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Sample records for absolute perfusion values

  1. Easy Absolute Values? Absolutely

    ERIC Educational Resources Information Center

    Taylor, Sharon E.; Mittag, Kathleen Cage

    2015-01-01

    The authors teach a problem-solving course for preservice middle-grades education majors that includes concepts dealing with absolute-value computations, equations, and inequalities. Many of these students like mathematics and plan to teach it, so they are adept at symbolic manipulations. Getting them to think differently about a concept that they…

  2. Teaching Absolute Value Meaningfully

    ERIC Educational Resources Information Center

    Wade, Angela

    2012-01-01

    What is the meaning of absolute value? And why do teachers teach students how to solve absolute value equations? Absolute value is a concept introduced in first-year algebra and then reinforced in later courses. Various authors have suggested instructional methods for teaching absolute value to high school students (Wei 2005; Stallings-Roberts…

  3. Be Resolute about Absolute Value

    ERIC Educational Resources Information Center

    Kidd, Margaret L.

    2007-01-01

    This article explores how conceptualization of absolute value can start long before it is introduced. The manner in which absolute value is introduced to students in middle school has far-reaching consequences for their future mathematical understanding. It begins to lay the foundation for students' understanding of algebra, which can change…

  4. Investigating Absolute Value: A Real World Application

    ERIC Educational Resources Information Center

    Kidd, Margaret; Pagni, David

    2009-01-01

    Making connections between various representations is important in mathematics. In this article, the authors discuss the numeric, algebraic, and graphical representations of sums of absolute values of linear functions. The initial explanations are accessible to all students who have experience graphing and who understand that absolute value simply…

  5. Teaching Absolute Value Inequalities to Mature Students

    ERIC Educational Resources Information Center

    Sierpinska, Anna; Bobos, Georgeana; Pruncut, Andreea

    2011-01-01

    This paper gives an account of a teaching experiment on absolute value inequalities, whose aim was to identify characteristics of an approach that would realize the potential of the topic to develop theoretical thinking in students enrolled in prerequisite mathematics courses at a large, urban North American university. The potential is…

  6. Solving Absolute Value Equations Algebraically and Geometrically

    ERIC Educational Resources Information Center

    Shiyuan, Wei

    2005-01-01

    The way in which students can improve their comprehension by understanding the geometrical meaning of algebraic equations or solving algebraic equation geometrically is described. Students can experiment with the conditions of the absolute value equation presented, for an interesting way to form an overall understanding of the concept.

  7. The absolute CBF response to activation is preserved during elevated perfusion: Implications for neurovascular coupling measures.

    PubMed

    Whittaker, Joseph R; Driver, Ian D; Bright, Molly G; Murphy, Kevin

    2016-01-15

    Functional magnetic resonance imaging (fMRI) techniques in which the blood oxygenation level dependent (BOLD) and cerebral blood flow (CBF) response to a neural stimulus are measured, can be used to estimate the fractional increase in the cerebral metabolic rate of oxygen consumption (CMRO2) that accompanies evoked neural activity. A measure of neurovascular coupling is obtained from the ratio of fractional CBF and CMRO2 responses, defined as n, with the implicit assumption that relative rather than absolute changes in CBF and CMRO2 adequately characterise the flow-metabolism response to neural activity. The coupling parameter n is important in terms of its effect on the BOLD response, and as potential insight into the flow-metabolism relationship in both normal and pathological brain function. In 10 healthy human subjects, BOLD and CBF responses were measured to test the effect of baseline perfusion (modulated by a hypercapnia challenge) on the coupling parameter n during graded visual stimulation. A dual-echo pulsed arterial spin labelling (PASL) sequence provided absolute quantification of CBF in baseline and active states as well as relative BOLD signal changes, which were used to estimate CMRO2 responses to the graded visual stimulus. The absolute CBF response to the visual stimuli were constant across different baseline CBF levels, meaning the fractional CBF responses were reduced at the hyperperfused baseline state. For the graded visual stimuli, values of n were significantly reduced during hypercapnia induced hyperperfusion. Assuming the evoked neural responses to the visual stimuli are the same for both baseline CBF states, this result has implications for fMRI studies that aim to measure neurovascular coupling using relative changes in CBF. The coupling parameter n is sensitive to baseline CBF, which would confound its interpretation in fMRI studies where there may be significant differences in baseline perfusion between groups. The absolute change in

  8. A Conceptual Approach to Absolute Value Equations and Inequalities

    ERIC Educational Resources Information Center

    Ellis, Mark W.; Bryson, Janet L.

    2011-01-01

    The absolute value learning objective in high school mathematics requires students to solve far more complex absolute value equations and inequalities. When absolute value problems become more complex, students often do not have sufficient conceptual understanding to make any sense of what is happening mathematically. The authors suggest that the…

  9. Using, Seeing, Feeling, and Doing Absolute Value for Deeper Understanding

    ERIC Educational Resources Information Center

    Ponce, Gregorio A.

    2008-01-01

    Using sticky notes and number lines, a hands-on activity is shared that anchors initial student thinking about absolute value. The initial point of reference should help students successfully evaluate numeric problems involving absolute value. They should also be able to solve absolute value equations and inequalities that are typically found in…

  10. Preschoolers' Success at Coding Absolute Size Values.

    ERIC Educational Resources Information Center

    Russell, James

    1980-01-01

    Forty-five 2-year-old and forty-five 3-year-old children coded relative and absolute sizes using 1.5-inch, 6-inch, and 18-inch cardboard squares. Results indicate that absolute coding is possible for children of this age. (Author/RH)

  11. Supplementary and Enrichment Series: Absolute Value. Teachers' Commentary. SP-25.

    ERIC Educational Resources Information Center

    Bridgess, M. Philbrick, Ed.

    This is one in a series of manuals for teachers using SMSG high school supplementary materials. The pamphlet includes commentaries on the sections of the student's booklet, answers to the exercises, and sample test questions. Topics covered include addition and multiplication in terms of absolute value, graphs of absolute value in the Cartesian…

  12. Supplementary and Enrichment Series: Absolute Value. SP-24.

    ERIC Educational Resources Information Center

    Bridgess, M. Philbrick, Ed.

    This is one in a series of SMSG supplementary and enrichment pamphlets for high school students. This series is designed to make material for the study of topics of special interest to students readily accessible in classroom quantity. Topics covered include absolute value, addition and multiplication in terms of absolute value, graphs of absolute…

  13. Absolute Value Boundedness, Operator Decomposition, and Stochastic Media and Equations

    NASA Technical Reports Server (NTRS)

    Adomian, G.; Miao, C. C.

    1973-01-01

    The research accomplished during this period is reported. Published abstracts and technical reports are listed. Articles presented include: boundedness of absolute values of generalized Fourier coefficients, propagation in stochastic media, and stationary conditions for stochastic differential equations.

  14. An improved generalized Newton method for absolute value equations.

    PubMed

    Feng, Jingmei; Liu, Sanyang

    2016-01-01

    In this paper, we suggest and analyze an improved generalized Newton method for solving the NP-hard absolute value equations [Formula: see text] when the singular values of A exceed 1. We show that the global and local quadratic convergence of the proposed method. Numerical experiments show the efficiency of the method and the high accuracy of calculation. PMID:27462490

  15. Absolute Value Inequalities: High School Students' Solutions and Misconceptions

    ERIC Educational Resources Information Center

    Almog, Nava; Ilany, Bat-Sheva

    2012-01-01

    Inequalities are one of the foundational subjects in high school math curricula, but there is a lack of academic research into how students learn certain types of inequalities. This article fills part of the research gap by presenting the findings of a study that examined high school students' methods of approaching absolute value inequalities,…

  16. Absolute neutrophil values in malignant patients on cytotoxic chemotherapy.

    PubMed

    Madu, A J; Ibegbulam, O G; Ocheni, S; Madu, K A; Aguwa, E N

    2011-01-01

    A total of eighty patients with various malignancies seen between September 2008 and April 2009 at the University of Nigeria Teaching Hospital (UNTH) Ituku Ozalla, Enugu, Nigeria, had their absolute neutrophil counts, done at Days 0 and 12 of the first cycle of their various chemotherapeutic regimens. They were adult patients who had been diagnosed of various malignancies, consisting of Breast cancer 36 (45%), Non-Hodgkin's lymphoma 8 (10%), Hodgkin's lymphoma 13 (16.25%), Colorectal carcinoma 6 (7.5%), Multiple myeloma 7 (8.75%), Cervical carcinoma 1 (1.25%) and other malignancies 9 (11.25%), Manual counting of absolute neutrophil count was done using Turks solution and improved Neubauer counting chamber and Galen 2000 Olympus microscope. The socio demographic data of the patients were assessed from a questionnaire. There were 27 males (33.75%) and 53 females (66.25%). Their ages ranged from 18 - 80 years with a median of 45 years. The mean absolute neutrophil count of the respondents pre-and post chemotherapy was 3.7 +/- 2.1 x 10(9)/L and 2.5 +/- 1.6 x 10(9)/L respectively. There were significant differences in both the absolute neutrophil count (p=0.00) compared to the pre-chemotherapy values. Chemotherapeutic combinations containing cyclophosphamide and Adriamycin were observed to cause significant reduction in absolute neutrophil.

  17. Absolute perfusion measurements and associated iodinated contrast agent time course in brain metastasis: a study for contrast-enhanced radiotherapy.

    PubMed

    Obeid, Layal; Deman, Pierre; Tessier, Alexandre; Balosso, Jacques; Estève, François; Adam, Jean-François

    2014-04-01

    Contrast-enhanced radiotherapy is an innovative treatment that combines the selective accumulation of heavy elements in tumors with stereotactic irradiations using medium energy X-rays. The radiation dose enhancement depends on the absolute amount of iodine reached in the tumor and its time course. Quantitative, postinfusion iodine biodistribution and associated brain perfusion parameters were studied in human brain metastasis as key parameters for treatment feasibility and quality. Twelve patients received an intravenous bolus of iodinated contrast agent (CA) (40 mL, 4 mL/s), followed by a steady-state infusion (160 mL, 0.5 mL/s) to ensure stable intratumoral amounts of iodine during the treatment. Absolute iodine concentrations and quantitative perfusion maps were derived from 40 multislice dynamic computed tomography (CT) images of the brain. The postinfusion mean intratumoral iodine concentration (over 30 minutes) reached 1.94 ± 0.12 mg/mL. Reasonable correlations were obtained between these concentrations and the permeability surface area product and the cerebral blood volume. To our knowledge, this is the first quantitative study of CA biodistribution versus time in brain metastasis. The study shows that suitable and stable amounts of iodine can be reached for contrast-enhanced radiotherapy. Moreover, the associated perfusion measurements provide useful information for the patient recruitment and management processes.

  18. Rate Change Graph Technology: Absolute Value Point Methodology

    NASA Astrophysics Data System (ADS)

    Strickland, Ken; Duvernois, Michael

    2011-10-01

    Absolute Value Point Methodology (AVPM) is a new theoretical tool for science research centered on Rate Change Graph Technology (RCGT). The modeling techniques of AVPM surpass conventional methods by extending the geometrical rules of mathematics. Exact geometrical structures of matter and energy become clearer revealing new ways to compile advanced data. RCGT mechanics is realized from geometrical intersections that are the result of plotting changing value vs. changing geometry. RCGT methods ignore size and value to perform an objective analysis in geometry. Value and size are then re-introduced back into the analytical system for a clear and concise solution. Available AVPM applications reveal that a massive amount of data from the Big Bang to vast super-clusters is untouched by human thought. Once scientists learn to design tools from RCGT Mechanics, new and formidable approaches to experimentation and theory may lead to new discoveries. In the creation of AVPM, it has become apparent there is a particle-world that exists between strings and our familiar universe. These unrealized particles in their own nature exhibit inflation like properties and may be the progenitor of the implements of our universe. Thus space, time, energy, motion, space-time and gravity are born from its existence and decay. This announcement will be the beginning of many new ideas from the study of RCGT mechanics.

  19. The preference of visualization in teaching and learning absolute value

    NASA Astrophysics Data System (ADS)

    Cihan Konyalioğlu, Alper; Aksu, Zeki; Özge Şenel, Esma

    2012-07-01

    Visualization is mostly despised although it complements and - sometimes - guides the analytical process. This study mainly investigates teachers' preferences concerning the use of the visualization method and determines the extent to which they encourage their students to make use of it within the problem-solving process. This study was conducted for the ninth-grade students and their mathematics teacher in a social science intensive public school in the city of Erzurum, Turkey. Utilizing case study as the preferred method, data were collected through observations, interviews and student evaluations. This study revealed that visualization has a positive effect at the preliminary phases of teaching the absolute value concept but generates a lack of stimulation during problem solving in further phases of the instruction. This could be explained as a result of current examination system which requires a habituation of the analytical process in solving mathematical questions.

  20. Precision absolute value amplifier for a precision voltmeter

    DOEpatents

    Hearn, William E.; Rondeau, Donald J.

    1985-01-01

    Bipolar inputs are afforded by the plus inputs of first and second differential input amplifiers. A first gain determining resister is connected between the minus inputs of the differential amplifiers. First and second diodes are connected between the respective minus inputs and the respective outputs of the differential amplifiers. First and second FETs have their gates connected to the outputs of the amplifiers, while their respective source and drain circuits are connected between the respective minus inputs and an output lead extending to a load resister. The output current through the load resister is proportional to the absolute value of the input voltage difference between the bipolar input terminals. A third differential amplifier has its plus input terminal connected to the load resister. A second gain determining resister is connected between the minus input of the third differential amplifier and a voltage source. A third FET has its gate connected to the output of the third amplifier. The source and drain circuit of the third transistor is connected between the minus input of the third amplifier and a voltage-frequency converter, constituting an output device. A polarity detector is also provided, comprising a pair of transistors having their inputs connected to the outputs of the first and second differential amplifiers. The outputs of the polarity detector are connected to gates which switch the output of the voltage-frequency converter between up and down counting outputs.

  1. Precision absolute-value amplifier for a precision voltmeter

    DOEpatents

    Hearn, W.E.; Rondeau, D.J.

    1982-10-19

    Bipolar inputs are afforded by the plus inputs of first and second differential input amplifiers. A first gain determining resistor is connected between the minus inputs of the differential amplifiers. First and second diodes are connected between the respective minus inputs and the respective outputs of the differential amplifiers. First and second FETs have their gates connected to the outputs of the amplifiers, while their respective source and drain circuits are connected between the respective minus inputs and an output lead extending to a load resistor. The output current through the load resistor is proportional to the absolute value of the input voltage difference between the bipolar input terminals. A third differential amplifier has its plus input terminal connected to the load resistor. A second gain determining resistor is connected between the minus input of the third differential amplifier and a voltage source. A third FET has its gate connected to the output of the third amplifier. The source and drain circuit of the third transistor is connected between the minus input of the third amplifier and a voltage-frequency converter, constituting an output device. A polarity detector is also provided, comprising a pair of transistors having their inputs connected to the outputs of the first and second differential amplifiers. The outputs of the polarity detector are connected to gates which switch the output of the voltage-frequency converter between up and down counting outputs.

  2. A Special Application of Absolute Value Techniques in Authentic Problem Solving

    ERIC Educational Resources Information Center

    Stupel, Moshe

    2013-01-01

    There are at least five different equivalent definitions of the absolute value concept. In instances where the task is an equation or inequality with only one or two absolute value expressions, it is a worthy educational experience for learners to solve the task using each one of the definitions. On the other hand, if more than two absolute value…

  3. Absolute value equations - what can we learn from their graphical representation?

    NASA Astrophysics Data System (ADS)

    Stupel, Moshe; Ben-Chaim, David

    2014-08-01

    Understanding graphical representations of algebraic equations, particularly graphical representations of absolute value equations, significantly improves students' mathematical comprehension and ignites within them an appreciation of the beauty and aesthetics of mathematics. In this paper, we focus on absolute value equations of linear and quadratic expressions, by examining various cases, presenting different methods of solving them by graphical representation, exhibiting the advantage of using dynamic software such as GeoGebra in solving them, and illustrating some examples of interesting graphical solutions. We recommend that teachers take advantage of the rapid development in technology to help learners tangibly visualize the solutions of absolute value equations before proceeding to the analytical solutions.

  4. The Interaction of Spatial Visualization and General Reasoning Abilities with Instructional Treatment on Absolute Value Equations

    ERIC Educational Resources Information Center

    Eastman, Phillip M.; Salhab, Mohammed

    1978-01-01

    One group of elementary education majors received an algebraic instructional treatment of a unit on linear absolute value equations while another received a geometric treatment. The hypothesis of an aptitude-by-treatment interaction was statistically confirmed. (MN)

  5. Relation between regional myocardial uptake of /sup 82/Rb and perfusion: absolute reduction of cation uptake in ischemia

    SciTech Connect

    Selwyn, A.P.; Allan, R.M.; L'Abbate, A.; Horlock, P.; Camici, P.; Clark, J.; O'Brien, H.A.; Grant, P.M.

    1982-07-01

    Experiments were undertaken using /sup 82/Rb and position tomography to examine the relation between myocardial perfusion and cation uptake during acute ischemia. /sup 82/Rb was repeatedly eluted from a /sup 82/Sr-/sup 82/Rb generator. In six dogs emission tomograms were used to measure the delivered arterial and myocardial concentrations at rest and after coronary stenosis, stress and ischemia. There was a poor overall relation between regional myocardial uptake and flow measured by microspheres and a large individual variability. Extraction of /sup 82/Rb was inversely related to flow. Significant regional reduction of cation uptake was detected in the tomograms when regional flow decreased by more than 35 percent. This reduction was significantly greater when ischemia was present. A small but significantly greater when ischemia was present. A small but significant decrease (33.0 +/- 9.1 percent, mean +/- standard deviation) in the myocardial uptake of /sup 82/Rb was detected only when flow was increased by more than 120 percent in relation to a control area after administration of dypiridamole. The technique using /sup 82/Rb and tomography was applied in five volunteers and five patients with angina pectoris and coronary artery disease. Myocardial tomograms recorded at rest and after exercise in the volunteers showed homogeneous uptake of cation in reproducible and repeatable scans. In contrast, the patients with coronary artery disease showed an absolute mean decrease of 36 +/- 14 percent in regional myocardial uptake of /sup 82/Rb after exercise. These abnormalities persisted in serial tomograms for more than 20 minutes after the symptoms and electrocardiographic signs of ischemia.

  6. Phase-based metamorphosis of diffusion lesion in relation to perfusion values in acute ischemic stroke.

    PubMed

    Rekik, Islem; Allassonnière, Stéphanie; Luby, Marie; Carpenter, Trevor K; Wardlaw, Joanna M

    2015-01-01

    Examining the dynamics of stroke ischemia is limited by the standard use of 2D-volume or voxel-based analysis techniques. Recently developed spatiotemporal models such as the 4D metamorphosis model showed promise for capturing ischemia dynamics. We used a 4D metamorphosis model to evaluate acute ischemic stroke lesion morphology from the acute diffusion-weighted imaging (DWI) to final T2-weighted imaging (T2-w). In 20 representative patients, we metamorphosed the acute lesion to subacute lesion to final infarct. From the DWI lesion deformation maps we identified dynamic lesion areas and examined their association with perfusion values inside and around the lesion edges, blinded to reperfusion status. We then tested the model in ten independent patients from the STroke Imaging Repository (STIR). Perfusion values varied widely between and within patients, and were similar in contracting and expanding DWI areas in many patients in both datasets. In 25% of patients, the perfusion values were higher in DWI-contracting than DWI-expanding areas. A similar wide range of perfusion values and ongoing expansion and contraction of the DWI lesion were seen subacutely. There was more DWI contraction and less expansion in patients who received thrombolysis, although with widely ranging perfusion values that did not differ. 4D metamorphosis modeling shows promise as a method to improve use of multimodal imaging to understand the evolution of acute ischemic tissue towards its fate. PMID:26288755

  7. A special application of absolute value techniques in authentic problem solving

    NASA Astrophysics Data System (ADS)

    Stupel, Moshe

    2013-06-01

    There are at least five different equivalent definitions of the absolute value concept. In instances where the task is an equation or inequality with only one or two absolute value expressions, it is a worthy educational experience for learners to solve the task using each one of the definitions. On the other hand, if more than two absolute value expressions are involved, the definition that is most helpful is the one involving solving by intervals and evaluating critical points. In point of fact, application of this technique is one reason that the topic of absolute value is important in mathematics in general and in mathematics teaching in particular. We present here an authentic practical problem that is solved using absolute values and the 'intervals' method, after which the solution is generalized with surprising results. This authentic problem also lends itself to investigation using educational technological tools such as GeoGebra dynamic geometry software: mathematics teachers can allow their students to initially cope with the problem by working in an inductive environment in which they conduct virtual experiments until a solid conjecture has been reached, after which they should prove the conjecture deductively, using classic theoretical mathematical tools.

  8. Value of Dynamic Susceptibility Contrast Perfusion MRI in the Acute Phase of Transient Global Amnesia

    PubMed Central

    Förster, Alex; Al-Zghloul, Mansour; Kerl, Hans U.; Böhme, Johannes; Mürle, Bettina; Groden, Christoph

    2015-01-01

    Purpose Transient global amnesia (TGA) is a transitory, short-lasting neurological disorder characterized by a sudden onset of antero- and retrograde amnesia. Perfusion abnormalities in TGA have been evaluated mainly by use of positron emission tomography (PET) or single-photon emission computed tomography (SPECT). In the present study we explore the value of dynamic susceptibility contrast perfusion-weighted MRI (PWI) in TGA in the acute phase. Methods From a MRI report database we identified TGA patients who underwent MRI including PWI in the acute phase and compared these to control subjects. Quantitative perfusion maps (cerebral blood flow (CBF) and volume (CBV)) were generated and analyzed by use of Signal Processing In NMR-Software (SPIN). CBF and CBV values in subcortical brain regions were assessed by use of VOI created in FIRST, a model-based segmentation tool in the Oxford Centre for Functional Magnetic Resonance Imaging of the Brain (FMRIB) Software Library (FSL). Results Five TGA patients were included (2 men, 3 women). On PWI, no relevant perfusion alterations were found by visual inspection in TGA patients. Group comparisons for possible differences between TGA patients and control subjects showed significant lower rCBF values bilaterally in the hippocampus, in the left thalamus and globus pallidus as well as bilaterally in the putamen and the left caudate nucleus. Correspondingly, significant lower rCBV values were observed bilaterally in the hippocampus and the putamen as well as in the left caudate nucleus. Group comparisons for possible side differences in rCBF and rCBV values in TGA patients revealed a significant lower rCBV value in the left caudate nucleus. Conclusions Mere visual inspection of PWI is not sufficient for the assessment of perfusion changes in TGA in the acute phase. Group comparisons with healthy control subjects might be useful to detect subtle perfusion changes on PWI in TGA patients. However, this should be confirmed in

  9. A Multidimensional Approach to Explore the Understanding of the Notion of Absolute Value

    ERIC Educational Resources Information Center

    Gagatsis, Athanasios; Panaoura, Areti

    2014-01-01

    The study aimed to investigate students' conceptions on the notion of absolute value and their abilities in applying the specific notion in routine and non-routine situations. A questionnaire was constructed and administered to 17-year-old students. Data were analysed using the hierarchical clustering of variables and the implicative method,…

  10. Maple (Computer Algebra System) in Teaching Pre-Calculus: Example of Absolute Value Function

    ERIC Educational Resources Information Center

    Tuluk, Güler

    2014-01-01

    Modules in Computer Algebra Systems (CAS) make Mathematics interesting and easy to understand. The present study focused on the implementation of the algebraic, tabular (numerical), and graphical approaches used for the construction of the concept of absolute value function in teaching mathematical content knowledge along with Maple 9. The study…

  11. Students' Mathematical Work on Absolute Value: Focusing on Conceptions, Errors and Obstacles

    ERIC Educational Resources Information Center

    Elia, Iliada; Özel, Serkan; Gagatsis, Athanasios; Panaoura, Areti; Özel, Zeynep Ebrar Yetkiner

    2016-01-01

    This study investigates students' conceptions of absolute value (AV), their performance in various items on AV, their errors in these items and the relationships between students' conceptions and their performance and errors. The Mathematical Working Space (MWS) is used as a framework for studying students' mathematical work on AV and the…

  12. Multiphase permittivity imaging using absolute value electrical capacitance tomography data and a level set algorithm.

    PubMed

    Al Hosani, E; Soleimani, M

    2016-06-28

    Multiphase flow imaging is a very challenging and critical topic in industrial process tomography. In this article, simulation and experimental results of reconstructing the permittivity profile of multiphase material from data collected in electrical capacitance tomography (ECT) are presented. A multiphase narrowband level set algorithm is developed to reconstruct the interfaces between three- or four-phase permittivity values. The level set algorithm is capable of imaging multiphase permittivity by using one set of ECT measurement data, so-called absolute value ECT reconstruction, and this is tested with high-contrast and low-contrast multiphase data. Simulation and experimental results showed the superiority of this algorithm over classical pixel-based image reconstruction methods. The multiphase level set algorithm and absolute ECT reconstruction are presented for the first time, to the best of our knowledge, in this paper and critically evaluated. This article is part of the themed issue 'Supersensing through industrial process tomography'. PMID:27185966

  13. Multiphase permittivity imaging using absolute value electrical capacitance tomography data and a level set algorithm.

    PubMed

    Al Hosani, E; Soleimani, M

    2016-06-28

    Multiphase flow imaging is a very challenging and critical topic in industrial process tomography. In this article, simulation and experimental results of reconstructing the permittivity profile of multiphase material from data collected in electrical capacitance tomography (ECT) are presented. A multiphase narrowband level set algorithm is developed to reconstruct the interfaces between three- or four-phase permittivity values. The level set algorithm is capable of imaging multiphase permittivity by using one set of ECT measurement data, so-called absolute value ECT reconstruction, and this is tested with high-contrast and low-contrast multiphase data. Simulation and experimental results showed the superiority of this algorithm over classical pixel-based image reconstruction methods. The multiphase level set algorithm and absolute ECT reconstruction are presented for the first time, to the best of our knowledge, in this paper and critically evaluated. This article is part of the themed issue 'Supersensing through industrial process tomography'.

  14. Absolute value optimization to estimate phase properties of stochastic time series

    NASA Technical Reports Server (NTRS)

    Scargle, J. D.

    1977-01-01

    Most existing deconvolution techniques are incapable of determining phase properties of wavelets from time series data; to assure a unique solution, minimum phase is usually assumed. It is demonstrated, for moving average processes of order one, that deconvolution filtering using the absolute value norm provides an estimate of the wavelet shape that has the correct phase character when the random driving process is nonnormal. Numerical tests show that this result probably applies to more general processes.

  15. The Impact of Different Absolute Solar Irradiance Values on Current Climate Model Simulations

    NASA Technical Reports Server (NTRS)

    Rind, David H.; Lean, Judith L.; Jonas, Jeffrey

    2014-01-01

    Simulations of the preindustrial and doubled CO2 climates are made with the GISS Global Climate Middle Atmosphere Model 3 using two different estimates of the absolute solar irradiance value: a higher value measured by solar radiometers in the 1990s and a lower value measured recently by the Solar Radiation and Climate Experiment. Each of the model simulations is adjusted to achieve global energy balance; without this adjustment the difference in irradiance produces a global temperature change of 0.48C, comparable to the cooling estimated for the Maunder Minimum. The results indicate that by altering cloud cover the model properly compensates for the different absolute solar irradiance values on a global level when simulating both preindustrial and doubled CO2 climates. On a regional level, the preindustrial climate simulations and the patterns of change with doubled CO2 concentrations are again remarkably similar, but there are some differences. Using a higher absolute solar irradiance value and the requisite cloud cover affects the model's depictions of high-latitude surface air temperature, sea level pressure, and stratospheric ozone, as well as tropical precipitation. In the climate change experiments it leads to an underestimation of North Atlantic warming, reduced precipitation in the tropical western Pacific, and smaller total ozone growth at high northern latitudes. Although significant, these differences are typically modest compared with the magnitude of the regional changes expected for doubled greenhouse gas concentrations. Nevertheless, the model simulations demonstrate that achieving the highest possible fidelity when simulating regional climate change requires that climate models use as input the most accurate (lower) solar irradiance value.

  16. Quantification of absolute myocardial perfusion at rest and during exercise with positron emission tomography after human cardiac transplantation

    SciTech Connect

    Krivokapich, J.; Stevenson, L.W.; Kobashigawa, J.; Huang, S.C.; Schelbert, H.R. )

    1991-08-01

    The maximal exercise capacity of cardiac transplant recipients is reduced compared with that of normal subjects. To determine if this reduced exercise capacity is related to inadequate myocardial perfusion during exercise, myocardial perfusion was measured noninvasively with use of positron emission tomography and nitrogen (N)-13 ammonia. Twelve transplant recipients with no angiographic evidence of accelerated coronary atherosclerosis were studied. Serial N-13 ammonia imaging was performed at rest and during supine bicycle exercise. The results were compared with those from 10 normal volunteers with a low probability of having cardiac disease. A two-compartment kinetic model for estimating myocardial perfusion was applied to the data. Transplant recipients achieved a significant lower exercise work load than did the volunteers (42 {plus minus} 16 vs. 128 {plus minus} 22 W), but a higher venous lactate concentration (31.3 {plus minus} 14.9 vs. 13.7 {plus minus} 4.1 mg/100 ml). Despite the difference in exercise work load, there was no significant difference in the cardiac work achieved by transplant recipients and normal subjects as evidenced by similar rate-pressure products of 24,000 {plus minus} 3,400 versus 21,300 {plus minus} 2,800 betas/min per mm Hg, respectively. In addition, myocardial blood flow during exercise was not significantly different between the two groups (1.70 {plus minus} 0.60 vs. 1.56 {plus minus} 0.71 ml/min per g, respectively). This study demonstrates that the myocardial flow response to the physiologic stress of exercise is appropriate in transplant recipients and does not appear to explain the decreased exercise capacity in these patients.

  17. Absolute continuity for operator valued completely positive maps on C*-algebras

    SciTech Connect

    Gheondea, Aurelian; Kavruk, Ali Samil

    2009-02-15

    Motivated by applicability to quantum operations, quantum information, and quantum probability, we investigate the notion of absolute continuity for operator valued completely positive maps on C*-algebras, previously introduced by Parthasarathy [in Athens Conference on Applied Probability and Time Series Analysis I (Springer-Verlag, Berlin, 1996), pp. 34-54]. We obtain an intrinsic definition of absolute continuity, we show that the Lebesgue decomposition defined by Parthasarathy is the maximal one among all other Lebesgue-type decompositions and that this maximal Lebesgue decomposition does not depend on the jointly dominating completely positive map, we obtain more flexible formulas for calculating the maximal Lebesgue decomposition, and we point out the nonuniqueness of the Lebesgue decomposition as well as a sufficient condition for uniqueness. In addition, we consider Radon-Nikodym derivatives for absolutely continuous completely positive maps that, in general, are unbounded positive self-adjoint operators affiliated to a certain von Neumann algebra, and we obtain a spectral approximation by bounded Radon-Nikodym derivatives. An application to the existence of the infimum of two completely positive maps is indicated, and formulas in terms of Choi's matrices for the Lebesgue decomposition of completely positive maps in matrix algebras are obtained.

  18. Diagnostic Value of Dual-Source Computerized Tomography Combined with Perfusion Imaging for Peripheral Pulmonary Embolism

    PubMed Central

    Mao, Xijin; Wang, Shanshan; Jiang, Xingyue; Zhang, Lin; Xu, Wenjian

    2016-01-01

    Background Pulmonary embolism has become the third most common cardiovascular disease, which can seriously harm human health. Objectives To investigate the diagnostic value of dual-source computerized tomography (CT) and perfusion imaging for peripheral pulmonary embolism. Patients and Methods Thirty-two patients with suspected pulmonary embolism underwent dual-source CT exams. To compare the ability of pulmonary embolism detection software (PED) with CT pulmonary angiography (CTPA) in determining the presence, numbers, and locations of pulmonary emboli, the subsequent images were reviewed by two radiologists using both imaging modalities. Also, the diagnostic consistency between PED and CTPA images and dual-energy pulmonary perfusion imaging (DEPI) for segmental pulmonary embolism was compared. Results CTPA images revealed 50 (7.81%) segmental and 56 (4.38%) sub-segmental pulmonary embolisms, while the PED images showed 68 (10.63%) segmental and 94 (7.34%) sub-segmental pulmonary embolisms. Thus, the detection rate on PED images for peripheral pulmonary embolism was significantly higher than that of the CTPA images (P < 0.05). There was good consistency for diagnosing segmental pulmonary embolism between PED and CTPA and DEPI (kappa = 0.85). The sensitivity and specificity of DEPI images for the diagnosis of pulmonary embolism were 91.7% and 97.5%, respectively. Conclusion PED software of dual-source CT combined with perfusion imaging can significantly improve the detection rate of peripheral pulmonary embolism.

  19. Digital controller design for absolute value function constrained nonlinear systems via scalar sign function approach.

    PubMed

    Wu, Jian; Singla, Mithun; Olmi, Claudio; Shieh, Leang S; Song, Gangbing

    2010-07-01

    In this paper, a scalar sign function-based digital design methodology is developed for modeling and control of a class of analog nonlinear systems that are restricted by the absolute value function constraints. As is found to be not uncommon, many real systems are subject to the constraints which are described by the non-smooth functions such as absolute value function. The non-smooth and nonlinear nature poses significant challenges to the modeling and control work. To overcome these difficulties, a novel idea proposed in this work is to use a scalar sign function approach to effectively transform the original nonlinear and non-smooth model into a smooth nonlinear rational function model. Upon the resulting smooth model, a systematic digital controller design procedure is established, in which an optimal linearization method, LQR design and digital implementation through an advanced digital redesign technique are sequentially applied. The example of tracking control of a piezoelectric actuator system is utilized throughout the paper for illustrating the proposed methodology.

  20. Prognostic value of combined visualization of MR diffusion and perfusion maps in glioblastoma.

    PubMed

    Deike, Katerina; Wiestler, Benedikt; Graf, Markus; Reimer, Caroline; Floca, Ralf O; Bäumer, Philipp; Kickingereder, Philipp; Heiland, Sabine; Schlemmer, Heinz-Peter; Wick, Wolfgang; Bendszus, Martin; Radbruch, Alexander

    2016-02-01

    We analyzed whether the combined visualization of decreased apparent diffusion coefficient (ADC) values and increased cerebral blood volume (CBV) in perfusion imaging can identify prognosis-related growth patterns in patients with newly diagnosed glioblastoma. Sixty-five consecutive patients were examined with diffusion and dynamic susceptibility-weighted contrast-enhanced perfusion weighted MRI. ADC and CBV maps were co-registered on the T1-w image and a region of interest (ROI) was manually delineated encompassing the enhancing lesion. Within this ROI pixels with ADC values values >the 70th percentile (CBVmax) and the intersection of pixels with ADCmin and CBVmax were automatically calculated and visualized. Initially, all tumors with a mean intersection greater than the upper quartile of the normally distributed mean intersection of all patients were subsumed to the first growth pattern termed big intersection (BI). Subsequently, the remaining tumors' growth patterns were categorized depending on the qualitative representation of ADCmin, CBVmax and their intersection. Log-rank test exposed a significantly longer overall survival of BI (n = 16) compared to non-BI group (n = 49) (p = 0.0057). Thirty-one, four and 14 patients of the non-BI group were classified as predominant ADC-, CBV- and mixed growth group, respectively. In a multivariate Cox regression model, the BI-, CBV- and mixed groups had significantly lower adjusted hazard ratios (p-value, α(Bonferroni) < 0.006) when compared to the reference group ADC: 0.29 (0.0027), 0.11 (0.038) and 0.33 (0.0059). Our study provides evidence that the combination of diffusion and perfusion imaging allows visualization of different glioblastoma growth patterns that are associated with prognosis. A possible biological hypothesis for this finding could be the interpretation of the ADCmin fraction as the invasion-front of tumor cells while the CBVmax fraction might represent

  1. (99m)Tc-DMSA absolute and relative renal uptake in cats: procedure and normal values.

    PubMed

    Vandermeulen, Eva; Ham, Hamphrey R; Dobbeleir, André A; De Sadeleer, Carlos; Piepsz, Amy; Waelbers, Tim; Vermeire, Simon T; Slegers, Guido; Peremans, Kathelijne Y

    2011-06-01

    In this study we investigated the influence of technical factors (positioning, background (BG) correction and attenuation correction) on qualitative and quantitative (absolute (AU) and relative (RU) uptake) assessment of feline kidneys with (99m)technetium labelled dimercaptosuccinic acid ((99m)Tc-DMSA). Eleven healthy adult cats were included. Influence of BG and depth correction on quantitative assessment was evaluated. Depth correction was based on the geometric mean method (using dorsal and ventral images) and the use of two standards placed over each individual kidney. Visual evaluation showed superiority of dorsal and ventral over lateral positioning due to increased separation of the kidneys permitting region of interest (ROI) placement without overlap. No apparent influence of BG correction was found for RU. However, AU was systematically overestimated without BG correction. Depth correction did not seem to affect RU in most cases, however, in some cats the differences were not negligible. The values for AU without depth correction were lower compared to depth corrected values.

  2. Cerebral CT angiography and CT perfusion in acute stroke detection: a systematic review of diagnostic value

    PubMed Central

    Subramaniam, Cantiriga; Sun, Zhonghua

    2014-01-01

    The purpose of this study was to analyse the diagnostic value of cerebral CT angiography (CTA) and CT perfusion (CTP) examinations in the detection of acute stroke based on a systematic review of the current literature. The review was conducted based on searching of seven databases for articles published between 1993 and 2013. Diagnostic value in terms of sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and accuracy was analysed from 21 articles which were found to meet selection criteria. The mean sensitivity, specificity, PPV, NPV and accuracy for CTA were significantly higher than those for CTP with 83.2% (95% CI: 57.9-100.0%), 95.0% (95% CI: 74.4-100%), 84.1% (95% CI: 50.0-100%), 97.1 (95% CI: 94.0-100%) and 94.0% (95% CI: 83.0-99.0) versus 69.9% (95% CI: 20.0-97.0%), 87.4 (95% CI: 61.0-100.0%), 76.4% (95% CI: 48.0-95.4%), 78.2% (95% CI: 55.8-93.9%) and 89.8% (95% CI: 75.7-97.1%), respectively. This analysis shows that CTA has high diagnostic value in detecting high degree of cerebral arterial stenosis (>70%) whereas CTP provides high specificity in the detection of ischemia and infarct tissue of brain. PMID:25202664

  3. Pulse perfusion value predicts eye opening after sevoflurane anaesthesia: an explorative study.

    PubMed

    Enekvist, Bruno; Johansson, Anders

    2015-08-01

    The variables measured in modern pulse oximetry apparatuses include a graphical pulse curve and a specified perfusion value (PV) that could be a sensitive marker for detecting differences in sympathetic activity. We hypothesized that there is a correlation between a reduction of PV and the time to eye opening after general anaesthesia. The objective was to investigate whether PV can predict eye opening after sevoflurane anaesthesia. Prospective, explorative clinical study included 20 patients, ASA physical status 1 or 2, at Skåne University Hospital, Lund, Sweden, from November 2012 to January 2013 scheduled for elective breast tumour surgery. A general anaesthesia was delivered with inhalation of oxygen, nitrous oxide and sevoflurane anaesthesia to a depth of 1.2 minimal alveolar concentration. Sevoflurane inspiratory and expiratory concentrations were measured. Bispectral index monitoring, PV as measured by pulse oximeter, heart rate and carbon dioxide were registered at before anaesthesia, 15 min after induction (at 1.2 minimal alveolar concentration), at end of surgery and at eye opening at the end of anaesthesia. PV values were lower before anaesthesia and at eye opening compared to at 15 min after induction and at end of surgery (P < 0.05). The reduction of PV between end of surgery and eye opening was 0.76. We conclude that the pulse oximeter PV could be a useful variable to assess the timing of recovery, in terms of eye opening after a general anaesthesia.

  4. Evaluation of activity through dynamic laser speckle using the absolute value of the differences

    NASA Astrophysics Data System (ADS)

    Braga, R. A.; Nobre, C. M. B.; Costa, A. G.; Sáfadi, T.; da Costa, F. M.

    2011-01-01

    When a material is illuminated with a laser beam, it is possible to verify a phenomenon known as dynamic speckle or biospeckle. It exhibits an interference image that contains lots of information about the process being analyzed, and one of its most important applications is determining the activity quantity from the materials under study. The numerical analysis of the dynamic speckle images can be carried out by means of a co-occurrence matrix (COM) that assembles the intensity distributions of a speckle pattern with regard to time. An operational method that is widely used on the biospeckle COMs is the inertia moment (IM). Some studies demonstrate that IM is more sensitive on analyzing processes that involve high activities or high frequencies if considering the spectral analysis of the phenomena. However, when this variation is not so intense, this method is less efficient. For low variations on the activity or low frequencies, qualitative methods such as wavelet based entropy and cross-spectrum analysis have presented better results; however, processes that are in the intermediate range of activity are not well covered for any of these techniques mentioned earlier. The contribution of this research is to present an alternative approach, based on the absolute value of the differences (AVD) when handling the biospeckle COM. By using AVD on the seed-drying process, was found that it is efficient on verifying the behavior of the intermediate frequencies. Accumulated sum test (Coates and Diggle) showed that AVD and IM are generated from the same stochastic process. Thus, AVD is useful as an alternative method in some cases or even as a complementary tool for analyzing the dynamic speckle, mainly when the information of the activity is not present on high frequencies.

  5. Prospective Teachers' Reactions to "Right-or-Wrong" Tasks: The Case of Derivatives of Absolute Value Functions

    ERIC Educational Resources Information Center

    Tsamir, Pessia; Rasslan, Shaker; Dreyfus, Tommy

    2006-01-01

    This paper illustrates the role of a "Thinking-about-Derivatives" task in identifying learners' derivative conceptions and for promoting their critical thinking about derivatives of absolute value functions. The task included three parts: "Define" the derivative of a function f(x) at x = x[subscript 0], "Solve-if-Possible" the derivative of f(x) =…

  6. Delta Procalcitonin Is a Better Indicator of Infection Than Absolute Procalcitonin Values in Critically Ill Patients: A Prospective Observational Study.

    PubMed

    Trásy, Domonkos; Tánczos, Krisztián; Németh, Márton; Hankovszky, Péter; Lovas, András; Mikor, András; Hajdú, Edit; Osztroluczki, Angelika; Fazakas, János; Molnár, Zsolt

    2016-01-01

    Purpose. To investigate whether absolute value of procalcitonin (PCT) or the change (delta-PCT) is better indicator of infection in intensive care patients. Materials and Methods. Post hoc analysis of a prospective observational study. Patients with suspected new-onset infection were included in whom PCT, C-reactive protein (CRP), temperature, and leukocyte (WBC) values were measured on inclusion (t 0) and data were also available from the previous day (t -1). Based on clinical and microbiological data, patients were grouped post hoc into infection- (I-) and noninfection- (NI-) groups. Results. Of the 114 patients, 85 (75%) had proven infection. PCT levels were similar at t -1: I-group (median [interquartile range]): 1.04 [0.40-3.57] versus NI-group: 0.53 [0.16-1.68], p = 0.444. By t 0 PCT levels were significantly higher in the I-group: 4.62 [1.91-12.62] versus 1.12 [0.30-1.66], p = 0.018. The area under the curve to predict infection for absolute values of PCT was 0.64 [95% CI = 0.52-0.76], p = 0.022; for percentage change: 0.77 [0.66-0.87], p < 0.001; and for delta-PCT: 0.85 [0.78-0.92], p < 0.001. The optimal cut-off value for delta-PCT to indicate infection was 0.76 ng/mL (sensitivity 80 [70-88]%, specificity 86 [68-96]%). Neither absolute values nor changes in CRP, temperature, or WBC could predict infection. Conclusions. Our results suggest that delta-PCT values are superior to absolute values in indicating infection in intensive care patients. This trial is registered with ClinicalTrials.gov identifier: NCT02311816. PMID:27597981

  7. Delta Procalcitonin Is a Better Indicator of Infection Than Absolute Procalcitonin Values in Critically Ill Patients: A Prospective Observational Study

    PubMed Central

    Hankovszky, Péter; Hajdú, Edit

    2016-01-01

    Purpose. To investigate whether absolute value of procalcitonin (PCT) or the change (delta-PCT) is better indicator of infection in intensive care patients. Materials and Methods. Post hoc analysis of a prospective observational study. Patients with suspected new-onset infection were included in whom PCT, C-reactive protein (CRP), temperature, and leukocyte (WBC) values were measured on inclusion (t0) and data were also available from the previous day (t−1). Based on clinical and microbiological data, patients were grouped post hoc into infection- (I-) and noninfection- (NI-) groups. Results. Of the 114 patients, 85 (75%) had proven infection. PCT levels were similar at t−1: I-group (median [interquartile range]): 1.04 [0.40–3.57] versus NI-group: 0.53 [0.16–1.68], p = 0.444. By t0 PCT levels were significantly higher in the I-group: 4.62 [1.91–12.62] versus 1.12 [0.30–1.66], p = 0.018. The area under the curve to predict infection for absolute values of PCT was 0.64 [95% CI = 0.52–0.76], p = 0.022; for percentage change: 0.77 [0.66–0.87], p < 0.001; and for delta-PCT: 0.85 [0.78–0.92], p < 0.001. The optimal cut-off value for delta-PCT to indicate infection was 0.76 ng/mL (sensitivity 80 [70–88]%, specificity 86 [68-96]%). Neither absolute values nor changes in CRP, temperature, or WBC could predict infection. Conclusions. Our results suggest that delta-PCT values are superior to absolute values in indicating infection in intensive care patients. This trial is registered with ClinicalTrials.gov identifier: NCT02311816. PMID:27597981

  8. Calculation of absolute free energy of binding for theophylline and its analogs to RNA aptamer using nonequilibrium work values

    NASA Astrophysics Data System (ADS)

    Tanida, Yoshiaki; Ito, Masakatsu; Fujitani, Hideaki

    2007-08-01

    The massively parallel computation of absolute binding free energy with a well-equilibrated system (MP-CAFEE) has been developed [H. Fujitani, Y. Tanida, M. Ito, G. Jayachandran, C.D. Snow, M.R. Shirts, E.J. Sorin, V.S. Pande, J. Chem. Phys. 123 (2005) 084108]. As an application, we perform the binding affinity calculations of six theophylline-related ligands with RNA aptamer. Basically, our method is applicable when using many compute nodes to accelerate simulations, thus a parallel computing system is also developed. To further reduce the computational cost, the adequate non-uniform intervals of coupling constant λ, connecting two equilibrium states, namely bound and unbound, are determined. The absolute binding energies Δ G thus obtained have effective linear relation between the computed and experimental values. If the results of two other different methods are compared, thermodynamic integration (TI) and molecular mechanics Poisson-Boltzmann surface area (MM-PBSA) by the paper of Gouda et al. [H. Gouda, I.D. Kuntz, D.A. Case, P.A. Kollman, Biopolymers 68 (2003) 16], the predictive accuracy of the relative values ΔΔ G is almost comparable to that of TI: the correlation coefficients ( R) obtained are 0.99 (this work), 0.97 (TI), and 0.78 (MM-PBSA). On absolute binding energies meanwhile, a constant energy shift of ˜-7 kcal/mol against the experimental values is evident. To solve this problem, several presumable reasons are investigated.

  9. Prediction of postoperative pulmonary function following thoracic operations. Value of ventilation-perfusion scanning

    SciTech Connect

    Bria, W.F.; Kanarek, D.J.; Kazemi, H.

    1983-08-01

    Surgical resection of lung cancer is frequently required in patients with severely impaired lung function resulting from chronic obstructive pulmonary disease. Twenty patients with obstructive lung disease and cancer (mean preoperative forced expiratory volume in 1 second (FEV1) . 1.73 L) were studied preoperatively and postoperatively by spirometry and radionuclide perfusion, single-breath ventilation, and washout techniques to test the ability of these methods to predict preoperatively the partial loss of lung function by the resection. Postoperative FEV1 and forced vital capacity (FVC) were accurately predicted by the formula: postoperative FEV1 (or FVC) . preoperative FEV1 X percent function of regions of lung not to be resected (r . 0.88 and 0.95, respectively). Ventilation and perfusion scans are equally effective in prediction. Washout data add to the sophistication of the method by permitting the qualitative evaluation of ventilation during tidal breathing. Criteria for patients requiring the study are suggested.

  10. Advances in the Metrology of Absolute Value Assignments to Isotopic Reference Materials: Consequences from the Avogadro Project

    NASA Astrophysics Data System (ADS)

    Vocke, Robert; Rabb, Savelas

    2015-04-01

    All isotope amount ratios (hereafter referred to as isotope ratios) produced and measured on any mass spectrometer are biased. This unfortunate situation results mainly from the physical processes in the source area where ions are produced. Because the ionized atoms in poly-isotopic elements have different masses, such processes are typically mass dependent and lead to what is commonly referred to as mass fractionation (for thermal ionization and electron impact sources) and mass bias (for inductively coupled plasma sources.) This biasing process produces a measured isotope ratio that is either larger or smaller than the "true" ratio in the sample. This has led to the development of numerous fractionation "laws" that seek to correct for these effects, many of which are not based on the physical processes giving rise to the biases. The search for tighter and reproducible precisions has led to two isotope ratio measurement systems that exist side-by-side. One still seeks to measure "absolute" isotope ratios while the other utilizes an artifact based measurement system called a delta-scale. The common element between these two measurement systems is the utilization of isotope reference materials (iRMs). These iRMs are used to validate a fractionation "law" in the former case and function as a scale anchor in the latter. Many value assignments of iRMs are based on "best measurements" by the original groups producing the reference material, a not entirely satisfactory approach. Other iRMs, with absolute isotope ratio values, have been produced by calibrated measurements following the Atomic Weight approach (AW) pioneered by NBS nearly 50 years ago. Unfortunately, the AW is not capable of calibrating the new generation of iRMs to sufficient precision. So how do we get iRMs with isotope ratios of sufficient precision and without bias? Such a focus is not to denigrate the extremely precise delta-scale measurements presently being made on non-traditional and tradition

  11. Influence of Thin Slice Reconstruction on CT Brain Perfusion Analysis

    PubMed Central

    Bennink, Edwin; Oosterbroek, Jaap; Horsch, Alexander D.; Dankbaar, Jan Willem; Velthuis, Birgitta K.; Viergever, Max A.; de Jong, Hugo W. A. M.

    2015-01-01

    Objectives Although CT scanners generally allow dynamic acquisition of thin slices (1 mm), thick slice (≥5 mm) reconstruction is commonly used for stroke imaging to reduce data, processing time, and noise level. Thin slice CT perfusion (CTP) reconstruction may suffer less from partial volume effects, and thus yield more accurate quantitative results with increased resolution. Before thin slice protocols are to be introduced clinically, it needs to be ensured that this does not affect overall CTP constancy. We studied the influence of thin slice reconstruction on average perfusion values by comparing it with standard thick slice reconstruction. Materials and Methods From 50 patient studies, absolute and relative hemisphere averaged estimates of cerebral blood volume (CBV), cerebral blood flow (CBF), mean transit time (MTT), and permeability-surface area product (PS) were analyzed using 0.8, 2.4, 4.8, and 9.6 mm slice reconstructions. Specifically, the influence of Gaussian and bilateral filtering, the arterial input function (AIF), and motion correction on the perfusion values was investigated. Results Bilateral filtering gave noise levels comparable to isotropic Gaussian filtering, with less partial volume effects. Absolute CBF, CBV and PS were 22%, 14% and 46% lower with 0.8 mm than with 4.8 mm slices. If the AIF and motion correction were based on thin slices prior to reconstruction of thicker slices, these differences reduced to 3%, 4% and 3%. The effect of slice thickness on relative values was very small. Conclusions This study shows that thin slice reconstruction for CTP with unaltered acquisition protocol gives relative perfusion values without clinically relevant bias. It does however affect absolute perfusion values, of which CBF and CBV are most sensitive. Partial volume effects in large arteries and veins lead to overestimation of these values. The effects of reconstruction slice thickness should be taken into account when absolute perfusion values are

  12. Differential diagnostic value of computed tomography perfusion combined with vascular endothelial growth factor expression in head and neck lesions

    PubMed Central

    WANG, JIE; TANG, ZUOHUA; WANG, SHUYI; ZENG, WENJIAO; QIAN, WEN; WU, LINGJIE; WANG, WENZHONG; LUO, JIANFENG

    2016-01-01

    There are numerous types of head and neck lesions (HNLs), and conventional computed tomography (CT) has low specificity and sensitivity in the definitive and differential diagnosis of HNLs. The aim of the present study was to evaluate the value of perfusion CT (CTP) combined with vascular endothelial growth factor (VEGF) expression in the differentiation between malignant and benign HNLs. In total, 41 HNLs, which were pathologically confirmed, underwent CTP and VEGF expression analysis. All lesions were divided into three groups: Group A, benign hypovascular lesions; Group B, benign hypervascular lesions; and Group C, malignant lesions. Time density curve (TDC) and CTP parameters [maximum intensity projection (MIP), blood volume (BV), blood flow (BF), mean transit time and capillary permeability] were analyzed. The association between perfusion measurements and VEGF was assessed using Pearson's correlation. TDCs were classified into three types, and type I was more frequently identified in benign tumors (Groups A and B) compared with malignant tumors (Group C) (P=0.003). Malignant tumors primarily had a TDC of type II and III. MIP, BF and BV were all significantly higher in Groups B and C compared to Group A (P<0.01). VEGF expression of malignant tumors was significantly higher than benign tumors (P=0.007). No correlation was identified between VEGF and any CTP parameter. The present findings suggest that CTP combined with VEGF may differentiate between malignant and benign HNLs, and between benign hypovascular and hypervascular lesions. PMID:27123114

  13. Predictive value of exercise myocardial perfusion imaging in the Medicare population: the impact of the ability to exercise

    PubMed Central

    Menon, Venu; Houghtaling, Penny; Lieber, Elizabeth; Brunken, Richard C.; Cerqueira, Manuel D.; Jaber, Wael A.

    2014-01-01

    Background Although the prognostic value of quantitative single photon emission computed tomography myocardial perfusion imaging (MPI) with exercise and pharmacologic stress is well established, the prognostic and management value in the Medicare age population is less clear. Methods The prospectively populated Cleveland Clinic nuclear cardiology database was used to identify 5,994 consecutive pateints, age >65 years [1,664 (28%) exercise MPI, mean age 72.4±5.1, 74% male], who underwent MPI between January 2004 and January 2008. Clinical baseline variables, post test 90 days revascularization and MPI variables were analyzed. Overall and stratified nonparametric survival estimates were obtained by Kaplan-Meier method. Median follow-up time was 2.4 years. Parametric hazard modeling with bootstrap bagging methods was used to determine prognostic variables predicting mortality. Results There was no difference in mortality in patients with an abnormal MPI vs. those with normal MPI. Amongst the patients who underwent exercise MPI, there were 103 (6%) deaths and 121 (8.2%) revascularizations. Only lower exercise capacity (<7 METs) and higher end systolic volume (ESV) predicted mortality. Although a larger amount of ischemia influenced down stream revascularization ischemia, revascularization of patients with an abnormal exercise MPI did not offer a survival benefit (log rank P value=0.01). Conclusions In the a Medicare age population, exercise MPI perfusion variables influenced rates of revascularization but failed to provide incremental significant risk-stratification beyond exercise capacity. Maximum METs achieved appears to be a better predictor of survival. PMID:24649419

  14. Reducing the Standard Deviation in Multiple-Assay Experiments Where the Variation Matters but the Absolute Value Does Not

    PubMed Central

    Echenique-Robba, Pablo; Nelo-Bazán, María Alejandra; Carrodeguas, José A.

    2013-01-01

    When the value of a quantity for a number of systems (cells, molecules, people, chunks of metal, DNA vectors, so on) is measured and the aim is to replicate the whole set again for different trials or assays, despite the efforts for a near-equal design, scientists might often obtain quite different measurements. As a consequence, some systems’ averages present standard deviations that are too large to render statistically significant results. This work presents a novel correction method of a very low mathematical and numerical complexity that can reduce the standard deviation of such results and increase their statistical significance. Two conditions are to be met: the inter-system variations of matter while its absolute value does not, and a similar tendency in the values of must be present in the different assays (or in other words, the results corresponding to different assays must present a high linear correlation). We demonstrate the improvements this method offers with a cell biology experiment, but it can definitely be applied to any problem that conforms to the described structure and requirements and in any quantitative scientific field that deals with data subject to uncertainty. PMID:24205158

  15. Eosinophil count - absolute

    MedlinePlus

    Eosinophils; Absolute eosinophil count ... the white blood cell count to give the absolute eosinophil count. ... than 500 cells per microliter (cells/mcL). Normal value ranges may vary slightly among different laboratories. Talk ...

  16. Intraoperative indocyanine green fluorescence angiography--an objective evaluation of anastomotic perfusion in colorectal surgery.

    PubMed

    Protyniak, Bogdan; Dinallo, Anthony M; Boyan, William P; Dressner, Roy M; Arvanitis, Michael L

    2015-06-01

    The essentials for any bowel anastomosis are: adequate perfusion, tension free, accurate tissue apposition, and minimal local spillage. Traditionally, perfusion is measured by assessing palpable pulses in the mesentery, active bleeding at cut edges, and lack of tissue discoloration. However, subjective methods lack predictive accuracy for an anastomotic leak. We used intraoperative indocyanine green (ICG) fluorescence angiography to objectively assess colon perfusion before a bowel anastomosis. Seventy-seven laparoscopic colorectal operations, between June 2013 and June 2014, were retrospectively reviewed. The perfusion to the colon and ileum was clinically assessed, and then measured using the SPY Elite Imaging System. The absolute value provided an objective number on a 0-256 gray-scale to represent differences in ICG fluorescence intensity. The lowest absolute value was used in data analysis for each anastomosis (including small bowel) to represent the theoretical least perfused/weakest anastomotic area. The lowest absolute value recorded was 20 in a patient who underwent a laparoscopic right hemicolectomy for an adenoma, with no postoperative complications. Four low anterior resection patients had additional segments of descending colon resected. There was one mortality in a patient who underwent a laparoscopic right hemicolectomy. This study illustrates an initial experience with the SPY system in colorectal surgery. The SPY provides an objective, numerical value of bowel perfusion. However, evidence is scant as to the significance of these numbers. Large-scale randomized controlled trials are required to determine specific cutoff values correlated with surgical outcomes, specifically anastomotic leak rates. PMID:26031270

  17. The Reproducibility and Absolute Values of Echocardiographic Measurements of Left Ventricular Size and Function in Children are Algorithm Dependent

    PubMed Central

    Margossian, Renee; Chen, Shan; Sleeper, Lynn A.; Tani, Lloyd Y.; Shirali, Girish; Golding, Fraser; Tierney, Elif Seda Selamet; Altmann, Karen; Campbell, Michael J.; Szwast, Anita; Sharkey, Angela; Radojewski, Elizabeth; Colan, Steven D.

    2015-01-01

    Background Several quantification algorithms for measuring left ventricular (LV) size and function are used in clinical and research settings. We investigated the effect of the measurement algorithm and beat averaging on the reproducibility of measurements of the LV and assessed the magnitude of agreement among the algorithms in children with dilated cardiomyopathy (DCM). Methods Echocardiograms were obtained on 169 children from 8 clinical centers. Inter- and intra-reader reproducibility were assessed on measurements of LV volumes using biplane Simpson, modified Simpson (MS), and 5/6 x area x length (5/6AL) algorithms. Percent error (%error) was calculated as the inter- or intra-reader difference / mean x 100. Single beat measurements and the 3-beat average (3BA) were compared. Intra-class correlation coefficients (ICC) were calculated to assess agreement. Results Single beat inter-reader reproducibility was lowest (%error was highest) using biplane Simpson; 5/6AL and MS were similar but significantly better than biplane Simpson (p<.05). Single beat intra-reader reproducibility was highest using 5/6AL (p<.05). 3BA improved reproducibility for almost all measures (p<.05). Reproducibility in both single and 3BA values fell with greater LV dilation and systolic dysfunction (p<.05). ICCs were > 0.95 across measures, although absolute volume and mass values were systematically lower for biplane Simpson compared to MS and to 5/6AL. Conclusions The reproducibility of LV size and function measurements in children with DCM is highest using the 5/6AL algorithm, and can be further improved by using 3BA. However, values derived from different algorithms are not interchangeable. PMID:25728351

  18. A model for filtered backprojection reconstruction artifacts due to time-varying attenuation values in perfusion C-arm CT.

    PubMed

    Fieselmann, Andreas; Dennerlein, Frank; Deuerling-Zheng, Yu; Boese, Jan; Fahrig, Rebecca; Hornegger, Joachim

    2011-06-21

    Filtered backprojection is the basis for many CT reconstruction tasks. It assumes constant attenuation values of the object during the acquisition of the projection data. Reconstruction artifacts can arise if this assumption is violated. For example, contrast flow in perfusion imaging with C-arm CT systems, which have acquisition times of several seconds per C-arm rotation, can cause this violation. In this paper, we derived and validated a novel spatio-temporal model to describe these kinds of artifacts. The model separates the temporal dynamics due to contrast flow from the scan and reconstruction parameters. We introduced derivative-weighted point spread functions to describe the spatial spread of the artifacts. The model allows prediction of reconstruction artifacts for given temporal dynamics of the attenuation values. Furthermore, it can be used to systematically investigate the influence of different reconstruction parameters on the artifacts. We have shown that with optimized redundancy weighting function parameters the spatial spread of the artifacts around a typical arterial vessel can be reduced by about 70%. Finally, an inversion of our model could be used as the basis for novel dynamic reconstruction algorithms that further minimize these artifacts.

  19. A model for filtered backprojection reconstruction artifacts due to time-varying attenuation values in perfusion C-arm CT

    NASA Astrophysics Data System (ADS)

    Fieselmann, Andreas; Dennerlein, Frank; Deuerling-Zheng, Yu; Boese, Jan; Fahrig, Rebecca; Hornegger, Joachim

    2011-06-01

    Filtered backprojection is the basis for many CT reconstruction tasks. It assumes constant attenuation values of the object during the acquisition of the projection data. Reconstruction artifacts can arise if this assumption is violated. For example, contrast flow in perfusion imaging with C-arm CT systems, which have acquisition times of several seconds per C-arm rotation, can cause this violation. In this paper, we derived and validated a novel spatio-temporal model to describe these kinds of artifacts. The model separates the temporal dynamics due to contrast flow from the scan and reconstruction parameters. We introduced derivative-weighted point spread functions to describe the spatial spread of the artifacts. The model allows prediction of reconstruction artifacts for given temporal dynamics of the attenuation values. Furthermore, it can be used to systematically investigate the influence of different reconstruction parameters on the artifacts. We have shown that with optimized redundancy weighting function parameters the spatial spread of the artifacts around a typical arterial vessel can be reduced by about 70%. Finally, an inversion of our model could be used as the basis for novel dynamic reconstruction algorithms that further minimize these artifacts.

  20. [Value of liver perfusion imaging of 256-slice CT 
in evaluation of the cirrhosis].

    PubMed

    Zhan, Yuefu; Wu, Yehua; Chen, Jianqiang; Liu, Fan; Han, Xiangjun

    2016-01-01

    目的:探讨256-CT灌注成像评价代偿期和失代偿期肝硬化的价值。方法:分析2012年12月至2014年6月经肝穿刺活检和影像学、血液学、生物化学检查筛选出的20例肝硬化患者,根据肝穿刺结果和Child-Pugh评分将患者分为肝硬化代偿期组(n=8)和肝硬化失代偿期组(n=12),并选择同期无肝脾疾病者作为对照组(n=11),利用256-CT进行肝灌注(256-CT liver perfusion,256-CTP)。采用256-CTP模式计算灌注参数,包括肝动脉灌注(hepatic arterial perfusion,HAP)、门静脉灌注(portal venous perfusion,PVP)、总肝灌注(total liver perfusion,TLP)、肝动脉灌注指数(hepatic perfusion index,HPI);采用大体灌注模式计算灌注参数,包括肝灌注(liver perfusion,LP)、增强峰值(peak enhanced,PE)、达峰时间(time to peak,TTP)、血容积(blood volume,BV)。采用非参数Spearman检验分析肝硬化分期与各灌注参数值之间的相关性;采用ROC曲线评价各灌注指标预测肝硬化程度的能力,选择约登指数最大作为截断点,计算曲线下面积(area under curve,AUC)、敏感度及特异度。结果:对照组、肝硬化代偿期组、肝硬化失代偿期组PVP分别为(76.63±37.26),(38.78±16.13)和(36.14±15.31) mL/(100 mL·min);TLP分别为(98.48±43.58),(55.63±14.47)和(54.41±
20.81) mL/(100 mL·min);PE分别为(55.62±18.25),(44.11±5.79)和(41.08±7.74) HU,均表现为逐渐下降趋势,各组间差异均有统计学意义(均P<0.05);HPI分别为(19.50±6.08)%,(31.81±16.48)%和(34.47±16.04)%;TTP分别为(37.32±8.59),(47.06±14.61)和(59.86±20.87) s,表现为逐渐上升趋势,各组间差异均有统计学意义(均P<0.05)。HAP,LP和BV各组间比较差异均无统计学意义(均P>0.05)。PVP,TLP,PE和LP与肝硬化分期呈负相关(分别r=−0.592,−0.567,−0.409和−0.569,均P<0.05);HPI,TTP与肝硬化分期呈正相关(分别r=0.434和0

  1. Generalized approach for using unbiased symmetric metrics with negative values: normalized mean bias factor and normalized mean absolute error factor

    EPA Science Inventory

    Unbiased symmetric metrics provide a useful measure to quickly compare two datasets, with similar interpretations for both under and overestimations. Two examples include the normalized mean bias factor and normalized mean absolute error factor. However, the original formulations...

  2. Comparison of Hemodynamic Effects and Negative Predictive Value of Normal Adenosine Gated Myocardial Perfusion Scan With or Without Caffeine Abstinence

    PubMed Central

    uz Zaman, Maseeh; Fatima, Nosheen; Zaman, Areeba; Zaman, Unaiza; Tahseen, Rabia

    2016-01-01

    For vasodilator stress, myocardial perfusion imaging (MPI) with at least 12-h caffeine abstinence is recommended, as it attenuates cardiovascular hyperemic response of adenosine and dipyridamole. However, many published conflicting results have shown no significant effect upon perfusion abnormalities in MPI performed without caffeine abstinence. The aim of this study was to compare the hemodynamic changes and negative predictive value (NPV) of normal MPIs with adenosine stress performed with or without caffeine abstinence. This was a prospective study that accrued 50 patients from May 2013 till September 2013 and followed till November 2014. These patients had a normal adenosine-gated MPI (GMPI) with technetium-99m methoxy isobutyl isonitrile (99mTc-MIBI) after 12-h caffeine abstinence (no-caffeine). Next day, all patients had a repeat adenosine stress within 60 min after ingestion of a cup of coffee (about 80 mg of caffeine) followed by no MPI in 30 patients due to concern about radiation dose (prior-caffeine adenosine—no MPI; group A). Twenty patients opted for a repeat MPI (prior-caffeine adenosine—MPI; group B). Adenosine-induced hemodynamic response and NPV of the normal MPI with no-caffeine and prior-caffeine protocols were compared. The mean age of the study cohort was 57 ± 9 years with a male-to-female ratio of 76:24% and mean body mass index (BMI) of 26.915 ± 4.121 kg/m2. Prevalence of hypertension, diabetes, dyslipidemia, and positive family history were 76%, 20%, 22%, and 17%, respectively. Comparison of group A with group B revealed no significant difference in demographic parameters, hemodynamic or electrocardiography (ECG) parameters, or left ventricular (LV) function parameters during adenosine intervention with prior-caffeine and no-caffeine protocols. During the follow-up, no fatal myocardial infarction (MI) was reported but 6 nonfatal MIs were reported based upon the history of short hospitalization for chest pain but without biochemical or

  3. Comparison of Hemodynamic Effects and Negative Predictive Value of Normal Adenosine Gated Myocardial Perfusion Scan With or Without Caffeine Abstinence

    PubMed Central

    uz Zaman, Maseeh; Fatima, Nosheen; Zaman, Areeba; Zaman, Unaiza; Tahseen, Rabia

    2016-01-01

    For vasodilator stress, myocardial perfusion imaging (MPI) with at least 12-h caffeine abstinence is recommended, as it attenuates cardiovascular hyperemic response of adenosine and dipyridamole. However, many published conflicting results have shown no significant effect upon perfusion abnormalities in MPI performed without caffeine abstinence. The aim of this study was to compare the hemodynamic changes and negative predictive value (NPV) of normal MPIs with adenosine stress performed with or without caffeine abstinence. This was a prospective study that accrued 50 patients from May 2013 till September 2013 and followed till November 2014. These patients had a normal adenosine-gated MPI (GMPI) with technetium-99m methoxy isobutyl isonitrile (99mTc-MIBI) after 12-h caffeine abstinence (no-caffeine). Next day, all patients had a repeat adenosine stress within 60 min after ingestion of a cup of coffee (about 80 mg of caffeine) followed by no MPI in 30 patients due to concern about radiation dose (prior-caffeine adenosine—no MPI; group A). Twenty patients opted for a repeat MPI (prior-caffeine adenosine—MPI; group B). Adenosine-induced hemodynamic response and NPV of the normal MPI with no-caffeine and prior-caffeine protocols were compared. The mean age of the study cohort was 57 ± 9 years with a male-to-female ratio of 76:24% and mean body mass index (BMI) of 26.915 ± 4.121 kg/m2. Prevalence of hypertension, diabetes, dyslipidemia, and positive family history were 76%, 20%, 22%, and 17%, respectively. Comparison of group A with group B revealed no significant difference in demographic parameters, hemodynamic or electrocardiography (ECG) parameters, or left ventricular (LV) function parameters during adenosine intervention with prior-caffeine and no-caffeine protocols. During the follow-up, no fatal myocardial infarction (MI) was reported but 6 nonfatal MIs were reported based upon the history of short hospitalization for chest pain but without biochemical or

  4. Comparison of Hemodynamic Effects and Negative Predictive Value of Normal Adenosine Gated Myocardial Perfusion Scan With or Without Caffeine Abstinence.

    PubMed

    Uz Zaman, Maseeh; Fatima, Nosheen; Zaman, Areeba; Zaman, Unaiza; Tahseen, Rabia

    2016-09-01

    For vasodilator stress, myocardial perfusion imaging (MPI) with at least 12-h caffeine abstinence is recommended, as it attenuates cardiovascular hyperemic response of adenosine and dipyridamole. However, many published conflicting results have shown no significant effect upon perfusion abnormalities in MPI performed without caffeine abstinence. The aim of this study was to compare the hemodynamic changes and negative predictive value (NPV) of normal MPIs with adenosine stress performed with or without caffeine abstinence. This was a prospective study that accrued 50 patients from May 2013 till September 2013 and followed till November 2014. These patients had a normal adenosine-gated MPI (GMPI) with technetium-99m methoxy isobutyl isonitrile ((99m)Tc-MIBI) after 12-h caffeine abstinence (no-caffeine). Next day, all patients had a repeat adenosine stress within 60 min after ingestion of a cup of coffee (about 80 mg of caffeine) followed by no MPI in 30 patients due to concern about radiation dose (prior-caffeine adenosine-no MPI; group A). Twenty patients opted for a repeat MPI (prior-caffeine adenosine-MPI; group B). Adenosine-induced hemodynamic response and NPV of the normal MPI with no-caffeine and prior-caffeine protocols were compared. The mean age of the study cohort was 57 ± 9 years with a male-to-female ratio of 76:24% and mean body mass index (BMI) of 26.915 ± 4.121 kg/m(2). Prevalence of hypertension, diabetes, dyslipidemia, and positive family history were 76%, 20%, 22%, and 17%, respectively. Comparison of group A with group B revealed no significant difference in demographic parameters, hemodynamic or electrocardiography (ECG) parameters, or left ventricular (LV) function parameters during adenosine intervention with prior-caffeine and no-caffeine protocols. During the follow-up, no fatal myocardial infarction (MI) was reported but 6 nonfatal MIs were reported based upon the history of short hospitalization for chest pain but without biochemical or

  5. Generalized approach for using unbiased symmetric metrics with negative values: normalized mean bias factor and normalized mean absolute error factor

    SciTech Connect

    Gustafson, William I.; Yu, Shaocai

    2012-10-23

    Unbiased symmetric metrics provide a useful measure to quickly compare two datasets, with similar interpretations for both under and overestimations. Two examples include the normalized mean bias factor and normalized mean absolute error factor. However, the original formulations of these metrics are only valid for datasets with positive means. This paper presents a methodology to use and interpret the metrics with datasets that have negative means. The updated formulations give identical results compared to the original formulations for the case of positive means, so researchers are encouraged to use the updated formulations going forward without introducing ambiguity.

  6. Absolute reliability of hamstring to quadriceps strength imbalance ratios calculated using peak torque, joint angle-specific torque and joint ROM-specific torque values.

    PubMed

    Ayala, F; De Ste Croix, M; Sainz de Baranda, P; Santonja, F

    2012-11-01

    The main purpose of this study was to determine the absolute reliability of conventional (H/Q(CONV)) and functional (H/Q(FUNC)) hamstring to quadriceps strength imbalance ratios calculated using peak torque values, 3 different joint angle-specific torque values (10°, 20° and 30° of knee flexion) and 4 different joint ROM-specific average torque values (0-10°, 11-20°, 21-30° and 0-30° of knee flexion) adopting a prone position in recreational athletes. A total of 50 recreational athletes completed the study. H/Q(CONV) and H/Q(FUNC) ratios were recorded at 3 different angular velocities (60, 180 and 240°/s) on 3 different occasions with a 72-96 h rest interval between consecutive testing sessions. Absolute reliability was examined through typical percentage error (CVTE), percentage change in the mean (CM) and intraclass correlations (ICC) as well as their respective confidence limits. H/Q(CONV) and H/Q(FUNC) ratios calculated using peak torque values showed moderate reliability values, with CM scores lower than 2.5%, CV(TE) values ranging from 16 to 20% and ICC values ranging from 0.3 to 0.7. However, poor absolute reliability scores were shown for H/Q(CONV) and H/Q(FUNC) ratios calculated using joint angle-specific torque values and joint ROM-specific average torque values, especially for H/Q(FUNC) ratios (CM: 1-23%; CV(TE): 22-94%; ICC: 0.1-0.7). Therefore, the present study suggests that the CV(TE) values reported for H/Q(CONV) and H/Q(FUNC) (≈18%) calculated using peak torque values may be sensitive enough to detect large changes usually observed after rehabilitation programmes but not acceptable to examine the effect of preventitive training programmes in healthy individuals. The clinical reliability of hamstring to quadriceps strength ratios calculated using joint angle-specific torque values and joint ROM-specific average torque values are questioned and should be re-evaluated in future research studies.

  7. The warm and cold neutral phase in the local interstellar medium at absolute value of B greater than or equal to 10 deg

    NASA Astrophysics Data System (ADS)

    Poppel, W. G. L.; Marronetti, P.; Benaglia, P.

    1994-07-01

    We made a systematic separation of both the neutral phases using the atlases of 21-cm profiles of Heiles & Habing (1974) and Colomb et al. (1980), complemented with other data. First, we fitted the emission of the warm neutral medium (WNM) by means of a broad Gaussian curve (velocity dispersion sigma approximately 10-14 km/s). We derived maps of the column densities NWH and the radial velocities VW of the WNM. Its overall distribution appears to be very inhomogeneous with a large hole in the range b greater than or equal to +50 deg. However, if the hole is excluded, the mean latitude-profiles admit a rough cosec absolute value of b-fit common to both hemispheres. A kinematical analysis of VW for the range 10 deg less than or equal to absolute value of b less than or equal to 40 deg indicates a mean differential rotation with a small nodal deviation. At absolute value of b greater than 50 deg VW is negative, with larger values and discontinuities in the north. On the mean, sigma increases for absolute value of b decreasing, as is expected from differential rotation. From a statistical study of the peaks of the residual profiles we derived some characteristics of the cold neutral medium (CNM). The latter is generally characterized by a single component of sigma approximately 2-6 km/s. Additionally we derived the sky-distribution of the column densities NCH and the radial velocities VC of the CNM within bins of 1.2 deg sec b x 1 deg in l, b. Furthermore, we focused on the characteristics of Linblad's feature A of cool gas by considering the narrow ridge of local H I, which appears in the b-V contour maps at fixed l (e.g. Schoeber 1976). The ridge appears to be the main component of the CNM. We suggest a scenario for the formulation and evolution of the Gould belt system of stars and gas on the basis of an explosive event within a shingle of cold dense gas tilted to the galactic plane. The scenario appears to be consistent with the results found for both the neutral

  8. Absolute Cerebral Blood Flow Infarction Threshold for 3-Hour Ischemia Time Determined with CT Perfusion and 18F-FFMZ-PET Imaging in a Porcine Model of Cerebral Ischemia

    PubMed Central

    Cockburn, Neil; Kovacs, Michael

    2016-01-01

    CT Perfusion (CTP) derived cerebral blood flow (CBF) thresholds have been proposed as the optimal parameter for distinguishing the infarct core prior to reperfusion. Previous threshold-derivation studies have been limited by uncertainties introduced by infarct expansion between the acute phase of stroke and follow-up imaging, or DWI lesion reversibility. In this study a model is proposed for determining infarction CBF thresholds at 3hr ischemia time by comparing contemporaneously acquired CTP derived CBF maps to 18F-FFMZ-PET imaging, with the objective of deriving a CBF threshold for infarction after 3 hours of ischemia. Endothelin-1 (ET-1) was injected into the brain of Duroc-Cross pigs (n = 11) through a burr hole in the skull. CTP images were acquired 10 and 30 minutes post ET-1 injection and then every 30 minutes for 150 minutes. 370 MBq of 18F-FFMZ was injected ~120 minutes post ET-1 injection and PET images were acquired for 25 minutes starting ~155–180 minutes post ET-1 injection. CBF maps from each CTP acquisition were co-registered and converted into a median CBF map. The median CBF map was co-registered to blood volume maps for vessel exclusion, an average CT image for grey/white matter segmentation, and 18F-FFMZ-PET images for infarct delineation. Logistic regression and ROC analysis were performed on infarcted and non-infarcted pixel CBF values for each animal that developed infarct. Six of the eleven animals developed infarction. The mean CBF value corresponding to the optimal operating point of the ROC curves for the 6 animals was 12.6 ± 2.8 mL·min-1·100g-1 for infarction after 3 hours of ischemia. The porcine ET-1 model of cerebral ischemia is easier to implement then other large animal models of stroke, and performs similarly as long as CBF is monitored using CTP to prevent reperfusion. PMID:27347877

  9. Absolute Cerebral Blood Flow Infarction Threshold for 3-Hour Ischemia Time Determined with CT Perfusion and 18F-FFMZ-PET Imaging in a Porcine Model of Cerebral Ischemia.

    PubMed

    Wright, Eric A; d'Esterre, Christopher D; Morrison, Laura B; Cockburn, Neil; Kovacs, Michael; Lee, Ting-Yim

    2016-01-01

    CT Perfusion (CTP) derived cerebral blood flow (CBF) thresholds have been proposed as the optimal parameter for distinguishing the infarct core prior to reperfusion. Previous threshold-derivation studies have been limited by uncertainties introduced by infarct expansion between the acute phase of stroke and follow-up imaging, or DWI lesion reversibility. In this study a model is proposed for determining infarction CBF thresholds at 3hr ischemia time by comparing contemporaneously acquired CTP derived CBF maps to 18F-FFMZ-PET imaging, with the objective of deriving a CBF threshold for infarction after 3 hours of ischemia. Endothelin-1 (ET-1) was injected into the brain of Duroc-Cross pigs (n = 11) through a burr hole in the skull. CTP images were acquired 10 and 30 minutes post ET-1 injection and then every 30 minutes for 150 minutes. 370 MBq of 18F-FFMZ was injected ~120 minutes post ET-1 injection and PET images were acquired for 25 minutes starting ~155-180 minutes post ET-1 injection. CBF maps from each CTP acquisition were co-registered and converted into a median CBF map. The median CBF map was co-registered to blood volume maps for vessel exclusion, an average CT image for grey/white matter segmentation, and 18F-FFMZ-PET images for infarct delineation. Logistic regression and ROC analysis were performed on infarcted and non-infarcted pixel CBF values for each animal that developed infarct. Six of the eleven animals developed infarction. The mean CBF value corresponding to the optimal operating point of the ROC curves for the 6 animals was 12.6 ± 2.8 mL·min-1·100g-1 for infarction after 3 hours of ischemia. The porcine ET-1 model of cerebral ischemia is easier to implement then other large animal models of stroke, and performs similarly as long as CBF is monitored using CTP to prevent reperfusion. PMID:27347877

  10. WE-G-18C-02: Estimation of Optimal B-Value Set for Obtaining Apparent Diffusion Coefficient Free From Perfusion in Non-Small Cell Lung Cancer

    SciTech Connect

    Karki, K; Hugo, G; Ford, J; Saraiya, S; Weiss, E; Olsen, K; Groves, R

    2014-06-15

    Purpose: Diffusion-weighted MRI (DW-MRI) is increasingly being investigated for radiotherapy planning and response assessment. Selection of a limited number of b-values in DW-MRI is important to keep geometrical variations low and imaging time short. We investigated various b-value sets to determine an optimal set for obtaining monoexponential apparent diffusion coefficient (ADC) close to perfusion-insensitive intravoxel incoherent motion (IVIM) model ADC (ADCIVIM) in nonsmall cell lung cancer. Methods: Seven patients had 27 DW-MRI scans before and during radiotherapy in a 1.5T scanner. Respiratory triggering was applied to the echo-planar DW-MRI with TR=4500ms approximately, TE=74ms, pixel size=1.98X1.98mm{sub 2}, slice thickness=4–6mm and 7 axial slices. Diffusion gradients were applied to all three axes producing traceweighted images with eight b-values of 0–1000μs/μm{sup 2}. Monoexponential model ADC values using various b-value sets were compared to ADCIVIM using all b-values. To compare the relative noise in ADC maps, intra-scan coefficient of variation (CV) of active tumor volumes was computed. Results: ADCIVIM, perfusion coefficient and perfusion fraction for tumor volumes were in the range of 880-1622 μm{sup 2}/s, 8119-33834 μm{sup 2}/s and 0.104–0.349, respectively. ADC values using sets of 250, 800 and 1000; 250, 650 and 1000; and 250–1000μs/μm{sup 2} only were not significantly different from ADCIVIM(p>0.05, paired t-test). Error in ADC values for 0–1000, 50–1000, 100–1000, 250–1000, 500–1000, and three b-value sets- 250, 500 and 1000; 250, 650 and 1000; and 250, 800 and 1000μs/μm{sup 2} were 15.0, 9.4, 5.6, 1.4, 11.7, 3.7, 2.0 and 0.2% relative to the reference-standard ADCIVIM, respectively. Mean intrascan CV was 20.2, 20.9, 21.9, 24.9, 32.6, 25.8, 25.4 and 24.8%, respectively, whereas that for ADCIVIM was 23.3%. Conclusion: ADC values of two 3 b-value sets

  11. Mapping the microvascular and the associated absolute values of oxy-hemoglobin concentration through turbid media via local off-set diffuse optical imaging

    NASA Astrophysics Data System (ADS)

    Chen, Chen; Klämpfl, Florian; Stelzle, Florian; Schmidt, Michael

    2014-11-01

    An imging resolution of micron-scale has not yet been discovered by diffuse optical imaging (DOI), while a superficial response was eliminated. In this work, we report on a new approach of DOI with a local off-set alignment to subvert the common boundary conditions of the modified Beer-Lambert Law (MBLL). It can resolve a superficial target in micron scale under a turbid media. To validate both major breakthroughs, this system was used to recover a subsurface microvascular mimicking structure under an skin equivalent phantom. This microvascular was included with oxy-hemoglobin solution in variant concentrations to distiguish the absolute values of CtRHb and CtHbO2 . Experimental results confirmed the feasibility of recovering the target vascular of 50 µm in diameter, and graded the values of the concentrations of oxy-hemoglobin from 10 g/L to 50 g/L absolutely. Ultimately, this approach could evolve into a non-invasive imaging system to map the microvascular pattern and the associated oximetry under a human skin in-vivo.

  12. Measurement of the B-->pi l nu branching fraction and determination of absolute value of V(ub) with tagged B mesons.

    PubMed

    Aubert, B; Barate, R; Bona, M; Boutigny, D; Couderc, F; Karyotakis, Y; Lees, J P; Poireau, V; Tisserand, V; Zghiche, A; Grauges, E; Palano, A; Chen, J C; Qi, N D; Rong, G; Wang, P; Zhu, Y S; Eigen, G; Ofte, I; Stugu, B; Abrams, G S; Battaglia, M; Brown, D N; Button-Shafer, J; Cahn, R N; Charles, E; Gill, M S; Groysman, Y; Jacobsen, R G; Kadyk, J A; Kerth, L T; Kolomensky, Yu G; Kukartsev, G; Lynch, G; Mir, L M; Orimoto, T J; Pripstein, M; Roe, N A; Ronan, M T; Wenzel, W A; del Amo Sanchez, P; Barrett, M; Ford, K E; Harrison, T J; Hart, A J; Hawkes, C M; Morgan, S E; Watson, A T; Held, T; Koch, H; Lewandowski, B; Pelizaeus, M; Peters, K; Schroeder, T; Steinke, M; Boyd, J T; Burke, J P; Cottingham, W N; Walker, D; Cuhadar-Donszelmann, T; Fulsom, B G; Hearty, C; Knecht, N S; Mattison, T S; McKenna, J A; Khan, A; Kyberd, P; Saleem, M; Sherwood, D J; Teodorescu, L; Blinov, V E; Bukin, A D; Druzhinin, V P; Golubev, V B; Onuchin, A P; Serednyakov, S I; Skovpen, Yu I; Solodov, E P; Todyshev, K Yu; Best, D S; Bondioli, M; Bruinsma, M; Chao, M; Curry, S; Eschrich, I; Kirkby, D; Lankford, A J; Lund, P; Mandelkern, M; Mommsen, R K; Roethel, W; Stoker, D P; Abachi, S; Buchanan, C; Foulkes, S D; Gary, J W; Long, O; Shen, B C; Wang, K; Zhang, L; Hadavand, H K; Hill, E J; Paar, H P; Rahatlou, S; Sharma, V; Berryhill, J W; Campagnari, C; Cunha, A; Dahmes, B; Hong, T M; Kovalskyi, D; Richman, J D; Beck, T W; Eisner, A M; Flacco, C J; Heusch, C A; Kroseberg, J; Lockman, W S; Nesom, G; Schalk, T; Schumm, B A; Seiden, A; Spradlin, P; Williams, D C; Wilson, M G; Albert, J; Chen, E; Dvoretskii, A; Fang, F; Hitlin, D G; Narsky, I; Piatenko, T; Porter, F C; Ryd, A; Samuel, A; Mancinelli, G; Meadows, B T; Mishra, K; Sokoloff, M D; Blanc, F; Bloom, P C; Chen, S; Ford, W T; Hirschauer, J F; Kreisel, A; Nagel, M; Nauenberg, U; Olivas, A; Ruddick, W O; Smith, J G; Ulmer, K A; Wagner, S R; Zhang, J; Chen, A; Eckhart, E A; Soffer, A; Toki, W H; Wilson, R J; Winklmeier, F; Zeng, Q; Altenburg, D D; Feltresi, E; Hauke, A; Jasper, H; Petzold, A; Spaan, B; Brandt, T; Klose, V; Lacker, H M; Mader, W F; Nogowski, R; Schubert, J; Schubert, K R; Schwierz, R; Sundermann, J E; Volk, A; Bernard, D; Bonneaud, G R; Grenier, P; Latour, E; Thiebaux, Ch; Verderi, M; Clark, P J; Gradl, W; Muheim, F; Playfer, S; Robertson, A I; Xie, Y; Andreotti, M; Bettoni, D; Bozzi, C; Calabrese, R; Cibinetto, G; Luppi, E; Negrini, M; Petrella, A; Piemontese, L; Prencipe, E; Anulli, F; Baldini-Ferroli, R; Calcaterra, A; de Sangro, R; Finocchiaro, G; Pacetti, S; Patteri, P; Peruzzi, I M; Piccolo, M; Rama, M; Zallo, A; Buzzo, A; Capra, R; Contri, R; Lo Vetere, M; Macri, M M; Monge, M R; Passaggio, S; Patrignani, C; Robutti, E; Santroni, A; Tosi, S; Brandenburg, G; Chaisanguanthum, K S; Morii, M; Wu, J; Dubitzky, R S; Marks, J; Schenk, S; Uwer, U; Bard, D J; Bhimji, W; Bowerman, D A; Dauncey, P D; Egede, U; Flack, R L; Nash, J A; Nikolich, M B; Panduro Vazquez, W; Behera, P K; Chai, X; Charles, M J; Mallik, U; Meyer, N T; Ziegler, V; Cochran, J; Crawley, H B; Dong, L; Eyges, V; Meyer, W T; Prell, S; Rosenberg, E I; Rubin, A E; Gritsan, A V; Denig, A G; Fritsch, M; Schott, G; Arnaud, N; Davier, M; Grosdidier, G; Höcker, A; Le Diberder, F; Lepeltier, V; Lutz, A M; Oyanguren, A; Pruvot, S; Rodier, S; Roudeau, P; Schune, M H; Stocchi, A; Wang, W F; Wormser, G; Cheng, C H; Lange, D J; Wright, D M; Chavez, C A; Forster, I J; Fry, J R; Gabathuler, E; Gamet, R; George, K A; Hutchcroft, D E; Payne, D J; Schofield, K C; Touramanis, C; Bevan, A J; Di Lodovico, F; Menges, W; Sacco, R; Cowan, G; Flaecher, H U; Hopkins, D A; Jackson, P S; McMahon, T R; Ricciardi, S; Salvatore, F; Wren, A C; Brown, D N; Davis, C L; Allison, J; Barlow, N R; Barlow, R J; Chia, Y M; Edgar, C L; Lafferty, G D; Naisbit, M T; Williams, J C; Yi, J I; Chen, C; Hulsbergen, W D; Jawahery, A; Lae, C K; Roberts, D A; Simi, G; Blaylock, G; Dallapiccola, C; Hertzbach, S S; Li, X; Moore, T B; Saremi, S; Staengle, H; Cowan, R; Sciolla, G; Sekula, S J; Spitznagel, M; Taylor, F; Yamamoto, R K; Kim, H; McLachlin, S E; Patel, P M; Robertson, S H; Lazzaro, A; Lombardo, V; Palombo, F; Bauer, J M; Cremaldi, L; Eschenburg, V; Godang, R; Kroeger, R; Sanders, D A; Summers, D J; Zhao, H W; Brunet, S; Côté, D; Simard, M; Taras, P; Viaud, F B; Nicholson, H; Cavallo, N; De Nardo, G; Fabozzi, F; Gatto, C; Lista, L; Monorchio, D; Paolucci, P; Piccolo, D; Sciacca, C; Baak, M; Raven, G; Snoek, H L; Jessop, C P; Losecco, J M; Allmendinger, T; Benelli, G; Gan, K K; Honscheid, K; Hufnagel, D; Jackson, P D; Kagan, H; Kass, R; Rahimi, A M; Ter-Antonyan, R; Wong, Q K; Blount, N L; Brau, J; Frey, R; Igonkina, O; Lu, M; Rahmat, R; Sinev, N B; Strom, D; Strube, J; Torrence, E; Gaz, A; Margoni, M; Morandin, M; Pompili, A; Posocco, M; Rotondo, M; Simonetto, F; Stroili, R; Voci, C; Benayoun, M; Chauveau, J; Briand, H; David, P; Del Buono, L; de la Vaissière, Ch; Hamon, O; Hartfiel, B L; John, M J J; Leruste, Ph; Malclès, J; Ocariz, J; Roos, L; Therin, G; Gladney, L; Panetta, J; Biasini, M; Covarelli, R; Angelini, C; Batignani, G; Bettarini, S; Bucci, F; Calderini, G; Carpinelli, M; Cenci, R; Forti, F; Giorgi, M A; Lusiani, A; Marchiori, G; Mazur, M A; Morganti, M; Neri, N; Paoloni, E; Rizzo, G; Walsh, J J; Haire, M; Judd, D; Wagoner, D E; Biesiada, J; Danielson, N; Elmer, P; Lau, Y P; Lu, C; Olsen, J; Smith, A J S; Telnov, A V; Bellini, F; Cavoto, G; D'Orazio, A; del Re, D; Di Marco, E; Faccini, R; Ferrarotto, F; Ferroni, F; Gaspero, M; Li Gioi, L; Mazzoni, M A; Morganti, S; Piredda, G; Polci, F; Safai Tehrani, F; Voena, C; Ebert, M; Schröder, H; Waldi, R; Adye, T; De Groot, N; Franek, B; Olaiya, E O; Wilson, F F; Aleksan, R; Emery, S; Gaidot, A; Ganzhur, S F; Hamel de Monchenault, G; Kozanecki, W; Legendre, M; Vasseur, G; Yèche, Ch; Zito, M; Chen, X R; Liu, H; Park, W; Purohit, M V; Wilson, J R; Allen, M T; Aston, D; Bartoldus, R; Bechtle, P; Berger, N; Claus, R; Coleman, J P; Convery, M R; Cristinziani, M; Dingfelder, J C; Dorfan, J; Dubois-Felsmann, G P; Dujmic, D; Dunwoodie, W; Field, R C; Glanzman, T; Gowdy, S J; Graham, M T; Halyo, V; Hast, C; Hryn'ova, T; Innes, W R; Kelsey, M H; Kim, P; Leith, D W G S; Li, S; Luitz, S; Luth, V; Lynch, H L; MacFarlane, D B; Marsiske, H; Messner, R; Muller, D R; O'Grady, C P; Ozcan, V E; Perazzo, A; Perl, M; Pulliam, T; Ratcliff, B N; Roodman, A; Salnikov, A A; Schindler, R H; Schwiening, J; Snyder, A; Stelzer, J; Su, D; Sullivan, M K; Suzuki, K; Swain, S K; Thompson, J M; Va'vra, J; van Bakel, N; Weaver, M; Weinstein, A J R; Wisniewski, W J; Wittgen, M; Wright, D H; Yarritu, A K; Yi, K; Young, C C; Burchat, P R; Edwards, A J; Majewski, S A; Petersen, B A; Roat, C; Wilden, L; Ahmed, S; Alam, M S; Bula, R; Ernst, J A; Jain, V; Pan, B; Saeed, M A; Wappler, F R; Zain, S B; Bugg, W; Krishnamurthy, M; Spanier, S M; Eckmann, R; Ritchie, J L; Satpathy, A; Schilling, C J; Schwitters, R F; Izen, J M; Lou, X C; Ye, S; Bianchi, F; Gallo, F; Gamba, D; Bomben, M; Bosisio, L; Cartaro, C; Cossutti, F; Della Ricca, G; Dittongo, S; Lanceri, L; Vitale, L; Azzolini, V; Martinez-Vidal, F; Banerjee, Sw; Bhuyan, B; Brown, C M; Fortin, D; Hamano, K; Kowalewski, R; Nugent, I M; Roney, J M; Sobie, R J; Back, J J; Harrison, P F; Latham, T E; Mohanty, G B; Pappagallo, M; Band, H R; Chen, X; Cheng, B; Dasu, S; Datta, M; Flood, K T; Hollar, J J; Kutter, P E; Mellado, B; Mihalyi, A; Pan, Y; Pierini, M; Prepost, R; Wu, S L; Yu, Z; Neal, H

    2006-11-24

    We report a measurement of the B-->pi l nu branching fraction based on 211 fb(-1) of data collected with the BABAR detector. We use samples of B0 and B+ mesons tagged by a second B meson reconstructed in a semileptonic or hadronic decay and combine the results assuming isospin symmetry to obtain B(B(0)-->pi- l+ nu) = (1.33+/-0.17stat+/-0.11syst) x 10(-4). We determine the magnitude of the Cabibbo-Kobayashi-Maskawa matrix element absolute value V(ub) by combining the partial branching fractions measured in ranges of the momentum transfer squared and theoretical calculations of the form factor. Using a recent lattice QCD calculation, we find absolute value V(ub) = (4.5+/-0.5stat+/-0.3syst(+0.7) -0.5FF x 10(-3), where the last error is due to the normalization of the form factor. PMID:17155736

  13. Absolute biological needs.

    PubMed

    McLeod, Stephen

    2014-07-01

    Absolute needs (as against instrumental needs) are independent of the ends, goals and purposes of personal agents. Against the view that the only needs are instrumental needs, David Wiggins and Garrett Thomson have defended absolute needs on the grounds that the verb 'need' has instrumental and absolute senses. While remaining neutral about it, this article does not adopt that approach. Instead, it suggests that there are absolute biological needs. The absolute nature of these needs is defended by appeal to: their objectivity (as against mind-dependence); the universality of the phenomenon of needing across the plant and animal kingdoms; the impossibility that biological needs depend wholly upon the exercise of the abilities characteristic of personal agency; the contention that the possession of biological needs is prior to the possession of the abilities characteristic of personal agency. Finally, three philosophical usages of 'normative' are distinguished. On two of these, to describe a phenomenon or claim as 'normative' is to describe it as value-dependent. A description of a phenomenon or claim as 'normative' in the third sense does not entail such value-dependency, though it leaves open the possibility that value depends upon the phenomenon or upon the truth of the claim. It is argued that while survival needs (or claims about them) may well be normative in this third sense, they are normative in neither of the first two. Thus, the idea of absolute need is not inherently normative in either of the first two senses. PMID:23586876

  14. Absolute biological needs.

    PubMed

    McLeod, Stephen

    2014-07-01

    Absolute needs (as against instrumental needs) are independent of the ends, goals and purposes of personal agents. Against the view that the only needs are instrumental needs, David Wiggins and Garrett Thomson have defended absolute needs on the grounds that the verb 'need' has instrumental and absolute senses. While remaining neutral about it, this article does not adopt that approach. Instead, it suggests that there are absolute biological needs. The absolute nature of these needs is defended by appeal to: their objectivity (as against mind-dependence); the universality of the phenomenon of needing across the plant and animal kingdoms; the impossibility that biological needs depend wholly upon the exercise of the abilities characteristic of personal agency; the contention that the possession of biological needs is prior to the possession of the abilities characteristic of personal agency. Finally, three philosophical usages of 'normative' are distinguished. On two of these, to describe a phenomenon or claim as 'normative' is to describe it as value-dependent. A description of a phenomenon or claim as 'normative' in the third sense does not entail such value-dependency, though it leaves open the possibility that value depends upon the phenomenon or upon the truth of the claim. It is argued that while survival needs (or claims about them) may well be normative in this third sense, they are normative in neither of the first two. Thus, the idea of absolute need is not inherently normative in either of the first two senses.

  15. Comparison of high energy gamma rays from absolute value of b greater than 30 deg with the galactic neutral hydrogen distribution

    NASA Technical Reports Server (NTRS)

    Ozel, M. E.; Ogelman, H.; Tumer, T.; Fichtel, C. E.; Hartman, R. C.; Kniffen, D. A.; Thompson, F. J.

    1978-01-01

    High-energy gamma-ray (energy above 35 MeV) data from the SAS 2 satellite have been used to compare the intensity distribution of gamma rays with that of neutral hydrogen (H I) density along the line of sight, at high galactic latitudes (absolute values greater than 30 deg). A model has been constructed for the case where the observed gamma-ray intensity has been assumed to be the sum of a galactic component proportional to the H I distribution plus an isotropic extragalactic emission. A chi-squared test of the model parameters indicates that about 30% of the total high-latitude emission may originate within the Galaxy.

  16. Assessment of prognostic value of semiquantitative parameters on gated single photon emission computed tomography myocardial perfusion scintigraphy in a large middle eastern population

    PubMed Central

    Chavoshi, Maryam; Fard-Esfahani, Armaghan; Fallahi, Babak; Emami-Ardekani, Alireza; Beiki, Davood; Hassanzadeh-Rad, Arman; Eftekhari, Mohammad

    2015-01-01

    Objectives: Coronary artery disease is the leading cause of mortality worldwide. The goal of this study is to determine the prognostic value of semiquantitative parameters of electrocardiogram-gated single photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI) in a large Middle Eastern (Iranian) population. Materials and Methods: This study was a prospective study including all patients referred to our center for myocardial perfusion scan. The patients were followed annually up to 24 months and their survival information was collected. Results: From 1148 patients, 473 (41.2%) men and 675 (58.8%) women, 40.6% had normal MPI, 13.3% near normal and 46.1% abnormal MPI. After follow-up of 929 patients, 97.4% of patients were alive, and 2.6% succumbed to cardiac deaths. Abnormal ejection fraction was related with cardiac events (P = 0.001), but neither transient ischemic dilation (TID) (P = 0.09) nor lung/heart ratio (P = 0.92) showed such relationship. Association between summed difference score (SDS) and soft cardiac events (P < 0.001) was significant. Summed motion score (SMS) and summed thickening score (STS) showed a significant relation with hard cardiac events, including myocardial infarction and cardiac death (P < 0.001 and P = 0.001, respectively). Totally, risk of all cardiac events was significantly higher in abnormal MPI group than normal group (P < 0.001, 0.02, and 0.025, respectively). No significant relationship was found between TID and total cardiac events (P = 0.478). Conclusion: Semiquantitative variables derived from gated SPECT MPI have independent prognostic value. Rate of total cardiac events is higher in patients with higher summed stress score and SDS. Total and hard cardiac events are higher in upper scores of functional parameters (SMS and STS). Total cardiac events are higher in patients with lower left ventricular ejection fraction. PMID:26170566

  17. Absolute Summ

    NASA Astrophysics Data System (ADS)

    Phillips, Alfred, Jr.

    Summ means the entirety of the multiverse. It seems clear, from the inflation theories of A. Guth and others, that the creation of many universes is plausible. We argue that Absolute cosmological ideas, not unlike those of I. Newton, may be consistent with dynamic multiverse creations. As suggested in W. Heisenberg's uncertainty principle, and with the Anthropic Principle defended by S. Hawking, et al., human consciousness, buttressed by findings of neuroscience, may have to be considered in our models. Predictability, as A. Einstein realized with Invariants and General Relativity, may be required for new ideas to be part of physics. We present here a two postulate model geared to an Absolute Summ. The seedbed of this work is part of Akhnaton's philosophy (see S. Freud, Moses and Monotheism). Most important, however, is that the structure of human consciousness, manifest in Kenya's Rift Valley 200,000 years ago as Homo sapiens, who were the culmination of the six million year co-creation process of Hominins and Nature in Africa, allows us to do the physics that we do. .

  18. Measurements of the absolute value of the penetration depth in high-T{sub c} superconductors using a low-T{sub c} superconductive coating

    SciTech Connect

    Prozorov, R.; Giannetta, R. W.; Carrington, A.; Fournier, P.; Greene, R. L.; Guptasarma, P.; Hinks, D. G.; Banks, A. R.

    2000-12-18

    A method is presented to measure the absolute value of the London penetration depth, {lambda}(T=0), from the frequency shift of a resonator. The technique involves coating a high-T{sub c} superconductor with film of low-T{sub c} material of known thickness and penetration depth. The method is applied to obtain {lambda}(YBa{sub 2}Cu{sub 3}O{sub 7-{delta}}){approx}1460{+-}150Aa, {lambda}(Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+{delta}}){approx}2690{+-}150Aa and {lambda}(Pr{sub 1.85}Ce{sub 0.15}CuO{sub 4-{delta}}){approx}2790{+-}150Aa. {lambda}(YBa{sub 2}Cu{sub 3}O{sub 7-{delta}}) from this method is very close to that obtained by several other techniques. For both Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+{delta}} and Pr{sub 1.85}Ce{sub 0.15}CuO{sub 4-{delta}} the values exceed those obtained by other methods.

  19. Estimation of optimal b-value sets for obtaining apparent diffusion coefficient free from perfusion in non-small cell lung cancer.

    PubMed

    Karki, Kishor; Hugo, Geoffrey D; Ford, John C; Olsen, Kathryn M; Saraiya, Siddharth; Groves, Robert; Weiss, Elisabeth

    2015-10-21

    The purpose of this study was to determine optimal sets of b-values in diffusion-weighted MRI (DW-MRI) for obtaining monoexponential apparent diffusion coefficient (ADC) close to perfusion-insensitive intravoxel incoherent motion (IVIM) model ADC (ADCIVIM) in non-small cell lung cancer. Ten subjects had 40 DW-MRI scans before and during radiotherapy in a 1.5 T MRI scanner. Respiratory triggering was applied to the echo-planar DW-MRI with TR ≈ 4500 ms, TE  =  74 ms, eight b-values of 0-1000 μs μm(-2), pixel size  =  1.98 × 1.98 mm(2), slice thickness  =  6 mm, interslice gap  =  1.2 mm, 7 axial slices and total acquisition time ≈6 min. One or more DW-MRI scans together covered the whole tumour volume. Monoexponential model ADC values using various b-value sets were compared to reference-standard ADCIVIM values using all eight b-values. Intra-scan coefficient of variation (CV) of active tumour volumes was computed to compare the relative noise in ADC maps. ADC values for one pre-treatment DW-MRI scan of each of the 10 subjects were computed using b-value pairs from DW-MRI images synthesized for b-values of 0-2000 μs μm(-2) from the estimated IVIM parametric maps and corrupted by various Rician noise levels. The square root of mean of squared error percentage (RMSE) of the ADC value relative to the corresponding ADCIVIM for the tumour volume of the scan was computed. Monoexponential ADC values for the b-value sets of 250 and 1000; 250, 500 and 1000; 250, 650 and 1000; 250, 800 and 1000; and 250-1000 μs μm(-2) were not significantly different from ADCIVIM values (p > 0.05, paired t-test). Mean error in ADC values for these sets relative to ADCIVIM were within 3.5%. Intra-scan CVs for these sets were comparable to that for ADCIVIM. The monoexponential ADC values for other sets-0-1000; 50-1000; 100-1000; 500-1000; and 250 and 800 μs μm(-2) were significantly different from the ADCIVIM values. From Rician noise

  20. Estimation of optimal b-value sets for obtaining apparent diffusion coefficient free from perfusion in non-small cell lung cancer

    NASA Astrophysics Data System (ADS)

    Karki, Kishor; Hugo, Geoffrey D.; Ford, John C.; Olsen, Kathryn M.; Saraiya, Siddharth; Groves, Robert; Weiss, Elisabeth

    2015-10-01

    The purpose of this study was to determine optimal sets of b-values in diffusion-weighted MRI (DW-MRI) for obtaining monoexponential apparent diffusion coefficient (ADC) close to perfusion-insensitive intravoxel incoherent motion (IVIM) model ADC (ADCIVIM) in non-small cell lung cancer. Ten subjects had 40 DW-MRI scans before and during radiotherapy in a 1.5 T MRI scanner. Respiratory triggering was applied to the echo-planar DW-MRI with \\text{TR}≈ 4500 ms, TE  =  74 ms, eight b-values of 0-1000 μs μm-2, pixel size  =  1.98× 1.98 mm2, slice thickness  =  6 mm, interslice gap  =  1.2 mm, 7 axial slices and total acquisition time ≈6 min. One or more DW-MRI scans together covered the whole tumour volume. Monoexponential model ADC values using various b-value sets were compared to reference-standard ADCIVIM values using all eight b-values. Intra-scan coefficient of variation (CV) of active tumour volumes was computed to compare the relative noise in ADC maps. ADC values for one pre-treatment DW-MRI scan of each of the 10 subjects were computed using b-value pairs from DW-MRI images synthesized for b-values of 0-2000 μs μm-2 from the estimated IVIM parametric maps and corrupted by various Rician noise levels. The square root of mean of squared error percentage (RMSE) of the ADC value relative to the corresponding ADCIVIM for the tumour volume of the scan was computed. Monoexponential ADC values for the b-value sets of 250 and 1000; 250, 500 and 1000; 250, 650 and 1000; 250, 800 and 1000; and 250-1000 μs μm-2 were not significantly different from ADCIVIM values (p>0.05 , paired t-test). Mean error in ADC values for these sets relative to ADCIVIM were within 3.5%. Intra-scan CVs for these sets were comparable to that for ADCIVIM. The monoexponential ADC values for other sets—0-1000 50-1000 100-1000 500-1000 and 250 and 800 μs μm-2 were significantly different from the ADCIVIM values. From Rician noise simulation

  1. Estimation of optimal b-value sets for obtaining apparent diffusion coefficient free from perfusion in non-small cell lung cancer

    PubMed Central

    Karki, Kishor; Hugo, Geoffrey D.; Ford, John C.; Olsen, Kathryn M.; Saraiya, Siddharth; Groves, Robert; Weiss, Elisabeth

    2015-01-01

    The purpose of this study was to determine optimal sets of b-values in diffusion-weighted MRI (DW-MRI) for obtaining monoexponential apparent diffusion coefficient (ADC) close to perfusion-insensitive intravoxel incoherent motion (IVIM) model ADC (ADCIVIM) in non-small cell lung cancer. Ten subjects had 40 DW-MRI scans before and during radiotherapy in a 1.5T MRI scanner. Respiratory triggering was applied to the echo-planar DW-MRI with TR ≈ 4500 ms, TE = 74 ms, eight b-values of 0–1000 µs/µm2, pixel size = 1.98×1.98 mm2, slice thickness = 6 mm, interslice gap = 1.2 mm, 7 axial slices and total acquisition time ≈ 6 min. One or more DW-MRI scans together covered the whole tumour volume. Monoexponential model ADC values using various b-value sets were compared to reference-standard ADCIVIM values using all eight b-values. Intra-scan coefficient of variation (CV) of active tumour volumes was computed to compare the relative noise in ADC maps. ADC values for one pre-treatment DW-MRI scan of each of the 10 subjects were computed using b-value pairs from DW-MRI images synthesized for b-values of 0–2000 µs/µm2 from the estimated IVIM parametric maps and corrupted by various Rician noise levels. The square root of mean of squared error percentage (RMSE) of the ADC value relative to the corresponding ADCIVIM for the tumour volume of the scan was computed. Monoexponential ADC values for the b-value sets of 250 and 1000; 250, 500 and 1000; 250, 650 and 1000; 250, 800 and 1000; and 250–1000 µs/µm2 were not significantly different from ADCIVIM values (p > 0.05, paired t-test). Mean error in ADC values for these sets relative to ADCIVIM were within 3.5%. Intra-scan CVs for these sets were comparable to that for ADCIVIM. The monoexponential ADC values for other sets- 0–1000; 50–1000; 100–1000; 500–1000; and 250 and 800 µs/µm2 were significantly different from the ADCIVIM values. From Rician noise simulation using b-value pairs, there was a wide range of

  2. Renal perfusion scintiscan

    MedlinePlus

    Renal perfusion scintigraphy; Radionuclide renal perfusion scan; Perfusion scintiscan - renal; Scintiscan - renal perfusion ... supply the kidneys. This is a condition called renal artery stenosis. Significant renal artery stenosis may be ...

  3. A full-dimensional model of ozone forming reaction: the absolute value of the recombination rate coefficient, its pressure and temperature dependencies.

    PubMed

    Teplukhin, Alexander; Babikov, Dmitri

    2016-07-28

    Rigorous calculations of scattering resonances in ozone are carried out for a broad range of rotational excitations. The accurate potential energy surface of Dawes is adopted, and a new efficient method for calculations of ro-vibrational energies, wave functions and resonance lifetimes is employed (which uses hyper-spherical coordinates, the sequential diagonalization/truncation approach, grid optimization and complex absorbing potential). A detailed analysis is carried out to characterize distributions of resonance energies and lifetimes, their rotational/vibrational content and their positions with respect to the centrifugal barrier. Emphasis is on the contribution of these resonances to the recombination process that forms ozone. It is found that major contributions come from localized resonances at energies near the top of the barrier. Delocalized resonances at higher energies should also be taken into account, while very narrow resonances at low energies (trapped far behind the centrifugal barrier) should be treated as bound states. The absolute value of the recombination rate coefficient, its pressure and temperature dependencies are obtained using the energy-transfer model developed in the earlier work. Good agreement with experimental data is obtained if one follows the suggestion of Troe, who argued that the energy transfer mechanism of recombination is responsible only for 55% of the recombination rate (with the remaining 45% coming from the competing chaperon mechanism). PMID:27364351

  4. A full-dimensional model of ozone forming reaction: the absolute value of the recombination rate coefficient, its pressure and temperature dependencies.

    PubMed

    Teplukhin, Alexander; Babikov, Dmitri

    2016-07-28

    Rigorous calculations of scattering resonances in ozone are carried out for a broad range of rotational excitations. The accurate potential energy surface of Dawes is adopted, and a new efficient method for calculations of ro-vibrational energies, wave functions and resonance lifetimes is employed (which uses hyper-spherical coordinates, the sequential diagonalization/truncation approach, grid optimization and complex absorbing potential). A detailed analysis is carried out to characterize distributions of resonance energies and lifetimes, their rotational/vibrational content and their positions with respect to the centrifugal barrier. Emphasis is on the contribution of these resonances to the recombination process that forms ozone. It is found that major contributions come from localized resonances at energies near the top of the barrier. Delocalized resonances at higher energies should also be taken into account, while very narrow resonances at low energies (trapped far behind the centrifugal barrier) should be treated as bound states. The absolute value of the recombination rate coefficient, its pressure and temperature dependencies are obtained using the energy-transfer model developed in the earlier work. Good agreement with experimental data is obtained if one follows the suggestion of Troe, who argued that the energy transfer mechanism of recombination is responsible only for 55% of the recombination rate (with the remaining 45% coming from the competing chaperon mechanism).

  5. The influence of walking with an orthosis on bone mineral density by determination of the absolute values of the loads applied on the limb.

    PubMed

    Karimi, Mohammad Taghi

    2012-03-01

    Spinal cord injury is damage to the spinal cord that results in loss of mobility and sensation below the level of injury. Most patients use various types of orthoses to stand and walk. It has been claimed that walking and standing with orthosis reduces bone osteoporosis, improves joint range of motion and decreases muscle spasm. Unfortunately, there are discrepancies regarding the clinical effects of walking and standing on bone mineral density. The aim of this research was to find the absolute values of the loads transmitted by body and orthosis in walking with use of an orthosis. 5 normal subjects were recruited to stand and walk with a new design of reciprocal gait orthosis. The loads transmitted through the orthosis and anatomy was measured by use of strain gauge and motion analysis systems. It has been shown that the loads applied on the anatomy were significantly more than that transmitted through the orthosis. Moreover, the patterns of the forces and moments of the orthosis and body completely differed from each other. As the most part of the loads applied on the complex transmitted by anatomy in walking with an orthosis, walking with orthosis can influence bone mineral density.

  6. Eleven-year prognostic value of dobutamine stress (99m)Tc-sestamibi myocardial perfusion imaging in patients with limited exercise capacity.

    PubMed

    Boiten, Hendrik J; van Domburg, Ron T; Valkema, Roelf; Schinkel, Arend F L

    2015-04-01

    Myocardial perfusion single-photon emission computed tomography is a routine technique for the evaluation of coronary artery disease. However, information on the very long term prognostic value of dobutamine stress single-photon emission computed tomographic myocardial perfusion imaging (MPI) in patients with limited exercise capacity is scarce. The aim of this study was to assess the long-term prognostic value of dobutamine stress technetium-99m ((99m)Tc)-sestamibi MPI in these patients. The study population consisted of a high-risk cohort of 531 consecutive patients with limited exercise capacity who underwent dobutamine stress (99m)Tc-sestamibi MPI for the assessment of known or suspected coronary artery disease. Follow-up was successful in 528 patients. Because of early revascularization, 55 patients were excluded. The present data are based on 473 patients. The end points were all-cause mortality, cardiac death, nonfatal myocardial infarction, and late (>60 days) coronary revascularization. Kaplan-Meier survival curves were performed and univariate and multivariate analyses were performed to identify predictors of very long term outcome. The mean age of the patients was 61 ± 12 years, and 58% were men. Abnormal results (defined as the presence of reversible or fixed defects) were observed in 312 patients (66%). During a mean follow-up period of 11.3 ± 6.7 years, 287 patients (61%) died (all-cause mortality), of whom 125 (26%) died due to cardiac causes. Nonfatal myocardial infarction occurred in 59 patients (12%). Late coronary revascularization was performed in 61 patients (13%). Univariate predictors of major cardiac events included age, male gender, previous infarction, diabetes mellitus, history of angina, heart failure, ST-segment changes, abnormal results on (99m)Tc-sestamibi scan, reversible defect, fixed defect, summed rest score, and summed stress score. Multivariate analysis identified abnormal results on MPI as a strong independent predictor of

  7. Value of Perfusion-Weighted MR Imaging in the Assessment of Early Cerebral Alterations in Neurologically Asymptomatic HIV-1-Positive and HCV-Positive Patients

    PubMed Central

    Bladowska, Joanna; Knysz, Brygida; Zimny, Anna; Małyszczak, Krzysztof; Kołtowska, Anna; Szewczyk, Paweł; Gąsiorowski, Jacek; Furdal, Michał; Sąsiadek, Marek J.

    2014-01-01

    Background and Purpose Asymptomatic central nervous system (CNS) involvement occurs in the early stage of the human immunodeficiency virus (HIV) infection. It has been documented that the hepatitis C virus (HCV) can replicate in the CNS. The aim of the study was to evaluate early disturbances in cerebral microcirculation using magnetic resonance (MR) perfusion-weighted imaging (PWI) in asymptomatic HIV-1-positive and HCV-positive patients, as well as to assess the correlation between PWI measurements and the clinical data. Materials and Methods Fifty-six patients: 17 HIV-1-positive non-treated, 18 HIV-1-positive treated with combination antiretroviral therapy (cART), 7 HIV-1/HCV-positive non-treated, 14 HCV-positive before antiviral therapy and 18 control subjects were enrolled in the study. PWI was performed with a 1.5T MR unit using dynamic susceptibility contrast (DSC) method. Cerebral blood volume (CBV) measurements relative to cerebellum (rCBV) were evaluated in the posterior cingulated region (PCG), basal ganglia (BG), temporoparietal (TPC) and frontal cortices (FC), as well as in white matter of frontoparietal areas. Correlations of rCBV values with immunologic data and liver histology activity index (HAI) were analyzed. Results Significantly lower rCBV values were found in the right TPC and left FC as well as in PCG in HIV-1-positive naïve (p = 0.009; p = 0.020; p = 0.012), HIV-1 cART treated (p = 0.007; p = 0.009; p = 0.033), HIV-1/HCV-positive (p = 0.007; p = 0.027; p = 0.045) and HCV-positive patients (p = 0.010; p = 0.005; p = 0.045) compared to controls. HIV-1-positive cART treated and HIV-1/HCV-positive patients demonstrated lower rCBV values in the right FC (p = 0.009; p = 0.032, respectively) and the left TPC (p = 0.036; p = 0.005, respectively), while HCV-positive subjects revealed lower rCBV values in the left TPC region (p = 0.003). We found significantly elevated rCBV values in

  8. Prognostic value of thallium-201 myocardial perfusion imaging in patients with unstable angina who respond to medical treatment

    SciTech Connect

    Brown, K.A. )

    1991-04-01

    Although the prognostic value of thallium-201 imaging is well established, its ability to risk stratify patients who present with unstable angina is unclear. Fifty-two consecutive patients admitted with unstable angina who responded to medical treatment and underwent stress thallium-201 imaging within 1 week of discharge were studied. Patients were followed up for 39 +/- 11 months. Cardiac events included cardiac death (n = 3), nonfatal myocardial infarction (n = 4) and admission for unstable angina or revascularization (n = 17). The ability of thallium-201 data (redistribution, fixed defects, normal) to predict cardiac events was compared with clinical data (age, gender, prior myocardial infarction, anginal syndrome, rest and stress electrocardiogram) and cardiac catheterization data using logistic regression. Thallium-201 redistribution was the only significant predictor of cardiac death or nonfatal myocardial infarction (p less than 0.05). The number of myocardial segments with thallium-201 redistribution (p less than 0.0005) and a history of prior myocardial infarction (p less than 0.05) were the only significant predictors of all cardiac events. Cardiac death or nonfatal myocardial infarction occurred more frequently in patients with thallium-201 redistribution (6 (26%) of 23) than in those without redistribution (1 (3%) of 29, p less than 0.05). Similarly, total cardiac events developed more frequently in patients with thallium-201 redistribution (p less than 0.001). Stress thallium-201 imaging has important prognostic value in patients admitted with unstable angina who respond to medical therapy and can identify subgroups at high versus low risk for future cardiac events.

  9. Comparative value of maximal treadmill testing, exercise thallium myocardial perfusion scintigraphy and exercise radionuclide ventriculography for distinguishing high- and low-risk patients soon after acute myocardial infarction

    SciTech Connect

    Hung, J.; Goris, M.L.; Nash, E.; Kraemer, H.C.; DeBusk, R.F.; Berger, W.E.; Lew, H.

    1984-05-01

    The prognostic value of symptom-limited treadmill exercise electrocardiography, exercise thallium myocardial perfusion scintigraphy and rest and exercise radionuclide ventriculography was compared in 117 men, aged 54 +/- 9 years, tested 3 weeks after a clinically uncomplicated acute myocardial infarction (MI). During a mean follow-up period of 11.6 months, 8 men experienced ''hard'' medical events (cardiac death, nonfatal ventricular fibrillation or recurrent MI) and 14 were hospitalized for unstable angina pectoris, congestive heart failure or coronary bypass surgery (total of 22 combined events). By multivariate analysis (Cox proportional hazards model), peak treadmill work load and the change in left ventricular ejection fraction (EF) during exercise were significant (p less than 0.01) predictors of hard medical events; these 2 risk factors and recurrent ischemic chest pain in the coronary care unit were also significantly predictive (p less than 0.001) for combined events. A peak treadmill work load of 4 METs or less or a decrease in EF of 5% or more below the value at rest during submaximal effort distinguished 22 high-risk patients (20% of the study population) from 89 low-risk patients. The rate of hard medical events within 12 months was 23% (5 of 22 patients), vs 2% (2 of 89 patients) in the high- and low-risk patient subsets, respectively (p less than 0.001). Thus, in patients who underwent evaluation 3 weeks after a clinically uncomplicated MI, exercise radionuclide ventriculography contributed independent prognostic information to that provided by symptom-limited treadmill testing and was superior to exercise thallium scintigraphy for this purpose.

  10. Prognostic Value of Major Cardiac Event Risk Score Estimated With Gated Myocardial Perfusion Imaging in Japanese Patients With Coronary Artery Disease.

    PubMed

    Yoda, Shunichi; Nakanishi, Kanae; Tano, Ayako; Hori, Yusuke; Hayase, Misa; Mineki, Takashi; Suzuki, Yasuyuki; Matsumoto, Naoya; Hirayama, Atsushi

    2016-07-27

    We published a cardiac event risk score (CERS) predicting the risk of major cardiac events (MCEs) within 3 years. The purpose of this study was to verify the prognostic value of the CERS before and after treatment in Japanese patients with coronary artery disease.We retrospectively investigated 612 patients who underwent rest (201)Tl and stress (99m)Tc-tetrofosmin myocardial perfusion single photon emission computed tomography (SPECT) between October 2004 and March 2013 and who had a significant stenosis with ≥ 75% narrowing of the arterial diameter detected by coronary angiography performed after confirmation of ≥ 5% ischemia with the SPECT. The patients underwent treatment including revascularization and medication, and thereafter, were re-evaluated with SPECT during a chronic phase and followed-up to confirm prognosis for ≥ 1 year. The endpoint was the onset of MCEs during the follow-up.During the follow-up (36.7 ± 14.5 months), 50 patients (8.7%) experienced MCEs comprising cardiac death (n = 16), non-fatal myocardial infarction (n = 4), and unstable angina pectoris (n = 30). The multivariate Cox proportional hazards regression model analysis for the actual occurrence of MCEs showed the summed difference score % and MCE risks estimated with the CERS after treatment to be significant independent variables. Ischemic reduction after treatment contributed significantly to a decrease in the MCE risks. The MCE risks estimated with the CERS after treatment were generally consistent with the incidence of the MCEs actually observed.The CERS after treatment is a valuable formula for predicting prognosis in Japanese patients with coronary artery disease. PMID:27357436

  11. Integration of Quantitative Positron Emission Tomography Absolute Myocardial Blood Flow Measurements in the Clinical Management of Coronary Artery Disease.

    PubMed

    Gewirtz, Henry; Dilsizian, Vasken

    2016-05-31

    In the >40 years since planar myocardial imaging with(43)K-potassium was introduced into clinical research and management of patients with coronary artery disease (CAD), diagnosis and treatment have undergone profound scientific and technological changes. One such innovation is the current state-of-the-art hardware and software for positron emission tomography myocardial perfusion imaging, which has advanced it from a strictly research-oriented modality to a clinically valuable tool. This review traces the evolving role of quantitative positron emission tomography measurements of myocardial blood flow in the evaluation and management of patients with CAD. It presents methodology, currently or soon to be available, that offers a paradigm shift in CAD management. Heretofore, radionuclide myocardial perfusion imaging has been primarily qualitative or at best semiquantitative in nature, assessing regional perfusion in relative terms. Thus, unlike so many facets of modern cardiovascular practice and CAD management, which depend, for example, on absolute values of key parameters such as arterial and left ventricular pressures, serum lipoprotein, and other biomarker levels, the absolute levels of rest and maximal myocardial blood flow have yet to be incorporated into routine clinical practice even in most positron emission tomography centers where the potential to do so exists. Accordingly, this review focuses on potential value added for improving clinical CAD practice by measuring the absolute level of rest and maximal myocardial blood flow. Physiological principles and imaging fundamentals necessary to understand how positron emission tomography makes robust, quantitative measurements of myocardial blood flow possible are highlighted.

  12. Integration of Quantitative Positron Emission Tomography Absolute Myocardial Blood Flow Measurements in the Clinical Management of Coronary Artery Disease.

    PubMed

    Gewirtz, Henry; Dilsizian, Vasken

    2016-05-31

    In the >40 years since planar myocardial imaging with(43)K-potassium was introduced into clinical research and management of patients with coronary artery disease (CAD), diagnosis and treatment have undergone profound scientific and technological changes. One such innovation is the current state-of-the-art hardware and software for positron emission tomography myocardial perfusion imaging, which has advanced it from a strictly research-oriented modality to a clinically valuable tool. This review traces the evolving role of quantitative positron emission tomography measurements of myocardial blood flow in the evaluation and management of patients with CAD. It presents methodology, currently or soon to be available, that offers a paradigm shift in CAD management. Heretofore, radionuclide myocardial perfusion imaging has been primarily qualitative or at best semiquantitative in nature, assessing regional perfusion in relative terms. Thus, unlike so many facets of modern cardiovascular practice and CAD management, which depend, for example, on absolute values of key parameters such as arterial and left ventricular pressures, serum lipoprotein, and other biomarker levels, the absolute levels of rest and maximal myocardial blood flow have yet to be incorporated into routine clinical practice even in most positron emission tomography centers where the potential to do so exists. Accordingly, this review focuses on potential value added for improving clinical CAD practice by measuring the absolute level of rest and maximal myocardial blood flow. Physiological principles and imaging fundamentals necessary to understand how positron emission tomography makes robust, quantitative measurements of myocardial blood flow possible are highlighted. PMID:27245647

  13. Microfluidic perfusion culture.

    PubMed

    Hattori, Koji; Sugiura, Shinji; Kanamori, Toshiyuki

    2014-01-01

    Microfluidic perfusion culture is a novel technique to culture animal cells in a small-scale microchamber with medium perfusion. Polydimethylsiloxane (PDMS) is the most popular material to fabricate a microfluidic perfusion culture chip. Photolithography and replica molding techniques are generally used for fabrication of a microfluidic perfusion culture chip. Pressure-driven perfusion culture system is convenient technique to carry out the perfusion culture of animal cells in a microfluidic device. Here, we describe a general theory on microfluid network design, microfabrication technique, and experimental technique for pressure-driven perfusion culture in an 8 × 8 microchamber array on a glass slide-sized microchip made out of PDMS. PMID:24297421

  14. Pulmonary ventilation/perfusion scan

    MedlinePlus

    V/Q scan; Ventilation/perfusion scan; Lung ventilation/perfusion scan ... A pulmonary ventilation/perfusion scan is actually two tests. They may be done separately or together. During the perfusion scan, a health care ...

  15. Multimodal imaging in diagnosis of Alzheimer's disease and amnestic mild cognitive impairment: value of magnetic resonance spectroscopy, perfusion, and diffusion tensor imaging of the posterior cingulate region.

    PubMed

    Zimny, Anna; Szewczyk, Pawel; Trypka, Elzbieta; Wojtynska, Renata; Noga, Leszek; Leszek, Jerzy; Sasiadek, Marek

    2011-01-01

    The purpose of this study was to assess metabolic, perfusion, and microstructural changes within the posterior cingulate area in patients with Alzheimer's disease (AD) and amnestic mild cognitive impairment (aMCI) using advanced MR techniques such as: spectroscopy (MRS), perfusion weighted imaging (PWI), and diffusion tensor imaging (DTI). Thirty patients with AD (mean age 71.5 y, MMSE 18), 23 with aMCI (mean age 66 y, MMSE 27.4), and 15 age-matched normal controls (mean age 69 y, MMSE 29.5) underwent conventional MRI followed by MRS, PWI, and DTI on 1.5 Tesla MR unit. Several metabolite ratios (N-acetylaspartate [NAA]/creatine [Cr], choline [Ch]/Cr, myoinositol [mI]/Cr, mI/NAA, mI/Cho) as well as parameters of cerebral blood volume relative to cerebellum and fractional anisotropy were obtained in the posterior cingulate region. The above parameters were correlated with the results of neuropsychological tests. AD patients showed significant abnormalities in all evaluated parameters while subjects with aMCI showed only perfusion and diffusion changes in the posterior cingulate area. Only PWI and DTI measurements revealed significant differences among the three evaluated subject groups. DTI, PWI, and MRS results showed significant correlations with neuropsychological tests. DTI changes correlated with both PWI and MRS abnormalities. Of neuroimaging methods, DTI revealed the highest accuracy in diagnosis of AD and aMCI (0.95, 0.79) followed by PWI (0.87, 0.67) and MRS (0.82, 0.47), respectively. In conclusion, AD is a complex pathology regarding both grey and white matter. DTI seems to be the most useful imaging modality to distinguish between AD, aMCI, and control group, followed by PWI and MRS. PMID:21841260

  16. Absolute Equilibrium Entropy

    NASA Technical Reports Server (NTRS)

    Shebalin, John V.

    1997-01-01

    The entropy associated with absolute equilibrium ensemble theories of ideal, homogeneous, fluid and magneto-fluid turbulence is discussed and the three-dimensional fluid case is examined in detail. A sigma-function is defined, whose minimum value with respect to global parameters is the entropy. A comparison is made between the use of global functions sigma and phase functions H (associated with the development of various H-theorems of ideal turbulence). It is shown that the two approaches are complimentary though conceptually different: H-theorems show that an isolated system tends to equilibrium while sigma-functions allow the demonstration that entropy never decreases when two previously isolated systems are combined. This provides a more complete picture of entropy in the statistical mechanics of ideal fluids.

  17. The added value of hybrid ventilation/perfusion SPECT/CT in patients with stable COPD or apparently healthy smokers. Cancer-suspected CT findings in the lungs are common when hybrid imaging is used.

    PubMed

    Jögi, Jonas; Markstad, Hanna; Tufvesson, Ellen; Bjermer, Leif; Bajc, Marika

    2015-01-01

    Ventilation/perfusion (V/P) single-photon emission computed tomography (SPECT) is recognized as a diagnostic method with potential beyond the diagnosis of pulmonary embolism. V/P SPECT identifies functional impairment in diseases such as heart failure (HF), pneumonia, and chronic obstructive pulmonary disease (COPD). The development of hybrid SPECT/computed tomography (CT) systems, combining functional with morphological imaging through the addition of low-dose CT (LDCT), may be useful in COPD, as these patients are prone to lung cancer and other comorbidities. The aim of this study was to investigate the added value of LDCT among healthy smokers and patients with stable COPD, when examined with V/P SPECT/CT hybrid imaging. Sixty-nine subjects, 55 with COPD (GOLD I-IV) and 14 apparently healthy smokers, were examined with V/P SPECT and LDCT hybrid imaging. Spirometry was used to verify COPD grade. Only one apparently healthy smoker and three COPD patients had a normal or nearly normal V/P SPECT. All other patients showed various degrees of airway obstruction, even when spirometry was normal. The same interpretation was reached on both modalities in 39% of the patients. LDCT made V/P SPECT interpretation more certain in 9% of the patients and, in 52%, LDCT provided additional diagnoses. LDCT better characterized the type of emphysema in 12 patients. In 19 cases, tumor-suspected changes were reported. Three of these 19 patients (ie, 4.3% of all subjects) were in the end confirmed to have lung cancer. The majority of LDCT findings were not regarded as clinically significant. V/P SPECT identified perfusion patterns consistent with decompensated left ventricular HF in 14 COPD patients. In 16 patients (23%), perfusion defects were observed. HF and perfusion defects were not recognized with LDCT. In COPD patients and long-time smokers, hybrid imaging had added value compared to V/P SPECT alone, by identifying patients with lung malignancy and more clearly identifying

  18. The added value of hybrid ventilation/perfusion SPECT/CT in patients with stable COPD or apparently healthy smokers. Cancer-suspected CT findings in the lungs are common when hybrid imaging is used.

    PubMed

    Jögi, Jonas; Markstad, Hanna; Tufvesson, Ellen; Bjermer, Leif; Bajc, Marika

    2015-01-01

    Ventilation/perfusion (V/P) single-photon emission computed tomography (SPECT) is recognized as a diagnostic method with potential beyond the diagnosis of pulmonary embolism. V/P SPECT identifies functional impairment in diseases such as heart failure (HF), pneumonia, and chronic obstructive pulmonary disease (COPD). The development of hybrid SPECT/computed tomography (CT) systems, combining functional with morphological imaging through the addition of low-dose CT (LDCT), may be useful in COPD, as these patients are prone to lung cancer and other comorbidities. The aim of this study was to investigate the added value of LDCT among healthy smokers and patients with stable COPD, when examined with V/P SPECT/CT hybrid imaging. Sixty-nine subjects, 55 with COPD (GOLD I-IV) and 14 apparently healthy smokers, were examined with V/P SPECT and LDCT hybrid imaging. Spirometry was used to verify COPD grade. Only one apparently healthy smoker and three COPD patients had a normal or nearly normal V/P SPECT. All other patients showed various degrees of airway obstruction, even when spirometry was normal. The same interpretation was reached on both modalities in 39% of the patients. LDCT made V/P SPECT interpretation more certain in 9% of the patients and, in 52%, LDCT provided additional diagnoses. LDCT better characterized the type of emphysema in 12 patients. In 19 cases, tumor-suspected changes were reported. Three of these 19 patients (ie, 4.3% of all subjects) were in the end confirmed to have lung cancer. The majority of LDCT findings were not regarded as clinically significant. V/P SPECT identified perfusion patterns consistent with decompensated left ventricular HF in 14 COPD patients. In 16 patients (23%), perfusion defects were observed. HF and perfusion defects were not recognized with LDCT. In COPD patients and long-time smokers, hybrid imaging had added value compared to V/P SPECT alone, by identifying patients with lung malignancy and more clearly identifying

  19. TU-A-12A-09: Absolute Blood Flow Measurement in a Cardiac Phantom Using Low Dose CT

    SciTech Connect

    Ziemer, B; Hubbard, L; Lipinski, J; Molloi, S

    2014-06-15

    Purpose: To investigate a first pass analysis technique to measure absolute flow from low dose CT images in a cardiac phantom. This technique can be combined with a myocardial mass assignment to yield absolute perfusion using only two volume scans and reduce the radiation dose to the patient. Methods: A four-chamber cardiac phantom and perfusion chamber were constructed from poly-acrylic and connected with tubing to approximate anatomical features. The system was connected to a pulsatile pump, input/output reservoirs and power contrast injector. Flow was varied in the range of 1-2.67 mL/s with the pump operating at 60 beats/min. The system was imaged once a second for 14 seconds with a 320-row scanner (Toshiba Medical Systems) using a contrast-enhanced, prospective-gated cardiac perfusion protocol. Flow was calculated by the following steps: subsequent images of the perfusion volume were subtracted to find the contrast entering the volume; this was normalized by an upstream, known volume region to convert Hounsfield (HU) values to concentration; this was divided by the subtracted images time difference. The technique requires a relatively stable input contrast concentration and no contrast can leave the perfusion volume before the flow measurement is completed. Results: The flow calculated from the images showed an excellent correlation with the known rates. The data was fit to a linear function with slope 1.03, intercept 0.02 and an R{sup 2} value of 0.99. The average root mean square (RMS) error was 0.15 mL/s and the average standard deviation was 0.14 mL/s. The flow rate was stable within 7.7% across the full scan and served to validate model assumptions. Conclusion: Accurate, absolute flow rates were measured from CT images using a conservation of mass model. Measurements can be made using two volume scans which can substantially reduce the radiation dose compared with current dynamic perfusion techniques.

  20. Comparison of cerebral tissue oxygenation values in full term and preterm newborns by the simultaneous use of two near-infrared spectroscopy devices: an absolute and a relative trending oximeter

    NASA Astrophysics Data System (ADS)

    Szczapa, Tomasz; Karpiński, Łukasz; Moczko, Jerzy; Weindling, Michael; Kornacka, Alicja; Wróblewska, Katarzyna; Adamczak, Aleksandra; Jopek, Aleksandra; Chojnacka, Karolina; Gadzinowski, Janusz

    2013-08-01

    The aim of this study is to compare a two-wavelength light emitting diode-based tissue oximeter (INVOS), which is designed to show trends in tissue oxygenation, with a four-wavelength laser-based oximeter (FORE-SIGHT), designed to deliver absolute values of tissue oxygenation. Simultaneous values of cerebral tissue oxygenation (StO2) are measured using both devices in 15 term and 15 preterm clinically stable newborns on the first and third day of life. Values are recorded simultaneously in two periods between which oximeter sensor positions are switched to the contralateral side. Agreement between StO2 values before and after the change of sensor position is analyzed. We find that mean cerebral StO2 values are similar between devices for term and preterm babies, but INVOS shows StO2 values spread over a wider range, with wider standard deviations than shown by the FORE-SIGHT. There is relatively good agreement with a bias up to 3.5% and limits of agreement up to 11.8%. Measurements from each side of the forehead show better repeatability for the FORE-SIGHT monitor. We conclude that performance of the two devices is probably acceptable for clinical purposes. Both performed sufficiently well, but the use of FORE-SIGHT may be associated with tighter range and better repeatability of data.

  1. Absolute nuclear material assay

    DOEpatents

    Prasad, Manoj K.; Snyderman, Neal J.; Rowland, Mark S.

    2012-05-15

    A method of absolute nuclear material assay of an unknown source comprising counting neutrons from the unknown source and providing an absolute nuclear material assay utilizing a model to optimally compare to the measured count distributions. In one embodiment, the step of providing an absolute nuclear material assay comprises utilizing a random sampling of analytically computed fission chain distributions to generate a continuous time-evolving sequence of event-counts by spreading the fission chain distribution in time.

  2. Absolute nuclear material assay

    DOEpatents

    Prasad, Manoj K.; Snyderman, Neal J.; Rowland, Mark S.

    2010-07-13

    A method of absolute nuclear material assay of an unknown source comprising counting neutrons from the unknown source and providing an absolute nuclear material assay utilizing a model to optimally compare to the measured count distributions. In one embodiment, the step of providing an absolute nuclear material assay comprises utilizing a random sampling of analytically computed fission chain distributions to generate a continuous time-evolving sequence of event-counts by spreading the fission chain distribution in time.

  3. Discovery of Cepheids in NGC 5253: Absolute peak brightness of SN Ia 1895B and SN Ia 1972E and the value of H(sub 0)

    NASA Technical Reports Server (NTRS)

    Saha, A.; Sandage, Allan; Labhardt, Lukas; Schwengeler, Hans; Tammann, G. A.; Panagia, N.; Macchetto, F. D.

    1995-01-01

    Observations of the Hubble Space Telescope (HST) between 1993 May 31 and 1993 July 19 in 20 epochs in the F555W passband and five epochs in the F785LP passband have led to the discovery of 14 Cepheids in the Amorphous galaxy NGC 5253. The apparent V distance modulus is (m-M)(sub AV) = 28.08 +/- 0.10 determined from the 12 Cepheids with normal amplitudes. The distance modulus using the F785LP data is consistent with the V value to within the errors. Five methods used to determine the internal reddening are consistent with zero differential reddening, accurate to a level of E(B-V) less than 0.05 mag, over the region occupied by Cepheids and the two supernovae (SNe) produced by NGC 5253. The apparent magnitudes at maximum for the two SNe in NGC 5253 are adopted as B(sub max) = 8.33 +/- 0.2 mag for SN 1895B, and B(sub max) = 8.56 +/- 0.1 and V(sub max) = 8.60 +/- 0.1 for SN 1972E which is a prototype SN of Type Ia. The apparent magnitude system used by Walker (1923) for SN 1859B has been corrected to the modern B scale and zero point to determine its adopted B(sub max) value.

  4. Absolute instability of the Gaussian wake profile

    NASA Technical Reports Server (NTRS)

    Hultgren, Lennart S.; Aggarwal, Arun K.

    1987-01-01

    Linear parallel-flow stability theory has been used to investigate the effect of viscosity on the local absolute instability of a family of wake profiles with a Gaussian velocity distribution. The type of local instability, i.e., convective or absolute, is determined by the location of a branch-point singularity with zero group velocity of the complex dispersion relation for the instability waves. The effects of viscosity were found to be weak for values of the wake Reynolds number, based on the center-line velocity defect and the wake half-width, larger than about 400. Absolute instability occurs only for sufficiently large values of the center-line wake defect. The critical value of this parameter increases with decreasing wake Reynolds number, thereby indicating a shrinking region of absolute instability with decreasing wake Reynolds number. If backflow is not allowed, absolute instability does not occur for wake Reynolds numbers smaller than about 38.

  5. Absolute Income, Relative Income, and Happiness

    ERIC Educational Resources Information Center

    Ball, Richard; Chernova, Kateryna

    2008-01-01

    This paper uses data from the World Values Survey to investigate how an individual's self-reported happiness is related to (i) the level of her income in absolute terms, and (ii) the level of her income relative to other people in her country. The main findings are that (i) both absolute and relative income are positively and significantly…

  6. Hepatic Perfusion Therapy.

    PubMed

    Rajeev, Rahul; Gamblin, T Clark; Turaga, Kiran K

    2016-04-01

    Isolated hepatic perfusion uses the unique vascular supply of hepatic malignancies to deliver cytotoxic chemotherapy. The procedure involves vascular isolation of the liver and delivery of chemotherapy via the hepatic artery and extraction from retrohepatic vena cava. Benefits of hepatic perfusion have been observed in hepatic metastases of ocular melanoma and colorectal cancer and primary hepatocellular carcinoma. Percutaneous and prophylactic perfusions are avenues of ongoing research.

  7. Diagnostic Performance of Dual-Energy CT Stress Myocardial Perfusion Imaging: Direct Comparison With Cardiovascular MRI

    PubMed Central

    Ko, Sung Min; Song, Meong Gun; Chee, Hyun Kun; Hwang, Hweung Kon; Feuchtner, Gudrun Maria; Min, James K.

    2014-01-01

    OBJECTIVE The purpose of this study was to assess the diagnostic performance of stress perfusion dual-energy CT (DECT) and its incremental value when used with coronary CT angiography (CTA) for identifying hemodynamically significant coronary artery disease. SUBJECTS AND METHODS One hundred patients with suspected or known coronary artery disease without chronic myocardial infarction detected with coronary CTA underwent stress perfusion DECT, stress cardiovascular perfusion MRI, and invasive coronary angiography (ICA). Stress perfusion DECT and cardiovascular stress perfusion MR images were used for detecting perfusion defects. Coronary CTA and ICA were evaluated in the detection of ≥ 50% coronary stenosis. The diagnostic performance of coronary CTA for detecting hemodynamically significant stenosis was assessed before and after stress perfusion DECT on a pervessel basis with ICA and cardiovascular stress perfusion MRI as the reference standard. RESULTS The performance of stress perfusion DECT compared with cardiovascular stress perfusion MRI on a per-vessel basis in the detection of perfusion defects was sensitivity, 89%; specificity, 74%; positive predictive value, 73%; negative predictive value, 90%. Per segment, these values were sensitivity, 76%; specificity, 80%; positive predictive value, 63%; and negative predictive value, 88%. Compared with ICA and cardiovascular stress perfusion MRI per vessel territory the sensitivity, specificity, positive predictive value, and negative predictive value of coronary CTA were 95%, 61%, 61%, and 95%. The values for stress perfusion DECT were 92%, 72%, 68%, and 94%. The values for coronary CTA and stress perfusion DECT were 88%, 79%, 73%, and 91%. The ROC AUC increased from 0.78 to 0.84 (p = 0.02) with the use of coronary CTA and stress perfusion DECT compared with coronary CTA alone. CONCLUSION Stress perfusion DECT plays a complementary role in enhancing the accuracy of coronary CTA for identifying hemodynamically

  8. Pancreas transplants: Evaluation using perfusion scintigraphy

    SciTech Connect

    Kuni, C.C.; du Cret, R.P.; Boudreau, R.J.

    1989-07-01

    To determine the value of scintigraphic perfusion studies in evaluating pancreas transplant patients, we reviewed 56 of these studies in 22 patients who had 27 transplants. Seventeen patients underwent two or more studies. The perfusion studies were performed with 20 mCi (740 MBq) of 99mTc-DTPA injected as a bolus followed by eight to 16 serial 2-sec images and a 500,000-count immediate static image. Images were evaluated for (1) the time and intensity of pancreatic peak radioactivity relative to the time and intensity of the iliac arterial peak; (2) relative pancreatic to iliac arterial intensity on the static image; and (3) size, homogeneity, and definition of the pancreas. Clinical diagnoses at the time of scintigraphy of normal function (n = 36), rejection (n = 13), pancreatitis (n = 6), or arterial thrombosis (n = 1) were based on insulin requirement, urine amylase, serum glucose, serum amylase, response to therapy, cultures, CT, MR, sonography, scintigraphy with 67Ga or 111In-WBCs, percutaneous drainage results, angiography, surgery, and pathologic examination of resected transplants. Three 99mTc-DTPA perfusion studies showed no pancreatic perfusion, four showed decreasing perfusion on serial studies, and five showed progressive loss of definition of the pancreas on serial studies. Of the three patients with no detectable perfusion, one had a normally functioning transplant, one had arterial thrombosis with transplant infarction, and one had severe rejection with minimal function. Decreasing perfusion was associated with rejection in three patients and pancreatitis in one. Decreasing definition was seen in four patients with rejection and one with pancreatitis. We conclude that perfusion scintigraphy is useful, primarily when performed serially, although nonspecific for evaluating pancreas transplants.

  9. A Phantom Tissue System for the Calibration of Perfusion Measurements

    PubMed Central

    Mudaliar, Ashvinikumar V.; Ellis, Brent E.; Ricketts, Patricia L.; Lanz, Otto I.; Scott, Elaine P.; Diller, Thomas E.

    2008-01-01

    A convenient method for testing and calibrating surface perfusion sensors has been developed. A phantom tissue model is used to simulate the nondirectional blood flow of tissue perfusion. A computational fluid dynamics (CFD) model was constructed in Fluent® to design the phantom tissue and validate the experimental results. The phantom perfusion system was used with a perfusion sensor based on clearance of thermal energy. A heat flux gage measures the heat flux response of tissue when a thermal event (convective cooling) is applied. The blood perfusion and contact resistance are estimated by a parameter estimation code. From the experimental and analytical results, it was concluded that the probe displayed good measurement repeatability and sensitivity. The experimental perfusion measurements in the tissue were in good agreement with those of the CFD models and demonstrated the value of the phantom tissue system. PMID:19045509

  10. Dynamic CT myocardial perfusion imaging: detection of ischemia in a porcine model with FFR verification

    NASA Astrophysics Data System (ADS)

    Fahmi, Rachid; Eck, Brendan L.; Vembar, Mani; Bezerra, Hiram G.; Wilson, David L.

    2014-03-01

    Dynamic cardiac CT perfusion (CTP) is a high resolution, non-invasive technique for assessing myocardial blood ow (MBF), which in concert with coronary CT angiography enable CT to provide a unique, comprehensive, fast analysis of both coronary anatomy and functional ow. We assessed perfusion in a porcine model with and without coronary occlusion. To induce occlusion, each animal underwent left anterior descending (LAD) stent implantation and angioplasty balloon insertion. Normal ow condition was obtained with balloon completely de ated. Partial occlusion was induced by balloon in ation against the stent with FFR used to assess the extent of occlusion. Prospective ECG-triggered partial scan images were acquired at end systole (45% R-R) using a multi-detector CT (MDCT) scanner. Images were reconstructed using FBP and a hybrid iterative reconstruction (iDose4, Philips Healthcare). Processing included: beam hardening (BH) correction, registration of image volumes using 3D cubic B-spline normalized mutual-information, and spatio-temporal bilateral ltering to reduce partial scan artifacts and noise variation. Absolute blood ow was calculated with a deconvolutionbased approach using singular value decomposition (SVD). Arterial input function was estimated from the left ventricle (LV) cavity. Regions of interest (ROIs) were identi ed in healthy and ischemic myocardium and compared in normal and occluded conditions. Under-perfusion was detected in the correct LAD territory and ow reduction agreed well with FFR measurements. Flow was reduced, on average, in LAD territories by 54%.

  11. The absolute path command

    2012-05-11

    The ap command traveres all symlinks in a given file, directory, or executable name to identify the final absolute path. It can print just the final path, each intermediate link along with the symlink chan, and the permissions and ownership of each directory component in the final path. It has functionality similar to "which", except that it shows the final path instead of the first path. It is also similar to "pwd", but it canmore » provide the absolute path to a relative directory from the current working directory.« less

  12. The absolute path command

    SciTech Connect

    Moody, A.

    2012-05-11

    The ap command traveres all symlinks in a given file, directory, or executable name to identify the final absolute path. It can print just the final path, each intermediate link along with the symlink chan, and the permissions and ownership of each directory component in the final path. It has functionality similar to "which", except that it shows the final path instead of the first path. It is also similar to "pwd", but it can provide the absolute path to a relative directory from the current working directory.

  13. PREOPERATIVE PREDICTION OF LUNG FUNCTION IN PNEUMONECTOMY BY SPIROMETRY AND LUNG PERFUSION SCINTIGRAPHY

    PubMed Central

    Cukic, Vesna

    2012-01-01

    Introduction: Nowadays an increasing number of lung resections are being done because of the rising prevalence of lung cancer that occurs mainly in patients with limited lung function, what is caused by common etiologic factor - smoking cigarettes. Loss of lung tissue in such patients can worsen much the postoperative pulmonary function. So it is necessary to asses the postoperative pulmonary function especially after maximal resection, i.e. pneumonectomy. Objective: To check over the accuracy of preoperative prognosis of postoperative lung function after pneumonectomy using spirometry and lung perfusion scinigraphy. Material and methods: The study was done on 17 patients operated at the Clinic for thoracic surgery, who were treated previously at the Clinic for Pulmonary Diseases “Podhrastovi” in the period from 01. 12. 2008. to 01. 06. 2011. Postoperative pulmonary function expressed as ppoFEV1 (predicted postoperative forced expiratory volume in one second) was prognosticated preoperatively using spirometry, i.e.. simple calculation according to the number of the pulmonary segments to be removed and perfusion lung scintigraphy. Results: There is no significant deviation of postoperative achieved values of FEV1 from predicted ones obtained by both methods, and there is no significant differences between predicted values (ppoFEV1) obtained by spirometry and perfusion scintigraphy. Conclusion: It is necessary to asses the postoperative pulmonary function before lung resection to avoid postoperative respiratory failure and other cardiopulmonary complications. It is absolutely necessary for pneumonectomy, i.e.. maximal pulmonary resection. It can be done with great possibility using spirometry or perfusion lung scintigraphy. PMID:23378687

  14. Brain tumors and synchrotron radiation: Methodological developments in quantitative brain perfusion imaging and radiation therapy

    SciTech Connect

    Adam, Jean-Francois

    2005-04-01

    High-grade gliomas are the most frequent type of primary brain tumors in adults. Unfortunately, the management of glioblastomas is still mainly palliative and remains a difficult challenge, despite advances in brain tumor molecular biology and in some emerging therapies. Synchrotron radiation opens fields for medical imaging and radiation therapy by using monochromatic intense x-ray beams. It is now well known that angiogenesis plays a critical role in the tumor growth process and that brain perfusion is representative of the tumor mitotic activity. Synchrotron radiation quantitative computed tomography (SRCT) is one of the most accurate techniques for measuring in vivo contrast agent concentration and thus computing precise and accurate absolute values of the brain perfusion key parameters. The methodological developments of SRCT absolute brain perfusion measurements as well as their preclinical validation are detailed in this thesis. In particular, absolute cerebral volume and blood brain barrier permeability high-resolution (pixel size <50x50 {mu}m{sup 2}) parametric maps were reported. In conventional radiotherapy, the treatment of these tumors remains a delicate challenge, because the damages to the surrounding normal brain tissue limit the amount of radiation that can be delivered. One strategy to overcome this limitation is to infuse an iodinated contrast agent to the patient during the irradiation. The contrast agent accumulates in the tumor, through the broken blood brain barrier, and the irradiation is performed with kilovoltage x rays, in tomography mode, the tumor being located at the center of rotation and the beam size adjusted to the tumor dimensions. The dose enhancement results from the photoelectric effect on the heavy element and from the irradiation geometry. Synchrotron beams, providing high intensity, tunable monochromatic x rays, are ideal for this treatment. The beam properties allow the selection of monochromatic irradiation, at the optimal

  15. Ex vivo lung perfusion.

    PubMed

    Reeb, Jeremie; Cypel, Marcelo

    2016-03-01

    Lung transplantation is an established life-saving therapy for patients with end-stage lung disease. Unfortunately, greater success in lung transplantation is hindered by a shortage of lung donors and the relatively poor early-, mid-, and long-term outcomes associated with severe primary graft dysfunction. Ex vivo lung perfusion has emerged as a modern preservation technique that allows for a more accurate lung assessment and improvement in lung quality. This review outlines the: (i) rationale behind the method; (ii) techniques and protocols; (iii) Toronto ex vivo lung perfusion method; (iv) devices available; and (v) clinical experience worldwide. We also highlight the potential of ex vivo lung perfusion in leading a new era of lung preservation. PMID:26700566

  16. Isolated lung perfusion.

    PubMed

    Cypel, Marcelo; Keshavjee, Shaf

    2012-01-01

    Isolated lung perfusion (ILP) has been historically used as a method to study basic lung physiologic concepts using animal models. More recently, ILP has been applied in lung transplantation and thoracic oncology. In lung transplantation, ILP has been used to assess physiological integrity of donor lungs after the organ is removed from the donor. This procedure is called Ex vivo Lung Perfusion (EVLP), and it has also been proposed as a method for active treatment and repair of injured unsuitable donor organs ex vivo. In oncology, ILP is an attractive method to deliver high dose chemotherapy to treat pulmonary metastatic disease. Since the lung vasculature is isolated in vivo, this technique is called in vivo lung perfusion (IVLP). This review will focus on the rationale, technical aspects, experimental and clinical experience of EVLP and IVLP. A perspective on the future use of these techniques is described. PMID:22202033

  17. [New developments in parameter-oriented roentgen densitometry perfusion analysis within the scope of heart catheter studies].

    PubMed

    Haude, M; Caspari, G; Baumgart, D; Spiller, P; Heusch, G; Erbel, R

    1997-04-01

    X-ray densitometric evaluation of digital subtraction coronary arteriograms allows a qualitative and quantitative detection of contrast medium propagation through the epicardial coronary arteries, the capillary system and the coronary venous system. So-called "time-density-curves" (TDCs) can be generated following Lambert-Beer's law similar to indicator dilution curves by using contrast medium as the indicator. Several time and density parameters can be derived from these TDCs, which are related to local myocardial perfusion. Different animal validation studies have shown the applicability of this concept for in-vivo evaluation of coronary blood flow and myocardial perfusion. Nevertheless, absolute measurement of volumetric coronary blood flow or myocardial perfusion failed. Therefore, relative changes in coronary blood flow or myocardial perfusion in response to pharmacologically induced maximum hyperemia were measured and coronary or myocardial perfusion reserve was calculated as the ratio of hyperemic flow or perfusion divided by baseline values. Despite theoretical attractions for an application during routine cardiac catheterization, this densitometric approach did not get a wide acceptance. Primary reason for this limited use in specialized centers was the time consuming process of densitometric evaluation of the subtraction coronary arteriograms, which require digital cine angiography and necessitates enormous computer hard ware. This main limitation has been overcome since more powerful computer hard ware (processor speed, hard disk space, digitization boards) has become rapidly available during the last years at more moderate pricing and digital techniques today are state of the art in cardiac catheterization laboratories. In addition, soft ware program packages allowed an automatization of the digitization and densitometric evaluation process. These programs include ECG triggered cine image digitization with improved temporal resolution, semiautomatic

  18. ABSOLUTE POLARIMETRY AT RHIC.

    SciTech Connect

    OKADA; BRAVAR, A.; BUNCE, G.; GILL, R.; HUANG, H.; MAKDISI, Y.; NASS, A.; WOOD, J.; ZELENSKI, Z.; ET AL.

    2007-09-10

    Precise and absolute beam polarization measurements are critical for the RHIC spin physics program. Because all experimental spin-dependent results are normalized by beam polarization, the normalization uncertainty contributes directly to final physics uncertainties. We aimed to perform the beam polarization measurement to an accuracy Of {Delta}P{sub beam}/P{sub beam} < 5%. The absolute polarimeter consists of Polarized Atomic Hydrogen Gas Jet Target and left-right pairs of silicon strip detectors and was installed in the RHIC-ring in 2004. This system features proton-proton elastic scattering in the Coulomb nuclear interference (CNI) region. Precise measurements of the analyzing power A{sub N} of this process has allowed us to achieve {Delta}P{sub beam}/P{sub beam} = 4.2% in 2005 for the first long spin-physics run. In this report, we describe the entire set up and performance of the system. The procedure of beam polarization measurement and analysis results from 2004-2005 are described. Physics topics of AN in the CNI region (four-momentum transfer squared 0.001 < -t < 0.032 (GeV/c){sup 2}) are also discussed. We point out the current issues and expected optimum accuracy in 2006 and the future.

  19. Relative indexes of cutaneous blood perfusion measured by real-time laser Doppler imaging (LDI) in healthy volunteers.

    PubMed

    Seyed Jafari, S Morteza; Schawkat, Megir; Van De Ville, Dimitri; Shafighi, Maziar

    2014-07-01

    We used real-time LDI to study regional variations in microcirculatory perfusion in healthy candidates to establish a new methodology for global perfusion body mapping that is based on intra-individual perfusion index ratios. Our study included 74 (37 female) healthy volunteers aged between 22 and 30 years (mean 24.49). Imaging was performed using a recent microcirculation-imaging camera (EasyLDI) for different body regions of each volunteer. The perfusion values were reported in Arbitrary Perfusion Units (APU). The relative perfusion indexes for each candidate's body region were then obtained by normalization with the perfusion value of the forehead. Basic parameters such as weight, height, and blood pressure were also measured and analyzed. The highest mean perfusion value was reported in the forehead area (259.21APU). Mean perfusion in the measured parts of the body correlated positively with mean forehead value, while there was no significant correlation between forehead blood perfusion values and room temperature, BMI, systolic blood pressure and diastolic blood pressure (p=0.420, 0.623, 0.488, 0.099, respectively). Analysis of the data showed that perfusion indexes were not significantly different between male and female volunteers except for the ventral upper arm area (p=.001). LDI is a non-invasive, fast technique that opens several avenues for clinical applications. The mean perfusion indexes are useful in clinical practice for monitoring patients before and after surgical interventions. Perfusion values can be predicted for different body parts for patients only by taking the forehead perfusion value and using the perfusion index ratios to obtain expected normative perfusion values. PMID:24788075

  20. Relative indexes of cutaneous blood perfusion measured by real-time laser Doppler imaging (LDI) in healthy volunteers.

    PubMed

    Seyed Jafari, S Morteza; Schawkat, Megir; Van De Ville, Dimitri; Shafighi, Maziar

    2014-07-01

    We used real-time LDI to study regional variations in microcirculatory perfusion in healthy candidates to establish a new methodology for global perfusion body mapping that is based on intra-individual perfusion index ratios. Our study included 74 (37 female) healthy volunteers aged between 22 and 30 years (mean 24.49). Imaging was performed using a recent microcirculation-imaging camera (EasyLDI) for different body regions of each volunteer. The perfusion values were reported in Arbitrary Perfusion Units (APU). The relative perfusion indexes for each candidate's body region were then obtained by normalization with the perfusion value of the forehead. Basic parameters such as weight, height, and blood pressure were also measured and analyzed. The highest mean perfusion value was reported in the forehead area (259.21APU). Mean perfusion in the measured parts of the body correlated positively with mean forehead value, while there was no significant correlation between forehead blood perfusion values and room temperature, BMI, systolic blood pressure and diastolic blood pressure (p=0.420, 0.623, 0.488, 0.099, respectively). Analysis of the data showed that perfusion indexes were not significantly different between male and female volunteers except for the ventral upper arm area (p=.001). LDI is a non-invasive, fast technique that opens several avenues for clinical applications. The mean perfusion indexes are useful in clinical practice for monitoring patients before and after surgical interventions. Perfusion values can be predicted for different body parts for patients only by taking the forehead perfusion value and using the perfusion index ratios to obtain expected normative perfusion values.

  1. Relation between geometric dimensions of coronary artery stenoses and myocardial perfusion reserve in man.

    PubMed

    Goldstein, R A; Kirkeeide, R L; Demer, L L; Merhige, M; Nishikawa, A; Smalling, R W; Mullani, N A; Gould, K L

    1987-05-01

    To determine the relation between stenosis anatomy and perfusion in man, 31 patients had quantitative coronary arteriography and positron imaging (PET) with Rb-82 or N-13 ammonia at rest and after dipyridamole-handgrip stress. 10 patients were also studied after angioplasty (total stenoses = 41). Percent narrowing and absolute cross-sectional luminal area were related through a quadratic function to myocardial perfusion reserve determined with PET. Arteriographically determined coronary flow reserve was linearly related to relative myocardial perfusion reserve as expected, based on the derivation of equations for stenosis flow reserve. All of the correlations had considerable scatter, indicating that no single measurement derived by coronary arteriography was a good indicator of perfusion reserve by PET in individual patients. This study provides the relation between all anatomic dimensions of coronary artery stenoses and myocardial perfusion reserve in man, and suggests that PET indicates the functional significance of coronary artery stenoses for clinical purposes.

  2. Developing a benchmarking process in perfusion: a report of the Perfusion Downunder Collaboration.

    PubMed

    Baker, Robert A; Newland, Richard F; Fenton, Carmel; McDonald, Michael; Willcox, Timothy W; Merry, Alan F

    2012-03-01

    Improving and understanding clinical practice is an appropriate goal for the perfusion community. The Perfusion Downunder Collaboration has established a multi-center perfusion focused database aimed at achieving these goals through the development of quantitative quality indicators for clinical improvement through benchmarking. Data were collected using the Perfusion Downunder Collaboration database from procedures performed in eight Australian and New Zealand cardiac centers between March 2007 and February 2011. At the Perfusion Downunder Meeting in 2010, it was agreed by consensus, to report quality indicators (QI) for glucose level, arterial outlet temperature, and pCOz management during cardiopulmonary bypass. The values chosen for each QI were: blood glucose > or =4 mmol/L and < or =10 mmol/L; arterial outlet temperature < or = 37 degrees C; and arterial blood gas pCO2 > or =35 and < or =45 mmHg. The QI data were used to derive benchmarks using the Achievable Benchmark of Care (ABC) methodology to identify the incidence of QIs at the best performing centers. Five thousand four hundred and sixty-five procedures were evaluated to derive QI and benchmark data. The incidence of the blood glucose QI ranged from 37-96% of procedures, with a benchmark value of 90%. The arterial outlet temperature QI occurred in 16-98% of procedures with the benchmark of 94%; while the arterial pCO2 QI occurred in 21-91%, with the benchmark value of 80%. We have derived QIs and benchmark calculations for the management of several key aspects of cardiopulmonary bypass to provide a platform for improving the quality of perfusion practice.

  3. Absolute neutrino mass measurements

    SciTech Connect

    Wolf, Joachim

    2011-10-06

    The neutrino mass plays an important role in particle physics, astrophysics and cosmology. In recent years the detection of neutrino flavour oscillations proved that neutrinos carry mass. However, oscillation experiments are only sensitive to the mass-squared difference of the mass eigenvalues. In contrast to cosmological observations and neutrino-less double beta decay (0v2{beta}) searches, single {beta}-decay experiments provide a direct, model-independent way to determine the absolute neutrino mass by measuring the energy spectrum of decay electrons at the endpoint region with high accuracy.Currently the best kinematic upper limits on the neutrino mass of 2.2eV have been set by two experiments in Mainz and Troitsk, using tritium as beta emitter. The next generation tritium {beta}-experiment KATRIN is currently under construction in Karlsruhe/Germany by an international collaboration. KATRIN intends to improve the sensitivity by one order of magnitude to 0.2eV. The investigation of a second isotope ({sup 137}Rh) is being pursued by the international MARE collaboration using micro-calorimeters to measure the beta spectrum. The technology needed to reach 0.2eV sensitivity is still in the R and D phase. This paper reviews the present status of neutrino-mass measurements with cosmological data, 0v2{beta} decay and single {beta}-decay.

  4. Improvements in the Quantitative Assessment of Cerebral Blood Volume and Flow with the Removal of Vessel Voxels from MR Perfusion Images

    PubMed Central

    Teng, Michael Mu Huo; Cho, I-Chieh; Kao, Yi-Hsuan; Chuang, Chi-Shuo; Chiu, Fang-Ying; Chang, Feng-Chi

    2013-01-01

    Objective. To improve the quantitative assessment of cerebral blood volume (CBV) and flow (CBF) in the brain voxels from MR perfusion images. Materials and Methods. Normal brain parenchyma was automatically segmented with the time-to-peak criteria after cerebrospinal fluid removal and preliminary vessel voxel removal. Two scaling factors were calculated by comparing the relative CBV and CBF of the segmented normal brain parenchyma with the absolute values in the literature. Using the scaling factors, the relative values were converted to the absolute CBV and CBF. Voxels with either CBV > 8 mL/100 g or CBF > 100 mL/100 g/min were characterized as vessel voxels and were excluded from the quantitative measurements. Results. The segmented brain parenchyma with normal perfusion was consistent with the angiographic findings for each patient. We confirmed the necessity of dual thresholds including CBF and CBV for proper removal of vessel voxels. The scaling factors were 0.208 ± 0.041 for CBV, and 0.168 ± 0.037, 0.172 ± 0.037 for CBF calculated using standard and circulant singular value decomposition techniques, respectively. Conclusion. The automatic scaling and vessel removal techniques provide an alternative method for obtaining improved quantitative assessment of CBV and CBF in patients with thromboembolic cerebral arterial disease. PMID:23586033

  5. A flow microcalorimeter system for the measurement of dynamic energy variables of isolated perfused hearts.

    PubMed

    Niesler, R A; Axon, D W

    1981-11-01

    An isothermic flow microcalorimeter system for fluid rates of 1-50 cm3 min -1 has been developed to measure the total heat flow produced by isolated perfused small animal hearts and its rate of change. The heat, which is absorbed by the perfusion fluid flowing through the coronary capillary system, is detected by passing the coronary effluent through a plate heat exchanger mounted in intimate contact with the internal surface of a gradient layer calorimeter. By employing electrical calibration, this heat flow detector gives a precision of +/- 0.2 m W for average effluent rates of about 15 cm3 min-1. The method provides direct comparison of the biologically produced heat flow with electrically generated energy flows. The response time to step changes in heat flow is 1 min to 90% of the total change. Possible systematic errors are analysed and quantified, using a heart bypass flow technique and a thermoelectric differential temperature meter. The accuracy of the measurement of constant heat sources with the complete system over the range of 5-40 mW is +/- 2% for fluid rates up to 40 cm3 min-1. Measurements with small rat hearts have given absolute values between 17 and 36 mW measured with an accuracy of +/- 3%. The rate of total myocardial energy turnover can be studied with the system.

  6. Low dose CT perfusion using k-means clustering

    NASA Astrophysics Data System (ADS)

    Pisana, Francesco; Henzler, Thomas; Schönberg, Stefan; Klotz, Ernst; Schmidt, Bernhard; Kachelrieß, Marc

    2016-03-01

    We aim at improving low dose CT perfusion functional parameters maps and CT images quality, preserving quantitative information. In a dynamic CT perfusion dataset, each voxel is measured T times, where T is the number of acquired time points. In this sense, we can think about a voxel as a point in a T-dimensional space, where the coordinates of the voxels would be the values of its time attenuation curve (TAC). Starting from this idea, a k-means algorithm was designed to group voxels in K classes. A modified guided time-intensity profile similarity (gTIPS) filter was implemented and applied only for those voxels belonging to the same class. The approach was tested on a digital brain perfusion phantom as well as on clinical brain and body perfusion datasets, and compared to the original TIPS implementation. The TIPS filter showed the highest CNR improvement, but lowest spatial resolution. gTIPS proved to have the best combination of spatial resolution and CNR improvement for CT images, while k-gTIPS was superior to both gTIPS and TIPS in terms of perfusion maps image quality. We demonstrate k-means clustering analysis can be applied to denoise dynamic CT perfusion data and to improve functional maps. Beside the promising results, this approach has the major benefit of being independent from the perfusion model employed for functional parameters calculation. No similar approaches were found in literature.

  7. Automated prediction of tissue outcome after acute ischemic stroke in computed tomography perfusion images

    NASA Astrophysics Data System (ADS)

    Vos, Pieter C.; Bennink, Edwin; de Jong, Hugo; Velthuis, Birgitta K.; Viergever, Max A.; Dankbaar, Jan Willem

    2015-03-01

    Assessment of the extent of cerebral damage on admission in patients with acute ischemic stroke could play an important role in treatment decision making. Computed tomography perfusion (CTP) imaging can be used to determine the extent of damage. However, clinical application is hindered by differences among vendors and used methodology. As a result, threshold based methods and visual assessment of CTP images has not yet shown to be useful in treatment decision making and predicting clinical outcome. Preliminary results in MR studies have shown the benefit of using supervised classifiers for predicting tissue outcome, but this has not been demonstrated for CTP. We present a novel method for the automatic prediction of tissue outcome by combining multi-parametric CTP images into a tissue outcome probability map. A supervised classification scheme was developed to extract absolute and relative perfusion values from processed CTP images that are summarized by a trained classifier into a likelihood of infarction. Training was performed using follow-up CT scans of 20 acute stroke patients with complete recanalization of the vessel that was occluded on admission. Infarcted regions were annotated by expert neuroradiologists. Multiple classifiers were evaluated in a leave-one-patient-out strategy for their discriminating performance using receiver operating characteristic (ROC) statistics. Results showed that a RandomForest classifier performed optimally with an area under the ROC of 0.90 for discriminating infarct tissue. The obtained results are an improvement over existing thresholding methods and are in line with results found in literature where MR perfusion was used.

  8. Absolute Identification by Relative Judgment

    ERIC Educational Resources Information Center

    Stewart, Neil; Brown, Gordon D. A.; Chater, Nick

    2005-01-01

    In unidimensional absolute identification tasks, participants identify stimuli that vary along a single dimension. Performance is surprisingly poor compared with discrimination of the same stimuli. Existing models assume that identification is achieved using long-term representations of absolute magnitudes. The authors propose an alternative…

  9. Comparing Quantitative Values of Two Generations of Laser-Assisted Indocyanine Green Dye Angiography Systems: Can We Predict Necrosis?

    PubMed Central

    Fourman, Mitchell S.; Rivara, Andrew; Dagum, Alexander B.; Huston, Tara L.; Ganz, Jason C.; Bui, Duc T.; Khan, Sami U.

    2014-01-01

    Objective: Several devices exist today to assist the intraoperative determination of skin flap perfusion. Laser-Assisted Indocyanine Green Dye Angiography (LAICGA) has been shown to accurately predict mastectomy skin flap necrosis using quantitative perfusion values. The laser properties of the latest LAICGA device (SPY Elite) differ significantly from its predecessor system (SPY 2001), preventing direct translation of previous published data. The purpose of this study was to establish a mathematical relationship of perfusion values between these 2 devices. Methods: Breast reconstruction patients were prospectively enrolled into a clinical trial where skin flap evaluation and excision was based on quantitative SPY Q values previously established in the literature. Initial study patients underwent mastectomy skin flap evaluation using both SPY systems simultaneously. Absolute perfusion unit (APU) values at identical locations on the breast were then compared graphically. Results: 210 data points were identified on the same patients (n = 4) using both SPY systems. A linear relationship (y = 2.9883x + 12.726) was identified with a high level or correlation (R2 = 0.744). Previously published values using SPY 2001 (APU 3.7) provided a value of 23.8 APU on the SPY Elite. In addition, postoperative necrosis in these patients correlated to regions of skin identified with the SPY Elite with APU less than 23.8. Conclusion: Intraoperative comparison of LAICGA systems has provided direct correlation of perfusion values predictive of necrosis that were previously established in the literature. An APU value of 3.7 from the SPY 2001 correlates to a SPY Elite APU value of 23.8. PMID:25525483

  10. Perfusion Bioreactor Module

    NASA Technical Reports Server (NTRS)

    Morrison, Dennis R.

    1990-01-01

    Perfusion bioreactor module, self-contained, closed-loop cell-culture system that operates in microgravity or on Earth. Equipment supports growth or long-term maintenance of cultures of human or other fragile cells for experiments in basic cell biology or process technology. Designed to support proliferation (initially at exponential rates of growth) of cells in complex growth medium and to maintain confluent cells in defined medium under conditions optimized to permit or encourage selected functions of cells, including secretion of products of cells into medium.

  11. Probing absolute spin polarization at the nanoscale.

    PubMed

    Eltschka, Matthias; Jäck, Berthold; Assig, Maximilian; Kondrashov, Oleg V; Skvortsov, Mikhail A; Etzkorn, Markus; Ast, Christian R; Kern, Klaus

    2014-12-10

    Probing absolute values of spin polarization at the nanoscale offers insight into the fundamental mechanisms of spin-dependent transport. Employing the Zeeman splitting in superconducting tips (Meservey-Tedrow-Fulde effect), we introduce a novel spin-polarized scanning tunneling microscopy that combines the probing capability of the absolute values of spin polarization with precise control at the atomic scale. We utilize our novel approach to measure the locally resolved spin polarization of magnetic Co nanoislands on Cu(111). We find that the spin polarization is enhanced by 65% when increasing the width of the tunnel barrier by only 2.3 Å due to the different decay of the electron orbitals into vacuum. PMID:25423049

  12. Asteroid absolute magnitudes and slope parameters

    NASA Technical Reports Server (NTRS)

    Tedesco, Edward F.

    1991-01-01

    A new listing of absolute magnitudes (H) and slope parameters (G) has been created and published in the Minor Planet Circulars; this same listing will appear in the 1992 Ephemerides of Minor Planets. Unlike previous listings, the values of the current list were derived from fits of data at the V band. All observations were reduced in the same fashion using, where appropriate, a single basis default value of 0.15 for the slope parameter. Distances and phase angles were computed for each observation. The data for 113 asteroids was of sufficiently high quality to permit derivation of their H and G. These improved absolute magnitudes and slope parameters will be used to deduce the most reliable bias-corrected asteroid size-frequency distribution yet made.

  13. Lung Ventilation/Perfusion Scan

    MedlinePlus

    ... from the NHLBI on Twitter. What Is a Lung Ventilation/Perfusion Scan? A lung ventilation/perfusion scan, or VQ scan, is a ... that measures air and blood flow in your lungs. A VQ scan most often is used to ...

  14. Ex-vivo lung perfusion.

    PubMed

    Van Raemdonck, Dirk; Neyrinck, Arne; Cypel, Marcelo; Keshavjee, Shaf

    2015-06-01

    This review outlines the new and promising technique of ex vivo lung perfusion and its clinical potential to increase the number of transplantable lungs and to improve the early and late outcome after transplantation. The rationale, the experimental background, the technique and protocols, and available devices for ex vivo lung perfusion are discussed. The current clinical experience worldwide and ongoing clinical trials are reviewed.

  15. Absolute photoionization cross sections of atomic oxygen

    NASA Technical Reports Server (NTRS)

    Samson, J. A. R.; Pareek, P. N.

    1985-01-01

    The absolute values of photoionization cross sections of atomic oxygen were measured from the ionization threshold to 120 A. An auto-ionizing resonance belonging to the 2S2P4(4P)3P(3Do, 3So) transition was observed at 479.43 A and another line at 389.97 A. The experimental data is in excellent agreement with rigorous close-coupling calculations that include electron correlations in both the initial and final states.

  16. Absolute photoionization cross sections of atomic oxygen

    NASA Technical Reports Server (NTRS)

    Samson, J. A. R.; Pareek, P. N.

    1982-01-01

    The absolute values of photoionization cross sections of atomic oxygen were measured from the ionization threshold to 120 A. An auto-ionizing resonance belonging to the 2S2P4(4P)3P(3Do, 3So) transition was observed at 479.43 A and another line at 389.97 A. The experimental data is in excellent agreement with rigorous close-coupling calculations that include electron correlations in both the initial and final states.

  17. Laser interferometry method for absolute measurement of the acceleration of gravity

    NASA Technical Reports Server (NTRS)

    Hudson, O. K.

    1971-01-01

    Gravimeter permits more accurate and precise absolute measurement of g without reference to Potsdam values as absolute standards. Device is basically Michelson laser beam interferometer in which one arm is mass fitted with corner cube reflector.

  18. Singular perturbation of absolute stability.

    NASA Technical Reports Server (NTRS)

    Siljak, D. D.

    1972-01-01

    It was previously shown (author, 1969) that the regions of absolute stability in the parameter space can be determined when the parameters appear on the right-hand side of the system equations, i.e., the regular case. Here, the effect on absolute stability of a small parameter attached to higher derivatives in the equations (the singular case) is studied. The Lur'e-Postnikov class of nonlinear systems is considered.

  19. Ex vivo normothermic machine perfusion and viability testing of discarded human donor livers.

    PubMed

    op den Dries, S; Karimian, N; Sutton, M E; Westerkamp, A C; Nijsten, M W N; Gouw, A S H; Wiersema-Buist, J; Lisman, T; Leuvenink, H G D; Porte, R J

    2013-05-01

    In contrast to traditional static cold preservation of donor livers, normothermic machine perfusion may reduce preservation injury, improve graft viability and potentially allows ex vivo assessment of graft viability before transplantation. We have studied the feasibility of normothermic machine perfusion in four discarded human donor livers. Normothermic machine perfusion consisted of pressure and temperature controlled pulsatile perfusion of the hepatic artery and continuous portal perfusion for 6 h. Two hollow fiber membrane oxygenators provided oxygenation of the perfusion fluid. Biochemical markers in the perfusion fluid reflected minimal hepatic injury and improving function. Lactate levels decreased to normal values, reflecting active metabolism by the liver (mean lactate 10.0 ± 2.3 mmol/L at 30 min to 2.3 ± 1.2 mmol/L at 6 h). Bile production was observed throughout the 6 h perfusion period (mean rate 8.16 ± 0.65 g/h after the first hour). Histological examination before and after 6 h of perfusion showed well-preserved liver morphology without signs of additional hepatocellular ischemia, biliary injury or sinusoidal damage. In conclusion, this study shows that normothermic machine perfusion of human donor livers is technically feasible. It allows assessment of graft viability before transplantation, which opens new avenues for organ selection, therapeutic interventions and preconditioning.

  20. A new formalism for the quantification of tissue perfusion by the destruction-replenishment method in contrast ultrasound imaging.

    PubMed

    Arditi, Marcel; Frinking, Peter J A; Zhou, Xiang; Rognin, Nicolas G

    2006-06-01

    A new formalism is presented for the destruction-replenishment perfusion quantification approach at low mechanical index. On the basis of physical considerations, best-fit methods should be applied using perfusion functions with S-shape characteristics. These functions are first described for the case of a geometry with a single flow velocity, then extended to the case of vascular beds with blood vessels having multiple flow velocity values and directions. The principles guiding the analysis are, on one hand, a linearization of video echo signals to overcome the log-compression of the imaging instrument, and, on the other hand, the spatial distribution of the transmit-receive ultrasound beam in the elevation direction. An in vitro model also is described; it was used to confirm experimentally the validity of the approach using a commercial contrast agent. The approach was implemented in the form of a computer program, taking as input a sequence of contrast-specific images, as well as parameters related to the ultrasound imaging equipment used. The generated output is either flow-parameter values computed in regions-of-interest, or parametric flow-images (e.g., mean velocity, mean transit time, mean flow, flow variance, or skewness). This approach thus establishes a base for extracting information about the morphology of vascular beds in vivo, and could allow absolute quantification provided that appropriate instrument calibration is implemented. PMID:16846144

  1. Ex vivo lung perfusion.

    PubMed

    Machuca, Tiago N; Cypel, Marcelo

    2014-08-01

    Lung transplantation (LTx) is an established treatment option for eligible patients with end-stage lung disease. Nevertheless, the imbalance between suitable donor lungs available and the increasing number of patients considered for LTx reflects in considerable waitlist mortality. Among potential alternatives to address this issue, ex vivo lung perfusion (EVLP) has emerged as a modern preservation technique that allows for more accurate lung assessment and also improvement of lung function. Its application in high-risk donor lungs has been successful and resulted in safe expansion of the donor pool. This article will: (I) review the technical details of EVLP; (II) the rationale behind the method; (III) report the worldwide clinical experience with the EVLP, including the Toronto technique and others; (IV) finally, discuss the growing literature on EVLP application for donation after cardiac death (DCD) lungs. PMID:25132972

  2. Ex vivo lung perfusion

    PubMed Central

    Machuca, Tiago N.

    2014-01-01

    Lung transplantation (LTx) is an established treatment option for eligible patients with end-stage lung disease. Nevertheless, the imbalance between suitable donor lungs available and the increasing number of patients considered for LTx reflects in considerable waitlist mortality. Among potential alternatives to address this issue, ex vivo lung perfusion (EVLP) has emerged as a modern preservation technique that allows for more accurate lung assessment and also improvement of lung function. Its application in high-risk donor lungs has been successful and resulted in safe expansion of the donor pool. This article will: (I) review the technical details of EVLP; (II) the rationale behind the method; (III) report the worldwide clinical experience with the EVLP, including the Toronto technique and others; (IV) finally, discuss the growing literature on EVLP application for donation after cardiac death (DCD) lungs. PMID:25132972

  3. Fast nonlinear regression method for CT brain perfusion analysis.

    PubMed

    Bennink, Edwin; Oosterbroek, Jaap; Kudo, Kohsuke; Viergever, Max A; Velthuis, Birgitta K; de Jong, Hugo W A M

    2016-04-01

    Although computed tomography (CT) perfusion (CTP) imaging enables rapid diagnosis and prognosis of ischemic stroke, current CTP analysis methods have several shortcomings. We propose a fast nonlinear regression method with a box-shaped model (boxNLR) that has important advantages over the current state-of-the-art method, block-circulant singular value decomposition (bSVD). These advantages include improved robustness to attenuation curve truncation, extensibility, and unified estimation of perfusion parameters. The method is compared with bSVD and with a commercial SVD-based method. The three methods were quantitatively evaluated by means of a digital perfusion phantom, described by Kudo et al. and qualitatively with the aid of 50 clinical CTP scans. All three methods yielded high Pearson correlation coefficients ([Formula: see text]) with the ground truth in the phantom. The boxNLR perfusion maps of the clinical scans showed higher correlation with bSVD than the perfusion maps from the commercial method. Furthermore, it was shown that boxNLR estimates are robust to noise, truncation, and tracer delay. The proposed method provides a fast and reliable way of estimating perfusion parameters from CTP scans. This suggests it could be a viable alternative to current commercial and academic methods. PMID:27413770

  4. Measurement of absolute gravity acceleration in Firenze

    NASA Astrophysics Data System (ADS)

    de Angelis, M.; Greco, F.; Pistorio, A.; Poli, N.; Prevedelli, M.; Saccorotti, G.; Sorrentino, F.; Tino, G. M.

    2011-01-01

    This paper reports the results from the accurate measurement of the acceleration of gravity g taken at two separate premises in the Polo Scientifico of the University of Firenze (Italy). In these laboratories, two separate experiments aiming at measuring the Newtonian constant and testing the Newtonian law at short distances are in progress. Both experiments require an independent knowledge on the local value of g. The only available datum, pertaining to the italian zero-order gravity network, was taken more than 20 years ago at a distance of more than 60 km from the study site. Gravity measurements were conducted using an FG5 absolute gravimeter, and accompanied by seismic recordings for evaluating the noise condition at the site. The absolute accelerations of gravity at the two laboratories are (980 492 160.6 ± 4.0) μGal and (980 492 048.3 ± 3.0) μGal for the European Laboratory for Non-Linear Spectroscopy (LENS) and Dipartimento di Fisica e Astronomia, respectively. Other than for the two referenced experiments, the data here presented will serve as a benchmark for any future study requiring an accurate knowledge of the absolute value of the acceleration of gravity in the study region.

  5. Myocardial perfusion imaging with dual energy CT.

    PubMed

    Jin, Kwang Nam; De Cecco, Carlo N; Caruso, Damiano; Tesche, Christian; Spandorfer, Adam; Varga-Szemes, Akos; Schoepf, U Joseph

    2016-10-01

    Dual-energy CT (DECT) enables simultaneous use of two different tube voltages, thus different x-ray absorption characteristics are acquired in the same anatomic location with two different X-ray spectra. The various DECT techniques allow material decomposition and mapping of the iodine distribution within the myocardium. Static dual-energy myocardial perfusion imaging (sCTMPI) using pharmacological stress agents demonstrate myocardial ischemia by single snapshot images of myocardial iodine distribution. sCTMPI gives incremental values to coronary artery stenosis detected on coronary CT angiography (CCTA) by showing consequent reversible or fixed myocardial perfusion defects. The comprehensive acquisition of CCTA and sCTMPI offers extensive morphological and functional evaluation of coronary artery disease. Recent studies have revealed that dual-energy sCTMPI shows promising diagnostic accuracy for the detection of hemodynamically significant coronary artery disease compared to single-photon emission computed tomography, invasive coronary angiography, and cardiac MRI. The aim of this review is to present currently available DECT techniques for static myocardial perfusion imaging and recent clinical applications and ongoing investigations.

  6. Absolute radiometry and the solar constant

    NASA Technical Reports Server (NTRS)

    Willson, R. C.

    1974-01-01

    A series of active cavity radiometers (ACRs) are described which have been developed as standard detectors for the accurate measurement of irradiance in absolute units. It is noted that the ACR is an electrical substitution calorimeter, is designed for automatic remote operation in any environment, and can make irradiance measurements in the range from low-level IR fluxes up to 30 solar constants with small absolute uncertainty. The instrument operates in a differential mode by chopping the radiant flux to be measured at a slow rate, and irradiance is determined from two electrical power measurements together with the instrumental constant. Results are reported for measurements of the solar constant with two types of ACRs. The more accurate measurement yielded a value of 136.6 plus or minus 0.7 mW/sq cm (1.958 plus or minus 0.010 cal/sq cm per min).

  7. [Extracorporeal perfusion of the sheep rumen].

    PubMed

    Leng, L; Bajo, M; Várady, J; Szányiová, M

    1977-06-01

    We constructed a modified perfusion apparatus and elaborated a method of extracorporal perfusion of the rumen of sheep. As perfusates we used the bovine plasma diluted in a ratio of 1:1 of an isotonic sodium chloride (NaCl) solution and the whole autologous blood. Transaminases GOT and GPT, ammonia and pH were determined in the perfusate. The different perfusions were evaluated according to previously determined perfusion conditions and criteria. A subject for discussion is the question of suitability of the parameters under examination for judging the state of the perfused organ. The described method is suitable for the study of metabolical processes in the rumen wal.

  8. Effect of x-ray tube current on the accuracy of cerebral perfusion parameters obtained by CT perfusion studies

    NASA Astrophysics Data System (ADS)

    Murase, Kenya; Nanjo, Takafumi; Satoshi, Ii; Miyazaki, Shohei; Hirata, Masaaki; Sugawara, Yoshifumi; Kudo, Masayuki; Sasaki, Kousuke; Mochizuki, Teruhito

    2005-11-01

    The purpose of this study was to investigate the effect of x-ray tube current on the accuracy of cerebral perfusion parameters obtained by CT perfusion studies using multi-detector row CT (MDCT). Following the standard CT perfusion study protocol, continuous (cine) scans (1 s/rotation × 60 s) consisting of four 5 mm thick contiguous slices were performed using an MDCT scanner with a tube voltage of 80 kVp and a tube current of 200 mA. We generated the simulated images with tube currents of 50 mA, 100 mA and 150 mA by adding the corresponding noise to the raw scan data of the original image acquired above using a noise simulation tool. From the original and simulated images, we generated the functional images of cerebral blood flow (CBF), cerebral blood volume (CBV) and mean transit time (MTT) in seven patients with cerebrovascular disease, and compared the correlation coefficients (CCs) between the perfusion parameter values obtained from the original and simulated images. The coefficients of variation (CVs) in the white matter were also compared. The CC values deteriorated with decreasing tube current. There was a significant difference between 50 mA and 100 mA for all perfusion parameters. The CV values increased with decreasing tube current. There were significant differences between 50 mA and 100 mA and between 100 mA and 150 mA for CBF. For CBV and MTT, there was also a significant difference between 150 mA and 200 mA. This study will be useful for understanding the effect of x-ray tube current on the accuracy of cerebral perfusion parameters obtained by CT perfusion studies using MDCT, and for selecting the tube current.

  9. Distributed perfusion educational model: a shift in perfusion economic realities.

    PubMed

    Austin, Jon W; Evans, Edward L; Hoerr, Harry R

    2005-12-01

    In recent years, a steady decline in the number of perfusion education programs in the United States has been noted. At the same time, there has been a parallel decline in the number of students graduated from perfusion educational programs in the United States. Also, as noted by several authors, there has been an increase in demand for perfusion graduates. The decline in programs and graduates has also been noted in anesthesia and surgical residency programs. The shift is caused by a combination of economic and clinical factors. First, decreased reimbursement has led to reallocation of hospital resources. Second, the original enthusiasm for beating heart coronary artery bypass surgery was grossly overestimated and has led to further reallocation of hospital resources and denigration of cardiopulmonary bypass. This paper describes two models of perfusion education programs: serial perfusion education model (SPEM) and the distributed perfusion education model (DPEM). Arguments are presented that the SPEM has some serious limitations and challenges for long-term economic survival. The authors feel the DPEM along with dependence on tuition funding can survive the current clinical and economic conditions and allow the profession to adapt to changes in scope of practice. PMID:16524152

  10. Mechanical and metabolic viability of a placental perfusion system in vitro under oxygenated and anoxic conditions.

    PubMed

    Illsley, N P; Aarnoudse, J G; Penfold, P; Bardsley, S E; Coade, S B; Stacey, T E; Hytten, F E

    1984-01-01

    In vitro dual circuit perfusion of the placenta with well-oxygenated medium results in the continuous and stable consumption of oxygen and glucose over a 2-h perfusion period. This is reflected in a stable production of lactate and an energy charge which is higher at the end of the perfusion period than that seen in fresh placental tissue immediately after vaginal delivery. Anoxic perfusion causes an increase in glucose consumption which is more than twofold higher than that seen in the oxygenated perfusion, resulting finally in placental uptake of glucose not only from the maternal but also from the fetal circulation. Lactate production is increased during the anoxic perfusion, while the final tissue energy charge value lies between the values observed for fresh tissue and for the oxygenated perfusion. The shift to anaerobic metabolism shown by placental tissue in anoxic conditions enables continued functioning of the tissue over the 2-h perfusion period but it appears that under anoxic conditions the tissue may incur an energy debt not observed in oxygenated perfusions.

  11. Ex-vivo lung perfusion.

    PubMed

    Van Raemdonck, Dirk; Neyrinck, Arne; Cypel, Marcelo; Keshavjee, Shaf

    2015-06-01

    This review outlines the new and promising technique of ex vivo lung perfusion and its clinical potential to increase the number of transplantable lungs and to improve the early and late outcome after transplantation. The rationale, the experimental background, the technique and protocols, and available devices for ex vivo lung perfusion are discussed. The current clinical experience worldwide and ongoing clinical trials are reviewed. PMID:24629039

  12. Absolute flux scale for radioastronomy

    SciTech Connect

    Ivanov, V.P.; Stankevich, K.S.

    1986-07-01

    The authors propose and provide support for a new absolute flux scale for radio astronomy, which is not encumbered with the inadequacies of the previous scales. In constructing it the method of relative spectra was used (a powerful tool for choosing reference spectra). A review is given of previous flux scales. The authors compare the AIS scale with the scale they propose. Both scales are based on absolute measurements by the ''artificial moon'' method, and they are practically coincident in the range from 0.96 to 6 GHz. At frequencies above 6 GHz, 0.96 GHz, the AIS scale is overestimated because of incorrect extrapolation of the spectra of the primary and secondary standards. The major results which have emerged from this review of absolute scales in radio astronomy are summarized.

  13. Complete inhibition of creatine kinase in isolated perfused rat hearts

    SciTech Connect

    Fossel, E.T.; Hoefeler, H.

    1987-01-01

    Transient exposure of an isolated isovolumic perfused rat heart to low concentrations (0.5 mM) of perfusate-born iodoacetamide resulted in complete inhibition of creatine kinase and partial inhibition of glyceraldehyde-3-phosphate dehydrogenase in the heart. At low levels of developed pressure, hearts maintained mechanical function, ATP, and creatine phosphate levels at control values. However, iodoacetamide-inhibited hearts were unable to maintain control values of end diastolic pressure or peak systolic pressure as work load increased. Global ischemia resulted in loss of all ATP without loss of creatine phosphate, indicating lack of active creatine kinase. These results indicate that isovolumic perfused rat hearts are able to maintain normal function and normal levels of high-energy phosphates without active creatine kinase at low levels of developed pressure. /sup 31/P-NMR of the heart was carried out.

  14. Hydrostatic determinants of cerebral perfusion

    SciTech Connect

    Wagner, E.M.; Traystman, R.J.

    1986-05-01

    We examined the cerebral blood flow response to alterations in perfusion pressure mediated through decreases in mean arterial pressure, increases in cerebrospinal fluid (CSF) pressure, and increases in jugular venous (JV) pressure in 42 pentobarbital anesthetized dogs. Each of these three pressures was independently controlled. Cerebral perfusion pressure was defined as mean arterial pressure minus JV or CSF pressure, depending on which was greater. Mean hemispheric blood flow was measured with the radiolabeled microsphere technique. Despite 30-mm Hg reductions in mean arterial pressure or increases in CSF or JV pressure, CBF did not change as long as the perfusion pressure remained greater than approximately 60 mm Hg. However, whenever perfusion pressure was reduced to an average of 48 mm Hg, cerebral blood flow decreased 27% to 33%. These results demonstrate the capacity of the cerebral vascular bed to respond similarly to changes in the perfusion pressure gradient obtained by decreasing mean arterial pressure, increasing JV pressure or increasing CSF pressure, and thereby support the above definition of cerebral perfusion pressure.

  15. Regional time-density measurement of myocardial perfusion

    NASA Astrophysics Data System (ADS)

    Eusemann, Christian D.; Breen, Jerome F.; Robb, Richard A.

    2003-05-01

    The measurement of time-density relationships of the myocardium in studies of Magnetic Resonance perfusion data sets is a clinical technique used in assessing myocardial perfusion. Traditionally, to measure the time-density relationship a physician draws a region on the same 2-D image of the myocardium in sequential cardiac cycles. Throughout multiple cardiac cycles the density changes in this region are measured. A major limitation of this technique is change in anatomy relative to the selected region on the myocardium during consecutive cardiac cycles. This causes measurement errors, which are amplified if the traced region does not encompass the entire myocardial thickness, or includes a boundary exterior to the epicardial or endocardial surface. The technique described in this paper uses approximately the same myocardial region throughout the entire perfusion study, which insures inclusion of the entire endocardial to epicardial region and exclusion of exterior regions. Moreover, this region can be subdivided into smaller regions of interest. This can be accomplished by careful segmentation and reformatting of the data into polar coordinates. This allows sectioning both axially and transaxially through the myocardium permitting regional assessment of perfusion specific values such as maximum and/or the time to reach maximum density. These values can then be illustrated using density-mapped colors or time-density curves. This measurement and display technique may provide enhanced detection and evaluation of regional deficits in myocardial contractility and perfusion.

  16. Relativistic Absolutism in Moral Education.

    ERIC Educational Resources Information Center

    Vogt, W. Paul

    1982-01-01

    Discusses Emile Durkheim's "Moral Education: A Study in the Theory and Application of the Sociology of Education," which holds that morally healthy societies may vary in culture and organization but must possess absolute rules of moral behavior. Compares this moral theory with current theory and practice of American educators. (MJL)

  17. Absolute transition probabilities of phosphorus.

    NASA Technical Reports Server (NTRS)

    Miller, M. H.; Roig, R. A.; Bengtson, R. D.

    1971-01-01

    Use of a gas-driven shock tube to measure the absolute strengths of 21 P I lines and 126 P II lines (from 3300 to 6900 A). Accuracy for prominent, isolated neutral and ionic lines is estimated to be 28 to 40% and 18 to 30%, respectively. The data and the corresponding theoretical predictions are examined for conformity with the sum rules.-

  18. Absolute rate theories of epigenetic stability

    NASA Astrophysics Data System (ADS)

    Walczak, Aleksandra M.; Onuchic, José N.; Wolynes, Peter G.

    2005-12-01

    Spontaneous switching events in most characterized genetic switches are rare, resulting in extremely stable epigenetic properties. We show how simple arguments lead to theories of the rate of such events much like the absolute rate theory of chemical reactions corrected by a transmission factor. Both the probability of the rare cellular states that allow epigenetic escape and the transmission factor depend on the rates of DNA binding and unbinding events and on the rates of protein synthesis and degradation. Different mechanisms of escape from the stable attractors occur in the nonadiabatic, weakly adiabatic, and strictly adiabatic regimes, characterized by the relative values of those input rates. rate theory | stochastic gene expression | gene switches

  19. Absolute method of measuring magnetic susceptibility

    USGS Publications Warehouse

    Thorpe, A.; Senftle, F.E.

    1959-01-01

    An absolute method of standardization and measurement of the magnetic susceptibility of small samples is presented which can be applied to most techniques based on the Faraday method. The fact that the susceptibility is a function of the area under the curve of sample displacement versus distance of the magnet from the sample, offers a simple method of measuring the susceptibility without recourse to a standard sample. Typical results on a few substances are compared with reported values, and an error of less than 2% can be achieved. ?? 1959 The American Institute of Physics.

  20. Aortic arch surgery with a single centrifugal pump for selective cerebral perfusion and systemic circulation.

    PubMed

    Iwata, Keiji; Shimazaki, Yasuhisa; Sakamoto, Tomohiko; Ueda, Hideki; Nakagawa, Masashi; Yamada, Hideto; Doi, Teruo; Ooue, Takuya

    2010-01-01

    In aortic arch surgery, two pumps are required for systemic perfusion and selective cerebral perfusion (SCP). A new technique with a single centrifugal pump for systemic perfusion and SCP was developed and its efficacy and safety evaluated. This technique was adopted for total arch replacement in 22 consecutive patients with true aneurysms (13) and aortic dissection (nine) from January 2005 to January 2008. Cerebral perfusion lines branched from the main perfusion line. During SCP, right radial arterial pressure was maintained at 50 mm Hg and left common carotid arterial pressure at 60 mm Hg, and the regional cerebral oxygen saturation (rSO(2)) values were maintained at approximately >80% of the baseline value. Two operative deaths (9%) occurred due to pneumonia and hemorrhage in the left lung, respectively. Stroke occurred in one patient (5%). This simple circuit system can thus be easily and safely applied for aortic arch surgery.

  1. In-flight absolute radiometric calibration of the thematic mapper

    NASA Technical Reports Server (NTRS)

    Castle, K. R.; Holm, R. G.; Kastner, C. J.; Palmer, J. M.; Slater, P. N.; Dinguirard, M.; Ezra, C. E.; Jackson, R. D.; Savage, R. K.

    1983-01-01

    The TM multispectral scanner system was calibrated in an absolute manner before launch. To determine the temporal changes of the absolute radiometric calibration of the entire system, spectroradiometric measurements of the ground and the atmosphere were made simultaneously with TM collections over White Sands, New Mexico. By entering the measured values in an atmospheric radiative transfer program, the radiance levels of the in four of the spectral bands of the TM were determined. Tables show values for the reflectance of snow at White Sands measured by a modular 8 channel radiometer, and values for exoatmospheric irradiance within the TM passbands, calculated for the Earth-Sun distance using a solar radiometer.

  2. USE OF A PROGRAMMABLE CALCULATOR IN CARDIOPULMONARY PERFUSION

    PubMed Central

    Mills, J. David; Tallent, Jerome H.

    1978-01-01

    This study describes a hand-held, battery-powered, programmable instrument (Calculator Model SR-52) that can be taken directly into the operating room by cardiopulmonary perfusionists. Three programs are described in detail: 1) Cardiopulmonary perfusion parameters and estimated blood volume; 2) blood gas parameters and saturations, with temperature corrections; and 3) cardiopulmonary oxygen transfer and oxygenator efficiency. This inexpensive calculator allows perfusion personnel to manipulate easily-derived data into values which heretofore have required elaborate nomograms or special slide rules—or were not available within a reasonable computational time. PMID:15216068

  3. Contrast-enhanced CT- and MRI-based perfusion assessment for pulmonary diseases: basics and clinical applications

    PubMed Central

    Ohno, Yoshiharu; Koyama, Hisanobu; Lee, Ho Yun; Miura, Sachiko; Yoshikawa, Takeshi; Sugimura, Kazuro

    2016-01-01

    Assessment of regional pulmonary perfusion as well as nodule and tumor perfusions in various pulmonary diseases are currently performed by means of nuclear medicine studies requiring radioactive macroaggregates, dual-energy computed tomography (CT), and dynamic first-pass contrast-enhanced perfusion CT techniques and unenhanced and dynamic first-pass contrast enhanced perfusion magnetic resonance imaging (MRI), as well as time-resolved three-dimensional or four-dimensional contrast-enhanced magnetic resonance angiography (MRA). Perfusion scintigraphy, single-photon emission tomography (SPECT) and SPECT fused with CT have been established as clinically available scintigraphic methods; however, they are limited by perfusion information with poor spatial resolution and other shortcomings. Although positron emission tomography with 15O water can measure absolute pulmonary perfusion, it requires a cyclotron for generation of a tracer with an extremely short half-life (2 min), and can only be performed for academic purposes. Therefore, clinicians are concentrating their efforts on the application of CT-based and MRI-based quantitative and qualitative perfusion assessment to various pulmonary diseases. This review article covers 1) the basics of dual-energy CT and dynamic first-pass contrast-enhanced perfusion CT techniques, 2) the basics of time-resolved contrast-enhanced MRA and dynamic first-pass contrast-enhanced perfusion MRI, and 3) clinical applications of contrast-enhanced CT- and MRI-based perfusion assessment for patients with pulmonary nodule, lung cancer, and pulmonary vascular diseases. We believe that these new techniques can be useful in routine clinical practice for not only thoracic oncology patients, but also patients with different pulmonary vascular diseases. PMID:27523813

  4. Contrast-enhanced CT- and MRI-based perfusion assessment for pulmonary diseases: basics and clinical applications.

    PubMed

    Ohno, Yoshiharu; Koyama, Hisanobu; Lee, Ho Yun; Miura, Sachiko; Yoshikawa, Takeshi; Sugimura, Kazuro

    2016-01-01

    Assessment of regional pulmonary perfusion as well as nodule and tumor perfusions in various pulmonary diseases are currently performed by means of nuclear medicine studies requiring radioactive macroaggregates, dual-energy computed tomography (CT), and dynamic first-pass contrast-enhanced perfusion CT techniques and unenhanced and dynamic first-pass contrast enhanced perfusion magnetic resonance imaging (MRI), as well as time-resolved three-dimensional or four-dimensional contrast-enhanced magnetic resonance angiography (MRA). Perfusion scintigraphy, single-photon emission tomography (SPECT) and SPECT fused with CT have been established as clinically available scintigraphic methods; however, they are limited by perfusion information with poor spatial resolution and other shortcomings. Although positron emission tomography with 15O water can measure absolute pulmonary perfusion, it requires a cyclotron for generation of a tracer with an extremely short half-life (2 min), and can only be performed for academic purposes. Therefore, clinicians are concentrating their efforts on the application of CT-based and MRI-based quantitative and qualitative perfusion assessment to various pulmonary diseases. This review article covers 1) the basics of dual-energy CT and dynamic first-pass contrast-enhanced perfusion CT techniques, 2) the basics of time-resolved contrast-enhanced MRA and dynamic first-pass contrast-enhanced perfusion MRI, and 3) clinical applications of contrast-enhanced CT- and MRI-based perfusion assessment for patients with pulmonary nodule, lung cancer, and pulmonary vascular diseases. We believe that these new techniques can be useful in routine clinical practice for not only thoracic oncology patients, but also patients with different pulmonary vascular diseases.

  5. Contrast-enhanced CT- and MRI-based perfusion assessment for pulmonary diseases: basics and clinical applications.

    PubMed

    Ohno, Yoshiharu; Koyama, Hisanobu; Lee, Ho Yun; Miura, Sachiko; Yoshikawa, Takeshi; Sugimura, Kazuro

    2016-01-01

    Assessment of regional pulmonary perfusion as well as nodule and tumor perfusions in various pulmonary diseases are currently performed by means of nuclear medicine studies requiring radioactive macroaggregates, dual-energy computed tomography (CT), and dynamic first-pass contrast-enhanced perfusion CT techniques and unenhanced and dynamic first-pass contrast enhanced perfusion magnetic resonance imaging (MRI), as well as time-resolved three-dimensional or four-dimensional contrast-enhanced magnetic resonance angiography (MRA). Perfusion scintigraphy, single-photon emission tomography (SPECT) and SPECT fused with CT have been established as clinically available scintigraphic methods; however, they are limited by perfusion information with poor spatial resolution and other shortcomings. Although positron emission tomography with 15O water can measure absolute pulmonary perfusion, it requires a cyclotron for generation of a tracer with an extremely short half-life (2 min), and can only be performed for academic purposes. Therefore, clinicians are concentrating their efforts on the application of CT-based and MRI-based quantitative and qualitative perfusion assessment to various pulmonary diseases. This review article covers 1) the basics of dual-energy CT and dynamic first-pass contrast-enhanced perfusion CT techniques, 2) the basics of time-resolved contrast-enhanced MRA and dynamic first-pass contrast-enhanced perfusion MRI, and 3) clinical applications of contrast-enhanced CT- and MRI-based perfusion assessment for patients with pulmonary nodule, lung cancer, and pulmonary vascular diseases. We believe that these new techniques can be useful in routine clinical practice for not only thoracic oncology patients, but also patients with different pulmonary vascular diseases. PMID:27523813

  6. Laser Doppler perfusion monitoring and imaging of blood microcirculation

    NASA Astrophysics Data System (ADS)

    Nilsson, Gert E.; Wardell, Karin

    1994-07-01

    Laser Doppler perfusion monitoring is a method of assessing tissue perfusion based on measurements performed using Doppler broadening of monochromatic light scattered in moving blood cells. Ever since laser Doppler perfusion monitors became available about 15 years ago they have been used in numerous applications in both clinical and laboratory settings. The high spatial resolution has in practice manifested itself as one of the main limitations of the method. The reason for this is the difficulty in attaining reproducible values at successive measurement sites because most skin tissue possesses a substantial variation in blood flow even at adjacent measurement sites. In order to overcome this difficulty the laser Doppler perfusion imager was developed. In this camera-like device, the laser beam successively scans the tissue and the Doppler components of the backscattered light are detected by a remote photodiode. After a scanning procedure is complete, a color-coded perfusion map showing the spatial variation of skin blood flow is displayed on a monitor. The operating principle and early applications of this emerging technology are addressed in further detail.

  7. Absolute Antenna Calibration at the US National Geodetic Survey

    NASA Astrophysics Data System (ADS)

    Mader, G. L.; Bilich, A. L.

    2012-12-01

    Geodetic GNSS applications routinely demand millimeter precision and extremely high levels of accuracy. To achieve these accuracies, measurement and instrument biases at the centimeter to millimeter level must be understood. One of these biases is the antenna phase center, the apparent point of signal reception for a GNSS antenna. It has been well established that phase center patterns differ between antenna models and manufacturers; additional research suggests that the addition of a radome or the choice of antenna mount can significantly alter those a priori phase center patterns. For the more demanding GNSS positioning applications and especially in cases of mixed-antenna networks, it is all the more important to know antenna phase center variations as a function of both elevation and azimuth in the antenna reference frame and incorporate these models into analysis software. Determination of antenna phase center behavior is known as "antenna calibration". Since 1994, NGS has computed relative antenna calibrations for more than 350 antennas. In recent years, the geodetic community has moved to absolute calibrations - the IGS adopted absolute antenna phase center calibrations in 2006 for use in their orbit and clock products, and NGS's CORS group began using absolute antenna calibration upon the release of the new CORS coordinates in IGS08 epoch 2005.00 and NAD 83(2011,MA11,PA11) epoch 2010.00. Although NGS relative calibrations can be and have been converted to absolute, it is considered best practice to independently measure phase center characteristics in an absolute sense. Consequently, NGS has developed and operates an absolute calibration system. These absolute antenna calibrations accommodate the demand for greater accuracy and for 2-dimensional (elevation and azimuth) parameterization. NGS will continue to provide calibration values via the NGS web site www.ngs.noaa.gov/ANTCAL, and will publish calibrations in the ANTEX format as well as the legacy ANTINFO

  8. Application of time sampling in brain CT perfusion imaging for dose reduction

    NASA Astrophysics Data System (ADS)

    Lee, S. H.; Kim, J. H.; Kim, K. G.; Park, S. J.; Im, Jung Gi

    2007-03-01

    The purpose of this study is to determine a stable sampling rate not to be affected by sampling shift for reducing radiation exposure with time sampling and interpolation in cerebral perfusion CT examination. Original images were obtained every 1 second for 40 time series from 3 patients, respectively. Time sampling was performed with sampling intervals (SI) from 2 to 10 seconds. Sampling shift was applied from +1 to SI-1 for each sampling rate. For each patient, 30 tissue concentration time-course data were collected, and arterial input curves were fitted by gamma-variate function. The sinc function was introduced for interpolation. Deconvolution analysis based on SVD was performed for quantifying perfusion parameters. The perfusion values through time-varying sampling and interpolation were statistically compared with the original perfusion values. The mean CBF values with increase of sampling interval and shift magnitude from the collected data had a wider fluctuation pattern centering around the original mean CBF. The mean CBV values had a similar tendency to the mean CBF values, but a relatively narrower deviation. The mean MTT values were fluctuated reversely to the trend of the mean CBF values. The stable sampling interval for quantifying perfusion parameters with lower radiation exposure was statistically acceptable up to 4 seconds. These results indicate that sampling shift limits sampling rate for acquiring acceptable perfusion values. This study will help in selecting more reasonable sampling rate for low-radiation-dose CT examination.

  9. Optomechanics for absolute rotation detection

    NASA Astrophysics Data System (ADS)

    Davuluri, Sankar

    2016-07-01

    In this article, we present an application of optomechanical cavity for the absolute rotation detection. The optomechanical cavity is arranged in a Michelson interferometer in such a way that the classical centrifugal force due to rotation changes the length of the optomechanical cavity. The change in the cavity length induces a shift in the frequency of the cavity mode. The phase shift corresponding to the frequency shift in the cavity mode is measured at the interferometer output to estimate the angular velocity of absolute rotation. We derived an analytic expression to estimate the minimum detectable rotation rate in our scheme for a given optomechanical cavity. Temperature dependence of the rotation detection sensitivity is studied.

  10. Moral absolutism and ectopic pregnancy.

    PubMed

    Kaczor, C

    2001-02-01

    If one accepts a version of absolutism that excludes the intentional killing of any innocent human person from conception to natural death, ectopic pregnancy poses vexing difficulties. Given that the embryonic life almost certainly will die anyway, how can one retain one's moral principle and yet adequately respond to a situation that gravely threatens the life of the mother and her future fertility? The four options of treatment most often discussed in the literature are non-intervention, salpingectomy (removal of tube with embryo), salpingostomy (removal of embryo alone), and use of methotrexate (MXT). In this essay, I review these four options and introduce a fifth (the milking technique). In order to assess these options in terms of the absolutism mentioned, it will also be necessary to discuss various accounts of the intention/foresight distinction. I conclude that salpingectomy, salpingostomy, and the milking technique are compatible with absolutist presuppositions, but not the use of methotrexate.

  11. Moral absolutism and ectopic pregnancy.

    PubMed

    Kaczor, C

    2001-02-01

    If one accepts a version of absolutism that excludes the intentional killing of any innocent human person from conception to natural death, ectopic pregnancy poses vexing difficulties. Given that the embryonic life almost certainly will die anyway, how can one retain one's moral principle and yet adequately respond to a situation that gravely threatens the life of the mother and her future fertility? The four options of treatment most often discussed in the literature are non-intervention, salpingectomy (removal of tube with embryo), salpingostomy (removal of embryo alone), and use of methotrexate (MXT). In this essay, I review these four options and introduce a fifth (the milking technique). In order to assess these options in terms of the absolutism mentioned, it will also be necessary to discuss various accounts of the intention/foresight distinction. I conclude that salpingectomy, salpingostomy, and the milking technique are compatible with absolutist presuppositions, but not the use of methotrexate. PMID:11262641

  12. The Absolute Spectrum Polarimeter (ASP)

    NASA Technical Reports Server (NTRS)

    Kogut, A. J.

    2010-01-01

    The Absolute Spectrum Polarimeter (ASP) is an Explorer-class mission to map the absolute intensity and linear polarization of the cosmic microwave background and diffuse astrophysical foregrounds over the full sky from 30 GHz to 5 THz. The principal science goal is the detection and characterization of linear polarization from an inflationary epoch in the early universe, with tensor-to-scalar ratio r much greater than 1O(raised to the power of { -3}) and Compton distortion y < 10 (raised to the power of{-6}). We describe the ASP instrument and mission architecture needed to detect the signature of an inflationary epoch in the early universe using only 4 semiconductor bolometers.

  13. Classification images predict absolute efficiency.

    PubMed

    Murray, Richard F; Bennett, Patrick J; Sekuler, Allison B

    2005-02-24

    How well do classification images characterize human observers' strategies in perceptual tasks? We show mathematically that from the classification image of a noisy linear observer, it is possible to recover the observer's absolute efficiency. If we could similarly predict human observers' performance from their classification images, this would suggest that the linear model that underlies use of the classification image method is adequate over the small range of stimuli typically encountered in a classification image experiment, and that a classification image captures most important aspects of human observers' performance over this range. In a contrast discrimination task and in a shape discrimination task, we found that observers' absolute efficiencies were generally well predicted by their classification images, although consistently slightly (approximately 13%) higher than predicted. We consider whether a number of plausible nonlinearities can account for the slight under prediction, and of these we find that only a form of phase uncertainty can account for the discrepancy.

  14. Absolute calibration of optical flats

    DOEpatents

    Sommargren, Gary E.

    2005-04-05

    The invention uses the phase shifting diffraction interferometer (PSDI) to provide a true point-by-point measurement of absolute flatness over the surface of optical flats. Beams exiting the fiber optics in a PSDI have perfect spherical wavefronts. The measurement beam is reflected from the optical flat and passed through an auxiliary optic to then be combined with the reference beam on a CCD. The combined beams include phase errors due to both the optic under test and the auxiliary optic. Standard phase extraction algorithms are used to calculate this combined phase error. The optical flat is then removed from the system and the measurement fiber is moved to recombine the two beams. The newly combined beams include only the phase errors due to the auxiliary optic. When the second phase measurement is subtracted from the first phase measurement, the absolute phase error of the optical flat is obtained.

  15. Temporal Dynamics of Microbial Rhodopsin Fluorescence Reports Absolute Membrane Voltage

    PubMed Central

    Hou, Jennifer H.; Venkatachalam, Veena; Cohen, Adam E.

    2014-01-01

    Plasma membrane voltage is a fundamentally important property of a living cell; its value is tightly coupled to membrane transport, the dynamics of transmembrane proteins, and to intercellular communication. Accurate measurement of the membrane voltage could elucidate subtle changes in cellular physiology, but existing genetically encoded fluorescent voltage reporters are better at reporting relative changes than absolute numbers. We developed an Archaerhodopsin-based fluorescent voltage sensor whose time-domain response to a stepwise change in illumination encodes the absolute membrane voltage. We validated this sensor in human embryonic kidney cells. Measurements were robust to variation in imaging parameters and in gene expression levels, and reported voltage with an absolute accuracy of 10 mV. With further improvements in membrane trafficking and signal amplitude, time-domain encoding of absolute voltage could be applied to investigate many important and previously intractable bioelectric phenomena. PMID:24507604

  16. Construction and validation of a microprocessor controlled extracorporal circuit in rats for the optimization of isolated limb perfusion.

    PubMed

    Gürtler, Ulrich; Fuchs, Peter; Stangelmayer, Achim; Bernhardt, Günther; Buschauer, Armin; Spruss, Thilo

    2004-12-01

    Although a few experimental approaches to isolated limb perfusion (ILP) are described in the literature, none of these animal models mimics the clinical perfusion techniques adequately to improve the technique of ILP on the basis of valid preclinical data. Therefore, we developed an ILP setup in rats allowing online monitoring of essential perfusion parameters such as temperature (in perfusate, various tissues, and rectum), pH (perfusate), perfusion pressure, and O(2) concentration (in perfusate, tissue), by a tailor-made data acquisition system. This setup permits close supervision of vital parameters during ILP. Various interdependencies, concerning the flow rate and the pressure of perfusate as well as tissue oxygenation were registered. For the measurement of pO(2) values in the perfusate and in different regions of the perfused hind limb, a novel type of microoptode based on quenching of a fluorescent dye was devised. Stable normothermic (37 degrees C) perfusion conditions were maintained at a constant perfusion pressure in the range of 40-60 mm Hg by administration of the spasmo lytic moxaverine (0.5 mg/mL of perfusate as initial dose) at a perfusate flow rate of 0.5 mL/min for 60 min. At the end of an ILP, there were no signs of tissue damage, neither concerning laboratory data (K(+), myoglobin, creatine kinase, lactic dehydrogenase) nor histopathological criteria. The reported ILP model is not only well suited to investigate the effects of hyperthermia but also to assess the efficacy of new antineoplastic approaches, when nude rats, bearing human tumours in the hind limbs, are used.

  17. Dopaminergic Therapy Modulates Cortical Perfusion in Parkinson Disease With and Without Dementia According to Arterial Spin Labeled Perfusion Magnetic Resonance Imaging

    PubMed Central

    Lin, Wei-Che; Chen, Pei-Chin; Huang, Yung-Cheng; Tsai, Nai-Wen; Chen, Hsiu-Ling; Wang, Hung-Chen; Lin, Tsu-Kung; Chou, Kun-Hsien; Chen, Meng-Hsiang; Chen, Yi-Wen; Lu, Cheng-Hsien

    2016-01-01

    Abstract Arterial spin labeling (ASL) magnetic resonance imaging analyses allow for the quantification of altered cerebral blood flow, and provide a novel means of examining the impact of dopaminergic treatments. The authors examined the cerebral perfusion differences among 17 Parkinson disease (PD) patients, 17 PD with dementia (PDD) patients, and 17 healthy controls and used ASL-MRI to assess the effects of dopaminergic therapies on perfusion in the patients. The authors demonstrated progressive widespread cortical hypoperfusion in PD and PDD and robust effects for the dopaminergic therapies. Specifically, dopaminergic medications further decreased frontal lobe and cerebellum perfusion in the PD and PDD groups, respectively. These patterns of hypoperfusion could be related to cognitive dysfunctions and disease severity. Furthermore, desensitization to dopaminergic therapies in terms of cortical perfusion was found as the disease progressed, supporting the concept that long-term therapies are associated with the therapeutic window narrowing. The highly sensitive pharmaceutical response of ASL allows clinicians and researchers to easily and effectively quantify the absolute perfusion status, which might prove helpful for therapeutic planning. PMID:26844450

  18. Dopaminergic Therapy Modulates Cortical Perfusion in Parkinson Disease With and Without Dementia According to Arterial Spin Labeled Perfusion Magnetic Resonance Imaging.

    PubMed

    Lin, Wei-Che; Chen, Pei-Chin; Huang, Yung-Cheng; Tsai, Nai-Wen; Chen, Hsiu-Ling; Wang, Hung-Chen; Lin, Tsu-Kung; Chou, Kun-Hsien; Chen, Meng-Hsiang; Chen, Yi-Wen; Lu, Cheng-Hsien

    2016-02-01

    Arterial spin labeling (ASL) magnetic resonance imaging analyses allow for the quantification of altered cerebral blood flow, and provide a novel means of examining the impact of dopaminergic treatments. The authors examined the cerebral perfusion differences among 17 Parkinson disease (PD) patients, 17 PD with dementia (PDD) patients, and 17 healthy controls and used ASL-MRI to assess the effects of dopaminergic therapies on perfusion in the patients. The authors demonstrated progressive widespread cortical hypoperfusion in PD and PDD and robust effects for the dopaminergic therapies. Specifically, dopaminergic medications further decreased frontal lobe and cerebellum perfusion in the PD and PDD groups, respectively. These patterns of hypoperfusion could be related to cognitive dysfunctions and disease severity. Furthermore, desensitization to dopaminergic therapies in terms of cortical perfusion was found as the disease progressed, supporting the concept that long-term therapies are associated with the therapeutic window narrowing. The highly sensitive pharmaceutical response of ASL allows clinicians and researchers to easily and effectively quantify the absolute perfusion status, which might prove helpful for therapeutic planning.

  19. Non-Invasive Method of Determining Absolute Intracranial Pressure

    NASA Technical Reports Server (NTRS)

    Yost, William T. (Inventor); Cantrell, John H., Jr. (Inventor); Hargens, Alan E. (Inventor)

    2004-01-01

    A method is presented for determining absolute intracranial pressure (ICP) in a patient. Skull expansion is monitored while changes in ICP are induced. The patient's blood pressure is measured when skull expansion is approximately zero. The measured blood pressure is indicative of a reference ICP value. Subsequently, the method causes a known change in ICP and measured the change in skull expansion associated therewith. The absolute ICP is a function of the reference ICP value, the known change in ICP and its associated change in skull expansion; and a measured change in skull expansion.

  20. The Absolute Radiometric Calibration of Space - Sensors.

    NASA Astrophysics Data System (ADS)

    Holm, Ronald Gene

    1987-09-01

    The need for absolute radiometric calibration of space-based sensors will continue to increase as new generations of space sensors are developed. A reflectance -based in-flight calibration procedure is used to determine the radiance reaching the entrance pupil of the sensor. This procedure uses ground-based measurements coupled with a radiative transfer code to characterize the effects the atmosphere has on the signal reaching the sensor. The computed radiance is compared to the digital count output of the sensor associated with the image of a test site. This provides an update to the preflight calibration of the system and a check on the on-board internal calibrator. This calibration procedure was used to perform a series of five calibrations of the Landsat-5 Thematic Mapper (TM). For the 12 measurements made in TM bands 1-3, the RMS variation from the mean as a percentage of the mean is (+OR-) 1.9%, and for measurements in the IR, TM bands 4,5, and 7, the value is (+OR-) 3.4%. The RMS variation for all 23 measurements is (+OR-) 2.8%. The absolute calibration techniques were put to another test with a series of three calibration of the SPOT-1 High Resolution Visible, (HRV), sensors. The ratio, HRV-2/HRV-1, of absolute calibration coefficients compared very well with ratios of histogrammed data obtained when the cameras simultaneously imaged the same ground site. Bands PA, B1 and B3 agreed to within 3%, while band B2 showed a 7% difference. The procedure for performing a satellite calibration was then used to demonstrate how a calibrated satellite sensor can be used to quantitatively evaluate surface reflectance over a wide range of surface features. Predicted reflectance factors were compared to values obtained from aircraft -based radiometer data. This procedure was applied on four dates with two different surface conditions per date. A strong correlation, R('2) = .996, was shown between reflectance values determined from satellite imagery and low-flying aircraft

  1. Artificial tissues in perfusion culture.

    PubMed

    Sittinger, M; Schultz, O; Keyszer, G; Minuth, W W; Burmester, G R

    1997-01-01

    In the stagnant environment of traditional culture dishes it is difficult to generate long term experiments or artificial tissues from human cells. For this reason a perfusion culture system with a stable supply of nutrients was developed. Human chondrocytes were seeded three-dimensionally in resorbable polymer fleeces. The cell-polymer tissues were then mounted in newly developed containers (W.W. Minuth et al, Biotechniques, 1996) and continuously perfused by fresh medium for 40 days. Samples from the effluate were analyzed daily, and the pH of the medium and glucose concentration remained stable during this period. The lactid acid concentration increased from 0.17 mg/ml to 0.35 mg/ml, which was influenced by the degradation of the resorbable polymer fibers used as three dimensional support material for the cells. This perfusion system proved to be reliable especially in long term cultures. Any components in the culture medium of the cells could be monitored without disturbances as caused by manual medium replacement. These results suggest the described perfusion culture system to be a valuable and convenient tool for many applications in tissue engineering, especially in the generation of artificial connective tissue.

  2. Developing a tissue perfusion sensor.

    PubMed

    Harvey, S L R; Parker, K H; O'Hare, D

    2007-01-01

    The development of a electrochemical tissue perfusion sensor is presented. The sensor is a platinum/platinum ring-disc microelectrode that relies on the principle of collector-generator to monitor mass transport within its vicinity. Tissue perfusion is a mass transport mechanism that describes the movement of respiratory gases, nutrients and metabolites in tissue. The sensor's capability of detecting perfusion at the cellular level in a continuous fashion is unique. This sensor will provide insight into the way nutrients and metabolites are transported in tissue especially in cases were perfusion is low such as in wounds or ischemic tissue. We present experimental work for the development and testing of the sensors in vitro. Experimental flow recordings in free steam solutions as well as the flow through tissue-like media are shown. Tests on post operative human tissue are also presented. The sensor's feature such as the continuous recoding capacities, spatial resolution and the measurement range from ml/min to microl/min are highlighted. PMID:18002549

  3. Repeated Positron Emission Tomography-Computed Tomography and Perfusion-Computed Tomography Imaging in Rectal Cancer: Fluorodeoxyglucose Uptake Corresponds With Tumor Perfusion

    SciTech Connect

    Janssen, Marco H.M.; Aerts, Hugo J.W.L.; Buijsen, Jeroen; Lambin, Philippe; Lammering, Guido; Oellers, Michel C.

    2012-02-01

    Purpose: The purpose of this study was to analyze both the intratumoral fluorodeoxyglucose (FDG) uptake and perfusion within rectal tumors before and after hypofractionated radiotherapy. Methods and Materials: Rectal cancer patients, referred for preoperative hypofractionated radiotherapy (RT), underwent FDG-positron emission tomography (PET)-computed tomography (CT) and perfusion-CT (pCT) imaging before the start of hypofractionated RT and at the day of the last RT fraction. The pCT-images were analyzed using the extended Kety model, quantifying tumor perfusion with the pharmacokinetic parameters K{sup trans}, v{sub e}, and v{sub p}. The mean and maximum FDG uptake based on the standardized uptake value (SUV) and transfer constant (K{sup trans}) within the tumor were correlated. Also, the tumor was subdivided into eight subregions and for each subregion the mean and maximum SUVs and K{sup trans} values were assessed and correlated. Furthermore, the mean FDG uptake in voxels presenting with the lowest 25% of perfusion was compared with the FDG uptake in the voxels with the 25% highest perfusion. Results: The mean and maximum K{sup trans} values were positively correlated with the corresponding SUVs ({rho} = 0.596, p = 0.001 and {rho} = 0.779, p < 0.001). Also, positive correlations were found for K{sup trans} values and SUVs within the subregions (mean, {rho} = 0.413, p < 0.001; and max, {rho} = 0.540, p < 0.001). The mean FDG uptake in the 25% highest-perfused tumor regions was significantly higher compared with the 25% lowest-perfused regions (10.6% {+-} 5.1%, p = 0.017). During hypofractionated radiotherapy, stable mean (p = 0.379) and maximum (p = 0.280) FDG uptake levels were found, whereas the mean (p = 0.040) and maximum (p = 0.003) K{sup trans} values were found to significantly increase. Conclusion: Highly perfused rectal tumors presented with higher FDG-uptake levels compared with relatively low perfused tumors. Also, intratumor regions with a high FDG

  4. The AFGL absolute gravity program

    NASA Technical Reports Server (NTRS)

    Hammond, J. A.; Iliff, R. L.

    1978-01-01

    A brief discussion of the AFGL's (Air Force Geophysics Laboratory) program in absolute gravity is presented. Support of outside work and in-house studies relating to gravity instrumentation are discussed. A description of the current transportable system is included and the latest results are presented. These results show good agreement with measurements at the AFGL site by an Italian system. The accuracy obtained by the transportable apparatus is better than 0.1 microns sq sec 10 microgal and agreement with previous measurements is within the combined uncertainties of the measurements.

  5. Familial Aggregation of Absolute Pitch

    PubMed Central

    Baharloo, Siamak; Service, Susan K.; Risch, Neil; Gitschier, Jane; Freimer, Nelson B.

    2000-01-01

    Absolute pitch (AP) is a behavioral trait that is defined as the ability to identify the pitch of tones in the absence of a reference pitch. AP is an ideal phenotype for investigation of gene and environment interactions in the development of complex human behaviors. Individuals who score exceptionally well on formalized auditory tests of pitch perception are designated as “AP-1.” As described in this report, auditory testing of siblings of AP-1 probands and of a control sample indicates that AP-1 aggregates in families. The implications of this finding for the mapping of loci for AP-1 predisposition are discussed. PMID:10924408

  6. Motion compensation of ultrasonic perfusion images

    NASA Astrophysics Data System (ADS)

    Schäfer, Sebastian; Nylund, Kim; Gilja, Odd H.; Tönnies, Klaus D.

    2012-03-01

    Contrast-enhanced ultrasound (CEUS) is a rapid and inexpensive medical imaging technique to assess tissue perfusion with a high temporal resolution. It is composed of a sequence with ultrasound brightness values and a contrast sequence acquired simultaneously. However, the image acquisition is disturbed by various motion influences. Registration is needed to obtain reliable information of spatial correspondence and to analyze perfusion characteristics over time. We present an approach to register an ultrasonography sequence by using a feature label map. This label map is generated from the b-mode data sequence by a Markov-Random-Field (MRF) based analysis, where each location is assigned to one of the user-defined regions according to its statistical parameters. The MRF reduces the chance that outliers are represented in the label map and provides stable feature labels over the time frames. A registration consisting of rigid and non-rigid transformations is determined consecutively using the generated label map of the respective frames for similarity calculation. For evaluation, the standard deviation within specific regions in intestinal CEUS images has been measured before and after registration resulting in an average decrease of 8.6 %. Additionally, this technique has proven to be more robust against noise influence compared to similarity calculation based on image intensities only. The latter leads only to 7.6 % decrease of the standard deviation.

  7. Evaluation of CT Perfusion Biomarkers of Tumor Hypoxia

    PubMed Central

    Qi, Qi; Yeung, Timothy Pok Chi; Lee, Ting-Yim; Bauman, Glenn; Crukley, Cathie; Morrison, Laura; Hoffman, Lisa; Yartsev, Slav

    2016-01-01

    Background Tumor hypoxia is associated with treatment resistance to cancer therapies. Hypoxia can be investigated by immunohistopathologic methods but such procedure is invasive. A non-invasive method to interrogate tumor hypoxia is an attractive option as such method can provide information before, during, and after treatment for personalized therapies. Our study evaluated the correlations between computed tomography (CT) perfusion parameters and immunohistopathologic measurement of tumor hypoxia. Methods Wistar rats, 18 controls and 19 treated with stereotactic radiosurgery (SRS), implanted with the C6 glioma tumor were imaged using CT perfusion on average every five days to monitor tumor growth. A final CT perfusion scan and the brain were obtained on average 14 days (8–22 days) after tumor implantation. Tumor hypoxia was detected immunohistopathologically with pimonidazole. The tumor, necrotic, and pimonidazole-positive areas on histology samples were measured. Percent necrotic area and percent hypoxic areas were calculated. Tumor volume (TV), blood flow (BF), blood volume (BV), and permeability-surface area product (PS) were obtained from the CT perfusion studies. Correlations between CT perfusion parameters and histological parameters were assessed by Spearman’s ρ correlation. A Bonferroni-corrected P value < 0.05 was considered significant. Results BF and BV showed significant correlations with percent hypoxic area ρ = -0.88, P < 0.001 and ρ = -0.81, P < 0.001, respectively, for control animals and ρ = -0.7, P < 0.001 and ρ = -0.6, P = 0.003, respectively, for all animals, while TV and BV were correlated (ρ = -0.64, P = 0.01 and ρ = -0.43, P = 0.043, respectively) with percent necrotic area. PS was not correlated with either percent necrotic or percent hypoxic areas. Conclusions Percent hypoxic area provided significant correlations with BF and BV, suggesting that CT perfusion parameters are potential non-invasive imaging biomarkers of tumor

  8. Global absolut gravity reference system as replacement of IGSN 71

    NASA Astrophysics Data System (ADS)

    Wilmes, Herbert; Wziontek, Hartmut; Falk, Reinhard

    2015-04-01

    The determination of precise gravity field parameters is of great importance in a period in which earth sciences are achieving the necessary accuracy to monitor and document global change processes. This is the reason why experts from geodesy and metrology joined in a successful cooperation to make absolute gravity observations traceable to SI quantities, to improve the metrological kilogram definition and to monitor mass movements and smallest height changes for geodetic and geophysical applications. The international gravity datum is still defined by the International Gravity Standardization Net adopted in 1971 (IGSN 71). The network is based upon pendulum and spring gravimeter observations taken in the 1950s and 60s supported by the early free fall absolute gravimeters. Its gravity values agreed in every case to better than 0.1 mGal. Today, more than 100 absolute gravimeters are in use worldwide. The series of repeated international comparisons confirms the traceability of absolute gravity measurements to SI quantities and confirm the degree of equivalence of the gravimeters in the order of a few µGal. For applications in geosciences where e.g. gravity changes over time need to be analyzed, the temporal stability of an absolute gravimeter is most important. Therefore, the proposition is made to replace the IGSN 71 by an up-to-date gravity reference system which is based upon repeated absolute gravimeter comparisons and a global network of well controlled gravity reference stations.

  9. Does machine perfusion decrease ischemia reperfusion injury?

    PubMed

    Bon, D; Delpech, P-O; Chatauret, N; Hauet, T; Badet, L; Barrou, B

    2014-06-01

    In 1990's, use of machine perfusion for organ preservation has been abandoned because of improvement of preservation solutions, efficient without perfusion, easy to use and cheaper. Since the last 15 years, a renewed interest for machine perfusion emerged based on studies performed on preclinical model and seems to make consensus in case of expanded criteria donors or deceased after cardiac death donations. We present relevant studies highlighted the efficiency of preservation with hypothermic machine perfusion compared to static cold storage. Machines for organ preservation being in constant evolution, we also summarized recent developments included direct oxygenation of the perfusat. Machine perfusion technology also enables organ reconditioning during the last hours of preservation through a short period of perfusion on hypothermia, subnormothermia or normothermia. We present significant or low advantages for machine perfusion against ischemia reperfusion injuries regarding at least one primary parameter: risk of DFG, organ function or graft survival.

  10. Sodium efflux from perfused giant algal cells.

    PubMed

    Clint, G M; Macrobbie, E A

    1987-06-01

    Internodal cells of the giant alga Chara corallina were perfused internally to replace the native cytoplasm, tonoplast and vacuole with artificial cytoplasm. Sodium efflux from perfused cells, measured by including (22)Na in the perfusion media, was increased by increasing the internal sodium concentration and by decreasing the external pH, and was inhibited by external application of the renal diuretic amiloride. The sodium efflux was markedly ATP-dependent, with a 50-fold decrease in efflux observed after perfusion with media lacking ATP. Efflux in the presence of ATP was reduced by 33% by inclusion of 10 μM N,N'-dicyclohexylcarbodiimide in the perfusion medium. The membrane potential of the perfused cells approximated that of intact cells from the same culture. It is suggested that sodium efflux in perfused Chara cells proceeds via a secondary antiporter with protons, regulated by ATP in a catalytic role and with the proton motive force acting as the energy source.

  11. Characteristics of Misclassified CT Perfusion Ischemic Core in Patients with Acute Ischemic Stroke

    PubMed Central

    Geuskens, Ralph R. E. G.; Borst, Jordi; Lucas, Marit; Boers, A. M. Merel; Berkhemer, Olvert A.; Roos, Yvo B. W. E. M.; van Walderveen, Marianne A. A.; Jenniskens, Sjoerd F. M.; van Zwam, Wim H.; Dippel, Diederik W. J.; Majoie, Charles B. L. M.; Marquering, Henk A.

    2015-01-01

    Background CT perfusion (CTP) is used to estimate the extent of ischemic core and penumbra in patients with acute ischemic stroke. CTP reliability, however, is limited. This study aims to identify regions misclassified as ischemic core on CTP, using infarct on follow-up noncontrast CT. We aim to assess differences in volumetric and perfusion characteristics in these regions compared to areas that ended up as infarct on follow-up. Materials and Methods This study included 35 patients with >100 mm brain coverage CTP. CTP processing was performed using Philips software (IntelliSpace 7.0). Final infarct was automatically segmented on follow-up noncontrast CT and used as reference. CTP and follow-up noncontrast CT image data were registered. This allowed classification of ischemic lesion agreement (core on CTP: rMTT≥145%, aCBV<2.0 ml/100g and infarct on follow-up noncontrast CT) and misclassified ischemic core (core on CTP, not identified on follow-up noncontrast CT) regions. False discovery ratio (FDR), defined as misclassified ischemic core volume divided by total CTP ischemic core volume, was calculated. Absolute and relative CTP parameters (CBV, CBF, and MTT) were calculated for both misclassified CTP ischemic core and ischemic lesion agreement regions and compared using paired rank-sum tests. Results Median total CTP ischemic core volume was 49.7ml (IQR:29.9ml-132ml); median misclassified ischemic core volume was 30.4ml (IQR:20.9ml-77.0ml). Median FDR between patients was 62% (IQR:49%-80%). Median relative mean transit time was 243% (IQR:198%-289%) and 342% (IQR:249%-432%) for misclassified and ischemic lesion agreement regions, respectively. Median absolute cerebral blood volume was 1.59 (IQR:1.43–1.79) ml/100g (P<0.01) and 1.38 (IQR:1.15–1.49) ml/100g (P<0.01) for misclassified ischemic core and ischemic lesion agreement, respectively. All CTP parameter values differed significantly. Conclusion For all patients a considerable region of the CTP ischemic core

  12. Using Flat-Panel Perfusion Imaging to Measure Cerebral Hemodynamics

    PubMed Central

    Lin, Chung-Jung; Guo, Wan-Yuo; Chang, Feng-Chi; Hung, Sheng-Che; Chen, Ko-Kung; Yu, Deuerling-Zheng; Wu, Chun-Hsien Frank; Liou, Jy-Kang Adrian

    2016-01-01

    Abstract Flat-detector CT perfusion (FD-CTP) imaging has demonstrated efficacy in qualitatively accessing the penumbra in acute stroke equivalent to that of magnetic resonance perfusion (MRP). The aim of our study was to evaluate the feasibility of quantifying oligemia in the brain in patients with carotid stenosis. Ten patients with unilateral carotid stenosis of >70% were included. All MRPs and FD-CTPs were performed before stenting. Region-of-interests (ROIs) including middle cerebral artery territory at basal ganglia level on both stenotic and contralateral sides were used for quantitative analysis. Relative time to peak (rTTP) was defined as TTP of the stenotic side divided by TTP of the contralateral side, and so as relative cerebral blood volume (rCBV), relative mean transit time (rMTT), and relative cerebral blood flow (rCBF). Absolute and relative TTP, CBV, MTT, CBF between two modalities were compared. For absolute quantitative analysis, the correlation of TTP was highest (r = 0.56), followed by CBV (r = 0.47), MTT (r = 0.47), and CBF (r = 0.43); for relative quantitative analysis, rCBF was the highest (r = 0.79), followed by rTTP (r = 0.75) and rCBV (r = 0.50). We confirmed that relative quantitative assessment of FD-CTP is feasible in chronic ischemic disease. Absolute quantitative measurements between MRP and FD-CTP only expressed moderate correlations. Optimization of acquisitions and algorithms is warranted to achieve better quantification. PMID:27196456

  13. [Prognostic value of absolute monocyte count in chronic lymphocytic leukaemia].

    PubMed

    Szerafin, László; Jakó, János; Riskó, Ferenc

    2015-04-01

    Bevezetés: Az alacsony perifériás lymphocyta- és magas monocytaszám kedvezőtlen prognózisra utal különböző típusú lymphomákban és egyéb daganatos megbetegedésekben. Krónikus lymphoid leukaemiában azonban az abszolút monocytaszám prognosztikus értékéről csak kevés adat ismert. Célkitűzés: A szerzők krónikus lymphoid leukaemiás betegeik diagnóziskor mért abszolút monocytaszámának hatását vizsgálták a kezelésig eltelt időre és a túlélésre. Módszer: 2005. január 1. és 2012. december 31. között diagnosztizált 223 krónikus lymphoid leukaemiás beteg adatait rögzítették. Értékelték a kezelést igénylő betegek arányát, a kezelésig eltelt idő és a túlélés relatív kockázatát, valamint a halálokokat a Rai-stádiumtól függően, a CD38-, ZAP-70-pozitivitásnak és az abszolút monocytaszámnak megfelelően. Eredmények: Rai 0, I., II., III. és IV. stádiumban a betegek 21,1%-a, 57,4%-a, 88,9%-a, 88,9%-a és 100%-a, CD38-, illetve ZAP-70-pozitivitás esetén a betegek 61,9%-a, illetve 60,8%-a, továbbá, ha az abszolút monocytaszámuk <0,25 G/l, 0,25–0,75 G/l és >0,75 G/l volt, akkor a betegek 76,9%-a, 21,2%-a és 66,2%-a szorult kezelésre. A kezelés elkezdéséig tartó medián idő, illetve a túlélés medián ideje a monocytaszámtól függően 19,5, 65 és 35,5 hónap, illetve 41,5, 65 és 49,5 hónap volt. A kezelésmegkezdés szükségességének relatív kockázata, RR = 1,62 (p<0,01) volt a 0,25 G/l alatti vagy 0,75 G/l feletti és a 0,25–0,75 G/l abszolút monocytaszámú betegek összehasonlításakor, míg a túlélésé RR = 2,41 (p<0,01) volt, ha a 0,25 G/l alatti és feletti abszolút monocytaszámú betegeket hasonlították össze. A relatív kockázatok Rai 0 stádiumú betegekben vizsgálva is szignifikánsak maradtak. A fő halálokok alacsony abszolút monocytaszám esetén fertőzések (41,7%) és a krónikus lymphoid leukaemia (58,3%), míg közepes és magas monocytaszámnál elsősorban egyéb daganatok (25,9% és 35,3%) és egyéb kórokok (48,1% és 11,8%) voltak. Következtetések: Az alacsony és a magas abszolút monocytaszámú betegek kezeléséig eltelt időtartam rövidebb, mint a köztes alcsoportba tartozóké. Az alacsony abszolút monocytaszám – a fertőzéses szövődmények és a krónikus lymphoid leukaemia miatt – megnövekedett halálozással társul. Az abszolút monocytaszám Rai 0 stádiumban is többlet prognosztikus információt tud adni. Orv. Hetil., 2015, 156(15), 592–597.

  14. The Preference of Visualization in Teaching and Learning Absolute Value

    ERIC Educational Resources Information Center

    Konyalioglu, Alper Cihan; Aksu, Zeki; Senel, Esma Ozge

    2012-01-01

    Visualization is mostly despised although it complements and--sometimes--guides the analytical process. This study mainly investigates teachers' preferences concerning the use of the visualization method and determines the extent to which they encourage their students to make use of it within the problem-solving process. This study was conducted…

  15. The ileal brake--inhibition of jejunal motility after ileal fat perfusion in man.

    PubMed Central

    Spiller, R C; Trotman, I F; Higgins, B E; Ghatei, M A; Grimble, G K; Lee, Y C; Bloom, S R; Misiewicz, J J; Silk, D B

    1984-01-01

    The possibility that malabsorbed fat passing through the human ileum exerts an inhibitory feedback control on jejunal motility has been investigated in 24 normal subjects by perfusing the ileum with a fat containing solution designed to produce ileal luminal fat concentrations similar to those in steatorrhoea (30-40 mg/ml). Mean transit times through a 30 cm saline perfused jejunal segment were measured by a dye dilution technique. Thirty minutes after ileal fat perfusion, mean transit times rose markedly to 18.9 +/- 2.5 minutes from a control value of 7.5 +/- 0.9 minutes (n = 5; p less than 0.05). This was associated with an increase in volume of the perfused segment which rose to 175.1 +/- 22.9 ml (control 97.6 +/- 10.3 ml, n = 5; p less than 0.05). Transit times and segmental volumes had returned towards basal values 90 minutes after completing the fat perfusion. Further studies showed that ileal fat perfusion produced a pronounced inhibition of jejunal pressure wave activity, percentage duration of activity falling from a control level of 40.3 +/- 5.0% to 14.9 +/- 2.8% in the hour after ileal perfusion (p less than 0.01). Ileal fat perfusion was associated with marked rises in plasma enteroglucagon and neurotensin, the peak values (218 +/- 37 and 68 +/- 13.1 pmol/l) being comparable with those observed postprandially in coeliac disease. These observations show the existence in man of an inhibitory intestinal control mechanism, whereby ileal fat perfusion inhibits jejunal motility and delays caudal transit of jejunal contents. PMID:6706215

  16. Effect of shed blood retransfusion on pulmonary perfusion after total knee arthroplasty: a prospective controlled study

    PubMed Central

    Kaya, Eser; Kose, Kamil Cagri; Fidan, Fatma; Ergan, Volkan; Fidan, Hüseyin

    2006-01-01

    Postoperative shed blood retransfusion (autotransfusion) is a commonly used salvage method following major surgical operations, such as total knee arthroplasty (TKA). The systemic effects of shed blood are still unclear. We studied the effect of residual substances in the retransfused shed blood, on lung perfusion after TKA. Fifteen unilateral and one bilateral TKAs were performed with autotransfusion (the study group) and 15 unilateral and three bilateral TKAs were performed in a control group. Lung X-rays, arterial blood gases (ABG), D-dimer values, and lung perfusion scintigraphies were performed preoperatively and postoperatively. A mean of 300.0 ± 335.6 ml of bank blood was needed in the autotransfusion group and a mean of 685.7 ± 365.5 ml of bank blood was needed in the control group (p=0.001). There was a postoperative segmental perfusion defect at the lateral segment of the superior lobe of the left lung in one patient of the control group and he also had risk factors for thrombosis. Although both groups had a decrease in lung perfusion postoperatively, there were no significant differences among the groups regarding the lung perfusion scintigraphy, chest X-rays, ABG, and D-dimer values. In conclusion, although pulmonary perfusion diminishes following TKA, shed blood retransfusion does not add any risk to pulmonary perfusion. PMID:17115155

  17. Absolute calibration of remote sensing instruments

    NASA Astrophysics Data System (ADS)

    Biggar, S. F.; Bruegge, C. J.; Capron, B. A.; Castle, K. R.; Dinguirard, M. C.; Holm, R. G.; Lingg, L. J.; Mao, Y.; Palmer, J. M.; Phillips, A. L.

    1985-12-01

    Source-based and detector-based methods for the absolute radiometric calibration of a broadband field radiometer are described. Using such a radiometer, calibrated by both methods, the calibration of the integrating sphere used in the preflight calibration of the Thematic Mapper was redetermined. The results are presented. The in-flight calibration of space remote sensing instruments is discussed. A method which uses the results of ground-based reflectance and atmospheric measurements as input to a radiative transfer code to predict the radiance at the instrument is described. A calibrated, helicopter-mounted radiometer is used to determine the radiance levels at intermediate altitudes to check the code predictions. Results of such measurements for the calibration of the Thematic Mapper on Landsat 5 and an analysis that shows the value of such measurements are described.

  18. Lyman alpha SMM/UVSP absolute calibration and geocoronal correction

    NASA Technical Reports Server (NTRS)

    Fontenla, Juan M.; Reichmann, Edwin J.

    1987-01-01

    Lyman alpha observations from the Ultraviolet Spectrometer Polarimeter (UVSP) instrument of the Solar Maximum Mission (SMM) spacecraft were analyzed and provide instrumental calibration details. Specific values of the instrument quantum efficiency, Lyman alpha absolute intensity, and correction for geocoronal absorption are presented.

  19. Europe's Other Poverty Measures: Absolute Thresholds Underlying Social Assistance

    ERIC Educational Resources Information Center

    Bavier, Richard

    2009-01-01

    The first thing many learn about international poverty measurement is that European nations apply a "relative" poverty threshold and that they also do a better job of reducing poverty. Unlike the European model, the "absolute" U.S. poverty threshold does not increase in real value when the nation's standard of living rises, even though it is…

  20. Cosmology with negative absolute temperatures

    NASA Astrophysics Data System (ADS)

    Vieira, J. P. P.; Byrnes, Christian T.; Lewis, Antony

    2016-08-01

    Negative absolute temperatures (NAT) are an exotic thermodynamical consequence of quantum physics which has been known since the 1950's (having been achieved in the lab on a number of occasions). Recently, the work of Braun et al. [1] has rekindled interest in negative temperatures and hinted at a possibility of using NAT systems in the lab as dark energy analogues. This paper goes one step further, looking into the cosmological consequences of the existence of a NAT component in the Universe. NAT-dominated expanding Universes experience a borderline phantom expansion (w < ‑1) with no Big Rip, and their contracting counterparts are forced to bounce after the energy density becomes sufficiently large. Both scenarios might be used to solve horizon and flatness problems analogously to standard inflation and bouncing cosmologies. We discuss the difficulties in obtaining and ending a NAT-dominated epoch, and possible ways of obtaining density perturbations with an acceptable spectrum.

  1. Apparatus for absolute pressure measurement

    NASA Technical Reports Server (NTRS)

    Hecht, R. (Inventor)

    1969-01-01

    An absolute pressure sensor (e.g., the diaphragm of a capacitance manometer) was subjected to a superimposed potential to effectively reduce the mechanical stiffness of the sensor. This substantially increases the sensitivity of the sensor and is particularly useful in vacuum gauges. An oscillating component of the superimposed potential induced vibrations of the sensor. The phase of these vibrations with respect to that of the oscillating component was monitored, and served to initiate an automatic adjustment of the static component of the superimposed potential, so as to bring the sensor into resonance at the frequency of the oscillating component. This establishes a selected sensitivity for the sensor, since a definite relationship exists between resonant frequency and sensitivity.

  2. Cosmology with negative absolute temperatures

    NASA Astrophysics Data System (ADS)

    Vieira, J. P. P.; Byrnes, Christian T.; Lewis, Antony

    2016-08-01

    Negative absolute temperatures (NAT) are an exotic thermodynamical consequence of quantum physics which has been known since the 1950's (having been achieved in the lab on a number of occasions). Recently, the work of Braun et al. [1] has rekindled interest in negative temperatures and hinted at a possibility of using NAT systems in the lab as dark energy analogues. This paper goes one step further, looking into the cosmological consequences of the existence of a NAT component in the Universe. NAT-dominated expanding Universes experience a borderline phantom expansion (w < -1) with no Big Rip, and their contracting counterparts are forced to bounce after the energy density becomes sufficiently large. Both scenarios might be used to solve horizon and flatness problems analogously to standard inflation and bouncing cosmologies. We discuss the difficulties in obtaining and ending a NAT-dominated epoch, and possible ways of obtaining density perturbations with an acceptable spectrum.

  3. Validation of Perfusion Quantification with 3D Gradient Echo Dynamic Contrast-Enhanced Magnetic Resonance Imaging Using a Blood Pool Contrast Agent in Skeletal Swine Muscle

    PubMed Central

    Hindel, Stefan; Sauerbrey, Anika; Maaß, Marc; Maderwald, Stefan; Schlamann, Marc; Lüdemann, Lutz

    2015-01-01

    The purpose of our study was to validate perfusion quantification in a low-perfused tissue by dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) with shared k-space sampling using a blood pool contrast agent. Perfusion measurements were performed in a total of seven female pigs. An ultrasonic Doppler probe was attached to the right femoral artery to determine total flow in the hind leg musculature. The femoral artery was catheterized for continuous local administration of adenosine to increase blood flow up to four times the baseline level. Three different stable perfusion levels were induced. The MR protocol included a 3D gradient-echo sequence with a temporal resolution of approximately 1.5 seconds. Before each dynamic sequence, static MR images were acquired with flip angles of 5°, 10°, 20°, and 30°. Both static and dynamic images were used to generate relaxation rate and baseline magnetization maps with a flip angle method. 0.1 mL/kg body weight of blood pool contrast medium was injected via a central venous catheter at a flow rate of 5 mL/s. The right hind leg was segmented in 3D into medial, cranial, lateral, and pelvic thigh muscles, lower leg, bones, skin, and fat. The arterial input function (AIF) was measured in the aorta. Perfusion of the different anatomic regions was calculated using a one- and a two-compartment model with delay- and dispersion-corrected AIFs. The F-test for model comparison was used to decide whether to use the results of the one- or two-compartment model fit. Total flow was calculated by integrating volume-weighted perfusion values over the whole measured region. The resulting values of delay, dispersion, blood volume, mean transit time, and flow were all in physiologically and physically reasonable ranges. In 107 of 160 ROIs, the blood signal was separated, using a two-compartment model, into a capillary and an arteriolar signal contribution, decided by the F-test. Overall flow in hind leg muscles, as measured by the

  4. Validation of Perfusion Quantification with 3D Gradient Echo Dynamic Contrast-Enhanced Magnetic Resonance Imaging Using a Blood Pool Contrast Agent in Skeletal Swine Muscle.

    PubMed

    Hindel, Stefan; Sauerbrey, Anika; Maaß, Marc; Maderwald, Stefan; Schlamann, Marc; Lüdemann, Lutz

    2015-01-01

    The purpose of our study was to validate perfusion quantification in a low-perfused tissue by dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) with shared k-space sampling using a blood pool contrast agent. Perfusion measurements were performed in a total of seven female pigs. An ultrasonic Doppler probe was attached to the right femoral artery to determine total flow in the hind leg musculature. The femoral artery was catheterized for continuous local administration of adenosine to increase blood flow up to four times the baseline level. Three different stable perfusion levels were induced. The MR protocol included a 3D gradient-echo sequence with a temporal resolution of approximately 1.5 seconds. Before each dynamic sequence, static MR images were acquired with flip angles of 5°, 10°, 20°, and 30°. Both static and dynamic images were used to generate relaxation rate and baseline magnetization maps with a flip angle method. 0.1 mL/kg body weight of blood pool contrast medium was injected via a central venous catheter at a flow rate of 5 mL/s. The right hind leg was segmented in 3D into medial, cranial, lateral, and pelvic thigh muscles, lower leg, bones, skin, and fat. The arterial input function (AIF) was measured in the aorta. Perfusion of the different anatomic regions was calculated using a one- and a two-compartment model with delay- and dispersion-corrected AIFs. The F-test for model comparison was used to decide whether to use the results of the one- or two-compartment model fit. Total flow was calculated by integrating volume-weighted perfusion values over the whole measured region. The resulting values of delay, dispersion, blood volume, mean transit time, and flow were all in physiologically and physically reasonable ranges. In 107 of 160 ROIs, the blood signal was separated, using a two-compartment model, into a capillary and an arteriolar signal contribution, decided by the F-test. Overall flow in hind leg muscles, as measured by the

  5. Validation of Perfusion Quantification with 3D Gradient Echo Dynamic Contrast-Enhanced Magnetic Resonance Imaging Using a Blood Pool Contrast Agent in Skeletal Swine Muscle.

    PubMed

    Hindel, Stefan; Sauerbrey, Anika; Maaß, Marc; Maderwald, Stefan; Schlamann, Marc; Lüdemann, Lutz

    2015-01-01

    The purpose of our study was to validate perfusion quantification in a low-perfused tissue by dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) with shared k-space sampling using a blood pool contrast agent. Perfusion measurements were performed in a total of seven female pigs. An ultrasonic Doppler probe was attached to the right femoral artery to determine total flow in the hind leg musculature. The femoral artery was catheterized for continuous local administration of adenosine to increase blood flow up to four times the baseline level. Three different stable perfusion levels were induced. The MR protocol included a 3D gradient-echo sequence with a temporal resolution of approximately 1.5 seconds. Before each dynamic sequence, static MR images were acquired with flip angles of 5°, 10°, 20°, and 30°. Both static and dynamic images were used to generate relaxation rate and baseline magnetization maps with a flip angle method. 0.1 mL/kg body weight of blood pool contrast medium was injected via a central venous catheter at a flow rate of 5 mL/s. The right hind leg was segmented in 3D into medial, cranial, lateral, and pelvic thigh muscles, lower leg, bones, skin, and fat. The arterial input function (AIF) was measured in the aorta. Perfusion of the different anatomic regions was calculated using a one- and a two-compartment model with delay- and dispersion-corrected AIFs. The F-test for model comparison was used to decide whether to use the results of the one- or two-compartment model fit. Total flow was calculated by integrating volume-weighted perfusion values over the whole measured region. The resulting values of delay, dispersion, blood volume, mean transit time, and flow were all in physiologically and physically reasonable ranges. In 107 of 160 ROIs, the blood signal was separated, using a two-compartment model, into a capillary and an arteriolar signal contribution, decided by the F-test. Overall flow in hind leg muscles, as measured by the

  6. Neural Sensitivity to Absolute and Relative Anticipated Reward in Adolescents

    PubMed Central

    Vaidya, Jatin G.; Knutson, Brian; O'Leary, Daniel S.; Block, Robert I.; Magnotta, Vincent

    2013-01-01

    Adolescence is associated with a dramatic increase in risky and impulsive behaviors that have been attributed to developmental differences in neural processing of rewards. In the present study, we sought to identify age differences in anticipation of absolute and relative rewards. To do so, we modified a commonly used monetary incentive delay (MID) task in order to examine brain activity to relative anticipated reward value (neural sensitivity to the value of a reward as a function of other available rewards). This design also made it possible to examine developmental differences in brain activation to absolute anticipated reward magnitude (the degree to which neural activity increases with increasing reward magnitude). While undergoing fMRI, 18 adolescents and 18 adult participants were presented with cues associated with different reward magnitudes. After the cue, participants responded to a target to win money on that trial. Presentation of cues was blocked such that two reward cues associated with $.20, $1.00, or $5.00 were in play on a given block. Thus, the relative value of the $1.00 reward varied depending on whether it was paired with a smaller or larger reward. Reflecting age differences in neural responses to relative anticipated reward (i.e., reference dependent processing), adults, but not adolescents, demonstrated greater activity to a $1 reward when it was the larger of the two available rewards. Adults also demonstrated a more linear increase in ventral striatal activity as a function of increasing absolute reward magnitude compared to adolescents. Additionally, reduced ventral striatal sensitivity to absolute anticipated reward (i.e., the difference in activity to medium versus small rewards) correlated with higher levels of trait Impulsivity. Thus, ventral striatal activity in anticipation of absolute and relative rewards develops with age. Absolute reward processing is also linked to individual differences in Impulsivity. PMID:23544046

  7. Neural sensitivity to absolute and relative anticipated reward in adolescents.

    PubMed

    Vaidya, Jatin G; Knutson, Brian; O'Leary, Daniel S; Block, Robert I; Magnotta, Vincent

    2013-01-01

    Adolescence is associated with a dramatic increase in risky and impulsive behaviors that have been attributed to developmental differences in neural processing of rewards. In the present study, we sought to identify age differences in anticipation of absolute and relative rewards. To do so, we modified a commonly used monetary incentive delay (MID) task in order to examine brain activity to relative anticipated reward value (neural sensitivity to the value of a reward as a function of other available rewards). This design also made it possible to examine developmental differences in brain activation to absolute anticipated reward magnitude (the degree to which neural activity increases with increasing reward magnitude). While undergoing fMRI, 18 adolescents and 18 adult participants were presented with cues associated with different reward magnitudes. After the cue, participants responded to a target to win money on that trial. Presentation of cues was blocked such that two reward cues associated with $.20, $1.00, or $5.00 were in play on a given block. Thus, the relative value of the $1.00 reward varied depending on whether it was paired with a smaller or larger reward. Reflecting age differences in neural responses to relative anticipated reward (i.e., reference dependent processing), adults, but not adolescents, demonstrated greater activity to a $1 reward when it was the larger of the two available rewards. Adults also demonstrated a more linear increase in ventral striatal activity as a function of increasing absolute reward magnitude compared to adolescents. Additionally, reduced ventral striatal sensitivity to absolute anticipated reward (i.e., the difference in activity to medium versus small rewards) correlated with higher levels of trait Impulsivity. Thus, ventral striatal activity in anticipation of absolute and relative rewards develops with age. Absolute reward processing is also linked to individual differences in Impulsivity. PMID:23544046

  8. Intestinal perfusion monitoring using photoplethysmography

    NASA Astrophysics Data System (ADS)

    Akl, Tony J.; Wilson, Mark A.; Ericson, M. Nance; Coté, Gerard L.

    2013-08-01

    In abdominal trauma patients, monitoring intestinal perfusion and oxygen consumption is essential during the resuscitation period. Photoplethysmography is an optical technique potentially capable of monitoring these changes in real time to provide the medical staff with a timely and quantitative measure of the adequacy of resuscitation. The challenges for using optical techniques in monitoring hemodynamics in intestinal tissue are discussed, and the solutions to these challenges are presented using a combination of Monte Carlo modeling and theoretical analysis of light propagation in tissue. In particular, it is shown that by using visible wavelengths (i.e., 470 and 525 nm), the perfusion signal is enhanced and the background contribution is decreased compared with using traditional near-infrared wavelengths leading to an order of magnitude enhancement in the signal-to-background ratio. It was further shown that, using the visible wavelengths, similar sensitivity to oxygenation changes could be obtained (over 50% compared with that of near-infrared wavelengths). This is mainly due to the increased contrast between tissue and blood in that spectral region and the confinement of the photons to the thickness of the small intestine. Moreover, the modeling results show that the source to detector separation should be limited to roughly 6 mm while using traditional near-infrared light, with a few centimeters source to detector separation leads to poor signal-to-background ratio. Finally, a visible wavelength system is tested in an in vivo porcine study, and the possibility of monitoring intestinal perfusion changes is showed.

  9. Modeling of nanotherapeutics delivery based on tumor perfusion

    PubMed Central

    van de Ven, Anne L.; Abdollahi, Behnaz; Martinez, Carlos J.; Burey, Lacey A.; Landis, Melissa D.; Chang, Jenny C.; Ferrari, Mauro; Frieboes, Hermann B.

    2013-01-01

    Heterogeneities in the perfusion of solid tumors prevent optimal delivery of nanotherapeutics. Clinical imaging protocols to obtain patient-specific data have proven difficult to implement. It is challenging to determine which perfusion features hold greater prognostic value and to relate measurements to vessel structure and function. With the advent of systemically administered nanotherapeutics, whose delivery is dependent on overcoming diffusive and convective barriers to transport, such knowledge is increasingly important. We describe a framework for the automated evaluation of vascular perfusion curves measured at the single vessel level. Primary tumor fragments, collected from triple-negative breast cancer patients and grown as xenografts in mice, were injected with fluorescence contrast and monitored using intravital microscopy. The time to arterial peak and venous delay, two features whose probability distributions were measured directly from time-series curves, were analyzed using a Fuzzy C-mean (FCM) supervised classifier in order to rank individual tumors according to their perfusion characteristics. The resulting rankings correlated inversely with experimental nanoparticle accumulation measurements, enabling modeling of nanotherapeutics delivery without requiring any underlying assumptions about tissue structure or function, or heterogeneities contained within. With additional calibration, these methodologies may enable the study of nanotherapeutics delivery strategies in a variety of tumor models. PMID:24039540

  10. Parallel imaging for first-pass myocardial perfusion.

    PubMed

    Irwan, Roy; Lubbers, Daniël D; van der Vleuten, Pieter A; Kappert, Peter; Götte, Marco J W; Sijens, Paul E

    2007-06-01

    Two parallel imaging methods used for first-pass myocardial perfusion imaging were compared in terms of signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR) and image artifacts. One used adaptive Time-adaptive SENSitivity Encoding (TSENSE) and the other used GeneRalized Autocalibrating Partially Parallel Acquisition (GRAPPA), which are both applied to a gradient-echo sequence. Both methods were tested on 12 patients with coronary artery disease. The order of perfusion sequences was inverted in every other patient. Image acquisition was started during the administration of a contrast bolus followed by a 20-ml saline flush (3 ml/s), and the next perfusion was started at least 15 min thereafter using an identical bolus. An acceleration rate of 2 was used in both methods, and acquisition was performed during breath-holding. Significantly higher SNR, CNR and image quality were obtained with GRAPPA images than with TSENSE images. GRAPPA, however, did not yield a higher CNR when applied after the second bolus. GRAPPA perfusion imaging produced larger differences between subjects than did TSENSE. Compared to TSENSE, GRAPPA produced significantly better CNR on the first bolus. More consistent SNR and CNR were obtained from TSENSE images than from GRAPPA images, indicating that the diagnostic value of TSENSE may be better.

  11. Modeling of nanotherapeutics delivery based on tumor perfusion

    NASA Astrophysics Data System (ADS)

    van de Ven, Anne L.; Abdollahi, Behnaz; Martinez, Carlos J.; Burey, Lacey A.; Landis, Melissa D.; Chang, Jenny C.; Ferrari, Mauro; Frieboes, Hermann B.

    2013-05-01

    Heterogeneities in the perfusion of solid tumors prevent optimal delivery of nanotherapeutics. Clinical imaging protocols for obtaining patient-specific data have proven difficult to implement. It is challenging to determine which perfusion features hold greater prognostic value and to relate measurements to vessel structure and function. With the advent of systemically administered nanotherapeutics whose delivery is dependent on overcoming diffusive and convective barriers to transport, such knowledge is increasingly important. We describe a framework for the automated evaluation of vascular perfusion curves measured at the single vessel level. Primary tumor fragments, collected from triple-negative breast cancer patients and grown as xenografts in mice, were injected with fluorescence contrast and monitored using intravital microscopy. The time to arterial peak and venous delay, two features whose probability distributions were measured directly from time-series curves, were analyzed using a fuzzy c-mean supervised classifier in order to rank individual tumors according to their perfusion characteristics. The resulting rankings correlated inversely with experimental nanoparticle accumulation measurements, enabling the modeling of nanotherapeutics delivery without requiring any underlying assumptions about tissue structure or function, or heterogeneities contained therein. With additional calibration, these methodologies may enable the investigation of nanotherapeutics delivery strategies in a variety of tumor models.

  12. Absolute photon-flux measurements in the vacuum ultraviolet

    NASA Technical Reports Server (NTRS)

    Samson, J. A. R.; Haddad, G. N.

    1974-01-01

    Absolute photon-flux measurements in the vacuum ultraviolet have extended to short wavelengths by use of rare-gas ionization chambers. The technique involves the measurement of the ion current as a function of the gas pressure in the ion chamber. The true value of the ion current, and hence the absolute photon flux, is obtained by extrapolating the ion current to zero gas pressure. Examples are given at 162 and 266 A. The short-wavelength limit is determined only by the sensitivity of the current-measuring apparatus and by present knowledge of the photoionization processes that occur in the rate gases.

  13. Ultrasound perfusion signal processing for tumor detection

    NASA Astrophysics Data System (ADS)

    Kim, MinWoo; Abbey, Craig K.; Insana, Michael F.

    2016-04-01

    Enhanced blood perfusion in a tissue mass is an indication of neo-vascularity and a sign of a potential malignancy. Ultrasonic pulsed-Doppler imaging is a preferred modality for noninvasive monitoring of blood flow. However, the weak blood echoes and disorganized slow flow make it difficult to detect perfusion using standard methods without the expense and risk of contrast enhancement. Our research measures the efficiency of conventional power-Doppler (PD) methods at discriminating flow states by comparing measurement performance to that of an ideal discriminator. ROC analysis applied to the experimental results shows that power Doppler methods are just 30-50 % efficient at perfusion flows less than 1ml/min, suggesting an opportunity to improve perfusion assessment through signal processing. A new perfusion estimator is proposed by extending the statistical discriminator approach. We show that 2-D perfusion color imaging may be enhanced using this approach.

  14. Method for estimating absolute lung volumes at constant inflation pressure.

    PubMed

    Hills, B A; Barrow, R E

    1979-10-01

    A method has been devised for measuring functional residual capacity in the intact killed animal or absolute lung volumes in any excised lung preparation without changing the inflation pressure. This is achieved by titrating the absolute pressure of a chamber in which the preparation is compressed until a known volume of air has entered the lungs. This technique was used to estimate the volumes of five intact rabbit lungs and five rigid containers of known dimensions by means of Boyle's law. Results were found to agree to within +/- 1% with values determined by alternative methods. In the discussion the advantage of determining absolute lung volumes at almost any stage in a study of lung mechanics without the determination itself changing inflation pressure and, hence, lung volume is emphasized. PMID:511699

  15. Arterial Spin Labeling Measurements of Cerebral Perfusion Territories in Experimental Ischemic Stroke

    PubMed Central

    Leoni, Renata F.; Paiva, Fernando F.; Kang, Byeong-Teck; Henning, Erica C.; Nascimento, George C.; Tannús, Alberto; De Araújo, Dráulio B.; Silva, Afonso C.

    2016-01-01

    Collateral circulation, defined as the supplementary vascular network that maintains cerebral blood flow (CBF) when the main vessels fail, constitutes one important defense mechanism of the brain against ischemic stroke. In the present study, continuous arterial spin labeling (CASL) was used to quantify CBF and obtain perfusion territory maps of the major cerebral arteries in spontaneously hypertensive rats (SHR) and their normotensive Wistar-Kyoto (WKY) controls. Results show that both WKY and SHR have complementary, yet significantly asymmetric perfusion territories. Right or left dominances were observed in territories of the anterior (ACA), middle and posterior cerebral arteries, and the thalamic artery. Magnetic resonance angiography showed that some of the asymmetries were correlated with variations of the ACA. The leptomeningeal circulation perfusing the outer layers of the cortex was observed as well. Significant and permanent changes in perfusion territories were obtained after temporary occlusion of the right middle cerebral artery in both SHR and WKY, regardless of their particular dominance. However, animals with right dominance presented a larger volume change of the left perfusion territory (23 ± 9%) than animals with left dominance (7 ± 5%, P < 0.002). The data suggest that animals with contralesional dominance primarily safeguard local CBF values with small changes in contralesional perfusion territory, while animals with ipsilesional dominance show a reversal of dominance and a substantial increase in contralesional perfusion territory. These findings show the usefulness of CASL to probe the collateral circulation. PMID:24323754

  16. Functional MRI detects perfusion impairment in renal allografts with delayed graft function.

    PubMed

    Hueper, Katja; Gueler, Faikah; Bräsen, Jan Hinrich; Gutberlet, Marcel; Jang, Mi-Sun; Lehner, Frank; Richter, Nicolas; Hanke, Nils; Peperhove, Matti; Martirosian, Petros; Tewes, Susanne; Vo Chieu, Van Dai; Großhennig, Anika; Haller, Hermann; Wacker, Frank; Gwinner, Wilfried; Hartung, Dagmar

    2015-06-15

    Delayed graft function (DGF) after kidney transplantation is not uncommon, and it is associated with long-term allograft impairment. Our aim was to compare renal perfusion changes measured with noninvasive functional MRI in patients early after kidney transplantation to renal function and allograft histology in biopsy samples. Forty-six patients underwent MRI 4-11 days after transplantation. Contrast-free MRI renal perfusion images were acquired using an arterial spin labeling technique. Renal function was assessed by estimated glomerular filtration rate (eGFR), and renal biopsies were performed when indicated within 5 days of MRI. Twenty-six of 46 patients had DGF. Of these, nine patients had acute rejection (including borderline), and eight had other changes (e.g., tubular injury or glomerulosclerosis). Renal perfusion was significantly lower in the DGF group compared with the group with good allograft function (231 ± 15 vs. 331 ± 15 ml·min(-1)·100 g(-1), P < 0.001). Living donor allografts exhibited significantly higher perfusion values compared with deceased donor allografts (P < 0.001). Renal perfusion significantly correlated with eGFR (r = 0.64, P < 0.001), resistance index (r = -0.57, P < 0.001), and cold ischemia time (r = -0.48, P < 0.01). Furthermore, renal perfusion impairment early after transplantation predicted inferior renal outcome and graft loss. In conclusion, noninvasive functional MRI detects renal perfusion impairment early after kidney transplantation in patients with DGF.

  17. [The influence of extracellular calcium on volume, enzyme and calcium secretion in the isolated perfused canine pancreas (author's transl)].

    PubMed

    Teufel, H; Stock, P; Rohrmoser, H; Forell, M M

    1977-01-28

    1. The kinetics of Ca++ and enzyme secretion are of corresponding pattern as well at hydrokinetic as at ecbolic stimulation. 2. Physiological respectively pathophysiologically relevant changes of perfusate Ca++ concentrations do not influence pancreatic Ca++ secretion. Extracellular Ca++ concentrations beyond 12 mEq/1 initiate an enzyme independent Ca++ secretion. 3. Hydrokinetic or ecbolic stimulated pancreatic secretion do not distinguish in calcium/protein ratio. 4. Basal and stimulated enzyme secretion of isolated perfused canine pancreas remain unaffected by increments of extracellular Ca++ concentrations even at pharmacological values. 5. The stimulated enzyme- and Ca++ secretion remain constant during hypocalcemic perfusate conditions but decrease to basal values in Ca++ free media, rapidly and completely reversible by recalcification of the perfusate. 6. The secretin stimulated volume secretion remains unchanged either by extremely hypercalcemic or Ca++ depleted perfusate conditions.

  18. [The influence of extracellular calcium on volume, enzyme and calcium secretion in the isolated perfused canine pancreas (author's transl)].

    PubMed

    Teufel, H; Stock, P; Rohrmoser, H; Forell, M M

    1977-01-28

    1. The kinetics of Ca++ and enzyme secretion are of corresponding pattern as well at hydrokinetic as at ecbolic stimulation. 2. Physiological respectively pathophysiologically relevant changes of perfusate Ca++ concentrations do not influence pancreatic Ca++ secretion. Extracellular Ca++ concentrations beyond 12 mEq/1 initiate an enzyme independent Ca++ secretion. 3. Hydrokinetic or ecbolic stimulated pancreatic secretion do not distinguish in calcium/protein ratio. 4. Basal and stimulated enzyme secretion of isolated perfused canine pancreas remain unaffected by increments of extracellular Ca++ concentrations even at pharmacological values. 5. The stimulated enzyme- and Ca++ secretion remain constant during hypocalcemic perfusate conditions but decrease to basal values in Ca++ free media, rapidly and completely reversible by recalcification of the perfusate. 6. The secretin stimulated volume secretion remains unchanged either by extremely hypercalcemic or Ca++ depleted perfusate conditions. PMID:841188

  19. Absolute configuration of isovouacapenol C

    PubMed Central

    Fun, Hoong-Kun; Yodsaoue, Orapun; Karalai, Chatchanok; Chantrapromma, Suchada

    2010-01-01

    The title compound, C27H34O5 {systematic name: (4aR,5R,6R,6aS,7R,11aS,11bR)-4a,6-dihy­droxy-4,4,7,11b-tetra­methyl-1,2,3,4,4a,5,6,6a,7,11,11a,11b-dodeca­hydro­phenanthro[3,2-b]furan-5-yl benzoate}, is a cassane furan­oditerpene, which was isolated from the roots of Caesalpinia pulcherrima. The three cyclo­hexane rings are trans fused: two of these are in chair conformations with the third in a twisted half-chair conformation, whereas the furan ring is almost planar (r.m.s. deviation = 0.003 Å). An intra­molecular C—H⋯O inter­action generates an S(6) ring. The absolute configurations of the stereogenic centres at positions 4a, 5, 6, 6a, 7, 11a and 11b are R, R, R, S, R, S and R, respectively. In the crystal, mol­ecules are linked into infinite chains along [010] by O—H⋯O hydrogen bonds. C⋯O [3.306 (2)–3.347 (2) Å] short contacts and C—H⋯π inter­actions also occur. PMID:21588364

  20. Perfusion patterns of ischemic stroke on computed tomography perfusion.

    PubMed

    Lin, Longting; Bivard, Andrew; Parsons, Mark W

    2013-09-01

    CT perfusion (CTP) has been applied increasingly in research of ischemic stroke. However, in clinical practice, it is still a relatively new technology. For neurologists and radiologists, the challenge is to interpret CTP results properly in the context of the clinical presentation. In this article, we will illustrate common CTP patterns in acute ischemic stroke using a case-based approach. The aim is to get clinicians more familiar with the information provided by CTP with a view towards inspiring them to incorporate CTP in their routine imaging workup of acute stroke patients.

  1. Frequency-domain analysis of absolute gravimeters

    NASA Astrophysics Data System (ADS)

    Svitlov, S.

    2012-12-01

    An absolute gravimeter is analysed as a linear time-invariant system in the frequency domain. Frequency responses of absolute gravimeters are derived analytically based on the propagation of the complex exponential signal through their linear measurement functions. Depending on the model of motion and the number of time-distance coordinates, an absolute gravimeter is considered as a second-order (three-level scheme) or third-order (multiple-level scheme) low-pass filter. It is shown that the behaviour of an atom absolute gravimeter in the frequency domain corresponds to that of the three-level corner-cube absolute gravimeter. Theoretical results are applied for evaluation of random and systematic measurement errors and optimization of an experiment. The developed theory agrees with known results of an absolute gravimeter analysis in the time and frequency domains and can be used for measurement uncertainty analyses, building of vibration-isolation systems and synthesis of digital filtering algorithms.

  2. The Relationship Between Some Complete Blood Count Parameters and Myocardial Perfusion: A Scintigraphic Approach

    PubMed Central

    Ozdemir, Semra; Barutcu, Ahmet; Gazi, Emine; Tan, Yusuf Ziya; Turkon, Hakan

    2015-01-01

    Recent studies have shown that there is a relationship between some inflammatory and biochemical markers derived from complete blood count (CBC) such as neutrophil/lymphocyte (N/L) ratio, platelet/lymphocyte (P/L) ratio, platelet distribution width (PDW), red blood cell distribution width (RDW), and coronary artery disease (CAD). The aim of this study was to determine N/L ratio, P/L ratio, PDW values, and RDW values, which are associated with myocardial perfusion in patients diagnosed with CAD. This study included 262 patients (149 with myocardial ischemia/infarction and 113 with normal myocardial perfusion) undergoing myocardial perfusion scintigraphy (MPS) with CBC within 90 days of MPS. Myocardial perfusion parameters such as summed stress score and summed difference score (SDS) were compared with N/L ratio, P/L ratio, PDW values, and RDW values. Neutrophil counts and N/L ratios were significantly higher in patients diagnosed with myocardial ischemia and/or infarct. However, there was no statistically significant relationship between myocardial perfusion abnormalities and P/L ratio, PDW values, and RDW values. This study showed that N/L ratio is related to myocardial ischemia/infarction and correlated to left ventricular ejection fraction (LVEF). PMID:26420991

  3. Intestinal perfusion monitoring using photoplethysmography

    PubMed Central

    Wilson, Mark A.; Ericson, M. Nance; Coté, Gerard L.

    2013-01-01

    Abstract. In abdominal trauma patients, monitoring intestinal perfusion and oxygen consumption is essential during the resuscitation period. Photoplethysmography is an optical technique potentially capable of monitoring these changes in real time to provide the medical staff with a timely and quantitative measure of the adequacy of resuscitation. The challenges for using optical techniques in monitoring hemodynamics in intestinal tissue are discussed, and the solutions to these challenges are presented using a combination of Monte Carlo modeling and theoretical analysis of light propagation in tissue. In particular, it is shown that by using visible wavelengths (i.e., 470 and 525 nm), the perfusion signal is enhanced and the background contribution is decreased compared with using traditional near-infrared wavelengths leading to an order of magnitude enhancement in the signal-to-background ratio. It was further shown that, using the visible wavelengths, similar sensitivity to oxygenation changes could be obtained (over 50% compared with that of near-infrared wavelengths). This is mainly due to the increased contrast between tissue and blood in that spectral region and the confinement of the photons to the thickness of the small intestine. Moreover, the modeling results show that the source to detector separation should be limited to roughly 6 mm while using traditional near-infrared light, with a few centimeters source to detector separation leads to poor signal-to-background ratio. Finally, a visible wavelength system is tested in an in vivo porcine study, and the possibility of monitoring intestinal perfusion changes is showed. PMID:23942635

  4. Effects of ethanol and hyperosmotic perfusates on albumin synthesis and release

    SciTech Connect

    Rothschild, M.A.; Oratz, M.; Schreiber, S.S.; Mongelli, J.

    1986-11-01

    Sucrose and ethanol inhibit albumin synthesis; sucrose via an osmotic mechanism and ethanol during its metabolism. The present study was undertaken to compare the effects of both of these agents on albumin synthesis and secretion, and to see if ethanol inhibition could be related to an osmotic effect. Male, fed rabbits served as liver donors in all studies. There were a total of 35 studies: 13 control; 10 ethanol (39 to 52 mM); 4 cycloheximide (0.5 mM), and 8 sucrose (1%). Plasma volume was measured with /sup 125/I-albumin (human) and extracellular volume measured with either /sup 99m/Tc diethylenetriamine pentaacetic acid or (/sup 14/C)sucrose. During perfusion, rabbit albumin content in the perfusate was measured immunologically every 15 to 30 min for 225 min. Interstitial albumin efflux was measured by the rate of appearance in the perfusate of /sup 125/I-albumin given to 10 other rabbits 3 days prior to hepatic removal and perfusion. During the initial 75 min of perfusion, 74% of the in vivo equilibrated exchangeable /sup 125/I-albumin appeared in the perfusate, and during this period the rabbit albumin that entered the perfusate was taken to represent efflux from the interstitial volume plus synthesis. Rabbit albumin appearing in the perfusate during the later period of 150 min was taken to represent mainly synthesis and was used to calculate the amount of albumin that would be synthesized in 75 min. The difference between these two values would be hepatic interstitial albumin appearing in the perfusate.

  5. Technical Pitfalls of Signal Truncation in Perfusion MRI of Glioblastoma.

    PubMed

    Wong, Kelvin K; Fung, Steve H; New, Pamela Z; Wong, Stephen T C

    2016-01-01

    Dynamic susceptibility contrast (DSC) perfusion-weighted imaging (PWI) is widely used in clinical settings for the radiological diagnosis of brain tumor. The signal change in brain tissue in gradient echo-based DSC PWI is much higher than in spin echo-based DSC PWI. Due to its exquisite sensitivity, gradient echo-based sequence is the preferred method for imaging of all tumors except those near the base of the skull. However, high sensitivity also comes with a dynamic range problem. It is not unusual for blood volume to increase in gene-mediated cytotoxic immunotherapy-treated glioblastoma patients. The increase of fractional blood volume sometimes saturates the MRI signal during first-pass contrast bolus arrival and presents signal truncation artifacts of various degrees in the tumor when a significant amount of blood exists in the image pixels. It presents a hidden challenge in PWI, as this signal floor can be either close to noise level or just above and can go no lower. This signal truncation in the signal intensity time course is a significant issue that deserves attention in DSC PWI. In this paper, we demonstrate that relative cerebral blood volume and relative cerebral blood flow (rCBF) are underestimated due to signal truncation in DSC perfusion, in glioblastoma patients. We propose the use of second-pass tissue residue function in rCBF calculation using least-absolute-deviation deconvolution to avoid the underestimation problem. PMID:27531989

  6. Technical Pitfalls of Signal Truncation in Perfusion MRI of Glioblastoma

    PubMed Central

    Wong, Kelvin K.; Fung, Steve H.; New, Pamela Z.; Wong, Stephen T. C.

    2016-01-01

    Dynamic susceptibility contrast (DSC) perfusion-weighted imaging (PWI) is widely used in clinical settings for the radiological diagnosis of brain tumor. The signal change in brain tissue in gradient echo-based DSC PWI is much higher than in spin echo-based DSC PWI. Due to its exquisite sensitivity, gradient echo-based sequence is the preferred method for imaging of all tumors except those near the base of the skull. However, high sensitivity also comes with a dynamic range problem. It is not unusual for blood volume to increase in gene-mediated cytotoxic immunotherapy-treated glioblastoma patients. The increase of fractional blood volume sometimes saturates the MRI signal during first-pass contrast bolus arrival and presents signal truncation artifacts of various degrees in the tumor when a significant amount of blood exists in the image pixels. It presents a hidden challenge in PWI, as this signal floor can be either close to noise level or just above and can go no lower. This signal truncation in the signal intensity time course is a significant issue that deserves attention in DSC PWI. In this paper, we demonstrate that relative cerebral blood volume and relative cerebral blood flow (rCBF) are underestimated due to signal truncation in DSC perfusion, in glioblastoma patients. We propose the use of second-pass tissue residue function in rCBF calculation using least-absolute-deviation deconvolution to avoid the underestimation problem. PMID:27531989

  7. Mathematical Model for Absolute Magnetic Measuring Systems in Industrial Applications

    NASA Astrophysics Data System (ADS)

    Fügenschuh, Armin; Fügenschuh, Marzena; Ludszuweit, Marina; Mojsic, Aleksandar; Sokół, Joanna

    2015-09-01

    Scales for measuring systems are either based on incremental or absolute measuring methods. Incremental scales need to initialize a measurement cycle at a reference point. From there, the position is computed by counting increments of a periodic graduation. Absolute methods do not need reference points, since the position can be read directly from the scale. The positions on the complete scales are encoded using two incremental tracks with different graduation. We present a new method for absolute measuring using only one track for position encoding up to micrometre range. Instead of the common perpendicular magnetic areas, we use a pattern of trapezoidal magnetic areas, to store more complex information. For positioning, we use the magnetic field where every position is characterized by a set of values measured by a hall sensor array. We implement a method for reconstruction of absolute positions from the set of unique measured values. We compare two patterns with respect to uniqueness, accuracy, stability and robustness of positioning. We discuss how stability and robustness are influenced by different errors during the measurement in real applications and how those errors can be compensated.

  8. A simple mathematical model and practical approach for evaluating citric acid cycle fluxes in perfused rat hearts by 13C-NMR and 1H-NMR spectroscopy.

    PubMed

    Tran-Dinh, S; Hoerter, J A; Mateo, P; Bouet, F; Herve, M

    1997-04-15

    We propose a simple mathematical model and a practical approach for evaluating the flux constant and the absolute value of flux in the citric acid cycle in perfused organs by 13C-NMR and 1H-NMR spectroscopy. We demonstrate that 13C-NMR glutamate spectra are independent of the relative sizes of the mitochondrial and cytosolic compartments and the exchange rates of glutamates, unless there is a difference in 13C chemical shifts of glutamate carbons between the two compartments. Wistar rat hearts (five beating and four KCl-arrested hearts) were aerobically perfused with 100% enriched [2-(13)C]acetate and the kinetics of glutamate carbon labeling from perchloric acid extracts were studied at various perfusion times. Under our experimental conditions, the citric acid cycle flux constant, which represents the fraction of glutamate in exchange with the citric acid cycle per unit time, is about 0.350 +/- 0.003 min(-1) for beating hearts and 0.0741 +/- 0.004 min(-1) for KCl-arrested hearts. The absolute values of the citric acid flux for beating hearts and for KCl-arrested hearts are 1.06 +/- 0.06 micromol x min(-1) x mg(-1) and 0.21 +/- 0.02 micromol x min(-1) x g(-1), respectively. The fraction of unlabeled acetate determined from the proton signal of the methyl group is small and essentially the same in beating and arrested hearts (7.4 +/- 1.7% and 8.8 +/- 2.1%, respectively). Thus, the large difference in the Glu C2/C4 between beating and arrested hearts is not due to the important contribution from anaplerotic sources in arrested hearts but simply to a substantial difference in citric acid cycle fluxes. Our model fits the experimental data well, indicating a fast exchange between 2-oxoglutarate and glutamate in the mitochondria of rat hearts. Analysis of the flux constant, calculated from the half-time of glutamate C4 labeling given in the literature, allows for a comparison of the citric acid flux for various working conditions in different animal species.

  9. Measuring blood delivery to solitary pulmonary nodules using perfusion magnetic resonance imaging

    NASA Astrophysics Data System (ADS)

    Zheng, Wei; Wang, Zhifeng; Shen, Li; Gao, Ling; Ford, James C.; Makedon, Fillia S.; Pearlman, Justin D.

    2006-03-01

    With perfusion magnetic resonance imaging (pMRI), perfusion describes the amount of blood passing through a block of tissue in a certain period of time. In pMRI, the tissue having more blood passing through will show higher intensity value as more contrast-labeled blood arrives. Perfusion reflects the delivery of essential nutrients to a block of tissue, and is an important parameter for the tissue status. Considering solitary pulmonary nodules (SPN), perfusion differences between malignant and benign nodules have been studied by different techniques. Much effort has been put into its characterization. In this paper, we proposed and implemented extraction of the SPN time intensity profile to measure blood delivery to solitary pulmonary nodules, describing their perfusion effects. In this method, a SPN time intensity profile is created based on intensity values of the solitary pulmonary nodule in lung pMRI images over time. This method has two steps: nodule tracking and profile clustering. Nodule tracking aligns the solitary pulmonary nodule in pMRI images taken at different time points, dealing with nodule movement resulted from breathing and body movement. Profile clustering implements segmentation of the nodule region and extraction of the time intensity profile of a solitary pulmonary nodule. SPN time intensity profiles reflect patterns of blood delivery to solitary pulmonary nodules, giving us a description of perfusion effect and indirect evidence of tumor angiogenesis. Analysis on SPN time intensity profiles will help the diagnosis of malignant nodules for early lung cancer detection.

  10. Long term perfusion system supporting adipogenesis.

    PubMed

    Abbott, Rosalyn D; Raja, Waseem K; Wang, Rebecca Y; Stinson, Jordan A; Glettig, Dean L; Burke, Kelly A; Kaplan, David L

    2015-08-01

    Adipose tissue engineered models are needed to enhance our understanding of disease mechanisms and for soft tissue regenerative strategies. Perfusion systems generate more physiologically relevant and sustainable adipose tissue models, however adipocytes have unique properties that make culturing them in a perfusion environment challenging. In this paper we describe the methods involved in the development of two perfusion culture systems (2D and 3D) to test their applicability for long term in vitro adipogenic cultures. It was hypothesized that a silk protein biomaterial scaffold would provide a 3D framework, in combination with perfusion flow, to generate a more physiologically relevant sustainable adipose tissue engineered model than 2D cell culture. Consistent with other studies evaluating 2D and 3D culture systems for adipogenesis we found that both systems successfully model adipogenesis, however 3D culture systems were more robust, providing the mechanical structure required to contain the large, fragile adipocytes that were lost in 2D perfused culture systems. 3D perfusion also stimulated greater lipogenesis and lipolysis and resulted in decreased secretion of LDH compared to 2D perfusion. Regardless of culture configuration (2D or 3D) greater glycerol was secreted with the increased nutritional supply provided by perfusion of fresh media. These results are promising for adipose tissue engineering applications including long term cultures for studying disease mechanisms and regenerative approaches, where both acute (days to weeks) and chronic (weeks to months) cultivation are critical for useful insight. PMID:25843606

  11. Sumatriptan and cerebral perfusion in healthy volunteers.

    PubMed

    Scott, A K; Grimes, S; Ng, K; Critchley, M; Breckenridge, A M; Thomson, C; Pilgrim, A J

    1992-04-01

    1. The effect of sumatriptan on regional cerebral perfusion was studied in healthy volunteers. 2. Intravenous sumatriptan (2 mg) had no detectable effect on regional cerebral perfusion as measured using a SPECT system with 99technetiumm labelled hexemethylpropyleneamineoxime. 3. Sumatriptan had no effect on pulse, blood pressure or ECG indices. 4. All six volunteers experienced minor adverse effects during the intravenous infusion.

  12. Personality factors correlate with regional cerebral perfusion.

    PubMed

    O'Gorman, R L; Kumari, V; Williams, S C R; Zelaya, F O; Connor, S E J; Alsop, D C; Gray, J A

    2006-06-01

    There is an increasing body of evidence pointing to a neurobiological basis of personality. The purpose of this study was to investigate the biological bases of the major dimensions of Eysenck's and Cloninger's models of personality using a noninvasive magnetic resonance perfusion imaging technique in 30 young, healthy subjects. An unbiased voxel-based analysis was used to identify regions where the regional perfusion demonstrated significant correlation with any of the personality dimensions. Highly significant positive correlations emerged between extraversion and perfusion in the basal ganglia, thalamus, inferior frontal gyrus and cerebellum and between novelty seeking and perfusion in the cerebellum, cuneus and thalamus. Strong negative correlations emerged between psychoticism and perfusion in the basal ganglia and thalamus and between harm avoidance and perfusion in the cerebellar vermis, cuneus and inferior frontal gyrus. These observations suggest that personality traits are strongly associated with resting cerebral perfusion in a variety of cortical and subcortical regions and provide further evidence for the hypothesized neurobiological basis of personality. These results may also have important implications for functional neuroimaging studies, which typically rely on the modulation of cerebral hemodynamics for detection of task-induced activation since personality effects may influence the intersubject variability for both task-related activity and resting cerebral perfusion. This technique also offers a novel approach for the exploration of the neurobiological correlates of human personality.

  13. Long term perfusion system supporting adipogenesis

    PubMed Central

    Abbott, Rosalyn D.; Raja, Waseem K.; Wang, Rebecca Y.; Stinson, Jordan A.; Glettig, Dean L.; Burke, Kelly A.; Kaplan, David L.

    2015-01-01

    Adipose tissue engineered models are needed to enhance our understanding of disease mechanisms and for soft tissue regenerative strategies. Perfusion systems generate more physiologically relevant and sustainable adipose tissue models, however adipocytes have unique properties that make culturing them in a perfusion environment challenging. In this paper we describe the methods involved in the development of two perfusion culture systems (2D and 3D) to test their applicability for long term in vitro adipogenic cultures. It was hypothesized that a silk protein biomaterial scaffold would provide a 3D framework, in combination with perfusion flow, to generate a more physiologically relevant sustainable adipose tissue engineered model than 2D cell culture. Consistent with other studies evaluating 2D and 3D culture systems for adipogenesis we found that both systems successfully model adipogensis, however 3D culture systems were more robust, providing the mechanical structure required to contain the large, fragile adipocytes that were lost in 2D perfused culture systems. 3D perfusion also stimulated greater lipogenesis and lipolysis and resulted in decreased secretion of LDH compared to 2D perfusion. Regardless of culture configuration (2D or 3D) greater glycerol was secreted with the increased nutritional supply provided by perfusion of fresh media. These results are promising for adipose tissue engineering applications including long term cultures for studying disease mechanisms and regenerative approaches, where both acute (days to weeks) and chronic (weeks to months) cultivation are critical for useful insight. PMID:25843606

  14. Long term perfusion system supporting adipogenesis.

    PubMed

    Abbott, Rosalyn D; Raja, Waseem K; Wang, Rebecca Y; Stinson, Jordan A; Glettig, Dean L; Burke, Kelly A; Kaplan, David L

    2015-08-01

    Adipose tissue engineered models are needed to enhance our understanding of disease mechanisms and for soft tissue regenerative strategies. Perfusion systems generate more physiologically relevant and sustainable adipose tissue models, however adipocytes have unique properties that make culturing them in a perfusion environment challenging. In this paper we describe the methods involved in the development of two perfusion culture systems (2D and 3D) to test their applicability for long term in vitro adipogenic cultures. It was hypothesized that a silk protein biomaterial scaffold would provide a 3D framework, in combination with perfusion flow, to generate a more physiologically relevant sustainable adipose tissue engineered model than 2D cell culture. Consistent with other studies evaluating 2D and 3D culture systems for adipogenesis we found that both systems successfully model adipogenesis, however 3D culture systems were more robust, providing the mechanical structure required to contain the large, fragile adipocytes that were lost in 2D perfused culture systems. 3D perfusion also stimulated greater lipogenesis and lipolysis and resulted in decreased secretion of LDH compared to 2D perfusion. Regardless of culture configuration (2D or 3D) greater glycerol was secreted with the increased nutritional supply provided by perfusion of fresh media. These results are promising for adipose tissue engineering applications including long term cultures for studying disease mechanisms and regenerative approaches, where both acute (days to weeks) and chronic (weeks to months) cultivation are critical for useful insight.

  15. Introducing the Mean Absolute Deviation "Effect" Size

    ERIC Educational Resources Information Center

    Gorard, Stephen

    2015-01-01

    This paper revisits the use of effect sizes in the analysis of experimental and similar results, and reminds readers of the relative advantages of the mean absolute deviation as a measure of variation, as opposed to the more complex standard deviation. The mean absolute deviation is easier to use and understand, and more tolerant of extreme…

  16. Monolithically integrated absolute frequency comb laser system

    DOEpatents

    Wanke, Michael C.

    2016-07-12

    Rather than down-convert optical frequencies, a QCL laser system directly generates a THz frequency comb in a compact monolithically integrated chip that can be locked to an absolute frequency without the need of a frequency-comb synthesizer. The monolithic, absolute frequency comb can provide a THz frequency reference and tool for high-resolution broad band spectroscopy.

  17. Estimating the absolute wealth of households

    PubMed Central

    Gerkey, Drew; Hadley, Craig

    2015-01-01

    Abstract Objective To estimate the absolute wealth of households using data from demographic and health surveys. Methods We developed a new metric, the absolute wealth estimate, based on the rank of each surveyed household according to its material assets and the assumed shape of the distribution of wealth among surveyed households. Using data from 156 demographic and health surveys in 66 countries, we calculated absolute wealth estimates for households. We validated the method by comparing the proportion of households defined as poor using our estimates with published World Bank poverty headcounts. We also compared the accuracy of absolute versus relative wealth estimates for the prediction of anthropometric measures. Findings The median absolute wealth estimates of 1 403 186 households were 2056 international dollars per capita (interquartile range: 723–6103). The proportion of poor households based on absolute wealth estimates were strongly correlated with World Bank estimates of populations living on less than 2.00 United States dollars per capita per day (R2 = 0.84). Absolute wealth estimates were better predictors of anthropometric measures than relative wealth indexes. Conclusion Absolute wealth estimates provide new opportunities for comparative research to assess the effects of economic resources on health and human capital, as well as the long-term health consequences of economic change and inequality. PMID:26170506

  18. Absolute optical metrology : nanometers to kilometers

    NASA Technical Reports Server (NTRS)

    Dubovitsky, Serge; Lay, O. P.; Peters, R. D.; Liebe, C. C.

    2005-01-01

    We provide and overview of the developments in the field of high-accuracy absolute optical metrology with emphasis on space-based applications. Specific work on the Modulation Sideband Technology for Absolute Ranging (MSTAR) sensor is described along with novel applications of the sensor.

  19. Assessment of the exercise electrocardiogram in women versus men using tomographic myocardial perfusion imaging as the reference standard.

    PubMed

    Miller, T D; Roger, V L; Milavetz, J J; Hopfenspirger, M R; Milavetz, D L; Hodge, D O; Gibbons, R J

    2001-04-01

    The exercise electrocardiogram (ECG) is widely believed to be less accurate in women, primarily due to a high prevalence of false-positive tests. The purpose of this study was to examine the relative accuracy of the exercise ECG in women versus men in 8,671 patients (3,213 women, 5,458 men) using myocardial perfusion imaging as the reference standard. More women (14%) than men (10%) had a false-positive ECG (p <0.001), but the absolute difference was relatively small. The false-negative rate was considerably lower in women (17% vs 32%, p <0.001). Compared with men, women had lower test sensitivity (30% vs 42%, p <0.001) and positive predictive value (34% vs 70%, p <0.001) but higher specificity (82% vs 78%, p = 0.002), negative predictive value (78% vs 52%, p <0.001), and accuracy (69% vs 58%, p <0.001). In patients with a false-negative exercise ECG, "high-risk" scans were less prevalent in women (12% vs 19%, p <0.001). In the smaller subset of patients referred for coronary angiography (205 women, 838 men), the false-positive electrocardiographic rate was again higher in women (13% vs 7%, p = 0.003), but neither specificity (69% vs 74%, p = NS) nor accuracy (60% vs 66%, p = NS) was different between the sexes. Thus, the percentage of patients with a false-positive exercise ECG was higher in women than men but low in absolute terms (<15%) for both sexes. Test specificity was not lower in women. These results suggest that gender should not be a major determinant for selecting stress imaging over standard treadmill testing.

  20. [Assessing myocardial perfusion with positron emission tomography].

    PubMed

    vom Dahl, J

    2001-11-01

    Positron emission tomography (PET) of the heart has gained widespread scientific and clinical acceptance with regard to two indications: 1) The detection of perfusion abnormalities by qualitative and semiquantitative analyses of perfusion images at rest and during physical or pharmacological stress using well-validated perfusion tracers, such as N-13 ammonia, Rb-82 rubidium chloride, or O-15 labeled water. 2) Viability imaging of myocardial regions with reduced contractility by combining perfusion measurements with substrate metabolism as assessed from F-18 deoxyglucose utilization. This overview summarizes the use of PET as a perfusion imaging method. With a sensitivity > 90% in combination with high specificity, PET is today the best-validated available nuclear imaging technique for the diagnosis of coronary artery disease (CAD). The short half-life of the perfusion tracers in combination with highly sophisticated hard- and software enables rapid PET studies with high patient throughput. The high diagnostic accuracy and the methological advantages as compared to conventional scintigraphy allows one to use PET perfusion imaging to detect subtle changes in the perfusion reserve for the detection of CAD in high risk but asymptomatic patients as well as in patients with proven CAD undergoing various treatment forms such as risk factor reduction or coronary revascularization. In patients following orthotopic heart transplantation, evolving transplant vasculopathy can be detected at an early stage. Quantitative PET imaging at rest allows for detection of myocardial viability since cellular survival is based on maintenance of a minimal perfusion and structural changes correlate to the degree of perfusion reduction. Furthermore, quantitative assessment of the myocardial perfusion reserve detects the magnitude and competence of collaterals in regions with occluded epicardial collaterals and, thus, imaging of several coronary distribution territories in one noninvasive

  1. Cardiac PET Perfusion: Prognosis, Risk Stratification, Clinical Management

    PubMed Central

    Dorbala, Sharmila; Di Carli, Marcelo F.

    2014-01-01

    Myocardial perfusion imaging (MPI) with positron emission tomography (PET) has expanded significantly over the past decade. With the wider availability of PET scanners and the routine use of quantitative blood flow imaging, the clinical use of PET MPI is expected to increase further. PET MPI is a powerful tool to identify risk, to quantify risk, and to guide therapy in patients with known or suspected coronary artery disease (CAD). A large body of evidence supports the prognostic value of PET MPI and ejection fraction in intermediate to high risk subjects, in women, in obese individuals and in post coronary artery bypass grafting (CABG) individuals. A normal perfusion study indicates low risk (< 1% annualized rate of cardiac events of cardiac death and non-fatal myocardial infarction), while an abnormal study indicates high risk. With accurate risk stratification, high quality images, and quantitation PET MPI may transform the management of patients with known or suspected CAD. PMID:25234079

  2. Quantification of brain perfusion with tracers retained by the brain

    SciTech Connect

    Pupi, A.; Bacciottini, L.; De Cristofaro, M.T.R.; Formiconi, A.R.; Castagnoli, A.

    1991-12-31

    Almost a decade ago, tracers, labelled with {sup 123}I and {sup 99m}Tc, that are retained by the brain, started to be used for studies of regional brain perfusion (regional cerebral blood flow, rCBF). To date, these tracers have been used for brain perfusion imaging with SPECT in brain disorders as well as for physiological activation protocols. Only seldom, however, have they been used in protocols that quantitatively measure rCBF. Nevertheless, comparative studies with perfusion reference tracers have repeatedly demonstrated that the brain uptake of these brain-retained tracers is correlated to perfusion, the major determinant of the distribution of these tracers in the brain. The brain kinetics of {sup 99m}Tc HMPAO, which is the tracer most commonly used, was described with a two-compartment tissue model. The theoretical approach, which is, in itself, sufficient for modeling quantitative measurements with {sup 99m}Tc HMPAO, initially suggested the possibility of empirically narrowing the distance between the brain`s regional uptake of the tracer and rCBF with a linearization algorithm which uses the cerebellum as the reference region. The value of this empirical method is hampered by the fact that the cerebellum can be involved in cerebrovascular disease (i.e. cerebellar diaschisis) as well as in several other brain disorders (e.g. anxiety, and dementia of the Alzheimer type). It also was proposed that different reference regions (occipital, whole slice, or whole brain) should be selected in relation to the brain disorder under study. However, this approach does not solve the main problem because it does not equip us with a reliable tool to evaluate rCBF with a high predictive value, and, at the same time, to reduce intersubject variability. The solution would be to measure a quantitative parameter which directly reflects rCBF, such as the unidirectional influx constant of the freely diffusible flow-limited tracers. 45 refs., 3 figs., 1 tab.

  3. Absolute Gravity Datum in the Age of Cold Atom Gravimeters

    NASA Astrophysics Data System (ADS)

    Childers, V. A.; Eckl, M. C.

    2014-12-01

    The international gravity datum is defined today by the International Gravity Standardization Net of 1971 (IGSN-71). The data supporting this network was measured in the 1950s and 60s using pendulum and spring-based gravimeter ties (plus some new ballistic absolute meters) to replace the prior protocol of referencing all gravity values to the earlier Potsdam value. Since this time, gravimeter technology has advanced significantly with the development and refinement of the FG-5 (the current standard of the industry) and again with the soon-to-be-available cold atom interferometric absolute gravimeters. This latest development is anticipated to provide improvement in the range of two orders of magnitude as compared to the measurement accuracy of technology utilized to develop ISGN-71. In this presentation, we will explore how the IGSN-71 might best be "modernized" given today's requirements and available instruments and resources. The National Geodetic Survey (NGS), along with other relevant US Government agencies, is concerned about establishing gravity control to establish and maintain high order geodetic networks as part of the nation's essential infrastructure. The need to modernize the nation's geodetic infrastructure was highlighted in "Precise Geodetic Infrastructure, National Requirements for a Shared Resource" National Academy of Science, 2010. The NGS mission, as dictated by Congress, is to establish and maintain the National Spatial Reference System, which includes gravity measurements. Absolute gravimeters measure the total gravity field directly and do not involve ties to other measurements. Periodic "intercomparisons" of multiple absolute gravimeters at reference gravity sites are used to constrain the behavior of the instruments to ensure that each would yield reasonably similar measurements of the same location (i.e. yield a sufficiently consistent datum when measured in disparate locales). New atomic interferometric gravimeters promise a significant

  4. On the Absolute Continuity of the Blackwell Measure

    NASA Astrophysics Data System (ADS)

    Bárány, Balázs; Kolossváry, István

    2015-04-01

    In 1957, Blackwell expressed the entropy of hidden Markov chains using a measure which can be characterised as an invariant measure for an iterated function system with place-dependent weights. This measure, called the Blackwell measure, plays a central role in understanding the entropy rate and other important characteristics of fundamental models in information theory. We show that for a suitable set of parameter values the Blackwell measure is absolutely continuous for almost every parameter in the case of binary symmetric channels.

  5. Engine performance and the determination of absolute ceiling

    NASA Technical Reports Server (NTRS)

    Diehl, Walter S

    1924-01-01

    This report contains a brief study of the variation of engine power with temperature and pressure. The variation of propeller efficiency in standard atmosphere is obtained from the general efficiency curve which is developed in NACA report no. 168. The variation of both power available and power required are then determined and curves plotted, so that the absolute ceiling may be read directly from any known sea-level value of the ratio of power available to power required.

  6. The development of a multiorgan ex vivo perfused model: results with the porcine liver-kidney circuit over 24 hours.

    PubMed

    Chung, Wen Yuan; Gravante, Gianpiero; Al-Leswas, Dhya; Arshad, Ali; Sorge, Roberto; Watson, Chris C; Pollard, Cristina; Metcalfe, Matthew S; Dennison, Ashley R

    2013-05-01

    We already developed an ex vivo liver-kidney model perfused for 6 h in which the kidney acted as a homeostatic organ to improve the circuit milieu compared to liver alone. In the current study, we extended the multiorgan perfusions to 24 h to evaluate the results and eventual pitfalls manifesting with longer durations. Five livers and kidneys were harvested from female pigs and perfused over 24 h. The extracorporeal circuit included a centrifugal pump, heat exchanger, and oxygenator. The primary end point of the study was the evaluation of the organ functions as gathered from biochemical and acid-base parameters. In the combined liver-kidney circuit, the organs survived and maintained an acceptable homeostasis for different lengths of time, longer for the liver (up to 19-23 h of perfusions) than the kidney (9-13 h of perfusions). Furthermore, glucose and creatinine values decreased significantly over time (from the 5th and 9th hour of perfusion onward). The addition of a kidney to the perfusion circuit improved the biochemical environment by removing excess products from ongoing metabolic processes. The consequence is a more physiological milieu that could improve results from future experimental studies. However, it is likely that long perfusions require some nutritional support over the hours to maintain the organ's vitality and functionality throughout the experiments. PMID:23489088

  7. Machine Perfusion Enhances Hepatocyte Isolation Yields From Ischemic Livers

    PubMed Central

    Izamis, Maria-Louisa; Perk, Sinem; Calhoun, Candice; Uygun, Korkut; Yarmush, Martin L.; Berthiaume, François

    2015-01-01

    Background High-quality human hepatocytes form the basis of drug safety and efficacy tests, cell-based therapies, and bridge-to-transplantation devices. Presently the only supply of cells derives from an inadequate pool of suboptimal disqualified donor livers. Here we evaluated whether machine perfusion could ameliorate ischemic injury that many of these livers experience prior to hepatocyte isolation. Methods Non-heparinized female Lewis rat livers were exposed to an hour of warm ischemia (34°C) and then perfused for 3 hours. Five different perfusion conditions that utilized the cell isolation apparatus were investigated, namely: (1) modified Williams Medium E and (2) Lifor, both with active oxygenation (95%O2/5%CO2), as well as (3) Lifor passively oxygenated with ambient air (21%O2/0.04%CO2), all at ambient temperatures (20±2°C). At hypothermic temperatures (5±1°C) and under passive oxygenation were (4) University of Wisconsin solution (UW) and (5) Vasosol. Negative and positive control groups comprised livers that had ischemia (WI) and livers that did not (Fresh) prior to cell isolation, respectively. Results Fresh livers yielded 32±9 million cells/g liver while an hour of ischemia reduced the cell yield to 1.6±0.6 million cells/g liver. Oxygenated Williams medium E and Lifor recovered yields of 39±11 and 31±2.3 million cells/g liver, respectively. The passively oxygenated groups produced 15±7 (Lifor), 13±7 (Vasosol), and 10±6 (UW) million cells/g liver. Oxygenated Williams Medium E was most effective at sustaining pH values, avoiding the accumulation of lactate, minimizing edematous weight gain and producing bile during perfusion. Conclusions Machine perfusion results in a dramatic increase in cell yields from livers that have had up to an hour of warm ischemia, but perfusate choice significantly impacts the extent of recovery. Oxygenated Williams Medium E at room temperature is superior to Lifor, UW and Vasosol, largely facilitated by its high

  8. Processing of pulse oximeter signals using adaptive filtering and autocorrelation to isolate perfusion and oxygenation components

    NASA Astrophysics Data System (ADS)

    Ibey, Bennett; Subramanian, Hariharan; Ericson, Nance; Xu, Weijian; Wilson, Mark; Cote, Gerard L.

    2005-03-01

    A blood perfusion and oxygenation sensor has been developed for in situ monitoring of transplanted organs. In processing in situ data, motion artifacts due to increased perfusion can create invalid oxygenation saturation values. In order to remove the unwanted artifacts from the pulsatile signal, adaptive filtering was employed using a third wavelength source centered at 810nm as a reference signal. The 810 nm source resides approximately at the isosbestic point in the hemoglobin absorption curve where the absorbance of light is nearly equal for oxygenated and deoxygenated hemoglobin. Using an autocorrelation based algorithm oxygenation saturation values can be obtained without the need for large sampling data sets allowing for near real-time processing. This technique has been shown to be more reliable than traditional techniques and proven to adequately improve the measurement of oxygenation values in varying perfusion states.

  9. Pattern of brain blood perfusion in tinnitus patients using technetium-99m SPECT imaging

    PubMed Central

    Mahmoudian, Saeid; Farhadi, Mohammad; Gholami, Saeid; Saddadi, Fariba; Karimian, Ali Reza; Mirzaei, Mohammad; Ghoreyshi, Esmaeel; Ahmadizadeh, Majid; Lenarz, Thomas

    2012-01-01

    Background and Purpose: Tinnitus is associated with an increased activity in central auditory system as demonstrated by neuroimaging studies. Brain perfusion scanning using single photon emission computed tomography (SPECT) was done to understand the pattern of brain blood perfusion of tinnitus subjects and find the areas which are mostly abnormal in these patients. Materials and Methods: A number of 122 patients with tinnitus were enrolled to this cross-sectional study. They underwent SPECT and magnetic resonance imaging (MRI) of brain, and the images were fused to find the regions with abnormal perfusion. Results: SPECT scan results were abnormal in 101 patients (83%). Most patients had bilateral abnormal perfusion (N = 65, 53.3%), and most subjects had abnormality in middle-temporal gyrus (N = 83, 68%) and temporoparietal cortex (N = 46, 37.7%). Patients with multifocal involvement had the least mean age than other 2 groups (patients with no abnormality and unifocal abnormality) (P value = 0.045). Conclusions: Brain blood perfusion pattern differs in patient with tinnitus than others. These patients have brain perfusion abnormality, mostly in auditory gyrus (middle temporal) and associative cortex (temporoparietal cortex). Multifocal abnormalities might be due to more cognitive and emotional brain centers involvement due to tinnitus or more stress and anxiety of tinnitus in the young patients. PMID:23267375

  10. Cochlear perfusion with a viscous fluid.

    PubMed

    Wang, Yi; Olson, Elizabeth S

    2016-07-01

    The flow of viscous fluid in the cochlea induces shear forces, which could provide benefit in clinical practice, for example to guide cochlear implant insertion or produce static pressure to the cochlear partition or wall. From a research standpoint, studying the effects of a viscous fluid in the cochlea provides data for better understanding cochlear fluid mechanics. However, cochlear perfusion with a viscous fluid may damage the cochlea. In this work we studied the physiological and anatomical effects of perfusing the cochlea with a viscous fluid. Gerbil cochleae were perfused at a rate of 2.4 μL/min with artificial perilymph (AP) and sodium hyaluronate (Healon, HA) in four different concentrations (0.0625%, 0.125%, 0.25%, 0.5%). The different HA concentrations were applied either sequentially in the same cochlea or individually in different cochleae. The perfusion fluid entered from the round window and was withdrawn from basal scala vestibuli, in order to perfuse the entire perilymphatic space. Compound action potentials (CAP) were measured after each perfusion. After perfusion with increasing concentrations of HA in the order of increasing viscosity, the CAP thresholds generally increased. The threshold elevation after AP and 0.0625% HA perfusion was small or almost zero, and the 0.125% HA was a borderline case, while the higher concentrations significantly elevated CAP thresholds. Histology of the cochleae perfused with the 0.0625% HA showed an intact Reissner's membrane (RM), while in cochleae perfused with 0.125% and 0.25% HA RM was torn. Thus, the CAP threshold elevation was likely due to the broken RM, likely caused by the shear stress produced by the flow of the viscous fluid. Our results and analysis indicate that the cochlea can sustain, without a significant CAP threshold shift, up to a 1.5 Pa shear stress. Beside these finding, in the 0.125% and 0.25% HA perfusion cases, a temporary CAP threshold shift was observed, perhaps due to the presence and

  11. Cochlear perfusion with a viscous fluid.

    PubMed

    Wang, Yi; Olson, Elizabeth S

    2016-07-01

    The flow of viscous fluid in the cochlea induces shear forces, which could provide benefit in clinical practice, for example to guide cochlear implant insertion or produce static pressure to the cochlear partition or wall. From a research standpoint, studying the effects of a viscous fluid in the cochlea provides data for better understanding cochlear fluid mechanics. However, cochlear perfusion with a viscous fluid may damage the cochlea. In this work we studied the physiological and anatomical effects of perfusing the cochlea with a viscous fluid. Gerbil cochleae were perfused at a rate of 2.4 μL/min with artificial perilymph (AP) and sodium hyaluronate (Healon, HA) in four different concentrations (0.0625%, 0.125%, 0.25%, 0.5%). The different HA concentrations were applied either sequentially in the same cochlea or individually in different cochleae. The perfusion fluid entered from the round window and was withdrawn from basal scala vestibuli, in order to perfuse the entire perilymphatic space. Compound action potentials (CAP) were measured after each perfusion. After perfusion with increasing concentrations of HA in the order of increasing viscosity, the CAP thresholds generally increased. The threshold elevation after AP and 0.0625% HA perfusion was small or almost zero, and the 0.125% HA was a borderline case, while the higher concentrations significantly elevated CAP thresholds. Histology of the cochleae perfused with the 0.0625% HA showed an intact Reissner's membrane (RM), while in cochleae perfused with 0.125% and 0.25% HA RM was torn. Thus, the CAP threshold elevation was likely due to the broken RM, likely caused by the shear stress produced by the flow of the viscous fluid. Our results and analysis indicate that the cochlea can sustain, without a significant CAP threshold shift, up to a 1.5 Pa shear stress. Beside these finding, in the 0.125% and 0.25% HA perfusion cases, a temporary CAP threshold shift was observed, perhaps due to the presence and

  12. Temperature controlled machine perfusion system for liver.

    PubMed

    Obara, H; Matsuno, N; Shigeta, T; Hirano, T; Enosawa, S; Mizunuma, H

    2013-06-01

    Organ preservation using machine perfusion is an effective method compared with conventional preservation techniques using static cold storage. A newly developed MP preservation system to control perfusate temperatures from hypothermic to subnormothermic conditions is introduced. This system is useful not only for liver preservation, but also for evaluation of graft viability for recovery. This novel method has been proposed for preservation of porcine liver grafts. An innovative preservation system is especially important to obtain viable organs from extended criteria or donation after cardiac death donors. In this study, we introduce a new machine perfusion preservation system (NES-01) to evaluate graft viability for recovery of liver functions, using porcine grafts.

  13. Prilocaine elimination by isolated perfused rat lung and liver.

    PubMed

    Geng, W P; Ebke, M; Foth, H

    1995-01-01

    Prilocaine is assumed to undergo significant elimination by extrahepatic organs and to differ in this respect from other commonly used local anaesthetics. In order to clarify whether the lung may play an important role as a site of elimination of prilocaine, the kinetic parameters were studied in isolated perfused rat lungs and were compared to those of isolated livers. Furthermore, the structurally related compounds bupivacaine and mepivacaine were also investigated in this system. Prilocaine was dispersed into a relatively large apparent distribution volume in perfused rat lung (139 ml versus 97 ml in controls). In single-pass perfused lungs the observed maximum of concentration was decreased by about 60% compared to controls. The mean residence time was prolonged by about 40%. These observations suggest that prilocaine is substantially retained by rat lung and that this effect occurs particularly during first-pass. However, the ability of rat lung to degrade prilocaine was relatively low. The clearance values were about 0.3 ml/min equal to about 20% of the hepatic capacity calculated per g of tissue. Thus it must be assumed that prilocaine is only transiently retained by the lung and will gain systemic availability later on. In rat lungs the kinetics of prilocaine elimination were not substantially different from those of bupivacaine and mepivacaine (16 and 12%). These observations do not support the assumption that especially prilocaine undergoes extrahepatic elimination.

  14. Inhomogeneity of pulmonary perfusion during sustained microgravity on SLS-1

    NASA Technical Reports Server (NTRS)

    Prisk, G. Kim; Guy, Harold J. B.; Elliott, Ann R.; West, John B.

    1994-01-01

    We studied the effects of gravity on the inhomogeneity of pulmonary perfusion in humans by performing hyperventilation-breath-hold single-breath measurements before, during, and after 9 days of continuous exposure to microgravity during the Spacelab Life Sciences-1 (SLS-1) mission. In microgravity the indicators of inhomogeneity of perfusion, especially the size of cardiogenic oscillations in expired CO2 and the height of phase IV, were markedly reduced. Cardiogenic oscillations were reduced to approximately 60% of their preflight standing size, and the height of phase IV was between 0 and -8% (a terminal fall became a small terminal rise) of the preflight standing value. The terminal change in expired CO2 was nearly abolished in microgravity, indicating more uniformity of blood flow between lung units that close and those that remain open at the end of expiration. A possible explanation of this observation is the disappearance of gravity-dependent topographic inequality of blood flow. The residual cardiogenic oscillations in expired CO2 imply a persisting inhomogeneity of perfusion in the absence of gravity, probably in lung regions that are not within the same acinus.

  15. Absolute magnitudes of trans-neptunian objects

    NASA Astrophysics Data System (ADS)

    Duffard, R.; Alvarez-candal, A.; Pinilla-Alonso, N.; Ortiz, J. L.; Morales, N.; Santos-Sanz, P.; Thirouin, A.

    2015-10-01

    Accurate measurements of diameters of trans- Neptunian objects are extremely complicated to obtain. Radiomatric techniques applied to thermal measurements can provide good results, but precise absolute magnitudes are needed to constrain diameters and albedos. Our objective is to measure accurate absolute magnitudes for a sample of trans- Neptunian objects, many of which have been observed, and modelled, by the "TNOs are cool" team, one of Herschel Space Observatory key projects grantes with ~ 400 hours of observing time. We observed 56 objects in filters V and R, if possible. These data, along with data available in the literature, was used to obtain phase curves and to measure absolute magnitudes by assuming a linear trend of the phase curves and considering magnitude variability due to rotational light-curve. In total we obtained 234 new magnitudes for the 56 objects, 6 of them with no reported previous measurements. Including the data from the literature we report a total of 109 absolute magnitudes.

  16. A New Gimmick for Assigning Absolute Configuration.

    ERIC Educational Resources Information Center

    Ayorinde, F. O.

    1983-01-01

    A five-step procedure is provided to help students in making the assignment absolute configuration less bothersome. Examples for both single (2-butanol) and multi-chiral carbon (3-chloro-2-butanol) molecules are included. (JN)

  17. The Simplicity Argument and Absolute Morality

    ERIC Educational Resources Information Center

    Mijuskovic, Ben

    1975-01-01

    In this paper the author has maintained that there is a similarity of thought to be found in the writings of Cudworth, Emerson, and Husserl in his investigation of an absolute system of morality. (Author/RK)

  18. Electrical constants of arterially perfused rabbit papillary muscle.

    PubMed Central

    Kléber, A G; Riegger, C B

    1987-01-01

    1. Right ventricular rabbit papillary muscles were arterially perfused with a mixture of Tyrode solution, bovine erythrocytes, dextran and albumin. In the recording chamber, they were surrounded by a H2O-saturated atmosphere of O2 and CO2 which served as an electrical insulator. 2. Conduction velocity and passive electrical properties were determined from intra- and extracellular potentials measured during excitation and during flow of subthreshold current. 3. The propagation of the action potential was linear along the muscle at a velocity of 55.6 cm/s. The extracellular wave-front voltage was 51.5 mV. 4. The following values for passive cable properties were obtained: (i) a ratio of extra- to intracellular longitudinal resistance of 1.2; (ii) an extracellular specific resistance (Ro) of 63 omega cm; (iii) an intracellular specific resistance (Ri) of 166 omega cm; (iv) a space constant lambda of 0.357 mm; (v) a membrane time constant tau of 2.57 ms. The space constant lambda* recalculated for zero extracellular resistance was 0.528 mm. 5. Arresting perfusion with drop of perfusion pressure was associated with an immediate increase of the extracellular longitudinal resistance by 35% and a decrease of conduction velocity by 13%. 6. The present results demonstrate the important contribution of the extracellular resistance to electrotonic interaction and propagation in densely packed myocardial tissue. Moreover, changes in perfusion pressure are associated with changes in extracellular resistance, probably as a consequence of changes in intravascular volume. PMID:3656162

  19. Absolute V-R colors of trans-Neptunian objects

    NASA Astrophysics Data System (ADS)

    Alvarez-Candal, Alvaro; Ayala-Loera, Carmen; Ortiz, Jose-Luis; Duffard, Rene; Estela, Fernandez-Valenzuela; Santos-Sanz, Pablo

    2016-10-01

    The absolute magnitude of a minor body is the apparent magnitude that the body would have if observed from the Sun at a distance of 1AU. Absolute magnitudes are measured using phase curves, showing the change of the magnitude, normalized to unit helio and geo-centric distance, vs. phase angle. The absolute magnitude is then the Y-intercept of the curve. Absolute magnitudes are related to the total reflecting surface of the body and thus bring information of its size, coupled with the reflecting properties.Since 2011 our team has been collecting data from several telescopes spread in Europe and South America. We complemented our data with those available in the literature in order to construct phase curves of trans-Neptunian objects with at least three points. In a first release (Alvarez-Candal et al. 2016, A&A, 586, A155) we showed results for 110 trans-Neptunian objects using V magnitudes only, assuming an overall linear trend and taking into consideration rotational effects, for objects with known light-curves.In this contribution we show results for more than 130 objects, about 100 of them with phase curves in two filters: V and R. We compute absolute magnitudes and phase coefficients in both filters, when available. The average values are HV = 6.39 ± 2.37, βV = (0.09 ± 0.32) mag per degree, HR = 5.38 ± 2.30, and βR = (0.08 ± 0.42) mag per degree.

  20. GNSS Absolute Antenna Calibration at the National Geodetic Survey

    NASA Astrophysics Data System (ADS)

    Mader, G. L.; Bilich, A. L.; Geoghegan, C.

    2011-12-01

    Geodetic GNSS applications routinely demand millimeter precision and extremely high levels of accuracy. To achieve these accuracies, measurement and instrument biases at the centimeter to millimeter level must be understood. One of these biases is the antenna phase center, the apparent point of signal reception for a GNSS antenna. It has been well established that phase center patterns differ between antenna models and manufacturers; additional research suggests that the addition of a radome or the choice of antenna mount can significantly alter those a priori phase center patterns. For the more demanding GNSS positioning applications and especially in cases of mixed-antenna networks, it is all the more important to know antenna phase center variations as a function of both elevation and azimuth in the antenna reference frame and incorporate these models into analysis software. To help meet the needs of the high-precision GNSS community, the National Geodetic Survey (NGS) now operates an absolute antenna calibration facility. Located in Corbin, Virginia, this facility uses field measurements and actual GNSS satellite signals to quantitatively determine the carrier phase advance/delay introduced by the antenna element. The NGS facility was built to serve traditional NGS constituents such as the surveying and geodesy communities, however calibration services are open and available to all GNSS users as the calibration schedule permits. All phase center patterns computed by this facility will be publicly available and disseminated in both the ANTEX and NGS formats. We describe the NGS calibration facility, and discuss the observation models and strategy currently used to generate NGS absolute calibrations. We demonstrate that NGS absolute phase center variation (PCV) patterns are consistent with published values determined by other absolute antenna calibration facilities, and compare absolute calibrations to the traditional NGS relative calibrations.

  1. Effect of isolated proximal coronary stenotic lesions on distal myocardial perfusion during exercise

    SciTech Connect

    Nichols, A.B.; Buczek, J.A.; Schwann, T.A.; Esser, P.D.; Blood, D.K.

    1988-07-01

    This study tested the hypothesis that the absolute dimension of a coronary stenotic lesion is a more important determinant of its hemodynamic effect on regional myocardial perfusion during exercise than is relative percent stenosis. In 31 patients with an isolated lesion of the left anterior descending coronary artery, regional myocardial perfusion was determined from thallium-201 scans recorded in the left anterior oblique projection after symptom-limited treadmill exercise. Thallium-201 uptake in the distribution of the left anterior descending coronary artery was expressed as a ratio of thallium-201 uptake in the left circumflex artery distribution. Percent area stenosis, minimal cross-sectional area and mean diameter of each stenotic lesion were measured by computer-assisted cinevideodensitometric analysis of projected coronary arteriograms digitized in a 512 X 512 pixel matrix with 256 gray levels. Thallium-201 uptake in the left anterior descending coronary artery distribution, expressed as a ratio, correlated poorly (r = 0.65) with relative percent stenosis, but correlated significantly (r = 0.83; p less than 0.05) with absolute lesion area. For all 16 patients with reduced regional perfusion in the left anterior descending coronary artery distribution during exercise, lesion cross-sectional area was less than 1.8 mm2 (mean 0.9 +/- 0.6); for 13 of the 15 patients with normal distal perfusion, the area of the stenotic lesion was greater than 1.8 mm2 (mean 2.7 +/- 0.7; p less than 0.001). Percent coronary stenosis failed to predict flow-limiting lesions.

  2. Microcirculation Perfusion Monitor on the Back of the Health Volunteers

    PubMed Central

    Li, Yanqi; Li, Xiaomei; Zhou, Dan; Wang, Kang; Liu, Yangyang; Guo, Yi; Qiu, Shuang; Zhai, Tianchen; Liu, Shuang; Liu, Jingjing; Ming, Dong

    2013-01-01

    Objective. To observe the dermal microcirculation blood perfusion characterization of meridians channels (acupoints). Methods. 20 healthy human subjects were monitored using Pericam Perfusion Speckle Imager (PSI) for the changes in dermal microcirculation blood perfusion on governor meridian and other respective dermal regions as a control. Result. The microcirculation blood perfusion on Governor Meridian is higher than its control area. Conclusion. The dermal microcirculation blood perfusion on certain parts of Governor Meridian of healthy human subjects showed specifics. PMID:24371463

  3. Luminal distension as a possible consequence of experimental intestinal perfusion

    PubMed Central

    Wingate, David; Hyams, Ashley; Phillips, Sidney

    1974-01-01

    In an experimental jejunal perfusion study, distress in healthy subjects occurred during eight out of 16 perfusions in which intestinal secretion was provoked. Calculation demonstrates the volumetric consequences of inadequate recovery of secretory perfusates, and analysis of the perfusion studies shows that distress was significantly associated with poor recovery of the perfusate. These observations are pertinent to increasing interest in the phenomenon of intestinal fluid secretion. PMID:4435588

  4. Is misery perfusion still a predictor of stroke in symptomatic major cerebral artery disease?

    PubMed

    Yamauchi, Hiroshi; Higashi, Tatsuya; Kagawa, Shinya; Nishii, Ryuichi; Kudo, Takashi; Sugimoto, Kanji; Okazawa, Hidehiko; Fukuyama, Hidenao

    2012-08-01

    Studies in the 1990s demonstrated that misery perfusion is a predictor of subsequent stroke in medically treated patients with symptomatic major cerebral artery disease. A recent randomized controlled trial demonstrated no benefit of bypass surgery for such patients. In this light, outcome in patients with misery perfusion has regained interest. The purpose of this study was to determine whether misery perfusion is still a predictor of subsequent stroke despite recent improvements in medical treatment for secondary prevention of stroke, and if so, whether the predictive value of misery perfusion has changed in recent years. We prospectively studied 165 non-disabled patients with symptomatic atherosclerotic internal carotid artery or middle cerebral artery occlusive diseases who underwent positron emission tomography from 1999 to 2008. Misery perfusion was defined as decreased cerebral blood flow, increased oxygen extraction fraction and decreased ratio of cerebral blood flow to blood volume in the hemisphere supplied by the diseased artery. All patients were followed up for 2 years until stroke recurrence or death. Bypass surgery was performed in 19 of 35 patients with and 16 of 130 patients without misery perfusion. The 2-year incidence of ipsilateral ischaemic stroke was six and four patients with and without misery perfusion, including two and one after surgery, respectively (P < 0.002). Total strokes occurred in nine patients with misery perfusion and 12 patients without (P < 0.01). The relative risk conferred by misery perfusion in whole sample was 6.3 (95% confidence interval 1.7-22.4, P < 0.005) for ipsilateral ischaemic stroke and 3.5 (95% confidence interval 1.4-8.9, P < 0.01) for all strokes, while the respective values in medically treated patients were 12.6 (95% confidence interval 2.7-57.8, P < 0.005) and 4.7 (95% confidence interval 1.3-16.3, P < 0.02). The all-stroke incidence in patients entering the study from 2004 to 2008

  5. Ex vivo lung perfusion and reconditioning.

    PubMed

    Yeung, Jonathan C; Cypel, Marcelo; Massad, Ehab; Keshavjee, Shaf

    2011-01-01

    Normothermic ex vivo lung perfusion can act as a platform for the evaluation and repair of donor lungs. An acellular hyperosmolar solution is perfused anterograde through the donor lungs at 40% of the estimated cardiac output. Following oxygenation of the perfusate by the lung, it passes through a hollow fiber oxygenator supplied with a hypoxic gas mixture to remove oxygen and to maintain physiological carbon dioxide levels. Flow through a heat exchanger to maintain normothermia and a leukocyte filter to remove demarginated leukocytes completes the circuit. Lung function can be measured by the difference in PO2 between the perfusate postlung and postmembrane and by physiological parameters. Utilization of this method of ex vivo donor lung evaluation should reduce concerns of primary graft dysfunction and increase utilization rates of donor lungs. PMID:24412979

  6. Noninvasive methods of measuring bone blood perfusion

    PubMed Central

    Dyke, J.P.; Aaron, R.K.

    2010-01-01

    Measurement of bone blood flow and perfusion characteristics in a noninvasive and serial manner would be advantageous in assessing revascularization after trauma and the possible risk of avascular necrosis. Many disease states, including osteoporosis, osteoarthritis, and bone neoplasms, result in disturbed bone perfusion. A causal link between bone perfusion and remodeling has shown its importance in sustained healing and regrowth following injury. Measurement of perfusion and permeability within the bone was performed with small and macromolecular contrast media, using dynamic contrast-enhanced magnetic resonance imaging in models of osteoarthritis and the femoral head. Bone blood flow and remodeling was estimated using 18F-Fluoride positron emission tomography in fracture healing and osteoarthritis. Multimodality assessment of bone blood flow, permeability, and remodeling by using noninvasive imaging techniques may provide information essential in monitoring subsequent rates of healing and response to treatment as well as identifying candidates for additional therapeutic or surgical interventions. PMID:20392223

  7. Bubble dynamics in perfused tissue undergoing decompression.

    PubMed

    Meisel, S; Nir, A; Kerem, D

    1981-02-01

    A mathematical model describing bubble dynamics in a perfused tissue undergoing decompression is presented, taking into account physical expansion and inward diffusion from surrounding supersaturated tissue as growth promoting factors and tissue gas elimination by perfusion, tissue elasticity, surface tension and inherent unsaturation as resolving driving forces. The expected behavior after a step reduction of pressure of a bubble initially existing in the tissue, displaying both growth and resolution has been demonstrated. A strong perfusion-dependence of bubble resolution time at low perfusion rates is apparent. The model can account for various exposure pressures and saturation fractions of any inert gas-tissue combination for which a set of physical and physiological parameters is available.

  8. Absolute photoionization cross-section of the propargyl radical

    SciTech Connect

    Savee, John D.; Welz, Oliver; Taatjes, Craig A.; Osborn, David L.; Soorkia, Satchin; Selby, Talitha M.

    2012-04-07

    Using synchrotron-generated vacuum-ultraviolet radiation and multiplexed time-resolved photoionization mass spectrometry we have measured the absolute photoionization cross-section for the propargyl (C{sub 3}H{sub 3}) radical, {sigma}{sub propargyl}{sup ion}(E), relative to the known absolute cross-section of the methyl (CH{sub 3}) radical. We generated a stoichiometric 1:1 ratio of C{sub 3}H{sub 3} : CH{sub 3} from 193 nm photolysis of two different C{sub 4}H{sub 6} isomers (1-butyne and 1,3-butadiene). Photolysis of 1-butyne yielded values of {sigma}{sub propargyl}{sup ion}(10.213 eV)=(26.1{+-}4.2) Mb and {sigma}{sub propargyl}{sup ion}(10.413 eV)=(23.4{+-}3.2) Mb, whereas photolysis of 1,3-butadiene yielded values of {sigma}{sub propargyl}{sup ion}(10.213 eV)=(23.6{+-}3.6) Mb and {sigma}{sub propargyl}{sup ion}(10.413 eV)=(25.1{+-}3.5) Mb. These measurements place our relative photoionization cross-section spectrum for propargyl on an absolute scale between 8.6 and 10.5 eV. The cross-section derived from our results is approximately a factor of three larger than previous determinations.

  9. Vicarious Audiovisual Learning in Perfusion Education

    PubMed Central

    Rath, Thomas E.; Holt, David W.

    2010-01-01

    Abstract: Perfusion technology is a mechanical and visual science traditionally taught with didactic instruction combined with clinical experience. It is difficult to provide perfusion students the opportunity to experience difficult clinical situations, set up complex perfusion equipment, or observe corrective measures taken during catastrophic events because of patient safety concerns. Although high fidelity simulators offer exciting opportunities for future perfusion training, we explore the use of a less costly low fidelity form of simulation instruction, vicarious audiovisual learning. Two low fidelity modes of instruction; description with text and a vicarious, first person audiovisual production depicting the same content were compared. Students (n = 37) sampled from five North American perfusion schools were prospectively randomized to one of two online learning modules, text or video. These modules described the setup and operation of the MAQUET ROTAFLOW standalone centrifugal console and pump. Using a 10 question multiple-choice test, students were assessed immediately after viewing the module (test #1) and then again 2 weeks later (test #2) to determine cognition and recall of the module content. In addition, students completed a questionnaire assessing the learning preferences of today’s perfusion student. Mean test scores from test #1 for video learners (n = 18) were significantly higher (88.89%) than for text learners (n = 19) (74.74%), (p < .05). The same was true for test #2 where video learners (n = 10) had an average score of 77% while text learners (n = 9) scored 60% (p < .05). Survey results indicated video learners were more satisfied with their learning module than text learners. Vicarious audiovisual learning modules may be an efficacious, low cost means of delivering perfusion training on subjects such as equipment setup and operation. Video learning appears to improve cognition and retention of learned content and may play an important

  10. Improved exercise myocardial perfusion during lidoflazine therapy

    SciTech Connect

    Shapiro, W.; Narahara, K.A.; Park, J.

    1983-11-01

    Lidoflazine is a synthetic drug with calcium-channel blocking effects. In a study of 6 patients with severe classic angina pectoris, single-blind administration of lidoflazine was associated with improved myocardial perfusion during exercise as determined by thallium-201 stress scintigraphy. These studies demonstrate that lidoflazine therapy is associated with relief of angina, an increased physical work capacity, and improved regional myocardial perfusion during exercise.

  11. Correlation of magnetic resonance signal characteristics and perfusion parameters assessed by volume perfusion computed tomography in hepatocellular carcinoma: Impact on lesion characterization

    PubMed Central

    Grözinger, Gerd; Bitzer, Michael; Syha, Roland; Ketelsen, Dominik; Nikolaou, Konstantin; Lauer, Ulrich; Horger, Marius

    2016-01-01

    AIM To find out if magnetic resonance (MR)-signal characteristics of hepatocellular carcinomas (HCC) correlate with perfusion parameters assessed by volume perfusion computed tomography (VPCT). METHODS From October 2009 to January 2014, 26 (mean age, 69.3 years) patients with 36 HCC lesions who underwent both VPCT and MR liver imaging were analysed. We compared signal intensity in the T1w- and T2w-images and wash-in/wash-out kinetics on post-contrast MR images with mean values of blood flow (BF, mL/100 mL per minute), blood volume (BV, mL/100 mL), k-trans (mL/100 mL per minute), arterial liver perfusion (mL/100 mL per minute), portal venous perfusion and hepatic perfusion index (HPI, %) obtained by VPCT. Signal intensity on magnetic resonance imaging (MRI) was classified hyper/iso/hypointense compared with surrounding liver parenchyma. RESULTS Signal intensity on native T1w- and T2w-images was hyper/iso/hypo in 4/16/16 and 21/14/1 lesions, respectively. Wash-in and wash-out contrast kinetics were found on MRI in 33 of 36 lesions (91.7%) and 25 of 36 lesions (69.4%), respectively. The latter was observed significantly more often in higher graded lesions (P < 0.005). HPI was 94.7% ± 6.5%. There was no significant relationship between lesion’s MR-signal intensity, MR signal combinations, size and any of the VPCT-perfusion parameters. However HPI was constantly high in all HCC lesions. CONCLUSION VPCT parameters add limited value to MR-lesion characterization. However in HCC lesions with atypical MR signal characteristics HPI can add a parameter to ensure HCC diagnosis. PMID:27551338

  12. In-flight Absolute Radiometric Calibration of the Thematic Mapper

    NASA Technical Reports Server (NTRS)

    Castle, K. R.; Holm, R. G.; Kastner, C. J.; Palmer, J. M.; Slater, P. N.; Dinguirard, M.; Ezra, C. E.; Jackson, D.; Savage, R. K.

    1984-01-01

    The Thematic Mapper (TM) multispectral scanner system was placed into Earth orbit on July 16, 1982, as part of NASA's LANDSAT 4 payload. To determine temporal changes of the absolute radiometric calibration of the entire system in flight, spectroradiometric measurements of the ground and the atmosphere are made simultaneously with TM image acquisitions over the White Sands, New Mexico area. By entering the measured values into an atmospheric radiative transfer program, the radiance levels at the entrance pupil of the TM in four of the TM spectral bands are determined. These levels are compared to the output digital counts from the detectors that sampled the radiometrically measured ground area, thus providing an absolute radiometric calibration of the entire TM system utilizing those detectors. By reference to an adjacent, larger uniform area, the calibration is extended to all 16 detectors in each of the three bands.

  13. Absolute measurement of the extreme UV solar flux

    NASA Technical Reports Server (NTRS)

    Carlson, R. W.; Ogawa, H. S.; Judge, D. L.; Phillips, E.

    1984-01-01

    A windowless rare-gas ionization chamber has been developed to measure the absolute value of the solar extreme UV flux in the 50-575-A region. Successful results were obtained on a solar-pointing sounding rocket. The ionization chamber, operated in total absorption, is an inherently stable absolute detector of ionizing UV radiation and was designed to be independent of effects from secondary ionization and gas effusion. The net error of the measurement is + or - 7.3 percent, which is primarily due to residual outgassing in the instrument, other errors such as multiple ionization, photoelectron collection, and extrapolation to the zero atmospheric optical depth being small in comparison. For the day of the flight, Aug. 10, 1982, the solar irradiance (50-575 A), normalized to unit solar distance, was found to be 5.71 + or - 0.42 x 10 to the 10th photons per sq cm sec.

  14. In-flight absolute radiometric calibration of the thematic mapper

    NASA Technical Reports Server (NTRS)

    Castle, K. R.; Holm, R. G.; Kastner, C. J.; Palmer, J. M.; Slater, P. N.; Dinguirard, M.; Ezra, C. E.; Jackson, R. D.; Savage, R. K.

    1984-01-01

    In order to determine temporal changes of the absolute radiometric calibration of the entire TM system in flight spectroradiometric measurements of the ground and the atmosphere were made simultaneously with TM image collections over the White Sands, New Mexico area. By entering the measured values in an atmospheric radiative transfer program, the radiance levels in four of the spectral bands of the TM were determined, band 1:0.45 to 0.52 micrometers, band 2:0.53 to 0.61 micrometers band 3:0.62 to 0.70 micrometers and 4:0.78 to 0.91 micrometers. These levels were compared to the output digital counts from the detectors that sampled the radiometrically measured ground area, thus providing an absolute radiometric calibration of the entire TM system utilizing those detectors.

  15. In-flight absolute radiometric calibration of the Thematic Mapper

    NASA Technical Reports Server (NTRS)

    Castle, K. R.; Holm, R. G.; Kastner, C. J.; Palmer, J. M.; Slater, P. N.; Dinguirard, M.; Ezra, C. E.; Jackson, R. D.; Savage, R. K.

    1984-01-01

    In order to determine temporal changes of the absolute radiometric calibration of the entire TM system in flight spectroradiometric measurements of the ground and the atmosphere were made simultaneously with TM image collections over the White Sands, NM area. By entering the measured values in an atmospheric radiative transfer program, the radiance levels in four of the spectral bands of the TM were determined, band 1: 0.45 to 0.52 micrometers, band 2: 0.53 to 0.61 micrometers, band 3: 0.62 to 0.70 micrometers, and 4: 0.78 to 0.91 micrometers. These levels were compared to the output digital counts from the detectors that sampled the radiometrically measured ground area, thus providing an absolute radiometric calibration of the entire TM system utilizing those detectors. Previously announced in STAR as N84-15633

  16. Absolute concentration measurements inside a jet plume using video digitization

    NASA Astrophysics Data System (ADS)

    Vauquelin, O.

    An experimental system based on digitized video image analysis is used to measure the local value of the concentration inside a plume. Experiments are carried out in a wind-tunnel for a smoke-seeded turbulent jet plume illuminated with a laser beam. Each test is filmed, subsequently video images are digitized and analysed in order to determine the smoke absolute concentration corresponding to each pixel gray level. This non-intrusive measurement technique is first calibrated and different laws connecting gray level to concentration are established. As a first application, concentration measurements are made inside a turbulent jet plume and compared with measurements conducted using a classic gas analysis method. We finally present and discuss the possibilities offered for the measurements of absolute concentration fluctuations.

  17. Absolute magnitude calibration using trigonometric parallax - Incomplete, spectroscopic samples

    NASA Technical Reports Server (NTRS)

    Ratnatunga, Kavan U.; Casertano, Stefano

    1991-01-01

    A new numerical algorithm is used to calibrate the absolute magnitude of spectroscopically selected stars from their observed trigonometric parallax. This procedure, based on maximum-likelihood estimation, can retrieve unbiased estimates of the intrinsic absolute magnitude and its dispersion even from incomplete samples suffering from selection biases in apparent magnitude and color. It can also make full use of low accuracy and negative parallaxes and incorporate censorship on reported parallax values. Accurate error estimates are derived for each of the fitted parameters. The algorithm allows an a posteriori check of whether the fitted model gives a good representation of the observations. The procedure is described in general and applied to both real and simulated data.

  18. Perfusion visualization and analysis for pulmonary embolism

    NASA Astrophysics Data System (ADS)

    Vaz, Michael S.; Kiraly, Atilla P.; Naidich, David P.; Novak, Carol L.

    2005-04-01

    Given the nature of pulmonary embolism (PE), timely and accurate diagnosis is critical. Contrast enhanced high-resolution CT images allow physicians to accurately identify segmental and sub-segmental emboli. However, it is also important to assess the effect of such emboli on the blood flow in the lungs. Expanding upon previous research, we propose a method for 3D visualization of lung perfusion. The proposed method allows users to examine perfusion throughout the entire lung volume at a single glance, with areas of diminished perfusion highlighted so that they are visible independent of the viewing location. This may be particularly valuable for better accuracy in assessing the extent of hemodynamic alterations resulting from pulmonary emboli. The method also facilitates user interaction and may help identify small peripheral sub-segmental emboli otherwise overlooked. 19 patients referred for possible PE were evaluated by CT following the administration of IV contrast media. An experienced thoracic radiologist assessed the 19 datasets with 17 diagnosed as being positive for PE with multiple emboli. Since anomalies in lung perfusion due to PE can alter the distribution of parenchymal densities, we analyzed features collected from histograms of the computed perfusion maps and demonstrate their potential usefulness as a preliminary test to suggest the presence of PE. These histogram features also offer the possibility of distinguishing distinct patterns associated with chronic PE and may even be useful for further characterization of changes in perfusion or overall density resulting from associated conditions such as pneumonia or diffuse lung disease.

  19. A comparative analysis of the dependences of the hemodynamic parameters on changes in ROI's position in perfusion CT scans

    NASA Astrophysics Data System (ADS)

    Choi, Yong-Seok; Cho, Jae-Hwan; Namgung, Jang-Sun; Kim, Hyo-Jin; Yoon, Dae-Young; Lee, Han-Joo

    2013-05-01

    This study performed a comparative analysis of cerebral blood volume (CBV), cerebral blood flow (CBF), mean transit time (MTT), and mean time-to-peak (TTP) obtained by changing the region of interest's (ROI) anatomical positions, during CT brain perfusion. We acquired axial source images of perfusion CT from 20 patients undergoing CT perfusion exams due to brain trauma. Subsequently, the CBV, CBF, MTT, and TTP values were calculated through data-processing of the perfusion CT images. The color scales for the CBV, CBF, MTT, and TTP maps were obtained using the image data. Anterior cerebral artery (ACA) was taken as the standard ROI for the calculations of the perfusion values. Differences in the hemodynamic average values were compared in a quantitative analysis by placing ROI and the dividing axial images into proximal, middle, and distal segments anatomically. By performing the qualitative analysis using a blind test, we observed changes in the sensory characteristics by using the color scales of the CBV, CBF, and MTT maps in the proximal, middle, and distal segments. According to the qualitative analysis, no differences were found in CBV, CBF, MTT, and TTP values of the proximal, middle, and distal segments and no changes were detected in the color scales of the the CBV, CBF, MTT, and TTP maps in the proximal, middle, and distal segments. We anticipate that the results of the study will useful in assessing brain trauma patients using by perfusion imaging.

  20. Jasminum flexile flower absolute from India--a detailed comparison with three other jasmine absolutes.

    PubMed

    Braun, Norbert A; Kohlenberg, Birgit; Sim, Sherina; Meier, Manfred; Hammerschmidt, Franz-Josef

    2009-09-01

    Jasminum flexile flower absolute from the south of India and the corresponding vacuum headspace (VHS) sample of the absolute were analyzed using GC and GC-MS. Three other commercially available Indian jasmine absolutes from the species: J. sambac, J. officinale subsp. grandiflorum, and J. auriculatum and the respective VHS samples were used for comparison purposes. One hundred and twenty-one compounds were characterized in J. flexile flower absolute, with methyl linolate, benzyl salicylate, benzyl benzoate, (2E,6E)-farnesol, and benzyl acetate as the main constituents. A detailed olfactory evaluation was also performed.

  1. Long-term outdoor cultivation by perfusing spent medium for biodiesel production from Chlorella minutissima.

    PubMed

    Oh, Sung Ho; Kwon, Min Chul; Choi, Woon Yong; Seo, Yong Chang; Kim, Ga Bin; Kang, Do Hyung; Lee, Shin Young; Lee, Hyeon Yong

    2010-08-01

    A unique perfusion process was developed to maintain high concentrations of marine alga, Chlorella minutissima. This method is based on recycling cells by continuous feeding with warm spent sea water from nuclear power plants, which has very similar properties as sea water. A temperature of at least 30 degrees C in a 200 L photo-bioreactor was maintained in this system by perfusion of the thermal plume for 80 days in the coldest season. The maximum cell concentration and total lipid content was 8.3 g-dry wt./L and 23.2 %, w/w, respectively, under mixotrophic conditions. Lipid production was found to be due to a partially or non-growth related process, which implies that large amounts of biomass are needed for a high accumulation of lipids within the cells. At perfusion rates greater than 1.5 L/h, the temperature of the medium inside the reactor was around 30 degrees C, which was optimal for cell growth. For this system, a perfusion rate of 2.8 L/h was determined to be optimal for maintaining rapid cell growth and lipid production during outdoor cultivation. It was absolutely necessary to maintain the appropriate perfusion rate so that the medium temperature was optimal for cell growth. In addition, the lipids produced using this process were shown to be feasible for biodiesel production since the lipid composition of C. minutissima grown under these conditions consisted of 17 % (w/w) of C(16) and 47% (w/w) of C(18). The combined results of this study clearly demonstrated that the discharged energy of the thermal plume could be reused to cultivate marine alga by maintaining a relatively constant temperature in an outdoor photo-bioreactor without the need for supplying any extra energy, which could allow for cheap production of biodiesel from waste energy.

  2. Technical aspects of MR perfusion.

    PubMed

    Sourbron, Steven

    2010-12-01

    The most common methods for measuring perfusion with MRI are arterial spin labelling (ASL), dynamic susceptibility contrast (DSC-MRI), and T(1)-weighted dynamic contrast enhancement (DCE-MRI). This review focuses on the latter approach, which is by far the most common in the body and produces measures of capillary permeability as well. The aim is to present a concise but complete overview of the technical issues involved in DCE-MRI data acquisition and analysis. For details the reader is referred to the references. The presentation of the topic is essentially generic and focuses on technical aspects that are common to all DCE-MRI measurements. For organ-specific problems and illustrations, we refer to the other papers in this issue. In Section 1 "Theory" the basic quantities are defined, and the physical mechanisms are presented that provide a relation between the hemodynamic parameters and the DCE-MRI signal. Section 2 "Data acquisition" discusses the issues involved in the design of an optimal measurement protocol. Section 3 "Data analysis" summarizes the steps that need to be taken to determine the hemodynamic parameters from the measured data. PMID:20363574

  3. Universal Cosmic Absolute and Modern Science

    NASA Astrophysics Data System (ADS)

    Kostro, Ludwik

    The official Sciences, especially all natural sciences, respect in their researches the principle of methodic naturalism i.e. they consider all phenomena as entirely natural and therefore in their scientific explanations they do never adduce or cite supernatural entities and forces. The purpose of this paper is to show that Modern Science has its own self-existent, self-acting, and self-sufficient Natural All-in Being or Omni-Being i.e. the entire Nature as a Whole that justifies the scientific methodic naturalism. Since this Natural All-in Being is one and only It should be considered as the own scientifically justified Natural Absolute of Science and should be called, in my opinion, the Universal Cosmic Absolute of Modern Science. It will be also shown that the Universal Cosmic Absolute is ontologically enormously stratified and is in its ultimate i.e. in its most fundamental stratum trans-reistic and trans-personal. It means that in its basic stratum. It is neither a Thing or a Person although It contains in Itself all things and persons with all other sentient and conscious individuals as well, On the turn of the 20th century the Science has begun to look for a theory of everything, for a final theory, for a master theory. In my opinion the natural Universal Cosmic Absolute will constitute in such a theory the radical all penetrating Ultimate Basic Reality and will substitute step by step the traditional supernatural personal Absolute.

  4. Renal perfusion evaluation by alternating current biosusceptometry of magnetic nanoparticles

    NASA Astrophysics Data System (ADS)

    Quini, Caio C.; Matos, Juliana F.; Próspero, André G.; Calabresi, Marcos Felipe F.; Zufelato, Nicholas; Bakuzis, Andris F.; Baffa, Oswaldo; Miranda, José Ricardo A.

    2015-04-01

    Alternating current susceptometry, a simple and affordable technique, was employed to study the sensitivity of this approach to assess rat kidney perfusion by the injection of 200 μL of magnetic nanoparticles with a concentration of 23 mg/mL in the femoral vein and the measurement of the signal above the kidney. The instrument was able to detect the signal and the transit time of the first and second pass were measured in five animals with average values of 13.6±4.3 s and 20.6±7.1 s.

  5. Quantification of myocardial perfusion based on signal intensity of flow sensitized MRI

    NASA Astrophysics Data System (ADS)

    Abeykoon, Sumeda B.

    maximum percentage deviation is about 5%. Then the SI-method was used in comparison to a delayed enhanced method to qualitatively and quantitatively assess perfusion deficits in an ischemia-reperfusion (IR) mouse model. The infarcted region of the perfusion map is comparable to the hyper intense region of the delayed enhanced image of the IR mouse. The SI method also used to record a chronological comparison of perfusion on delta sarcoglycan null (DSG) mice. Perfusion of DSG and wild-type (WT) mice at ages of 12 weeks and 32 weeks were compared and percentage change of perfusion was estimated. The result shows that in DSG mice perfusion changes considerably. Finally, the SI method was implemented on a 3 Tesla Philip scanner by modifying to data acquisition method. The perfusion obtained in this is consistent with literature values but further adjustment of pulse sequence and modification of numerical solution is needed. The most important benefit of the SI method is that it reduces scan time 30%--40% and lessens motion artifacts of images compared to the T1 method. This study demonstrates that the signal intensity-based ASL method is a robust alternative to the conventional T1-method.

  6. An efficient polyenergetic SART (pSART) reconstruction algorithm for quantitative myocardial CT perfusion

    SciTech Connect

    Lin, Yuan Samei, Ehsan

    2014-02-15

    Purpose: In quantitative myocardial CT perfusion imaging, beam hardening effect due to dense bone and high concentration iodinated contrast agent can result in visible artifacts and inaccurate CT numbers. In this paper, an efficient polyenergetic Simultaneous Algebraic Reconstruction Technique (pSART) was presented to eliminate the beam hardening artifacts and to improve the CT quantitative imaging ability. Methods: Our algorithm made threea priori assumptions: (1) the human body is composed of several base materials (e.g., fat, breast, soft tissue, bone, and iodine); (2) images can be coarsely segmented to two types of regions, i.e., nonbone regions and noniodine regions; and (3) each voxel can be decomposed into a mixture of two most suitable base materials according to its attenuation value and its corresponding region type information. Based on the above assumptions, energy-independent accumulated effective lengths of all base materials can be fast computed in the forward ray-tracing process and be used repeatedly to obtain accurate polyenergetic projections, with which a SART-based equation can correctly update each voxel in the backward projecting process to iteratively reconstruct artifact-free images. This approach effectively reduces the influence of polyenergetic x-ray sources and it further enables monoenergetic images to be reconstructed at any arbitrarily preselected target energies. A series of simulation tests were performed on a size-variable cylindrical phantom and a realistic anthropomorphic thorax phantom. In addition, a phantom experiment was also performed on a clinical CT scanner to further quantitatively validate the proposed algorithm. Results: The simulations with the cylindrical phantom and the anthropomorphic thorax phantom showed that the proposed algorithm completely eliminated beam hardening artifacts and enabled quantitative imaging across different materials, phantom sizes, and spectra, as the absolute relative errors were reduced

  7. Effects of Steroid Hormones on Sex Differences in Cerebral Perfusion.

    PubMed

    Ghisleni, Carmen; Bollmann, Steffen; Biason-Lauber, Anna; Poil, Simon-Shlomo; Brandeis, Daniel; Martin, Ernst; Michels, Lars; Hersberger, Martin; Suckling, John; Klaver, Peter; O'Gorman, Ruth L

    2015-01-01

    Sex differences in the brain appear to play an important role in the prevalence and progression of various neuropsychiatric disorders, but to date little is known about the cerebral mechanisms underlying these differences. One widely reported finding is that women demonstrate higher cerebral perfusion than men, but the underlying cause of this difference in perfusion is not known. This study investigated the putative role of steroid hormones such as oestradiol, testosterone, and dehydroepiandrosterone sulphate (DHEAS) as underlying factors influencing cerebral perfusion. We acquired arterial spin labelling perfusion images of 36 healthy adult subjects (16 men, 20 women). Analyses on average whole brain perfusion levels included a multiple regression analysis to test for the relative impact of each hormone on the global perfusion. Additionally, voxel-based analyses were performed to investigate the sex difference in regional perfusion as well as the correlations between local perfusion and serum oestradiol, testosterone, and DHEAS concentrations. Our results replicated the known sex difference in perfusion, with women showing significantly higher global and regional perfusion. For the global perfusion, DHEAS was the only significant predictor amongst the steroid hormones, showing a strong negative correlation with cerebral perfusion. The voxel-based analyses revealed modest sex-dependent correlations between local perfusion and testosterone, in addition to a strong modulatory effect of DHEAS in cortical, subcortical, and cerebellar regions. We conclude that DHEAS in particular may play an important role as an underlying factor driving the difference in cerebral perfusion between men and women.

  8. Quantum theory allows for absolute maximal contextuality

    NASA Astrophysics Data System (ADS)

    Amaral, Barbara; Cunha, Marcelo Terra; Cabello, Adán

    2015-12-01

    Contextuality is a fundamental feature of quantum theory and a necessary resource for quantum computation and communication. It is therefore important to investigate how large contextuality can be in quantum theory. Linear contextuality witnesses can be expressed as a sum S of n probabilities, and the independence number α and the Tsirelson-like number ϑ of the corresponding exclusivity graph are, respectively, the maximum of S for noncontextual theories and for the theory under consideration. A theory allows for absolute maximal contextuality if it has scenarios in which ϑ /α approaches n . Here we show that quantum theory allows for absolute maximal contextuality despite what is suggested by the examination of the quantum violations of Bell and noncontextuality inequalities considered in the past. Our proof is not constructive and does not single out explicit scenarios. Nevertheless, we identify scenarios in which quantum theory allows for almost-absolute-maximal contextuality.

  9. Absolute calibration in vivo measurement systems

    SciTech Connect

    Kruchten, D.A.; Hickman, D.P.

    1991-02-01

    Lawrence Livermore National Laboratory (LLNL) is currently investigating a new method for obtaining absolute calibration factors for radiation measurement systems used to measure internally deposited radionuclides in vivo. Absolute calibration of in vivo measurement systems will eliminate the need to generate a series of human surrogate structures (i.e., phantoms) for calibrating in vivo measurement systems. The absolute calibration of in vivo measurement systems utilizes magnetic resonance imaging (MRI) to define physiological structure, size, and composition. The MRI image provides a digitized representation of the physiological structure, which allows for any mathematical distribution of radionuclides within the body. Using Monte Carlo transport codes, the emission spectrum from the body is predicted. The in vivo measurement equipment is calibrated using the Monte Carlo code and adjusting for the intrinsic properties of the detection system. The calibration factors are verified using measurements of existing phantoms and previously obtained measurements of human volunteers. 8 refs.

  10. Stimulus probability effects in absolute identification.

    PubMed

    Kent, Christopher; Lamberts, Koen

    2016-05-01

    This study investigated the effect of stimulus presentation probability on accuracy and response times in an absolute identification task. Three schedules of presentation were used to investigate the interaction between presentation probability and stimulus position within the set. Data from individual participants indicated strong effects of presentation probability on both proportion correct and response times. The effects were moderated by the ubiquitous stimulus position effect. The accuracy and response time data were predicted by an exemplar-based model of perceptual cognition (Kent & Lamberts, 2005). The bow in discriminability was also attenuated when presentation probability for middle items was relatively high, an effect that will constrain future model development. The study provides evidence for item-specific learning in absolute identification. Implications for other theories of absolute identification are discussed. (PsycINFO Database Record

  11. Quantitative standards for absolute linguistic universals.

    PubMed

    Piantadosi, Steven T; Gibson, Edward

    2014-01-01

    Absolute linguistic universals are often justified by cross-linguistic analysis: If all observed languages exhibit a property, the property is taken to be a likely universal, perhaps specified in the cognitive or linguistic systems of language learners and users. In many cases, these patterns are then taken to motivate linguistic theory. Here, we show that cross-linguistic analysis will very rarely be able to statistically justify absolute, inviolable patterns in language. We formalize two statistical methods--frequentist and Bayesian--and show that in both it is possible to find strict linguistic universals, but that the numbers of independent languages necessary to do so is generally unachievable. This suggests that methods other than typological statistics are necessary to establish absolute properties of human language, and thus that many of the purported universals in linguistics have not received sufficient empirical justification.

  12. Absolute photoacoustic thermometry in deep tissue.

    PubMed

    Yao, Junjie; Ke, Haixin; Tai, Stephen; Zhou, Yong; Wang, Lihong V

    2013-12-15

    Photoacoustic thermography is a promising tool for temperature measurement in deep tissue. Here we propose an absolute temperature measurement method based on the dual temperature dependences of the Grüneisen parameter and the speed of sound in tissue. By taking ratiometric measurements at two adjacent temperatures, we can eliminate the factors that are temperature irrelevant but difficult to correct for in deep tissue. To validate our method, absolute temperatures of blood-filled tubes embedded ~9 mm deep in chicken tissue were measured in a biologically relevant range from 28°C to 46°C. The temperature measurement accuracy was ~0.6°C. The results suggest that our method can be potentially used for absolute temperature monitoring in deep tissue during thermotherapy.

  13. Molecular iodine absolute frequencies. Final report

    SciTech Connect

    Sansonetti, C.J.

    1990-06-25

    Fifty specified lines of {sup 127}I{sub 2} were studied by Doppler-free frequency modulation spectroscopy. For each line the classification of the molecular transition was determined, hyperfine components were identified, and one well-resolved component was selected for precise determination of its absolute frequency. In 3 cases, a nearby alternate line was selected for measurement because no well-resolved component was found for the specified line. Absolute frequency determinations were made with an estimated uncertainty of 1.1 MHz by locking a dye laser to the selected hyperfine component and measuring its wave number with a high-precision Fabry-Perot wavemeter. For each line results of the absolute measurement, the line classification, and a Doppler-free spectrum are given.

  14. Absolute Measurements of Radiation Damage in Nanometer Thick Films

    PubMed Central

    Alizadeh, Elahe; Sanche, Léon

    2013-01-01

    We address the problem of absolute measurements of radiation damage in films of nanometer thicknesses. Thin films of DNA (~ 2–160nm) are deposited onto glass substrates and irradiated with varying doses of 1.5 keV X-rays under dry N2 at atmospheric pressure and room temperature. For each different thickness, the damage is assessed by measuring the loss of the supercoiled configuration as a function of incident photon fluence. From the exposure curves, the G-values are deduced, assuming that X-ray photons interacting with DNA, deposit all of their energy in the film. The results show that the G-value (i.e., damage per unit of deposited energy) increases with film thickness and reaches a plateau at 30±5 nm. This thickness dependence provides a correction factor to estimate the actual G-value for films with thicknesses below 30nm thickness. Thus, the absolute values of damage can be compared with that of films of any thickness under different experimental conditions. PMID:22562941

  15. Comparison of Myocardial Perfusion Estimates From Dynamic Contrast-Enhanced Magnetic Resonance Imaging With Four Quantitative Analysis Methods

    PubMed Central

    Pack, Nathan A.; DiBella, Edward V. R.

    2012-01-01

    Dynamic contrast-enhanced MRI has been used to quantify myocardial perfusion in recent years. Published results have varied widely, possibly depending on the method used to analyze the dynamic perfusion data. Here, four quantitative analysis methods (two-compartment modeling, Fermi function modeling, model-independent analysis, and Patlak plot analysis) were implemented and compared for quantifying myocardial perfusion. Dynamic contrast-enhanced MRI data were acquired in 20 human subjects at rest with low-dose (0.019 ± 0.005 mmol/kg) bolus injections of gadolinium. Fourteen of these subjects were also imaged at adenosine stress (0.021 ± 0.005 mmol/kg). Aggregate rest perfusion estimates were not significantly different between all four analysis methods. At stress, perfusion estimates were not significantly different between two-compartment modeling, model-independent analysis, and Patlak plot analysis. Stress estimates from the Fermi model were significantly higher (~20%) than the other three methods. Myocardial perfusion reserve values were not significantly different between all four methods. Model-independent analysis resulted in the lowest model curve-fit errors. When more than just the first pass of data was analyzed, perfusion estimates from two-compartment modeling and model-independent analysis did not change significantly, unlike results from Fermi function modeling. PMID:20577976

  16. The correlation of contrast-enhanced ultrasound and MRI perfusion quantitative analysis in rabbit VX2 liver cancer.

    PubMed

    Xiang, Zhiming; Liang, Qianwen; Liang, Changhong; Zhong, Guimian

    2014-12-01

    Our objective is to explore the value of liver cancer contrast-enhanced ultrasound (CEUS) and MRI perfusion quantitative analysis in liver cancer and the correlation between these two analysis methods. Rabbit VX2 liver cancer model was established in this study. CEUS was applied. Sono Vue was applied in rabbits by ear vein to dynamically observe and record the blood perfusion and changes in the process of VX2 liver cancer and surrounding tissue. MRI perfusion quantitative analysis was used to analyze the mean enhancement time and change law of maximal slope increasing, which were further compared with the pathological examination results. Quantitative indicators of liver cancer CEUS and MRI perfusion quantitative analysis were compared, and the correlation between them was analyzed by correlation analysis. Rabbit VX2 liver cancer model was successfully established. CEUS showed that time-intensity curve of rabbit VX2 liver cancer showed "fast in, fast out" model while MRI perfusion quantitative analysis showed that quantitative parameter MTE of tumor tissue increased and MSI decreased: the difference was statistically significant (P < 0.01). The diagnostic results of CEUS and MRI perfusion quantitative analysis were not significantly different (P > 0.05). However, the quantitative parameter of them were significantly positively correlated (P < 0.05). CEUS and MRI perfusion quantitative analysis can both dynamically monitor the liver cancer lesion and surrounding liver parenchyma, and the quantitative parameters of them are correlated. The combined application of both is of importance in early diagnosis of liver cancer.

  17. Absolute Stability And Hyperstability In Hilbert Space

    NASA Technical Reports Server (NTRS)

    Wen, John Ting-Yung

    1989-01-01

    Theorems on stabilities of feedback control systems proved. Paper presents recent developments regarding theorems of absolute stability and hyperstability of feedforward-and-feedback control system. Theorems applied in analysis of nonlinear, adaptive, and robust control. Extended to provide sufficient conditions for stability in system including nonlinear feedback subsystem and linear time-invariant (LTI) feedforward subsystem, state space of which is Hilbert space, and input and output spaces having finite numbers of dimensions. (In case of absolute stability, feedback subsystem memoryless and possibly time varying. For hyperstability, feedback system dynamical system.)

  18. Correction of NIM-3A absolute gravimeter for self-attraction effect

    NASA Astrophysics Data System (ADS)

    Li, Chunjian; Xu, Jin-yi; Feng, Jin-yang; SU, Duo-wu; Wu, Shu-qing

    2015-02-01

    The mass of free-fall absolute gravimeter can produce vertical gravitational attraction to the free-falling test body during the measurement of acceleration due to gravity. The vertical gravitational attraction can cause an artificial deviation to the measured value of gravitational acceleration. This paper describes the operating principle of a free-fall absolute gravimeter and the method used to determine the reference height of a gravimeter. It also describes the physical structure of NIM-3A absolute gravimeter lately developed by National Institute of Metrology (China), and studies the correction of gravimeter for Self-attraction effect.

  19. Frog intestinal perfusion to evaluate drug permeability: application to p-gp and cyp3a4 substrates

    PubMed Central

    Yerasi, Neelima; Vurimindi, Himabindu; Devarakonda, Krishna

    2015-01-01

    To evaluate the reliability of using in situ frog intestinal perfusion technique for permeability assessment of carrier transported drugs which are also substrates for CYP enzymes. Single Pass Intestinal Perfusion (SPIP) studies were performed in frogs of the species Rana tigrina using established method for rats with some modifications after inducing anesthesia. Effective permeability coefficient (Peff) of losartan and midazolam was calculated in the presence and absence of inhibitors using the parallel-tube model. Peff of losartan when perfused alone was found to be 0.427 ± 0.27 × 10-4cm/s and when it was co-perfused with inhibitors, significant change in Peff was observed. Peff of midazolam when perfused alone was found to be 2.03 ± 0.07 × 10-4cm/s and when it was co-perfused with inhibitors, no significant change in Peff was observed. Comparison of Peff calculated in frog with that of other available models and also humans suggested that the Peff-values are comparable and reflected well with human intestinal permeability. It is possible to determine the Peff-value for compounds which are dual substrates of P-glycoprotein and CYP3A4 using in situ frog intestinal perfusion technique. The calculated Peff-values correlated well with reported Peff-values of probe drugs. comparison of the Peff-value of losartan obtained with that of reported human’s Peff and Caco 2 cell data, and comparison of the Peff-value of midazolam with that of reported rat’s Peff, we could conclude that SPIP from model can be reliably used in preclinical studies for permeability estimation. This model may represent a valuable alternative to the low speed and high cost of conventional animal models (typically rodents) for the assessment of intestinal permeability. PMID:26236236

  20. Partial volume correction of brain perfusion estimates using the inherent signal data of time-resolved arterial spin labeling.

    PubMed

    Ahlgren, André; Wirestam, Ronnie; Petersen, Esben Thade; Ståhlberg, Freddy; Knutsson, Linda

    2014-09-01

    Quantitative perfusion MRI based on arterial spin labeling (ASL) is hampered by partial volume effects (PVEs), arising due to voxel signal cross-contamination between different compartments. To address this issue, several partial volume correction (PVC) methods have been presented. Most previous methods rely on segmentation of a high-resolution T1 -weighted morphological image volume that is coregistered to the low-resolution ASL data, making the result sensitive to errors in the segmentation and coregistration. In this work, we present a methodology for partial volume estimation and correction, using only low-resolution ASL data acquired with the QUASAR sequence. The methodology consists of a T1 -based segmentation method, with no spatial priors, and a modified PVC method based on linear regression. The presented approach thus avoids prior assumptions about the spatial distribution of brain compartments, while also avoiding coregistration between different image volumes. Simulations based on a digital phantom as well as in vivo measurements in 10 volunteers were used to assess the performance of the proposed segmentation approach. The simulation results indicated that QUASAR data can be used for robust partial volume estimation, and this was confirmed by the in vivo experiments. The proposed PVC method yielded probable perfusion maps, comparable to a reference method based on segmentation of a high-resolution morphological scan. Corrected gray matter (GM) perfusion was 47% higher than uncorrected values, suggesting a significant amount of PVEs in the data. Whereas the reference method failed to completely eliminate the dependence of perfusion estimates on the volume fraction, the novel approach produced GM perfusion values independent of GM volume fraction. The intra-subject coefficient of variation of corrected perfusion values was lowest for the proposed PVC method. As shown in this work, low-resolution partial volume estimation in connection with ASL perfusion

  1. Absolute GNSS Antenna Calibration at the National Geodetic Survey

    NASA Astrophysics Data System (ADS)

    Mader, G.; Bilich, A.; Geoghegan, C.

    2012-04-01

    Geodetic GNSS applications routinely demand millimeter precision and extremely high levels of accuracy. To achieve these accuracies, measurement and instrument biases at the centimeter to millimeter level must be understood. One of these biases is the antenna phase center, the apparent point of signal reception for a GNSS antenna. It has been well established that phase center patterns differ between antenna models and manufacturers; additional research suggests that the addition of a radome or the choice of antenna mount can significantly alter those a priori phase center patterns. For the more demanding GNSS positioning applications and especially in cases of mixed-antenna networks, it is all the more important to know antenna phase center variations as a function of both elevation and azimuth in the antenna reference frame and incorporate these models into analysis software. To help meet the needs of the high-precision GNSS community, the National Geodetic Survey (NGS) now operates an absolute antenna calibration facility. Located in Corbin, Virginia, this facility uses field measurements and actual GNSS satellite signals to quantitatively determine the carrier phase advance/delay introduced by the antenna element. The NGS facility was built to serve traditional NGS constituents such as the surveying and geodesy communities, however calibration services are open and available to all GNSS users as the calibration schedule permits. All phase center patterns computed by this facility will be publicly available and disseminated in both the ANTEX and NGS formats. We describe the NGS calibration facility, and discuss the observation models and strategy currently used to generate NGS absolute calibrations. We demonstrate that NGS absolute phase center variation (PCV) patterns are consistent with published values determined by other absolute antenna calibration facilities, and outline future planned refinements to the system.

  2. Radionuclide cerebral perfusion imaging: Normal pattern

    SciTech Connect

    Goldsmith, S.J.; Stritzke, P.; Losonczy, M.; Vallabhajosula, S.; Holan, V.; DaCosta, M.; Muzinic, M.

    1991-12-31

    Regional cerebral perfusion imaging using a new class of {sup 99m}Tc and {sup 123}I labeled compounds which traverse the blood brain barrier and SPECT imaging technology provides an opportunity to assess this physiologic phenomenon during normal cerebral function and as a manifestation of disease in the central nervous system disease. These applications pose a challenge to the nuclear medicine physician for several reasons: (a) the complex and somewhat unfamiliar functional anatomy, (b) the marked regional differences in regional cerebral perfusion at rest, (c) the lack of understanding of the effect of variations in ambient conditions on regional cerebral perfusion. The difficulties in interpretation are augmented by the display itself. There is frequently no difficulty in differentiating between gray and white matter. However, the frequently used {open_quotes}hot body{close_quotes} color maps, introduce a good deal of contrast, producing displays with apparent interruption in regional cortical perfusion whereas black and white displays provide minimal contrast in the regional cortical activity. The authors sought to define how much variation in regional cerebral perfusion is {open_quotes}allowed{close_quotes} under controlled conditions, to establish a basis to interpret if changes in the environment, psychological interventions, or disease states are accompanied by a measurable change. 2 figs., 1 tab.

  3. Perfusion harmonic imaging of the human brain

    NASA Astrophysics Data System (ADS)

    Metzler, Volker H.; Seidel, Guenter; Wiesmann, Martin; Meyer, Karsten; Aach, Til

    2003-05-01

    The fast visualisation of cerebral microcirculation supports diagnosis of acute cerebrovascular diseases. However, the commonly used CT/MRI-based methods are time consuming and, moreover, costly. Therefore we propose an alternative approach to brain perfusion imaging by means of ultrasonography. In spite of the low signal/noise-ratio of transcranial ultrasound and the high impedance of the skull, flow images of cerebral blood flow can be derived by capturing the kinetics of appropriate contrast agents by harmonic ultrasound image sequences. In this paper we propose three different methods for human brain perfusion imaging, each of which yielding flow images indicating the status of the patient's cerebral microcirculation by visualising local flow parameters. Bolus harmonic imaging (BHI) displays the flow kinetics of bolus injections, while replenishment (RHI) and diminution harmonic imaging (DHI) compute flow characteristics from contrast agent continuous infusions. RHI measures the contrast agents kinetics in the influx phase and DHI displays the diminution kinetics of the contrast agent acquired from the decay phase. In clinical studies, BHI- and RHI-parameter images were found to represent comprehensive and reproducible distributions of physiological cerebral blood flow. For DHI it is shown, that bubble destruction and hence perfusion phenomena principally can be displayed. Generally, perfusion harmonic imaging enables reliable and fast bedside imaging of human brain perfusion. Due to its cost efficiency it complements cerebrovascular diagnostics by established CT/MRI-based methods.

  4. Flicker stimulated retinal perfusion changes assessed with high-speed Doppler tomography

    NASA Astrophysics Data System (ADS)

    Schmoll, Tilman; Singh, Amardeep S. G.; Frily, Karine; Blatter, Cedric; Villiger, Martin; Pache, Christoph; Lasser, Theo; Leitgeb, R. A.

    2010-02-01

    We developed a high speed Doppler tomography system together with flow extraction algorithms that provide a flexible tool to assess retinal perfusion. The aim of the present study is to stimulate perfusion by flickering with light of adjustable color and to measure changes depending on light frequency and flicker location. We observed relative changes in arterial flow velocity during flicker stimulation up to 50%. We found in arteries close to the optic nerve head the highest flicker response at a frequency of 8Hz. We believe that a multimodal functional imaging concept is of high value for an accurate and early diagnosis and understanding of retinal pathologies and pathogenesis.

  5. Production of Epigastric Pain in Duodenal Ulcer by Lower Oesophageal Acid Perfusion

    PubMed Central

    Earlam, Richard J.

    1970-01-01

    Thirty-six patients with duodenal ulceration were divided into group 1 (30), who had epigastric pain, and group 2 (6), who had pain in the upper abdomen but not in the epigastrium, and were studied by perfusing the lower oesophagus with dilute acid in an attempt to reproduce epigastric pain. In group 1, 25 suffered epigastric pain, indistinguishable from that which they normally had, after perfusion of 30 ml. of 0·1N HC1 in under four minutes (mean values), but none of group 2 had pain. ImagesFig. 1 PMID:5491256

  6. [Absorption of amino acids from the perfused ovine rumen].

    PubMed

    L' Leng; Tomás, J; Várady, J; Szányiová, M

    1978-06-01

    The experiments with extracoroporeal perfusion of sheep rumen were performed [Leng et al., 1977]. Bovine plasma, diluted in a 1:1ratio with an isotonic solution of sodium chloride, was used for four perfusions, and autologous blood was used for two perfusions in the course of 150 minutes. After 60 minutes perfusion 20 g enzymatic casein hydrolyzate were applied to the rumen. The levels of free amino acids in the perfusate were recorded after 60 minutes' perfusion [the first phase of perfusion] and at the end of the experiment [the second phase]. The levels of lysine, aspartic acid and glutamic acid increased after perfusions with bovine plasma during the first phase, the levels of glutamic acid, phenylalanine, and in one case of alanine, increased after perfusions with autologus blood. Simultaneously the level of valine decreased after perfusions with bovine plasma, and after perfusions with blood the levels of arginine and valine, and/or lysine, dropped. During the second phase of perfusion, the levels of all the observed amino acids except methionine [bovine plasma], and/or orginine and methionine [blood] rose in the perfusate. The experiments showed that the level of amino acids in the rumen content presented a decisive factor affecting amino acid absorption from the rumen into the blood. Transformation of the amino acids during their passage through the remen wall may be assumed, and glutamic acid is one of the chief products of this process.

  7. Absolute Points for Multiple Assignment Problems

    ERIC Educational Resources Information Center

    Adlakha, V.; Kowalski, K.

    2006-01-01

    An algorithm is presented to solve multiple assignment problems in which a cost is incurred only when an assignment is made at a given cell. The proposed method recursively searches for single/group absolute points to identify cells that must be loaded in any optimal solution. Unlike other methods, the first solution is the optimal solution. The…

  8. Absolute partial photoionization cross sections of ozone.

    SciTech Connect

    Berkowitz, J.; Chemistry

    2008-04-01

    Despite the current concerns about ozone, absolute partial photoionization cross sections for this molecule in the vacuum ultraviolet (valence) region have been unavailable. By eclectic re-evaluation of old/new data and plausible assumptions, such cross sections have been assembled to fill this void.

  9. Stimulus Probability Effects in Absolute Identification

    ERIC Educational Resources Information Center

    Kent, Christopher; Lamberts, Koen

    2016-01-01

    This study investigated the effect of stimulus presentation probability on accuracy and response times in an absolute identification task. Three schedules of presentation were used to investigate the interaction between presentation probability and stimulus position within the set. Data from individual participants indicated strong effects of…

  10. Increasing Capacity: Practice Effects in Absolute Identification

    ERIC Educational Resources Information Center

    Dodds, Pennie; Donkin, Christopher; Brown, Scott D.; Heathcote, Andrew

    2011-01-01

    In most of the long history of the study of absolute identification--since Miller's (1956) seminal article--a severe limit on performance has been observed, and this limit has resisted improvement even by extensive practice. In a startling result, Rouder, Morey, Cowan, and Pfaltz (2004) found substantially improved performance with practice in the…

  11. Absolute Radiometric Calibration Of The Thematic Mapper

    NASA Astrophysics Data System (ADS)

    Slater, P. N.; Biggar, S. F.; Holm, R. G.; Jackson, R. D.; Mao, Y.; Moran, M. S.; Palmer, J. M.; Yuan, B.

    1986-11-01

    The results are presented of five in-flight absolute radiometric calibrations, made in the period July 1984 to November 1985, at White Sands, New Mexico, of the solar reflective bands of the Landsat-5 Thematic Mapper (TM) . The 23 bandcalibrations made on the five dates show a ± 2.8% RMS variation from the mean as a percentage of the mean.

  12. On Relative and Absolute Conviction in Mathematics

    ERIC Educational Resources Information Center

    Weber, Keith; Mejia-Ramos, Juan Pablo

    2015-01-01

    Conviction is a central construct in mathematics education research on justification and proof. In this paper, we claim that it is important to distinguish between absolute conviction and relative conviction. We argue that researchers in mathematics education frequently have not done so and this has lead to researchers making unwarranted claims…

  13. In-vivo regional myocardial perfusion measurements in a porcine model by ECG-gated multislice computed tomography

    NASA Astrophysics Data System (ADS)

    Stantz, Keith M.; Liang, Yun; Meyer, Cristopher A.; Teague, Shawn; Stecker, Michael; Hutchins, Gary; McLennan, Gordon; Persohn, Scott

    2003-05-01

    Purpose: To evaluate whether functional multi-slice computed tomography (MSCT) can identify regional areas of normally perfused and ischemic myocardium in a porcine model. Material and Methods: Three out bred pigs, two of which had ameroids surgically implanted to constrict flow within the LAD and LCx coronary arteries, were injected with 25 mL of iopromide (Isovue) at a rate of 5 mL/second via the femoral or jugular vein. Sixty axial scans along the short axis of the heart was acquired on a 16-slice CT scanner (Philips MX8000-IDT) triggered at end-diastole of the cardiac cycle and acquiring an image within 270 msec. A second series of scans were taken after an intravenous injection of a vasodilator, 150 μg/kg/min of adenosine. ROIs were drawn around the myocardial tissue and the resulting time-density curves were used to extract perfusion values. Results: Determination of the myocardial perfusion and fractional blood volume implementing three different perfusion models. A 5-point averaging or 'smoothing' algorithm was employed to effectively filter the data due to its noisy nature. The (preliminary) average perfusion and fractional blood volume values over selected axial slices for the pig without an artificially induced stenosis were measured to be 84 +/- 22 mL/min/100g-tissue and 0.17 +/- 0.04 mL/g-tissue, the former is consistent with PET scan and EBCT results. The pig with a stenosis in the left LAD coronary artery showed a reduced global perfusion value -- 45 mL/min/100g-tissue. Correlations in regional perfusion values relative to the stenosis were weak. During the infusion of adenosine, averaged perfusion values for the three subjects increased by 46 (+/-45) percent, comparable to increases measured with PET. Conclusion: Quantifying global perfusion values using MDCT appear encouraging. Future work will focus resolving the systematic effects from noise due to signal fluctuation from the porcine tachyardia (80-93 BPM) and provide a more robust measurement

  14. Kinetics of reversible-sequestration of leukocytes by the isolated perfused rat lung

    SciTech Connect

    Goliaei, B.

    1980-08-01

    The kinetics and morphology of sequestration and margination of rat leukocytes were studied using an isolated perfused and ventilated rat lung preparation. Whole rat blood, bone marrow suspension, or leukocyte suspensions, were used to perfuse the isolated rat lung. The lung was also perfused with latex particle suspensions and the passage of particles through the lung capillaries was studied. When a leukocyte suspension was perfused through the lung in the single-pass mode, the rate of sequestration decreased as more cells were perfused. In contrast, latex particles of a size comparable to that of leukocytes were totally stopped by the lung. When the leukocyte suspension was recirculated through the lung, cells were rapidly removed from circulation until a steady state was reached, after which no net removal of cells by the lung occurred. These results indicate that leukocytes are reversibly sequestered from circulation. The sequestered cells marginated and attached to the luminal surface of the endothelium of post-capillary venules and veins. A mathematical model was developed based on the assumption that the attachment and detachment of leukocytes to blood vessel walls follows first-order kinetics. The model correctly predicts the following characteristics of the system: (a) the kinetics of the sequestration of leukocytes by the lung; (b) the existence of a steady state when a suspension of leukocytes is recirculated through the lung; and (c) the independence of the fraction of cells remaining in circulation from the starting concentration for all values of starting concentration. (ERB)

  15. In situ perfusion in rodents to explore intestinal drug absorption: challenges and opportunities.

    PubMed

    Stappaerts, Jef; Brouwers, Joachim; Annaert, Pieter; Augustijns, Patrick

    2015-01-30

    The in situ intestinal perfusion technique in rodents is a very important absorption model, not only because of its predictive value, but it is also very suitable to unravel the mechanisms underlying intestinal drug absorption. This literature overview covers a number of specific applications for which the in situ intestinal perfusion set-up can be applied in favor of established in vitro absorption tools, such as the Caco-2 cell model. Qualities including the expression of drug transporters and metabolizing enzymes relevant for human intestinal absorption and compatibility with complex solvent systems render the in situ technique the most designated absorption model to perform transporter-metabolism studies or to evaluate the intestinal absorption from biorelevant media. Over the years, the in situ intestinal perfusion model has exhibited an exceptional ability to adapt to the latest challenges in drug absorption profiling. For instance, the introduction of the mesenteric vein cannulation allows determining the appearance of compounds in the blood and is of great use, especially when evaluating the absorption of compounds undergoing intestinal metabolism. Moreover, the use of the closed loop intestinal perfusion set-up is interesting when compounds or perfusion media are scarce. Compatibility with emerging trends in pharmaceutical profiling, such as the use of knockout or transgenic animals, generates unparalleled possibilities to gain mechanistic insight into specific absorption processes. Notwithstanding the fact that the in situ experiments are technically challenging and relatively time-consuming, the model offers great opportunities to gain insight into the processes determining intestinal drug absorption.

  16. Prelaunch absolute radiometric calibration of LANDSAT-4 protoflight Thematic Mapper

    NASA Technical Reports Server (NTRS)

    Barker, J. L.; Ball, D. L.; Leung, K. C.; Walker, J. A.

    1984-01-01

    Results are summarized and analyzed from several prelaunch tests with a 122 cm integrating sphere used as part of the absolute radiometric calibration experiments for the protoflight TM sensor carried on the LANDSAT-4 satellite. The calibration procedure is presented and the radiometric sensitivity of the TM is assessed. The internal calibrator and dynamic range after calibration are considered. Tables show dynamic range after ground processing, spectral radiance to digital number and digital number to spectral radiance values for TM bands 1, 2, 3, 4, 5, 7 and for channel 4 of band 6.

  17. On the convective-absolute nature of river bedform instabilities

    NASA Astrophysics Data System (ADS)

    Vesipa, Riccardo; Camporeale, Carlo; Ridolfi, Luca; Chomaz, Jean Marc

    2014-12-01

    River dunes and antidunes are induced by the morphological instability of stream-sediment boundary. Such bedforms raise a number of subtle theoretical questions and are crucial for many engineering and environmental problems. Despite their importance, the absolute/convective nature of the instability has never been addressed. The present work fills this gap as we demonstrate, by the cusp map method, that dune instability is convective for all values of the physical control parameters, while the antidune instability exhibits both behaviors. These theoretical predictions explain some previous experimental and numerical observations and are important to correctly plan flume experiments, numerical simulations, paleo-hydraulic reconstructions, and river works.

  18. Evidence for myocardial CT perfusion imaging in the diagnosis of hemodynamically significant coronary artery disease

    PubMed Central

    2015-01-01

    This editorial discusses a recent paper published in the August issue of Radiology about the diagnostic value of myocardial computer tomography (CT) perfusion imaging in the detection of hemodynamically significant coronary stenosis when compared to single-photon emission CT (SPECT) imaging based on a secondary analysis of CORE320 study. Three aspects including high diagnostic sensitivity of CT perfusion imaging, moderate specificity of SPECT imaging and lack of use of attenuation correction in SPECT imaging have been discussed with reference to the current literature, and some suggestions have been highlighted for future studies to improve the diagnostic performance of CT perfusion and SPECT imaging in the diagnostic evaluation of coronary artery disease. PMID:25774349

  19. Cardiac tissue engineering using perfusion bioreactor systems

    PubMed Central

    Radisic, Milica; Marsano, Anna; Maidhof, Robert; Wang, Yadong; Vunjak-Novakovic, Gordana

    2009-01-01

    This protocol describes tissue engineering of synchronously contractile cardiac constructs by culturing cardiac cell populations on porous scaffolds (in some cases with an array of channels) and bioreactors with perfusion of culture medium (in some cases supplemented with an oxygen carrier). The overall approach is ‘biomimetic’ in nature as it tends to provide in vivo-like oxygen supply to cultured cells and thereby overcome inherent limitations of diffusional transport in conventional culture systems. In order to mimic the capillary network, cells are cultured on channeled elastomer scaffolds that are perfused with culture medium that can contain oxygen carriers. The overall protocol takes 2–4 weeks, including assembly of the perfusion systems, preparation of scaffolds, cell seeding and cultivation, and on-line and end-point assessment methods. This model is well suited for a wide range of cardiac tissue engineering applications, including the use of human stem cells, and high-fidelity models for biological research. PMID:18388955

  20. Endoscopic ICG perfusion imaging for flap transplants: technical development

    NASA Astrophysics Data System (ADS)

    Stepp, Herbert; Schachenmayr, Hilmar; Ehrhardt, André; Göbel, Werner; Zhorzel, Sven; Betz, Christian Stephan

    2010-02-01

    Objective: Following tumour surgery in the head and neck region, skin flap transplants are usually required to cover the resection area. The purpose of the development was to provide a simple and reliable means to assess whether the transplanted flap is sufficiently perfused. Methods: Fluorescence of intravenously injected Indocyanine green (ICG) was detected with a slightly modified 3-chip CCD camera. Appropriately coated optical filters allow for excitation of ICG with NIR light and detection of NIR ICGfluorescence with the blue channel of the camera. In addition, low intensities of white light can be transmitted to allow for simultaneous display of a remission image in the green and red channels of the camera. Further processing was performed with a LabVIEW program. Results: A satisfactory white light image (red, green and blue display (RGB)) could be calculated from the remission images recorded with the green and red channels of the camera via a look-up table. The look-up table was programmed to provide an optimized blue intensity value for each combination of red and green values. This was generated using a reference image. Implementation of image tracking and intensity measurements in regions of interest (ROIs) in the images is useful to reliably monitor perfusion kinetics of flap and adjacent normal tissue.

  1. Kidney in potassium depletion. II. K/sup +/ handling by the isolated perfused rat kidney

    SciTech Connect

    Hayashi, M.; Katz, A.I.

    1987-03-01

    In a companion paper the authors reported a large increment in Na/sup +/-K/sup +/-ATPase activity and (/sup 3/H)ouabain binding the inner stripe of outer medullary collecting tubules from K-depleted rats. To test the hypothesis that the increased number of Na/sup +/-K/sup +/ pumps in these animals may be involved in potassium reabsorption they examined the effect of ouabain on K excretion by isolated, perfused kidneys from rats fed a K-free diet for 3 wk. Kidneys from K-depleted rats retain potassium avidly, both the fractional (FE/sub K/) and absolute K excretion being approximately fivefold lower than in control kidneys. Ouabain (5 mM) increased FE/sub K/ in kidneys from each K-depleted rat; similar results were obtained when kidneys were perfused with low and high potassium concentrations. In contrast, ouabain produced a variable effect in control kidneys, that depended on the perfusate potassium concentration. In K-depleted rats amiloride did not significantly alter K excretion and did not block the ouabain-induced kaliuresis, suggesting that the latter is not due to enhanced secretion secondary to increased distal fluid delivery. These results provide evidence for ouabain-sensitive potassium reabsorption in kidneys of chronically K-depleted rats, and suggest an explanation for the increased Na/sup +/-K/sup +/-ATPase observed in such animals.

  2. Combined Use of Absolute and Differential Seismic Arrival Time Data to Improve Absolute Event Location

    NASA Astrophysics Data System (ADS)

    Myers, S.; Johannesson, G.

    2012-12-01

    Arrival time measurements based on waveform cross correlation are becoming more common as advanced signal processing methods are applied to seismic data archives and real-time data streams. Waveform correlation can precisely measure the time difference between the arrival of two phases, and differential time data can be used to constrain relative location of events. Absolute locations are needed for many applications, which generally requires the use of absolute time data. Current methods for measuring absolute time data are approximately two orders of magnitude less precise than differential time measurements. To exploit the strengths of both absolute and differential time data, we extend our multiple-event location method Bayesloc, which previously used absolute time data only, to include the use of differential time measurements that are based on waveform cross correlation. Fundamentally, Bayesloc is a formulation of the joint probability over all parameters comprising the multiple event location system. The Markov-Chain Monte Carlo method is used to sample from the joint probability distribution given arrival data sets. The differential time component of Bayesloc includes scaling a stochastic estimate of differential time measurement precision based the waveform correlation coefficient for each datum. For a regional-distance synthetic data set with absolute and differential time measurement error of 0.25 seconds and 0.01 second, respectively, epicenter location accuracy is improved from and average of 1.05 km when solely absolute time data are used to 0.28 km when absolute and differential time data are used jointly (73% improvement). The improvement in absolute location accuracy is the result of conditionally limiting absolute location probability regions based on the precise relative position with respect to neighboring events. Bayesloc estimates of data precision are found to be accurate for the synthetic test, with absolute and differential time measurement

  3. Perfusion safety: new initiatives and enduring principles.

    PubMed

    Kurusz, M

    2011-09-01

    Perfusion safety has been studied and discussed extensively for decades. Many initiatives occurred through efforts of professional organizations to achieve recognition, establish accreditation and certification, promote consensus practice guidelines, and develop peer-reviewed journals as sources for dissemination of clinical information. Newer initiatives have their basis in other disciplines and include systems approach, Quality Assurance/Quality Improvement processes, error recognition, evidence-based methodologies, registries, equipment automation, simulation, and the Internet. Use of previously established resources such as written protocols, checklists, safety devices, and enhanced communication skills has persisted to the present in promoting perfusion safety and has reduced current complication rates to negligible levels.

  4. Effects of laser acupuncture on blood perfusion rate

    NASA Astrophysics Data System (ADS)

    Wang, Xian-ju; Zeng, Chang-chun; Liu, Han-ping; Liu, Song-hao; Liu, Liang-gang

    2006-09-01

    Based on Pennes equation, the influences of the intensity and the impulse frequency of laser acupuncture on the point tissues' blood flow perfusion rate are discussed. We find that the blood perfusion rate of point tissue increases with the intensity of laser acupuncture increasing. After impulse laser acupuncture the point tissue blood perfusion rate increase little, but after continuum laser acupuncture the point tissues blood perfusion rate increase much.

  5. [Design of the Rolling Type Nasal Feeding Perfusion Apparatus].

    PubMed

    Yu, Dong; Yang, Yonghuan; Hu, Huiqin; Luo, Hongjun; Feng, Yunhao; Hao, Xiali

    2015-09-01

    At present, the existing problem in nasal feeding perfusion apparatus is laborious and instability. Designing the rolling type perfusion apparatus by using a roller pump, the problem is solved. Compared with the traditional perfusion apparatus, the advantage lies in liquid carrying only need once and simulating human swallowing process. Through testing and verification, the apparatus can be used in nasal feeding perfusion for elderly or patients.

  6. Absolute Transition Probabilities of Lines in the Spectra of Astrophysical Atoms, Molecules, and Ions

    NASA Technical Reports Server (NTRS)

    Parkinson, W. H.; Smith, P. L.; Yoshino, K.

    1984-01-01

    Progress in the investigation of absolute transition probabilities (A-values or F values) for ultraviolet lines is reported. A radio frequency ion trap was used for measurement of transition probabilities for intersystem lines seen in astronomical spectra. The intersystem line at 2670 A in Al II, which is seen in pre-main sequence stars and symbiotic stars, was studied.

  7. Ethanol Promotes Arteriogenesis and Restores Perfusion to Chronically Ischemic Myocardium

    PubMed Central

    Lassaletta, Antonio D.; Elmadhun, Nassrene Y.; Liu, Yuhong; Feng, Jun; Burgess, Thomas A.; Karlson, Nicholas W.; Laham, Roger J.; Sellke, Frank W.

    2014-01-01

    Background Moderate alcohol consumption is known to be cardioprotective as compared to either heavy drinking or complete abstinence. We assessed the hypothesis that ethanol supplementation would improve myocardial function in the setting of chronic ischemia. Methods and Results Sixteen male Yorkshire swine underwent placement of an ameroid constrictor to the left circumflex artery to induce chronic myocardial ischemia. Post-operatively animals were supplemented with either 90 ml of ethanol daily (50%/V, EtOH) or 80 g of sucrose of equal caloric value (SUC) serving as controls. Seven weeks after ameroid placement, arteriolar density (1.74 ± 0.210 vs. 3.11 ± 0.368 % area of arterioles per low-powered field in SUC vs. EtOH, p = 0.004), myocardial perfusion (ratio of blood flow to the at-risk myocardium compared to the normal ventricle during demand pacing was 0.585 ± 0.107 vs. 1.08 ± 0.138 for SUC vs. EtOH, p = 0.014), and microvascular reactivity were significantly increased in the ethanol-treated animals compared to controls in the at-risk myocardium. Analysis of VEGF and NOTCH pathway signaling suggested pro-neovascular and proliferative activity in the ischemic area. The average peak blood alcohol level in the treatment group was 40 ± 4 mg/dL consistent with levels of moderate drinking in humans. Conclusions Ethanol supplementation increased arteriolar density and significantly improved myocardial perfusion and endothelium-dependent vasorelaxation in chronically ischemic myocardium. These findings suggest that at moderate doses, ethanol directly promotes vasculogenesis and improves microvascular function resulting in significant improvements in myocardial perfusion in the setting of chronic ischemia. PMID:24030397

  8. Quantification of myocardial perfusion using CMR with a radial data acquisition: comparison with a dual-bolus method

    PubMed Central

    2010-01-01

    Background Quantitative estimates of myocardial perfusion generally require accurate measurement of the arterial input function (AIF). The saturation of signal intensity in the blood that occurs with most doses of contrast agent makes obtaining an accurate AIF challenging. This work seeks to evaluate the performance of a method that uses a radial k-space perfusion sequence and multiple saturation recovery times (SRT) to quantify myocardial perfusion with cardiovascular magnetic resonance (CMR). Methods Perfusion CMR was performed at 3 Tesla with a saturation recovery radial turboFLASH sequence with 72 rays. Fourteen subjects were given a low dose (0.004 mmol/kg) of dilute (1/5 concentration) contrast agent (Gd-BOPTA) and then a higher non-dilute dose of the same volume (0.02 mmol/kg). AIFs were calculated from the blood signal in three sub-images with differing effective saturation recovery times. The full and sub-images were reconstructed iteratively with a total variation constraint. The images from the full 72 ray data were processed to obtain six tissue enhancement curves in two slices of the left ventricle in each subject. A 2-compartment model was used to determine absolute flows Results The proposed multi-SRT method resulted in AIFs that were similar to those obtained with the dual-bolus method. Myocardial blood flow (MBF) estimates from the dual-bolus and the multi-SRT methods were related by MBFmulti-SRT = 0.85MBFdual-bolus + 0.18 (r = 0.91). Conclusions The multi-SRT method, which uses a radial k-space perfusion sequence, can be used to obtain an accurate AIF and thus quantify myocardial perfusion for doses of contrast agent that result in a relatively saturated AIF. PMID:20653961

  9. An alternative method for neonatal cerebro-myocardial perfusion.

    PubMed

    Luciani, Giovanni Battista; De Rita, Fabrizio; Faggian, Giuseppe; Mazzucco, Alessandro

    2012-05-01

    Several techniques have already been described for selective cerebral perfusion during repair of aortic arch pathology in children. One method combining cerebral with myocardial perfusion has also been proposed. A novel technique is reported here for selective and independent cerebro-myocardial perfusion for neonatal and infant arch surgery. Technical aspects and potential advantages are discussed.

  10. Role of hypothermic machine perfusion in liver transplantation.

    PubMed

    Schlegel, Andrea; Dutkowski, Philipp

    2015-06-01

    Machine liver perfusion has significantly evolved during the last ten years to optimize extended criteria liver grafts and to address the worldwide organ shortage. This review gives an overview on available ex vivo and in vivo data on hypothermic machine liver perfusion. We discuss also possible protective pathways and show most recent clinical applications of hypothermic machine liver perfusion in human.

  11. An absolute measure for a key currency

    NASA Astrophysics Data System (ADS)

    Oya, Shunsuke; Aihara, Kazuyuki; Hirata, Yoshito

    It is generally considered that the US dollar and the euro are the key currencies in the world and in Europe, respectively. However, there is no absolute general measure for a key currency. Here, we investigate the 24-hour periodicity of foreign exchange markets using a recurrence plot, and define an absolute measure for a key currency based on the strength of the periodicity. Moreover, we analyze the time evolution of this measure. The results show that the credibility of the US dollar has not decreased significantly since the Lehman shock, when the Lehman Brothers bankrupted and influenced the economic markets, and has increased even relatively better than that of the euro and that of the Japanese yen.

  12. From Hubble's NGSL to Absolute Fluxes

    NASA Technical Reports Server (NTRS)

    Heap, Sara R.; Lindler, Don

    2012-01-01

    Hubble's Next Generation Spectral Library (NGSL) consists of R-l000 spectra of 374 stars of assorted temperature, gravity, and metallicity. Each spectrum covers the wavelength range, 0.18-1.00 microns. The library can be viewed and/or downloaded from the website, http://archive.stsci.edu/prepds/stisngsll. Stars in the NGSL are now being used as absolute flux standards at ground-based observatories. However, the uncertainty in the absolute flux is about 2%, which does not meet the requirements of dark-energy surveys. We are therefore developing an observing procedure that should yield fluxes with uncertainties less than 1 % and will take part in an HST proposal to observe up to 15 stars using this new procedure.

  13. Impact of Winko on absolute discharges.

    PubMed

    Balachandra, Krishna; Swaminath, Sam; Litman, Larry C

    2004-01-01

    In Canada, case laws have had a significant impact on the way mentally ill offenders are managed, both in the criminal justice system and in the forensic mental health system. The Supreme Court of Canada's decision with respect to Winko has set a major precedent in the application of the test of significant risk to the safety of the public in making dispositions by the Ontario Review Board and granting absolute discharges to the mentally ill offenders in the forensic health system. Our study examines the impact of the Supreme Court of Canada's decision before and after Winko. The results show that the numbers of absolute discharges have increased post-Winko, which was statistically significant, but there could be other factors influencing this increase.

  14. Absolute-magnitude distributions of supernovae

    SciTech Connect

    Richardson, Dean; Wright, John; Jenkins III, Robert L.; Maddox, Larry

    2014-05-01

    The absolute-magnitude distributions of seven supernova (SN) types are presented. The data used here were primarily taken from the Asiago Supernova Catalogue, but were supplemented with additional data. We accounted for both foreground and host-galaxy extinction. A bootstrap method is used to correct the samples for Malmquist bias. Separately, we generate volume-limited samples, restricted to events within 100 Mpc. We find that the superluminous events (M{sub B} < –21) make up only about 0.1% of all SNe in the bias-corrected sample. The subluminous events (M{sub B} > –15) make up about 3%. The normal Ia distribution was the brightest with a mean absolute blue magnitude of –19.25. The IIP distribution was the dimmest at –16.75.

  15. Absolute and relative dosimetry for ELIMED

    SciTech Connect

    Cirrone, G. A. P.; Schillaci, F.; Scuderi, V.; Cuttone, G.; Candiano, G.; Musumarra, A.; Pisciotta, P.; Romano, F.; Carpinelli, M.; Presti, D. Lo; Raffaele, L.; Tramontana, A.; Cirio, R.; Sacchi, R.; Monaco, V.; Marchetto, F.; Giordanengo, S.

    2013-07-26

    The definition of detectors, methods and procedures for the absolute and relative dosimetry of laser-driven proton beams is a crucial step toward the clinical use of this new kind of beams. Hence, one of the ELIMED task, will be the definition of procedures aiming to obtain an absolute dose measure at the end of the transport beamline with an accuracy as close as possible to the one required for clinical applications (i.e. of the order of 5% or less). Relative dosimetry procedures must be established, as well: they are necessary in order to determine and verify the beam dose distributions and to monitor the beam fluence and the energetic spectra during irradiations. Radiochromic films, CR39, Faraday Cup, Secondary Emission Monitor (SEM) and transmission ionization chamber will be considered, designed and studied in order to perform a fully dosimetric characterization of the ELIMED proton beam.

  16. Relative errors can cue absolute visuomotor mappings.

    PubMed

    van Dam, Loes C J; Ernst, Marc O

    2015-12-01

    When repeatedly switching between two visuomotor mappings, e.g. in a reaching or pointing task, adaptation tends to speed up over time. That is, when the error in the feedback corresponds to a mapping switch, fast adaptation occurs. Yet, what is learned, the relative error or the absolute mappings? When switching between mappings, errors with a size corresponding to the relative difference between the mappings will occur more often than other large errors. Thus, we could learn to correct more for errors with this familiar size (Error Learning). On the other hand, it has been shown that the human visuomotor system can store several absolute visuomotor mappings (Mapping Learning) and can use associated contextual cues to retrieve them. Thus, when contextual information is present, no error feedback is needed to switch between mappings. Using a rapid pointing task, we investigated how these two types of learning may each contribute when repeatedly switching between mappings in the absence of task-irrelevant contextual cues. After training, we examined how participants changed their behaviour when a single error probe indicated either the often-experienced error (Error Learning) or one of the previously experienced absolute mappings (Mapping Learning). Results were consistent with Mapping Learning despite the relative nature of the error information in the feedback. This shows that errors in the feedback can have a double role in visuomotor behaviour: they drive the general adaptation process by making corrections possible on subsequent movements, as well as serve as contextual cues that can signal a learned absolute mapping. PMID:26280315

  17. The absolute spectrophotometric catalog by Anita Cochran

    NASA Astrophysics Data System (ADS)

    Burnashev, V. I.; Burnasheva, B. A.; Ruban, E. V.; Hagen-Torn, E. I.

    2014-06-01

    The absolute spectrophotometric catalog by Anita Cochran is presented in a machine-readable form. The catalog systematizes observations acquired at the McDonald Observatory in 1977-1978. The data are compared with other sources, in particular, the calculated broadband stellar magnitudes are compared with photometric observations by other authors, to show that the observational data given in the catalog are reliable and suitable for a variety of applications. Observations of variable stars of different types make Cochran's catalog especially valuable.

  18. Absolute magnitudes and kinematics of barium stars.

    NASA Astrophysics Data System (ADS)

    Gomez, A. E.; Luri, X.; Grenier, S.; Prevot, L.; Mennessier, M. O.; Figueras, F.; Torra, J.

    1997-03-01

    The absolute magnitude of barium stars has been obtained from kinematical data using a new algorithm based on the maximum-likelihood principle. The method allows to separate a sample into groups characterized by different mean absolute magnitudes, kinematics and z-scale heights. It also takes into account, simultaneously, the censorship in the sample and the errors on the observables. The method has been applied to a sample of 318 barium stars. Four groups have been detected. Three of them show a kinematical behaviour corresponding to disk population stars. The fourth group contains stars with halo kinematics. The luminosities of the disk population groups spread a large range. The intrinsically brightest one (M_v_=-1.5mag, σ_M_=0.5mag) seems to be an inhomogeneous group containing barium binaries as well as AGB single stars. The most numerous group (about 150 stars) has a mean absolute magnitude corresponding to stars in the red giant branch (M_v_=0.9mag, σ_M_=0.8mag). The third group contains barium dwarfs, the obtained mean absolute magnitude is characteristic of stars on the main sequence or on the subgiant branch (M_v_=3.3mag, σ_M_=0.5mag). The obtained mean luminosities as well as the kinematical results are compatible with an evolutionary link between barium dwarfs and classical barium giants. The highly luminous group is not linked with these last two groups. More high-resolution spectroscopic data will be necessary in order to better discriminate between barium and non-barium stars.

  19. Use of intensity quotients and differences in absolute structure refinement.

    PubMed

    Parsons, Simon; Flack, Howard D; Wagner, Trixie

    2013-06-01

    Several methods for absolute structure refinement were tested using single-crystal X-ray diffraction data collected using Cu Kα radiation for 23 crystals with no element heavier than oxygen: conventional refinement using an inversion twin model, estimation using intensity quotients in SHELXL2012, estimation using Bayesian methods in PLATON, estimation using restraints consisting of numerical intensity differences in CRYSTALS and estimation using differences and quotients in TOPAS-Academic where both quantities were coded in terms of other structural parameters and implemented as restraints. The conventional refinement approach yielded accurate values of the Flack parameter, but with standard uncertainties ranging from 0.15 to 0.77. The other methods also yielded accurate values of the Flack parameter, but with much higher precision. Absolute structure was established in all cases, even for a hydrocarbon. The procedures in which restraints are coded explicitly in terms of other structural parameters enable the Flack parameter to correlate with these other parameters, so that it is determined along with those parameters during refinement. PMID:23719469

  20. Chemical composition of French mimosa absolute oil.

    PubMed

    Perriot, Rodolphe; Breme, Katharina; Meierhenrich, Uwe J; Carenini, Elise; Ferrando, Georges; Baldovini, Nicolas

    2010-02-10

    Since decades mimosa (Acacia dealbata) absolute oil has been used in the flavor and perfume industry. Today, it finds an application in over 80 perfumes, and its worldwide industrial production is estimated five tons per year. Here we report on the chemical composition of French mimosa absolute oil. Straight-chain analogues from C6 to C26 with different functional groups (hydrocarbons, esters, aldehydes, diethyl acetals, alcohols, and ketones) were identified in the volatile fraction. Most of them are long-chain molecules: (Z)-heptadec-8-ene, heptadecane, nonadecane, and palmitic acid are the most abundant, and constituents such as 2-phenethyl alcohol, methyl anisate, and ethyl palmitate are present in smaller amounts. The heavier constituents were mainly triterpenoids such as lupenone and lupeol, which were identified as two of the main components. (Z)-Heptadec-8-ene, lupenone, and lupeol were quantified by GC-MS in SIM mode using external standards and represents 6%, 20%, and 7.8% (w/w) of the absolute oil. Moreover, odorant compounds were extracted by SPME and analyzed by GC-sniffing leading to the perception of 57 odorant zones, of which 37 compounds were identified by their odorant description, mass spectrum, retention index, and injection of the reference compound. PMID:20070087

  1. A Methodology for Absolute Isotope Composition Measurement

    NASA Astrophysics Data System (ADS)

    Shen, J. J.; Lee, D.; Liang, W.

    2007-12-01

    Double spike technique was a well defined method for isotope composition measurement by TIMS of samples which have natural mass fractionation effect, but it is still a problem to define the isotope composition for double spike itself. In this study, we modified the old double spike technique and found that we could use the modified technique to solve the ¡§true¡¨ isotope composition of double spike itself. According the true isotope composition of double spike, we can measure the absolute isotope composition if the sample has natural fractionation effect. A new vector analytical method has been developed in order to obtain the true isotopic composition of a 42Ca-48Ca double spike, and this is achieved by using two different sample-spike mixtures combined with the double spike and the natural Ca data. Because the natural sample, the two mixtures, and the spike should all lie on a single mixing line, we are able to constrain the true isotopic composition of our double spike using this new approach. This method not only can be used in Ca system but also in Ti, Cr, Fe, Ni, Zn, Mo, Ba and Pb systems. The absolute double spike isotopic ratio is important, which can save a lot of time to check different reference standards. Especially for Pb, radiogenic isotope system, the decay systems embodied in three of four naturally occurring isotopes induce difficult to obtain true isotopic ratios for absolute dating.

  2. Chemical composition of French mimosa absolute oil.

    PubMed

    Perriot, Rodolphe; Breme, Katharina; Meierhenrich, Uwe J; Carenini, Elise; Ferrando, Georges; Baldovini, Nicolas

    2010-02-10

    Since decades mimosa (Acacia dealbata) absolute oil has been used in the flavor and perfume industry. Today, it finds an application in over 80 perfumes, and its worldwide industrial production is estimated five tons per year. Here we report on the chemical composition of French mimosa absolute oil. Straight-chain analogues from C6 to C26 with different functional groups (hydrocarbons, esters, aldehydes, diethyl acetals, alcohols, and ketones) were identified in the volatile fraction. Most of them are long-chain molecules: (Z)-heptadec-8-ene, heptadecane, nonadecane, and palmitic acid are the most abundant, and constituents such as 2-phenethyl alcohol, methyl anisate, and ethyl palmitate are present in smaller amounts. The heavier constituents were mainly triterpenoids such as lupenone and lupeol, which were identified as two of the main components. (Z)-Heptadec-8-ene, lupenone, and lupeol were quantified by GC-MS in SIM mode using external standards and represents 6%, 20%, and 7.8% (w/w) of the absolute oil. Moreover, odorant compounds were extracted by SPME and analyzed by GC-sniffing leading to the perception of 57 odorant zones, of which 37 compounds were identified by their odorant description, mass spectrum, retention index, and injection of the reference compound.

  3. The Carina Project: Absolute and Relative Calibrations

    NASA Astrophysics Data System (ADS)

    Corsi, C. E.; Bono, G.; Walker, A. R.; Brocato, E.; Buonanno, R.; Caputo, F.; Castellani, M.; Castellani, V.; Dall'Ora, M.; Marconi, M.; Monelli, M.; Nonino, M.; Pulone, L.; Ripepi, V.; Smith, H. A.

    We discuss the reduction strategy adopted to perform the relative and the absolute calibration of the Wide Field Imager (WFI) available at the 2.2m ESO/MPI telescope and of the Mosaic Camera (MC) available at the 4m CTIO Blanco telescope. To properly constrain the occurrence of deceptive systematic errors in the relative calibration we observed with each chip the same set of stars. Current photometry seems to suggest that the WFI shows a positional effect when moving from the top to the bottom of individual chips. Preliminary results based on an independent data set collected with the MC suggest that this camera is only marginally affected by the same problem. To perform the absolute calibration we observed with each chip the same set of standard stars. The sample covers a wide color range and the accuracy both in the B and in the V-band appears to be of the order of a few hundredths of magnitude. Finally, we briefly outline the observing strategy to improve both relative and absolute calibrations of mosaic CCD cameras.

  4. On determining absolute entropy without quantum theory or the third law of thermodynamics

    NASA Astrophysics Data System (ADS)

    Steane, Andrew M.

    2016-04-01

    We employ classical thermodynamics to gain information about absolute entropy, without recourse to statistical methods, quantum mechanics or the third law of thermodynamics. The Gibbs–Duhem equation yields various simple methods to determine the absolute entropy of a fluid. We also study the entropy of an ideal gas and the ionization of a plasma in thermal equilibrium. A single measurement of the degree of ionization can be used to determine an unknown constant in the entropy equation, and thus determine the absolute entropy of a gas. It follows from all these examples that the value of entropy at absolute zero temperature does not need to be assigned by postulate, but can be deduced empirically.

  5. Asynchronicity of facial blood perfusion in migraine.

    PubMed

    Zaproudina, Nina; Teplov, Victor; Nippolainen, Ervin; Lipponen, Jukka A; Kamshilin, Alexei A; Närhi, Matti; Karjalainen, Pasi A; Giniatullin, Rashid

    2013-01-01

    Asymmetrical changes in blood perfusion and asynchronous blood supply to head tissues likely contribute to migraine pathophysiology. Imaging was widely used in order to understand hemodynamic variations in migraine. However, mapping of blood pulsations in the face of migraineurs has not been performed so far. We used the Blood Pulsation Imaging (BPI) technique, which was recently developed in our group, to establish whether 2D-imaging of blood pulsations parameters can reveal new biomarkers of migraine. BPI characteristics were measured in migraineurs during the attack-free interval and compared to healthy subjects with and without a family history of migraine. We found a novel phenomenon of transverse waves of facial blood perfusion in migraineurs in contrast to healthy subjects who showed synchronous blood delivery to both sides of the face. Moreover, the amplitude of blood pulsations was symmetrically distributed over the face of healthy subjects, but asymmetrically in migraineurs and subjects with a family history of migraine. In the migraine patients we found a remarkable correlation between the side of unilateral headache and the direction of the blood perfusion wave. Our data suggest that migraine is associated with lateralization of blood perfusion and asynchronous blood pulsations in the facial area, which could be due to essential dysfunction of the autonomic vascular control in the face. These findings may further enhance our understanding of migraine pathophysiology and suggest new easily available biomarkers of this pathology. PMID:24324592

  6. Simplified prototyping of perfusable polystyrene microfluidics

    PubMed Central

    Tran, Reginald; Ahn, Byungwook; R. Myers, David; Qiu, Yongzhi; Sakurai, Yumiko; Moot, Robert; Mihevc, Emma; Trent Spencer, H.; Doering, Christopher; A. Lam, Wilbur

    2014-01-01

    Cell culture in microfluidic systems has primarily been conducted in devices comprised of polydimethylsiloxane (PDMS) or other elastomers. As polystyrene (PS) is the most characterized and commonly used substrate material for cell culture, microfluidic cell culture would ideally be conducted in PS-based microsystems that also enable tight control of perfusion and hydrodynamic conditions, which are especially important for culture of vascular cell types. Here, we report a simple method to prototype perfusable PS microfluidics for endothelial cell culture under flow that can be fabricated using standard lithography and wet laboratory equipment to enable stable perfusion at shear stresses up to 300 dyn/cm2 and pumping pressures up to 26 kPa for at least 100 h. This technique can also be extended to fabricate perfusable hybrid PS-PDMS microfluidics of which one application is for increased efficiency of viral transduction in non-adherent suspension cells by leveraging the high surface area to volume ratio of microfluidics and adhesion molecules that are optimized for PS substrates. These biologically compatible microfluidic devices can be made more accessible to biological-based laboratories through the outsourcing of lithography to various available microfluidic foundries. PMID:25379106

  7. Nuclear cardiology: Myocardial perfusion and function

    SciTech Connect

    Seldin, D.W. )

    1991-08-01

    Myocardial perfusion studies continue to be a major focus of research, with new investigations of the relationship of exercise-redistribution thallium imaging to diagnosis, prognosis, and case management. The redistribution phenomenon, which seemed to be fairly well understood a few years ago, is now recognized to be much more complex than originally thought, and various strategies have been proposed to clarify the meaning of persistent defects. Pharmacologic intervention with dipyridamole and adenosine has become available as an alternative to exercise, and comparisons with exercise imaging and catheterization results have been described. Thallium itself is no longer the sole single-photon perfusion radiopharmaceutical; two new technetium agents are now widely available. In addition to perfusion studies, advances in the study of ventricular function have been made, including reports of studies performed in conjunction with technetium perfusion studies, new insights into cardiac physiology, and the prognostic and case-management information that function studies provide. Finally, work has continued with monoclonal antibodies for the identification of areas of myocyte necrosis. 41 references.

  8. Whole-Brain CT Perfusion to Quantify Acute Ischemic Penumbra and Core.

    PubMed

    Lin, Longting; Bivard, Andrew; Krishnamurthy, Venkatesh; Levi, Christopher R; Parsons, Mark W

    2016-06-01

    Purpose To validate the use of perfusion computed tomography (CT) with whole-brain coverage to measure the ischemic penumbra and core and to compare its performance to that of limited-coverage perfusion CT. Materials and Methods Institutional ethics committee approval and informed consent were obtained. Patients (n = 296) who underwent 320-detector CT perfusion within 6 hours of the onset of ischemic stroke were studied. First, the ischemic volume at CT perfusion was compared with the penumbra and core reference values at magnetic resonance (MR) imaging to derive CT perfusion penumbra and core thresholds. Second, the thresholds were tested in a different group of patients to predict the final infarction at diffusion-weighted imaging 24 hours after CT perfusion. Third, the change in ischemic volume delineated by the optimal penumbra and core threshold was determined as the brain coverage was gradually reduced from 160 mm to 20 mm. The Wilcoxon signed-rank test, concordance correlation coefficient (CCC), and analysis of variance were used for the first, second, and third steps, respectively. Results CT perfusion at penumbra and core thresholds resulted in the least volumetric difference from MR imaging reference values with delay times greater than 3 seconds and delay-corrected cerebral blood flow of less than 30% (P = .34 and .33, respectively). When the thresholds were applied to the new group of patients, prediction of the final infarction was allowed with delay times greater than 3 seconds in patients with no recanalization of the occluded artery (CCC, 0.96 [95% confidence interval: 0.92, 0.98]) and with delay-corrected cerebral blood flow less than 30% in patients with complete recanalization (CCC, 0.91 [95% confidence interval: 0.83, 0.95]). However, the ischemic volume with a delay time greater than 3 seconds was underestimated when the brain coverage was reduced to 80 mm (P = .04) and the core volume measured as cerebral blood flow less than 30% was

  9. Quantitative Myocardial Perfusion with Dynamic Contrast-Enhanced Imaging in MRI and CT: Theoretical Models and Current Implementation

    PubMed Central

    Handayani, A.; Dijkstra, H.; Prakken, N. H. J.; Slart, R. H. J. A.; Oudkerk, M.; Van Ooijen, P. M. A.; Vliegenthart, R.; Sijens, P. E.

    2016-01-01

    Technological advances in magnetic resonance imaging (MRI) and computed tomography (CT), including higher spatial and temporal resolution, have made the prospect of performing absolute myocardial perfusion quantification possible, previously only achievable with positron emission tomography (PET). This could facilitate integration of myocardial perfusion biomarkers into the current workup for coronary artery disease (CAD), as MRI and CT systems are more widely available than PET scanners. Cardiac PET scanning remains expensive and is restricted by the requirement of a nearby cyclotron. Clinical evidence is needed to demonstrate that MRI and CT have similar accuracy for myocardial perfusion quantification as PET. However, lack of standardization of acquisition protocols and tracer kinetic model selection complicates comparison between different studies and modalities. The aim of this overview is to provide insight into the different tracer kinetic models for quantitative myocardial perfusion analysis and to address typical implementation issues in MRI and CT. We compare different models based on their theoretical derivations and present the respective consequences for MRI and CT acquisition parameters, highlighting the interplay between tracer kinetic modeling and acquisition settings. PMID:27088083

  10. Comparing Normothermic Machine Perfusion Preservation With Different Perfusates on Porcine Livers From Donors After Circulatory Death.

    PubMed

    Liu, Q; Nassar, A; Farias, K; Buccini, L; Mangino, M J; Baldwin, W; Bennett, A; O'Rourke, C; Iuppa, G; Soliman, B G; Urcuyo-Llanes, D; Okamoto, T; Uso, T D; Fung, J; Abu-Elmagd, K; Miller, C; Quintini, C

    2016-03-01

    The utilization of normothermic machine perfusion (NMP) may be an effective strategy to resuscitate livers from donation after circulatory death (DCD). There is no consensus regarding the efficacy of different perfusates on graft and bile duct viability. The aim of this study was to compare, in an NMP porcine DCD model, the preservation potential of three different perfusates. Twenty porcine livers with 60 min of warm ischemia were separated into four preservation groups: cold storage (CS), NMP with Steen solution (Steen; XVIVO Perfusion Inc., Denver, CO), Steen plus red blood cells (RBCs), or whole blood (WB). All livers were preserved for 10 h and reperfused to simulate transplantation for 24 h. During preservation, the NMP with Steen group presented the highest hepatocellular injury. At reperfusion, the CS group had the lowest bile production and the worst hepatocellular injury compared with all other groups, followed by NMP with Steen; the Steen plus RBC and WB groups presented the best functional and hepatocellular injury outcomes, with WB livers showing lower aspartate aminotransferase release and a trend toward better results for most parameters. Based on our results, a perfusate that contains an oxygen carrier is most effective in a model of NMP porcine DCD livers compared with Steen solution. Specifically, WB-perfused livers showed a trend toward better outcomes compared with Steen plus RBCs. PMID:26663737

  11. Bayesian hemodynamic parameter estimation by bolus tracking perfusion weighted imaging.

    PubMed

    Boutelier, Timothé; Kudo, Koshuke; Pautot, Fabrice; Sasaki, Makoto

    2012-07-01

    A delay-insensitive probabilistic method for estimating hemodynamic parameters, delays, theoretical residue functions, and concentration time curves by computed tomography (CT) and magnetic resonance (MR) perfusion weighted imaging is presented. Only a mild stationarity hypothesis is made beyond the standard perfusion model. New microvascular parameters with simple hemodynamic interpretation are naturally introduced. Simulations on standard digital phantoms show that the method outperforms the oscillating singular value decomposition (oSVD) method in terms of goodness-of-fit, linearity, statistical and systematic errors on all parameters, especially at low signal-to-noise ratios (SNRs). Delay is always estimated sharply with user-supplied resolution and is purely arterial, by contrast to oSVD time-to-maximum TMAX that is very noisy and biased by mean transit time (MTT), blood volume, and SNR. Residue functions and signals estimates do not suffer overfitting anymore. One CT acute stroke case confirms simulation results and highlights the ability of the method to reliably estimate MTT when SNR is low. Delays look promising for delineating the arterial occlusion territory and collateral circulation. PMID:22410325

  12. Perfusion pressure control by adenosine triphosphate given during cardiopulmonary bypass.

    PubMed

    Hashimoto, K; Kurosawa, H; Horikoshi, S; Miyamoto, H; Suzuki, K

    1993-01-01

    Administration of exogenous adenosine triphosphate (ATP) as a vasodilator during cardiopulmonary bypass was assessed in consecutive adult patients (n = 24) who demonstrated a high arterial perfusion pressure (mean, > 90 mm Hg). The action of ATP was characterized by rapid induction and stabilization of the blood pressure level. The dose of ATP ranged from 0.68 to 2.68 mg/min. Within 1 minute after the administration, there was a significant reduction in the perfusion pressure from 102 +/- 18 mm Hg (mean +/- standard deviation) to 72 +/- 19 mm Hg. The ATP was then able to maintain the desired pressure of 69 +/- 12 mm Hg at 5 minutes, 67 +/- 12 mm Hg at 10 minutes, and consistent values thereafter. After the ATP administration was discontinued, there was a prompt recovery of pressure without bradyarrhythmia. The frequency and amount of inotropes used were consistent with the control group (n = 26). Although the administration of ATP reduced the increase in serum catecholamine concentration, there were no significant changes in other vasoactive mediators (eicosanoid, angiotensin II, endothelin) between the two groups during cardiopulmonary bypass. There was neither an accumulation of metabolic products (uric acid, phosphate) nor a decrease in the level of divalent cation (Ca2+), which is observed when the cations combine with phosphates or adenosine nucleotides. This study confirmed the efficacy and safety of ATP infusion during cardiopulmonary bypass. PMID:8417658

  13. Recent developments and future prospects of SPECT myocardial perfusion imaging.

    PubMed

    Zaman, Maseeh Uz; Hashmi, Ibrahim; Fatima, Nosheen

    2010-10-01

    Myocardial perfusion SPECT imaging is the most commonly performed functional imaging for assessment of coronary artery disease. High diagnostic accuracy and incremental prognostic value are the major benefits while suboptimal spatial resolution and significant radiation exposure are the main limitations. Its ability to detect hemodynamic significance of lesions seen on multidetector CT angiogram (MDCTA) has paved the path for a successful marriage between anatomical and functional imaging modalities in the form of hybrid SPECT/MDCTA system. In recent years, there have been enormous efforts by industry and academia to develop new SPECT imaging systems with better sensitivity, resolution, compact design and new reconstruction algorithms with ability to improve image quality and resolution. Furthermore, expected arrival of Tc-99m-labeled deoxyglucose in next few years would further strengthen the role of SPECT in imaging hibernating myocardium. In view of these developments, it seems that SPECT would enjoy its pivotal role in spite of major threat to be replaced by fluorine-18-labeled positron emission tomography perfusion and glucose metabolism imaging agents. PMID:20652774

  14. Choice of the regularization parameter for perfusion quantification with MRI

    NASA Astrophysics Data System (ADS)

    Sourbron, S.; Luypaert, R.; Van Schuerbeek, P.; Dujardin, M.; Stadnik, T.

    2004-07-01

    Truncated singular value decomposition (TSVD) is an effective method for the deconvolution of dynamic contrast enhanced (DCE) MRI. Two robust methods for the selection of the truncation threshold on a pixel-by-pixel basis—generalized cross validation (GCV) and the L-curve criterion (LCC)—were optimized and compared to paradigms in the literature. GCV and LCC were found to perform optimally when applied with a smooth version of TSVD, known as standard form Tikhonov regularization (SFTR). The methods lead to improvements in the estimate of the residue function and of its maximum, and converge properly with SNR. The oscillations typically observed in the solution vanish entirely, and perfusion is more accurately estimated at small mean transit times. This results in improved image contrast and increased sensitivity to perfusion abnormalities, at the cost of 1-2 min in calculation time and hyperintense clusters in the image. Preliminary experience with clinical data suggests that the latter problem can be resolved using spatial continuity and/or hybrid thresholding methods. In the simulations GCV and LCC are equivalent in terms of performance, but GCV thresholding is faster.

  15. Preliminary Study of Open Quotient in an Ex-Vivo Perfused Human Larynx Model

    PubMed Central

    Mendelsohn, Abie H.; Zhang, Zhaoyan; Luegmair, Georg; Orestes, Michael; Berke, Gerald S.

    2016-01-01

    Importance Scientific understanding human voice production to date is a product of indirect investigations including animal models, cadaveric tissue study, or computational modeling. Due to its invasive nature, direct experimentation of human voice production has previously not been possible. The feasibility of an ex-vivo perfused human phonatory model has recently allowed systematic investigation in virtually living human larynges with parametric laryngeal muscle stimulation. Objective In this study, the relationship between adductor muscle group stimulation and the open quotient (OQ) of vocal fold vibration was investigated using an ex-vivo perfused human larynx. Design Human perfused tissue study. Setting Physiology Laboratory. Participants Human larynx is recovered from research-consented organ donors within two hours of cardiac death. Interventions, Main Outcomes and Measures Perfusion with donated human blood is re-established shortly after cardiac death. Human perfused phonation is achieved by providing subglottal airflow under graded neuromuscular electrical stimulation bilaterally to the intrinsic adductor groups and cricothyroid muscles. The phonation resulting from the graded states of neuromuscular stimulations are evaluated through high-speed vibratory imaging. OQ is derived through digital kymography and glottal area waveform analysis. Results Under constant glottal flow, step-wise increase in adductor muscle group stimulation decreased OQ. Quantitatively, OQ values reached a lower limit of 0.42. Increased stimulation above maximal muscle deformation was unable to affect OQ beyond this lower limit. Conclusions and Relevance For the first time in a neuromuscularly activated human larynx, a negative relationship between adductor muscle group stimulation and phonatory OQ was demonstrated. Further experience with the ex-vivo perfused human phonatory model will work to systematically define this causal relationship. PMID:26181642

  16. Effects of CT-based attenuation correction of rat microSPECT images on relative myocardial perfusion and quantitative tracer uptake

    SciTech Connect

    Strydhorst, Jared H. Ruddy, Terrence D.; Wells, R. Glenn

    2015-04-15

    Purpose: Our goal in this work was to investigate the impact of CT-based attenuation correction on measurements of rat myocardial perfusion with {sup 99m}Tc and {sup 201}Tl single photon emission computed tomography (SPECT). Methods: Eight male Sprague-Dawley rats were injected with {sup 99m}Tc-tetrofosmin and scanned in a small animal pinhole SPECT/CT scanner. Scans were repeated weekly over a period of 5 weeks. Eight additional rats were injected with {sup 201}Tl and also scanned following a similar protocol. The images were reconstructed with and without attenuation correction, and the relative perfusion was analyzed with the commercial cardiac analysis software. The absolute uptake of {sup 99m}Tc in the heart was also quantified with and without attenuation correction. Results: For {sup 99m}Tc imaging, relative segmental perfusion changed by up to +2.1%/−1.8% as a result of attenuation correction. Relative changes of +3.6%/−1.0% were observed for the {sup 201}Tl images. Interscan and inter-rat reproducibilities of relative segmental perfusion were 2.7% and 3.9%, respectively, for the uncorrected {sup 99m}Tc scans, and 3.6% and 4.3%, respectively, for the {sup 201}Tl scans, and were not significantly affected by attenuation correction for either tracer. Attenuation correction also significantly increased the measured absolute uptake of tetrofosmin and significantly altered the relationship between the rat weight and tracer uptake. Conclusions: Our results show that attenuation correction has a small but statistically significant impact on the relative perfusion measurements in some segments of the heart and does not adversely affect reproducibility. Attenuation correction had a small but statistically significant impact on measured absolute tracer uptake.

  17. 24-h Langendorff-perfused neonatal rat heart used to study the impact of adenoviral gene transfer.

    PubMed

    Wiechert, S; El-Armouche, A; Rau, T; Zimmermann, W-H; Eschenhagen, T

    2003-08-01

    The human genome project has increased the demand for simple experimental systems that allow the impact of gene manipulations to be studied under controlled ex vivo conditions. We hypothesized that, in contrast to adult hearts, neonatal hearts allow long-term perfusion and efficient gene transfer ex vivo. A Langendorff perfusion system was modified to allow perfusion for >24 h with particular emphasis on uncompromised contractile activity, sterility, online measurement of force of contraction, inotropic response to beta-adrenergic stimulation, and efficient gene transfer. The hearts were perfused with serum-free medium (DMEM + medium 199, 4 + 1) supplemented with hydrocortisone, triiodothyronine, ascorbic acid, insulin, pyruvate, l-carnitine, creatine, taurine, l-glutamine, mannitol, and antibiotics recirculating (500 ml/2 hearts) at 1 ml/min. Hearts from 2 day-old rats beat constantly at 135-155 beats/min and developed active force of 1-2 mN. During 24 h of perfusion, twitch tension increased to approximately 165% of initial values (P < 0.05), whereas the inotropic response to isoprenaline remained constant. A decrease in total protein content of 10% and histological examination indicated moderate edema, but actin and calsequestrin concentration remained unchanged and perfusion pressure remained constant at 7-11 mmHg. Perfusion with a LacZ-encoding adenovirus at 3 x 108 active virus particles yielded homogeneous transfection of approximately 80% throughout the heart and did not affect heart rate, force of contraction, or response to isoprenaline compared with uninfected controls (n = 7 each). Taken together, the 24-h Langendorff-perfused neonatal rat heart is a relatively simple, inexpensive, and robust new heart model that appears feasible as a test bed for functional genomics.

  18. Absolute Radiometric Calibration of EUNIS-06

    NASA Technical Reports Server (NTRS)

    Thomas, R. J.; Rabin, D. M.; Kent, B. J.; Paustian, W.

    2007-01-01

    The Extreme-Ultraviolet Normal-Incidence Spectrometer (EUNIS) is a soundingrocket payload that obtains imaged high-resolution spectra of individual solar features, providing information about the Sun's corona and upper transition region. Shortly after its successful initial flight last year, a complete end-to-end calibration was carried out to determine the instrument's absolute radiometric response over its Longwave bandpass of 300 - 370A. The measurements were done at the Rutherford-Appleton Laboratory (RAL) in England, using the same vacuum facility and EUV radiation source used in the pre-flight calibrations of both SOHO/CDS and Hinode/EIS, as well as in three post-flight calibrations of our SERTS sounding rocket payload, the precursor to EUNIS. The unique radiation source provided by the Physikalisch-Technische Bundesanstalt (PTB) had been calibrated to an absolute accuracy of 7% (l-sigma) at 12 wavelengths covering our bandpass directly against the Berlin electron storage ring BESSY, which is itself a primary radiometric source standard. Scans of the EUNIS aperture were made to determine the instrument's absolute spectral sensitivity to +- 25%, considering all sources of error, and demonstrate that EUNIS-06 was the most sensitive solar E W spectrometer yet flown. The results will be matched against prior calibrations which relied on combining measurements of individual optical components, and on comparisons with theoretically predicted 'insensitive' line ratios. Coordinated observations were made during the EUNIS-06 flight by SOHO/CDS and EIT that will allow re-calibrations of those instruments as well. In addition, future EUNIS flights will provide similar calibration updates for TRACE, Hinode/EIS, and STEREO/SECCHI/EUVI.

  19. Clock time is absolute and universal

    NASA Astrophysics Data System (ADS)

    Shen, Xinhang

    2015-09-01

    A critical error is found in the Special Theory of Relativity (STR): mixing up the concepts of the STR abstract time of a reference frame and the displayed time of a physical clock, which leads to use the properties of the abstract time to predict time dilation on physical clocks and all other physical processes. Actually, a clock can never directly measure the abstract time, but can only record the result of a physical process during a period of the abstract time such as the number of cycles of oscillation which is the multiplication of the abstract time and the frequency of oscillation. After Lorentz Transformation, the abstract time of a reference frame expands by a factor gamma, but the frequency of a clock decreases by the same factor gamma, and the resulting multiplication i.e. the displayed time of a moving clock remains unchanged. That is, the displayed time of any physical clock is an invariant of Lorentz Transformation. The Lorentz invariance of the displayed times of clocks can further prove within the framework of STR our earth based standard physical time is absolute, universal and independent of inertial reference frames as confirmed by both the physical fact of the universal synchronization of clocks on the GPS satellites and clocks on the earth, and the theoretical existence of the absolute and universal Galilean time in STR which has proved that time dilation and space contraction are pure illusions of STR. The existence of the absolute and universal time in STR has directly denied that the reference frame dependent abstract time of STR is the physical time, and therefore, STR is wrong and all its predictions can never happen in the physical world.

  20. Achieving Climate Change Absolute Accuracy in Orbit

    NASA Technical Reports Server (NTRS)

    Wielicki, Bruce A.; Young, D. F.; Mlynczak, M. G.; Thome, K. J; Leroy, S.; Corliss, J.; Anderson, J. G.; Ao, C. O.; Bantges, R.; Best, F.; Bowman, K.; Brindley, H.; Butler, J. J.; Collins, W.; Dykema, J. A.; Doelling, D. R.; Feldman, D. R.; Fox, N.; Huang, X.; Holz, R.; Huang, Y.; Jennings, D.; Jin, Z.; Johnson, D. G.; Jucks, K.; Kato, S.; Kratz, D. P.; Liu, X.; Lukashin, C.; Mannucci, A. J.; Phojanamongkolkij, N.; Roithmayr, C. M.; Sandford, S.; Taylor, P. C.; Xiong, X.

    2013-01-01

    The Climate Absolute Radiance and Refractivity Observatory (CLARREO) mission will provide a calibration laboratory in orbit for the purpose of accurately measuring and attributing climate change. CLARREO measurements establish new climate change benchmarks with high absolute radiometric accuracy and high statistical confidence across a wide range of essential climate variables. CLARREO's inherently high absolute accuracy will be verified and traceable on orbit to Système Internationale (SI) units. The benchmarks established by CLARREO will be critical for assessing changes in the Earth system and climate model predictive capabilities for decades into the future as society works to meet the challenge of optimizing strategies for mitigating and adapting to climate change. The CLARREO benchmarks are derived from measurements of the Earth's thermal infrared spectrum (5-50 micron), the spectrum of solar radiation reflected by the Earth and its atmosphere (320-2300 nm), and radio occultation refractivity from which accurate temperature profiles are derived. The mission has the ability to provide new spectral fingerprints of climate change, as well as to provide the first orbiting radiometer with accuracy sufficient to serve as the reference transfer standard for other space sensors, in essence serving as a "NIST [National Institute of Standards and Technology] in orbit." CLARREO will greatly improve the accuracy and relevance of a wide range of space-borne instruments for decadal climate change. Finally, CLARREO has developed new metrics and methods for determining the accuracy requirements of climate observations for a wide range of climate variables and uncertainty sources. These methods should be useful for improving our understanding of observing requirements for most climate change observations.

  1. Absolute calibration of the Auger fluorescence detectors

    SciTech Connect

    Bauleo, P.; Brack, J.; Garrard, L.; Harton, J.; Knapik, R.; Meyhandan, R.; Rovero, A.C.; Tamashiro, A.; Warner, D.

    2005-07-01

    Absolute calibration of the Pierre Auger Observatory fluorescence detectors uses a light source at the telescope aperture. The technique accounts for the combined effects of all detector components in a single measurement. The calibrated 2.5 m diameter light source fills the aperture, providing uniform illumination to each pixel. The known flux from the light source and the response of the acquisition system give the required calibration for each pixel. In the lab, light source uniformity is studied using CCD images and the intensity is measured relative to NIST-calibrated photodiodes. Overall uncertainties are presently 12%, and are dominated by systematics.

  2. Characterization of the DARA solar absolute radiometer

    NASA Astrophysics Data System (ADS)

    Finsterle, W.; Suter, M.; Fehlmann, A.; Kopp, G.

    2011-12-01

    The Davos Absolute Radiometer (DARA) prototype is an Electrical Substitution Radiometer (ESR) which has been developed as a successor of the PMO6 type on future space missions and ground based TSI measurements. The DARA implements an improved thermal design of the cavity detector and heat sink assembly to minimize air-vacuum differences and to maximize thermal symmetry of measuring and compensating cavity. The DARA also employs an inverted viewing geometry to reduce internal stray light. We will report on the characterization and calibration experiments which were carried out at PMOD/WRC and LASP (TRF).

  3. Absolute Priority for a Vehicle in VANET

    NASA Astrophysics Data System (ADS)

    Shirani, Rostam; Hendessi, Faramarz; Montazeri, Mohammad Ali; Sheikh Zefreh, Mohammad

    In today's world, traffic jams waste hundreds of hours of our life. This causes many researchers try to resolve the problem with the idea of Intelligent Transportation System. For some applications like a travelling ambulance, it is important to reduce delay even for a second. In this paper, we propose a completely infrastructure-less approach for finding shortest path and controlling traffic light to provide absolute priority for an emergency vehicle. We use the idea of vehicular ad-hoc networking to reduce the imposed travelling time. Then, we simulate our proposed protocol and compare it with a centrally controlled traffic light system.

  4. Development and validation of a segmentation-free polyenergetic algorithm for dynamic perfusion computed tomography.

    PubMed

    Lin, Yuan; Samei, Ehsan

    2016-07-01

    Dynamic perfusion imaging can provide the morphologic details of the scanned organs as well as the dynamic information of blood perfusion. However, due to the polyenergetic property of the x-ray spectra, beam hardening effect results in undesirable artifacts and inaccurate CT values. To address this problem, this study proposes a segmentation-free polyenergetic dynamic perfusion imaging algorithm (pDP) to provide superior perfusion imaging. Dynamic perfusion usually is composed of two phases, i.e., a precontrast phase and a postcontrast phase. In the precontrast phase, the attenuation properties of diverse base materials (e.g., in a thorax perfusion exam, base materials can include lung, fat, breast, soft tissue, bone, and metal implants) can be incorporated to reconstruct artifact-free precontrast images. If patient motions are negligible or can be corrected by registration, the precontrast images can then be employed as a priori information to derive linearized iodine projections from the postcontrast images. With the linearized iodine projections, iodine perfusion maps can be reconstructed directly without the influence of various influential factors, such as iodine location, patient size, x-ray spectrum, and background tissue type. A series of simulations were conducted on a dynamic iodine calibration phantom and a dynamic anthropomorphic thorax phantom to validate the proposed algorithm. The simulations with the dynamic iodine calibration phantom showed that the proposed algorithm could effectively eliminate the beam hardening effect and enable quantitative iodine map reconstruction across various influential factors. The error range of the iodine concentration factors ([Formula: see text]) was reduced from [Formula: see text] for filtered back-projection (FBP) to [Formula: see text] for pDP. The quantitative results of the simulations with the dynamic anthropomorphic thorax phantom indicated that the maximum error of iodine concentrations can be reduced from

  5. Luminal perfusion of isolated gastric glands.

    PubMed

    Waisbren, S J; Geibel, J; Boron, W F; Modlin, I M

    1994-04-01

    We have extended to rabbit gastric glands the technique for perfusing single isolated renal tubules. We isolated glands by hand dissection and used concentric glass pipettes to hold them and perfuse their lumina. Parietal cells (PCs), which tended to be located toward the gland opening, were identified by their pyramidal shape, large size, and autofluorescence. Chief cells (CCs) were identified by their round shape and smaller size. In some experiments, we perfused the lumen with hydroxypyrenetrisulfonate, a pH-sensitive fluorophore, at pH 7.4 and used digital image processing to monitor luminal pH (pH1). Solutions were buffered with N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid to pH 7.4 at 37 degrees C. With fast perfusion, we found no evidence of decreased pH1, even with stimulation by 10 microM carbachol. With slow perfusion, pH1 often fell below the dye's sensitive range (pH < 5), especially at low perfusate buffering power. In other experiments, we loaded cells with the pH-sensitive dye 2',7'-bis(2-carboxyethyl)-5(6)-carboxyfluorescein and monitored intracellular pH (pHi) in multiple individual PCs and CCs in a single gland. Mean pHi was 7.21 +/- 0.02 (n = 136 cells) for PCs and 7.27 +/- 0.03 (n = 103) for CCs. To examine the response to decreased pH1 and basolateral pH (pHb), we lowered pHb to 6.4 or lowered pH1 to 3.4 or 1.4. Lowering pHb to 6.4 for approximately 1 min caused pHi to fall reversibly by 0.39 +/- 0.05 (n = 53) in PCs and 0.58 +/- 0.03 (n = 50) in CCs. Lowering pH1 to 3.4 or 1.4 caused no significant pHi changes in PCs (n = 38 and 82) or in CCs (n = 44 and 77). Carbachol did not affect the response to changes in pH1 or pHb. We conclude that the apical surfaces of PCs and CCs are unusually resistant to extreme pH gradients.

  6. Is the Increased Septal Perfusion the Signal of Asymmetrical Septal Hypertrophy?

    PubMed

    Ozdemir, Semra; Tan, Yusuf Ziya; Gazi, Emine

    2016-09-01

    In this study, we have compared scintigraphic and echocardiographic data in order to investigate whether increased septal perfusion represents asymmetrical septal hypertrophy (ASH), which is a symptom followed in the scintigraphy of myocardial perfusion. The study consists of a total of 186 patients (120 females and 66 males with an average age of 59.45 ± 11.54 years) who had normal myocardial perfusion scintigraphy and echocardiography examinations. Statistical comparison of septal wall thickness measurements obtained from echocardiography and septal-to-lateral wall ratios (S/L ratio) was performed scintigraphically. Left ventricular mass values were obtained as both scintigraphic and echocardiographic data and their correlations were evaluated in order to assess the presence of left ventricular hypertrophy (LVH). In statistical analyses, the values of interventricular septal thickness in diastole (IVSd), left ventricle posterior wall thickness in diastole (LVPWd), left ventricle mass (LVM), and left ventricle mass index (LVMI) were found to be significantly higher in group 2 (S/L ratio >1) compared to group 1 (S/L ratio <1). In addition, S/L ratio is significantly correlated with echocardiographic IVSd, LVPWd, LVM, LVMI, and scintigraphic LVM (rest) values. Furthermore, echocardiographic LVM and LVMI values were significantly correlated with LVM and LVMI values obtained from scintigraphy. It should be known that increased S/L ratio that can be monitored during scintigraphic studies can be an indicator of septal hypertrophy and/or LVH, however, further examination and close follow-ups should be performed in necessary cases. PMID:27651739

  7. Is the Increased Septal Perfusion the Signal of Asymmetrical Septal Hypertrophy?

    PubMed Central

    Ozdemir, Semra; Tan, Yusuf Ziya; Gazi, Emine

    2016-01-01

    In this study, we have compared scintigraphic and echocardiographic data in order to investigate whether increased septal perfusion represents asymmetrical septal hypertrophy (ASH), which is a symptom followed in the scintigraphy of myocardial perfusion. The study consists of a total of 186 patients (120 females and 66 males with an average age of 59.45 ± 11.54 years) who had normal myocardial perfusion scintigraphy and echocardiography examinations. Statistical comparison of septal wall thickness measurements obtained from echocardiography and septal-to-lateral wall ratios (S/L ratio) was performed scintigraphically. Left ventricular mass values were obtained as both scintigraphic and echocardiographic data and their correlations were evaluated in order to assess the presence of left ventricular hypertrophy (LVH). In statistical analyses, the values of interventricular septal thickness in diastole (IVSd), left ventricle posterior wall thickness in diastole (LVPWd), left ventricle mass (LVM), and left ventricle mass index (LVMI) were found to be significantly higher in group 2 (S/L ratio >1) compared to group 1 (S/L ratio <1). In addition, S/L ratio is significantly correlated with echocardiographic IVSd, LVPWd, LVM, LVMI, and scintigraphic LVM (rest) values. Furthermore, echocardiographic LVM and LVMI values were significantly correlated with LVM and LVMI values obtained from scintigraphy. It should be known that increased S/L ratio that can be monitored during scintigraphic studies can be an indicator of septal hypertrophy and/or LVH, however, further examination and close follow-ups should be performed in necessary cases.

  8. Is the Increased Septal Perfusion the Signal of Asymmetrical Septal Hypertrophy?

    PubMed Central

    Ozdemir, Semra; Tan, Yusuf Ziya; Gazi, Emine

    2016-01-01

    In this study, we have compared scintigraphic and echocardiographic data in order to investigate whether increased septal perfusion represents asymmetrical septal hypertrophy (ASH), which is a symptom followed in the scintigraphy of myocardial perfusion. The study consists of a total of 186 patients (120 females and 66 males with an average age of 59.45 ± 11.54 years) who had normal myocardial perfusion scintigraphy and echocardiography examinations. Statistical comparison of septal wall thickness measurements obtained from echocardiography and septal-to-lateral wall ratios (S/L ratio) was performed scintigraphically. Left ventricular mass values were obtained as both scintigraphic and echocardiographic data and their correlations were evaluated in order to assess the presence of left ventricular hypertrophy (LVH). In statistical analyses, the values of interventricular septal thickness in diastole (IVSd), left ventricle posterior wall thickness in diastole (LVPWd), left ventricle mass (LVM), and left ventricle mass index (LVMI) were found to be significantly higher in group 2 (S/L ratio >1) compared to group 1 (S/L ratio <1). In addition, S/L ratio is significantly correlated with echocardiographic IVSd, LVPWd, LVM, LVMI, and scintigraphic LVM (rest) values. Furthermore, echocardiographic LVM and LVMI values were significantly correlated with LVM and LVMI values obtained from scintigraphy. It should be known that increased S/L ratio that can be monitored during scintigraphic studies can be an indicator of septal hypertrophy and/or LVH, however, further examination and close follow-ups should be performed in necessary cases. PMID:27651739

  9. Absolute Temperature Monitoring Using RF Radiometry in the MRI Scanner.

    PubMed

    El-Sharkawy, Abdel-Monem M; Sotiriadis, Paul P; Bottomley, Paul A; Atalar, Ergin

    2006-11-01

    Temperature detection using microwave radiometry has proven value for noninvasively measuring the absolute temperature of tissues inside the body. However, current clinical radiometers operate in the gigahertz range, which limits their depth of penetration. We have designed and built a noninvasive radiometer which operates at radio frequencies (64 MHz) with ∼100-kHz bandwidth, using an external RF loop coil as a thermal detector. The core of the radiometer is an accurate impedance measurement and automatic matching circuit of 0.05 Ω accuracy to compensate for any load variations. The radiometer permits temperature measurements with accuracy of ±0.1°K, over a tested physiological range of 28° C-40° C in saline phantoms whose electric properties match those of tissue. Because 1.5 T magnetic resonance imaging (MRI) scanners also operate at 64 MHz, we demonstrate the feasibility of integrating our radiometer with an MRI scanner to monitor RF power deposition and temperature dosimetry, obtaining coarse, spatially resolved, absolute thermal maps in the physiological range. We conclude that RF radiometry offers promise as a direct, noninvasive method of monitoring tissue heating during MRI studies and thereby providing an independent means of verifying patient-safe operation. Other potential applications include titration of hyper- and hypo-therapies. PMID:18026562

  10. Simulation of absolute amplitudes of ultrasound signals using equivalent circuits.

    PubMed

    Johansson, Jonny; Martinsson, Pär-Erik; Delsing, Jerker

    2007-10-01

    Equivalent circuits for piezoelectric devices and ultrasonic transmission media can be used to cosimulate electronics and ultrasound parts in simulators originally intended for electronics. To achieve efficient system-level optimization, it is important to simulate correct, absolute amplitude of the ultrasound signal in the system, as this determines the requirements on the electronics regarding dynamic range, circuit noise, and power consumption. This paper presents methods to achieve correct, absolute amplitude of an ultrasound signal in a simulation of a pulse-echo system using equivalent circuits. This is achieved by taking into consideration loss due to diffraction and the effect of the cable that connects the electronics and the piezoelectric transducer. The conductive loss in the transmission line that models the propagation media of the ultrasound pulse is used to model the loss due to diffraction. Results show that the simulated amplitude of the echo follows measured values well in both near and far fields, with an offset of about 10%. The use of a coaxial cable introduces inductance and capacitance that affect the amplitude of a received echo. Amplitude variations of 60% were observed when the cable length was varied between 0.07 m and 2.3 m, with simulations predicting similar variations. The high precision in the achieved results show that electronic design and system optimization can rely on system simulations alone. This will simplify the development of integrated electronics aimed at ultrasound systems. PMID:18019234

  11. Feasibility of quantitative lung perfusion by 4D CT imaging by a new dynamic-scanning protocol in an animal model

    NASA Astrophysics Data System (ADS)

    Wang, Yang; Goldin, Jonathan G.; Abtin, Fereidoun G.; Brown, Matt; McNitt-Gray, Mike

    2008-03-01

    The purpose of this study is to test a new dynamic Perfusion-CT imaging protocol in an animal model and investigate the feasibility of quantifying perfusion of lung parenchyma to perform functional analysis from 4D CT image data. A novel perfusion-CT protocol was designed with 25 scanning time points: the first at baseline and 24 scans after a bolus injection of contrast material. Post-contrast CT scanning images were acquired with a high sampling rate before the first blood recirculation and then a relatively low sampling rate until 10 minutes after administrating contrast agent. Lower radiation techniques were used to keep the radiation dose to an acceptable level. 2 Yorkshire swine with pulmonary emboli underwent this perfusion- CT protocol at suspended end inspiration. The software tools were designed to measure the quantitative perfusion parameters (perfusion, permeability, relative blood volume, blood flow, wash-in & wash-out enhancement) of voxel or interesting area of lung. The perfusion values were calculated for further lung functional analysis and presented visually as contrast enhancement maps for the volume being examined. The results show increased CT temporal sampling rate provides the feasibility of quantifying lung function and evaluating the pulmonary emboli. Differences between areas with known perfusion defects and those without perfusion defects were observed. In conclusion, the techniques to calculate the lung perfusion on animal model have potential application in human lung functional analysis such as evaluation of functional effects of pulmonary embolism. With further study, these techniques might be applicable in human lung parenchyma characterization and possibly for lung nodule characterization.

  12. Sentinel-2/MSI absolute calibration: first results

    NASA Astrophysics Data System (ADS)

    Lonjou, V.; Lachérade, S.; Fougnie, B.; Gamet, P.; Marcq, S.; Raynaud, J.-L.; Tremas, T.

    2015-10-01

    Sentinel-2 is an optical imaging mission devoted to the operational monitoring of land and coastal areas. It is developed in partnership between the European Commission and the European Space Agency. The Sentinel-2 mission is based on a satellites constellation deployed in polar sun-synchronous orbit. It will offer a unique combination of global coverage with a wide field of view (290km), a high revisit (5 days with two satellites), a high resolution (10m, 20m and 60m) and multi-spectral imagery (13 spectral bands in visible and shortwave infra-red domains). CNES is involved in the instrument commissioning in collaboration with ESA. This paper reviews all the techniques that will be used to insure an absolute calibration of the 13 spectral bands better than 5% (target 3%), and will present the first results if available. First, the nominal calibration technique, based on an on-board sun diffuser, is detailed. Then, we show how vicarious calibration methods based on acquisitions over natural targets (oceans, deserts, and Antarctica during winter) will be used to check and improve the accuracy of the absolute calibration coefficients. Finally, the verification scheme, exploiting photometer in-situ measurements over Lacrau plain, is described. A synthesis, including spectral coherence, inter-methods agreement and temporal evolution, will conclude the paper.

  13. Experimental results for absolute cylindrical wavefront testing

    NASA Astrophysics Data System (ADS)

    Reardon, Patrick J.; Alatawi, Ayshah

    2014-09-01

    Applications for Cylindrical and near-cylindrical surfaces are ever-increasing. However, fabrication of high quality cylindrical surfaces is limited by the difficulty of accurate and affordable metrology. Absolute testing of such surfaces represents a challenge to the optical testing community as cylindrical reference wavefronts are difficult to produce. In this paper, preliminary results for a new method of absolute testing of cylindrical wavefronts are presented. The method is based on the merging of the random ball test method with the fiber optic reference test. The random ball test assumes a large number of interferograms of a good quality sphere with errors that are statistically distributed such that the average of the errors goes to zero. The fiber optic reference test utilizes a specially processed optical fiber to provide a clean high quality reference wave from an incident line focus from the cylindrical wave under test. By taking measurements at different rotation and translations of the fiber, an analogous procedure can be employed to determine the quality of the converging cylindrical wavefront with high accuracy. This paper presents and discusses the results of recent tests of this method using a null optic formed by a COTS cylindrical lens and a free-form polished corrector element.

  14. Absolute Electron Extraction Efficiency of Liquid Xenon

    NASA Astrophysics Data System (ADS)

    Kamdin, Katayun; Mizrachi, Eli; Morad, James; Sorensen, Peter

    2016-03-01

    Dual phase liquid/gas xenon time projection chambers (TPCs) currently set the world's most sensitive limits on weakly interacting massive particles (WIMPs), a favored dark matter candidate. These detectors rely on extracting electrons from liquid xenon into gaseous xenon, where they produce proportional scintillation. The proportional scintillation from the extracted electrons serves to internally amplify the WIMP signal; even a single extracted electron is detectable. Credible dark matter searches can proceed with electron extraction efficiency (EEE) lower than 100%. However, electrons systematically left at the liquid/gas boundary are a concern. Possible effects include spontaneous single or multi-electron proportional scintillation signals in the gas, or charging of the liquid/gas interface or detector materials. Understanding EEE is consequently a serious concern for this class of rare event search detectors. Previous EEE measurements have mostly been relative, not absolute, assuming efficiency plateaus at 100%. I will present an absolute EEE measurement with a small liquid/gas xenon TPC test bed located at Lawrence Berkeley National Laboratory.

  15. Why to compare absolute numbers of mitochondria.

    PubMed

    Schmitt, Sabine; Schulz, Sabine; Schropp, Eva-Maria; Eberhagen, Carola; Simmons, Alisha; Beisker, Wolfgang; Aichler, Michaela; Zischka, Hans

    2014-11-01

    Prompted by pronounced structural differences between rat liver and rat hepatocellular carcinoma mitochondria, we suspected these mitochondrial populations to differ massively in their molecular composition. Aiming to reveal these mitochondrial differences, we came across the issue on how to normalize such comparisons and decided to focus on the absolute number of mitochondria. To this end, fluorescently stained mitochondria were quantified by flow cytometry. For rat liver mitochondria, this approach resulted in mitochondrial protein contents comparable to earlier reports using alternative methods. We determined similar protein contents for rat liver, heart and kidney mitochondria. In contrast, however, lower protein contents were determined for rat brain mitochondria and for mitochondria from the rat hepatocellular carcinoma cell line McA 7777. This result challenges mitochondrial comparisons that rely on equal protein amounts as a typical normalization method. Exemplarily, we therefore compared the activity and susceptibility toward inhibition of complex II of rat liver and hepatocellular carcinoma mitochondria and obtained significant discrepancies by either normalizing to protein amount or to absolute mitochondrial number. Importantly, the latter normalization, in contrast to the former, demonstrated a lower complex II activity and higher susceptibility toward inhibition in hepatocellular carcinoma mitochondria compared to liver mitochondria. These findings demonstrate that solely normalizing to protein amount may obscure essential molecular differences between mitochondrial populations.

  16. Absolute Proper Motions of Southern Globular Clusters

    NASA Astrophysics Data System (ADS)

    Dinescu, D. I.; Girard, T. M.; van Altena, W. F.

    1996-05-01

    Our program involves the determination of absolute proper motions with respect to galaxies for a sample of globular clusters situated in the southern sky. The plates cover a 6(deg) x 6(deg) area and are taken with the 51-cm double astrograph at Cesco Observatory in El Leoncito, Argentina. We have developed special methods to deal with the modelling error of the plate transformation and we correct for magnitude equation using the cluster stars. This careful astrometric treatment leads to accuracies of from 0.5 to 1.0 mas/yr for the absolute proper motion of each cluster, depending primarily on the number of measurable cluster stars which in turn is related to the cluster's distance. Space velocities are then derived which, in association with metallicities, provide key information for the formation scenario of the Galaxy, i.e. accretion and/or dissipational collapse. Here we present results for NGC 1851, NGC 6752, NGC 6584, NGC 6362 and NGC 288.

  17. Relational versus absolute representation in categorization.

    PubMed

    Edwards, Darren J; Pothos, Emmanuel M; Perlman, Amotz

    2012-01-01

    This study explores relational-like and absolute-like representations in categorization. Although there is much evidence that categorization processes can involve information about both the particular physical properties of studied instances and abstract (relational) properties, there has been little work on the factors that lead to one kind of representation as opposed to the other. We tested 370 participants in 6 experiments, in which participants had to classify new items into predefined artificial categories. In 4 experiments, we observed a predominantly relational-like mode of classification, and in 2 experiments we observed a shift toward an absolute-like mode of classification. These results suggest 3 factors that promote a relational-like mode of classification: fewer items per group, more training groups, and the presence of a time delay. Overall, we propose that less information about the distributional properties of a category or weaker memory traces for the category exemplars (induced, e.g., by having smaller categories or a time delay) can encourage relational-like categorization.

  18. Transient absolute robustness in stochastic biochemical networks.

    PubMed

    Enciso, German A

    2016-08-01

    Absolute robustness allows biochemical networks to sustain a consistent steady-state output in the face of protein concentration variability from cell to cell. This property is structural and can be determined from the topology of the network alone regardless of rate parameters. An important question regarding these systems is the effect of discrete biochemical noise in the dynamical behaviour. In this paper, a variable freezing technique is developed to show that under mild hypotheses the corresponding stochastic system has a transiently robust behaviour. Specifically, after finite time the distribution of the output approximates a Poisson distribution, centred around the deterministic mean. The approximation becomes increasingly accurate, and it holds for increasingly long finite times, as the total protein concentrations grow to infinity. In particular, the stochastic system retains a transient, absolutely robust behaviour corresponding to the deterministic case. This result contrasts with the long-term dynamics of the stochastic system, which eventually must undergo an extinction event that eliminates robustness and is completely different from the deterministic dynamics. The transiently robust behaviour may be sufficient to carry out many forms of robust signal transduction and cellular decision-making in cellular organisms. PMID:27581485

  19. Simultaneous acquisition of perfusion and permeability from corrected relaxation rates with dynamic susceptibility contrast dual gradient echo.

    PubMed

    Kim, Eun-Ju; Kim, Dae-Hong; Lee, Sang Hoon; Huh, Yong-Min; Song, Ho-Taek; Suh, Jin-Suck

    2004-04-01

    This study compared two methods, corrected (separation of T(1) and T(2)* effects) and uncorrected, in order to determine the suitability of the perfusion and permeability measures through Delta R(2)* and Delta R(1) analyses. A dynamic susceptibility contrast dual gradient echo (DSC-DGE) was used to image the fixed phantoms and flow phantoms (Sephadex perfusion phantoms and dialyzer phantom for the permeability measurements). The results confirmed that the corrected relaxation rate was linearly proportional to gadolinium-diethyltriamine pentaacetic acid (Gd-DTPA) concentration, whereas the uncorrected relaxation rate did not in the fixed phantom and simulation experiments. For the perfusion measurements, it was found that the correction process was necessary not only for the Delta R(1) time curve but also for the Delta R(2)* time curve analyses. Perfusion could not be measured without correcting the Delta R(2)* time curve. The water volume, which was expressed as the perfusion amount, was found to be closer to the theoretical value when using the corrected Delta R(1) curve in the calculations. However, this may occur in the low concentration of Gd-DTPA in tissue used in this study. For the permeability measurements based on the two-compartment model, the permeability factor (k(ev); e = extravascular, v = vascular) from the outside to the inside of the hollow fibers was greater in the corrected Delta R(1) method than in the uncorrected Delta R(1) method. The differences between the corrected and the uncorrected Delta R(1) values were confirmed by the simulation experiments. In conclusion, this study proposes that the correction for the relaxation rates, Delta R(2)* and Delta R(1), is indispensable in making accurate perfusion and permeability measurements, and that DSC-DGE is a useful method for obtaining information on perfusion and permeability, simultaneously. PMID:15062926

  20. Imaging of drug effects in perfused liver

    NASA Astrophysics Data System (ADS)

    Dammann, Marc; Mahlke, Christine; Kessler, Manfred D.

    2002-06-01

    Various medications affect the systemic circulation and organ oxygenation causing dilatation or constriction of blood vessels. Imminent liver failure can be generated by reduced perfusion of different origins. In this case hepatic vasodilatation would be a therapeutical approach for improving patient's condition. Our examinations have been performed in perfused rat liver using spectrometric methods. Two defined areas of the liver were measured punctually. We compared the influence of Tetramethylpyrazine and Glyceroltrinitrate on hemoglobin oxygenation (HbO2) and concentration (Hb-conc.) in rat liver after application of Norepinephrine, which caused a mid decrease in hemoglobin oxygenation of 47,9 %. Both increased the HbO2, but differed from each other in manner of time and extent. Tetramethylpyrazine indicated a longer effect than Glyceroltrinitrate. Furthermore, HbO2 and Hb-conc. showed a conversed relation. From the shape of the absorption spectra it is possible to derive the oxygenation of hemoglobin.

  1. Clinical Decision Making With Myocardial Perfusion Imaging in Patients With Known or Suspected Coronary Artery Disease

    PubMed Central

    Cremer, Paul; Hachamovitch, Rory; Tamarappoo, Balaji

    2015-01-01

    Myocardial perfusion imaging (MPI) to diagnose coronary artery disease (CAD) is best performed in patients with intermediate pretest likelihood of disease; unfortunately, pretest likelihood is often overestimated, resulting in the inappropriate use of perfusion imaging. A good functional capacity often predicts low risk, and MPI for diagnosing CAD should be reserved for individuals with poor exercise capacity, abnormal resting electrocardiography, or an intermediate or high probability of CAD. With respect to anatomy-based testing, coronary CT angiography has a good negative predictive value, but stenosis severity correlates poorly with ischemia. Therefore decision making with respect to revascularization may be limited when a purely noninvasive anatomical test is used. Regarding perfusion imaging, the diagnostic accuracies of SPECT, PET, and cardiac magnetic resonance are similar, though fewer studies are available with cardiac magnetic resonance. PET coronary flow reserve may offer a negative predictive value sufficiently high to exclude severe CAD such that patients with mild to moderate reversible perfusion defects can forego invasive angiography. In addition, combined anatomical and perfusion-based imaging may eventually offer a definitive evaluation for diagnosing CAD, even in higher risk patients. Any remarkable findings on single-photon emission computed tomography and PET MPI studies are valuable for prognostication. Furthermore, assessment of myocardial blood flow with PET is particularly powerful for prognostication as it reflects the end result of many processes that lead to atherosclerosis. Decision making with respect to revascularization is limited for cardiac MRI and PET MPI. In contrast, retrospective radionuclide studies have identified an ischemic threshold, but randomized trials are needed. In patients with at least moderately reduced left ventricular systolic function, viable myocardium as assessed by PET or MRI, appears to identify patients

  2. Automatic detection of CT perfusion datasets unsuitable for analysis due to head movement of acute ischemic stroke patients.

    PubMed

    Fahmi, Fahmi; Marquering, Henk A; Streekstra, Geert J; Beenen, Ludo F M; Janssen, Natasja N Y; Majoie, Charles B L; van Bavel, Ed

    2014-01-01

    Head movement during brain Computed Tomography Perfusion (CTP) can deteriorate perfusion analysis quality in acute ischemic stroke patients. We developed a method for automatic detection of CTP datasets with excessive head movement, based on 3D image-registration of CTP, with non-contrast CT providing transformation parameters. For parameter values exceeding predefined thresholds, the dataset was classified as 'severely moved'. Threshold values were determined by digital CTP phantom experiments. The automated selection was compared to manual screening by 2 experienced radiologists for 114 brain CTP datasets. Based on receiver operator characteristics, optimal thresholds were found of respectively 1.0°, 2.8° and 6.9° for pitch, roll and yaw, and 2.8 mm for z-axis translation. The proposed method had a sensitivity of 91.4% and a specificity of 82.3%. This method allows accurate automated detection of brain CTP datasets that are unsuitable for perfusion analysis. PMID:24691387

  3. The evolution of perfusion education in America.

    PubMed

    Toomasian, John M; Searles, Bruce; Kurusz, Mark

    2003-07-01

    Clinical cardiopulmonary perfusion has evolved significantly during its 50 years. The science, technology and educational processes related to cardiopulmonary bypass have undergone continual change and metamorphosis. Perfusionists were initially trained on the job or in the laboratory, but with the advent of myocardial revascularization and the explosion in cardiac surgery, the need for formal educational training programs became apparent. The American Society of Extracorporeal Technology began the arduous processes of credentialing and developing certification guidelines that have continued under the American Board of Cardiovascular Perfusion. Licensure has also been adopted in many states during the past 10 years where nearly 50% of all perfusionists are covered by some legislative act. One additonal challenge has been developing minimal standards in which perfusionists practice. The initial standards included the use of a checklist and have evolved to monitoring and recording the significant events and parameters of each clinical procedure. The education of perfusionists will continue to be a challenge related primarily to reduced fiscal resources, the applicant pool and the ever-changing demands for extracorporeal circulation services. According to demographic and census information, it is expected the overall number of cardiovascular interventions will increase dramatically towards the latter end of the current decade in the US. The question arises as to what role perfusionists will play, as treatment strategies continue to change. If the number of education programs and new graduates continue to decline, the total number of perfusionists will decline, especially as many senior perfusionists leave the field or retire. It may be difficult to predict the total number of cardiovascular interventions that will be required in the next several years. However, if the total number of cardiovascular interventions that require perfusion services increase as a function

  4. Inhomogeneity of pulmonary perfusion during sustained microgravity

    NASA Technical Reports Server (NTRS)

    Prisk, G. Kim; Guy, Harold J. B.; Elliott, Ann R.; West, John B.

    1994-01-01

    The effects of gravity on the inhomogeneity of pulmonary perfusion in man were studied by performing hyperventilation-breathhold single-breath measurements before, during and after 9 days of continuous exposure to microgravity. In microgravity the indicators of inhomogeneity of perfusion, especially the size of cardiogenic oscillations in expired CO2 and the height of phase 4, were both markedly reduced. Cardiogenic oscillations were reduced to approximately 60 of their preflight standing size, while the height of phase 4 was between 0 and -8% (a terminal fall became a small terminal rise) of preflights standing. The terminal change in CO2 was nearly abolished in microgravity indicating more uniformity of blood flow between lung units that close at the end of expiration and units that remain open. This may result from the disappearance of gravity-dependent topographical inequality of blood flow. The residual cardiographic oscillations in expired CO2 imply a persisting inhomogeneity of perfusion in the absence of gravity at a level larger than acinar.

  5. Noncontact blood perfusion mapping in clinical applications

    NASA Astrophysics Data System (ADS)

    Iakovlev, Dmitry; Dwyer, Vincent; Hu, Sijung; Silberschmidt, Vadim

    2016-04-01

    Non-contact imaging photoplethysmography (iPPG) to detect pulsatile blood microcirculation in tissue has been selected as a successor to low spatial resolution and slow scanning blood perfusion techniques currently employed by clinicians. The proposed iPPG system employs a novel illumination source constructed of multiple high power LEDs with narrow spectral emission, which are temporally modulated and synchronised with a high performance sCMOS sensor. To ensure spectrum stability and prevent thermal wavelength drift due to junction temperature variations, each LED features a custom-designed thermal management system to effectively dissipate generated heat and auto-adjust current flow. The use of a multi-wavelength approach has resulted in simultaneous microvascular perfusion monitoring at various tissue depths, which is an added benefit for specific clinical applications. A synchronous detection algorithm to extract weak photoplethysmographic pulse-waveforms demonstrated robustness and high efficiency when applied to even small regions of 5 mm2. The experimental results showed evidences that the proposed system could achieve noticeable accuracy in blood perfusion monitoring by creating complex amplitude and phase maps for the tissue under examination.

  6. Perfusion computed tomography in renal cell carcinoma

    PubMed Central

    Das, Chandan J; Thingujam, Usha; Panda, Ananya; Sharma, Sanjay; Gupta, Arun Kumar

    2015-01-01

    Various imaging modalities are available for the diagnosis, staging and response evaluation of patients with renal cell carcinoma (RCC). While contrast enhanced computed tomography (CT) is used as the standard of imaging for size, morphological evaluation and response assessment in RCC, a new functional imaging technique like perfusion CT (pCT), goes down to the molecular level and provides new perspectives in imaging of RCC. pCT depicts regional tumor perfusion and vascular permeability which are indirect parameters of tumor angiogenesis and thereby provides vital information regarding tumor microenvironment. Also response evaluation using pCT may predate the size criteria used in Response Evaluation Criteria in Solid Tumors, as changes in the perfusion occurs earlier following tissue kinase inhibitors before any actual change in size. This may potentially help in predicting prognosis, better selection of therapy and more accurate and better response evaluation in patients with RCC. This article describes the techniques and role of pCT in staging and response assessment in patients with RCCs. PMID:26217456

  7. CT perfusion: principles, applications, and problems

    NASA Astrophysics Data System (ADS)

    Lee, Ting-Yim

    2004-10-01

    The fast scanning speed of current slip-ring CT scanners has enabled the development of perfusion imaging techniques with intravenous injection of contrast medium. In a typical CT perfusion study, contrast medium is injected and rapid scanning at a frequency of 1-2 Hz is used to monitor the first circulation of the injected contrast medium through a 1-2 cm thick slab of tissue. From the acquired time-series of CT images, arteries can be identified within the tissue slab to derive the arterial contrast concentration curve, Ca(t) while each individual voxel produces a tissue residue curve, Q(t) for the corresponding tissue region. Deconvolution between the measured Ca(t) and Q(t) leads to the determination of cerebral blood flow (CBF), cerebral blood volume (CBV) and mean transit time (MTT) in brain studies. In this presentation, an important application of CT perfusion in acute stroke studies - the identification of the ischemic penumbra via the CBF/CBV mismatch and factors affecting the quantitative accuracy of deconvolution, including partial volume averaging, arterial delay and dispersion are discussed.

  8. Regulation of skeletal muscle perfusion during exercise

    NASA Technical Reports Server (NTRS)

    Delp, M. D.; Laughlin, M. H.

    1998-01-01

    For exercise to be sustained, it is essential that adequate blood flow be provided to skeletal muscle. The local vascular control mechanisms involved in regulating muscle perfusion during exercise include metabolic control, endothelium-mediated control, propagated responses, myogenic control, and the muscle pump. The primary determinant of muscle perfusion during sustained exercise is the metabolic rate of the muscle. Metabolites from contracting muscle diffuse to resistance arterioles and act directly to induce vasodilation, or indirectly to inhibit noradrenaline release from sympathetic nerve endings and oppose alpha-adrenoreceptor-mediated vasoconstriction. The vascular endothelium also releases vasodilator substances (e.g., prostacyclin and nitric oxide) that are prominent in establishing basal vascular tone, but these substances do not appear to contribute to the exercise hyperemia in muscle. Endothelial and smooth muscle cells may also be involved in propagating vasodilator signals along arterioles to parent and daughter vessels. Myogenic autoregulation does not appear to be involved in the exercise hyperemia in muscle, but the rhythmic propulsion of blood from skeletal muscle veins facilitates venous return to the heart and muscle perfusion. It appears that the primary determinants of sustained exercise hyperemia in skeletal muscle are metabolic vasodilation and increased vascular conductance via the muscle pump. Additionally, sympathetic neural control is important in regulating muscle blood flow during exercise.

  9. The "kidney-liver" multiorgan ex vivo perfused model improves the circuit's biochemical milieu during perfusion compared to the "liver-kidney" counterpart.

    PubMed

    Chung, Wen Yuan; Gravante, Gianpiero; Eltweri, Amar; Sorge, Roberto; Ong, Seok Ling; Pollard, Cristina; Metcalfe, Mathew; Dennison, Ashley

    2015-06-01

    The multiorgan ex vivo perfused liver-kidney model allows studying the hepatic pathophysiology and purifying waste products. We tested if the addition of the kidney first followed by the liver (KL circuit) produces better results compared to the classic liver-first approach (LK). Intact livers and kidneys were obtained post mortem from ten female domestic white pigs, five experiments were conducted with the KL circuit and five with the LK. Bile, urine production, arterial blood gases, glucose, renal and liver tests were collected hourly during the perfusions. The KL circuit had values more close to physiological ranges, more stable over time and showed less variability compared to the LK circuit for urine production, glucose, PH, anion gap, lactate, urea, sodium, potassium and Alanine Transaminase (ANOVA test for repeated measures p < 0.05). The KL circuit produced a more physiological and reliable biochemical milieu.

  10. Evaluation of perfusion-related and true diffusion in vertebral bone marrow: a preliminary study.

    PubMed

    Ohno, Naoki; Miyati, Tosiaki; Kasai, Harumasa; Arai, Nobuyuki; Kawano, Makoto; Shibamoto, Yuta; Kobayashi, Satoshi; Gabata, Toshifumi; Matsui, Osamu

    2015-01-01

    Our aim in this study was to obtain noninvasively more detailed information on perfusion and diffusion in vertebral bone marrow. We analyzed two diffusion components using a biexponential function. Eleven healthy volunteers were examined. By a 1.5-T MRI, we performed single-shot diffusion magnetic resonance imaging to acquire diffusion-weighted images (DWIs) with multiple b values. We determined perfusion-related diffusion and true diffusion coefficients (D* and D), the fraction of the perfusion-related diffusion component (F), and the apparent diffusion coefficient (ADC) in the lumbar vertebral body. Then, we compared these diffusion parameters with the bone mineral density (BMD) obtained with dual-energy X-ray absorptiometry. Moreover, the fat fraction (FF) of the bone marrow was calculated by use of double gradient-echo images with and without spectral adiabatic inversion recovery in the same subject. The BMD showed a significant positive correlation with D*, whereas there was no significant correlation between the other diffusion parameters and BMD. There was a negative correlation between the D or ADC and FF, although no correlation was found between D* or F and FF. Diffusion analysis with a biexponential function made it possible to obtain detailed information on bone perfusion and diffusion in healthy young volunteers.

  11. Three-dimensional first-pass myocardial perfusion MRI using a stack-of-spirals acquisition

    PubMed Central

    Shin, Taehoon; Nayak, Krishna S.; Santos, Juan M.; Nishimura, Dwight G.; Hu, Bob S.; McConnell, Michael V.

    2014-01-01

    Three-dimensional (3D) cardiac magnetic resonance (CMR) perfusion imaging is promising for the precise sizing of defects and for providing high perfusion contrast, but remains an experimental approach primarily due to the need for large-dimensional encoding, which, for traditional 3DFT imaging, requires either impractical acceleration factors or sacrifices in spatial resolution. We demonstrated the feasibility of rapid 3D CMR perfusion imaging using a stack-of-spirals acquisition accelerated by non-Cartesian k-t SENSE, which enables entire myocardial coverage with an in-plane resolution of 2.4 mm. The optimal under-sampling pattern was employed to achieve the largest separation between true and aliased signals, which is a pre-requisite for k-t SENSE reconstruction. Flip angle and saturation recovery time were chosen to ensure negligible magnetization variation during the transient data acquisition. We compared the proposed 3D perfusion method with the standard 2DFT approach by consecutively acquiring both data during each R-R interval in cardiac patients. The mean and standard deviation of the correlation coefficients between time intensity curves (TICs) of 3D vs 2DFT were 0.94 and 0.06 across seven subjects. The linear correlation between the two sets of upslope values was significant (r=0.78, P<0.05). PMID:22556062

  12. PROTOPLASMIC POTENTIALS IN HALICYSTIS : IV. VACUOLAR PERFUSION WITH ARTIFICIAL SAP AND SEA WATER.

    PubMed

    Blinks, L R

    1935-01-20

    Perfusion of the vacuole of living cells of Halicystis is described, the method employing two longitudinally fused capillaries as entrance and exit tubes. Natural sap, artificial sap, and sea water have been successfully perfused, with various additions and deficiencies, within the limits of physiological balance. In H. ovalis the P.D. remains positive and scarcely reduced in value when normal sea water, at pH 8.1, is perfused in the vacuole. In H. Osterhoutii the P.D. reverses in sign when the perfused solution has a higher pH than 6.5. In both cases a large P.D. persists when the solutions are the same on both sides of the protoplasm. In the absence of external gradients, there must be some internal gradient or asymmetry of the protoplasm itself to account for the P.D. Since appreciable currents are produced, there must be some metabolic activity as a source of energy. The higher normal P.D. in H. ovalis is not due to the higher KCl content of its sap (as earlier suggested by the author) since it persists nearly unchanged when sea water is substituted for sap.

  13. Ventilation-perfusion imaging in evaluating regional lung function in nonpenetrating injury to the chest.

    PubMed

    Van Eeden, S F; Klopper, J F; Alheit, B; Bardin, P G

    1989-03-01

    The extent of chest wall and lung injury after nonpenetrating injury to the chest (NIC) determine how aggressive and invasive management modalities should be. We investigated the value of ventilation (133Xe) and perfusion (99mTc) studies as indicators of extent of lung injury in 28 patients with moderate to severe unilateral NIC. The ventilation-perfusion (V/Q) abnormalities were compared with parameters conventionally used to evaluate NIC. All studies were carried out within 24 h of NIC and repeated 24 h later. Ventilation (p less than 0.001) and perfusion (p less than 0.01) abnormalities were more extensive soon after NIC than suggested by chest roentgenograms. Chest x-ray film changes lagged behind V/Q changes on admission and also after 24 h. The extent of ventilation, perfusion, and chest x-ray film abnormalities on admission were all predictors of increased morbidity. V/Q studies may be useful to define the extent as well as the changes in regional lung function following NIC.

  14. Assessment of the myocardial perfusion pattern in patients with multivessel coronary artery disease

    SciTech Connect

    Iskandrian, A.S.; Hakki, A.H.; Segal, B.L.; Kane, S.A.; Amenta, A.

    1983-11-01

    A total of 42 symptomatic patients with coronary artery disease involving two or three vessels were studied using exercise thallium-201 myocardial scintigraphy. Qualitative analysis of the images predicted multivessel disease in 75% of the patients with two-vessel disease and in 82% of the patients with three-vessel disease. Quantitative analysis of the size of the perfusion defect indicated that approximately 40% of the left ventricular perimeter showed abnormal perfusion pattern during stress in these patients, and there was no significant difference in the size of the defect in patients with two-vessel disease or three-vessel disease (41 +/- 17% vs 42 +/- 14%, respectively, mean +/- SD). The exercise heart rate, exercise ECG response, and severity of narrowing did not correlate with the size of the perfusion defect. Patients with anterior infarction had larger defects in the distribution of the left anterior descending artery than those without infarction. Collaterals offered partial protection during exercise only when they were not jeopardized. This study confirms the value of qualitative analysis of exercise thallium-201 imaging in predicting multivessel disease, and describes a simple method of assessing the extent of perfusion abnormalities during stress in patients with multivessel disease. The results may be important in patient management and prognosis.

  15. An absolute scale for measuring the utility of money

    NASA Astrophysics Data System (ADS)

    Thomas, P. J.

    2010-07-01

    Measurement of the utility of money is essential in the insurance industry, for prioritising public spending schemes and for the evaluation of decisions on protection systems in high-hazard industries. Up to this time, however, there has been no universally agreed measure for the utility of money, with many utility functions being in common use. In this paper, we shall derive a single family of utility functions, which have risk-aversion as the only free parameter. The fact that they return a utility of zero at their low, reference datum, either the utility of no money or of one unit of money, irrespective of the value of risk-aversion used, qualifies them to be regarded as absolute scales for the utility of money. Evidence of validation for the concept will be offered based on inferential measurements of risk-aversion, using diverse measurement data.

  16. Absolute stress measurements at the rangely anticline, Northwestern Colorado

    USGS Publications Warehouse

    de la Cruz, R. V.; Raleigh, C.B.

    1972-01-01

    Five different methods of measuring absolute state of stress in rocks in situ were used at sites near Rangely, Colorado, and the results compared. For near-surface measurements, overcoring of the borehole-deformation gage is the most convenient and rapid means of obtaining reliable values for the magnitude and direction of the state of stress in rocks in situ. The magnitudes and directions of the principal stresses are compared to the geologic features of the different areas of measurement. The in situ stresses are consistent in orientation with the stress direction inferred from the earthquake focal-plane solutions and existing joint patterns but inconsistent with stress directions likely to have produced the Rangely anticline. ?? 1972.

  17. First derivative versus absolute spectral reflectance of citrus varieties

    NASA Astrophysics Data System (ADS)

    Blazquez, Carlos H.; Nigg, H. N.; Hedley, Lou E.; Ramos, L. E.; Sorrell, R. W.; Simpson, S. E.

    1996-06-01

    Spectral reflectance measurements from 400 to 800 nm were taken from immature and mature leaves of grapefruit ('McCarty' and 'Rio Red'), 'Minneola' tangelo, 'Satsuma' mandarin, 'Dancy' tangerine, 'Nagami' oval kumquat, and 'Valencia' sweet orange, at the Florida Citrus Arboretum, Division of Plant Industry, Winter Haven, Florida. Immature and mature leaves of 'Minneola' tangelo had greater percent reflectance in the 400 to 800 nm range than the other varieties and leaf ages measured. The slope of the citrus spectral curves in the 800 nm range was not as sharp as conventional spectrometers, but had a much higher reflectance value than those obtained with a DK-2 spectrometer. Statistical analyses of absolute spectral data yielded significant differences between mature and immature leaves and between varieties. First derivative data analyses did not yield significant differences between varieties.

  18. Absolute Radiation Measurements in Earth and Mars Entry Conditions

    NASA Technical Reports Server (NTRS)

    Cruden, Brett A.

    2014-01-01

    This paper reports on the measurement of radiative heating for shock heated flows which simulate conditions for Mars and Earth entries. Radiation measurements are made in NASA Ames' Electric Arc Shock Tube at velocities from 3-15 km/s in mixtures of N2/O2 and CO2/N2/Ar. The technique and limitations of the measurement are summarized in some detail. The absolute measurements will be discussed in regards to spectral features, radiative magnitude and spatiotemporal trends. Via analysis of spectra it is possible to extract properties such as electron density, and rotational, vibrational and electronic temperatures. Relaxation behind the shock is analyzed to determine how these properties relax to equilibrium and are used to validate and refine kinetic models. It is found that, for some conditions, some of these values diverge from non-equilibrium indicating a lack of similarity between the shock tube and free flight conditions. Possible reasons for this are discussed.

  19. A direct comparison of the sensitivity of CT and MR cardiac perfusion using a myocardial perfusion phantom

    PubMed Central

    Otton, James; Morton, Geraint; Schuster, Andreas; Bigalke, Boris; Marano, Riccardo; Olivotti, Luca; Nagel, Eike; Chiribiri, Amedeo

    2013-01-01

    Background Direct comparison of CT and magnetic resonance (MR) perfusion techniques has been limited and in vivo assessment is affected by physiological variability, timing of image acquisition, and parameter selection. Objective We precisely compared high-resolution k-t SENSE MR cardiac perfusion at 3 T with single-phase CT perfusion (CTP) under identical imaging conditions. Methods We used a customized MR imaging and CT compatible dynamic myocardial perfusion phantom to represent the human circulation. CT perfusion studies were performed with a Philips iCT (256 slice) CT, with isotropic resolution of 0.6 mm3. MR perfusion was performed with k-t SENSE acceleration at 3 T and spatial resolution of 1.2 × 1.2 × 10 mm. The image contrast between normal and underperfused myocardial compartments was quantified at various perfusion and photon energy settings. Noise estimates were based on published clinical data. Results Contrast by CTP highly depends on photon energy and also timing of imaging within the myocardial perfusion upslope. For an identical myocardial perfusion deficit, the native image contrast-to-noise ratio (CNR) generated by CT and MR are similar. If slice averaging is used, the CNR of a perfusion deficit is expected to be greater for CTP than MR perfusion (MRP). Perfect timing during single time point CTP imaging is difficult to achieve, and CNR by CT decreases by 24%–31% two seconds from the optimal imaging time point. Although single-phase CT perfusion offers higher spatial resolution, MRP allows multiple time point sampling and quantitative analysis. Conclusion The ability of CTP and current optimal MRP techniques to detect simulated myocardial perfusion deficits is similar. PMID:23622506

  20. Use of Absolute and Comparative Performance Feedback in Absolute and Comparative Judgments and Decisions

    ERIC Educational Resources Information Center

    Moore, Don A.; Klein, William M. P.

    2008-01-01

    Which matters more--beliefs about absolute ability or ability relative to others? This study set out to compare the effects of such beliefs on satisfaction with performance, self-evaluations, and bets on future performance. In Experiment 1, undergraduate participants were told they had answered 20% correct, 80% correct, or were not given their…

  1. Towards robust deconvolution of low-dose perfusion CT: Sparse perfusion deconvolution using online dictionary learning

    PubMed Central

    Fang, Ruogu; Chen, Tsuhan; Sanelli, Pina C.

    2014-01-01

    Computed tomography perfusion (CTP) is an important functional imaging modality in the evaluation of cerebrovascular diseases, particularly in acute stroke and vasospasm. However, the post-processed parametric maps of blood flow tend to be noisy, especially in low-dose CTP, due to the noisy contrast enhancement profile and the oscillatory nature of the results generated by the current computational methods. In this paper, we propose a robust sparse perfusion deconvolution method (SPD) to estimate cerebral blood flow in CTP performed at low radiation dose. We first build a dictionary from high-dose perfusion maps using online dictionary learning and then perform deconvolution-based hemodynamic parameters estimation on the low-dose CTP data. Our method is validated on clinical data of patients with normal and pathological CBF maps. The results show that we achieve superior performance than existing methods, and potentially improve the differentiation between normal and ischemic tissue in the brain. PMID:23542422

  2. MO-G-18C-05: Real-Time Prediction in Free-Breathing Perfusion MRI

    SciTech Connect

    Song, H; Liu, W; Ruan, D; Jung, S; Gach, M

    2014-06-15

    Purpose: The aim is to minimize frame-wise difference errors caused by respiratory motion and eliminate the need for breath-holds in magnetic resonance imaging (MRI) sequences with long acquisitions and repeat times (TRs). The technique is being applied to perfusion MRI using arterial spin labeling (ASL). Methods: Respiratory motion prediction (RMP) using navigator echoes was implemented in ASL. A least-square method was used to extract the respiratory motion information from the 1D navigator. A generalized artificial neutral network (ANN) with three layers was developed to simultaneously predict 10 time points forward in time and correct for respiratory motion during MRI acquisition. During the training phase, the parameters of the ANN were optimized to minimize the aggregated prediction error based on acquired navigator data. During realtime prediction, the trained ANN was applied to the most recent estimated displacement trajectory to determine in real-time the amount of spatial Results: The respiratory motion information extracted from the least-square method can accurately represent the navigator profiles, with a normalized chi-square value of 0.037±0.015 across the training phase. During the 60-second training phase, the ANN successfully learned the respiratory motion pattern from the navigator training data. During real-time prediction, the ANN received displacement estimates and predicted the motion in the continuum of a 1.0 s prediction window. The ANN prediction was able to provide corrections for different respiratory states (i.e., inhalation/exhalation) during real-time scanning with a mean absolute error of < 1.8 mm. Conclusion: A new technique enabling free-breathing acquisition during MRI is being developed. A generalized ANN development has demonstrated its efficacy in predicting a continuum of motion profile for volumetric imaging based on navigator inputs. Future work will enhance the robustness of ANN and verify its effectiveness with human

  3. Absolute doubly differential bremsstrahlung cross sections from rare gas atoms

    NASA Astrophysics Data System (ADS)

    Portillo, Salvador

    The absolute doubly differential bremsstrahlung cross section has been measured for 28 and 50 keV electrons incident on the rare gases Xe, Kr, Ar and Ne. The cross sections are differential with respect to energy and photon emission. A SiLi solid state detector measured data at 90° with respect to the beam line. A thorough analysis of the experimental systematic error yielded a high degree of confidence in the experimental data. The absolute bremsstrahlung doubly differential cross sections provided for a rigorous test of the normal bremsstrahlung theory, tabulated by Kissel, Quarles and Pratt1 (KQP) and of the SA theory2 that includes the contribution from polarization bremsstrahlung. To test the theories a comparison of the overall magnitude of the cross section as well as comparison of the photon energy dependence was carried out. The KQP theoretical values underestimated the magnitude of the cross section for all targets and for both energies. The SA values were in excellent agreement with the 28 keV data. For the 50keV data the fit was also very good. However, there were energy regions where there was a small discrepancy between the theory and the data. This suggests that the Polarization Bremsstrahlung (PB) mechanism does contribute to the overall spectrum and is detectable in this parameter space. 1Kissel, L., Quarles, C. A., Pratt, R. H., Atom. Data Nucl. Data Tables 28, 381 (1983). 2Avdonina N. B., Pratt, R. H., J. Phys. B: At. Mol. Opt. Phys. 32 4261 (1999).

  4. Brain perfusion: computed tomography and magnetic resonance techniques.

    PubMed

    Copen, William A; Lev, Michael H; Rapalino, Otto

    2016-01-01

    Cerebral perfusion imaging provides assessment of regional microvascular hemodynamics in the living brain, enabling in vivo measurement of a variety of different hemodynamic parameters. Perfusion imaging techniques that are used in the clinical setting usually rely upon X-ray computed tomography (CT) or magnetic resonance imaging (MRI). This chapter reviews CT- and MRI-based perfusion imaging techniques, with attention to image acquisition, clinically relevant aspects of image postprocessing, and fundamental differences between CT- and MRI-based techniques. Correlations with cerebrovascular physiology and potential clinical applications of perfusion imaging are reviewed, focusing upon the two major classes of neurologic disease in which perfusion imaging is most often performed: primary perfusion disorders (including ischemic stroke, transient ischemic attack, and reperfusion syndrome), and brain tumors.

  5. Effect of vasodilators on pulmonary perfusion defects in asthma using sequential Kr-81m perfusion imaging

    SciTech Connect

    Ertle, A.R.; Tashkin, D.P.; Webber, M.M.; Soffer, M.J.; Frank, G.W.

    1984-01-01

    The investigation was undertaken to determine if vasodilator agents may enhance the diagnostic utility of perfusion lung imaging (Q) by normalizing regional perfusion abnormalities in bronchospastic patients. The effect of oxygen (02), nitroglycerine (NTG), hydralazine (H), and nifedipine (N) on regional lung perfusion defects was studied in 6 mild to severe asthmatics (ages defects was studied in 6 mild to severe asthmatics (ages 31-72yrs) using sequential Kr-81m imaging which permits repetitive imaging due to very low radiation dose and 13 sec T-1/2. Each patient was studied once weekly for 3 wks. Baseline Q scans were obtained using 10mCi of I.V. Kr-81m. the best view showing perfusion defects was used for subsequent images. At each visits, 30% 02 by ventimask was given for 20 min followed by a repeat Q scan. Subsequently, on separate visits, subjects were given either 1 dose of sublingual (sl)N 20 mg or 2 doses (1 hr between) of s1 NTG 1/150gr or po H 25mg according to a random-order crossover design. Q scans were obtained 2 min after NTG, 60 min after H, and 30 and 60 min after N. 30% 02 was given again for 20 min, and a final scan was obtained. Scan were reviewed by 2 observers and showed relatively fixed defects in 4 pts improvement in defects in 3 pts with NTG, 1 with N, 1 with H, and 2 with 02 alone. Additive effects of 02 and N or NTG were seen in 2 pts. These preliminary results suggest that vasodilators and 02 may improve regional perfusion in patients with bronchospastic disease and that this effect may be additive. These medications may thus improve the specificity of perfusion lung scanning in the diagnostic evaluation of pulmonary embolism.

  6. Absolute radiometric calibration of the CCRS SAR

    NASA Astrophysics Data System (ADS)

    Ulander, Lars M. H.; Hawkins, Robert K.; Livingstone, Charles E.; Lukowski, Tom I.

    1991-11-01

    Determining the radar scattering coefficients from SAR (synthetic aperture radar) image data requires absolute radiometric calibration of the SAR system. The authors describe an internal calibration methodology for the airborne Canada Centre for Remote Sensing (CCRS) SAR system, based on radar theory, a detailed model of the radar system, and measurements of system parameters. The methodology is verified by analyzing external calibration data acquired over a 6-month period in 1988 by the C-band radar using HH polarization. The results indicate that the overall error is +/- 0.8 dB (1-sigma) for incidence angles +/- 20 deg from antenna boresight. The dominant error contributions are due to the antenna radome and uncertainties in the elevation angle relative to the antenna boresight.

  7. Absolute calibration of ultraviolet filter photometry

    NASA Technical Reports Server (NTRS)

    Bless, R. C.; Fairchild, T.; Code, A. D.

    1972-01-01

    The essential features of the calibration procedure can be divided into three parts. First, the shape of the bandpass of each photometer was determined by measuring the transmissions of the individual optical components and also by measuring the response of the photometer as a whole. Secondly, each photometer was placed in the essentially-collimated synchrotron radiation bundle maintained at a constant intensity level, and the output signal was determined from about 100 points on the objective. Finally, two or three points on the objective were illuminated by synchrotron radiation at several different intensity levels covering the dynamic range of the photometers. The output signals were placed on an absolute basis by the electron counting technique described earlier.

  8. Absolute measurements of fast neutrons using yttrium

    SciTech Connect

    Roshan, M. V.; Springham, S. V.; Rawat, R. S.; Lee, P.; Krishnan, M.

    2010-08-15

    Yttrium is presented as an absolute neutron detector for pulsed neutron sources. It has high sensitivity for detecting fast neutrons. Yttrium has the property of generating a monoenergetic secondary radiation in the form of a 909 keV gamma-ray caused by inelastic neutron interaction. It was calibrated numerically using MCNPX and does not need periodic recalibration. The total yttrium efficiency for detecting 2.45 MeV neutrons was determined to be f{sub n}{approx}4.1x10{sup -4} with an uncertainty of about 0.27%. The yttrium detector was employed in the NX2 plasma focus experiments and showed the neutron yield of the order of 10{sup 8} neutrons per discharge.

  9. Absolute geostrophic currents in global tropical oceans

    NASA Astrophysics Data System (ADS)

    Yang, Lina; Yuan, Dongliang

    2016-11-01

    A set of absolute geostrophic current (AGC) data for the period January 2004 to December 2012 are calculated using the P-vector method based on monthly gridded Argo profiles in the world tropical oceans. The AGCs agree well with altimeter geostrophic currents, Ocean Surface Current Analysis-Real time currents, and moored current-meter measurements at 10-m depth, based on which the classical Sverdrup circulation theory is evaluated. Calculations have shown that errors of wind stress calculation, AGC transport, and depth ranges of vertical integration cannot explain non-Sverdrup transport, which is mainly in the subtropical western ocean basins and equatorial currents near the Equator in each ocean basin (except the North Indian Ocean, where the circulation is dominated by monsoons). The identified non-Sverdrup transport is thereby robust and attributed to the joint effect of baroclinicity and relief of the bottom (JEBAR) and mesoscale eddy nonlinearity.

  10. Absolute Measurement of Electron Cloud Density

    SciTech Connect

    Covo, M K; Molvik, A W; Cohen, R H; Friedman, A; Seidl, P A; Logan, G; Bieniosek, F; Baca, D; Vay, J; Orlando, E; Vujic, J L

    2007-06-21

    Beam interaction with background gas and walls produces ubiquitous clouds of stray electrons that frequently limit the performance of particle accelerator and storage rings. Counterintuitively we obtained the electron cloud accumulation by measuring the expelled ions that are originated from the beam-background gas interaction, rather than by measuring electrons that reach the walls. The kinetic ion energy measured with a retarding field analyzer (RFA) maps the depressed beam space-charge potential and provides the dynamic electron cloud density. Clearing electrode current measurements give the static electron cloud background that complements and corroborates with the RFA measurements, providing an absolute measurement of electron cloud density during a 5 {micro}s duration beam pulse in a drift region of the magnetic transport section of the High-Current Experiment (HCX) at LBNL.

  11. Micron Accurate Absolute Ranging System: Range Extension

    NASA Technical Reports Server (NTRS)

    Smalley, Larry L.; Smith, Kely L.

    1999-01-01

    The purpose of this research is to investigate Fresnel diffraction as a means of obtaining absolute distance measurements with micron or greater accuracy. It is believed that such a system would prove useful to the Next Generation Space Telescope (NGST) as a non-intrusive, non-contact measuring system for use with secondary concentrator station-keeping systems. The present research attempts to validate past experiments and develop ways to apply the phenomena of Fresnel diffraction to micron accurate measurement. This report discusses past research on the phenomena, and the basis of the use Fresnel diffraction distance metrology. The apparatus used in the recent investigations, experimental procedures used, preliminary results are discussed in detail. Continued research and equipment requirements on the extension of the effective range of the Fresnel diffraction systems is also described.

  12. Absolute radiometric calibration of the Thematic Mapper

    NASA Technical Reports Server (NTRS)

    Slater, P. N.; Biggar, S. F.; Holm, R. G.; Jackson, R. D.; Mao, Y.

    1986-01-01

    Calibration data for the solar reflective bands of the Landsat-5 TM obtained from five in-flight absolute radiometric calibrations from July 1984-November 1985 at White Sands, New Mexico are presented and analyzed. Ground reflectance and atmospheric data were utilized to predict the spectral radiance at the entrance pupil of the TM and the average number of digital counts in each TM band. The calibration of each of the TM solar reflective bands was calculated in terms of average digital counts/unit spectral radiance for each band. It is observed that for the 12 reflectance-based measurements the rms variation from the means as a percentage of the mean is + or - 1.9 percent; for the 11 measurements in the IR bands, it is + or - 3.4 percent; and the rms variation for all 23 measurements is + or - 2.8 percent.

  13. Swarm's Absolute Scalar Magnetometer metrological performances

    NASA Astrophysics Data System (ADS)

    Leger, J.; Fratter, I.; Bertrand, F.; Jager, T.; Morales, S.

    2012-12-01

    The Absolute Scalar Magnetometer (ASM) has been developed for the ESA Earth Observation Swarm mission, planned for launch in November 2012. As its Overhauser magnetometers forerunners flown on Oersted and Champ satellites, it will deliver high resolution scalar measurements for the in-flight calibration of the Vector Field Magnetometer manufactured by the Danish Technical University. Latest results of the ground tests carried out to fully characterize all parameters that may affect its accuracy, both at instrument and satellite level, will be presented. In addition to its baseline function, the ASM can be operated either at a much higher sampling rate (burst mode at 250 Hz) or in a dual mode where it also delivers vector field measurements as a by-product. The calibration procedure and the relevant vector performances will be discussed.

  14. MAGSAT: Vector magnetometer absolute sensor alignment determination

    NASA Technical Reports Server (NTRS)

    Acuna, M. H.

    1981-01-01

    A procedure is described for accurately determining the absolute alignment of the magnetic axes of a triaxial magnetometer sensor with respect to an external, fixed, reference coordinate system. The method does not require that the magnetic field vector orientation, as generated by a triaxial calibration coil system, be known to better than a few degrees from its true position, and minimizes the number of positions through which a sensor assembly must be rotated to obtain a solution. Computer simulations show that accuracies of better than 0.4 seconds of arc can be achieved under typical test conditions associated with existing magnetic test facilities. The basic approach is similar in nature to that presented by McPherron and Snare (1978) except that only three sensor positions are required and the system of equations to be solved is considerably simplified. Applications of the method to the case of the MAGSAT Vector Magnetometer are presented and the problems encountered discussed.

  15. 99mTc-ECD brain perfusion SPECT imaging for the assessment of brain perfusion in cerebral palsy (CP) patients with evaluation of the effect of hyperbaric oxygen therapy

    PubMed Central

    Asl, Mina Taghizadeh; Yousefi, Farzaneh; Nemati, Reza; Assadi, Majid

    2015-01-01

    Objective: The present study was carried out to evaluate cerebral perfusion in different types of cerebral palsy (CP) patients. For those patients who underwent hyperbaric oxygen therapy, brain perfusion before and after the therapy was compared. Methods: A total of 11 CP patients were enrolled in this study, of which 4 patients underwent oxygen therapy. Before oxygen therapy and at the end of 40 sessions of oxygen treatment, 99mTc-ECD brain perfusion single photon emission computed tomography (SPECT) was performed , and the results were compared. Results: A total of 11 CP patients, 7 females and 4 males with an age range of 5-27 years participated in the study. In brain SPECT studies, all the patients showed perfusion impairments. The region most significantly involved was the frontal lobe (54.54%), followed by the temporal lobe (27.27%), the occipital lobe (18.18%), the visual cortex (18.18%), the basal ganglia (9.09%), the parietal lobe (9.09%), and the cerebellum (9.09%). Frontal-lobe hypoperfusion was seen in all types of cerebral palsy. Two out of 4 patients (2 males and 2 females) who underwent oxygen therapy revealed certain degree of brain perfusion improvement. Conclusion: This study demonstrated decreased cerebral perfusion in different types of CP patients. The study also showed that hyperbaric oxygen therapy improved cerebral perfusion in a few CP patients. However, it could keep the physiological discussion open and strenghten a link with other areas of neurology in which this approach may have some value. PMID:25785099

  16. A method of thymic perfusion and its evaluation

    PubMed Central

    Ekwueme, O.

    1973-01-01

    The development and evaluation of a method of isolated ex vivo perfusion of the rabbit thymus using diluted autologous blood is described. The data indicate that the viability of the preparation is maintained at a satisfactory level during the period of perfusion. These results suggest that the isolated perfused thymus would be a useful new approach to studies of thymus function. ImagesFig. 2Fig. 8Fig. 9Fig. 10Fig. 11 PMID:4747584

  17. Scintigraphic perfusion patterns in patients with diffuse lung disease

    SciTech Connect

    Newman, G.E.; Sullivan, D.C.; Gottschalk, A.; Putman, C.E.

    1982-04-01

    Perfusion scintigrams of 55 patients with radiographic evidence of diffuse lung disease were reviewed. Thirty-nine had acute and/or chronic changes caused by congestive heart failure, and 16 had diffuse reticulonodular disease. A normal or near-normal perfusion pattern was seen in 40/55 (73%), and this finding was equally common in the two groups. The authors conclude that perfusion scintigraphy is useful in excluding pulmonary embolism in patients with radiographic evidence of diffuse, symmetrical lung disease.

  18. Perfusion Scintigraphy and Patient Selection for Lung Volume Reduction Surgery

    PubMed Central

    Chandra, Divay; Lipson, David A.; Hoffman, Eric A.; Hansen-Flaschen, John; Sciurba, Frank C.; DeCamp, Malcolm M.; Reilly, John J.; Washko, George R.

    2010-01-01

    Rationale: It is unclear if lung perfusion can predict response to lung volume reduction surgery (LVRS). Objectives: To study the role of perfusion scintigraphy in patient selection for LVRS. Methods: We performed an intention-to-treat analysis of 1,045 of 1,218 patients enrolled in the National Emphysema Treatment Trial who were non–high risk for LVRS and had complete perfusion scintigraphy results at baseline. The median follow-up was 6.0 years. Patients were classified as having upper or non–upper lobe–predominant emphysema on visual examination of the chest computed tomography and high or low exercise capacity on cardiopulmonary exercise testing at baseline. Low upper zone perfusion was defined as less than 20% of total lung perfusion distributed to the upper third of both lungs as measured on perfusion scintigraphy. Measurements and Main Results: Among 284 of 1,045 patients with upper lobe–predominant emphysema and low exercise capacity at baseline, the 202 with low upper zone perfusion had lower mortality with LVRS versus medical management (risk ratio [RR], 0.56; P = 0.008) unlike the remaining 82 with high perfusion where mortality was unchanged (RR, 0.97; P = 0.62). Similarly, among 404 of 1,045 patients with upper lobe–predominant emphysema and high exercise capacity, the 278 with low upper zone perfusion had lower mortality with LVRS (RR, 0.70; P = 0.02) unlike the remaining 126 with high perfusion (RR, 1.05; P = 1.00). Among the 357 patients with non–upper lobe–predominant emphysema (75 with low and 282 with high exercise capacity) there was no improvement in survival with LVRS and measurement of upper zone perfusion did not contribute new prognostic information. Conclusions: Compared with optimal medical management, LVRS reduces mortality in patients with upper lobe–predominant emphysema when there is low rather than high perfusion to the upper lung. PMID:20538961

  19. Measurement of continuous distributions of ventilation-perfusion ratios - Theory

    NASA Technical Reports Server (NTRS)

    Wagner, P. D.; Saltzman, H. A.; West, J. B.

    1974-01-01

    The resolution of the technique considered is sufficient to describe smooth distributions containing blood flow to unventilated regions (shunt), ventilation to unperfused regions (dead space), and up to three additional modes over the range of finite ventilation-perfusion ratios. In particular, areas whose ventilation-perfusion ratios are low can be separated from unventilated regions and those whose ventilation-perfusion ratios are high can similarly be distinguished from unperfused areas.

  20. SU-E-I-36: A KWIC and Dirty Look at Dose Savings and Perfusion Metrics in Simulated CT Neuro Perfusion Exams

    SciTech Connect

    Hoffman, J; Martin, T; Young, S; McNitt-Gray, M; Wang, D

    2015-06-15

    Purpose: CT neuro perfusion scans are one of the highest dose exams. Methods to reduce dose include decreasing the number of projections acquired per gantry rotation, however conventional reconstruction of such scans leads to sampling artifacts. In this study we investigated a projection view-sharing reconstruction algorithm used in dynamic MRI – “K-space Weighted Image Contrast” (KWIC) – applied to simulated perfusion exams and evaluated dose savings and impacts on perfusion metrics. Methods: A FORBILD head phantom containing simulated time-varying objects was developed and a set of parallel-beam CT projection data was created. The simulated scans were 60 seconds long, 1152 projections per turn, with a rotation time of one second. No noise was simulated. 5mm, 10mm, and 50mm objects were modeled in the brain. A baseline, “full dose” simulation used all projections and reduced dose cases were simulated by downsampling the number of projections per turn from 1152 to 576 (50% dose), 288 (25% dose), and 144 (12.5% dose). KWIC was further evaluated at 72 projections per rotation (6.25%). One image per second was reconstructed using filtered backprojection (FBP) and KWIC. KWIC reconstructions utilized view cores of 36, 72, 144, and 288 views and 16, 8, 4, and 2 subapertures respectively. From the reconstructed images, time-to-peak (TTP), cerebral blood flow (CBF) and the FWHM of the perfusion curve were calculated and compared against reference values from the full-dose FBP data. Results: TTP, CBF, and the FWHM were unaffected by dose reduction (to 12.5%) and reconstruction method, however image quality was improved when using KWIC. Conclusion: This pilot study suggests that KWIC preserves image quality and perfusion metrics when under-sampling projections and that the unique contrast weighting of KWIC could provided substantial dose-savings for perfusion CT scans. Evaluation of KWIC in clinical CT data will be performed in the near future. R01 EB014922, NCI

  1. Extracorporeal Free Flap Perfusion in Case of Prolonged Ischemia Time

    PubMed Central

    Präbst, K.; Beier, J. P.; Meyer, A.; Horch, R. E.

    2016-01-01

    Summary: In free flap surgery, a clinically established concept still has to be found for the reduction of ischemia-related cell damage in the case of prolonged ischemia. Although promising results using extracorporeal free flap perfusion in the laboratory have been published in the past, until now this concept has not yet paved its way into clinical routine. This might be due to the complexity of perfusion systems and a lack of standardized tools. Here, we want to present the results of the first extracorporeal free flap perfusion in a clinical setting using a simple approach without the application of a complex perfusion machinery. PMID:27200244

  2. Effect of Defocused CO2 Laser on Equine Tissue Perfusion

    PubMed Central

    Bergh, A; Nyman, G; Lundeberg, T; Drevemo, S

    2006-01-01

    Treatment with defocused CO2 laser can have a therapeutic effect on equine injuries, but the mechanisms involved are unclear. A recent study has shown that laser causes an increase in equine superficial tissue temperature, which may result in an increase in blood perfusion and a stimulating effect on tissue regeneration. However, no studies have described the effects on equine tissue perfusion. The aim of the present study was to investigate the effect of defocused CO2 laser on blood perfusion and to correlate it with temperature in skin and underlying muscle in anaesthetized horses. Differences between clipped and unclipped haircoat were also assessed. Eight horses and two controls received CO2 laser treatment (91 J/cm2) in a randomised order, on a clipped and unclipped area of the hamstring muscles, respectively. The significant increase in clipped skin perfusion and temperature was on average 146.3 ± 33.4 perfusion units (334%) and 5.5 ± 1.5°C, respectively. The significant increase in perfusion and temperature in unclipped skin were 80.6 ± 20.4 perfusion units (264%) and 4.8 ± 1.4°C. No significant changes were seen in muscle perfusion or temperature. In conclusion, treatment with defocused CO2 laser causes a significant increase in skin perfusion, which is correlated to an increase in skin temperature. PMID:16722304

  3. Radionuclide Tracers for Myocardial Perfusion Imaging and Blood Flow Quantification.

    PubMed

    deKemp, Robert A; Renaud, Jennifer M; Klein, Ran; Beanlands, Rob S B

    2016-02-01

    Myocardial perfusion imaging is performed most commonly using Tc-99m-sestamibi or tetrofosmin SPECT as well as Rb-82-rubidium or N-13-ammonia PET. Diseased-to-normal tissue contrast is determined by the tracer retention fraction, which decreases nonlinearly with flow. Reduced tissue perfusion results in reduced tracer retention, but the severity of perfusion defects is typically underestimated by 20% to 40%. Compared to SPECT, retention of the PET tracers is more linearly related to flow, and therefore, the perfusion defects are measured more accurately using N-13-ammonia or Rb-82. PMID:26590778

  4. Ex Situ Normothermic Machine Perfusion of Donor Livers.

    PubMed

    Karimian, Negin; Matton, Alix P M; Westerkamp, Andrie C; Burlage, Laura C; Op den Dries, Sanna; Leuvenink, Henri G D; Lisman, Ton; Uygun, Korkut; Markmann, James F; Porte, Robert J

    2015-01-01

    In contrast to conventional static cold preservation (0-4 °C), ex situ machine perfusion may provide better preservation of donor livers. Continuous perfusion of organs provides the opportunity to improve organ quality and allows ex situ viability assessment of donor livers prior to transplantation. This video article provides a step by step protocol for ex situ normothermic machine perfusion (37 °C) of human donor livers using a device that provides a pressure and temperature controlled pulsatile perfusion of the hepatic artery and continuous perfusion of the portal vein. The perfusion fluid is oxygenated by two hollow fiber membrane oxygenators and the temperature can be regulated between 10 °C and 37 °C. During perfusion, the metabolic activity of the liver as well as the degree of injury can be assessed by biochemical analysis of samples taken from the perfusion fluid. Machine perfusion is a very promising tool to increase the number of livers that are suitable for transplantation.

  5. New imaging technology: measurement of myocardial perfusion by contrast echocardiography

    NASA Technical Reports Server (NTRS)

    Rubin, D. N.; Thomas, J. D.

    2000-01-01

    Myocardial perfusion imaging has long been a goal for the non-invasive echocardiographic assessment of the heart. However, many factors at play in perfusion imaging have made this goal elusive. Harmonic imaging and triggered imaging with newer contrast agents have made myocardial perfusion imaging potentially practical in the very near future. The application of indicator dilution theory to the coronary circulation and bubble contrast agents is fraught with complexities and sources of error. Therefore, quantification of myocardial perfusion by non-invasive echocardiographic imaging requires further investigation in order to make this technique clinically viable.

  6. [Assessment of cicatrisation potential in arteritic patients by means of an isotopic method employing technetium 99 m to measure cutaneous perfusion pressure (author's transl)].

    PubMed

    Le Héron, D; Serise, J M; Busquet, J; Tingaud, R

    1981-01-01

    Cicatrisation potential was assessed in arteritic patients by an isotopic method employing technetium 99 m to measure cutaneous perfusion pressures. Pressure threshold-values obtained showed that cicatrisation was absent when pressure was below 35 cm of water, that infectious complications developed in half of the cases with values between 35 and 65 cm, and that cicatrisation generally occurred at values above 65 cm.

  7. Transmural myocardial perfusion gradients in relation to coronary artery stenoses severity assessed by cardiac multidetector computed tomography.

    PubMed

    Linde, Jesper James; Kühl, Jørgen Tobias; Hove, Jens Dahlgaard; Sørgaard, Mathias; Kelbæk, Henning; Nielsen, Walter Bjørn; Kofoed, Klaus Fuglsang

    2015-01-01

    To assess the relationship between epicardial coronary artery stenosis severity and the corresponding regional transmural perfusion at rest and during adenosine stress, using multidetector computed tomography (MDCT). We evaluated the relationship between the severity of coronary artery diameter stenosis assessed by MDCT angiography and semi-quantitative myocardial MDCT perfusion in 200 symptomatic patients. The perfusion index (PI = mean myocardial attenuation density/mean left ventricular lumen attenuation density) at rest and during adenosine stress, the myocardial perfusion reserve (MPR = stress - PI/rest - PI), and the transmural perfusion ratio (TPR = subendocardium/subepicardium) were calculated. A coronary artery stenosis ≥50 % was present in 49 patients (25 %). Rest-PI and rest-TPR values were similar in patients with and without a coronary artery stenosis ≥50 %, whereas stress-PI, stress-TPR and MPR were significantly reduced in patients with a stenosis ≥50 % (p < 0.001, p < 0.0001 and p = 0.02, respectively). Subendocardial PI was significantly higher than subepicardial PI at rest and during stress for patients without a significant stenosis, whereas this difference was blurred during stress in patients with ≥50 % stenosis. In a broad spectrum of stenosis severity groups, TPR at rest remained unchanged until the group of patients with total occlusions, whereas TPR during stress decreased progressively when a threshold of 50 % was superseded. In this study we establish the relationship between semi-quantitative perfusion measurements by MDCT and severity of coronary artery stenoses and find the transmural myocardial perfusion ratio to be a potential strong functional index of the hemodynamic significance of coronary artery atherosclerotic lesions.

  8. Using absolute gravimeter data to determine vertical gravity gradients

    USGS Publications Warehouse

    Robertson, D.S.

    2001-01-01

    The position versus time data from a free-fall absolute gravimeter can be used to estimate the vertical gravity gradient in addition to the gravity value itself. Hipkin has reported success in estimating the vertical gradient value using a data set of unusually good quality. This paper explores techniques that may be applicable to a broader class of data that may be contaminated with "system response" errors of larger magnitude than were evident in the data used by Hipkin. This system response function is usually modelled as a sum of exponentially decaying sinusoidal components. The technique employed here involves combining the x0, v0 and g parameters from all the drops made during a site occupation into a single least-squares solution, and including the value of the vertical gradient and the coefficients of system response function in the same solution. The resulting non-linear equations must be solved iteratively and convergence presents some difficulties. Sparse matrix techniques are used to make the least-squares problem computationally tractable.

  9. Modeling laser speckle imaging of perfusion in the skin (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Regan, Caitlin; Hayakawa, Carole K.; Choi, Bernard

    2016-02-01

    Laser speckle imaging (LSI) enables visualization of relative blood flow and perfusion in the skin. It is frequently applied to monitor treatment of vascular malformations such as port wine stain birthmarks, and measure changes in perfusion due to peripheral vascular disease. We developed a computational Monte Carlo simulation of laser speckle contrast imaging to quantify how tissue optical properties, blood vessel depths and speeds, and tissue perfusion affect speckle contrast values originating from coherent excitation. The simulated tissue geometry consisted of multiple layers to simulate the skin, or incorporated an inclusion such as a vessel or tumor at different depths. Our simulation used a 30x30mm uniform flat light source to optically excite the region of interest in our sample to better mimic wide-field imaging. We used our model to simulate how dynamically scattered photons from a buried blood vessel affect speckle contrast at different lateral distances (0-1mm) away from the vessel, and how these speckle contrast changes vary with depth (0-1mm) and flow speed (0-10mm/s). We applied the model to simulate perfusion in the skin, and observed how different optical properties, such as epidermal melanin concentration (1%-50%) affected speckle contrast. We simulated perfusion during a systolic forearm occlusion and found that contrast decreased by 35% (exposure time = 10ms). Monte Carlo simulations of laser speckle contrast give us a tool to quantify what regions of the skin are probed with laser speckle imaging, and measure how the tissue optical properties and blood flow affect the resulting images.

  10. A spatially-distributed computational model to quantify behaviour of contrast agents in MR perfusion imaging

    PubMed Central

    Cookson, A.N.; Lee, J.; Michler, C.; Chabiniok, R.; Hyde, E.; Nordsletten, D.; Smith, N.P.

    2014-01-01

    Contrast agent enhanced magnetic resonance (MR) perfusion imaging provides an early, non-invasive indication of defects in the coronary circulation. However, the large variation of contrast agent properties, physiological state and imaging protocols means that optimisation of image acquisition is difficult to achieve. This situation motivates the development of a computational framework that, in turn, enables the efficient mapping of this parameter space to provide valuable information for optimisation of perfusion imaging in the clinical context. For this purpose a single-compartment porous medium model of capillary blood flow is developed which is coupled with a scalar transport model, to characterise the behaviour of both blood-pool and freely-diffusive contrast agents characterised by their ability to diffuse through the capillary wall into the extra-cellular space. A parameter space study is performed on the nondimensionalised equations using a 2D model for both healthy and diseased myocardium, examining the sensitivity of system behaviour to Peclet number, Damköhler number (Da), diffusivity ratio and fluid porosity. Assuming a linear MR signal response model, sample concentration time series data are calculated, and the sensitivity of clinically-relevant properties of these signals to the model parameters is quantified. Both upslope and peak values display significant non-monotonic behaviour with regard to the Damköhler number, with these properties showing a high degree of sensitivity in the parameter range relevant to contrast agents currently in use. However, the results suggest that signal upslope is the more robust and discerning metric for perfusion quantification, in particular for correlating with perfusion defect size. Finally, the results were examined in the context of nonlinear signal response, flow quantification via Fermi deconvolution and perfusion reserve index, which demonstrated that there is no single best set of contrast agent parameters

  11. Correlation of CT perfusion and CT volumetry in patients with Alzheimer’s disease

    PubMed Central

    Czarnecka, Anna; Zimny, Anna; Sąsiadek, Marek

    2010-01-01

    Summary Background: Both brain atrophy and decrease of perfusion are observed in dementive diseases. The aim of the study was to correlate the results of brain perfusion CT (pCT) and CT volumetry in patients with Alzheimer’s disease (AD). Material/Methods: Forty-eight patients with AD (mean age of 71.3 years) underwent brain pCT and CT volumetry. The pCT was performed at the level of basal ganglia after the injection of contrast medium (50 ml, 4 ml/sec.) with serial scanning (delay 7 sec, 50 scans, 1 scan/sec). Volumetric measurements were carried out on the basis of source images, with the use of a dedicated CT software combined with manual outlining of the regions of interest in extracerebral and intraventricular CSF spaces. Perfusion parameters of the cerebral blood flow (CBF) and cerebral blood volume (CBV) from the grey matter of frontal and temporal as well as basal ganglia were compared statistically with the volumetric measurements of frontal and temporal cortical atrophy as well as subcortical atrophy. Results: A statistically significant positive correlation was found between the values of CBF and CBV in the basal ganglia and the volumes of the lateral and third ventricles. The comparison of CBF and CBV results with the volumetric measurements in the areas of the frontal and temporal lobes showed mostly negative correlations, but none of them was of statistical significance. Conclusions: In patients with AD, the degree of cortical atrophy is not correlated with the decrease of perfusion in the grey matter and subcortical atrophy is not correlated with the decrease of perfusion in the basal ganglia region. It suggests that functional and structural changes in AD are not related to each other. PMID:22802771

  12. Tissue distribution of cefquinome after intramammary and "systemic" administration in the isolated perfused bovine udder.

    PubMed

    Ehinger, A M; Schmidt, H; Kietzmann, M

    2006-07-01

    Mammary glands taken at slaughter from healthy lactating cows were perfused in vitro with warmed and gassed Tyrode solution. Cefquinome (88.8mg cefquinome sulphate per 8mL) was administered by the intramammary route to all quarters and/or "systemically" via the perfusion fluid at concentrations similar to those measured in plasma following intramuscular administration of 1mg cefquinome per kg body weight. Samples of the perfusate were taken over a 6-h period and from the regional lymph nodes after 6h. Using a scalpel, sections of glandular tissue - at different distances from and vertical to the teat right up to the udder base - were gathered from four quarters each per route of administration at 2, 4 and 6h. The cefquinome content of the tissue samples was analysed by high performance liquid chromatography with diode array detection and of the perfusate samples by bioassay. After intramammary administration, the concentration of cefquinome in the glandular tissue decreased exponentially with increasing distance from the teat. The addition of cefquinome to the perfusion fluid produced a mean concentration of 0.2-0.5microg/g at all glandular tissue sites. Combined intramammary and systemic treatment ensured that concentrations exceeded the MIC(90) values of the most common mastitis pathogens in all areas of the udder by 2h post-administration. There was considerable variability in the tissue concentrations of cefquinome, particularly after intramammary administration. These results suggest that for the treatment of acute mastitis a combination of both intramammary and systemic administration is likely to be advantageous in order to rapidly produce maximum cefquinome concentrations in all regions of the udder. PMID:16772139

  13. Investigation of tomosynthetic perfusion measurements using the scanning-beam digital x-ray (SBDX) system

    NASA Astrophysics Data System (ADS)

    Nett, Brian E.; Chen, Guang-Hong; Van Lysel, Michael S.; Betts, Timothy; Speidel, Michael; Rowley, Howard A.; Aagaard Kienitz, Beverly D.; Mistretta, Charles A.

    2004-10-01

    The feasibility of making regional perfusion measurements using a tomosynthetic digital subtraction angiography (TDSA) acquisition has been demonstrated. The study of tomosynthetic perfusion measurements was motivated by the clinical desire for perfusion measurements in an interventional angiography suite. These pilot studies were performed using the scanning-beam digital x-ray (SBDX) system which is an inverse-geometry imaging device which utilizes an electromagnetically-scanned x-ray source, and a small CdTe direct conversion photon counting detector. The scanning electron source was used to acquire planar-tomographic images of a 12.5 x 12.5 cm field of view at a frame rate of 15 frames/sec during dynamic contrast injection. A beagle animal model was used to evaluate the tomosynthetic perfusion measurements. A manual bolus injection of iodinated contrast solution was used in order to resolve the parameters of the contrast pass curve. The acquired planar tomosynthetic dataset was reconstructed with a simple back-projection algorithm. Digital subtraction techniques were used to visualize the change in contrast agent intensity in each reconstructed plane. Given the TDSA images, region of interest based analysis was used in the selection of the image pixels corresponding to the artery and tissue bed. The mean transit time (MTT), regional cerebral blood volume (rCBV) and regional cerebral blood flow (rCBF) were extracted from the tomosynthetic data for selected regions in each of the desired reconstructed planes. For the purpose of this study, the arterial contrast enhancement curve was fit with a combination of gamma variate terms, and the MTT was calculated using a deconvolution based on the singular value decomposition (SVD). The results of the contrast pass curves derived with TDSA were consistent with the results from perfusion measurements as implemented with CT acquisition.

  14. Attempt to rescue discarded human liver grafts by end ischemic hypothermic oxygenated machine perfusion.

    PubMed

    Vekemans, K; van Pelt, J; Komuta, M; Wylin, T; Heedfeld, V; Detry, O; Monbaliu, D; Pirenne, J

    2011-11-01

    In a porcine liver transplant model, a brief period of oxygenated hypothermic machine perfusion (HMP) at the end of simple cold storage (SCS) has been shown to improve the viability of damaged liver grafts. To test the clinical validity of this strategy, we randomized SCS-discarded human liver grafts to either 4 hours of HMP (n = 13) or an additional 4 hours of SCS (n = 14). All livers were then warm reperfused to mimic ischemia-reperfusion injury ex vivo. The settings for HMP were: portal vein: 3 mm Hg, 300 mL/min and hepatic artery: 20 mm Hg, pO(2): 300 mm Hg. Perfusion used Kidney Machine Perfusion Solution at 4°C to 8°C. During warm reperfusion, aspartate aminotransferase (AST) and lactate dehydrogenase (LDH) values were higher (P < .015) among the SCS versus HMP methods at all times. The AST slope was lower in HMP versus SCS (P = .01). The LDH slope tended to be lower for HMP versus SCS (P = .07). Morphological scores were not different between HMP and SCS. At the start of warm reperfusion, MAPK was lower in HMP versus SCS (P = .02). Endothelin-1 (EDN1) and ICAM-1 tended to be lower in HMP versus SCS (P = .1 and .07, respectively). No difference was noted in MAPK, EDN1, and ICAM-1 after 60 or 120 minutes of warm reperfusion. In conclusion, HMP down-regulated MAPK and tended to reduce EDN1 and ICAM-1 mRNA in human liver grafts. During warm reperfusion, HMP versus SCS livers showed reduced AST and LDH release but no morphological difference. Further optimization of liver HMP may require different timing/duration of perfusion and/or an higher perfusion temperature.

  15. Myocardial Perfusion MRI Using SW-CG-HYPR in Canine with Stenotic Coronary Arteries

    PubMed Central

    Ge, Lan; Kino, Aya; Lee, Daniel; Dharmakumar, Rohan; Carr, James C.; Li, Debiao

    2010-01-01

    Purpose First-pass perfusion MRI is a promising technique for detecting ischemic heart disease. However, the diagnostic value of the method is limited by the low spatial coverage, resolution, SNR, and cardiac motion related image artifacts. A combination of sliding window and CG-HYPR method has been proposed in healthy volunteer studies to reduce the acquisition window for each slice while maintaining the temporal resolution of one frame per heartbeat in myocardial perfusion MR imaging. This method allows for improved spatial coverage, resolution and SNR. Materials and Methods In this study, we use a controlled animal model to test whether the myocardial territory supplied by a stenotic coronary artery can be detected accurately by SW-CG-HYPR perfusion method under pharmacological stress. Results Results from six mongrel dogs (15–25 kg) studies demonstrate the feasibility of SW-CG-HYPR to detect regional perfusion defects. Using this method, the acquisition time per cardiac cycle was reduced by a factor of 4, and the spatial coverage was increased from 2–3 to 6 slices as compared to the conventional techniques including both turbo-FLASH and EPI. The SNR of the healthy myocardium at peak enhancement with SW-CG-HYPR (12.68±2.46) is significantly higher (p<0.01) than the turbo-FLASH (8.65±1.93) and EPI (5.48±1.24). The spatial resolution of SW-CG-HYPR images is 1.2×1.2×8.0 mm3, which is better than the turbo-FLASH (1.8×1.8×8.0 mm3) and EPI (2.0×1.8×8.0 mm3). Conclusion SW-CG-HYPR is a promising technique for myocardial perfusion MRI. This technique provides higher image quality with respect to significantly improved SNR and spatial resolution of the myocardial perfusion images, which might improve myocardial perfusion imaging in a clinical setting. PMID:20861770

  16. Valuing Essays: Essaying Values

    ERIC Educational Resources Information Center

    Badley, Graham

    2010-01-01

    The essay regularly comes under attack. It is criticised for being rigidly linear rather than flexible and reflective. I first challenge this view by examining reasons why the essay should be valued as an important genre. Secondly, I propose that in using the essay form students and academics necessarily exemplify their own critical values. Essays…

  17. ROI for outlining an entire tumor is a reliable approach for quantification of lung cancer tumor vascular parameters using CT perfusion

    PubMed Central

    Ma, Ensen; Ren, An; Gao, Baoxiang; Yang, Minxing; Zhao, Qichao; Wang, Wu; Li, Kefeng

    2016-01-01

    Objective To investigate the effect of position and size of tumor region of interest (ROI) on the estimation of lung cancer vascular parameters using 256-slice computed tomography (CT) perfusion. Methods After institutional review board approval and written informed consent, 16 men and 11 women with lung cancer were enrolled in this CT perfusion study. Perfusion, blood volume, and peak enhancement were determined for 60 or 120 mm2 circular ROIs placed at the edge, center, and around (outlining) the visible tumor. Average values were obtained by performing ROI analysis twice by the same observers without any procedural changes. Results Perfusion, blood volume, and peak enhancement measurements were substantially higher at the edge than at the center for both 60 and 120 mm2 ROIs (all P<0.05). Measurements varied substantially depending on the ROI size. Perfusion, blood volume, and peak enhancement for the ROIs outlining tumor were intermediate between those at the tumor edge and center. There were significant correlations between median values and interquartile ranges as follows; perfusion (12.51 [7.91–28.10] mL⋅min−1⋅100 mL−1), blood volume (29.31 [21.82–37.65] mL⋅100 g−1), peak enhancement (12.93 [2.42–22.50]) for the ROIs outlining the tumor, and microvascular density ([19.43±8.78] vessels/0.74 mm2), respectively (r values were 0.732, 0.590, and 0.544 respectively, all P<0.05). Conclusion Spatial and size selection of ROI significantly affects CT perfusion analysis. ROI outlining of entire tumor provides efficient and reliable measurements for clinical assessment of lung cancer using CT perfusion. PMID:27175083

  18. Testicular perfusion after standing laparoscopic peritoneal flap hernioplasty in stallions.

    PubMed

    Gracia-Calvo, L A; Duque, J; Balao da Silva, C; Ezquerra, J; Ortega-Ferrusola, C

    2015-09-15

    Acquired inguinal herniation is a very common condition in stallions, usually leading to unilateral or bilateral castration to prevent future recurrence. Recently, several surgical techniques such as the standing laparoscopic peritoneal flap hernioplasty (SLPFH) have been developed to avoid herniation recurrence and also preserve the breeding activity of high economic value stallions. However, studies on SLPFH lack more comprehensive and systematic data about reproductive-related adverse effects and outcomes. The aim of this study was to evaluate whether SLPFH of the internal inguinal rings produces changes in the testicular blood flow in a 1-year follow-up. For that purpose, six healthy stallions were used and testicular blood flow was assessed before, 3, 6, and 12 months (T0, T3, T6, and T12) after the procedure. Blood flow was evaluated ultrasonographically, using the pulsed-wave color Doppler mode. Peak systolic velocity, end-diastolic velocity, the time-averaged maximum velocity, and the derived indexes (resistive index) and pulsatility index) of the testicular artery were measured in two localizations: in the spermatic cord and on the caudal epididymal edge of the testicle. On the spermatic cord, the peak systolic velocity of the testicular artery increased significantly at T12. However, on the epididymal edge location of the artery, the pulsatility and resistive indexes were decreased at T12 (P < 0.05). This pattern of blood flow was related to a hyperemic process. Furthermore, SLPFH might have compressed the spermatic cord, causing a slight occlusion of the testicular artery and triggering a compensatory hyperemia to compensate the deficit of blood flow that supplies the testes. The SLPFH of the internal inguinal ring affected the testicular perfusion in stallions in a 1 year follow-up, although there was no effect on sperm production during this time. The spectral Doppler ultrasound is a useful tool to asses the testicular perfusion after reproductive

  19. Testicular perfusion after standing laparoscopic peritoneal flap hernioplasty in stallions.

    PubMed

    Gracia-Calvo, L A; Duque, J; Balao da Silva, C; Ezquerra, J; Ortega-Ferrusola, C

    2015-09-15

    Acquired inguinal herniation is a very common condition in stallions, usually leading to unilateral or bilateral castration to prevent future recurrence. Recently, several surgical techniques such as the standing laparoscopic peritoneal flap hernioplasty (SLPFH) have been developed to avoid herniation recurrence and also preserve the breeding activity of high economic value stallions. However, studies on SLPFH lack more comprehensive and systematic data about reproductive-related adverse effects and outcomes. The aim of this study was to evaluate whether SLPFH of the internal inguinal rings produces changes in the testicular blood flow in a 1-year follow-up. For that purpose, six healthy stallions were used and testicular blood flow was assessed before, 3, 6, and 12 months (T0, T3, T6, and T12) after the procedure. Blood flow was evaluated ultrasonographically, using the pulsed-wave color Doppler mode. Peak systolic velocity, end-diastolic velocity, the time-averaged maximum velocity, and the derived indexes (resistive index) and pulsatility index) of the testicular artery were measured in two localizations: in the spermatic cord and on the caudal epididymal edge of the testicle. On the spermatic cord, the peak systolic velocity of the testicular artery increased significantly at T12. However, on the epididymal edge location of the artery, the pulsatility and resistive indexes were decreased at T12 (P < 0.05). This pattern of blood flow was related to a hyperemic process. Furthermore, SLPFH might have compressed the spermatic cord, causing a slight occlusion of the testicular artery and triggering a compensatory hyperemia to compensate the deficit of blood flow that supplies the testes. The SLPFH of the internal inguinal ring affected the testicular perfusion in stallions in a 1 year follow-up, although there was no effect on sperm production during this time. The spectral Doppler ultrasound is a useful tool to asses the testicular perfusion after reproductive

  20. New identification method for Hammerstein models based on approximate least absolute deviation

    NASA Astrophysics Data System (ADS)

    Xu, Bao-Chang; Zhang, Ying-Dan

    2016-07-01

    Disorder and peak noises or large disturbances can deteriorate the identification effects of Hammerstein non-linear models when using the least-square (LS) method. The least absolute deviation technique can be used to resolve this problem; however, its absolute value cannot meet the need of differentiability required by most algorithms. To improve robustness and resolve the non-differentiable problem, an approximate least absolute deviation (ALAD) objective function is established by introducing a deterministic function that exhibits the characteristics of absolute value under certain situations. A new identification method for Hammerstein models based on ALAD is thus developed in this paper. The basic idea of this method is to apply the stochastic approximation theory in the process of deriving the recursive equations. After identifying the parameter matrix of the Hammerstein model via the new algorithm, the product terms in the matrix are separated by calculating the average values. Finally, algorithm convergence is proven by applying the ordinary differential equation method. The proposed algorithm has a better robustness as compared to other LS methods, particularly when abnormal points exist in the measured data. Furthermore, the proposed algorithm is easier to apply and converges faster. The simulation results demonstrate the efficacy of the proposed algorithm.

  1. Swine experimental model to evaluate stem cells implant post myocardial infarction by perfusion gated-SPET.

    PubMed

    Niccoli-Asabella, Artor; Ferlan, Giovanni; Crovace, Antonio; Notaristefano, Antonio; Rubini, Domenico; Altini, Corinna; Pisani, Antonio; Rubini, Giuseppe

    2012-01-01

    Autologous bone marrow stromal cells (BMSC) implant after swine experimental myocardial infarct (MI) was investigated by serial technetium-99m ((99m)Tc)-tetrofosmin gated single photon emission tomography (G-SPET) and compared with immuno-histochemical findings. The aim was to evaluate if intramyocardial BMSC implant produces any prolonged effect in the left ventricle (LV) perfusion and function. Eleven pigs underwent left anterior descending artery (LAD) ligature; in seven of them BMSC were injected in the border zone of the MI, while in the remaining four saline solution was injected at the same site. After LAD ligature G-SPET scans at 48h and at 5 and 10 weeks (w) after the implant were performed. Uptake defect size and LV function analysis were performed comparing 48h to 5w and 10w studies. Statistical evaluation was performed with Friedman test and unpaired Wilcoxon test. The comparison between a progressive reduction of Perfusion Image Score was observed from 48h to 5w and to 10w in the treated group (Friedman test: χ²= 13.56; P=0.01). No variation was observed in the control group (Friedman test: χ²=3; P= 0.223). Comparison of the absolute variation (Δ) between treated and control group resulted significant (Wilcoxon test W=10; P=0.007). Similar positive results were also observed for the relative extension of the uptake defect, wall motion and LVEF analysis. Histological data of our swine model demonstrated that autologous BMSC implanted in the damaged myocardium area had survived and differentiated into cells with typical features of myocardiocytes. Gated SPET is a reliable tool to evaluate prolonged positive effects of autologous BMSC implant in swine experimental MI model. In conclusion, autologous BMSC implanted can improve perfusion, induce cell regeneration, reduce wall motion abnormalities and prevent severe LV dysfunction in swines.

  2. Sounding rocket measurement of the absolute solar EUV flux utilizing a silicon photodiode

    NASA Technical Reports Server (NTRS)

    Ogawa, H. S.; Mcmullin, D.; Judge, D. L.; Canfield, L. R.

    1990-01-01

    A newly developed stable and high quantum efficiency silicon photodiode was used to obtain an accurate measurement of the integrated absolute magnitude of the solar extreme UV photon flux in the spectral region between 50 and 800 A. The adjusted daily 10.7-cm solar radio flux and sunspot number were 168.4 and 121, respectively. The unattenuated absolute value of the solar EUV flux at 1 AU in the specified wavelength region was 6.81 x 10 to the 10th photons/sq cm per s. Based on a nominal probable error of 7 percent for National Institute of Standards and Technology detector efficiency measurements in the 50- to 500-A region (5 percent on longer wavelength measurements between 500 and 1216 A), and based on experimental errors associated with the present rocket instrumentation and analysis, a conservative total error estimate of about 14 percent is assigned to the absolute integral solar flux obtained.

  3. Measurement of absolute optical thickness of mask glass by wavelength-tuning Fourier analysis.

    PubMed

    Kim, Yangjin; Hbino, Kenichi; Sugita, Naohiko; Mitsuishi, Mamoru

    2015-07-01

    Optical thickness is a fundamental characteristic of an optical component. A measurement method combining discrete Fourier-transform (DFT) analysis and a phase-shifting technique gives an appropriate value for the absolute optical thickness of a transparent plate. However, there is a systematic error caused by the nonlinearity of the phase-shifting technique. In this research the absolute optical-thickness distribution of mask blank glass was measured using DFT and wavelength-tuning Fizeau interferometry without using sensitive phase-shifting techniques. The error occurring during the DFT analysis was compensated for by using the unwrapping correlation. The experimental results indicated that the absolute optical thickness of mask glass was measured with an accuracy of 5 nm.

  4. STANDARDIZING TYPE Ia SUPERNOVA ABSOLUTE MAGNITUDES USING GAUSSIAN PROCESS DATA REGRESSION

    SciTech Connect

    Kim, A. G.; Aldering, G.; Aragon, C.; Bailey, S.; Childress, M.; Fakhouri, H. K.; Nordin, J.; Thomas, R. C.; Antilogus, P.; Bongard, S.; Canto, A.; Cellier-Holzem, F.; Guy, J.; Baltay, C.; Buton, C.; Kerschhaggl, M.; Kowalski, M.; Chotard, N.; Copin, Y.; Gangler, E.; and others

    2013-04-01

    We present a novel class of models for Type Ia supernova time-evolving spectral energy distributions (SEDs) and absolute magnitudes: they are each modeled as stochastic functions described by Gaussian processes. The values of the SED and absolute magnitudes are defined through well-defined regression prescriptions, so that data directly inform the models. As a proof of concept, we implement a model for synthetic photometry built from the spectrophotometric time series from the Nearby Supernova Factory. Absolute magnitudes at peak B brightness are calibrated to 0.13 mag in the g band and to as low as 0.09 mag in the z = 0.25 blueshifted i band, where the dispersion includes contributions from measurement uncertainties and peculiar velocities. The methodology can be applied to spectrophotometric time series of supernovae that span a range of redshifts to simultaneously standardize supernovae together with fitting cosmological parameters.

  5. Assessment of tissue perfusion changes in port wine stains after vascular targeted photodynamic therapy: a short-term follow-up study.

    PubMed

    Ren, Jie; Li, Pengcheng; Zhao, Hongyou; Chen, Defu; Zhen, Jie; Wang, Ying; Wang, Yucheng; Gu, Ying

    2014-03-01

    The occlusion effect of vascular targeted photodynamic therapy (V-PDT) for malformed vessels in port wine stains (PWS) often last for some time after the treatment. A relatively longer period after V-PDT is needed to accurately assess the final response of PWS microcirculation to the treatment. In this study, we intended to use laser speckle imaging (LSI) to assess the tissue perfusion changes of PWS at follow-up after V-PDT and preliminarily analyze the relationship between perfusion change and color bleaching. Seventeen patients with 40 PWS lesions were scanned by LSI before and 3-6 months after they received V-PDT. The speckle flow indices of PWS lesions and normal skin before and at follow-up after V-PDT were recorded. We also performed analyses on the correlation between perfusion changes and color bleaching. Before V-PDT, the 40 PWS lesions showed higher perfusion than the normal skin (1,421 ± 463 and 1,115 ± 386 perfusion unit (PU), respectively, P < 0.01). The PWS lesions scanned at follow-up showed decreased perfusion level compared to the preoperative values (1,282 ± 460 and 1,421 ± 463 PU, respectively, P < 0.01). After V-PDT, the perfusion change rates coincide well with the color bleaching rates (correlation coefficient, 0.73). In conclusion, the LSI system is capable of imaging PWS perfusion precisely, and it has shown promising results in assessing the changes of tissue perfusion of V-PDT for PWS, with objective and quantitative data, real-time images, and a shorter detection time. It may also provide an effectiveness assessment method for the treatment of PWS. PMID:23975603

  6. Assessment of tissue perfusion changes in port wine stains after vascular targeted photodynamic therapy: a short-term follow-up study.

    PubMed

    Ren, Jie; Li, Pengcheng; Zhao, Hongyou; Chen, Defu; Zhen, Jie; Wang, Ying; Wang, Yucheng; Gu, Ying

    2014-03-01

    The occlusion effect of vascular targeted photodynamic therapy (V-PDT) for malformed vessels in port wine stains (PWS) often last for some time after the treatment. A relatively longer period after V-PDT is needed to accurately assess the final response of PWS microcirculation to the treatment. In this study, we intended to use laser speckle imaging (LSI) to assess the tissue perfusion changes of PWS at follow-up after V-PDT and preliminarily analyze the relationship between perfusion change and color bleaching. Seventeen patients with 40 PWS lesions were scanned by LSI before and 3-6 months after they received V-PDT. The speckle flow indices of PWS lesions and normal skin before and at follow-up after V-PDT were recorded. We also performed analyses on the correlation between perfusion changes and color bleaching. Before V-PDT, the 40 PWS lesions showed higher perfusion than the normal skin (1,421 ± 463 and 1,115 ± 386 perfusion unit (PU), respectively, P < 0.01). The PWS lesions scanned at follow-up showed decreased perfusion level compared to the preoperative values (1,282 ± 460 and 1,421 ± 463 PU, respectively, P < 0.01). After V-PDT, the perfusion change rates coincide well with the color bleaching rates (correlation coefficient, 0.73). In conclusion, the LSI system is capable of imaging PWS perfusion precisely, and it has shown promising results in assessing the changes of tissue perfusion of V-PDT for PWS, with objective and quantitative data, real-time images, and a shorter detection time. It may also provide an effectiveness assessment method for the treatment of PWS.

  7. Convective-to-absolute instability transition in a viscoelastic capillary jet subject to unrelaxed axial elastic tension.

    PubMed

    Mohamed, A Said; Herrada, M A; Gañán-Calvo, A M; Montanero, J M

    2015-08-01

    The convective-to-absolute instability transition in an Oldroyd-B capillary jet subject to unrelaxed axial stress is examined theoretically. There is a critical Weber number below which the jet is absolutely unstable under axisymmetric perturbations. We analyze the dependence of this critical parameter with respect to the Reynolds and Deborah numbers, as well as the unrelaxed axial stress. For small Deborah numbers, the unrelaxed stress destabilizes the viscoelastic jet, increasing the critical Weber number for which the convective-to-absolute instability transition takes place. If the Deborah number takes higher values, then the transitional Weber number decreases as the unrelaxed stress increases until two solution branches cross each other. The dominant branch for large axial stress leads to a threshold of this quantity above which the viscoelastic jet becomes absolutely unstable independently of the Weber number. The threshold depends on neither the Reynolds nor the Deborah number for sufficiently large values of these parameters.

  8. Convective-to-absolute instability transition in a viscoelastic capillary jet subject to unrelaxed axial elastic tension.

    PubMed

    Mohamed, A Said; Herrada, M A; Gañán-Calvo, A M; Montanero, J M

    2015-08-01

    The convective-to-absolute instability transition in an Oldroyd-B capillary jet subject to unrelaxed axial stress is examined theoretically. There is a critical Weber number below which the jet is absolutely unstable under axisymmetric perturbations. We analyze the dependence of this critical parameter with respect to the Reynolds and Deborah numbers, as well as the unrelaxed axial stress. For small Deborah numbers, the unrelaxed stress destabilizes the viscoelastic jet, increasing the critical Weber number for which the convective-to-absolute instability transition takes place. If the Deborah number takes higher values, then the transitional Weber number decreases as the unrelaxed stress increases until two solution branches cross each other. The dominant branch for large axial stress leads to a threshold of this quantity above which the viscoelastic jet becomes absolutely unstable independently of the Weber number. The threshold depends on neither the Reynolds nor the Deborah number for sufficiently large values of these parameters. PMID:26382502

  9. Comparison of Two Algorithms for Analysis of Perfusion Computed Tomography Data for Evaluation of Cerebral Microcirculation in Chronic Subdural Hematoma.

    PubMed

    Trofimov, Alexey O; Kalentiev, George; Voennov, Oleg; Yuriev, Michail; Agarkova, Darya; Trofimova, Svetlana; Bragin, Denis E

    2016-01-01

    The aim of this work was comparison of two algorithms of perfusion computed tomography (PCT) data analysis for evaluation of cerebral microcirculation in the perifocal zone of chronic subdural hematoma (CSDH). Twenty patients with CSDH after polytrauma were included in the study. The same PCT data were assessed quantitatively in cortical brain region beneath the CSDH (zone 1), and in the corresponding contralateral brain hemisphere (zone 2) without and with the use of perfusion calculation mode excluding vascular pixel 'Remote Vessels' (RV); 1st and 2nd analysis method, respectively. Comparison with normal values for perfusion indices in the zone 1 in the 1st analysis method showed a significant (p < 0.01) increase in CBV and CBF, and no significant increase in MTT and TTP. Use of the RV mode (2nd analysis method) showed no statistically reliable change of perfusion parameters in the microcirculatory blood flow of the 2nd zone. Maintenance of microcirculatory blood flow perfusion reflects the preservation of cerebral blood flow autoregulation in patients with CSDH. PMID:27526170

  10. Glutathione S-transferase iso-enzymes in perfusate from pumped kidneys are associated with delayed graft function.

    PubMed

    Hall, I E; Bhangoo, R S; Reese, P P; Doshi, M D; Weng, F L; Hong, K; Lin, H; Han, G; Hasz, R D; Goldstein, M J; Schröppel, B; Parikh, C R

    2014-04-01

    Accurate and reliable assessment tools are needed in transplantation. The objective of this prospective, multi-center study was to determine the associations of the alpha and pi iso-enzymes of glutathione S-transferase (GST), measured from perfusate solution at the start and end (base and post) of kidney allograft machine perfusion, with subsequent delayed graft function (DGF). We also compared GST iso-enzyme perfusate levels from discarded versus transplanted kidneys. A total of 428 kidneys were linked to outcomes as recorded by the United Network of Organ Sharing. DGF, defined as any dialysis in the first week of transplant, occurred in 141 recipients (32%). Alpha- and pi-GST levels significantly increased during machine perfusion. The adjusted relative risks (95% confidence interval) of DGF with each log-unit increase in base and post pi-GST were 1.14 (1.0-1.3) and 1.36 (1.1-1.8), respectively. Alpha-GST was not independently associated with DGF. There were no significant differences in GST values between discarded and transplanted kidneys, though renal resistance was significantly higher in discarded kidneys. We found pi-GST at the end of machine perfusion to be independently associated with DGF. Further studies should elucidate the utility of GST for identifying injured kidneys with regard to organ allocation, discard and recipient management decisions.

  11. Is correction necessary when clinically determining quantitative cerebral perfusion parameters from multi-slice dynamic susceptibility contrast MR studies?

    NASA Astrophysics Data System (ADS)

    Salluzzi, M.; Frayne, R.; Smith, M. R.

    2006-01-01

    Several groups have modified the standard singular value decomposition (SVD) algorithm to produce delay-insensitive cerebral blood flow (CBF) estimates from dynamic susceptibility contrast (DSC) perfusion studies. However, new dependences of CBF estimates on bolus arrival times and slice position in multi-slice studies have been recently recognized. These conflicting findings can be reconciled by accounting for several experimental and algorithmic factors. Using simulation and clinical studies, the non-simultaneous measurement of arterial and tissue concentration curves (relative slice position) in a multi-slice study is shown to affect time-related perfusion parameters, e.g. arterial-tissue-delay measurements. However, the current clinical impact of relative slice position on amplitude-related perfusion parameters, e.g. CBF, can be expected to be small unless any of the following conditions are present individually or in combination: (a) high concentration curve signal-to-noise ratios, (b) small tissue mean transit times, (c) narrow arterial input functions or (d) low temporal resolution of the DSC image sequence. Recent improvements in magnetic resonance (MR) technology can easily be expected to lead to scenarios where these effects become increasingly important sources of inaccuracy for all perfusion parameter estimates. We show that using Fourier interpolated (high temporal resolution) residue functions reduces the systematic error of the perfusion parameters obtained from multi-slice studies. Preliminary results associated with this paper were presented at ISMRM 12th Scientific Meeting and Exhibition, Kyoto, Japan, 2004.

  12. Antiausterity activity of arctigenin enantiomers: importance of (2R,3R)-absolute configuration.

    PubMed

    Awale, Suresh; Kato, Mamoru; Dibwe, Dya Fita; Li, Feng; Miyoshi, Chika; Esumi, Hiroyasu; Kadota, Shigetoshi; Tezuka, Yasuhiro

    2014-01-01

    From a MeOH extract of powdered roots of Wikstroemia indica, six dibenzyl-gamma-butyrolactone-type lignans with (2S,3S)-absolute configuration [(+)-arctigenin (1), (+)-matairesinol (2), (+)-trachelogenin (3), (+)-nortrachelogenin (4), (+)-hinokinin (5), and (+)-kusunokinin (6)] were isolated, whereas three dibenzyl-gamma-butyrolactone-type lignans with (2R,3R)-absolute configuration [(-)-arctigenin (1*), (-)-matairesinol (2*), (-)-trachelogenin (3*)] were isolated from Trachelospermum asiaticum. The in vitro preferential cytotoxic activity of the nine compounds was evaluated against human pancreatic PANC-1 cancer cells in nutrient-deprived medium (NDM), but none of the six lignans (1-6) with (2S,3S)-absolute configuration showed preferential cytotoxicity. On the other hand, three lignans (1*-3*) with (2R,3R)-absolute configuration exhibited preferential cytotoxicity in a concentration-dependent manner with PC50 values of 0.54, 6.82, and 5.85 microM, respectively. Furthermore, the effect of (-)- and (+)-arctigenin was evaluated against the activation of Akt, which is a key process in the tolerance to nutrition starvation. Interestingly, only (-)-arctigenin (1*) strongly suppressed the activation of Akt. These results indicate that the (2R,3R)-absolute configuration of (-)-enantiomers should be required for the preferential cytotoxicity through the inhibition of Akt activation.

  13. Utilizing a reference material for assessing absolute tumor mechanical properties in modality independent elastography

    NASA Astrophysics Data System (ADS)

    Kim, Dong Kyu; Weis, Jared A.; Yankeelov, Thomas E.; Miga, Michael I.

    2014-03-01

    There is currently no reliable method for early characterization of breast cancer response to neoadjuvant chemotherapy (NAC) [1,2]. Given that disruption of normal structural architecture occurs in cancer-bearing tissue, we hypothesize that further structural changes occur in response to NAC. Consequently, we are investigating the use of modalityindependent elastography (MIE) [3-8] as a method for monitoring mechanical integrity to predict long term outcomes in NAC. Recently, we have utilized a Demons non-rigid image registration method that allows 3D elasticity reconstruction in abnormal tissue geometries, making it particularly amenable to the evaluation of breast cancer mechanical properties. While past work has reflected relative elasticity contrast ratios [3], this study improves upon that work by utilizing a known stiffness reference material within the reconstruction framework such that a stiffness map becomes an absolute measure. To test, a polyvinyl alcohol (PVA) cryogel phantom and a silicone rubber mock mouse tumor phantom were constructed with varying mechanical stiffness. Results showed that an absolute measure of stiffness could be obtained based on a reference value. This reference technique demonstrates the ability to generate accurate measurements of absolute stiffness to characterize response to NAC. These results support that `referenced MIE' has the potential to reliably differentiate absolute tumor stiffness with significant contrast from that of surrounding tissue. The use of referenced MIE to obtain absolute quantification of biomarkers is also translatable across length scales such that the characterization method is mechanics-consistent at the small animal and human application.

  14. Antiausterity activity of arctigenin enantiomers: importance of (2R,3R)-absolute configuration.

    PubMed

    Awale, Suresh; Kato, Mamoru; Dibwe, Dya Fita; Li, Feng; Miyoshi, Chika; Esumi, Hiroyasu; Kadota, Shigetoshi; Tezuka, Yasuhiro

    2014-01-01

    From a MeOH extract of powdered roots of Wikstroemia indica, six dibenzyl-gamma-butyrolactone-type lignans with (2S,3S)-absolute configuration [(+)-arctigenin (1), (+)-matairesinol (2), (+)-trachelogenin (3), (+)-nortrachelogenin (4), (+)-hinokinin (5), and (+)-kusunokinin (6)] were isolated, whereas three dibenzyl-gamma-butyrolactone-type lignans with (2R,3R)-absolute configuration [(-)-arctigenin (1*), (-)-matairesinol (2*), (-)-trachelogenin (3*)] were isolated from Trachelospermum asiaticum. The in vitro preferential cytotoxic activity of the nine compounds was evaluated against human pancreatic PANC-1 cancer cells in nutrient-deprived medium (NDM), but none of the six lignans (1-6) with (2S,3S)-absolute configuration showed preferential cytotoxicity. On the other hand, three lignans (1*-3*) with (2R,3R)-absolute configuration exhibited preferential cytotoxicity in a concentration-dependent manner with PC50 values of 0.54, 6.82, and 5.85 microM, respectively. Furthermore, the effect of (-)- and (+)-arctigenin was evaluated against the activation of Akt, which is a key process in the tolerance to nutrition starvation. Interestingly, only (-)-arctigenin (1*) strongly suppressed the activation of Akt. These results indicate that the (2R,3R)-absolute configuration of (-)-enantiomers should be required for the preferential cytotoxicity through the inhibition of Akt activation. PMID:24660468

  15. Quantification of nonuniform distribution of hemi-lung perfusion in chronic obstructive pulmonary disease.

    PubMed

    Mitomo, Osamu

    2016-01-01

    Nonuniform distribution (NUD) of perfusion on single photon emission computed tomography (SPECT) is caused by impaired perfusion-related fluctuations of the functional volume (FFV). It was determined if digital analysis of NUD in each hemi-lung damaged by chronic obstructive pulmonary disease (COPD) could improve the whole lung impairment assessment. We examined 665 subjects and 8 controls by SPECT. The basic whole lung SPECT volume was defined at 10% of maximum whole lung count cutoff threshold (T h). For the whole lung and each hemi-lung, the 10% T h width volume, FFV rate, and misfit from the control were calculated at every T h width number (n) from 1 to 9 for every additional 10% T h from 10 to 100%. The misfit value integrated from 1 to 9 of n was defined by 3 NUD indices: D, whole lung NUD index; D rl , the index for the sum of each hemi-lung NUD; and D (I) , the NUD index with every interpolating pattern in which FFV rates of hemi-lungs comprised negative and positive value at the same n. D rl index was the sum of D and D (I) indices in all patients. D rl and D indices significantly increased in pulmonary disease subjects relative to those of the normal group and non-pulmonary disease subjects. D rl and D indices increased in COPD subjects. Progressive COPD subjects had larger D rl index values and "diffuse and even" hemi-lung impairment. The three indices quantizing FFV itself leading to NUD helped to digitally evaluate the degree of lung impairment of perfusion. Clinically, it is expected that the NUD indices and images obtained by SPECT, which visually and digitally show the pathological fluctuations in perfusion caused by lung impairment, will be able to provide specific and useful information for improving treatment and/or care of subjects with COPD.

  16. Cylindrical Taylor states conserving total absolute magnetic helicity

    NASA Astrophysics Data System (ADS)

    Low, B. C.; Fang, F.

    2014-09-01

    The Taylor state of a three-dimensional (3D) magnetic field in an upright cylindrical domain V is derived from first principles as an extremum of the total magnetic energy subject to a conserved, total absolute helicity Habs. This new helicity [Low, Phys. Plasmas 18, 052901 (2011)] is distinct from the well known classical total helicity and relative total helicity in common use to describe wholly-contained and anchored fields, respectively. A given field B, tangential along the cylindrical side of V, may be represented as a unique linear superposition of two flux systems, an axially extended system along V and a strictly transverse system carrying information on field-circulation. This specialized Chandrasekhar-Kendall representation defines Habs and permits a neat formulation of the boundary-value problem (BVP) for the Taylor state as a constant-α force-free field, treating 3D wholly-contained and anchored fields on the same conceptual basis. In this formulation, the governing equation is a scalar integro-partial differential equation (PDE). A family of series solutions for an anchored field is presented as an illustration of this class of BVPs. Past treatments of the constant-α field in 3D cylindrical geometry are based on a scalar Helmholtz PDE as the governing equation, with issues of inconsistency in the published field solutions discussed over time in the journal literature. The constant-α force-free equation reduces to a scalar Helmholtz PDE only as special cases of the 3D integro-PDE derived here. In contrast, the constant-α force-free equation and the scalar Helmholtz PDE are absolutely equivalent in the spherical domain as discussed in Appendix. This theoretical study is motivated by the investigation of the Sun's corona but the results are also relevant to laboratory plasmas.

  17. Measurement of absolute T cell receptor rearrangement diversity.

    PubMed

    Baum, Paul D; Young, Jennifer J; McCune, Joseph M

    2011-05-31

    T cell receptor (TCR) diversity is critical for adaptive immunity. Existing methods for measuring such diversity are qualitative, expensive, and/or of uncertain accuracy. Here, we describe a method and associated reagents for estimating the absolute number of unique TCR Vβ rearrangements present in a given number of cells or volume of blood. Compared to next generation sequencing, this method is rapid, reproducible, and affordable. Diversity of a sample is calculated based on three independent measurements of one Vβ-Jβ family of TCR rearrangements at a time. The percentage of receptors using the given Vβ gene is determined by flow cytometric analysis of T cells stained with anti-Vβ family antibodies. The percentage of receptors using the Vβ gene in combination with the chosen Jβ gene is determined by quantitative PCR. Finally, the absolute clonal diversity of the Vβ-Jβ family is determined with the AmpliCot method of DNA hybridization kinetics, by interpolation relative to PCR standards of known sequence diversity. These three component measurements are reproducible and linear. Using titrations of known numbers of input cells, we show that the TCR diversity estimates obtained by this approach approximate expected values within a two-fold error, have a coefficient of variation of 20%, and yield similar results when different Vβ-Jβ pairs are chosen. The ability to obtain accurate measurements of the total number of different TCR gene rearrangements in a cell sample should be useful for basic studies of the adaptive immune system as well as in clinical studies of conditions such as HIV disease, transplantation, aging, and congenital immunodeficiencies. PMID:21385585

  18. On the absolute alignment of GONG images

    NASA Astrophysics Data System (ADS)

    Toner, C. G.

    2001-01-01

    In order to combine data from the six instruments in the GONG network the alignment of all of the images must be known to a fairly high precision (~0°.1 for GONG Classic and ~0°.01 for GONG+). The relative orientation is obtained using the angular cross-correlation method described by (Toner & Harvey, 1998). To obtain the absolute orientation the Project periodically records a day of drift scans, where the image of the Sun is allowed to drift across the CCD repeatedly throughout the day. These data are then analyzed to deduce the direction of Terrestrial East-West as a function of hour angle (i.e., time) for that instrument. The transit of Mercury on Nov. 15, 1999, which was recorded by three of the GONG instruments, provided an independent check on the current alignment procedures. Here we present a comparison of the alignment of GONG images as deduced from both drift scans and the Mercury transit for two GONG sites: Tucson (GONG+ camera) and Mauna Loa (GONG Classic camera). The agreement is within ~0°.01 for both cameras, however, the scatter is substantially larger for GONG Classic: ~0°.03 compared to ~0°.01 for GONG+.

  19. Climate Absolute Radiance and Refractivity Observatory (CLARREO)

    NASA Technical Reports Server (NTRS)

    Leckey, John P.

    2015-01-01

    The Climate Absolute Radiance and Refractivity Observatory (CLARREO) is a mission, led and developed by NASA, that will measure a variety of climate variables with an unprecedented accuracy to quantify and attribute climate change. CLARREO consists of three separate instruments: an infrared (IR) spectrometer, a reflected solar (RS) spectrometer, and a radio occultation (RO) instrument. The mission will contain orbiting radiometers with sufficient accuracy, including on orbit verification, to calibrate other space-based instrumentation, increasing their respective accuracy by as much as an order of magnitude. The IR spectrometer is a Fourier Transform spectrometer (FTS) working in the 5 to 50 microns wavelength region with a goal of 0.1 K (k = 3) accuracy. The FTS will achieve this accuracy using phase change cells to verify thermistor accuracy and heated halos to verify blackbody emissivity, both on orbit. The RS spectrometer will measure the reflectance of the atmosphere in the 0.32 to 2.3 microns wavelength region with an accuracy of 0.3% (k = 2). The status of the instrumentation packages and potential mission options will be presented.

  20. Absolute flux measurements for swift atoms

    NASA Technical Reports Server (NTRS)

    Fink, M.; Kohl, D. A.; Keto, J. W.; Antoniewicz, P.

    1987-01-01

    While a torsion balance in vacuum can easily measure the momentum transfer from a gas beam impinging on a surface attached to the balance, this measurement depends on the accommodation coefficients of the atoms with the surface and the distribution of the recoil. A torsion balance is described for making absolute flux measurements independent of recoil effects. The torsion balance is a conventional taut suspension wire design and the Young modulus of the wire determines the relationship between the displacement and the applied torque. A compensating magnetic field is applied to maintain zero displacement and provide critical damping. The unique feature is to couple the impinging gas beam to the torsion balance via a Wood's horn, i.e., a thin wall tube with a gradual 90 deg bend. Just as light is trapped in a Wood's horn by specular reflection from the curved surfaces, the gas beam diffuses through the tube. Instead of trapping the beam, the end of the tube is open so that the atoms exit the tube at 90 deg to their original direction. Therefore, all of the forward momentum of the gas beam is transferred to the torsion balance independent of the angle of reflection from the surfaces inside the tube.

  1. Gyrokinetic Statistical Absolute Equilibrium and Turbulence

    SciTech Connect

    Jian-Zhou Zhu and Gregory W. Hammett

    2011-01-10

    A paradigm based on the absolute equilibrium of Galerkin-truncated inviscid systems to aid in understanding turbulence [T.-D. Lee, "On some statistical properties of hydrodynamical and magnetohydrodynamical fields," Q. Appl. Math. 10, 69 (1952)] is taken to study gyrokinetic plasma turbulence: A finite set of Fourier modes of the collisionless gyrokinetic equations are kept and the statistical equilibria are calculated; possible implications for plasma turbulence in various situations are discussed. For the case of two spatial and one velocity dimension, in the calculation with discretization also of velocity v with N grid points (where N + 1 quantities are conserved, corresponding to an energy invariant and N entropy-related invariants), the negative temperature states, corresponding to the condensation of the generalized energy into the lowest modes, are found. This indicates a generic feature of inverse energy cascade. Comparisons are made with some classical results, such as those of Charney-Hasegawa-Mima in the cold-ion limit. There is a universal shape for statistical equilibrium of gyrokinetics in three spatial and two velocity dimensions with just one conserved quantity. Possible physical relevance to turbulence, such as ITG zonal flows, and to a critical balance hypothesis are also discussed.

  2. Issues in Absolute Spectral Radiometric Calibration: Intercomparison of Eight Sources

    NASA Technical Reports Server (NTRS)

    Goetz, Alexander F. H.; Kindel, Bruce; Pilewskie, Peter

    1998-01-01

    The application of atmospheric models to AVIRIS and other spectral imaging data to derive surface reflectance requires that the sensor output be calibrated to absolute radiance. Uncertainties in absolute calibration are to be expected, and claims of 92% accuracy have been published. Measurements of accurate surface albedos and cloud absorption to be used in radiative balance calculations depend critically on knowing the absolute spectral-radiometric response of the sensor. The Earth Observing System project is implementing a rigorous program of absolute radiometric calibration for all optical sensors. Since a number of imaging instruments that provide output in terms of absolute radiance are calibrated at different sites, it is important to determine the errors that can be expected among calibration sites. Another question exists about the errors in the absolute knowledge of the exoatmospheric spectral solar irradiance.

  3. Absolute nuclear material assay using count distribution (LAMBDA) space

    SciTech Connect

    Prasad, Mano K.; Snyderman, Neal J.; Rowland, Mark S.

    2015-12-01

    A method of absolute nuclear material assay of an unknown source comprising counting neutrons from the unknown source and providing an absolute nuclear material assay utilizing a model to optimally compare to the measured count distributions. In one embodiment, the step of providing an absolute nuclear material assay comprises utilizing a random sampling of analytically computed fission chain distributions to generate a continuous time-evolving sequence of event-counts by spreading the fission chain distribution in time.

  4. Absolute nuclear material assay using count distribution (LAMBDA) space

    DOEpatents

    Prasad, Manoj K.; Snyderman, Neal J.; Rowland, Mark S.

    2012-06-05

    A method of absolute nuclear material assay of an unknown source comprising counting neutrons from the unknown source and providing an absolute nuclear material assay utilizing a model to optimally compare to the measured count distributions. In one embodiment, the step of providing an absolute nuclear material assay comprises utilizing a random sampling of analytically computed fission chain distributions to generate a continuous time-evolving sequence of event-counts by spreading the fission chain distribution in time.

  5. Antifungal activity of tuberose absolute and some of its constituents.

    PubMed

    Nidiry, Eugene Sebastian J; Babu, C S Bujji

    2005-05-01

    The antifungal activity of the absolute of tuberose (Polianthes tuberosa ) and some of its constituents were evaluated against the mycelial growth of Colletotrichum gloeosporioides on potato-dextrose-agar medium. Tuberose absolute showed only mild activity at a concentration of 500 mg/L. However, three constituents present in the absolute, namely geraniol, indole and methyl anthranilate exhibited significant activity showing total inhibition of the mycelial growth at this concentration.

  6. Magnetic Resonance Perfusion Imaging in the Study of Language

    ERIC Educational Resources Information Center

    Hillis, Argye E.

    2007-01-01

    This paper provides a brief review of various uses of magnetic resonance perfusion imaging in the investigation of brain/language relationships. The reviewed studies illustrate how perfusion imaging can reveal areas of brain where dysfunction due to low blood flow is associated with specific language deficits, and where restoration of blood flow…

  7. Tissue-specific sparse deconvolution for brain CT perfusion.

    PubMed

    Fang, Ruogu; Jiang, Haodi; Huang, Junzhou

    2015-12-01

    Enhancing perfusion maps in low-dose computed tomography perfusion (CTP) for cerebrovascular disease diagnosis is a challenging task, especially for low-contrast tissue categories where infarct core and ischemic penumbra usually occur. Sparse perfusion deconvolution has been recently proposed to effectively improve the image quality and diagnostic accuracy of low-dose perfusion CT by extracting the complementary information from the high-dose perfusion maps to restore the low-dose using a joint spatio-temporal model. However the low-contrast tissue classes where infarct core and ischemic penumbra are likely to occur in cerebral perfusion CT tend to be over-smoothed, leading to loss of essential biomarkers. In this paper, we propose a tissue-specific sparse deconvolution approach to preserve the subtle perfusion information in the low-contrast tissue classes. We first build tissue-specific dictionaries from segmentations of high-dose perfusion maps using online dictionary learning, and then perform deconvolution-based hemodynamic parameters estimation for block-wise tissue segments on the low-dose CTP data. Extensive validation on clinical datasets of patients with cerebrovascular disease demonstrates the superior performance of our proposed method compared to state-of-art, and potentially improve diagnostic accuracy by increasing the differentiation between normal and ischemic tissues in the brain. PMID:26055434

  8. Tissue-specific sparse deconvolution for brain CT perfusion.

    PubMed

    Fang, Ruogu; Jiang, Haodi; Huang, Junzhou

    2015-12-01

    Enhancing perfusion maps in low-dose computed tomography perfusion (CTP) for cerebrovascular disease diagnosis is a challenging task, especially for low-contrast tissue categories where infarct core and ischemic penumbra usually occur. Sparse perfusion deconvolution has been recently proposed to effectively improve the image quality and diagnostic accuracy of low-dose perfusion CT by extracting the complementary information from the high-dose perfusion maps to restore the low-dose using a joint spatio-temporal model. However the low-contrast tissue classes where infarct core and ischemic penumbra are likely to occur in cerebral perfusion CT tend to be over-smoothed, leading to loss of essential biomarkers. In this paper, we propose a tissue-specific sparse deconvolution approach to preserve the subtle perfusion information in the low-contrast tissue classes. We first build tissue-specific dictionaries from segmentations of high-dose perfusion maps using online dictionary learning, and then perform deconvolution-based hemodynamic parameters estimation for block-wise tissue segments on the low-dose CTP data. Extensive validation on clinical datasets of patients with cerebrovascular disease demonstrates the superior performance of our proposed method compared to state-of-art, and potentially improve diagnostic accuracy by increasing the differentiation between normal and ischemic tissues in the brain.

  9. Perfusion Electronic Record Documentation Using Epic Systems Software.

    PubMed

    Riley, Jeffrey B; Justison, George A

    2015-12-01

    The authors comment on Steffens and Gunser's article describing the University of Wisconsin adoption of the Epic anesthesia record to include perfusion information from the cardiopulmonary bypass patient experience. We highlight the current-day lessons and the valuable quality and safety principles the Wisconsin-Epic model anesthesia-perfusion record provides.

  10. Effects of increased heart work on glycolysis and adenine nucleotides in the perfused heart of normal and diabetic rats

    PubMed Central

    Opie, L. H.; Mansford, K. R. L.; Owen, Patricia

    1971-01-01

    1. In the isolated perfused rat heart, the contractile activity and the oxygen uptake were varied by altering the aortic perfusion pressure, or by the atrial perfusion technique (`working heart'). 2. The maximum increase in the contractile activity brought about an eightfold increase in the oxygen uptake. The rate of glycolytic flux rose, while tissue contents of hexose monophosphates, citrate, ATP and creatine phosphate decreased, and contents of ADP and AMP rose. 3. The changes in tissue contents of adenine nucleotides during increased heart work were time-dependent. The ATP content fell temporarily (30s and 2min) after the start of left-atrial perfusion; at 5 and 10min values were normal; and at 30 and 60min values were decreased. ADP and AMP values were increased in the first 15min, but were at control values 30 or 60min after the onset of increased heart work. 4. During increased heart work changes in the tissue contents of adenine nucleotide and of citrate appeared to play a role in altered regulation of glycolysis at the level of phosphofructokinase activity. 5. In recirculation experiments increased heart work for 30min was associated with increased entry of [14C]glucose (11.1mm) and glycogen into glycolysis and a comparable increase in formation of products of glycolysis (lactate, pyruvate and 14CO2). There was no major accumulation of intermediates. Glycogen was not a major fuel for respiration. 6. Increased glycolytic flux in Langendorff perfused and working hearts was obtained by the addition of insulin to the perfusion medium. The concomitant increases in the tissue values of hexose phosphates and of citrate contrasted with the decreased values of hexose monophosphates and of citrate during increased glycolytic flux obtained by increased heart work. 7. Decreased glycolytic flux in Langendorff perfused hearts was obtained by using acute alloxan-diabetic and chronic streptozotocin-diabetic rats; in the latter condition there were decreased tissue

  11. Dynamic response of the coronary circulation to a rapid change in its perfusion in the anaesthetized goat.

    PubMed Central

    Dankelman, J; Spaan, J A; Van der Ploeg, C P; Vergroesen, I

    1989-01-01

    1. We tested predictions of a mathematical formulation of a hypothesis of dynamic control of coronary blood flow by tissue oxygen tension. 2. The rate of change of adjustment of the coronary circulation to a step change in arterial perfusion was analysed in the cannulated main stem preparation of the anaesthetized goat. The variable studied was the ratio between driving pressure and coronary flow, each averaged per heart beat. The response of this ratio was measured following a sudden change in perfusion pressure with constant-pressure perfusion and a sudden change in flow with constant-flow perfusion. 3. The rate of change of the pressure-flow ratio was quantified by t50, the time required to establish half of the completed response. For a pressure decrease t50 was 4.9 +/- 0.2 s (n = 35) (mean +/- S.E.M., n = number of individual measurements), 11.3 +/- 1.2 s (n = 25) for a flow decrease, 14.5 +/- 1.6 (n = 34) for a pressure increase and 25.1 +/- 2.3 (n = 19) for a flow increase. 4. No effect of the level of flow or pressure on t50 was found for a decrease in perfusion. Furthermore, with a flow increase, the t50 value did not depend on the level of flow, which is in agreement with the outcome of earlier experiments where the response to a change in heart rate was measured. With a pressure increase, the mean t50 value of the pressure-flow ratio was lower at high perfusion pressure but the difference with low perfusion pressure was not significant (P = 0.11). 5. The t50 value in the cases of an increase in pressure and flow are similar to those found for a change of heart rate in an earlier study. 6. Unlike step changes of metabolic rate, some of the measured responses to mechanical step changes were not predicted by the oxygen hypothesis. It is suggested that the increased rate of coronary adjustment induced by the reduction of coronary perfusion is due to arteriolar smooth muscle mechanics which apparently differ in strength depending on the direction of change of

  12. The absolute disparity anomaly and the mechanism of relative disparities.

    PubMed

    Chopin, Adrien; Levi, Dennis; Knill, David; Bavelier, Daphne

    2016-06-01

    There has been a long-standing debate about the mechanisms underlying the perception of stereoscopic depth and the computation of the relative disparities that it relies on. Relative disparities between visual objects could be computed in two ways: (a) using the difference in the object's absolute disparities (Hypothesis 1) or (b) using relative disparities based on the differences in the monocular separations between objects (Hypothesis 2). To differentiate between these hypotheses, we measured stereoscopic discrimination thresholds for lines with different absolute and relative disparities. Participants were asked to judge the depth of two lines presented at the same distance from the fixation plane (absolute disparity) or the depth between two lines presented at different distances (relative disparity). We used a single stimulus method involving a unique memory component for both conditions, and no extraneous references were available. We also measured vergence noise using Nonius lines. Stereo thresholds were substantially worse for absolute disparities than for relative disparities, and the difference could not be explained by vergence noise. We attribute this difference to an absence of conscious readout of absolute disparities, termed the absolute disparity anomaly. We further show that the pattern of correlations between vergence noise and absolute and relative disparity acuities can be explained jointly by the existence of the absolute disparity anomaly and by the assumption that relative disparity information is computed from absolute disparities (Hypothesis 1).

  13. The absolute disparity anomaly and the mechanism of relative disparities

    PubMed Central

    Chopin, Adrien; Levi, Dennis; Knill, David; Bavelier, Daphne

    2016-01-01

    There has been a long-standing debate about the mechanisms underlying the perception of stereoscopic depth and the computation of the relative disparities that it relies on. Relative disparities between visual objects could be computed in two ways: (a) using the difference in the object's absolute disparities (Hypothesis 1) or (b) using relative disparities based on the differences in the monocular separations between objects (Hypothesis 2). To differentiate between these hypotheses, we measured stereoscopic discrimination thresholds for lines with different absolute and relative disparities. Participants were asked to judge the depth of two lines presented at the same distance from the fixation plane (absolute disparity) or the depth between two lines presented at different distances (relative disparity). We used a single stimulus method involving a unique memory component for both conditions, and no extraneous references were available. We also measured vergence noise using Nonius lines. Stereo thresholds were substantially worse for absolute disparities than for relative disparities, and the difference could not be explained by vergence noise. We attribute this difference to an absence of conscious readout of absolute disparities, termed the absolute disparity anomaly. We further show that the pattern of correlations between vergence noise and absolute and relative disparity acuities can be explained jointly by the existence of the absolute disparity anomaly and by the assumption that relative disparity information is computed from absolute disparities (Hypothesis 1). PMID:27248566

  14. Confidentiality: a modified value.

    PubMed Central

    Emson, H E

    1988-01-01

    In its original expression as a medical value confidentiality may have been absolute; this concept has become eroded by patient consent, legal actions and change in the climate of public opinion. In particular requirements arising out of legal statutes and common law judgements have greatly modified the confidentiality of the doctor-patient relationship in societies deriving their law from English origins. Despite this, confidentiality remains a value which the physician must strive to preserve. He cannot however do this without considering its effect upon possible innocent third parties. PMID:3392723

  15. The absolute radiometric calibration of space-based sensors

    NASA Astrophysics Data System (ADS)

    Holm, Ronald Gene

    A reflectance based inflight calibration procedure is used to determine the radiance reaching the entrance pupil of a sensor. This procedure uses ground based measurements coupled with a radiative transfer code to characterize the effects the atmosphere has on the signal reaching the sensor. The computed radiance is compared to the digital count output of the sensor associated with the image of a test site. This provides an update to the preflight calibration of the system and a check on the on-board internal calibrator. This calibration procedure was used to perform a series of 5 calibrations of the LANDSAT-5 Thematic Mapper. The absolute calibration techniques were put to another test with a series of 3 calibration of the SPOT-1 High Resolution Visible sensors. The procedure for performing a satellite calibration was then used to demonstrate how a calibrated satellite sensor can be used to quantitatively evaluate surface reflectance over a wide range of surface features. Predicted reflectance factors were compared to values obtained from aircraft based radiometer data. A strong correlation was shown between reflectance values determined from satellite imagery and low flying aircraft data.

  16. The pediatric template of brain perfusion.

    PubMed

    Avants, Brian B; Duda, Jeffrey T; Kilroy, Emily; Krasileva, Kate; Jann, Kay; Kandel, Benjamin T; Tustison, Nicholas J; Yan, Lirong; Jog, Mayank; Smith, Robert; Wang, Yi; Dapretto, Mirella; Wang, Danny J J

    2015-01-01

    Magnetic resonance imaging (MRI) captures the dynamics of brain development with multiple modalities that quantify both structure and function. These measurements may yield valuable insights into the neural patterns that mark healthy maturation or that identify early risk for psychiatric disorder. The Pediatric Template of Brain Perfusion (PTBP) is a free and public neuroimaging resource that will help accelerate the understanding of childhood brain development as seen through the lens of multiple modality neuroimaging and in relation to cognitive and environmental factors. The PTBP uses cross-sectional and longitudinal MRI to quantify cortex, white matter, resting state functional connectivity and brain perfusion, as measured by Arterial Spin Labeling (ASL), in 120 children 7-18 years of age. We describe the PTBP and show, as a demonstration of validity, that global summary measurements capture the trajectories that demarcate critical turning points in brain maturation. This novel resource will allow a more detailed understanding of the network-level, structural and functional landmarks that are obtained during normal adolescent brain development. PMID:25977810

  17. The pediatric template of brain perfusion

    PubMed Central

    Avants, Brian B; Duda, Jeffrey T; Kilroy, Emily; Krasileva, Kate; Jann, Kay; Kandel, Benjamin T; Tustison, Nicholas J; Yan, Lirong; Jog, Mayank; Smith, Robert; Wang, Yi; Dapretto, Mirella; Wang, Danny J J

    2015-01-01

    Magnetic resonance imaging (MRI) captures the dynamics of brain development with multiple modalities that quantify both structure and function. These measurements may yield valuable insights into the neural patterns that mark healthy maturation or that identify early risk for psychiatric disorder. The Pediatric Template of Brain Perfusion (PTBP) is a free and public neuroimaging resource that will help accelerate the understanding of childhood brain development as seen through the lens of multiple modality neuroimaging and in relation to cognitive and environmental factors. The PTBP uses cross-sectional and longitudinal MRI to quantify cortex, white matter, resting state functional connectivity and brain perfusion, as measured by Arterial Spin Labeling (ASL), in 120 children 7–18 years of age. We describe the PTBP and show, as a demonstration of validity, that global summary measurements capture the trajectories that demarcate critical turning points in brain maturation. This novel resource will allow a more detailed understanding of the network-level, structural and functional landmarks that are obtained during normal adolescent brain development. PMID:25977810

  18. Strong thermal leptogenesis and the absolute neutrino mass scale

    SciTech Connect

    Bari, Pasquale Di; King, Sophie E.; Fiorentin, Michele Re E-mail: sk1806@soton.ac.uk

    2014-03-01

    We show that successful strong thermal leptogenesis, where the final asymmetry is independent of the initial conditions and in particular a large pre-existing asymmetry is efficiently washed-out, favours values of the lightest neutrino mass m{sub 1}∼>10 meV for normal ordering (NO) and m{sub 1}∼>3 meV for inverted ordering (IO) for models with orthogonal matrix entries respecting |Ω{sub ij}{sup 2}|∼<2. We show analytically why lower values of m{sub 1} require a higher level of fine tuning in the seesaw formula and/or in the flavoured decay parameters (in the electronic for NO, in the muonic for IO). We also show how this constraint exists thanks to the measured values of the neutrino mixing angles and could be tightened by a future determination of the Dirac phase. Our analysis also allows us to place a more stringent constraint for a specific model or class of models, such as SO(10)-inspired models, and shows that some models cannot realise strong thermal leptogenesis for any value of m{sub 1}. A scatter plot analysis fully supports the analytical results. We also briefly discuss the interplay with absolute neutrino mass scale experiments concluding that they will be able in the coming years to either corner strong thermal leptogenesis or find positive signals pointing to a non-vanishing m{sub 1}. Since the constraint is much stronger for NO than for IO, it is very important that new data from planned neutrino oscillation experiments will be able to solve the ambiguity.

  19. Biliary secretion of copper in healthy man. Quantitation by an intestinal perfusion technique.

    PubMed

    van Berge Henegouwen, G P; Tangedahl, T N; Hofmann, A F; Northfield, T C; LaRusso, N F; McCall, J T

    1977-06-01

    A duodenal perfusion technique which permitted a normal daytime eating pattern of three liquid meals and an overnight fast was used to measure the 24-hr output of copper in bile in 19 studies in 14 persons with normal hepatic and gallbladder function. Daily biliary output was also determined by direct measurement on four 24-hr bile collections obtained from 3 patients with complete biliary diversion, and in 4 patients measurements of dietary copper intake and fecal copper output were also made. A mean bile copper output of 25 +/- 13 microng per kg-day (1.7 mg +/- 0.8) (mean +/- SD) was obtained in 19 perfusion studies; the range was 9.0 to 53.0 microng per kg-day. The values in the 24-hr bile collections were similiar to those obtained using the perfusion method. Biliary copper output was similar during the day and night, and there was no correlation between hourly rates of copper output and hourly rates of bile acid output, nor was there any correlation between daily copper output and daily bile acid output. The similar values for dietary intake, biliary output, and fecal output provide additional support for the current view that in healthy man copper balance is maintained by biliary secretion and subsequent fecal excretion of copper which has been absorbed in the stomach and proximal duodenum.

  20. A constant temperature perfusion system for myocardial energetics.

    PubMed

    Niesler, R A; Axon, D W; Eggert, M A

    1981-11-01

    A constant temperature perfusion system employing four heat exchangers has been developed in which perfusion fluid is heated from room temperature to 37 +/- 10 -4 degrees C for precision heat flow measurements on isolated working rat hearts. The temperature characteristics have been established and mathematical expressions developed to identify and quantify spurious thermal events. The system is a refinement of existing perfusion systems for metabolic and mechanical investigations which meets the complete requirements of myocardial energetics. It can also be used for experiments which include high precision temperature measurements on isolated working hearts or for thermal investigations on other isolated perfused organs where a highly stabilised temperature base line is required over perfusion flows from 0-100 cm3 min -1. PMID:7323145

  1. Hepatic perfusion abnormalities during CT angiography: Detection and interpretation

    SciTech Connect

    Freeny, P.C.; Marks, W.M.

    1986-06-01

    Twenty-seven perfusion abnormalities were detected in 17 of 50 patients who underwent computed tomographic angiography (CTA) of the liver. All but one of the perfusion abnormalities occurred in patients with primary or metastatic liver tumors. Perfusion abnormalities were lobar in nine cases, segmental in 11, and subsegmental in seven; 14 were hypoperfusion and 13 were hyperperfusion abnormalities. The causes for the abnormalities included nonperfusion of a replaced hepatic artery (n = 11), cirrhosis and nodular regeneration (n = 3), altered hepatic hemodynamics (e.g., siphoning, laminar flow) caused by tumor (n = 7), contrast media washout from a nonperfused vessel (n = 1), compression of adjacent hepatic parenchyma (n = 1), and unknown (n = 4). Differentiation of perfusion abnormalities from tumor usually can be made by comparing the morphology of the known tumor with the suspected perfusion abnormality, changes of each on delayed CTA scans, and review of initial angiograms and other imaging studies.

  2. Absolute Plate Velocities from Seismic Anisotropy

    NASA Astrophysics Data System (ADS)

    Kreemer, Corné; Zheng, Lin; Gordon, Richard

    2015-04-01

    The orientation of seismic anisotropy inferred beneath plate interiors may provide a means to estimate the motions of the plate relative to the sub-asthenospheric mantle. Here we analyze two global sets of shear-wave splitting data, that of Kreemer [2009] and an updated and expanded data set, to estimate plate motions and to better understand the dispersion of the data, correlations in the errors, and their relation to plate speed. We also explore the effect of using geologically current plate velocities (i.e., the MORVEL set of angular velocities [DeMets et al. 2010]) compared with geodetically current plate velocities (i.e., the GSRM v1.2 angular velocities [Kreemer et al. 2014]). We demonstrate that the errors in plate motion azimuths inferred from shear-wave splitting beneath any one tectonic plate are correlated with the errors of other azimuths from the same plate. To account for these correlations, we adopt a two-tier analysis: First, find the pole of rotation and confidence limits for each plate individually. Second, solve for the best fit to these poles while constraining relative plate angular velocities to consistency with the MORVEL relative plate angular velocities. The SKS-MORVEL absolute plate angular velocities (based on the Kreemer [2009] data set) are determined from the poles from eight plates weighted proportionally to the root-mean-square velocity of each plate. SKS-MORVEL indicates that eight plates (Amur, Antarctica, Caribbean, Eurasia, Lwandle, Somalia, Sundaland, and Yangtze) have angular velocities that differ insignificantly from zero. The net rotation of the lithosphere is 0.25±0.11° Ma-1 (95% confidence limits) right-handed about 57.1°S, 68.6°E. The within-plate dispersion of seismic anisotropy for oceanic lithosphere (σ=19.2° ) differs insignificantly from that for continental lithosphere (σ=21.6° ). The between-plate dispersion, however, is significantly smaller for oceanic lithosphere (σ=7.4° ) than for continental

  3. Quantitative Perfusion and Permeability Biomarkers in Brain Cancer from Tomographic CT and MR Images

    PubMed Central

    Eilaghi, Armin; Yeung, Timothy; d’Esterre, Christopher; Bauman, Glenn; Yartsev, Slav; Easaw, Jay; Fainardi, Enrico; Lee, Ting-Yim; Frayne, Richard

    2016-01-01

    Dynamic contrast-enhanced perfusion and permeability imaging, using computed tomography and magnetic resonance systems, are important techniques for assessing the vascular supply and hemodynamics of healthy brain parenchyma and tumors. These techniques can measure blood flow, blood volume, and blood–brain barrier permeability surface area product and, thus, may provide information complementary to clinical and pathological assessments. These have been used as biomarkers to enhance the treatment planning process, to optimize treatment decision-making, and to enable monitoring of the treatment noninvasively. In this review, the principles of magnetic resonance and computed tomography dynamic contrast-enhanced perfusion and permeability imaging are described (with an emphasis on their commonalities), and the potential values of these techniques for differentiating high-grade gliomas from other brain lesions, distinguishing true progression from posttreatment effects, and predicting survival after radiotherapy, chemotherapy, and antiangiogenic treatments are presented. PMID:27398030

  4. Evaluation of the Absolute Regional Temperature Potential

    NASA Technical Reports Server (NTRS)

    Shindell, D. T.

    2012-01-01

    The Absolute Regional Temperature Potential (ARTP) is one of the few climate metrics that provides estimates of impacts at a sub-global scale. The ARTP presented here gives the time-dependent temperature response in four latitude bands (90-28degS, 28degS-28degN, 28-60degN and 60-90degN) as a function of emissions based on the forcing in those bands caused by the emissions. It is based on a large set of simulations performed with a single atmosphere-ocean climate model to derive regional forcing/response relationships. Here I evaluate the robustness of those relationships using the forcing/response portion of the ARTP to estimate regional temperature responses to the historic aerosol forcing in three independent climate models. These ARTP results are in good accord with the actual responses in those models. Nearly all ARTP estimates fall within +/-20%of the actual responses, though there are some exceptions for 90-28degS and the Arctic, and in the latter the ARTP may vary with forcing agent. However, for the tropics and the Northern Hemisphere mid-latitudes in particular, the +/-20% range appears to be roughly consistent with the 95% confidence interval. Land areas within these two bands respond 39-45% and 9-39% more than the latitude band as a whole. The ARTP, presented here in a slightly revised form, thus appears to provide a relatively robust estimate for the responses of large-scale latitude bands and land areas within those bands to inhomogeneous radiative forcing and thus potentially to emissions as well. Hence this metric could allow rapid evaluation of the effects of emissions policies at a finer scale than global metrics without requiring use of a full climate model.

  5. Absolute Radiometric Calibration of KOMPSAT-3A

    NASA Astrophysics Data System (ADS)

    Ahn, H. Y.; Shin, D. Y.; Kim, J. S.; Seo, D. C.; Choi, C. U.

    2016-06-01

    This paper presents a vicarious radiometric calibration of the Korea Multi-Purpose Satellite-3A (KOMPSAT-3A) performed by the Korea Aerospace Research Institute (KARI) and the Pukyong National University Remote Sensing Group (PKNU RSG) in 2015.The primary stages of this study are summarized as follows: (1) A field campaign to determine radiometric calibrated target fields was undertaken in Mongolia and South Korea. Surface reflectance data obtained in the campaign were input to a radiative transfer code that predicted at-sensor radiance. Through this process, equations and parameters were derived for the KOMPSAT-3A sensor to enable the conversion of calibrated DN to physical units, such as at-sensor radiance or TOA reflectance. (2) To validate the absolute calibration coefficients for the KOMPSAT-3A sensor, we performed a radiometric validation with a comparison of KOMPSAT-3A and Landsat-8 TOA reflectance using one of the six PICS (Libya 4). Correlations between top-of-atmosphere (TOA) radiances and the spectral band responses of the KOMPSAT-3A sensors at the Zuunmod, Mongolia and Goheung, South Korea sites were significant for multispectral bands. The average difference in TOA reflectance between KOMPSAT-3A and Landsat-8 image over the Libya 4, Libya site in the red-green-blue (RGB) region was under 3%, whereas in the NIR band, the TOA reflectance of KOMPSAT-3A was lower than the that of Landsat-8 due to the difference in the band passes of two sensors. The KOMPSAT-3Aensor includes a band pass near 940 nm that can be strongly absorbed by water vapor and therefore displayed low reflectance. Toovercome this, we need to undertake a detailed analysis using rescale methods, such as the spectral bandwidth adjustment factor.

  6. Orion Absolute Navigation System Progress and Challenge

    NASA Technical Reports Server (NTRS)

    Holt, Greg N.; D'Souza, Christopher

    2012-01-01

    The absolute navigation design of NASA's Orion vehicle is described. It has undergone several iterations and modifications since its inception, and continues as a work-in-progress. This paper seeks to benchmark the current state of the design and some of the rationale and analysis behind it. There are specific challenges to address when preparing a timely and effective design for the Exploration Flight Test (EFT-1), while still looking ahead and providing software extensibility for future exploration missions. The primary onboard measurements in a Near-Earth or Mid-Earth environment consist of GPS pseudo-range and delta-range, but for future explorations missions the use of star-tracker and optical navigation sources need to be considered. Discussions are presented for state size and composition, processing techniques, and consider states. A presentation is given for the processing technique using the computationally stable and robust UDU formulation with an Agee-Turner Rank-One update. This allows for computational savings when dealing with many parameters which are modeled as slowly varying Gauss-Markov processes. Preliminary analysis shows up to a 50% reduction in computation versus a more traditional formulation. Several state elements are discussed and evaluated, including position, velocity, attitude, clock bias/drift, and GPS measurement biases in addition to bias, scale factor, misalignment, and non-orthogonalities of the accelerometers and gyroscopes. Another consideration is the initialization of the EKF in various scenarios. Scenarios such as single-event upset, ground command, and cold start are discussed as are strategies for whole and partial state updates as well as covariance considerations. Strategies are given for dealing with latent measurements and high-rate propagation using multi-rate architecture. The details of the rate groups and the data ow between the elements is discussed and evaluated.

  7. Absolute determination of local tropospheric OH concentrations

    NASA Technical Reports Server (NTRS)

    Armerding, Wolfgang; Comes, Franz-Josef

    1994-01-01

    Long path absorption (LPA) according to Lambert Beer's law is a method to determine absolute concentrations of trace gases such as tropospheric OH. We have developed a LPA instrument which is based on a rapid tuning of the light source which is a frequency doubled dye laser. The laser is tuned across two or three OH absorption features around 308 nm with a scanning speed of 0.07 cm(exp -1)/microsecond and a repetition rate of 1.3 kHz. This high scanning speed greatly reduces the fluctuation of the light intensity caused by the atmosphere. To obtain the required high sensitivity the laser output power is additionally made constant and stabilized by an electro-optical modulator. The present sensitivity is of the order of a few times 10(exp 5) OH per cm(exp 3) for an acquisition time of a minute and an absorption path length of only 1200 meters so that a folding of the optical path in a multireflection cell was possible leading to a lateral dimension of the cell of a few meters. This allows local measurements to be made. Tropospheric measurements have been carried out in 1991 resulting in the determination of OH diurnal variation at specific days in late summer. Comparison with model calculations have been made. Interferences are mainly due to SO2 absorption. The problem of OH self generation in the multireflection cell is of minor extent. This could be shown by using different experimental methods. The minimum-maximum signal to noise ratio is about 8 x 10(exp -4) for a single scan. Due to the small size of the absorption cell the realization of an open air laboratory is possible in which by use of an additional UV light source or by additional fluxes of trace gases the chemistry can be changed under controlled conditions allowing kinetic studies of tropospheric photochemistry to be made in open air.

  8. Nifedipine and thallium-201 myocardial perfusion in progressive systemic sclerosis

    SciTech Connect

    Kahan, A.; Devaux, J.Y.; Amor, B.; Menkes, C.J.; Weber, S.; Nitenberg, A.; Venot, A.; Guerin, F.; Degeorges, M.; Roucayrol, J.C.

    1986-05-29

    Heart disease in patients with progressive systemic sclerosis may be due in part to myocardial ischemia caused by a disturbance of the coronary microcirculation. To determine whether abnormalities of myocardial perfusion in this disorder are potentially reversible, we evaluated the effect of the coronary vasodilator nifedipine on myocardial perfusion assessed by thallium-201 scanning in 20 patients. Thallium-201 single-photon-emission computerized tomography was performed under control conditions and 90 minutes after 20 mg of oral nifedipine. The mean (+/- SD) number of left ventricular segments with perfusion defects decreased from 5.3 +/- 2.0 to 3.3 +/- 2.2 after nifedipine (P = 0.0003). Perfusion abnormalities were quantified by a perfusion score (0 to 2.0) assigned to each left ventricular segment and by a global perfusion score (0 to 18) for the entire left ventricle. The mean perfusion score in segments with resting defects increased from 0.97 +/- 0.24 to 1.26 +/- 0.44 after nifedipine (P less than 0.00001). The mean global perfusion score increased from 11.2 +/- 1.7 to 12.8 +/- 2.4 after nifedipine (P = 0.003). The global perfusion score increased by at least 2.0 in 10 patients and decreased by at least 2.0 in only 1. These observations reveal short-term improvement in thallium-201 myocardial perfusion with nifedipine in patients with progressive systemic sclerosis. The results are consistent with a potentially reversible abnormality of coronary vasomotion in this disorder, but the long-term therapeutic effects of nifedipine remain to be determined.

  9. Critical inclination for absolute/convective instability transition in inverted falling films

    NASA Astrophysics Data System (ADS)

    Scheid, Benoit; Kofman, Nicolas; Rohlfs, Wilko

    2016-04-01

    Liquid films flowing down the underside of inclined plates are subject to the interaction between the hydrodynamic and the Rayleigh-Taylor (R-T) instabilities causing a patterned and wavy topology at the free surface. The R-T instability results from the denser liquid film being located above a less dense ambient gas, and deforming into an array of droplets, which eventually drip if no saturation mechanism arises. Such saturation mechanism can actually be provided by a fluid motion along the inclined plate. Using a weighted integral boundary layer model, this study examines the critical inclination angle, measured from the vertical, that separates regimes of absolute and convective instability. If the instability is of absolute type, growing perturbations stay localized in space potentially leading to dripping. If the instability is of convective type, growing perturbations move downwards the inclined plate, forming waves and eventually, but not necessarily, droplets. Remarkably, there is a minimum value of the critical angle below which a regime of absolute instability cannot exist. This minimum angle decreases with viscosity: it is about 85° for water, about 70° for silicon oil 20 times more viscous than water, and reaches a limiting value for liquid with a viscosity larger than about 1000 times the one of water. It results that for any fluid, absolute dripping can only exist for inclination angle (taken from the vertical) larger than 57.4°.

  10. Diminishing the impact of the partial volume effect in cardiac SPECT perfusion imaging.

    PubMed

    Pretorius, P Hendrik; King, Michael A

    2009-01-01

    The partial volume effect (PVE) significantly restricts the absolute quantification of regional myocardial uptake and thereby limits the accuracy of absolute measurement of blood flow and coronary flow reserve by SPECT. The template-projection-reconstruction method has been previously developed for PVE compensation. This method assumes the availability of coregistered high-spatial resolution anatomical information as is now becoming available with commercial dual-modality imaging systems such as SPECT/CTs. The objective of this investigation was to determine the extent to which the impact of the PVE on cardiac perfusion SPECT imaging can be diminished if coregistered high-spatial resolution anatomical information is available. For this investigation the authors introduced an additional parameter into the template-projection-reconstruction compensation equation called the voxel filling fraction (F). This parameter specifies the extent to which structure edge voxels in the emission reconstruction are filled by the structure in question as determined by the higher spatial-resolution imaging modality and the fractional presence of the structure at different states of physiological motion as in combining phases of cardiac motion. During correction the removal of spillover to the cardiac region from the surrounding structures is performed first by using reconstructed templates of neighboring structures (liver, blood pool, lungs) to calculate spillover fractions. This is followed by determining recovery coefficients for all voxels within the heart wall from the reconstruction of the template projections of the left and right ventricles (LV and RV). The emission data are subsequently divided by these recovery coefficients taking into account the filling fraction F. The mathematical cardiac torso phantom was used for investigation correction of PVE for a normal LV distribution, a defect in the inferior wall, and a defect in the anterior wall. PVE correction resulted in a

  11. Application of hidden Markov random field approach for quantification of perfusion/diffusion mismatch in acute ischemic stroke.

    PubMed

    Dwyer, Michael G; Bergsland, Niels; Saluste, Erik; Sharma, Jitendra; Jaisani, Zeenat; Durfee, Jacqueline; Abdelrahman, Nadir; Minagar, Alireza; Hoque, Romy; Munschauer, Frederick E; Zivadinov, Robert

    2008-10-01

    The perfusion/diffusion 'mismatch model' in acute ischemic stroke provides the potential to more accurately understand the consequences of thrombolytic therapy on an individual patient basis. Few methods exist to quantify mismatch extent (ischemic penumbra) and none have shown a robust ability to predict infarcted tissue outcome. Hidden Markov random field (HMRF) approaches have been used successfully in many other applications. The aim of the study was to develop a method for rapid and reliable identification and quantification of perfusion/diffusion mismatch using an HMRF approach. An HMRF model was used in combination with automated contralateral identification to segment normal tissue from non-infarcted tissue with perfusion abnormality. The infarct was used as a seed point to initialize segmentation, along with the contralateral mirror tissue. The two seeds were then allowed to compete for ownership of all unclassified tissue. In addition, a novel method was presented for quantifying tissue salvageability by weighting the volume with the degree of hypoperfusion, allowing the penumbra voxels to contribute unequal potential damage estimates. Simulated and in vivo datasets were processed and compared with results from a conventional thresholding approach. Both simulated and in vivo experiments demonstrated a dramatic improvement in accuracy with the proposed technique. For the simulated dataset, the mean absolute error decreased from 171.9% with conventional thresholding to 2.9% for the delay-weighted HMRF approach. For the in vivo dataset, the mean absolute error decreased from 564.6% for thresholding to 34.2% for the delay-weighted HMRF approach. The described method represents a significant improvement over thresholding techniques.

  12. Mid-infrared absolute spectral responsivity scale based on an absolute cryogenic radiometer and an optical parametric oscillator laser

    NASA Astrophysics Data System (ADS)

    Zhao, Kun; Shi, Xueshun; Chen, Haidong; Liu, Yulong; Liu, Changming; Chen, Kunfeng; Li, Ligong; Gan, Haiyong; Ma, Chong

    2016-06-01

    We are reporting on a laser-based absolute spectral responsivity scale in the mid-infrared spectral range. By using a mid-infrared tunable optical parametric oscillator as the laser source, the absolute responsivity scale has been established by calibrating thin-film thermopile detectors against an absolute cryogenic radiometer. The thin-film thermopile detectors can be then used as transfer standard detectors. The extended uncertainty of the absolute spectral responsivity measurement has been analyzed to be 0.58%–0.68% (k  =  2).

  13. Mid-infrared absolute spectral responsivity scale based on an absolute cryogenic radiometer and an optical parametric oscillator laser

    NASA Astrophysics Data System (ADS)

    Zhao, Kun; Shi, Xueshun; Chen, Haidong; Liu, Yulong; Liu, Changming; Chen, Kunfeng; Li, Ligong; Gan, Haiyong; Ma, Chong

    2016-06-01

    We are reporting on a laser-based absolute spectral responsivity scale in the mid-infrared spectral range. By using a mid-infrared tunable optical parametric oscillator as the laser source, the absolute responsivity scale has been established by calibrating thin-film thermopile detectors against an absolute cryogenic radiometer. The thin-film thermopile detectors can be then used as transfer standard detectors. The extended uncertainty of the absolute spectral responsivity measurement has been analyzed to be 0.58%-0.68% (k  =  2).

  14. What Value "Value Added"?

    ERIC Educational Resources Information Center

    Richards, Andrew

    2015-01-01

    Two quantitative measures of school performance are currently used, the average points score (APS) at Key Stage 2 and value-added (VA), which measures the rate of academic improvement between Key Stage 1 and 2. These figures are used by parents and the Office for Standards in Education to make judgements and comparisons. However, simple…

  15. Absolute photoabsorption cross sections of Sr I from the 5s ionization threshold to the 5p threshold

    NASA Astrophysics Data System (ADS)

    Chu, C. C.; Fung, H. S.; Wu, H. H.; Yih, T. S.

    1998-09-01

    We have measured the absolute photoabsorption cross sections of Sr I from its 5s ionization threshold up to the 0953-4075/31/17/010/img1 thresholds. The spectrum includes the Sr I 0953-4075/31/17/010/img2, 0953-4075/31/17/010/img3, 0953-4075/31/17/010/img4 and 0953-4075/31/17/010/img5 doubly excited series which converge to the 0953-4075/31/17/010/img6 or 0953-4075/31/17/010/img1 series limits. Synchrotron radiation, from the 1 m Seya-Namioka beam line of the Synchrotron Radiation Research Center at Hsin-Chu, Taiwan, was used as the background continuum. The absolute column density was determined by measuring simultaneously the temperature distribution profiles and the total pressure in a heatpipe. Absolute cross sections were obtained using the Beer-Lambert law. The measured absolute cross section for the 5s ionization threshold was 0953-4075/31/17/010/img8. At the most significant autoionizing resonance, 0953-4075/31/17/010/img9 around 0953-4075/31/17/010/img10, the absolute cross section was measured as 0953-4075/31/17/010/img11. The absolute cross sections presented here are larger than those based on saturated vapour-pressure data, and less than those based on the f-value measurements. All the absolute cross sections in this work are compared with both recent experiments and

  16. Predicting radiotherapy-induced cardiac perfusion defects

    SciTech Connect

    Das, Shiva K.; Baydush, Alan H.; Zhou Sumin; Miften, Moyed; Yu Xiaoli; Craciunescu, Oana; Oldham, Mark; Light, Kim; Wong, Terence; Blazing, Michael; Borges-Neto, Salvador; Dewhirst, Mark W.; Marks, Lawrence B.

    2005-01-01

    The purpose of this work is to compare the efficacy of mathematical models in predicting the occurrence of radiotherapy-induced left ventricular perfusion defects assessed using single-photon emission computed tomography (SPECT). The basis of this study is data from 73 left-sided breast/chestwall patients treated with tangential photon fields. The mathematical models compared were three commonly used parametric models [Lyman normal tissue complication probability (LNTCP), relative serialty (RS), generalized equivalent uniform dose (gEUD)] and a nonparametric model (Linear discriminant analysis--LDA). Data used by the models were the left ventricular dose--volume histograms, or SPECT-based dose-function histograms, and the presence/absence of SPECT perfusion defects 6 months postradiation therapy (21 patients developed defects). For the parametric models, maximum likelihood estimation and F-tests were used to fit the model parameters. The nonparametric LDA model step-wise selected features (volumes/function above dose levels) using a method based on receiver operating characteristics (ROC) analysis to best separate the groups with and without defects. Optimistic (upper bound) and pessimistic (lower bound) estimates of each model's predictive capability were generated using ROC curves. A higher area under the ROC curve indicates a more accurate model (a model that is always accurate has area=1). The areas under these curves for different models were used to statistically test for differences between them. Pessimistic estimates of areas under the ROC curve using dose-volume histogram/dose-function histogram inputs, in order of increasing prediction accuracy, were LNTCP (0.79/0.75), RS (0.80/0.77), gEUD (0.81/0.78), and LDA (0.84/0.86). Only the LDA model benefited from SPECT-based regional functional information. In general, the LDA model was statistically superior to the parametric models. The LDA model selected as features the left ventricular volumes above

  17. Novalis' Poetic Uncertainty: A "Bildung" with the Absolute

    ERIC Educational Resources Information Center

    Mika, Carl

    2016-01-01

    Novalis, the Early German Romantic poet and philosopher, had at the core of his work a mysterious depiction of the "absolute." The absolute is Novalis' name for a substance that defies precise knowledge yet calls for a tentative and sensitive speculation. How one asserts a truth, represents an object, and sets about encountering things…

  18. Absolute Pitch in Infant Auditory Learning: Evidence for Developmental Reorganization.

    ERIC Educational Resources Information Center

    Saffran, Jenny R.; Griepentrog, Gregory J.

    2001-01-01

    Two experiments examined 8-month-olds' use of absolute and relative pitch cues in a tone-sequence statistical learning task. Results suggest that, given unsegmented stimuli that do not conform to rules of musical composition, infants are more likely to track patterns of absolute pitches than of relative pitches. A third experiment found that adult…

  19. Absolute dimensions of unevolved O type close binaries

    SciTech Connect

    Doom, C.; de Loore, C.

    1984-03-15

    A method is presented to derive the absolute dimensions of early-type detached binaries by combining the observed parameters with results of evolutionary computations. The method is used to obtain the absolute dimensions of nine close binaries. We find that most systems have an initial masss ratio near 1.

  20. Absolute Humidity and the Seasonality of Influenza (Invited)

    NASA Astrophysics Data System (ADS)

    Shaman, J. L.; Pitzer, V.; Viboud, C.; Grenfell, B.; Goldstein, E.; Lipsitch, M.

    2010-12-01

    Much of the observed wintertime increase of mortality in temperate regions is attributed to seasonal influenza. A recent re-analysis of laboratory experiments indicates that absolute humidity strongly modulates the airborne survival and transmission of the influenza virus. Here we show that the onset of increased wintertime influenza-related mortality in the United States is associated with anomalously low absolute humidity levels during the prior weeks. We then use an epidemiological model, in which observed absolute humidity conditions temper influenza transmission rates, to successfully simulate the seasonal cycle of observed influenza-related mortality. The model results indicate that direct modulation of influenza transmissibility by absolute humidity alone is sufficient to produce this observed seasonality. These findings provide epidemiological support for the hypothesis that absolute humidity drives seasonal variations of influenza transmission in temperate regions. In addition, we show that variations of the basic and effective reproductive numbers for influenza, caused by seasonal changes in absolute humidity, are consistent with the general timing of pandemic influenza outbreaks observed for 2009 A/H1N1 in temperate regions. Indeed, absolute humidity conditions correctly identify the region of the United States vulnerable to a third, wintertime wave of pandemic influenza. These findings suggest that the timing of pandemic influenza outbreaks is controlled by a combination of absolute humidity conditions, levels of susceptibility and changes in population mixing and contact rates.