bluuebunny/crossref_metadata_2025_split huggingface dataset:
On the potential of ultrasound elastography for pressure ulcer early detection
Authors: Deprez Jean‐François , Brusseau Elisabeth , Fromageau Jérémie , Cloutier Guy , Basset Olivier 
Published: April 2011

Purpose:Pressure ulcers are areas of soft tissue breakdown induced by a sustained mechanical stress that damages the skin and underlying tissues. They represent a considerable burden to the society in terms of health care and cost. Yet, techniques for prevention and detection of pressure ulcers still remain very limited. In this article, the authors investigated the potential of ultrasound elastography for pressure ulcer early detection. Elastography is an imaging technique providing local information on biological tissue mechanical properties. It is relevant for pressure ulcer detection as this pathology is associated with a gradual stiffening of damaged tissues, beginning in the deeper tissues and progressing toward the skin surface.Methods:A 2D ultrasound elastography method was proposed and its ability in terms of pressure ulcer detection was validated through numerical simulations and physical acquisitions on pressure ulcer mimicking phantoms.In vivo experiments on a rat model are also reported. A maintained pressure was applied on the animal thigh, with a view to generate a pressure ulcer, and ultrasound data were acquired and processed before and after application of this pressure.Results:Numerical simulations demonstrated that a pressure ulcer can theoretically be detected at a very early stage with ultrasound elastography. Even when the ulcer region was characterized by a low stiffening (ratio of 1.8 relative to normal tissues), the corresponding elastogram clearly underlined the pathological area. This observation was confirmed by the results obtained on a physical phantom mimicking a pressure ulcer at an early stage. Computed elastograms showed strain differences between areas mimicking healthy and pathological tissues. Results corresponding toin vivo experiments revealed a difference in the way tissues behaved before and after the pressure was applied on the animal thigh, which strongly suggests the presence of a pathological area.Conclusions:Experiments demonstrated that ultrasound elastography is a promising technique for pressure ulcer detection, especially at an early stage of the pathology, when the disease is still visually undetectable. In the absence of any gold standard method, this is also a first step toward the development of a quantitative technique.
A spatially encoded dose difference maximal intensity projection map for patient dose evaluation: A new first line patient quality assurance tool
Authors: Hu Weigang , Graff Pierre , Boettger Thomas , Pouliot Jean 
Published: April 2011

Purpose:To develop a spatially encoded dose difference maximal intensity projection (DD‐MIP) as an online patient dose evaluation tool for visualizing the dose differences between the planning dose and dose on the treatment day.Methods:Megavoltage cone‐beam CT (MVCBCT) images acquired on the treatment day are used for generating the dose difference index. Each index is represented by different colors for underdose, acceptable, and overdose regions. A maximal intensity projection (MIP) algorithm is developed to compress all the information of an arbitrary 3D dose difference index into a 2D DD‐MIP image. In such an algorithm, a distance transformation is generated based on the planning CT. Then, two new volumes representing the overdose and underdose regions of the dose difference index are encoded with the distance transformation map. The distance‐encoded indices of each volume are normalized using the skin distance obtained on the planning CT. After that, two MIPs are generated based on the underdose and overdose volumes with green‐to‐blue and green‐to‐red lookup tables, respectively. Finally, the two MIPs are merged with an appropriate transparency level and rendered in planning CT images.Results:The spatially encoded DD‐MIP was implemented in a dose‐guided radiotherapy prototype and tested on 33 MVCBCT images from six patients. The user can easily establish the threshold for the overdose and underdose. A 3% difference between the treatment and planning dose was used as the threshold in the study; hence, the DD‐MIP shows red or blue color for the dose difference or , respectively. With such a method, the overdose and underdose regions can be visualized and distinguished without being overshadowed by superficial dose differences.Conclusions:A DD‐MIP algorithm was developed that compresses information from 3D into a single or two orthogonal projections while hinting the user whether the dose difference is on the skin surface or deeper.
Dose response of alanine detectors irradiated with carbon ion beams
Authors: Herrmann Rochus , Jäkel Oliver , Palmans Hugo , Sharpe Peter , Bassler Niels 
Published: April 2011

Purpose:The dose response of the alanine detector shows a dependence on particle energy and type when irradiated with ion beams. The purpose of this study is to investigate the response behavior of the alanine detector in clinical carbon ion beams and compare the results to model predictions.Methods:Alanine detectors have been irradiated with carbon ions with an energy range of 89–400 MeV/u. The relative effectiveness of alanine has been measured in this regime. Pristine and spread out Bragg peak depth‐dose curves have been measured with alanine dosimeters. The track structure based alanine response model developed by Hansen and Olsen has been implemented in the Monte Carlo codeFLUKA and calculations were compared to experimental results.Results:Calculations of the relative effectiveness deviate less than 5% from the measured values for monoenergetic beams. Measured depth‐dose curves deviate from predictions in the peak region, most pronounced at the distal edge of the peak.Conclusions:The used model and its implementation show a good overall agreement for quasimonoenergetic measurements. Deviations in depth‐dose measurements are mainly attributed to uncertainties of the detector geometry implemented in the Monte Carlo simulations.
Elastic registration of multimodal prostate MRI and histology via multiattribute combined mutual information
Authors: Chappelow Jonathan , Bloch B. Nicolas , Rofsky Neil , Genega Elizabeth , Lenkinski Robert , DeWolf William , Madabhushi Anant 
Published: April 2011

Purpose:By performing registration of preoperative multiprotocolin vivo magnetic resonance (MR) images of the prostate with corresponding whole‐mount histology (WMH) sections from postoperative radical prostatectomy specimens, an accurate estimate of the spatial extent of prostate cancer (CaP) on in vivo MR imaging (MRI) can be retrospectively established. This could allow for definition of quantitative image‐based disease signatures and lead to development of classifiers for disease detection on multiprotocol in vivo MRI. Automated registration of MR and WMH images of the prostate is complicated by dissimilar image intensities, acquisition artifacts, and nonlinear shape differences.Methods:The authors present a method for automated elastic registration of multiprotocolin vivo MRI and WMH sections of the prostate. The method, multiattribute combined mutual information (MACMI), leverages all available multiprotocol image data to drive image registration using a multivariate formulation of mutual information.Results:Elastic registration using the multivariate MI formulation is demonstrated for 150 corresponding sets of prostate images from 25 patient studies with T2‐weighted and dynamic‐contrast enhanced MRI and 85 image sets from 15 studies with an additional functional apparent diffusion coefficient MRI series. Qualitative results of MACMI evaluation via visual inspection suggest that an accurate delineation of CaP extent on MRI is obtained. Results of quantitative evaluation on 150 clinical and 20 synthetic image sets indicate improved registration accuracy using MACMI compared to conventional pairwise mutual information‐based approaches.Conclusions:The authors' approach to the registration ofin vivo multiprotocol MRI and ex vivo WMH of the prostate using MACMI is unique, in that (1) information from all available image protocols is utilized to drive the registration with histology, (2) no additional, intermediate ex vivo radiology or gross histology images need be obtained in addition to the routinely acquired in vivo MRI series, and (3) no corresponding anatomical landmarks are required to be identified manually or automatically on the images.
Deconvolution by finite‐size‐source effects of x‐ray phase‐contrast images
Authors: De Caro Liberato , Scattarella Francesco , Tangaro Sabina , Pelliccia Daniele , Giannini Cinzia , Bottigli Ubaldo , Bellotti Roberto 
Published: April 2011

Purpose:In the hard x‐ray region, the cross sections for the phase shift of low‐ elements are about 1000 times larger than the absorption ones. As a consequence, phase contrast is detectable even when absorption contrast is minimal or absent. Therefore, phase‐contrast imaging could become a valid alternative to absorption contrast without delivering high dose to tissue/human body parts.Methods:To enhance the quality of phase‐contrast images without increasing the dose, a possible approach could be the partial deconvolution of the finite source size effects by experimental phase‐contrast images. The deconvolution procedure, the authors propose, employs the acquisition of two images on a suitable well‐known test sample, one in contact and the other in phase‐contrast conditions. Both acquired images are used along with a simulated phase‐contrast image (obtained from the test sample in ideal conditions of pointlike source illumination) to correctly retrieve the experimental source distribution function. This information allows a generic experimental phase‐contrast image, acquired in the same conditions, to be partially deconvolved by finite source size effects.Results:The performed experimental tests indicate that deconvolved images are equivalent to those which would be obtained with a source 40% smaller than the actual size. In turn, this finding is equivalent to an increase of the “effective” lateral spatial coherence length. The corresponding quality improvement of the phase‐contrast imaging is directly deducible by the presence of many Fresnel fringes, much better visible with respect to the original experimental phase‐contrast images.Conclusions:The use of a test standard sample, always possible in every experimental setup, to partially deconvolve the finite‐size‐source blurring effects shows that higher quality phase‐contrast images could be readily available, making easier diagnoses and tissue/sample analyses. The method could give, in the future, the possibility to further lower the delivered dose to patients, organs, and tissues when compact room‐sized and brilliant microfocus x‐ray sources will be available for clinical applications in hospitals.
An opposite view data replacement approach for reducing artifacts due to metallic dental objects
Authors: Yazdi Mehran , Lari Meghdad Asadi , Bernier Gaston , Beaulieu Luc 
Published: April 2011

Purpose:To present a conceptually new method for metal artifact reduction (MAR) that can be used on patients with multiple objects within the scan plane that are also of small sized along the longitudinal (scanning) direction, such as dental fillings.Methods:The proposed algorithm, named opposite view replacement, achieves MAR by first detecting the projection data affected by metal objects and then replacing the affected projections by the corresponding opposite view projections, which are not affected by metal objects. The authors also applied a fading process to avoid producing any discontinuities in the boundary of the affected projection areas in the sinogram. A skull phantom with and without a variety of dental metal inserts was made to extract the performance metric of the algorithm. A head and neck case, typical of IMRT planning, was also tested.Results:The reconstructed CT images based on this new replacement scheme show a significant improvement in image quality for patients with metallic dental objects compared to the MAR algorithms based on the interpolation scheme. For the phantom, the authors showed that the artifact reduction algorithm can efficiently recover the CT numbers in the area next to the metallic objects.Conclusions:The authors presented a new and efficient method for artifact reduction due to multiple small metallic objects. The obtained results from phantoms and clinical cases fully validate the proposed approach.
Performance of topological texture features to classify fibrotic interstitial lung disease patterns
Authors: Huber Markus B. , Nagarajan Mahesh B. , Leinsinger Gerda , Eibel Roger , Ray Lawrence A. , Wismüller Axel 
Published: April 2011

Purpose:Topological texture features were compared in their ability to classify “honeycombing,” a morphological pattern that is considered indicative for the presence of fibrotic interstitial lung disease in high‐resolution computed tomography (HRCT) images.Methods:For 14 patients with known occurrence of honeycombing, a stack of 70 axial, lung kernel reconstructed images was acquired from HRCT chest exams. A set of 964 regions of interest of both healthy and pathological (356) lung tissue was identified by an experienced radiologist. Texture features were extracted using statistical features (Stat), six properties calculated from gray‐level co‐occurrence matrices (GLCMs), Minkowski dimensions (MDs), and three Minkowski functionals (MFs) (e.g., MF.Euler). A naïve Bayes (NB) and ‐nearest‐neighbor (‐NN) classifier, a multilayer radial basis functions network (RBFN), and a support vector machine with a radial basis function (SVMrbf) kernel were optimized in a tenfold cross‐validation for each texture vector, and the classification accuracy was calculated on independent test sets as a quantitative measure of automated tissue characterization. A Wilcoxon signed‐rank test was used to compare two accuracy distributions and the significance thresholds were adjusted for multiple comparisons by the Bonferroni correction.Results:The best classification results were obtained by the MF features, which performed significantly better than all the standard Stat, GLCM, and MD features for both classifiers. The highest accuracies were found for MF.Euler (93.6%, 94.9%, 94.2%, and 95.0% for NB, ‐NN, RBFN, and SVMrbf, respectively). The best groups of standard texture features were a Stat and GLCM (“homogeneity”) feature set (up to 91.8%).Conclusions:The results indicate that advanced topological texture features derived from MFs can provide superior classification performance in computer‐assisted diagnosis of fibrotic interstitial lung disease patterns when compared to standard texture analysis methods.
Crescent artifacts in cone‐beam CT
Authors: Giles William , Bowsher James , Li Hao , Yin Fang‐Fang 
Published: April 2011

Purpose:In image‐guided radiation therapy, cone‐beam CT has been adopted for three‐dimensional target localization in the treatment room. In many of these cone‐beam CT images, dark and light crescent artifacts can be seen. This study investigates potential causes of this artifact and a technique for mitigating the crescents.Methods:Three deviations from an ideal geometry were simulated to assess their ability to cause crescent artifacts: Bowtie filter sag, x‐ray tube sag, and x‐ray tube rotation. The magnitudes of these deviations were estimated by matching shifts in simulated projections to those observed with clinical systems. To correct the artifacts, angle‐dependent blank projections were acquired and incorporated into image reconstruction. The degree of artifact reduction was evaluated with varying numbers (1–380) of blank projections. Scanner‐acquired phantom and patient studies were conducted to demonstrate the effectiveness of the proposed correction method.Results:All three investigated causes of the crescent artifact introduced similar mismodeling of the acquired projections and similar crescent artifacts. The deviations required for these artifacts were in the range of 0.5–5 mm or 0.1°. RMS error is reduced from to for 1–380 blank projections over a 200° scan angle. In the patient and phantom studies, reconstructions that utilized 380 blank projections largely mitigated the crescent artifacts.Conclusions:Small deviations from an ideal geometry can result in crescent artifacts due to steep gradients in the bowtie filter. Angle‐dependent blank projections can largely alleviate the artifacts.
Objective method to report planner‐independent skin/rib maximal dose in balloon‐based high dose rate (HDR) brachytherapy for breast cancer
Authors: Kim Yongbok , Trombetta Mark G. 
Published: April 2011

Purpose:An objective method was proposed and compared with a manual selection method to determine planner‐independent skin and rib maximal dose in balloon‐based high dose rate (HDR) brachytherapy planning.Methods:The maximal dose to skin and rib was objectively extracted from a dose volume histogram (DVH) of skin and rib volumes. A virtual skin volume was produced by expanding the skin surface in three dimensions (3D) external to the breast with a certain thickness in the planning computed tomography (CT) images. Therefore, the maximal dose to this volume occurs on the skin surface the same with a conventional manual selection method. The rib was also delineated in the planning CT images and its maximal dose was extracted from its DVH. The absolute and relative maximal skin and rib dose differences between the manual selection method and the objective method were measured for 50 balloon‐based HDR (25 MammoSite® and 25 Contura®) patients.Results:The deviation of maximal dose difference was of the prescribed dose (PD). No statistical difference was observed between MammoSite® and Contura® patients for both Abdiff and Rediff[%] values. However, a statistically significant difference ( value ) was observed in maximal rib dose difference compared with maximal skin dose difference for both Abdiff ( vs ) and Rediff[%] ( vs ). In general, rib has a more irregular contour and it is more proximally located to the balloon for 50 HDR patients. Due to the inverse square law factor, more dose difference was observed in higher dose range compared with lower dose range : vs with value of 0.0049. However, the Rediff[%] analysis eliminated the inverse square factor and there was no statistically significant difference between high and low dose ranges.Conclusions:The objective method using volumetric information of skin and rib can determine the planner‐independent maximal dose compared with the manual selection method. However, the difference was of PD, on average, if appropriate attention is paid to selecting a manual dose point in 3D planning CT images.
A robust link-translating proxy server mirroring the whole web
Authors: Mao Ziqing , Herley Cormac 
Published: April 2011

Link-translating proxies are widely used for anonymous browsing, policy circumvention and WebVPN functions. These are implemented by encoding the destination URL in the path of the URL submitted to the proxy and rewriting all links before returning the document to the client. Commonly these are based on the CGIProxy implementation or a variant. While popular, broken links and very slow load times are common. This is so, since the use of scripting languages makes finding and translating links (the essential task of such a proxy) very difficult. Some web-sites become entirely non-functional when loaded.
This paper proposes a novel architecture for a link-translating proxy. By using a sub-domain mapping technique we entirely eliminate the need to translate (or even find") relative links in content. This makes the link rewriting algorithm very simple and robust. We have implemented, deployed, and tested the proxy extensively. We conducted a comparison between the our proxy and CGIProxy. Both the theoretical analysis and experimental evaluation show that our proxy is significantly better in terms of robustness, performance, and security. We call our system Address Bar Only Proxy or ABOProxy. We suggest several novel applications.
Should we worry about memory loss?
Authors: Perks O. , Hammond S. D. , Pennycook S. J. , Jarvis S. A. 
Published: April 2011

In recent years the High Performance Computing (HPC) industry has benefited from the development of higher density multi-core processors. With recent chips capable of executing up to 32 tasks in parallel, this rate of growth also shows no sign of slowing. Alongside the development of denser micro-processors has been the considerably more modest rate of improvement in random access memory (RAM). The effect has been that the available memory-per-core has reduced and current projections suggest that this is set to reduce still further.
In this paper we present three studies into the use and measurement of memory in parallel applications; our aim is to capture, understand and, if possible, reduce the memory-per-core needed by complete multi-component applications. First, we present benchmarked memory usage and runtimes of a six scientific benchmarks, which represent algorithms that are common to a host of production-grade codes. Memory usage of each benchmark is measured and reported for a variety of compiler toolkits, and we show >30% variation in memory high-water mark requirements between compilers. Second, we utilise this benchmark data combined with runtime data, to simulate via the Maui scheduler simulator, the effect on a multi-science workow if memory-per-core is reduced from 1.5GB-per-core to only 256MB. Finally, we present initial results from a new memory profiling tool currently in development at the University of Warwick. This tool is applied to a finite-element benchmark and is able to map high-water-mark memory allocations to individual program functions. This demonstrates a lightweight and accurate method of identifying potential memory problems, a technique we expect to become commonplace as memory capacities decrease.