo simulation inGEANT4 of anthropomorphic neck and abdomen phantoms exposed to a simplified model of CT scanner was set up in order to calculate the increase of dose to thyroid, liver, spleen, kidneys, and pancreas as a function of the quantity of iodine accumulated; a series of experimental measurements of Hounsfield unit (HU) increment for known concentrations of iodinated contrast medium was carried out on a Siemens Sensation 16 CT scanner in order to obtain a relationship between the increment in HU and the relative dose increase in the organs studied. The authors applied such a method to calculate the average dose increase in three patients who underwent standard CT protocols consisting of one native scan in absence of contrast, followed by a contrast‐enhanced scan in venous phase.

Results:

The authors validated theirGEANT4 Monte Carlo simulation by comparing the resulting dose increases for iodine solutions in water with the ones presented in literature and with their experimental data obtained through a Roentgen therapy unit. The relative dose increases as a function of the iodine mass fraction accumulated and as a function of the Hounsfield unit increment between the contrast‐enhanced scan and the native scan are presented. The data shown for the three patients exhibit an average relative dose increase between 22% for liver and 74% for kidneys; also, spleen (34%), pancreas (28%), and thyroid (48%) show a remarkable average increase.

Conclusions:

The method developed allows a simple evaluation of the dose increase when iodinated contrast medium is used in CT scans, basing on the increment in Hounsfield units observed on the patients’ organs. Since many clinical protocols employ multiple scans at different circulatory phases after administration of contrast medium, such a method can be useful to evaluate the total dose to the patient, also in view of potential clinical protocol optimizations.
Influence of skull conductivity perturbations on EEG dipole source analysis
Authors: Chen Fangmin , Hallez Hans , Staelens Steven
Published: July 2010

Purpose:

Electroencephalogram (EEG) source analysis is a noninvasive technique used in the presurgical of epilepsy. In this study, the dipole location and orientation errors due to skull conductivity perturbations were investigated in two groups of three‐dimensional head models: A spherical head model and a realistic head model.

Methods:

In each group, the head model had a brain‐to‐skull conductivity ratio within the range of 10–40. Solving the forward problem in the head model with skull conductivity perturbations along with the inverse problem in the baseline head model with permitted the derivation of the dipole estimation errors.

Results:

Perturbations in the skull conductivity generated dipole location and orientation errors: The larger the perturbations, the larger the errors and the error ranges. The dipole orientation error due to skull conductivity perturbations was not great (maximal mean of) in this study, but the dipole location error was notable (maximal mean of ).

Conclusions:

Therefore, the influence of skull conductivity perturbations on EEG dipole source analysis cannot be neglected. This study suggests that it is necessary to measure the skull conductivity of the individual patients in order to achieve accurate EEG source analysis.
Dosimetric characteristics of a single use MOSFET dosimeter for in vivo dosimetry in proton therapy
Authors: Cheng Chee‐Wai , Wolanski Mark , Zhao Q. , Fanelli Leia , Gautam Archana , Pack Daniel , Das Indra J.
Published: July 2010

Purpose:

Entrance dose (or skin dose) is an important part of patient quality assurance in external beam radiation therapy. However, entrance dose verification in proton beam is not routinely performed. In this study, the OneDose single use MOSFET detector system forin vivo dosimetry measurement in proton therapy is investigated.

Methods:

Using a solid water phantom, several fundamental dosimetric characteristics of the OneDose system are studied with a proton beam: The reproducibility (consistency) of the dosimeter, the linearity with dose and dose rate, energy dependence, directional dependence, LET dependence, and fading (delay readout with time) is studied.

Results:

OneDose detectors show dose and dose rate linearity but exhibit pronounced energy dependence at depth and a large variation in dose response with LET. On the other hand, the detector response remain relatively constant (within 3%) at surface over a wide range of energies. There is also a slight angular dependence (about 2%) up to 60° angle of incidence. However, detector orientation such that incidence along the long axis of the detector should be avoided as the proton beam will have to traverse a large amount of the copper backing. Since mostin vivo dosimetry involves entrance dose measurement, the OneDose at surface appears to be well suited for such application. OneDose exhibits small intrabatch variation ( at one SD) indicating that it is only necessary to calibration a few detectors from each batch. The interbatch variation is generally within 3%.

Conclusions:

The small detector size and its relatively flexible design of OneDose allow dose measurement to be performed on a curved surface or in small cavities that is otherwise difficult with the conventional diode detectors. The slight drawback in its angular dependence can be easily handled by angular dependence table. However, since OneDose is a single use detector, the intrabatch consistency must be verified before the remaining detectors from the same batch could be used forin vivo dosimetry. It is advisable that the detectors from the same batch be taken for the same application to reduce the dosimetric uncertainty. For detectors from different batches, interbatch consistency should also be verified to obtain reliable results. OneDose provides an opportunity to measure in vivo dose with proton beam within acceptable clinical criterion of ±(5.0%–6.5%).
Technical note: Optimization for improved tube‐loading efficiency in the dual‐energy computed tomography coupled with balanced filter method
Authors: Saito Masatoshi
Published: July 2010

Purpose:

This article describes the spectral optimization of dual‐energy computed tomography using balanced filters (bf‐DECT) to reduce the tube loadings and dose by dedicating to the acquisition of electron density information, which is essential for treatment planning in radiotherapy.

Methods:

For the spectral optimization of bf‐DECT, the author calculated the beam‐hardening error and air kerma required to achieve a desired noise level in an electron density image of a 50‐cm‐diameter cylindrical water phantom. The calculation enables the selection of beam parameters such as tube voltage, balanced filter material, and its thickness.

Results:

The optimal combination of tube voltages was 80 kV/140 kV in conjunction with Tb/Hf and Bi/Mo filter pairs; this combination agrees with that obtained in a previous study [M. Saito, “Spectral optimization for measuring electron density by the dual‐energy computed tomography coupled with balanced filter method,” Med. Phys. 36, 3631–3642 (2009)], although the thicknesses of the filters that yielded a minimum tube output were slightly different from those obtained in the previous study. The resultant tube loading of a low‐energy scan of the present bf‐DECT significantly decreased from 57.5 to 4.5 times that of a high‐energy scan for conventional DECT. Furthermore, the air kerma of bf‐DECT could be reduced to less than that of conventional DECT, while obtaining the same figure of merit for the measurement of electron density and effective atomic number.

Conclusions:

The tube‐loading and dose efficiencies of bf‐DECT were considerably improved by sacrificing the quality of the noise level in the images of effective atomic number.
Planar Cell Polarity Acts Through Septins to Control Collective Cell Movement and Ciliogenesis
Authors: Kim Su Kyoung , Shindo Asako , Park Tae Joo , Oh Edwin C. , Ghosh Srimoyee , Gray Ryan S. , Lewis Richard A. , Johnson Colin A. , Attie-Bittach Tania , Katsanis Nicholas , Wallingford John B.
Published: July 2010

Form and Function

The Planar Cell Polarity (PCP) signaling pathway governs cell movements that drive axis elongation and neural tube closure in vertebrate embryos, and certain vertebrate PCP proteins have also been implicated in ciliogenesis. Likewise, the septin cytoskeleton controls diverse cell behaviors, such as cytokinesis and cell migration, but little is known about how septin functions are regulated in vivo.

Kim
et al.

(p.
1337
, published online 29 July; see the Perspective by

Barral

) found that control of septins by the PCP effector protein, Fritz, was a crucial control point for morphogenesis and ciliogenesis. During neural tube closure, Fritz-mediated septin localization maintained cell shape but not cell polarity. In ciliated epithelial cells, Fritz was required for assembly of the septin rings at the base of cilia, which are needed for normal ciliogenesis and signaling.
Elevated D-dimers are also a marker of underlying malignancy and increased mortality in the absence of venous thromboembolism
Authors: Knowlson L , Bacchu S , Paneesha S , McManus A , Randall K , Rose P
Published: July 2010

Background

D-dimers are used in conjunction with clinical probability scores in the assessment of venous thromboembolism (VTE), and they are elevated in other conditions, including malignancy, infection and arrhythmias. High levels of D-dimers in VTE are associated with adverse outcomes, including increased mortality. Their significance in patients without VTE has not previously been established.

Aims

To establish the clinical significance of elevated D-dimer levels in patients without VTE.

Methods

This prospective study included 2263 patient episodes of suspected deep vein thrombosis, which were excluded radiologically. Patients were followed up for survival and adverse events for a median of 22 months.

Results

D-dimer levels greater than 4000 ng FEU/ml (4.9% of patients), and greater than 8000 ng FEU/ml (1.8%) were associated with a reduced overall survival. D-dimer levels greater than 8000 ng FEU/ml and age over 60 years were independent poor prognostic factors for overall survival (p<0.001.). D-dimer levels greater than 8000 ng FEU/ml were associated with an increased incidence of malignancy (p=0.003).

Conclusions

This study provides evidence of very high D-dimer levels in patients with cancer who do not have VTE. This suggests that elevated D-dimer levels in patients with VTE and malignancy are not solely due to presence of thrombus. High D-dimer levels in malignancy are likely to reflect the biology of the underlying tumour, with higher levels observed in breast, prostate and bowel cancers.
Comparative validation of the SP6 antibody to Ki67 in breast cancer
Authors: Zabaglo Lila , Salter Janine , Anderson Helen , Quinn Emma , Hills Margaret , Detre Simone , A'Hern Roger , Dowsett Mitch
Published: July 2010

Aim

To compare SP6 and MIB1 antibodies for Ki67 staining in breast cancer.

Background

Immunohistochemical detection of Ki67 has been widely used to assess the proliferative fraction in breast cancer. Ki67 is used prognostically and is the primary end-point for some presurgical trials. MIB1 has been the preferred antibody, but SP6 has become available, with apparently improved performance. The importance of Ki67 led us to systematically compare SP6 with MIB1.

Methods

Two sets of tissue microarrays were used. These were constructed from formalin-fixed paraffin-embedded breast cancers: (i) 177 cancers with data on response to an aromatase inhibitor for advanced disease (cohort 1); (ii) 200 mainly oestrogen-receptor-positive cancers without response data (cohort 2). Twenty-eight pairs of core-cut biopsies taken before and after aromatase inhibitor treatment were also assessed (cohort 3). Stained sections were examined either visually or by using an image analysis system (Ariol).

Results

There was a strong correlation between the two antibodies in all cohorts of samples scored visually (cohort 1: n=161, r=0.93, p<0.0001; cohort 2: n=194, r=0.84, p<0.0001; cohort 3: n=54, r=0.89, p<0.0001). Correlation between visual and Ariol scores was markedly better with the SP6 antibody (r=0.71 and r=0.88 for MIB1 and SP6, respectively). Ki67 related similarly with time-to-treatment failure with the two antibodies (cohort 1). Changes in Ki67 values with the two antibodies after 2 weeks of aromatase inhibitor treatment also correlated strongly.

Conclusions

SP6 and MIB1 provide highly comparable measures of Ki67 that predict progression of advanced disease similarly. SP6 is substantially better suited than MIB1 to image analysis.
Lymphoma occurring in patients with cutaneous melanoma
Authors: Verwer Nick , Murali Rajmohan , Winstanley Julie , Cooper Wendy A , Stretch Jonathan R , Thompson John F , Scolyer Richard A
Published: July 2010

Background

Non-melanoma malignancies are not uncommon in patients with melanoma. This study sought to determine the incidence of lymphoma in patients with melanoma compared with the general population, and to characterise their clinical and pathological features.

Methods

Patients diagnosed with melanoma and lymphoma between January 1992 and December 2007 were identified from the databases of Melanoma Institute Australia (MIA) and the Department of Tissue Pathology and Diagnostic Oncology, Royal Prince Alfred Hospital (RPAH). The clinical histories of the patients in the MIA database and pathology reports in the RPAH archives were reviewed. The incidence risk for melanoma and non-Hodgkin lymphoma was obtained from Australian Cancer Incidence and Mortality registry data.

Results

Of 18 226 patients with melanoma, 55 (0.3%) had lymphoma. Lymphoma was diagnosed subsequent to melanoma in 23 (41.8%) patients, prior to melanoma in 7 (12.7%) patients, and concurrently with melanoma in 25 (45.5%) patients. 53 (96.4%) patients developed non-Hodgkin lymphoma (NHL), the most common subtypes being chronic lymphocytic leukaemia/small lymphocytic lymphoma (49.1%), follicular lymphoma (23.6%) and diffuse large B-cell lymphoma (16.4%). Two (3.6%) patients developed Hodgkin lymphoma. Melanoma patients had a significantly higher risk of developing NHL than the general population (standardised incidence rate 3.5).

Conclusions

A small but significant proportion of patients with melanoma develop lymphoma, either synchronously or metachronously. Lymph node specimens from melanoma patients might harbour lymphoma, and might represent the first recognised site of disease. A high index of suspicion for lymphoma when evaluating lymph nodes from patients with melanoma will ensure prompt diagnosis and appropriate management.
Without ‘informed consent’? Ethics and ancient mummy research
Authors: Kaufmann I M , Rühli F J
Published: July 2010

Ethical issues are of foremost importance in modern bio-medical science. Ethical guidelines and socio-cultural public awareness exist for modern samples, whereas for ancient mummy studies both are de facto lacking. This is particularly striking considering the fact that examinations are done without informed consent or that the investigations are invasive due to technological aspects and that it affects personality traits. The aim of this study is to show the pro and contra arguments of ancient mummy research from an ethical point of view with a particular focus on the various stakeholders involved in this research. Relevant stakeholders in addition to the examined individual are, for example, a particular researcher, and the science community in general, likely descendents of the mummy or any future generation. Our broad discussion of the moral dilemma of mummy research should help to extract relevant decision-making criteria for any such study in future. We specifically do not make any recommendations about how to rate these decision-factors, since this is highly dependent on temporal and cultural affiliations of the involved researcher. The sustainability of modern mummy research is dependent on ethical orientation, which can only be given and eventually settled in an interdisciplinary approach such as the one we attempt to present here.