bluuebunny/crossref_metadata_2025_split huggingface dataset:
Number of partitions (gates) needed to obtain motion‐free images in a respiratory gated 4D‐PET/CT study as a function of the lesion size and motion displacement
Authors: Bettinardi V. , Rapisarda E. , Gilardi M. C. 
Published: November 2009

Purpose:In this study we evaluate the number of data partitions (gates) needed to sort 4D‐PET and 4D‐CT data to obtain motion‐free images as a function of lesion size and motion displacement.Methods:Plexiglas spheres of various diameters (8, 10, 15, 20, and 25 mm) were filled with a radioactive solution of water and. A PET/CT study was acquired for each sphere in a rest condition to reconstruct a motion‐free image as a reference in terms of radioactivity concentration and spatial distribution. Each sphere was then moved sinusoidally in the superior‐inferior direction over different motion displacements (5, 10, 15, 20, and 25 mm) with a periodic motion of 4 s. During motion a 4D‐CT scan followed by a 4D‐PET scan were acquired. Each set of 4D‐CT and 4D‐PET data was retrospectively sorted to generate one, two, four, six, eight, ten, and 12 partitions (gates) over the whole cycle of motion. 4D‐PET gates were reconstructed by using the corresponding 4D‐CT gates for attenuation correction, while PET data acquired, with the sphere in the rest condition were corrected for attenuation by using the corresponding CT image set. For each series of PET images, data analysis was performed by measuring (1) the maximum value of the radioactivity concentration in a VOI encompassing the radioactivity distribution over the volume of motion and (2) the axial‐profile of the radioactivity distribution (Ax‐p).Results:The results show that radioactivity concentration is strongly underestimated due to motion in most conditions considered in this study. In particular, the underestimation of for the smallest sphere varied from −10.6% to −66.3% with motion displacements ranging from 5 to 25 mm. For the largest sphere, errors ranged from −1.4% to −26.7%. The 4D‐PET/CT methodology allows motion‐free or nearly motion‐free images to be obtained. It also permits both radioactivity concentration and Ax‐p to be recovered with residual differences with respect to the rest condition, depending on the number of partitions used to process the data. Within the limitation of the regular sinusoidal motion, used to simulate a general breathing condition, a scheme describing the number of partitions needed to obtain nearly motion‐free images with Ax‐p differences of around 10% with respect to the rest data is presented as a function of the lesion size and motion displacement. Such a scheme is proposed to guide the setup of a 4D‐PET/CT acquisition and processing protocol for clinical applications.Conclusions:By using the 4D‐PET/CT acquisition technique, it is possible to compensate for the degradation effect of lesion motion on the reconstructed PET images.
Temporal subtraction in chest radiography: Mutual information as a measure of image quality
Authors: Armato Samuel G. , Sensakovic William F. , Passen Samantha J. , Engelmann Roger , MacMahon Heber 
Published: November 2009

Purpose:Temporal subtraction is used to detect the interval change in chest radiographs and aid radiologists in patient diagnosis. This method registers two temporally different images by geometrically warping the lung region, or “lung mask,” of a previous radiographic image to align with the current image. The gray levels of every pixel in the current image are subtracted from the gray levels of the corresponding pixels in the warped previous image to form a temporal subtraction image. While temporal subtraction images effectively enhance areas of pathologic change, misregistration of the images can mislead radiologists by obscuring the interval change or by creating artifacts that mimic change. The purpose of this study was to investigate the utility of mutual information computed between two registered radiographic chest images as a metric for distinguishing between clinically acceptable and clinically unacceptable temporal subtraction images.Methods:A radiologist subjectively rated the image quality of 138 temporal subtraction images using a 1 (poor) to 5 (excellent) scale. To objectively assess the registration accuracy depicted in the temporal subtraction images, which is the main factor that affects the quality of these images, mutual information was computed on the two constituent registered images prior to their subtraction to generate a temporal subtraction image. Mutual information measures the joint entropy of the current image and the warped previous image, yielding a higher value when the gray levels of spatially matched pixels in each image are consistent. Mutual information values were correlated with the radiologist's subjective ratings. To improve this correlation, mutual information was computed from a spatially limited lung mask, which was cropped from the bottom by 10%–60%. Additionally, the number of gray‐level values used in the joint entropy histogram was varied. The ability of mutual information to predict the clinical acceptability of a temporal subtraction image was evaluated through receiver operating characteristic (ROC) analysis.Results:The mean correlation coefficient obtained between mutual information computed on constituent images and the subjective rating of temporal subtraction image quality was 0.785. ROC analysis yielded an average value of 0.852 for the ability of mutual information to distinguish between temporal subtraction images of clinically acceptable and clinically unacceptable quality.Conclusions:The results of this study establish a relationship between mutual information and temporal subtraction registration accuracy and demonstrate the ability of mutual information to objectively indicate the presence of misregistration artifacts.
High‐DQE EPIDs based on thick, segmented BGO and CsI:Tl scintillators: Performance evaluation at extremely low dose
Authors: Wang Yi , Antonuk Larry E. , Zhao Qihua , El‐Mohri Youcef , Perna Louis 
Published: November 2009

Purpose:Electronic portal imaging devices (EPIDs) based on active matrix, flat‐panel imagers (AMFPIs) have become the gold standard for portal imaging and are currently being investigated for megavoltage cone‐beam computed tomography (CBCT) and cone‐beam digital tomosynthesis (CBDT). However, the practical realization of such volumetric imaging techniques is constrained by the relatively low detective quantum efficiency (DQE) of AMFPI‐based EPIDs at radiotherapy energies, at 6 MV. In order to significantly improve DQE, the authors are investigating thick, segmented scintillators, consisting of 2D matrices of scintillating crystals separated by septal walls.Methods:A newly constructed segmented BGO scintillator (11.3 mm thick) and three segmented CsI:Tl scintillators (11.4, 25.6, and 40.0 mm thick) were evaluated using a 6 MV photon beam. X‐ray sensitivity, modulation transfer function, noise power spectrum, DQE, and phantom images were obtained using prototype EPIDs based on the four scintillators.Results:The BGO and CsI:Tl prototypes were found to exhibit improvement in DQE ranging from to 25 times that of a conventional AMFPI‐based EPID at zero spatial frequency. All four prototype EPIDs provide significantly improved contrast resolution at extremely low doses, extending down to a single beam pulse. In particular, the BGO prototype provides contrast resolution comparable to that of the conventional EPID, but at 20 times less dose, with spatial resolution sufficient for identifying the boundaries of low‐contrast objects. For this prototype, however, the BGO scintillator exhibited an undesirable radiation‐induced variation in x‐ray sensitivity.Conclusions:Prototype EPIDs based on thick, segmented BGO and CsI:Tl scintillators provide significantly improved portal imaging performance at extremely low dose (i.e., down to 1 beam pulse corresponding to), creating the possibility of soft‐tissue visualization using MV CBCT and CBDT at clinically practical dose.
Simulation of large x‐ray fields using independently measured source and geometry details
Authors: Sawkey D. , Faddegon B. A. 
Published: November 2009

Purpose:Obtain an accurate simulation of the dose from the 6 and 18 MV x‐ray beams from a Siemens Oncor linear accelerator by comparing simulation to measurement. Constrain the simulation by independently determining parameters of the treatment head and incident beam, in particular, the energy and spot size.Methods:Measurements were done with the treatment head in three different configurations: (1) The clinical configuration, (2) the flattening filter removed, and (3) the target and flattening filter removed. Parameters of the incident beam and treatment head were measured directly. Incident beam energy and spectral width were determined from the percent‐depth ionization of the raw beam (as described previously), spot size was determined using a spot camera, and the densities of the flattening filters were determined by weighing them. Simulations were done with EGSnrc/BEAMnrc code. An asymmetric simulation was used, including offsets of the spot, primary collimator, and flattening filter from the collimator rotation axis.Results:Agreement between measurement and simulation was obtained to the least restrictive of 1% or 1 mm at 6 MV, both with and without the flattening filter in place, except for the buildup region. At 18 MV, the agreement was 1.5%/1.5 mm with the flattening filter in place and 1%/1 mm with it removed, except for in the buildup region. In the buildup region, the discrepancy was 2%/2 mm at 18 MV and 1.5%/1.5 mm at 6 MV with the flattening filter either removed or in place. The methodology for measuring the source and geometry parameters for the treatment head simulation is described. Except to determine the density of the flattening filter, no physical modification of the treatment head is necessary to obtain those parameters. In particular, the flattening filter does not need to be removed as was done in this work.Conclusions:Good agreement between measured and simulated dose distributions was obtained, even in the buildup region. The simulation was tightly constrained by independent measurements of parameters of the incident beam and treatment head. The method of obtaining the input parameters is described, and can be carried out on a clinical linear accelerator.
Partial scan artifact reduction (PSAR) for the assessment of cardiac perfusion in dynamic phase‐correlated CT
Authors: Stenner Philip , Schmidt Bernhard , Bruder Herbert , Allmendinger Thomas , Haberland Ulrike , Flohr Thomas , Kachelrieß Marc 
Published: November 2009

Purpose:Cardiac CT achieves its high temporal resolution by lowering the scan range from to plus fan angle (partial scan). This, however, introduces CT‐value variations, depending on the angular position of the range. These partial scan artifacts are of the order of a few HU and prevent the quantitative evaluation of perfusion measurements. The authors present the new algorithm partial scan artifact reduction (PSAR) that corrects a dynamic phase‐correlated scan without a priori information.Methods:In general, a full scan does not suffer from partial scan artifacts since all projections in [0,] contribute to the data. To maintain the optimum temporal resolution and the phase correlation, PSAR creates an artificial full scan by projectionwise averaging a set of neighboring partial scans from the same perfusion examination (typically phase‐correlated partial scans distributed over and ). Corresponding to the angular range of each partial scan, the authors extract virtual partial scans from the artificial full scan . A standard reconstruction yields the corresponding images , , and . Subtracting the virtual partial scan image from the artificial full scan image yields an artifact image that can be used to correct the original partial scan image: , where is the corrected image.Results:The authors evaluated the effects of scattered radiation on the partial scan artifacts using simulated and measured water phantoms and found a strong correlation. The PSAR algorithm has been validated with a simulated semianthropomorphic heart phantom and with measurements of a dynamic biological perfusion phantom. For the stationary phantoms, real full scans have been performed to provide theoretical reference values. The improvement in the root mean square errors between the full and the partial scans with respect to the errors between the full and the corrected scans is up to 54% for the simulations and 90% for the measurements.Conclusions:The phase‐correlated data now appear accurate enough for a quantitative analysis of cardiac perfusion.
Autoadaptive phase‐correlated (AAPC) reconstruction for 4D CBCT
Authors: Bergner Frank , Berkus Timo , Oelhafen Markus , Kunz Patrik , Pan Tinsu , Kachelrieß Marc 
Published: November 2009

Purpose:Kilovoltage cone‐beam computed tomography (CBCT) is widely used in image‐guided radiation therapy for exact patient positioning prior to the treatment. However, producing time series of volumetric images (4D CBCT) of moving anatomical structures remains challenging. The presented work introduces a novel method, combining high temporal resolution inside anatomical regions with strong motion and image quality improvement in regions with little motion.Methods:In the proposed method, the projections are divided into regions that are subject to motion and regions at rest. The latter ones will be shared among phase bins, leading thus to an overall reduction in artifacts and noise. An algorithm based on the concept of optical flow was developed to analyze motion‐induced changes between projections. The technique was optimized to distinguish patient motion and motion deriving from gantry rotation. The effectiveness of the method is shown in numerical simulations and patient data.Results:The images reconstructed from the presented method yield an almost the same temporal resolution in the moving volume segments as a conventional phase‐correlated reconstruction, while reducing the noise in the motionless regions down to the level of a standard reconstruction without phase correlation. The proposed simple motion segmentation scheme is yet limited to rotation speeds of less than.Conclusions:The method reduces the noise in the reconstruction and increases the image quality. More data are introduced for each phase‐correlated reconstruction, and therefore the applied dose is used more efficiently.
Intrapulmonary Pharmacokinetics of S-013420, a Novel Bicyclolide Antibacterial, in Healthy Japanese Subjects
Authors: Furuie Hidetoshi , Saisho Yutaka , Yoshikawa Takayoshi , Shimada Jingoro 
Published: November 2009

ABSTRACTS-013420 (EDP-420) is a novel bicyclolide (bridged bicyclic macrolide) antibacterial currently under development for the treatment of respiratory tract infections. The objective of the present study was to determine the plasma and intrapulmonary pharmacokinetic parameters of orally administered S-013420 in healthy volunteers. Twenty-eight healthy Japanese male subjects who never smoked were randomly allocated to seven groups of four subjects each who underwent bronchoalveolar lavage (BAL) at different times after dosing (2, 4, 6, 8, 10, 12, or 24 h). Blood samples were also taken at 0, 0.5, 1, 2, 4, 6, 8, 10, 12, 24, 48, and 72 h after dosing. The S-013420 concentrations in plasma, epithelial lining fluid (ELF), and alveolar macrophages (AMs) were measured by using a combined high-performance liquid chromatography-mass spectrometric technique. A pharmacokinetic analysis of the plasma, ELF, and AM S-013420 concentration profiles was performed. S-013420 was rapidly absorbed in plasma, and the mean time to the maximum concentration in plasma was 2.27 h. S-013420 was rapidly distributed to the ELF and was slowly distributed to AMs. The areas under the concentration-time curves from time zero to 24 h (AUC0-24) for S-013420 were 20.3 times higher in ELF than in plasma and 244.6 times higher in AMs than in plasma. The mean maximum concentration in plasma was higher in ELF than in plasma and was much higher in AM than in plasma. Furthermore, pharmacodynamic calculations were done by using the AUC0-24/MIC90ratio for common pneumonia pathogens (Staphylococcus aureus,Streptococcus pneumoniae,Haemophilus influenzae, andMoraxella catarrhalis). The AUC0-24for plasma/MIC90s for these four organisms were 41.8, 83.6, 1.3, and 20.9, respectively. The AUC0-24for ELF/MIC90s were 849.6, 1,699.2, 26.6, and 424.8, respectively. Considering the good efficacy shown in a subsequent phase 2 study (S. Kohno, K. Yamaguchi, Y. Tanigawara, A. Watanabe, A. Aoki, Y. Niki, and J. Fujita, Abstr. 47th Intersci. Conf. Antimicrob. Agents Chemother., abstr. L-485), the good distribution of S-013420 in AMs and ELF observed in the present study is predictive of the good efficacy of S-013420 against respiratory pathogens.
Polyphyletic Emergence of Linezolid-Resistant Staphylococci in the United States
Authors: Wong Agnes , Reddy Shilpa P. , Smyth Davida S. , Aguero-Rosenfeld Maria E. , Sakoulas George , Robinson D. Ashley 
Published: November 2009

ABSTRACT

Since the year 2000, linezolid has been used in the United States to treat infections caused by antimicrobial-resistant Gram-positive cocci. At present, linezolid-resistant (Lin
r
)
Staphylococcus aureus
and
Staphylococcus epidermidis
strains are rare and the diversity of their genetic backgrounds is unknown. We performed sequence-based strain typing and resistance gene characterization of 46 Lin
r
isolates that were collected from local and national sources between the years 2004 and 2007. Resistance was found to occur in at least three clonal complexes (CCs; lineages) of
S. aureus
and in at least four subclusters of a predominant, phylogenetically unstable CC of
S. epidermidis
. New candidate resistance mutations in 23S rRNA and the L4 riboprotein were identified among the
S. epidermidis
isolates. These findings suggest that linezolid resistance has emerged independently in multiple clones of
S. aureus
and with a variety of ribosomal mutations in multiple clones of
S. epidermidis
.
Differential Patterns of Liver Proteins in Experimental Murine Hepatosplenic Schistosomiasis
Authors: Manivannan B. , Rawson P. , Jordan T. W. , Secor W. E. , La Flamme A. C. 
Published: November 2009

ABSTRACTSchistosoma mansonieggs produced by adult worms in the mesenteric vasculature become trapped in the liver, where they induce granulomatous lesions and strong immune responses. Infected individuals suffer from intestinal schistosomiasis (INT) in 90% of cases, whereas the remaining 10% present with severe hepatosplenic schistosomiasis (HS). The CBA/J mouse model mimics human disease, with 20% of infected mice developing hypersplenomegaly syndrome (HSS) that resembles HS and 80% developing moderate splenomegaly syndrome (MSS) similar to INT. We studied differential patterns of protein expression in livers of 20-week-infected CBA/J mice with MSS or HSS to understand the molecular changes that underlie these two disease forms. Using differential in-gel electrophoresis to identify differentially expressed protein spots, we found 80 protein spots significantly changed with infection and 35 changes specific to severe disease. In particular, the abundances of prohibitin 2, transferrin isoforms, and major urinary protein isoforms were significantly altered in HSS mice. Furthermore, annexin 5, glutathioneS-transferase pi class, andS. mansoniphosphoenolpyruvate carboxykinase expression levels changed significantly with schistosome infection. Additionally, levels of major urinary protein decreased and levels of transferrin increased significantly in the sera of HSS mice compared to levels in sera of MSS or control mice, and these differences correlated to the degree of splenomegaly. These findings indicate that the liver protein abundances differ between MSS and HSS mice and may be used for the development of diagnostic markers for the early detection of hepatosplenic schistosomiasis.
Yersinia pestisTwo-Component Gene Regulatory Systems Promote Survival in Human Neutrophils
Authors: O'Loughlin Jason L. , Spinner Justin L. , Minnich Scott A. , Kobayashi Scott D. 
Published: November 2009

ABSTRACTHuman polymorphonuclear leukocytes (PMNs, or neutrophils) are the most abundant innate immune cell and kill most invading bacteria through combined activities of reactive oxygen species (ROS) and antimicrobial granule constituents. Pathogens such asYersinia pestisresist destruction by the innate immune system and are able to survive in macrophages and neutrophils. The specific molecular mechanisms used byY. pestisto survive following phagocytosis by human PMNs are incompletely defined. To gain insight into factors that governY. pestisintracellular survival in neutrophils, we inactivated 25 two-component gene regulatory systems (TCSs) with known or inferred function and assessed susceptibility of these mutant strains to human PMN granule extracts.Y. pestisstrains deficient for PhoPQ, KdpED, CheY, CvgSY, and CpxRA TCSs were selected for further analysis, and all five strains were altered for survival following interaction with PMNs. Of these five strains, onlyY. pestisΔphoPQdemonstrated global sensitivity to a panel of seven individual neutrophil antimicrobial peptides and serine proteases. Notably,Y. pestisΔphoPQwas deficient for intracellular survival in PMNs. Iterative analysis withY. pestisstrains lacking the PhoP-regulated genesugdandpmrKindicated that the mechanism most likely responsible for increased resistance to killing is 4-amino-4-deoxy-l-arabinose modification of lipid A. Together, the data provide new information aboutY. pestisevasion of the innate immune system.
Protease-Activated Receptor 2 Has Pivotal Roles in Cellular Mechanisms Involved in Experimental Periodontitis
Authors: Wong David M. , Tam Vivian , Lam Roselind , Walsh Katrina A. , Tatarczuch Liliana , Pagel Charles N. , Reynolds Eric C. , O'Brien-Simpson Neil M. , Mackie Eleanor J. , Pike Robert N. 
Published: November 2009

ABSTRACTThe tissue destruction seen in chronic periodontitis is commonly accepted to involve extensive upregulation of the host inflammatory response. Protease-activated receptor 2 (PAR-2)-null mice infected withPorphyromonas gingivalisdid not display periodontal bone resorption in contrast to wild-type-infected and PAR-1-null-infected mice. Histological examination of tissues confirmed the lowered bone resorption in PAR-2-null mice and identified a substantial decrease in mast cells infiltrating the periodontal tissues of these mice. T cells fromP. gingivalis-infected or immunized PAR-2-null mice proliferated less in response to antigen than those from wild-type animals. CD90 (Thy1.2) expression on CD4+and CD8+T-cell-receptor β (TCRβ) T cells was significantly (P< 0.001) decreased in antigen-immunized PAR-2-null mice compared to sham-immunized PAR-2-null mice; this was not observed in wild-type controls. T cells from infected or antigen-immunized PAR-2-null mice had a significantly different Th1/inflammatory cytokine profile from wild-type cells: in particular, gamma interferon, interleukins (interleukin-2, -3, and -17), granulocyte-macrophage colony-stimulating factor, and tumor necrosis factor alpha demonstrated lower expression than wild-type controls. The absence of PAR-2 therefore appears to substantially decrease T-cell activation and the Th1/inflammatory response. Regulation of such proinflammatory mechanisms in T cells and mast cells by PAR-2 suggests a pivotal role in the pathogenesis of the disease.